Fracture toughness prediction method incorporating sample size effect

Abstract

The invention provides a fracture toughness prediction method incorporating a sample size effect. The fracture toughness prediction method comprises the following steps: measuring fracture toughness Jc of samples with different thicknesses and different shapes; calculating a numerical solution of a constraint parameter T11 in the crack tip surfaces of the samples with different thicknesses and different shapes, and calculating a numerical solution of a constraint parameter T33 outside the crack tip surfaces of the samples with different thicknesses and different shapes; and establishing a nonlinear relationship between the fracture toughness Jc and the in-plane constraint parameter T11 and the out-plane constraint parameter T33 of the crack tip so as to predict the fracture toughness Jc-p of the sample with any size. According to the prediction method, empirical formulas of the fracture toughness and the in-plane constraint parameters and the out-plane constraint parameters of the crack tip are constructed based on low-flux experiments and simulation results, accurate prediction of the fracture toughness of samples of the same material and any size can be achieved, and a feasible scheme is provided for scientific evaluation of the fracture strength of in-service defective equipment.

Description

Technical Field

[0001] The present invention belongs to the technical fields such as fracture mechanics, and particularly relates to a fracture toughness prediction method incorporating specimen size effect. Background Art

[0002] Metal materials usually have the ductile-brittle transition characteristic, that is, as the temperature decreases, the fracture mode of metal materials will gradually transition from ductile fracture to brittle fracture. Existing studies have shown that in the ductile-brittle transition temperature range, the fracture toughness of metal materials exhibits size effect, that is, the fracture toughness values of specimens of the same material with different sizes under the same test conditions vary greatly. Such differences make it difficult to scientifically evaluate the fracture strength of defective equipment. How to solve the size effect problem of fracture toughness and realize the prediction of the fracture strength of mechanical equipment from small-sized specimens has always been the research focus in the field of fracture mechanics.

[0003] In the past more than a decade, scholars have proposed many new theories for explaining the size effect of fracture toughness. Among them, the crack tip constraint theory is considered to have good engineering application potential. As a crack tip constraint parameter, the in-plane component T 11 and the out-of-plane component T 33 of T can be used to characterize the in-plane size effect and out-of-plane size effect of fracture toughness respectively. It should be emphasized that the in-plane size effect and out-of-plane size effect of fracture toughness exist simultaneously, and the correlation analysis between fracture toughness and the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 has not been systematically carried out, so a fracture toughness prediction scheme incorporating specimen size effect cannot be established. Summary of the Invention

[0004] The object of the present invention is to provide a fracture toughness prediction method incorporating specimen size effect. This method constructs an empirical formula between fracture toughness and the in-plane and out-of-plane constraint parameters at the crack tip based on low-throughput experiments and simulation results, and can accurately predict the fracture toughness of specimens of any size of the same material, providing a feasible scheme for scientifically evaluating the fracture strength of in-service defective equipment. The method includes the following steps: Step S1. Measure the fracture toughness J c of specimens with different thicknesses and different shapes; Step S2. Calculate the numerical solution of the in-plane constraint parameter T 11 at the crack tip of specimens with different thicknesses and different shapes; Step S3. Calculate the numerical solution of the out-of-plane constraint parameter T 33 at the crack tip of specimens with different thicknesses and different shapes; Step S4. Establish a non-linear relationship between the fracture toughness J c and the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 at the crack tip; Step S5. Predict the fracture toughness J c-p。

[0005] The technical solution specifically adopted by the present invention to solve its technical problems is as follows:

[0006] A method for predicting fracture toughness incorporating specimen size effects: measuring the fracture toughness J of specimens with different thicknesses and different shapes c ; calculating the numerical solutions of the in-plane constraint parameter T at the crack tip of specimens with different thicknesses and different shapes, and calculating the numerical solutions of the out-of-plane constraint parameter T at the crack tip of specimens with different thicknesses and different shapes 11 ; establishing the non-linear relationship between the fracture toughness J 33 and the in-plane constraint parameter T c at the crack tip and the out-of-plane constraint parameter T 11 at the crack tip to predict the fracture toughness J of specimens of any size 33 。 c-p 。

[0007] Further, the measurement of the fracture toughness J of specimens with different thicknesses and different shapes c is achieved by the following method: conducting fracture toughness tests on three-point bending specimens and compact tension specimens with two different thicknesses respectively, obtaining the load-displacement curve and the fracture load P during the test c ; based on the fracture load P c , calculating the critical stress intensity factor K at fracture for three-point bending specimens and compact tension specimens with different thicknesses respectively c ; based on the critical stress intensity factor K c , calculating the elastic component J of the fracture toughness for three-point bending specimens and compact tension specimens with different thicknesses respectively el ; based on the load-displacement curve, calculating the plastic component J of the fracture toughness for three-point bending specimens and compact tension specimens with different thicknesses respectively pl ; based on the elastic component J el and the plastic component J pl of the fracture toughness, measuring the fracture toughness J of specimens with different thicknesses and different shapes c 。

[0008] Further, the numerical solution of calculating the in-plane constraint parameter T 11 at the crack tip of specimens with different thicknesses and different shapes is achieved by the following method: establishing a finite element analysis model with the same shape and size as the specimen, setting the material, boundary conditions and load of the corresponding model, and conducting linear elastic fracture mechanics simulations using finite element analysis software; obtaining the numerical solution of the in-plane constraint parameter T 11 at the crack tip at the center of the plate thickness for three-point bending specimens and compact tension specimens with different thicknesses using the interference integral method.

[0009] Further, the numerical solution of calculating the out-of-plane constraint parameter T of the crack tip for specimens with different thicknesses and different shapes is realized by the following method: on the basis of establishing a finite element analysis model with the same shape and size as the specimen, setting the material, boundary conditions and loads of the corresponding model, and carrying out linear elastic fracture mechanics simulation by using finite element analysis software, the out-of-plane strain ε of the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses is obtained. 33 Based on the numerical solution of the in-plane constraint parameter T of the crack tip and the out-of-plane strain ε of the crack tip, the numerical solution of the out-of-plane constraint parameter T of the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses is calculated. 33 ; Based on the numerical solution of the in-plane constraint parameter T of the crack tip 11 and the out-of-plane strain ε of the crack tip 33 , the numerical solution of the out-of-plane constraint parameter T of the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses is calculated. 33

[0010] Further, the establishment of the non-linear relationship between the fracture toughness J c and the in-plane constraint parameter T of the crack tip 11 and the out-of-plane constraint parameter T 33 is realized by the following method: using the least square method to fit the fracture toughness J of three-point bending specimens and compact tension specimens with different thicknesses c , the numerical solution of the in-plane constraint parameter T of the crack tip of three-point bending specimens and compact tension specimens with different thicknesses 11 and the numerical solution of the out-of-plane constraint parameter T of the crack tip of three-point bending specimens and compact tension specimens with different thicknesses 33 , so as to establish the non-linear relationship between the fracture toughness J c and the in-plane constraint parameter T of the crack tip 11 and the out-of-plane constraint parameter T 33 .

[0011] Further, the specific method for predicting the fracture toughness of specimens with any size is as follows: obtaining the geometric size and crack size of the specimen to be tested; carrying out finite element simulation on the specimen to be tested, and calculating the in-plane constraint parameter T and the out-of-plane constraint parameter T of the crack tip at the center of the plate thickness of the specimen; substituting the calculated in-plane constraint parameter T and the out-of-plane constraint parameter T into the non-linear relationship between the fracture toughness J and the in-plane constraint parameter T and the out-of-plane constraint parameter T of the crack tip to estimate the fracture toughness J of the specimen to be tested. 11 ; Substitute the calculated in-plane constraint parameter T 33 and the out-of-plane constraint parameter T of the crack tip at the center of the plate thickness of the specimen into the non-linear relationship between the fracture toughness J 11 and the in-plane constraint parameter T and the out-of-plane constraint parameter T of the crack tip to estimate the fracture toughness J 33 of the specimen to be tested. c ; Substitute the calculated in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 into the non-linear relationship between the fracture toughness J c-p to estimate the fracture toughness J of the specimen to be tested.

[0012] In addition, an electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of a fracture toughness prediction method incorporating specimen size effect as described above are implemented.

[0013] A non-transitory computer-readable storage medium stores a computer program thereon. When the computer program is executed by a processor, the steps of a fracture toughness prediction method incorporating specimen size effect as described above are implemented.

[0014] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects:

[0015] 1. By comprehensively considering the effects of different specimen thicknesses and shapes, numerical solutions of the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 at different specimen thicknesses and shape conditions are obtained.

[0016] 2. A non-linear relationship between the fracture toughness J c and the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 of the crack tip is established. Based on this relationship, the fracture toughness values of specimens of any size made of the same material can be estimated by simply performing a linear elastic fracture mechanics simulation. This significantly reduces the test cost and simplifies the process of obtaining the fracture toughness, providing a method reference for promoting the prediction of the fracture strength of defective mechanical equipment from small-size specimens. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below with reference to the drawings and specific embodiments:

[0018] Figure 1 is a flowchart of the fracture toughness prediction method according to an embodiment of the present invention.

[0019] Figure 2 is a flowchart of measuring the fracture toughness according to an embodiment of the present invention.

[0020] Figure 3 is a flowchart of calculating the numerical solutions of the in-plane constraint parameter and the out-of-plane constraint parameter of the crack tip according to an embodiment of the present invention.

[0021] Figure 4 is a flowchart of establishing the non-linear relationship between the fracture toughness and the in-plane constraint parameter and the out-of-plane constraint parameter of the crack tip according to an embodiment of the present invention.

[0022] Figure 5 is a flowchart of predicting the fracture toughness of specimens of any size according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To make the features and advantages of this patent more obvious and understandable, specific embodiments are given below for detailed description as follows:

[0024] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] As Figure 1 shown, the embodiment of the present invention provides a fracture toughness prediction method incorporating specimen size effects, including the following steps:

[0027] Step S1: Measure the fracture toughness J of specimens with different thicknesses and different shapes c ;

[0028] As Figure 2 shown, as a preferred solution of this embodiment, it specifically includes the following steps:

[0029] Step S11: According to the American Society for Testing and Materials ASTM E1921 standard, conduct fracture toughness tests on three-point bending specimens and compact tension specimens with two different thicknesses respectively, and obtain the load-displacement curve and fracture load P during the test c ;

[0030] Step S12: Based on the fracture load P obtained in Step S11 c , calculate the critical stress intensity factor K at fracture for three-point bending specimens and compact tension specimens with different thicknesses respectively c . Specifically, the calculation formula for the critical stress intensity factor K c of the three-point bending specimen is shown in a), and the calculation formula for the critical stress intensity factor K c of the compact tension specimen is shown in b):

[0031] a) Three-point bending specimen:

[0032]

[0033] In the formula, K c is the critical stress intensity factor, P cis the fracture load, S is the span between the two loading rollers in the three-point bending test, B is the specimen thickness, B N is the net thickness of the specimen between the two side grooves, W is the specimen width, a is the crack length, and f(a / W) is a dimensionless function of a / W;

[0034] b) Compact tension specimen:

[0035]

[0036] wherein, K c is the critical stress intensity factor, P c is the fracture load, B is the specimen thickness, B N is the net thickness of the specimen between the two side grooves, W is the specimen width, a is the crack length, and f(a / W) is a dimensionless function of a / W;

[0037] Step S13: Based on the critical stress intensity factor K c obtained in Step S12, calculate the elastic component J el of the fracture toughness of three-point bending specimens and compact tension specimens with different thicknesses respectively;

[0038]

[0039] wherein, J el is the elastic component of the fracture toughness, K c is the critical stress intensity factor, ν is the Poisson's ratio, and E is the Young's modulus;

[0040] Step S14: Based on the load-displacement curve obtained in Step S11, calculate the plastic component J pl of the fracture toughness of three-point bending specimens and compact tension specimens with different thicknesses respectively;

[0041]

[0042] wherein, J pl is the plastic component of the fracture toughness, η is a dimensionless geometric factor, A pl is the plastic component of the area under the load-displacement curve, B N is the net thickness of the specimen between the two side grooves, W is the specimen width; a is the crack length;

[0043] Step S15: Based on the elastic component J el of the fracture toughness calculated in Step S13 and the plastic component J pl of the fracture toughness calculated in Step S14, determine the fracture toughness J c of specimens with different thicknesses and different shapes;

[0044] J c = J el+J pl

[0045] wherein, J c is the fracture toughness, J el is the elastic component of the fracture toughness, and J pl is the plastic component of the fracture toughness.

[0046] Step S2: Calculate the numerical solutions of the in-plane constraint parameter T 11 at the crack tip of specimens with different thicknesses and different shapes;

[0047] As shown in Figure 3 , as a preferred solution of this embodiment, it specifically includes the following steps:

[0048] Step S21: Establish a finite element analysis model with the same specimen shape and size as in Step S11, set the materials, boundary conditions, and loads of the corresponding model, and perform linear elastic fracture mechanics simulations using finite element analysis software;

[0049] Step S22: Based on the simulations in Step S21, use the interference integral method to obtain the numerical solutions of the in-plane constraint parameter T 11 at the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses.

[0050] Step S3: Calculate the numerical solutions of the out-of-plane constraint parameter T 33 at the crack tip of specimens with different thicknesses and different shapes;

[0051] As shown in Figure 3 , as a preferred solution of this embodiment, it specifically includes the following steps:

[0052] Step S31: Based on the simulation results in Step S21, obtain the out-of-plane strain ε 33 at the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses;

[0053] Step S32: Based on the numerical solutions of the in-plane constraint parameter T 11 obtained in Step S22 and the out-of-plane strain ε 33 obtained in Step S31, calculate the numerical solutions of the out-of-plane constraint parameter T 33 at the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses;

[0054] T 33 = Eε 33 + νT 11

[0055] wherein, T 33 is the out-of-plane constraint parameter, E is Young's modulus, and ε 33is the out-of-plane strain at the crack tip, ν is the Poisson's ratio, and T 11 is the in-plane constraint parameter at the crack tip;

[0056] Step S4: Establish the nonlinear relationship between the fracture toughness J c and the in-plane constraint parameter T 11 at the crack tip and the out-of-plane constraint parameter T 33 at the crack tip;

[0057] As Figure 4 shown, as the preferred solution of this embodiment, it specifically includes the following steps:

[0058] Step S41: Organize the fracture toughness J c of the three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S1, the numerical solutions of the in-plane constraint parameter T 11 at the crack tip of the three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S2, and the numerical solutions of the out-of-plane constraint parameter T 33 at the crack tip of the three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S3 into a data table;

[0059] Step S42: Use the least squares method to fit the data organized in Step S41, and establish the nonlinear relationship between the fracture toughness J c and the in-plane constraint parameter T 11 at the crack tip and the out-of-plane constraint parameter T 33 at the crack tip;

[0060] J c = f(T 11 , T 33 )

[0061] In the formula, J c is the fracture toughness, T 11 is the in-plane constraint parameter at the crack tip, T 33 is the out-of-plane constraint parameter at the crack tip, and f is the binary function relationship between J c and T 11 , T 33 ;

[0062] Step S5: Predict the fracture toughness of specimens with any size;

[0063] As Figure 5 shown, as the preferred solution of this embodiment, it specifically includes the following steps:

[0064] Step S51: Determine the geometric dimensions and crack dimensions of the specimen to be tested;

[0065] Step S52: Conduct a finite element simulation for the specimen to be tested, and calculate the in-plane constraint parameter T 11In-plane restraint parameter T of dough kneading 33 ;

[0066] Step S53: Substitute the in-plane restraint parameter T calculated in step S52 11 and the out-of-plane restraint parameter T 33 into the non-linear relationship between the fracture toughness J c established in step S4 and the in-plane restraint parameter T 11 and the out-of-plane restraint parameter T 33 at the crack tip to estimate the fracture toughness J c-p of the specimen to be tested.

[0067] Embodiment

[0068] The following takes three-point bending specimens and compact tension specimens made of medium carbon steel as examples to give a specific embodiment of the present invention. The geometric dimensions and crack dimensions of the three-point bending specimens and compact tension specimens are as follows: specimen width W = 25 mm, ratio of crack length to specimen width a / W = 0.50, ratio of specimen thickness to specimen width B / W = 0.25, 0.50, ratio of the net thickness of the specimen between the two grooves to the specimen thickness B N / B = 0.80.

[0069] Now, use the present invention to construct the non-linear relationship between the fracture toughness J c of the three-point bending specimen and the compact tension specimen and the in-plane restraint parameter T 11 and the out-of-plane restraint parameter T 33 at the crack tip to estimate the fracture toughness J c-p of specimens with other dimensions. The process is as follows:

[0070] Step S1: Measure the fracture toughness J c of specimens with different thicknesses and different shapes;

[0071] Step S11: According to the American Society for Testing and Materials ASTM E1921 standard, conduct fracture toughness tests on three-point bending specimens and compact tension specimens with different thicknesses at 20 °C respectively to obtain the load-displacement curve and the fracture load P c , where the fracture load P c see Table 1;

[0072] Step S12: Based on the fracture load P c obtained in step S11, calculate the critical stress intensity factor K c at fracture for three-point bending specimens and compact tension specimens with different thicknesses respectively, see Table 1; specifically, the calculation formula for the critical stress intensity factor K c of the three-point bending specimen is as shown in a), and the calculation formula for the critical stress intensity factor K c of the compact tension specimen is as shown in b):

[0073] a) Three-point bending specimen:

[0074]

[0075] where K c is the critical stress intensity factor, P c is the fracture load, S is the span between the two loading rollers in the three-point bending test, B is the specimen thickness, B N is the net thickness of the specimen between the two side grooves, W is the specimen width, a is the crack length, and f(a / W) is a dimensionless function of a / W;

[0076] b) Compact tension specimen:

[0077]

[0078] where K c is the critical stress intensity factor, P c is the fracture load, B is the specimen thickness, B N is the net thickness of the specimen between the two side grooves, W is the specimen width, a is the crack length, and f(a / W) is a dimensionless function of a / W;

[0079] Table 1 Fracture loads and critical stress intensity factors of specimens with different thicknesses and different shapes

[0080]

[0081]

[0082] Step S13: Based on the critical stress intensity factor K c obtained in step S12, calculate the elastic component J el of the fracture toughness of three-point bending specimens and compact tension specimens with different thicknesses respectively, see Table 2;

[0083]

[0084] where J el is the elastic component of the fracture toughness, K c is the critical stress intensity factor, ν is the Poisson's ratio, and E is the Young's modulus;

[0085] Step S14: Based on the load-displacement curve obtained in step S11, calculate the plastic component J pl of the fracture toughness of three-point bending specimens and compact tension specimens with different thicknesses respectively, see Table 2;

[0086]

[0087] where J plis the plastic component of the fracture toughness, η is a dimensionless geometric factor, A pl is the plastic component of the area under the load-displacement curve, B N is the net thickness of the specimen between the two side grooves, W is the specimen width; a is the crack length;

[0088] Step S15: Based on the elastic component J of the fracture toughness calculated in Step S13 el and the plastic component J of the fracture toughness calculated in Step S14 pl , determine the fracture toughness J of specimens with different thicknesses and different shapes c , see Table 2;

[0089] J c = J el + J pl

[0090] In the formula, J c is the fracture toughness, J el is the elastic component of the fracture toughness, J pl is the plastic component of the fracture toughness.

[0091] Table 2 Elastic component, plastic component and fracture toughness of fracture toughness of specimens with different thicknesses and different shapes

[0092]

[0093] Step S2: Calculate the numerical solution of the in-plane constraint parameter T at the crack tip of specimens with different thicknesses and different shapes 11 ;

[0094] Step S21: Establish a finite element analysis model with the same specimen shape and size as in Step S11, set the material, boundary conditions and load of the corresponding model, and use the finite element analysis software ABAQUS to carry out linear elastic fracture mechanics simulation. Among them, the Young's modulus E in the material properties is 206000 MPa, and the Poisson's ratio ν is 0.3; the load of each analysis model is the corresponding fracture load P in Table 1 c ;

[0095] Step S22: Based on the simulation in Step S21, use the interference integral method to obtain the numerical solution of the in-plane constraint parameter T at the crack tip at the center of the plate thickness of three-point bending specimens and compact tension specimens with different thicknesses, see Table 3; 11 ;

[0096] Step S3: Calculate the numerical solution of the out-of-plane constraint parameter T at the crack tip of specimens with different thicknesses and different shapes 33 ;

[0097] Step S31: Based on the simulation results of Step S21, obtain the crack tip out-of-plane strain ε at the center of the plate thickness for three-point bending specimens and compact tension specimens with different thicknesses; see Table 3. 33 , see Table 3;

[0098] Step S32: Based on the numerical solution of the crack tip in-plane restraint parameter T obtained in Step S22 and the crack tip out-of-plane strain ε obtained in Step S31, calculate the numerical solution of the crack tip out-of-plane restraint parameter T at the center of the plate thickness for three-point bending specimens and compact tension specimens with different thicknesses; see Table 3. 11 The numerical solution of and the crack tip out-of-plane strain ε obtained in Step S31 33 , calculate the numerical solution of the crack tip out-of-plane restraint parameter T at the center of the plate thickness for three-point bending specimens and compact tension specimens with different thicknesses; see Table 3. 33 , see Table 3;

[0099] T 33 = Eε 33 + vT 11

[0100] In the formula, T 33 is the crack tip out-of-plane restraint parameter, E is Young's modulus, ε 33 is the crack tip out-of-plane strain, ν is Poisson's ratio, T 11 is the crack tip in-plane restraint parameter;

[0101] Table 3 Numerical solutions of the crack tip in-plane restraint parameter and out-of-plane restraint parameter for specimens with different thicknesses and different shapes

[0102]

[0103] Step S4: Establish a non-linear relationship between the fracture toughness J c and the crack tip in-plane restraint parameter T 11 and the crack tip out-of-plane restraint parameter T 33 ;

[0104] Step S41: Organize the fracture toughness J of three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S1 c , the numerical solution of the crack tip in-plane restraint parameter T of three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S2 11 and the numerical solution of the crack tip out-of-plane restraint parameter T of three-point bending specimens and compact tension specimens with different thicknesses obtained in Step S3 33 into a data table;

[0105] Step S42: Use the least squares method to fit the data organized in Step S41 and establish a non-linear relationship between the fracture toughness J c and the crack tip in-plane restraint parameter T 11 and the crack tip out-of-plane restraint parameter T 33 ;

[0106] J c= 40 + 1.15×10 -3 T 11 -0.63 *|T 33 | 2.78

[0107] Step S5: Predict the fracture toughness of specimens of any size;

[0108] Step S51: Identify the specimen to be tested as a compact tension specimen, with its geometric dimensions and crack size being: specimen width W = 25 mm, ratio of crack length to specimen width a / W = 0.50, ratio of specimen thickness to specimen width B / W = 1.0, ratio of the net thickness of the specimen between the two grooves to the specimen thickness B N / B = 0.8;

[0109] Step S52: Conduct a finite element simulation for the specimen to be tested, and calculate the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 at the crack tip in the center of the plate thickness; here, the calculated in-plane constraint parameter T 11 at the crack tip is 148.40 MPa, and the out-of-plane constraint parameter T 33 at the crack tip is -5.79 MPa;

[0110] Step S53: Substitute the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 calculated in Step S42 into the non-linear relationship between the fracture toughness J c established in Step S4 and the in-plane constraint parameter T 11 and the out-of-plane constraint parameter T 33 at the crack tip to estimate the fracture toughness J c-p of the specimen to be tested. Thus, J c-p = 40.01 N / mm;

[0111] To verify the accuracy of the predicted fracture toughness value J c-p , in this embodiment, compact tension specimens of the same size are taken to conduct 3 repeated fracture toughness tests respectively. The average fracture toughness J c-ave measured in the 3 tests is compared with the estimated fracture toughness J c-p . The comparison results are shown in Table 4. The difference between the two is only 0.87%, which indicates that the present invention can make a good prediction of the fracture toughness of specimens of any size.

[0112] Table 4 Comparison results of average fracture toughness and estimated fracture toughness

[0113]

[0114] Based on the same inventive concept, the present invention further provides a computer device, which includes: one or more processors, and a memory for storing one or more computer programs; the program includes program instructions, and the processor is configured to execute the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is used to implement one or more instructions. Specifically, it is used to load and execute one or more instructions in the computer storage medium to implement the above method.

[0115] It should be further noted that, based on the same inventive concept, the present invention further provides a computer storage medium, on which a computer program is stored, and the computer program executes the above method when being run by a processor. The storage medium may adopt any combination of one or more computer-readable media. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium may, for example, but not be limited to, an electrical, magnetic, optical, electrical, magnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (non-exhaustive list) of the computer-readable storage medium include: an electrical connection having one or more wires, a portable computer disk, a hard disk, a Random Access Memory (RAM), a Read-Only Memory (ROM), an Erasable Programmable Read-Only Memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, the computer-readable storage medium may be any tangible medium that contains or stores a program, and the program can be used by or combined with an instruction execution system, apparatus, or device.

[0116] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0117] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

[0118] This patent is not limited to the above best mode. Anyone inspired by this patent can obtain various other forms of a fracture toughness prediction method incorporating specimen size effects. All equal changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by this patent.

Claims

1. A fracture toughness prediction method incorporating sample size effect, characterized by: Determination of fracture toughness of specimens of different thicknesses and shapes J c ; Calculate the in-plane constraint parameters at the crack tip of specimens with different thicknesses and shapes T 11 The numerical solution of the crack tip out-of-plane constraint parameters of samples with different thicknesses and shapes is also calculated. T 33 Numerical solution of fracture toughness J c The in-plane constraint parameters at the crack tip T 11 and out-of-plane constraint parameters T 33 The nonlinear relationship between the fracture toughness of the specimens of any size can be used to predict the fracture toughness of the specimens of any size. J c-p .

2. A fracture toughness prediction method incorporating sample size effect according to claim 1, characterized in that: Determination of fracture toughness of samples of different thicknesses and shapes J c This is achieved by the following method: fracture toughness tests are carried out on three-point bending specimens and compact tensile specimens of two different thicknesses, and the load-displacement curves and fracture loads during the test are obtained. P c ; Based on the breaking load P c , respectively calculate the critical stress intensity factors of three-point bending specimens and compact tensile specimens of different thicknesses when they break K c ; Based on the critical stress intensity factor K c , respectively calculate the elastic component of the fracture toughness of three-point bending specimens and compact tensile specimens of different thicknesses J el Based on the load-displacement curve, the plastic component of the fracture toughness of three-point bending specimens and compact tensile specimens of different thicknesses is calculated respectively. J pl ; Based on the elastic component of the fracture toughness J el and plastic component J pl , determine the fracture toughness of samples of different thicknesses and shapes J c .

3. A fracture toughness prediction method incorporating sample size effect according to claim 2, characterized in that: The calculation of the in-plane constraint parameters of the crack tip of samples with different thicknesses and shapes T 11 The numerical solution is achieved by the following method: establish a finite element analysis model with the same shape and size as the specimen, set the material, boundary conditions and load of the corresponding model, and use finite element analysis software to carry out linear elastic fracture mechanics simulation; use the interference integral method to obtain the in-plane constraint parameters of the crack tip at the center of the plate thickness for three-point bending specimens of different thicknesses and compact tensile specimens T 11 Numerical solution of .

4. A fracture toughness prediction method incorporating sample size effect according to claim 3, characterized in that: The calculation of the out-of-plane constraint parameters of the crack tip of samples with different thicknesses and shapes T 33 The numerical solution is achieved by the following method: a finite element analysis model with the same shape and size as the specimen is established, the material, boundary conditions and loads of the corresponding model are set, and the finite element analysis software is used to carry out linear elastic fracture mechanics simulation to obtain the out-of-plane strain at the crack tip of three-point bending specimens with different thicknesses and compact tensile specimens at the center of the plate thickness. ; Based on the crack tip in-plane constraint parameter T 11 Numerical solution and out-of-plane strain at crack tip , calculate the out-of-plane constraint parameters of the crack tip at the center of the plate thickness for three-point bending specimens of different thicknesses and compact tension specimens T 33 Numerical solution of .

5. A fracture toughness prediction method incorporating sample size effect according to claim 4, characterized in that: The fracture toughness J c The in-plane constraint parameters at the crack tip T 11 and out-of-plane constraint parameters T 33 The nonlinear relationship is realized by the following method: The fracture toughness of three-point bending specimens and compact tensile specimens with different thicknesses is calculated by the least square method. J c , In-plane constraint parameters at crack tip of three-point bending specimens and compact tensile specimens with different thicknesses T 11 Numerical solutions and out-of-plane constraint parameters at the crack tip of three-point bending specimens and compact tensile specimens with different thicknesses T 33 The fracture toughness is established by fitting the numerical solution of J c The in-plane constraint parameters at the crack tip T 11 and out-of-plane constraint parameters T 33 non-linear relationship.

6. A fracture toughness prediction method incorporating sample size effect according to claim 5, characterized in that: The specific method for predicting the fracture toughness of a sample of any size is as follows: obtaining the geometric dimensions and crack dimensions of the sample to be tested; performing finite element simulation on the sample to be tested, and calculating the in-plane constraint parameters of the crack tip of the sample at the center of the plate thickness. T 11 and out-of-plane constraint parameters T 33 ; The calculated in-plane constraint parameters T 11 and out-of-plane constraint parameters T 33 Substituting fracture toughness J c The in-plane constraint parameters at the crack tip T 11 and out-of-plane constraint parameters T 33 In the nonlinear relationship of J c-p .

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of a fracture toughness prediction method incorporating a specimen size effect as described in any one of claims 1 to 6 are implemented.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the fracture toughness prediction method incorporating the specimen size effect as claimed in any one of claims 1 to 6 are implemented.

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