Evaluation method for stress intensity factor distribution of crack front edge of pressure vessel connecting pipe

Abstract

The invention relates to a method for evaluating stress intensity factor distribution of a crack front edge of a connecting pipe of a pressure vessel, and belongs to the field of structural integrity evaluation of pressure-bearing vessels. The method comprises the following steps: carrying out finite element analysis on cracks of pressure vessel connecting pipes with different sizes; constructing a correction factor database of the pressure vessel connecting pipe crack front edge; establishing a weight function equation suitable for the pressure vessel connecting pipe crack; and evaluating the stress intensity factor distribution of the pressure vessel connecting pipe crack front edge under the complex stress condition. According to the method, a finite element analysis result and a weight function theory are coupled, the stress intensity factor distribution evaluation method suitable for the wide-size-range pressure vessel connecting pipe crack front edge under the complex load condition is provided, and the problems of large-scale fracture mechanical numerical simulation, astringency misjudgment and the like can be avoided; and the structural integrity evaluation precision and efficiency of the crack-containing pressure vessel connecting pipe are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of structural integrity assessment of pressure vessels, and specifically relates to a method for assessing the distribution of stress intensity factor at the crack leading edge of a pressure vessel nozzle. Background Technology

[0002] In practical engineering applications, pressure vessels need to be connected to other structural components to achieve their overall function. Among the many connection points of a pressure vessel, the nozzle area has a complex geometry, which can lead to significant stress concentration under pressure, promoting crack initiation or propagation. To ensure the service safety of the nozzles in pressure vessels, it is necessary to calculate the stress intensity factor of cracks in the nozzle area to conduct a structural integrity assessment of the pressure vessel nozzles.

[0003] Currently, the cracks considered in the pressure vessel nozzle area are mainly quarter-circular surface cracks. Technical specifications for this type of crack (such as the US Boiler and Pressure Vessel Code, Volume XI, and the Nuclear Power Plant Safety Assessment Code of the Japanese Institute of Mechanical Engineers) provide empirical formulas for calculating the stress intensity factor at the deepest point of the crack. However, recent studies have found that these empirical formulas are based on two-dimensional finite element analysis and do not consider the influence of different three-dimensional structural dimensions of nozzles in actual engineering, making them difficult to apply widely. Furthermore, the stress intensity factor at the deepest point of a pressure vessel nozzle crack is generally lower than that at other locations along the crack lead. Using these empirical formulas to assess the structural integrity of in-service pressure vessel nozzles may lead to unconservative assessment results, affecting the service safety of the nozzles. Therefore, there is an urgent need to develop a method that can scientifically assess the distribution of stress intensity factor at the crack lead of pressure vessel nozzles. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the distribution of stress intensity factor at the crack leading edge of a pressure vessel nozzle.

[0005] To achieve the above objectives, the technical solution of the present invention is: a method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle, comprising:

[0006] Finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes.

[0007] Based on the finite element analysis results, a correction factor database for the crack lead of the nozzle of the pressure vessel is constructed.

[0008] Based on the correction factor database, a weight function equation for pressure vessel nozzle cracks is established;

[0009] Input the nozzle size and crack size of the pressure vessel to be evaluated. Based on the correction factor database and weight function equation, evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions acting on the crack surface of the pressure vessel nozzle.

[0010] Furthermore, finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes, specifically including:

[0011] Set the pressure vessel nozzle dimensions and pressure vessel nozzle crack dimensions;

[0012] Set the material properties of the pressure vessel;

[0013] Set the applied stress on the crack surface of the pressure vessel nozzle;

[0014] Based on the set conditions, a three-dimensional model of a pressure vessel nozzle with cracks was established, and finite element analysis was performed on the cracks in the nozzles of pressure vessels of different sizes.

[0015] Furthermore, based on the theory of linear elastic fracture mechanics, finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes.

[0016] Furthermore, based on the finite element analysis results, a correction factor database for the crack lead of the pressure vessel nozzle is constructed, specifically including:

[0017] Based on the finite element analysis results, calculate the J integral of the crack front of the pressure vessel nozzle;

[0018] Based on the J-integral, the distribution data of reference fracture parameters at the crack front of the pressure vessel nozzle are calculated.

[0019] The reference fracture parameter distribution data is dimensionless to construct a correction factor database for the crack front of the pressure vessel nozzle.

[0020] Furthermore, the J-integral of the crack front at the nozzle of the pressure vessel is calculated using the contour integral method.

[0021] Furthermore, based on the correction factor database, a weighting function equation for pressure vessel nozzle cracks is established, specifically including:

[0022] Based on the correction factor database, the weight coefficients in the general weight function for three-dimensional cracks are solved;

[0023] Based on the solved weight coefficients, a weight function equation for pressure vessel nozzle cracks is established.

[0024] Furthermore, the weight coefficients in the universal weight function for three-dimensional cracks are solved using weight function theory.

[0025] Furthermore, by inputting the dimensions of the pressure vessel nozzle and the crack size of the pressure vessel nozzle to be evaluated, and based on the correction factor database and weighting function equation, the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions acting on the crack surface of the pressure vessel nozzle to be evaluated is assessed, specifically including:

[0026] Determine the dimensions of the nozzle and the crack size of the nozzle of the pressure vessel to be evaluated;

[0027] Determine the complex stress conditions acting on the crack surface of the nozzle of the pressure vessel to be evaluated;

[0028] Based on the nozzle size and crack size of the pressure vessel to be evaluated, and combined with the correction factor database, the correction factor of the crack front of the nozzle of the pressure vessel to be evaluated is calculated by interpolation.

[0029] Substitute the calculated correction factor into the weight function equation of the pressure vessel nozzle crack to obtain the weight function of the pressure vessel nozzle crack to be evaluated.

[0030] Based on the complex stress conditions acting on the surface of the pressure vessel nozzle crack and the calculated weight function of the pressure vessel nozzle crack, the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions is evaluated.

[0031] The present invention also provides an evaluation system for the distribution of stress intensity factor at the crack leading edge of a pressure vessel nozzle, comprising a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, it can implement the steps of any of the methods described above.

[0032] The present invention also provides a computer-readable storage medium having stored thereon computer program instructions executable by a processor, wherein when the processor executes the computer program instructions, it can implement the steps of any of the methods described above.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention establishes a correction factor database for the crack front of pressure vessel nozzles. This database comprehensively considers the influence of the three-dimensional structural dimensions of the pressure vessel nozzles, crack size, and multiple stresses, providing data support for the structural integrity assessment of cracked pressure vessel nozzles in actual engineering projects.

[0035] 2. This invention proposes an evaluation method for the stress intensity factor distribution at the crack front of a pressure vessel nozzle based on a weighted function. This method avoids large-scale complex fracture numerical simulation calculations and can quickly and accurately evaluate the stress intensity factor distribution at the crack front of a pressure vessel nozzle with a wide size range under complex stress conditions. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for evaluating the distribution of stress intensity factor at the crack front edge of a pressure vessel nozzle according to the present invention.

[0037] Figure 2 This is a schematic diagram of a crack in a pressure vessel nozzle.

[0038] Figure 3 The diagram shows the stress distribution on the crack surface of the pressure vessel nozzle, where (a) is a diagram of uniform stress distribution, (b) is a diagram of linear stress distribution, and (c) is a diagram of secondary stress distribution.

[0039] Figure 4 This is a three-dimensional model of a pressure vessel nozzle containing cracks.

[0040] Figure 5 A diagram defining the angle of the crack leading edge in a pressure vessel nozzle.

[0041] Figure 6 This is a schematic diagram of the complex stress acting on the crack surface of the nozzle of the pressure vessel to be evaluated.

[0042] Figure 7 This is a comparison of the stress intensity factor distribution results calculated by the method of this invention and the three-dimensional finite element numerical simulation method at the crack front edge of the pressure vessel nozzle. Detailed Implementation

[0043] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0045] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0046] This invention provides a method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle, comprising:

[0047] Finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes.

[0048] Based on the finite element analysis results, a correction factor database for the crack lead of the nozzle of the pressure vessel is constructed.

[0049] Based on the correction factor database, a weight function equation for pressure vessel nozzle cracks is established;

[0050] Input the nozzle size and crack size of the pressure vessel to be evaluated. Based on the correction factor database and weight function equation, evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions acting on the crack surface of the pressure vessel nozzle.

[0051] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] like Figure 1 As shown, the present invention provides a method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle, comprising the following steps:

[0053] Step S1: Conduct finite element analysis of nozzle cracks in pressure vessels of different sizes;

[0054] Step S11: Set the dimensions of the pressure vessel nozzle and crack, including the pressure vessel inner diameter R1, pressure vessel thickness t1, nozzle inner diameter R2, nozzle thickness t2, crack depth a, and effective thickness t of the pressure vessel nozzle. m (The dimensions of each parameter are defined as follows) Figure 2 (as shown)

[0055] Step S12: Set the material properties of the pressure vessel, including Young's modulus E and Poisson's ratio v;

[0056] Step S13: Set the applied stress on the crack surface of the pressure vessel nozzle (e.g., Figure 3 As shown in the figure, the stress distribution expression is as follows:

[0057]

[0058] In the formula: σ i Let p be the stress acting on the crack surface, x be the distance from any point on the crack surface to the origin O, a be the depth of the crack in the pressure vessel nozzle, and i = 0, 1, and 2 represent uniform stress distribution, linear stress distribution, and secondary stress distribution acting on the crack surface, respectively (e.g., ...). Figure 3 (as shown)

[0059] Step S14: Based on the conditions set in steps S11, S12, and S13, establish a three-dimensional model of the pressure vessel nozzle containing the crack (e.g., Figure 4 As shown, finite element analysis of nozzle cracks in pressure vessels of different sizes was carried out based on the theory of linear elastic fracture mechanics.

[0060] Step S2: Construct a database of correction factors for the crack front of the pressure vessel nozzle;

[0061] Step S21: Based on the finite element analysis in S14, the J-integral, J(θ), of the crack front edge of the pressure vessel nozzle is calculated using the contour integral method. The crack front angle θ is defined as follows: Figure 5 As shown;

[0062] Step S22: Based on the J integral obtained in step S21, calculate the reference fracture parameter distribution data of the crack front edge of the pressure vessel nozzle, and the reference fracture parameter K of the crack front edge. eq The formula for calculating (θ) is as follows:

[0063]

[0064] In the formula: K eq (θ) represents the reference fracture parameter at the crack tip, θ is the crack tip angle, J(θ) is the J integral of the crack tip of the pressure vessel nozzle calculated in step S21, E is the Young's modulus mentioned in step S12, and v is the Poisson's ratio mentioned in step S12; based on the three stress distribution forms given in step S13, through the formula... The reference fracture parameter distribution K at the crack tip can be obtained under uniform stress distribution, linear stress distribution, and secondary stress distribution conditions. eq0 (θ), K eq1 (θ), K eq2 (θ);

[0065] Step S23: The reference fracture parameter distribution data obtained in step S22 is dimensionless, and a correction factor database for the crack lead of the pressure vessel nozzle is constructed. The calculation formula for the correction factor of the crack lead is as follows:

[0066]

[0067] In the formula: C(θ) is the correction factor for the crack tip, θ is the crack tip angle, and K... eq (θ) represents the reference fracture parameter at the crack tip, p is the stress coefficient, and a is the depth of the crack in the pressure vessel nozzle; the distribution K of the reference fracture parameter obtained in step S22 is also considered. eq0 (θ), K eq1 (θ), K eq2 (θ), through the formula The correction factor distributions C0(θ), C1(θ), and C2(θ) at the crack tip under uniform stress distribution, linear stress distribution, and quadratic stress distribution can be obtained;

[0068] Step S3: Establish a weighted function equation applicable to pressure vessel nozzle cracks;

[0069] Step S31: Based on the correction factor database constructed in step S23, the weight coefficients in the general weight function for three-dimensional cracks are solved using weight function theory. The formula for calculating the weight coefficients is as follows:

[0070]

[0071]

[0072]

[0073] In the formula: D1(θ), D2(θ), and D3(θ) are three weight coefficients in the three-dimensional crack general weight function, θ is the crack tip angle, and C0(θ), C1(θ), and C2(θ) are the distribution of the crack tip correction factor.

[0074] Step S32: Based on the weighting coefficients obtained in step S31, establish a weighting function equation applicable to pressure vessel nozzle cracks. The weighting function equation is as follows:

[0075]

[0076] In the formula: F(x, a, θ) is the weight function equation applicable to pressure vessel nozzle cracks, x is the distance from any point on the crack surface to the origin O, a is the depth of the pressure vessel nozzle crack, θ is the crack leading edge angle, and D1(θ), D2(θ), and D3(θ) are three weight coefficients in the three-dimensional crack universal weight function.

[0077] Step S4: Evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions;

[0078] Step S41: Determine the dimensions of the nozzle and crack size of the pressure vessel to be evaluated, including the pressure vessel inner diameter R1, pressure vessel thickness t1, nozzle inner diameter R2, nozzle thickness t2, crack depth a, and effective thickness t of the pressure vessel nozzle. m ;

[0079] Step S42: Determine the complex stress conditions acting on the crack surface of the nozzle of the pressure vessel to be evaluated. The stress distribution expression is as follows:

[0080]

[0081] In the formula: σ c Let n represent the complex stresses acting on the crack surface, and p represent the different stress conditions acting on the crack surface. jdenoted as the stress coefficient under different stress conditions, x is the distance from any point on the crack surface to the origin O, and a is the depth of the crack in the pressure vessel nozzle.

[0082] Step S43: Based on the pressure vessel nozzle size and crack size determined in step S41, and combined with the correction factor database constructed in step S23, interpolate to calculate the correction factor of the crack front of the pressure vessel nozzle to be evaluated.

[0083] Step S44: Substitute the correction factor calculated in step S43 into the weight function equation established in step S32 to obtain the weight function of the pressure vessel nozzle crack to be evaluated.

[0084] Step S45: Based on the complex stress conditions determined in step S42 and the weighting function obtained in step S44, evaluate the stress intensity factor distribution K(θ) at the crack front of the pressure vessel nozzle under complex stress conditions:

[0085]

[0086] In the formula: K(θ) represents the stress intensity factor distribution at the crack tip of the pressure vessel nozzle under complex stress conditions, θ is the crack tip angle, a is the depth of the crack in the pressure vessel nozzle, and σ c Let θ be the complex stress acting on the crack surface, x be the distance from any point on the crack surface to the origin O, and F(x, a, θ) be the weight function equation applicable to the nozzle crack of the pressure vessel.

[0087] Example

[0088] The following is a specific embodiment of the present invention, using a cracked pressure vessel nozzle in a power plant as an example. Specifically, the method proposed in this invention is used to calculate the stress intensity factor distribution at the crack front edge of the pressure vessel nozzle under complex stress conditions. The calculation process is as follows:

[0089] Step S1: Conduct finite element analysis of nozzle cracks in pressure vessels of different sizes;

[0090] Step S11: Set the dimensions of the pressure vessel nozzle and crack, including the pressure vessel inner diameter R1, pressure vessel thickness t1, nozzle inner diameter R2, nozzle thickness t2, crack depth a, and effective thickness t of the pressure vessel nozzle. m (The dimensions of each parameter are defined as follows) Figure 2 (As shown), detailed information is in Table 1:

[0091] Table 1 Information on Pressure Vessel Nozzles and Crack Dimensions

[0092]

[0093] Step S12: Set the material properties of the pressure vessel, including Young's modulus E and Poisson's ratio v. See Table 2 for details.

[0094] Table 2 Material Property Information Table

[0095]

[0096] Step S13: Set the applied stress on the crack surface of the pressure vessel nozzle (e.g., Figure 3 As shown in the figure, the stress distribution expression is as follows:

[0097]

[0098] In the formula: σ i Let p be the stress acting on the crack surface, x be the distance from any point on the crack surface to the origin O, a be the depth of the crack in the pressure vessel nozzle, and i = 0. 1 and 2 represent uniform stress distribution, linear stress distribution, and secondary stress distribution acting on the crack surface, respectively (e.g., ...). Figure 3 (as shown)

[0099] Step S14: Based on the conditions set in steps S11, S12, and S13, establish a three-dimensional model of the pressure vessel nozzle containing the crack (e.g., Figure 4 As shown, finite element analysis of nozzle cracks in pressure vessels of different sizes was carried out based on the theory of linear elastic fracture mechanics.

[0100] Step S2: Construct a database of correction factors for crack leads in pressure vessel nozzles.

[0101] Step S21: Based on the finite element analysis in S14, the J-integral, J(θ), of the crack front edge of the pressure vessel nozzle is calculated using the contour integral method. The crack front angle θ is defined as follows: Figure 5 As shown;

[0102] Step S22: Based on the J integral obtained in step S21, calculate the reference fracture parameter distribution data of the crack front edge of the pressure vessel nozzle, and the reference fracture parameter K of the crack front edge. eq The formula for calculating (θ) is as follows:

[0103]

[0104] In the formula: K eq (θ) represents the reference fracture parameter at the crack tip, θ is the crack tip angle, J(θ) is the J integral of the crack tip of the pressure vessel nozzle calculated in step S21, E is the Young's modulus mentioned in step S12, and v is the Poisson's ratio mentioned in step S12. Based on the three stress distribution forms given in step S13, the reference fracture parameter distribution K at the crack tip under uniform stress distribution, linear stress distribution, and quadratic stress distribution conditions can be obtained through the above formula.eq0 (θ), K eq1 (θ), K eq2 (θ);

[0105] Step S23: The reference fracture parameter distribution data obtained in step S22 is dimensionless, and a correction factor database for the crack lead of the pressure vessel nozzle is constructed. The calculation formula for the correction factor of the crack lead is as follows:

[0106]

[0107] In the formula: C(θ) is the correction factor for the crack tip, θ is the crack tip angle, and K... eq (θ) represents the reference fracture parameters at the crack tip, p is the stress coefficient, and a is the depth of the crack in the pressure vessel nozzle. The distribution K of the reference fracture parameters obtained in step S22 is... eq0 (θ), K eq1 (θ), K eq2 (θ), the correction factor distributions C0(θ), C1(θ), and C2(θ) of the crack front under uniform stress distribution, linear stress distribution, and quadratic stress distribution can be obtained by the above formula;

[0108] Step S3: Establish a weighted function equation applicable to pressure vessel nozzle cracks;

[0109] Step S31: Based on the correction factor database constructed in step S23, the weight coefficients in the general weight function for three-dimensional cracks are solved using weight function theory. The formula for calculating the weight coefficients is as follows:

[0110]

[0111]

[0112]

[0113] In the formula: D1(θ), D2(θ), and D3(θ) are three weight coefficients in the three-dimensional crack general weight function, θ is the crack tip angle, and C0(θ), C1(θ), and C2(θ) are the distribution of the crack tip correction factor.

[0114] Step S32: Based on the weighting coefficients obtained in step S31, establish a weighting function equation applicable to pressure vessel nozzle cracks. The weighting function equation is as follows:

[0115]

[0116] In the formula: F(x, a, θ) is the weight function equation applicable to pressure vessel nozzle cracks, x is the distance from any point on the crack surface to the origin O, a is the depth of the pressure vessel nozzle crack, θ is the crack leading edge angle, and D1(θ), D2(θ), and D3(θ) are three weight coefficients in the three-dimensional crack universal weight function.

[0117] Step S4: Evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions;

[0118] Step S41: Determine the dimensions of the nozzle and crack size of the pressure vessel to be evaluated, including the pressure vessel inner diameter R1, pressure vessel thickness t1, nozzle inner diameter R2, nozzle thickness t2, crack depth a, and effective thickness t of the pressure vessel nozzle. m For detailed information, please refer to Table 3:

[0119] Table 3 Information on nozzles and crack dimensions of the pressure vessel to be evaluated

[0120]

[0121] Step S42: Determine the complex stress conditions acting on the crack surface of the nozzle of the pressure vessel to be evaluated (e.g., Figure 6 As shown in the figure, its stress distribution expression is as follows:

[0122]

[0123] In the formula: σ c Let be the complex stress acting on the crack surface (here we consider a fourth-order polynomial stress distribution), and x be the distance from any point on the crack surface to the origin O.

[0124] Step S43: Based on the pressure vessel nozzle size and crack size determined in step S41, and combined with the correction factor database constructed in step S23, the correction factor for the crack front of the pressure vessel nozzle to be evaluated is calculated by interpolation. Some interpolation results are shown in Table 4:

[0125] Table 4. Interpolation results of correction factors for crack leads in the nozzles of the pressure vessel to be evaluated.

[0126]

[0127] Step S44: Substitute the correction factor calculated in step S43 into the weight function equation established in step S32 to obtain the weight function for the pressure vessel nozzle crack to be evaluated, as shown in Table 5:

[0128] Table 5 Weighting function for nozzle cracks in the pressure vessel to be evaluated

[0129]

[0130] Step S45: Based on the complex stress conditions determined in step S42 and the weighting function obtained in step S44, evaluate the stress intensity factor distribution K(θ) at the crack front of the pressure vessel nozzle under complex stress conditions (specific values ​​are shown in Table 6):

[0131]

[0132] In the formula: K(θ) represents the stress intensity factor distribution at the crack tip of the pressure vessel nozzle under complex stress conditions, θ is the crack tip angle, a is the depth of the crack in the pressure vessel nozzle, and σ c Let θ be the complex stress acting on the crack surface, x be the distance from any point on the crack surface to the origin O, and F(x, a, θ) be the weight function equation applicable to the nozzle crack of the pressure vessel.

[0133] Table 6. Stress intensity factor distribution at the crack lead of the nozzle of the pressure vessel to be evaluated.

[0134]

[0135] To further verify the reliability of the method of the present invention, Figure 7 The paper also presents a comparison of the stress intensity factor distribution results calculated using the method of this invention and the three-dimensional finite element numerical simulation method for the crack front of the pressure vessel nozzle. It can be seen that the stress intensity factor distribution results calculated by the two methods are in excellent agreement, with relative errors of less than 0.5%. At the same time, the calculation based on the method of this invention only takes a few minutes, while the three-dimensional finite element numerical simulation calculation takes more than 1 hour. It is evident that the method of this invention has good application advantages in terms of calculation accuracy and efficiency.

[0136] The present invention also provides an evaluation system for the distribution of stress intensity factor at the crack leading edge of a pressure vessel nozzle, comprising a memory, a processor, and computer program instructions stored in the memory and executable by the processor. When the processor executes the computer program instructions, it can implement the steps of any of the methods described above.

[0137] The present invention also provides a computer-readable storage medium having stored thereon computer program instructions executable by a processor, wherein when the processor executes the computer program instructions, it can implement the steps of any of the methods described above.

[0138] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific embodiments of the present invention are limited to these. The present invention can be further derived or modified based on the dimensions of the pressure vessel nozzle, crack size, and material properties. All simple variations made in accordance with the claims and specification of this application fall within the scope of protection of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for evaluating the distribution of stress intensity factor at the crack front edge of a pressure vessel nozzle, characterized in that, include: Finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes. Based on the finite element analysis results, a correction factor database for the crack lead of the nozzle of the pressure vessel is constructed. Based on the correction factor database, a weight function equation for pressure vessel nozzle cracks is established; Input the nozzle size and crack size of the pressure vessel to be evaluated. Based on the correction factor database and weight function equation, evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions acting on the crack surface of the pressure vessel nozzle.

2. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 1, characterized in that, Finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes, specifically including: Set the pressure vessel nozzle dimensions and pressure vessel nozzle crack dimensions; Set the material properties of the pressure vessel; Set the applied stress on the crack surface of the pressure vessel nozzle; Based on the set conditions, a three-dimensional model of a pressure vessel nozzle with cracks was established, and finite element analysis was performed on the cracks in the nozzles of pressure vessels of different sizes.

3. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 2, characterized in that, Finite element analysis was performed on the nozzle cracks of pressure vessels of different sizes based on the theory of linear elastic fracture mechanics.

4. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 1, characterized in that, Based on the finite element analysis results, a correction factor database for the crack lead of pressure vessel nozzles is constructed, specifically including: Based on the finite element analysis results, calculate the J integral of the crack front of the pressure vessel nozzle; Based on the J-integral, the distribution data of reference fracture parameters at the crack front of the pressure vessel nozzle are calculated. The reference fracture parameter distribution data is dimensionless to construct a correction factor database for the crack front of the pressure vessel nozzle.

5. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 4, characterized in that, The J-integral of the crack leading edge of the nozzle in a pressure vessel is calculated using the contour integral method.

6. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 1, characterized in that, Based on the correction factor database, a weighting function equation for pressure vessel nozzle cracks is established, specifically including: Based on the correction factor database, the weight coefficients in the general weight function for three-dimensional cracks are solved; Based on the solved weight coefficients, a weight function equation for pressure vessel nozzle cracks is established.

7. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 6, characterized in that, The weight coefficients in the universal weight function for three-dimensional cracks are solved using weight function theory.

8. The method for evaluating the stress intensity factor distribution at the crack front edge of a pressure vessel nozzle according to claim 1, characterized in that, Input the dimensions of the pressure vessel nozzle and the crack size of the pressure vessel nozzle to be evaluated. Based on the correction factor database and weight function equation, evaluate the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions acting on the crack surface of the pressure vessel nozzle, specifically including: Determine the dimensions of the nozzle and the crack size of the nozzle of the pressure vessel to be evaluated; Determine the complex stress conditions acting on the crack surface of the nozzle of the pressure vessel to be evaluated; Based on the nozzle size and crack size of the pressure vessel to be evaluated, and combined with the correction factor database, the correction factor of the crack front of the nozzle of the pressure vessel to be evaluated is calculated by interpolation. Substitute the calculated correction factor into the weight function equation of the pressure vessel nozzle crack to obtain the weight function of the pressure vessel nozzle crack to be evaluated. Based on the complex stress conditions acting on the surface of the pressure vessel nozzle crack and the calculated weight function of the pressure vessel nozzle crack, the stress intensity factor distribution at the crack front of the pressure vessel nozzle under complex stress conditions is evaluated.

9. A system for evaluating the distribution of stress intensity factor at the crack front of a pressure vessel nozzle, characterized in that, It includes a memory, a processor, and computer program instructions stored in the memory and executable by the processor, which, when executed by the processor, enable the implementation of the steps of the method as described in any one of claims 1-8.

10. A computer-readable storage medium having stored thereon computer program instructions executable by a processor, wherein when the processor executes the computer program instructions, it is able to implement the steps of the method as described in any one of claims 1-8.

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