Experimental studies of necking and fracture limits of boron steel sheet under hot stamping conditions

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Title: Experimental studies of necking and fracture limits of boron steel sheet under hot stamping conditions
Authors: Zhang, R
Shi, Z
Yardley, VA
Lin, J
Item Type: Journal Article
Abstract: Boron steel is the most widely used material in hot stamping applications for forming automotive body panels with complex shapes and ultra-high strength. Due to the high austenitic transformation temperatures and the complex thermal cycle required for hot stamping, however, it is difficult to evaluate the formability of the material using standard punch test methods developed for room-temperature testing. In this study, a high-temperature modification of a recently developed biaxial test method has been used to determine, in a single test procedure and for the first time, forming limit curves (FLCs) and fracture forming limit curves (FFLCs) for 22MnB5 boron steel sheet with a thickness of 1.5 mm under thermal conditions that are representative of industrial hot stamping processes. A direct resistance heating strategy has been developed, and a recently proposed cruciform specimen design has been modified for high-temperature use. For tests with target temperatures in the range of 750 to 925 °C, the resulting test specimens had the highest temperature at the specimen centre and a temperature difference of less than 45 °C in the gauge area and fracture occurred close to the centre of this area under all test conditions investigated. Limit strains at the onset of necking and at fracture for the material have been determined by applying digital image correlation (DIC) to obtain full-field strain measurements, providing an experimental foundation for constructing both FLCs and FFLCs for industrial applications.
Issue Date: 1-Apr-2022
Date of Acceptance: 26-Dec-2021
URI: http://hdl.handle.net/10044/1/93830
DOI: 10.1016/j.jmatprotec.2021.117481
ISSN: 0924-0136
Publisher: Elsevier BV
Journal / Book Title: Journal of Materials Processing Technology
Volume: 302
Copyright Statement: © 2022 Elsevier B.V. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: EP/R001715/1 / PO 2105860
Keywords: Materials
0910 Manufacturing Engineering
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status: Published
Embargo Date: 2022-12-27
Article Number: ARTN 117481
Online Publication Date: 2021-12-28
Appears in Collections:Mechanical Engineering
Faculty of Engineering

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