Material damage detection method and device

Abstract

The present invention provides a material damage detection method and device, the method includes preparing a conductive layer on a material substrate, wherein when the surface of the material substrate is cracked, the conductive layer is cracked to the same extent; current is passed through the conductive layer in at least two different directions, and the change in the resistance value of the conductive layer in each direction is measured; according to the change in the resistance value in each direction, the crack size on the surface of the material substrate is calculated. The method and device realize efficient and high-precision detection of the fracture and damage of the surface of the material structure, and are suitable for a variety of detected material substrates and material substrate surfaces with complex structures and large areas.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a material damage detection method and device. Background Art

[0002] In order to ensure that the material can be used normally as a main component in various occasions, and to meet the requirements for the integrity of the material components or structures themselves, especially in aerospace applications, the integrity of the material structural parts directly affects the safety and reliability of the aircraft, and the structural integrity of the material needs to be monitored.

[0003] Currently, methods for testing the structural integrity of materials include fiber optic testing and strain gauge testing. Fiber optic testing requires embedding optical fibers within the material, which can create stress concentration areas within the material, affecting the integrity and continuity of the matrix and causing a decrease in the material's mechanical properties. Applying strain gauges can measure strain / stress at localized locations, but due to their size and lead-in method, they cannot cover the entire surface of the material. If a crack occurs, a strain gauge attached to that location will break and become ineffective. Summary of the Invention

[0004] (1) Technical issues to be solved

[0005] In response to the existing technical problems, the present invention provides a material damage detection method and device, which are used to at least partially solve the above technical problems.

[0006] (2) Technical solution

[0007] The present invention provides a material damage detection method, comprising: preparing a conductive layer on a material substrate, wherein when a crack occurs on the surface of the material substrate, the conductive layer also cracks to the same extent; passing a current through the conductive layer in at least two different directions, and measuring the change in the resistance value of the conductive layer in each direction; and calculating the crack size on the surface of the material substrate based on the change in the resistance value in each direction.

[0008] Optionally, a conductive layer is prepared on the material substrate, and the crack size on the surface of the material substrate is calculated according to the change in resistance value in each direction, including: according to the formula:

[0009]

[0010] Calculate the crack size on the material matrix surface, where ΔR1 is the resistance change of the conductive layer in the first direction, ΔR2 is the resistance change of the conductive layer in the second direction, ρ is the resistivity of the conductive layer, h is the thickness of the conductive layer, L is the length of the conductive layer in the first direction, w is the length of the conductive layer in the second direction, L2 is the crack length of the material matrix surface in the first direction, and w2 is the crack length of the material matrix surface in the second direction.

[0011] Optionally, a composite film layer comprising at least two conductive layers is prepared on a material substrate, wherein the conductive layers are insulated from each other, and the size of the crack on the surface of the material substrate is calculated based on the change in resistance value in each direction, including: calculating the crack size by selecting two conductive layers from the at least two conductive layers, and the calculation formula is:

[0012]

[0013] Where, ΔR 31 is the change in resistance of the first conductive layer in the first direction, ΔR 42 is the change in resistance of the second conductive layer in the second direction, ρ a is the resistivity of the first conductive layer, ρ b is the resistivity of the second conductive layer, h a is the thickness of the first conductive layer, h b is the thickness of the second conductive layer, w 12 is the length of the first conductive layer in the second direction, L 21 is the length of the second conductive layer in the first direction, L2 is the crack length of the material matrix surface in the first direction, and w2 is the crack length of the material matrix surface in the second direction.

[0014] Optionally, the composite film layer is prepared by combining one or more of sol-gel, surface spraying, surface coating and surface chemical reaction.

[0015] Optionally, passing current through the conductive layer in at least two different directions and measuring the change in resistance in each direction includes: passing current in a first direction of the conductive layer and measuring the change in resistance in the first direction of the conductive layer; after the measurement is completed, passing current in a second direction of the conductive layer and measuring the change in resistance in the second direction of the conductive layer.

[0016] Optionally, passing current through the conductive layer in at least two different directions and measuring the change in resistance in each direction includes: simultaneously passing current in a first direction of the first conductive layer and in a second direction of the second conductive layer, and measuring the change in resistance in the first direction of the first conductive layer and in the second direction of the second conductive layer; or, passing current in the first direction of the first conductive layer, measuring the change in resistance in the first direction of the first conductive layer, and after the measurement is completed, passing current in the second direction of the first conductive layer, and measuring the change in resistance in the second direction of the first conductive layer.

[0017] On the other hand, the present invention provides a material damage detection device, comprising: a sensor, wherein the sensor includes a conductive layer or a composite film layer containing at least two conductive layers, the conductive layer and the surface cracks of the material matrix are consistent, and an insulating layer is provided between the conductive layers of the composite film layer; a measuring unit, used to pass current through the conductive layer in at least two different directions and measure the change in resistance value of the conductive layer in each direction; and a calculation unit, used to calculate the crack size on the surface of the material matrix based on the change in resistance value in each direction.

[0018] Optionally, the material of the conductive layer is one conductive material or a mixture of multiple conductive materials, and the material of the insulating layer is one insulating material or a mixture of multiple insulating materials.

[0019] Optionally, an insulating protective layer is coated on the outside of the sensor.

[0020] Optionally, the thickness of the conductive layer, the insulating layer, and the insulating protective layer are all 1 nm to 1 mm, and the total thickness of the sensor and the insulating protective layer does not exceed 1 mm.

[0021] (3) Beneficial effects

[0022] The present invention provides a material damage detection method, which comprises preparing a conductive layer on a material substrate, passing current through the conductive layer from different directions, detecting resistance changes in each direction, and then calculating the fracture size corresponding to the resistance change caused by the same fracture in the conductive layer as in the material substrate. The calculation is simple and efficient, and high-precision detection of fracture and damage on the surface of a material structure is achieved.

[0023] The device also provides a material damage detection device with a small size, light weight, and simple structure. It is suitable for a variety of materials and complex, large-area surfaces, and is particularly suitable for applications where volume and weight requirements are stringent. Furthermore, while covering the entire surface of the material, the device requires fewer leads, resolving the issues of existing detection devices with numerous leads and failure due to damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A block diagram of a detection device according to an embodiment of the present invention is schematically shown;

[0025] Figure 2 The schematic diagram of the sensor structure of the embodiment of the present invention is shown;

[0026] Figure 3 Schematically shows Figure 2 AA sectional view;

[0027] Figure 4 Schematically shows Figure 2 BB cross-sectional view;

[0028] Figure 5 The following schematically shows a flow chart of a detection method provided by an embodiment of the present invention;

[0029] Figure 6 A schematic diagram of a sensor structure at a fractured portion of a material matrix according to an embodiment of the present invention is shown;

[0030] Figure 7 A schematic diagram showing the distribution area of ​​resistance values ​​at a rupture point of a sensor according to an embodiment of the present invention is shown;

[0031] Figure 8 Schematically shows Figure 6 CC sectional view;

[0032] Figure 9 Schematically shows Figure 6 DD section view.

[0033] [Description of Reference Numerals]

[0034] 1-Material matrix;

[0035] 20-composite film layer;

[0036] 21-the first conductive layer in the composite film layer;

[0037] 22-Insulating layer in the composite film layer;

[0038] 23-the second conductive layer in the composite film layer;

[0039] 30-Cracks in the composite film layer caused by cracks in the material substrate;

[0040] 31-Cracks in the first conductive layer caused by cracks in the material matrix;

[0041] 32-Cracks in the insulating layer caused by cracks in the material matrix;

[0042] 33-Cracks in the second conductive layer caused by cracks in the material matrix;

[0043] 100-Material damage detection device;

[0044] 110-Sensor;

[0045] 120- measuring unit;

[0046] 130-arithmetic unit. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0048] Figure 1The block diagram of the detection device according to the embodiment of the present invention is schematically shown.

[0049] like Figure 1 As shown, an embodiment of the present invention provides a material damage detection device, the device 100 includes: a sensor 110, including a conductive layer or a composite film layer containing at least two conductive layers, the conductive layer and the surface rupture of the material matrix are consistent, and an insulating layer is provided between the conductive layers of the composite film layer.

[0050] Figure 2 The schematic diagram of the sensor structure of the first embodiment of the present invention is shown; Figure 3 Schematically shows Figure 2 AA sectional view; Figure 4 Schematically shows Figure 2 BB sectional view; Figure 2-Figure 4 As shown, a composite film layer 20 for detecting fracture conditions is provided on the material substrate 1 .

[0051] According to an embodiment of the present invention, the thickness of the composite film layer 20 does not exceed 1 mm and can be composed of at least three film layers, each of which has a thickness ranging from approximately 1 nm to 1 mm, namely a conductive layer 21 for detecting fractures in the x-direction, a conductive layer 23 for detecting fractures in the y-direction, and an insulating layer 22 for ensuring that the two are not conductive.

[0052] The conductive layers 21 and 23 are made of conductive materials, such as a mixture of one or more metals, carbon nanotubes, etc. The insulating layer 22 is made of insulating materials, such as oxides, nitrides, or a mixture of one or more non-metallic insulating materials.

[0053] According to an embodiment of the present invention, to prevent failure of the composite film layer 20, one or more protective layers made of insulating material can be formed on the outermost layer of the conductive layer 23. Damage refers to rupture damage, such as cracks or spalling. If a crack occurs, due to the very small thickness of the composite film layer of the present invention, it can be considered to have occurred simultaneously. If spalling occurs, the composite film layer will naturally spall at that location, creating a void in the composite film layer at that location, resulting in a change in resistance. For a strain gauge, similar damage will cause the metal wire of the strain gauge to break, causing it to fail. Even if a protective layer is added to the strain gauge, the impact on small cracks is negligible, but it also means that the tiny crack may not be detected. For large cracks or spalling, the broken metal wire renders the strain gauge ineffective. The material damage detection device of the present invention does not contain a metal wire, and the detection mechanisms of the two are different, so this will not cause failure. Furthermore, the insulating protective layer prevents the unsafe conditions caused by direct exposure of the outermost conductive layer to air and the impact of the external environment on the detection of the outermost conductive layer, thereby increasing the service life of the material damage detection device of the present invention.

[0054] In addition, the material damage detection device of the present invention can cover the entire surface of the material substrate to be tested. If a conductive film is manufactured using a process similar to spray painting, it is entirely feasible to cover the entire tested area.

[0055] According to an embodiment of the present invention, in actual application, due to the limitations of the manufacturing process and the actual material and shape of the object to be measured, it may be necessary to cover the entire surface in a splicing manner. However, the size of each sub-area is not limited and is mainly limited by the manufacturing process. For example, in the spraying and painting methods, the size is not limited, while in the magnetron sputtering method, the maximum size is limited by the size of the magnetron target. Thin films on different areas can be combined in series / parallel and can be regarded as the same film. Separate leads can also be used for detection. When separate leads are used, the location of the rupture can be located more accurately, but the number of leads is increased. Even so, the number of leads is much smaller than that of the strain gauge method.

[0056] While strain gauges can be made large, they can be considered a single, bent wire. Even within the area where they are attached, they have blind spots and cannot cover the entire surface. This solution eliminates this issue, as the film can cover the entire surface. Furthermore, strain gauges are more suitable for flat surfaces. They are less suitable for non-flat areas, especially those with significant curvature. This solution is unaffected, allowing testing on any surface.

[0057] Regarding the number of leads, in the traditional strain gauge solution, ordinary strain gauges require two pins to lead out the signal. Due to the small coverage area, when a large area needs to be measured, multiple strain gauges are required, and the number of leads increases dramatically. The device in the embodiment of the present invention can be regarded as a surface resistor, using a layer or multiple layers of film to directly cover the measured area, which can be large or small, depending on the measured area. Regardless of the size of the area, only two lead points need to be set in the detection direction to measure the size of the resistance value in the corresponding direction. Therefore, in terms of coverage area and number of leads, it is significantly better than ordinary strain gauges. When measuring large areas, due to the size of the strain gauge itself, an array layout must be adopted, and it must be discretely arranged in the measured area, not continuously measured. If the rupture occurs in the blank area between the strain gauges, the rupture cannot be detected, and the detection device in the embodiment of the present invention has full coverage and will not miss the rupture.

[0058] The measuring unit 120 is configured to pass current through the conductive layer in at least two different directions and measure a change in resistance of the conductive layer in each direction.

[0059] The calculation unit 130 is used to calculate the crack size on the surface of the material matrix according to the change in the resistance value in each direction. The calculation method can adopt the detection method described in the following embodiment, for example.

[0060] Figure 5 The flowchart of the detection method according to the embodiment of the present invention is schematically shown.

[0061] like Figure 5 As shown, the material damage detection method includes:

[0062] S1, preparing a conductive layer on a material substrate, wherein when cracks occur on the surface of the material substrate, the conductive layer also cracks to the same extent.

[0063] According to an embodiment of the present invention, taking two conductive layers as an example, Figure 3 A conductive layer 21 is formed on the material substrate 1, an insulating layer 22 is formed on the conductive layer 21, and a conductive layer 23 is formed on the insulating layer 22. Each layer of the composite film 20 can be formed by one or more methods including sol-gel, surface spraying, surface coating, or surface chemical reaction.

[0064] According to an embodiment of the present invention, the bottommost conductive layer 21 of the composite film layer 20 is insulated from the material matrix 1. If the material matrix 1 is a conductor, insulation treatment must be performed between the two, such as adding an insulating layer.

[0065] Since the composite film layer 20 is tightly attached to the material matrix 1 and the thickness of the composite film layer is very small, when fatigue cracks appear in the material matrix 1, since the thickness of the film layer is at the micro-nano level and very thin, it is negligible relative to the size of the material matrix. The composite film layer 20 will also have the same crack 30 at the same position, and each layer will also have the same rupture, that is, the distribution of rupture 31, rupture 32, and rupture 33 in each layer is the same size.

[0066] In other embodiments of the present invention, a conductive layer may be prepared on a material substrate to detect cracks in the material substrate. The preparation method may also be one or more of sol-gel, surface spraying, surface coating, or surface chemical reaction. The preparation of a conductive layer on a material substrate for detecting cracks in the material substrate, with the exception of the number of conductive layers being different from that when at least two conductive layers are prepared for detecting cracks in the material substrate, other operations to meet detection needs or extend product life, such as insulation treatment or preparation of a protective layer, are the same as those for the preparation of at least two conductive layers for detecting cracks in the material substrate, and are not further described here.

[0067] S2, passing current through the conductive layer in at least two different directions, and measuring the change in resistance of the conductive layer in each direction.

[0068] According to an embodiment of the present invention, to detect the resistance of a conductive layer, for example, a lead point is set at each end of conductive layer 21 in the x-direction, and a lead point is set at each end of conductive layer 23 in the y-direction. Current flows in the x-direction through conductive layer 21, and current flows in the y-direction through conductive layer 23. The x- and y-directions herein refer to the directions of material fracture to be detected and can be perpendicular to each other or at other angles. To facilitate explanation of the measurement principle, the x-direction is assumed to be horizontal, with positive values ​​to the right, and the y-direction is assumed to be perpendicular to the x-direction and positive values ​​to the upward direction.

[0069] According to an embodiment of the present invention, Figure 4 As shown, the crack 30 will cause the resistance value of each conductive layer in the composite film layer 20 to change. The size of the crack 30 can be determined by detecting the change in the resistance value.

[0070] According to embodiments of the present invention, a single conductive layer can actually measure cracks, but detection must be performed in both the x and y directions (or, depending on the actual use case, more directions). Simultaneous detection cannot be performed simultaneously, as simultaneous detection would interfere with each other. Multiple conductive layers can avoid this interference. Specifically, if two conductive layers are used, detection can be performed simultaneously in the x and y directions, respectively, without affecting each other. The second layer can also serve as a redundant detection layer, improving reliability. If more conductive layers are used, detection can be performed simultaneously in more directions, also serving as a redundant detection layer, improving reliability.

[0071] In addition, if different materials are used in each layer, the sensitivity to cracks may be slightly different. According to the occurrence of cracks, the layout can be arranged according to the development process of cracks from small to large, which can more effectively monitor the occurrence and development of cracks.

[0072] S3, calculate the crack size on the surface of the material matrix according to the change in resistance value in each direction.

[0073] According to an embodiment of the present invention, the structure of the conductive layer 21 is as follows: Figure 6 、 Figure 8 、 Figure 9 For example, if its length is L, width is w, and thickness is h, then when there is no break 31, its resistance value R in the x direction is:

[0074]

[0075] Here, ρ is the resistivity of the conductive layer 21 .

[0076] The crack 31 may be of any shape. To explain the measurement principle, it is assumed that the crack 31 is rectangular. When the crack 31 exists, its size is L2×w2. The resistance of the conductive layer 21 can be calculated as Figure 7The method shown is divided into equivalent resistances after 9 small resistors are connected in series and parallel, where L=L1+L2+L3 and w=w1+w2+w3.

[0077] In the x direction, the resistance R′ of the conductive layer 21 is equivalent to R1 (R 11 、R 12 、R 13 parallel), R2(R 21 、R 23 parallel), R3(R 31 、R 32 、R 33 Parallel connection) series connection:

[0078]

[0079] Similarly, Formula 1 can be changed to a similar form:

[0080]

[0081] R'2 is equivalent to R 21 With R 23 Parallel connection:

[0082]

[0083]

[0084] Substituting Equation 5 into Equation 2, we obtain:

[0085]

[0086] The change in resistance ΔR is:

[0087]

[0088] make Then we have:

[0089]

[0090] It can be seen that ΔR is related to the length L2 and width w2 of the rupture 31 .

[0091] The conductive layer 23 has the same size as the conductive layer 21, and the direction of the current inside it is the y direction. y Equivalent to R 1y (R 11 、R 21 、R 31 Parallel), R 2y (R 12 、R 22 、R 32 Parallel), R3y (R 13 、R 23 、R 33 Parallel connection) series connection:

[0092]

[0093] When the crack 33 exists, the resistance becomes R' y :

[0094]

[0095] R' 2y Equivalent to R 12 With R 32 Parallel connection:

[0096]

[0097] So:

[0098]

[0099] The change in resistance ΔR y for:

[0100]

[0101] make Then we have:

[0102]

[0103] Combining Formula 8 and Formula 14, we obtain a quadratic equation for the sizes of rupture 31 and rupture 33:

[0104]

[0105] Among them, K, K y , L, and w are known quantities, and solving this equation can give the dimensions L2 and w2 of the rupture 31.

[0106] According to an embodiment of the present invention, for example, a conductive layer may be prepared on a material substrate, and the crack size on the surface of the material substrate may be calculated based on the change in resistance value in each direction, including:

[0107] According to the formula:

[0108]

[0109] Calculate the crack size on the material matrix surface, where ΔR1 is the resistance change of the conductive layer in the first direction, ΔR2 is the resistance change of the conductive layer in the second direction, ρ is the resistivity of the conductive layer, h is the thickness of the conductive layer, L is the length of the conductive layer in the first direction, w is the length of the conductive layer in the second direction, L2 is the crack length of the material matrix surface in the first direction, and w2 is the crack length of the material matrix surface in the second direction.

[0110] Note that when deriving Formula 15, it is assumed that the material, thickness, length and width dimensions of the conductive layer 21 and the conductive layer 23 are the same (that is, ρ, h, L and w of the two are the same), but in fact, because ρ, h, L and w have no correlation with the crack size, even if ρ, h, L and w are different, substituting the actual values ​​into Formula 15 can also obtain the dimensions L2 and w2 of the crack 31.

[0111] According to an embodiment of the present invention, for example, a composite film layer comprising at least two conductive layers can be prepared on a material substrate, where the conductive layers are insulated from each other. Calculating the size of a crack on the surface of the material substrate based on the change in resistance values ​​in each direction includes:

[0112] Calculate the crack size by selecting two conductive layers from at least two conductive layers, and the calculation formula is:

[0113]

[0114] Where: ΔR 31 is the change in resistance of the first conductive layer in the first direction, ΔR 42 is the change in resistance of the second conductive layer in the second direction, ρ a is the resistivity of the first conductive layer, ρ b is the resistivity of the second conductive layer, h a is the thickness of the first conductive layer, h b is the thickness of the second conductive layer, w 12 is the length of the first conductive layer in the second direction, L 21 is the length of the second conductive layer in the first direction, L2 is the crack length of the material matrix surface in the first direction, and w2 is the crack length of the material matrix surface in the second direction.

[0115] Note: To illustrate the measurement principle, the x-direction in Equation 15 is assumed to be horizontal, with positive values ​​to the right, and the y-direction is perpendicular to the x-direction, with positive values ​​to the upward direction. Other angles can be calculated using coordinate transformation.

[0116] For non-rectangular ruptures 30 and ruptures at more than one location, further detailed calculations can be performed referring to the above derivation method to ultimately obtain the size of the rupture.

[0117] According to an embodiment of the present invention, the aforementioned detection method is an embodiment of two conductive layers, and a single conductive layer can also be used to detect the cracks of the material.

[0118] According to an embodiment of the present invention, a conductive layer 21 for detecting fracture conditions is plated on the material base 1 , and the conductive layer 21 is insulated from the material base 1 .

[0119] With reference to the aforementioned formulas 8, 14, and 15, by detecting the change in the resistance value R of the conductive layer 21 , it is possible to qualitatively determine whether there is a crack and the extent of the crack. The larger the ΔR, the larger the crack.

[0120] Alternatively, referring to the above formula, by measuring the resistance value R of the conductive layer 21 in the x direction x and the resistance value R in the y direction y The size of the rupture 30 can be calculated according to formula 15 based on the change in .

[0121] According to an embodiment of the present invention, the aforementioned embodiment of a single conductive layer is only used to illustrate that a single conductive layer can be used to detect the cracks of a material. The parts not described in detail refer to the aforementioned embodiment of two conductive layers and will not be repeated here, but this does not mean that the embodiment does not contain corresponding technical features.

[0122] The detection device disclosed in the present invention is suitable for detecting the cracks of various materials, including the detection of cracks in composite materials and the detection of cracks in other metal and non-metal materials, such as the detection of cracks in the surface of metal components and the detection of cracks in the surface of ceramic components.

[0123] In summary, the embodiments of the present invention provide a material damage detection method and device. By preparing a conductive layer on a material substrate, when a crack occurs on the surface of the material substrate, the conductive layer will produce the same degree of cracks; current is passed through the conductive layer in at least two different directions, and the change in the resistance value of the conductive layer in each direction is measured; based on the change in the resistance value in each direction, the crack size on the surface of the material substrate is calculated. Through this simple calculation method, the surface fracture and damage of the material structure can be detected efficiently and accurately. The material damage detection device proposed in the embodiment of the present invention has the characteristics of small size, light weight, and simple structure. It is suitable for a variety of material substrates to be detected and the surface of material substrates with complex structures and large areas. It is especially suitable for occasions with strict volume and weight requirements. In addition, the device can cover the entire surface of the material and has fewer leads, while solving the problems of many leads and damage failure of existing detection devices.

[0124] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A material damage detection method, characterized in that: Preparing a conductive layer on a material substrate, wherein when the surface of the material substrate is cracked, the conductive layer is cracked to the same extent; Passing current through the conductive layer in at least two different directions, and measuring the change in resistance value of the conductive layer in each direction; Calculating the crack size on the surface of the material matrix according to the change in the resistance value in each direction; When preparing a conductive layer on a material substrate, the method of calculating the crack size on the surface of the material substrate according to the change in the resistance value in each direction includes: According to the formula: Calculate the crack size of the material matrix surface, wherein ΔR1 is the resistance change of the conductive layer in the first direction, ΔR2 is the resistance change of the conductive layer in the second direction, ρ is the resistivity of the conductive layer, h is the thickness of the conductive layer, L is the length of the conductive layer in the first direction, w is the length of the conductive layer in the second direction, L2 is the crack length of the material matrix surface in the first direction, and w2 is the crack length of the material matrix surface in the second direction; When a composite film layer containing at least two conductive layers is prepared on a material substrate, the conductive layers are insulated from each other, and the size of the crack on the surface of the material substrate is calculated according to the change in the resistance value in each direction, including: The rupture size is calculated by selecting two of the at least two conductive layers and the calculation formula is: Among them, ΔR 31 is the change in resistance of the first conductive layer in the first direction, ΔR 42 is the change in resistance of the second conductive layer in the second direction, ρ a is the resistivity of the first conductive layer, ρ b is the resistivity of the second conductive layer, h a is the thickness of the first conductive layer, h b is the thickness of the second conductive layer, w 12 is the length of the first conductive layer in the second direction, L 21 is the length of the second conductive layer in the first direction, L2 is the fracture length of the material matrix surface in the first direction, and w2 is the fracture length of the material matrix surface in the second direction.

2. The material damage detection method according to claim 1, characterized in that: The composite film layer is prepared by combining one or more of the following methods: sol-gel, surface spraying, surface coating and surface chemical reaction.

3. The material damage detection method according to claim 1, characterized in that: The step of passing current through the conductive layer in at least two different directions and measuring the change in resistance value in each direction comprises: A current is passed through the conductive layer in a first direction to measure the resistance change of the conductive layer in the first direction. After the measurement is completed, a current is passed through the conductive layer in a second direction to measure the resistance change of the conductive layer in the second direction.

4. The material damage detection method according to claim 1, characterized in that: The step of passing current through the conductive layer in at least two different directions and measuring the change in resistance value in each direction comprises: Simultaneously, current is passed through the first conductive layer in a first direction and the second conductive layer in a second direction, and a resistance change amount of the first conductive layer in the first direction and the second conductive layer in the second direction is measured; Alternatively, a current is passed through the first conductive layer in a first direction to measure the resistance change of the first conductive layer in the first direction, and after the measurement is completed, a current is passed through the first conductive layer in a second direction to measure the resistance change of the first conductive layer in the second direction.

5. A material damage detection device, characterized in that: The material damage detection method for implementing any one of claims 1 to 4 comprises: A sensor, wherein the sensor comprises a conductive layer or a composite film layer comprising at least two conductive layers, wherein the conductive layer and the surface fracture of the material matrix are consistent, and an insulating layer is provided between the conductive layers of the composite film layer; A measuring unit, used for passing current through the conductive layer in at least two different directions to measure a change in resistance value of the conductive layer in each direction; The calculation unit is used to calculate the crack size on the surface of the material matrix according to the change amount of the resistance value in each direction.

6. The material damage detection device according to claim 5, characterized in that: An insulating protective layer is coated on the outside of the sensor.

7. The material damage detection device according to claim 6, characterized in that: The thickness of the conductive layer, the insulating layer and the insulating protective layer are all 1 nm to 1 mm, and the total thickness of the sensor and the insulating protective layer does not exceed 1 mm.

8. The material damage detection device according to claim 5, characterized in that: The material of the conductive layer is one conductive material or a mixture of multiple conductive materials, and the material of the insulating layer is one insulating material or a mixture of multiple insulating materials.

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