Influence of Machine Stiffness on the Portevin-Le Chatelier Effect of Ti-12Mo Alloy Based on a Modified McCormick Constitutive Model

An improved 3D FE model, considering machine stiffness effect and strain dependent parameters in an embedded modified McCormick's constitutive model, is developed to numerically investigate the spatiotemporal characteristics of the PLC effect in Ti-12Mo alloy tensile tests. The material parameters of the modified McCormick's model are calibrated in details, and the simulated results are compared with experiment and literature ones. Then, the influence of machine stiffness on the spatiotemporal behaviors of the PLC effect in Ti-12Mo alloy are quantitatively analyzed. The results show that the improved FE model has a higher simulation accuracy in term of stress drop frequency. Moreover, the average stress drop magnitude decreases and the number of stress drops increases with the increase of machine stiffness, which are mainly owing to the decrease of aging time. Furthermore, the PLC band width decreases as increasing machine stiffness, which is attributed to the decrease of driving force for band nucleation. Besides, the continuous and hopping propagations of the PLC band are observed, and the propagation continuity obviously increases as increasing machine stiffness, which is mainly related to the increase of spatial coupling force.