In this paper, the problem of determining the opening mode (mode I) stress intensity factor (SIF) from the photoelastic isochromatic fringe pattern associated with a surface crack located in the ligament region between two radial nozzle-cylinder junctions of pressure vessel has been investigated. The objective is to determine the influence of geometry, size and location of the surface flaw with respect to the radial nozzles. Starting from the crack tip stress field formulation of Etheridge and Dally using three parameters (1)† a new method suited to the analysis of photoelastic data obtained from a single isochromatic fringe loop to extract the SIF has been introduced. This new method has been used to predict SIFs for a range of pressure vessel nozzle spacings when photoelastic models are subjected to internal pressure loading.
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