Clinching with divided punch to prevent critical neck thicknesses

Abstract

Abstract. Clinching thin sheet metal into a thicker part can result in low neck thicknesses or even neck cracks. How these critical low values for neck thickness can be counteracted is described in this paper, using a two-part punch, which is devided in an inner and outer unit. At the beginning, both move parallel in the direction of the die until the outer punch stops at a defined position and only the inner one moves further down and forms the clinch point, with its characteristic contour and the geometric values of interlock and neck thickness. Due to the large punch diameter at the beginning of the process, more material initially flows into the neck area than in conventional clinching, so that a greater neck thickness can be achieved. Numerical simulation was used to create the concept and verify it experimentally. The greater neck thickness has a positive effect on the shear tensile strength and can also be transferred to the typical joining direction for clinching (thick into thin material).