Temperature dependence of the luminescent photoelastic coating technique

This paper presents the optical strain response results of a luminescent photoelastic coating (LPC) at elevated temperatures up to 100 °C. The LPC technique is used to acquire full-field stress and strain measurements on structural components. Differing from traditional reflective photoelastic coatings, an LPC uses a luminescent dye that partially retains the induced polarization changes in the illumination field through the coating and provides a relatively high signal response at oblique incidence angles. These characteristics enable the LPC technique to measure the full-field separated principal strains and their directions using oblique excitation. The strain-dependent response of the coating is affected by several parameters such as the luminescent polarization efficiency, optical sensitivity, coating absorptivity, and effective excitation or emission wavelength. The effect of temperature elevation on these parameters is important to characterize if the technique is extended to high-temperature or cyclic-temperature environments. Temperature sensitivity is documented and measurement uncertainty is addressed. Overall, the measured optical strain response decreased by 77 per cent between 24 °C and 92 °C with a steepest decent of –8 per cent/°C at 65 °C.