PROGRESSIVE STRESS DAMAGE AND STRENGTH OF CENTRIFUGALLY CAST, COLDWORKED GUN TUBES
WATERTOWN ARSENAL LABS MA
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The report presents the results of the hydraulic fatigue tests of centrifugally cast coldworked 75 and 76mm. gun tubes made of steel. In order to obtain data which the engineer could use in designing for resistance to progressive stress damage, test cylinders with wall ratio ranging from 1.2 to 1. 8 were used. In the preparation of the test cylinders considerable metal was removed from the outside surface of the coldworked rifled tube. The yield strength of some of these test cylinders was therefore measured in order to determine the influence of the removal of the coldworked metal upon strength. The slope of the elastic expansion curve of the cylinders was also calculated and compared with the theoretical one based on 30,000,000 psi as being the value for Youngs modulus. The resistance to progressive stress damage of the coldworked tubes was compared with that of heattreated-to-strength centrifugal castings and forgings in order to evaluate the benefit of coldworking.