An investigation on the Bauschinger effect in titanium alloys for aerospace applications: strain rate and pressure dependence

A comprehensive study of the reverse loading in Ti-6Al-4V hereafter, Ti64 alloys including strain rate and pressure effects (strength differential), is conducted in order to improve the understanding of the deformation mechanisms in Ti64 and characterise its Bauschinger effect. Strain controlled quasi-static, and high strain rate reverse loading tests are performed, providing novel data to conduct a series of explicit finite element (FEA) simulations with the objective to determine the capabilities of widely used constitutive models to predict the material response under cyclic loading. The analysis of the experimental data shows that the Bauschinger effect (B.E.) in the material is manifested principally as the loss of a distinct transition between elastic and plastic dominated deformation regions (transient softening), leading to the lowering of the plastic work expended during the straining of the material. The analysis of the strain rate effects on the cyclic response of the material, allows to identify an inversely proportional relationship between strain rate and B.E. as well as a higher prominence of the aforementioned drop in the plastic work when the loading is conducted in the opposite direction to the pre-strain. The numerical study conducted shows that general, widely used constitutive models calibrated with monotonic data are not able to accurately predict the cyclic loading response of Ti-6Al-4V alloys, proving the importance of the Bauschinger effect as factor to consider in order to obtain reliable models of the material’s response to complex loading.