CRACK-TIP PRINCIPAL STRESSES BY ISOCHROMATIC AND ISOPACHIC FRINGES AT A BI-MATERIAL INTERFACE

摘要

An experimental method of the principal stresses estimation which is based on photoelasticity and isopachic methods is presented. The principal stresses at the bi-material interface crack-tip are theoretically determined using the combination photoelastic and isopachic fringes. The size and the shape of crack-tip isochromatic and isopachic fringes, at a bi-material interface under static load, are studied. When the crack-tip, which is perpendicular to interface, is placed at the interface of the bi-material, the isochromatic and the isopachic fringes depend on the properties of the two materials. Thus, the isochromatic and the isopachic fringes are divided into two branches, which present a jump of values at the interface. The size of the two branches mainly depends on the elastic modulus and the Poisson' s ratio of the two materials. From the combination of the isochromatic and the isopachic fringes, the principal stresses sigma_1 and sigma_2 can be estimated and the contour curves around the crack-tip can be plotted.