Method and device for measuring dynamic fracture toughness

Abstract

The invention discloses a method and a device for measuring dynamic fracture toughness, relates to the technical field of material mechanical property testing, and mainly aims to solve the problem that the relationship between a J-R resistance curve and a loading rate under a constant-speed loading condition cannot be obtained by an existing method. Dividing the samples into a plurality of test groups with the same number; configuring different loading speeds for each test group, and carrying out constant-speed loading treatment with different displacement loading amounts on each sample in the test group according to different loading speeds to obtain a loading point displacement-load curve corresponding to each sample; determining the crack propagation amount of the loaded three-point bending sample, and determining J integral corresponding to each three-point bending sample based on the crack propagation amount and the loading point displacement-load curve; and drawing a J-R resistance curve based on the crack propagation amount in each test group and the corresponding J integral to obtain a J-R resistance curve corresponding to each loading speed.

Description

Technical Field

[0001] The present invention relates to the technical field of material mechanical property testing, and in particular to a method and device for determining dynamic fracture toughness, a storage medium, and a computer device. Background Art

[0002] The research on dynamic fracture theory and test methods of materials and structures has always been a hot topic and difficulty in the field of fracture mechanics. However, since the British physicist NF Fott proposed fracture dynamics in 1948, although a large number of research attempts have been made on the dynamic fracture problem in different periods of history, a systematic theory has not yet been formed. This is due to insufficient test conditions. Although the existing dynamic fracture toughness test methods have certain feasibility, they have not deviated from the essence of the "impact" test method. The resulting test technology "bottlenecks" such as poor load stability, discontinuous loading, large signal disturbance, and unstable loading rate have restricted the development of dynamic fracture test technology.

[0003] Elastic-plastic fracture toughness of ductile materials J IC The JR resistance curve is an essential key mechanical performance parameter in the structural safety and integrity assessment. With the development of material testing technology, high-speed material testing machines are gradually entering the market. This type of testing machine can achieve uniform and stable loading at any rate within the range of 0.001m / s-20m / s, filling the gap in material dynamic testing technology. However, since the dynamic loading process of the high-speed material testing machine is continuous and cannot be stopped, it is impossible to directly obtain the relationship between the JR resistance curve and the loading rate under uniform loading conditions by means of load control. Summary of the invention

[0004] In view of this, the present invention provides a method and device for determining dynamic fracture toughness, the main purpose of which is to solve the problem that the existing dynamic fracture toughness testing method cannot obtain the relationship between the JR resistance curve and the loading rate under uniform loading conditions.

[0005] According to one aspect of the present invention, a method for determining dynamic fracture toughness is provided, comprising:

[0006] Prefabricate a plurality of three-point bending specimens, and divide the three-point bending specimens into a plurality of test groups of equal number;

[0007] Different loading speeds are configured for each of the test groups, and uniform loading processes with different displacement loads are performed on each of the three-point bending specimens in the group according to the loading speeds corresponding to each of the test groups, so as to obtain loading point displacement-load curves corresponding to each of the three-point bending specimens;

[0008] Determine the crack extension of the three-point bending specimen after loading, and determine the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve;

[0009] A JR resistance curve is plotted based on the crack extension amount and the corresponding J integral in each of the test groups to obtain the JR resistance curve corresponding to each loading speed.

[0010] Furthermore, the three-point bending specimens are made of ductile material to be analyzed, each of the three-point bending specimens has the same specification, and initial cracks of the same length are arranged at the same position of a plurality of the three-point bending specimens.

[0011] Furthermore, before performing uniform speed loading processing with different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, the method further includes:

[0012] Numbering each of the three-point bending specimens in the test group to obtain a specimen number corresponding to each of the three-point bending specimens;

[0013] A corresponding displacement load is configured for each of the sample numbers, so that the displacement load configured for the three-point bending samples with the same sample number in each of the test groups is also the same.

[0014] Furthermore, the uniform speed loading process of different displacement loading amounts is performed on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, including:

[0015] Obtaining the displacement load corresponding to each of the sample numbers in the test group to be loaded;

[0016] The lowest loading position of the high-speed material testing machine is determined by adjusting the length of the upper support rod in the high-speed material testing machine, so that the lowest loading position corresponds to the displacement loading amount corresponding to each of the sample numbers;

[0017] Based on the loading speed corresponding to the test group to be loaded and in accordance with the displacement load corresponding to the sample number, the adjusted high-speed material testing machine is used to perform uniform speed loading processing on each of the three-point bending samples in the group.

[0018] Further, the method further comprises: performing uniform loading processing with different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups to obtain a loading point displacement-load curve corresponding to each of the three-point bending specimens;

[0019] During the uniform loading process, the displacement of the loading point of the three-point bending specimen and the load of the high-speed material testing machine are monitored in real time;

[0020] A curve is drawn based on the corresponding relationship between the loading point displacement and the load to obtain the loading point displacement-load curve corresponding to the three-point bending specimen.

[0021] Further, the determining of the crack extension of the three-point bending specimen after loading, and determining the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve, includes:

[0022] Determine the crack extension of the three-point bending specimen after loading by thermal coloring method or secondary fatigue line drawing method;

[0023] Obtaining a plastic component based on the displacement-load curve of the loading point;

[0024] A J-integral corresponding to each of the three-point bending specimens is determined based on the plastic component and the crack extension amount.

[0025] Further, the JR resistance curve is drawn based on the crack extension amount and the corresponding J integral in each test group to obtain the JR resistance curve corresponding to each loading speed, including:

[0026] Respectively obtaining the crack extension amount and the corresponding J integral in each test group;

[0027] Performing curve fitting processing based on the crack extension amount and the corresponding J integral to obtain a JR resistance curve corresponding to each of the test groups;

[0028] The loading speed configured for each test group is obtained, and the loading speed is associated with the JR resistance curve to obtain the JR resistance curve corresponding to each loading speed.

[0029] Furthermore, the method further comprises:

[0030] Compare and process the JR resistance curves corresponding to various loading speeds to obtain a comparison result;

[0031] An influence of a loading speed on the JR resistance curve is determined based on the comparison result.

[0032] According to another aspect of the present invention, there is provided a dynamic fracture toughness determination device, comprising a high-speed material testing machine, a three-point bending test fixture, a mounting base, a loading support roller, and an upper support rod;

[0033] The mounting base is fixedly connected to the base of the high-speed material testing machine, and the three-point bending test fixture is fixed on the mounting base;

[0034] The three-point bending specimen is fixed on the high-speed material testing machine by the three-point bending test fixture, and the length of the upper support rod is adjusted by the loading support roller so that the upper support rod provides different displacement loads to the three-point bending specimen.

[0035] Furthermore, the device also includes a displacement sensor and a load sensor;

[0036] The displacement sensor is used to collect the displacement of the loading point of the three-point bending specimen during the uniform loading process;

[0037] The load sensor is used to collect the load corresponding to the displacement of the loading point.

[0038] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0039] The present invention provides a method and device for determining dynamic fracture toughness. Compared with the prior art, the present invention prefabricates a plurality of three-point bending specimens and divides the three-point bending specimens into a plurality of test groups of equal number; configures different loading speeds for each test group, and performs uniform loading processing of different displacement loading amounts on each three-point bending specimen in the group according to the loading speed corresponding to each test group, so as to obtain the loading point displacement-load curve corresponding to each three-point bending specimen; determines the crack extension of the three-point bending specimen after loading, and determines the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve; draws the JR resistance curve based on the crack extension in each test group and the corresponding J integral, so as to obtain the JR resistance curve corresponding to each loading speed. The present invention obtains the dynamic JR resistance curve of the material at the same loading rate through a multi-specimen test method, and has the characteristics of simple and reliable structure, easy operation and accurate measurement.

[0040] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0042] Figure 1 A schematic flow chart of a method for determining dynamic fracture toughness provided by an embodiment of the present invention is shown;

[0043] Figure 2 A schematic diagram of a displacement-load curve of a loading point corresponding to a three-point bending specimen in a test group provided by an embodiment of the present invention is shown;

[0044] Figure 3 A schematic diagram of a JR resistance curve corresponding to a certain test group provided by an embodiment of the present invention is shown;

[0045] Figure 4 A schematic diagram of a JR resistance curve corresponding to different loading speeds provided by an embodiment of the present invention is shown;

[0046] Figure 5 A schematic flow chart of another method for determining dynamic fracture toughness provided by an embodiment of the present invention is shown;

[0047] Figure 6 A schematic flow chart of another method for determining dynamic fracture toughness provided by an embodiment of the present invention is shown;

[0048] Figure 7 A schematic flow chart of another method for determining dynamic fracture toughness provided by an embodiment of the present invention is shown;

[0049] Figure 8 A schematic flow chart of another method for determining dynamic fracture toughness provided in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0050] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0051] The embodiment of the present invention provides a method for determining dynamic fracture toughness, such as Figure 1 As shown, the method includes:

[0052] 101. Prefabricate a plurality of three-point bending specimens, and divide the three-point bending specimens into a plurality of test groups of equal number;

[0053] In the embodiment of the present invention, a plurality of three-point bending specimens (Singleedged notched bending), referred to as SEB, are prefabricated before the specimen loading process is performed. The prefabricated three-point bending specimens are divided and processed to obtain a plurality of test groups, each of which includes the same number of three-point bending specimens. For example, the three-point bending specimens are divided into 4 groups, each of which includes 8 three-point bending specimens, and 32 three-point bending specimens need to be prefabricated; the three-point bending specimens are divided into 3 groups, each of which includes 9 three-point bending specimens, and 27 three-point bending specimens need to be prefabricated, etc. The embodiment of the present invention does not make specific limitations.

[0054] It should be noted that the three-point bending specimen in the embodiment of the present invention is made of a ductile material to be analyzed, wherein the ductile material to be analyzed includes gold, copper, aluminum, a certain alloy steel, etc., which is not specifically limited in the embodiment of the present invention. The prefabricated three-point bending specimens have the same specifications, that is, the length, width, height, weight and other specification parameters are all equal, which is not specifically limited in the embodiment of the present invention. In addition, an initial crack of the same length is set at the same position of each three-point bending specimen for judging the morphological change after the loading treatment.

[0055] 102. configuring different loading speeds for each of the test groups, and performing uniform loading processing with different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speeds corresponding to each of the test groups, so as to obtain a loading point displacement-load curve corresponding to each of the three-point bending specimens;

[0056] In the embodiment of the present invention, different loading speeds are configured for each test group. At present, high-speed material testing machines have been used to complete material tensile performance tests, non-contact digital image correlation tests, and compression performance tests at different loading rates. High-speed material testing machines have not yet been used to test the dynamic fracture toughness of materials under uniform loading conditions, and there is no description of the elastic-plastic dynamic fracture toughness test of materials under medium and low uniform loading conditions. Therefore, in the embodiment of the present invention, the configured loading speed can be set to a medium and low uniform speed of 0.01 to 0.25 m / s, etc. The loading speed can be specifically configured according to the experimental requirements, and the embodiment of the present invention does not make specific restrictions. After configuring the loading speed, each three-point bending specimen in the group is subjected to uniform loading processing with different displacement loads according to the loading speed corresponding to each test group, and a loading point displacement-load curve corresponding to each three-point bending specimen is obtained; for example, at a loading speed of 0.01m / s corresponding to test group 1, the 8 three-point bending specimens in the group are subjected to uniform loading processing with different displacement loads, and 8 corresponding loading point displacement-load curves are obtained; then, at a loading speed of 0.05m / s corresponding to test group 2, the 8 three-point bending specimens in the group are subjected to uniform loading processing with different displacement loads, and 8 corresponding loading point displacement-load curves are obtained; then, at a loading speed of 0.25m / s corresponding to test group 3, the 8 three-point bending specimens in the group are subjected to uniform loading processing with different displacement loads, and 8 corresponding loading point displacement-load curves are obtained, and so on, until all the loading processing of the three-point bending specimens in all the test groups is completed, and the embodiments of the present invention do not make specific limitations. Figure 2 As shown, it represents the eight loading point displacement-load curves corresponding to the eight three-point bending specimens numbered “1#”, “2#” to “8#” in a test group.

[0057] 103. Determine the crack extension of the three-point bending specimen after loading, and determine the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve;

[0058] In the embodiment of the present invention, after all the specimens are loaded, the crack extension of the three-point bending specimen after loading is determined, which is recorded as △a; then the J integral corresponding to each three-point bending specimen is determined based on the crack extension and the loading point displacement-load curve obtained in step 102. Among them, the J integral is an essential key mechanical performance parameter in the structural safety and integrity assessment of ductile materials.

[0059] 104. Draw a JR resistance curve based on the crack extension amount and the corresponding J integral in each of the test groups to obtain the JR resistance curve corresponding to each loading speed.

[0060] In the embodiment of the present invention, a JR resistance curve is drawn based on the crack extension Δa and the corresponding J integral in each test group obtained in step 103, such as Figure 3 As shown in FIG. 1 , it represents the JR resistance curve corresponding to a certain test group. Since each test group is configured with a different loading speed, the JR resistance curve corresponding to each test group is the JR resistance curve corresponding to each different loading speed, such as Figure 4 As shown, Figure 4 It includes the JR resistance curves corresponding to the three test groups under medium and low average speed loading conditions. Since the loading speeds of 0.01m / s, 0.05m / s and 0.25m / s were configured for the three test groups respectively, the JR resistance curves corresponding to the loading speeds of 0.01m / s, 0.05m / s and 0.25m / s were obtained respectively.

[0061] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to compare the dynamic fracture toughness under different loading speeds, another method for determining the dynamic fracture toughness is provided, such as Figure 5 As shown, before the step of performing uniform speed loading processing of different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, the method further includes:

[0062] 201. Numbering each of the three-point bending specimens in the test group to obtain a specimen number corresponding to each of the three-point bending specimens;

[0063] In the embodiment of the present invention, the three-point bending specimens in the test group divided in step 101 are numbered to obtain specimen numbers corresponding to the three-point bending specimens. Figure 2 As shown, the sample numbers in a certain test group are respectively “1#”, “2#”, “3#”, “4#”, etc., which are not specifically limited in the embodiment of the present invention.

[0064] 202. Configure a corresponding displacement load for each of the sample numbers, so that the displacement loads configured for the three-point bending samples with the same sample number in each of the test groups are also the same.

[0065] In the embodiment of the present invention, a corresponding displacement load is configured for each specimen number. It should be noted that the displacement load corresponding to each specimen number is different. However, the three-point bending specimens with the same specimen number in each test group are configured with the same displacement load. For example, the displacement load of the "1#" three-point bending specimen in test groups 1, 2, 3, etc. is F1; the displacement load of the "2#" three-point bending specimen in test groups 1, 2, 3, etc. is F2; ​​the displacement load of the "3#" three-point bending specimen in test groups 1, 2, 3, etc. is F3, etc. The embodiment of the present invention does not make specific limitations.

[0066] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to overcome the problem that the displacement or load control of the loading process cannot be achieved due to the continuous and unstoppable dynamic loading process of the high-speed material testing machine, another method for determining the dynamic fracture toughness is provided, such as Figure 6 As shown, the steps of performing uniform speed loading processing with different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups include:

[0067] 301. Obtain the displacement load corresponding to each sample number in the test group to be loaded;

[0068] 302. Determine the lowest loading position of the high-speed material testing machine by adjusting the length of the upper support rod in the high-speed material testing machine, so that the lowest loading position corresponds to the displacement loading amount corresponding to each of the sample numbers;

[0069] 303. Based on the loading speed corresponding to the test group to be loaded and in accordance with the displacement load corresponding to the sample number, the adjusted high-speed material testing machine is used to perform uniform speed loading processing on each of the three-point bending samples in the group.

[0070] In the embodiment of the present invention, the corresponding displacement load configured for each sample number in the test group to be loaded is obtained. Then, the lowest loading position of the high-speed material testing machine is determined by adjusting the length of the upper support rod in the high-speed material testing machine, so that the adjusted lowest loading position corresponds to the displacement load corresponding to each sample number; then, based on the loading speed corresponding to the test group to be loaded, according to the displacement load corresponding to the sample number, the adjusted high-speed material testing machine is used to perform uniform speed loading on each three-point bending sample in the group.

[0071] It should be noted that the steps in the embodiment of the present invention further include: performing uniform loading processing of different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups to obtain the loading point displacement-load curve corresponding to each of the three-point bending specimens;

[0072] 304. During the uniform speed loading process, real-time monitoring is performed on the loading point displacement of the three-point bending specimen and the load of the high-speed material testing machine;

[0073] 305. Draw a curve based on the corresponding relationship between the loading point displacement and the load to obtain the loading point displacement-load curve corresponding to the three-point bending specimen.

[0074] In the embodiment of the present invention, during the uniform speed loading process of each three-point bending specimen, a sampling displacement sensor and a load sensor are required to respectively monitor the loading point displacement of the three-point bending specimen and the load of the high-speed material testing machine in real time; then, a curve is drawn based on the corresponding relationship between the loading point displacement and the load to obtain a loading point displacement-load curve corresponding to each three-point bending specimen, such as Figure 2 As shown, there are eight loading point displacement-load curves corresponding to the 1# three-point bending specimen to the 8# three-point bending specimen in a certain loading test group.

[0075] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to accurately obtain the key mechanical performance parameter J integral, another method for determining dynamic fracture toughness is provided, such as Figure 7 As shown, the step determines the crack extension of the three-point bending specimen after loading, and determines the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve, including:

[0076] 401. Determine the crack extension of the three-point bending specimen after loading by a thermal coloring method or a secondary fatigue line drawing method;

[0077] 402. Obtaining a plastic component based on the loading point displacement-load curve;

[0078] 403. Determine the J-integral corresponding to each of the three-point bending specimens based on the plastic component and the crack extension.

[0079] In the embodiment of the present invention, the crack extension △a of each three-point bending specimen after loading is determined by a thermal coloring method or a secondary fatigue line drawing method; then, the loading point displacement-load curve corresponding to each three-point bending specimen obtained from step 304 to step 305 is obtained, and the plastic component is obtained based on the loading point displacement-load curve, which is recorded as U p ; Based on the plastic component U p The J integral corresponding to each of the three-point bending specimens is determined by the crack extension △a. The specific formula is as follows:

[0080]

[0081] Where F is the applied force, S is the span, B is the thickness of the three-point bending specimen, and B N is the net thickness of the specimen between the two side grooves, W is the width of the three-point bending specimen, a is the nominal crack length, The value can be found in Appendix B of GB / T 21143, v is Poisson's ratio, E is the elastic modulus at the test temperature, U pis the plastic component of the area under the force and displacement curve of the force application point, a0 is the initial crack length, and Δa is the stable crack extension including the passive zone.

[0082] Further, as a refinement and extension of the above-mentioned specific implementation method, in order to obtain the JR resistance curve corresponding to different loading speeds, another method for determining the dynamic fracture toughness is provided, such as Figure 8 As shown, the step of drawing a JR resistance curve based on the crack extension amount and the corresponding J integral in each test group to obtain the JR resistance curve corresponding to each loading speed includes:

[0083] 501. Obtain the crack extension amount and the corresponding J integral in each test group respectively;

[0084] 502. Performing curve fitting processing based on the crack extension amount and the corresponding J integral to obtain a JR resistance curve corresponding to each of the test groups;

[0085] 503. Obtain the loading speed configured for each test group, and associate the loading speed with the JR resistance curve to obtain the JR resistance curve corresponding to each loading speed.

[0086] In the embodiment of the present invention, the crack extension amount and the corresponding J integral in each test group are obtained respectively. For example, if the test group contains 8 three-point bending specimens, 8 groups of crack extension amount △a and corresponding J integral data groups are obtained, and the embodiment of the present invention does not make specific restrictions. Then, based on the obtained crack extension amount △a and the corresponding J integral data group, curve fitting processing is performed to obtain the JR resistance curve corresponding to each test group; then the loading speed configured for each test group is obtained, and the loading speed is associated with the JR resistance curve to obtain the JR resistance curve corresponding to each loading speed.

[0087] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to study the influence of loading speed on dynamic fracture toughness, another method for determining dynamic fracture toughness is provided, the method further comprising:

[0088] Compare and process the JR resistance curves corresponding to various loading speeds to obtain a comparison result;

[0089] An influence of a loading speed on the JR resistance curve is determined based on the comparison result.

[0090] In the embodiment of the present invention, the JR resistance curves corresponding to each loading speed are compared and processed to obtain a comparison result; Figure 4As shown in FIG. 1 , the JR resistance curve corresponding to the static loading speed of 0.01 m / s and the JR resistance curve corresponding to the dynamic loading speeds of 0.01 m / s, 0.05 m / s and 0.25 m / s are placed in a curve chart for comparative analysis to obtain a comparison result. Based on the comparison result, the influence of the loading speed on the JR resistance curve is determined. Figure 4 It can be seen that the effect of dynamic loading rate on the dynamic fracture toughness of ductile materials is different from the effect of static loading rate on the dynamic fracture toughness of ductile materials.

[0091] The embodiment of the present invention provides a method for determining dynamic fracture toughness. Compared with the prior art, the present invention prefabricates a plurality of three-point bending specimens and divides the three-point bending specimens into a plurality of test groups of equal number; configures different loading speeds for each of the test groups, and performs uniform loading processing of different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, so as to obtain the loading point displacement-load curve corresponding to each of the three-point bending specimens; determines the crack extension of the three-point bending specimen after loading, and determines the J integral corresponding to each of the three-point bending specimens based on the crack extension and the loading point displacement-load curve; draws the JR resistance curve based on the crack extension and the corresponding J integral in each of the test groups, so as to obtain the JR resistance curve corresponding to each loading speed. The present invention obtains the dynamic JR resistance curve of the material at the same loading rate through a multi-specimen test method, and has the characteristics of simple and reliable structure, easy operation, and accurate measurement.

[0092] As the above Figure 1 To implement the method shown, an embodiment of the present invention provides a device for measuring dynamic fracture toughness, the device comprising:

[0093] High-speed materials testing machine, three-point bend test fixture, mounting base, loading support rollers and upper support rod;

[0094] The mounting base is fixedly connected to the base of the high-speed material testing machine, and the three-point bending test fixture is fixed on the mounting base;

[0095] The three-point bending specimen is fixed on the high-speed material testing machine by the three-point bending test fixture, and the length of the upper support rod is adjusted by the loading support roller so that the upper support rod provides different displacement loads to the three-point bending specimen.

[0096] Furthermore, the device also includes a displacement sensor and a load sensor;

[0097] The displacement sensor is used to collect the displacement of the loading point of the three-point bending specimen during the uniform loading process;

[0098] The load sensor is used to collect the load corresponding to the displacement of the loading point.

[0099] The embodiment of the present invention provides a dynamic fracture toughness determination device. Compared with the prior art, the present invention prefabricates a plurality of three-point bending specimens and divides the three-point bending specimens into a plurality of test groups of equal number; configures different loading speeds for each of the test groups, and performs uniform loading processing of different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, so as to obtain the loading point displacement-load curve corresponding to each of the three-point bending specimens; determines the crack extension of the three-point bending specimen after loading, and determines the J integral corresponding to each of the three-point bending specimens based on the crack extension and the loading point displacement-load curve; draws the JR resistance curve based on the crack extension and the corresponding J integral in each of the test groups, so as to obtain the JR resistance curve corresponding to each loading speed. The present invention obtains the dynamic JR resistance curve of the material at the same loading rate through a multi-specimen test method, and has the characteristics of simple and reliable structure, easy operation, and accurate measurement.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining dynamic fracture toughness, characterized in that: include: Prefabricate a plurality of three-point bending specimens, and divide the three-point bending specimens into a plurality of test groups of equal number; Different loading speeds are configured for each of the test groups, and uniform loading processes with different displacement loads are performed on each of the three-point bending specimens in the group according to the loading speeds corresponding to each of the test groups, so as to obtain loading point displacement-load curves corresponding to each of the three-point bending specimens; Determine the crack extension of the three-point bending specimen after loading, and determine the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve; A JR resistance curve is plotted based on the crack extension amount and the corresponding J integral in each of the test groups to obtain the JR resistance curve corresponding to each loading speed.

2. The method according to claim 1, characterized in that The three-point bending specimens are made of ductile materials to be analyzed, each of the three-point bending specimens has the same specification, and initial cracks with the same length are arranged at the same position of a plurality of the three-point bending specimens.

3. The method according to claim 1, characterized in that Before performing uniform speed loading processing with different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, the method further includes: Numbering each of the three-point bending specimens in the test group to obtain a specimen number corresponding to each of the three-point bending specimens; A corresponding displacement load is configured for each of the sample numbers, so that the displacement load configured for the three-point bending samples with the same sample number in each of the test groups is also the same.

4. The method according to claim 3, characterized in that The uniform speed loading process of different displacement loading amounts is performed on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups, including: Obtaining the displacement load corresponding to each of the sample numbers in the test group to be loaded; The lowest loading position of the high-speed material testing machine is determined by adjusting the length of the upper support rod in the high-speed material testing machine, so that the lowest loading position corresponds to the displacement loading amount corresponding to each of the sample numbers; Based on the loading speed corresponding to the test group to be loaded and in accordance with the displacement load corresponding to the sample number, the adjusted high-speed material testing machine is used to perform uniform speed loading processing on each of the three-point bending samples in the group.

5. The method according to claim 1, characterized in that The method further comprises: performing uniform loading processing of different displacement loading amounts on each of the three-point bending specimens in the group according to the loading speed corresponding to each of the test groups to obtain a loading point displacement-load curve corresponding to each of the three-point bending specimens. During the uniform loading process, the displacement of the loading point of the three-point bending specimen and the load of the high-speed material testing machine are monitored in real time; A curve is drawn based on the corresponding relationship between the loading point displacement and the load to obtain the loading point displacement-load curve corresponding to the three-point bending specimen.

6. The method according to claim 1, characterized in that The method of determining the crack extension of the three-point bending specimen after loading, and determining the J integral corresponding to each three-point bending specimen based on the crack extension and the loading point displacement-load curve, comprises: Determine the crack extension of the three-point bending specimen after loading by thermal coloring method or secondary fatigue line drawing method; Obtaining a plastic component based on the displacement-load curve of the loading point; A J-integral corresponding to each of the three-point bending specimens is determined based on the plastic component and the crack extension amount.

7. The method according to claim 1, characterized in that The method of drawing a JR resistance curve based on the crack extension amount and the corresponding J integral in each test group to obtain the JR resistance curve corresponding to each loading speed includes: Respectively obtaining the crack extension amount and the corresponding J integral in each test group; Performing curve fitting processing based on the crack extension amount and the corresponding J integral to obtain a JR resistance curve corresponding to each of the test groups; The loading speed configured for each test group is obtained, and the loading speed is associated with the JR resistance curve to obtain the JR resistance curve corresponding to each loading speed.

8. The method according to any one of claims 1 to 7, characterized in that: The method further comprises: Compare and process the JR resistance curves corresponding to various loading speeds to obtain a comparison result; An influence of a loading speed on the JR resistance curve is determined based on the comparison result.

9. A dynamic fracture toughness measuring device, characterized in that: Includes a high-speed material testing machine, a three-point bending test fixture, a mounting base, a loading support roller, and an upper support rod; The mounting base is fixedly connected to the base of the high-speed material testing machine, and the three-point bending test fixture is fixed on the mounting base; The three-point bending specimen is fixed on the high-speed material testing machine by the three-point bending test fixture, and the length of the upper support rod is adjusted by the loading support roller so that the upper support rod provides different displacement loads to the three-point bending specimen.

10. The device according to claim 9, characterized in that The device also includes a displacement sensor and a load sensor; The displacement sensor is used to collect the displacement of the loading point of the three-point bending specimen during the uniform loading process; The load sensor is used to collect the load corresponding to the displacement of the loading point.

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