Material Forming Processes
This text covers techniques such as injection molding, composites forming, die extrusion, hydro-forming, blowing, forging, machining and cutting, super plastic forming, as well as a number of other specific processes.
TABLE OF CONTENTS Material Forming Processes
Chapter 7: Comparison of Ductile Damage Models
Cyril Bordreuil, Emmanuelle Vidal-Sall and Jean-Claude Boyer
INSA de Lyon - Laboratoire de M canique des Solides, Lyon, France
1. Introduction
| Note | Publisher Error on missing text in paragraph below. |
In previous published work, dissipation potentials for damage prediction deduced from local void growth models of Gurson [GUR 77] or Rice and Tracey [RIC 81] have b presented by several authors. Most of these discussions consider only the behaviour of em voids under hydrostatic loading. In this paper, four yield functions are applied to the v known collar test and to an upsetting of shaped workpiece between conical dies un isothermal conditions. The first two yield functions are improvements of the original work Gurson [GUR 77] formulated by Tvergaard [TVE 81] on the one hand and by Oudin et [OUD 95] on the other hand. The third and the fourth yield functions are identified with local Rice and Tracey model but the last is also formulated for voids initially filled with inclusion and is sensitive to each component of the stress tensor. The influence of the differ plastic dilatant stress-strain laws on the change on the void volume fraction used as dam parameter are analysed at different stages of both different forming processes.
2. Dissipation potentials
2.1. The Gurson-Tvergaard yield function
The classical Berg-Gurson potential, ? 1, [GUR 77] predicts a dilatational plastic strain rate D kk only sensitive to the mean stress ? m or to the triaxiality ratio 3 ? m/2 ? 0
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