Test method for determining the fracture properties of materials obtained based on 0.5T-CT specimen regeneration technology

Abstract

The present invention relates to the technical field of mechanical property testing of metallic materials, and more particularly to a method for testing the fracture properties of materials obtained based on 0.5T-CT test piece recycling technology. The method for testing the fracture properties of materials obtained based on 0.5T-CT test piece recycling technology includes the steps of: preparing a 0.5T-CT initial test piece of a base material, conducting a fracture property test, and obtaining a 0.5T-CT test piece residue after the test; conducting tests and analyses on the base material to obtain a whole-process equivalent stress-strain relationship curve of the base material; determining the range of materials that can be used to prepare the recycled test piece; recycling the test piece by welding reusable materials and auxiliary materials to obtain a 0.5T-CT recycled test piece; conducting tests and analyses on the weld seam material to obtain a stress-strain relationship curve of the weld seam material; determining the fracture parameters of the 0.5T-CT recycled test piece; and conducting a fracture toughness test on the 0.5T-CT recycled test piece based on the fracture parameters to obtain the fracture properties of the base material and / or the weld seam material. The test method of the present invention is simple and the test results are accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical property tests of metal materials, and specifically relates to a test method for the fracture properties of materials obtained based on the 0.5T-CT specimen regeneration technology.

Background Art

[0002] In order to monitor the neutron irradiation embrittlement degree of the reactor pressure vessel (RPV) in a nuclear power plant, RPV irradiation monitoring specimens are installed near the inside of the RPV. In order to obtain the fracture toughness of the RPV material, the monitoring specimens are taken out periodically and hot cell tests are performed. Thereby, the life of the RPV against rapid brittle fracture is evaluated, and the P-T curve (pressure-temperature limit curve), which is an index for the start / stop, hydrostatic test, and normal operation of the RPV, is determined. This is extremely important for nuclear power plants and is highly regarded in the industry.

[0003] However, in the stage of extending the operating license of a nuclear power plant, there may be a problem of insufficient monitoring specimens. Therefore, in order to solve the difficult problem in the actual process of insufficient specimens, attempts have been made to reuse by returning the residual materials of the used monitoring specimens back into the reactor pressure vessel for continuous irradiation and taking out these residual materials to regenerate new monitoring specimens when necessary.

[0004] The regeneration technology for test specimens makes it possible to effectively utilize limited irradiation monitoring materials and obtain fracture toughness data for materials corresponding to longer service lives. For example, Patent Document 1 discloses a method for determining the minimum insert size in the regeneration technology for Charpy impact test specimens. However, the means for producing a regenerated Charpy impact test specimen and the method for determining the performance of the regenerated test specimen provided in Patent Document 1 are applicable only to Charpy test specimens for obtaining impact characteristics and are not applicable to compact tension test specimens. Furthermore, Patent Document 2 discloses a method for producing a regenerated compact tension test specimen. Patent Document 2 provides the acquisition of the insert area range based on DIC technology and a new method for producing test specimens, but it does not mention the selection of welding parameters or the method for obtaining fracture parameters of the regenerated test specimen. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Chinese Patent Application No. 201410060019.5 [Patent Document 2] Chinese Patent Application No. 202210846785.9 [Overview of the project] [Problems that the invention aims to solve]

[0006] In view of the above, and in order to overcome the shortcomings of the prior art, the object of the present invention is to provide a method for testing the fracture properties of a material obtained based on a 0.5T-CT specimen regeneration technology applied to fracture toughness testing of reactor pressure vessel materials in pressurized water nuclear power plants. [Means for solving the problem]

[0007] To achieve the above objectives, the technical means used in this invention are as follows.

[0008] The test method for determining the fracture properties of materials obtained based on 0.5T-CT specimen regeneration technology includes the following steps:

[0009] Initial 0.5T-CT test specimens of the base material are prepared, fracture characteristic tests are conducted, and the remaining 0.5T-CT test specimen material after the tests is obtained.

[0010] For the aforementioned base material, the equivalent stress-strain relationship curve for the entire process—proportional elongation-yielding-strengthening-necking-fracture—is tested and analyzed to determine the equivalent stress-strain relationship curve for the entire process.

[0011] The size of the crack tip plastic region in the remaining specimen material is calculated to determine the range of materials that can be used to produce recycled specimens.

[0012] The non-plastic deformation regions on both sides of the remaining specimen material are cut out to form reusable material, and the specimen is regenerated by welding the reusable material and auxiliary material to obtain a 0.5T-CT regenerated specimen.

[0013] We will perform tests and analyses of stress-strain relationship curves for welded joint materials to obtain the stress-strain relationship curves for welded joint materials.

[0014] Based on the equivalent stress-strain relationship curve for the entire process and the stress-strain relationship curve for the welded joint material, the fracture parameters of the 0.5T-CT regenerated specimen are determined.

[0015] Based on the fracture parameters, fracture toughness tests are performed on 0.5T-CT regenerated specimens to obtain the fracture characteristics of the base material and / or the welded joint material.

[0016] According to some preferred embodiments of the present invention, when testing and analyzing the overall equivalent stress-strain relationship curve for the above-mentioned base material, the load-displacement curve of a tensile test specimen obtained by combining the overall equivalent stress-strain relationship curve with finite element iterative analysis is performed iteratively until the load-displacement curve of the tensile test specimen obtained by combining the overall equivalent stress-strain relationship curve with finite element iterative analysis overlaps with the load-displacement curve obtained by the tensile test, thereby determining the overall equivalent stress-strain relationship curve.

[0017] Specifically, in some embodiments, the stress-strain relationship of the material is obtained as an initial construct relationship by a uniaxial tensile test, and the load-displacement relationship of the funnel-shaped specimen is calculated by inputting this into a finite element system. At the same time, an iterative analysis is performed with the load-displacement relationship of the funnel-shaped specimen obtained by the test. Next, the input stress-strain relationship is further updated until the load-displacement relationship of the funnel-shaped specimen obtained by the finite element calculation almost overlaps with the load-displacement obtained by the test. The stress-strain relationship input at this point becomes the equivalent stress-strain relationship of the material over the entire process.

[0018] According to some preferred embodiments of the present invention, in calculating the size of the crack tip plastic region of the initial 0.5T-CT specimen, the determined overall equivalent stress-strain relationship curve is input to the finite elements as the constitutive relationship of the base material.

[0019] According to some preferred embodiments of the present invention, when determining the range of materials that can be used to produce the above-mentioned regenerated specimens, the exact location and size of the non-plastic deformation region used to produce the 0.5T-CT regenerated specimens are calculated using the overall equivalent stress-strain relationship curve determined by finite element iterative analysis.

[0020] According to some preferred embodiments of the present invention, the welding is electron beam welding, and the arc start point in the welding process is located outside the area of ​​the reusable material. In some embodiments, the welding parameters are an acceleration voltage of 140-160kV, a focusing current of 1200-1400mA, a welding current of 10-25mA, and a welding speed of 900-1100mm / min. Preferably, the acceleration voltage is 150kV, the focusing current is 1300mA, the welding current is 10-25mA, and the welding speed is 1000mm / min.

[0021] According to some preferred embodiments of the present invention, the overall width of the welded joint and heat-affected zone is approximately 2.376 mm.

[0022] According to some preferred embodiments of the present invention, the auxiliary material is a material of the same type as the base material.

[0023] According to some preferred embodiments of the present invention, the fracture parameters include a stress intensity factor K and a J integral J.

[0024] According to some preferred embodiments of the present invention, the integral J is the elastic integral J e The determination of the J integral J and stress intensity factor K in the fracture parameters of a 0.5T-CT regenerated specimen includes the following steps:

[0025] Based on the aforementioned equivalent stress-strain relationship curve for the entire process and the stress-strain relationship curve for the welded joint material, and combining the principle of energy equivalence, the load P and elastic displacement h of the 0.5T-CT regenerated test specimen are determined. e , elastic strain energy U e Relationship

[0026]

number

[0027] To lead.

[0028] In the formula

[0029]

number

[0030] This represents the characteristic elastic strain energy,

[0031]

number

[0032] That is the case.

[0033]

number

[0034] This represents the characteristic elastic load,

[0035] [Numerical]

[0036] is V. * represents the characteristic volume, and V * = A * h * is h. * h represents the characteristic displacement of the 0.5T - CT regeneration test piece. A * represents the characteristic area of the 0.5T - CT regeneration test piece. P represents the load. h e represents the elastic displacement, and U e represents the elastic strain energy.

[0037] From Equation (1), the relationship between the strain energy U e and the load P is

[0038] [Numerical]

[0039] is obtained.

[0040] The energy definition formula of the J - integral J

[0041] [Numerical]

[0042] By combining

[0043] [Numerical]

[0044] is obtained.

[0045] In the formula, U represents the crack tip energy. B represents the thickness of the 0.5T-CT regenerated specimen. a represents the crack length. P represents the load. k0 represents the undetermined coefficient. E represents the elastic modulus of the material. The material includes the base metal and / or welded joint material.

[0046] The aforementioned elastic integral J e This is equal to the energy G and can be obtained by transforming the stress intensity factor K. Elastic integral J e The relationship between the stress intensity factor K and the above-mentioned stress intensity factor is as follows:

[0047]

number

[0048] In the formula, E' represents the equivalent modulus of the material. e represents the elastic integral J. K represents the stress intensity factor. G represents energy.

[0049] Elasticity J integral J e Based on the relationship with the stress intensity factor K, the formula for calculating the stress intensity factor K is as follows:

[0050]

number

[0051] Obtain it.

[0052] A finite element model of the 0.5T-CT regenerated specimen is constructed, and load and displacement data are extracted by performing elastic finite element simulation analysis on the 0.5T-CT regenerated specimen. Equations (3) and (5) are determined by calibrating the undetermined coefficient k0 in equations (3) and (5) based on these results.

[0053] The J integral J and the stress intensity factor K are obtained by performing calculations based on the determined equations (3) and (5).

[0054] According to some preferred embodiments of the present invention, the J integral J is the pure plastic J integral J pThis includes the integral J of pure plasticity in the fracture parameters of the 0.5T-CT regenerated specimen. p The decision involves the following steps:

[0055] Based on the principle of energy equivalence, the load P, displacement h, and pure plastic deformation capacity U of the 0.5T-CT regenerated test specimen are determined. p Relationship

[0056]

number

[0057] To lead.

[0058] Characteristics of the formula: Plastic strain energy

[0059]

number

[0060] , characteristic load

[0061]

number

[0062] , Feature index m p These can be expressed as follows:

[0063]

number

[0064] In the equation, k1 represents the first undetermined coefficient, k2 represents the second undetermined coefficient, k3 represents the third undetermined coefficient, and k4 represents the fourth undetermined coefficient. The first, second, third, and fourth undetermined coefficients can be obtained by finite element analysis. R V represents the material coefficient. N represents the material index. * V represents the characteristic volume of the test specimen. * =h * A* h * This represents the characteristic displacement of the test specimen. A * This represents the characteristic area of ​​the test specimen.

[0065] For the 0.5T-CT regenerated test specimen, the following settings will be made.

[0066]

number

[0067] In the formula, W represents the width of the 0.5T-CT regenerated specimen, B represents the thickness of the 0.5T-CT regenerated specimen, and a represents the crack length of the 0.5T-CT regenerated specimen. m represents the effective volume loss parameter related to the crack length of the 0.5T-CT regenerated specimen.

[0068] By substituting into equations (6) and (7), the pure plastic deformation capacity U p Relationship between load P

[0069]

number

[0070] You can obtain this.

[0071] Definition of the energy U of the J integral J

[0072]

number

[0073] By combining these, the pure plasticity J integral of the test specimen is p The formula for calculation

[0074]

number

[0075] You can obtain this.

[0076] During preprocessing in finite element software, the tensile mechanical parameters of the material are input to calculate load-displacement curves under different a / W conditions, and geometrically irrelevant processing (P / A) is performed. * -h / h * The parameter m can be obtained by performing the following. Then, a pure plasticity calculation is performed on the initial test specimen. From equation (6), at different stress hardening levels

[0077]

number

[0078] , m p This is obtained. Then, by combining equation (7) and calibrating the first undetermined coefficient, the second undetermined coefficient, the third undetermined coefficient, and the fourth undetermined coefficient, equation (10) is determined.

[0079] By calculating using the determined equation (10), the pure plastic J integral J p Obtain it.

[0080] According to some preferred embodiments of the present invention, stress-strain relationship data of the welded joint material is obtained by the indentation method. Then, the stress-strain data of the base material over the entire process at different temperatures and the stress-strain relationship data of the welded joint material are input into a finite element model of a 0.5T-CT regenerated test specimen including the welded joint and calculated to obtain a load-displacement curve obtained by finite element calculation and a J integral J that takes into account the differences in material properties.

[0081] J integral J and J integral J calculated using the standard formula 標準試験片 We analyze the proportional relationship between and and and calibrate the proportionality constant β in equation (11).

[0082] From equation (11), it is possible to obtain the formula for calculating the J integral J of the fracture parameter and thus obtain the J integral J of the fracture parameter.

[0083]

number

[0084] In the formula

[0085]

number

[0086] Furthermore, J represents the J integral J at the crack tip in the 0.5T-CT regenerated specimen, and J 標準試験片 is the integral J of the crack tip in the base material, calculated using the standard formula. β represents the proportionality constant. F represents the applied load. B represents the thickness of the test specimen. N θ represents the net thickness of the specimen. a represents the crack length of the 0.5T-CT regenerated specimen, and W represents the crack width of the 0.5T-CT regenerated specimen. E represents the equivalent modulus of elasticity. ν represents Poisson's ratio. η p represents the plasticity factor. p represents the plastic deformability added to the 0.5T-CT regenerated specimen. a0 represents the initial crack length of the 0.5T-CT regenerated specimen. [Effects of the Invention]

[0087] Compared to the prior art, the advantages of the present invention are as follows:

[0088] The present invention provides a method for testing the fracture properties of materials obtained based on the 0.5T-CT specimen regeneration technology. This method combines finite element interpolation testing with the overall equivalent stress-strain relationship curve test of the material under different temperatures to obtain the distribution law of the crack tip plastic region, thereby accurately determining the reusable range of the remaining material after fracture testing of the 0.5T-CT specimen. Furthermore, a 0.5T-CT regenerated specimen is fabricated by welding. By determining a method for calculating the fracture parameters of the 0.5T-CT regenerated specimen based on the principles of fracture mechanics and the elastoplastic finite element interpolation testing method, the fracture properties of the 0.5T-CT regenerated specimen can be effectively obtained. Moreover, the fracture test results of the regenerated specimen and the base material are relatively consistent, making it possible to improve the material utilization rate by three times. The test method of the present invention is simple, and the test results are accurate.

[0089] To more clearly explain the technical means of the embodiments of the present invention, the drawings required for use in describing the embodiments are briefly described below. Needless to say, the drawings described below represent only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without requiring any creative work. [Brief explanation of the drawing]

[0090] [Figure 1] Figure 1 is a schematic diagram of a 0.5T-CT test specimen in a preferred embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of the welding of a regenerated test specimen in a preferred embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the funnel-shaped test specimen in a preferred embodiment of the present invention. [Figure 4] Figure 4 shows the overall equivalent stress-strain relationship curve of the material at -20°C in a preferred embodiment of the present invention. [Figure 5] Figure 5 shows the finite element mesh model of the initial 0.5T-CT test specimen in a preferred embodiment of the present invention. [Figure 6] Figure 6 shows a schematic of the size of the crack tip plastic region in a 0.5T-CT specimen at -20°C in a preferred embodiment of the present invention. [Figure 7] Figure 7 shows the load-displacement diagrams of fracture tests for initial and regenerated 0.5T-CT specimens in a preferred embodiment of the present invention. [Figure 8] Figure 8 shows a finite element mesh model of a 0.5T-CT regenerated specimen in a preferred embodiment of the present invention. [Figure 9] Figure 9 is a comparative diagram of the fracture test results of the initial 0.5T-CT test specimen and the regenerated test specimen in a preferred embodiment of the present invention. [Modes for carrying out the invention]

[0091] To facilitate a better understanding of the technical means of the present invention for those skilled in the art, the technical means in the embodiments of the present invention will be described clearly and concisely below, in conjunction with drawings relating to embodiments of the present invention. Needless to say, the embodiments described are only a selection of embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention, without requiring any creative work, shall all fall within the scope of the protection of the present invention.

[0092] The method for testing the fracture properties of a material obtained based on the 0.5T-CT specimen regeneration technology of the present invention comprises four parts: testing the fracture properties of the material based on the initial 0.5T-CT specimen, obtaining the equivalent stress-strain relationship curve for the entire process of the (base material), determining the material range of the initial 0.5T-CT specimen that can be used to prepare the regenerated specimen, and testing the fracture properties of the material based on the regenerated 0.5T-CT specimen. Furthermore, 0.5T-CT stands for compact tension.

[0093] Specifically, the method for testing the fracture properties of a material obtained based on the 0.5T-CT specimen regeneration technology in this embodiment includes the following steps.

[0094] Step (a): Prepare initial 0.5T-CT test specimens of the base material, conduct fracture property tests, and obtain the remaining 0.5T-CT test specimen material after testing.

[0095] The load and structure outlined when preparing the initial 0.5T-CT fracture toughness test specimens for the research material are shown in Figure 1. In the figure, P is the applied load, and V is the load. LL ∫ is the load line displacement of the 0.5T-CT specimen, B is the specimen thickness, and b is the length of the remaining ligament. Also, the left side of Figure 1 is a front view of the structure, and the right side of Figure 1 is a left side view of the structure.

[0096] Step (b): For the base material, the equivalent stress-strain relationship curve for the entire process of proportional elongation-yielding-strengthening-necking-fracture is tested and analyzed to obtain the equivalent stress-strain relationship curve for the entire process of the base material.

[0097] For the full-process equivalent stress-strain relationship curve test of the base material, the test specimens will be funnel-shaped round bar specimens (shown in Figure 3). Furthermore, by combining this with interpolation finite element iterative analysis, it is necessary to complete tensile tests on at least three effective test specimens until the load-displacement curve of the standard tensile test specimen, calculated based on the full-process equivalent stress-strain relationship curve input to the finite elements, nearly overlaps with the tensile load-displacement curve obtained from the test, thereby obtaining the full-process stress-strain relationship curve until the specimen fractures.

[0098] Proportional extension-yielding-strengthening-necking-fracture is the entire process of equivalent stress-strain throughout.

[0099] Specifically, in this embodiment, first, a stress-strain relationship is obtained as the initial constructive relationship by a uniaxial tensile test, and the load-displacement relationship of the funnel-shaped specimen is calculated by inputting this into a finite element system, while iterative analysis is performed with the load-displacement relationship of the funnel-shaped specimen obtained by the test. Next, the input stress-strain relationship is further updated until the load-displacement relationship of the funnel-shaped specimen obtained by the finite element calculation almost overlaps with the load-displacement obtained by the test. The stress-strain relationship input at this point becomes the equivalent stress-strain relationship of the material over the entire process.

[0100] In some feasible embodiments, when testing and analyzing the entire process equivalent stress-strain relationship curve for the base material, the load-displacement curve of a tensile test specimen obtained by combining the entire process equivalent stress-strain relationship curve with finite element iterative analysis is performed iteratively until the curve obtained by the tensile test overlaps with the curve obtained by the tensile test and the entire process equivalent stress-strain relationship curve is determined.

[0101] Step (c): Calculate the size of the crack tip plastic region of the initial specimen to determine the range of materials that can be used to prepare the regenerated specimen.

[0102] Specifically, in calculating the size of the crack tip plastic region of the initial 0.5T-CT specimen, the obtained equivalent stress-strain relationship curve for the entire process of the base material is input as the material's constitutive relationship. Furthermore, when determining the range of materials usable for the fabrication of regenerated specimens, the equivalent stress-strain relationship curve for the entire process of the base material obtained by finite element iterative analysis is used to calculate the precise location and size of the non-plastic deformation region used for fabricating the regenerated specimens.

[0103] In some embodiments, step (c) further includes performing a fracture toughness test on the initial fracture toughness 0.5T-CT specimen.

[0104] Specifically, fracture toughness tests performed on the surface of 0.5T-CT specimens are carried out in accordance with GB / T 21143-2014, and the real-time crack length of the specimen is measured using the load separation method recommended in Appendix J.

[0105] Step (d): The non-plastic deformation regions (regions other than the crack tip plastic region) on both sides of the 0.5T-CT specimen residue are cut out to form reusable material. Then, the specimen is regenerated by welding the reusable material and auxiliary material to obtain a regenerated 0.5T-CT specimen.

[0106] The welding will be performed using electron beam welding, and the test specimen will be regenerated referring to the welding method shown in Figure 2. The welding method in Figure 2 has three weld seams. Of these, one is a vertical weld seam and two are horizontal weld seams. To the right of the vertical weld seam and between the two horizontal weld seams, there is reusable material and auxiliary material. The reusable material is closer to the vertical weld seam, and the auxiliary material is located to the right of the reusable material. Except for this area, which is reusable material, all other areas are auxiliary material. Furthermore, no welding is performed between the reusable material between the two horizontal weld seams and the auxiliary material to its right. According to the welding method in Figure 2, since the arc start points during the welding process are all located outside the area of ​​the reusable material, the influence of residual stress on the test specimen is avoided.

[0107] In several other feasible embodiments, the overall width of the weld seam and heat-affected zone is small, not exceeding 3 mm. Furthermore, the mechanical properties of the auxiliary material and the reusable material are similar, and the base material is preferred.

[0108] After regenerating the material by welding the auxiliary material and the reusable material according to Figure 2, a 0.5T-CT regenerated test specimen is fabricated based on the structure in Figure 1, so that some of the initial cracks and their tips are located on the reusable material. This allows for the regeneration of two or more test specimens from the non-plastic deformation region of the material, improving the material utilization rate by more than three times.

[0109] Step (e): Test and analyze the stress-strain relationship curve for the welded joint material to obtain the stress-strain relationship curve for the welded joint material.

[0110] Specifically, the weld joint material is the material of the weld joint formed after welding the auxiliary material and the reusable material, and is usually a mixed material formed during the welding of the auxiliary material and the reusable material.

[0111] In this embodiment, the welding parameters are an acceleration voltage of 150kV, a convergence current of 1300mA, a welding current of 10-25mA, and a welding speed of 1000mm / min. In some other embodiments, the welding parameters are preferably an acceleration voltage of 140-160kV, a convergence current of 1200-1400mA, a welding current of 10-25mA, and a welding speed of 900-1100mm / min. According to the welding method and corresponding welding parameters in Figure 2, the heat-affected zone is reduced and the welding residual stress is decreased, so the influence of welding on the stress-strain field at the crack tip becomes extremely small.

[0112] Step (f): Determine the fracture parameters of the 0.5T-CT regenerated specimen based on the overall equivalent stress-strain relationship curve of the base material and the stress-strain relationship curve of the welded joint material.

[0113] The fracture parameters include the stress intensity factor K and the J integral J. The whole-process equivalent stress-strain relationship curve of the material obtained in step (b) is input as the material's constitutive relationship, and the coefficients in the fracture parameter calculation formula for the 0.5T-CT regenerated specimen are determined based on fracture mechanics theory and elastoplastic finite element interpolation analysis techniques. This ensures accurate and reliable calculation of the fracture parameters at the crack tip and eliminates the influence of welding on the regenerated specimen.

[0114] Furthermore, the integral J is the elasticity integral J e and pure plastic J integral J p This includes... Depending on the application and material, the fracture parameters may include only the stress intensity factor K, or the elastic integral J. e And may include the stress intensity factor, and the pure plastic J integral J p It may include one, or it may include all three.

[0115] In some feasible embodiments, the J integral J is the elastic J integral J e The determination of the J integral J and stress intensity factor K in the fracture parameters of a 0.5T-CT regenerated specimen includes the following steps:

[0116] Based on the entire process equivalent stress-strain relationship curve of the base material and the stress-strain relationship curve of the welded joint material, and combining the principle of energy equivalence, the load P and elastic displacement h of the 0.5T-CT regenerated test specimen were determined. e , elastic strain energy U e Relationship

[0117]

number

[0118] To lead.

[0119] In the formula

[0120]

number

[0121] This represents the characteristic elastic strain energy,

[0122]

number

[0123] That is the case.

[0124]

number

[0125] This represents the characteristic elastic load,

[0126]

number

[0127] V * V represents the characteristic volume, * =A * h * h * This represents the characteristic displacement of the 0.5T-CT regenerated specimen. A * represents the characteristic area of ​​the 0.5T-CT regenerated specimen. P represents the load. h e represents elastic displacement, U e This represents the elastic strain energy.

[0128] From equation (1), the strain energy U e The relationship between and load P is

[0129]

number

[0130] To obtain that it is true.

[0131] Definition of energy J integral

[0132]

number

[0133] By combining them,

[0134]

number

[0135] You can obtain this.

[0136] In the formula, U represents the crack tip energy. B represents the thickness of the 0.5T-CT regenerated specimen. a represents the crack length. P represents the load. k0 represents the undetermined coefficient. E represents the elastic modulus of the material. The material includes the base metal and / or welded joint material.

[0137] The elastic part of the J integral J is represented by the elastic J integral J. e This is equal to the energy G and can be obtained by transforming the stress intensity factor K. Elastic integral J e The relationship between and the stress intensity factor K is as follows:

[0138]

number

[0139] Furthermore, K is the stress intensity factor.

[0140] In the formula, E' represents the equivalent modulus of the material. e represents the elastic integral J. K represents the stress intensity factor. G represents energy.

[0141] Furthermore, the formula for calculating the stress intensity factor K of a 0.5T-CT regenerated test specimen.

[0142]

number

[0143] Obtain it.

[0144] A finite element model of the regenerated specimen is constructed, and elastic finite element simulation analysis is performed to extract load and displacement data. By calibrating the undetermined parameter in equation (1), the formula for calculating the stress intensity factor K of the 0.5T-CT regenerated specimen is obtained. Then, by calculating using equation (5), the stress intensity factor K of the 0.5T-CT regenerated specimen is obtained.

[0145] Furthermore, by calculating using equation (3), the elastic J integral of the 0.5T-CT regenerated specimen can be obtained. e Obtain it.

[0146] J integral J is pure plasticity J integral J p Includes. Pure plasticity J integral J in the fracture parameters of 0.5T-CT regenerated specimens. p The decision involves the following steps:

[0147] Based on the principle of energy equivalence, the load P, displacement h, and pure plastic deformation capacity U of the 0.5T-CT regenerated test specimen are determined. p Relationship

[0148]

number

[0149] To lead.

[0150] Characteristics of the formula: Plastic strain energy

[0151]

number

[0152] , characteristic load

[0153]

number

[0154] , Feature index m p These can be expressed as follows:

[0155]

number

[0156] In the equation, k1 represents the first undetermined coefficient, k2 represents the second undetermined coefficient, k3 represents the third undetermined coefficient, and k4 represents the fourth undetermined coefficient. The first, second, third, and fourth undetermined coefficients can be obtained by finite element analysis. R V represents the material coefficient. N represents the material index. * V represents the characteristic volume of the crack test specimen. * =h * A * h * This represents the characteristic displacement of the test specimen. A * represents the characteristic area of ​​the specimen. W and B represent the width and thickness of the specimen, respectively. m represents the effective volume loss parameter related to the crack length a of the specimen.

[0157] The following assumptions are made regarding the 0.5T-CT regenerated test specimen.

[0158]

number

[0159] In the formula, W represents the width of the 0.5T-CT regenerated specimen, B represents the thickness of the 0.5T-CT regenerated specimen, and a represents the crack length of the 0.5T-CT regenerated specimen. Also, m represents the effective volume loss parameter related to the crack length of the 0.5T-CT regenerated specimen.

[0160] By substituting into equations (6) and (7), the pure plastic deformation capacity U p Relationship between load P

[0161]

number

[0162] You can obtain this.

[0163] Definition of energy J integral

[0164]

number

[0165] By combining these, the pure plasticity J integral of the test specimen is p The formula for calculation

[0166]

number

[0167] You can obtain this.

[0168] During preprocessing in finite element software, the tensile mechanical parameters of the material are input to calculate load-displacement curves under different a / W conditions, and geometrically irrelevant processing (P / A) is performed. * -h / h * The parameter m can be obtained by performing the following. Then, a pure plasticity calculation is performed on the test specimen. From equation (6), at different stress hardening levels

[0169]

number

[0170] , m p This is obtained. Then, by combining equation (7) and calibrating the first, second, third, and fourth undetermined coefficients, equation (10) is determined.

[0171] Specifically, the tensile mechanical parameters of a material include hardness, yield, strength, and fracture. Depending on the J calculation formulas that require calculation, one or more of these parameters are selected and input into the finite element software before processing to participate in the finite element calculation.

[0172] By combining the collected physical parameters with equation (10) after determining the first, second, third, and fourth undetermined coefficients, the pure plastic J integral J is obtained. p You can obtain this.

[0173] In some feasible examples, stress-strain relationship data for the welded joint material is further obtained using the indentation method. Then, the stress-strain data for the entire process of the base material and the stress-strain relationship data for the welded joint material at different temperatures are input into a finite element model of a 0.5T-CT regenerated test specimen including the welded joint, and the load-displacement curve obtained by finite element calculation and the J integral J, which takes into account the differences in material properties, are obtained.

[0174] The J integral of the fracture parameter J and the J integral J calculated using the standard formula. 標準試験片 We analyze the proportional relationship between and and and calibrate the proportionality constant β in equation (11).

[0175] From equation (11), it is possible to obtain the formula for calculating the J integral of the fracture parameter, and thus obtain the J integral of the fracture parameter.

[0176]

number

[0177] In the formula

[0178]

number

[0179] Furthermore, J is the integral J of the crack tip of the regenerated specimen, and J 標準試験片 is the integral J of the crack tip in the standard specimen of the base material. β is the proportionality constant. F is the applied load. B is the thickness of the specimen, and B N is the net thickness of the specimen. a and W are the crack length and width of the specimen, respectively. E is the equivalent modulus of elasticity. ν is Poisson's ratio. η p represents the plasticity factor. prepresents the plastic deformability applied to the specimen. a0 is the initial crack length of the specimen.

[0180] Furthermore, the standard formula is J of formula (11). 標準試験片 This is the corresponding formula. The base material standard test specimen includes the initial test specimen.

[0181] Step (g): Based on the determined fracture parameters of the regenerated 0.5T-CT specimen, a fracture toughness test is performed on the regenerated 0.5T-CT specimen to obtain the fracture characteristics of the material. Verification revealed that the test results could represent the fracture characteristics of the original material.

[0182] When conducting fracture toughness tests on 0.5T-CT regenerated specimens, it is necessary to verify the reliability of the crack length measurement method during the test process, taking into full consideration the influence of material non-uniformity in different regions of the welded joint of the regenerated specimen. Therefore, it is necessary to determine the parameters of the fracture characteristics of the regenerated specimen based on the calculation formula for fracture parameters applied to the regenerated specimen determined in step (f). The fracture parameters include the J integral J and the stress intensity factor K, but these are specifically determined according to the needs of the test.

[0183] One feasible embodiment of a test method for determining the fracture properties of a material obtained based on 0.5T-CT specimen regeneration technology included the following steps:

[0184] Step (1): Testing the fracture properties of the material based on the initial 0.5T-CT specimen.

[0185] For the metallic material, 0.5T-CT test specimens were fabricated based on the structure shown in Figure 1, and the J-integral J-Δa curve of the material at -20°C was obtained referring to the GB / T 21143-2014 standard.

[0186] Step (2): Obtain the equivalent stress-strain relationship curve for the entire process of the base material.

[0187] Based on the structure shown in Figure 3, funnel-shaped test specimens were fabricated and tensile tests were conducted at -20°C. In addition, by using interpolated finite element iterative analysis in combination with tensile tests of standard round bar specimens, stress-strain relationship curves for the entire process until the base material fractured at -20°C were obtained, as shown in Figure 4.

[0188] In some other embodiments, depending on the needs of the situation, other standard methods may be combined, such as testing with plate-shaped tensile specimens or testing with equal-diameter round bar tensile specimens.

[0189] Step (3): Determining the material range of the 0.5T-CT initial specimens that can be used to prepare the regenerated specimens.

[0190] The stress-strain relationship curve obtained in step (2) for the entire process until the base material fractures at -20°C was input into a finite element model as the material's constitutive relationship, and a finite element model of the 0.5T-CT specimen shown in Figure 5 was constructed. Then, as shown in Figure 6, the size distribution of the crack tip plastic region of the 0.5T-CT specimen at different load levels was calculated. The coordinate origin represents the crack tip, and λ = P / (σ0Bb) represents the dimensionless height of the load level. In the equation, P is the applied load, σ0 is the yield stress of the material, B is the thickness of the specimen, and b is the length of the remaining ligament. From Figure 6, the range usable for specimen regeneration was determined by calculating the size of the plastic region with an applied load.

[0191] Step (4): Testing stress-strain relationship data of welded joint material. Stress-strain relationship data of the material in each minute region of the welded joint was obtained using the indentation method.

[0192] Step (5): Material fracture property testing techniques based on 0.5T-CT regenerated test specimens.

[0193] As shown in Figure 7, load-displacement curves were collected during fracture testing of the 0.5T-CT regenerated specimen. The stress-strain relationship curves obtained in step (2) for the entire process until the material fractured at -20°C were input into a finite element as the material's constitutive relationship, and a finite element mesh model of the 0.5T-CT specimen shown in Figure 8 was constructed. Corresponding parameters were input into this model, and load-displacement curves under different a / W conditions were calculated to perform geometrically independent processing (P / A). * -h / h * The parameter m could be obtained by performing the following. Then, pure plasticity calculations were performed on the test specimens. From equation (6), at different stress hardening levels

[0194]

number

[0195] , m p The following was obtained. Then, by combining equation (7) and calibrating k1 to k4, the corresponding fracture parameters were obtained.

[0196] Finite element calibration revealed that the proportionality constant β in equation (11) is 0.88. This made it possible to calculate the fracture parameters of the 0.5T-CT regenerated specimen.

[0197] Furthermore, the J-integral J-Δa curve of the material from the regenerated 0.5T-CT specimen was obtained through testing. Figure 9 shows the fracture J-integral J-Δa curves of the initial and regenerated 0.5T-CT specimens at -20°C. From this, it became clear that the fracture characteristics of the material obtained from the regenerated 0.5T-CT specimen can effectively represent the fracture characteristics of the base material.

[0198] The method for testing the fracture properties of a material obtained based on the 0.5T-CT specimen regeneration technology of the present invention includes the following steps.

[0199] (a) Prepare initial 0.5T-CT test specimens of the base material, conduct fracture characteristic tests, and obtain the remaining 0.5T-CT test specimen material after the tests.

[0200] (b) For the base material, conduct tests and analyses on the full-process equivalent stress-strain relationship curve to obtain the full-process equivalent stress-strain relationship curve of the base material.

[0201] (c) Calculate the size of the plastic zone at the crack tip of the initial test piece to determine the material range that can be used for fabricating the reproduced test piece.

[0202] (d) Cut off the non-plastic deformation regions on both sides of the test piece to form reusable material. Then, weld the reusable material and the auxiliary material to reproduce the test piece and obtain a 0.5T-CT reproduced test piece.

[0203] (e) Conduct tests and analyses on the stress-strain relationship curve of the weld joint material to obtain the stress-strain relationship curve of the weld joint material.

[0204] (f) Based on the full-process equivalent stress-strain relationship curve of the base material and the stress-strain relationship curve of the weld joint material, determine the fracture parameters of the 0.5T-CT reproduced test piece.

[0205] (g) Based on the fracture parameters, conduct a fracture toughness test on the 0.5T-CT reproduced test piece to obtain the fracture characteristics of the base material and / or the weld joint material.

[0206] In the present invention, by combining the finite element interpolation test technology with the full-process equivalent stress-strain relationship curve test of materials at different temperatures to obtain the distribution law of the plastic zone at the crack tip, the reusable range in the remaining material after conducting the fracture test on the 0.5T-CT test piece can be accurately determined. Also, a 0.5T-CT reproduced test piece is fabricated by welding. And by determining the calculation formula for the fracture parameters of the 0.5T-CT reproduced test piece based on the principle of fracture mechanics and the elastic-plastic finite element interpolation test method, the fracture characteristics of the 0.5T-CT reproduced test piece can be effectively obtained. Moreover, the fracture test results of the reproduced test piece and the base material are relatively consistent, and it is possible to improve the material utilization rate by three times. The test method of the present invention is simple and the test results are accurate.

[0207] The above embodiments are merely for the purpose of illustrating the technical concept and characteristics of the present invention, and are intended to enable those familiar with this technology to understand and implement the content of the present invention; therefore, the scope of protection of the present invention should not be limited by them. Substantially equivalent modifications and supplements made in accordance with the spirit of the present invention shall all be included within the scope of protection of the present invention.

Claims

1. A method for testing the fracture properties of a material obtained based on 0.5T-CT specimen regeneration technology, The process involves preparing an initial 0.5T-CT test specimen of the base material, conducting a fracture characteristics test, and obtaining the remaining 0.5T-CT test specimen after the test. The first step is to conduct tests and analyses of the equivalent stress-strain relationship curve for the entire process, from proportional elongation to yielding, strengthening, necking, and fracture, with respect to the aforementioned base material, in order to determine the equivalent stress-strain relationship curve for the entire process. The steps include: calculating the size of the crack tip plastic region of the remaining specimen material to determine the range of material that can be used to produce a recycled specimen; The steps include: cutting out the non-plastic deformation regions on both sides of the remaining specimen material to form reusable material, regenerating the specimen by welding the reusable material and auxiliary material, and obtaining a 0.5T-CT regenerated specimen; The process involves testing and analyzing the stress-strain relationship curve of the welded joint material to obtain the stress-strain relationship curve for the welded joint material, and The steps include determining the fracture parameters of the 0.5T-CT regenerated specimen based on the aforementioned equivalent stress-strain relationship curve for the entire process and the stress-strain relationship curve of the welded joint material, The steps include: performing a fracture toughness test on a 0.5T-CT regenerated specimen based on the fracture parameters to obtain the fracture characteristics of the base material and / or the welded joint material; A test method characterized by including [a certain component].

2. The test method according to claim 1, characterized in that when performing the test and analysis of the overall equivalent stress-strain relationship curve for the base material, the load-displacement curve of a tensile test specimen obtained by combining the overall equivalent stress-strain relationship curve with a finite element iterative analysis method is performed iteratively until the overall equivalent stress-strain relationship curve is determined by overlapping the curve obtained by the tensile test with the load-displacement curve of a tensile test specimen obtained by combining the overall equivalent stress-strain relationship curve with a finite element iterative analysis method.

3. The test method according to claim 2, characterized in that, in calculating the size of the crack tip plastic region of the initial 0.5T-CT test specimen, the determined overall equivalent stress-strain relationship curve is input to the finite elements as the construct relationship of the base material.

4. The test method according to claim 2, characterized in that, when determining the range of materials that can be used to produce the above-mentioned regenerated test specimens, the precise location and size of the non-plastic deformation region used to produce the 0.5T-CT regenerated test specimen are calculated using the all-process equivalent stress-strain relationship curve obtained by the finite element iterative analysis method.

5. The test method according to claim 1, characterized in that the welding is electron beam welding, the arc start point in the welding process is located outside the area of ​​the reusable material, the welding temperature in the welding process is 300°C or less, and the overall width of the weld joint and heat-affected zone does not exceed 3 mm.

6. The test method according to claim 1, characterized in that the auxiliary material is of the same type as the base material.

7. The test method according to claim 1, characterized in that the fracture parameters include the stress intensity factor K and / or the integral J.

8. The above J integral J is the elastic J integral J ｅ The determination of the J integral J and the stress intensity factor K in the fracture parameters of the 0.5T-CT regenerated specimen, Based on the aforementioned equivalent stress-strain relationship curve for the entire process and the stress-strain relationship curve for the welded joint material, and combining the principle of energy equivalence, the load P and elastic displacement h of the 0.5T-CT regenerated test specimen are determined. ｅ , elastic strain energy U ｅ Relationship [Number 44] Leading to, In the formula [Number 45] This represents the characteristic elastic strain energy, [Number 46] And, [Number 47] This represents the characteristic elastic load, [Number 48] and V ＊ represents the characteristic volume, and V ＊ = A ＊ h ＊ where h ＊ represents the characteristic displacement of the 0.5T-CT regeneration test piece, and A ＊ represents the characteristic area of the 0.5T-CT regeneration test piece, P represents the load, and h ｅ represents the elastic displacement, and U ｅ represents the elastic strain energy From equation (1), the strain energy U ｅ The relationship between and load P is [Number 49] Obtaining that, The definition of the energy J integral mentioned above [Number 50] By combining them, [Number 51] Obtained, In the formula, U represents the crack tip energy, B represents the thickness of the 0.5T-CT regenerated specimen, a represents the crack length, P represents the load, and k ０ represents an undetermined coefficient, E represents the elastic modulus of the material, and the material includes the base material and / or welded joint material. The aforementioned elastic integral J ｅ This is equal to the energy G and can be obtained by transforming the stress intensity factor K, and the elastic integral J ｅ The relationship between the stress intensity factor K and the above-mentioned stress intensity factor K is, [Number 52] And, In the formula, E' represents the equivalent modulus of the material, and J ｅ represents the elastic integral J, K represents the stress intensity factor, and G represents energy. Elasticity J, integral J ｅ Based on the relationship with the stress intensity factor K, the formula for calculating the stress intensity factor K is as follows: [Number 53] Obtain, A finite element model of the 0.5T-CT regenerated specimen was constructed, and elastic finite element simulation analysis was performed on the 0.5T-CT regenerated specimen to extract the load and displacement, and the undetermined coefficient k in equations (3) and (5) was calculated. ０ By calibrating, equations (3) and (5) are determined. The J integral J and the stress intensity factor K are obtained by performing calculations based on the determined equations (3) and (5). The test method according to claim 7, characterized by including the step of

9. J integral J is pure plasticity J integral J ｐ The integral J of pure plasticity in the fracture parameters of the 0.5T-CT regenerated specimen includes the integral J of pure plasticity. ｐ The decision was, Based on the principle of energy equivalence, the load P, displacement h, and pure plastic deformation capacity U of the 0.5T-CT regenerated test specimen are determined. ｐ Relationship [Number 54] Leading to, Characteristics of the formula: Plastic strain energy [Number 55] , characteristic load [Number 56] , Feature index m ｐ These are, [Number 57] It can be expressed as follows: k in the formula １ represents the first undetermined coefficient, k ２ represents the second undetermined coefficient, k ３ represents the third undetermined coefficient, k ４ represents the fourth undetermined coefficient, and the first, second, third, and fourth undetermined coefficients can be obtained by finite element analysis, K Ｒ represents the material coefficient, N represents the material index, and V ＊ V represents the characteristic volume of the test specimen. ＊ = h ＊ A ＊ h ＊ This represents the characteristic displacement of the test specimen, A ＊ This represents the characteristic area of ​​the test specimen. Regarding 0.5T-CT regenerated test specimens, [Number 58] Set it as follows: In the formula, W represents the width of the 0.5T-CT regenerated specimen, B represents the thickness of the 0.5T-CT regenerated specimen, a represents the crack length of the 0.5T-CT regenerated specimen, and m represents the effective volume loss parameter related to the crack length of the 0.5T-CT regenerated specimen. By substituting into equations (6) and (7), the pure plastic deformation capacity U ｐ Relationship between load P [Number 59] Obtained, Definition of the energy of J integral [Number 60] By combining these, the pure plasticity J integral J of the 0.5T-CT regenerated test specimen is obtained. ｐ The formula for calculation [Number 61] Obtained, During preprocessing in finite element software, the tensile mechanical parameters of the material are input to calculate load-displacement curves under different a / W conditions, and geometrically irrelevant processing (P / A) is performed. ＊ -h / h ＊ The parameter m can be obtained by performing the following: Pure plasticity calculations are performed on the initial specimen, and from equation (6), at different stress hardening levels [Number 62] , m ｐ This is obtained, and by combining equation (7) and calibrating the first undetermined coefficient, the second undetermined coefficient, the third undetermined coefficient and the fourth undetermined coefficient, equation (10) is determined. By calculating using the determined equation (10), the pure plastic J integral J ｐ To obtain The test method according to claim 7, characterized by including the step of

10. By obtaining stress-strain relationship data for the welded joint material using the indentation method, and inputting the stress-strain data for the entire process of the base material under different temperatures and the stress-strain relationship data for the welded joint material into a finite element model of a 0.5T-CT regenerated test specimen including the welded joint, the load-displacement curve obtained by finite element calculation and the J integral J, which takes into account the differences in material properties, are obtained. The J integral J of the aforementioned failure parameter and the J integral J calculated using the standard formula 標準試験片 By analyzing the proportional relationship between them, we calibrate the proportionality constant β in equation (11). From equation (11), it is possible to obtain the formula for calculating the integral J of the fracture parameter and to obtain the integral J of the fracture parameter. [Number 63] In the formula [Number 64] Here, J represents the J integral J at the crack tip in the 0.5T-CT regenerated specimen, and J 標準試験片 is the integral J of the crack tip of the base material obtained by calculation using the standard formula, β is the proportionality constant, F is the applied load, and B is the thickness of the 0.5T-CT regenerated test specimen. Ｎ ν represents the net thickness of the 0.5T-CT regenerated specimen, a represents the crack length of the 0.5T-CT regenerated specimen, W represents the crack width of the 0.5T-CT regenerated specimen, E represents the equivalent modulus of elasticity, ν represents Poisson's ratio, and η represents the equivalent modulus of elasticity. ｐ represents the plasticity factor, U ｐ This represents the plastic deformability added to the 0.5T-CT regenerated test specimen, and a ０ The test method according to claim 7, characterized in that represents the initial crack length of a 0.5T-CT regenerated test specimen.

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