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Stretch Zone Width Measurement of Side-Grooved HSLA 80 Fracture Specimens

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Martec Limited Halifax, N.S. Canada

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Stereoscopic imaging with a scanning electron microscope was used to measure stretch zone width on the fracture surfaces of side grooved HSLA 80 SENB fracture specimens which were tested over a range of temperatures -42 degrees C to 22 degrees C and loading rates 0.01 to 2710 mms. The data were examined to determine the relationship between stretch zone width and temperature at constant loading rate, and the relationship between stretch zone width and loading rate at constant temperature. Measurement error, the limited number of data points, and intrinsic variability collectively limit the confidence with which trends could be determined. For loading rates below 2 mms, the stretch zone width increased with temperature until a limiting temperature of -20 degrees C was reached. Beyond this temperature the variation in stretch zone was less than the measurement error. At a loading rate of 2710 mms, the stretch zone width appeared to increase linearly with temperature over the range of -5 degrees C to 15 degrees C. The variation in stretch zone width with loading rate was less than the measurement error over the range of 0.01 to 60 mms. There appeared to be a decrease in stretch zone width when the loading rate was increased to 2710 mms. For specimens which exhibited stable crack growth after blunting, the stretch zone width was greater in the central region of the specimen than at the edges. For specimens which exhibited unstable brittle crack extension immediately after the stretch zone, the stretch zone width was essentially uniform across the specimen.

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Technical Report



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Approved For Public Release;

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