Fatigue crack propagation method and device, terminal and storage medium

Abstract

The invention provides a fatigue crack propagation method and device, a terminal and a storage medium. The method comprises the steps that a to-be-tested piece is tested through a crack propagation test, an elastic component and a non-elastic component under a load-displacement curve in the fatigue cyclic loading stage are determined respectively, and the to-be-tested piece is AM-NiTi SMAs; obtaining the thickness and width of the to-be-tested piece and the crack depth on the to-be-tested piece; and according to the thickness, the width, the crack depth on the to-be-tested piece, the elastic component and the inelastic component, respectively calculating J integrals of the to-be-tested piece corresponding to different crack propagation tests. According to the method, the calculation of fatigue crack propagation of AM-NiTi SMAs can be realized, and the problem that a method for fatigue crack propagation of AM-NiTi SMAs does not exist in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal fatigue crack analysis, and in particular to a fatigue crack extension method, device, terminal and storage medium. Background Art

[0002] Nickel-titanium (NiTi) shape memory alloys (SMAs) are smart materials with characteristic deformation responses to thermal stimuli. This deformation originates from a first-order displacement reversible solid-solid phase transition from high-temperature austenite to low-temperature martensite. Repeated cyclic phase transitions lead to the gradual accumulation of dislocations. The areas where austenite to martensite transformation does not occur reduce the ability of SMAs to deform according to external stimuli. Potential microcracks will eventually lead to failure or fracture after a sufficient number of cycles.

[0003] At present, the research on fatigue crack growth of NiTi SMAs prepared by traditional methods such as casting and rolling has been carried out, and the effects of reversible phase transformation, martensitic reorientation and thermo-mechanical coupling on fatigue and overload fracture of SMAs have been studied in detail. Compared with NiTi SMAs prepared by traditional methods, the microstructure of NiTi alloys produced by additive manufacturing (AM) is significantly different, which makes the reversible phase transformation, martensitic reorientation and thermo-mechanical coupling of SMAs very different, resulting in different fatigue crack growth behavior from that of NiTi SMAs prepared by traditional methods.

[0004] However, there are few studies on fatigue crack growth of AM-NiTi SMAs. Therefore, a reliable method is urgently needed to comprehensively describe the fatigue crack growth of AM-NiTi SMAs. Summary of the invention

[0005] The embodiments of the present invention provide a fatigue crack propagation method, device, terminal and storage medium to solve the problem that there is no method for fatigue crack propagation of AM-NiTi SMAs in the prior art.

[0006] In a first aspect, an embodiment of the present invention provides a method for fatigue crack propagation, comprising:

[0007] The test piece is tested by a crack extension test to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, respectively, and the test piece is AM-NiTi SMAs;

[0008] Obtaining the thickness and width of the test piece and the crack depth on the test piece;

[0009] The J integral of the test piece corresponding to different crack extension tests is calculated respectively according to the thickness, the width, the crack depth on the test piece, the elastic component and the inelastic component.

[0010] In a possible implementation, when the crack growth test is a mechanical fatigue crack growth test, determining the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage includes:

[0011] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0012] according to Determine the inelastic component of the load-displacement curve during the loading phase of a fatigue cycle;

[0013] in, represents the elastic component under the load-displacement curve during the loading stage of the fatigue cycle, P min It represents the initial load applied to the test piece at the beginning of a cycle of mechanical fatigue crack growth test, P max It represents the final load applied to the test piece at the end of one cycle in a mechanical fatigue crack growth test. represents the displacement variable corresponding to the fatigue cycle unloading process in the mechanical fatigue crack growth test, C represents the unloading elastic compliance during the fatigue cycle unloading, represents the inelastic component under the load-displacement curve during the fatigue cycle loading phase, P represents the current load, and v min represents the initial displacement of the test piece at the beginning of a cycle of the mechanical fatigue crack growth test, v max It represents the final displacement of the test piece at the end of one cycle of the mechanical fatigue crack growth test.

[0014] In a possible implementation, when the crack growth test is a driven fatigue crack growth test, determining the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage includes:

[0015] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0016] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0017] in, represents the elastic component under the load-displacement curve during the loading phase of the fatigue cycle, represents the inelastic component under the load-displacement curve during the loading stage of the fatigue cycle, P biasrepresents the constant load applied at the end of the fatigue crack growth test, represents the displacement variable corresponding to the fatigue cycle unloading process in the driven fatigue crack growth test, v min ' represents the initial displacement of the test piece at the beginning of a cycle of the driving fatigue crack growth test, v max ' represents the final displacement of the test piece at the end of one cycle of the driven fatigue crack growth test.

[0018] In a possible implementation, the calculating the J integral of the test piece corresponding to different crack extension tests according to the thickness, the width, the crack depth on the test piece, the elastic component and the inelastic component respectively includes:

[0019] Calculating the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece;

[0020] Calculate the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the elastic component;

[0021] Calculate the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the inelastic component;

[0022] The J integral of the test piece is calculated according to the elastic component of the J integral and the inelastic component of the J integral.

[0023] In a possible implementation, calculating the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece includes:

[0024] The difference between the width and the crack depth on the test piece is used as the length of the unbroken ligament on the test piece;

[0025] Calculating the J integral of the test piece according to the elastic component of the J integral and the inelastic component of the J integral includes:

[0026] The sum of the elastic component of the J integral and the inelastic component of the J integral is taken as the J integral of the test piece.

[0027] In a possible implementation, calculating the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the elastic component includes:

[0028] according to Calculating the elastic component of the J integral of the test piece;

[0029] Among them, Jel represents the elastic component of the J integral of the test piece, η el represents the first geometric correlation factor, A el It represents the corresponding elastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

[0030] In a possible implementation, calculating the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the inelastic component includes:

[0031] according to Calculating the elastic component of the J integral of the test piece;

[0032] Among them, J in represents the inelastic component of the J integral of the test piece, η in represents the second geometric correlation factor, A in It represents the corresponding inelastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

[0033] In a second aspect, an embodiment of the present invention provides a fatigue crack propagation device, comprising:

[0034] A calculation module, for testing a test piece by a crack extension test, and determining elastic components and inelastic components under a load-displacement curve in a fatigue cycle loading stage, respectively, wherein the test piece is AM-NiTi SMAs;

[0035] An acquisition module, used for acquiring the thickness and width of the test piece and the crack depth on the test piece;

[0036] The calculation module is further used to calculate the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth on the test piece, the elastic component and the inelastic component.

[0037] In a third aspect, an embodiment of the present invention provides a terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the fatigue crack propagation method as described in the first aspect or any possible implementation of the first aspect are implemented.

[0038] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the fatigue crack propagation method described in the first aspect or any possible implementation method of the first aspect are implemented.

[0039] The embodiment of the present invention provides a fatigue crack propagation method, device, terminal and storage medium. By adopting a crack propagation test to test a test piece, the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage are respectively determined, and the test piece is AM-NiTi SMAs; the thickness, width and crack depth of the test piece are obtained; according to the thickness, width, crack depth, elastic component and inelastic component of the test piece, the J integral of the test piece corresponding to different crack propagation tests is calculated respectively, so as to realize the calculation of fatigue crack propagation of AM-NiTi SMAs, and solve the problem that there is no method for fatigue crack propagation of AM-NiTi SMAs in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 is a flow chart of a method for fatigue crack propagation provided by an embodiment of the present invention;

[0042] Figure 2-1 is a schematic diagram of the load applied in a mechanical fatigue crack growth test provided by an embodiment of the present invention;

[0043] Figure 2-2 is a schematic diagram of the temperature used in the mechanical fatigue crack growth test provided by the embodiment of the present invention;

[0044] Figure 2-3 It is a load-displacement schematic diagram in a mechanical fatigue crack growth test provided by an embodiment of the present invention;

[0045] Figure 3-1 is a schematic diagram of a constant load applied in a driven fatigue crack growth experiment provided by an embodiment of the present invention;

[0046] Figure 3-2 is a schematic diagram of the temperature used in the driving fatigue crack growth experiment provided by an embodiment of the present invention;

[0047] Figure 3-3It is a load-displacement schematic diagram in a driving fatigue crack growth experiment provided by an embodiment of the present invention;

[0048] Figure 4 It is a structural schematic diagram of a fatigue crack extension device provided by an embodiment of the present invention;

[0049] Figure 5 is a schematic diagram of a terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0051] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0052] Figure 1 A flowchart of a method for fatigue crack propagation provided by an embodiment of the present invention is described in detail as follows:

[0053] Step 101 , a crack extension test is performed on a test piece to respectively determine an elastic component and an inelastic component under a load-displacement curve in a fatigue cycle loading stage, wherein the test piece is AM-NiTi SMAs.

[0054] The test piece tested in this embodiment is AM-NiTi SMAs. The microstructure of this smart material is significantly different from that of the current NiTi SMAs, resulting in significant differences in reversible phase transformation, Martensitic reorientation and thermal-mechanical coupling, which causes the fatigue crack growth behavior of AM-NiTi SMAs to be different from that of NiTi SMAs prepared by traditional methods. Therefore, in this embodiment, mechanical fatigue crack growth test and driven fatigue crack growth test are respectively used to test the test piece, so as to calculate the J integral to describe the relationship between the J integral and the deformation work.

[0055] In this step, the crack growth test may include a mechanical fatigue crack growth test and a driven fatigue crack growth test, wherein the mechanical fatigue crack growth test is a mechanical cyclic loading of a pre-cracked specimen on the test piece under an external load of a certain periodic frequency and waveform. It should be noted that in the mechanical fatigue crack growth test, the temperature used is constant. At the beginning of the mechanical fatigue crack growth test, the load applied to the test piece is set to P min, the initial displacement of the test piece is v min The final load applied to the test piece at the end of a cycle in a mechanical fatigue crack growth test is P max , the final displacement of the test piece at the end of the mechanical fatigue crack growth test is v max See also Figure 2-1 Schematic diagram of the load applied in the mechanical fatigue crack growth test. Figure 2-2 Indicates that the temperature used in the mechanical fatigue crack growth test is constant, thus obtaining Figure 2-3 Figure 2 shows the load-displacement diagram in a mechanical fatigue crack growth test. Figure 2-3 In the figure, the horizontal axis represents displacement, the vertical axis represents load, and the area of ​​the shaded portion represents the area used in the definition of the cyclic J integral under the mechanical load cyclic frame load. In this embodiment, the elastic component and the inelastic component are determined according to the load-displacement curve.

[0056] In one embodiment, determining the elastic component and the inelastic component under the load-displacement curve during the loading phase of the fatigue cycle may include:

[0057] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0058] according to Determine the inelastic component of the load-displacement curve during the loading phase of a fatigue cycle;

[0059] in, represents the elastic component under the load-displacement curve during the loading stage of the fatigue cycle, P min It represents the initial load applied to the test piece at the beginning of a cycle of mechanical fatigue crack growth test, P max It represents the final load applied to the test piece at the end of a cycle of mechanical fatigue crack growth test. represents the displacement variable corresponding to the fatigue cycle unloading process in the mechanical fatigue crack growth test, C represents the unloading elastic compliance during the fatigue cycle unloading, represents the inelastic component under the load-displacement curve during the fatigue cycle loading phase, P represents the current load, and v min represents the initial displacement of the test piece at the beginning of a cycle of the mechanical fatigue crack growth test, v max It represents the final displacement of the test piece at the end of one cycle of mechanical fatigue crack growth test.

[0060] In this embodiment, the driven fatigue crack growth test is an experiment in which a pre-cracked specimen of the test piece is subjected to thermal cycling under a constant bias load. In this experiment, the applied load is constant such as Figure 3-1As shown, the temperature is not constant, and it cycles between the lower critical temperature (LCT) and the upper critical temperature (UCT) at a certain heating / cooling rate, as shown in Figure 3-2 Temperature variation shown. It should be noted that although the load is constant, the displacement changes continuously with the test cycle. This is due to the change caused by phase change. Consider a single drive cycle. If the applied bias load is P bias , at the beginning of cooling, the displacement has an initial value v min ', and increases to v at the end of the cooldown max '. Although the applied load is constant in the far field, the phase transformations induced by the thermal cycles lead to stress redistribution, thus changing the stress field at the crack tip. Therefore, similar to mechanical loading, the J-integral under thermal driving can be inferred and in this case, the elastic compliance is needed to distinguish between the elastic and inelastic components of the area under the load-displacement curve. This can be measured by a partial unloading / reloading sequence at the end of cooling during a driven fatigue crack growth test. If the unloading / reloading sequence is performed at the end of heating, the compliance of the specimen may be different even if the crack size is the same due to the mismatch in the elastic moduli between the austenite and martensite phases. As Figure 3-3 Figure 2 shows the schematic diagram of the displacement change under constant load in a driven fatigue crack growth test. The shaded area represents the area used in the definition of the cyclic J-integral of the driving load cycle.

[0061] In one embodiment, when the crack growth test is a driven fatigue crack growth test, determining the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage may include:

[0062] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0063] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0064] in, represents the elastic component under the load-displacement curve during the loading phase of the fatigue cycle, represents the inelastic component under the load-displacement curve during the loading stage of the fatigue cycle, P bias represents the constant load applied at the end of the fatigue crack growth test, represents the displacement variable corresponding to the fatigue cycle unloading process in the driven fatigue crack growth test, v min ' represents the initial displacement of the test piece at the beginning of a cycle of the driving fatigue crack growth test, vmax ' represents the final displacement of the test piece at the end of one cycle of the driven fatigue crack growth test.

[0065] Step 102: Obtain the thickness and width of the test piece and the crack depth on the test piece.

[0066] The thickness, width and crack depth of the test piece can be directly measured.

[0067] Step 103 , calculating the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth, elastic component and inelastic component on the test piece.

[0068] In order to describe the crack growth resistance of materials under cyclic loading, the crack tip stress intensity factor range ΔK defined by linear elasticity is widely used in the engineering community.

[0069] Right now, Where a represents the depth of the crack on the test piece, and N represents the number of stress cycles. C' and m are material constants that can be determined experimentally. The above form of the Paris equation requires a small-scale yield condition, that is, the specimen size is relatively high compared to the characteristic size of the crack morphology, that is, the inelastic deformation is limited to a small size area. If a parameter similar to the ΔJ integral is used instead of ΔK, the requirements on the specimen size are relatively low. Under the assumption of quasi-static, monotonic and proportional thermomechanical loads, the temperature is uniformly distributed, and in the absence of body forces and heat sources, an extended J integral can be derived, expressed as follows:

[0070]

[0071] Among them J * is the J integral to be measured. J represents an integral in elastic-plastic fracture mechanics. Γ represents the integral defined on any contour, which means defining the integral around the crack; w * is the total work per unit volume of stress at a material point at a given temperature. i =σ ij n j , σ represents stress, n represents the normal unit vector on the contour, u i is the displacement vector, x and y are the rectangular coordinates of the crack tip, ds is the length increment, ε represents the strain, T represents the temperature, and J is defined under the assumption of a "1-1" correspondence between stress σ and strain ε. * integral, this should be a valid approximation for the SMA for a wide range of proportional thermomechanical loading paths, but the calculation of J * Many parameters in the integral cannot be measured directly, or the measurement accuracy is not high, so the above method is not used to calculate J in this embodiment.* integral.

[0072] In one embodiment, calculating the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth, elastic component and inelastic component on the test piece may include:

[0073] Calculate the length of the unbroken ligament on the test piece based on the width and the crack depth on the test piece;

[0074] Calculate the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the elastic component;

[0075] Calculate the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the inelastic component;

[0076] The J integral of the test piece is calculated based on the elastic component of the J integral and the inelastic component of the J integral.

[0077] Optionally, calculating the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece may include: taking the difference between the width and the crack depth on the test piece as the length of the unbroken ligament on the test piece.

[0078] Optionally, calculating the J integral of the test piece according to the elastic component of the J integral and the inelastic component of the J integral includes:

[0079] The sum of the elastic component of the J integral and the inelastic component of the J integral is taken as the J integral of the test piece.

[0080] In this embodiment, for different fatigue crack growth tests, the same calculation method of the elastic component of the J integral and the inelastic component of the J integral can be used, as detailed as follows:

[0081] Calculating the elastic component of the J integral of the test piece based on the thickness, the length of the unbroken ligament on the test piece, and the elastic component may include:

[0082] according to Calculate the elastic component of the J integral of the test piece;

[0083] Among them, J el represents the elastic component of the J integral of the test piece, η el represents the first geometric correlation factor, A el The corresponding elastic component under the load-displacement curve in the fatigue cycle loading stage of any crack growth test can be or B represents the thickness of the test piece, b represents the length of the unbroken ligament on the test piece, and b=Ba.

[0084] The inelastic component of the J integral of the test piece is calculated based on the thickness, the length of the unbroken ligament on the test piece, and the inelastic component, including:

[0085] according to Calculate the elastic component of the J integral of the test piece;

[0086] Among them, J in represents the inelastic component of the J integral of the test piece, η in represents the second geometric correlation factor, A in A represents the corresponding inelastic component under the load-displacement curve in the fatigue cycle loading stage of any crack growth test. in Can be or B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

[0087] Optionally, calculating the J integral of the test piece according to the elastic component of the J integral and the inelastic component of the J integral includes:

[0088] The sum of the elastic component of the J integral and the inelastic component of the J integral is taken as the J integral of the test piece. That is, according to J=J el +J in Calculate the J-integral of the test piece.

[0089] The embodiment of the present invention tests the test piece by using a crack extension test to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, and the test piece is AM-NiTi SMAs; the thickness, width and crack depth of the test piece are obtained; the J integral of the test piece corresponding to the test piece under different crack extension tests is calculated according to the thickness, width, crack depth, elastic component and inelastic component of the test piece, so as to realize the calculation of fatigue crack extension of AM-NiTi SMAs, and solve the problem that there is no method for fatigue crack extension of AM-NiTi SMAs in the prior art. In addition, when calculating the J integral of AM-NiTi SMAs, the test piece is tested by using a crack extension test to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, and then the J integral of AM-NiTi SMAs is obtained according to the elastic component and the inelastic component, so as to solve the problem that some parameters are difficult to measure when calculating the J integral in the prior art, and the calculation range of the inelastic deformation can be relaxed to realize the accurate calculation of the fatigue crack extension of AM-NiTi SMAs.

[0090] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0091] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0092] Figure 4 A schematic diagram of the structure of a fatigue crack extension device provided by an embodiment of the present invention is shown. For ease of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0093] like Figure 4 As shown, a fatigue crack extension device 4 includes: a calculation module 41 and an acquisition module 42 .

[0094] A calculation module 41 is used to test the test piece by using a crack extension test to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, respectively, and the test piece is AM-NiTi SMAs;

[0095] An acquisition module 42 is used to acquire the thickness and width of the test piece and the crack depth on the test piece;

[0096] The calculation module 41 is further used to calculate the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth, elastic component and inelastic component on the test piece.

[0097] In a possible implementation, when the crack growth test of the calculation module 41 is a mechanical fatigue crack growth test, when determining the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, it is used to:

[0098] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0099] according to Determine the inelastic component of the load-displacement curve during the loading phase of a fatigue cycle;

[0100] in, represents the elastic component under the load-displacement curve during the loading stage of the fatigue cycle, P min It represents the initial load applied to the test piece at the beginning of a cycle of mechanical fatigue crack growth test, P max It represents the final load applied to the test piece at the end of one cycle in a mechanical fatigue crack growth test. represents the displacement variable corresponding to the fatigue cycle unloading process in the mechanical fatigue crack growth test, C represents the unloading elastic compliance during the fatigue cycle unloading, represents the inelastic component under the load-displacement curve during the fatigue cycle loading phase, P represents the current load, and v min represents the initial displacement of the test piece at the beginning of a cycle of the mechanical fatigue crack growth test, v max It represents the final displacement of the test piece at the end of one cycle of mechanical fatigue crack growth test.

[0101] In a possible implementation, when the crack growth test of the calculation module 41 is a driven fatigue crack growth test, when determining the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, it is used to:

[0102] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0103] according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle;

[0104] in, represents the elastic component under the load-displacement curve during the loading phase of the fatigue cycle, represents the inelastic component under the load-displacement curve during the loading stage of the fatigue cycle, P bias represents the constant load applied at the end of the fatigue crack growth test, represents the displacement variable corresponding to the fatigue cycle unloading process in the driven fatigue crack growth test, v min ' represents the initial displacement of the test piece at the beginning of a cycle of the driving fatigue crack growth test, v max ' represents the final displacement of the test piece at the end of one cycle of the driven fatigue crack growth test.

[0105] In a possible implementation, the calculation module 41 calculates the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth, elastic component and inelastic component on the test piece, and is used to:

[0106] Calculate the length of the unbroken ligament on the test piece based on the width and the crack depth on the test piece;

[0107] Calculate the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the elastic component;

[0108] Calculate the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the inelastic component;

[0109] The J integral of the test piece is calculated based on the elastic component of the J integral and the inelastic component of the J integral.

[0110] In a possible implementation, when the calculation module 41 calculates the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece, it is used to:

[0111] The difference between the width and the crack depth on the test piece is taken as the length of the unbroken ligament on the test piece;

[0112] According to the elastic component of the J integral and the inelastic component of the J integral, the J integral of the test piece is calculated, including:

[0113] The sum of the elastic component of the J integral and the inelastic component of the J integral is taken as the J integral of the test piece.

[0114] In a possible implementation, when the calculation module 41 calculates the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the elastic component, it is used to:

[0115] according to Calculate the elastic component of the J integral of the test piece;

[0116] Among them, J el represents the elastic component of the J integral of the test piece, η el represents the first geometric correlation factor, A el It represents the corresponding elastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

[0117] In a possible implementation, when the calculation module 41 calculates the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece, and the inelastic component, it is used to:

[0118] according to Calculate the elastic component of the J integral of the test piece;

[0119] Among them, J in represents the inelastic component of the J integral of the test piece, η in represents the second geometric correlation factor, A in It represents the corresponding inelastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

[0120] The above-mentioned fatigue crack extension device uses a crack extension test to test the test piece through a calculation module, and determines the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage respectively, and the test piece is AM-NiTi SMAs; the acquisition module obtains the thickness, width and crack depth of the test piece to be tested; according to the thickness, width, crack depth, elastic component and inelastic component of the test piece to be tested, the calculation module calculates the J integral of the corresponding test piece under different crack extension tests respectively, thereby realizing the calculation of fatigue crack extension of AM-NiTi SMAs, solving the problem that there is no method for fatigue crack extension of AM-NiTi SMAs in the prior art. In addition, when calculating the J-integral of AM-NiTiSMAs, the crack extension test is performed on the test piece to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, respectively, and then the J-integral of AM-NiTiSMAs is obtained based on the elastic component and the inelastic component, thereby solving the problem that some parameters are difficult to measure when calculating the J-integral in the prior art. In addition, the calculation range of the inelastic deformation can be relaxed to achieve accurate calculation of the fatigue crack extension of AM-NiTi SMAs.

[0121] Figure 5 is a schematic diagram of a terminal provided by an embodiment of the present invention. Figure 5 As shown, the terminal 5 of this embodiment includes: a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, the steps in the above-mentioned fatigue crack growth method embodiments are implemented, for example Figure 1 Alternatively, when the processor 50 executes the computer program 52, the functions of each module / unit in the above-mentioned device embodiments are realized, for example, Figure 4 Functions of the modules / units 41 to 42 are shown.

[0122] Exemplarily, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 52 in the terminal 5. For example, the computer program 52 may be divided into Figure 4 Modules / units 41 to 42 are shown.

[0123] The terminal 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will appreciate that Figure 5It is only an example of terminal 5 and does not constitute a limitation on terminal 5. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal may also include input and output devices, network access devices, buses, etc.

[0124] The processor 50 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0125] The memory 51 may be an internal storage unit of the terminal 5, such as a hard disk or memory of the terminal 5. The memory 51 may also be an external storage device of the terminal 5, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal 5. Further, the memory 51 may also include both an internal storage unit of the terminal 5 and an external storage device. The memory 51 is used to store the computer program and other programs and data required by the terminal. The memory 51 may also be used to temporarily store data that has been output or is to be output.

[0126] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0127] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0128] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0129] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0130] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0131] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0132] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned fatigue crack extension method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium.

[0133] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for fatigue crack growth, characterized in that: include: The test piece is tested by a crack extension test to determine the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage, respectively, and the test piece is AM-NiTi SMAs; Obtaining the thickness and width of the test piece and the crack depth on the test piece; The J integral of the test piece corresponding to different crack extension tests is calculated respectively according to the thickness, the width, the crack depth on the test piece, the elastic component and the inelastic component.

2. The fatigue crack growth method according to claim 1, characterized in that: When the crack growth test is a mechanical fatigue crack growth test, the determination of the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage includes: according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle; according to Determine the inelastic component of the load-displacement curve during the loading phase of a fatigue cycle; in, represents the elastic component under the load-displacement curve during the loading stage of the fatigue cycle, P min It represents the initial load applied to the test piece at the beginning of a cycle of mechanical fatigue crack growth test, P max It represents the final load applied to the test piece at the end of one cycle in a mechanical fatigue crack growth test. represents the displacement variable corresponding to the fatigue cycle unloading process in the mechanical fatigue crack growth test, C represents the unloading elastic compliance during the fatigue cycle unloading, represents the inelastic component under the load-displacement curve during the fatigue cycle loading phase, P represents the current load, and v min represents the initial displacement of the test piece at the beginning of a cycle of the mechanical fatigue crack growth test, v max It represents the final displacement of the test piece at the end of one cycle of the mechanical fatigue crack growth test.

3. The fatigue crack growth method according to claim 1, characterized in that: When the crack growth test is a driven fatigue crack growth test, the elastic component and the inelastic component under the load-displacement curve in the fatigue cycle loading stage are determined, including: according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle; according to Determine the elastic component under the load-displacement curve during the loading phase of the fatigue cycle; in, represents the elastic component under the load-displacement curve during the loading phase of the fatigue cycle, represents the inelastic component under the load-displacement curve during the loading stage of the fatigue cycle, P bias represents the constant load applied at the end of the fatigue crack growth test, represents the displacement variable corresponding to the fatigue cycle unloading process in the driven fatigue crack growth test, v min ' represents the initial displacement of the test piece at the beginning of a cycle of the driving fatigue crack growth test, v max ' represents the final displacement of the test piece at the end of one cycle of the driven fatigue crack growth test.

4. The method for fatigue crack growth according to any one of claims 1 to 3, characterized in that: The step of calculating the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth on the test piece, the elastic component and the inelastic component comprises: Calculating the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece; Calculate the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the elastic component; Calculate the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the inelastic component; The J integral of the test piece is calculated according to the elastic component of the J integral and the inelastic component of the J integral.

5. The fatigue crack growth method according to claim 4, characterized in that: Calculating the length of the unbroken ligament on the test piece according to the width and the crack depth on the test piece includes: The difference between the width and the crack depth on the test piece is used as the length of the unbroken ligament on the test piece; Calculating the J integral of the test piece according to the elastic component of the J integral and the inelastic component of the J integral includes: The sum of the elastic component of the J integral and the inelastic component of the J integral is taken as the J integral of the test piece.

6. The fatigue crack growth method according to claim 5, characterized in that: Calculating the elastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the elastic component includes: according to Calculating the elastic component of the J integral of the test piece; Among them, J el represents the elastic component of the J integral of the test piece, η el represents the first geometric correlation factor, A el It represents the corresponding elastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

7. The fatigue crack growth method according to claim 5, characterized in that: Calculating the inelastic component of the J integral of the test piece according to the thickness, the length of the unbroken ligament on the test piece and the inelastic component includes: according to Calculating the elastic component of the J integral of the test piece; Among them, J in represents the inelastic component of the J integral of the test piece, η in represents the second geometric correlation factor, A in It represents the corresponding inelastic component under the load-displacement curve in the fatigue cycle loading stage in any crack growth test, B represents the thickness of the test piece, and b represents the length of the unbroken ligament on the test piece.

8. A fatigue crack growth device, characterized in that: include: A calculation module, for testing a test piece by a crack extension test, and determining elastic components and inelastic components under a load-displacement curve in a fatigue cycle loading stage, respectively, wherein the test piece is AM-NiTi SMAs; An acquisition module, used for acquiring the thickness and width of the test piece and the crack depth on the test piece; The calculation module is further used to calculate the J integral of the test piece corresponding to different crack extension tests according to the thickness, width, crack depth on the test piece, the elastic component and the inelastic component.

9. A terminal comprising a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory, characterized in that: When the processor executes the computer program, the steps of the fatigue crack growth method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the fatigue crack growth method according to any one of claims 1 to 7 are implemented.

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