Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
802816 | Mechanics of Materials | 2014 | 12 Pages |
•Nucleation, propagation, orientation and kinematics of PLC bands in a TWIP steel.•An algorithm is proposed to include the elongating effect in kinematics analysis.•Applied strain rate has little effect on PLC band width.•PLC band width increases with true strain when considering the elongating effect.•PLC band propagating velocity decreases with increasing true strain.
Uniaxial tensile tests at three strain rates are performed with the aid of the digital image correlation (DIC) technique to experimentally investigate the spatio-temporal behavior of PLC bands in a twinning induced plasticity (TWIP) steel. The whole strain fields of tensile specimens are acquired throughout the tests. Significant serration crests corresponding to band nucleation are observed on the true stress vs. true strain curves derived from DIC results beyond a critical true strain. The work hardening exponent (n-value) increases from ∼0.08 to ∼0.5 when true strain increases to the critical true strain, and beyond that, the n-value exhibits serrations with increasing true strain. Two typical nucleation modes of Type-A Portevin–Le Châtelier (PLC) bands are observed in all tests. Nucleation and propagation of PLC bands are described in details based on these two nucleation modes of Type-A PLC bands. The PLC band orientation, which indicates the angle between the normal direction of a PLC band and tensile direction, fluctuates during propagation, and the fluctuation amplitude increases during the development of a localized necking band from a PLC band before fracture. In particular, the effect of strain rate on the kinematics of Type-A PLC bands (band strain, band width and band propagating speed etc.) in the TWIP steel is quantitatively analyzed, and a new algorithm based on the DIC results is presented which includes the elongating effect of tensile specimens during deformation to show the actual kinematics of Type-A PLC bands.