DEVELOPMENT OF EQUIPMENT AND TECHNIQUES FOR COMPLEX FATIGUE LOADING
Final technical rept.
AEROPROJECTS INC WEST CHESTER PA
Pagination or Media Count:
Fatigue testing apparatus for simultaneous application of high- frequency, low-frequency, and static loading was designed and constructed. The equipment provided for the introduction of high-frequency vibratory energy at 15,000 cycles per second at one end of a specimen, and static loading and low- frequency vibration at 2000 cycles per minute at the opposite end. Specimens with a necked-down test section were designed for resonance at the high frequency, and the specimen holding arrangement insured effective delivery of the high-frequency energy into the specimen. The feasibility of the apparatus as a fatigue test instrument was demonstrated in limited tests on integral specimens of 4340 steel, 2014-T6 aluminum alloy, and 6Al-4V titanium alloy, and on joint specimens of 4340 steel involving fusion-welded, riveted, adhesive- bonded, and brazed joints. With constant low-frequency and static loads, the specimens generally demonstrated shorter elapsed time to failure as the high- frequency power input was increased. The titanium alloy, however, appeared to be insensitive to the high-frequency vibration at the power levels used, possibly because of its internal hysteresis characteristics. The equipment provides a means for laboratory testing of materials and joint designs for knowledge of materials behavior under conditions encountered in rocket-propelled vehicles. It was recommended that comprehensive fatigue testing be carried out with this apparatus and that methodology be evolved for evaluation and use of the test data.
- Metallurgy and Metallography