Showing papers by "K. Ramesh published in 2018"
TL;DR: In this article, a systematic study is done to determine the choice of suitable individual displacements or a combination to evaluate not only mode-I SIF but also T-stress.
25 citations
TL;DR: A novel normalization methodology is developed to improve the dynamic range in both low and high fringe density areas and it is demonstrated that while applying normalization for stretching the dynamicrange, one has to use only an experimentally recorded calibration table that is normalized.
23 citations
TL;DR: In this article, a semi-automatic contact point refinement algorithm is proposed to evaluate the unknown contact parameters by post processing the whole field fringe order data obtained from reflection photoelasticity in a nonlinear least squares sense.
23 citations
TL;DR: In this article, the explicit equations recently reported in the literature for a flat punch with rounded edges are generalized so that a single set of equations can be used for Hertzian contacts with arbitrary radii of curvatures, and the generality of the governing equations is verified by plotting isochromatics for conformal and non-conformal contact situations.
Abstract: Experimental studies to exploit photoelastic data of conformal geometries to extract contact parameters are non-existent because closed-form stress field equations were not available until recently. In this paper, the explicit equations recently reported in the literature for a flat punch with rounded edges are generalized so that a single set of equations can be used for a flat punch with rounded edges and Hertzian contacts with arbitrary radii of curvatures. The generality of the governing equations is verified by plotting isochromatics for conformal and non-conformal contact situations. A generic method to evaluate unknown contact parameters from the whole-field isochromatic data for conformal and non-conformal geometries is implemented. The methodology is initially verified using theoretically generated isochromatic data and is then used to experimentally evaluate two contact situations. In view of high-fringe gradient zones, the suitability of various digital photoelastic methods is compared. A novel four-step phase shifting technique is proposed in which isochromatic and isoclinic data can be evaluated using the minimum number of images.
18 citations
TL;DR: In this paper, the photoplastic behavior of polycarbonate is studied using digital image correlation (DIC) to determine the relation between fringe order and principal strain difference for strains of up to 60%.
Abstract: Earlier studies on photoplastic behaviour of polycarbonate are limited to the strain at which the localized yielding (necking) initiates (about 6% strain). In this study, the photoplastic behaviour of polycarbonate is studied using digital image correlation (DIC). Two cases are considered: one in which no localized yielding is observed and the other in which initiation and propagation of the localized yielding is observed. For the first case, a modified dog bone specimen is proposed to evaluate the photoplastic constant. In the second case, a conventional tensile test specimen is used. Both photoplasticity (transmission and reflection) and DIC experiments are performed on the specimens to determine the relation between fringe order and principal strain difference for strains of up to 60%. It is observed that the photoplastic constant is a function of strain. Finally, the behaviour of the tensile test specimen is numerically simulated. The true stress-strain curve of polycarbonate needed for FE simulation is determined using DIC experiments on the standard tensile test specimen. By post-processing the FE results, isochromatic fringes are plotted and compared with experimental results.
4 citations