EFFECTS OF SPOT WELD CONNECTING MODELS ON THE PREDICTION ACCURACY OF STRUCTURAL STIFFNESS BY FINITE ELEMENT ANALYSIS

For complex structures such as automotive bodies, the finite element analysis and prediction accuracy of their stiffness and eigen-frequencies (representing dynamic stiffness) are usually greatly influenced by the selected modeling methods for large amount of spot welds. Based on two analytical models, this paper investigates effects of spot weld connecting models (SWCMs), together with their respective meshing-scheme- dependent properties, on the FE analysis and prediction accuracy of local structural stiffness. It is found that SWCMs affect stiffness prediction mainly through the spreading area of the force transmitted by a spot weld. Enlarging local mesh size of a spot weld will result in increased local stiffness prediction for direct SWCM. But for RBE3 SWCM, the effects is more complicated and opposite results may be observed due to extra influencing factors such as the relative positioning of spot weld center point and local meshes. Enlarging spot weld diameter also results in increased local stiffness prediction for RBE3 SWCM, while the variation sensitivity may reach a minimum by properly adjusting local meshing scheme. Several finite element modeling schemes and corresponding stiffness and vibration mode analysis results of a double-hat welded thin-walled beam structure are discussed, which demonstrates the effectiveness of the proposed analytical analysis methods and the correctness of related conclusions.