Accession Number:

AD0263911

Title:

DETERMINATION OF THE DRIVING FORCE FOR CRACK INITIATION FROM ACOUSTIC RECORDS OF G SUB C TESTS ON HIGH-STRENGTH METALS FOR ROCKET MOTOR CASINGS

Descriptive Note:

Corporate Author:

NAVAL WEAPONS LAB DAHLGREN VA

Personal Author(s):

Report Date:

1961-10-04

Pagination or Media Count:

1.0

Abstract:

Fracture instability tests with a double-inking procedure were employed with the center-notched G sub c, test specimen to establish conditions at crack initiation. With this information anACOUSTIC METHOD WAS USED TO DETER INE THE DRIVING FORCE G sub Nc required to initiate cracking from a machined notch. The audio instrumentation can be added to the G sub c test without affecting standard procedure. Tests with recuded length of starting slot indicated that G sub Nc for a given type of notch is a relatively constant material property similar to the critical G sub c value for fast fracture. The G sub Nc value can be used in fracture toughness equations for the motor case to predict a slot size at which cracking should just initiate in a single cycle of stressing the material to yield strength. The general equivalence of K sub Nc to K sub Ic was an indication of adequate notch sharpness. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE