Author(s)

Y.C. Li & L.H.N. Lee

Abstract

Transitional contact and wrinkling in sheet metal forming Y.C. Li, L.H.N. Lee Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA ABSTRACT The penalty method, in a form of a Winkler foundation and a modified Coulomb friction on the tool surface, is employed to analyze the effects of the transitional tool-sheet contact on the wrinkling development in forming a sheet metal. A nested iteration scheme is developed to determine the local and global conditions of contact or separation, stick or slip, elastic or plastic and bifurcating or not. A finite element computer program for an incremental solution of the problem is written. As illustrations, numerical results of forming a rectangular pan with round corners are shown. INTRODUCTION In forming a sheet metal, wrinkling or geometric deviations may develop in any stage depending on many factors such as blank and tool geometry, hold-down pressure, tool-sheet contact friction and

Keywords