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Spot-welded joints was wiedly used in vehicle body structure welding. Car body structure as the most important part of vehicle stiffness, the life of the car, due to the process through a variety of working conditions, their own needs to withstand the force generated by a variety of loads. Spot welding structure must be correctly calculated, the analysis works reliably fatigue failure, dynamic and impact response and structural optimization. However, there is still a lack of reliable non-destructive testing methods, quality of welding process can only rely on destructive testing of specimens and artifacts to examine, as well as by a variety of monitoring techniques to guarantee. If the welding process simulation approach adopted to calculate the reliability of the welding quality, then, because there are a lot of car body joints, using a detailed finite element model to simulate the huge workload, the project is very difficult to implement, and in modeling of the metal in the melting and solidification, the complex structure itself will not be reflected. For this reason, most of today using the simplified model to analyze the spot welding. In order to meet the requirements analysis and calculation, simplified connection model must be able to display for the very precise spot on the connected load, stress and deformation, with a more accurate three-dimensional solid model structure comparison.To this end, this paper describes the spot through the careful study of several types of simplified finite element structural connection model, the completion of several mesh refinement and refining the results, and compare the three-dimensional finite element model were evaluated. Considering various loading conditions and welding parameters, the evaluation is relatively rigid structure on the basis of welding done here also provides some detailed error analysis.First, the use of CATIA to establish 4 spot welding connections simplified model, (a) single-bar model, (b) radial bar model, (c) composite rigid bar model and (d) solid model. Most models are in use today spot the 4 model described above to those patterns. Then the finite element model a variety of optimization of each grid, the grid the more refined the more accurate finite element solution.Second, the production of experimental samples. Because in order to reduce the amount of calculation and results of the tests at the same time credible, so select the above four forms of the simplified model produced in the three test pieces. Each produce a simplified model corresponds to the sample, and samples must be able to reflect what it stands for spot welding the structural characteristics of the simplified model, simplified model of these three samples as a group. Will produce three groups of samples, only three groups of samples is different from the flat sheet size, for convenience, they are called sample 1, sample 2 (which the sample size in the plane 1,2 times) and sample 3 (they are sample size in a plane 10 times.) Thickness of the sample plate 2mm, nugget diameter 6mm (weld nugget region by the cylindrical representation).Finally, four different specimens of each level of mesh refinement, a basic grid of 8 elements in the circumferential direction, the second refining elements generated 2 times the base mesh, the element in order to double fourth grid refinement. This model is used to observe the spot when the grid refinement is not the main source of simplification error. Applied to each specimen in five basic load, because the general conditions are available under the 5 that a linear combination of base load. These conditions are called load 1 (tension), load 2 (out-plane distortion), load 3 (out-plane bending), load 4 (plane distortion), load 5 (shear plane). Then take the specimen the displacement data, a detailed comparison with the three-dimensional model to evaluate the three simplified model system for spot welding performance of rigid structure.It was found that most of the simplified model and detailed analysis of welded mesh in tension, torsion, and bending plane has good accuracy. However, the in-plane torsion and shear plane under the conditions of the analysis will produce a large error, even with a more detailed mesh.The paper refers to examples from weizhi V2 vehicles which top and side welded jionts has split and Xiali N5 vehicles suspension spring bearing solder split problems to demonstrate the accuracy of the results of the this study, and its practicability. And summarized to full text, discussed the future research direction.
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