Date of Award

Winter 2018

Project Type

Dissertation

Program or Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Marko Knezevic

Second Advisor

Irene J Beyerlein

Third Advisor

Todd S Gross

Abstract

An optimal sheet metal forming process shapes a metal part to the accurate geometry, while avoiding instabilities causing localization of deformation and fracture. Understanding the underlying mechanisms responsible for deformation localization and deviation of final part geometry from the desired geometry facilitates the search for the optimal sheet metal forming process. Accurate modeling of forming processes allows prediction of the formed part shape and can provide insight into the material behavior by interpretation of experimental measurements and prediction of variables not accessible to experimental characterization. In this work, a micromechanical material model is coupled with finite elements to create a multi-scale model of a metal forming process. In addition, extensions to the micromechanical material model have been implemented to accurately describe the material behavior during complex deformation paths observed during forming processes. An implicit numerical integration procedure of the micromechanical model equations is developed for purpose of reducing high computational times characteristic for multi-scale simulations. The developed material model is calibrated against experimental data and used in a finite element simulation of a cup drawing forming process of aluminum alloy AA6022-T4 to predict the formed cup geometry. Furthermore, the multi-scale modeling approach is utilized to study the mechanics of bending under tension deformation state as a mechanism for postponing the instabilities in deformation processes. The model of the process is capable of capturing the experimentally observed trends in mechanical response and offers insight into the microstructure evolution. The developed modeling framework is computationally intensive, but feasible.

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