Moire methods for engineering and science - Moire interferometry and shadow Moire

Moire interferometry and shadow moire are extraordinarily versatile and eff ective methods for determining in-plane and out-of-plane displacement field s, respectively. The basic concepts are reviewed for both methods, topics o n practice and analysis are addressed, and numerous examples of important a pplications are presented. The moire data are received as whole-field fringe patterns, or contour maps , of displacements. For moire interferometry with the typical reference gra ting frequency of 2400 lines/mm, the contour interval is 0.417 mu m per fri nge order; the sensitivity is 2.4 fringes per mu m displacement. Orthogonal U and V displacements are measured, and normal and shear strains are deter mined from these in-plane displacement fields. For microscopic moire interf erometry, sensitivity corresponding to 17 nm per fringe contour has been ac hieved by means of the optical/digital fringe multiplication algorithm. The patterns of moire interferometry are characterized by excellent fringe contrast and spatial resolution, including patterns from complex applicatio ns. The applications reviewed here address laminated composites, including the study of free-edge effects along the cylindrical surface of holes in la minated plates; thermal deformation of microelectronics devices; the damage wake along a crack path, and a micromechanics study of grain deformations in titanium. The examples of shadow moire show the out-of-plane displacements W for preb uckling and post-buckling of columns; and W displacements of electronic pac kages subjected to temperature changes. Phase-stepping analyses were used f or the electronic packages to increase sensitivity, providing 12.54 mu m pe r fringe contour. Since W is typically much larger than U and V, the sensit ivity of shadow moire can be adjusted to serve broad categories of engineer ing applications.