Application of a locking-free element in modeling of joining by clinching

Mechanical clinching is recognized as a promising industrial technique to join dissimilar metal sheets by cold forming. In this technique, the metallic layers are joined by local hemming with a punch and die. The present paper aims at providing a finite element model for the mechanical clinching processes. To accomplish this, a locking-free element formulation (Q1SP) is employed which is essentially based on the reduced integration technique with hourglass stabilization. The performance of Q1SP element against locking is first demonstrated through a benchmark test. Then, a finite element model for the clinching process is developed. It is shown that the Q1SP element can efficiently reproduce the severe plastic deformations observed in a real clinching process. The results obtained by the FE model are then compared with experimental data. Additionally, the performance of the employed element is compared with the standard Q1 element. It is also shown that the standard Q1 element exhibits an artificial stiffness which may result in the underestimation of mechanical interlocking value. This deficiency can be adequately overcome by applying the Q1SP formulation.