Investigation of the coating parameters for the luminescent photoelastic coating technique

Abstract

The luminescent photoelastic coating (LPC) technique is an optical method to measure the full-field strain on 2D and 3D structural components. The maximum shear strain - or separated principal strain when oblique incidence is performed - and its corresponding principal strain direction are related to the relative changes in emission magnitude with respect to analyzer position. The amplitude of the emission change is termed optical strain response, OSR, and is a function of maximum shear strain, γ max, in the plane perpendicular to light propagation and two coating calibration parameters: the polarization efficiency, φ, and the coating characteristic, η. Determining the coating parameters plays an important role since they affect the accuracy of the measurement. Generally, the coating parameters are calibrated in-situ with strain gage measurements and assumed independent of surface inclination. A better theoretical understanding of the two calibration coefficients, specifically the polarization efficiency, φ dependence on oblique excitation or emission inclination is necessary to improve full-field, strain-separation accuracy of the measurement. This study investigates and reports the effects of the coating parameters on OSR, and the current methods to determine the coating parameters. ©2010 Society for Experimental Mechanics Inc.