Mechanical Engineering
2 total works
Moire patterns (which form when two regular patterns of comparable frequency interfere) are sensitive indicators of changes of shape as objects rotate, heat up, or are otherwise affected by external forces. Applications include non-destructive testing and evaluation, and quality and process control. This text explains the theory and practice of physical measurements by high-sensitivity moire - principally moire interferometry, focusing on the mechanics and micromechanics of materials and structural elements. Moire interferometry is unique in providing maps of in-plane displacements from which can be derived normal and shear strains. Typical moire sensitivities are on the order of 2-4 fringes per fm displacement, but sensitivities of 17 nm per fringe contour can be reached. The applications discussed include: advanced composite materials, thermal stresses, electronic packaging, fracture, metallurgy, time-dependence, and strain gage calibration. The methods discussed in the text can be applied for whole-field measurements on nearly solid and solid bodies.