Material and temperature dependent behaviour of single macro-asperity tip when crushed against flat platen

Thermo-mechanical forming of metals is of special concern due to its complex nature which involves temperature, load and particularly tribological parameters at elevated temperatures. Previous studies have given much emphasis to the deformation behaviour of surface asperities at micro level which in turn determines quality and surface finish of a component produced by thermo-mechanical forming. In this work, special attention is given to the deformation behaviour in the case when a single macro-asperity tip is crushed by a flat platen, dependent on the constitutive behaviour of the asperity material and the asperity temperature. Different cone-shaped single asperity tips with two different cone angles, as well as with top-flat facets, were studied bearing in mind that a surface may contain these forms of asperities. Experiments were conducted on the Al-alloy AA6082 at room temperature (RT) and FEM analyses were run to study the behaviour at high temperature (450°C). This work gives deep insight into the deformation behaviour of the macro-asperity tips, with regard to for instance lateral spread of the tip, and its ability to provide contact pressure against the crushing platen. The analysis also reveals how high and low friction against the platen affects the deformation behaviour of the asperity tips.