Numerical simulation of the drawing process of tungsten wires

Tungsten wires for lamp filaments sometimes develop longitudinal cracks of substantial length during processing, mainly during wire drawing. In this work, the drawing process is analysed with a finite element model to determine the factors that are responsible for these so-called splits. The material behaviour of tungsten is described using a viscoplastic material law containing internal variables. Special attention is paid to the residual stresses in the wire after passing through the die. These residual stresses are used in a fracture mechanics analysis of a split wire.