Resume 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. Le modele de resistance thermique de contact (RTC) dynamique propose est destine a etre implante dans des codes de calcul de thermomecanique avec comme premiere application: l’interface piece–outil de forgeage. Tous les parametres d’interfaces sont des fonctions temporelles. Le taux reel de contact est represente par le rapport contrainte normale locale sur contrainte d’ecoulement de la piece correspondant a la temperature de contact locale. La premiere est calculee par le code et la seconde est une donnee rheologique. Le principe du modele propose consiste a relier le taux reel de contact a la densite de points de contact et a l’epaisseur interstitielle moyenne par des fonctions que l’on etablit a partir d’un traitement des releves topographiques des surfaces de la piece et de l’outil avant l’operation de forgeage. Calcule a chaque pas de temps, le taux reel de contact permet d’acceder ainsi aux autres parametres et donc d’estimer la RTC instantanee.
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