Several alternative test specimens for the determination of the fracture strength of a brittle material have been studied. These include a ring-supported ball-loaded thin circular disc, a disc symmetrically supported on three equispaced balls and loaded at the centre through a fourth ball, a cylinder under axial compressive point-loading, and a ‘pure shear’ beam specimen. The stress distributions in these specimens have been determined photoelastically and the stress data used to interpret fracture test data for batches of each specimen made from reactor-grade graphite. The stochastic nature of the fracture data has also been considered.
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