Transient tensile behavior of interstitial-free steel and 70/30 brass following plane-strain deformation

Abstract

The transient behavior of interstitial-free (IF) steel and 70/30 brass which results from an abrupt change in strain state has been investigated experimentally and modeled analytically. After a plane-strain prestrain, reloading in uniaxial tension results in a negative stress transient for brass and a positive stress transient for IF steel. The strain behavior during the stress transient was studied by measuring the local axial and transverse strains using resistance strain gages. The monotonic data exhibited a constant plastic strain ratio, whereas the prestrain data showed decreasing plastic strain ratios with increasing axial strain for both IF steel and brass. A simple analysis of the transient was performed by modifying Hill's nonquadratic yield surface to allow variable plastic anisotropy (via r) during the transient. By choosing an appropriate variation ofr, the stress transient could be reproduced. The predicted variations in strain ratios by the model agreed qualitatively with measurements for brass but were of the opposite sign to measurements for steel. Although not conclusive, this result suggests that the normality condition is violated during a stress transient induced by an abrupt change in strain path.