A collision simulation method for automobile cold metal transition welding connection

Abstract

The present invention relates to a collision simulation method for automobile cold metal transition welding connection, including sample-level joint mechanical property test; cold metal transition welding joint process simulation; cold metal transition welding joint model establishment; adjusting the node thickness to make the simulation model thickness consistent with the process simulation result; cold metal transition welding simplified model establishment and calibration, to obtain the cold metal transition welding simulation failure model. The simulation method of the present invention provides a detailed joint failure model, combined with the different material settings of the base material and the affected area, it can accurately simulate the mechanical property non-uniformity of the cold metal transition welding joint; the parameters used are all obtained from sample blocks, component tests and simulation calibration, to ensure that the present invention is easy to implement, by adjusting a small number of parameters, it can quickly realize the simulation of cold metal transition welding joints with different process parameters; it can accurately simulate the failure process of the cold metal transition welding joint of the vehicle body in the collision of the whole vehicle, to guide the development of the safety performance of the vehicle body connection.

Description

Technical Field

[0001] The invention belongs to the technical field of finite element analysis, and in particular relates to a collision simulation method for automobile cold metal transition welding connection. Background Art

[0002] Aluminum alloy structural parts in the car body are mostly connected by welding. Cold metal transition welding (CMT) is the best choice for aluminum alloy welding due to its advantages such as small heat input and small welding deformation. The strength of the cold metal transition welding joint of the car body directly affects the overall collision safety of the car. Therefore, the key to ensuring the impact resistance and collision safety of the vehicle is to ensure that the strength of the welding joint meets certain engineering requirements. As far as the current joint forms of aluminum alloy body structural parts are concerned, there are mainly lap joints, corner joints and butt joints. These joint forms are also the key issues that need to be considered when the car body collides.

[0003] The existing simulation methods for cold metal transition welding joints mainly include the common node method, rigid unit connection method, beam unit connection method and solid unit modeling method. Among them, the common node method and rigid unit connection method have the characteristics of no failure, while the beam unit connection method and solid unit modeling method can simulate the failure of the connection point, but cannot accurately simulate the non-uniformity of the mechanical properties of the cold metal transition welding joint. The overall accuracy of the existing simulation methods is less than 50%. With the popularization of cold metal transition welding technology, it is particularly important to develop a high-accuracy joint simulation method. Summary of the invention

[0004] The purpose of the present invention is to provide a CAE simulation method of a car body cold metal transition weld joint with high computational stability and high accuracy, so as to solve the problem of low CAE simulation accuracy of the existing car body cold metal transition weld joint. This method uses LS-DYNA software and uses shell elements to characterize the performance of the base material and the weld joint area respectively, thereby realizing accurate simulation of the cold metal transition weld connection in the automobile collision condition.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A collision simulation method for automobile cold metal transition welding connection comprises the following steps:

[0007] A. Mechanical properties test of sample-level joints

[0008] The mechanical characteristic parameters of cold metal transfer welding joints were obtained through sample tests under three working conditions: lap joint, fillet joint and butt joint.

[0009] B. Cold metal transition welding process simulation

[0010] Obtain the molten pool morphology and temperature distribution through process simulation;

[0011] C. Establishment of cold metal transfer welding joint model

[0012] The shell element model is established and the model is divided into the base metal area and the welding joint area according to the process simulation temperature distribution;

[0013] D. Adjust the node thickness to make the simulation model thickness consistent with the process simulation result;

[0014] E. Establishment and calibration of simplified model of cold metal transition welding

[0015] A simplified shell unit model was established, and relevant parameters were adjusted and optimized until the CORA fitting degree of the simulation and experimental force-displacement curves reached more than 90%, and the aging area was ensured to be consistent with the experiment, so as to obtain the simulation failure model of cold metal transition welding.

[0016] Furthermore, in step A, the mechanical characteristic parameters of the cold metal transition welding joint are obtained by a multifunctional tensile testing machine.

[0017] Furthermore, in step A, the mechanical characteristic parameters are load-displacement mechanical characteristic parameters.

[0018] Furthermore, step B is specifically as follows: establishing a cold metal transition welding process forming simulation model, carrying out cold metal transition welding forming process simulation, and obtaining the joint molten pool morphology and temperature distribution diagram.

[0019] Furthermore, step C is specifically as follows: according to the joint sample geometry file, the mesh is divided, the model is modeled using a fully integral shell element, and according to the process simulation temperature distribution diagram, the sample is divided into two parts, namely, a base material and a welding joint area, to establish a cold metal transition welding joint model.

[0020] Furthermore, the mesh size is 1.2 mm.

[0021] Furthermore, according to the process simulation temperature distribution diagram, the area where the temperature difference with the edge area is greater than 200°C is the welding joint area, and the rest is the base material area.

[0022] Furthermore, in step D, the node thickness is adjusted specifically by adjusting the node thickness of the model welding joint area according to the process simulation molten pool morphology.

[0023] Furthermore, the element node thickness can be adjusted via the ELEMENT_SHELL_THICKNESS keyword.

[0024] Furthermore, in step E, the specific steps of adjusting and optimizing relevant parameters are: based on the parameters of the parent material, appropriately adjusting the material parameters, assigning the materials to the welding joint area respectively, carrying out calibration, and adjusting the material parameters of the upper joint area.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Compared with the existing simulation methods of common nodes and rigid unit connections, the simulation method of the present invention provides a detailed joint failure model, which can accurately simulate the inhomogeneity of mechanical properties of cold metal transition welding joints by combining different material settings of the parent material and the affected area;

[0027] 2. The parameters used in the present invention are all obtained from sample blocks, component tests and simulation calibration, which ensures that the present invention is easy to implement. By adjusting a small number of parameters, the simulation of cold metal transition welding joints with different process parameters can be quickly realized;

[0028] 3. The present invention can accurately simulate the failure process of the cold metal transition welding joint of the vehicle body in the collision of the whole vehicle, so as to guide the development of the safety performance of the vehicle body connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a flow chart of the method of the present invention;

[0031] Figure 2 It is a simplified model schematic diagram of the splicing joint in the present invention;

[0032] Figure 3 This is a simplified model schematic diagram of the corner joint in the present invention;

[0033] Figure 4 It is a schematic diagram of a simplified model of a butt joint in the present invention;

[0034] Figure 5a-5c Molten pool morphology. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with embodiments:

[0036] like Figure 1 As shown, the collision simulation method of automobile cold metal transition welding connection of the present invention uses the shell unit in LS-DYNA software to characterize the mechanical properties of the base material and the welding joint area, and combines the relevant mechanical characteristic parameters of the base material and the joint area, through keyword parameters, heat-affected zone range and material mechanical property attenuation degree, grid size, etc. to achieve accurate simulation of cold metal transition welding connection in automobile collision conditions. It includes the following steps:

[0037] The first step is to test the mechanical properties of the sample joint

[0038] Joint specimens of three working conditions, lap joint, corner joint and butt joint, were prepared, and the mechanical characteristic parameters of the cold metal transition welding joint were obtained by a multifunctional tensile testing machine.

[0039] The second step is the cold technology transition welding forming process simulation

[0040] A cold metal transition welding process forming simulation model is established, and cold metal transition welding forming process simulation is carried out to obtain the joint molten pool morphology and temperature distribution diagram.

[0041] Step 3: Establish the cold metal transfer welding joint model

[0042] According to the joint sample geometry file, the mesh is divided with a mesh size of 1.2 mm and the fully integrated shell element is used for modeling. According to the process simulation temperature distribution diagram, the sample is divided into two parts: the base material and the welding joint area, and the cold metal transition welding joint model is established.

[0043] Step 4: Adjust the thickness of the cold metal transition welding joint model

[0044] According to the process simulation molten pool morphology, the node thickness of the model welding joint area is adjusted to make the thickness distribution of the simulation model consistent with the process simulation results.

[0045] Step 5: Cold Metal Transfer Welding Model Calibration

[0046] Carry out calibration of detailed models and joint mechanical properties results. Based on the parameters of the parent material, adjust the material parameters appropriately and assign the materials to the welding joint area. Carry out calibration and adjust the material parameters of the upper joint area until the CORA fit between the force-displacement curves of the three joint simulation models and the test results reaches more than 90%, and the failure position of the simulation model is consistent with the test.

[0047] Example 1

[0048] A collision simulation method for automobile cold metal transition welding connection comprises the following steps:

[0049] 1. Carry out sample-level joint mechanical property tests, and obtain the load-displacement mechanical characteristic parameters of cold metal transition welding joints through sample tests under three working conditions: lap joint, corner joint, and butt joint.

[0050] 2. Carry out process forming simulation of three joints to obtain the molten pool morphology after welding of three joints, as shown in Figure 5, and the temperature distribution after welding. Compared with the traditional method of physical cutting and measuring the sample, by carrying out process simulation, the geometric shape of the joint molten pool morphology can be obtained more accurately to obtain a more accurate simulation model, and at the same time, the cost of sample cutting can be reduced.

[0051] 3. According to the size of the joint sample, divide the grid in the Hypermesh software and establish a simulation model. The model is modeled with fully integrated shell elements. In order to balance the calculation accuracy and efficiency, the unit size is 1.2mm. The detailed model is divided into two parts: the base material and the welded joint. The partition is based on the process simulation temperature distribution map. The welded joint area is greater than 200°C from the edge area, and the rest is the base material area. The selection of mesh size and unit type ensures that both accuracy and efficiency are taken into account; partitioning based on the process simulation cloud map can ensure the accuracy of the partition boundary; the sample is divided into two parts: the base material and the welded joint area, which ensures the simplicity and usability of the simulation model and improves the calculation efficiency.

[0052] 4. According to the process simulation molten pool morphology, the ELEMENT_SHELL_THICKNESS keyword is used to adjust the unit node thickness so that the thickness distribution of the simulation model welding joint area is consistent with the process simulation model. By adjusting the node thickness, the consistency of the simulation model and the sample size can be guaranteed to the greatest extent, so that the complex geometric shape represented by the shell unit meets the requirements.

[0053] 5. Based on the parameters of the parent material, adjust the material parameters appropriately and assign the materials to the welding joint area. Carry out calibration and adjust the material parameters of the upper joint area until the CORA fitting degree of the force-displacement curve of the three joint simulation models and the test results is ≥90%, and the failure position of the simulation model is consistent with the test. Obtain the simulation failure model of cold metal transition welding.

[0054] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A collision simulation method for automobile cold metal transition welding connection, characterized in that: The following steps are involved: A. Mechanical properties test of sample-level joints The mechanical characteristic parameters of cold metal transfer welding joints were obtained through sample tests under three working conditions: lap joint, fillet joint and butt joint. B. Cold metal transition welding process simulation The molten pool morphology and temperature distribution are obtained through process simulation; specifically: a cold metal transition welding process forming simulation model is established, cold metal transition welding forming process simulation is carried out, and the molten pool morphology and temperature distribution diagram of the joint are obtained; C. Establishment of cold metal transfer welding joint model Establish a shell unit model and divide the model into the base metal area and the welding joint area according to the process simulation temperature distribution; specifically: divide the mesh according to the joint sample geometry file, use the full integral shell unit modeling, and divide the sample into two parts, the base metal and the welding joint area according to the process simulation temperature distribution map, and establish the cold metal transition welding joint model; D. Adjust the node thickness to make the simulation model thickness consistent with the process simulation result; E. Establishment and calibration of the simplified model of cold metal transition welding A simplified shell unit model was established, and relevant parameters were adjusted and optimized until the CORA fitting degree of the simulation and experimental force-displacement curves reached more than 90%, and the aging area was ensured to be consistent with the experiment, so as to obtain the simulation failure model of cold metal transition welding.

2. The collision simulation method for automobile cold metal transition welding connection according to claim 1 is characterized in that: Step A: The mechanical characteristic parameters of the cold metal transition welding joint are obtained by a multifunctional tensile testing machine.

3. The collision simulation method for automobile cold metal transition welding connection according to claim 1 is characterized in that: In step A, the mechanical characteristic parameters are load-displacement mechanical characteristic parameters.

4. The collision simulation method for automobile cold metal transition welding connection according to claim 1 is characterized in that: The mesh size is 1.2 mm.

5. The collision simulation method for automobile cold metal transition welding connection according to claim 1 is characterized in that: The temperature distribution diagram of the process simulation is used for zoning. The area with a temperature difference of more than 200°C from the edge area is the welding joint area, and the rest is the base material area.

6. The collision simulation method for automobile cold metal transition welding connection according to claim 1, characterized in that: Step D, the adjustment of the node thickness is specifically: adjusting the node thickness of the model welding joint area according to the process simulation molten pool morphology.

7. The collision simulation method for automobile cold metal transition welding connection according to claim 6 is characterized in that: The thickness of element nodes can be adjusted using the ELEMENT_SHELL_THICKNESS keyword.

8. The collision simulation method for automobile cold metal transition welding connection according to claim 1 is characterized in that: Step E, the specific steps of adjusting and optimizing relevant parameters are: based on the parameters of the parent material, appropriately adjust the material parameters, assign the materials to the welding joint area respectively, carry out calibration, and adjust the material parameters of the upper joint area.

Images