Fracture toughness evaluation method considering thickness-direction fracture performance change of plate

Abstract

The invention relates to a fracture toughness evaluation method considering the fracture performance change in the thickness direction of a plate. The method comprises the following steps: S1, representing the change rule of the fracture performance in the thickness direction of the plate; s2, establishing a function relationship between the fracture performance and the reference temperature; s3, establishing a fracture toughness distribution model considering the thickness-direction fracture performance change of the plate; s4, the fracture toughness of any thickness layer of the plate is evaluated; according to the method, the characterization model of the fracture performance change rule in the thickness direction is introduced into the fracture toughness main curve, scientific calculation of fracture toughness probability distribution at any thickness layer of the plate can be achieved, and a new technical support is provided for reasonably evaluating the service safety of reactor pressure vessel steel.

Description

Technical Field

[0001] This invention relates to a method for evaluating fracture toughness that takes into account the changes in thickness fracture properties of plates, belonging to the technical field of performance evaluation of metallic materials. Background Technology

[0002] Current approaches to structural integrity assessment of reactor pressure vessels advocate for fracture testing of small specimens cut at one-quarter of the plate thickness. The lower fracture toughness is used to represent the overall structural fracture strength, aiming for a conservative assessment. The master fracture toughness curve is a method developed based on this approach, applicable to assessing the fracture performance of reactor pressure vessel steel. However, reactor pressure vessels are welded from approximately 200mm thick steel plates. During manufacturing and heat treatment, variations in thickness deformation lead to differences in microstructure evolution, resulting in non-uniform mechanical properties along the plate thickness. Existing structural integrity assessment methods ignore this characteristic, making it difficult to scientifically assess the fracture performance distribution along the thickness direction of the reactor pressure vessel and hindering reliable assessment of the service performance of reactor pressure vessel steel after long-term service. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a fracture toughness evaluation method that takes into account the changes in the fracture performance of the plate in the thickness direction. By introducing a characterization model of the fracture performance variation law in the thickness direction into the fracture toughness master curve, the scientific calculation of the fracture toughness probability distribution at any thickness layer of the plate can be realized, providing new technical support for the reasonable evaluation of the service safety of reactor pressure vessel steel.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a fracture toughness evaluation method considering the change of fracture performance in the thickness direction of the plate, the specific steps of which are as follows: Step S1: characterize the variation law of fracture performance along the thickness direction of the plate; Step S2: establish the functional relationship between fracture performance and reference temperature; Step S3: establish a fracture toughness distribution model considering the change of fracture performance in the thickness direction of the plate; Step S4: evaluate the fracture toughness at any thickness layer of the plate.

[0005] Further, the variation law of fracture performance along the thickness direction of the plate is achieved by the following method: Step S11: Mark the plate thickness as t, cut the plate into samples along the thickness direction, and record the normalized distance r / t from the surface of the plate of different thickness layers; Step S12: Process Charpy impact specimens from the plate of different thickness layers cut in Step S11, and place the Charpy impact specimens of each thickness layer in a multi-temperature environment chamber from low temperature to high temperature for static placement; Step S13: Conduct impact tests on the Charpy impact specimens statically placed in the multi-temperature environment chamber in Step S12, and obtain the impact absorbed energy when the specimen fractures at each temperature; Step S14: Based on the test results of Step S13, calculate the test temperature at which the impact absorbed energy of the fracture specimens of different thickness layers is 41 joules, i.e., the fracture performance T of the specimen. 41J Step S15: Organize the fracture properties T of different thickness layers obtained in step S14. 41J By combining the normalized distance r / t recorded in step S11, the variation law of fracture properties along the thickness direction of the plate is obtained. The least squares method is used to mathematically characterize this variation law, thereby establishing T 41J The nonlinear relationship with r / t.

[0006] Further, the establishment of the functional relationship between fracture performance and reference temperature is achieved through the following method: Step S21: Process a compact tensile specimen from the sheet metal of any thickness layer cut in step S11, and conduct a fracture toughness test on the specimen under a single temperature condition; Step S22: Based on the test data of step S21, calculate the reference temperature T0 characterizing the fracture toughness with reference to the American Society for Testing and Materials (ASTM) E1921 standard; Step S23: Based on T0 obtained in step S15... 41J The nonlinear relationship with r / t determines the fracture performance T at the same thickness layer corresponding to the compact tensile specimen in step S21. 41J Step S24: Using the reference temperature T0 calculated in step S22 and the fracture performance T determined in step S23 41J Establish T0 and T 41J The functional relationship.

[0007] Furthermore, the fracture toughness distribution model considering the variation of the thickness fracture properties of the plate is established by the following method: Step S31: Based on the fracture properties T obtained in step S15 41J The nonlinear relationship between the normalized distance r / t and the reference temperature T0 established in step S24 and the fracture performance T 41J The functional relationship between T0 and r / t is established; Step S32: Substitute the nonlinear relationship between the reference temperature T0 and the normalized distance r / t established in step S31 into the fracture toughness master curve to obtain a fracture toughness probability distribution model that takes into account the change in the thickness fracture performance of the plate.

[0008] Furthermore, the evaluation of fracture toughness at any thickness layer of the plate is achieved through the following method: Step S41: Set the normalized distance r / t corresponding to the target thickness layer; Step S42: Assume the cumulative failure probability P f Step S43: Combine the normalized distance r / t set in step S41 and the cumulative failure probability P assumed in step S42. f Substitute the fracture toughness probability distribution model obtained in step S32 into the model to evaluate the fracture toughness at the target thickness layer.

[0009] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the steps of a fracture toughness assessment method that takes into account variations in the thickness fracture properties of a plate.

[0010] A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a fracture toughness assessment method that takes into account variations in the thickness fracture properties of a plate.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. A model is proposed to quantify the variation law of fracture performance in the thickness direction of plate, which can reasonably characterize the fracture toughness distribution characteristics caused by material manufacturing process.

[0013] 2. Based on the relationship between fracture performance and reference temperature, a fracture toughness distribution model that takes into account the variation of fracture performance in the thickness direction of the plate was constructed for the first time, which can realize the scientific calculation of the fracture toughness probability distribution at any thickness layer.

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 This is a flowchart of the fracture toughness evaluation method according to an embodiment of the present invention.

[0016] Figure 2a This is a schematic diagram of the geometric dimensions of the Charpy impact specimen used in this embodiment of the invention. Figure 1 .

[0017] Figure 2b This is a second schematic diagram showing the geometric dimensions of the Charpy impact specimen used in this embodiment of the invention.

[0018] Figure 3 This is a nonlinear relationship diagram between fracture performance and normalized distance obtained in an embodiment of the present invention.

[0019] Figure 4aThis is a schematic diagram of the geometric dimensions of the compact tensile specimen used in the embodiments of the present invention. Figure 1 .

[0020] Figure 4b This is a second schematic diagram showing the geometric dimensions of the compact tensile specimen used in an embodiment of the present invention.

[0021] Figure 5 This is a graph showing the predicted fracture toughness temperature distribution curve obtained in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] like Figures 1-5 As shown, this embodiment provides a fracture toughness assessment method that takes into account the changes in the thickness fracture properties of a plate, including the following steps:

[0026] Step S1: Characterize the variation of fracture properties along the thickness direction of the plate;

[0027] Step S11: Mark the thickness of the board as t, cut and sample the board along the thickness direction, and record the normalized distance r / t between the board of different thickness layers and the surface;

[0028] Step S12: Process Charpy impact test specimens from the plates of different thicknesses cut in step S11, and place the Charpy impact test specimens of each thickness in a multi-temperature environment chamber ranging from low temperature to high temperature for static treatment.

[0029] Step S13: Conduct an impact test on the Charpy impact specimen that was placed in the multi-temperature environment chamber in step S12, and obtain the impact absorbed energy when the specimen breaks at each temperature.

[0030] Step S14: Based on the test results of step S13, calculate the test temperature at which the impact absorption energy is 41 Joules for fracture specimens of different thicknesses, i.e., the fracture performance T of the specimen.41J ;

[0031] Step S15: Organize the fracture properties T of different thickness layers obtained in step S14 41J By combining the normalized distance r / t recorded in step S11, the variation law of fracture properties along the thickness direction of the plate is obtained. The least squares method is used to mathematically characterize this variation law, thereby establishing T 41J Nonlinear relationship with r / t;

[0032] T 41J =f(r / t)

[0033] In the formula, T 41J For fracture performance, r / t is the normalized distance, and f is T. 41J The univariate functional relationship between r / t;

[0034] Step S2: Establish the functional relationship between fracture performance and reference temperature;

[0035] Step S21: Process a compact tensile specimen from the sheet material of any thickness layer cut in step S11, and conduct a fracture toughness test on the specimen under a single temperature condition.

[0036] Step S22: Based on the test data from step S21, and referring to the American Society for Testing and Materials (ASTM) E1921 standard, calculate the reference temperature T0 characterizing fracture toughness.

[0037] Step S23: Based on T obtained in step S15 41J The nonlinear relationship with r / t determines the fracture performance T at the same thickness layer corresponding to the compact tensile specimen in step S21. 41J ;

[0038] Step S24: Using the reference temperature T0 calculated in step S22 and the fracture performance T determined in step S23 41J Establish T0 and T 41J The functional relationship;

[0039] T0 = ​​T 41J +α

[0040] In the formula, T0 is the reference temperature, T 41J For fracture properties, α is an undetermined coefficient;

[0041] Step S3: Establish a fracture toughness distribution model that takes into account the variation of the thickness fracture properties of the plate.

[0042] Step S31: Based on the fracture performance T obtained in step S15 41J The nonlinear relationship between the normalized distance r / t and the reference temperature T0 established in step S24 and the fracture performance T41J The functional relationship is used to construct the nonlinear relationship between T0 and r / t;

[0043] T0=f(r / t)+α

[0044] In the formula, T0 is the reference temperature, r / t is the normalized distance, α is the given coefficient in step S24, and f is the T value. 41J The univariate functional relationship between r / t;

[0045] Step S32: Substitute the nonlinear relationship between the reference temperature T0 and the normalized distance r / t constructed in step S31 into the fracture toughness master curve to obtain a fracture toughness probability distribution model that takes into account the change in the thickness fracture performance of the plate.

[0046]

[0047] In the formula, K Jc For fracture toughness, P f The cumulative failure probability is given by T, the test temperature is given by r / t, the normalized distance is given by α, and the coefficient given in step S24 is given by α.

[0048] Step S4: Evaluate the fracture toughness at any thickness layer of the plate;

[0049] Step S41: Set the normalized distance r / t corresponding to the target thickness layer;

[0050] Step S42: Assume the cumulative failure probability P f ;

[0051] Step S43: Combine the normalized distance r / t set in step S41 and the cumulative failure probability P assumed in step S42. f Substitute the fracture toughness probability distribution model obtained in step S32 into the model to evaluate the fracture toughness at the target thickness layer.

[0052] Example

[0053] The following is a specific embodiment of the present invention, using a 167mm thick low-alloy steel plate as an example. Specifically, the fracture toughness assessment method proposed in this invention, which considers the variation in thickness-direction fracture properties of the plate, is used to quantitatively assess the probability distribution of fracture toughness at any thickness layer. The process is as follows:

[0054] Step S1: Characterize the variation of fracture properties along the thickness direction of the plate;

[0055] Step S11: Mark the thickness of the board as t, cut the board into samples along the thickness direction, and record the normalized distance r / t between the board of different thickness layers and the surface. The total number of sampling layers is 13.

[0056] Step S12: Process Charpy impact test specimens from the different thickness layers of the sheet metal cut in Step S11, and place the Charpy impact test specimens of each thickness layer in a multi-temperature environment chamber ranging from low temperature to high temperature for static treatment. The specimen shapes are shown in [details omitted]. Figures 2a-2b The sample width W is 10mm, the sample thickness B is 10mm, and the sample length L is 55mm.

[0057] Step S13: Conduct an impact test on the Charpy impact specimen that was placed in the multi-temperature environment chamber in step S12, and obtain the impact absorbed energy when the specimen breaks at each temperature.

[0058] Step S14: Based on the test results of step S13, calculate the test temperature at which the impact absorption energy is 41 Joules for fracture specimens of different thicknesses, i.e., the fracture performance T of the specimen. 41J The results are shown in Table 1.

[0059] Table 1. Fracture properties of plates with different thicknesses

[0060]

[0061] Step S15: Organize the fracture properties T of different thickness layers obtained in step S14 41J By combining the normalized distance r / t recorded in step S11, the variation law of fracture properties along the thickness direction of the plate is obtained. The least squares method is used to mathematically characterize this variation law, thereby establishing T 41J The nonlinear relationship with r / t is shown in the fitting results. Figure 3 ;

[0062]

[0063] In the formula, T 41J For fracture performance, r / t is the normalized distance;

[0064] Step S2: Establish the functional relationship between fracture performance and reference temperature;

[0065] Step S21: Process a compact tensile specimen from the first layer of sheet material cut in step S11, and conduct a fracture toughness test on the specimen under a single temperature condition. The test shape is as follows. Figures 4a-4b As shown, the sample width W is 8 mm, the sample thickness B is 4 mm, and the crack length a is 4 mm.

[0066] Step S22: Based on the test data from Step S21, and referring to the American Society for Testing and Materials (ASTM) E1921 standard, calculate the reference temperature T0 = -137℃ to characterize the fracture toughness;

[0067] Step S23: Based on T obtained in step S15 41JDetermine the fracture property T at the same thickness layer corresponding to the compact tension specimen in step S21 based on the non-linear relationship with r / t 41J =-126 °C;

[0068] Step S24: Use the reference temperature T0 calculated in step S22 and the fracture property T determined in step S23 41J , establish the functional relationship between T0 and T 41J ;

[0069] T0 = T 41J -11

[0070] In the formula, T0 is the reference temperature, and T 41J is the fracture property;

[0071] Step S3: Establish a fracture toughness distribution model considering the variation of fracture properties in the thickness direction of the sheet

[0072] Step S31: Based on the non-linear relationship between the fracture property T obtained in step S15 41J and the normalized distance r / t, as well as the functional relationship between the reference temperature T0 and the fracture property T established in step S24 41J , construct the non-linear relationship between T0 and r / t

[0073]

[0074] In the formula, T0 is the reference temperature, and r / t is the normalized distance;

[0075] Step S32: Substitute the non-linear relationship between the reference temperature T0 and the normalized distance r / t constructed in step S31 into the master curve of fracture toughness to obtain a fracture toughness probability distribution model considering the variation of fracture properties in the thickness direction of the sheet

[0076] When 0 ≤ r / t ≤ 0.5,

[0077]

[0078] When 0.5 < r / t ≤ 1.0,

[0079]

[0080] In the formula, K Jc is the fracture toughness, P f is the cumulative failure probability, T is the test temperature, and r / t is the normalized distance;

[0081] Step S4: Evaluate the fracture toughness at any thickness layer of the sheet

[0082] Step S41: Set the normalized distance r / t corresponding to the target thickness layer. Here, four target thickness layer positions are selected, with r / t = 0.05, r / t = 0.1, r / t = 0.25, and r / t = 0.5 respectively.

[0083] Step S42: Assume the cumulative failure probability P f It is 50%;

[0084] Step S43: Combine the four normalized distances r / t set in step S41 and the cumulative failure probability P assumed in step S42. f Substituting the fracture toughness probability distribution model obtained in step S32, the fracture toughness at the target thickness layer was evaluated, and the fracture toughness temperature distribution curves at different target thickness layers were plotted. The results are shown in […]. Figure 5 .

[0085] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the program includes program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.

[0086] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for evaluating fracture toughness considering the variation in thickness-direction fracture properties of plates, characterized in that: The specific steps are as follows: Step S1: Characterize the variation law of fracture performance along the thickness direction of the plate; Step S2: Establish the functional relationship between fracture performance and reference temperature; Step S3: Establish a fracture toughness distribution model that takes into account the variation of fracture performance in the thickness direction of the plate; Step S4: Evaluate the fracture toughness at any thickness layer of the plate.

2. The fracture toughness assessment method considering the variation of thickness fracture properties in plates according to claim 1, characterized in that: The variation law of the fracture performance along the thickness direction of the plate is achieved by the following method: Step S11: Mark the thickness of the plate as... t The board material was cut and sampled along the thickness direction, and the normalized distance from the surface of the board material of different thickness layers was recorded. r / t Step S12: Process Charpy impact specimens from the plates of different thicknesses cut in Step S11, and place the Charpy impact specimens of each thickness in a multi-temperature environmental chamber ranging from low temperature to high temperature for static placement; Step S13: Conduct impact tests on the Charpy impact specimens statically placed in the multi-temperature environmental chamber in Step S12, and obtain the impact absorbed energy at which the specimen fractures at each temperature; Step S14: Based on the test results of Step S13, calculate the test temperature at which the impact absorbed energy of the fractured specimens of different thicknesses is 41 Joules, i.e., the fracture performance of the specimens. T 41J Step S15: Compile the fracture properties of layers of different thicknesses obtained in step S14. T 41J and the normalized distance recorded in step S11 r / t The variation law of fracture properties along the thickness direction of the plate was obtained, and the least squares method was used to mathematically characterize this variation law, thereby establishing... T 41J and r / t The nonlinear relationship.

3. The fracture toughness assessment method considering the variation of thickness fracture properties in plates according to claim 2, characterized in that: The establishment of the functional relationship between fracture performance and reference temperature is achieved through the following method: Step S21: Process a compact tensile specimen from the sheet material of any thickness layer cut in Step S11, and conduct a fracture toughness test on the specimen under a single temperature condition; Step S22: Based on the test data of Step S21, calculate the reference temperature characterizing fracture toughness with reference to the American Society for Testing and Materials (ASTM) E1921 standard. T 0; Step S23: Based on the information obtained in step S15 T 41J and r / t The nonlinear relationship is used to determine the fracture properties at the same thickness layer corresponding to the compact tensile specimen in step S21. T 41J Step S24: Use the reference temperature calculated in step S22 T Fracture properties determined in step S23 and step S23 T 41J ,Establish T 0 and T 41J The functional relationship.

4. The fracture toughness assessment method considering the variation of thickness fracture properties in plates according to claim 3, characterized in that: The fracture toughness distribution model considering the variation of thickness fracture properties of the plate is established by the following method: Step S31: Based on the fracture properties obtained in step S15 T 41J With normalized distance r / t The nonlinear relationship, and the reference temperature established in step S24. T 0 and fracture properties T 41J Functional relationships, construct T 0 and r / t The nonlinear relationship; Step S32: The reference temperature constructed in step S31 T 0 and normalized distance r / t Substituting the nonlinear relationship into the fracture toughness master curve, we obtain a fracture toughness probability distribution model that takes into account the variation of the thickness fracture performance of the plate.

5. The fracture toughness evaluation method considering the variation of thickness fracture properties in plates according to claim 4, characterized in that: The fracture toughness at any thickness layer of the plate is evaluated by the following method: Step S41: Set the normalized distance corresponding to the target thickness layer. r / t Step S42: Assume cumulative failure probability P f ; Step S43: Set the normalized distance in step S41. r / t and the cumulative failure probability assumed in step S42 P f Substitute the fracture toughness probability distribution model obtained in step S32 into the model to evaluate the fracture toughness at the target thickness layer.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, it implements the steps of the fracture toughness evaluation method that takes into account the variation of thickness fracture properties of plate as described in any one of claims 1-5.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a fracture toughness assessment method considering changes in the thickness fracture properties of a plate as described in any one of claims 1-5.

Images