Analysis Of Entropy Generation In Sheet Metal Forming

Entropy generation, which is one of important concepts in the thermodynamic theory, is generalized and plays a great role in quantum theory, information, system theory, life science and cosmology. Increment of entropy in inreversable process such as heat exchange, pervasion and chemistry reaction is called entropy generation. In this paper, the concept of entropy generation is used to analyse the inreversable process of sheet metal forming.The process of sheet metal forming, which is regarded as a thermodynamic system, is divided into two subsystems: a tool and a work-piece. Then metal sheet and die are defined as work-piece and the tool subsystem, respectively. Based on fundamental equations in continuum mechanics related to a deformable solid and the basic laws of the thermodynamics, a mathematical model of the thermodynamic system has been derived and the equation of entropy generation has been obtained.With help of the finite element software MARC and its user subroutine, the investigation of entropy generation in sheet forming has been carried out. The numerical results show that when wrinkling occurs, the entropy generation rapidly increases at first, and then decreases speedly. The variation of such an entropy generation with time is more complicated in regions of both cracking and thinning during the sheet forming.It is possible to judge whether wrinkling had happen or not in a region by analyzing the variation of the entropy generation in sheet forming.