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

Abstract

The present application relates to a kind of nuclear power plant small branch pipe welding joint fatigue life curve establishment method, device, storage medium and electronic equipment, comprising: determining to be analyzed sample;Determine the first natural frequency of to be analyzed sample;To be analyzed sample is carried out structural excitation and alternating stress control and structural stress calculation, determine the fatigue life of to be analyzed sample;Equivalent structural stress of to be analyzed sample is obtained;Equivalent structural stress and fatigue life are analyzed based on, obtain the equivalent structural stress and fatigue life relationship of to be analyzed test;According to equivalent structural stress and fatigue life relationship carries out curve fitting, obtains the structural stress fatigue life curve of to be analyzed sample.The present application carries out analysis calculation to welding joint, with good adaptability, improve the scientific nature, accuracy of small branch pipe weld vibration stress reliability evaluation result, provide basis for reasonable arrangement maintenance plan of power plant, avoid unnecessary excessive maintenance to improve economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration analysis, and more particularly to a method and device for establishing a fatigue life curve of a small branch pipe welding joint in a nuclear power plant, a storage medium and an electronic device. BACKGROUND

[0002] Vibration fatigue failure of small branch pipe welding 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 small branch pipes that have an impact on the operation of the unit, may cause shutdown or shutdown, have a high risk of failure, and carry high-energy media (considered as high-risk small branch pipes), once a leak occurs, it not only may pose a safety threat to personnel or the environment, but also may 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 pipes, the existing ASME Boiler and Pressure Vessel Code (BPVC) and Règles de Conception et de Construction des Matériels (RCC-M) standards are widely used. These standards are usually based on experimental data of smooth base material samples when establishing fatigue life curves, and do not fully consider the influence of small branch pipe welding joints. In actual engineering applications, due to the influence of factors such as the geometric opening of the welding joint, the material microstructure, and the residual stress, the use of existing ASME BPVC or RCC-M standards for fatigue analysis of small branch pipe welding joints often leads to insufficient accuracy of the analysis results, affecting engineering design and safety assessment. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method and device for establishing a fatigue life curve of a small branch pipe welding joint in a nuclear power plant, a storage medium and an electronic device to solve the problems in the prior art.

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

[0006] determining a sample to be analyzed;

[0007] determining the first natural frequency of the sample to be analyzed;

[0008] based on the first natural frequency of the sample to be analyzed, performing structure excitation and alternating stress control 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] According to the equivalent structural stress and the fatigue life of the sample to be analyzed, a relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed is obtained;

[0011] According to the relationship between the equivalent structural stress and the fatigue life, a structural stress fatigue life curve of the sample to be analyzed is obtained.

[0012] In the establishment of the fatigue life curve of the small branch pipe welding joint of the nuclear power plant, the determination of the sample to be analyzed comprises:

[0013] According to the service material of the small branch pipe, a test material is determined;

[0014] A sample size is determined;

[0015] A welding process is determined;

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

[0017] In the establishment of the fatigue life curve of the small branch pipe welding joint of the nuclear power plant, the determination of the first-order natural frequency of the sample to be analyzed comprises:

[0018] The sample to be analyzed is placed on a vibration table for testing;

[0019] The test is performed with a preset interval to increase the excitation frequency;

[0020] During the test, vibration acceleration data of the sample to be analyzed is recorded;

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

[0022] In the establishment of the fatigue life curve of the small branch pipe welding joint of the nuclear power plant, the determination of the fatigue life of the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, the structural excitation and the alternating stress control of the sample to be analyzed comprises:

[0023] A strain gauge is installed on the sample to be analyzed;

[0024] Based on the first-order natural frequency, the sample to be analyzed is excited by a sinusoidal wave;

[0025] The stress of the strain gauge is tested and collected;

[0026] According to the stress of the strain gauge, a test stress of the sample to be analyzed is obtained;

[0027] It is judged whether the test stress is within a preset amplitude.

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

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

[0030] In the establishment of the fatigue life curve of the small branch pipe welded joint of the nuclear power plant, the equivalent structural stress of the sample to be analyzed is obtained by performing equivalent structural stress calculation, comprising:

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

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

[0033] Calculating the unit length matrix;

[0034] According to the force matrix, the moment matrix and the unit length matrix, the line force and the line moment are obtained by calculation;

[0035] According to the line force and the line moment, the structural stress of each node is obtained by calculation;

[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 the fatigue life curve of the small branch pipe welded joint of the nuclear power plant, the finite element modeling and stress calculation on the sample to be analyzed to make the calculated stress of the sample to be analyzed consistent with the measured stress comprise:

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

[0039] Performing harmonic response calculation;

[0040] 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 measured stress.

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

[0042] Establishing a Cartesian coordinate system perpendicular to the pipe weld toe section of the X coordinate axis;

[0043] Extracting the node force of all nodes perpendicular to the pipe section where the weld toe is located;

[0044] Group the node forces in the wall thickness direction to obtain grouping data;

[0045] Based on the grouping data, calculate to obtain the force matrix and the moment matrix on the neutral surface.

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

[0047] A sample determination unit is configured to determine a sample to be analyzed.

[0048] A frequency determination unit is configured to determine a first-order natural frequency of the sample to be analyzed.

[0049] A structure excitation and stress control unit is configured to perform structure excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, and determine the fatigue life of the sample to be analyzed.

[0050] An equivalent stress calculation unit is configured to perform equivalent structure stress calculation to obtain the equivalent structure stress of the sample to be analyzed.

[0051] A fatigue life analysis unit is configured to analyze the equivalent structure stress and the fatigue life of the sample to be analyzed to obtain the relationship between the equivalent structure stress and the fatigue life of the sample to be analyzed.

[0052] A fatigue life curve fitting unit is configured to perform curve fitting based on the relationship between the equivalent structure stress and the fatigue life to obtain the structure stress fatigue life curve of the sample to be analyzed.

[0053] The application also provides a storage medium storing a computer program, wherein the computer program is adapted to be loaded by a processor to execute the steps of the method for establishing a fatigue life curve of a small branch pipe welding joint of a nuclear power plant.

[0054] The application also provides an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the steps of the method for establishing a fatigue life curve of a small branch pipe welding joint of a nuclear power plant by calling the computer program stored in the memory.

[0055] The nuclear power plant small branch pipe welding joint fatigue life curve establishing method, device, storage medium and electronic equipment provided by the present application have the following beneficial effects: the method comprises the following steps: determining a to-be-analyzed sample; determining the first-order natural frequency of the to-be-analyzed sample; performing structural excitation, alternating stress control and structural stress calculation on the to-be-analyzed sample to determine the fatigue life of the to-be-analyzed sample; obtaining the equivalent structural stress of the to-be-analyzed sample; analyzing the equivalent structural stress and the fatigue life to obtain the relationship between the equivalent structural stress and the fatigue life of the to-be-analyzed sample; and performing 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 to-be-analyzed sample. The present application analyzes and calculates the welding joint, has good adaptability, improves the scientificity and accuracy of the small branch pipe welding vibration stress reliability evaluation result, provides a basis for the reasonable arrangement of the maintenance plan of the power plant, avoids unnecessary excessive maintenance, and thus improves the economy. BRIEF DESCRIPTION OF DRAWINGS

[0056] The present application will be further described below in combination with the drawings and embodiments, and the drawings are as follows:

[0057] Figure 1 FIG. 1 is a flowchart of the nuclear power plant small branch pipe welding joint fatigue life curve establishing method provided by the present application;

[0058] Figure 2 FIG. 2 is a flowchart of one embodiment of the present application;

[0059] Figure 3 FIG. 3 is a structural diagram of the to-be-analyzed sample provided by the present application;

[0060] Figure 4 FIG. 4 is a welding joint structural stress S-N curve diagram of one embodiment of the present application;

[0061] Figure 5 FIG. 5 is a principle block diagram of the nuclear power plant small branch pipe welding joint fatigue life curve establishing device provided by the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0063] In order to significantly improve the accuracy of the equivalent structural stress fatigue life analysis of the nuclear power plant small branch pipe welding joint, the present application provides a nuclear power plant small branch pipe welding joint fatigue life curve establishing method, which can provide technical reference for the life cycle management of the small branch pipe of the nuclear power plant.

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

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

[0066] In the embodiment of the present application, determining the sample to be analyzed comprises: 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 the embodiment of the present application, 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; increasing the excitation frequency at a preset interval for testing; recording the vibration acceleration data of the sample to be analyzed during the testing; and determining the first-order natural frequency of the sample to be analyzed according to the vibration acceleration data. The preset interval can be 0.1 HZ.

[0069] Step S103: Based on the first-order natural frequency of the sample to be analyzed, the structure of the sample to be analyzed is excited and the alternating stress is controlled to determine the fatigue life of the sample to be analyzed.

[0070] In the embodiment of the present application, based on the first-order natural frequency of the sample to be analyzed, the structure of the sample to be analyzed is excited and the alternating stress is controlled to determine the fatigue life of the sample to be analyzed, which comprises: installing a strain gauge on the sample to be analyzed; exciting the sample to be analyzed with a sinusoidal wave excitation acceleration based on the first-order natural frequency; testing and collecting the stress of the strain gauge; calculating the test stress of the sample to be analyzed according to the stress of the strain gauge; 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; and continuously exciting the sample to be analyzed until a through-wall crack appears at the welding 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 the embodiment of the present application, performing 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 to make the calculated stress of the sample to be analyzed consistent with the test measured stress; calculating the force matrix and the moment matrix on the neutral plane; calculating the unit length matrix; calculating the line force and the line moment based on the force matrix, the moment matrix and the unit length matrix; calculating the structural stress of each node based on the line force and the line moment; 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] The process of performing finite element modeling and stress calculation on the specimen to be analyzed, so that the calculated stress of the specimen is consistent with the experimentally measured stress, includes: performing finite element modeling on the specimen to be analyzed; performing harmonic response calculation; and adjusting the structural damping parameters according to the harmonic response calculation results until the calculated stress of the specimen is consistent with the experimentally measured stress.

[0074] In this embodiment of the invention, calculating the force matrix and moment matrix on the neutral surface includes: establishing a Cartesian coordinate system with the X-axis perpendicular to the pipe weld toe section; extracting 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 grouped data; and calculating the force matrix and moment matrix on the neutral surface based on the grouped data.

[0075] Step S104: Analyze the equivalent structural stress and fatigue life of the specimen to be analyzed to obtain the relationship between the equivalent structural stress and fatigue life of the specimen to be analyzed.

[0076] Step S105: Perform curve fitting based on the relationship between equivalent structural stress and fatigue life to obtain the structural stress fatigue life curve of the specimen to be analyzed.

[0077] Specifically, such as Figure 2 As shown, the first step is to design the experiment to determine the test specimen. This involves selecting the test material for the branch pipe based on its actual service material, such as 304 stainless steel or other commonly used piping materials in nuclear power plants. The specimen dimensions are then determined, including the branch pipe's diameter, wall thickness, and weld width, to ensure the representativeness of the test results. Simultaneously, an appropriate welding process, such as TIG welding or arc welding, needs to be selected to ensure the weld quality meets nuclear power plant standards.

[0078] After identifying the specimen to be analyzed, the first step is to determine the first natural frequency of the current branch pipe (i.e., the specimen). Specifically, the specimen is mounted on a vibration table, and the excitation frequency is gradually increased in 0.1 Hz intervals while simultaneously recording the vibration acceleration of the specimen. This continues until a distinct peak value is observed; the frequency corresponding to this peak value is the first natural frequency of the specimen. An accelerometer or a laser displacement sensor can be used to measure the vibration acceleration of the specimen.

[0079] Next, after determining the first natural frequency of the specimen to be analyzed, the specimen is subjected to constant frequency excitation and strain testing (i.e., structural excitation and alternating stress control) to control the stress level of the specimen. Specifically, strain gauges are installed near the weld toe of the small branch pipe welded joint, and then constant frequency excitation and strain testing are performed. At the same time, the strain at the weld toe of the welded joint is monitored by using the response of the strain gauges, and the alternating stress is calculated according to equation (1).

[0080]

[0081] (1) where E is the material Young's modulus, 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 wave excitation acceleration excitation 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 welded joint meets the predetermined amplitude. The excitation is continued until a through crack appears at the welded 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, first, finite element modeling is carried out on the sample to be analyzed, harmonic response calculation is carried out, and structural damping parameters are adjusted until the calculated strain (i.e. calculated stress) near the weld toe is consistent with the measured strain. Then, a Cartesian coordinate system is established with the X coordinate axis perpendicular to the pipe weld toe section, the node forces of all nodes perpendicular to the pipe section where the weld toe is located are extracted, and the node forces are grouped in the wall thickness direction. The force matrix F i and the moment matrix M i on the neutral surface are calculated.

[0084]

[0085] (3) where x 0i , y 0i , z 0i are the coordinates of the i-th node on the neutral surface, and x i,j , y i,j , z i,j are the coordinates of the pipe section node corresponding to the neutral surface node.

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

[0087]

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

[0089] The line force f and the line moment m

[0090]

[0091] The structural stress σ s of each node is calculated, and for the i-th node:

[0092]

[0093] Calculate the equivalent structural stress ΔS of each node s For the ith node:

[0094]

[0095] (8) In the formula:

[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 the calculation of the equivalent structural stress is completed, the test results and the corresponding structural stress calculation results are sorted out. Among them, for a single sample, the maximum value of the equivalent structural stress of the node is taken as the equivalent structural stress ΔS of the sample to be analyzed s , combined with the corresponding fatigue life N obtained by the test, the relationship between the equivalent structural stress and the fatigue life of all samples is obtained.

[0102] Finally, the structural stress fatigue life curve fitting is carried out:

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

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

[0105] log(ΔS s ) = alog(N) + b (9);

[0106] The least square method is used to fit the linear model, and the regression coefficients a and b are solved:

[0107]

[0108]

[0109] Confidence interval fitting:

[0110] The confidence interval is used to evaluate the uncertainty of the estimated value. For the parameter b in the regression model, the confidence interval thereof can be calculated.

[0111] The residual is the difference between the actual data point and the regression fitting line, and the calculation formula of the standard deviation σ residual of the residual 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 = b - z · σ residual (14).

[0116] In the formula, z is the critical value of the standard normal distribution, and for a 95% confidence interval, z is about 1.96.

[0117] As Figure 3 shown, Figure 3 a structure of a test sample provided by an embodiment of the present application is shown.

[0118] In this embodiment, 316L stainless steel is selected as the test material to simulate the welding joint of a small branch pipe of a nuclear power plant. The structure of the test sample to be analyzed is shown in Figure 3 , 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 detection is used to ensure that the weld is free of defects.

[0119] The test sample to be analyzed is installed on the vibration table, and an accelerometer is used to measure the vibration response. By gradually increasing the excitation frequency, the response data is recorded, and finally the first-order natural frequency is determined to be 74Hz.

[0120] Strain gauges are installed near the weld toe of the welding joint, and the alternating stress is calculated using the following formula, and the target alternating stress is set to 120MPa, 160MPa, 180MPa, and 200MPa, respectively. At least 4 sets of parallel samples 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, and ε max and ε min are the maximum and minimum strains measured, respectively. By adjusting the sine wave acceleration on the vibration table, the stress level is ensured to be within the predetermined amplitude, and the excitation is continued until a through-wall crack appears at the welding joint.

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

[0124] Table 1: Equivalent structural stress calculation results

[0125]

[0126] In the double logarithmic coordinate system, the S-N curve of the 316L stainless steel welded joint is fitted as shown in Figure 4

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

[0128] Table 2: Fitting parameters

[0129]

[0130]

[0131] The structural stress of the present application is based on the calculation of the line force and the line moment of the node, and is aimed at the specific pipeline structure welded joint, has good adaptability, and has the characteristics of grid insensitivity, avoids the influence of structural discontinuous zone stress concentration effect; the structural stress has good consistency with the weld fatigue life, adopts the structural stress S-N curve (weld sample), reduces the uncertainty of the selection of the fatigue curve when analyzing the weld fatigue by using the nominal stress method, improves the scientificity and accuracy of the small branch pipe weld vibration stress reliability evaluation result, provides a basis for the reasonable arrangement of the maintenance plan of the power plant, avoids unnecessary excessive maintenance and improves the economy.

[0132] When the conventional vibration speed evaluation is unacceptable, and the unit state does not have vibration treatment conditions, relying on the structural stress method to carry out scientific, reasonable and quantitative evaluation can maximize the service value of the small branch pipe under the premise of ensuring safety.

[0133] Reference Figure 5 , Figure 5 The principle block diagram of the nuclear power plant small branch pipe welded joint fatigue life curve establishing device provided by the present application is shown.

[0134] Specifically, as shown in the figure, the nuclear power plant small branch pipe welded joint fatigue life curve establishing device includes: Figure 5

[0135] The sample determining unit 501 is used for determining the sample to be analyzed. ​​

[0136] The frequency determining unit 502 is configured to determine the first natural frequency of the sample to be analyzed.

[0137] The structure excitation and stress control unit 503 is configured to perform structure excitation and alternating stress control on the sample to be analyzed based on the first natural frequency of the sample to be analyzed, and determine the fatigue life of the sample to be analyzed.

[0138] The equivalent stress calculating unit 504 is configured to perform equivalent structure stress calculation to obtain the equivalent structure stress of the sample to be analyzed.

[0139] The fatigue life analyzing unit 505 is configured to analyze the equivalent structure stress and the fatigue life of the sample to be analyzed to obtain the relationship between the equivalent structure stress and the fatigue life of the sample to be analyzed.

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

[0141] Specifically, the cooperation operation process between each unit in the nuclear power plant small branch pipe welding joint fatigue life curve establishing device can refer to the above-mentioned nuclear power plant small branch pipe welding joint fatigue life curve establishing method, which will not be repeated here.

[0142] In addition, the electronic device of the present application includes a memory and a processor; the memory is used to store the computer program; the processor is used to execute the computer program to realize the nuclear power plant small branch pipe welding joint fatigue life curve establishing method of any one of the above. Specifically, according to the embodiments of the present application, the processes described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments of the present application include a computer program product, which includes a computer program carried on a computer readable medium, and the computer program includes program codes for executing the method shown in the flowchart. In such embodiments, the computer program can be downloaded and installed by the electronic device and executed to perform the above-mentioned functions defined in the method of the embodiments of the present application. The electronic device in the present application can be a notebook, a desktop, a tablet computer, a smart phone, etc. terminal, and can also be a server.

[0143] In addition, the present application also provides a storage medium storing a computer program, which is executed by a processor to implement the method for establishing a fatigue life curve of a small branch pipe welding joint of a nuclear power plant according to any one of the above. Specifically, it should be noted that the storage medium of the present application can be a computer readable signal medium or a computer readable storage medium, or any combination of the two. The computer readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination of the above. More specific examples of the computer readable storage medium can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, 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 application, the 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, device or apparatus. In the present application, the computer readable signal medium can include a data signal carried in a baseband or as a part of a carrier wave, which carries computer readable program code. Such a propagated data signal can take various forms, including but not limited to an electromagnetic signal, an optical signal or any suitable combination of the above. The computer readable signal medium can also be any computer readable medium other than the computer readable storage medium, which can send, propagate or transmit a program for use by or in conjunction with an instruction execution system, device or apparatus. The program code contained in the computer readable medium can be transmitted by any suitable medium, including but not limited to a wire, a cable, an RF (radio frequency) or the like, or any suitable combination of the above.

[0144] The above computer readable medium can be included in the above electronic device; or can exist separately and not be assembled into the electronic device.

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

[0146] Those skilled in the art will further realize that the mere conception of the examples described herein is not inducing any patentable instrument, and that each example presents only one illustrative aspect of the present application. The present application is thus deemed to cover any and all adaptations or variations of preferred examples. It is intended to embrace each and every possible modification and change as fall within the scope of the present application. However, various current or future technical solutions in the art can be used in the technical solutions disclosed in the present application. Thus, technical details that can not be described in detail in the present application are deemed to be known to those skilled in the art.

[0147] The steps of the methods or algorithms described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in random access memory (RAM), flash memory, read-only memory (ROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0148] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it accordingly, and cannot limit the protection scope of the present application. Any equivalent changes and modifications made within the scope of the claims of the present application shall be deemed to fall within the scope of the claims of the present application.

Claims

1. A method for establishing a fatigue life curve for a small branch weld joint in a nuclear power plant, characterized by, The method comprises the following steps: determining a sample to be analyzed; determining the first natural frequency of the sample to be analyzed; based on the first natural frequency of the sample to be analyzed, the structure of the sample to be analyzed is excited and the alternating stress control is determined, and the fatigue life of the sample to be analyzed is determined; the fatigue life of the sample to be analyzed is determined based on the first natural frequency of the sample to be analyzed, the structure of the sample to be analyzed is excited and the alternating stress control is determined, and the fatigue life of the sample to be analyzed is determined; install a strain gauge on the sample to be analyzed; based on the first natural frequency, the sample to be analyzed is excited by a sinusoidal acceleration; the stress of the strain gauge is tested and collected; the test stress of the sample to be analyzed is obtained according to the stress of the strain gauge; it is judged whether the test stress is within the preset amplitude; if not, adjust the amplitude of the sinusoidal wave excitation until the test stress is within the preset amplitude; continue to excite the sample to be analyzed until a through crack appears at the welded joint of the sample to be analyzed, and the fatigue life of the sample to be analyzed is obtained; equivalent structural stress calculation is performed to obtain the equivalent structural stress of the sample to be analyzed; the equivalent structural stress calculation is performed to obtain the equivalent structural stress of the sample to be analyzed, which comprises: finite element modeling and stress calculation are performed on the sample to be analyzed, so that the calculated stress of the sample to be analyzed is consistent with the test measured stress; the force matrix and the moment matrix on the neutral plane are calculated; the unit length matrix is calculated; the line force and the line moment are obtained by calculating the force matrix, the moment matrix and the unit length matrix; the structural stress of each node is obtained by calculating the line force and the line moment; based on the structural stress of each node, the equivalent structural stress of each node is calculated, and the equivalent structural stress of the sample to be analyzed is obtained; the relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed is analyzed according to the equivalent structural stress and the fatigue life of the sample to be analyzed, and the relationship between the equivalent structural stress and the fatigue life of the sample to be analyzed is obtained; curve fitting is performed according to the relationship between the equivalent structural stress and the fatigue life, and the structural stress fatigue life curve of the sample to be analyzed is obtained.

2. The method of establishing a fatigue life curve for a small branch weld joint of a nuclear power plant according to claim 1, characterized in that, The determination of the sample to be analyzed comprises: determining the test material according to the service material of the small branch pipe; determining the sample size; determining the welding process; based on the test material, the sample size and the welding process, the sample to be analyzed is determined.

3. The method of claim 1, wherein the method is characterized by: The determination of the first natural frequency of the sample to be analyzed comprises: 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, record the vibration acceleration data of the sample to be analyzed; determine the first natural frequency of the sample to be analyzed according to the vibration acceleration data.

4. The method of claim 1, wherein the method is characterized by: The finite element modeling and stress calculation of the sample to be analyzed are performed to make the calculated stress of the sample to be analyzed consistent with the test measured stress, which comprises: finite element modeling is performed on the sample to be analyzed; performing harmonic response calculation; adjust 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 test measured stress.

5. The method of claim 1, wherein, The calculation of the force matrix and the moment matrix on the neutral plane comprises: A Cartesian coordinate system is established with the X coordinate axis being perpendicular to the pipe weld toe section; Node forces of all nodes in the pipe section perpendicular to the weld toe are extracted; The node forces are grouped in the thickness direction to obtain grouping data; Based on the grouping data, a force matrix and a moment matrix on the neutral plane are calculated.

6. A device for establishing a fatigue life curve of a small branch pipe welded joint of a nuclear power plant, characterized by, It comprises: a sample determination unit for determining a sample to be analyzed; a frequency determination unit for determining the first-order natural frequency of the sample to be analyzed; a structure excitation and stress control unit for performing structure excitation and alternating stress control on the sample to be analyzed based on the first-order natural frequency of the sample to be analyzed, and determining the fatigue life of the sample to be analyzed; the structure excitation and stress control unit comprises: installing a strain gauge on the sample to be analyzed; performing sinusoidal 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 the test stress of the sample to be analyzed based on the stress of the strain gauge; 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; and continuously exciting the sample to be analyzed until a through-wall crack appears at the welded joint of the sample to be analyzed, thereby obtaining the fatigue life of the sample to be analyzed; an equivalent structural stress calculation unit for performing equivalent structural stress calculation to obtain the equivalent structural stress of the sample to be analyzed; the equivalent structural stress calculation unit comprises: performing finite element modeling and stress calculation on the sample to be analyzed to make the calculated stress of the sample to be analyzed consistent with the test measured stress; calculating a force matrix and a moment matrix on the neutral plane; calculating a unit length matrix; calculating line forces and line moments based on the force matrix, the moment matrix, and the unit length matrix; calculating structural stresses of each node based on the line forces and the line moments; and calculating equivalent structural stresses of the nodes based on the structural stresses of the nodes to obtain the equivalent structural stress of the sample to be analyzed; a fatigue life analysis unit for analyzing 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; a fatigue life curve fitting unit for performing curve fitting based on the relationship between the equivalent structural stress and the fatigue life to obtain a structural stress fatigue life curve of the sample to be analyzed.

7. A storage medium, characterized by The storage medium stores a computer program, which is adapted to be loaded by a processor to execute the steps of the nuclear power plant small branch pipe welded joint fatigue life curve establishment method according to any one of claims 1 to 5.

8. An electronic device, comprising: It comprises a memory and a processor, and the memory stores a computer program, and the processor executes the steps of the nuclear power plant small branch pipe welded joint fatigue life curve establishment method according to any one of claims 1 to 5 by calling the computer program stored in the memory.

Images