IRUS Total

Strain measurement and error analysis in thermo-mechanical tensile tests of sheet metals for hot stamping applications

Title: Strain measurement and error analysis in thermo-mechanical tensile tests of sheet metals for hot stamping applications
Authors: Shao, Z
Li, N
Lin, J
Dean, TA
Item Type: Journal Article
Abstract: In order to conduct uniaxial tensile tests for hot stamping applications, tests are normally performed by using a Gleeble thermo-mechanical materials simulator so that rapid heating and cooling processes can be obtained. However, temperature gradients in a specimen tested on Gleeble are inevitable due to resistance heating principles and heat loss to grips and water-cooled jaws. In this research, a pair of purpose-built grips made of stainless steel with low thermal conductivity and significantly reduced contacting area for clamping, as well as a flat dog-bone specimen with maximised parallel length (80 mm) were designed, for the purpose of improving the temperature uniformity within the concerned gauge section area of the specimen. Uniaxial tensile tests on AA6082 were performed, after controlled heating and cooling processes, at constant deformation temperatures in the range of 400 ℃–500 ℃ and at constant strain rate in the range of 0.1–4/s, to simulate its hot stamping conditions. The digital image correlation system was adopted to enable strain distributions in specimens to be measured. The temperature distributions in specimens were investigated and an effective gauge length of 14 mm was specified accordingly to ensure temperature gradients less than 10 ℃ within it at all tested temperatures. True stress–true strain curves of AA6082 were obtained based on results of strain measurements along the defined effective gauge length and used to calibrate a set of advanced material model. Error analysis was carried out by using thermo-electrical and thermo-mechanical FE models on ABAQUS, in which the calibrated material constitutive equations were implemented via subroutines. The error of stress–strain curves of AA6082 measured based on the specified gauge length was investigated and quantified by analysing the distribution of axial strain and axial stress.
Issue Date: 1-Jun-2018
Date of Acceptance: 16-May-2017
URI: http://hdl.handle.net/10044/1/49823
DOI: https://dx.doi.org/10.1177/0954406217714011
ISSN: 0954-4062
Publisher: Sage Publications
Start Page: 1944
End Page: 2008
Journal / Book Title: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
Volume: 232
Issue: 11
Copyright Statement: © 2017 by Institution of Mechanical Engineers
Sponsor/Funder: Commission of the European Communities
Funder's Grant Number: NMP3-SE-2013-604240
Keywords: Science & Technology
Engineering, Mechanical
Strain measurement
hot stamping
thermo-mechanical testing
uniaxial tensile test
sheet metal forming
0913 Mechanical Engineering
Publication Status: Published
Online Publication Date: 2017-06-09
Appears in Collections:Mechanical Engineering
Dyson School of Design Engineering
Faculty of Engineering