Determination of Crack Tip Plastic Zone Using Dynamically Visible Mechanochromic Luminescence Response

The plastic zone shields the crack tip from high stress and plays an important role in the fracture of structures. Determination of the plastic zone is a significant challenge in large-scale and complex structures. In the present work, a detection method using mechanochromic luminescent (MCL) sensing film has been proposed to detect the plastic zone near the crack tip. The deformation near the crack tip is converted into visible green fluorescence emission. A comprehensive post-processing protocol and a feature quantification scheme for fluorescence images are introduced. A significant correlation is obtained between the characteristic values of fluorescence images and the parameters of the plastic zone (i.e., maximum equivalent strain and plastic zone size), indicating that the fluorescence response provides effective characterization parameters within the forward model. The plastic zone parameters determined using the MRL-based method agree well with the results measured using the DIC method. This indicates that the plastic zone near the crack tip can be effectively analyzed by capturing loading conditions and fluorescence response.