Predictive model of dynamic thermal contact resistance adapted to the workpiece-die interface during hot forging process

We propose a model of dynamic thermal contact resistance. This model is intended to be implanted in numerical codes of thermomechanics with as first application: the workpiece-die interface during a hot forging process. All the interfacial parameters are temporal functions. The real rate of contact is represented by the ratio local normal stress on flow stress of the workpiece corresponding to the contact temperature. The principle of the model suggested consists to connect the real rate of contact to the density of contact spot and to the average interstitial thickness. These parameters are functions which are established from a surface analysis processing of the workpiece and die before the forging operation. Calculated at each step of time, the real rate of contact gives access thus to the other parameters and thus to the instantaneous thermal resistance of contact.