Premium
On the identification of an effective cross section for a cruciform specimen
Author(s) -
Härtel M.,
Pfeiffer S.,
Schmaltz S.,
Söhngen B.,
Kulawinski D.,
Willner K.,
Henkel S.,
Biermann H.,
Wagner M. F.X.
Publication year - 2018
Publication title -
strain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.477
H-Index - 47
eISSN - 1475-1305
pISSN - 0039-2103
DOI - 10.1111/str.12257
Subject(s) - cruciform , materials science , ultimate tensile strength , tensile testing , structural engineering , composite material , stress (linguistics) , yield (engineering) , transverse plane , sheet metal , aluminium , engineering , linguistics , philosophy
Biaxial tensile testing of sheet metals is becoming increasingly popular for sheet metal forming. Determining equivalent stresses in biaxial tensile specimens is more complicated than in conventional uniaxial tensile specimens. In the present study, we compare four different approaches to calculate effective stresses during biaxial tensile loading of a cruciform specimen: (a) partial unloading method, where stresses are determined based on force–strain curves; (b) identification with uniaxial tensile testing; (c) an analysis of equivalent biaxial tests; and (d) numerical simulations. Considering experimental results for an AA1050 aluminium alloy and for a low‐carbon steel DC06, we show that, for the cruciform sample studied here, two methods do not yield physically reasonable results: The uniaxial approach does not properly take into account the effect of transverse loading, and the equivalent biaxial approach exhibits uncertainties in strain measurement data. The most comprehensible approach is the numerical method, because it also yields detailed information about the local stress and strain states. The numerical results are in excellent agreement with the partial unloading method in terms of the initial flow stress and of effective stress–strain curves for strains up to 0.02, with both methods predicting a similar effective cross section of 18.0 mm 2 for the considered specimen.