Current trends in obtaining deformation data from grids

Summary This paper briefly describes some of the methods which are being actively investigated as ways of extending the range of structured grid methods. Many of these techniques apply new hardware technology to old ideas as a means of achieving this goal. Solid-state imaging devices along with digital-image processing and pattern recognition have had a dramatic impact on grid methods. The three methods described here by no means represent an exhaustive account of all current research. Digital autocorrelation23 can certainly be classified as a grid method, where the grid is random instead of structured. Digital autocorrelation methods applied to solid mechanics are techniques which grew out of the image-processing hardware, as opposed to adapting image-processing hardware to existing techniques. Microstructural grid methods based on centroiding and autocorrelation, though not yet fully automatic, are also very exciting. 24,25 These methods define a grid from the natural features in the microstructure; therefore these methods are also classified as unstructured grid methods. Diffraction methods for out-of-plane motion are also worthy of mention.26