photoelasticity
An Innovative Polariscope for Photoelastic Stress Analysis
Jon R. Lesniak 1, Michael J. Zickel1 , Christopher S. Welch2, Deonna F. Johnson2
Abstract
An innovative polariscope involving a single rotating optical element and a digital camera for full-field image acquisition allows automated data to be acquired quickly and efficiently.
Software analysis presents the data in an easy to interpret image format depicting the magnitude of the shear strains and the directions of the principal strains.
automated grey-field polariscope has been devised that painlessly collects both magnitude and direction data without user intervention. Although the new polariscope is capable of making multiple fringe measurements, it has its greatest impact in sub-fringe applications where the output parallels the description of the stress state of an object given by Mohr’s circle. Grey-field Polariscope
Introduction
Photoelastic stress analysis has long been a faithful and productive technology offering the measurement community one of the earliest forms of full-field stress analysis.
Unfortunately, its maturity has led to the misconception that the technology is no longer fertile ground for interesting developments, and consequently, photoelastic stress analysis is often overlooked by younger scientists. Several new automated polariscope systems aimed at improving the efficiency and accuracy of photoelastic stress analysis have been introduced over the past several years [1, 2, 3, 4, 5]; however, each of these systems involves one or more complicated procedures such as fringe counting or phase stepping [6, 7] often making the polariscope hard to use and the results difficult to interpret and not very intuitive. It is certainly true that many talented scientists have invented numerous photoelastic techniques, establishing many as fundamental concepts, but there are still many fields to plow. The importance of shear based failure criterion persists as
Jon R. Lesniak 1, Michael J. Zickel1 , Christopher S. Welch2, Deonna F. Johnson2
Abstract
An innovative polariscope involving a single rotating optical element and a digital camera for full-field image acquisition allows automated data to be acquired quickly and efficiently.
Software analysis presents the data in an easy to interpret image format depicting the magnitude of the shear strains and the directions of the principal strains.
automated grey-field polariscope has been devised that painlessly collects both magnitude and direction data without user intervention. Although the new polariscope is capable of making multiple fringe measurements, it has its greatest impact in sub-fringe applications where the output parallels the description of the stress state of an object given by Mohr’s circle. Grey-field Polariscope
Introduction
Photoelastic stress analysis has long been a faithful and productive technology offering the measurement community one of the earliest forms of full-field stress analysis.
Unfortunately, its maturity has led to the misconception that the technology is no longer fertile ground for interesting developments, and consequently, photoelastic stress analysis is often overlooked by younger scientists. Several new automated polariscope systems aimed at improving the efficiency and accuracy of photoelastic stress analysis have been introduced over the past several years [1, 2, 3, 4, 5]; however, each of these systems involves one or more complicated procedures such as fringe counting or phase stepping [6, 7] often making the polariscope hard to use and the results difficult to interpret and not very intuitive. It is certainly true that many talented scientists have invented numerous photoelastic techniques, establishing many as fundamental concepts, but there are still many fields to plow. The importance of shear based failure criterion persists as
References: Automated Photoelastic Analysis of Complex Components,” Strain, May, 49-56, 1991. Experimental Mechanics, December, 486-491, 1974. Synchronized Polarizer-Analyzer Rotation,” Experimental Mechanics, June, 221-224, 1976. Experimental Mechanics, May, 224-232, 1967. Photoelasticity: A New Approach to Whole-field Stress Analysis,” Experimental Mechanics, September, 304-313, 1983. Conference on Experimental Stress Analysis, May, 535-542, 1986. Experimental Techniques, January/February, 19-23, 1993. Measurements Group, Inc., P.O. Box 27777, Raleigh, NC, 1977.