Energy Storage and Dissipation in Consecutive Tensile Load-Unload Cycles of Gum Metal

Multifunctional beta-titanium alloy Gum Metal, characterized by a relatively low elastic modulus, superelastic-like behavior and high strength, was subjected to cyclic tensile loadings. The characteristics of macroscopic scale energy storage and dissipation in the consecutive loading-unloading cycles were studied. Various kinds of energy components related to the alloy deformation process were determined experimentally and analyzed using thermodynamic relations. The values of the entire work needed to deform the alloy W-ext, the work used for recoverable deformation W-rec consisting of the elastic deformation energy W-el, the superelastic-like energy W-pt, and the energy of thermoelastic effect E-th, were derived from the Gum Metal stress and temperature vs. strain curves. The irrecoverable mechanical energy Wir expended on plastic deformation, the dissipation energy Q, and finally the stored energy E-s were estimated. The stored energy represents a change in the internal energy of the deformed material and is an essential measure of cold-worked state. The E-s value turned out to be not large for the Gum Metal, which confirms the alloy low hardening property. The energy components determined for each of the 24 loading cycles enabled us to analyze various stages of the Gum Metal deformation process, including necking and damage.