Measurement of residual birefringence in thin glass plates using digital photoelasticity
02 Jun 2014-Vol. 9234, pp 129-134
TL;DR: In this article, an automatic polariscope is used to employ Phase Shifting Technique (PST) to determine the residual integrated retardations over the thickness of a glass plate, and a code is developed in MATLAB to stitch the retardation data for the upper and lower regions.
Abstract: Residual stresses in glass causes it birefringent, affecting its optical properties. Annealed P-LASF47%trade; glass plates of 75 × 20 × 5 mm are subjected to two different thermal cycles. An automatic polariscope is used to employ Phase Shifting Technique (PST) to determine the residual integrated retardations over the thickness. Smaller field of view of the polariscope necessitates analysing the glass plate separately for the upper and lower regions of the glass plate. A code is developed in MATLAB to stitch the retardation data for the upper and lower region. The integrated retardation for the whole field is plotted as a contour plot using OriginPro software. Maximum retardation is observed in small regions at the free surfaces of the glass plate. It is noted that the nature of the thermal cycle has an influence on the retardation distribution.
Citations
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TL;DR: In this article, photoelasticity is applied to the analysis of stress field in two classes of structural materials, namely tempered glasses and thermoset polymers, to investigate the development of swelling stresses and changes in fracture toughness as induced by water uptake aging.
Abstract: 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 aging.
24 citations
TL;DR: In this paper, the thermal boundary conditions (BCs) of a glass disk specimen for three different cooling rates are evaluated by measuring the residual birefringence of the glass disk with digital photoelasticity.
Abstract: Process parameters of Precision Glass Molding (PGM) are often sought by Finite Element (FE) simulation. Mechanical as well as thermal boundary conditions (BCs) are necessary for FE simulation in which mechanical BCs are usually known or easily determinable. However, most of the thermal BCs are generally assumed in the FE simulation as they cannot be measured directly. The focus of this article is to propose a novel method for evaluating the thermal BC of glass–N2 gas. FE simulations as well as thermal cycling experiments are carried out for a glass disk specimen for three different cooling rates. CFD analysis of N2 flow in the PGM machine is performed to understand the heat extraction mechanism. Based on this, adhoc values for equivalent heat transfer coefficient (heqv) are obtained by lumped system analysis. A novel methodology is then proposed for obtaining accurate heqv values by measurement of integrated residual birefringence in glass using digital photoelasticity. FE simulation is repeated for different values of heqv until the integrated birefringence based on simulation matches with that of the experiment. For the same cooling rates, two aspherical glass lenses are molded and their residual birefringence is measured and compared with the glass disk specimen.
15 citations
Patent•
08 Aug 2019
TL;DR: In this article, a method for simulating the quench marks visible on a glazed panel (34, 40, 59, 78) combining several heat-strengthened glazed elements (1, 2) was proposed.
Abstract: The invention concerns a method for simulating the quench marks visible on a glazed panel (34, 40, 59, 78) combining several heat-strengthened glazed elements (1, 2), that comprises determining the optical delay of each glazed element (1, 2) in the area (7, 9; 8, 10) of same in alignment with an area of the glazed panel, said alignment being considered in a direction (11, 12) normal to the glazed panel, and then comprises determining the sum of the optical delays of the areas (7, 8; 9, 10) of the glazed elements (1, 2) in alignment with said area of the glazed panel, this applying to several areas (7, 8, 9, 10) of the glazed panel.
2 citations
Patent•
02 Aug 2019
TL;DR: In this paper, a methode d'estimation du retard optique is proposed to predire la fleur de trempe d'un panneau vitre avant son assemblage a partir de plusieurs elements vitres.
Abstract: L'invention concerne une methode d'estimation du retard optique en au moins une zone d'un panneau vitre comprenant plusieurs elements vitres, comprenant la determination du retard optique de chaque element vitre en sa zone en alignement avec ladite zone du panneau vitre, ledit alignement etant considere selon une direction normale au panneau vitre, puis comprenant la determination de la somme des retards optiques relatifs aux zones en alignement dans le panneau vitre de tous les elements vitres, ladite somme representant le retard optique estime en ladite zone du panneau vitre. La methode permet de predire la fleur de trempe d'un panneau vitre avant son assemblage a partir de plusieurs elements vitres.
TL;DR: In this paper , a three-point bending experiment is used to simulate the glass cold bending forming process, and the feasibility of the photoelastic method to detect the real-time bending stress in the pure cold bending state is analyzed.
Abstract: Glass bending is an important process in glass device manufacturing, and real-time stress detection is essential for regulating bending mold pressure. A three-point bending experiment is used to simulate the glass cold bending forming process, and the feasibility of the photoelastic method to detect the real-time bending stress in the pure cold bending state is analyzed. The conventional division-of-amplitude polarimeter is optimized to obtain a smaller spot diameter, fewer system conditions, and a wider stress detection range. The Stokes parameter error of the optimized system is 0.05, and the optical path difference measurement accuracy is 4.284 nm. The test quality of the photoelastic stress detection system during the three-point bending was not affected by the glass size or bending span. However, the various curvatures of the incident surface were found to cause different stress values in unloaded glass and fluctuations in y-values (the distance from the test beam to the neutral surface of the glass) to occur outside the normal range. The less the curvature of the glass is, the closer it is to normal incidence, and the more accurate the stress value is. After the heat treatment of the borosilicate glass, the experimental results show that the isotropic structure of the glass does not change significantly. The exploration of testing quality of bending stress provides an effective reference for practical high-precision bending glass manufacturing.
References
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Book•
20 May 2012
TL;DR: In this paper, the authors proposed a method for the detection of residual stresses in composite glass by using the Scattered Light Method with Unpolarized Incident Light (SLM) and the Babinet-Soleil Compensators.
Abstract: One The Basics of Photoelasticity and Glass.- 1 Basic Elasticity.- 1.1 Elasticity.- 1.2 Force and Stress.- 1.3 Plane Stress.- 1.4 Equations of Equilibrium.- 1.5 Boundary Conditions.- 1.6 Strain.- 1.7 Relations Between Stresses and Strains.- 1.8 Plane Strain.- 1.9 Equations of Compatibility.- 1.10 Stress Function.- 2 Residual Stresses in Glass.- 2.1 Introduction.- 2.2 Dependence of the Mechanical Strength on Residual Stresses.- 2.3 Stresses Due to Indentations.- 2.4 Residual Stresses Due to Thermal Annealing or Tempering.- 2.4.1 The First Approaches.- 2.4.2 The Viscoelastic Theory.- 2.4.3 The Structural Theory.- 2.4.4 Membrane Stresses and Form Stresses.- 2.4.5 Stress Redistribution by Cutting.- 2.5 Stresses Due to Chemical Tempering.- 2.5.1 Stress Buildup.- 2.5.2 Strengthening of Glass.- 2.6 Stresses Created in Glass by Radiations.- 2.6.1 Corpuscular Radiation.- 2.6.2 Electromagnetic Radiation.- Thermal Effects.- Color Centers.- 2.7 Stresses Due to Heterogeneities.- 2.8 Stresses in Composite Glass Articles.- 2.8.1 Stresses in Glazes and Enamels.- 2.8.2 Stresses in Optical Fibers.- 2.8.3 Stresses in Glass-Metal and Glass-Ceramic Seals.- 2.8.4 Stresses Due to Inclusions.- 3 Basic Photoelasticity.- 3.1 Polarized Light.- 3.1.1 Nature of Light.- 3.1.2 Natural and Polarized Light.- 3.1.3 Different Descriptions of Polarized Light.- 3.2 Artificial Double Refraction.- 3.3 Stress-Optic Law.- 3.4 The Plane Polariscope.- 3.5 The Circular Polariscope.- 3.6 Use of Double-Exposure Photography for the Elimination of the Isoclinics.- 3.7 Construction of Polariscopes.- 3.8 Measurement of Optical Retardation.- 3.8.1 Color Matching.- 3.8.2 Polariscope with a Tint Plate.- 3.8.3 The Babinet and Babinet-Soleil Compensators.- 3.8.4 Senarmont Method.- 3.8.5 The Azimuth Method.- 4 Two-Dimensional Photoelasticity.- 4.1 General.- 4.2 Stress Trajectories.- 4.3 Separation of Principal Stresses.- 4.3.1 Oblique Incidence Method.- 4.3.2 Shear Difference Method.- 4.3.3 Numerical Solution of the Compatibility Equation.- 4.3.4 Methods Based on Hooke's Law.- 4.4 Superposition of States of Stress.- 4.5 Determination of the Photoelastic Constant.- 5 The Scattered Light Method.- 5.1 Introduction.- 5.2 Scattering of Light.- 5.3 The Scattered Light Method with Polarized Incident Light.- 5.4 The Scattered Light Method with Unpolarized Incident Light.- 5.5 Using Interference of Coherent Scattered Light Beams.- 6 Integrated Photoelasticity.- 6.1 Introduction.- 6.2 Principle of Integrated Photoelasticity.- 6.3 Basic Equations.- 6.4 Theory of Characteristic Directions.- 6.5 Symmetric Photoelastic Media.- 6.6 The Case of Constant Principal Stress Axes.- 6.7 The Case of Weak Birefringence.- 6.8 Integrated Photoelasticity as Optical Tomography of the Stress Field.- 6.9 Investigation of the General Three-Dimensional State of Stress.- 6.10 Axisymmetric State of Stress Due to External Loads.- 7 Photoelastic Properties of Glass.- 7.1 Introduction.- 7.2 Discovery of the Photoelastic Effect in Glass.- 7.3 Influence of the Glass Composition.- 7.4 Theories of the Photoelastic Effect.- 7.5 Influence of the Temperature and of the Thermal History.- 7.6 Dependence of the Photoelastic Constant on Wavelength.- 7.7 Anomalous Birefringence.- Two Stress Analysis in Flat Glass.- 8 Thickness Stresses.- 8.1 Different Kinds of Thickness Stresses.- 8.2 Measurement of Thickness Stresses.- 8.2.1 Using the Bending of the Light Rays.- 8.2.2 Conventional Photoelasticity.- 9 Membrane Stresses.- 9.1 Introduction.- 9.2 Uniaxial Membrane Stresses.- 9.2.1 Edge Stresses.- 9.2.2 Stresses Across a Ribbon.- 9.3 Bidimensional Membrane Stresses.- 10 Determination of the Total Stresses.- 10.1 Introduction.- 10.2 The Measurement of Surface Stresses.- 10.2.1 Differential Refractometry.- 10.2.2 The "Mirage" Methods.- Observation of the Guided Waves Close to the Surface.- The Case of Flat Samples.- The Case of Curved Samples.- The Case of Stress Gradient Near the Surface.- Observation of the Guided Waves at Infinity.- Theory of the Differential Refractometry with Guided Waves.- Linear Index Profile.- Determination of Stresses.- An Example.- Alternative Numerical Methods.- Curved Surface.- Thermally Tempered Glass.- 10.3 Measurement of Total Residual Stresses.- 10.3.1 The Scattered Light Method.- Spatial Modulation Method.- Phase Modulation Method.- 10.3.2 Magnetophotoelasticity.- Three Stresses in Glass Articles of Complicated Shape.- 11 Axisymmetric Glass Articles.- 11.1 General Case of Axisymmetric Residual Stress Distribution.- 11.1.1 Peculiarities of the Determination of the Residual Stress.- 11.1.2 Determination of the Axial and Shear Stress Distributions.- 11.1.3 Additional Tomographic Measurements.- 11.2 Application of the Equilibrium and Boundary Conditions.- 11.3 Stresses on the External Surface.- 11.4 Average Value of the Circumferential Stress.- 11.5 Stresses in Long Cylinders.- 11.6 Spherical Symmetry.- 11.6.1 Stress Distribution in Spheres.- 11.6.2 Quenching Stresses Around a Spherical Inclusion.- 11.7 Bending of Light Rays.- 11.8 Determination of the Components of the Dielectric Tensor.- 11.9 Optimization of the Number of Terms in Stress Polynomials.- 11.10 Experimental Technique.- 11.10.1 Polariscopes.- 11.10.2 Immersion Technique.- 11.10.3 The Case of Mismatching Immersion.- 11.11 Examples.- 11.11.1 Quenched Long Cylinder.- 11.11.2 An Article of Optical Glass.- 11.11.3 High Voltage Insulator.- 11.11.4 Closed Tube.- 11.11.5 Two Bonded Tubes.- 12 Containers and Other Thin-Walled Glassware.- 12.1 Introduction.- 12.2 Traditional Methods.- 12.3 Determination of Stress in Cylindrical Part of the Container.- 12.4 Axial Stress in an Arbitrary Section.- 12.5 Determination of the Stresses Due to the Internal Pressure.- 12.6 Sandwich Glassware.- 12.7 Examples.- 12.7.1 A Champagne Bottle.- 12.7.2 A Beer Bottle.- 12.7.3 Tumbler N 1.- 12.7.4 Tumbler N 2.- 12.7.5 Salad Bowl.- 12.7.6 Electric Lamp.- 12.7.7 Ampule of a Fire Extinguisher System.- 13 Optical Fibers and Fiber Preforms.- 13.1 Introduction.- 13.2 Axisymmetric Fibers and Fiber Preforms.- 13.2.1 Refractive Index Profiles.- 13.2.2 Determination of the Stress Distribution.- 13.2.3 Application of the Method of Oblique Incidence.- 13.2.4 Examples.- 13.3 Fiber Preforms of Arbitrary Cross Section.- 13.3.1 Determination of the Axial Stress Distribution.- 13.3.2 Determination of Other Stress Components.- 13.3.3 Internal Rotation of the Birefringence Axes in Polarization-Holding Fibers.- 13.3.4 Examples.- Author Index.
187 citations
TL;DR: This review thematically classifies all the developments in digital photoelasticity and highlights the relative merits and drawbacks of the various techniques to allow an end-user to make an informed choice on the type of technique to be used in a particular situation.
Abstract: Digital photoelasticity has rapidly progressed in the last few years and has matured into an industry-friendly technique. This review thematically classifies all the developments in digital photoelasticity and highlights the relative merits and drawbacks of the various techniques. The overall objective is to provide enough information and guidance to allow an end-user to make an informed choice on the type of technique to be used in a particular situation.
78 citations
TL;DR: In this article, photoelastic calibration of the glass material has been performed using the carrier fringe method (CFM) and phase shifting technique (PST) in digital photo elasticity.
Abstract: Quantification of residual stresses in glass articles necessitates the knowledge of photoelastic constant of the glass material. The recent developments in digital photoelasticity have increased its applicability in residual stress analysis of glass. In this paper, photoelastic calibration of the glass material has been performed using the carrier fringe method (CFM) and phase shifting technique (PST) in digital photoelasticity. The retardations measured by both of these techniques are used for the calculation of photoelastic constant of the glass material and they were found to be in good agreement with each other. Calibration of glass by CFM is recommended for industrial applications since it requires only a few images as compared to PST.
20 citations