Simple assessment method for T stress of axial crack under surfacing layer of pressure-bearing container

Abstract

The invention relates to a simple assessment method for axial crack T stress under a surfacing layer of a pressure-bearing container. The simple assessment method comprises the following steps: S1, constructing a reference fracture parameter database of axial cracks under the surfacing layer of the pressure-bearing container under a non-uniform stress condition; s2, calculating the three-dimensional stress of the crack-free pressure-bearing container under the actual operation condition; s3, virtual fracture parameters at the virtual crack tip in the crack-free pressure-bearing container under the actual operation working condition are calculated; and S4, evaluating the T stress of the lower axial crack of the surfacing layer of the pressure-bearing container under the actual operation condition. The simple evaluation method for the axial crack T stress under the surfacing layer of the pressure-bearing container is provided based on the fracture mechanics superposition principle, reliability analysis of the pressure-bearing container containing the axial crack under any surfacing layer can be achieved, the output bottleneck of large-scale numerical simulation is effectively relieved, and the precision and efficiency of structural integrity evaluation of the in-service pressure container are improved.

Description

Technical Field

[0001] This invention relates to a simplified method for assessing the axial crack stress T under the weld overlay of a pressure vessel, belonging to the field of pressure vessel safety assessment. Background Technology

[0002] Pressure vessels can develop cracks during long-term service, affecting their structural integrity and service life. To ensure long-term, high-reliability service of pressure vessels, fracture toughness tests are currently conducted on small-sized specimens made of the same material as the vessel to assess the structural integrity of in-service pressure vessels. Existing research shows that different sized specimens exhibit varying levels of crack tip restraint, leading to significant differences in their fracture toughness. Therefore, assessing the structural integrity of actual pressure vessels based on the fracture toughness of small-sized specimens may result in unreasonable evaluations. To quantify the differences in restraint levels caused by different specimen sizes, the academic community has proposed a mechanical parameter, Tstress, to characterize the crack tip restraint effect, providing a methodological reference for predicting the fracture strength of cracked pressure vessels based on the fracture toughness of small-sized specimens.

[0003] To reasonably assess the structural integrity of in-service pressure vessels, a T-stress database for cracked pressure vessels needs to be constructed. However, the existing T-stress calculations for cracked structures are mainly obtained through the finite element method (FEM), a method with high theoretical and technical barriers, hindering its widespread application in practical engineering. In particular, FEM-based T-stress calculations require engineers to systematically build finite element models of the cracked structures and perform fracture mechanics simulations, finally obtaining the T-stress through numerical calculations. For cylindrical engineering structures like pressure vessels, FEM-based T-stress solutions suffer from complex modeling processes, difficulty in achieving convergence, and time-consuming calculations, making it impossible to quickly and accurately assess the structural integrity of in-service pressure vessels. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a simple evaluation method for the axial crack T-stress under the weld overlay of a pressure vessel. The method pre-constructs a reference fracture parameter database of axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions. Combined with the principle of fracture mechanics superposition, it can realize the T-stress evaluation of any axial crack under the weld overlay in a pressure vessel under actual operating conditions, effectively improving the accuracy and efficiency of the structural integrity assessment of in-service pressure vessels.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a simplified evaluation method for axial crack T-stress under the weld overlay of a pressure vessel, comprising the following steps: Step S1: constructing a reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions; Step S2: calculating the triaxial stress of a crack-free pressure vessel under actual operating conditions; Step S3: calculating the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions; Step S4: evaluating the T-stress of axial cracks under the weld overlay of a pressure vessel under actual operating conditions.

[0006] Furthermore, the specific method for constructing the reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions is as follows: Step S11: Set the dimensions of the axial cracks under the pressure vessel and weld overlay; Step S12: Set the Young's modulus and Poisson's ratio of the weld overlay and the base material of the pressure vessel; Step S13: Based on the axial crack size information of the pressure vessel and weld overlay set in Step S11, and the Young's modulus and Poisson's ratio information of the weld overlay and the base material set in Step S12, establish a corresponding finite element model, and calculate the initial fracture parameter A of the axial cracks under the weld overlay of the pressure vessel under non-uniform stress conditions based on the interference integral method. 11 and A 33 Step S14: Apply the initial fracture parameters A obtained in step S13. 11 and A 33 Normalization was performed to construct a reference fracture parameter database A for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions. * 11 and A * 33 .

[0007] Further, the specific method for calculating the triaxial stress of the crack-free pressure vessel under actual operating conditions is as follows: Step S21: Determine the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions of the crack-free pressure vessel; Step S22: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the axial stress of the crack-free pressure vessel under actual operating conditions using elasticity theory; Step S23: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the circumferential stress of the crack-free pressure vessel under actual operating conditions using elasticity theory; Step S24: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the radial stress of the crack-free pressure vessel under actual operating conditions using elasticity theory.

[0008] Further, the specific method for calculating the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions is as follows: Step S31: Based on the axial stress, circumferential stress, and radial stress of the crack-free pressure vessel under actual operating conditions calculated in steps S22, S23, and S24, calculate the stress components at the virtual crack tip in the crack-free pressure vessel; Step S32: Based on the stress components at the virtual crack tip calculated in step S31, use the crack tip stress field theory to calculate the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel under actual operating conditions. 11 and B 33 .

[0009] Further, the specific method for evaluating the T-stress of the axial crack under the weld overlay of the pressure vessel under actual operating conditions is as follows: Step S41: Based on the circumferential stress of the pressure vessel without cracks under actual operating conditions calculated in step S23, the least squares method is used to fit the circumferential stress distribution in the thickness direction of the pressure vessel with the axial crack under the weld overlay in the form of a polynomial function; Step S42: Combined with the reference fracture parameter database A constructed in step S14 * 11 and A * 33 And the circumferential stress distribution along the thickness direction of the pressure vessel containing the axial crack under the weld overlay, fitted in step S41, are used to calculate the fracture parameter C of the axial crack under the weld overlay of the pressure vessel under actual operating conditions. 11 and C 33 Step S43: Based on the virtual fracture parameter B at the virtual crack tip in the crackless pressure vessel calculated in step S32. 11 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 11 Calculate the in-plane stress component TA of the axial crack under the weld overlay of a pressure vessel under actual operating conditions. 11 Step S44: Based on the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel calculated in step S32. 33 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 33 Calculate the out-of-plane stress component TA of the axial crack under the weld overlay of the pressure vessel under actual operating conditions. 33 .

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1. This invention establishes a reference fracture parameter database for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions. The database takes into account the influence of typical pressure vessel size, crack configuration and material properties, and can provide data support for assessing the service reliability of pressure vessels.

[0012] 2. Based on the superposition principle, this invention innovatively proposes a simplified evaluation method for axial crack T-stress under the weld overlay of pressure vessels. This method effectively avoids the complex finite element modeling process and eliminates the need for convergence verification of the numerical solution of T-stress, significantly improving the accuracy and efficiency of structural integrity assessment for in-service pressure vessels.

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0014] Figure 1a This is a schematic diagram of the overall pressure vessel according to an embodiment of the present invention.

[0015] Figure 1b This is a simplified model diagram of the central region of a pressure vessel according to an embodiment of the present invention.

[0016] Figure 1c for Figure 1b BB cross-sectional view.

[0017] Figure 1d This is a schematic diagram of a crack under the axial weld overlay in an embodiment of the present invention.

[0018] Figure 2 This is a flowchart of a simplified evaluation method according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of stress coordinate transformation according to an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. 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 application pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] As shown in Figures 1-3, this embodiment provides a simple method for evaluating the axial crack stress T under the weld overlay of a pressure vessel. Figures 1a-1d In the context of pressure vessels, the inner diameter is R. iThe thickness of the weld overlay is t c The thickness of the base material is t b Here, it is assumed that the axial crack under the weld overlay is a semi-elliptical crack, the distance from the deepest point of the crack to the interface between the weld overlay and the base material is the crack depth a, and the distance between the two intersection points of the crack and the interface between the weld overlay and the base material is the crack length l. The stress T is evaluated using the deepest point of the crack as an example.

[0024] like Figure 2 As shown, a simplified method for assessing the axial crack stress T under the weld overlay of a pressure vessel includes the following steps:

[0025] Step S1: Construct a reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions;

[0026] Step S11: Set the size of the axial crack under the pressure vessel and the weld overlay;

[0027] Step S12: Set the Young's modulus and Poisson's ratio of the pressure vessel weld overlay and the base material;

[0028] Step S13: Based on the axial crack size information of the pressure vessel and the weld overlay set in Step S11, and the Young's modulus and Poisson's ratio information of the pressure vessel weld overlay and the base material set in Step S12, establish the corresponding finite element model, and calculate the initial fracture parameter A of the axial crack under the pressure vessel weld overlay under non-uniform stress conditions based on the interference integral method. 11 and A 33 ;

[0029] Step S14: Apply the initial fracture parameters A obtained in step S13. 11 and A 33 Normalization was performed to construct a reference fracture parameter database A for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions. * 11 and A * 33 ;

[0030] Step S2: Calculate the triaxial stress of the crack-free pressure vessel under actual operating conditions;

[0031] Step S21: Determine the inner diameter R of the crack-free pressure vessel. i Thickness of weld overlay t c Base material thickness t b and the load p exerted on the container under actual operating conditions;

[0032] Step S22: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i Thickness of weld overlay t c Base material thickness t bBased on the load p experienced by the vessel under actual operating conditions and combined with the theory of elasticity, the axial stress σ of the crack-free pressure vessel under actual operating conditions is calculated. z ;

[0033] σ z =0

[0034] In the formula, σ z The axial stress is 0 MPa, since the influence of the end cap load is not considered.

[0035] Step S23: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i Thickness of weld overlay t c Base material thickness t b Based on the load p experienced by the vessel under actual operating conditions and combined with the theory of elasticity, the circumferential stress σ of the crack-free pressure vessel under actual operating conditions is calculated. θ ;

[0036]

[0037] In the formula, σ θ ρ is the circumferential stress, p is the load on the vessel under actual operating conditions, ρ is the ratio of the inner to outer diameter, and R is the circumferential stress. i t is the inner diameter of the pressure vessel. c t represents the thickness of the weld overlay. b Where r is the thickness of the base material, and r is the radius at any point inside the pressure vessel (e.g., ...). Figure 1c (as shown);

[0038] Step S24: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i Thickness of weld overlay t c Base material thickness t b Based on the load p experienced by the vessel under actual operating conditions and combined with the theory of elasticity, the radial stress σ of the crack-free pressure vessel under actual operating conditions is calculated. r ;

[0039]

[0040] In the formula, σ r Where ρ is the radial stress, p is the load on the vessel under actual operating conditions, ρ is the ratio of the inner to outer diameter, and R is the radial stress. i t is the inner diameter of the pressure vessel. c t represents the thickness of the weld overlay. b Where r is the thickness of the base material, and r is the radius at any point inside the pressure vessel (e.g., ...). Figure 1c (as shown);

[0041] Step S3: Calculate the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions;

[0042] Step S31: Based on the axial stress, circumferential stress, and radial stress of the crack-free pressure vessel under actual operating conditions calculated in steps S22, S23, and S24, calculate the stress component σ at the tip of the virtual crack in the crack-free pressure vessel. 11 σ 22 and σ 33 (like Figure 3 (as shown);

[0043] Step S32: Based on the stress components at the virtual crack tip calculated in step S31, the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel under actual operating conditions is calculated using the crack tip stress field theory. 11 and B 33 ;

[0044] B 11 =σ 11 -σ 22

[0045] B 33 =σ 33 -2v2σ 22

[0046] In the formula, B 11 and B 33 σ represents the virtual fracture parameter at the tip of a virtual crack in a crack-free pressure vessel. 11 σ 22 and σ 33 ν1 represents the stress component at the virtual crack tip, and ν2 represents the Poisson's ratio of the parent material.

[0047] Step S4: Evaluate the T-stress of the axial crack under the weld overlay of the pressure vessel under actual operating conditions;

[0048] Step S41: Based on the circumferential stress of the pressure vessel without cracks under actual operating conditions calculated in step S23, the least squares method is used to fit the circumferential stress distribution in the thickness direction of the pressure vessel with axial cracks under the weld overlay in the form of a polynomial function.

[0049]

[0050] In the formula, The polynomial for the circumferential stress distribution along the thickness direction of the pressure vessel is given by i = 0, 1, and 2, and x is the coordinate axis originating from the interface between the weld overlay and the base material (x = r - (R...). i +t c ),like Figure 1d (As shown), a is the crack depth, σ i These are the polynomial coefficients for the circumferential stress distribution along the thickness direction of the pressure vessel.

[0051] Step S42: Combine the reference fracture parameter database A constructed in step S14 * 11 and A * 33 Based on the circumferential stress distribution along the thickness direction of the pressure vessel with axial cracks under the weld overlay fitted in step S41, the fracture parameter C of the axial cracks under the weld overlay of the pressure vessel under actual operating conditions is calculated. 11 and C 33 ;

[0052]

[0053] In the formula, C 11 and C 33 σ represents the fracture parameter of the axial crack under the weld overlay of a pressure vessel under actual operating conditions. i A represents the polynomial coefficients for the circumferential stress distribution along the thickness direction of the pressure vessel. * 11 and A * 33 This serves as a reference fracture parameter database for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions.

[0054] Step S43: Based on the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel calculated in step S32. 11 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 11 Calculate the in-plane stress component TA of the axial crack under the weld overlay of a pressure vessel under actual operating conditions. 11 ;

[0055] T 11 =B 11 +C 11

[0056] In the formula, T 11 B represents the in-plane T-stress component of the axial crack beneath the weld overlay of a pressure vessel under actual operating conditions. 11 C represents the virtual fracture parameter at the virtual crack tip in a crack-free pressure vessel. 11 The fracture parameters of axial cracks under the weld overlay of pressure vessels under actual operating conditions;

[0057] Step S44: Based on the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel calculated in step S32. 33 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 33 Calculate the out-of-plane stress component TA of the axial crack under the weld overlay of the pressure vessel under actual operating conditions. 33 ;

[0058] T33 =B 33 +C 33

[0059] In the formula, T 33 B represents the out-of-plane T-stress component of the axial crack beneath the weld overlay of a pressure vessel under actual operating conditions. 33 C represents the virtual fracture parameter at the virtual crack tip in a crack-free pressure vessel. 33 These are the fracture parameters for axial cracks under the weld overlay of a pressure vessel under actual operating conditions.

[0060] The following practical application example illustrates this technical solution in detail:

[0061] Assuming a pressure vessel has an axial crack beneath the weld overlay, it is necessary to calculate its stress T under actual operating conditions. The inner diameter R of the pressure vessel... i =2050mm, weld overlay thickness t c =5mm, base material thickness t b =200mm, crack depth a=50mm, crack length l=300mm, Young's modulus of weld overlay E1=163200MPa, Young's modulus of base material E2=204000MPa, Poisson's ratio of weld overlay ν1=0.3, Poisson's ratio of base material ν2=0.3, load on the vessel under actual operating conditions p=15MPa, with the deepest point of crack (see...) Figure 1d For example, the stress T is evaluated.

[0062] The present invention is used to evaluate the T-stress of the axial crack under the weld overlay, and the process is as follows:

[0063] Step S1: Construct a reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions;

[0064] Step S11: Set the dimensions of the axial cracks under the pressure vessel and the weld overlay, including: the inner diameter R of the pressure vessel. i Thickness of weld overlay t c Base material thickness t b The inner diameter R of the pressure vessel i With total thickness (t) b +t c The ratio of R to ) i / (t b +t c Crack depth a and base material thickness t b The ratio a / t b The ratio of crack depth a to crack length l, a / l, and the size information of axial cracks under the pressure vessel and weld overlay are shown in Table 1.

[0065] Step S12: Set the Young's modulus and Poisson's ratio of the pressure vessel weld overlay and the base material, including: the ratio of the Young's modulus E1 of the weld overlay to the Young's modulus E2 of the base material, E1 / E2; the Poisson's ratio ν1 of the pressure vessel weld overlay and the Poisson's ratio ν2 of the base material; the Young's modulus and Poisson's ratio information of the pressure vessel are shown in Table 1.

[0066] Table 1. Information on the size, Young's modulus, and Poisson's ratio of axial cracks under the pressure vessel and weld overlay.

[0067]

[0068]

[0069] Step S13: Based on the axial crack size information of the pressure vessel and the weld overlay set in Step S11, and the Young's modulus and Poisson's ratio information of the pressure vessel weld overlay and the base material set in Step S12, establish the corresponding finite element model, and calculate the initial fracture parameter A of the axial crack under the pressure vessel weld overlay under non-uniform stress conditions based on the interference integral method. 11 and A 33 ;

[0070] Step S14: Apply the initial fracture parameters A obtained in step S13. 11 and A 33 Normalization was performed to construct a reference fracture parameter database A for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions. * 11 and A * 33 ;

[0071] Step S2: Calculate the triaxial stress of the crack-free pressure vessel under actual operating conditions;

[0072] Step S21: Determine the inner diameter R of the crack-free pressure vessel. i =2050mm, weld overlay thickness t c =5mm, base material thickness t b =200mm and the load p=15MPa on the container under actual operating conditions;

[0073] Step S22: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i =2050mm, weld overlay thickness t c =5mm, base material thickness t b =200mm and the load p=15MPa on the vessel under actual operating conditions, the axial stress σ of the crack-free pressure vessel under actual operating conditions is calculated using elasticity theory. z ;

[0074] σ z =0

[0075] In the formula, σ z The axial stress is 0 MPa, since the influence of the end cap load is not considered.

[0076] Step S23: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i =2050mm, weld overlay thickness t c =5mm, base material thickness t b =200mm and the load p=15MPa on the vessel under actual operating conditions. Based on the theory of elasticity, the circumferential stress σ of the crack-free pressure vessel under actual operating conditions is calculated. θ ;

[0077]

[0078] In the formula, σ θ ρ is the circumferential stress, p is the load on the vessel under actual operating conditions, ρ is the ratio of the inner to outer diameter, and R is the circumferential stress. i t is the inner diameter of the pressure vessel. c t represents the thickness of the weld overlay. b Where r is the thickness of the base material, and r is the radius at any point inside the pressure vessel (e.g., ...). Figure 1c (as shown);

[0079] Step S24: Based on the inner diameter R of the crack-free pressure vessel determined in step S21 i =2050mm, weld overlay thickness t c =5mm, base material thickness t b =200mm and the load p=15MPa on the vessel under actual operating conditions. Based on the theory of elasticity, the radial stress σ of the crack-free pressure vessel under actual operating conditions is calculated. r ;

[0080]

[0081] In the formula, σ r Where ρ is the radial stress, p is the load on the vessel under actual operating conditions, ρ is the ratio of the inner to outer diameter, and R is the radial stress. i t is the inner diameter of the pressure vessel. c t represents the thickness of the weld overlay. b Where r is the thickness of the base material, and r is the radius at any point inside the pressure vessel (e.g., ...). Figure 1c (as shown);

[0082] Step S3: Calculate the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions;

[0083] Step S31: Based on the axial stress, circumferential stress, and radial stress of the crack-free pressure vessel under actual operating conditions calculated in steps S22, S23, and S24, calculate the stress component σ at the tip of the virtual crack in the crack-free pressure vessel. 11 = -10.61MPa, σ 22 =154.23MPa and σ 33 =0MPa (e.g.) Figure 3 (as shown);

[0084] Step S32: Based on the stress components at the virtual crack tip calculated in step S31, the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel under actual operating conditions is calculated using the crack tip stress field theory. 11 =-164.84MPa and B 33 = -92.54 MPa;

[0085] B 11 =σ 11 -σ 22

[0086] B 33 =σ 33 -2v2σ 22

[0087] In the formula, B 11 and B 33 σ represents the virtual fracture parameter at the tip of a virtual crack in a crack-free pressure vessel. 11 σ 22 and σ 33 ν1 represents the stress component at the virtual crack tip, and ν2 represents the Poisson's ratio of the parent material.

[0088] Step S4: Evaluate the T-stress of the axial crack under the weld overlay of the pressure vessel under actual operating conditions;

[0089] Step S41: Based on the circumferential stress of the pressure vessel without cracks under actual operating conditions calculated in step S23, the least squares method is used to fit the circumferential stress distribution in the thickness direction of the pressure vessel with axial cracks under the weld overlay in the form of a polynomial function.

[0090]

[0091] In the formula, The polynomial for the circumferential stress distribution along the thickness direction of the pressure vessel is given by i = 0, 1, and 2, and x is the coordinate axis originating from the interface between the weld overlay and the base material (x = r - (R...). i +t c ),like Figure 1d (As shown), a is the crack depth, σ i These are the polynomial coefficients for the circumferential stress distribution along the thickness direction of the pressure vessel.

[0092] Step S42: Combine the reference fracture parameter database A constructed in step S14 * 11 and A * 33 Based on the circumferential stress distribution along the thickness direction of the pressure vessel with axial cracks under the weld overlay fitted in step S41, the fracture parameter C of the axial cracks under the weld overlay of the pressure vessel under actual operating conditions is calculated. 11 =13.91MPa and C 33 = -6.68MPa;

[0093]

[0094] In the formula, C 11 and C 33 σ represents the fracture parameter of the axial crack under the weld overlay of a pressure vessel under actual operating conditions. i A represents the polynomial coefficients for the circumferential stress distribution along the thickness direction of the pressure vessel. * 11 and A * 33 This serves as a reference fracture parameter database for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions.

[0095] Step S43: Based on the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel calculated in step S32. 11 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 11 Calculate the in-plane stress component TA of the axial crack under the weld overlay of a pressure vessel under actual operating conditions. 11 = -150.93 MPa;

[0096] T 11 =B 11 +C 11

[0097] In the formula, T 11 B represents the in-plane T-stress component of the axial crack beneath the weld overlay of a pressure vessel under actual operating conditions. 11 C represents the virtual fracture parameter at the virtual crack tip in a crack-free pressure vessel. 11 The fracture parameters of axial cracks under the weld overlay of pressure vessels under actual operating conditions;

[0098] Step S44: Based on the virtual fracture parameter B at the virtual crack tip in the crack-free pressure vessel calculated in step S32. 33 The fracture parameter C of the axial crack under the weld overlay of the pressure vessel calculated in step S42. 33Calculate the out-of-plane stress component TA of the axial crack under the weld overlay of the pressure vessel under actual operating conditions. 33 = -99.22MPa;

[0099] T 33 =B 33 +C 33

[0100] In the formula, T 33 B represents the out-of-plane T-stress component of the axial crack beneath the weld overlay of a pressure vessel under actual operating conditions. 33 C represents the virtual fracture parameter at the virtual crack tip in a crack-free pressure vessel. 33 These are the fracture parameters for axial cracks under the weld overlay of a pressure vessel under actual operating conditions.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An axial crack under the weld overlay of a pressure vessel T A simplified method for stress assessment, characterized by: Including the following Steps: Step S1: Construct a reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions; Step S2: Calculate the triaxial stress of a crack-free pressure vessel under actual operating conditions; Step S3: Calculate the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions; Step S4: Evaluate the axial cracks under the weld overlay of a pressure vessel under actual operating conditions. T stress.

2. Axial cracks under the weld overlay of the pressure vessel as described in claim 1 T A simplified method for stress assessment, characterized by: The specific method for constructing a reference fracture parameter database for axial cracks under the weld overlay of a pressure vessel under non-uniform stress conditions is as follows: Step S11: Set the dimensions of the axial cracks under the pressure vessel and weld overlay; Step S12: Set the Young's modulus and Poisson's ratio of the weld overlay and the base material of the pressure vessel; Step S13: Based on the axial crack size information of the pressure vessel and weld overlay set in Step S11, and the Young's modulus and Poisson's ratio information of the weld overlay and the base material set in Step S12, establish a corresponding finite element model, and calculate the initial fracture parameters of the axial cracks under the weld overlay of the pressure vessel under non-uniform stress conditions using the interferometric integral method. A 11 and A 33 Step S14: Apply the initial fracture parameters calculated in step S13. A 11 and A 33 Normalization was performed to construct a reference fracture parameter database for axial cracks under the weld overlay of pressure vessels under non-uniform stress conditions. A * 11 and A * 33 .

3. Axial cracks under the weld overlay of the pressure vessel as described in claim 2 T A simplified method for stress assessment, characterized by: The specific method for calculating the triaxial stress of a crack-free pressure vessel under actual operating conditions is as follows: Step S21: Determine the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions of the crack-free pressure vessel; Step S22: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the axial stress of the crack-free pressure vessel under actual operating conditions using elasticity theory; Step S23: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the circumferential stress of the crack-free pressure vessel under actual operating conditions using elasticity theory; Step S24: Based on the inner diameter, weld overlay thickness, base material thickness, and load on the vessel under actual operating conditions determined in Step S21, calculate the radial stress of the crack-free pressure vessel under actual operating conditions using elasticity theory.

4. Axial cracks under the weld overlay of the pressure vessel as described in claim 3 T A simplified method for stress assessment, characterized by: The specific method for calculating the virtual fracture parameters at the virtual crack tip in a crack-free pressure vessel under actual operating conditions is as follows: Step S31: Based on the axial stress, circumferential stress, and radial stress of the crack-free pressure vessel under actual operating conditions calculated in steps S22, S23, and S24, calculate the stress components at the virtual crack tip in the crack-free pressure vessel; Step S32: Based on the stress components at the virtual crack tip calculated in step S31, use the crack tip stress field theory to calculate the virtual fracture parameters at the virtual crack tip in the crack-free pressure vessel under actual operating conditions. B 11 and B 33 .

5. Axial cracks under the weld overlay of the pressure vessel as described in claim 4 T A simplified method for stress assessment, characterized by: The assessment describes the axial cracks beneath the weld overlay of a pressure vessel under actual operating conditions. T The specific method for stress analysis is as follows: Step S41: Based on the circumferential stress of the pressure vessel without cracks under actual operating conditions calculated in Step S23, the least squares method is used to fit the circumferential stress distribution in the thickness direction of the pressure vessel with axial cracks under the weld overlay in the form of a polynomial function; Step S42: Combined with the reference fracture parameter database constructed in Step S14 A * 11 and A * 33 And the circumferential stress distribution along the thickness direction of the pressure vessel containing the axial crack under the weld overlay, fitted in step S41, are used to calculate the fracture parameters of the axial crack under the weld overlay of the pressure vessel under actual operating conditions. C 11 and C 33 Step S43: Based on the virtual fracture parameters at the virtual crack tip in the crack-free pressure vessel calculated in step S32. B 11 Fracture parameters of axial cracks under the weld overlay of the pressure vessel calculated in step S42 C 11 Calculate the in-plane axial cracks under the weld overlay of a pressure vessel under actual operating conditions. T Stress components T 11 Step S44: Based on the virtual fracture parameters at the virtual crack tip in the crack-free pressure vessel calculated in step S32. B 33 Fracture parameters of axial cracks under the weld overlay of the pressure vessel calculated in step S42 C 33 Calculate the out-of-plane axial cracks under the weld overlay of a pressure vessel under actual operating conditions. T Stress components T 33 .

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