Modelling strategy for clinched joints in large assemblies

Clinching is a mechanical joining technique that involves severe local plastic deformation of two or more sheet metal parts, resulting in a permanent mechanical interlock. This interlock is achieved by using simple tools like a die, a punch and a blank holder. Since no additional elements are used, the strength of the clinched connection is determined by the clinch geometry resulting from the die and punch geometry.

Clinching is currently adopted as a reliable joining technique for ductile materials in automotive, HVAC and general steel constructions, with combined sheet thicknesses up to 8 mm. In general, clinched connections are used for shear loaded joints, as the pull-out strength of a clinched joint is significantly smaller than its shear capacity. As a result, clinched connections are often used for non-critical, low-load bearing assemblies. There is a substantial lack of knowledge on the complete mechanical behaviour of these connections.

The clinched region is a complex shaped zone where the material state varies from point to point. If a structure contains many such connections, it is unrealistic - because of the computational cost – to build a numerical model of an assembly containing a huge number of detailed submodels of the complex joints. In this research, it is the objective to replace the complex joint by an equivalent joint element which simulates the global response of the joint. This equivalent model incorporates a number of parameters which have to be identified. Conventionally, the parameters are identified by using experimental data from different loading cases.