GUM METAL MECHANICAL PROPERTIES INVESTIGATED BY INFRARED CAMERA AND DIGITAL IMAGE CORRELATION
E.A. Pieczyska, K. Golasiński1, M. Maj, M. Staszczak, S. Kuramoto and T. Furuta
Results of thermomechanical couplings and digital image correlation in Gum metal - new multifunctional β-Ti alloy, subjected to tension at various strain rates are presented. The alloy ultralow elastic modulus, high strength, as well as development of the strain localization were studied. Temperature changes accompanying the deformation process, estimated by fast and sensitive infrared camera, were used to indicate the alloy Yield limit with high accuracy. It was found that the maximal drop in Gum metal temperature occurs significantly earlier than so long limit of its mechanically reversible nonlinear deformation. The temperature increase proves a dissipative character of the process also at this stage and is related to presence of α" and ω phases induced during the alloy fabrication and their exothermic phase transformations activated under loading. During plastic deformation, both the strain and temperature distributions demonstrate that at higher strain rates strain localization starts nucleating just after the Yield limit leading to the specimen necking and rupture. Macroscopically, it is exhibited as softening of the stress-strain curve in contrast to the strain hardening observed at lower strain rates. The research has been carried out in the Institute of Fundamental Technological Research IPPT PAN with cooperation of the Toyota Central Research & Development Laboratories and Department of Mechanical Engineering, Ibaraki University. Support of the Polish National Science Centre under Grants 2014/13/B/ST8/04280 and 2017/27/B/ST8/03074 is acknowledged.