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Journal Article•DOI•

Towards RGB photoelasticity: Full-field automated photoelasticity in white light

Augusto Ajovalasit, Sandro Barone, Giovanni Petrucci
01 Sep 1995-Experimental Mechanics (Kluwer Academic Publishers)-Vol. 35, Iss: 3, pp 193-200
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.
Citations
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Journal Article•DOI•
Complete Fringe Order Determination in Digital Photoelasticity Using Fringe Combination Matching

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I.A. Jones1, P. Wang1•
University of Nottingham1
01 Aug 2003-Strain
TL;DR: In this paper, a novel approach is presented for obtaining the complete (integer and fractional) value of isochromatic parameters in digital imaging photoelasticity, which takes the form of a new variant on the existing technique of RGB photo elasticity.
Abstract: A novel approach is presented for obtaining the complete (integer and fractional) value of isochromatic parameters in digital imaging photoelasticity. This takes the form of a new variant on the existing technique of RGB photoelasticity, involving the matching of combinations of isochromatic fringe value measured on the three colour planes or channels rather than the usual RGB method of matching colour combinations directly. The new variant of RGB photoelasticity avoids the need for calibration for specific materials. This approach is demonstrated with real photoelastic data and compared with results from a conventional unwrapping process and from manual readings.

22 citations

Journal Article•DOI•
Photoelastic Analysis of Edge Residual Stresses in Glass by Automated “Test Fringes” Methods

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Augusto Ajovalasit1, Giovanni Petrucci1, Michele Scafidi1•
University of Palermo1
01 Oct 2012-Experimental Mechanics
TL;DR: In this paper, 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 are based on RGB photoelasticity in white light.
Abstract: 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 analysis of residual stresses in glass.

22 citations

Cites methods from "Towards RGB photoelasticity: Full-f..."

  • ...This effect may enhance the accuracy of methods based on the use of white light, which can be prone to large errors for low levels of retardation, like in the case of the RGB method [7]....

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Journal Article•DOI•
Novel calibration and color adaptation schemes in three-fringe RGB photoelasticity

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Digendranath Swain1, Binu P. Thomas1, Jeby Philip1, S. Annamala Pillai1•
Indian Space Research Organisation1
01 Mar 2015-Optics and Lasers in Engineering
TL;DR: RGB demodulation based on a theoretically constructed LUT has been attempted to exploit the advantages of color adaptation schemes and a new color adaptation algorithm is proposed using quadratic Lagrangian interpolation polynomials, which is numerically better than the two-point linear interpolations available in the literature.

22 citations

Journal Article•DOI•
The influence of the quarter wave plates in automated photoelasticity

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Augusto Ajovalasit1, Sandro Barone2, Giovanni Petrucci1, Bernardo Zuccarello1•
University of Palermo1, University of Pisa2
01 Jul 2002-Optics and Lasers in Engineering
TL;DR: In this article, the influence of the errors of quarter wave plates in some of the most common automated photoelastic methods is reviewed and procedures to reduce, or eliminate, them are also suggested.

21 citations

Journal Article•DOI•
A critical assessment of automatic photoelastic methods for the analysis of edge residual stresses in glass

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Augusto Ajovalasit1, Giovanni Petrucci1, Michele Scafidi1•
University of Palermo1
15 Jan 2014-Journal of Strain Analysis for Engineering Design
TL;DR: In this paper, the determination of membrane residual stresses of glass plates by digital photoelasticity is considered and a critical assessment concerning the automated methods based on gray-field polariscope, spectral content analysis, phase shifting, RGB photo elasticity, test fringes, and tint plate method is presented.
Abstract: 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.

21 citations

Cites methods from "Towards RGB photoelasticity: Full-f..."

  • ...The use of the tint plate is particularly useful near the fringe of 0th order where the retardation is low and significant measurement errors could be committed when RGB photoelasticity is used, as it is well known.(38) The use of RGB photoelasticity, jointly to the tint plate, initially proposed in a qualitative way,(29) has been further developed in Ajovalasit et al....

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  • ...The effect of the incorrect positioning of the tint plate optical axes with respect to the stress directions is experimentally analyzed by Ajovalasit et al.30 Such analysis shows that the misalignment is not critical....

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  • ...The simplified methods used in this article are based on the Tardy setup, as initially proposed by Asundi,45 and on the Sénarmont setup as initially proposed by Ajovalasit et al.23 In this article, the simplified methods mentioned above, based on the setup of Tardy and Sénarmont, are concisely referred as the Tardy phaseshifting method (TPSM) and the Sénarmont PSM....

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  • ...Since the realization of a glass calibration specimen in bending is not simple in some instances, an alternative self-calibration procedure, defined briefly as SelfCal, has been proposed by Ajovalasit et al.26 The SelfCal procedure consists in creating the LUT using a glass equal to that to be analyzed, subjected to residual stresses not lower than those to be measured....

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  • ...In this case, at each pixel, the three Ri, Gi and Bi levels assume similar values, and the RGB method is not able to eliminate the influence of the possible fluctuation of the reference light field and of electronic noise, as also reported in Ajovalasit et al.38...

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References
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Book•
Handbook on experimental mechanics

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Albert S. Kobayashi
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

Journal Article•DOI•
Towards full field automated photoelastic analysis of complex components

[...]

Eann A. Patterson1, Z F Wang1•
University of Sheffield1
01 May 1991-Strain
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

Journal Article•DOI•
Half-fringe photoelasticity: A new approach to whole-field stress analysis

[...]

Arkady Voloshin1, C. P. Burger1•
Iowa State University1
01 Sep 1983-Experimental Mechanics
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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Book Chapter•DOI•
Computer-Aided Measurement of Relative Retardations in Plane Photoelasticity

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F. W. Hecker1, B. Morche•
Braunschweig University of Technology1
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

Journal Article•DOI•
Photoelastic measurements by means of computer-assisted spectral-contents analysis

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Alex S. Redner
01 Jun 1985-Experimental Mechanics
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

Related Papers (5)
Towards full field automated photoelastic analysis of complex components

[...]

01 May 1991-Strain
Eann A. Patterson, Z F Wang
Three fringe photoelasticity ‐ use of colour image processing hardware to automate ordering of isochromatics

[...]

01 Aug 1996-Strain
K. Ramesh, Sanjeev S. Deshmukh
Half-fringe photoelasticity: A new approach to whole-field stress analysis

[...]

01 Sep 1983-Experimental Mechanics
Arkady Voloshin, C. P. Burger
Photoelastic measurements by means of computer-assisted spectral-contents analysis

[...]

01 Jun 1985-Experimental Mechanics
Alex S. Redner
Digital photoelasticity: Principles, practice and potential

[...]

01 Feb 2002-Strain
Eann A. Patterson