Measurement of the Bauschinger Behavior of Sheet Metals by Three-point Bending Springback Test with Pre-strained Strips

In numerical simulation of sheet metal
forming process, the cyclic mechanical behavior of metallic sheet is
required to calibrate the material parameters of the combined
isotropic-kinematic hardening model. Therefore the development of
experimental device and method is an important work in order to
measure the cyclic mechanical behavior of metallic sheet. There are
several experimental devices which can measure this cyclic mechanical
behavior of sheet metal mainly to measure the Bauschinger behavior.
Often, these experiments can be classified into three main
categories: (i) in-plane tension-compression test; (ii) in-plane
cyclic simple shear test; (iii) bending-reverse bending test.

In this paper, a novel approach is
proposed to measure the Bauschinger effect, transient behavior and
permanent softening of metallic sheet subjected to reverse loading.
The hardening parameters related to the Bauschinger effect, transient
behavior and permanent softening are optimized from the springback
profiles of three-point bending tests with pre-strained sheets.
Taking the dual phase steel sheet DP780 as an example, its
Bauschinger effect, transient behavior and permanent softening
determined from the new approach are compared with those of the
cyclic simple shear method. Finite element simulations are also
performed for three-point bending and U-draw/bending of base
(as-received) and pre-strained DP780 steel sheets to validate the
suggested approach. The results show that the aforementioned
hardening behavior determined from the new approach shows good
agreements with those of cyclic simple shear tests. Moreover,
reasonable springback predictions for three-point bending and
U-draw/bending tests are obtained as well.

Comparing with the existing techniques,
the suggested approach only involves the uni-axial tension
with/without unloading and three-point bending test. These tests are
easily available with the help of the common material test system and
not required for complicated strain measurement devices. Thus the new
approach seems quite suitable for the industrial applications

Shun-lai Zang, Myoung-Gyu Lee, Li Sun, Ji Hoon Kim. Measurement of the Bauschinger behavior of sheet metals by three-point bending pringback test with pre-strained strips. Int. J. Plasticity (2014), http://dx.doi.org/10.1016/j.ijplas.2014.03.015

http://www.sciencedirect.com/science/article/pii/S0749641914000655