Determination of the real contact area for numerical simulation

The knowledge of the real area of contact plays an important role in metal forming processes as it influences friction and heat transfer in the tool–workpiece interface. In accurate finite element analysis, friction and heat transfer have to be faced by numerical interface models that consider the real contact area in dependence of the applied normal load. Up-to-date methods for the calculation of the real contact area–load relation are either oversimplified or too complex to be used in interface models. This paper presents a new method for evaluating the real contact area in dependence of the normal load that takes the material properties and real asperity slopes into consideration, and simplification (compared to e.g. the work of Neumaier [Zur Optimierung der Verfahrensauswahl von Kalt-, Halbwarm- und Warmmassivumformverfahren, Fortschritt-Berichte VDI: Reihe 2, Fertigungstechnik, vol. 637. Düsseldorf: VDI Verlag, 2003] is achieved by making use of the statistical character of real surfaces. The main idea of the new concept is to obtain the real contact area–load relation by combining the bearing area curve and a model asperity with correct representation of the mean asperity slope.