Experimental Study of Stress Intensity Factors in Rotating Disk Having the Cracks by Photoelasticity and Caustics Method (Single Crack and Branched Crack)

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Fracture of blades or disks due to centrifugal force in rotary machines has often caused serious accidents. To optimize their dimensions and to ensure their safety in service, a practical study of the strength under centrifugal force is necessary. In this paper, stress intensity factors were determined by using the photoelastic and caustics method. Stress intensity factors in a single crack are calculated as a function of the inclination crack of length 2a, the position at different velocities and at different values of the inclination crack angle φ and are measured in models of rotating disks using a photoelastic stress freezing method. The ratio (KII/KI) of the stress intensity factors determined by using the isochromatic fringe loops angle θm near the crack tip. The results of this experiment coincided favorably with the theoretical analysis results of Ishida and Terada (1). Branched cracks are frequently encountered in the unstable fracture of various brittle materials. Stress intensity factors KI and KII were determined by using the photoelastic and caustics method, as a function of the branched crack of length ratio aII/aI and at different values of the branched crack angles 2θ at two velocities. The interaction in branched cracks was also discussed, together with a comparison of the results of these experimental methods.
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