Fatigue crack propagation inhibition / detection method, and fatigue crack propagation inhibition / detection sheet

Abstract

To provide fatigue crack growth suppression / detection methods and fatigue crack growth suppression / detection sheets capable of effectively suppressing growth of crack even at a crack tip portion, which has been difficult conventionally, by a wedge effect of corrosion products generated by easily creating wet corrosion environment on site in a locally limited manner, and capable of easily and visually detecting the crack.SOLUTION: A water-containing material 10 containing water is made to face opening parts 3a and 3b of crack fatigue 3 of a metal base material 2; the water-containing material 10 is covered by sheet means 20 preventing drying of water; the inside of the fatigue crack 3 is retained in wet corrosion environment by the water of the water-containing material 10 and atmospheric air or oxygen supplied from an oxidant to generate corrosion products of the base material 2; and thereby suppressing the growth of the fatigue crack 3 by the wedge effect of swelling corrosion products and / or detecting the growth of the fatigue crack 3 by discoloration due to the corrosion products of the base material 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fatigue crack propagation inhibition / detection method and a fatigue crack propagation inhibition / detection sheet for inhibiting or detecting the propagation of fatigue cracks that occur in base materials of various structures such as ships, bridges, vehicles, aircraft, machine tools, etc. [Background technology]

[0002] Various structures such as ships, bridges, vehicles, aircraft, and machine tools are mainly composed of base materials (including metal structural members and welds) made of metals such as iron and aluminum, or their alloys (steel, aluminum alloys, etc.), but when repeated loads are applied to these base materials, cracks can occur due to metal fatigue, especially in the areas where stress is concentrated. Such fatigue cracks gradually grow as the number of repeated loads increases over time, and if the crack length exceeds the structural limit, it may lead to serious damage or accidents, so it is necessary to discover the cracks while they are still short and take measures to effectively suppress or stop their growth. Patent documents 1 and 2 describe a method for inhibiting and detecting the progression of fatigue cracks, in which a paste containing fine particles with a hardness equal to or greater than that of the base material and viscous oil is applied to the surface of a structure; when a crack occurs in the structure, the paste flows into the crack and the wedge effect of the fine particles inhibits the progression of the fatigue crack; and further, the powder of the metal base material ground into fine particles turns black and develops on the surface of the paste, making it possible to detect the occurrence and progression of the crack.

[0003] On the other hand, Non-Patent Document 1 shows that the crack growth rate may be suppressed by the wedge effect of the corrosion products, which is that the corrosion products generated in the crack increase the crack opening stress and reduce the stress amplitude at the crack tip. Since the fatigue crack growth behavior in a corrosive environment is a conflict between two opposing actions, namely, the suppression of crack growth due to the wedge effect of the corrosion products as described above and the accelerating action of crack growth due to the dissolution of metal ions from the crack surface, i.e., corrosion dissolution, the former suppression action is relatively prominent and dominant, and by creating a moderate wet corrosion environment in the crack (to the extent that moderate corrosion products (rust) are generated on the crack surface without significant dissolution of metal ions on the crack surface as in the immersion state), it becomes possible to effectively suppress the growth of the crack. As an example of such a moderately wet corrosion environment, Non-Patent Document 2 shows that when dry-wet cycles are repeated, such as in the splash zone of an offshore structure, a rust layer with good adhesion is formed within the cracks, and the wedge effect becomes prominent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-028462 A [Patent Document 2] JP 2009-214254 A [Non-patent literature]

[0005] [Non-Patent Document 1] Kenjiro Komai, Takusuke Shikida, Yoshiro Endo: Study on the wedge effect of corrosion products in corrosion fatigue crack propagation, Transactions of the Japan Society of Mechanical Engineers (Series A), Vol. 50, No. 456 (1984), pp. 1453-1460. [Non-Patent Document 2] Kenjiro Komai: Current Status and Prospects of Corrosion Fatigue Research, Tetsu-to-Haganen, No. 7, 69th year (1983), pp. 728-736. Summary of the Invention [Problem to be solved by the invention]

[0006] In the method shown in Patent Document 1 or 2, the fine particles can only enter the cracks up to the part where the cracks open larger than the particle size, and in principle, a wedge cannot be formed at the tip of the crack where the fine particles cannot enter, and the crack propagation suppression effect due to the wedge effect does not work at the tip of the crack. In addition, at the tip of the crack where a wedge is not formed, the metal base material powder ground into fine particles does not turn black and color on the paste surface, so there is often a slight deviation between the actual crack length and the length of the black coloring area (crack length ≧ length of the black coloring area). Furthermore, the paste needs to be a viscous fluid with appropriate fluidity, and there is a possibility that it will be removed by external factors such as contact with other objects or pressure from the fluid. Patent Document 2 also describes a resin protective film to protect the paste, but it takes a considerable amount of time and effort to form a resin protective film, and there is a limit to the external pressure that the protective film can withstand. Furthermore, unlike the marine structures described in Non-Patent Document 2, artificially creating a wet-dry cycle at the crack detection site of a normal structure requires considerable equipment and effort. In addition, it is difficult to use methods such as spraying or immersion in a localized manner only at the opening of the crack, which may lead to corrosion deterioration of structural parts unrelated to the crack.

[0007] On the other hand, there is no technology available that can easily and locally create a wet corrosive environment on-site that does not significantly dissolve metal ions from the crack surface as occurs in an immersed state, and that is sufficient to produce moderate corrosion products (rust) on the crack surface, and that can maintain this environment for a certain period of time. Therefore, the present invention aims to provide a fatigue crack propagation inhibition / detection method and a fatigue crack propagation inhibition / detection sheet that can easily and locally create a wet corrosive environment such as the one described above on-site, and by using the wedge effect of the resulting corrosion products, can effectively inhibit the propagation of a crack even at the tip of the crack, which was previously difficult to do, and can easily detect the crack visually. [Means for solving the problem]

[0008] A method for inhibiting / detecting the progression of a fatigue crack in a base material according to claim 1 comprises: providing a water-retaining material that holds water at the opening of a fatigue crack in a metallic base material; covering the water-retaining material with a sheet means that prevents the water from drying; maintaining the inside of the fatigue crack in a wet corrosive environment with the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent, thereby generating corrosion products in the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products; and / or detecting the progression of the fatigue crack by the discoloration of the base material caused by the corrosion products. In the above, when the fatigue crack is a through crack penetrating the base material, a water-containing material and a sheet means or an oxidizing agent covered with a sheet means are placed at the opening on the back side of the through crack, and oxygen is supplied through the opening on the front side of the through crack and / or from the breathable sheet means or the oxidizing agent. It is characterized by: According to the present invention described in claim 1, a wet corrosion environment is easily and locally created on-site, where metal ions on the crack surface do not significantly dissolve as in the immersion state, and a moderate amount of corrosion products (rust) are generated on the crack surface, and the wedge effect of the generated corrosion products makes it possible to effectively suppress the crack growth even at the tip of the crack, which was previously difficult, and also makes it possible to easily detect the crack visually. Furthermore, since it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance. In addition, the amount of oxygen supplied to the fatigue crack can be secured to facilitate the formation of corrosion products. The base material includes metal structural members, metal structural members and their welds, and the welds of metal structural members themselves. The base material may also include paint films. Water includes not only ordinary water, but also water with inorganic salts such as NaCl dissolved in it, and liquids containing electrolytes that cause corrosion in the same way as water. In addition, the front side and the back side are not related to the front side and the back side at the installation site of the base material. In addition, the crack can penetrate the base material from the front side to the back side, or can propagate in the lateral direction of the base material.

[0009] The present invention as recited in claim 2 is characterized in that the sheet means has air permeability, and oxygen is supplied through the sheet means. According to the present invention as defined in claim 2, the amount of oxygen supplied to the fatigue crack can be secured, making it easier to generate corrosion products.

[0010] The present invention as recited in claim 3 is characterized in that oxygen is supplied from an oxidizer provided and covered with a sheet means. According to the present invention as defined in claim 3, oxygen is smoothly supplied from the oxidizing agent to the fatigue cracks, which makes it easier to generate corrosion products. In addition, the oxygen supplied from the oxidizer includes oxidizing gases such as ozone and nitrogen monoxide in addition to oxygen. 。

[0011] request request 4 The present invention described is characterized in that the sheet means is not breathable and utilizes oxygen supplied through openings on the front side. Claim 4 According to the present invention described above, it is possible to prevent the moisture-containing material exposed to the opening on the back side from drying out, while supplying oxygen into the fatigue crack from the opening on the front side to produce corrosion products.

[0012] Claim 5 The present invention described above is characterized in that the opening on the front side of the through crack is covered with an anti-drying film. Claim 5 According to the present invention described above, the amount of water vapor released from the opening can be reduced to prevent the water-containing material from drying out excessively.

[0013] Claim 6 The invention described is characterized in that the sheet means is not breathable and an oxidizing agent is applied to the openings on the front side. Claim 6 According to the present invention described above, it is possible to prevent the moisture-containing material exposed to the opening on the back side from drying out, while supplying an oxidizing gas such as oxygen from the opening on the front side into the fatigue crack, thereby producing corrosion products.

[0014] Claim 7 The present invention is characterized in that the application of an oxidizing agent to the opening on the front side is intermittently repeated as the fatigue crack progresses. Claim 7 According to the present invention described above, the crack propagation suppression effect can be maintained from the initial stage to the final stage of crack propagation.

[0015] Claim 8 The present invention described above is characterized in that a moisture-containing material and a sheet means or an oxidizing agent covered with a sheet means are provided at the opening on the front side of the through crack. Claim8 According to the present invention described above, moisture or oxygen is supplied from the front side as well as the back side, and a wedge effect is generated throughout the crack by the corrosion products, thereby making it possible to further suppress the progression of the crack and to make it easier to detect the crack.

[0016] Claim 9 The present invention described above is characterized in that a water-containing material and a sheet means or an oxidizing agent covered with a sheet means are provided in advance at a location of a base material where fatigue cracks are likely to occur. Claim 9 According to the present invention described above, it is possible to reliably suppress the growth of and detect microcracks immediately after their occurrence.

[0017] Claim 10 The present invention described is characterized in that the water-bearing material is replaced when the water in the water-bearing material becomes low. Claim 10 According to the present invention described above, a wet corrosive environment can be maintained inside the crack, making it easier for corrosion products to be produced.

[0018] Claim 11 The present invention described above is characterized in that the thickness of the water-bearing material is changed according to the plate thickness of the base material. Claim 11 According to the present invention described above, the volume of the crack when it opens is roughly proportional to the thickness of the base material, so that corrosion products can be effectively generated by changing the thickness of the water-bearing material according to the thickness of the base material.

[0019] Claim 12 description In a method for suppressing / detecting fatigue crack growth, teeth, A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: placing a water-retaining material over an opening of a fatigue crack in a metallic base material, covering the water-retaining material with a sheet means for preventing the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment with the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent, causing corrosion products in the base material to form; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products in the base material, The water-containing material is characterized in that a plurality of holes are provided in the material to allow ventilation, and the holes are shaped like slits and are positioned on the predicted propagation path of fatigue cracks. Claim 12 According to the present invention described above, even if a fatigue crack propagates in a direction different from the initially predicted path, the position of the opening falls within the range of the hole, and oxygen is smoothly supplied to the crack through the hole, making it easier to produce corrosion products.

[0020] Claim 13 description In a method for suppressing / detecting fatigue crack growth, teeth, A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: placing a water-retaining material that holds water over an opening of a fatigue crack in a metallic base material; covering the water-retaining material with a sheet means that prevents the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment with the water in the water-retaining material and at least oxygen supplied from an oxidizing agent, thereby generating corrosion products in the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products in the base material, The water-containing material is characterized in that a plurality of holes are provided in the water-containing material to store an oxidizing agent, and the holes are shaped like slits and are positioned on the predicted propagation path of the fatigue crack. Claim 13 According to the present invention described above, even if a fatigue crack propagates in a direction different from the initially predicted path, the position of the opening falls within the range of the oxidizer storage means, and oxygen is smoothly supplied from the oxidizer to the crack, making it easier to produce corrosion products.

[0021] Claim 14 The present invention is characterized in that the intervals between the multiple slit-shaped holes are increased or decreased depending on the length and / or the crack growth rate of the fatigue crack. Claim 14 According to the present invention described above, by changing the interval between the holes depending on the state of the crack, oxygen can be effectively supplied into the crack, and corrosion products can be produced in a shorter period of time.

[0022] Claim 15 The present invention is characterized in that, when the base material is magnetic, a sheet means having magnetic force is attached to the base material. Claim 15 According to the present invention described in , the sheet means can be easily attached and detached, and can be used repeatedly. In addition, a constant pressing force is always applied to the water-bearing material sandwiched between the sheet means and the base material due to the magnetic force (attraction force), which further promotes the penetration of water into the cracks, making it easier for corrosion products to be generated.

[0023] Claim 16 description In a method for suppressing / detecting fatigue crack growth, teeth, A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: placing a water-retaining material over an opening of a fatigue crack in a metallic base material, covering the water-retaining material with a sheet means for preventing the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment with the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent, causing corrosion products in the base material to form; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products in the base material, A galvanic cathode is provided between the sheet means and the water-containing material, and is electrically connected to the base material and has a smaller ionization tendency than the base material. and , A corrosion cell is formed by the base material and a water-containing material interposed between the galvanic cathode and the base material, Base material Within the fatigue crack It is characterized by accelerating the generation of corrosion products. Claim 16According to the present invention described above, the generation of corrosion products from the base material can be promoted, and the crack propagation inhibition effect and crack detection effect due to the wedge effect of the corrosion products can be further improved.

[0024] Claim 17 description In a method for suppressing / detecting fatigue crack growth, teeth, A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: placing a water-retaining material over an opening of a fatigue crack in a metallic base material, covering the water-retaining material with a sheet means for preventing the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment with the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent, causing corrosion products in the base material to form; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products in the base material, A direct current is applied between the base material and a durable electrode provided between the sheet means and the water-containing material; forming a corrosion cell with the durable electrode, the base material, and a water-containing material interposed between the durable electrode and the base material; Base material Within the fatigue crack It is characterized by accelerating the generation of corrosion products. Claim 17 According to the present invention described above, the generation of corrosion products from the base material can be promoted, and the crack propagation inhibition effect and crack detection effect due to the wedge effect of the corrosion products can be further improved.

[0025] Claim 18 The present invention described is characterized in that when the base material is steel or iron and red rust occurs as a corrosion product of fatigue cracks, a rust converter is used to convert it into black rust. Claim 18 According to the present invention described in the above, by transforming red rust into black rust, a stronger and more stable rust layer can be formed, and deterioration of the material due to subsequent excessive corrosion reactions can be prevented.

[0026] Claim 19 The present invention described above is characterized in that, when the installation environment of the base material is cold, the fatigue crack is heated to an appropriate temperature by a heating means from the outside of the sheet means or by a heating means provided on the sheet means. Claim 19 According to the present invention described in the above, by heating the fatigue crack to an appropriate temperature, corrosion products can be generated in a shorter period of time.

[0027] Claim 20The fatigue crack propagation inhibition / detection sheet corresponding to the description is a fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of a fatigue crack in a base material, and is provided with a water-retaining material that is placed in contact with an opening of a fatigue crack that has occurred in a metal base material, sheet means that prevents the water covering the surface of the water-retaining material from drying, and attachment means that exposes the water-retaining material to the opening via the sheet means, The water-retaining material has a plurality of holes penetrating at least from the surface to the bottom surface of the water-retaining material, The water in the water-containing material and oxygen supplied from the atmosphere make it possible to maintain a moist corrosive environment inside the fatigue crack. Claim 20 According to the present invention described in , a wet corrosion environment in which metal ions on the crack surface do not significantly dissolve as in an immersion state, and a moderate amount of corrosion products (rust) are generated on the crack surface, can be easily and locally generated on the crack surface, and the corrosion products can be generated on the crack surface in a relatively short period of time. The wedge effect of the generated corrosion products makes it possible to effectively suppress the propagation of the crack even at the tip of the crack, which was previously difficult. Discoloration due to corrosion products It is possible to easily detect cracks visually. Furthermore, because it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance. In addition, oxygen is smoothly supplied into the cracks through the holes, which makes it easier for corrosion products to form.

[0028] Claim 21 The fatigue crack propagation inhibition / detection sheet corresponding to the description is a fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of a fatigue crack in a base material, and includes a water-retaining water-retaining material that is to be exposed to an opening of a fatigue crack occurring in a metal base material, sheet means for preventing the water covering the surface of the water-retaining material from drying, an oxidizing agent covered by the sheet means, and attachment means for exposing the water-retaining material to the opening via the sheet means, The water-retaining material has a plurality of holes penetrating at least from the surface to the bottom surface of the water-retaining material, The water in the water-containing material and the oxygen supplied by the oxidizing agent make it possible to maintain a moist corrosive environment inside the fatigue crack. Claim 21According to the present invention described in , a wet corrosion environment in which metal ions on the crack surface do not significantly dissolve as in an immersion state, and a moderate amount of corrosion products (rust) are generated on the crack surface, can be easily and locally generated on the crack surface, and the corrosion products can be generated on the crack surface in a relatively short period of time. The wedge effect of the generated corrosion products makes it possible to effectively suppress the propagation of the crack even at the tip of the crack, which was previously difficult. Discoloration due to corrosion products It is possible to easily detect cracks by visual inspection. Furthermore, because it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance. In addition, it is possible to ensure the amount of oxygen supplied to the fatigue crack, making it easier to generate corrosion products. In addition, oxygen is smoothly supplied into the cracks through the holes, which makes it easier for corrosion products to form.

[0029] Claim 22 The invention described is characterized in that the hydrous material consists of a hydrous gel which retains water. Claim 22 According to the present invention described above, the water-retaining material can be easily handled, and at the same time, the fluidity of the water contained in the water-retaining material is reduced, so that the water-retaining material can be easily exposed regardless of the position of the opening.

[0030] Claim 23 The invention described is characterized in that the sheet means has micro-holes which are permeable to oxygen. Claim 23 According to the present invention described above, the amount of oxygen supplied to the fatigue crack can be secured to facilitate the formation of corrosion products.

[0031] Claim 24 The invention described is characterized in that the sheet means is impermeable to oxygen. Claim 24 According to the present invention described above, it is possible to more effectively prevent the water-containing material from drying out.

[0032] Claim 25 The invention described is characterized in that it has a support made of a flexible material between the water-containing material and the sheet means. Claim 25According to the present invention described in , the moisture-retaining material can be stably maintained in a state where it faces the opening. In addition, since the support has flexibility, it can be applied to a base material (including a welded part) that has a three-dimensional curved surface. 。

[0033] request request 26 The present invention described above is characterized in that an oxidizing agent is stored in an oxidizing agent storage means that fits into the pores of the water-containing material. Claim 26 According to the present invention described above, the oxidizing agent can be stably retained.

[0034] Claim 27 The present invention described is characterized in that the oxidizer storage means has a shape with a closed top and an opening at the bottom, and is configured to be filled with a gel or liquid oxidizer inside, or to have a certain amount of space between the gel or solid oxidizer and the lower end surface. Claim 27 According to the present invention described in the above, an oxidizing agent can be directly introduced into the fatigue crack, or only an oxidizing gas generated from the oxidizing agent can be introduced into the fatigue crack to generate corrosion products.

[0035] Claim 28 The present invention described is characterized in that the oxidizing agent storage means has the function of adjusting the amount of oxidizing agent or oxidizing gas supplied from the oxidizing agent by the opening area of ​​the opening or the gas-permeable membrane covering the opening. Claim 28 According to the present invention described above, the amount of oxygen supplied into the fatigue crack can be made appropriate.

[0036] Claim 29 The present invention described above is characterized in that the oxidant storage means penetrates the water-retaining material and the support body to expose the surface of the sheet means, and the closed upper surface is configured to be openable and closable, thereby making it possible to replenish oxidant from the outside. Claim 29 According to the present invention described above, oxygen can be supplied from an oxidizing agent into the fatigue crack for a long period of time.

[0037] Claim 30 The present invention is characterized in that a plurality of sets of a moisture-retaining material and a support, each formed in a rectangular shape, are arranged at intervals on a sheet means. Claim 30 According to the present invention described above, oxygen is smoothly supplied into the cracks through the gaps, which makes it easier to produce corrosion products.

[0038] Claim 31 The invention described is characterised in that the sheet means is flexible and transparent or translucent. Claim 31 According to the present invention described in , since the sheet means has flexibility, it can cover the water-retaining material tightly to prevent drying. Also, since the sheet means is transparent or semi-transparent, the appearance change of the water-retaining material or the support can be observed from the outside of the sheet means.

[0039] Claim 32 The present invention is characterized in that the sheet means is a magnetic sheet having magnetic force, and the magnetic sheet also serves as a means for attaching to a magnetic base material. Claim 32 According to the present invention described in , the sheet means can be easily attached and detached, and can be used repeatedly. In addition, a constant pressing force is always applied to the water-bearing material sandwiched between the sheet means and the base material due to the magnetic force (attraction force), which further promotes the penetration of water into the cracks, making it easier for corrosion products to be generated.

[0040] Claim 33 description In the fatigue crack propagation inhibition / detection sheet corresponding to teeth, A fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of fatigue cracks in a base material, comprising: a water-retaining material that is placed in contact with an opening of a fatigue crack that has occurred in a metal base material; sheet means that prevents the water covering the surface of the water-retaining material from drying; and attachment means that exposes the water-retaining material to the opening via the sheet means. Between the sheet means and the water-containing material, a galvanic cathode having a smaller ionization tendency than the base material, which can be electrically contacted directly or through a conductor with the base material, is provided. And picture A corrosion cell can be formed by a galvanic cathode, a base material, and a water-containing material interposed between the galvanic cathode and the base material. It is characterized by the fact that Claim 33 According to the present invention described in the above, the corrosion cell effect of the galvanic cathode promotes the generation of corrosion products from the base material, and the wedge effect of the corrosion products inhibits crack growth. Discoloration due to corrosion products The crack detection function can be further improved.

[0041] Claim 34 description In the fatigue crack propagation inhibition / detection sheet corresponding to teeth, A fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of fatigue cracks in a base material, comprising: a water-retaining material that is placed in contact with an opening of a fatigue crack that has occurred in a metal base material; sheet means that prevents the water covering the surface of the water-retaining material from drying; and attachment means that exposes the water-retaining material to the opening via the sheet means. a durable electrode provided between the sheet means and the water-containing material; and a DC power supply means for supplying a DC current between the durable electrode and the base material. Equipped with picture A corrosion cell can be formed by the durable electrode, the base material, and the water-containing material interposed between the durable electrode and the base material. It is characterized by the fact that Claim 34 According to the present invention described in the above, the corrosion cell effect of the durable electrode and the DC power source promotes the generation of corrosion products from the base material, and the wedge effect of the corrosion products inhibits crack growth. Discoloration due to corrosion products The crack detection function can be further improved.

[0042] The present invention as recited in claim 35 is characterized in that the device further comprises an oxidizer covered with a sheet means. According to the present invention as defined in claim 35, oxygen is smoothly supplied from the oxidizing agent to the fatigue crack, which makes it easier to generate corrosion products.

[0043] Claim 36 The present invention is characterized in that the sheet means has a heating means for heating the fatigue cracks. do. Claim 36 According to the present invention described in the above, by heating the fatigue crack to an appropriate temperature, corrosion products can be generated in a shorter period of time. Effect of the Invention

[0044] According to the fatigue crack propagation inhibition / detection method of the present invention, a wet corrosion environment is easily and locally created on-site, where metal ions on the crack surface are not significantly eluted as in the immersion state, and a moderate amount of corrosion products (rust) are generated on the crack surface, and the wedge effect of the generated corrosion products makes it possible to effectively inhibit the propagation of the crack even at the tip of the crack, which was previously difficult, and also makes it possible to easily detect the crack by visual inspection. Furthermore, since it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance.

[0045] Furthermore, in the case where the sheet means has air permeability and oxygen is supplied through the sheet means, the amount of oxygen supplied into the fatigue crack can be secured, making it easier to generate corrosion products.

[0046] Furthermore, when oxygen is supplied from an oxidizer provided so as to be covered with a sheet means, oxygen is smoothly supplied from the oxidizer to the fatigue cracks, which makes it easier to generate corrosion products.

[0047] In addition, when the fatigue crack is a through crack penetrating the base material, a water-containing material and a sheet means or an oxidizing agent covered with a sheet means are placed at the opening on the back side of the through crack, and oxygen is supplied through the opening on the front side of the through crack and / or from the breathable sheet means or oxidizing agent. By This ensures a sufficient amount of oxygen to be supplied into the fatigue crack, making it easier for corrosion products to form.

[0048] In addition, when the sheet means is not breathable and oxygen is supplied through the opening on the front side, it is possible to supply oxygen from the opening on the front side into the fatigue cracks to produce corrosion products while preventing the moisture-containing material exposed to the opening on the back side from drying out.

[0049] In addition, if the opening on the front side of the through crack is covered with a drying prevention film, the amount of water vapor released from the opening can be reduced, preventing excessive drying of the water-containing material.

[0050] In addition, when the sheet means is not breathable and an oxidizing agent is applied to the opening on the front side, it is possible to supply an oxidizing gas such as oxygen from the opening on the front side into the fatigue crack while preventing the moisture-containing material exposed to the opening on the back side from drying out, thereby producing corrosion products.

[0051] Furthermore, when the application of the oxidizing agent to the opening on the front side is repeated intermittently as the fatigue crack progresses, the progress suppression effect can be maintained from the initial stage to the final stage of crack progression.

[0052] In addition, if a moisture-containing material and a sheet means or an oxidizing agent covered with a sheet means are placed at the opening on the front side of a through crack, moisture or oxygen is supplied from the front side as well as the back side, and a wedge effect is generated by the corrosion products evenly within the crack, thereby further suppressing the progression of the crack and making it easier to detect the crack.

[0053] Furthermore, when a water-containing material and a sheet means or an oxidizing agent covered with a sheet means are provided in advance at a location in the base material where fatigue cracks are likely to occur, it is possible to reliably suppress the progression of and detect microcracks immediately after they occur.

[0054] Furthermore, if the water-bearing material is replaced when the amount of water in the water-bearing material becomes low, the moist corrosive environment inside the crack can be maintained, making it easier for corrosion products to be produced.

[0055] Furthermore, when the thickness of the water-bearing material is changed according to the thickness of the base material, the volume of the crack when it opens is roughly proportional to the thickness of the base material. Therefore, by changing the thickness of the water-bearing material according to the thickness of the base material, corrosion products can be effectively produced.

[0056] In addition, multiple holes are provided in the water-containing material to allow ventilation, and the holes are shaped like slits to face the predicted propagation path of the fatigue crack. By Even if the fatigue crack propagates in a direction different from the originally predicted path, the opening position will be within the range of the hole, and oxygen will be smoothly supplied to the crack through the hole, making it easier for corrosion products to form.

[0057] In addition, a plurality of holes are provided in the water-containing material to store the oxidizing agent, and the holes are shaped like slits to face the predicted propagation path of the fatigue crack. By Even if the fatigue crack propagates in a direction different from the originally predicted path, the position of the opening falls within the range of the oxidizer storage means, and oxygen is smoothly supplied from the oxidizer to the crack, making it easier to produce corrosion products.

[0058] In addition, when the spacing between the multiple slit-shaped holes is increased or decreased depending on the length and / or crack propagation rate of the fatigue crack, by changing the spacing between the holes depending on the condition of the crack, oxygen can be effectively supplied into the crack, and corrosion products can be produced in a shorter period of time.

[0059] In addition, if the base material is magnetic, and a magnetic sheet means is attached to the base material, the sheet means can be easily attached and detached, and can be used repeatedly. In addition, the magnetic force (attraction force) acting between the sheet means and the base material always exerts a constant pressing force on the water-containing material sandwiched between them, which further promotes the penetration of moisture into the cracks and makes it easier for corrosion products to be generated.

[0060] In addition, a galvanic cathode is provided between the sheet means and the water-containing material, and is electrically connected to the base material. The galvanic cathode has a smaller ionization tendency than the base material. and , A corrosion cell is formed by the base material and a water-containing material interposed between the galvanic cathode and the base material, Base material Within the fatigue crack Accelerates the generation of corrosion products By This promotes the generation of corrosion products from the base material, and further enhances the crack propagation inhibition effect and crack detection effect due to the wedge effect of the corrosion products.

[0061] Also, a direct current is applied between the base material and a durable electrode provided between the sheet means and the water-containing material, forming a corrosion cell with the durable electrode, the base material, and a water-containing material interposed between the durable electrode and the base material; Base material Within the fatigue crack Accelerates the generation of corrosion products By This promotes the generation of corrosion products from the base material, and further enhances the crack propagation inhibition effect and crack detection effect due to the wedge effect of the corrosion products.

[0062] In addition, when the base material is steel or iron and red rust occurs as a corrosion product of fatigue cracks, if a rust converter is used to convert it to black rust, converting the red rust to black rust forms a stronger and more stable rust layer, making it possible to prevent subsequent material deterioration due to excessive corrosion reactions.

[0063] In addition, when the installation environment of the base material is cold, if the fatigue crack is heated to an appropriate temperature by a heating means from the outside of the sheet means or by a heating means provided on the sheet means, by heating the fatigue crack to an appropriate temperature, corrosion products can be produced in a shorter period of time.

[0064] In addition, the fatigue crack propagation inhibition / detection sheet of the present invention does not significantly dissolve metal ions from the crack surface as occurs in a immersed state, and can easily and locally create a moist corrosive environment on-site that produces a moderate amount of corrosion products (rust) on the crack surface, causing the corrosion products to form on the crack surface in a relatively short period of time. The wedge effect of the corrosion products thus produced makes it possible to effectively inhibit the propagation of a crack even at the tip of the crack, which was previously difficult to achieve. Discoloration due to corrosion products It is possible to easily detect cracks visually. Furthermore, because it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance.

[0065] Furthermore, the fatigue crack propagation inhibition / detection sheet of the present invention can ensure the amount of oxygen supplied into the fatigue crack, making it easier to produce corrosion products.

[0066] Furthermore, when the water-containing material is made of a water-containing gel that holds water, the water-containing material becomes easier to handle and at the same time, the fluidity of the water contained in the water-containing material becomes smaller, making it easier to expose the water-containing material regardless of the position of the opening.

[0067] Furthermore, when the sheet means has minute air holes through which oxygen can pass, it is possible to ensure a sufficient amount of oxygen to be supplied into the fatigue cracks, making it easier for corrosion products to be produced.

[0068] Furthermore, when the sheet means is impermeable to oxygen, the moisture-containing material can be further prevented from drying out.

[0069] In addition, when a support made of a flexible material is provided between the water-retaining material and the sheet means, the water-retaining material can be stably maintained facing the opening. In addition, since the support has flexibility, it can be applied to a base material having a three-dimensional curved surface.

[0070] The water-retaining material has a plurality of holes penetrating at least from the surface to the bottom surface of the water-retaining material. By doing Since oxygen is smoothly supplied to the cracks through the holes, corrosion products can be easily generated.

[0071] Furthermore, when an oxidizing agent is stored in the oxidizing agent storage means that fits into the holes of the water-containing material, the oxidizing agent can be stably held.

[0072] In addition, when the oxidizer storage means has a shape with a closed top and an opening at the bottom, and is configured to be filled with a gel or liquid oxidizer inside, or to have a certain gap between the gel or solid oxidizer and the lower end surface, the oxidizer can be flowed directly into the fatigue crack, or only the oxidizing gas generated from the oxidizer can be flowed in, thereby producing corrosion products.

[0073] In addition, when the oxidant storage means has the function of adjusting the amount of oxidant or oxidizing gas supplied from the oxidant by the opening area of ​​the opening or a gas-permeable membrane covering the opening, the amount of oxygen supplied into the fatigue crack can be made appropriate.

[0074] In addition, the oxidant storage means penetrates the water-containing material and the support to expose the surface of the sheet means, and the closed upper surface is configured to be openable and closable, so that if oxidant can be replenished from the outside, oxygen can be supplied from the oxidant into the fatigue cracks for a long period of time.

[0075] In addition, when multiple sets of water-bearing material and support material formed in strips are arranged at intervals on a sheet means, oxygen is smoothly supplied into the cracks through the gaps, making it easier to produce corrosion products.

[0076] In addition, when the sheet means is flexible and transparent or translucent, the sheet means is flexible and can tightly cover the moisture-retaining material to prevent drying. In addition, because the sheet means is transparent or translucent, the changes in the appearance of the moisture-retaining material and the support can be observed from the outside of the sheet means.

[0077] Furthermore, when the sheet means is a magnetic sheet having magnetic force and the magnetic sheet also serves as a means for attaching to the magnetic base material, the sheet means can be easily attached and detached, and can be used repeatedly. In addition, the magnetic force (attraction force) acting between the sheet means and the base material always exerts a constant pressing force on the water-containing material sandwiched between them, which further promotes the penetration of moisture into the cracks and makes it easier for corrosion products to be generated.

[0078] In addition, a galvanic cathode having a smaller ionization tendency than the base material and capable of electrically contacting the base material directly or via a conductor is provided between the sheet means and the water-containing material. And picture A corrosion cell can be formed by a galvanic cathode, a base material, and a water-containing material interposed between the galvanic cathode and the base material. Ta By The corrosion cell effect of the galvanic cathode promotes the generation of corrosion products from the base material, and the wedge effect of the corrosion products inhibits crack growth. Discoloration due to corrosion products The crack detection function can be further improved.

[0079] A durable electrode is provided between the sheet means and the water-containing material, and a DC power supply means is provided for passing a DC current between the durable electrode and the base material. Equipped with picture A corrosion cell can be formed by the durable electrode, the base material, and the water-containing material interposed between the durable electrode and the base material. Ta By The corrosion cell effect of the durable electrode and DC power source promotes the generation of corrosion products from the base material, and the wedge effect of the corrosion products inhibits crack growth. Discoloration due to corrosion products The crack detection function can be further improved.

[0080] Furthermore, when an oxidizer covered with a sheet means is further provided, oxygen is smoothly supplied from the oxidizer to the fatigue cracks, making it easier to generate corrosion products.

[0081] Furthermore, when the sheet means has a heating means for heating the fatigue crack, the fatigue crack can be heated to an appropriate temperature, thereby allowing corrosion products to be produced in a shorter period of time. [Brief description of the drawings]

[0082] [Figure 1] Cross-sectional view showing examples of crack morphology in the base material [Diagram 2] 1 is a schematic diagram of a first example of a fatigue crack propagation suppression / detection sheet according to an embodiment of the present invention; [Diagram 3]Schematic diagram of the second example of the fatigue crack propagation suppression / detection sheet [Figure 4] Schematic diagram of the third example of the fatigue crack propagation suppression / detection sheet [Diagram 5] Schematic diagram of the fourth example of the fatigue crack propagation suppression / detection sheet [Figure 6] Schematic diagram of the fifth example of the fatigue crack propagation suppression / detection sheet [Figure 7] Schematic diagram of the sixth example of the fatigue crack propagation suppression / detection sheet [Figure 8] Schematic diagram of the seventh example of the fatigue crack propagation suppression / detection sheet [Figure 9] Schematic diagram of the eighth example of the fatigue crack propagation suppression / detection sheet [Figure 10] Schematic diagram showing the first application form including cracks [Figure 11] Schematic diagram showing the second application form including cracks [Figure 12] Schematic diagram showing the eighth application form including cracks [Figure 13] A diagram showing the test specimen used in the fatigue crack growth test. [Figure 14] Photograph showing the appearance of the fatigue crack propagation suppression / detection sheet in Example 2 of the fatigue crack propagation test [Figure 15] FIG. 1 shows crack growth curves as a result of fatigue crack growth tests for each comparative example and example. [Figure 16] Enlarged photograph of the fracture surface of Comparative Example 1 where a fatigue crack growth test was conducted [Figure 17] Enlarged photograph of the fracture surface of Example 1 where a fatigue crack growth test was conducted [Figure 18] Enlarged photograph of the fracture surface of Example 6 where a fatigue crack growth test was carried out [Figure 19] Photographs showing changes in fatigue fracture surfaces caused by oxidizing agents and rust converters in verification tests [Figure 20] Photograph showing the results of detecting cracks using the fatigue crack propagation suppression / detection sheet in Example 2, in which a fatigue crack propagation test was performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0083] Hereinafter, a fatigue crack propagation inhibiting / detecting method and a fatigue crack propagation inhibiting / detecting sheet according to an embodiment of the present invention will be described.

[0084] FIG. 1 is a cross-sectional view showing an example of the form of a crack occurring in a base material. The fatigue crack 3 shown in Fig. 1(a) is a through crack that penetrates from one surface (front side) to the other surface (back side) of the metallic base material 2. Therefore, the openings of the fatigue crack 3 are formed on both sides, an opening 3a on the front side and an opening 3b on the back side. The fatigue crack 3 shown in Fig. 1(b) is a non-penetrating crack that occurs on one surface (front side) of the metallic base material 2 and does not reach the other surface (back side). Therefore, the opening of the fatigue crack 3 is only an opening 3a formed on the front side.

[0085] FIG. 2 is a schematic diagram of a first example of a fatigue crack propagation suppression / detection sheet according to this embodiment, where FIG. 2(a) is a plan view and FIG. 2(b) is a cross-sectional view taken along the line A-A'. The first example of a fatigue crack progression inhibition / detection sheet 1 (1A) comprises a water-containing material 10 that holds water, a sheet means 20 that prevents the water held in the water-containing material 10 from drying out, a support 30 that supports the water-containing material 10, and an attachment means 40 that exposes the water-containing material 10 to the openings 3a, 3b of the fatigue crack 3 via the sheet means 20. The fatigue crack propagation inhibition / detection sheet 1 has a configuration in which a water-containing material 10 having a high water content is supported by a flexible support 30 and a sheet means 20 covers the upper surface side of the support 30. The attachment means 40 has adhesive force and is provided on a bottom surface 20a of the sheet means 20. When applying the fatigue crack propagation inhibition / detection sheet 1 to a base material 2, the fatigue crack propagation inhibition / detection sheet 1 is attached to the surface of the base material 2 or to the surface of the coating film formed on the surface of the base material 2 so that the bottom surface 10a of the moisture-containing material 10 covers the openings 3a, 3b of fatigue cracks that occur in the base material 2.

[0086] The water-containing material 10 is used to create a localized moist state within the fatigue crack 3. The water-containing material 10 in the first example of the fatigue crack propagation inhibition / detection sheet 1A does not have any ventilation holes. It is preferable that the water-containing material 10 has a high water content (50% or more), is flexible enough to fit snugly onto the surface of the base material 2 to which it is applied, and has moderate adhesiveness. Moreover, the water-containing material 10 is preferably made of a water-containing gel that holds water. This makes it easy to handle the water-containing material 10 and reduces the fluidity of the water held in the water-containing material 10, so that the fatigue crack propagation suppression / detection sheet 1 can be attached regardless of the positions of the openings 3a, 3b, for example, by having the water-containing material 10 face the side of the openings 3a, 3b generated on a vertical surface, or by having the water-containing material 10 face the openings 3a, 3b extending horizontally from below. Furthermore, by making the water-containing material 10 a water-containing gel, it becomes easier to provide flexibility and appropriate adhesiveness.

[0087] The support 30 supports the water-containing material 10. This makes it possible to stably maintain the state in which the water-containing material 10 faces the openings 3a, 3b. The support 30 is preferably made of a material that is three-dimensionally flexible and has appropriate flexibility so that it can fit without gaps on the surface of a metal base material 2 (including welds) that has a three-dimensional curved surface or on the surface of a coating film formed on the surface of the base material 2, and it is even more preferable that the support 30 has appropriate strength to prevent tearing during application.

[0088] After the fatigue crack propagation inhibition / detection sheet 1 is applied to the openings 3a and / or 3b, the moisture-containing material 10 gradually dries over time, so it is preferable to replace (re-apply) the fatigue crack propagation inhibition / detection sheet 1 according to the degree of dryness. This makes it possible to maintain a moist corrosive environment inside the crack and facilitate the generation of corrosion products. The frequency of replacement required varies greatly depending on the type and application of the fatigue crack propagation suppression / detection sheet 1, but can be adjusted to some extent by appropriately selecting the thickness of the water-containing material 10. Furthermore, since the volume of the crack when it opens is approximately proportional to the plate thickness of the base material 2, it is desirable to increase or decrease the thickness of the water-bearing material 10 proportionally according to the plate thickness of the base material 2. By changing the thickness of the water-bearing material 10 according to the plate thickness of the base material 2, corrosion products can be effectively generated.

[0089] The liquid contained in the water-containing material 10 does not necessarily have to be pure water. In addition to ordinary water, water in which inorganic salts such as NaCl are dissolved, liquids containing electrolytes that cause corrosion similar to water, and the like can also be used. Examples of liquids that further promote the wedge effect include the following. (1) Liquids that promote corrosion (rust formation) include aqueous solutions of sodium chloride (table salt) (concentration: approximately 1-3%) and aqueous solutions of inorganic halogen compounds. (2) Liquids that produce solid precipitates on the crack surfaces include aqueous solutions of inorganic salts such as magnesium chloride, magnesium sulfate, calcium sulfate, potassium chloride, etc. (3) Artificial seawater, etc., made by combining the above-mentioned sodium chloride solution with inorganic salts, etc.

[0090] A cooling gel sheet for fatigue recovery that is commercially available has a structure in which a water-containing gel with a high water content is supported by a flexible woven support, and may be used as is as the water-containing material 10 and support 30. However, as described above, it is preferable to set the thickness of the water-containing material (water-containing gel) 10 appropriately depending on the frequency of replacing the fatigue crack progression inhibition / detection sheet 1, which is determined by the breathability and the usage environmental conditions (especially humidity). Examples of cooling gel sheets for fatigue recovery that are commercially available include Lion Corporation's "Ashi Refreshing Sheet Kyusoku Jikan (registered trademark)" and "Hiepita (registered trademark) 8-hour cooling." These products use the company's highly water-containing gel PAC-55, which is made by forming polymers into a mesh (sponge-like) shape and trapping moisture inside, and the moisture content is 85% according to the manufacturer's indication.

[0091] The sheet means 20 is provided on the surface of the support 30 opposite to the surface that contacts the water-containing material 10. The sheet means 20 serves as a drying prevention layer that prevents the water-containing material 10 from drying out in a short time due to moisture diffusing to the outside. The sheet means 20 can be made breathable, but the sheet means 20 in the first example of the fatigue crack progression suppression / detection sheet 1A does not have breathability. This makes it difficult for the water-containing material 10 to dry out. However, if ventilation with the outside air is completely blocked, oxygen in the crack will be deficient and corrosion products (rust) will be difficult to generate, so when the first example of the fatigue crack progression suppression / detection sheet 1A is applied to the fatigue crack 3, it is necessary to ensure a certain level of breathability by some means. Moreover, in order to enhance adhesion to the water-containing material 10 and the support 30, the sheet means 20 preferably has flexibility. In addition, the sheet means 20 is preferably transparent or semi-transparent, which makes it possible to observe changes in the appearance of the water-containing material 10 and the support 30 (such as the penetration of rust fluid) from the outside of the sheet means 20. The transparent or semi-transparent material for the sheet means 20 may be polyurethane, polyethylene, polypropylene, polyester, vinyl, polyamide, or the like.

[0092] When the base material 2 is magnetic, the sheet means 20 may be a magnetic sheet that has magnetic force and can flexibly change shape. In this case, the magnetic sheet can also serve as the attachment means 40 to the base material 2. When the sheet means (magnetic sheet) 20 is attached to the base material 2 by magnetic force rather than adhesive force, it is easy to attach and detach, and can be used repeatedly. Moreover, by temporarily peeling off the magnet sheet 20, the state of the water-containing material 10 and the support 30 disposed inside the magnet sheet 20 can be easily grasped. In addition, due to the magnetic force (attraction force) acting between the magnetic sheet 20 and the base material 2, a constant pressing force is always applied to the water-containing material 10 sandwiched between them, which further promotes the penetration of moisture into the cracks and makes it easier for corrosion products to be produced. In addition, since the magnet sheet 20 has an appropriate bending rigidity, the moisture-containing material 10 and the support 30 are not completely sealed, and some gaps are formed at the ends of the magnet sheet 20. This ensures a certain level of breathability without blocking air. The gaps at the ends can be ensured while controlling breathability by providing irregularities or grooves on the contact surface of the magnet sheet 20 that contacts the base material 2. Furthermore, if the base material 2 is a conductor, the crack surface will vibrate finely in the magnetic field created by the magnetic sheet 20, which may generate a weak current locally and promote corrosion within the crack. Furthermore, since the magnet sheet 20 can be used repeatedly as described above, when the fatigue crack progression suppression / detection sheet 1 becomes dried out, it is possible to replace only the moisture-containing material 10 and the support 30. The magnet sheet 20 may be integrated with the water-containing material 10 and the support 30 in advance, or may be placed over the water-containing material 10 and the support 30 after they have been attached to the openings 3a, 3b.

[0093] 3A and 3B are schematic diagrams of a second example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 3A is a plan view and Fig. 3B is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used to designate components having the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and their explanation will be omitted. The second example of the fatigue crack propagation suppression / detection sheet 1 ( 1 B) includes a water-containing material 10 , sheet means 20 , a support 30 , attachment means 40 , a galvanic cathode 50 , and a conductive wire 60 . The layer of the galvanic cathode 50 is provided between the water-containing material 10 and the support 30. When the support 30 is not provided, the layer of the galvanic cathode 50 is provided between the water-containing material 10 and the sheet means 20. One end of the conductor 60 is connected to an end of the galvanic cathode 50. The other end of the conductor 60 is connected to the metallic base material 2. The galvanic cathode 50 is made of a film of a metal that has a smaller ionization tendency (is more electrically noble) than the metallic base material 2 (for example, if the base material 2 is steel, the galvanic cathode 50 is made of copper), or a hydrous gel containing a high concentration of powder of the same metal. As a result, the base material 2, the water-containing material 10, the galvanic cathode 50, and the conductive wire 60 collectively form a corrosion cell, which promotes the corrosion reaction within the fatigue crack 3 that has occurred in the base material 2, thereby further enhancing the wedge effect of the corrosion products to inhibit crack progression. Alternatively, instead of using the conductive wire 60, the layer of the galvanic cathode 50 may be extended to the surface of the metallic base material 2 and brought into contact with it.

[0094] 4A and 4B are schematic diagrams of a third example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 4A is a plan view and Fig. 4B is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used to designate components having the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and their explanation will be omitted. The third example of the fatigue crack propagation inhibition / detection sheet 1 ( 1 C) includes a water-containing material 10 , sheet means 20 , a support 30 , attachment means 40 , a conductive wire 60 , a durable electrode 70 , and a DC power supply means 80 . The layer of durable electrode 70 is provided between the water-retaining material 10 and the support 30. When the support 30 is not present, the layer of durable electrode 70 is provided between the water-retaining material 10 and the sheet means 20. One end of the conductor 60 is connected to an end of the durable electrode 70. The other end of the conductor 60 is connected to the metallic base material 2. DC power supply means 80 for passing a direct current is provided between one end and the other end of the conductor 60. In this case, the anode of the DC power supply means 80 is arranged on the base material 2 side. The durable electrode 70 is made of a film of a highly corrosion-resistant metal that is resistant to corrosion, or a hydrous gel containing a high concentration of powder of the same metal. As a result, the base material 2, water-containing material 10, conducting wire 60, durable electrode 70, and DC power supply means 80 collectively form a corrosion cell, which promotes the corrosion reaction within the fatigue crack 3 that has occurred in the base material 2, thereby further enhancing the wedge effect of the corrosion products to inhibit crack progression.

[0095] Fig. 5 is a schematic diagram of a fourth example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 5(a) is a plan view, Fig. 5(b) is an A-A' cross-sectional view, and Fig. 5(c) is a B-B' cross-sectional view. Note that the same reference numerals are used to designate components with the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and descriptions thereof will be omitted. The fourth example of the fatigue crack propagation suppression / detection sheet 1 ( 1 D) includes a water-containing material 10 , sheet means 20 , a support 30 , and attachment means 40 . The fatigue crack propagation inhibition / detection sheet 1A of the first example does not have any ventilation holes in the water-containing material 10 and the support 30, whereas the fatigue crack propagation inhibition / detection sheet 1D of the fourth example has a plurality of holes 11 as ventilation holes penetrating the water-containing material 10 and the support 30. Since ventilation is performed through the holes 11 and oxygen is smoothly supplied to the cracks, it is possible to easily generate corrosion products. Since the provision of the holes 11 makes the water-containing material 10 easier to dry, it is preferable to prevent the water-containing material 10 from drying excessively by providing a resin film that does not allow water or water vapor to pass through on the side surface 10b of the water-containing material 10 along the holes 11. The sheet means 20 in the fourth example of the fatigue crack propagation suppression / detection sheet 1D has minute air holes (not shown) through which oxygen can pass. Since the sheet means 20 has air permeability and oxygen is supplied through the sheet means 20, the amount of oxygen supplied to the fatigue crack 3 can be secured, making it easier to produce corrosion products. In particular, it is preferable to use a flexible film for the sheet means 20 that has a large number of minute air holes that allow gaseous oxygen molecules and water vapor to pass through but not liquid water molecules. An example of such a film is the medical hygiene film "Yuhada (registered trademark) Permiroll (registered trademark) HS" manufactured by Nitoms Corporation.

[0096] When applying the fourth example of the fatigue crack propagation inhibition / detection sheet 1D, the fourth example of the fatigue crack propagation inhibition / detection sheet 1D is attached to the surface of the base material 2 or to the surface of the coating formed on the surface of the base material 2 so that the bottom surface 10a of the moisture-containing material 10 covers the openings 3a, 3b of the fatigue crack 3 that occurs in the base material 2 and so that the predicted crack propagation path line (line A-A' in Figure 5(a)) roughly follows the openings 3a, 3b of the fatigue crack 3 that occurs in the base material 2. In addition, since an actual fatigue crack 3 often propagates in a manner that deviates from the originally predicted path, it is preferable that the shape of the hole 11 be a slit shape having an appropriate width in the direction perpendicular to line A-A' (the predicted crack propagation path line) so that even if the crack propagates in a manner that deviates from the originally predicted path, the position of the crack openings 3a, 3b falls within the range of the hole 11 and oxygen is supplied to the crack smoothly. In addition, it is preferable to set the interval between the holes 11 in the fatigue crack propagation suppression / detection sheet 1D of the fourth example according to the length and propagation speed of the crack. In general, it is preferable to proportionally widen or narrow the interval between the holes 11 according to the length and propagation speed of the crack, such that the interval between the holes 11 is small when the crack is short and the propagation speed is small, and the interval between the holes 11 is large when the crack is long and the propagation speed is large. By changing the interval between the holes 11 according to the state of the crack, oxygen can be effectively supplied into the crack to generate corrosion products in a shorter period of time.

[0097] Fig. 6 is a schematic diagram of a fifth example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 6(a) is a plan view and Fig. 6(b) is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used to designate components having the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and their explanation will be omitted. The fatigue crack propagation suppression / detection sheet 1 of the fifth example comprises a water-containing material 10, sheet means 20, a support 30, and attachment means 40. The fifth example of the fatigue crack propagation inhibition / detection sheet 1 (1E) is formed by arranging, at intervals, a plurality of sets of water-containing materials 10 and supports 30, each of which does not have rectangular holes 11, on a sheet means 20. The gaps 12 between the sets function as the holes 11 in the fourth example of the fatigue crack propagation inhibition / detection sheet 1D. Oxygen is smoothly supplied into the cracks through the gaps 12, making it easier to produce corrosion products. In addition, since the provision of the gaps 12 makes the strip-shaped water-containing material 10 easier to dry, it is preferable to prevent excessive drying of the water-containing material 10 by, for example, providing a resin film that does not allow water or water vapor to pass through on the side 10b of the water-containing material 10 along the gaps 12.

[0098] 7A and 7B are schematic diagrams of a sixth example of the fatigue crack propagation suppression / detection sheet according to the present embodiment, in which Fig. 7A is a plan view and Fig. 7B is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used to designate components having the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and their explanation will be omitted. The sixth example of the fatigue crack propagation inhibition / detection sheet 1 (1F) includes a moisture-containing material 10, a sheet means 20, a support 30, an attachment means 40, and a heating means 110 for heating the fatigue crack 3. The heating means 110 is disposed in the sheet means 20. The heating means 110 has a heating wire 111 such as a nichrome wire, a variable voltage power source 112, and a switch 113. The heating wire 111 is folded back multiple times so as to be evenly distributed within the sheet means 20. The power source 112 and the switch 113 are disposed outside the sheet means 20. When applying the fatigue crack propagation suppression / detection sheet 1 in a cold environment (approximately less than 10°C) where the base material 2 is installed, such as in winter or in cold regions, where the location where the fatigue crack 3 occurs is low temperature and the corrosion reaction is significantly suppressed, the fatigue crack 3 can be heated to an appropriate temperature (approximately 10°C or higher, more preferably 20°C to 40°C) by the heating means 110 provided on the sheet means 20 as in this example, so that the corrosion product can be generated in a shorter period of time. Although not shown, instead of the configuration shown in Fig. 7, the sheet means 20 can be covered from the outside with a sheet-like heating means 110 such as a rubber heater. The upper limit of the heating temperature can be determined taking into consideration the heat resistance of the heating means 110, power consumption, the effect of temperature on the surroundings, and the like.

[0099] Since the fatigue crack progress suppression / detection sheet 1F of the sixth embodiment is used in a humid environment, it is preferable that the heating means 110 be made of a material that is highly insulating and completely waterproof. Moreover, in order to bring the inside of the sheet means 20 (particularly in the vicinity of the fatigue crack 3) to a temperature suitable for the corrosion reaction, it is preferable that the output of the heating means 110 can be appropriately adjusted by a variable voltage power supply 112 or the like.

[0100] Fig. 8 is a schematic diagram of a seventh example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 8(a) is a plan view, Fig. 8(b) is an A-A' cross-sectional view, and Fig. 8(c) is a B-B' cross-sectional view. Note that the same reference numerals are used to designate components with the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and descriptions thereof will be omitted. The seventh example of the fatigue crack propagation inhibition / detection sheet 1 (1G) includes a moisture-containing material 10, sheet means 20, a support 30, an attachment means 40, and an oxidizing agent 120 covered with the sheet means 20. An oxidizing gas such as oxygen is smoothly supplied into the fatigue crack 3 from the oxidizing agent 120 provided to cover the fatigue crack 3, which makes it easier to generate corrosion products. Note that examples of the oxidizing gas supplied from the oxidizing agent 120 include ozone and nitrogen monoxide, in addition to oxygen. The water-containing material 10, such as a water-containing gel formed in close contact with the support 30, has a plurality of holes 11 penetrating at least from the surface to the bottom surface of the water-containing material 10. An oxidizing agent storage means 130 is formed in each hole 11 so as to fit snugly into the hole. The upper part of the oxidizing agent storage means 130 is closed by an upper surface 130b, and the upper surface 130b is bonded to the support 30. Meanwhile, the lower part of the oxidizing agent storage means 130 forms an oxidizing agent storage means opening 130a that opens downward. The inside of the oxidizing agent storage means 130 is filled with a gel-like oxidizing agent 120. Oxidizing gas such as oxygen is smoothly supplied from the oxidizing agent 120 to the cracks, which makes it easier to generate corrosion products. In addition, since the oxidizing agent 120 is stored in the oxidizing agent storage means 130 that is fitted into the hole 11 of the water-containing material 10, the oxidizing agent 120 can be stably held.

[0101] In addition, the amount of oxidant 120 or oxidizing gas supplied to the inside of the crack within a certain period of time can be adjusted by appropriately adjusting the opening area of ​​the oxidizing agent storage means opening 130a, for example, by providing a lower cover with a hole, or by covering the oxidizing agent storage means opening 130a with a gas-permeable membrane or the like. In this way, the oxidizing agent storage means 130 has the function of adjusting the amount of oxidizing agent 120 or oxidizing gas supplied from the oxidizing agent 120, so that the amount of oxygen supplied to the fatigue crack can be made appropriate. Generally, since the oxidizing agent 120 that promotes the generation of metal corrosion products (rust) is highly reactive and easily vaporized, it is desirable to use a resin such as polyethylene or polypropylene, which has high chemical stability and airtightness, for the oxidizing agent storage means 130.

[0102] When applying the seventh example of the fatigue crack propagation inhibition / detection sheet 1G, after filling the oxidant storage means 130 with the oxidant 120, the seventh example of the fatigue crack propagation inhibition / detection sheet 1G is attached to the surface of the base material 2 or the coating film formed on the surface of the base material 2 so that the bottom surface 10a of the water-containing material 10 covers the openings 3a, 3b of the fatigue crack 3 occurring in the base material 2, or the expected crack propagation path, and so that the expected crack propagation path line (line A-A' in Figure 8(a)) roughly follows the openings 3a, 3b of the fatigue crack 3 occurring in the base material 2. At this time, the oxidant storage means opening 130a of the oxidant storage means 130 is in close contact with the base material 2 or the surface of the coating film formed on the surface of the base material 2, and the oxidant 120 is sealed inside the closed space formed by the oxidant storage means 130 and the base material 2 or the surface of the coating film formed on the surface of the base material 2, so that the oxidant 120 can maintain a stable state without undergoing chemical changes until the fatigue crack 3 propagates and passes directly below the oxidant storage means opening 130a. The fatigue crack 3 often grows in a direction that deviates from the initial predicted growth path. Even if the fatigue crack 3 grows in a direction that deviates from the predicted growth path, the positions of the openings 3a and 3b are within the range of the oxidizer storage means 130, and the oxidizer 120 or the oxidizing gas generated therefrom is preferably shaped like a slit having an appropriate width in the direction perpendicular to the predicted growth path line (line A-A' in FIG. 8(a)) so that the supply of the oxidizer 120 or the oxidizing gas generated therefrom into the fatigue crack 3 can be performed smoothly.

[0103] There are two possible methods for filling the oxidant 120 into the oxidant storage means 130: 1) filling the oxidant 120 in gel or fluid form up to the oxidant storage means opening 130a so that the oxidant 120 flows directly into the fatigue crack 3, and 2) providing a certain gap between the oxidant storage means opening 130a and the lower end surface of the gel or solid oxidant 120 so that only the oxidizing gas generated from the oxidant 120 flows into the fatigue crack 3. It is preferable to appropriately select which method to use, taking into consideration the type of structure to which it is applied, the operating environment, the shape of the target crack, the period for which the fatigue crack progression suppression / detection sheet 1G is used, etc. In this way, the oxidant storage means 130 has a shape with a closed upper surface 130b and an opening (oxidant storage means opening 130a) at the bottom, and is configured to be filled with gel-like or liquid oxidant 120 inside, or to have a certain gap between the gel-like or solid oxidant 120 and the lower end surface, so that an oxidizing gas such as oxygen can be supplied into the fatigue cracks to produce corrosion products. Incidentally, if the inside of the fatigue crack 3 is sufficiently moistened due to environmental factors such as rainwater or the action of another fatigue crack propagation inhibition / detection sheet 1 affixed to the back side of the base plate 2, the fatigue crack propagation inhibition / detection sheet 1G of the seventh example does not necessarily need to include the moisture-retaining material 10. Therefore, the fatigue crack propagation inhibition / detection sheet 1G of the seventh example can be made into an "oxidizer supply sheet" with limited functions that does not have the function of creating a localized moistened state inside the fatigue crack 3, by replacing the moisture-retaining material 10 with another soft molding material.

[0104] Fig. 9 is a schematic diagram of an eighth example of the fatigue crack propagation suppression / detection sheet according to this embodiment, in which Fig. 9(a) is a plan view, Fig. 9(b) is an A-A' cross-sectional view, and Fig. 9(c) is a B-B' cross-sectional view. Note that the same reference numerals are used to designate components with the same functions as those in the fatigue crack propagation suppression / detection sheet described above, and descriptions thereof will be omitted. The eighth example of the fatigue crack progression inhibition / detection sheet 1 (1H) is similar to the seventh example of the fatigue crack progression inhibition / detection sheet 1G in that it comprises a moisture-containing material 10, a sheet means 20, a support 30, an attachment means 40, and an oxidizer 120, but differs from the seventh example of the fatigue crack progression inhibition / detection sheet 1G in that the hole portion 11 forming the oxidizer storage means 130 penetrates not only the moisture-containing material 10 but also the support 30. A plurality of holes 11 are formed penetrating the water-containing material 10 and the support 30, and an oxidizing agent storage means 130 is formed so as to fit snugly into each hole 11. In this example, the top of the oxidizing agent storage means 130 is closed by the upper surface 130b, but a removable upper lid or the like may be formed on the upper surface 130b so that the oxidizing agent 120 can be appropriately injected from there. The oxidizing agent storage means 130 penetrates the water-containing material 10 and the support 30 to face the surface of the sheet means 20, and the closed upper surface 130b is configured to be openable and closable so that the oxidizing agent 120 can be replenished from the outside, thereby making it possible to supply oxidizing gas into the fatigue cracks for a long period of time.

[0105] Although not shown in the figures, the fatigue crack propagation inhibition / detection sheet 1 can also be configured to have both a hole portion 11 as an air hole, as in the fatigue crack propagation inhibition / detection sheet 1D of the fourth example, and a hole portion 11 in which an oxidizing agent storage means 130 is fitted, as in the fatigue crack propagation inhibition / detection sheet 1H of the eighth example. In this case, for example, two consecutive holes 11 as air vents are located next to one hole 11 fitted with oxidizer storage means 130, and next to that another two consecutive holes 11 as air vents are located, so that the holes 11 as air vents (vacant holes) and the holes 11 filled with oxidizer 120 can be arranged in a regular or irregular manner.

[0106] Next, examples of application of the fatigue crack propagation suppression / detection sheet 1 to the base material 2 will be described. The metallic base material 2 to which the fatigue crack propagation inhibition / detection is applied is a structural metal such as iron or steel where fatigue cracks 3 are a problem and which is prone to the formation of corrosion products (rust) in a wet environment. The main structural parts to which the method is applied include stress concentration parts such as notches and welds (places where fatigue cracks 3 are expected to occur).

[0107] Table 1 below summarizes eight possible application modes of fatigue crack propagation inhibition / detection, depending on the type of fatigue crack3 in question. [Table 1]

[0108] First, when the crack is a through crack penetrating the base material 2, the opening 3b of the crack on the back side can be either a fatigue crack progression inhibition / detection sheet 1 in which the water-containing material 10 and the support 30 are not provided with holes 11 or gaps 12 (hereinafter, sometimes referred to as "fatigue crack progression inhibition / detection sheet 1 without oxygen supply"), or a fatigue crack progression inhibition / detection sheet 1 in which the sheet means 20 is breathable and the water-containing material 10 and the support 30 are provided with holes 11 or gaps 12 (hereinafter, sometimes referred to as "fatigue crack progression inhibition / detection sheet 1 with oxygen supply"). Note that the holes 11 may be used as vent holes as described above, or may be fitted with oxidizing agent storage means 130. In the first application form, the fatigue crack propagation suppression / detection sheet 1 without oxygen supply is attached to the rear opening 3b, and the front crack opening 3a is left open with nothing attached. In this case, the moisture-containing material 10 facing the rear opening 3b is prevented from drying, while sufficient air (oxygen) is taken into the crack from the front opening 3a, so that corrosion products (rust) are generated on the crack surface, which creates a wedge effect and suppresses crack propagation. In the second application form, the fatigue crack propagation suppression / detection sheet 1 without oxygen supply is attached to the rear opening 3b, and the front opening 3a is partially covered with an anti-drying film. By covering the front opening 3a with an anti-drying film, the amount of water vapor released from the front opening 3a can be reduced to prevent excessive drying of the water-containing material 10, while corrosion products can be generated. In this case, sufficient air (oxygen) is taken into the crack from the front opening 3a, so that corrosion products (rust) are generated on the crack surface, which exerts a wedge effect and suppresses crack propagation. If the anti-drying film has air permeability, the front opening 3a may be entirely covered with the anti-drying film. In the third application form, the fatigue crack propagation suppression / detection sheet 1 with oxygen supply is attached to the opening 3b on the back side, and the opening 3a on the front side is left open with nothing attached. In this case, sufficient air (oxygen) is taken into the crack through the opening 3a on the front side and the fatigue crack propagation suppression / detection sheet 1 with oxygen supply attached to the opening 3b on the back side, so that corrosion products (rust) are produced on the crack surface, which creates a wedge effect and suppresses crack propagation. In the fourth application form, the fatigue crack propagation suppression / detection sheet 1 with oxygen supply is attached to the rear opening 3b, and the front opening 3a is covered with an anti-drying film. In this case, sufficient air (oxygen) is taken into the crack through the fatigue crack propagation suppression / detection sheet 1 with oxygen supply attached to the rear opening 3b, so that corrosion products (rust) are generated on the crack surface, which exerts a wedge effect and suppresses crack propagation. When the front opening 3a is partially covered with an anti-drying film, or completely covered with an air-permeable anti-drying film, air (oxygen) can be taken into the crack from the front opening 3a as well. In the fifth application form, the fatigue crack propagation inhibition / detection sheet 1 with oxygen supply is attached to the rear opening 3b and the front opening 3a. In this case, sufficient air (oxygen) is taken into the crack via the fatigue crack propagation inhibition / detection sheet 1 with oxygen supply attached to the front opening 3a and the rear opening 3b, respectively, so that corrosion products (rust) are generated on the crack surface, creating a wedge effect and inhibiting crack propagation. Also, moisture is supplied from the front side in addition to the rear side, and a wedge effect is generated by the corrosion products evenly within the crack, further inhibiting crack propagation. Discoloration due to corrosion products This makes it even easier to detect cracks. In the sixth application form, the fatigue crack propagation suppression / detection sheet 1 with oxygen supply is attached to the rear opening 3b, and the fatigue crack propagation suppression / detection sheet 1 without oxygen supply is attached to the front opening 3a. In this case, sufficient air (oxygen) is taken into the crack through the fatigue crack propagation suppression / detection sheet 1 with oxygen supply attached to the rear opening 3b, so that corrosion products (rust) are generated on the crack surface, which exhibits a wedge effect, and crack propagation is suppressed. In the seventh application form, the fatigue crack propagation suppression / detection sheet 1 without oxygen supply is attached to the rear opening 3b, and a gel or liquid oxidizing agent 120 is applied to the front opening 3a. In this case, while preventing the moisture-containing material 10 facing the rear opening 3b from drying, oxidizing gas such as oxygen is taken into the crack from the front opening 3a, so that corrosion products (rust) are generated on the crack surface, which exhibits a wedge effect, and crack propagation is suppressed. The type of oxidizing agent 120 is arbitrary, but for example, gelled hypochlorite is used. The method and timing of injecting the oxidizing agent 120 are also arbitrary, but if the gelled oxidizing agent 120 is applied to the front opening 3a, it is expected that the oxidizing agent 120 will be automatically transported into the fatigue crack 3 by the pump effect and capillary phenomenon associated with the crack opening and closing. However, since the effect of the oxidizing agent 120 after application often disappears in a relatively short time, it is preferable to repeat the manual application work intermittently as the fatigue crack 3 progresses. This makes it possible to maintain the progress suppression effect from the initial stage of crack progress to the final stage.

[0109] On the other hand, if the crack is a non-penetrating crack that does not penetrate the base material 2, the fatigue crack propagation inhibition / detection sheet 1 without oxygen supply cannot be applied because it cannot supply oxygen into the crack. In contrast, the fatigue crack propagation inhibition / detection sheet 1 with oxygen supply can supply oxygen into the crack through the sheet means 20, support 30, and water-containing material 10, or from the oxidizing agent 120, without taking in oxygen from the crack. Therefore, the eighth application form is a case where there is no opening 3b due to a fatigue crack 3 on the back side and there is an opening 3a only on the front side, in which a fatigue crack propagation inhibition / detection sheet 1 with oxygen supply is attached to the opening 3a on the front side.

[0110] Fig. 10 is a schematic diagram showing the first application form including the crack. Note that, although the actual crack surface is not flat, it is shown as a flat surface in Fig. 10 for simplicity. For a fatigue crack 3 that has occurred in a metal base material 2 and penetrates the plate thickness, the bottom surface 10a of the moisture-containing material 10 of the first example of the fatigue crack propagation suppression / detection sheet 1A is pressed against and adhered to the bottom surface 10a from below so as to cover the rear opening 3b. The sheet means 20 is provided so as to cover the support 30 of the moisture-containing material 10, and the bottom surface 20a is in close contact with the rear surface 2a of the base material 2. In the first example of the fatigue crack propagation inhibition / detection sheet 1A, the sheet means 20 is not breathable and no air holes are provided in the water-containing material 10 or the support 30, but in this case the opening 3a of the crack on the opposite side (front side) is open and sufficient air (oxygen) is taken into the crack from the opening 3a, causing corrosion products (rust) to form on the crack surface, creating a wedge effect and inhibiting crack propagation.

[0111] Fig. 11 is a schematic diagram showing the second application form including the crack. Note that, although the actual crack surface is not flat, it is shown as a flat surface in Fig. 11 for simplicity. 10, the second application form is different in that the front opening 3a is covered with an anti-drying film 90 having a certain degree of breathability, but otherwise is the same. In this case as well, sufficient air (oxygen) is taken into the crack from the opening 3a through the anti-drying film 90, so that corrosion products (rust) are generated on the crack surface, which exerts a wedge effect and suppresses the crack growth.

[0112] Fig. 12 is a schematic diagram showing the eighth application form including a crack. Note that, although an actual crack surface is not flat, it is shown as a flat surface in Fig. 12 for simplicity. For a non-thickness-penetrating fatigue crack 3 occurring in a metal base material 2, the bottom surface 10a of the moisture-containing material 10 of the fatigue crack propagation suppression / detection sheet 1D of the fourth example is pressed against and adhered to the front opening 3a. The sheet means 20 is provided so as to cover the support 30 of the moisture-containing material 10, and the bottom surface 20a is in close contact with the surface of the base material 2. The sheet means 20 having minute air holes does not block air, and sufficient air (oxygen) is taken into the inside of the crack through the holes 11 provided in the moisture-containing material 10 and the support 30, so that corrosion products (rust) are produced on the crack surface, creating a wedge effect and suppressing the progression of the crack.

[0113] The moisture-containing material 10 and the sheet means 20, or the oxidizing agent 120 covered with the sheet means 20, may be provided in advance at a location of the base material 2 where fatigue cracks 3 may occur. By attaching the fatigue crack propagation inhibition / detection sheet 1 to the base material 2 before fatigue cracks 3 occur, it is possible to reliably inhibit the propagation and detect microcracks immediately after they occur.

[0114] Furthermore, when the base material 2 is made of steel or iron and the fatigue crack propagation inhibition / detection sheet 1 with oxygen supply is applied, red rust (Fe2O3) is mainly generated as a corrosion product on the crack surface. When this red rust occurs, it may be preferable to use a rust converter to convert it to black rust. Since red rust is relatively brittle and easily falls off, using a rust converter to convert it to black rust (Fe3O4) makes the rust layer stronger and more stable, and it is possible to prevent subsequent material deterioration due to excessive corrosion reactions. The type of rust converter is not limited, but for example, a mixture of tannic acid and latex is used as the rust converter.

[0115] Next, a fatigue crack propagation test using a notched steel plate specimen that was conducted to verify the effects of the fatigue crack propagation inhibition method and the crack propagation inhibition / detection sheet of the present invention will be described.

[0116] FIG. 13 shows a test piece used in the fatigue crack growth test. The test piece 100 used was a flat test piece made of JIS SM490A steel having a thickness of 5 mm and having a notch of 10 mm in length and 0.3 mm in width machined in the center. The test machine used was an electro-hydraulic servo type fatigue testing machine (manufactured by Shimadzu Corporation, dynamic capacity 10 tonf). In addition, in the laboratory where the test machine was installed, the air conditioner was operated at all times during the test, and the temperature around the test area was kept at room temperature (22℃ to 30℃). The test conditions are as follows. (a) Normal test: Nominal stress range Δσ in an unnotched cross section n = 104 MPa, stress ratio R = 0 (fully pulsating tension side), load frequency f = 5.1 Hz. (b) When beach marks are formed: The maximum stress is kept the same as in (a), but the minimum stress is increased and the stress range is reduced to about 1 / 4 of that in (a), and the load frequency is f = 13 Hz. The timing of beach mark formation was appropriately set while measuring the surface crack length.

[0117] The details of Comparative Examples 1 and 2 and Examples 1 to 6 in which fatigue crack growth tests were carried out are summarized in the following Table 2. The form of the fatigue crack 3 in all cases was a through crack. [Table 2]

[0118] In Comparative Example 1, the test piece 100 (metallic base material 2) was tested as it was without using the fatigue crack propagation inhibition / detection sheet 1. In Comparative Example 2, fatigue crack propagation suppression / detection sheets 1 without oxygen supply were attached to the crack openings 3a and 3b on both the front and back sides of the test piece 100, and a magnetic sheet was used as the sheet means 20. On the other hand, Example 1 embodies the second application form described above, in which the first example of fatigue crack propagation inhibition / detection sheet 1A without oxygen supply is attached to the crack opening 3b on the back side of test piece 100, and the crack opening 3a on the front side is left open, but cellophane tape is attached only to the central cutout as a drying prevention film 90 to prevent excessive drying. Moreover, both of Example 2 and Example 3 embody the fifth application form described above, and the fourth example of the fatigue crack propagation suppression / detection sheet 1D with oxygen supply, in which the moisture-containing material 10 and the support 30 have holes 11, are attached to the crack openings 3a and 3b on both the front and back sides of the test piece 100. In Example 2, a porous film ("Yuhada Permiroll HS", medical hygiene film manufactured by Nitoms Corporation) is used as the sheet means 20. In Example 3, a magnetic sheet having a thickness of 0.9 mm is used as the sheet means 20. FIG. 14 is a photograph showing the appearance (front side, before load application) of the fourth example of the fatigue crack propagation suppression / detection sheet 1D in Example 2. Moreover, in Example 4, the second application form described above is embodied like Example 1, but the drying prevention film 90 (cellophane tape) is not applied to the opening 3a of the crack on the front side to be in an open state. Furthermore, while Examples 1 to 3 use water as the liquid contained in the water-containing material 10, Example 4 alone uses a 3% NaCl aqueous solution instead of water as the liquid contained in the water-containing material 10. Specifically, the water-containing material 10 used in the other Examples (Examples 1 to 3) was once dried and then immersed in a 3% NaCl aqueous solution to impregnate the water-containing material 10 with the 3% NaCl aqueous solution.

[0119] Moreover, both Examples 5 and 6 embody the above-mentioned seventh application form, and the fatigue crack propagation inhibition / detection sheet 1A of the first example without oxygen supply is attached to the crack opening 3b on the back side of the test piece 100. In Examples 5 and 6, a magnetic sheet is used as the sheet means 20, and a gel-like oxidizing agent 120 (Mold removal cleaning agent "Kabitordes Pro (Strong gel type)" manufactured by UYEKI Co., Ltd., ingredients: hypochlorite, potassium hydroxide (1.0%), gelling agent, stabilizing agent, anti-mold agent) is applied to the crack opening 3a on the front side of the test piece 100. In Example 5, the oxidizing agent 120 was applied only once at the start of the test to the vicinity of the predicted crack propagation path, including the notch end of the test piece 100. On the other hand, in Example 6, the oxidizing agent 120 was applied in dots to the notch end at the start of the test, and then when an appropriate number of load repetitions had been reached, the already applied oxidizing agent 120 was wiped off with industrial wiper paper, and new oxidizing agent 120 was applied near the tip of the crack. Thereafter, the process of wiping off the oxidizing agent 120 and applying the oxidizing agent 120 was intermittently repeated at appropriate load repetition intervals until the end of the test.

[0120] Figure 15 is a diagram showing crack growth curves as the results of fatigue crack growth tests for each comparative example and example, with the vertical axis being the one-sided crack length (= the average length of two cracks growing in the plate width direction from both ends of the notch) [mm], and the horizontal axis being the number of cycles (number of repeated load cycles) [times]. In Figure 15, "●" indicates the results of Comparative Example 1, "■" indicates Comparative Example 2, "□" indicates Example 1, "◯" indicates Example 2, "△" indicates Example 3, "□ (filled in gray)" indicates Example 4, "◇" indicates Example 5, and "▽" indicates Example 6, and the dotted lines indicate the fracture life for each. Table 3 below shows the fracture life as a result of the fatigue crack growth test for each of the comparative examples and the examples. The life ratio is based on Comparative Example 1. [Table 3]

[0121] As can be seen from FIG. 15 and Table 3, a slight crack propagation inhibition effect was observed in Comparative Example 2 in which no oxygen was supplied, compared to Comparative Example 1 in which test piece 100 (base material 2) was used as is, but the fracture life ratio was 1.11, and the degree of the effect was minor. On the other hand, in Example 1 embodying the second application form, a significant crack growth suppression effect was observed from the early stage of crack growth, and the fracture life ratio to Comparative Example 1 was 1.63. Here, Fig. 16 is an enlarged photograph of the fracture surface of Comparative Example 1, and Fig. 17 is an enlarged photograph of the fracture surface of Example 1. In both cases, fatigue crack 3 initiated from the notch end on the right side of the photograph, and then propagated toward the left side of the photograph with repeated loading, leading to fracture. In the fracture surface of Comparative Example 1 in FIG. 16, beach marks on elliptical arcs formed at intervals on the fracture surface of the test piece 100 are clearly observed. On the other hand, in the fracture surface of Example 1 in FIG. 17, immediately after the crack occurs, a noticeable wedge (a part that looks whitish with a slight gloss) is formed on the fracture surface from the front and back surfaces of the test piece 100 to the center part of the plate thickness, and the formation of a continuous wedge is observed in a range exceeding a one-sided crack length of 15 mm (three times the plate thickness). Although there are some parts of the test piece 100 where a beach mark pattern is partially unclear, it can be seen that the fracture surface of the test piece 100 has turned blackish due to a corrosion reaction in the crack caused by the effect of the fatigue crack propagation suppression / detection sheet 1. Furthermore, as shown in FIG. 15 and Table 3, in Example 4, in which a 3% NaCl aqueous solution was used as the liquid to be contained in the water-containing material 10, a particularly significant propagation inhibition effect was observed once the one-sided crack length exceeded 4 mm, and the fracture life ratio relative to Comparative Example 1 was 3.77, showing the greatest life extension effect among Examples 1 to 6. In addition, in Examples 2 and 3 which embody the fifth application form, the crack propagation inhibition effect appears from the early stage of crack propagation, as in Example 1, and the fracture life ratios relative to Comparative Example 1 are both about 1.4, which is slightly lower than that of Example 1, but shows a clear life extension effect.

[0122] On the other hand, in Example 5, in which the oxidizing agent 120 was applied only once at the beginning, the effect of the oxidizing agent 120 in suppressing crack growth was slightly greater than that of Examples 2 and 3 in the region of 500,000 cycles or less in the first half of the test, but thereafter the relationship between the two was reversed, and the final fracture life ratio was 1.34. The possible causes of this reversal are that the effect of the oxidizing agent 120 does not last long when applied only once, and that the remaining film of the oxidizing agent 120 actually worsens the breathability, etc. In contrast, in Example 6, in which the application and removal of the oxidizing agent 120 was intermittently repeated, a significant crack propagation inhibition effect was consistently observed from the initial stage to the final stage of crack propagation, and the fracture life ratio relative to Comparative Example 1 was 1.86, indicating a relatively large life extension effect. Here, FIG. 18 is an enlarged photograph of the fracture surface of Example 6. In the case of Example 6, as in Comparative Example 1 (FIG. 16) and Example 1 (FIG. 17), a crack also occurred from the notch end on the right side of the photograph, and then progressed to the left side of the photograph with repeated loading, leading to fracture. The difference between Example 6 (FIG. 18) and Comparative Example 1 (FIG. 16) is clear, and in Example 6, a wedge of noticeable corrosion products was formed on the fracture surface immediately after the crack occurred, and the beach marks could not be distinguished due to the corrosion products in the range of about 15 mm (three times the plate thickness) of the crack length on one side. Furthermore, several beach marks were observed in the area where the crack had progressed, but they were greatly distorted on the front and back of the test piece 100 (top and bottom of the image), and a black rust-like substance was noticeably generated on the fracture surface near the front side (top of the image) where the oxidizing agent 120 was applied, and it can be seen from the shape of the beach marks that the progress of the crack was more significantly suppressed compared to the center of the plate thickness and the back side.

[0123] Figure 19 is a set of photographs showing the changes in fatigue fracture surfaces due to an oxidizing agent and a rust converter. Figure 19(a) shows the fatigue fracture surface of steel, Figure 19(b) shows the fracture surface one day after the oxidizing agent was applied, and Figure 19(c) shows the fracture surface two days after the rust converter was applied. In order to examine the effects of moisture, oxidizing agent 120 and rust converter acting on the fatigue fracture surface of steel, a verification test was conducted using the fatigue fracture surface of a steel flat plate test piece 100A which was thicker than the test piece 100. The test fracture surface used in the test was a fatigue fracture surface of a 10 mm thick flat plate specimen made of JIS SM400B steel (see Figure 19(a)). The crack initiated from the notch end on the right end of the fracture surface, propagated to the left of the image, and then caused ductile fracture at the left end of the fracture surface. The oxidizing agent used in the test was the same gel-type oxidizing agent 120 used in Examples 5 and 6. The rust converter used in the test was a commercially available rust converter ("Sabi Change" manufactured by Nippe Home Products Co., Ltd., ingredients: tannic acid, latex).

[0124] After the oxidizing agent 120 was evenly applied to the test fracture surface, the entire fracture surface was covered with industrial wiper paper soaked in tap water to keep it wet. As shown in Fig. 19(b), red rust was observed all over the fracture surface about one day after the application of the oxidizing agent 120. Next, the oxidizing agent 120 was removed from the test fracture surface with wiper paper, and then the rust converter was applied evenly. As shown in Fig. 19(c), about two days after the rust converter was applied, the entire fracture surface was covered with a black anti-rust coating.

[0125] Figure 20 is a set of photographs showing the results of crack detection using fatigue crack propagation prevention / detection sheet 1 in Example 2, where Figure 20(a) shows the results when the number of load repetitions was N=480,000, Figure 20(b) shows the results when the number of load repetitions was N=576,000, Figure 20(c) shows the results when the number of load repetitions was N=672,000, and Figure 20(d) shows the results when the number of load repetitions was N=798,000. A fatigue crack 3 initiates and propagates from both ends of the notch in the test piece 100, and grows as the number of load cycles N increases. In Example 2, however, corrosion products (rust) are produced within the crack due to the action of the fatigue crack propagation inhibition / detection sheet 1, and the corrosion products are transferred to the surface of the water-containing material 10 that is in close contact with the crack opening 3a, following the shape of the crack opening 3a, and the shape of the crack opening 3a is transferred as a replica. The white lines and length indications shown in each diagram in Fig. 20 indicate the total actual crack length (the length of the notch + the sum of the left and right fatigue crack lengths on the surface of the test piece 100) at each load repetition number N. The total actual crack length is 19.0 mm in Fig. 20(a), 22.5 mm in Fig. 20(b), 27.3 mm in Fig. 20(c), and 51.1 mm in Fig. 20(d). The replica of the crack shape transferred onto the fatigue crack growth inhibition / detection sheet 1 corresponds well to the actual crack shape, and it can be seen that visual crack detection is possible.

[0126] As described above, the fatigue crack propagation inhibition / detection method and propagation inhibition / detection sheet according to the present invention can easily and locally create a wet corrosion environment on-site in a manner that does not significantly dissolve metal ions from the crack surface as occurs in a immersed state, and produces a moderate amount of corrosion products (rust) on the crack surface. The wedge effect of the corrosion products thus produced can effectively inhibit the propagation of a crack even at the tip of the crack, which was previously difficult to achieve. Discoloration due to corrosion products It is possible to easily detect cracks visually. Furthermore, because it is resistant to external pressure and contact, it is possible to improve workability and environmental resistance. [Industrial Applicability]

[0127] The present invention can be applied to various metal structures in which fatigue cracks have occurred or where there is a concern that fatigue cracks may occur, such as ships, marine structures, vehicles, aircraft, bridges, and machine tools. [Explanation of symbols]

[0128] 1. Fatigue crack propagation inhibition / detection sheet 2 Base material 3. Fatigue cracks 3a, 3b Fatigue crack opening 10 Hydrated materials (hydrating gels) 11 Hole 20 Sheet means (magnetic sheet) 30 Support 40 Attachment means 50 Galvanic cathode 60 Conductor 70 durable electrode 80 DC power supply means 90 Anti-drying film 110 Heating means 120 Oxidizer 130 Oxidizer storage means 130a Opening (Oxidizer storage means opening) 130b top surface

Claims

1. A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: providing a water-retaining material that holds water at an opening of the fatigue crack in the metal base material; covering the water-retaining material with a sheet means that prevents the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment using the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent to produce corrosion products of the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products of the base material; and, when the fatigue crack is a through crack that penetrates the base material, providing the water-retaining material and the sheet means or the oxidizing agent covered by the sheet means at an opening on the back side of the through crack; and utilizing the oxygen supplied through an opening on the front side of the through crack and / or from the breathable sheet means or the oxidizing agent.

2. 2. The method for inhibiting and detecting the progress of a fatigue crack according to claim 1, wherein the sheet means has air permeability, and the oxygen is supplied through the sheet means.

3. 2. The method for inhibiting and detecting fatigue crack growth according to claim 1, wherein the oxygen is supplied from the oxidizer provided and covered by the sheet means.

4. 2. The method for inhibiting and detecting the progress of a fatigue crack according to claim 1, wherein the sheet means is not air-permeable and utilizes the oxygen supplied through the openings on the front side.

5. 5. The method for inhibiting and detecting fatigue crack growth according to claim 1, wherein the opening on the front side of the through crack is covered with an anti-drying film.

6. 2. The method for inhibiting and detecting fatigue crack growth according to claim 1, wherein the sheet means is non-permeable, and the oxidizing agent is applied to the opening on the front side.

7. 7. The method for inhibiting and detecting the propagation of a fatigue crack according to claim 6, characterized in that the application of the oxidizing agent to the opening on the front side is intermittently repeated as the fatigue crack propagates.

8. A method for inhibiting / detecting fatigue crack growth as described in claim 1, characterized in that the moisture-containing material and the sheet means or the oxidizing agent covered with the sheet means are provided at the front opening of the through crack.

9. A method for inhibiting / detecting the progression of a fatigue crack as described in any one of claims 1 to 8, characterized in that the moisture-containing material and the sheet means or the oxidizing agent covered with the sheet means are provided in advance at a location of the base material where the fatigue crack is likely to occur.

10. 10. The method for inhibiting / detecting the progression of a fatigue crack according to claim 1, further comprising replacing the water-bearing material when the amount of water in the water-bearing material decreases.

11. 11. The method for inhibiting and detecting the progress of a fatigue crack according to claim 1, wherein a thickness of the water-containing material is changed depending on a plate thickness of the base material.

12. A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: providing a water-retaining material to face an opening of the fatigue crack in the metallic base material; covering the water-retaining material with a sheet means for preventing the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment using the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent to produce corrosion products of the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products of the base material, comprising providing a plurality of holes in the water-retaining material to allow ventilation, and having the holes shaped like slits to face the predicted progression path of the fatigue crack.

13. A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: providing a water-retaining material to face an opening of the fatigue crack in the metallic base material, and covering the water-retaining material with a sheet means for preventing the water from drying out; maintaining the inside of the fatigue crack in a moist corrosive environment using the water in the water-retaining material and oxygen supplied from at least an oxidizing agent to produce corrosion products of the base material, and inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration caused by the corrosion products of the base material, comprising providing a plurality of holes in the water-retaining material to store the oxidizing agent, and having the holes shaped like slits to face the predicted progression path of the fatigue crack.

14. A method for suppressing / detecting the propagation of a fatigue crack as described in claim 12 or claim 13, characterized in that the spacing between the multiple slit-shaped holes is increased or decreased depending on the length and / or crack propagation rate of the fatigue crack.

15. A method for inhibiting / detecting the progression of a fatigue crack according to any one of claims 1 to 14, characterized in that, when the base material is magnetic, the sheet means having magnetic force is attached to the base material.

16. A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: providing a water-retaining material that holds water at an opening of the fatigue crack in the metallic base material; covering the water-retaining material with sheet means that prevents the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment with the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent to produce corrosion products of the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration due to the corrosion products of the base material, the method comprising: forming a corrosion cell with a galvanic cathode that is electrically connected to the base material and has a smaller ionization tendency than the base material, the base material, and the water-retaining material interposed between the galvanic cathode and the base material, and promoting the generation of the corrosion products in the fatigue crack in the base material.

17. A method for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: providing a water-retaining material that holds water at an opening of the fatigue crack in the metallic base material; covering the water-retaining material with a sheet means that prevents the water from drying; maintaining the inside of the fatigue crack in a moist corrosive environment using the water in the water-retaining material and oxygen supplied from the atmosphere or an oxidizing agent to produce corrosion products of the base material; inhibiting the progression of the fatigue crack by the wedge effect of the expanding corrosion products and / or detecting the progression of the fatigue crack by discoloration due to the corrosion products of the base material; passing a direct current between the base material and a durable electrode provided between the sheet means and the water-retaining material; forming a corrosion cell between the durable electrode, the base material, and the water-retaining material interposed between the durable electrode and the base material, and promoting the generation of the corrosion products in the fatigue crack in the base material.

18. A method for inhibiting / detecting the progression of a fatigue crack as described in any one of claims 1 to 17, characterized in that when the base material is steel or iron, and red rust occurs as the corrosion product of the fatigue crack, a rust converter is used to convert it into black rust.

19. A method for suppressing / detecting the progression of a fatigue crack described in any one of claims 1 to 18, characterized in that when the installation environment of the base material is cold, the fatigue crack is heated to an appropriate temperature by a heating means from the outside of the sheet means or by the heating means provided on the sheet means.

20. A fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of a fatigue crack in a base material, comprising: a water-retaining material that holds water to be exposed to an opening of a fatigue crack that has occurred in the metal base material; sheet means that covers the surface of the water-retaining material and prevents the water from drying; and attachment means that exposes the water-retaining material to the opening via the sheet means, wherein the water-retaining material has a plurality of holes that penetrate at least from the surface to the bottom surface of the water-retaining material, and the water in the water-retaining material and oxygen supplied from the atmosphere make it possible to maintain a moist corrosive environment inside the fatigue crack.

21. A fatigue crack propagation inhibition / detection sheet for inhibiting / detecting the propagation of a fatigue crack in a base material, comprising: a water-containing material that holds water to be exposed to an opening of a fatigue crack that has occurred in the metal base material; sheet means that covers the surface of the water-containing material and prevents the water from drying; an oxidizing agent covered by the sheet means; and attachment means that exposes the water-containing material to the opening through the sheet means, wherein the water-containing material has a plurality of holes that penetrate at least from the surface to the bottom surface of the water-containing material, and the water in the water-containing material and oxygen supplied from the oxidizing agent make it possible to maintain a moist corrosive environment inside the fatigue crack.

22. The fatigue crack propagation inhibition / detection sheet according to claim 20 or 21, characterized in that the water-containing material is made of a water-containing gel that holds the water.

23. 23. The fatigue crack propagation suppression / detection sheet according to any one of claims 20 to 22, characterized in that the sheet means has minute air holes through which the oxygen can pass.

24. 23. The fatigue crack propagation inhibition / detection sheet according to any one of claims 20 to 22, characterized in that the sheet means is impermeable to the oxygen.

25. A fatigue crack propagation inhibition / detection sheet according to any one of claims 20 to 24, characterized in that a support made of a flexible material is provided between the moisture-containing material and the sheet means.

26. 22. A fatigue crack propagation inhibition / detection sheet according to claim 21, characterized in that the oxidizing agent is stored in an oxidizing agent storage means fitted into the hole of the water-containing material.

27. The fatigue crack propagation prevention / detection sheet of claim 26, characterized in that the oxidizer storage means has a shape with a closed top and an opening at the bottom, and is configured to be filled with the oxidizer in a gel or liquid form inside, or to have a certain gap between the gel or solid oxidizer and the lower end surface.

28. The fatigue crack propagation suppression / detection sheet described in claim 27, characterized in that the oxidant storage means has the function of adjusting the amount of the oxidant or the oxidizing gas supplied from the oxidant by the opening area of ​​the opening or a gas-permeable membrane covering the opening.

29. A fatigue crack propagation inhibition / detection sheet as described in claim 27 or 28, characterized in that the oxidant storage means penetrates the water-containing material and support to expose the surface of the sheet means, and the closed upper surface is configured to be openable and closable, thereby making it possible to replenish the oxidant from the outside.

30. A fatigue crack propagation inhibition / detection sheet as described in any one of claims 25 to 29, characterized in that the sheet means comprises multiple sets of the moisture-containing material and the support, each formed in a strip shape, arranged at intervals.

31. 31. The fatigue crack propagation suppression / detection sheet according to any one of claims 20 to 30, characterized in that the sheet means is flexible and transparent or translucent.

32. A fatigue crack propagation suppression / detection sheet described in any one of claims 20 to 31, characterized in that the sheet means is a magnetic sheet having magnetic force, and the magnetic sheet also serves as the attachment means for the magnetic base material.

33. A fatigue crack progression inhibition / detection sheet for inhibiting / detecting the progression of a fatigue crack in a base material, comprising: a water-retaining material that is brought into contact with an opening of a fatigue crack that has occurred in the metallic base material; sheet means that covers the surface of the water-retaining material and prevents the water from drying; attachment means that brings the water-retaining material into contact with the opening via the sheet means; and a galvanic cathode that has a lower ionization tendency than the base material and can come into electrical contact directly with the base material or via a conductor, between the sheet means and the water-retaining material, wherein a corrosion cell can be formed by the galvanic cathode, the base material, and the water-retaining material interposed between the galvanic cathode and the base material.

34. A fatigue crack progression inhibition / detection sheet for inhibiting / detecting the progression of a fatigue crack in a base material, comprising a water-retaining material that is brought into contact with an opening of a fatigue crack that has occurred in the metallic base material, sheet means that covers the surface of the water-retaining material and prevents the water from drying, attachment means that brings the water-retaining material into contact with the opening via the sheet means, a durable electrode provided between the sheet means and the water-retaining material, and DC power supply means that passes a DC current between the durable electrode and the base material, characterized in that a corrosion cell can be formed by the durable electrode, the base material, and the water-retaining material interposed between the durable electrode and the base material.

35. A fatigue crack progression inhibition / detection sheet as described in claim 33 or claim 34, characterized in that it further comprises an oxidizer covered by the sheet means.

36. 36. A fatigue crack propagation suppression / detection sheet according to any one of claims 20 to 35, characterized in that the sheet means has heating means for heating the fatigue crack.

Images