A method for quickly calculating mechanical properties of arc-welded structural members

Abstract

The application provides a quick calculation method for mechanical properties of arc-welded structural members, and the steps include: determining arc-welding process parameters to obtain inherent strain library; dividing the grid of the welding member, defining the mechanical parameters of the material, creating a heat-affected zone node group to record all nodes of the heat-affected zone of the welding member, and creating a welding path positioning node group to record each positioning point on the welding path; creating a process file to record the type and direction of the welding path of all welds and the welding sequence; developing an inherent strain library calling program, according to the coordinates of all weld positioning points and the coordinates of the positioning points in the inherent strain library, interpolating the inherent strain in the inherent strain library to the nodes of the heat-affected zone of the welding member as boundary conditions according to the welding path and the welding sequence in the process file; starting a finite element calculation solver to read the grid, material parameters and boundary conditions to complete the calculation and obtain the mechanical properties of the welding member. The application has the advantages of fast calculation speed, high precision and convenience for modular industrial software application.

Description

Technical Field

[0001] This invention belongs to the field of welding mechanics analysis, specifically a rapid calculation method for the mechanical properties of arc-welded structural components. Background Technology

[0002] Arc welding is a process that first utilizes the heat and melting of the material caused by the approach of an electric arc, and then utilizes the cooling and solidification of the material after the arc is removed to achieve material bonding. It is one of the most widely used, efficient, and important fusion welding processes. The stress and deformation laws of arc welding of complex components are complex, and the main analysis and prediction methods include: thermo-elastic-plastic simulation methods and inherent strain methods.

[0003] Mesh-based finite volume methods and finite element methods are the most effective methods for fluid-thermal-mechanical coupling analysis of deformation and stress, providing highly accurate deformation and stress calculation results for complex components. However, to obtain highly accurate calculation results, a massive number of mesh elements and time load steps that match the mesh density and conform to the welding path and sequence are required. This results in high computational costs, which is not conducive to large-scale numerical sampling, process planning, and engineering application.

[0004] The inherent strain method primarily uses the coefficient of linear expansion as a process parameter, applied to the weld location of complex components, and then obtains the overall deformation and stress of the weldment through the finite element method. Compared with the thermo-elastic-plastic simulation method, it has high computational efficiency and short cycle time. However, its drawback is that it sets the strain distribution in the weld zone as a uniform value—the coefficient of linear expansion. This not only fails to accurately represent the residual strain state at various locations in the fusion weld zone, but also cannot simulate the welding path and welding sequence, thus limiting the accuracy of mechanical property calculations for arc-welded structural components. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid calculation method for the mechanical properties of arc-welded structural components. Based on welding process parameters and geometric parameters of the welded structural components, a geometric model of the complex weldment is established and meshed. A node group of welding path positioning points is created. According to the node coordinates of the positioning points, the inherent strain in the inherent strain library is interpolated onto the nodes of the heat-affected zone of the weldment according to the welding path and welding sequence in the process document, and mechanical calculation is performed to maximize the balance between calculation accuracy and efficiency.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] Step 1: Determine the arc welding process parameters and obtain the inherent strain library of these welding process parameters, including the coordinates of the positioning points, discrete points, and plastic strain indices of the weld and heat-affected zone.

[0008] Step 2: Establish the geometric model of the welded component, including the weld seam, mesh it, define the material parameters of the weldment and the weld seam, and generate the finite element analysis input file;

[0009] Step 3: In the finite element analysis input file, create a heat-affected zone node group to record all nodes in the heat-affected zone, and a welding path positioning point node group to record each positioning point on the welding path. Group, name, and number the above positioning points according to the welding path type.

[0010] Step 4: Create process documents to record the welding path type, welding direction, and welding sequence for all welds;

[0011] Step 5: Develop an inherent strain library calling program. According to the path type, welding direction and welding sequence in the process file of Step 4, interpolate the data in the inherent strain library of Step 1 to the corresponding nodes of the heat-affected zone in the weldment mesh model, and write the inherent strain index of the complex weldment as the displacement constraint of the corresponding node in the heat-affected zone.

[0012] Step 6: Start the finite element calculation solver, input the finite element analysis input file successfully processed in steps 3 and 5, perform a calculation, and obtain the mechanical properties of the complex weldment.

[0013] Compared with the prior art, the present invention has the following significant advantages:

[0014] (1) The calculated distribution of inherent welding strain in complex weldments is more accurate. The two-dimensional data in the inherent strain library are two-dimensional nodal displacements with anisotropic strain states. Combined with the normal of the weld, the strain state in three directions on any cross section of the weld in complex weldments can be determined simultaneously.

[0015] (2) By applying the inherent strain of welding in a reasonable manner, the computational efficiency is higher than that of the pure thermo-elastic-plastic finite element analysis method, which greatly reduces the calculation cost of the mechanical properties of complex welded components. In addition, the calculation accuracy is higher than that of the inherent strain method with defined linear expansion coefficient.

[0016] (3) Modular industrial applications are more standardized. Various inherent strain parameters of arc welding are calculated in advance, a rich knowledge base of arc welding process is built, and an interface compatible with commercial software file formats is developed. For welds of complex components, loading is performed according to process type, welding path and sequence, which is more in line with the standardized requirements of modular calling of industrial software. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method proposed in this invention.

[0018] Figure 2This is a schematic diagram of the complex weldment, weld, and weld cross-section in the embodiment.

[0019] Figure 3 The data format of the inherent strain library in the embodiment is shown.

[0020] Figure 4 The solid element mesh for complex weldments and welds in the embodiment is shown.

[0021] Figure 5 The examples show the element type, node, mesh field, and welding path node group field in the finite element analysis input file.

[0022] Figure 6 The fields for part contact surface, heat-affected zone, and welding path in the welding process file of the embodiment are shown.

[0023] Figure 7 The coordinates of key points on the surface of the actual weldment obtained through experiments and the methods in this invention are shown in the examples. Detailed Implementation

[0024] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0025] Figure 2 This is a complex weldment, formed by welding four bent thin plates 1, 2, 3, and 4 and a disc-shaped thin plate 5 using shielded metal arc welding (SMAW) and intermittent welding. After welding, four welded joints 6, 7, 8, and 9 are formed. Taking welded joint 9 as an example, this joint includes two continuous welds, one long and one short. The welding paths of the long weld include: fixed-axis rotation paths 9-2, 9-4, 9-6, 9-10, 9-12, and 9-14; circular arc movement paths 9-1, 9-5, and 9-11; and linear movement paths 9-3 and 9-13. The welding paths of the short weld include: fixed-axis rotation paths 9-7 and 9-9; and circular arc movement path 9-8. Planar region 10 shows the cross-sectional shape of these welds. The weldment material is 304L stainless steel, the welding voltage U is 27V, the welding current I is 65A, and the electrode movement speed v is 12mm / s. The electrode type is E308-16, and the electrode thermal efficiency η is taken as 0.80.

[0026] Combination Figure 1 The present invention provides a rapid calculation method for the mechanical properties of arc-welded structural components, comprising the following steps:

[0027] Step 1: Based on the arc welding process parameters, obtain the inherent strain library based on the arc welding process parameters. This mainly includes the coordinates of the positioning points, discrete points, and plastic strain indices of the weld and heat-affected zone. (Refer to...) Figure 3 .

[0028] Step 2: Establish the geometric model of the welded component, including the weld seam, with a mesh as follows: Figure 4 As shown, the material parameters of the weldment and weld are defined as follows: elastic modulus, Poisson's ratio, and density are 200 GPa, 0.3, and 7.93 g / cm³, respectively. 3 This generates a finite element analysis input file, which contains information such as nodes, elements, materials, and boundary conditions.

[0029] Step 3: Configure the finite element analysis input file from Step 2 as follows: Create a node group and an element group for each part and weld, for a total of 9 node groups and 9 element groups; create an element group for the heat-affected zone, for a total of 8 element groups; create 1 node group for this heat-affected zone; define corresponding node groups for each weld path, with each weld having 2 circular paths, 2 straight paths, and 4 fixed-axis rotation paths. Refer to the reference for the positioning point node groups of the welding path in the finite element input file. Figure 5 . Figure 5 The fields GCIRLCE, GLINE, and GROTATE represent three path types: circular motion, linear motion, and fixed-axis rotation, respectively.

[0030] Step 4: Create the process document for the complex weldment, referring to... Figure 6 Among them, the field weld_area represents the welding heat-affected zone; the numbers 8, 8, and 32 following the fields arc_area, line_cmp, and rotate_cmp represent the number of the three welding paths in the weldment: circular movement, linear movement, and fixed-axis rotation, respectively; the fields GCIRLCE, GLINE, and GROTATE represent the three path types: circular movement, linear movement, and fixed-axis rotation, respectively, and the numbers following them represent the welding direction and sequence.

[0031] Step 5: Using Fortran and batch processing languages, develop an application program that integrates the process documents and finite element analysis input files to form an inherent strain library calling program. The program's steps are as follows: Following the welding path types, welding directions, and welding sequences (circular movement, linear movement, fixed-axis rotation, etc.) in the process documents from Step 4, iterates through the finite element analysis input files from Step 3. Figure 5 The positioning points in the node group shown in the black box are transformed by translating and rotating the inherent strain library constructed in step 1. Figure 3 The location point in the inherent strain library coincides with the current location point in step 3. Through nearest-point interpolation, the inherent strain index is written as the displacement constraint of the corresponding node in the heat-affected zone of the welded component. After traversal is complete, the boundary conditions for mechanical calculation (displacement constraints of the heat-affected zone) are formed and added to the finite element analysis input file in step 2. Besides nearest-point interpolation, other methods such as linear interpolation of adjacent points and nonlinear interpolation are also applicable to this step.

[0032] Step 6: Start the ANSYS solver, read the finite element analysis input file successfully processed in steps 3 and 5, perform a calculation, and obtain the mechanical properties of the complex weldment.

[0033] The creation of the inherent strain library took 6 days, and the loading of inherent strain and subsequent mechanical property calculation took 40 minutes. It is not difficult to find that after obtaining the inherent strain library of the arc welding process, the calculation method in this invention can greatly improve the calculation efficiency for complex components with many welds.

[0034] To reveal the calculation accuracy of this invention, the influence of part fitting error on the calculation results was introduced, and simulation and experimental verification were carried out respectively. Two rows of key points at different heights were extracted from the surface of the complex weldment for result comparison. Figure 7 This is a view showing the coordinates of two rows of key points in the global view and their magnified local view. Based on the projection scale of the key points on the projection plane, the error between the experimental and simulation results is no more than 0.4 mm, indicating good agreement.

[0035] The above process is a modular program developed using the nearest point interpolation algorithm, ANSYS finite element model, and APDL file specification system. Programs using other programming languages ​​and finite element software are also within the scope of protection of this invention.

Claims

1. A rapid calculation method for the mechanical properties of arc-welded structural components, characterized in that, Includes the following steps: Step 1: Determine the arc welding process parameters and obtain the inherent strain library of these welding process parameters, including the coordinates of the positioning points, discrete points, and plastic strain indices of the weld and heat-affected zone. Step 2: Establish the geometric model of the welded component, including the weld seam, mesh it, define the material parameters of the weldment and the weld seam, and generate the finite element analysis input file; Step 3: In the finite element analysis input file, create a heat-affected zone node group to record all nodes in the heat-affected zone, and a welding path positioning point node group to record each positioning point on the welding path. Group, name, and number the above positioning points according to the welding path type. Step 4: Create process documents to record the welding path type, welding direction, and welding sequence for all welds; Step 5: Develop an inherent strain library calling program. According to the path type, welding direction and welding sequence in the process file of Step 4, interpolate the data in the inherent strain library of Step 1 to the corresponding nodes in the heat-affected zone of the weldment mesh model, and write the inherent strain index of the weldment as the displacement constraint of the corresponding node in the heat-affected zone. Step 6: Start the finite element calculation solver, input the finite element analysis input file successfully processed in steps 3 and 5, perform a calculation, and obtain the mechanical properties of the weldment.

2. The rapid calculation method for the mechanical properties of arc-welded structural components according to claim 1, characterized in that, The path types in step 4 include circular movement, linear movement, and fixed-axis rotation.

3. The rapid calculation method for the mechanical properties of arc-welded structural components according to claim 1, characterized in that, The procedure for calling the inherent strain library in step 5 is as follows: according to the welding direction and welding sequence in the process file of step 4, traverse each positioning point on each welding path in the finite element analysis input file of step 3, perform translation and rotation of the inherent strain data, so that the positioning point in the inherent strain data coincides with the current positioning point on the welding path in the finite element analysis input file of step 3, and interpolate the data in the inherent strain library to the corresponding position in the heat-affected zone of the weldment through a numerical interpolation algorithm. After the traversal is completed, the inherent strain index of the heat-affected zone of the weldment is written as the displacement constraint of the heat-affected zone and added to the finite element analysis input file in step 2.

4. The rapid calculation method for the mechanical properties of arc-welded structural components according to claim 1, characterized in that, Steps 5 and 6 involve using a computer program to automatically apply the inherent strain as the displacement constraint boundary condition of the finite element analysis model of the weldment based on the inherent strain library, process documents, welding and welding path positioning point node group, and finally start the finite element calculation solver to calculate the mechanical properties of the weldment.

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