Method for suppressing the propagation of fatigue cracks, and sheet for suppressing the propagation of fatigue cracks.

Abstract

To provide a progress suppression method of fatigue crack for effectively suppressing progress of crack, by a wedge effect of electrodeposition deposit, and a progress suppression sheet of the fatigue crack.SOLUTION: A fatigue crack progress suppression sheet 1 comprising a water-containing material 10 containing an electrolytic solution and an electrode material 30 laminated on the outside of the water-containing material 10 is placed to a portion of a metal base material 2 of the structure where the fatigue crack 3 occurred or a portion where it may occur in contact with the water-containing material 10 to form a wet environment; a potential is applied by connecting directly between an electrode material 30 and the metal base material 2 or via conductor wires 50A, 50B to make the metal base material 2 a cathode, and carbon dioxide is supplied to the water-containing material 10 to form an electrochemical circuit including the metal base material 2, the water-containing material 10, and the electrode material 30 to form electrodeposited deposits 4 in the fatigue crack 3 to suppress the progress of the fatigue crack 3 by a wedge effect of the electrodeposited deposit 4.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a method for suppressing the propagation of fatigue cracks occurring in various metal structures such as ships, bridges, vehicles, aircraft, and machine tools, and to a fatigue crack propagation suppression sheet used therefor. [Background technology]

[0002] Various structures such as ships, bridges, vehicles, aircraft, and machine tools are mainly composed of structural members made of metals such as iron and aluminum, or their alloys (steel, aluminum alloys, etc.). When repeated loads are applied to these metal structural members, metal fatigue can cause cracks, especially at stress concentration points. Such fatigue cracks in structures gradually propagate as time passes and the number of load cycles increases. If the crack length exceeds the structural limit, it can lead to serious damage or accidents. Therefore, it is necessary to detect cracks while they are still short and take measures to effectively suppress or stop their propagation. Patent documents 1 to 3 describe methods for suppressing the propagation of fatigue cracks, in which a paste made of fine particles having a hardness greater than or equal to the hardness of the base material and a viscous oil is applied to the surface of a structure, and when a crack occurs in the structure, the paste flows into the crack, and the propagation of the fatigue crack is suppressed by the wedge effect of the fine particles.

[0003] Furthermore, Non-Patent Literature 1 describes that when a fatigue crack propagation test is performed on a Ti-6Al-4V alloy specimen immersed in artificial seawater while a cathode potential is applied, electrodeposits such as calcium carbonate and magnesium hydroxide are deposited on the crack surface, and a crack propagation delay effect is observed due to the wedge effect of these precipitates. It also states that the above-mentioned electrodeposits are deposited in larger quantities at an artificial seawater temperature of 80°C than at 25°C, and that the delay effect is more pronounced. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-28462 [Patent Document 2] Japanese Patent Publication No. 2009-214254 [Patent Document 3] Japanese Patent Publication No. 2015-85509 [Non-patent literature]

[0005] [Non-Patent Document 1] Toshio Niwa, Yoshihisa Tanaka, Kazuhiko Takahashi, and Kenkichi Tamura: Fatigue crack propagation characteristics of Ti-6Al-4V alloy under cathode potential load in seawater - A study on material selection for deep-water risers (Part 1) -, Journal of the Japan Society of Marine Engineering, Vol. 41, No. 2 (2006), pp. 291-296. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the methods described in Patent Documents 1 to 3, the fine particles can only penetrate as far as the crack opening beyond the particle size. In principle, a wedge cannot be formed at the crack tip where the fine particles cannot penetrate, and the crack propagation suppression effect due to the wedge effect does not work at the crack tip. Furthermore, the paste needs to be a viscous fluid with appropriate fluidity, and it may 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 for protecting the paste, but forming a resin protective film requires considerable effort and time, and there is a limit to the external pressure that the protective film can withstand.

[0007] On the other hand, the crack delay phenomenon caused by electrodeposited deposits described in Non-Patent Document 1 can occur when cathodic protection is applied to structures immersed in seawater, but there is no mention of suppressing crack propagation in structures operating in a nearly dry state in the atmosphere. Therefore, the present invention aims to provide a method for suppressing fatigue crack propagation and a fatigue crack propagation suppression sheet, which can effectively suppress crack propagation even at the crack tip, which was previously difficult, by forming an electrochemical circuit containing a sufficiently humid environment on-site that allows electrodeposited deposits to form on the crack surface, and maintaining it therefor for a certain period of time, thereby utilizing the wedge effect of the formed electrodeposited deposits. [Means for solving the problem]

[0008] In the method for suppressing the propagation of fatigue cracks corresponding to claim 1, It contains at least bicarbonate ions and calcium ions. A fatigue crack propagation suppression sheet comprising a water-containing material containing an electrolyte and an electrode material laminated on the outside of the water-containing material is placed in contact with the location where fatigue cracks have occurred or are likely to occur in the metal base material of a structure, thereby creating a humid environment; the electrode material and the metal base material are connected directly or via a wire to apply a potential with the metal base material as the cathode; Cover the moisture-containing material with a drying-preventing material that also applies pressure. This forms an electrochemical circuit including a metal base material, a water-containing material, and an electrode material. When fatigue cracks occur This method is characterized by generating electrodeposited deposits within fatigue cracks, and suppressing the propagation of fatigue cracks through the wedge effect of these deposits. According to the present invention as described in claim 1, a localized humid environment and electrochemical circuit can be easily formed on-site, causing electrodeposited deposits to form within fatigue cracks in a relatively short period of time. Therefore, even at the crack tip, where it was previously difficult to form wedges, the wedge effect of the resulting electrodeposited deposits promotes crack closure and effectively suppresses the propagation of fatigue cracks. Furthermore, even if the metal base material is a metal that is resistant to corrosion, it is possible to generate electrodeposited deposits on the crack surface as wedge material, thus offering excellent versatility. In addition, it is more resistant to external pressure and contact than when using viscous fluids, and offers superior workability and environmental resistance. Furthermore, by covering the moisture-containing material with a drying-preventing material, it is possible to prevent the moisture-containing material from drying out in a short period of time, thereby maintaining a moist state within the fatigue crack for a long period of time.

[0010] Claim 2 The present invention, as described, provides a fatigue crack propagation suppression sheet for water-containing materials. To supply carbon dioxide A key feature is the selection of a model that includes a ventilation channel for introducing air. Claim 2 According to the present invention described in claim, carbon dioxide contained in the air can be smoothly supplied to the water-containing material through the ventilation path, making it easier to generate electrodeposits.

[0011] Claim 3 The present invention described in claim, the fatigue crack growth suppression sheet To supply carbon dioxide to water-containing material has a carbon dioxide agent in which carbon dioxide is enclosed so as to be able to leak to the outside, and is characterized by selecting one in which carbon dioxide is supplied from the carbon dioxide agent to the water-containing material. Claim 3 According to the present invention described in claim, carbon dioxide can be supplied to the water-containing material by the carbon dioxide agent, making it easier to generate electrodeposits.

[0012] Claim 4 The present invention described in claim, the thickness of the water-containing material is set based on at least one of the replacement frequency of the fatigue crack growth suppression sheet and the plate thickness of the metal base material. Claim 4 According to the present invention described in claim, by appropriately setting the thickness of the water-containing material, the necessary replacement frequency can be adjusted. Also, by setting the thickness of the water-containing material according to the plate thickness of the metal base material, electrodeposits can be effectively generated.

[0013] Claim 5 The present invention described in claim, a coating film is formed on a portion of the metal base material where a fatigue crack has occurred or is likely to occur, and a fatigue crack growth suppression sheet is disposed on the surface of the coating film. Claim 5 According to the present invention described in claim, it is possible to prevent the electrolyte in the water-containing material from being electrodeposited and wasted on unnecessary portions such as the surface of the metal base material.

[0014] Claim 6The present invention, as described, is characterized in that, when a fatigue crack penetrates a metal base material from one surface to the other, a fatigue crack propagation suppression sheet is placed at the opening of the fatigue crack on the other surface, and the opening of the fatigue crack on the one surface is made air-adjustable. Claim 6 According to the present invention described above, air taken into the fatigue crack from one side reaches the fatigue crack propagation suppression sheet located on the other side, thereby supplying carbon dioxide contained in the air to the water-containing material. This ensures a sufficient amount of carbon dioxide is supplied to the water-containing material, making it easier to generate electrodeposited precipitates.

[0015] Claim 7 The present invention is characterized by partially covering the opening of a fatigue crack on one surface with a non-permeable membrane material that does not allow for airflow, or by covering the entire opening with a permeable membrane material that does allow for airflow. Claim 7 According to the present invention as described above, the amount of water vapor released from the opening can be reduced, thereby preventing excessive drying of the water-containing material.

[0016] Claim 8 The present invention, as described, is characterized in that, when a fatigue crack penetrates a metal base material from one surface to the other, a fatigue crack propagation suppression sheet, in which a water-containing material is covered with a drying-preventing material, is placed at the opening of the fatigue crack on the other surface, and a carbonic acid agent, in which carbon dioxide is sealed so as to be able to leak to the outside, is placed at the opening of the fatigue crack on the one surface. Claim 8 According to the present invention as described above, it is possible to prevent the water-containing material placed in the opening on the other side from drying out, while supplying carbon dioxide (carbonic acid gas) to the water-containing material from the opening on one side to generate electrodeposited precipitates.

[0017] Claim 9 The present invention, as described, is a case in which a fatigue crack penetrates a metal base material from one surface to the other surface, and ventilation is provided at the opening of the fatigue crack on the other surface. RoadA sheet to suppress the propagation of fatigue cracks is placed, and the entire opening of the fatigue crack on one side is covered with a non-permeable membrane material that does not allow for airflow. Alternatively, a fatigue crack propagation suppression sheet having a ventilation channel is placed at the opening of the fatigue crack on one side and at the opening of the fatigue crack on the other side. It is characterized by the following. Claim 9 According to the present invention as described above, the amount of water vapor released from the opening is reduced, preventing excessive drying of the water-containing material, while allowing for ventilation. Road By supplying carbon dioxide to a water-containing material, electrodeposited deposits can be generated. Alternatively, the electrodeposition reaction within the fatigue crack is promoted from both the one and the other side, and the resulting wedge effect from the electrodeposited precipitates further suppresses the propagation of the fatigue crack.

[0018] Claim 10 The present invention described above applies when a fatigue crack penetrates a metal base material from one surface to the other. On the other side, a fatigue crack propagation suppression sheet containing a carbonic acid agent is placed at the opening of the fatigue crack, and the entire opening of the fatigue crack on one side is covered with a non-permeable membrane material that does not allow for airflow, or The opening of the fatigue crack on one side and the opening of the fatigue crack on the other side charcoal The invention is characterized by the placement of fatigue crack propagation suppression sheets containing an acid agent. Claim 10 According to the present invention described above, By reducing the amount of water vapor released from the opening, excessive drying of the water-containing material can be prevented, while carbon dioxide can be supplied to the water-containing material from the carbonate to generate electrodeposited precipitates. Electrodeposition reactions within fatigue cracks are promoted from both sides, and the resulting wedge effect from the generated electrodeposited deposits further suppresses the propagation of fatigue cracks.

[0019] Claim 11 The present invention is characterized by heating a fatigue crack propagation suppression sheet placed on a metal base material. Claim 11 According to the present invention described above, by heating the fatigue crack propagation suppression sheet, the fatigue crack surface of the metal base material can be warmed, thereby preventing the electrodeposition reaction from being suppressed by low temperatures in winter or cold regions.

[0020] Claim 12The present invention is characterized by suppressing the occurrence of rust in areas of the metal base material where fatigue cracks have occurred or are likely to occur, and in the surrounding areas where fatigue cracks have not occurred or are unlikely to occur, through an electrochemical protective action by an electrochemical circuit formed by the arrangement of fatigue crack propagation suppression sheets. Claim 12 According to the present invention as described above, the area where the fatigue crack propagation suppression sheet is installed, including the area around the fatigue crack, is less prone to rusting due to the cathodic protection effect. Therefore, it is a particularly effective rust prevention method for metals whose base material is susceptible to corrosion.

[0021] Claim 13 In the fatigue crack propagation suppression sheet corresponding to the description, It contains at least bicarbonate ions and calcium ions. The structure comprises a water-containing material containing an electrolyte, an electrode material laminated on the outside of the water-containing material, and a connecting material used to connect the metal base material and the electrode material in order to apply a potential with the metal base material of the structure as the cathode, wherein the water-containing material is attached in contact with the location in the metal base material where fatigue cracks have occurred or are likely to occur. Cover the moisture-containing material with a drying-preventing material that also applies pressure. This forms an electrochemical circuit including a metal base material, a water-containing material, an electrode material, and a connecting material. When fatigue cracks occur This method is characterized by generating electrodeposited deposits within fatigue cracks, and suppressing the propagation of fatigue cracks through the wedge effect of these deposits. Claim 13 According to the present invention described above, a localized humid environment and electrochemical circuit can be easily formed on-site, allowing electrodeposited deposits to be generated within fatigue cracks in a relatively short period of time. Therefore, even at the crack tip, where wedge formation was previously difficult, the wedge effect of the generated electrodeposited deposits promotes crack closure and effectively suppresses the propagation of fatigue cracks. Furthermore, even if the metal base material is a metal that is resistant to corrosion, it is possible to generate electrodeposited deposits on the crack surface as wedge material, thus offering excellent versatility. In addition, it is more resistant to external pressure and contact than when using viscous fluids, and offers superior workability and environmental resistance. Furthermore, because the moisture-containing material is covered with a drying-preventing material, it is possible to prevent the moisture-containing material from drying out in a short period of time, thereby maintaining a moist state within the fatigue crack for a long period of time.

[0022] Claim 14The present invention described herein is characterized in that the moisture content of the water-containing material is 50% or more. Claim 14 According to the present invention described herein, a moist condition within a fatigue crack sufficient to generate electrodeposited deposits can be created in a short period of time.

[0024] Claim 15 The present invention described herein relates to a water-containing material. To supply carbon dioxide It is characterized by having a ventilation channel for introducing air. Claim 15 According to the present invention described above, carbon dioxide contained in the air is supplied smoothly to the water-containing material through the ventilation channel, making it easier to generate electrodeposited deposits.

[0025] Claim 16 The present invention is characterized in that, as a ventilation channel, the drying prevention material is provided with a plurality of microscopic pores that allow gaseous carbon dioxide molecules and water vapor to pass through but not liquid water molecules. Claim 16 According to the present invention described above, it is possible to suppress the drying of the water-containing material while ensuring the amount of carbon dioxide supplied to the water-containing material, thereby facilitating the formation of electrodeposited precipitates.

[0026] Claim 17 The present invention is characterized in that a plurality of through holes are provided in the water-containing material and electrode material in the thickness direction as ventilation passages. Claim 17 According to the present invention described above, air enters the fatigue crack through the through-hole and carbon dioxide is supplied to the water-containing material without interruption, making it easier to generate electrodeposited deposits.

[0027] Claim 18 The present invention described herein is characterized in that the through hole has an elongated shape. Claim 18According to the present invention described above, even if a fatigue crack propagates outside the initially expected path, the location of the opening remains within the range of the through-hole, allowing air to enter the fatigue crack through the through-hole and supplying carbon dioxide to the water-containing material without interruption, thus facilitating the formation of electrodeposited deposits.

[0028] Claim 19 The present invention is characterized in that the water-containing material and the electrode material are each aggregates of a plurality of small pieces, and gaps that serve as ventilation passages are formed by arranging the small pieces apart from each other. Claim 19 According to the present invention described above, air enters the fatigue crack through the gap and carbon dioxide is supplied to the water-containing material without interruption, making it easier to generate electrodeposited deposits.

[0029] Claim 20 The present invention is characterized in that the sides of the water-containing material are provided with side drying prevention materials to suppress the leakage of water and water vapor from the water-containing material to the outside. Claim 20 According to the present invention as described above, the presence of through holes or gaps makes the water-containing material prone to drying, but by providing a side drying prevention material, the diffusion of moisture from the sides can be suppressed, thereby preventing excessive drying of the water-containing material.

[0030] Claim 21 The present invention described herein is To supply carbon dioxide to water-containing material The invention is characterized by comprising a carbonic acid agent sealed in such a way that carbon dioxide can leak out to the outside, and a carbonic acid agent container having an opening that houses the carbonic acid agent. Claim 21 According to the present invention described above, carbon dioxide is supplied smoothly from the carbonate to the water-containing material, making it easier to generate electrodeposited precipitates.

[0031] Claim 22 The present invention is characterized in that a water-containing material is provided with a plurality of elongated through-holes that penetrate in the thickness direction, and a carbonate is contained in a carbonate container arranged in the through-holes. Claim22 According to the present invention described above, it is possible to introduce a carbonate agent into the fatigue crack, or to introduce only the carbon dioxide generated from the carbonate agent into the fatigue crack, thereby facilitating the formation of electrodeposited precipitates. Furthermore, because the through-hole is elongated, even if the fatigue crack propagates deviating from the initially expected path, the position of the opening can be kept within the arrangement range of the carbonate agent container.

[0032] Claim 23 The present invention is characterized in that the water-containing material and the electrode material are each aggregates of a plurality of small pieces, gaps are formed by arranging the small pieces apart, and the carbonate is contained in a carbonate container arranged in the gaps. Claim 23 According to the present invention as described above, it is possible to introduce a carbonate agent into the fatigue crack, or to introduce only the carbon dioxide generated from the carbonate agent into the fatigue crack, thereby facilitating the formation of electrodeposited deposits.

[0033] Claim 24 The present invention is characterized in that the carbonate agent contains an electrolyte. Claim 24 According to the present invention described herein, it is possible to further facilitate the formation of electrodeposits.

[0034] Claim 25 The present invention is characterized in that the opening of the carbonate container is provided with an opening area variable material for adjusting the opening area, or a gas permeable membrane material that covers the entire opening. Claim 25 According to the present invention described herein, the amount of carbon dioxide supplied from the carbonate to the water-containing material within a certain period can be made appropriate.

[0035] Claim 26 The present invention is characterized in that the drying prevention material is a magnetic sheet having magnetic force and flexibility, and when the magnetic sheet is attached to the metal base material by magnetic force, a gap that serves as a ventilation passage is created between the magnetic sheet and the metal base material. Claim26 According to the present invention described above, the drying prevention material can be easily attached and detached and reused. Furthermore, the magnetic force (attraction force) acting between the drying prevention material and the metal base material applies a constant pressing force to the water-containing material sandwiched between them, thereby further promoting moisture penetration into fatigue cracks and making it easier to form a wet state. In addition, the gap between the drying prevention material and the metal base material allows air to enter the inside of the drying prevention material, ensuring a sufficient supply of carbon dioxide to the water-containing material, thus making it easier to form electrodeposited deposits.

[0036] Claim 27 The present invention is characterized in that the water-containing material is gel-like, and the gel-like water-containing material is supported by a flexible support. Claim 27 According to the present invention described herein, handling of the water-containing material becomes easier. Furthermore, because the fluidity of the electrolyte contained in the water-containing material is reduced, it becomes easier to attach the water-containing material regardless of the position of the opening.

[0037] Claim 28 The present invention is characterized in that the electrode material is a galvanic anode composed of a metal having a greater ionization tendency than the metal matrix, and the connecting material is either a conductor connecting the galvanic anode and the metal matrix, or an extension extending from the galvanic anode and in contact with the metal matrix. Claim 28 According to the present invention as described above, the metal matrix, water-containing material, galvanic anode, and connecting material form an electrochemical circuit as a whole, promoting the electrodeposition reaction within fatigue cracks in the metal matrix, and exhibiting a crack propagation suppression effect due to the wedge effect of the electrodeposited precipitates.

[0038] Claim 29 The present invention is characterized in that the electrode material is a durable electrode made of a corrosion-resistant metal, and the connecting material is a conductor connecting the durable electrode and the metal base material, and a DC power supply provided in the middle of the conductor with the cathode on the metal base material side. Claim 29According to the present invention as described above, the metal base material, water-containing material, durable electrode, and connecting material form an electrochemical circuit as a whole, promoting the electrodeposition reaction within fatigue cracks in the metal base material, and exhibiting a crack propagation suppression effect due to the wedge effect of the electrodeposited precipitates.

[0039] Claim 30 The present invention is characterized in that, as a heating material for preventing fatigue cracks, it is provided with electric heating wires arranged in a planar manner inside, on the surface, or on the back surface of the drying prevention material, or a sheet-shaped heater covering the drying prevention material. Claim 30 According to the present invention described above, by heating the fatigue crack propagation suppression sheet, the fatigue crack surface of the metal base material can be warmed, thereby preventing the electrodeposition reaction from being suppressed by low temperatures in winter or cold regions. [Effects of the Invention]

[0040] According to the present invention's method for suppressing fatigue crack propagation, a localized humid environment and electrochemical circuit can be easily formed on-site, allowing electrodeposited deposits to be generated within the fatigue crack in a relatively short period of time. Therefore, even at the crack tip, where wedge formation was previously difficult, the wedge effect of the generated electrodeposited deposits promotes crack closure and effectively suppresses fatigue crack propagation. Furthermore, even if the metal base material is a metal that is resistant to corrosion, it is possible to generate electrodeposited deposits on the crack surface as wedge material, thus offering excellent versatility. In addition, it is more resistant to external pressure and contact than when using viscous fluids, and offers superior workability and environmental resistance. Furthermore, by covering the moisture-containing material with a drying-preventing material, it is possible to prevent the moisture-containing material from drying out in a short period of time, thereby maintaining a moist state within the fatigue crack for a long period of time.

[0042] Furthermore, the fatigue crack propagation suppression sheet is used in water-containing materials. To supply carbon dioxide When selecting a system that includes an air intake channel, carbon dioxide contained in the air is supplied smoothly to the water-containing material through the channel, making it easier to generate electrodeposited deposits.

[0043] Furthermore, the fatigue crack propagation suppression sheet is To supply carbon dioxide to water-containing material When selecting a carbonic acid agent that contains a carbonic acid agent that allows carbon dioxide to leak out, and from the carbonic acid agent to supply carbon dioxide to the water-containing material, it is possible to supply carbon dioxide to the water-containing material using the carbonic acid agent, making it easier to generate electrodeposited deposits.

[0044] Furthermore, if the thickness of the water-containing material is set based on at least one of the replacement frequency of the fatigue crack propagation suppression sheet and the thickness of the metal base material, the frequency of replacement can be adjusted by appropriately setting the thickness of the water-containing material. In addition, by setting the thickness of the water-containing material according to the thickness of the metal base material, electrodeposited deposits can be effectively generated.

[0045] Furthermore, when a coating is formed on areas of the metal base material where fatigue cracks have occurred or are likely to occur, and a fatigue crack propagation suppression sheet is placed on the surface of the coating, it is possible to prevent the electrolyte in the water-containing material from being wasted by electrodeposition onto unwanted areas such as the surface of the metal base material.

[0046] Furthermore, when a fatigue crack penetrates the metal base material from one side to the other, if a fatigue crack propagation suppression sheet is placed at the opening of the fatigue crack on the other side, and the opening of the fatigue crack on the one side is left open to air, then air taken into the fatigue crack from the one side reaches the fatigue crack propagation suppression sheet on the other side, supplying carbon dioxide contained in the air to the water-containing material. This ensures a sufficient amount of carbon dioxide is supplied to the water-containing material, making it easier to generate electrodeposited deposits.

[0047] Furthermore, if the opening of a fatigue crack on one surface is partially covered with a non-permeable membrane material, or entirely covered with a permeable membrane material, the amount of water vapor released from the opening can be reduced, thereby preventing excessive drying of the water-containing material.

[0048] Furthermore, when a fatigue crack penetrates a metal base material from one side to the other, if a fatigue crack propagation suppression sheet, which is a water-containing material covered with a drying prevention material, is placed at the opening of the fatigue crack on the other side, and a carbonic acid agent, which is sealed in a way that allows carbon dioxide to leak to the outside, is placed at the opening of the fatigue crack on the one side, then it is possible to prevent the water-containing material placed at the opening on the other side from drying out, while supplying carbon dioxide (carbonic acid gas) to the water-containing material from the opening on the one side to generate electrodeposited deposits.

[0049] Furthermore, when a fatigue crack penetrates the metal base material from one surface to the other, ventilation is provided at the opening of the fatigue crack on the other surface. Road When a fatigue crack propagation suppression sheet is placed and the entire opening of a fatigue crack on one side is covered with a non-permeable membrane material that does not allow for airflow. or when a fatigue crack propagation suppression sheet having a ventilation channel is placed at the opening of a fatigue crack on one side and at the opening of a fatigue crack on the other side, respectively. This reduces the amount of water vapor released from the opening, preventing excessive drying of the moisture-containing material, while also allowing for ventilation. Road By supplying carbon dioxide to a water-containing material, electrodeposited deposits can be generated. Alternatively, the electrodeposition reaction within the fatigue crack is promoted from both the one and the other side, and the resulting wedge effect from the electrodeposited precipitates further suppresses the propagation of the fatigue crack.

[0050] Furthermore, in cases where a fatigue crack penetrates the metal base material from one surface to the other, When a fatigue crack propagation suppression sheet containing a carbonic acid agent is placed at the opening of a fatigue crack on the other side, and the entire opening of the fatigue crack on one side is covered with a non-permeable membrane material, The opening of the fatigue crack on one side and the opening of the fatigue crack on the other side charcoal When arranging fatigue crack propagation suppression sheets containing an acid agent, By reducing the amount of water vapor released from the opening, excessive drying of the water-containing material can be prevented, while carbon dioxide can be supplied to the water-containing material from the carbonate to generate electrodeposited precipitates. Electrodeposition reactions within fatigue cracks are promoted from both sides, and the resulting wedge effect from the generated electrodeposited deposits further suppresses the propagation of fatigue cracks.

[0051] Furthermore, when heating the fatigue crack propagation suppression sheet placed on the metal base material, heating the fatigue crack propagation suppression sheet can warm the fatigue crack surface of the metal base material, thus preventing the electrodeposition reaction from being suppressed by low temperatures in winter or cold regions.

[0052] Furthermore, when suppressing rust formation in areas of the metal base material where fatigue cracks have occurred or are likely to occur, and in surrounding areas where fatigue cracks have not occurred or are unlikely to occur, the electrochemical circuit formed by the placement of the fatigue crack propagation suppression sheet provides cathodic protection. Therefore, the areas where the fatigue crack propagation suppression sheet is installed, including the surrounding areas of the fatigue cracks, can be made less susceptible to rust due to the cathodic protection effect. This makes it a particularly effective rust prevention method for metals that are prone to corrosion.

[0053] The fatigue crack propagation suppression sheet of the present invention allows for the simple formation of a localized humid environment and electrochemical circuit on-site, generating electrodeposited deposits within fatigue cracks in a relatively short period of time. Therefore, even at the crack tip, where wedge formation was previously difficult, the wedge effect of the generated electrodeposited deposits promotes crack closure and effectively suppresses fatigue crack propagation. Furthermore, even when the metal base material is a metal that is resistant to corrosion, it is possible to generate electrodeposited deposits on the crack surface as wedge material, thus offering excellent versatility. In addition, it is more resistant to external pressure and contact than when using viscous fluids, and offers superior workability and environmental resistance. Furthermore, because the moisture-containing material is covered with a drying-preventing material, it is possible to prevent the moisture-containing material from drying out in a short period of time, thereby maintaining a moist state within the fatigue crack for a long period of time.

[0054] Furthermore, if the moisture content of the water-containing material is 50% or higher, a sufficiently wet state within the fatigue crack to generate electrodeposited deposits can be created in a short period of time.

[0056] Also, to water-containing material To supply carbon dioxide If there is a ventilation channel for introducing air, carbon dioxide contained in the air is supplied smoothly to the water-containing material through the ventilation channel, making it easier to generate electrodeposited deposits.

[0057] Furthermore, if the drying prevention material is provided with multiple microscopic pores that allow gaseous carbon dioxide molecules and water vapor to pass through but not liquid water molecules, it is possible to suppress the drying of the water-containing material while ensuring a sufficient amount of carbon dioxide is supplied to the water-containing material, thereby facilitating the formation of electrodeposited deposits.

[0058] Furthermore, if multiple through-holes are provided in the thickness direction of the water-containing material and electrode material as ventilation channels, air can enter the fatigue crack through the through-holes and carbon dioxide can be supplied to the water-containing material without interruption, thus facilitating the formation of electrodeposited deposits.

[0059] Furthermore, if the through-hole is elongated, even if the fatigue crack propagates outside the initially expected path, the opening will remain within the range of the through-hole. This allows air to enter the fatigue crack through the through-hole and carbon dioxide to be supplied to the water-containing material without interruption, thus facilitating the formation of electrodeposited deposits.

[0060] Furthermore, since the water-containing material and electrode material are each aggregates of multiple small pieces, if gaps are formed as ventilation channels by arranging the small pieces apart, air can enter the fatigue crack through the gaps and carbon dioxide can be supplied to the water-containing material without interruption, making it easier to generate electrodeposited deposits.

[0061] Furthermore, if a side drying prevention material is provided on the side of the moisture-containing material to suppress the leakage of water and water vapor from the moisture-containing material to the outside, the moisture-containing material will dry out more easily due to the presence of through holes or gaps. However, by providing a side drying prevention material, the diffusion of moisture from the sides can be suppressed, and excessive drying of the moisture-containing material can be prevented.

[0062] Also, To supply carbon dioxide to water-containing material When a carbonate agent is sealed in a way that allows carbon dioxide to leak out, and a carbonate agent container with an opening is provided to house the carbonate agent, carbon dioxide is supplied smoothly from the carbonate agent to the water-containing material, making it easier to generate electrodeposited deposits.

[0063] Furthermore, if multiple elongated through-holes are provided in the water-containing material in the thickness direction, and a carbonate is contained in a carbonate container placed in the through-hole, the carbonate can be allowed to flow into the fatigue crack, or only the carbon dioxide generated from the carbonate can flow into the fatigue crack, making it easier to form electrodeposited precipitates. In addition, because the through-holes are elongated, even if the fatigue crack propagates deviating from the initially expected path, the position of the opening can be kept within the range of the carbonate container.

[0064] Furthermore, the water-containing material and electrode material are each aggregates of multiple small pieces, and gaps are formed by arranging the small pieces apart. When a carbonate is contained in a carbonate container placed in the gaps, it is possible to allow the carbonate to flow into the fatigue crack, or to allow only the carbon dioxide generated from the carbonate to flow into the fatigue crack, thereby facilitating the formation of electrodeposited deposits.

[0065] Furthermore, if the carbonate contains an electrolyte, it can make it easier to generate electrodeposits.

[0066] Furthermore, if the opening of the carbon dioxide container is provided with an opening area adjustment material to adjust the opening area, or a gas-permeable membrane material that covers the entire opening, the amount of carbon dioxide supplied from the carbon dioxide to the water-containing material over a certain period of time can be made appropriate.

[0067] Furthermore, the drying prevention material is a magnetic sheet with magnetic force and flexibility. When the magnetic sheet is attached to the metal base material by magnetic force, if a gap that serves as a ventilation channel is created between the magnetic sheet and the metal base material, the drying prevention material can be easily attached and detached and reused. In addition, the magnetic force (attraction force) acting between the drying prevention material and the metal base material constantly applies a constant compressive force to the moisture-containing material sandwiched between them, which further promotes moisture penetration into fatigue cracks and makes it easier to form a wet state. Moreover, the gap between the drying prevention material and the metal base material allows air to enter the inside of the drying prevention material and ensures a sufficient supply of carbon dioxide to the moisture-containing material, thus making it easier to form electrodeposited deposits.

[0068] Furthermore, if the water-containing material is gel-like and supported by a flexible support, handling of the water-containing material becomes easier. Also, because the fluidity of the electrolyte contained in the water-containing material is reduced, it becomes easier to attach the water-containing material regardless of the position of the opening.

[0069] Furthermore, if the electrode material is a galvanic anode composed of a metal with a greater ionization tendency than the metal matrix, and the connecting material is a conductor connecting the galvanic anode and the metal matrix, or an extension extending from the galvanic anode and in contact with the metal matrix, then the metal matrix, water-containing material, galvanic anode, and connecting material as a whole form an electrochemical circuit, promoting the electrodeposition reaction within fatigue cracks in the metal matrix, and exhibiting a crack propagation suppression effect due to the wedge effect of the electrodeposited deposits.

[0070] Furthermore, if the electrode material is a durable electrode made of corrosion-resistant metal, and the connecting material is a conductor connecting the durable electrode and the metal base material, and a DC power supply provided in the middle of the conductor with the cathode on the metal base material side, then the metal base material, water-containing material, durable electrode, and connecting material as a whole form an electrochemical circuit, which promotes the electrodeposition reaction within fatigue cracks formed in the metal base material and can exert a crack propagation suppression effect due to the wedge effect of the electrodeposited deposits.

[0071] Furthermore, if the drying prevention material is equipped with heating elements such as electric heating wires arranged planarly inside, on the surface, or on the back surface, or a sheet-shaped heater covering the drying prevention material, the fatigue crack surface of the metal base material can be warmed by heating the fatigue crack propagation suppression sheet. This prevents the electrodeposition reaction from being suppressed by low temperatures in winter or cold regions. [Brief explanation of the drawing]

[0072] [Figure 1] Cross-sectional view showing an example of the morphology of cracks that occurred in the base material. [Figure 2] Schematic diagram of the first example of a fatigue crack propagation suppression sheet according to an embodiment of the present invention. [Figure 3] Schematic diagram of the electrodeposition reaction when the fatigue crack propagation suppression sheet from the first example is applied. [Figure 4] Schematic diagram of the second example of the fatigue crack propagation suppression sheet. [Figure 5] Schematic diagram of the electrodeposition reaction when the fatigue crack propagation suppression sheet from the second example is applied. [Figure 6] Schematic diagram of the third example of the fatigue crack propagation suppression sheet. [Figure 7] Schematic diagram of the fourth example of the fatigue crack propagation suppression sheet. [Figure 8] Schematic diagram of the fifth example of the fatigue crack propagation suppression sheet. [Figure 9] Schematic diagram of the sixth example of the fatigue crack propagation suppression sheet. [Figure 10] Schematic diagram of the seventh example of the fatigue crack propagation suppression sheet. [Figure 11] A schematic diagram showing the first application form, including fatigue cracks. [Figure 12] A schematic diagram showing the eighth application form, including fatigue cracks. [Figure 13] Diagram showing the specimens used in the fatigue crack propagation test. [Figure 14] Schematic diagrams of fatigue crack propagation suppression sheets in Examples 1 and 2. [Figure 15] Photograph of the appearance of the fatigue crack propagation suppression sheet in Example 2. [Figure 16] The figure shows the crack propagation curves as a result of fatigue crack propagation tests for the comparative example and both embodiments. [Figure 17] Magnified photographs of the fracture surfaces of the comparative example, Example 1, and Example 2. [Modes for carrying out the invention]

[0073] The following describes a method for suppressing fatigue crack propagation and a fatigue crack propagation suppression sheet according to embodiments of the present invention. Figure 1 is a cross-sectional view showing examples of crack morphologies in the base material, where Figure 1(a) shows through cracks and Figure 1(b) shows non-through cracks. Figure 2 is a schematic diagram of the first example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 2(a) is a plan view and Figure 2(b) is a cross-sectional view taken along A-A'. The first example of a fatigue crack propagation suppression sheet 1(1A) comprises a water-containing material 10 with a high water content containing an electrolyte, a flexible support 20 that supports the water-containing material 10, an electrode material 30 laminated on the outside of the water-containing material 10, a drying prevention material 40 (sheet means) that covers the water-containing material 10, the support 20 and the electrode material 30, and a connecting material 50 used to connect the metal base material 2 and the electrode material 30 in order to apply a potential with the metal base material 2 of the structure as the cathode. As described above, various structures such as ships, which are mainly composed of structural members (metal base material 2) made of metal or alloy, may develop cracks, particularly at stress concentration points, due to metal fatigue when repeated loads are applied to the metal base material 2. The fatigue crack 3 shown in Figure 1(a) is a through-crack that penetrates from one surface (front side) 2a to the other surface (back side) 2b of the metal base material 2 of the structure. Therefore, openings are formed on both sides of the fatigue crack 3, namely the opening 3a on the front side and the opening 3b on the back side. The fatigue crack 3 shown in Figure 1(b) is a non-penetrating crack that occurs on one surface (front side) 2a of the metal base material 2 of the structure and does not extend to the other surface (back side) 2b. Therefore, the only opening of the fatigue crack 3 is the opening 3a formed on the front side. The fatigue crack propagation suppression sheet 1 (crack propagation suppression sheet) is placed in the metal base material 2 at locations where fatigue cracks 3 have occurred or are likely to occur.

[0074] The metal base material 2 to which the fatigue crack propagation suppression method and fatigue crack propagation suppression sheet 1 are applied is a structural metal that is prone to fatigue cracks 3 and is electrically conductive, such as iron, steel, aluminum alloy, or titanium alloy. The main structural parts to which it is applied include stress concentration areas such as notches and welds (locations where the occurrence of fatigue cracks 3 is expected). In the method for suppressing the propagation of fatigue cracks, the fatigue crack propagation suppression sheet 1 is placed on the metal base material 2 so that the bottom surface 10a of the water-containing material 10 covers the openings 3a and 3b of the fatigue cracks occurring in the metal base material 2, creating a sufficiently humid environment; the electrode material 30 is connected to the metal base material 2 to apply a potential with the metal base material 2 as the cathode; and carbon dioxide is supplied to the water-containing material 10 to form an electrochemical circuit including the metal base material 2, the water-containing material 10, and the electrode material 30, thereby generating electrodeposited deposits 4 (see Figures 3 and 5) within the fatigue crack 3, and the propagation of the fatigue crack 3 is suppressed by the wedge effect of the electrodeposited deposits 4. Furthermore, the electrochemical circuit formed by the placement of the fatigue crack propagation suppression sheet 1 provides cathodic protection, which suppresses rust formation in the areas of the metal base material 2 where fatigue cracks 3 have occurred or are likely to occur, as well as in the surrounding areas where fatigue cracks 3 have not occurred or are unlikely to occur. As a result, the areas where the fatigue crack propagation suppression sheet 1 is installed, including the areas surrounding the fatigue cracks 3, are less susceptible to rust due to the cathodic protection, making it a particularly effective rust prevention method for metals that are prone to corrosion.

[0075] The water-containing material 10 creates a localized wet state within the fatigue crack 3. The water-containing material 10 preferably has a high moisture content of 50% or more, and possesses flexibility that allows it to fit seamlessly to the surface of the target metal base material 2, as well as moderate adhesiveness. The high moisture content of the water-containing material 10 allows for the creation of a sufficiently wet state within the fatigue crack 3 in a short period of time, which is necessary for the formation of electrodeposited deposits 4. Furthermore, the water-containing material 10 is preferably in gel form. This makes the water-containing material 10 easier to handle and reduces the fluidity of the water contained in the water-containing material 10. Therefore, the fatigue crack propagation suppression sheet 1 can be applied regardless of the position of the openings 3a and 3b, for example, by applying the water-containing material 10 from the side to openings 3a and 3b that occur in a vertical plane, or by applying the water-containing material 10 from below to horizontally extending openings 3a and 3b. Moreover, making it gel-like makes it easier to give the water-containing material 10 flexibility and appropriate adhesiveness. Note that the water contained in the water-containing material 10 does not necessarily have to be pure water.

[0076] The support 20 supports the water-containing material 10. This allows the water-containing material 10 to be stably attached to the openings 3a and 3b. The support 20 is made of a three-dimensionally flexible material that fits seamlessly onto the surface of the metal base material 2 (including the welded part), which has a three-dimensional curved surface. Preferably, it has moderate flexibility and is even more preferably has moderate strength to prevent tearing during installation. Commercially available cooling gel sheets for fatigue recovery have a structure in which a high-water-content gel is supported by a flexible woven support, and in some cases they can be used as the water-retaining material 10 and support 20 as is. Examples of this include Lion Corporation's products "Foot Refreshing Sheet Kyusoku Jikan (registered trademark)" and "Hiepita (registered trademark) 8-Hour Cooling," which have a structure in which the company's high-water-content gel PAC-55 (water content of 85% according to the manufacturer's stated value), which is made of polymers in a mesh-like (sponge-like) structure that holds moisture inside, is supported by a flexible woven support. However, it is preferable to appropriately set the thickness of the water-retaining material 10 according to the frequency of replacement of the fatigue crack propagation suppression sheet 1, which is determined by the performance of the ventilation channel described later and the usage environment conditions (especially humidity).

[0077] As the liquid (electrolyte) to be included in the water-containing material 10, a material that readily forms an electrochemical circuit and deposits electrodeposited material on the crack surface should be selected, as exemplified below. (1) Liquids that form electrochemical circuits: Sodium chloride (table salt) aqueous solution (concentration of about 1-3%), potassium chloride aqueous solution, and aqueous solutions of inorganic halogen compounds, etc. (2) Liquids that readily deposit electrodeposits on crack surfaces: aqueous solutions of inorganic salts such as magnesium chloride, magnesium sulfate, calcium sulfate, potassium chloride, etc. (3) Artificial seawater, etc., obtained by combining the above sodium chloride aqueous solution with inorganic salts, etc.

[0078] The drying prevention material 40 is in sheet form and is used to cover the moisture-containing material 10, etc. This prevents the moisture in the moisture-containing material 10 from diffusing to the outside and drying out in a short period of time, thereby maintaining a moist state within the fatigue crack 3 for a long period of time. In the first example, the drying prevention material 40 does not have air permeability as it does not have micropores that serve as one of the ventilation channels for introducing air into the moisture-containing material 10. However, if ventilation with the outside is completely blocked, carbon dioxide (CO2) in the fatigue crack 3 will be depleted, making it difficult for electrodeposited precipitates 4 to form. Therefore, it is necessary to ensure the supply of CO2 to the moisture-containing material 10 by providing some form of ventilation to ensure a certain level of air permeability. The method of supplying CO2 to the moisture-containing material 10 when using a fatigue crack propagation suppression sheet 1 in which the drying prevention material 40 does not have air permeability will be described later.

[0079] After the fatigue crack propagation suppression sheet 1 is applied to the openings 3a and 3b, the water-containing material 10 gradually dries out over time. Therefore, it is preferable to replace (reapply) the fatigue crack propagation suppression sheet 1 according to the degree of drying. This maintains a moist environment inside the crack, making it easier to generate electrodeposited precipitates 4. The frequency of replacement varies greatly depending on the type and application of the fatigue crack propagation suppression sheet 1, but it can be adjusted to some extent by appropriately selecting the thickness of the water-containing material 10. Therefore, it is preferable to appropriately set the thickness of the water-containing material 10 according to the frequency of replacement of the fatigue crack propagation suppression sheet 1. Furthermore, since the crack volume at the time of opening is approximately proportional to the thickness of the metal base material 2, it is preferable that the thickness of the water-containing material 10 be proportionally increased or decreased according to the thickness of the metal base material 2. By setting the thickness of the water-containing material 10 according to the thickness of the metal base material 2, electrodeposited precipitates 4 can be effectively generated. Furthermore, it is preferable to first form a coating film on the areas of the metal base material 2 where fatigue cracks 3 have occurred or are likely to occur, and then attach the fatigue crack propagation suppression sheet 1 to the surface of the formed coating film, rather than directly attaching it to the metal base material 2. This limits the formation of electrodeposited deposits 4 to within the cracks and prevents the electrolyte in the water-containing material 10 from being wasted by electrodepositing onto unwanted areas such as the surface of the metal base material 2.

[0080] In the first example, the electrode material 30 is a galvanic anode 30A composed of a metal with a higher ionization tendency (electrically less noble) than the metal base material 2. For example, if the metal base material 2 is steel, the galvanic anode 30A layer is made of a magnesium alloy or zinc film, or a water-containing gel containing a high concentration of the same metal powder. The galvanic anode 30A layer is provided between the water-containing material 10 and the support 20. If the support 20 is not provided, the galvanic anode 30A layer is placed between the water-containing material 10 and the drying prevention material 40. In this example, the connecting material 50 is a conductor 50A that connects the galvanic anode 30A and the metal base material 2. One end of the conductor 50A is connected to the end of the galvanic anode 30A, and the other end is connected to the metal base material 2. In this way, the layers of the metal base material 2, the water-containing material 10, the galvanic anode 30A, and the conductor 50A as a whole form an electrochemical circuit, which promotes the electrodeposition deposition reaction within the fatigue crack 3 that has formed in the metal base material 2, thereby promoting the crack propagation suppression effect due to the wedge effect of the precipitates within the crack. Furthermore, if the support 20 is made of a water-absorbing material such as a woven fabric, and the support 20 becomes sufficiently water-containing during use of the fatigue crack propagation suppression sheet 1, then it becomes possible to form an electrochemical circuit including the support 20, and the galvanic anode 30A layer may be placed on the outside of the support 20. In this case, the positional relationship between the galvanic anode 30A layer and the support 20 in Figure 1 will be reversed. Alternatively, instead of using the conductor wire 50A, an extension portion 50D (see Figure 14) formed by extending the layer of the galvanic anode 30A directly to the surface of the metal base material 2 may be used as the connecting material 50, and the galvanic anode 30A may be brought into direct contact with the metal base material 2.

[0081] Figure 3 is a schematic diagram of the electrodeposition reaction when the fatigue crack propagation suppression sheet of the first example is applied. Figure 3 schematically shows the chemical reactions that occur in the fatigue crack 3 and around the fatigue crack propagation suppression sheet 1A when the sheet 1A is applied to the fatigue crack 3 in the metal base material 2. Note that the drying prevention material 40 does not directly contribute to the chemical reaction and is therefore not shown in this figure. The water-containing material 10 of the fatigue crack propagation suppression sheet 1A is impregnated with an electrolytic (water-soluble) solution containing various electrolytes, so that an electrochemical circuit including the metal matrix 2 is formed. The reactions at each part are described in detail below. <Interface between water-containing material 10 and the atmosphere> Carbon dioxide from the atmosphere is incorporated into the water-containing material 10, and the following reaction occurs. CO2 + H2O → H2CO3 → H + + HCO3 - <Interface between electrolyte and metal matrix 2 (cathode) (including crack surface)> Electrons act on the electrolyte in the water-containing material 10 or within the fatigue crack 3, causing the following reaction to occur. 2H2O → H2↑ + 2OH - This reaction does not occur in areas where the coating film 5 is present on the surface of the metal base material 2. <Cracked surface> Various electrolyte ions in the hydrated gel (in this example, metal ions such as calcium and magnesium) combine with bicarbonate ions and hydroxide ions in the electrolyte solution and precipitate as electrodeposited material on the crack surface (indicated by 4 in Figure 3: electrodeposited deposit). Ca 2+ + HCO3 - + OH - → CaCO3 + H2O Mg 2+ + 2OH - → Mg(OH)2 This reaction does not occur in areas where the coating film 5 is present on the surface of the metal base material 2.

[0082] Figure 4 is a schematic diagram of a second example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 4(a) is a plan view and Figure 4(b) is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The second example of the fatigue crack propagation suppression sheet 1(1B) comprises a water-containing material 10, an electrode material 30 located outside the water-containing material 10, a support 20 located outside the electrode material 30, a drying prevention material 40 (non-permeable) that covers the water-containing material 10, the support 20, and the electrode material 30, and a connecting material 50. Furthermore, if the support 20 is made of a water-absorbing material such as a woven fabric, and the support 20 becomes sufficiently water-containing during the use of the fatigue crack propagation suppression sheet 1B, then it becomes possible to form an electrochemical circuit including the support 20, and the electrode material 30 may be placed outside the support 20. In this case, the positional relationship between the electrode material 30 and the support 20 in Figure 4 will be reversed.

[0083] In the second example, the electrode material 30 is a durable electrode 30B made of a corrosion-resistant metal. The layer of the durable electrode 30B is provided between the water-containing material 10 and the support 20. If the support 20 is absent, the layer of the durable electrode 30B is provided between the water-containing material 10 and the drying prevention material 40. The layer of the durable electrode 30B uses a film of a highly corrosion-resistant metal that is resistant to corrosion, or a water-containing gel containing a high concentration of powder of the same metal. In this example, the connecting material 50 consists of a conductor 50B connecting the durable electrode 30B and the metal base material 2, and a DC power supply 50C provided in the middle of the conductor 50B with the cathode on the metal base material 2 side. One end of the conductor 50B is connected to the end of the durable electrode 30B. The other end of the conductor 50B is connected to the metal base material 2. The DC power supply 50C, which carries DC current, is provided between one end and the other end of the conductor 50B. At this time, the cathode of the DC power supply 50C is on the metal base material 2 side. By doing so, the metal base material 2, the water-containing material 10, the durable electrode 30B layer, the conductor 50B, and the DC power supply 50C form an electrochemical circuit as a whole, promoting the electrodeposition reaction within the fatigue crack 3 formed in the metal base material 2, thereby exhibiting a crack propagation suppression effect due to the wedge effect of the precipitates within the crack.

[0084] Figure 5 is a schematic diagram of the electrodeposition reaction when the fatigue crack propagation suppression sheet of the second example is applied. Figure 5 schematically shows the chemical reactions that occur in the fatigue crack 3 and around the fatigue crack propagation suppression sheet 1B when the fatigue crack propagation suppression sheet 1B is applied to the fatigue crack 3 that has formed in the metal base material 2. Note that the drying prevention material 40 does not directly contribute to the chemical reaction and is therefore not shown in this figure. The water-containing material 10 of the fatigue crack propagation suppression sheet 1B is impregnated with an electrolytic (water-soluble) solution containing various electrolytes, so that an electrochemical circuit including the metal matrix 2 is formed. The reactions at each part are the same as in the case of Figure 3 (first example) described above.

[0085] Figure 6 is a schematic diagram of a third example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 6(a) is a plan view and Figure 6(b) is a cross-sectional view taken along line A-A'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The third example of the fatigue crack propagation suppression sheet 1(1C) is similar to the first example of the fatigue crack propagation suppression sheet 1A in that it comprises a water-containing material 10, a galvanic anode 30A as an electrode material 30 located outside the water-containing material 10, a support 20 located outside the galvanic anode 30A, a drying prevention material 40 (non-permeable) covering the water-containing material 10, the support 20 and the electrode material 30, and a conductor 50A as a connecting material 50, but it differs in that it further comprises a heating material 60. The heating element 60 includes a heating element 61 such as a nichrome wire, a voltage-adjustable power supply 62, and a switch 63. The heating element 61 is folded multiple times and arranged so that it is evenly distributed within the drying prevention material 40. The heating element 61 is arranged planarly on the inside, surface, or back surface of the drying prevention material 40, while the power supply 62 and switch 63 are located outside the drying prevention material 40.

[0086] When applying the fatigue crack propagation suppression sheet 1 in cold environments (generally below 10°C) where the metal base material 2 is installed, such as during winter or in cold regions, if the location of the fatigue crack 3 in the metal base material 2 becomes cold and the electrodeposition deposition reaction is suppressed, the suppression of the electrodeposition deposition reaction can be prevented by heating the location of the fatigue crack 3 to an appropriate temperature using the heating material 60 provided on the fatigue crack propagation suppression sheet 1C, as in this example. Although not shown in the diagram, instead of the configuration shown in Figure 6, the heating material 60 can be replaced with a sheet-type heater such as a rubber heater, and the drying prevention material 40 can be covered from the outside with the sheet-type heater. Furthermore, since the fatigue crack propagation suppression sheet 1 is used in a humid environment, it is preferable to use a heating material 60 that is highly insulating and completely waterproof. Furthermore, in order to bring the inside of the drying prevention material 40 (especially near the fatigue cracks 3) to a temperature suitable for the electrodeposition deposition reaction, it is preferable that the output of the heating material 60 be appropriately adjusted by a voltage-variable power supply 62 or the like. The upper limit of the heating temperature is determined considering the heat resistance of the heating material 60, power consumption, and the temperature influence on the surroundings.

[0087] Figure 7 is a schematic diagram of the fourth example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 7(a) is a plan view, Figure 7(b) is a cross-sectional view along A-A', and Figure 7(c) is a cross-sectional view along B-B'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The fourth example of the fatigue crack propagation suppression sheet 1(1D) comprises a water-containing material 10, a galvanic anode 30A as an electrode material 30 located outside the water-containing material 10, a support 20 located outside the layer of the galvanic anode 30A, a drying prevention material 40 covering the water-containing material 10, the support 20 and the electrode material 30, and a conductor 50A as a connecting material 50. In the fatigue crack propagation suppression sheet 1D, numerous micropores formed in the drying prevention material 40 serve as ventilation channels for introducing air into the water-containing material 10, and there are multiple through-holes 11 that penetrate the water-containing material 10, the support 20, and the galvanic anode 30A in the thickness direction. As a result, air enters the fatigue crack 3 through the micropores and through-holes 11, and carbon dioxide contained in the air is supplied to the water-containing material 10 without obstruction, making it easier to generate electrodeposited deposits 4. Furthermore, since the moisture-containing material 10 dries more easily when a ventilation passage is provided, it is preferable to prevent excessive drying of the moisture-containing material 10 by providing a side drying prevention material such as a resin film that does not allow water or water vapor to pass through on the side surface 10b of the moisture-containing material 10 along the through hole 11. The drying prevention material 40 is preferably a flexible film having numerous microscopic pores that allow gaseous CO2 molecules and water vapor to pass through but not liquid water molecules. This suppresses the drying of the water-containing material 10 while ensuring a sufficient amount of carbon dioxide is supplied to the water-containing material 10, making it easier to generate electrodeposited precipitates 4. An example of such a film is the medical and hygienic film "Yuuki (registered trademark) Permiroll (registered trademark) HS" manufactured by Nitoms Corporation. In particular, by using a translucent resin film, it becomes possible to observe changes in the appearance of the support 20 from the outside of the drying prevention material 40.

[0088] In applying the fatigue crack propagation suppression sheet 1D in the fourth example, the fatigue crack propagation suppression sheet 1D is attached to the surface of the metal base material 2 or the coating film 5 formed on the surface of the metal base material 2 such that the bottom surface 10a of the water-containing material 10 covers the openings 3a and 3b of the fatigue crack 3 occurring in the metal base material 2, and the expected crack propagation path line (line A-A' in Figure 7(a)) roughly follows the openings 3a and 3b of the fatigue crack 3 occurring in the metal base material 2. Furthermore, since actual fatigue cracks 3 often propagate deviating from the initially predicted path, it is preferable that the shape of the through-hole 11 be an elongated hole (slit shape) with an appropriate width in the direction perpendicular to the A-A' line (predicted crack propagation path line), so that even if the crack propagates deviating from the initially predicted path, the positions of the crack openings 3a and 3b remain within the range of the through-hole 11, and CO2 is supplied to the fatigue crack 3 and, consequently, to the water-containing material 10 without interruption. Furthermore, it is preferable to set the spacing between the through-holes 11 in the fatigue crack propagation suppression sheet 1D according to the length of the crack and the crack propagation rate. Generally, it is preferable to proportionally widen or narrow the spacing between the through-holes 11 according to the length of the crack and the crack propagation rate, such as narrowing the spacing between the through-holes 11 when the crack is short and the propagation rate is low, and widening the spacing between the through-holes 11 when the crack is long and the propagation rate is high. By changing the spacing between the through-holes 11 according to the state of the crack, carbon dioxide can be effectively supplied into the crack, and electrodeposited precipitates 4 can be generated in a shorter period of time.

[0089] Figure 8 is a schematic diagram of the fifth example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 8(a) is a plan view and Figure 8(b) is a cross-sectional view taken along line B-B'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The fifth example of the fatigue crack propagation suppression sheet 1(1E) comprises a water-containing material 10, a galvanic anode 30A as an electrode material 30 located outside the water-containing material 10, a support 20 located outside the layer of the galvanic anode 30A, a drying prevention material 40 covering the water-containing material 10, the support 20 and the electrode material 30, and a conductor 50A as a connecting material 50. The water-containing material 10, the support 20, and the electrode material 30 are each made up of multiple small pieces. The small pieces are in the shape of strips, and one piece each of the water-containing material 10, support 20, and electrode material 30 is stacked to form one set, which are then arranged with gaps between them. This arrangement of spaced-out pieces creates multiple gaps 12 in the thickness direction on the inside of the drying prevention material 40. Multiple small pieces arranged at predetermined intervals in the layer of the galvanic anode 30A are all connected to a single conductor 50A along the B-B' line, and one end of the conductor 50A is connected to the metal base material 2.

[0090] In the fatigue crack propagation suppression sheet 1E, numerous micropores and multiple gaps 12 formed in the drying prevention material 40 serve as ventilation channels for introducing air into the water-containing material 10. As a result, air enters the fatigue crack 3 through the micropores and gaps 12, and carbon dioxide contained in the air is supplied to the water-containing material 10 without obstruction, making it easier to generate electrodeposited precipitates 4. Furthermore, since the moisture-containing material 10 dries more easily when a ventilation passage is provided, it is preferable to prevent excessive drying of the moisture-containing material 10 by suppressing moisture diffusion from the side surface 10b of the moisture-containing material 10, such as by providing a side drying prevention material such as a resin film that does not allow water or water vapor to pass through, along the through hole 11.

[0091] Figure 9 is a schematic diagram of the sixth example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 9(a) is a plan view, Figure 9(b) is a cross-sectional view along A-A', and Figure 9(c) is a cross-sectional view along B-B'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The sixth example of the fatigue crack propagation suppression sheet 1(1F) comprises a water-containing material 10, a galvanic anode 30A as an electrode material 30 located outside the water-containing material 10, a support 20 located outside the layer of the galvanic anode 30A, a drying prevention material 40 (non-permeable) covering the water-containing material 10, the support 20 and the electrode material 30, a conductor 50A as a connecting material 50, a gel-like carbon dioxide agent 70 (carbonated gel) sealed in which carbon dioxide (carbonic acid gas) can leak to the outside, and a carbon dioxide agent storage body 80 (carbonated gel storage means) having an opening 80a and housing the carbon dioxide agent 70. The moisture-containing material 10 of the fatigue crack propagation suppression sheet 1F has multiple through holes 11 that penetrate in the thickness direction, and a carbonate container 80 with its opening 80a facing the bottom surface 10a of the moisture-containing material 10 is fitted snugly into each through hole 11. The end of the carbon dioxide container 80 opposite the opening 80a is closed by the upper surface 80b, and the outer surface of the upper surface 80b is adhered to the layer of the galvanic anode 30A. The inside of the carbon dioxide container 80 is filled with a gel-like carbon dioxide 70. It is preferable to use a resin such as polyethylene or polypropylene that has high chemical stability and airtightness for the carbon dioxide container 80. Carbon dioxide leaking from the carbonate agent 70 is supplied to the water-containing material 10 via the opening 80a of the carbonate agent container 80 and the fatigue crack 3, thus facilitating the formation of electrodeposited deposits 4. Furthermore, by housing the carbonate agent 70 in the carbonate agent container 80, the carbonate agent 70 can be stably maintained. Various electrolytes for electrodeposition can also be included in the carbonate agent 70. This makes it easier to further generate electrodeposits within the fatigue crack 3. Furthermore, it is preferable to provide the opening 80a of the carbonic acid container 80 with either an opening area variable material to adjust the opening area, or a gas-permeable membrane material that covers the entire opening 80a. This allows for adjustment of the amount of gel-like carbonic acid 70 or carbon dioxide that enters the fatigue crack 3 within a certain period of time, thereby ensuring an appropriate supply of carbon dioxide to the water-containing material 10. Examples of the opening area variable material include a lid that covers a part of the opening 80a, or a lid with a vent that covers the entire opening 80a.

[0092] There are two possible methods for filling the carbonate container 80 with the carbonate 70: 1) filling the container 80a with gel-like or fluid carbonate 70 so that the carbonate 70 flows directly into the fatigue crack 3; and 2) creating a certain gap between the opening 80a and the bottom surface of the carbonate container 80 containing the gel-like or solid carbonate 70 so that only carbon dioxide generated from the carbonate 70 flows into the fatigue crack 3. It is preferable to select which method to use as appropriate, taking into consideration the type of structure to be used, the operating environment, the form of the fatigue crack 3, and the period for which the fatigue crack propagation suppression sheet 1F is used. Furthermore, if environmental factors such as rainwater, or the action of other fatigue crack propagation suppression sheets 1 attached to the back side of the metal base material 2 in the case of through cracks, result in a sufficiently moist environment within the fatigue crack 3, the fatigue crack propagation suppression sheet 1F does not necessarily need to contain a high-moisture-content material 10. It is possible to substitute it with another soft molding material containing an electrolyte, thereby creating a "carbon dioxide supply sheet" with limited functionality that does not create a locally moist environment within the fatigue crack 3.

[0093] When applying the fatigue crack propagation suppression sheet 1F, after filling the carbonate container 80 with carbonate 70, the fatigue crack propagation suppression sheet 1F is attached to the surface of the metal base material 2 or the coating film 5 formed on the surface of the metal base material 2 such that the bottom surface 10a of the water-containing material 10 covers the openings 3a, 3b of the fatigue cracks 3 occurring in the metal base material 2, or the expected propagation path of the fatigue cracks 3, and that the expected propagation path line of the fatigue cracks 3 (line A-A' in Figure 9(a)) roughly follows the openings 3a, 3b of the fatigue cracks 3 occurring in the metal base material 2, or the expected propagation path of the fatigue cracks 3. At this time, the opening 80a of the carbonic acid container 80 is in close contact with the surface of the metal base material 2 or the coating film 5 formed on the surface of the metal base material 2, and the carbonic acid 70 is sealed inside the closed space formed by the carbonic acid container 80 and the surface of the metal base material 2 or the coating film 5 formed on the surface of the metal base material 2. As a result, the carbonic acid 70 can maintain a stable state without undergoing any changes until the fatigue crack 3 propagates and passes directly below the opening 80a. Furthermore, fatigue cracks 3 often propagate deviating from the initially predicted propagation path. Even if fatigue cracks 3 propagate deviating from the predicted propagation path, the positions of the openings 3a and 3b remain within the range of the carbonic acid container 80, and the supply of carbonic acid 70 or carbon dioxide generated therefrom into the fatigue cracks 3 is carried out without interruption. Therefore, it is preferable that the shape of the carbonic acid container 80 be an elongated hole shape (slit shape) having an appropriate width perpendicular to the predicted propagation path line (line A-A' in Figure 9(a)), as in this example.

[0094] Figure 10 is a schematic diagram of the seventh example of a fatigue crack propagation suppression sheet according to this embodiment, where Figure 10(a) is a plan view, Figure 10(b) is a cross-sectional view along A-A', and Figure 10(c) is a cross-sectional view along B-B'. Note that the same reference numerals are used for functional members identical to the fatigue crack propagation suppression sheet described above, and their descriptions are omitted. The fatigue crack propagation suppression sheet 1(1G) of the seventh example is similar to the fatigue crack propagation suppression sheet 1F of the sixth example in that it comprises a water-containing material 10, a galvanic anode 30A as an electrode material 30 located outside the water-containing material 10, a support 20 located outside the layer of the galvanic anode 30A, a drying prevention material 40 (non-permeable) covering the water-containing material 10, the support 20 and the electrode material 30, a conductor 50A as a connecting material 50, a gel-like carbon dioxide agent 70 sealed to allow carbon dioxide (carbonic acid gas) to leak to the outside, and a carbon dioxide agent housing 80 having an opening 80a and housing the carbon dioxide agent 70. However, it differs in that the through-hole 11 into which the carbon dioxide agent housing 80 is fitted penetrates not only the water-containing material 10 but also the galvanic anode 30A and the support 20. The fatigue crack propagation suppression sheet 1G has multiple through holes 11 that penetrate the water-containing material 10, the galvanic anode 30A, and the support 20. A carbon dioxide container 80, with its opening 80a facing the bottom surface 10a of the water-containing material 10, is fitted snugly into each through hole 11. The end of the carbon dioxide container 80 opposite the opening 80a is closed by the top surface 80b. The inside of the carbon dioxide container 80 is filled with a gel-like carbon dioxide 70. Furthermore, instead of closing the end of the carbon dioxide container 80 opposite the opening 80a with the top surface 80b, a removable top cover or the like may be provided so that the carbon dioxide 70 can be injected from that end as needed. This makes it easier to replenish the carbon dioxide container 80 with the carbon dioxide 70, and allows carbon dioxide to be supplied to the water-containing material 10 over a long period of time.

[0095] Although not shown in the diagram, the fatigue crack propagation suppression sheet 1 can also be configured to combine the supply of carbon dioxide through a ventilation channel, as in the fatigue crack propagation suppression sheet 1D of the fourth example, and the supply of carbon dioxide through a carbonic acid agent 70, as in the fatigue crack propagation suppression sheet 1G of the seventh example. In this case, for example, the drying prevention material 40 is made breathable, and two through-holes 11 into which the carbon dioxide container 80 is fitted are placed next to one through-hole 11 that serves as a ventilation passage, and then two more through-holes 11 into which the carbon dioxide container 80 is fitted are placed next to that, so that the carbon dioxide container 80 containing the carbon dioxide and the through-holes 11 through which air passes are used in combination, and the two are arranged in a regular or irregular manner.

[0096] Furthermore, although not shown in the diagram, if the fatigue crack propagation suppression sheet 1 is equipped with a carbonic acid agent 70, as in the fifth example of the fatigue crack propagation suppression sheet 1E, one small piece of water-containing material 10, one small piece of support 20, and one small piece of electrode material 30 can be laminated together to form one set, and by arranging the sets with gaps between them, multiple gaps 12 can be formed in the thickness direction inside the drying prevention material 40, and the carbonic acid agent container 80 can be fitted into each of these gaps 12. This makes it easier to allow the carbonate agent 70 to flow into the fatigue crack 3, or to allow only the carbon dioxide generated from the carbonate agent 70 to flow into the fatigue crack 3, thereby facilitating the formation of electrodeposited precipitates 4.

[0097] The above describes an example of a fatigue crack propagation suppression sheet 1. In a fatigue crack propagation suppression method, it is also effective to supply carbon dioxide into the fatigue crack 3 by manually applying a gel-like or fluid carbon dioxide agent 70 around the openings 3a and 3b of the fatigue crack 3 in order to promote the deposition of electrodeposits on the crack surface. The method and timing of injecting the carbon dioxide agent 70 are arbitrary, but if a gel-like carbon dioxide agent 70 is applied to the openings 3a and 3b of the fatigue crack 3, it can be expected that it will be automatically transported into the fatigue crack 3 by the pump effect and capillary action associated with the opening and closing of the crack. However, since the effect of the carbon dioxide agent 70 after application often disappears in a relatively short time, it is preferable to repeat the manual application work intermittently as the fatigue crack 3 propagates. This makes it possible to maintain the propagation suppression effect from the initial stage to the final stage of crack propagation.

[0098] Next, we will describe examples of how the fatigue crack propagation suppression sheet 1 can be applied to the metal base material 2. Table 1 below summarizes eight application methods for suppressing fatigue crack propagation, which are expected to be based on the type of fatigue crack 3 being targeted. [Table 1]

[0099] First, if the fatigue crack 3 is a through-crack penetrating the metal base material 2, air entering from the opening 3a on one side (front side) 2a reaches the opening 3b on the other side (back side) 2b. Therefore, both a fatigue crack propagation suppression sheet 1 without a ventilation passage or carbon dioxide container 80 (hereinafter sometimes referred to as "fatigue crack propagation suppression sheet 1 without CO2 supply") and a fatigue crack propagation suppression sheet 1 with a ventilation passage or carbon dioxide container 80 (hereinafter sometimes referred to as "fatigue crack propagation suppression sheet 1 with CO2 supply") are applicable to the opening 3b of the fatigue crack 3 on the other side (back side) 2b. Depending on how the opening 3a of the fatigue crack 3 on one side 2a is addressed, the first to seventh application forms can be considered. Next, if the fatigue crack 3 is a non-penetrating crack that does not penetrate the metal base material 2, it is not possible to supply air to the openings 3a and 3b on the opposite side using the penetrating crack, and therefore the fatigue crack propagation suppression sheet 1 without CO2 supply cannot be applied. On the other hand, the fatigue crack propagation suppression sheet 1 with CO2 supply can supply carbon dioxide to the water-containing material 10 without taking in carbon dioxide from the opposite side (in this case, one side 2a), so an eighth application form can be considered.

[0100] Figure 11 is a schematic diagram showing the first application mode, including fatigue cracks. Note that actual crack surfaces are not planar, but for simplicity, they are schematically represented as planar in Figure 11. For a fatigue crack 3 (through crack) that penetrates the thickness of the metal base material 2, the bottom surface 10a of the moisture-containing material 10 of the fatigue crack propagation suppression sheet 1A of the first example is pressed against it from below to cover the opening 3b on the other surface (back side) 2b, and is adhered to it. In addition, the drying prevention material 40 is provided to cover the moisture-containing material 10, the galvanic anode 30A, and the support 20, and its bottom surface 40a is in close contact with the other surface 2b of the metal base material 2 by adhesive tape or the like. In the first example, the fatigue crack propagation suppression sheet 1A does not have a ventilation channel or a carbon dioxide container 80. However, in this case, the opening 3a of the fatigue crack 3 on the opposite side (front side) 2a is opened, allowing air to enter and exit. Air taken into the fatigue crack 3 from the side 2a reaches the fatigue crack propagation suppression sheet 1A located on the other side 2b, supplying carbon dioxide contained in the air to the water-containing material 10. This ensures a sufficient amount of carbon dioxide is supplied to the water-containing material 10, making it easier to generate electrodeposited precipitates 4. As a result, electrodeposited precipitates 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation.

[0101] Figure 12 is a schematic diagram showing the eighth application mode, including fatigue cracks. Note that the actual crack surface is not planar, but for simplicity, it is schematicly shown as planar in Figure 12. For a non-penetrating fatigue crack 3 (non-penetrating crack) occurring in the metal base material 2, the bottom surface 10a of the moisture-containing material 10 of the fatigue crack propagation suppression sheet 1D of the fourth example is pressed from above to cover the opening 3a on one side (front side) 2a, and adheres to it. In addition, the drying prevention material 40 is provided to cover the moisture-containing material 10, the galvanic anode 30A and the support 20, and its bottom surface 40a is in close contact with one side 2a of the metal base material 2 by adhesive tape or the like. The drying prevention material 40, which has numerous micropores, does not block air, and sufficient air (carbon dioxide) is taken into the fatigue crack 3 through the micropores and through holes 11 and supplied to the water-containing material 10. As a result, electrodeposited deposits 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation.

[0102] Although not shown in the diagrams, the second to seventh application forms are specifically as follows. The second application method involves attaching a fatigue crack propagation suppression sheet 1 without CO2 supply to the opening 3b of the other side (back side) 2b, and covering the opening 3a of one side (front side) 2a with a drying prevention film. By covering the opening 3a of one side 2a with a drying prevention film, the amount of water vapor released from the opening 3a of one side 2a can be reduced, thereby preventing excessive drying of the water-containing material 10. The drying prevention membrane shall be either a non-permeable membrane material that does not allow air to pass through, or a permeable membrane material that does allow air to pass through. If a non-permeable membrane material is used, the opening 3a shall be partially covered with the non-permeable membrane material; if a permeable membrane material is used, the entire opening 3a shall be covered with the permeable membrane material. In this case, sufficient air (carbon dioxide) is supplied to the moisture-containing material 10 of the fatigue crack propagation suppression sheet 1 attached to the other surface 2b through the opening 3a on one surface 2a, passing through the fatigue crack 3. As a result, electrodeposited precipitates 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation.

[0103] The third application method involves attaching a fatigue crack propagation suppression sheet 1 without CO2 supply to the opening 3b on the other side (back side) 2b, and applying a gel-like or liquid carbon dioxide agent 70, which contains carbon dioxide that can leak to the outside, to the opening 3a on the other side (front side) 2a. In this case, by using a fatigue crack propagation suppression sheet 1 that does not allow air to pass through, drying of the water-containing material 10 is prevented, and carbon dioxide (carbonic acid gas) is supplied to the water-containing material 10 through a through crack from a carbonate agent 70 placed in the opening 3a on one side 2a, thereby generating electrodeposited precipitates 4 on the crack surface, and crack propagation can be suppressed by the wedge effect.

[0104] The fourth application method involves attaching a fatigue crack propagation suppression sheet 1 with CO2 supply to the opening 3b on the other side (back side) 2b, while leaving the opening 3a on the other side (front side) 2a open without anything attached. In this case, carbon dioxide is supplied to the water-containing material 10 of the fatigue crack propagation suppression sheet 1 attached to the other surface 2b from the opening 3a on one surface 2a and from the ventilation passage or carbon dioxide container 80, so that electrodeposited precipitates 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation.

[0105] The fifth application method involves attaching a fatigue crack propagation suppression sheet 1 with CO2 supply to the opening 3b on the other side (back side) 2b, and covering the opening 3a on the other side (front side) 2a with a drying prevention film. In this case, by covering the opening 3a of one surface 2a with a non-permeable drying prevention film, the amount of water vapor released from the opening 3a of one surface 2a is reduced, preventing excessive drying of the water-containing material 10, while carbon dioxide can be supplied to the water-containing material 10 from the ventilation passage or the carbonic acid agent 70. As a result, electrodeposited deposits 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation. Furthermore, if the opening 3a of one surface 2a is partially covered with a non-permeable drying prevention film (non-permeable film material), or if it is entirely covered with a permeable drying prevention film (permeable film material), then air (carbon dioxide) can be supplied to the water-containing material 10 through the through cracks from the opening 3a of one surface 2a.

[0106] The sixth application method involves attaching a fatigue crack propagation suppression sheet 1 with CO2 supply to the opening 3b on the other side (back side) 2b and the opening 3a on the one side (front side) 2a. In this case, carbon dioxide is supplied to each of the water-containing materials 10 from the ventilation passage or carbon dioxide container 80, causing electrodeposited precipitates 4 to form on the crack surface, exhibiting a wedge effect and suppressing crack propagation. Furthermore, the wedge effect caused by the electrodeposited deposits 4 occurs not only on the other surface 2b but also on the one surface 2a, which further suppresses the propagation of fatigue cracks 3.

[0107] The seventh application method involves attaching a fatigue crack propagation suppression sheet 1 with CO2 supply to the opening 3b on the other side (back side) 2b, and attaching a fatigue crack propagation suppression sheet 1 without CO2 supply to the opening 3a on the other side (front side) 2a. In this case, each water-containing material 10 is supplied with sufficient air (carbon dioxide) via a fatigue crack propagation suppression sheet 1 with CO2 supply attached to the opening 3b of the other surface 2b. As a result, electrodeposited deposits 4 are formed on the crack surface, exhibiting a wedge effect and suppressing crack propagation. Furthermore, the wedge effect caused by the electrodeposited deposits 4 occurs not only on the other surface 2b but also on the one surface 2a, which further suppresses crack propagation.

[0108] Next, a fatigue crack growth test using a steel notched flat test piece, which was conducted to verify the effect of the fatigue crack growth suppression method and the fatigue crack growth suppression sheet in the present invention, will be described.

[0109] FIG. 13 is a view showing the test piece used in the fatigue crack growth test. The test piece 100 used was a flat test piece made of JIS SM490A steel with a thickness of 5 mm, having a notch with a length of 10 mm and a width of 0.3 mm processed in the central part. The testing machine used was an electro-hydraulic servo type fatigue testing machine (manufactured by Shimadzu Corporation, dynamic capacity 10 tonf). The test conditions are as follows. (a) During normal test: nominal stress range Δσ n = 104.4 to 104.5 MPa, stress ratio R = 0 (fully reversed tension side), load frequency f = 5.1 Hz. (b) When forming a beach mark: While keeping the maximum stress the same as in (a), the minimum stress was increased to reduce the stress range to about 1 / 4 of that in (a), and the load frequency f = 13 Hz. The timing of beach mark formation was appropriately set while measuring the surface crack length.

[0110] The contents of Comparative Example 1 and Examples 1 and 2 in which the fatigue crack growth test was carried out are summarized in Table 2 below. The form of fatigue crack 3 is a through crack in all cases. [Table 2]

[0111] Comparative Example 1 was tested with the test piece 100 (metal base material 2) without using the fatigue crack growth suppression sheet 1. On the other hand, Examples 1 and 2 embody the above-described first application form. The fatigue crack growth suppression sheet 1A of the first example without CO2 supply was attached to the opening 3b of the fatigue crack 3 on the other surface (back side) 2b of the test piece 100, and the opening 3a of the fatigue crack 3 on one surface (front side) 2a was left open. In Examples 1 and 2, Lion Corporation's product "Foot Refreshing Sheet Kyusoku Jikan (registered trademark)" was used as the water-containing material 10 and support 20. As described above, this product is a gel sheet with a structure in which a high-water-content water-containing gel is supported by a flexible woven support 20, and the original water-containing gel contains water and trace amounts of fragrance components. In Example 1, the gel sheet was completely immersed in a 3% sodium chloride (NaCl) aqueous solution for more than 24 hours and used as a water-containing gel with 3% saline solution. As mentioned above, 3% saline solution is a liquid that readily forms electrochemical circuits. On the other hand, in Example 2, the gel sheet was completely immersed in artificial seawater for more than 24 hours and used as a water-containing gel with artificial seawater. As described above, artificial seawater is a liquid that readily forms electrochemical circuits and readily deposits hard electrodeposited deposits 4 on crack surfaces. The artificial seawater was prepared using "Aquamarine®," a metal corrosion test agent from Yashima Pharmaceutical Co., Ltd.

[0112] Figure 14 is a schematic diagram of the fatigue crack propagation suppression sheet in Examples 1 and 2, where Figure 14(a) is a plan view and Figure 14(b) is a cross-sectional view taken along line A-A'. In the fatigue crack propagation suppression sheet 1A shown in Figures 1 and 11, the layers are stacked from the inside in the order of water-containing material 10 → galvanic anode 30A → support 20. However, in the fatigue crack propagation suppression sheet 1 of Examples 1 and 2, the stacking order was as follows from the inside in the order of water-containing material 10 → support 20 → galvanic anode 30A, as shown in Figure 14. For the 30A galvanic anode layer, we used ZAP® tape (0.1mm thick, 25mm wide), a zinc corrosion protection tape commercially available for corrosion prevention from Mitsui Sumitomo Metal Mining Copper Co., Ltd. This product has a high-purity zinc foil with a conductive adhesive on one side, and conductivity is created simply by applying the tape to the target metal surface, providing sacrificial corrosion protection. In the fatigue crack propagation suppression sheet 1A shown in Figures 1 and 11, a conductor 50A is provided as a connecting material 50 to connect the galvanic anode layer 30A and the metal base material 2. However, in the fatigue crack propagation suppression sheet 1 of Examples 1 and 2, the conductor 50A is omitted, and an extension portion 50D that extends from the galvanic anode 30A and contacts the metal base material 2 is used as the connecting material 50. That is, by extending the zinc corrosion-resistant tape directly to the metal base material 2 and attaching the conductive adhesive surface to make contact, electrical conductivity as an electrochemical circuit is ensured.

[0113] A 0.7mm thick magnetic sheet was used for the drying prevention material 40. If the metal base material 2 is a magnetic material, a magnetic sheet that has magnetic properties and can flexibly change shape can be used as the drying prevention material 40. Using a magnetic sheet has the following advantages: (1) It is easy to attach and detach and can be used repeatedly. Also, by temporarily peeling off the magnetic sheet, the internal state that was covered by the magnetic sheet can be easily understood. (2) Due to the magnetic force (attraction force) acting between the magnet sheet and the metal 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 fatigue crack 3. (3) Because the magnetic sheet has moderate bending rigidity, a certain amount of gap is created at the edges of the magnetic sheet without completely sealing the water-containing material 10 and the support 20. This gap acts as a ventilation channel, ensuring a certain degree of ventilation without blocking the airflow. Here, Figure 15 is a photograph of the fatigue crack propagation suppression sheet in Example 2. Figure 15 shows the sheet attached to the back of test piece 100, before the magnetic sheet was attached and before the load was applied. The drying prevention material 40 has the role of protecting the fatigue crack propagation suppression sheet 1 and preventing the moisture-containing material 10 from drying out while applying a constant pressing force. However, the zinc corrosion-preventive tape used as the galvanic anode 30A in Examples 1 and 2 has a certain strength of its own and can also be expected to have a drying prevention effect. In such cases, the layer of the galvanic anode 30A can also serve the role of the drying prevention material 40, and it is possible to omit the drying prevention material 40, as shown in Figure 15.

[0114] Figure 16 shows the crack propagation curves as a result of fatigue crack propagation tests for the comparative example and both embodiments. The vertical axis represents the crack length on one side [mm], and the horizontal axis represents the number of cycles (number of load repetitions) [times]. In Figure 15, "●" indicates the comparative example, "△" indicates the results for Embodiment 1, and "〇" indicates the results for Embodiment 2. The dotted lines indicate the fracture life for each. Table 3 below shows the fracture life as a result of fatigue crack propagation tests for the comparative example and both examples. The life ratio is based on the comparative example. [Table 3]

[0115] As shown in Figure 16 and Table 3, compared to the comparative example using test piece 100 (metal base material 2) as is, Example 1, which embodies the first application form and uses 3% saline solution as the electrolyte to be contained in the water-containing gel (water-containing material 10), shows a slight suppression of fracture progression starting from around 400,000 cycles, and the fracture life ratio is approximately 1.6 times higher. On the other hand, in Example 2, which also embodies the first application form and uses artificial seawater as the electrolyte solution to be included in the water-containing gel (water-containing material 10), a significant crack propagation suppression effect was observed from the initial stages of crack propagation, and the fracture life ratio was approximately 6 times higher.

[0116] Figure 17 shows magnified photographs of the fracture surface; Figure 17(a) shows a comparative example, Figure 17(b) shows Example 1, and Figure 17(c) shows Example 2. Note that Figure 17(a) is a composite image created by stitching together multiple images. In all three cases, fatigue crack 3 originated from the notch end on the right side of the photograph, and subsequently propagated to the left side of the photograph with repeated loading, eventually leading to fracture. In the fracture surface of the comparative example shown in Figure 17(a), elliptical arc-shaped beach marks formed at intervals on the fracture surface of the textured test piece 100 (metal base material 2) are clearly visible. In contrast, in the fracture surface of Example 1 shown in Figure 17(b), a thin, film-like substance (the gray area) is formed on the fracture surface of test piece 100, and the shape of the beach marks, which are barely visible on the fracture surface of test piece 100 (metal base material 2), is irregular and distorted. This is presumed to be because the effect of the fatigue crack propagation suppression sheet 1, which uses 3% saline solution as an electrolyte, causes a slight electrodeposition reaction within the fatigue crack 3, and the precipitates electrodeposited on the crack surface mildly compress the crack surface of the metal base material 2 that tries to close during unloading. As a result, the fracture surface of the metal base material 2 turns gray, causing differences in the wedge effect depending on the location on the crack surface, and resulting in differences in the crack propagation rate. On the other hand, in the fracture surface of Example 2 shown in Figure 17(c), a prominent wedge (the dark-looking portion) is formed on the fracture surface of the test piece 100 immediately after the occurrence of the fatigue crack 3, and the formation of a continuous wedge layer is observed in an area with a crack length of about 20 mm on one side (four times the plate thickness). This is presumed to be because the effect of the fatigue crack propagation suppression sheet 1, which uses artificial seawater as an electrolyte, causes a significant electrodeposition deposition reaction within the fatigue crack 3, and the hard precipitates electrodeposited on the crack surface act as wedges, continuously and strongly compressing the crack surface of the metal base material 2 that tries to close during unloading, which in turn causes the fracture surface of the metal base material 2 to turn dark.

[0117] As described above, the fatigue crack propagation suppression method and propagation suppression sheet according to the present invention can easily form a localized humid environment and electrochemical circuit on-site, generating electrodeposited deposits within the fatigue crack in a relatively short period of time. Therefore, even at the crack tip, where it was previously difficult to form wedges, the wedge effect of the generated electrodeposited deposits promotes crack closure and effectively suppresses fatigue crack propagation. Furthermore, even if the metal base material is a metal that is resistant to corrosion, it is possible to generate electrodeposited deposits on the crack surface as wedge material, thus offering excellent versatility. In addition, it is more resistant to external pressure and contact than when using viscous fluids, and offers superior workability and environmental resistance. [Industrial applicability]

[0118] This invention can be applied to various metal structures that have fatigue cracks or are at risk of developing fatigue cracks, such as ships, offshore structures, vehicles, aircraft, bridges, and machine tools. [Explanation of Symbols]

[0119] 1. Fatigue crack propagation suppression sheet 2 Metal base material 2a One side 2b The other side 3. Fatigue cracks 3a Opening on one side 3b Opening on the other side 4 Electrodeposited deposits 5. Coating 10 Water-containing material 10b side 11 Through hole 12 Gap 20 Support 30 Electrode material 30A galvanic anode 30B durable electrode 40 Anti-drying material 50 connecting materials 50A, 50B conductor 50C DC power supply 50D extension 60 Heating material 61 Heating wire 70 Carbonated Agent 80 Carbonated Agent Storage Unit 80a aperture

Claims

1. A fatigue crack propagation suppression sheet comprising a water-containing material having an electrolyte containing at least bicarbonate ions and calcium ions, and an electrode material laminated on the outside of the water-containing material, is placed in a location in the metal base material of a structure where fatigue cracks have occurred or are likely to occur, with the water-containing material in contact with the location, thereby creating a humid environment. The electrode material and the metal base material are connected directly or via a wire to apply a potential to the metal base material, with the metal base material acting as the cathode. By covering the aforementioned water-containing material with a drying-preventing material that also applies pressing pressure, A method for suppressing the progression of fatigue cracks, characterized in that when a fatigue crack occurs after forming an electrochemical circuit including the metal matrix, the water-containing material, and the electrode material, electrodeposited deposits are generated within the fatigue crack, and the progression of the fatigue crack is suppressed by the wedge effect of the electrodeposited deposits.

2. The fatigue crack propagation suppression method according to claim 1, characterized in that the fatigue crack propagation suppression sheet is selected to have a ventilation channel for introducing air in order to supply carbon dioxide to the water-containing material.

3. The fatigue crack propagation suppression method according to claim 1, characterized in that the fatigue crack propagation suppression sheet has a carbonic acid agent sealed inside that allows carbon dioxide to leak out in order to supply carbon dioxide to the water-containing material, and the carbon dioxide is supplied from the carbonic acid agent to the water-containing material.

4. The fatigue crack propagation suppression method according to claim 1, characterized in that the thickness of the water-containing material is set based on at least one of the replacement frequency of the fatigue crack propagation suppression sheet and the plate thickness of the metal base material.

5. A coating film is formed on the metal base material at the location where the fatigue crack has occurred or is likely to occur. The method for suppressing the propagation of fatigue cracks according to claim 1, characterized in that the fatigue crack propagation suppression sheet is placed on the surface of the coating film.

6. In the case where the fatigue crack penetrates the metal base material from one surface to the other, The method for suppressing the progression of a fatigue crack according to claim 1, characterized in that the fatigue crack propagation suppression sheet is placed in the opening of the fatigue crack on the other surface, and the opening of the fatigue crack on the one surface is made in a state in which air can enter and exit.

7. The method for suppressing the propagation of fatigue cracks according to claim 6, characterized in that the opening of the fatigue crack on one of the aforementioned surfaces is partially covered with a non-permeable membrane material that does not allow for airflow, or the entire opening is covered with a permeable membrane material that does allow for airflow.

8. In the case where the fatigue crack penetrates the metal base material from one surface to the other, A fatigue crack propagation suppression sheet, in which the water-containing material is covered with the drying prevention material, is placed at the opening of the fatigue crack on the other surface. The method for suppressing the propagation of a fatigue crack according to claim 2, characterized in that a carbonic acid agent, which contains carbon dioxide that can leak out to the outside, is placed in the opening of the fatigue crack on one of the aforementioned surfaces.

9. In the case where the fatigue crack penetrates the metal base material from one surface to the other, The method for suppressing the progression of a fatigue crack according to claim 2, characterized in that the fatigue crack propagation suppression sheet having a ventilation channel is placed at the opening of the fatigue crack on the other surface, and the entire opening of the fatigue crack on the one surface is covered with a non-permeable membrane material that does not allow for airflow, or the fatigue crack propagation suppression sheet having a ventilation channel is placed at the opening of the fatigue crack on the one surface and at the opening of the fatigue crack on the other surface, respectively.

10. The fatigue crack propagation suppression method according to claim 3, characterized in that, when the fatigue crack penetrates the metal base material from one surface to the other surface, the fatigue crack propagation suppression sheet having the carbonic acid is placed at the opening of the fatigue crack on the other surface, and the entire opening of the fatigue crack on one surface is covered with a non-permeable membrane material that does not allow for airflow, or the fatigue crack propagation suppression sheet having the carbonic acid is placed at the opening of the fatigue crack on one surface and the opening of the fatigue crack on the other surface, respectively.

11. The method for suppressing the propagation of fatigue cracks according to claim 1, characterized in that the fatigue crack propagation suppression sheet placed on the metal base material is heated.

12. The method for suppressing the progression of fatigue cracks according to claim 1, characterized in that the electrochemical circuit formed by the arrangement of the fatigue crack propagation suppression sheet suppresses the occurrence of rust in the metal base material at locations where fatigue cracks have occurred or are likely to occur, and in the surrounding areas where fatigue cracks have not occurred or are not likely to occur.

13. A water-containing material comprising an electrolyte having at least bicarbonate ions and calcium ions, An electrode material laminated on the outside of the aforementioned water-containing material, The structure comprises a connecting material used to connect the metal base material and the electrode material in order to apply a potential with the metal base material as the cathode, A fatigue crack propagation suppression sheet characterized in that the moisture-containing material is attached to a location in the metal base material where fatigue cracks have occurred or are likely to occur, in contact with the location, and the moisture-containing material is covered with a drying prevention material that also applies pressure, thereby forming an electrochemical circuit including the metal base material, the moisture-containing material, the electrode material and the connecting material, so that when fatigue cracks occur, electrodeposited deposits are formed in the fatigue cracks, and the propagation of the fatigue cracks is suppressed by the wedge effect of the electrodeposited deposits.

14. The fatigue crack propagation suppression sheet according to claim 13, characterized in that the moisture content of the water-containing material is 50% or more.

15. The fatigue crack propagation suppression sheet according to claim 14, characterized in that it has a ventilation channel for introducing air to supply carbon dioxide to the water-containing material.

16. The fatigue crack propagation suppression sheet according to claim 15, characterized in that the drying prevention material is provided with a plurality of micropores that allow gaseous carbon dioxide molecules and water vapor to pass through but not liquid water molecules to pass through as ventilation channels.

17. The fatigue crack propagation suppression sheet according to claim 15, characterized in that the ventilation passages include a plurality of through holes that penetrate the water-containing material and the electrode material in the thickness direction.

18. The fatigue crack propagation suppression sheet according to claim 17, characterized in that the through-hole is elongated in shape.

19. The fatigue crack propagation suppression sheet according to claim 17, characterized in that the water-containing material and the electrode material are each aggregates of a plurality of small pieces, and gaps as ventilation passages are formed by arranging the small pieces apart from each other.

20. The fatigue crack propagation suppression sheet according to claim 17 or 18, characterized in that a side drying prevention material is provided on the side surface of the water-containing material to suppress leakage of water and water vapor from the water-containing material to the outside.

21. The fatigue crack propagation suppression sheet according to claim 14, further comprising a carbonic acid agent sealed in such a way that carbon dioxide can leak out to the outside in order to supply carbon dioxide to the water-containing material, and a carbonic acid agent housing having an opening and housing the carbonic acid agent.

22. The fatigue crack propagation suppression sheet according to claim 21, characterized in that the water-containing material is provided with a plurality of elongated through-holes that penetrate in the thickness direction, and the carbonate is contained in the carbonate container arranged in the through-holes.

23. The fatigue crack propagation suppression sheet according to claim 21, characterized in that the water-containing material and the electrode material are each aggregates of a plurality of small pieces, gaps are formed by arranging the small pieces apart from each other, and the carbonate is contained in the carbonate container arranged in the gaps.

24. The fatigue crack propagation suppression sheet according to claim 21, characterized in that the carbonate contains an electrolyte.

25. The fatigue crack propagation suppression sheet according to claim 21, characterized in that the opening of the carbonate housing is provided with an opening area variable material for adjusting the opening area, or a gas permeable membrane material that covers the entire opening.

26. The aforementioned drying prevention material is a magnetic sheet having magnetic force and flexibility. The fatigue crack propagation suppression sheet according to claim 15, characterized in that when the magnet sheet is attached to the metal base material by the magnetic force, a gap that serves as a ventilation passage is formed between the magnet sheet and the metal base material.

27. The fatigue crack propagation suppression sheet according to claim 13, characterized in that the water-containing material is in the form of a gel, and the gel-like water-containing material is supported by a flexible support.

28. The electrode material is a galvanic anode composed of a metal having a greater ionization tendency than the metal matrix, The fatigue crack propagation suppression sheet according to claim 13, characterized in that the connecting material is a conductor connecting the galvanic anode and the metal base material, or an extension extending from the galvanic anode and in contact with the metal base material.

29. The electrode material is a durable electrode made of a corrosion-resistant metal. The fatigue crack propagation suppression sheet according to claim 13, characterized in that the connecting material comprises a conductor connecting the durable electrode and the metal base material, and a DC power supply provided in the middle of the conductor with the cathode on the metal base material side.

30. The fatigue crack propagation suppression sheet according to claim 14, characterized in that, as a heating material for the fatigue crack, it is provided with electric heating wires arranged in a planar manner on the inside, surface, or back surface of the drying prevention material, or a sheet-shaped heater covering the drying prevention material.

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