Measurement of elastic moduli using spherical indentation and digital speckle pattern interferometry with automated data processing

The Young's modulus and the Poisson's ratio of an isotropic material are measured using digital speckle pattern interferometry. The technique is based on the determination of the permanent local displacement field generated in a specimen after it is plastically deformed with a spherical indenter. Using a phase shifting technique and a phase unwrapping algorithm, the phase distribution coded in the speckle interferograms can be quickly obtained. By adjusting the displacement field generated by the indentation to an empirical model produced by a point force in a semi-infinite elastic medium, the values of both elastic moduli can be determined by applying a least-squares inversion method to the evaluated continuous phase distribution. The performance, accuracy, advantages and limitations of this technique are determined by evaluating the elastic moduli of bronze.