Forming-induced damage and its effects on product properties

Damage is caused in the microstructure of metals during forming. Damage is not a failure, but affects the mechanical properties of the component under service loads. This paper explores experimentally the effect of metal forming process parameters on the evolution of damage and the resulting product properties. As a representative for bulk forming processes, cold forging is investigated. It is shown that an increase of the extrusion ratio leads to lower damage and increased fatigue strength. Air bending, as a sheet forming process, is analysed, exhibiting that damage can be influenced by process design such as the superposition of stresses.