Showing papers by "K. Ramesh published in 2017"

Birefringence measurement for validation of simulation of precision glass molding process

Abstract: During fabrication of glass lens by precision glass molding (PGM), residual stresses are setup which adversely affect the optical performance of lens Residual stresses can be obtained by measuring the residual birefringence Numerical simulation is used in the industry to optimize the manufacturing process Material properties of glass, contact conductance and friction coefficient at the glass-mold interface are important parameters needed for simulations In literature, these values are usually assumed without enough experimental justifications Here, the viscoelastic thermo-rheological simple (TRS) behavior of glass are experimentally characterized by four-point bending test Contact conductance and friction coefficient at P-SK57™ glass and Pt-Ir coated WC mold interface are experimentally measured A plano-convex lens of P-SK57™ glass is fabricated by PGM for two different cooling rates and whole field birefringence of the finished lens is measured by digital photoelasticity The fabrication process is simulated using finite element method The simulation is validated, for different stages of PGM process, by comparing the load acting on the mold and displacement of the molds At the end of the process, the birefringence distribution is compared with the experimental data A novel plotting scheme is developed for computing birefringence from FE simulation for any shape of lens This article is protected by copyright All rights reserved

Evaluation of Hertzian contact parameters from whole field displacement data

Abstract: Evaluation of contact parameters in Hertzian contact from displacement data is studied. Based on complex potential approach, generic explicit equations for displacement field in the vicinity of the...

Contact Zone Evaluation of Dental Implants Using Digital Photoelasticity

Abstract: Use of dental implants in case of missing natural dentition is now common in clinical dentistry. The tilted implant configurations, which are inevitable in many clinical situations, are prone to higher stresses. The orientation of implants has a great influence on its structural integrity as high stresses around the implants adversely affect the osseointegration process and eventually fail due to the bone resorption. Hence, complete understanding of such complex systems demand better understanding of the bio-mechanics involved. Photoelasticity, a whole-field optical technique, is the right choice for analysing such implant configurations. Recent advancements in digital photoelasticity make it possible to evaluate isochromatics as well as isoclinic parameters over the entire model domain with considerable accuracy. However, these techniques have not been exploited in the field of implant dentistry and photoelasticity has been mostly used as a visualisation tool. This paper explores the use of modern photoelastic techniques for analysing the stress distribution due to an implant with an inclination of 15°. Further, this work also studies the high stress zones in the coronal region of this angled implant. The isochromatic data is post processed using least squares method for determining the contact parameters such as effective contact length and frictional coefficient.