A method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response

Abstract

This invention discloses a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response, relating to the field of non-destructive testing technology for wheels. Addressing the shortcomings of existing non-destructive testing methods in accurately characterizing early-closing fatigue cracks in wheels, insufficient depiction of physical field features under complex crack scenarios, and poor adaptability to dynamic loads, this method comprehensively covers typical fatigue crack morphologies and service conditions of wheels by constructing a composite angular crack defect model, analyzing the influence of crack filling, establishing a semi-contact weak conductivity defect simulation model, and a load-crack thermal response coupling model. The method accurately recreates the eddy current distribution and heat conduction process around the crack, clarifies the correspondence between key crack parameters and electromagnetic thermal response, significantly improves the detectability and parameter accuracy of early-closing cracks, and is applicable to fatigue damage detection of rail transit wheels, and can also be extended to the field of fatigue crack detection of similar metal components.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology for wheels, and in particular to a method and system for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response. Background Technology

[0002] With the rapid development of high-speed and heavy-haul railways, the problem of wheel-rail rolling contact fatigue is becoming increasingly prominent. Early and accurate detection of wheel fatigue cracks has become a core requirement for ensuring railway operational safety. Existing non-destructive testing methods for wheels mainly include ultrasonic testing, magnetic particle testing, and eddy current testing. However, these methods have the following drawbacks when dealing with early closed fatigue cracks: First, existing non-destructive testing methods for wheels are difficult to accurately characterize early closed fatigue cracks and do not fully consider the influence of crack geometry (such as "L"-shaped composite angles) and internal filling materials (rust / air) on electromagnetic and thermal distribution, resulting in insufficient targeting and accuracy of crack detection. Second, the weak conductivity formed by local contact on the sidewalls of fatigue cracks makes the eddy current and temperature distribution complex. Existing models cannot effectively characterize the physical field characteristics under this contact state, making it difficult to measure parameters such as crack depth. Furthermore, the stress-conductivity-Joule heating-temperature coupling relationship of unsteady-state fatigue cracks under load is unclear, and there is a lack of models that can reflect this dynamic process, making it difficult to adapt to the crack detection needs of wheels under load in actual operation.

[0003] Therefore, there is an urgent need for a method and system for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response to solve the existing technical problems. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response.

[0005] In a first aspect, embodiments of the present invention provide a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response, wherein...

[0006] A method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response includes:

[0007] A composite angular crack defect model was constructed, and the composite angular crack defect model was simulated to analyze the heat conduction process and excitation field distribution of the crack in inductive thermal imaging detection, and to obtain the quantitative detection law of vertical crack depth and the temperature response characteristics of composite crack.

[0008] Two models, air-filled open crack and rust-filled closed crack, were constructed. Simulations were performed on these two models to obtain the influence characteristics of the filling material inside the crack on the detection effect.

[0009] A semi-contact type weak conductivity defect model is constructed, and the semi-contact type weak conductivity defect model is simulated to obtain the weak conductivity characteristics formed by local contact on the sidewall of fatigue crack.

[0010] A load-crack thermal response coupling model was constructed, and the model was simulated to obtain the univariate functional relationship between the peak value of the thermal response in the crack region and the axial stress under load conditions.

[0011] Furthermore, the method for constructing a composite angular crack defect model includes: combining the "L"-shaped hidden damage characteristics of rolling contact fatigue cracks in the rail transit field, equating the "L"-shaped hidden damage characteristics to a composite angular defect composed of oblique cracks and planar cracks, establishing a finite element model of the composite angular crack defect, and simulating and analyzing the influence of defect depth, angle, and length on the heat conduction process and excitation field distribution in inductive thermal imaging detection.

[0012] Furthermore, in the process of constructing the composite angle crack defect model, based on the typical vertical crack eddy current and thermal field distribution characteristics, the angle of the oblique crack, the depth of the planar crack, the transverse length, and the distance between each crack are set to ensure that the heat distribution does not affect each other.

[0013] Furthermore, during the construction of the composite angular crack defect model, the magnitude, frequency, lift-off distance, and heating duration of the excitation current are set, and the temperature change data within a preset time is recorded by a camera.

[0014] Furthermore, two models, air-filled open cracks and rust-filled closed cracks, were constructed to obtain the influence characteristics of the filling material inside the crack on the detection effect. Specific methods include:

[0015] The parameters of crack length and the angle between the crack and the surface of the specimen were set to construct two models: an air-open crack and a rust-filled closed crack. The eddy current distribution and temperature field characteristics of the two models were analyzed.

[0016] The eddy current distribution and temperature field characteristics were verified by experiments. The specific experimental methods included: taking the test block sample from the wheel rim, artificially processing oblique cracks with the same size as the simulation model, simulating closed cracks by rusting the interior of a set of open cracks using chemical methods, conducting experiments with the same excitation parameters as the simulation, recording the temperature and its derivative curves of characteristic points on the surface of the test block, and comparing and analyzing the differences in the first-order temperature response trend and eddy current density distribution between the initial heating stage and the continuous heating stage.

[0017] Furthermore, the method for constructing a semi-contact type weak conductivity defect model includes: for the weak conductivity characteristics formed by local contact on the crack sidewall, establishing a finite element model covering three scenarios: contact depth > skin depth, defect depth > skin depth > contact depth, and skin depth > defect depth, and analyzing the influence of local contact on eddy current distribution and heat conduction.

[0018] Furthermore, the simulation model of the semi-contact type weak conductivity defect is based on one-dimensional thermal conductivity theory. Ignoring lateral conduction, the expression for the upper surface temperature is:

[0019]

[0020] Where x1 represents the horizontal projection of the upper end of the point contact, x2 represents the horizontal projection of the lower end of the point contact, x3 represents the horizontal projection of the deepest point of the diagonal crack, t is time, α is the thermal diffusivity, ρ, C p , where k represents the material density, specific heat capacity, and thermal conductivity, respectively.

[0021] Furthermore, a coupled model of load and crack thermal response is constructed to obtain the univariate functional relationship between the peak thermal response of the crack region and the axial stress under load conditions. Specific methods include:

[0022] When a load is applied to a material, the electrical conductivity of the material is correlated with the temperature change amplitude using Hooke's law, piezoresistive effect, Joule's law, specific heat formula, and radiation law.

[0023] The force change of the specimen under static load was calculated using the Hollomon model. The resistivity change of the metallic material under axial tension is given by the formula... Characterization, in which, The initial resistivity, This is the change in resistivity caused by stress;

[0024] Based on the relationship between the change in heat and the change in temperature, and the relationship between Joule heat, eddy current density, and electric field strength, the univariate functional relationship between peak temperature and axial stress is finally obtained.

[0025] Furthermore, the relationship between the change in heat and the change in temperature is expressed as follows: ,in, For changes in heat, For specific heat capacity, For quality, The peak value of the thermal response in a specific direction. The initial temperature is given; the Joule heat is proportional to the eddy current density and the electric field strength.

[0026] Secondly, the present invention also discloses an electronic device, comprising:

[0027] One or more processors;

[0028] Memory, used to store one or more programs;

[0029] When the one or more programs are executed by the one or more processors, the one or more processors implement the method.

[0030] This invention discloses a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response. Addressing the shortcomings of existing non-destructive testing methods, such as difficulty in accurately characterizing early-closing fatigue cracks in wheels, insufficient depiction of physical field features under complex crack scenarios, and poor adaptability to dynamic loads, this method comprehensively covers typical fatigue crack morphologies and service conditions in wheels by constructing a composite angular crack defect model, analyzing the impact of crack filling, establishing a semi-contact weak conductivity defect simulation model, and a load-crack thermal response coupling model. The method accurately recreates the eddy current distribution and heat conduction process around the crack, clarifies the correspondence between key crack parameters and electromagnetic thermal response, significantly improves the detectability and parameter accuracy of early-closing cracks, and is applicable to fatigue damage detection of rail transit wheels. It can also be extended to the field of fatigue crack detection of similar metal components.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Comprehensive model coverage: The constructed composite angle, different filling types, semi-contact weak conductivity and load coupling related defect models comprehensively cover the typical morphology and service state of wheel fatigue cracks, accurately restore the eddy current distribution and heat conduction process around the crack, and fill the gap in the existing models for representing complex crack scenarios.

[0033] 2. Improved accuracy: The correspondence between crack geometry parameters, filling material, contact state, load conditions and electromagnetic thermal response has been clarified, providing reliable theoretical support for the quantitative assessment of fatigue cracks and significantly improving the detectability and parameter accuracy of early closed cracks.

[0034] 3. Strong engineering applicability: The model is based on the eddy current pulse thermal response principle and is highly compatible with actual detection technology. It can directly provide a basis for the optimization of wheel fatigue crack non-destructive testing system, helping to meet the stringent requirements of high-speed and heavy-haul railways for wheel and rail safety testing. At the same time, it can be extended to the field of fatigue crack testing of similar metal components, with broad application prospects. Attached Figure Description

[0035] Figure 1 A flowchart illustrating a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response, provided in an embodiment of the present invention;

[0036] Figure 2This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0038] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0039] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0041] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0042] In the technical solution of this invention, the collection, storage, use, processing, transmission, provision, and disclosure of user personal information all comply with relevant laws and regulations and do not violate public order and good morals. The use of user data in this technical solution follows relevant national laws and regulations (e.g., the "Information Security Technology - Personal Information Security Specification"). For example: appropriate measures are taken for personal information access control; restrictions are imposed on the display of personal information; the purpose of using personal information does not exceed the scope of direct or reasonable association; and explicit identity targeting is eliminated when using personal information to avoid precisely locating a specific individual.

[0043] To address at least one of the technical problems existing in the aforementioned related technologies, this invention provides a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response.

[0044] This embodiment discloses a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response, such as... Figure 1 ,include:

[0045] S100. Construct a composite angle crack defect model, simulate the composite angle crack defect model, analyze the heat conduction process and excitation field distribution of the crack in inductive thermal imaging detection, and obtain the quantitative detection law of vertical crack depth and the temperature response characteristics of composite crack.

[0046] In this embodiment, the method for constructing a composite angular crack defect model includes: combining the "L"-shaped hidden damage characteristics of rolling contact fatigue cracks in the rail transit field, equating the "L"-shaped hidden damage characteristics to a composite angular defect composed of oblique cracks and planar cracks, establishing a finite element model of the composite angular crack defect, and simulating and analyzing the influence of defect depth, angle, and length on the heat conduction process and excitation field distribution in inductive thermal imaging detection.

[0047] Specifically, based on the eddy current and thermal field distribution characteristics of typical vertical cracks, and combined with the geometric morphology of rolling contact fatigue cracks in the rail transit field, the fatigue crack geometry is typically an "L"-shaped hidden defect. This "L"-shaped hidden defect is equated to a composite angular defect composed of oblique and planar cracks, and a finite element model of the composite angular crack defect is established. Simulation studies were conducted on the effects of defect depth, angle, and length, analyzing the heat conduction process and excitation field distribution of the crack defect in the induction thermal imaging nondestructive testing method. A simulation experiment was carried out to quantitatively detect the depth of vertical cracks. Simulation studies of quantitative analysis of Notch-type defects using COMSOL software were conducted, extracting and comparing the side temperature and eddy current distribution results of cracks with different depths (skin depth = 1 mm).

[0048] In this embodiment, during the construction of the composite angle crack defect model, based on the typical vertical crack eddy current and thermal field distribution characteristics, the angle of the oblique crack, the depth of the planar crack, the transverse length, and the distance between each crack are set to ensure that the heat distribution does not affect each other.

[0049] For example, the model parameters are defined as follows: the angle of the oblique crack is set to be 0°-20°, the depth of the planar crack is 0.5mm-5mm, the transverse length is 30mm, and the distance between each crack is 25mm, to ensure that the heat distribution of each crack does not interfere with each other.

[0050] In this embodiment, during the construction of the composite angular crack defect model, the magnitude, frequency, lift-off distance, and heating duration of the excitation current are set, and the temperature change data within a preset time is recorded by a camera.

[0051] For example, the simulation parameters are set as follows: one long side of a rectangular coil is used for excitation, the excitation current is 350A, the frequency is 170KHz, the lift-off is 3mm, the heating time is 200ms, the recording time is 5s, and the camera shooting frame rate is 200fps.

[0052] The simulation results show that when the defect depth is within the skin depth (d<1mm), the eddy current distribution on the sidewall is mainly divided into two parts: increasing and decreasing, and the location of the maximum eddy current density corresponds to its crack length. When the defect depth is greater than twice the skin depth (d>2mm), the eddy current density distribution can be divided into three parts along its longitudinal extension, with a relatively stable region before reaching the maximum eddy current density. For composite cracks, the smaller the angle of the oblique crack, the higher the tip temperature and the more obvious the temperature gradient. The maximum frequency of a planar crack is generally linearly related to the depth; the shallower the depth, the larger the absolute value of the maximum phase. The heating rate of the oblique crack region in an L-crack is similar to that of a single oblique crack.

[0053] To better understand this embodiment, we will take the construction and verification of a composite angular crack defect model as an example:

[0054] First, test blocks were prepared: metal test blocks containing vertical cracks, oblique cracks (angles of 5°, 10°, 15°, 20°), and L-shaped composite cracks were processed, with crack depths of 0.5 mm, 1.0 mm, 2.0 mm, 3.0 mm, and 5.0 mm, respectively, a transverse length of 30 mm, and a crack spacing of 25 mm.

[0055] Then, the simulation settings were performed: a finite element model with the same size as the test block was established using COMSOL software, and the excitation current was set to 350A, the frequency to 170KHz, the lift-off time to 3mm, the heating time to 200ms, and the recording time to 5s.

[0056] Next, experimental tests were conducted: the test block was tested using an eddy current pulse thermal imaging detection system with a camera frame rate of 200fps to collect surface temperature data of the test block.

[0057] Finally, the results were analyzed: the eddy current distribution and temperature response curves obtained from simulation and experiment were compared to verify the accuracy of the model. The results showed that the error between the simulation and experimental data was less than 5%, indicating that the model can accurately characterize the electromagnetic and thermal distribution characteristics of the composite angle crack.

[0058] S200. Construct two models: an air-filled open crack and a rust-filled closed crack. Simulate the two models to obtain the characteristics of the influence of the filling material inside the crack on the detection effect.

[0059] In this embodiment, to accurately characterize the influence of the filling material inside the crack on the detection effect, the present invention establishes two models: air-filled open cracks and rust-filled closed cracks. The study is conducted through a combination of simulation and experimentation, specifically including:

[0060] Simulation model construction: The parameters of crack length and the angle between the crack and the surface of the test block were set, and two models, one for an air-open crack and the other for a rust-filled closed crack, were constructed. The eddy current distribution and temperature field characteristics of the two models were analyzed.

[0061] Experimental verification was conducted: The eddy current distribution and temperature field characteristics were verified by experiments. The specific experimental methods included: taking the test block sample from the wheel rim, artificially processing oblique cracks with the same size as the simulation model, simulating closed cracks by rusting the inside of a set of open cracks using chemical methods, conducting experiments with the same excitation parameters as the simulation, recording the temperature and its derivative curves of characteristic points on the surface of the test block, and comparing and analyzing the differences in the first-order temperature response trend and eddy current density distribution between the initial heating stage and the continuous heating stage.

[0062] Simulation experiments show that the eddy current distribution of closed and open cracks exhibits both similarities and differences. The areas with the highest eddy current density are located on the side with the larger crack angle. Due to the weak electrical conductivity of the rust material, eddy currents flow through the area filling the closed crack, which differs significantly from that of the open crack. In the initial heating stage, the first-order temperature response trends of closed and open cracks are similar. However, as heating time continues, the temperature rise efficiency of the open crack is higher than that of the closed crack. This is because the air filling inside the open crack results in low thermal diffusion, hindering heat propagation into the material, leading to a higher surface temperature and a higher temperature rise efficiency.

[0063] To better understand this embodiment, examples of detection experiments for cracks with different filling types are given:

[0064] Preparation of test blocks: Two sets of oblique crack test blocks of the same size (2 mm in length and 20° in angle) were processed. One set was kept open (air-filled), and the other set was closed by chemical etching (rust-filled).

[0065] Test the test blocks: Use the same test parameters as S100 to test the two sets of test blocks and record the temperature change curves of surface feature points;

[0066] Results analysis: The temperature rise rate of the open crack is 0.8 K / ms, the temperature rise rate of the closed crack is 0.3 K / ms, and the peak eddy current density of the open crack is... The peak value of the eddy current density in the closed crack is The results are consistent with the model simulation results, verifying the model's ability to characterize cracks with different filling types.

[0067] S300. Construct a semi-contact type weak conductivity defect model and simulate the semi-contact type weak conductivity defect model to obtain the weak conductivity characteristics formed by local contact on the fatigue crack sidewall. In this embodiment, in order to study the influence of the closed stability state of the crack, the weak conductivity phenomenon caused by local contact and its induced eddy current distribution, heat conduction and defect response were studied. A finite element model was established in Comsol. In order to further study the eddy current-temperature distribution characteristics of the closed crack, the method of constructing the semi-contact type weak conductivity defect model includes: for the weak conductivity characteristics formed by local contact on the crack sidewall, establish a finite element model covering three scenarios: contact depth > skin depth, defect depth > skin depth > contact depth, and skin depth > defect depth, and analyze the influence of local contact on eddy current distribution and heat conduction.

[0068] In this embodiment, ignoring the difference in temperature accumulation between open and closed cracks during the heating period and disregarding lateral conduction, according to the one-dimensional thermal conductivity theory, the expression for the upper surface temperature within the range of x∈(x1,x2)U(x3,∞) is:

[0069]

[0070] Where x1 represents the horizontal projection of the upper end of the point contact, x2 represents the horizontal projection of the lower end of the point contact, x3 represents the horizontal projection of the deepest point of the diagonal crack, t is time, α is the thermal diffusivity, ρ, C p , where k represents the material density, specific heat capacity, and thermal conductivity, respectively.

[0071] Specifically, in S300 of this embodiment, the model scenario is first defined, and a finite element model is constructed based on COMSOL software, covering three typical scenarios: contact depth > skin depth, defect depth > skin depth > contact depth, and skin depth > defect depth. Then, the theoretical basis is analyzed. Ignoring the different temperature accumulation of open and closed cracks during the heating period and not considering lateral conduction, according to the one-dimensional thermal conductivity theory, within the range of x∈(x1, x2)∪(x3, ∞), where the intersection of the upper surface of the oblique crack is taken as the origin, the upper end of the point contact is X1 on the horizontal projection, the lower end of the point contact is X2 on the horizontal projection, and X3 represents the projection of the deepest part of the oblique crack in the horizontal direction to obtain the expression for the upper surface temperature. Finally, simulation analysis is performed: the eddy current distribution, heat conduction, and defect response characteristics under different contact scenarios are studied. The results show that after the skin depth increases, more eddies flow through the closed region, and the eddies no longer flow close to the geometric edge of the defect. There are high-density eddies flowing directly above the closed region, resulting in heat accumulation.

[0072] S400. Construct a load-crack thermal response coupling model, simulate the load-crack thermal response coupling model, and obtain the univariate functional relationship between the peak value of the thermal response in the crack region and the axial stress under load conditions.

[0073] In this embodiment, a coupled load and crack thermal response model is constructed to obtain the univariate functional relationship between the peak thermal response of the crack region and the axial stress under load conditions. The specific method includes:

[0074] When a load is applied to a material, the electrical conductivity of the material is correlated with the temperature change amplitude using Hooke's law, piezoresistive effect, Joule's law, specific heat formula, and radiation law.

[0075] The force change of the specimen under static load was calculated using the Hollomon model. The resistivity change of the metallic material under axial tension is given by the formula... Characterization, in which, The initial resistivity, This is the change in resistivity caused by stress;

[0076] Based on the relationship between the change in heat and the change in temperature, and the relationship between Joule heat, eddy current density, and electric field strength, the univariate functional relationship between peak temperature and axial stress is finally obtained.

[0077] Specifically, the theoretical derivation is carried out first: after a load is applied to the material, the material's conductivity is correlated with the amplitude of temperature change through Hooke's law (relationship between stress and strain), piezoresistive effect (relationship between strain and conductivity), Joule's law (relationship between conductivity and Joule heat), specific heat formula (relationship between Joule heat and temperature change), and radiation law (relationship between temperature and thermal response).

[0078] Then, model construction was performed: the Hollomon model was used to calculate the force change of the specimen under static load. The resistivity change of the metallic material under axial tension is given by the formula... Characterization, in which, The initial resistivity, This is the change in resistivity caused by stress;

[0079] Finally, the relationship is established: based on the expression relating the change in heat to the change in temperature (… ,in, For changes in heat, For specific heat capacity, For quality, The peak value of the thermal response in a specific direction. The initial temperature and Joule heat are proportional to the relationship between eddy current density and electric field strength, ultimately yielding the peak temperature. With axial stress The univariate functional relationship.

[0080] Specifically, taking crack detection experiments under load conditions as an example:

[0081] First, test block preparation was carried out: a test block of wheel rim material was selected, and a 2mm deep oblique crack was machined on it;

[0082] Then, loading and testing are carried out: axial stress of 0-500MPa is applied to the specimen using a tensile testing machine, and eddy current pulse thermal imaging system is used to detect it under different stress conditions;

[0083] Finally, the results were analyzed: Based on the established load-thermal response coupling model, the peak thermal response under different stresses was calculated and compared with the experimental data. The results showed that the peak thermal response increased linearly with increasing stress, and the error between the model prediction and the experimental value was less than 3%, indicating that the model can accurately reflect the thermal response characteristics of the crack under load conditions.

[0084] This embodiment discloses a method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response. By constructing a composite angular crack defect model, analyzing the crack filling effect, establishing a semi-contact weak conductivity defect simulation model, and a load-crack thermal response coupling model, it comprehensively covers typical fatigue crack morphologies and service conditions of wheels. The method disclosed in this invention accurately reproduces the eddy current distribution and heat conduction process around the crack, clarifies the correspondence between key crack parameters and electromagnetic thermal response, significantly improves the detectability and parameter accuracy of early-closing cracks, and is applicable to fatigue damage detection of rail transit wheels. It can also be extended to the field of fatigue crack detection of similar metal components.

[0085] Based on the same inventive concept, embodiments of the present invention also provide an electronic device. Figure 2This is a structural block diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 2 As shown, an embodiment of the present invention provides an electronic device including: one or more processors 101, a memory 102, and one or more I / O interfaces 103. The memory 102 stores one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement any of the model construction methods described in the above embodiments; the one or more I / O interfaces 103 are connected between the processor and the memory, configured to enable information interaction between the processor and the memory.

[0086] The processor 101 is a device with data processing capabilities, including but not limited to a central processing unit (CPU); the memory 102 is a device with data storage capabilities, including but not limited to random access memory (RAM, more specifically SDRAM, DDR, etc.), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and flash memory (FLASH); the I / O interface (read / write interface) 103 is connected between the processor 101 and the memory 102, and can realize information interaction between the processor 101 and the memory 102, including but not limited to a data bus (Bus).

[0087] In some embodiments, the processor 101, memory 102, and I / O interface 103 are interconnected via bus 104, and thus connected to other components of the computing device.

[0088] In some embodiments, the one or more processors 101 include a field-programmable gate array.

[0089] This invention also provides a computer-readable medium. The computer-readable medium stores a computer program, which, when executed by a processor, implements the steps of any of the model construction methods described in the above embodiments. The computer-readable storage medium can be volatile or non-volatile.

[0090] This invention also provides a computer program product, including computer-readable code, or a non-volatile computer-readable storage medium carrying computer-readable code. When the computer-readable code is run in the processor of an electronic device, the processor in the electronic device executes the above-described model building method.

[0091] Those skilled in the art will understand that all or some of the steps, systems, and apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software can be distributed on a computer-readable storage medium, which may include computer storage media (or non-transitory media) and communication media (or transient media).

[0092] As is known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable program instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), static random access memory (SRAM), flash memory or other memory technologies, portable compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, it is known to those skilled in the art that communication media typically contain computer-readable program instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0093] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0094] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.

[0095] The computer program product described herein can be implemented specifically through hardware, software, or a combination thereof. In one alternative embodiment, the computer program product is specifically embodied in a computer storage medium; in another alternative embodiment, the computer program product is specifically embodied in a software product, such as a software development kit (SDK), etc.

[0096] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0097] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0098] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0099] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction, which contains one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0100] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A method for constructing a fatigue crack quantity defect model based on eddy current pulse thermal response, characterized in that, include: A composite angular crack defect model was constructed, and the composite angular crack defect model was simulated to analyze the heat conduction process and excitation field distribution of the crack in inductive thermal imaging detection, and to obtain the quantitative detection law of vertical crack depth and the temperature response characteristics of composite crack. Two models, air-filled open crack and rust-filled closed crack, were constructed. Simulations were performed on these two models to obtain the influence characteristics of the filling material inside the crack on the detection effect. A semi-contact type weak conductivity defect model is constructed, and the semi-contact type weak conductivity defect model is simulated to obtain the weak conductivity characteristics formed by local contact on the sidewall of fatigue crack. The method for constructing a semi-contact type weak conductivity defect model includes: for the weak conductivity characteristics formed by local contact on the crack sidewall, establishing a finite element model covering three scenarios: contact depth > skin depth, defect depth > skin depth > contact depth, and skin depth > defect depth, and analyzing the influence of local contact on eddy current distribution and heat conduction. A coupled load-crack thermal response model is constructed, and simulation is performed on the coupled load-crack thermal response model to obtain the univariate functional relationship between the peak thermal response of the crack region and the axial stress under load conditions. The specific method for constructing the coupled load-crack thermal response model to obtain the univariate functional relationship between the peak thermal response of the crack region and the axial stress under load conditions includes: When a load is applied to a material, the electrical conductivity of the material is correlated with the temperature change amplitude using Hooke's law, piezoresistive effect, Joule's law, specific heat formula, and radiation law. The force change of the specimen under static load was calculated using the Hollomon model. The resistivity change of the metallic material under axial tension is given by the formula... Characterization, in which, The initial resistivity, This is the change in resistivity caused by stress; Based on the relationship between the change in heat and the change in temperature, and the relationship between Joule heat, eddy current density, and electric field strength, the univariate functional relationship between peak temperature and axial stress is finally obtained.

2. The model construction method as described in claim 1, characterized in that, The method for constructing a composite angular crack defect model includes: combining the "L"-shaped hidden damage characteristics of rolling contact fatigue cracks in the rail transit field, equating the "L"-shaped hidden damage characteristics to a composite angular defect composed of oblique cracks and planar cracks, establishing a finite element model of the composite angular crack defect, and simulating and analyzing the influence of defect depth, angle, and length on the heat conduction process and excitation field distribution in inductive thermal imaging detection.

3. The model construction method as described in claim 2, characterized in that, In the process of constructing the composite angle crack defect model, based on the typical vertical crack eddy current and thermal field distribution characteristics, the angle of the oblique crack, the depth of the planar crack, the transverse length, and the distance between each crack are set to ensure that the heat distribution does not affect each other.

4. The model construction method as described in claim 2, characterized in that, In the process of constructing a composite angular crack defect model, the magnitude, frequency, lift-off distance, and heating duration of the excitation current are set, and the temperature change data within a preset time is recorded by a camera.

5. The model construction method according to claim 1, characterized in that, Two models, air-filled open cracks and rust-filled closed cracks, were constructed to obtain the influence characteristics of the internal filling material on the detection effect. Specific methods included: The parameters of crack length and the angle between the crack and the surface of the specimen were set to construct two models: an air-open crack and a rust-filled closed crack. The eddy current distribution and temperature field characteristics of the two models were analyzed. The eddy current distribution and temperature field characteristics were verified by experiments. The specific experimental methods included: taking the test block sample from the wheel rim, artificially processing oblique cracks with the same size as the simulation model, simulating closed cracks by rusting the interior of a set of open cracks using chemical methods, conducting experiments with the same excitation parameters as the simulation, recording the temperature and its derivative curves of characteristic points on the surface of the test block, and comparing and analyzing the differences in the first-order temperature response trend and eddy current density distribution between the initial heating stage and the continuous heating stage.

6. The model construction method according to claim 1, characterized in that, The simulation model of the semi-contact type weak conductivity defect is based on one-dimensional thermal conductivity theory. When lateral conduction is ignored, the expression for the upper surface temperature is: ； Where x1 represents the horizontal projection of the upper end of the point contact, x2 represents the horizontal projection of the lower end of the point contact, x3 represents the horizontal projection of the deepest point of the diagonal crack, t is time, α is the thermal diffusivity, ρ, C p , where k represents the material density, specific heat capacity, and thermal conductivity, respectively.

7. The model construction method according to claim 1, characterized in that, The relationship between the change in heat and the change in temperature is expressed as follows: ,in, For changes in heat, For specific heat capacity, For quality, The peak value of the thermal response in a specific direction. The initial temperature is given; the Joule heat is proportional to the eddy current density and the electric field strength.

8. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the model building method as described in any one of claims 1 to 7.

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