ANALYSIS OF MIXED-MODE ISOCHROMATIC CRACK-TIP FRINGE PATTERNS

Westergaard stress function representations of the stress field around the tip of a stationary crack subjected to mixed-mode loading are employed to develop a general relationship between the isochromatic fringe order N, its position parameters r and θ and the general stress field expressed in terms of several parameters, the stress intensities K1, K2, a far field stress parameter α, and higher order term parameters β1 and β2. These parameters are varied and isochromatic crack tip fringe patterns are constructed for a set of classified combinations. Since the size, shape, orientation, and other particular features of the fringe patterns depend strongly on the combination of parameters chosen they can be used to classify crack tip fringe patterns. The introduction of fringe loop diagrams not only facilitates the classification procedure and enables a classification without plotting fringe patterns, but it also permits qualitative and quantitative evaluation of the isochromatic patterns. Isochromatics which classify fourtyeight different states of stress are investigated and the majority of them have been illustrated. © 1979 Springer-Verlag.