A discussion of model asperities as a method to study friction in metal forming

The present work discusses the use of model asperities as a method for studying asperity flattening in metal forming. Asperity flattening and the resulting real contact area largely influence friction in metal forming. In order to gain a fundamental understanding of asperity flattening, a method of choice often is to use model asperities. Here, macroscopic model surfaces are emulating real surface topographies. The work presents the method in a historic context, explains the method, lists advantages and disadvantages, and discusses the method in terms of whether the insights gained on model asperities are of qualitative or quantitative nature. In conclusion, the method is a valid tool to fundamentally study asperity flattening. It is, however, not always possible to transfer obtained conclusions quantitatively from model surfaces to real surfaces.