EXPLOSION TEAR TEST STUDIES OF HIGH-STRENGTH Q and T STEELS
NAVAL RESEARCH LAB WASHINGTON DC
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Cleavage brittle fractures, have been investigated extensively. Proof-test failures involving low energy shear fractures have been encountered under conditions of near-yield-point loading for structures rocket cases which utilized high-strength materials. This investigation was undertaken to develop a test method which would provide for the evaluation of tearing characteristics under explosive loadings for steels ranging in yield strength from 100 to 150 ksi. A new test, the explosion tear test, was developed. Preliminary results demonstrate that high-strength materials differ widely in tearing resistance. The relationship of Charpy V shelf level to tearing resistance has been examined. Shelf-level values significantly less than 40 to 50 ft-lb are shown to correlate with low energy shear characteristics in the explosion tear test. The quantitative correlation of Charpy V shelf level to tearing resistance of high- strength steels, however, is disclosed to be more complex than originally presumed. The complications, involving a yield-strength dependency and other factors, are discussed.