A method and apparatus for determining the tensile strain capacity of a girth weld joint

Abstract

The application provides a method and device for determining the tensile strain capacity of a girth welded joint, and relates to the technical field of girth welded joints of pipeline steel pipes. The method comprises the following steps: preparing a full-weld tensile sample and an instrumented impact sample; performing a tensile test on the full-weld tensile sample to obtain a test curve; performing an impact test on the instrumented impact sample to obtain test data; calculating the yield ratio of the full-weld tensile sample based on the test curve; calculating the crack initiation energy of the instrumented impact sample based on the test data; and calculating the tensile strain capacity of the girth welded joint according to the yield ratio and the crack initiation energy. The application greatly reduces the technical ability of personnel and the threshold of equipment requirements in the existing method, and greatly improves the universality of the technology. The operation process is simple, the cost is reduced, the test period is short, the strain capacity of the welded joint can be quickly reacted, the engineering needs are solved, the safety upgrading management requirements of oil and gas pipelines are met, the evaluation period is greatly shortened, and the application has good practicability.

Description

Technical Field

[0001] This invention relates to the field of pipeline steel pipe ring weld joint technology, and in particular to a method and apparatus for determining the tensile strain capacity of a ring weld joint. Background Technology

[0002] With the frequent occurrence of circumferential weld failures in high-strength steel pipelines, the strain capacity of circumferential welds has attracted much attention. Internationally, there are two existing methods for determining the strain capacity of circumferential welds:

[0003] One approach is primarily based on extrapolation from quasi-static low-constraint fracture toughness test (SENT) results;

[0004] Another method is to directly determine the result based on a full-size tensile test under pressure.

[0005] According to research, only 725 institutions and a few institutions such as Tianjin University in China can currently complete the SENT test. The test process itself and the determination of the validity of the test results are extremely difficult, requiring a high level of professional competence from practitioners. Moreover, this type of test is time-consuming and expensive, involving processes such as commissioning, contract signing, and sample mailing.

[0006] Full-scale tensile testing under pressure requires highly capable experimental equipment, especially for high-grade steel and large-diameter thick-walled oil and gas pipelines. Currently, only foreign countries have the capability to perform this test. The full-scale pipeline tensile testing machine from C-FER in Canada has the largest capacity (7100t, which can meet the testing requirements for X80 grade D1219mm specimens). The testing cost is high, and the test requires domestic sample preparation. In addition, the testing process involves long cycles of commissioning and logistics. Considering other influencing factors, the testing cycle is more than six months.

[0007] Therefore, there is an urgent need to develop a rapid, low-cost, and more universally applicable method for determining the strain capacity of circumferential welded joints to meet practical engineering needs. Summary of the Invention

[0008] In view of the above problems, the present invention is proposed to provide a method and apparatus for determining the tensile strain capacity of a ring weld joint in order to overcome or at least partially solve the above problems.

[0009] A first aspect of the present invention provides a method for determining the tensile strain capacity of a ring weld joint, the method comprising:

[0010] Prepare at least three full-weld tensile specimens and at least six instrumented impact specimens;

[0011] Tensile tests were performed on at least three of the full weld tensile specimens to obtain at least three sets of test curves;

[0012] At least six instrumented impact specimens were subjected to impact tests to obtain at least six sets of test data.

[0013] Based on at least three sets of the test curves, the yield strength ratio of each of the at least three full-weld tensile specimens was calculated.

[0014] Based on at least six sets of experimental data, the crack initiation energy of each of the at least six instrumented impact specimens was calculated.

[0015] The tensile strain capacity of the circumferential weld is calculated based on the yield strength ratio of at least three of the full weld tensile specimens and the crack initiation energy of at least six of the instrumented impact specimens.

[0016] Optionally, based on at least three sets of the test curves, the yield strength ratio of each of the at least three full-weld tensile specimens is calculated, including:

[0017] Based on at least three sets of test curves, obtain the values ​​of yield strength and tensile strength corresponding to each set of test curves;

[0018] Based on the yield strength and tensile strength values ​​corresponding to each set of test curves, the yield strength ratio of each full-weld tensile specimen is calculated.

[0019] Optionally, based on at least six sets of said test data, the crack initiation energy of each of the at least six instrumented impact specimens is calculated, including:

[0020] Copy each of the at least six sets of test data to a force-displacement coordinate system, wherein the force-displacement coordinate system has displacement as the abscissa and force as the ordinate;

[0021] Based on the force-displacement coordinate system and each set of test data, curve fitting is performed to obtain the equation curve corresponding to each set of test data;

[0022] Based on the equation curve corresponding to each set of test data, the crack initiation energy of each instrumented impact specimen is calculated.

[0023] Optionally, based on the equation curve corresponding to each set of test data, the crack initiation energy of each instrumented impact specimen is calculated, including:

[0024] Obtain the maximum stress value in the equation curve corresponding to each set of experimental data;

[0025] Based on the force-displacement coordinate system, the integral of the maximum stress is performed to obtain the integral area of ​​the corresponding equation curve, and the integral area represents the crack initiation work of each instrumented impact specimen.

[0026] Optionally, the tensile strain capacity of the circumferential weld is calculated based on the yield strength ratio of at least three of the full-weld tensile specimens and the crack initiation energy of at least six of the instrumented impact specimens, including:

[0027] Based on the yield strength ratio of each full-weld tensile specimen, calculate the average yield strength ratio corresponding to the yield strength ratio of all full-weld tensile specimens.

[0028] Based on the crack initiation energy of each instrumented impact specimen, the average crack initiation energy of all instrumented impact specimens is calculated.

[0029] The tensile strain capacity of the ring weld joint is calculated based on the average yield strength ratio and the average crack initiation energy.

[0030] Optionally, the formula for calculating the tensile strain capacity of the ring weld joint is:

[0031] TSC CVNi =(10.8E*CVN) i *10 -3 -0.27) (2.36-1.58k-0.101ξη) (1+16.1k -4.45 (-0.157+0.239ξ) -0.241 η -0.315 )

[0032]

[0033] Among them, TSC CVNi CVN represents the tensile strain capacity of the welded ring joint. i The value of the crack initiation work is represented by k, which represents the strength coefficient, k = (R P0.2 / R m ) 5 ξ represents the ratio of defect length to wall thickness, ξ = 2c / t, 1 ≤ ξ ≤ 10; η represents the ratio of defect height to wall thickness, η = a / t, or η = 2a / t, where a represents defect height, 2c represents defect length, t represents pipe wall thickness, a / t represents surface defects, and 2a / t represents burial depth defects; R P0.2 R represents the yield strength. m Indicates tensile strength.

[0034] Optionally, tensile tests are performed on the at least three full-weld tensile specimens, including:

[0035] Using a microcomputer-controlled electronic universal testing machine and employing national standard testing methods, tensile tests were conducted on at least three full-weld tensile specimens.

[0036] The tensile strength of the microcomputer-controlled electronic universal testing machine is not less than 600 kN.

[0037] Optionally, impact tests are performed on the at least six instrumented impact specimens, including:

[0038] Using an electronic oscilloscope pendulum impact testing machine and following national standard testing methods, impact tests were conducted on at least six instrumented impact specimens.

[0039] The test impact energy of the electronic oscilloscope pendulum impact testing machine is not less than 450J.

[0040] A second aspect of the present invention provides an apparatus for determining the tensile strain capacity of a ring weld joint, the apparatus comprising:

[0041] The preparation module is used to prepare at least three full-weld tensile specimens and at least six instrumented impact specimens.

[0042] The tensile module is used to perform tensile tests on at least three full weld tensile specimens respectively and obtain at least three sets of test curves.

[0043] The impact module is used to perform impact tests on at least six instrumented impact specimens and obtain at least six sets of test data.

[0044] The yield strength ratio calculation module is used to calculate the yield strength ratio of each of the at least three full-weld tensile specimens based on at least three sets of the test curves.

[0045] The crack initiation energy calculation module is used to calculate the crack initiation energy of at least six instrumented impact specimens based on at least six sets of test data.

[0046] The strain capacity calculation module is used to calculate the tensile strain capacity of the circumferential weld joint based on the yield strength ratio of each of the at least three full-weld tensile specimens and the crack initiation energy of each of the at least six instrumented impact specimens.

[0047] Optionally, the yield strength ratio calculation module includes:

[0048] The acquisition unit is used to acquire the values ​​of yield strength and tensile strength corresponding to each set of test curves based on at least three sets of test curves.

[0049] The yield strength ratio calculation unit is used to calculate the yield strength ratio of each full-weld tensile specimen based on the corresponding values ​​of yield strength and tensile strength on each set of test curves.

[0050] Optionally, the crack initiation work calculation module includes:

[0051] The copying unit is used to copy each of the at least six sets of test data to a force-displacement coordinate system, wherein the force-displacement coordinate system has displacement as the abscissa and force as the ordinate.

[0052] The fitting unit is used to perform curve fitting based on the force-displacement coordinate system and each set of test data to obtain the equation curve corresponding to each set of test data.

[0053] The crack initiation energy calculation unit is used to calculate the crack initiation energy of each instrumented impact specimen based on the equation curve corresponding to each set of test data.

[0054] Optionally, the crack initiation work calculation unit is specifically used for:

[0055] Obtain the maximum stress value in the equation curve corresponding to each set of experimental data;

[0056] Based on the force-displacement coordinate system, the integral of the maximum stress is performed to obtain the integral area of ​​the corresponding equation curve, and the integral area represents the crack initiation work of each instrumented impact specimen.

[0057] Optionally, the strain capacity calculation module includes:

[0058] The yield strength ratio averaging unit is used to calculate the average yield strength ratio of all full weld tensile specimens based on the yield strength ratio of each full weld tensile specimen.

[0059] The average crack initiation energy unit is used to calculate the average crack initiation energy of all instrumented impact specimens based on the crack initiation energy of each instrumented impact specimen.

[0060] The strain capacity calculation unit is used to calculate the tensile strain capacity of the ring weld joint based on the average yield strength ratio and the average crack initiation energy.

[0061] The method for determining the tensile strain capacity of a ring weld joint provided by the present invention firstly involves preparing at least three full weld tensile specimens and at least six instrumented impact specimens; the number of specimens prepared determines the accuracy of subsequent calculations, and the more specimens prepared, the higher the accuracy of subsequent calculations.

[0062] Tensile tests were then performed on at least three fully welded tensile specimens to obtain at least three sets of test curves; impact tests were then performed on at least six instrumented impact specimens to obtain at least six sets of test data; based on at least three sets of test curves, the yield strength ratio of each of the at least three fully welded tensile specimens was calculated; and based on at least six sets of test data, the crack initiation energy of each of the at least six instrumented impact specimens was calculated.

[0063] Finally, the tensile strain capacity of the circumferential weld can be calculated based on the yield strength ratio of at least three full-weld tensile specimens and the crack initiation work of at least six instrumented impact specimens.

[0064] This invention employs numerous round bar tensile, oscilloscope impact, and CTOD tests to obtain the correlation between crack initiation energy and CTOD, thereby enabling conventional tests to replace fracture toughness assessment methods. This significantly reduces the high barriers to entry for personnel technical skills and equipment requirements in existing methods for assessing the strain capacity of ring welded joints. It lowers the requirements for equipment and personnel technical levels and is applicable to the vast majority of testing and inspection institutions, making the assessment of the tensile strain capacity of ring welded joints no longer limited to individual institutions, thus greatly improving the universality of this technology.

[0065] In terms of equipment, only one computer-controlled electronic universal testing machine and one instrumented impact testing machine are required. Compared with fracture toughness testing (CTOD, fatigue testing, metallography, fracture mechanics), both equipment have simpler operation procedures, and the test data processing can be completed by referring to national standards, without the need for validity judgment. Regarding cost, the one-time assessment test cost is less than 2000 yuan (calculated based on 3 tensile tests and 6 instrumented impact tests of the entire weld), reducing costs. In terms of test cycle, this technology has a short test cycle of only 3 days, which can quickly reflect the strain capacity parameters of the welded joint, addressing urgent engineering needs. At the same time, this method provides simple, fast, and highly stable basic data acquisition with greater conservatism, better meeting the requirements for oil and gas pipeline safety upgrade management. It also significantly shortens the assessment cycle, lowers the technical threshold for practitioners, and has good practicality. Attached Figure Description

[0066] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 This is a flowchart of a method for determining the tensile strain capacity of a ring welded joint according to an embodiment of the present invention;

[0068] Figure 2 This is a schematic diagram of the force-displacement coordinate system corresponding to a certain set of test data in an embodiment of the present invention;

[0069] Figure 3 This is a block diagram of a device for determining the tensile strain capacity of a ring welded joint according to an embodiment of the present invention. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] Reference Figure 1 The flowchart illustrates a method for determining the tensile strain capacity of a ring welded joint according to an embodiment of the present invention, specifically including:

[0072] Step 101: Prepare at least three full-weld tensile specimens and at least six instrumented impact specimens.

[0073] Since the method for determining the tensile strain capacity of a ring welded joint proposed in this invention is based on tensile and impact tests, and the test data obtained from both tensile and impact tests fluctuate, a certain number of samples need to be tested to eliminate the impact of these fluctuations on the accuracy of the calculation. Therefore, the number of samples prepared determines the accuracy of the subsequent calculation; the more samples, the higher the accuracy of the subsequent calculation. Of course, the more samples, the more tests are required, and the higher the cost.

[0074] To ensure the accuracy requirements of subsequent calculations and considering cost factors, it is stipulated that at least three full-weld tensile test specimens and at least six instrumented impact test specimens must be prepared. This ensures the accuracy requirements of subsequent calculations while minimizing costs.

[0075] Step 102: Perform tensile tests on at least three full-weld tensile specimens and obtain at least three sets of test curves.

[0076] Step 103: Conduct impact tests on at least six instrumented impact specimens and obtain at least six sets of test data.

[0077] After the specimens were prepared, all the prepared full-weld tensile specimens and all the instrumented impact specimens were tested. For the full-weld tensile specimens, a set of test curves could be directly obtained for each full-weld tensile specimen. However, for the instrumented impact specimens, a set of test data could be obtained for each instrumented impact specimen, but the corresponding test curves could not be directly obtained.

[0078] Specifically, for tensile testing of full weld tensile specimens, a preferred method is to use a computer-controlled electronic universal testing machine and adopt national standard test methods (e.g., GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test methods at room temperature") to conduct tensile tests on all full weld tensile specimens separately; wherein, the tensile capacity of the computer-controlled electronic universal testing machine should not be less than 600 kN.

[0079] For instrumented impact testing of specimens, a preferred method is to use an electronic oscilloscope pendulum impact testing machine and adopt national standard test methods (e.g., GB / T 19748-2019 "Metallic Materials - Instrumented Test Method for Charpy V-Notch Pendulum Impact Test") to conduct impact tests on at least six instrumented impact specimens respectively; wherein, the test impact energy of the electronic oscilloscope pendulum impact testing machine should not be less than 450J.

[0080] Step 104: Based on at least three sets of test curves, calculate the yield strength ratio of each of the at least three full-weld tensile specimens.

[0081] Step 105: Based on at least six sets of test data, calculate the crack initiation energy of each of the at least six instrumented impact specimens.

[0082] After obtaining the test curves and test data, the yield strength ratio of each full-weld tensile specimen can be calculated based on each set of test curves. The crack initiation energy of each instrumented impact specimen can be calculated based on each set of test data.

[0083] Specifically, for the calculation of the yield strength ratio, based on each set of test curves, the corresponding values ​​of yield strength and tensile strength on each set of test curves are obtained; based on the corresponding values ​​of yield strength and tensile strength on each set of test curves, the yield strength ratio of each full weld tensile specimen is calculated.

[0084] Assume the yield strength on each set of test curves is represented by R. P0.2 (The stress value corresponding to strain of 0.002) is represented by the tensile strength Rm. Then the yield strength ratio λ = Rm for each full-weld tensile specimen is given by the formula. P0.2 / R m .

[0085] For the calculation of crack initiation work, each set of test data is first copied to the force-displacement coordinate system. This is because the electronic oscilloscope pendulum impact testing machine can only obtain test data and cannot save it directly. Therefore, each set of test data needs to be copied to the force-displacement coordinate system, which uses displacement as the horizontal axis and force as the vertical axis.

[0086] Then, based on the force-displacement coordinate system and each set of experimental data, curve fitting is performed to obtain the equation curve corresponding to each set of experimental data; that is, based on the experimental data in the coordinate system, an equation curve is fitted to represent the relationship between the data in the coordinate system.

[0087] After obtaining the equation curves, the initiation work of each instrumented impact specimen is calculated based on the equation curves corresponding to each set of experimental data. A preferred approach is to directly obtain the maximum stress value in the equation curve corresponding to each set of experimental data on the coordinate system; then, based on the force-displacement coordinate system, integrate the maximum stress value to obtain the integral area of ​​the corresponding equation curve, which represents the initiation work of each instrumented impact specimen.

[0088] Step 106: Calculate the tensile strain capacity of the circumferential weld joint based on the yield strength ratio of at least three full-weld tensile specimens and the crack initiation work of at least six instrumented impact specimens.

[0089] After obtaining the yield strength ratio of each full weld tensile specimen and the crack initiation energy of each instrumented impact specimen in steps 104 and 105, the tensile strain capacity of the circumferential weld can be calculated based on their respective yield strength ratios and crack initiation energy.

[0090] The specific method is as follows: First, based on the yield strength ratio of each full weld tensile specimen, calculate the average yield strength ratio corresponding to the yield strength ratio of all full weld tensile specimens; then, based on the crack initiation energy of each instrumented impact specimen, calculate the average crack initiation energy corresponding to the crack initiation energy of all instrumented impact specimens; finally, based on the average yield strength ratio and the average crack initiation energy, calculate the tensile strain capacity of the circumferential weld joint.

[0091] The formula for calculating the tensile strain capacity of a ring weld joint is:

[0092] TSC CVNi =(10.8E*CVN) i *10 -3 -0.27) (2.36-1.58k-0.101ξη) (1+16.1k -4.45 (-0.157+0.239ξ) -0.241 η -0.315 )

[0093]

[0094] Among them, TSC CVNi CVN represents the tensile strain capacity of the ring weld joint. i The value represents the average crack initiation energy, and k represents the strength coefficient, k = (R P0.2 / R m ) 5ξ represents the ratio of defect length to wall thickness, ξ = 2c / t, 1 ≤ ξ ≤ 10; η represents the ratio of defect height to wall thickness, η = a / t, or η = 2a / t, where a represents defect height, 2c represents defect length, t represents pipe wall thickness, a / t represents surface defects, and 2a / t represents burial depth defects; R P0.2 R represents the yield strength. m Indicates tensile strength.

[0095] To better illustrate the method of determining the tensile strain capacity of a ring welded joint according to the present invention, a specific example is given below.

[0096] The first step is to take samples. For tensile and oscilloscope impact test specimens, the preferred method for sampling is GB / T2649-1989 "Sampling Method for Mechanical Property Test of Welded Joints".

[0097] The second step involves specimen preparation and testing, with three full-weld tensile specimens and six instrumented impact specimens prepared. Tensile tests were conducted using a computer-controlled electronic universal testing machine, following GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Tests at room temperature". The tensile capacity of the computer-controlled electronic universal testing machine should not be less than 600 kN.

[0098] The impact test was conducted using a Zwick RKP 450 electronic oscilloscope pendulum impact tester, following the GBT19748-2019 standard "Metallic materials - Instrumented test method for Charpy V-notch pendulum impact test". The impact test was performed on six instrumented impact specimens. The impact energy of the electronic oscilloscope pendulum impact tester should not be less than 450J.

[0099] The third step is to process the experimental data. After the tensile test, R is read from the obtained experimental curve. P0.2 (Stress value corresponding to strain of 0.002) and R m (Tensile strength), then calculate the yield strength ratio λ = R P0.2 / R m The specific data obtained is shown in the table below:

[0100]

[0101] Similarly, after the impact test, the test data is copied to the force-displacement coordinate system, and curve fitting is performed to obtain the equation curve corresponding to each set of test data. (Refer to...) Figure 2The diagram shows a force-displacement coordinate system corresponding to a set of test data. Displacement is the horizontal axis, in mm; force is the vertical axis, in N. The black squares represent test data, and the gray curves represent the equation curves (i.e., the fitted data).

[0102] according to Figure 2 Using a coordinate system, determine the maximum stress value in the equation curve, then perform integration to obtain the integration area (i.e., the product of displacement and force) in the graph. This integration area represents the crack initiation work. Then, calculate the average value of the six sets of crack initiation works to obtain the average crack initiation work CVN. i The specific data obtained is shown in the table below:

[0103] Cracking work (J) 52.6 57.3 55.9 61.1 52.1 61.7 56.78 (average)

[0104] Finally, the strain capacity of the circumferential weld joint is calculated according to the aforementioned formula. In this embodiment of the invention, the strain capacity of the circumferential weld joint of a pipe with a defect size of 2×50mm and grade X80 D1219*18.4 is calculated. The input parameters are shown in the table below:

[0105]

[0106] Substituting the above parameters into the aforementioned TSC CVNi The formula was used to calculate the strain capacity of the circumferential weld joint of the defective pipe to be 1.46%.

[0107] Therefore, this invention employs numerous round bar tensile, oscilloscope impact, and CTOD tests to obtain the correlation between crack initiation energy and CTOD, thereby enabling conventional tests to replace fracture toughness assessment methods. This significantly reduces the high barriers to entry for personnel technical skills and equipment requirements in existing methods for assessing the strain capacity of ring welded joints, making it suitable for the vast majority of testing and inspection institutions. This also means that the assessment of the tensile strain capacity of ring welded joints is no longer limited to individual institutions, greatly improving the universality of this technology.

[0108] In terms of equipment, only one computer-controlled electronic universal testing machine and one instrumented impact testing machine are required. Compared with fracture toughness testing (CTOD, fatigue testing, metallography, fracture mechanics), both equipment have simpler operation procedures, and the test data processing can be completed by referring to national standards, without the need for validity judgment. Regarding cost, the one-time assessment test cost is less than 2000 yuan (calculated based on 3 tensile tests and 6 instrumented impact tests of the entire weld), reducing costs. In terms of test cycle, this technology has a short test cycle of only 3 days, which can quickly reflect the strain capacity parameters of the welded joint, addressing urgent engineering needs. At the same time, this method provides simple, fast, and highly stable basic data acquisition with greater conservatism, better meeting the requirements for oil and gas pipeline safety upgrade management. It also significantly shortens the assessment cycle, lowers the technical threshold for practitioners, and has good practicality.

[0109] Based on the above method for determining the tensile strain capacity of a ring weld joint, this embodiment of the invention also provides an apparatus for determining the tensile strain capacity of a ring weld joint. (Refer to...) Figure 3 The diagram illustrates a block diagram of an apparatus for determining the tensile strain capacity of a ring weld joint according to an embodiment of the present invention. The apparatus includes:

[0110] Preparation module 310 is used to prepare at least three full-weld tensile specimens and at least six instrumented impact specimens;

[0111] Tensile module 320 is used to perform tensile tests on at least three full weld tensile specimens respectively and obtain at least three sets of test curves;

[0112] Impact module 330 is used to perform impact tests on at least six instrumented impact specimens and obtain at least six sets of test data.

[0113] The yield strength ratio calculation module 340 is used to calculate the yield strength ratio of each of the at least three full-weld tensile specimens based on at least three sets of the test curves.

[0114] The crack initiation energy calculation module 350 is used to calculate the crack initiation energy of at least six instrumented impact specimens based on at least six sets of test data.

[0115] The strain capacity calculation module 360 ​​is used to calculate the tensile strain capacity of the circumferential weld joint based on the yield strength ratio of each of the at least three full weld tensile specimens and the crack initiation energy of each of the at least six instrumented impact specimens.

[0116] Optionally, the yield strength ratio calculation module 340 includes:

[0117] The acquisition unit is used to acquire the values ​​of yield strength and tensile strength corresponding to each set of test curves based on at least three sets of test curves.

[0118] The yield strength ratio calculation unit is used to calculate the yield strength ratio of each full-weld tensile specimen based on the corresponding values ​​of yield strength and tensile strength on each set of test curves.

[0119] Optionally, the crack initiation work calculation module 350 includes:

[0120] The copying unit is used to copy each of the at least six sets of test data to a force-displacement coordinate system, wherein the force-displacement coordinate system has displacement as the abscissa and force as the ordinate.

[0121] The fitting unit is used to perform curve fitting based on the force-displacement coordinate system and each set of test data to obtain the equation curve corresponding to each set of test data.

[0122] The crack initiation energy calculation unit is used to calculate the crack initiation energy of each instrumented impact specimen based on the equation curve corresponding to each set of test data.

[0123] Optionally, the crack initiation work calculation unit is specifically used for:

[0124] Obtain the maximum stress value in the equation curve corresponding to each set of experimental data;

[0125] Based on the force-displacement coordinate system, the integral of the maximum stress is performed to obtain the integral area of ​​the corresponding equation curve, and the integral area represents the crack initiation work of each instrumented impact specimen.

[0126] Optionally, the strain capacity calculation module 360 ​​includes:

[0127] The yield strength ratio averaging unit is used to calculate the average yield strength ratio of all full weld tensile specimens based on the yield strength ratio of each full weld tensile specimen.

[0128] The average crack initiation energy unit is used to calculate the average crack initiation energy of all instrumented impact specimens based on the crack initiation energy of each instrumented impact specimen.

[0129] The strain capacity calculation unit is used to calculate the tensile strain capacity of the ring weld joint based on the average yield strength ratio and the average crack initiation energy.

[0130] Through the above examples, the method of the present invention for determining the tensile strain capacity of a ring weld joint firstly prepares at least three full weld tensile specimens and at least six instrumented impact specimens; the number of specimens prepared determines the accuracy of subsequent calculations, and the more specimens prepared, the higher the accuracy of subsequent calculations.

[0131] Tensile tests were then performed on at least three fully welded tensile specimens to obtain at least three sets of test curves; impact tests were then performed on at least six instrumented impact specimens to obtain at least six sets of test data; based on at least three sets of test curves, the yield strength ratio of each of the at least three fully welded tensile specimens was calculated; and based on at least six sets of test data, the crack initiation energy of each of the at least six instrumented impact specimens was calculated.

[0132] Finally, the tensile strain capacity of the circumferential weld can be calculated based on the yield strength ratio of at least three full-weld tensile specimens and the crack initiation work of at least six instrumented impact specimens.

[0133] This invention employs numerous round bar tensile, oscilloscope impact, and CTOD tests to obtain the correlation between crack initiation energy and CTOD, thereby enabling conventional tests to replace fracture toughness assessment methods. This significantly reduces the high barriers to entry for personnel technical skills and equipment requirements in existing methods for assessing the strain capacity of ring welded joints. It lowers the requirements for equipment and personnel technical levels and is applicable to the vast majority of testing and inspection institutions, making the assessment of the tensile strain capacity of ring welded joints no longer limited to individual institutions, thus greatly improving the universality of this technology.

[0134] In terms of equipment, only one computer-controlled electronic universal testing machine and one instrumented impact testing machine are required. Compared with fracture toughness testing (CTOD, fatigue testing, metallography, fracture mechanics), both equipment have simpler operation procedures, and the test data processing can be completed by referring to national standards, without the need for validity judgment. Regarding cost, the one-time assessment test cost is less than 2000 yuan (calculated based on 3 tensile tests and 6 instrumented impact tests of the entire weld), reducing costs. In terms of test cycle, this technology has a short test cycle of only 3 days, which can quickly reflect the strain capacity parameters of the welded joint, addressing urgent engineering needs. At the same time, this method provides simple, fast, and highly stable basic data acquisition with greater conservatism, better meeting the requirements for oil and gas pipeline safety upgrade management. It also significantly shortens the assessment cycle, lowers the technical threshold for practitioners, and has good practicality.

[0135] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for determining the tensile strain capacity of a ring weld joint, characterized in that, The method includes: Prepare at least three full-weld tensile specimens and at least six instrumented impact specimens; Tensile tests were performed on at least three of the full weld tensile specimens to obtain at least three sets of test curves; At least six instrumented impact specimens were subjected to impact tests to obtain at least six sets of test data. Based on at least three sets of the test curves, the yield strength ratio of each of the at least three full-weld tensile specimens was calculated. Based on at least six sets of experimental data, the crack initiation energy of each of the at least six instrumented impact specimens was calculated. The tensile strain capacity of the circumferential weld joint is calculated based on the yield strength ratio of at least three full weld tensile specimens and the crack initiation energy of at least six instrumented impact specimens. The formula for calculating the tensile strain capacity of the ring weld joint is as follows: TSC CVNi =(10.8E*CVN) i *10 -3 -0.27) （2.36-1.58k-0.101ξη） (1+16.1k -4.45 )(-0.157+0.239ξ -0.241 or -0.315 ) Among them, TSC CVNi CVN represents the tensile strain capacity of the welded ring joint. i This represents the average crack initiation energy, and k represents the strength coefficient, k = (R P0.2 / R m ) 5 ξ represents the ratio of defect length to wall thickness, ξ = 2c / t, 1 ≤ ξ ≤ 10; η represents the ratio of defect height to wall thickness, η = a / t, or η = 2a / t, where a represents defect height, 2c represents defect length, t represents pipe wall thickness, a / t represents surface defects, and 2a / t represents burial depth defects; R P0.2 R represents the yield strength. m This represents the tensile strength, ω=1.

02.

2. The method according to claim 1, characterized in that, Based on at least three sets of test curves, the yield strength ratios of at least three of the full-weld tensile specimens are calculated, including: Based on at least three sets of test curves, obtain the values ​​of yield strength and tensile strength corresponding to each set of test curves; Based on the yield strength and tensile strength values ​​corresponding to each set of test curves, the yield strength ratio of each full-weld tensile specimen is calculated.

3. The method according to claim 2, characterized in that, Based on at least six sets of test data, the initiation energy of each of the at least six instrumented impact specimens was calculated, including: Copy each of the at least six sets of test data to a force-displacement coordinate system, wherein the force-displacement coordinate system has displacement as the abscissa and force as the ordinate; Based on the force-displacement coordinate system and each set of test data, curve fitting is performed to obtain the equation curve corresponding to each set of test data; Based on the equation curve corresponding to each set of test data, the crack initiation energy of each instrumented impact specimen is calculated.

4. The method according to claim 3, characterized in that, Based on the equation curve corresponding to each set of test data, the crack initiation energy of each instrumented impact specimen is calculated, including: Obtain the maximum stress value in the equation curve corresponding to each set of experimental data; Based on the force-displacement coordinate system, the integral of the maximum stress is performed to obtain the integral area of ​​the corresponding equation curve, and the integral area represents the crack initiation work of each instrumented impact specimen.

5. The method according to claim 4, characterized in that, The tensile strain capacity of the circumferential weld is calculated based on the yield strength ratio of at least three of the full-weld tensile specimens and the crack initiation energy of at least six of the instrumented impact specimens, including: Based on the yield strength ratio of each full-weld tensile specimen, calculate the average yield strength ratio corresponding to the yield strength ratio of all full-weld tensile specimens. Based on the crack initiation energy of each instrumented impact specimen, the average crack initiation energy of all instrumented impact specimens is calculated. The tensile strain capacity of the ring weld joint is calculated based on the average yield strength ratio and the average crack initiation energy.

6. The method according to claim 1, characterized in that, Tensile tests were performed on the at least three full-weld tensile specimens, including: Using a microcomputer-controlled electronic universal testing machine and employing national standard testing methods, tensile tests were conducted on at least three full-weld tensile specimens. The tensile strength of the microcomputer-controlled electronic universal testing machine is not less than 600 kN.

7. The method according to claim 1, characterized in that, Impact tests were performed on the at least six instrumented impact specimens, including: Using an electronic oscilloscope pendulum impact testing machine and following national standard testing methods, impact tests were conducted on at least six instrumented impact specimens. The test impact energy of the electronic oscilloscope pendulum impact testing machine is not less than 450J.

8. An apparatus for determining the tensile strain capacity of a ring weld joint, characterized in that, The device includes: The preparation module is used to prepare at least three full-weld tensile specimens and at least six instrumented impact specimens. The tensile module is used to perform tensile tests on at least three full weld tensile specimens respectively and obtain at least three sets of test curves. The impact module is used to perform impact tests on at least six instrumented impact specimens and obtain at least six sets of test data. The yield strength ratio calculation module is used to calculate the yield strength ratio of each of the at least three full-weld tensile specimens based on at least three sets of the test curves. The crack initiation energy calculation module is used to calculate the crack initiation energy of at least six instrumented impact specimens based on at least six sets of test data. The strain capacity calculation module is used to calculate the tensile strain capacity of the circumferential weld joint based on the yield strength ratio of each of the at least three full weld tensile specimens and the crack initiation energy of each of the at least six instrumented impact specimens. The formula for calculating the tensile strain capacity of the ring weld joint is as follows: TSC CVNi =(10.8E*CVN) i *10 -3 -0.27) （2.36-1.58k-0.101ξη） (1+16.1k -4.45 )(-0.157+0.239ξ -0.241 or -0.315 ) Among them, TSC CVNi CVN represents the tensile strain capacity of the welded ring joint. i This represents the average crack initiation energy, and k represents the strength coefficient, k = (R P0.2 / R m ) 5 ξ represents the ratio of defect length to wall thickness, ξ = 2c / t, 1 ≤ ξ ≤ 10; η represents the ratio of defect height to wall thickness, η = a / t, or η = 2a / t, where a represents defect height, 2c represents defect length, t represents pipe wall thickness, a / t represents surface defects, and 2a / t represents burial depth defects; R P0.2 R represents the yield strength. m This represents the tensile strength, ω=1.

02.

9. The apparatus according to claim 8, characterized in that, The yield strength ratio calculation module includes: The acquisition unit is used to acquire the values ​​of yield strength and tensile strength corresponding to each set of test curves based on at least three sets of test curves. The yield strength ratio calculation unit is used to calculate the yield strength ratio of each full-weld tensile specimen based on the corresponding values ​​of yield strength and tensile strength on each set of test curves.

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