Numerical and Experimental Analysis of Resistance Projection Welding of Square Nuts to Sheets

Abstract

Projection welding of nuts to sheets is a widely utilized manufacturing process in the automotive industry. The process entails challenges due the necessity of joining different sheet thicknesses and nut sizes made from dissimilar materials, and due to the fact of experiencing large local deformations ranging from room temperature to above the melting point. Heating is facilitated by resistance heating and is highly influenced by the contact area resulting from the amount of deformation, which is also temperature dependent due to material softening and frictional conditions. Resort to new materials and applications require a new level of understanding of the process by combining finite element modelling and experimentation. This paper draws from the challenge of developing a three-dimensional computer program for electro-thermo-mechanical modeling of resistance welding and presents, as far as the authors are aware, the first ever three-dimensional simulation of the projection welding of square nuts to sheets by means of finite element analysis. Results are compared with experimental observations and measurements produced by the authors with the aim and objective of assessing the accuracy, reliability and validity of the theoretical and numerical developments. Numerical simulations support the evaluation of the experiments by providing detailed information on the process like the initial heating location and the following temperature development, and allowing to analyze the weldability of the square nut to the sheet under different operating conditions.