Investigation on the Effect of Asymmetric Cyclic Loading on Ratcheting Deformation and Bulk Texture Development in HSLA Steel

Abstract

Ratcheting deformation in association with bulk texture evolution in HSLA steel is studied in this investigation. The cyclic deformation behaviors and damage modes of the specimens are obtained at room temperature, employing asymmetric stress-controlled tests under various combinations of mean stress and stress amplitudes. Bulk texture measurements of the specimens are done adopting an X-ray diffraction analysis. The results exhibit an increase in strain accumulation from 0.23 to 30.61% associated with a sharp reduction in ratcheting life from 3320 to 880 cycles by the increment in mean stress/stress amplitude. A continuous cyclic softening until the final failure is observed for all the ratcheting tests. It is noticed that variation of mean stress is more detrimental than stress amplitude in controlling strain accumulation while the effect of stress amplitude is more pronounced than mean stress for the reduction of ratcheting life. The fracture surface morphology indicates typical striation formation in the crack propagation region along with overload failure. The bulk texture studies indicate that there is a transition between ‘ϒ’ fiber and ‘ζ’ fiber during all loading conditions. The texture intensity is increased from 5.71 to 11.68 with progressive ratcheting strain accumulation. Here also, influence of stress amplitude is more significant than the mean stress.