NDT: Laser Shearography
Laser shearography (LS) is an optical interferometric technique, which provides surface deformation information of an element in real time.
The operation consists in illuminating the object under study by using an expanded laser, at different stress conditions. The last one, can be introduced in the test part by a partial vacuum, thermal excitation or vibration.
The stress induces the deformation of object surface, which is locally modified by subsurface defects such as delamination or debondings, for composite or sandwich structures, respectively.
After a quick comparison between both stress conditions, by calculating the induced deformation gradient, indications are easy detected.