Measurement and analysis of heterogeneous strain fields in uniaxial tensile tests for boron steel under hot stamping conditions
File(s)
Published version
Author(s)
Zhang, R
Shao, Z
Lin, J
Dean, TA
Type
Journal Article
Abstract
Background
A significant amount of uniaxial tensile tests has been carried out using Gleeble systems to investigate the viscoplastic deformation of boron steel (22MnB5) under hot stamping conditions. However, due to heat loss through the end clamps, a temperature gradient in the reduced parallel section of dog-bone shaped specimens is inevitable.
Objective
In the work reported in this paper, the effect of temperature gradient on measured outcomes is examined.
Methods
Uniaxial tensile tests on 1.5 mm thick boron steel specimens are carried out, under hot stamping conditions and strain fields are quantified using the digital image correlation (DIC) technique. The effect of gauge length on the properties of boron steel, as calculated from observed test results, is determined.
Results
Compared with the test at room temperature, a bell-shaped strain distribution occurs within the gauge length even before the appearance of the maximum load. Also, average strain within the gauge length, especially in the later stages, changes with gauge length within the investigated range, and thus, different engineering stress-strain curves and fracture strains are determined. In addition, normalized strain rate is significantly dependent on gauge length, which results in over 16% difference among the computed flow stresses by using a unified constitutive model.
Conclusions
The characterized properties of the material are dependent on gauge length and thus, a testing standard for measuring thermal-mechanical data of materials by using a Gleeble need to be defined.
A significant amount of uniaxial tensile tests has been carried out using Gleeble systems to investigate the viscoplastic deformation of boron steel (22MnB5) under hot stamping conditions. However, due to heat loss through the end clamps, a temperature gradient in the reduced parallel section of dog-bone shaped specimens is inevitable.
Objective
In the work reported in this paper, the effect of temperature gradient on measured outcomes is examined.
Methods
Uniaxial tensile tests on 1.5 mm thick boron steel specimens are carried out, under hot stamping conditions and strain fields are quantified using the digital image correlation (DIC) technique. The effect of gauge length on the properties of boron steel, as calculated from observed test results, is determined.
Results
Compared with the test at room temperature, a bell-shaped strain distribution occurs within the gauge length even before the appearance of the maximum load. Also, average strain within the gauge length, especially in the later stages, changes with gauge length within the investigated range, and thus, different engineering stress-strain curves and fracture strains are determined. In addition, normalized strain rate is significantly dependent on gauge length, which results in over 16% difference among the computed flow stresses by using a unified constitutive model.
Conclusions
The characterized properties of the material are dependent on gauge length and thus, a testing standard for measuring thermal-mechanical data of materials by using a Gleeble need to be defined.
Date Issued
2020-08-31
Date Acceptance
2020-08-10
Citation
Experimental Mechanics, 2020, 60, pp.1289-1300
ISSN
0014-4851
Publisher
Springer Science and Business Media LLC
Start Page
1289
End Page
1300
Journal / Book Title
Experimental Mechanics
Volume
60
Copyright Statement
© The Author(s) 2020. This article is licensed under a Creative Commons
Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as
you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were
made. The images or other third party material in this article are included
in the article's Creative Commons licence, unless indicated otherwise in a
credit line to the material. If material is not included in the article's
Creative Commons licence and your intended use is not permitted by
statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this
licence, visit http://creativecommons.org/licenses/by/4.0/.
Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as
you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were
made. The images or other third party material in this article are included
in the article's Creative Commons licence, unless indicated otherwise in a
credit line to the material. If material is not included in the article's
Creative Commons licence and your intended use is not permitted by
statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this
licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Sponsor
Engineering & Physical Science Research Council (E
Identifier
https://link.springer.com/article/10.1007%2Fs11340-020-00658-6
Grant Number
EP/R001715/1 / PO 2105860
Subjects
Science & Technology
Technology
Materials Science, Multidisciplinary
Mechanics
Materials Science, Characterization & Testing
Materials Science
Boron steel
Hot stamping
Temperature gradient
Uniaxial tensile test
Digital image correlation
FORMING LIMIT DIAGRAMS
SHEET METALS
MICROSTRUCTURE EVOLUTION
FORMABILITY
SYSTEM
22MNB5
Mechanical Engineering & Transports
0905 Civil Engineering
0913 Mechanical Engineering
0915 Interdisciplinary Engineering
Publication Status
Published
Date Publish Online
2020-08-31