Sheareography - a Practical Optical Testing and Measuring Method

Abstract

Shearography is a laser optical method which is suited for either nondestructive testing or for \nstrain analysis. Contrary to holography which measures surfach displacements, shearography \nmeasures derivatives of surface displacements. Since strains are functions of displacement \nderivatives, shearography allows strains to be determined without numerical differentiating \ndisplacement data. Defects in object normally create strain concentrations; it is easier using \nshearography to correlate defects with strain anomalies rather than displacement anomalies \napplying holography. Furthermore, rigid body motions do not produce strain, thus shearography \nis insensitive against such motions and does not need adopting any particular device for vibration \nisolation. It is an industrial tool suited very well for the following ares: \n1. strain measurement and strain analysis \n2. nondestructive testing and quality assurance system \n3. optimization ofmachine parts and structures of any material