Forming-Induced Residual Stress and Material Properties of Roll-Formed High-Strength Steels
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Forming-Induced Residual Stress and Material Properties of RollFormed High-Strength Steels Yong Sun1,2
•
Vladimir Luzin3,4 • Yixin Duan1 • Rameshkumar Varma1 • Lei Shi5 • Matthias Weiss1
Received: 27 April 2020 / Accepted: 16 July 2020 / Published online: 14 August 2020 Ó China Society of Automotive Engineers (China SAE) 2020
Abstract Martensitic steels are widely used in the automotive lightweight application but less understood in aspects of post-forming material properties. The steels show good ductility in roll forming but occasionally experience delayed (hydrogen) fracture issues, which are believed to be due to the formation of localized residual stress and a reduced product of strength and elongation. To characterize the effect of roll forming process on the formation of residual stress and material properties variation of martensitic steel components, this paper investigates the forming-induced longitudinal residual stress and material property variation in a roll-formed high-strength MS1180 automotive rocker panel. The finite element analysis results for residual stress are validated by neutron diffraction measurements. The numerical model is used to analyze the full evolution of residual stress during the roll forming process and the effect on material properties with major focus on the product of strength and elongation. It is found that the flower design, in particular the overbending stages, play a significant role in the formation of residual stress and the change in material properties. The product of strength and elongation is significantly reduced across the profile, in particular in the corners. The achieved understanding will assist researchers comprehend the material properties of roll-formed component and therefore assist future studies aimed at preventing the occurrence of hydrogen fracture. Keywords Roll forming Advanced high-strength steels Martensitic steels Forming-induced residual stress Neutron diffraction method Product of strength and elongation Abbreviations AHSS Advanced high strength steel EDM Electrical discharge machining FEA Finite element analysis MS Martensitic steel PSE Product of strength and elongation SEM Scanning electron microscope & Yong Sun [email protected] 1
Institute for Frontier Materials (IFM), Deakin University, Geelong, VIC 3216, Australia
2
School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
3
Australian Nuclear Science and Technology Organization (ANSTO), Lucas Heights, NSW 2234, Australia
4
School of Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia
5
Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China
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1 Introduction Roll forming is a promising and highly efficient cold forming method to confront the lightweight and crashworthiness requirements from the automotive industry. The process is particularly suitable for the forming of martensitic steel products which have high strength
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