Critical Strain Energy Density from Tensile Specimens
Defence Research Establishment Atlantic Dartmouth, Nova Scotia Canada
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Fracture has always been a serious concern in the design and repair of steel structures such as ships. Because of these concerns, much research has been ongoing in the causes of fractures and in ways which they could be predicted and thus prevented. The objective of this study was to find, test and evaluate a method for measuring the critical strain energy density with tensile specimens. Plastic strain at fracture real strain was measured for gauge lengths of 1.25 mm and 1.125 mm using an etched grid. Real stress, the force divided by the reduced area, was also measured. Complexities in these two measurements were dealt with by detailed numerical analysis resulting in approximate average real stress-real strain curves that, in the transition zone, displayed decreasing strain energy density with temperature.