Stress Intensity Factors from a Simple Photoelastic Method
Zhang Zhongping  Sun Zhongyu Sun Qiang
(Air Force Institute of Engineering 710038)  
(Air Force Institute of Telecommunication Engineering 710077)

Abstract: The nonlinear equation between stress intensity factors (SIF_s)K₁, K₂ for1-2 mixed mode crack and polar coordinates of the points on isochromatic fringe loops is founded by considering the effect of far-field nonsingularstress S_ox. In order to obtain K₁, K₂ and S_ox,the polar coordinates of four points on two fringe loops along the lines defined by O = 0 and by O = P/2 are taken into the equation respectively. Thus, a simple photoelastic method of determining SIFs is obtained. Finally,Epoxy and polycabonate are taken as examples, SIFs and S_xo in different cracks and loadings are determined. By comparison the results with theoretical ones, the principle in the present paper, is correct and the method is feasible.
Keywords: photoelasticity, isochromatic fringeloop, 1-2 mixed mode crack, stress intensity factor, farª²field nonsingular stress.