Measurement of in-plane surface strain by hologram interferometry

Abstract

It is shown that the interference fringe patterns obtained by hologram interferometry provide information about surface displacement resolved in one direction only. By recording holograms of the surface from different viewpoints and operating numerically upon the fringe order numbers at corresponding points on the surface, it is possible to measure the displacement in any chosen direction. As an example, the strain in the plane of a stretched metal foil was measured by recording two `frozen-fringe' holograms simultaneously and subtracting one set of fringe contours from the other.