Three-dimensional Strain Analysis And Measurement Of Surface Displacement Moire Interferometry

Based 6n successful combination of mordern optical information processing theory and wavefront interferometry theory of moire interferometry, three problems which are difficult and eager to solve in mordern photomechanics are investigated. 1.Simultaneous measurement of 3-D displacement fields by moire interferometry. Using high—frequency specimen gtratings of 600 and 1200 lines / mm, three approaches to the measurement of displacement fields with high sensitivity are achieved. (1) Real time method: By means of a specially arranged moire interferometry all the 3 displacement components, U,V,W are observed simultaneously in real time on 3 seperated image plane respectively. (2)Load-difference method. A 3-D Moire Interferometer is developed, by which 3-D deformation informations are recorded simultaneously on one plate for any load increament, and every load—induced displacement component is extracted by optical filtering. (3) Additive moire interferometry by which real time and load-induced out—of-plane displacement fields are obtained with an extremely high sensitivity of nearly a quarter of wavwlenghth. All the 3 methods above can be used in the treatment of both static and dynamic problems. 2.Simultaneous measurement of 3-D displacement derivative fields by shearing moire interferometry. A dual beam moire interferometry arrangement with a reference beam emerging normal to the surface of a specimen grating is proposed. 3-D displacement informations are recorded on the same plate by double-exposure method. Optical filtering and shearing techniques are applied to extracting the contour maps of 3-D displacement derivatives ((?)U/(?)X, (?)U/(?)Y, (?)V/(?)X, (?)V/(?)Y, (?)W/(?)X, (?)W/(?)Y). 3. Measuring in-plane displacement fields (V_θ,U_x) of a cylindrical curvature surface by moire interferometry. Two optical interferometry systems are suggested. One is a Two-cylindrical-wavefront-interferometry system measuring the circumferential displacement field(V_θ). The other is a dual—beam moire interferometry arrangement to measure the axial displacement field(U_x). A circuler. cylindrical shell specimen under an axial compression is studied as an experimental demonstration. Double exposures are made and displacement informations are recorded by a holography film stuck to the surface of the shell. In-plane displacement fields(V_θ, U_x) of the shell specimen are extracted later by optical filtering.All the methods above are recently suggested. Rigorous theoretical anlyses are given. Demonstration experiments are conducted successfully. Excellent interferometry fringes are obtained with high sensitivity and in wide measurement range. Experimental results agree well with theoretical and calculated values.