Method and device for establishing fatigue life curve of welded joint of small branch pipe of nuclear power plant, storage medium and electronic equipment

Abstract

The invention relates to a method and device for establishing a fatigue life curve of a small branch pipe welded joint of a nuclear power plant, a storage medium and electronic equipment. The method comprises the following steps: determining a to-be-analyzed sample; determining the first-order inherent frequency of the sample to be analyzed; performing structural excitation, alternating stress control and structural stress calculation on the to-be-analyzed sample, and determining the fatigue life of the to-be-analyzed sample; acquiring equivalent structural stress of the to-be-analyzed sample; analyzing based on the equivalent structural stress and the fatigue life to obtain the relationship between the equivalent structural stress and the fatigue life of the test to be analyzed; and performing curve fitting according to the relationship between the equivalent structural stress and the fatigue life to obtain a structural stress fatigue life curve of the to-be-analyzed sample. According to the method, the welded joint is analyzed and calculated, the method has good adaptability, the scientificity and the accuracy of the reliability evaluation result of the vibration stress of the small branch pipe welding seam are improved, a basis is provided for a power plant to reasonably arrange a maintenance plan, and unnecessary excessive maintenance is avoided, so that the economical efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration analysis, and more specifically to a method, device, storage medium and electronic equipment for establishing fatigue life curve of a small branch pipe welding joint of a nuclear power plant. Background Art

[0002] Vibration fatigue failure of small branch pipe welded joints has long been one of the main aging challenges faced by nuclear power plants, posing a potential threat to the safe and stable operation of nuclear power units. For those small branch pipes (considered as high-risk small branch pipes) that have an impact on unit operation, may cause shutdown or reactor shutdown, have a high risk of failure, and carry high-energy media, once a leak occurs, it may not only pose a safety threat to personnel or the environment, but may also force the power plant to shut down or shut down for maintenance, resulting in huge economic losses.

[0003] In the current fatigue analysis of nuclear power plant pipelines, the existing ASME Boiler and Pressure Vessel Code (BPVC) and Règles de Conception et de Construction des Matériels (RCC-M) standards are widely used. When establishing fatigue life curves, these standards are usually based on the experimental data of smooth parent material specimens, and do not fully consider the influence of small branch pipe welded joints. In actual engineering applications, due to the influence of factors such as the geometric switch of the welded joint, the microstructure of the material, and the residual stress, the use of the existing ASME BPVC or RCC-M standards for fatigue analysis of small branch pipe welded joints often leads to insufficient accuracy of the analysis results, affecting engineering design and safety assessment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method, device, storage medium and electronic equipment for establishing fatigue life curve of small branch pipe welding joints in nuclear power plants in view of the problems existing in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is: constructing a method for establishing a fatigue life curve of a small branch pipe welded joint of a nuclear power plant, comprising the following steps:

[0006] Determine the sample to be analyzed;

[0007] Determining the first-order natural frequency of the sample to be analyzed;

[0008] Based on the first-order natural frequency of the sample to be analyzed, structural excitation and alternating stress control are performed on the sample to be analyzed to determine the fatigue life of the sample to be analyzed;

[0009] Performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed;

[0010] Performing analysis based on the equivalent structural stress and the fatigue life of the sample to be analyzed to obtain a relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed;

[0011] Curve fitting is performed according to the relationship between the equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed.

[0012] In establishing the fatigue life curve of the small branch pipe welded joint of a nuclear power plant according to the present invention, the determination of the sample to be analyzed includes:

[0013] Determine the test material based on the service material of the small branch pipe;

[0014] Determine the specimen size;

[0015] Determine the welding process;

[0016] The sample to be analyzed is determined based on the test material, the sample size, and the welding process.

[0017] In establishing the fatigue life curve of the small branch pipe welded joint of a nuclear power plant according to the present invention, determining the first-order natural frequency of the sample to be analyzed includes:

[0018] Placing the sample to be analyzed on a vibration table for testing;

[0019] The test is conducted by increasing the excitation frequency at preset intervals;

[0020] During the test, recording the vibration acceleration data of the test to be analyzed;

[0021] The first-order natural frequency of the sample to be analyzed is determined according to the vibration acceleration data.

[0022] In the establishment of fatigue life curve of small branch pipe welded joint of nuclear power plant described in the present invention, the structural excitation and alternating stress control of the sample to be analyzed are performed based on the first-order natural frequency of the sample to be analyzed, and the fatigue life of the sample to be analyzed is determined, which includes:

[0023] Installing a strain gauge on the sample to be analyzed;

[0024] Performing a sinusoidal wave acceleration excitation on the sample to be analyzed based on the first-order natural frequency;

[0025] Testing and collecting the stress of the strain gauge;

[0026] Calculating according to the stress of the strain gauge to obtain the test stress of the sample to be analyzed;

[0027] Determining whether the test stress is within a preset amplitude;

[0028] If not, adjusting the amplitude of the sinusoidal wave excitation until the test stress is within the preset amplitude;

[0029] The sample to be analyzed is continuously excited until a through crack appears at a welding joint of the sample to be analyzed, and the fatigue life of the sample to be analyzed is obtained.

[0030] In the establishment of fatigue life curve of small branch pipe welded joint of nuclear power plant described in the present invention, the equivalent structural stress calculation is performed to obtain the equivalent structural stress of the sample to be analyzed, which includes:

[0031] Performing finite element modeling and stress calculation on the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress;

[0032] Calculate the force matrix and moment matrix on the neutral surface;

[0033] Calculate the cell length matrix;

[0034] Calculate according to the force matrix, the moment matrix and the unit length matrix to obtain the linear force and the linear moment;

[0035] Calculate according to the linear force and the linear moment to obtain the structural stress of each node;

[0036] Based on the structural stress of each node, the equivalent structural stress of each node is calculated to obtain the equivalent structural stress of the sample to be analyzed.

[0037] In the establishment of fatigue life curve of small branch pipe welded joint of nuclear power plant described in the present invention, the finite element modeling and stress calculation of the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress includes:

[0038] Performing finite element modeling on the sample to be analyzed;

[0039] Perform harmonic response calculations;

[0040] The structural damping parameters are adjusted according to the harmonic response calculation results until the calculated stress of the sample to be analyzed is consistent with the experimental measured stress.

[0041] In the establishment of fatigue life curve of small branch pipe welded joint of nuclear power plant described in the present invention, the force matrix and moment matrix on the calculation neutral surface include:

[0042] Establish a Cartesian coordinate system with the X-axis perpendicular to the pipe weld toe section;

[0043] Extract the nodal forces of all nodes perpendicular to the pipe section where the weld toe is located;

[0044] Grouping the nodal forces along the wall thickness direction to obtain grouping data;

[0045] Calculation is performed based on the grouped data to obtain the force matrix and moment matrix on the neutral plane.

[0046] The present invention also provides a device for establishing fatigue life curve of small branch pipe welding joints in a nuclear power plant, comprising:

[0047] A sample determination unit, used for determining a sample to be analyzed;

[0048] A frequency determination unit, used to determine the first-order natural frequency of the sample to be analyzed;

[0049] A structural excitation and stress control unit, used to perform structural excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, so as to determine the fatigue life of the sample to be analyzed;

[0050] An equivalent stress calculation unit, used for performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed;

[0051] A fatigue life analysis unit, used for performing analysis according to the equivalent structural stress and the fatigue life of the sample to be analyzed, and obtaining a relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed;

[0052] The fatigue life curve fitting unit is used to perform curve fitting according to the relationship between the equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed.

[0053] The present invention also provides a storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor to execute the steps of the method for establishing fatigue life curve of a small branch pipe welded joint of a nuclear power plant as described above.

[0054] The present invention also provides an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and the processor executes the steps of the method for establishing fatigue life curve of small branch pipe welded joints of a nuclear power plant as described above by calling the computer program stored in the memory.

[0055] The method, device, storage medium and electronic device for establishing fatigue life curve of small branch pipe welding joint of nuclear power plant implemented in the present invention have the following beneficial effects: including: determining the sample to be analyzed; determining the first-order natural frequency of the sample to be analyzed; performing structural excitation, alternating stress control and structural stress calculation on the sample to be analyzed to determine the fatigue life of the sample to be analyzed; obtaining the equivalent structural stress of the sample to be analyzed; performing analysis based on equivalent structural stress and fatigue life to obtain the relationship between equivalent structural stress and fatigue life of the test to be analyzed; performing curve fitting based on the relationship between equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed. The present invention performs analysis and calculation on welding joints, has good adaptability, improves the scientificity and accuracy of the reliability assessment results of vibration stress of small branch pipe welds, provides a basis for the power plant to reasonably arrange maintenance plans, avoids unnecessary excessive maintenance and thus improves economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0057] Figure 1 It is a schematic flow chart of a method for establishing fatigue life curve of a small branch pipe welding joint of a nuclear power plant provided by the present invention;

[0058] Figure 2 is a flow chart of an embodiment provided by the present invention;

[0059] Figure 3 It is a schematic diagram of the structure of the sample to be analyzed provided by the present invention;

[0060] Figure 4 is a stress SN curve diagram of a welded joint structure according to an embodiment of the present invention;

[0061] Figure 5 The invention provides a principle block diagram of a device for establishing fatigue life curves of small branch pipe welded joints in a nuclear power plant. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] In order to significantly improve the accuracy of equivalent structural stress fatigue life analysis of small branch pipe welded joints in nuclear power plants, the present invention provides a method for establishing fatigue life curves of small branch pipe welded joints in nuclear power plants, which can provide a technical reference for the full life cycle management of small branch pipes in nuclear power plants.

[0064] Specifically, Figure 1 As shown, the method for establishing the fatigue life curve of the small branch pipe welding joint of the nuclear power plant includes the following steps:

[0065] Step S101: determine the sample to be analyzed.

[0066] In an embodiment of the present invention, determining the sample to be analyzed includes: determining the test material according to the service material of the small branch pipe; determining the sample size; determining the welding process; and determining the sample to be analyzed based on the test material, the sample size and the welding process.

[0067] Step S102: Determine the first-order natural frequency of the sample to be analyzed.

[0068] In an embodiment of the present invention, determining the first-order natural frequency of the sample to be analyzed includes: placing the sample to be analyzed on a vibration table for testing; increasing the excitation frequency at a preset interval for testing; during the test, recording the vibration acceleration data of the test to be analyzed; and determining the first-order natural frequency of the sample to be analyzed based on the vibration acceleration data. The preset interval may be 0.1 Hz.

[0069] Step S103: Based on the first-order natural frequency of the sample to be analyzed, structural excitation and alternating stress control are performed on the sample to be analyzed to determine the fatigue life of the sample to be analyzed.

[0070] In an embodiment of the present invention, based on the first-order natural frequency of the sample to be analyzed, the sample to be analyzed is subjected to structural excitation and alternating stress control, and determining the fatigue life of the sample to be analyzed includes: installing a strain gauge on the sample to be analyzed; performing sinusoidal wave acceleration excitation on the sample to be analyzed based on the first-order natural frequency; testing and collecting the stress of the strain gauge; calculating according to the stress of the strain gauge to obtain the test stress of the sample to be analyzed; judging whether the test stress is within a preset amplitude; if not, adjusting the amplitude of the sinusoidal wave excitation until the test stress is within the preset amplitude; and continuously exciting the sample to be analyzed until a through crack appears at a weld joint of the sample to be analyzed to obtain the fatigue life of the sample to be analyzed.

[0071] Step S103: perform equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed.

[0072] In an embodiment of the present invention, performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed includes: performing finite element modeling and stress calculation on the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress; calculating the force matrix and the moment matrix on the neutral plane; calculating the unit length matrix; performing calculations based on the force matrix, the moment matrix and the unit length matrix to obtain the linear force and the linear moment; performing calculations based on the linear force and the linear moment to obtain the structural stress of each node; and calculating the equivalent structural stress of each node based on the structural stress of each node to obtain the equivalent structural stress of the sample to be analyzed.

[0073] Among them, performing finite element modeling and stress calculation on the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress includes: performing finite element modeling on the sample to be analyzed; performing harmonic response calculation; adjusting the structural damping parameters according to the harmonic response calculation results until the calculated stress of the sample to be analyzed is consistent with the experimental measured stress.

[0074] In an embodiment of the present invention, calculating the force matrix and the moment matrix on the neutral plane includes: establishing a Cartesian coordinate system with an X-coordinate axis perpendicular to the pipe weld toe section; extracting the nodal forces of all nodes perpendicular to the pipe cross section where the weld toe is located; grouping the nodal forces along the wall thickness direction to obtain grouped data; and performing calculations based on the grouped data to obtain the force matrix and the moment matrix on the neutral plane.

[0075] Step S104: performing analysis based on the equivalent structural stress and the fatigue life of the sample to be analyzed to obtain the relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed.

[0076] Step S105: performing curve fitting according to the relationship between equivalent structural stress and fatigue life to obtain a structural stress fatigue life curve of the sample to be analyzed.

[0077] Specifically, Figure 2 As shown in the figure, the test design is first carried out to determine the sample to be analyzed. That is, according to the actual service material of the small branch pipe of concern, the test material of the small branch pipe is selected, such as 304 stainless steel or other pipe materials commonly used in nuclear power plants. The sample size of the sample to be analyzed, such as the diameter, wall thickness, weld width, etc. of the small branch pipe, is determined to ensure that the test results are representative. At the same time, it is also necessary to select an appropriate welding process, such as TIG welding or arc welding, to ensure that the weld quality meets the standards of nuclear power plants.

[0078] After determining the sample to be analyzed, the first order natural frequency of the current small branch (i.e. the sample to be analyzed) needs to be determined. Specifically, the sample to be analyzed is installed on the vibration table, and then the excitation frequency is gradually increased at intervals of 0.1HZ, while recording the vibration acceleration of the sample to be analyzed until an obvious peak appears. At this time, the frequency corresponding to the obvious peak is the first order natural frequency of the sample to be analyzed. Among them, an accelerometer or a laser displacement sensor can be used to measure the vibration acceleration of the sample to be analyzed.

[0079] Then, after determining the first-order natural frequency of the sample to be analyzed, the sample to be analyzed is subjected to fixed-frequency excitation and strain test (i.e., structural excitation and alternating stress control) to control the stress level of the sample to be analyzed. Specifically, a strain gauge is installed near the weld toe of the small branch pipe welding joint, and then fixed-frequency excitation and strain test are performed. At the same time, the weld toe strain of the welding joint is monitored by using the response of the strain gauge, and the alternating stress is calculated according to formula (1).

[0080]

[0081] (1) Where E is the Young's modulus of the material, ε max and ε min are the maximum and minimum values ​​of the measured strain, respectively.

[0082] At the determined first-order natural frequency, a sinusoidal excitation acceleration is applied to the sample to be analyzed, and the excitation amplitude is adjusted to ensure that the stress level of the sample at the weld joint meets the predetermined amplitude. The excitation is continued until a through crack appears at the weld joint, and finally the fatigue life of the sample to be analyzed is obtained.

[0083] At the same time, the equivalent structural stress of the sample to be analyzed is calculated. Specifically, the finite element modeling of the sample to be analyzed is first performed, the harmonic response calculation is carried out, and the structural damping parameters are adjusted until the strain calculated near the weld toe (i.e., the calculated stress) is consistent with the experimental measured strain. Then, a Cartesian coordinate system with the X-axis perpendicular to the pipe weld toe section is established, and the nodal forces of all nodes perpendicular to the pipe section where the weld toe is located are extracted, and the nodal forces are grouped along the wall thickness direction, and the force matrix F on the neutral surface is calculated. i and the moment matrix M i .

[0084]

[0085] (3) In the formula, x 0i ,y 0i 、z 0i is the coordinate of the i-th node on the neutral surface, x i,j ,y i,j 、z i,j are the coordinates of the pipe section node corresponding to the midplane node.

[0086] Next, the unit length equivalent matrix L is calculated, and the calculation formula is shown in formula (4):

[0087]

[0088] (4) In the formula, it is assumed that there are n nodes in the circumferential direction, numbered from 1 to n, and the distance between the nodes along the circumferential direction of the wall thickness centerline is from l1 to l n .

[0089] Calculate the linear force f and linear moment m

[0090]

[0091] Calculate the structural stress σ at each node s , for the i-th node:

[0092]

[0093] Calculate the equivalent structural stress ΔS at each node s , for the i-th node:

[0094]

[0095] (8) Where:

[0096] m=3.6

[0097] t ess =16mm for t≤16mm

[0098] t ess =t for 16mm<t<150mm

[0099] t ess =150mm for t≥150mm

[0100]

[0101] After completing the calculation of the equivalent structural stress, the test results and the corresponding structural stress calculation results are sorted out. For a single specimen, the maximum value of the node equivalent structural stress is taken as the equivalent structural stress ΔS of the specimen to be analyzed. s , combined with the corresponding fatigue life N obtained from the test, the relationship between the equivalent structural stress and fatigue life of all specimens is obtained.

[0102] Finally, the structural stress fatigue life curve is fitted:

[0103] In the embodiment of the present invention, linear regression fitting is adopted.

[0104] In the linear regression model, the fitted formula is as follows:

[0105] log(ΔS s ) = alog(N) + b (9);

[0106] Use the least squares method to fit the linear model and solve the regression coefficients a and b:

[0107]

[0108]

[0109] Confidence interval fitting:

[0110] Confidence intervals are used to assess the uncertainty of an estimate. For parameter b in a regression model, a confidence interval can be calculated.

[0111] The residual is the difference between the actual data point and the regression line. The standard deviation of the residual is σ residual The calculation formula is:

[0112]

[0113] For parameter b, its confidence interval can be calculated by the following formula:

[0114] b upper =b+z·σ residual (13);

[0115] b lower = bz·σ residual (14).

[0116] Where z is the critical value of the standard normal distribution, which is approximately 1.96 for a 95% confidence interval.

[0117] like Figure 3 As shown, Figure 3 The structure of a sample to be analyzed is provided in one embodiment of the present invention.

[0118] In this example, 316L stainless steel was selected as the test material to simulate the small branch pipe welding joint of a nuclear power plant. Figure 3 As shown, the pipe size is 16*3mm, the weld width is 6.7mm, and the mass of the mass block is 0.85kg. TIG welding is used, and X-ray inspection is used to ensure that the weld is defect-free.

[0119] The sample to be analyzed was mounted on a vibration table and the vibration response was measured using an accelerometer. The excitation frequency was gradually increased and the response data was recorded, and the first-order natural frequency was finally determined to be 74 Hz.

[0120] Install strain gauges near the weld toe of the weld joint, and use the following formula to calculate the alternating stress. The target alternating stresses are set to 120MPa, 160MPa, 180MPa, and 200MPa, respectively. At least 4 sets of parallel specimens are carried out for each alternating stress level.

[0121] σ=E(ε max -ε min );

[0122] Where E is the Young's modulus of the material, ε max and ε min The sine wave acceleration on the vibration table is adjusted to ensure that the stress level is within the predetermined amplitude, and the excitation is continued until a through crack appears at the weld joint.

[0123] Finite element simulation was performed on the sample to be analyzed, and harmonic response analysis was performed using ANSYS software. The calculation parameters were adjusted to make the simulation results consistent with the actual measured strain data, and the equivalent structural stress was calculated on this basis. The structural stress and equivalent structural stress of each node were calculated by integrating the node force and node moment, and the maximum value of the structural stress in each node was taken. The equivalent structural stress of each sample is shown in Table 1.

[0124] Table 1 Calculation results of equivalent structural stress

[0125]

[0126] In the double logarithmic coordinate system, the SN curve of the 316L stainless steel welded joint is fitted as follows: Figure 4 As shown:

[0127] The fitting parameters at different confidence levels are shown in Table 2:

[0128] Table 2 Fitting parameters

[0129]

[0130]

[0131] The structural stress of the present invention is calculated based on the linear force and linear moment of the node, and is aimed at the specific pipeline structure welding joint. It has good adaptability and grid-insensitive characteristics, avoiding the influence of stress concentration effect in structural discontinuity areas; the structural stress has good consistency with the fatigue life of the weld, and adopts the structural stress SN curve (weld sample), which reduces the uncertainty of fatigue curve selection when analyzing welding fatigue using the nominal stress method, improves the scientificity and accuracy of the reliability evaluation results of the vibration stress of the small branch pipe weld, and provides a basis for the power plant to reasonably arrange the maintenance plan, avoid unnecessary excessive maintenance, and thus improve the economy.

[0132] When conventional vibration velocity evaluation is unacceptable and the unit condition does not meet the conditions for vibration control, a scientific, reasonable and quantitative evaluation based on the structural stress method can maximize the service value of the small branch pipe while ensuring safety.

[0133] refer to Figure 5 , Figure 5 The present invention is a principle block diagram of a device for establishing fatigue life curve of a small branch pipe welding joint of a nuclear power plant.

[0134] Specifically, Figure 5 As shown, the fatigue life curve establishment device of the small branch pipe welding joint of the nuclear power plant includes:

[0135] The sample determination unit 501 is used to determine the sample to be analyzed.

[0136] The frequency determination unit 502 is used to determine the first-order natural frequency of the sample to be analyzed.

[0137] The structural excitation and stress control unit 503 is used to perform structural excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, so as to determine the fatigue life of the sample to be analyzed.

[0138] The equivalent stress calculation unit 504 is used to perform equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed.

[0139] The fatigue life analysis unit 505 is used to perform analysis according to the equivalent structural stress and the fatigue life of the sample to be analyzed, so as to obtain the relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed.

[0140] The fatigue life curve fitting unit 506 is used to perform curve fitting according to the relationship between the equivalent structural stress and the fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed.

[0141] Specifically, the specific coordination operation process between the various units in the fatigue life curve establishment device for the small branch pipe welded joint of a nuclear power plant can refer to the above-mentioned method for establishing the fatigue life curve of the small branch pipe welded joint of a nuclear power plant, and will not be repeated here.

[0142] In addition, an electronic device of the present invention includes a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program to implement a method for establishing a fatigue life curve of a small branch pipe welded joint in a nuclear power plant as described in any of the above items. Specifically, according to an embodiment of the present invention, the process described with reference to the flowchart above can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program contains a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed by an electronic device and when executed, it executes the above functions defined in the method of the embodiment of the present invention. The electronic device in the present invention can be a terminal such as a notebook, a desktop, a tablet computer, a smart phone, or a server.

[0143] In addition, a storage medium of the present invention stores a computer program thereon, and when the computer program is executed by a processor, any one of the above methods for establishing fatigue life curves of small branch pipe welded joints in nuclear power plants is implemented. Specifically, it should be noted that the above storage medium of the present invention may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, device or device. In the present invention, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries a computer-readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (radio frequency), etc., or any suitable combination of the above.

[0144] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device.

[0145] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0146] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0147] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0148] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants, characterized in that: The following steps are involved: Determine the sample to be analyzed; Determining the first-order natural frequency of the sample to be analyzed; Based on the first-order natural frequency of the sample to be analyzed, structural excitation and alternating stress control are performed on the sample to be analyzed to determine the fatigue life of the sample to be analyzed; Performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed; Performing analysis based on the equivalent structural stress and the fatigue life of the sample to be analyzed to obtain a relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed; Curve fitting is performed according to the relationship between the equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed.

2. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 1, characterized in that: Determining the sample to be analyzed comprises: Determine the test material based on the service material of the small branch pipe; Determine the specimen size; Determine the welding process; The sample to be analyzed is determined based on the test material, the sample size, and the welding process.

3. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 1, characterized in that: Determining the first-order natural frequency of the sample to be analyzed comprises: Placing the sample to be analyzed on a vibration table for testing; The test is conducted by increasing the excitation frequency at preset intervals; During the test, recording the vibration acceleration data of the test to be analyzed; The first-order natural frequency of the sample to be analyzed is determined according to the vibration acceleration data.

4. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 1, characterized in that: The step of performing structural excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed to determine the fatigue life of the sample to be analyzed includes: Installing a strain gauge on the sample to be analyzed; Performing a sinusoidal wave acceleration excitation on the sample to be analyzed based on the first-order natural frequency; Testing and collecting the stress of the strain gauge; Calculating according to the stress of the strain gauge to obtain the test stress of the sample to be analyzed; Determining whether the test stress is within a preset amplitude; If not, adjusting the amplitude of the sinusoidal wave excitation until the test stress is within the preset amplitude; The sample to be analyzed is continuously excited until a through crack appears at a welding joint of the sample to be analyzed, and the fatigue life of the sample to be analyzed is obtained.

5. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 1, characterized in that: The performing of equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed comprises: Performing finite element modeling and stress calculation on the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress; Calculate the force matrix and moment matrix on the neutral surface; Calculate the cell length matrix; Calculate according to the force matrix, the moment matrix and the unit length matrix to obtain the linear force and the linear moment; Calculate according to the linear force and the linear moment to obtain the structural stress of each node; Based on the structural stress of each node, the equivalent structural stress of each node is calculated to obtain the equivalent structural stress of the sample to be analyzed.

6. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 5, characterized in that: The performing finite element modeling and stress calculation on the sample to be analyzed so that the calculated stress of the sample to be analyzed is consistent with the experimental measured stress includes: Performing finite element modeling on the sample to be analyzed; Perform harmonic response calculations; The structural damping parameters are adjusted according to the harmonic response calculation results until the calculated stress of the sample to be analyzed is consistent with the experimental measured stress.

7. The method for establishing fatigue life curve of small branch pipe welded joints in nuclear power plants according to claim 5, characterized in that: The force matrix and moment matrix on the calculation neutral surface include: Establish a Cartesian coordinate system with the X-axis perpendicular to the pipe weld toe section; Extract the nodal forces of all nodes perpendicular to the pipe section where the weld toe is located; Grouping the nodal forces along the wall thickness direction to obtain grouping data; Calculation is performed based on the grouped data to obtain the force matrix and moment matrix on the neutral plane.

8. A device for establishing fatigue life curve of small branch pipe welding joints in nuclear power plants, characterized in that: include: A sample determination unit, used for determining a sample to be analyzed; A frequency determination unit, used to determine the first-order natural frequency of the sample to be analyzed; A structural excitation and stress control unit, used to perform structural excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, so as to determine the fatigue life of the sample to be analyzed; An equivalent stress calculation unit, used for performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed; A fatigue life analysis unit, used for performing analysis according to the equivalent structural stress and the fatigue life of the sample to be analyzed, and obtaining a relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed; The fatigue life curve fitting unit is used to perform curve fitting according to the relationship between the equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the sample to be analyzed.

9. A storage medium, characterized in that: The storage medium stores a computer program, and the computer program is suitable for being loaded by a processor to execute the steps of the method for establishing a fatigue life curve of a small branch pipe welded joint of a nuclear power plant as described in any one of claims 1 to 7.

10. An electronic device, characterized in that: It comprises a memory and a processor, wherein the memory stores a computer program, and the processor executes the steps of the method for establishing fatigue life curve of small branch pipe welded joints of a nuclear power plant as described in any one of claims 1 to 7 by calling the computer program stored in the memory.

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