SAE International Application of Spot Weld and Sheet Metal Failure Prediction to Non-Linear Transient Finite Element Analysis of Automotive Structures 2009-01-0352

In early design phases vehicle safety testing has revealed the occurrence of both spot weld failure and sheet metal tearing that contributed to below specification performance. This would require redesign and additional testing to meet the specification. Because of cost and weight requirements in vehicle development, it is desirable to create efficient body designs for vehicle safety performance. To develop more efficient structures, it is useful to be able to predict both connection and material failure in a variety of loading conditions using finite element (FE) models. Two new FE methodologies were developed separately to aid in predicting these phenomena. Since it is a widely used explicit FE code, LS-DYNA 2x was chosen as the program with which to implement the new material and spot weld models. One methodology uses a force based failure criteria to model failure in, and next to, spot welds. A second methodology was developed to predict sheet material failure using the Forming Limit Diagram (FLD) for ferrous materials. These methodologies were confirmed separately using simple FE models and compared to actual test results. After each methodology was confirmed separately, the two new FE techniques were used in concert to predict automotive structural behavior with combined spot weld failure and sheet metal tearing present.