Stress Analysis and Photoelasticity

1- On the use of stereolithography built photoelastic models for stress analysis investigations - Elsevier

Abstract: When designing mechanical components, it is essential to investigate and provide crucial information for mechanical failure due to stress generation. Photoelasticity and numerical methods are well known for stress determination and design evaluation purposes. The rapid-prototyping technique of stereolithography allows complex models of components to be built, in a matter of hours, out of photoelastic resins. The objective of this study was to evaluate the feasibility of a commercially available epoxy-based photopolymer for photoelastic investigations. A number of experiments were undertaken to address critical material and fabrication issues related to stereolithography built photoelastic specimens. The data gathered from photoelastic model testing was compared to the ones generated by numerical analysis. The good correlation between them in terms of measured and calculated magnitudes of stress provide increased confidence in the investigated photopolymer for photoelastic stress analysis purposes, and consequently for validation of computer-based models, utilizing thus stereolithography models as complementary design tools.

2- Some observations on three-dimensional photoelasticity : IOPscience

Abstract: When a three-dimensional photoelastic model is viewed under polarized light the total relative retardation is due not only to the integrated effect of the secondary stresses but also to the rotation of the secondary principal axes. In investigations on a finite slice taken from such a model it is generally assumed that the birefringence and the isoclinic parameters refer to the state of stress in the mid-plane. The validity of this assumption and the errors involved are analysed.

3- Fundamental relations in photoplasticity - IOPscience

Abstract: Photoelastic methods of stress analysis have so far been limited to the study of problems of elasticity. The usefulness of such methods has been extended to cover inelastic behaviour by showing that the relative retardation due to loading is determined by the stress and strain components independently of the history of loading. A relation expressing relative retardation as a linear function of stress and strain differences has been derived. This fundamental relation has been verified experimentally for a wide variety of model materials.

A fundamental procedure for photoplastic investigations is proposed. This consists of taking two fringe photographs of the same model, one under load, the second immediately after removal of the load. The difference between the fringe counts at corresponding points gives the stress difference which in elastic problems is derived from a single photograph.

4- Stress distributions in doubly convex cylindrical discs under diametral loading - IOPscience

Abstract: Detailed stress distributions along the axes of symmetry of a series of doubly convex cylindrical discs subjected to diametral loading have been obtained using the 'frozen-stress' and 'scattered-light' photoelastic techniques. The dependence of these stresses on (i) face curvature and (ii) cylinder thickness has been established. The results are discussed in relation to the stress distributions and brittle fracture characteristics of the plane-faced disc (i.e. the 'Brazilian' disc specimen) in the same loading mode.