Modelling and characterisation of a servo self-piercing riveting (SPR) system

SPR is a cold mechanical joining process in which multiple sheets of material are riveted together without the need for a predrilled hole. It works by pushing a typically semi-tubular rivet into a target stack of material, during which the plastic deformation of the material and rivet are such that a mechanical lock is formed within the material stack. The process is used extensively in the automotive industry in car body construction, and is a competing technology to more established joining techniques such as resistance spot welding. As part of the ongoing development of the technique, there is a strong need to understand and simulate the dynamics of the process. In this work, a lumped parameter model of the SPR system with a non-parametric model of the joint is presented. Simulated results are compared with experimental data for a given joint configuration. Furthermore, the model is used to highlight the significance of the compliances within the system. It is shown that during rivet insertion, the stiffness of the C-frame structure is an influential factor in determining the dynamic response of the system. The results provide the basis for a more comprehensive sensitivity analysis into the factors which affect the quality of the resulting joint.