A study on a die wear model considering thermal softening: (I) Construction of the wear model

The service lives of tools in metal forming processes are to a large extent limited by wear, fatigue fracture and plastic deformation, etc. In elevated temperature forming processes, wear is the predominant factor in the operating lives of tools. To predict tool life by wear, Archard's wear model is generally applied. Usually the hardness of a die is considered to be a function of temperature in Archard's model, but the hardness of a die is a function not only of temperature, but also of the operating time of the die. To consider the softening of a die by repeated operations, it is necessary to express the hardness of the die by a function of temperature and operating time. By experiments into the reheating of dies, die-softening curves have been obtained. Finally a modified Archard's wear model, in which the hardness of the die is expressed as a function of the main tempering curve, is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.