Clinching is a mechanical joining technique that involves severe local plastic deformation of two or more metal sheet parts resulting in a permanent mechanical interlock. Today, it is a reliable joining technique used in heating, ventilation and air conditioning (HVAC), automotive and general steel constructions whilst still gaining interest. As it is not computationally feasible to include detailed sub models of these type of joints in FE simulations of clinched assemblies during the design stage, this paper proposes a simple methodology to represent these connections with simplified elements. The key point of the method is the use of uncoupled plastic behaviour to model the joint plastic properties. In order to calibrate the parameters governing the equivalent model, a simple shear lap and pull-out reference test of a single clinched joint was used. The presented methodology is validated using a modified Arcan test of a single joint, which enables to exert a combination of shear and pull-out loads. Finally, a peel test is conducted to study the influence of bending moments on the behaviour of the joint.

Lightweight and high strength sheet metal such as aluminium alloy sheets are used in a variety of industrial applications. Due to the limited weldability of these materials, mechanical joining techniques such as clinching are of interest. The challenge in this regard is that conventional round clinch forming locally induces large plastic deformations which potentially cannot be accommodated by materials with limited ductility. Ductile damage models are used to predict the occurrence of bottom cracks during conventional round clinch forming of EN AW-6082 T6 sheet. It is shown that cracks in the bottom of a clinched joint and the final static strength of a single lap shear specimen can be numerically reproduced provided that the post-necking strain hardening behavior and damage behavior of the base material are properly identified. The observed bottom cracks did not have a detrimental effect on the static strength and fatigue life of single shear lap specimens. It is hypothesised that fatigue cracks in single shear lap tests initiate due to fretting.

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Abstract. Clinching is a mechanical joining technique that involves severe local plastic deformation of two or more sheet metal parts using a punch and die. The local deformation results in a permanent mechanical interlock. It is widely applied as a reliable joining technique in automotive, heating, ventilation, air conditioning (HVAC) and general steel constructions and is still gaining interest. In FEA models of structures containing a large number of clinched joints, it is not computationally feasible to use detailed sub models of the joint. Therefore an equivalent model was proposed by Breda et al. to predict the force-displacement behaviour. This equivalent model was calibrated using a simple shear-lap and pull-out test. During the calibration step, some local effects due to the material properties are captured in the calibration parameters. This paper investigates the impact of the plastic material properties on this calibration method. The effect of strain hardening due to the bending process prior to pull-out testing, potential plastic anisotropy of the base material and their relation to the calibration parameters are investigated. This research has been validated with experimental results on mild deep drawing steel.