Open AccessImproved bendability characterization of UHSS sheets
Author(s) -
Leopold Wagner,
H. Schauer,
Heinrich Pauli,
J. Hinterdorfer
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/651/1/012019
Subject(s) - bending , curvature , radius of curvature , bend radius , bent molecular geometry , structural engineering , classification of discontinuities , radius , materials science , stamping , bending stiffness , finite element method , composite material , engineering , geometry , mathematics , computer science , mean curvature , metallurgy , mathematical analysis , computer security , mean curvature flow
Bendability characterization of UHSS sheets is often limited by punch-sheet-liftoff during standardized bending tests. This phenomenon is characterized by a smaller radius on the bent sheet than the desired tool radius and might lead to a misinterpretation of the admissible bending radii from such tests. An alternative bending setup is proposed suppressing punch-sheet-liftoff. The proposed setup aims at imitating bending in multistage stamping processes and to some extent also roll forming. The target bending radius to sheet thickness ratios of the investigated UHSS sheets were chosen to be 2.0. Alternative tool geometries are investigated as well. Short segments of an Euler spiral between the tool parts exhibiting the target curvature and the linear neighbor regions are used to avoid triggering strain localizations at these curvature discontinuities, further decreasing the admissible bending ratios. Finite element simulations of the proposed bending test were conducted in order to identify the optimal tool shape. All results were compared to corresponding results from standardized bending tests of the respective UHSS sheets. The proposed setup succeeded in suppressing punch-sheet-liftoff for the desired bending ratios and was able to provide smaller bending ratios for the investigated UHSS sheets as compared to the ratios from standardized bending tests.