Optimization methods for prediction of advanced constitutive models
OPEN ACCESS
Loading...
Author / Producer
Date
2020-12
Publication Type
Doctoral Thesis
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
The prediction of strain distribution in production of sheet metal parts directly influences predictions of hardening and failure, as strain and stress response are linked by the yield model. The prediction of strains in simulation is relied upon by tool design and process engineers in all states of development. However, optical measurement and simulation result do not always align, which questions the state of the art approach to define yield models, especially for aluminium alloy. The reason for this mismatch was thought to be the finite complexity of the models used, but, while studying the effect, this work shows that not model complexity but an improved foundation for fitting is a solution. Three advanced fitting strategies are presented for non-quadratic and free-shape yield formulations. The first is based on macroscopic measurement of cruciform tension specimen as specified in ISO16842 for simultaneous evaluation of strain and stress ratio. The second extracts all necessary information by application of inverse full field optimization using digital image correlation and global force measurement. The third method investigates the possibility of crystal plasticity calculation based on texture measurement. In order to evaluate performance and to be able to recommend one strategy for further use, a large validation study is conducted using Nakajima and cross die experiments. Both non-quadratic and free-shape models were able to outperform the original configuration based on the proposed strategies, with cruciform tension and inverse full-field proven to be most effective based on an additional cost analysis. All three strategies provide valuable information and challenge to reconsider common assumptions about the definition of yielding for aluminium alloy. In consequence, this work presents the basis for further research on optimal choice of fitting strategy, which opens up a new perspective on development of yield models.
Permanent link
Publication status
published
External links
Editor
Contributors
Examiner : Hora, Pavel
Examiner : Yoon, Jeong-Whan
Examiner : Mohr, Dirk
Book title
Journal / series
Volume
Pages / Article No.
Publisher
ETH Zurich
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
constitutive modeling; Optimization methods; Digital image correlation (DIC); FEM modeling; Cruciform
Organisational unit
03685 - Hora, Pavel (emeritus) / Hora, Pavel (emeritus)