A procedure for calculating through laser speckle interferometry the elastic constants of isotropic materials

The displacement suffered by the points located on one face of a parallelepipedic specimen made of isotropic elastic material is studied, while subject to simple compression, which generates not only strain but also both a translational and a rotation effect. The displacement is measured by double-exposure speckle photography. The elastic constants of a material are computed by measuring the in-plane displacement of three points. The effect of the in-plane and out-of-plane displacements due to translation and rotation are analyzed. Extreme values for the tilt angle are estimated, as well as the maximum diameter of the read-out beam. The systematic uncertainty of the method is also studied. Both Young's modulus and Poisson's ratio are experimentally measured in aluminum.