| In the finite element numerical simulation of rivetless connection, as the deformation of the sheet material increases, the problem of mesh distortion becomes increasingly severe, affecting the accuracy of the calculation results. To address this issue, this paper proposes an improved material point method (MPM) based on point-to-surface contact for numerical simulation analysis of rivetless connection processes. Based on the models and process parameters from existing literature, simulations were conducted using both the MPM and the finite element method (FEM), and a comparative analysis was performed on the joint morphology and stress cloud images. The results show that the joint morphology and stress cloud images obtained from both methods have a high degree of similarity, thereby validating the correctness of the improved MPM in handling contact problems. During the numerical simulation of rivetless connection with a groove structure at the bottom of the punch, in addition to mesh distortion, the FEM also exhibited the defect of partial mesh overlap. In response to this phenomenon, this paper analyzed the material flow and forming mechanism during the connection process and used both the MPM and the FEM to study the connection of the sheet material and the mold under different friction coefficients. As the friction coefficient decreases, the mesh overlap defect in the FEM is significantly improved, while the MPM remains free of overlap defects. The trends of the joint interlock value and neck thickness value obtained from both methods are consistent, with the maximum relative error 7.4%. The improved MPM proposed in this paper provides a new approach for rivetless connection and other metal forming processes. |
