An Investigation of Cracks and Stress Waves in Glass and Plastics by High-speed Photography

JSGT_1952_V36_T074_T089

A high-speed spark camera is described which will take a series of nine photographs at rates of 20,000 to 200,000 frames per second. The camera has been used to photograph the propagation of stress waves and the formation of cracks in sheets of glass and “Perspex.” The illustrated results show the effects of applying pressure pulses of from 2 to 40 µs duration to small plates of the materials. The reflection of the stress waves from the free edges of the plate is discussed with particular reference to the formation of fractures. Finally, the type of hackle structure appearing on some of the fracture surfaces is discussed in relation to the method of formation of the cracks.

D. G. Christie