Abstract
Abstract : Three separate investigations were undertaken to determine the applicability of the short rod fracture toughness measurement method to materials such as HF1 fragmentation steel, which is of particular interest to the Army. In the first study, short rod fracture toughness (K sub Ic SR) measurements were compared with ASTM E 399 measurements of toughness (K sub Ic) in a number of metallic materials. Very good agreement was found. In the second study, the methods of fabricating and testing ultra-small short rod specimens (6.35 mm diameter) were developed and used in measurements of HF1 material taken from actual shell casings. The agreement of the ultrasmall short rod measurements with the toughness as measured by precracked charpy specimens of the same material was rather poor. The third study was made to determine the sensitivity of the short rod toughness measurement to the size of the specimen used in the test. Short rods of various sizes of 4340 steel and two heat treatments of HF1 steel were tested. The specimen size independence of the 4340 steel was marginal, but it was excellent for the HF1 steel. A trend toward an increasing scatter in K sub IC SR data with decreasing specimen size was noted. Recommendations for decreasing the data scatter and automating the test are made.
Published Version
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