Forming limit and fracture mechanism of ferritic stainless steel sheets

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2011-03, Vol.528 (7), p.3113-3121
• Main Authors: Xu, Le, Barlat, Frédéric, Ahn, Deok Chan, Bressan, José Divo
• Format: Article
• Language: English
• Subjects: Applied sciences; Elasticity. Plasticity; Exact sciences and technology; Failure; Ferritic stainless steel sheets; Ferritic stainless steels; Formability; Forming; Forming limit curve; Fracture; Fractures; Limit strain; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Micrographs; Modeling; Necking; Production techniques; Shearing; Sheet metal; Strain rate sensitivity
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2011.01.011

▶ Forming limit curves of two ferritic stainless steel sheets were well predicted. ▶ Failure occurs by necking in uniaxial and plane strain tension for both materials. ▶ Failure occurs by shearing in balanced biaxial tension for both materials. ▶ Strain rate sensitivity does not affect the limit strains a lot for both materials. ▶ Strain rate sensitivity likely influences the failure mode for both materials. In this work, the forming limit curves (FLCs) of two ferritic stainless steel sheets, AISI409L and AISI430, were predicted with the Marciniak–Kuczynski (MK) and Bressan–William–Hill (BWH) models, combined with the Yld2000-2d yield function and the Swift hardening law. Uniaxial tension, disk compression and hydraulic bulge tests were performed to determine the yield loci and hardening curves of both materials. Meanwhile, the strain rate sensitivity (SRS) coefficient was measured through uniaxial tension tests carried out at different strain rates. Out-of-plane stretching tests were conducted in sheet specimens to obtain the surface limit strains under different linear strain paths. Micrographs of the specimens fractured in different stress states were obtained by optical and scanning electron microscopy. The overall results show that the BWH model can predict the FLC better than the MK model, and that the SRS does not have much effect on the limit strains for both materials. The predicted FLCs and micrograph analysis both indicate that failure occurs by surface localized necking in uniaxial and plane strain tension states, whereas it occurs by localized shearing in the through thickness direction in balanced biaxial tension state.