Fatigue Cracking Rates and Residual Strengths of Eight Aluminium Sheet Alloys

摘要

Eight aluminium sheet alloys were tested as 6 1/2'' wide 16 SWG panels containing 1/2'' central transverse slots, to compare the propagation rates of fatigue cracks which grew from the slots under P plus or minus p type stressing. The results are given as cracking rate vs crack length curves. With the lowest stress cycle, 14,000 plus or minus 2000 psi, cracking rates at 1'' crack lengths ranged from 0.0000016 in/cycle in Hiduminium 54 to 0.000011 in/cycle in DTD.687A, the rate in DTD.5070 sheet being 0.0000036 in/cycle. With the highest stress cycle, 18,000 plus or minus 4000 psi, cracking rates at 1'' crack lengths were about 10 to 20 times faster, and again the DTD.5070 sheet had an intermediate rate similar to those of DTD.546B and 2024-T81. Heating 2024-T81 and DTD.5070 panels for 1000 hours at 150C caused only small changes in cracking rates, and rates measured in tests at 150C were very similar to those at room temperature. Residual strengths at 1'' crack lengths ranged for 37% for X 2020 to 67% for DTD.546B and Hiduminium 54, with DTD.5070 retaining 64%. (Author)