多点拘束を利用したスポット溶接部の簡易モデルとその動的特性

概要

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In this paper, we focus on the ACM2 (Area Contact Model 2) model as a simplified spot weld model for the vibration analysis and reveal its dynamic characteristics. For the ACM2 model, a spot weld is modeled with a single solid element and the upper and lower plates are modeled with shell elements. The solid element and the shell elements are connected using multi-point constraint (MPC). First, the theory of MPC equations used in the ACM2 model is explained. Next, the effects of meshing of the plate surrounding the spot weld on the modal properties (natural frequency and mode shape) are examined in detail. Finally, a proper mesh size in the area of the spot weld is presented. As an example structure, the structure that consists of two steel plates jointed by three spot welds is used. The results show that the size and configuration of the patch (the group of shell elements in the ACM2 model) significantly affect the modal properties. When the centers of solid element and patch are coincident, the natural frequencies monotonically increase with patch size. When the centers of solid element and patch are not coincident and the element size is large, the natural frequencies vary widely. When the shell element size in the patch is equal or less than the solid element size that is determined by the spot weld diameter, the variation in the natural frequencies is small.