Analysis of the high speed sliding interaction between titanium alloy and tantalum
Résumé
Dry friction under extreme conditions between tantalum and titanium alloy (Ti-6Al-4V) was analyzed by using a finite element model of asperity interaction. To combine high sliding speed and high normal pressure, an experimental set-up based on a ballistic device with air gun launch, is presented. A single friction pass is realized at 38 m/s to understand the initial stage of the friction and wear process. Contribution of the interface mechanical phenomena on the rough surface contact is investigated through a finite element approach considering the contact at the scale of asperities. A thermoviscoplastic model coupled with damage law is proposed to explore the micro-contact conditions. Experimental observations obtained by light white profilometer are conducted to correlate the modeling. The simulation results show that the shearing of asperities occurs at high strain rate and large deformation. The material transfer mainly occurring from titanium alloy to tantalum, is the result of a competition between thermal softening and plastic hardening. The thermo-mechanical aspect seems to be the primary cause of metal transfer and wear. Shear localization may explain the frictional heating due to high strain rates. It was found that the localized temperatures combined with high normal pressures favor micro-weldings generated at the extremity of asperities.