Rigid Body Effects in Shearographic Strain Measurements

Abstract

Correlation fringes in shearography are in general more stable and less dense than in conventional ESPI. The fact, that both interfering beams travel much the same way tends to compensate for turbulent air and vibrations as well as for rigid body translations. However, residual artifacts from rigid body motions influence the results of quantitative shearographic analysis of displacement derivatives and strains. This presentation assesses the effect of the various components of rigid body motion on a quantitative shearographic measurement by analysing the sensitivity matrix. It further discusses the possibility to identify and correct for rigid body motions in the case that two shear directions are measured simultaneously.