Investigation of the plastic zone around the crack tip in small-scale pure Titanium specimens by means of Thermal Signal Analysis and Digital Image Correlation

The local plasticity characterizing the area around the crack tip affects the elastic strain field area due to the boundary interaction between the two zones. Its effects on the SIF and on the Paris' Law are known, hence it must be considered in the crack growth monitoring and the fatigue limit estimation. Among the different approaches developed, those focusing their attention on the interaction between the elastic stress field and the plastic area seems to be more promising in the evaluation of the crack growth behaviour. In this work, an experimental approach was adopted to identify the plastic zone around the crack. In particular the Thermal Signal Analysis was employed and the thermal footprint was compared with shape and size of the plastic zone predicted through the application of Digital Image Correlation (DIC) in combination with two theoretical models: Westergaard's model for the stress distribution around the crack tip and the more recent Christopher-James-Patterson (CJP) model