Paint-bake effect on the plasticity and fracture of pre-strained aluminum 6451 sheets

• Main Author: Abi Akl, Rami
• Other Authors: Tomasz Wierzbicki.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2017
• Subjects: Mechanical Engineering.
• Online Access: http://hdl.handle.net/1721.1/108903

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. === Cataloged from PDF version of thesis. === Includes bibliographical references (pages 54-58). === In automotive engineering, sheet metal components are subject to a 20 min heat treatment at 180°C during paint baking. This process may significantly alter the mechanical properties of 6000-series aluminum alloys through artificial ageing. Here, a comprehensive experimental program is carried out to characterize the anisotropic plasticity and the fracture initiation in prestrained artificially-aged aluminum 6451 sheets. It is found that the combination of pre-straining up to 5% strain and heat treatment mainly changes the material's strain hardening behavior and the stress-state sensitivity of its fracture response. The material parameters of the Yld2000-2d plasticity model with combined Swift-Voce hardening are identified for four distinct materials from uniaxial tension and shear experiments. The corresponding Hosford-Coulomb fracture model parameters are determined from smiley shear, V-bending and punch experiments. As an important byproduct of the research, the Yld2000-2d and Hosford-Coulomb models are successfully validated for all four materials through notched and central hole tension experiments. Simple empirical expressions are also provided to estimate the material properties as a function of the prestrain in engineering practice. === by Rami Abi Akl. === S.M.