Author(s)

Kunmin Zhao^1*, Wumei Fang², Baotang Wang², Daxin Ren²

¹Institute of Industrial and Equipment Technology, Hefei University of Technology, Hefei, China.
²School of Automotive Engineering, Dalian University of Technology, Dalian, China.

The loading-unloading-reloading process could affect the tensile deformation of metals with the combined function of stress relaxation and work hardening, which has been reported in multiple experiments. Nevertheless, the effects of different unloading positions and unloading times have not been investigated. In this study, unloading-reloading tests on three materials (AL6061, HSLA and Q195) were conducted. The stress exhibits a rapid rise momentarily upon reloading and stabilizes afterward while the post stress-strain curve deviates up or down from the monotonic tensile curve. The ductility is enhanced by the unloading-reloading process in general. Different unloading positions and unloading times have different degrees of influence on the stretching of these metals. The effect of loading conditions on a medium manganese steel was further studied. The functions to modify the post stress-strain relationship after unloading-reloading were established.

Sheet Metal, Stretch Forming, Unloading Positions and Times, Elongation, Stress-Strain

Zhao, K. , Fang, W. , Wang, B. and Ren, D. (2018) The Effect of Unloading Positions and Times on Sheet Metal’s Stress-Strain Curve. Journal of Minerals and Materials Characterization and Engineering, 6, 408-423. doi: 10.4236/jmmce.2018.63029.