Search results for "digital photoelasticity"
showing 5 items of 5 documents
RGB Photoelasticity: Review and Improvements
2010
: This paper considers the main developments of RGB photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals wherea…
Review of photoelastic image analysis applied to structural birefringent materials: glass and polymers
2015
Photoelasticity is particularly suitable for the analysis of the stress state in structural materials that are transparent and birefringent. Some techniques of digital photoelasticity (phase shifting and RGB) are applied to the analysis of stress field in two classes of structural materials. The first one consists of tempered glasses, such as those used in the automotive and architectural fields. The second one consists of thermoset polymers, typically used as matrices in fiber reinforced plastic structural composites. The birefringence of such resins is, in particular, exploited to investigate the development of swelling stresses and changes in fracture toughness as induced by water uptake…
Photoelastic Analysis of Edge Residual Stresses in Glass by Automated “Test Fringes” Methods
2011
Since the glass is a birefringent material, the analysis of residual stress in glass is usually carried out by means of photoelastic methods. This paper considers the automation of the “test fringes” method which is based on the use of a Babinet compensator or of a beam subjected to bending. In particular, two automated methods are proposed: the first one is based on the use of the centre fringe method in monochromatic light and the second one is based on the use of RGB photoelasticity in white light. The proposed methods have been applied to the analysis of membranal residual stresses in some tempered glasses, showing that they can effectively replace manual methods of photoelastic analysi…
Phase shifting photoelasticity in white light
2007
The availability of image acquisition systems has led to the development of digital photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB photoelasticity and phase shifting photoelasticity. Phase shifting photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting photoelasticity in the colour domain. Special attention i…
A critical assessment of automatic photoelastic methods for the analysis of edge residual stresses in glass
2014
The measurement of residual stresses is of great importance in the glass industry. The analysis of residual stresses in the glass is usually carried out by photoelastic methods since the glass is a photoelastic material. This article considers the determination of membrane residual stresses of glass plates by digital photoelasticity. In particular, it presents a critical assessment concerning the automated methods based on gray-field polariscope, spectral content analysis, phase shifting, RGB photoelasticity, “test fringes” methods and “tint plate” method. These methods can effectively automate manual methods currently specified in some standards.