Abstract
Damage initiation and kinetics in four α/ β titanium alloys have been experimentally and numerically investigated. Efforts were focused on triaxiality, χ=Σ m/ Σ eq (where Σ m is the hydrostatic stress and Σ eq the von Mises equivalent stress) and internal stresses (back stress X) effects. The study of void nucleation has provided nucleation criteria corresponding to voids at the α/ β interface. This macroscopic nucleation criterion, written as Σ m= f( ε peq), was explained with the help of microscopic observations. Microscopic parameters such as plastic strain in the α-phase or local hydrostatic stress σ loc m at the α/ β interface have been linked to the damage initiation. Also, the influence of the different heterogeneity levels on the macroscopic nucleation criterion was demonstrated. It has also been shown that internal stresses increased both nucleation and growth kinetics. Damage mechanisms are well described by a Gurson–Tvergaard model modified to take into account internal stresses. In particular, the existence of a material physical property, f c (void volume fraction at fracture) was shown.
Published Version
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