Path Independent Polar Effective Plastic Strain (PEPS) Diagram for Sheet Forming

Abstract

This paper reviews a pre-strain effect on necking limit of sheet metal, and discusses the importance of this phenomenon to industrial applications. The paper also discusses a solution to this challenge including adaption of the stress diagram. A new type of forming limit diagram, based on a Polar plot of the Effective Plastic Strain (PEPS) is proposed that appears to be an effective solution to the problem of nonlinear effects, with advantages of the familiar strain-based diagram for linear loading, and without the strain-hardening limitations of the stress diagram, or non-intuitive aspects of the alternate Cartesian diagrams based on effective plastic strain. The benefits and limitations of each method are discussed.