Prediction of Spot Weld Failure for Automotive Steels
Spot weld failure has a great influence on the crashworthiness of a vehicle since an automotive body is mostly assembled by spot welding. Spot weld failure was not a serious problem when using low strength steel, but as the strength of steels increases, spot weld failure became a hot issue for crash performance due to the low spot weld strength compared to material strength. Nowadays, the car design is based on CAE, and the crashworthiness is evaluated from crash simulation. Spot weld failure is a critical factor causing the discrepancy between the actual crash performance and simulation result. Of course, car designers want to get accurate simulation results and design to avoid spot weld failure based on simulation. There are a lot of studies on spot welding failure, but It is necessary to further enhance the accuracy. In this paper, we study how to predict accurate spot weld failure by macroscopic analysis of spot weld failure. Normal, shear, bending, and torsional load components act on spot welds, and many spot weld failure model consider that they act independently, destroying the spot weld. In this paper, normal and bending load components are considered together because loading direction and plane of normal and bending components are same. Spot weld failure model that normal and shear load components act independently and there is the interaction of normal and bending components, is newly proposed. Here, torsional component is ignored because of low influence on an automotive body. Spot weld failure tests are performed for various automotive steels, and coefficients of spot weld failure models are derived. Since an automotive body has mostly heterogeneous stack-ups of the strength and the thickness, the spot welding failure tests for heterogeneous stack-ups are also performed and it is verified that the new model describes dissimilar stack-ups well. Compared to conventional models, the new model has an advantage in the simplicity and the accuracy. Finally, the predicting method of coefficients of spot weld failure models is developed to consider spot weld failure in the crash simulation without experiments.
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Prediction of Spot Weld Failure for Automotive Steels
Spot weld failure has a great influence on the crashworthiness of a vehicle since an automotive body is mostly assembled by spot welding. Spot weld failure was not a serious problem when using low strength steel, but as the strength of steels increases, spot weld failure became a hot issue for crash performance due to the low spot weld strength compared to material strength. Nowadays, the car design is based on CAE, and the crashworthiness is evaluated from crash simulation. Spot weld failure is a critical factor causing the discrepancy between the actual crash performance and simulation result. Of course, car designers want to get accurate simulation results and design to avoid spot weld failure based on simulation. There are a lot of studies on spot welding failure, but It is necessary to further enhance the accuracy. In this paper, we study how to predict accurate spot weld failure by macroscopic analysis of spot weld failure. Normal, shear, bending, and torsional load components act on spot welds, and many spot weld failure model consider that they act independently, destroying the spot weld. In this paper, normal and bending load components are considered together because loading direction and plane of normal and bending components are same. Spot weld failure model that normal and shear load components act independently and there is the interaction of normal and bending components, is newly proposed. Here, torsional component is ignored because of low influence on an automotive body. Spot weld failure tests are performed for various automotive steels, and coefficients of spot weld failure models are derived. Since an automotive body has mostly heterogeneous stack-ups of the strength and the thickness, the spot welding failure tests for heterogeneous stack-ups are also performed and it is verified that the new model describes dissimilar stack-ups well. Compared to conventional models, the new model has an advantage in the simplicity and the accuracy. Finally, the predicting method of coefficients of spot weld failure models is developed to consider spot weld failure in the crash simulation without experiments.
Lim_POSCO.pdf
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