Abstract
Triangular plaster of Paris plates were subjected to contact explosives and photographs of the fracture patterns obtained are presented. The effect of the geometry and the form of loading on the fracture patterns and the length of the spalls are discussed. A simple analysis which employs cylindrical stress wave equations shows that, as a pulse propagates towards the apex, a compressive head and a tensile tail are developed, both becoming larger in magnitude as the pulse approaches the apex. Fracture is produced whenever the tensile stress reaches a magnitude just above the ultimate tensile stress of the plaster; further fractures are also predicted by the analysis. The method of images is used to explain the presence of the longitudinal crack.
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