DIRECT STRAIN AND SLOPE MEASUREMENT USING 3D DSPSI Wajdi Dandach a , Jerome Molimard b and Pascal Picart c a LTDS, UMR 5513, École Nationale Supérieure des Mines, SMS-EMSE, CNRS, Saint-Étienne, France b LCG, UMR CNRS 5146, École Nationale Supérieure des Mines, CIS-EMSE, CNRS, Saint-Étienne, France c LAUM, UMR CNRS 6613, ENSIM, Université du Maine, Rue Aristote - 72085 Le Mans cedex 09, France dandach@emse.fr, molimard@emse.fr, pascal.picart@univ-lemans.fr ABSTRACT: this communication presents a new implementation of DSPSI. Its main features are 1. an advanced model taking into account the beam divergence, 2. the coupling with a surface shape measurement in order to generalize DSPSI to non- planar surfaces 3. the use of small shear distance made possible using a precise measurement procedure. A first application on a modified Iosipescu shear test is presented and compared to classical DIC measurements. 1. INTRODUCTION Most of OFFT measure displacements (Electronic Speckle Pattern Interferometry, Grid Method, Moiré Interferometry and so on); one of the challenging parts of displacement measurement techniques is the calculation of the strain map from the displacement map. In particular, noise propagation and lens distortion has to be carefully treated. Adjacent to the methods measuring displacements, Shearography measures directly displacement derivatives of surfaces. More precisely, it eliminates the reference beam of holographic or speckle interferometry, which leads to a simplified optical set-up, not requiring special vibration isolation. These advantages have exhibited practically shearography a surface strain and rotation measurement system. A new implementation of shearography is presented here; its main features are 1. an advanced model taking into account the beam divergence, 2. the coupling with a surface shape measurement in order to generalize shearography to non-planar surfaces 3. the use of small shear distance made possible using a precise measurement procedure. Complete 3D feature is not presented here anyway, and a first application on a modified Iosipescu shear test is presented and compared to classical DIC measurements. 2. 2D/3D SHEAROGRAPHY SYSTEM 2.1. Description of shearography set-up The set-up main architecture is classical, but light is conducted using optical fibers, as presented previously in [1] (Figure 1). A tunable laser illuminates the front surface of the specimen. Light is sequentially injected in the four optical fibers by using an optical switch. The outputs fibers are attached to a device, manufactured in the laboratory, which allows the laser beam illuminating the surface of the specimen by four directions, with equivalent illumination angle. Due to the global geometry anyway, the beam are uncollimated, and illumination angle (and consequently the sensitivity vectors) are not constant over the map. The diffused beam from the specimen is sheared by Michelson interferometer. First mirror is fixed; the second is controlled by a 3-axis PTZ device PSH 1z NV from Piezo-system Jena, capable of tilting or translating a mirror. Shearing in x or y directions is obtained by tilting one mirror, similarly phase stepping is realized with a piston movement of the mirror. Figure 1. Sherarography set-up 1