Johan Anton

Modern Photoelasticity for Residual Stress Measurement in Glass

Residual stress is one of the important indicators of the quality of any glass product. The paper gives a review of the methods, which are nowadays used in glass industry for measuring residual stress both in architectural and automotive glass panels and in hollow glassware.

Photoelastic tomography for residual stress measurement in glass

The paper describes analgorithm of photoelastic tomography and its application for residual stress measurement in glass articles of complicated shape. The algorithm is based on a linearized solution of the equations of integrated photoelasticity. The problem of tensor field tomography is decomposed into several problems of scalar field tomography for normal stress components of the stress tensor. The method is implemented with an automated polariscope with a rotary stage. Several examples illustrateapplication of the method.

Generalized Onion-Peeling Method in Integrated Photoelasticity of Axisymmetric Problems

By measuring residual stress in axisymmetric glass articles, stress distribution is usually described with polynomials [1]. In case of cylinders, axial stress distribution can be measured also using a discrete algorithm, named “onion-peeling” [2]. In this method, the cylinder is considered as consisting of a number of concentric cylindrical rings (Fig. 1), in each of which the axial stress σz may be considered constant. Axial stress in the first ring σz(1) is determined through

On the Fracture Mechanics of Prince Rupert’s Drops

Stresses in several Prince Rupert’s drops (PRDs) were measured with integrated photoelasticity. Measurements show that the surface layer of thickness about 0.5 mm of the head of a PRD is under high compression stresses reaching at the surface the value of about 500 MPa. That explains the extraordinary strength of the heads of PRD’s. The external part of the tails of PRD’s is also under high compressive stress reaching at the surface the value of 600 MPa. Internal part of the tail is under high tensile stresses. Stress distribution in the tail is used to explain catastrophic disintegration of the tail when it is cut.

Effects of Ray Bending in Scattered Light Photoelasticity for Tempered and Annealed Glass Plates

Residual stresses in tempered glass plates can be measured with the scattered light method. Usually a rectilinear propagation of light is assumed. However, due to the gradients of the refractive index, the light rays curve. We have experimentally demonstrated this for tempered (surface stress 120 MPa and more) and annealed glass plates. For a laser beam of finite width this also results in broadening and loss of photoelastic modulation. While some features of the experimental picture (dependence of the period of modulation on depth), can be captured in the simple model of rectilinear propagation, the other observations need development of more elaborated models.