Method and device for determining maximum allowable stress of defect-containing welding structure

Abstract

The invention discloses a method and device for determining the maximum allowable stress of a defect-containing welding structure. The method comprises the steps that the normal distribution condition of the defect position size and the non-defect position size of the welding structure is obtained; respectively establishing a first finite element model corresponding to a defect position and a second finite element model corresponding to a non-defect position by utilizing a Monte Carlo method based on the normal distribution condition; according to the first finite element model and the second finite element model, a first probability density function corresponding to the first maximum stress of the defect position under the unit load, a second probability density function corresponding to the maximum strength factor and a second maximum stress of the non-defect position under the unit load are determined; using the first probability density function and the second probability density function to determine an average stress, a safety stress, an average strength factor and a safety strength factor; and according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor, the allowable stress of the welding structure in the defect-containing state is determined.

Description

Technical Field

[0001] The invention relates to a reliability design method for a structure, and in particular to a method and a device for determining the maximum allowable stress of a defective welded structure. Background Art

[0002] In the manufacturing and on-site installation of nuclear-grade equipment, welding technology is one of the most basic and important processing methods. Nuclear power welding components have complex structures and large numbers. Their welding quality is affected by many factors, including personnel operation, materials, processes, etc. During the operation of nuclear power plants, nuclear-grade equipment is affected by temperature, stress, vibration, wear and many other external factors. As a relatively weak area, welded structures are prone to the initiation and expansion of defects, resulting in a decrease in the mechanical properties of the structure. Common welding defects can be roughly divided into two categories: crack-type defects and hole-type defects. The former is narrower and longer in spatial shape than the latter. Both types of defects will destroy the continuity of the structural material, causing a large stress concentration at the defect location when the welded structure is in service, which may lead to the destruction of the structure designed in a defect-free state, thereby endangering the safety of the structure and system.

[0003] In order to accurately detect welding defects of nuclear-grade equipment, appropriate non-destructive testing methods are selected according to different welding structures, and then the welding area is tested with strict technical standards, which can generally obtain relatively accurate results. However, due to the complexity of nuclear power system materials and structures, there are undetectable and difficult-to-detect parts, which makes it impossible to effectively detect defects in some welding structure areas, and the welding quality and structural reliability of the weld cannot be effectively quantitatively evaluated, which may cause failures or even accidents.

[0004] The existing patent CN109885930A discloses a safety classification method for hazardous defects in welds, which includes the following steps: first, obtain the stress intensity factor K of weld defects at different stress levels, and obtain the fracture toughness Kc of the weld by experimental measurement or consulting manual materials; then calculate the safety factor and critical expansion size, obtain the defect size under the corresponding stress and draw a standard curve, and finally obtain the weld crack safety factor and classify the weld defects. This method focuses on achieving safety assessment of crack defects by classifying weld defects.

[0005] The existing patent CN111046534A discloses a strength assessment method based on the minimum reliable safety factor. The method first analyzes the mechanical structure to find the weak link or stress concentration area; then determines the stress distribution function of the area; determines the strength distribution function; further selects the corresponding minimum reliable safety factor calculation formula; finally determines the confidence level of the stress and strength limit values ​​to calculate the minimum reliable safety factor and assess the strength. This solution focuses on solving the design redundancy problem, but does not solve the problem of poor welding quality and structural reliability assessment in the prior art.

[0006] In summary, the above two existing patents have not solved the problem in the prior art that welding structural defects exist in undetectable or difficult to detect locations, and the welding quality and structural reliability assessment effects are poor. Summary of the invention

[0007] Based on the above technical problems, the present invention proposes a method and device for determining the maximum allowable stress of a defective welded structure, which solves the problem in the prior art that defects in welded structures exist in undetectable or difficult-to-detect locations, and the welding quality and structural reliability assessment effects are poor.

[0008] To achieve the above object, the present invention proposes a method for determining the maximum allowable stress of a defective welded structure.

[0009] A method for determining the maximum allowable stress of a defective welded structure, the method comprising:

[0010] Obtain the normal distribution of the size of the defect position and the normal distribution of the size of the non-defect position of the welding structure;

[0011] Based on the normal distribution of the size of the defect position and the normal distribution of the size of the non-defect position, a first finite element model corresponding to the defect position and a second finite element model corresponding to the non-defect position are established respectively by using the Monte Carlo method;

[0012] Determine, according to the first finite element model and the second finite element model, respectively a first probability density function corresponding to a first maximum stress at a defect position under a unit load, a second probability density function corresponding to a maximum intensity factor, and a second maximum stress at a non-defect position under a unit load;

[0013] Determine the average stress, the safety stress, the average strength factor and the safety strength factor by using the first probability density function and the second probability density function;

[0014] The allowable stress of the welded structure under defective state is determined based on the second maximum stress, average stress, safety stress, average strength factor and safety strength factor.

[0015] Further, determining a first probability density function corresponding to a first maximum stress at a defect position under a unit load according to the first finite element model includes:

[0016] Performing simulation calculation on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model;

[0017] The first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

[0018] Furthermore, determining a second probability density function corresponding to the maximum intensity factor of the defect position under unit load according to the first finite element model includes:

[0019] Based on the first finite element model, the maximum intensity factor and the second probability density function of the defect position under unit load are determined according to the interactive integration method. The interactive integration method is:

[0020]

[0021] Among them, n i is the loop integral normal vector, Γ is the integral loop, E′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

[0022] Further, the safety stress and the safety strength factor are determined by using the first probability density function and the second probability density function, including:

[0023] Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, formula 1, Among them, P C is the preset permitted intensity exceeding probability, σ c is the safety stress, f(σ) is the first probability density function;

[0024] Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2. Formula 2: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, and f(K) is the second probability density function.

[0025] Further, the allowable stress of the welded structure under the defective state is determined according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor, including:

[0026] Determine the amplification factor based on the mean stress, safety stress, mean strength factor and safety strength factor;

[0027] Based on the amplification factor, average stress and second maximum stress, the allowable stress of the welded structure in the defective state is determined.

[0028] Further, the amplification factor is determined according to the average stress, the safety stress, the average strength factor and the safety strength factor, including:

[0029] According to the average stress and safety stress, the stress amplification factor is determined by formula 3. Formula 3: Where β1 is the stress amplification factor, is the mean stress;

[0030] According to the average strength factor and the safety strength factor, the strength factor magnification factor is determined by formula 4. Formula 4: Among them, β2 is the intensity factor amplification coefficient, is the average intensity factor;

[0031] The maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

[0032] Further, based on the amplification factor, the average stress and the second maximum stress, the allowable stress of the welded structure in the defective state is determined, including:

[0033] Based on the amplification factor, the average stress and the second maximum stress, the safety factor is determined by Formula 5. Formula 5: Among them, α is the safety factor, β is the amplification factor, and σ0 is the second maximum stress;

[0034] According to the safety factor, the allowable stress of the welded structure under defective state is determined by formula 6. Formula 6: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure under defective state.

[0035] To achieve the same purpose as the above method, the present invention also provides a device for determining the maximum allowable stress of a defective welded structure.

[0036] A device for determining the maximum allowable stress of a defective welded structure, comprising:

[0037] An acquisition module is used to acquire the normal distribution of the size of the defect position of the welding structure and the normal distribution of the size of the non-defect position;

[0038] Establishing a module for establishing a first finite element model corresponding to the defect position and a second finite element model corresponding to the non-defect position respectively by using a Monte Carlo method based on the normal distribution of the defect position size and the normal distribution of the non-defect position size;

[0039] A first determination module is used to determine, according to the first finite element model and the second finite element model, a first probability density function corresponding to a first maximum stress at a defect position under a unit load, a second probability density function corresponding to a maximum intensity factor, and a second maximum stress at a non-defect position under a unit load;

[0040] A second determination module is used to determine the average stress, the safety stress, the average strength factor and the safety strength factor by using the first probability density function and the second probability density function;

[0041] The third determination module is used to determine the allowable stress of the welded structure in a defective state according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor.

[0042] Furthermore, the first determining module is used to:

[0043] Performing simulation calculation on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model;

[0044] The first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

[0045] Furthermore, the first determining module is used to:

[0046] Based on the first finite element model, the maximum intensity factor and the second probability density function of the defect position under unit load are determined according to the interactive integration method. The interactive integration method is:

[0047]

[0048] Among them, n i is the loop integral normal vector, Γ is the integral loop, E′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

[0049] Furthermore, the second determining module is used to:

[0050] Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, formula 1, Among them, P C is the preset permitted intensity exceeding probability, σ cis the safety stress, f(σ) is the first probability density function;

[0051] Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2. Formula 2: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, and f(K) is the second probability density function.

[0052] Furthermore, the third determination module is used to:

[0053] Determine the amplification factor based on the mean stress, safety stress, mean strength factor and safety strength factor;

[0054] Based on the amplification factor, average stress and second maximum stress, the allowable stress of the welded structure in the defective state is determined.

[0055] Further, the amplification factor is determined according to the average stress, the safety stress, the average strength factor and the safety strength factor, including:

[0056] According to the average stress and safety stress, the stress amplification factor is determined by formula 3. Formula 3: Where β1 is the stress amplification factor, is the mean stress;

[0057] According to the average strength factor and the safety strength factor, the strength factor magnification factor is determined by formula 4. Formula 4: Among them, β2 is the intensity factor amplification coefficient, is the average intensity factor;

[0058] The maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

[0059] Further, based on the amplification factor, the average stress and the second maximum stress, the allowable stress of the welded structure in the defective state is determined, including:

[0060] Based on the amplification factor, the average stress and the second maximum stress, the safety factor is determined by Formula 5. Formula 5: Among them, α is the safety factor, β is the amplification factor, and σ0 is the second maximum stress;

[0061] According to the safety factor, the allowable stress of the welded structure under defective state is determined by formula 6. Formula 6: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure under defective state.

[0062] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0063] 1. The present invention establishes a finite element model corresponding to the defect position size and non-defect position size of the welding structure, uses the finite element model to determine the corresponding strength factor and stress parameter, and then determines the maximum allowable stress that the welding structure can withstand under the defect state. The method and device can improve the welding quality and structural reliability assessment effect, and can effectively support the reliability assessment and analysis of the welding structure.

[0064] 2. The present invention takes into account the different effects brought by cracks and hole defects, selects the larger value of the stress magnification factor and the intensity factor magnification factor as the final magnification factor, and then determines the safety factor, so that the maximum allowable stress that the welded structure can withstand in the defective state is finally determined to have higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0066] Figure 1 A flow chart of a method for determining the maximum allowable stress of a defective welded structure according to an embodiment of the present invention;

[0067] Figure 2 A probability density function diagram of defect distribution at different size positions of a welding structure according to an embodiment of the present invention;

[0068] Figure 3 A stress cloud diagram corresponding to a first finite element model in a specific embodiment of the present invention;

[0069] Figure 4 It is an enlarged schematic diagram of a local stress cloud diagram corresponding to a first finite element model in a specific embodiment of the present invention;

[0070] Figure 5 A stress cloud diagram corresponding to the second finite element model in a specific embodiment of the present invention;

[0071] Figure 6 It is an enlarged schematic diagram of a local stress cloud diagram corresponding to the second finite element model in a specific embodiment of the present invention;

[0072] Figure 7 The probability distribution of the maximum stress caused by the first finite element model of different defect positions and sizes under unit load in one embodiment of the present invention;

[0073] Figure 8The probability distribution of the maximum strength factor caused by the first finite element model with different defect position sizes under unit load in one embodiment of the present invention;

[0074] Fig. 9 A flow chart of determining the amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor in one embodiment of the present invention;

[0075] Fig.10 The present invention is a schematic diagram of a device for determining the maximum allowable stress of a defective welded structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0076] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0077] The present invention is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed by the present invention.

[0078] Example

[0079] In order to solve the problem in the prior art that defects in welding structures exist in undetectable or difficult to detect locations, and the welding quality and structural reliability assessment effects are poor, the present invention proposes a method and device for determining the maximum allowable stress of a defective welding structure.

[0080] To achieve the above object, the present invention proposes a method for determining the maximum allowable stress of a defective welded structure.

[0081] like Figure 1 FIG. 1 is a flow chart showing a method for determining the maximum allowable stress of a defective welded structure according to an embodiment of the present invention. Figure 1 As shown, the method comprises the following steps:

[0082] S1, obtain the normal distribution of the size of the defect position of the welding structure and the normal distribution of the size of the non-defect position.

[0083] In this embodiment, the normal distribution of the size of the defect position and the size of the non-defect position of the welding structure is obtained through investigation. Specifically, the defects of the welding structure include holes, cracks and other defect types.

[0084] S2, based on the normal distribution of the defect position size and the normal distribution of the non-defect position size, using the Monte Carlo method to establish a first finite element model corresponding to the defect position and a second finite element model corresponding to the non-defect position.

[0085] In this step, based on the normal distribution obtained in step S1, the probability density function f of the defect location size and the non-defect location size can be fitted. d In mathematical form, the probability density function of the defect location size can be expressed as Among them, l represents the size of the defect, and l0 represents the defect size deviation, that is, the defect size with the highest probability of occurring in the actual processing process.

[0086] like Figure 2 The probability density function diagram of the defect distribution of different size positions of the welding structure is shown in FIG. Subsequently, according to the probability density function of the defect position size and the non-defect position size, based on the Monte Carlo method, the first finite element model corresponding to the defect position and the second finite element model corresponding to the non-defect position are respectively established using finite element software. The finite element software includes ANSYS, ABAQUS, NASTRAN, etc.

[0087] It should be understood that the first finite element model established in this embodiment includes multiple finite element models corresponding to different defect locations and sizes.

[0088] S3, determining, based on the first finite element model and the second finite element model, a first probability density function corresponding to a first maximum stress at a defect position under a unit load, a second probability density function corresponding to a maximum intensity factor, and a second maximum stress at a non-defect position under a unit load.

[0089] Further, determining a first probability density function corresponding to a first maximum stress at a defect position under a unit load according to the first finite element model includes the following two sub-steps:

[0090] Firstly, a simulation calculation is performed on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model.

[0091] Secondly, the first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

[0092] like Figure 3 FIG. 4 shows a stress cloud diagram corresponding to a first finite element model in a specific embodiment of the present invention, wherein the stress corresponding to region B is 3.30835 Pa, and the stress corresponding to region C is 155.296 Pa. Figure 4 The figure shows the enlarged schematic diagram of the stress cloud map corresponding to area A. Figure 4The stress corresponding to area D in the figure is 155.296Pa, the stress corresponding to area E is 231.29Pa, the stress corresponding to area F is 307.284Pa, and the stress corresponding to area G is 687.253Pa. In summary, the first maximum stress at the defect position under unit load in this embodiment is 687.253Pa. It should be noted that the stress cloud map corresponding to the first finite element model is a stress cloud map under different defect sizes, and there are multiple corresponding ones. Therefore, the first maximum stress at the defect position under unit load determined based on the stress cloud map also includes multiple ones. According to the first maximum stress of the defect position under unit load corresponding to different defect position sizes, the first probability density function can be fitted.

[0093] It can be understood that the method for determining the second maximum stress at the non-defective position under unit load is similar to the method for determining the first maximum stress at the defective position. By simulating the second finite element model, the stress cloud corresponding to the second finite element model is determined, and then the corresponding second maximum stress is determined. Figure 5 , a stress cloud diagram corresponding to the second finite element model in a specific embodiment of the present invention is shown, wherein the stress corresponding to region K is 74.7703Pa, the stress corresponding to region J is 62.8547Pa, the stress corresponding to region I is 50.9392Pa, and the stress corresponding to region H is 39.0236Pa. Figure 6 The diagram in Figure 2 shows an enlarged schematic diagram of the stress cloud map corresponding to region L. Figure 6 The stress in region N is 86.6858 Pa, and the stress in region M is 110.517 Pa. Figure 5 and Figure 6 It can be seen that the second maximum stress corresponding to the stress cloud diagram in this embodiment is 110.517Pa.

[0094] Furthermore, determining a second probability density function corresponding to the maximum intensity factor of the defect position under unit load according to the first finite element model includes:

[0095] Based on the first finite element model, the maximum intensity factor and the second probability density function of the defect position under unit load are determined according to the interactive integration method. The interactive integration method is:

[0096]

[0097] Among them, n i is the loop integral normal vector, Γ is the integral loop, E′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

[0098]

[0099] Among them, σ, ε, σ aux , ε aux are the true stress field, true strain field, auxiliary stress field, and auxiliary strain field, respectively. u, u aux are the real displacement field and the auxiliary displacement field respectively, δ is the Kronecker symbol, defined as The subscripts i, j, and k represent the directions of the spatial coordinates, respectively. The values ​​of i, j, and k can be 1, 2, and 3, respectively, where 1, 2, and 3 represent the directions of the spatial coordinates. 1i Substituting it into the equation of the interaction integral method, the interaction integral I can be first solved to obtain the maximum intensity factor, and then the second probability density function corresponding to the maximum lightness factor can be obtained by fitting.

[0100] S4, determining the average stress, the safety stress, the average strength factor and the safety strength factor using the first probability density function and the second probability density function.

[0101] Further, the safety stress and the safety strength factor are determined by using the first probability density function and the second probability density function, including:

[0102] Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, formula 1, Among them, P C is the preset permitted intensity exceeding probability, σ c is the safety stress, and f(σ) is the first probability density function.

[0103] Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2. Formula 2: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, and f(K) is the second probability density function.

[0104] The average stress and average strength factor can be directly determined according to the first probability density function and the second probability density function, respectively. Figure 7 Probability distribution of the maximum stress caused by the first finite element model under unit load for different defect location sizes. Figure 7 In is the mean stress, σ c is the permitted intensity exceeding probability P set according to engineering requirements c The corresponding safety stress. Figure 8 is the probability distribution of the maximum strength factor caused by the first finite element model with different defect location sizes under unit load, Figure 8In is the average intensity factor, K c is the permitted intensity exceeding probability P set according to engineering requirements c The corresponding security strength factor.

[0105] S5, determining the allowable stress of the welded structure in a defective state according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor.

[0106] Furthermore, the allowable stress of the welded structure in the defective state is determined according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor, including two sub-steps S501 and S502. The final amplification factor is first determined through step S501, and then based on the amplification factor, the allowable stress of the welded structure in the defective state is determined through step S502.

[0107] S501, determining an amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor.

[0108] like Fig. 9 FIG. 4 is a flowchart of determining the amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor in this embodiment. The flowchart mainly includes the following three sub-steps:

[0109] S5011, determine the stress amplification factor based on the average stress and safety stress using Formula 3.

[0110] The formula three is: Where β1 is the stress amplification factor, Substituting the average stress and the safety stress determined in step S4 into formula 3, the corresponding stress amplification factor can be obtained.

[0111] S5012, determine the intensity factor magnification factor according to the average intensity factor and the safety intensity factor using formula 4.

[0112] Formula 4: Among them, β2 is the intensity factor amplification coefficient, Substituting the average strength factor and the safety strength factor determined in step S4 into formula 4, the strength factor magnification coefficient can be obtained.

[0113] S5013, the maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

[0114] That is, the final amplification factor β=max(β1, β2).

[0115] S502, determining the allowable stress of the welded structure in a defective state based on the amplification factor, the average stress and the second maximum stress.

[0116] Further, based on the amplification factor, the average stress and the second maximum stress, the allowable stress of the welded structure in the defective state is determined, including:

[0117] S5021, determine the safety factor using Formula 5 based on the amplification factor, the average stress and the second maximum stress.

[0118] Formula 5, Wherein, α is the safety factor, β is the magnification factor, and σ0 is the second maximum stress. Substituting the final magnification factor β determined in step S501 and the second maximum stress determined in step S3 into formula 5, the safety factor can be determined.

[0119] S5022, based on the safety factor, determine the allowable stress of the welded structure under defective conditions using Formula 6.

[0120] Formula 6: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure under defective state.

[0121] To achieve the same purpose as the above method, the present invention also provides a device for determining the maximum allowable stress of a defective welded structure.

[0122] like Fig.10 A schematic diagram of a device for determining the maximum allowable stress of a defective welded structure according to an embodiment of the present invention is shown in FIG. The device includes an acquisition module 61, an establishment module 62, a first determination module 63, a second determination module 64 and a third determination module 65. The functions of the modules will be described in detail below.

[0123] The acquisition module 61 is used to acquire the normal distribution of the size of the defect position of the welding structure and the normal distribution of the size of the non-defect position.

[0124] The module 62 is established to establish a first finite element model corresponding to the defective position and a second finite element model corresponding to the non-defective position respectively by using the Monte Carlo method based on the normal distribution of the defective position size and the normal distribution of the non-defective position size.

[0125] The first determination module 63 is used to determine the first probability density function corresponding to the first maximum stress at the defect position under unit load, the second probability density function corresponding to the maximum intensity factor, and the second maximum stress at the non-defect position under unit load according to the first finite element model and the second finite element model.

[0126] Furthermore, the first determining module 63 is used to:

[0127] A simulation calculation is performed on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model.

[0128] The first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

[0129] Furthermore, the first determining module 63 is used to:

[0130] Based on the first finite element model, the maximum intensity factor and the second probability density function of the defect position under unit load are determined according to the interactive integration method. The interactive integration method is:

[0131]

[0132] Among them, n i is the loop integral normal vector, Γ is the integral loop, E′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

[0133] The second determination module 64 is used to determine the average stress, the safety stress, the average strength factor and the safety strength factor by using the first probability density function and the second probability density function.

[0134] Furthermore, the second determining module 64 is used to:

[0135] Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, formula 1, Among them, P C is the preset permitted intensity exceeding probability, σ c is the safety stress, and f(σ) is the first probability density function.

[0136] Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2. Formula 2: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, and f(K) is the second probability density function.

[0137] The third determination module 65 is used to determine the allowable stress of the welded structure in the defective state according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor.

[0138] Furthermore, the third determination module is used to:

[0139] The amplification factor is determined based on the average stress, safety stress, average strength factor and safety strength factor.

[0140] Further, the amplification factor is determined according to the average stress, the safety stress, the average strength factor and the safety strength factor, including:

[0141] According to the average stress and safety stress, the stress amplification factor is determined by formula 3. Formula 3: Where β1 is the stress amplification factor, is the average stress.

[0142] According to the average strength factor and the safety strength factor, the strength factor magnification factor is determined by formula 4. Formula 4: Among them, β2 is the intensity factor amplification coefficient, is the average intensity factor.

[0143] The maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

[0144] Based on the amplification factor, average stress and second maximum stress, the allowable stress of the welded structure in the defective state is determined.

[0145] Further, based on the amplification factor, the average stress and the second maximum stress, the allowable stress of the welded structure in the defective state is determined, including:

[0146] Based on the amplification factor, the average stress and the second maximum stress, the safety factor is determined by Formula 5. Formula 5: Among them, α is the safety factor, β is the amplification factor, and σ0 is the second maximum stress.

[0147] According to the safety factor, the allowable stress of the welded structure under defective state is determined by formula 6. Formula 6: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure under defective state.

[0148] It should be understood that the description of the embodiment of a device for determining the maximum allowable stress of a defective welded structure is consistent with the description of the corresponding method for determining the maximum allowable stress of a defective welded structure, so this embodiment will not be described in detail.

[0149] In summary, it can be seen from the above description that the above embodiments of the present invention achieve the following technical effects:

[0150] 1. The present invention establishes a finite element model corresponding to the defect position size and non-defect position size of the welding structure, uses the finite element model to determine the corresponding strength factor and stress parameter, and then determines the maximum allowable stress that the welding structure can withstand under the defect state. The method and device can improve the welding quality and structural reliability assessment effect, and can effectively support the reliability assessment and analysis of the welding structure.

[0151] 2. The present invention takes into account the different effects brought by cracks and hole defects, selects the larger value of the stress magnification factor and the intensity factor magnification factor as the final magnification factor, and then determines the safety factor, so that the maximum allowable stress that the welded structure can withstand in the defective state is finally determined to have higher reliability.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0153] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0154] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, which can be embodied in any computer-readable medium for use by an instruction execution system, apparatus or device (such as a computer-based system, a system including a processor or other system that can fetch instructions from an instruction execution system, apparatus or device and execute instructions), or used in combination with these instruction execution systems, apparatuses or devices.

[0155] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0156] It should be noted that, in the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A method for determining the maximum allowable stress of a defective welded structure, characterized in that: include: Obtain the normal distribution of the size of the defect position and the normal distribution of the size of the non-defect position of the welding structure; Based on the normal distribution of the size of the defect position and the normal distribution of the size of the non-defect position, a first finite element model corresponding to the defect position and a second finite element model corresponding to the non-defect position are respectively established by using the Monte Carlo method; Determine, according to the first finite element model and the second finite element model, respectively, a first probability density function corresponding to a first maximum stress at the defect position under a unit load, a second probability density function corresponding to a maximum intensity factor, and a second maximum stress at the non-defect position under a unit load; Determine average stress, safety stress, average strength factor and safety strength factor by using the first probability density function and the second probability density function; The allowable stress of the welded structure in a defective state is determined according to the second maximum stress, the average stress, the safety stress, the average strength factor, and the safety strength factor.

2. The method according to claim 1, characterized in that Determining a first probability density function corresponding to a first maximum stress at the defect position under a unit load according to the first finite element model includes: Performing simulation calculation on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model; The first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

3. The method according to claim 1, characterized in that Determining a second probability density function corresponding to the maximum intensity factor of the defect position under unit load according to the first finite element model includes: Based on the first finite element model, the maximum intensity factor of the defect position and the second probability density function under unit load are determined according to an interactive integration method, wherein the interactive integration method is: Among them, n i is the loop integral normal vector, Γ is the integral loop, E ′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

4. The method according to claim 1, characterized in that: Determining a safety stress and a safety strength factor by using the first probability density function and the second probability density function includes: Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, wherein: Among them, P C is the probability of exceeding the preset permitted intensity, σ c is the safety stress, f(σ) is the first probability density function; Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2, wherein: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, f(K) is the second probability density function.

5. The method according to claim 1, characterized in that Determining the allowable stress of the welded structure in a defective state according to the second maximum stress, the average stress, the safety stress, the average strength factor, and the safety strength factor comprises: determining an amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor; The allowable stress of the welded structure in a defective state is determined based on the amplification factor, the average stress and the second maximum stress.

6. The method according to claim 5, characterized in that Determining the amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor comprises: According to the average stress and the safety stress, the stress amplification factor is determined by formula 3, wherein: Wherein, β1 is the stress amplification factor, is the mean stress; According to the average strength factor and the safety strength factor, the strength factor magnification factor is determined by formula 4, wherein: Wherein, β2 is the intensity factor amplification coefficient, is the average intensity factor; The maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

7. The method according to claim 5, characterized in that Determining the allowable stress of the welded structure in a defective state based on the amplification factor, the average stress and the second maximum stress includes: Based on the amplification factor, the average stress and the second maximum stress, the safety factor is determined by formula 5, wherein: Wherein, α is the safety factor, β is the amplification factor, and σ0 is the second maximum stress; According to the safety factor, the allowable stress of the welded structure under defective state is determined by formula 6, wherein: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure in the defective state.

8. A device for determining the maximum allowable stress of a defective welded structure, characterized in that: include: An acquisition module is used to acquire the normal distribution of the size of the defect position of the welding structure and the normal distribution of the size of the non-defect position; An establishment module is used to establish a first finite element model corresponding to the defective position and a second finite element model corresponding to the non-defective position respectively by using a Monte Carlo method based on the normal distribution of the defective position size and the normal distribution of the non-defective position size; A first determination module is used to determine, according to the first finite element model and the second finite element model, a first probability density function corresponding to a first maximum stress at the defect position under a unit load, a second probability density function corresponding to a maximum intensity factor, and a second maximum stress at the non-defect position under a unit load; a second determination module, configured to determine average stress, safety stress, average strength factor and safety strength factor by using the first probability density function and the second probability density function; The third determination module is used to determine the allowable stress of the welded structure in a defective state according to the second maximum stress, the average stress, the safety stress, the average strength factor and the safety strength factor.

9. The device according to claim 8, characterized in that The first determining module is used to: Performing simulation calculation on the first finite element model to determine a stress cloud diagram corresponding to the first finite element model; The first maximum stress and the first probability density function of the defect position under unit load are determined based on the stress cloud diagram.

10. The device according to claim 8, characterized in that The first determining module is used to: Based on the first finite element model, the maximum intensity factor of the defect position and the second probability density function under unit load are determined according to an interactive integration method, wherein the interactive integration method is: Among them, n i is the loop integral normal vector, Γ is the integral loop, E ′ is a constant, K I , K II are the type I and type II stress intensity factors corresponding to the true displacement field, are the type I and II stress intensity factors corresponding to the auxiliary displacement field.

11. The device according to claim 8, characterized in that The second determining module is used to: Based on the first probability density function and the preset permissible strength exceeding probability, the safety stress is determined by formula 1, wherein: Among them, P C is the probability of exceeding the preset permitted intensity, σ c is the safety stress, f(σ) is the first probability density function; Based on the second probability density function and the preset permitted strength exceeding probability, the security strength factor is determined by formula 2, wherein: Among them, P C is the preset permitted intensity exceeding probability, K c is the security strength factor, and f(K) is the second probability density function.

12. The device according to claim 8, characterized in that The third determining module is used to: Determine an amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor; The allowable stress of the welded structure in a defective state is determined based on the amplification factor, the average stress and the second maximum stress.

13. The device according to claim 12, characterized in that Determining the amplification factor according to the average stress, the safety stress, the average strength factor and the safety strength factor comprises: According to the average stress and the safety stress, the stress amplification factor is determined by formula 3, wherein: Wherein, β1 is the stress amplification factor, is the mean stress; According to the average strength factor and the safety strength factor, the strength factor magnification factor is determined by formula 4, wherein: Wherein, β2 is the intensity factor amplification coefficient, is the average intensity factor; The maximum value of the stress magnification factor and the intensity factor magnification factor is taken as the magnification factor.

14. The device according to claim 12, characterized in that Determining the allowable stress of the welded structure in a defective state based on the amplification factor, the average stress and the second maximum stress includes: Based on the amplification factor, the average stress and the second maximum stress, the safety factor is determined by formula 5, wherein: Wherein, α is the safety factor, β is the amplification factor, and σ0 is the second maximum stress; According to the safety factor, the allowable stress of the welded structure under defective state is determined by formula 6, wherein: Among them, σ r is the allowable stress of the welded structure in the defect-free state, σ 许用 It is the allowable stress of the welded structure in the defective state.

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