Date of Award

Spring 2008

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Brad Kinsey

Abstract

Tearing failure in sheet metal forming has traditionally been predicted based on the strain state of the material. However, a concern with this failure prediction method is that the strain based forming limit curve exhibits significant strain path dependence. An alternative criterion has been proposed that is based on the stress in the material and has been shown to be less sensitive to the deformation path; however, it has not yet been experimentally validated. An innovative analytical approach to obtaining both a stress and strain based forming limit criterion has been developed. This method not only captures the path insensitivity of the stress based forming limit curve, but also allows for an understanding of why the strain based forming limit curve is path sensitive. The model has shown to match experimental results. In addition, preliminary work has been done on a bi-axial tensile device to validate the model and the path insensitivity of the stress based forming limit criterion. With the completion of this work, it will be clear that the stress based forming limit criterion is the most universal means of failure prediction in sheet forming of complex geometries.

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