Grid insensitive fillet weld fracture structure stress analysis method and system
By simplifying modeling and formula calculation, the lack of critical failure surface judgment criteria and mesh sensitivity issues in weld root cracking assessment are resolved, achieving efficient and accurate weld stress analysis, which is suitable for rapid design and evaluation of large structures.
Patent Information
- Application Number
- CN202511820364.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-02-17
AI Technical Summary
Existing technologies lack robust criteria for determining critical failure surfaces in weld root cracking assessment. Reliance on detailed modeling leads to low computational efficiency and susceptibility to mesh sensitivity, making them unsuitable for rapid assessment of large and complex structures.
A mesh-insensitive analytical method for fractured fillet welds is adopted. By simplifying modeling and formula calculation, the mechanical data of the 90° weld throat section is used to map the stress state at any angle and traverse to determine the critical failure plane, thus avoiding detailed modeling and mesh sensitivity.
It improves computational efficiency and accuracy, reduces reliance on modeling skills, is suitable for rapid design and fatigue assessment of large structures, and provides support for integrated lightweight and fatigue-resistant design.
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Figure CN121543353A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of structural stress analysis, and specifically to a method and system for analyzing the stress of a grid-insensitive fillet weld fracture structure. Background Technology
[0002] Fillet welds are one of the most common connection types in welded structures of ships, marine engineering, and heavy equipment. In their fatigue assessment, two main failure modes exist: "toe cracking" (Mode A), which begins at the weld toe and penetrates the base plate, and "root cracking" (Mode B), which begins at the weld root and penetrates the weld throat. The latter is generally considered a more dangerous failure mode due to its large fatigue life dispersion, lack of existing assessment methods, and difficulty in detection. In design, it is often avoided by excessively increasing the weld leg size, but this leads to increased structural weight and exacerbated weld deformation.
[0003] Several key technical problems urgently need to be solved in the existing technology: 1. Lack of Critical Failure Surface Determination Criteria and Unreasonable Assumptions: Existing studies, when predicting weld root cracking, typically presuppose a fixed angle of 45° or 90° for the critical fracture surface. However, in-depth research shows that the actual critical fracture surface angle dynamically varies between approximately 60° and 80° depending on the weld leg size and penetration depth. This method, based on empirical assumptions, lacks a solid mechanical foundation, leading to significant deviations between predicted results and actual conditions.
[0004] 2. The analysis method heavily relies on detailed modeling and complex post-processing: While the current mainstream finite element analysis method can calculate weld throat stress to some extent, its calculation accuracy heavily depends on the extremely fine mesh generation of the weld area, exhibiting a significant "mesh sensitivity" problem. Furthermore, this method requires extracting nodal forces along numerous pre-defined radial paths and performing complex conversions, a cumbersome process with low computational efficiency. It is also prone to missing maximum stress points because the pre-defined paths fail to cover the true critical angle, making it unsuitable for the engineering design and rapid evaluation of large and complex structures.
[0005] 3. Lack of efficient analytical methods applicable to engineering practice: Existing methods have failed to establish an analytical correlation between the structural stress at the easily obtainable weld toe and the stress at any angle of the weld throat. Engineers cannot quickly assess the potential failure modes and fatigue performance under different weld leg sizes and penetration levels through simple calculations, which restricts the realization of integrated lightweight and fatigue-resistant design. Summary of the Invention
[0006] To address the aforementioned technical problems, such as the lack of critical failure surface determination criteria and unreasonable assumptions, the heavy reliance on detailed modeling and complex post-processing in analytical methods, and the lack of efficient analytical means applicable to engineering practice, this invention provides a stress analysis method and system for fracture structures with mesh-insensitive fillet welds. This invention primarily utilizes readily available mechanical data of the 90° weld throat section. Through a set of analytical formulas satisfying equilibrium conditions, it maps the stress state on any assumed cutting plane at the weld root and traverses to determine the critical failure plane. This improves computational efficiency, accuracy, and reliability, avoids mesh sensitivity issues, enhances engineering applicability, avoids the difficulties of detailed weld modeling, and achieves reliable identification of failure modes and optimized weld size design.
[0007] The technical means employed in this invention are as follows: A stress analysis method for a mesh-insensitive fillet weld fracture structure includes the following steps: A structural model including welded joints was established using finite element software, and the weld throat area of the structural model was modeled using a simplified method. A working load is applied to the structural model, and a static solution is performed on the structural model after the working load is applied to obtain the overall stress distribution and nodal force information of the structure. A cutting path perpendicular to the substrate is defined at the weld root of the model. Based on the overall stress distribution and nodal force information, the stress results of the cutting path are extracted using the post-processing function of the finite element software. The stress results include linearized stress results, line force and line spacing. The linearized stress results include membrane stress, bending stress and shear stress. Based on the stress results and weld leg dimensions, the traction stress components under the cutting plane angle are calculated using a formula. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress. The formula iterates through the angles of the cutting plane to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane. Fatigue life assessment and weld structure optimization are performed based on the maximum stress value.
[0008] Furthermore, the step of calculating the traction stress component under the cutting plane angle using a formula based on the stress results and weld leg dimensions includes: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle:
[0009] in, This refers to the thickness of the weld throat. For solder lead size, For the angle of the cutting plane; Secondly, based on the linearized stress results, weld throat thickness, and cutting plane angle, the membrane component and bending component are calculated:
[0010]
[0011] in, For membrane components, For membrane stress, For shear stress, For the bending component, For bending stress; Subsequently, based on the membrane component, shear stress, weld bead size, and weld throat thickness, the transverse shear stress is calculated:
[0012] in, It is the transverse shear stress; Finally, by adding the membrane component and the bending component, the normal traction stress is obtained, and by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force, the in-plane shear stress is obtained.
[0013] Furthermore, the formula for calculating the membrane component of the longitudinal shear traction force is as follows:
[0014] in, The membrane component of the longitudinal shear traction force is given by the following formula:
[0015] in, This represents the bending component of the longitudinal shear traction force.
[0016] Furthermore, the step of calculating the traction stress component under the cutting plane angle using a formula based on the stress results and weld leg dimensions also includes: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle: ; Secondly, based on the linear force in the y-direction, the linear spacing in the z-direction, and the weld throat thickness, the membrane component and bending component are calculated:
[0017]
[0018] in, For membrane components, For the bending component, The linear force in the y-direction, The line spacing in the z-direction; Then, the membrane component and the bending component are added together to calculate the normal traction stress. The formula for calculating the normal traction stress is as follows:
[0019] in, Normal traction stress; Subsequently, the transverse shear stress is calculated based on the linear force in the x-direction and the weld throat thickness:
[0020] in, Let x be the linear force in the x-direction; Finally, the in-plane shear stress is obtained by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force.
[0021] Furthermore, the linear force and line spacing are obtained by solving the following formula:
[0022] in, These represent the nodal forces along the weld toe line from the first node to the nth node. These represent the element projection lengths corresponding to the first segment to the nth segment in the fractured fillet weld structure. These represent the linear forces corresponding to the first to the nth segments in the fracture structure of the fillet weld.
[0023] Furthermore, the linear force and spacing at the cutting plane angle satisfy the following equilibrium condition with the linearized stress result:
[0024]
[0025]
[0026] in, The linear force is along the x-direction. The linear force is along the y-direction. Let be the linear moment about the z-axis. The linear force in the y-direction at the angle to the cutting plane. The linear force in the x-direction at the angle to the cutting plane. For the angle of the cutting plane, The line spacing in the z-direction under the angle of the cutting plane. This represents bending stress.
[0027] Furthermore, the critical failure plane is determined by finding the angle corresponding to the maximum value of the finite traction stress. The finite traction stress is determined by the normal traction stress and the transverse shear stress, and the calculation formula for the finite traction stress includes:
[0028] in, For finite traction stress, For normal traction stress, This is the transverse shear traction stress. These are the weighting coefficients.
[0029] This invention also includes a stress analysis system for mesh-insensitive fillet weld fracture structures, used to implement the above-mentioned stress analysis method for mesh-insensitive fillet weld fracture structures, comprising: The finite element modeling module is used to create a structural model that includes welded joints, wherein the weld throat region of the structural model is modeled using a simplified method. The load application and solution module is used to apply working loads to the structural model and perform static solutions to obtain the overall stress distribution and nodal force information of the structure. The cross-section data extraction module is used to define a cutting path perpendicular to the substrate at the weld root of the model, and extract the stress results of the cutting path based on the overall stress distribution and nodal force information. The stress results include linearized stress results, linear force and linear moment obtained by integration, and the linearized stress results include membrane stress, bending stress and shear stress. The analytical calculation module is used to calculate the traction stress components at any cutting plane angle based on the stress results and weld leg size using a set of formulas. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress. The critical plane determination module is used to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane by traversing the angles of the cutting plane. The fatigue assessment and optimization module is used to assess fatigue life and optimize weld structure based on the maximum stress value.
[0030] Compared with the prior art, the present invention has the following advantages: 1. This invention requires only a single simple finite element calculation (to obtain the nodal forces on the 90° section) to instantly obtain the full-angle stress field using the analytical formula, improving computational efficiency by several orders of magnitude. It is particularly suitable for the rapid design and fatigue assessment of large structures (such as ships and offshore platforms). Traditional finite element methods require establishing a detailed three-dimensional solid model and performing tedious slicing and stress linearization operations for each angle of interest to obtain the weld throat stress distribution. This results in high computational costs and the process cannot be automated.
[0031] 2. The formulas in this invention are derived based on rigorous mechanical equilibrium principles, and the theory is sound. Verification through multiple typical cases shows that the calculation results of this method are in high agreement with the results of high-precision finite element analysis, proving its accuracy and reliability, and fully meeting the accuracy requirements of engineering design and analysis.
[0032] 3. This invention fundamentally avoids mesh sensitivity because the input is nodal force, and the results are inherently mesh-insensitive, ensuring the uniqueness and objectivity of the calculation results. Traditional finite element methods suffer from severe mesh sensitivity in stress concentration areas such as weld roots and weld toes, and the calculation results are easily affected by mesh density and morphology.
[0033] 4. This invention eliminates the need for detailed modeling of complex weld geometry. Engineers can use a much coarser mesh to quickly obtain accurate results, reducing reliance on modeling skills and making it possible to perform detailed local stress analysis based on a global model of shell elements, greatly simplifying the workflow.
[0034] 5. This invention provides a simplified parametric stress calculation method that can be easily integrated into design optimization algorithms, digital twin systems, or real-time health monitoring platforms, providing core algorithm support for real-time prediction of structural life and intelligent operation and maintenance management.
[0035] Based on the above reasons, this invention can be widely applied in fields such as structural stress analysis. Attached Figure Description
[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0037] Figure 1 This is a schematic diagram of the traction stress on a hypothetical cutting plane in the fillet weld of the present invention.
[0038] Figure 2 This is a schematic diagram illustrating the linear representation and decomposition of the traction stress components in this invention.
[0039] Figure 3 This is a schematic diagram of the force components in the analytical model of the fillet weld of this invention.
[0040] Figure 4 This is a schematic diagram of the rectangular hollow section (RHS) joint in Embodiment 1 of the present invention.
[0041] Figure 5This is a schematic diagram of a two-dimensional finite element model utilizing quarter-symmetry in Embodiment 1 of the present invention.
[0042] Figure 6 This is a comparison diagram of the analytical solution and the finite element solution of membrane stress in Embodiment 1 of the present invention.
[0043] Figure 7 This is a comparison diagram of the analytical solution and the finite element solution of bending stress in Embodiment 1 of the present invention.
[0044] Figure 8 This is a flowchart illustrating the stress analysis method for a mesh-insensitive fillet weld fracture structure according to the present invention. Detailed Implementation
[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0046] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.
[0047] To examine weld root cracking behavior, it is first necessary to introduce appropriate stress definitions and related calculation methods to consistently characterize the stress state associated with weld root fatigue cracking behavior. The mesh-insensitive structural stress method, later renamed the traction stress method, has been proven to effectively correlate the static shear strength of load-bearing fillet welds under both transverse and longitudinal shear load conditions. Therefore, in this invention, it is natural to examine the applicability of the same stress definition for characterizing weld root fatigue cracking. Two additional reasons are considered for the traction stress method here: First, this method is formulated by enforcing equilibrium conditions using relevant nodal forces available in the typical finite element method (FE). This suppresses stress singularities at the weld root and weld toe, thus achieving insensitivity to mesh size and mesh type when determining the traction stress at the weld root or weld toe.
[0048] Secondly, this method has been proven to effectively correlate fatigue test data of a large number of different component geometries and load modes onto a single main SN curve, and has been adopted by the 2007 ASME Div2 standard and API 579 RP-1 / ASME FFS-1 for handling weld toe failure modes.
[0049] Example 1 This invention provides a method for stress analysis of mesh-insensitive fillet weld fracture structures, the specific steps of which are as follows: S1. Use finite element software to establish a structural model including welded joints. The weld throat area of the structural model is modeled using a simplified method.
[0050] It is worth noting that this model does not require fine solid meshing of the weld throat area and a simplified modeling approach can be used, but it is necessary to ensure that the load can be accurately transferred.
[0051] S2. Apply working loads to the structural model, perform static solutions on the structural model after applying working loads, and obtain the overall stress distribution and nodal force information of the structure.
[0052] S3. Define a cutting path perpendicular to the substrate (i.e., the traditional weld toe section) at the weld root of the model. Based on the overall stress distribution and nodal force information, use the post-processing function of the finite element software to extract the stress results of the cutting path. The stress results include linearized stress results, line force and line spacing. The linearized stress results include membrane stress, bending stress and shear stress.
[0053] S4. Based on the stress results and weld leg dimensions, calculate the traction stress components under the cutting plane angle using the formula. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress.
[0054] Along the weld root, perpendicular to the horizontal plate Angle (e.g.) Figure 1 An arbitrary hypothetical cutting plane (as shown in a) exposes three traction stress components (such as...). Figure 1 (As shown in b), these components are balanced by the external load applied to the horizontal plate. In this invention, these three components are referred to as: normal traction stress, transverse shear stress, and in-plane shear stress, respectively. Due to the presence of weld roots, these traction stresses typically exhibit a complex distribution. In the prior art, Figure 1 The linear form of the three traction stress components on the cutting plane passing through the weld metal can be extracted in a statically equivalent manner. For example... Figure 2 As shown, and represented by its membrane portion and curved portion as follows:
[0055]
[0056]
[0057] in, For normal traction stress, For membrane stress, For bending stress, The linear force in the y-direction, This refers to the thickness of the weld throat. The line spacing in the z-direction. It is the transverse shear stress. The linear force in the x-direction, For in-plane shear stress, The membrane component representing the longitudinal shear traction force. The bending component of the longitudinal shear traction force. The linear force in the z-direction, The distance between the lines in the y-direction is denoted as .
[0058] Figure 1 The corresponding local coordinate system (x′) can be seen in the image. y′ These linear forces and moments can be solved using a matrix equation, which involves deriving the results from typical finite element analysis along... Figure 1 The corresponding nodal forces and moments obtained from the cutting plane shown in Figure a (for the fillet weld joint modeled using three-dimensional (3D) solid elements, and relative to the same local coordinate system).
[0059] In order to clearly establish the critical fatigue failure plane (on which stress-based fatigue parameters can be extracted and compared with the parameters corresponding to the weld toe failure mode), this invention proposes an analytical fillet weld model using methods proposed in the prior art.
[0060] consider Figure 3 For a fillet weld with a uniform weld leg size *s*, the tensile stress on the plane perpendicular to the weld leg at θ = 90° can be obtained using the above formula. The linear force and moment are solved by the following matrix equations:
[0061] in, These represent the nodal forces along the weld toe line from the first node to the nth node. These represent the element projection lengths corresponding to the first segment to the nth segment in the fractured fillet weld structure. These represent the linear forces corresponding to the first to nth segments in the fractured fillet weld structure. The nodal forces are the equilibrium nodal forces at each node along the weld toe line in the local coordinate system (x, y, z), and are known quantities directly extracted from the finite element analysis results. The element edge projection length is the projection of the element edge length between adjacent nodes along the weld toe line onto the weld direction. The linear force is the linear force per unit length along the weld toe line, and is an unknown quantity to be solved. The matrix is a coefficient matrix composed of element projections. This matrix is established based on the principle of work equivalence. The corresponding linear moment M can be calculated in the same way, simply by replacing the equilibrium nodal forces in the y-direction of the local coordinate system in the matrix formula with the equilibrium nodal moments about the x-axis.
[0062] Linear force (f) on the hypothetical cutting plane at any given angle θx ,f θy ) and line moment (m θz The traction condition represented by ) must satisfy the equilibrium condition within the framework of basic structural mechanics theory, thus yielding:
[0063]
[0064]
[0065] in, Let x be the linear force acting along the x-direction on the imaginary cutting plane. Let be the linear force acting along the y-direction on the imaginary cutting plane. Let be the linear moment acting on the imaginary cutting plane about the z-axis. The linear force in the y-direction at the angle to the cutting plane. The linear force in the x-direction at the angle to the cutting plane. For the angle of the cutting plane, The line spacing in the z-direction under the angle of the cutting plane. for.
[0066] There are two methods for calculating traction stress components. The first method (when the linearized stress result is known) is as follows: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle:
[0067] in, This refers to the thickness of the weld throat. For solder lead size, The angle of the cutting plane.
[0068] Secondly, based on the linearized stress results, weld throat thickness, and cutting plane angle, the membrane component and bending component are calculated:
[0069]
[0070] in, For membrane components, For membrane stress, For shear stress, For the bending component, This represents bending stress.
[0071] Subsequently, based on the membrane component, shear stress, weld bead size, and weld throat thickness, the transverse shear stress is calculated:
[0072] in, This is the transverse shear stress.
[0073] Finally, the normal traction stress is obtained by adding the membrane component and the bending component, and the in-plane shear stress is obtained by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force.
[0074] The second type (when the linear force and line spacing are known) is: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle: .
[0075] Secondly, based on the linear force in the y-direction, the linear spacing in the z-direction, and the weld throat thickness, the membrane component and bending component are calculated:
[0076]
[0077] in, The linear force in the y-direction, The distance between the lines in the z-direction is denoted as .
[0078] Subsequently, the transverse shear stress is calculated based on the linear force in the x-direction and the weld throat thickness:
[0079] in, Let x be the linear force in the x-direction.
[0080] Finally, the normal traction stress is obtained by adding the membrane component and the bending component, and the in-plane shear stress is obtained by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force.
[0081] The formula for calculating the membrane component of the longitudinal shear traction force is:
[0082] in, This represents the membrane component of the longitudinal shear traction force. The formula for calculating the bending component of the longitudinal shear traction force is:
[0083] in, This represents the bending component of the longitudinal shear traction force.
[0084] S5. Iterate through the angles of the cutting plane in the formula to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane.
[0085] The critical failure plane is determined by finding the angle corresponding to the maximum value of the finite traction stress. The finite traction stress is determined by the normal traction stress and the transverse shear stress. The calculation formula for the finite traction stress includes:
[0086] in, For finite traction stress, For normal traction stress, This is the transverse shear traction stress. This is the weighting coefficient, which is typically set to 3.
[0087] Specifically, the traversal method can be implemented using programming software or manual calculation in Excel.
[0088] As a preferred embodiment, the traversal angle ranges from 0° to 90°.
[0089] S6. Perform fatigue life assessment and weld structure optimization based on maximum stress value.
[0090] Specifically, the calculated critical stress is compared with the fatigue strength of the material, or substituted into the fatigue design curve (such as the SN curve) to predict the life, thereby determining whether the current design is safe, or optimizing the weld size.
[0091] The fatigue test specimen involved in this invention is a rectangular hollow section (RHS) fillet weld joint, designed to withstand axial and bending loads. This symmetrical specimen is made by welding two RHS profiles to a central plate, as shown below. Figure 4 As shown. The RHS profile has external dimensions of 120 mm × 80 mm and a wall thickness of 6 mm. The thickness of the intermediate plate is 15 mm. The numerical analysis uses a C3D8 mesh. The structural stress on the weld leg section is calculated based on the nodal forces extracted along the assumed cutting plane. F1 is the applied axial load, and F2 is the applied bending load, both with a magnitude of 1 MPa.
[0092] like Figure 5 As shown, this model utilizes quarter-symmetry to establish a two-dimensional finite element model. Figure 5 This is a schematic diagram of a two-dimensional finite element model of a cross-shaped corner joint geometry utilizing quarter-symmetry. Symmetrical boundary conditions were applied to the left and bottom boundaries of the model. This simulates the existence of the other three-quarters of the complete structure, ensuring that the mechanical behavior of the model is consistent with the complete joint. Modeling only one-quarter of the original joint greatly simplifies the calculations and reduces computational resource consumption.
[0093] Using this analytical method, only the nodal force data of the 90° section at the weld root (a section that is readily available) needs to be extracted to efficiently calculate the stress distribution in the weld throat region at any angle. Detailed distributions of the normal traction stress, transverse shear stress, and in-plane shear stress at the weld throat as a function of angle are presented under typical engineering load conditions.
[0094] like Figure 6 and Figure 7 As shown, the results demonstrate that the stress distribution in the weld throat region calculated using analytical formulas based on nodal force data from the 90° section in this invention agrees well with the analysis results of the high-precision refined finite element model. The stress distribution variation trends at various angles are highly consistent with the refined simulation results, effectively verifying the correctness of the analytical formulas and the reliability of the calculation results. This invention successfully reproduces the complex stress state at the weld throat, while completely avoiding the mesh sensitivity problem present in this region of the traditional finite element method, and significantly improving computational efficiency, providing an efficient and accurate stress analysis method for engineering applications.
[0095] Furthermore, compared with traditional finite element methods that rely on extremely fine meshes, the method of this invention can obtain stable and accurate stress results using only coarse meshes, completely overcoming the mesh sensitivity problem, greatly improving computational efficiency and engineering applicability, and providing a reliable basis for the standardization and intelligent design of weld fatigue assessment.
[0096] Example 2 Based on Example 1, the present invention also provides a stress analysis system for a grid-insensitive fillet weld fracture structure, used to implement the stress analysis method for a grid-insensitive fillet weld fracture structure in Example 1, comprising: The finite element modeling module is used to create structural models that include welded joints. The weld throat area of the structural model is modeled using a simplified approach.
[0097] The load application and solution module is used to apply working loads to the structural model and perform static solutions to obtain the overall stress distribution and nodal force information of the structure.
[0098] The cross-section data extraction module is used to define a cutting path perpendicular to the substrate at the weld root of the model, and extract the stress results of the cutting path based on the overall stress distribution and nodal force information. The stress results include linearized stress results, linear force and linear moment obtained by integration, and the linearized stress results include membrane stress, bending stress and shear stress.
[0099] The analytical calculation module is used to calculate the traction stress components at any cutting plane angle based on the stress results and weld leg size using a set of formulas. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress.
[0100] The critical plane determination module is used to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane by traversing the angles of the cutting plane.
[0101] The fatigue assessment and optimization module is used to assess fatigue life and optimize weld structure based on the maximum stress value.
[0102] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.
[0103] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.
[0104] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.
[0105] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0106] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0107] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.
[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for stress analysis of a mesh-insensitive fillet weld fracture structure, characterized in that, Includes the following steps: A structural model including welded joints was established using finite element software, and the weld throat area of the structural model was modeled using a simplified method. A working load is applied to the structural model, and a static solution is performed on the structural model after the working load is applied to obtain the overall stress distribution and nodal force information of the structure. A cutting path perpendicular to the substrate is defined at the weld root of the model. Based on the overall stress distribution and nodal force information, the stress results of the cutting path are extracted using the post-processing function of the finite element software. The stress results include linearized stress results, line force and line spacing. The linearized stress results include membrane stress, bending stress and shear stress. Based on the stress results and weld leg dimensions, the traction stress components under the cutting plane angle are calculated using a formula. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress. The formula iterates through the angles of the cutting plane to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane. Fatigue life assessment and weld structure optimization are performed based on the maximum stress value.
2. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 1, characterized in that, The calculation of the traction stress component under the cutting plane angle based on the stress results and weld leg size using a formula includes: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle: in, This refers to the thickness of the weld throat. For solder lead size, For the angle of the cutting plane; Secondly, based on the linearized stress results, weld throat thickness, and cutting plane angle, the membrane component and bending component are calculated: in, For membrane components, For membrane stress, For shear stress, For the bending component, For bending stress; Subsequently, based on the membrane component, shear stress, weld bead size, and weld throat thickness, the transverse shear stress is calculated: in, It is the transverse shear stress; Finally, by adding the membrane component and the bending component, the normal traction stress is obtained, and by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force, the in-plane shear stress is obtained.
3. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 2, characterized in that, The formula for calculating the membrane component of the longitudinal shear traction force is as follows: in, The membrane component of the longitudinal shear traction force is given by the following formula: in, This represents the bending component of the longitudinal shear traction force.
4. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 1, characterized in that, The step of calculating the traction stress component under the cutting plane angle using a formula based on the stress results and weld leg size also includes: First, calculate the weld throat thickness based on the weld leg size and the cutting plane angle: ； Secondly, based on the linear force in the y-direction, the linear spacing in the z-direction, and the weld throat thickness, the membrane component and bending component are calculated: in, For membrane components, For the bending component, The linear force in the y-direction, The line spacing in the z-direction; Then, the membrane component and the bending component are added together to calculate the normal traction stress. The formula for calculating the normal traction stress is as follows: in, Normal traction stress; Subsequently, the transverse shear stress is calculated based on the linear force in the x-direction and the weld throat thickness: in, Let x be the linear force in the x-direction; Finally, the in-plane shear stress is obtained by adding the membrane component of the longitudinal shear traction force and the bending component of the longitudinal shear traction force.
5. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 1, characterized in that, The linear force and line spacing are obtained by solving the following formula: in, These represent the nodal forces along the weld toe line from the first node to the nth node. These represent the element projection lengths corresponding to the first segment to the nth segment in the fractured fillet weld structure. These represent the linear forces corresponding to the first to the nth segments in the fracture structure of the fillet weld.
6. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 1, characterized in that, The linear force and spacing at the cutting plane angle satisfy the following equilibrium condition with the linearized stress result: in, The linear force is along the x-direction. The linear force is along the y-direction. Let be the linear moment about the z-axis. The linear force in the y-direction at the angle to the cutting plane. The linear force in the x-direction at the angle to the cutting plane. For the angle of the cutting plane, The line spacing in the z-direction under the angle of the cutting plane. This represents bending stress.
7. The stress analysis method for mesh-insensitive fillet weld fracture structures according to claim 1, characterized in that, The critical failure plane is determined by finding the angle corresponding to the maximum value of the finite traction stress. The finite traction stress is determined by the normal traction stress and the transverse shear stress. The calculation formula for the finite traction stress includes: in, For finite traction stress, For normal traction stress, This is the transverse shear traction stress. These are the weighting coefficients.
8. A stress analysis system for a grid-insensitive fillet weld fracture structure, used to implement the stress analysis method for a grid-insensitive fillet weld fracture structure according to any one of claims 1-7, characterized in that, include: The finite element modeling module is used to create a structural model that includes welded joints, wherein the weld throat region of the structural model is modeled using a simplified method. The load application and solution module is used to apply working loads to the structural model and perform static solutions to obtain the overall stress distribution and nodal force information of the structure. The cross-section data extraction module is used to define a cutting path perpendicular to the substrate at the weld root of the model, and extract the stress results of the cutting path based on the overall stress distribution and nodal force information. The stress results include linearized stress results, linear force and linear moment obtained by integration, and the linearized stress results include membrane stress, bending stress and shear stress. The analytical calculation module is used to calculate the traction stress components at any cutting plane angle based on the stress results and weld leg size using a set of formulas. The traction stress components include normal traction stress, transverse shear stress, and in-plane shear stress. The critical plane determination module is used to determine the critical failure plane and the maximum stress value corresponding to the critical failure plane by traversing the angles of the cutting plane. The fatigue assessment and optimization module is used to assess fatigue life and optimize weld structure based on the maximum stress value.