Development of a Computer-Based Measurement Methodology For Determination of General Parameters in Mechanics

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Measurement of the normal displacement of a three-dimensional body subjected to arbitrary loading or boundary displacements has been a major problem for experimentalists for the past century. Elaborate optical methods including holography and speckle interferometry are only applicable to the two dimensional problem where the specimen surface is plane. Recently, improvements in video cameras and computers (storage capacity) have led to significant advances in image analysis which can be effectively employed to record displacements. The approach is to record and store in pixel form the surface features of the specimen in its deformed and undeformed state. Intensity interpolation methods are then employed to identify small subsets on the specimen and to determine the displacement of these subsets. The method has been established for two-dimensional bodies undergoing plane deformation. The proposed program will extend these methods to three- dimensional specimens by utilizing two video cameras and stereo imaging procedures to obtain the images required for displacement determinations. Advanced methods of image correlation methods will be employed to achieve sub-pixel accuracy in the displacement measurements.