• Wittwer, Lukas
• Enzinger, Norbert

Abstract

Pin structures offer an innovative way of joining dissimilar materials such as metals and plastics based on an additional geometric link. Therefore pins are placed on a metal sheet substrate by use of a special arc welding technique called cold metal transfer (CMT), developed by Fronius International. The key element of the CMT process is a controlled back and forth movement of the wire during the welding process. This back and forth movement allows for welding pins. In the context of pin welding, the welding process consists of three stages, warm up, cooling and shaping. During the warm up phase the welding wire is welded on the base material (stainless steel AISI 304). In the cooling stage the zone of maximum temperature is migrating within the wire to a certain position. When applying a current in the shaping phase the electric resistance is highest in the zone of maximum temperature, consequently the ohmic heating is strongest in this zone. In addition to the ohmic heating in a well-defined area the wire is pulled back mechanically causing the wire to rip off at certain distance from the joint. The height of the pins is in the millimeter range. This work aims to describe the mechanical properties of a single pin based on its thermal history during the welding process. Thereby, we assume a given pin geometry derived from measurements of polished cross sections. In order to mimic the heat deposited in the welding process the Goldak heat source with optimized parameters is applied. Furthermore the occurring electric currents and voltages by means of an electro kinetic - thermal coupled analysis were taken into account.

Topics

• impedance spectroscopy
• polymer
• stainless steel
• phase
• wire
• joining