Determination of Surface Strains for Objects of Arbitrary Shape in Holographic-Moire Interferometry

摘要

Surface strains for objects of arbitrary shape are determined, using holographic-moire, with illumination in collimated light and observation from one point (camera). Contourline maps for the three orthogonal displacement components are used, from which the 'basic strains' are determined as if the object were flat. The shape of the object is determined by contouring holography or shadow-moire. The 'basic slopes' of the object are determined as if observation were from infinity. The photographs of the interference pattern and the shape of the object serve as reference planes. Formulas are derived in which the surface strains of a non rectangular surface element are expressed into the following known quantities of a rectangular reference element: coordinates of the regarded point, basic strains and basic slopes. By means of a Mohr's circle construction the principal strains and directions can be obtained.