Showing papers by "K. Ramesh published in 1992"
TL;DR: A new methodology, developed for thinning fringes in photomechanics, splits fringe thinning into two distinct steps, namely, fringe edge detection and fringe skeletonization and a new approach to automating fringe ordering is proposed.
Abstract: new methodology, developed for thinning fringes in photomechanics, splits fringe thinning into two distinct steps, namely, fringe edge detection and fringe skeletonization. A minimum intensity criterion is utilized to extract the fringe skeletons from broadbands. The algorithm is applicable to any orientations ofthe fringe. It is noniterative and requires less computations than the other reported methods. A novel scheme is developed to remove discontinuities and noise in the fringe skeleton. The various steps of the algorithm are explained by processing a test image free of noise. The applicability of the algorithm to actual experimental situations is verified by processing fringes obtained by photoelasticity and moire. Preprocessing of the fringes is discussed in detail. A method is also developed for determining the coordinates of any point chosen on the fringe contour. This step involves the use ofthe system characteristics of the PC-based image-processing system. Fringe ordering is kept interactive to utilize the experimentalist's expertise. A new approach to automating fringe ordering is proposed.
35 citations
01 Jan 1992
TL;DR: In this article, the effect of material orthotropy, change of material and a / w ratio in influencing the geometry of the fringe loops is studied in detail for mode I type of loading.
Abstract: Classification of crack-tip isochromatics in unidirectional orthotropic composites, when the crack is parallel to the fibre and perpendicular to the fibre direction, is considered for mode I, mode II and mixed-mode type of loadings. The knowledge of the mode of fracture helps in identifying the appropriate governing equation to evaluate the Stress Intensity Factor (SIF) from the experimental fringe patterns. The effect of material orthotropy, change of material and a / w ratio in influencing the geometry of the fringe loops is studied in detail for mode I type of loading. Typical experimental fringe patterns are obtained by photo-orthotropic elasticity for mode I, mode II and mixed-mode loadings. The inclusion of the term σ ox to the σ x stress term introduced by Mojtahed and Zachary is validated. The necessity for developing a higher order theory in evaluating the SIF from experimental fringe loops when the crack tip is closer to a free boundary is emphasised.