Heat dissipation and acoustic emission features of titanium alloys in cyclic deformation mode

The present work unveils the features of heat dissipation and acoustic emission accompanying the fatigue crack growth in a titanium alloy (Ti-0.8Al-0.8Mn and Ti Grade 2) using the compact tension and Charpy V-notch specimens. The quantitative measurements of the heat dissipation rate were carried out by an original heat flux sensor. The obtained results reveal that there exist two appreciably different stages of the crack propagation within the stable Paris regime. Relationships between the crack growth rate and the heat dissipation rate are proposed for both stages. The application of the non-supervised clustering algorithm to the continuously recorded acoustic emission signal helped to identify two dominant mechanisms of stress relaxation that occur ahead of the crack tip—mechanical twinning and crack opening. The correlation between the acoustic emission energy and heat dissipation was found to be a harbinger of the approaching transition from stable to unstable crack growth.