Towards RGB photoelasticity: Full-field automated photoelasticity in white light
TL;DR: A new full-field method for the automatic analysis of isochromatic fringes in white light, named RGB photoelasticity, which makes it possible to determine retardations uniquely in the range of 0–3 fringe orders.
Abstract: In this paper a new full-field method for the automatic analysis of isochromatic fringes in white light is presented. The method, named RGB photoelasticity, eliminates the typical drawbacks of the classical approach to photoelasticity in white light which requires a subjective analysis of colors and an experienced analyst to acquire and interpret the results.
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TL;DR: In this paper, the automation of the white light photoelastic method based on the use of a full-wave plate placed behind the glass plate is considered, and the proposed method has been applied to the analysis of membrane residual stresses in tempered glass.
Abstract: The analysis of residual stress in glass is usually carried out by means of photoelastic methods. This article considers the automation of the white light photoelastic method based on the use of a full-wave plate placed behind the glass plate. In particular, the method in based on the use of RGB photoelasticity in white light in conjunction with a full wave plate. The proposed method have been applied to the analysis of membrane residual stresses in tempered glass, showing that it can effectively replace manual methods of photoelastic analysis of residual stresses in glass when a low photoelastic retardation is present.
17 citations
TL;DR: In this article, the authors describe a CAE approach which combines finite element simulations and automatic photoelastic investigations for the stress analysis of face gear drives, made by stereolithography.
Abstract: The use of numerical and experimental methods to determine the stress field of mechanical components is well known. In particular, 3D photoelasticity can be considered the only experimental technique for the complete stress state evaluation of 3D components. The advent of rapid prototyping techniques has allowed the manufacturing of complex models in a matter of hours by using birifrangent materials. The present paper is focused on the description of a Computer Aided Engineering (CAE) approach which combines Finite Element (FE) simulations and automatic photoelastic investigations for the stress analysis of face gear drives, made by stereolithography. Computer Aided Design (CAD) geometries, used to manufacture the stereolithographic models, are directly used to perform FE analyses, thus allowing the stress analysis process to become simpler and easier. The substantial agreement observed between experimental and numerical results proved the potentialities of the adopted approach and the usefulness of FE simulations to optimize photoelastic analyses through cost- and time-effective experiments even for complex 3D shapes.
17 citations
Cites background or methods from "Towards RGB photoelasticity: Full-f..."
...photoelastic analysis of the fringe patterns was done by using the RGB method as proposed by [9]....
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...retardation is limited to three orders if incandescent lamps are used [9]....
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...The general procedure consists of [9]:...
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TL;DR: In this article, the formation of the anisotropies and their natural sources are discussed and a method for quantitative measurement of anisotropic is proposed and prescribed in detail, which can assist in the quality assurance process.
Abstract: Commonly, in the evaluation of the optical appearance of glass panes in building envelopes, anisotropies are a reason for a dispute between the architect or client and the facade manufacturer. Sometimes each party has a different perception, how strong the anisotropies are and what is permissible. This paper discusses in the first part the formation of the anisotropies and their natural sources. It is shown that the appearance of this phenomenon is dependent on the environmental conditions of the building site as well as the glass quality. If the application of thermally tempered glass cannot be avoided, the quality assurance of the production process has to be carefully planned. Furthermore a method for the quantitative measurement of anisotropies is proposed and prescribed in detail. This method can assist in the quality assurance process. Measurements are showing that probably the best tempered glass offers slight anisotropies and that under unfavorable conditions these anisotropies can become evident.
16 citations
16 citations
TL;DR: In this article, an experimental approach to two-dimensional, viscoelastic, steadily moving rolling contact is described, where photoviscoelastic technique is employed for the analysis of rolling contact stresses between a viscous plate and a rigid rolling cylinder in which the principal axes of stress, strain and birefringence are not coincident with each other.
Abstract: An experimental approach to two-dimensional, viscoelastic, steadily moving rolling contact is described. The photoviscoelastic technique is employed for the analysis of rolling contact stresses between a viscoelastic plate and a rigid rolling cylinder in which the principal axes of stress, strain and birefringence are not coincident with each other. Using an elliptically polarized white light, the distribution of isochromatic fringe order and the principal axes of birefringence at an instant are determined from a single photoviscoelastic image. The time variations of the differences of the principal stresses and strains, as well as their directions, are obtained by use of the optical constitutive equations of photoviscoelasticity. The experimental results involving the time variation of the stresses around the contact surface and their distributions are analyzed.
16 citations
References
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Book•
01 Jan 1987
TL;DR: The "Handbook on Experimental Mechanics" as mentioned in this paper is a comprehensive reference in the field of experimental mechanics and has been used extensively in the past 50 years for a wide range of applications.
Abstract: The "Handbook on Experimental Mechanics" is a comprehensive reference in the field. Since 1950, new experimental techniques, such as holography, laser speckle interferometry, optical heterodyning and modal analysis, have emerged as practical tools in the broader field of experimental mechanics. The emergence of new materials and new disciplines, such as composite materials and fracture mechanics, resulted in the evolution of traditional experimental techniques to new fields such as orthotropic photoelasticity and experimental fracture techniques. The new revised edition of the handbook includes, among other things, one new chapter on digital image processing; key sections of the handbook have been entirely rewritted or updated. The handbook should be useful to any mechanical engineer or anyone interested in stress analysis of materials.
504 citations
TL;DR: The design of a automated system for photoelastic analysis of complex components and the potential of the system for providing detailed data over the full field of view is demonstrated by the analysis of a slice from a model of a bolt.
Abstract: The design of a automated system for photoelastic analysis of complex components is described, and an outline of the theory used in its operation is given. The potential of the system for providing detailed data over the full field of view is demonstrated by the analysis of a slice from a model of a bolt.
221 citations
TL;DR: In this paper, the half-fringe photoelasticity (HFP) method is proposed for whole-field stress analysis based on a symbiosis of two techniques, namely classical photo elasticity and modern digital image analysis.
Abstract: This paper presents a new method for whole-field stress analysis based on a symbiosis of two techniques—classical photoelasticity and modern digital image analysis. The resulting method is called ‘half-fringe photoelasticity (HFP)’. Classical photoelasticity demands materials with high birefringence, which leads to extensive use of plastics as model materials. Since the behavior of these materials is often different from that of the prototype materials, their use distorts the similitude relationships. In many contemporary problems this distortion is untenable. HFP offers a way out of this dilemma. It permits materials and loads to be chosen so that no more than one half of a fringe order appears in the area of interest. Thus, for example, glass, which behaves linearly up to high stress levels and over a wide range of temperatures, could be used as model material. Alternatively, models from polymeric materials could be used under very low load in order to stay within the linear part of the stress-strain diagram and to prevent large deformations. The half-fringe-photoelasticity system, which is described here, utilizes the resulting low levels of birefringence for effective stress analysis. This paper describes the system. It outlines a calibration routine and illustrates its application to two simple problems using glass models.
126 citations
"Towards RGB photoelasticity: Full-f..." refers background or methods in this paper
...The intensity eqs ( 9 ) and (10) can be used to evaluate A only if the Fi functions, the transfer function of the digital board (relationship between the RGB values and intensity values L Ig and Ib), the dispersion of birefringence and the isoclinic angle ~ are known....
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...The equations of polariscope ( 9 ) and (10) show that the influence of errors e of optical retarders depends on the isoclinic angle cx; there is maximum error where c~ = 0 deg (principal stresses parallel to polarizers), whereas no error occurs where a -- 45 deg (principal stresses parallel to retarders)....
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...For lower orders, using eqs ( 9 ) and (10) allows us to evaluate the unknown retardation A (or 8) by processing of the acquired RGB levels....
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01 Jan 1986
TL;DR: In the following a method is proposed, which enables the complete extraction of photoelastic information at local picture elements (pixel) from series of related images of the same stress state, and was modified to meet the special requirements ofphotoelastic patterns.
Abstract: Computer-aided methods for evaluation of photoelastic patterns use video technique and digital image processing. They are based on localization of fringe centers [ 1, 2, 3, 4]. Neighbourhood operations are needed to reduce the influence of nonuniform illumination, inhomogeneous optical components and models, etc. Fractional orders of the relative retardation and of the isoclinic parameter at points between the fringes are computed by spline- functions, if the components of the plane stress state have to be derived from photoelastic data. In the following a method is proposed, which enables the complete extraction of photoelastic information at local picture elements (pixel) from series of related images of the same stress state. For this purpose the well-established phase-shifting technique (see e. g. [ 5,6]) was modified to meet the special requirements of photoelastic patterns.
78 citations
TL;DR: In this paper, a new method of photoelastic measurement has been developed, where the light emerging from a polariscope is spectrally separated and projected on a photodiode array.
Abstract: A new method of photoelastic measurement has been developed. The light emerging from a polariscope is spectrally separated and projected on a photodiode array. It is shown that the relative retardation can be retrieved from light intensity measured at several wavelengths. Key parameters affecting the precision of this approach are discussed and evaluated.
76 citations