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In this paper we introduce a newly developed 3D stress/strain analysis technique, called digital volumetric speckle photography (DVSP), that has the capability of probing internal strain distribution inside opaque solids under load. We take advantage of X-ray computed tomography's ability to record 3D volumetric image of solids with internal markers such as impunities, voids, etc and treat them as 3D volumetric speckles. Under load these markers will move accordingly. We track their displacements via a two-stage 3D FFT process which is an extension of the 2D process used in 2D digital speckle photography technique developed in 1993 by F.P. Chiang and his coworkers. We have successfully applied DVSP to strain analysis of rocks, concrete, and composites. The resolution of the technique is a function of the hardware used. It varies from macro scale with a medical X-ray CT, to micro scale with an industrial X-ray CT, and to nano scale with a synchrotron radiation CT.

3D strain analysis;digital volumetric speckle photography; computed tomography;FFT.