Stress-Strain State Generation Within a Stress Concentration Zone Using the Photoelasticity Method

Abstract

Combined stress-strain state of composite assemblies and structures occurs within a stress concentration zone due to both the boundary form or “geometric factor” and the finite discontinuity of specified forced deformations, stress-strain characteristics appearing on the contact surface of structural elements. Analysis of the local stress-strain state within a composite range of essential structural non-homogeneity is valid for calculation and design of structural elements of nuclear power plants, power-generation facilities, waterworks in case of discontinuities of the structural boundary form, e.g. angular or stepped form. The article briefly describes analysis methods for specific solutions of the elasticity problem caused by the boundary form or “geometric factor”. The experimental photoelasticity method, which is a continual method, and the forced deformation unfreezing method enable the generation of the stress-strain state within the stress concentration zone on the contact surface of composite structures with a forced deformation jump on models made of an optically responsive material. Brief summary is provided regarding capabilities of the experimental method of deformation unfreezing for solution of forced deformation problems. The experimental solution was obtained on a model with an angular cut-out of the boundary, where the apex encloses the forced (thermal) deformation discontinuity. The fringe pattern, obtained on the model using the methods of photoelasticity and deformation unfreezing in the stress concentration zone – within the angular cut-out and forced deformation jump areas – is characterized by considerable gradients of experimental data: the fringe order (isochrome), parameters of isoclines, stresses and strains. Modern techniques of experimental data visualization based on digital shooting enhance capabilities of the photoelasticity method. The purpose of this work is to assess the capabilities for generation of stress state deformations within an area, which is as close as possible to the stress concentration area during digital shooting and data processing using standard stress separation methods.