Edge crack sensitivity of lightweight materials under different load conditions

IDDRG2016 conference on "Challenges in Forming High-Strength Sheets".

Tsoupis, I.^1 ; Merklein, M.^1

Institute of Manufacturing Technology, Department Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nüruberg (FAU), Egerlandstraße 13, Erlangen

91058, Germany^1

关键词: Aa5182 aluminum alloys;    Automotive component;    Hole-expansion ratios;    Lightweight materials;    Local deformations;    Machining operations;    Optical strain measurement;    Process parameters;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/159/1/012017/pdf
DOI  :  10.1088/1757-899X/159/1/012017

来源: IOP

【 摘 要 】

This study addresses the analysis of edge crack sensitivity of DP800 steel and AA5182 aluminum alloy in dependency of punching and machining operation as well as load case of subsequent forming. The inserting of a round hole by punching with defined punch-to- die-clearance, milling and drilling is compared. Subsequent forming is performed by standardized hole expansion test and by Nakajima-tests with three different specimen geometries. Local strain distribution at the surface for Nakajima-tests is measured by optical strain measurement technique and investigated in order to evaluate local deformation before failure. Additionally, resulting hole expansion ratio λ is determined. Significant higher X as well as local strain values maxare achieved by machined holes. This is directly coupled to higher local formability and stretchability for both materials. Furthermore, the load condition has a strong impact on the edge crack sensitivity of the material. Prior failure is observed with changing stress conditions using different specimen geometries also influencing the reachable maximum failure strain. Higher edge crack sensitivity is observed for DP800, which is in good accordance to the material properties in terms of ductility and strength. These data in dependency of the process parameter can be used for the design of automotive components.