Combination of 3-D deformation and shape measurement by electronic speckle-pattern interferometry for quantitative strain- stress analysis

Laser speckle interferometry as a full-field noncontact measuring technique offers interesting opportunities for strain-stress analysis on components. While its application in material testing and material research has already achieved some acceptance in research and industry, its application to complex industrial components like car bodies, gear boxes, engines, and suspensions has been limited. Basic difficulties have arisen from the relatively large rigid-body movements of components under test, harsh environmental conditions in the real test world, and the often complex shape of the analyzed component, especially in the most interesting areas. The commercial availability of a radically miniaturized 3-D speckle interferometer has led to the new laser-optical measuring device, the MicroStarâ„¢, which can be used for quantitative strain-stress measurement on nearly any industrial component. The device uses 3-D speckle interferometry to measure the shape and the 3-D deformation in the area of interest. The combination of shape and deformation provides all necessary data for quantitative 3-D strain analysis. The principal stresses as well as the bending and tensile components of the strains can be easily determined. In this paper, the principle and applications of this new system are presented.