The effect of the through-thickness normal stress on sheet formability. (January 2016)

• Record Type: Journal Article
• Authors: Ma, Bolin; Diao, Keshan; Wu, Xiangdong; Li, Xinjun; Wan, Min; Cai, Zhengyang
• Is Part Of: Journal of manufacturing processes. Volume 21(2016)
• Page Start: 134
• Page End: 140
• Publication Date: 2016-01
• Subjects: Sheet metal -- Forming limit curve -- 3D-stress states -- M-K model -- Through-thickness normal stress; Production management -- Data processing -- Periodicals; Manufacturing processes -- Periodicals; Procestechnologie; Productietechniek; Production -- Gestion -- Informatique -- Périodiques; Fabrication -- Périodiques; Manufacturing processes; Production management -- Data processing; Periodicals; 670.5
• DOI: 10.1016/j.jmapro.2015.12.006
• Languages: English
• ISSNs: 1526-6125

Abstract

Abstract: Sheet formability is limited by the onset of localized necking or fracture, and the limit strain is important to measuring sheet formability. The forming limit curve (FLC), which maps the limit strain under different strain paths into the strain space, provides a convenient and useful way to predict material failure in the sheet forming process. The FLC is closely related to many factors, such as the material mechanical properties, stress state, temperature and forming speed. This paper focuses on the influence of the through-thickness normal stress on the FLC, in which a modified M-K model with a corresponding algorithm under the 3D-stress state is proposed. The through-thickness normal stress is obtained by analyzing the Nakazima test and simplifying it. Both experimental and reference data are applied to the model validation, which indicates a higher prediction accuracy when the sheet thickness is introduced into the model. Theoretical FLCs under different ratios of t 0 / D show a linear relationship between the sheet thickness and the limit strain increment in tension–tension states.