Mechanoluminescent materials : a new way to analyze stress by light

The monitoring of stress changes in structural components under various kinds of dynamical loading is crucial for the assessment of their integrity and lifetime. In addition to many methodologies available, such as strain gauges, optical fiber sensors, X-Ray diffraction and digital image correlation, we introduce a novel non-contact method to visualize stress distributions based on mechanoluminescence (ML). ML is a phenomenon occurring in some materials that emit light upon an applied stress level. In this paper, we develop the ML material (Ca0.4Sr0.6)Al2Si2O8:1%Eu2+,1%Ho3+, a glow-in-the-dark material, to visualize stress distribution in a disc, as well as the stress field of an ultrasonic transducer. The properties of defects in the ML phosphors, which are responsible for ML in this material, are vital for stress visualization