FATIGUE TESTS ON NOTCHED AND UNNOTCHED SHEET SPECIMENS OF 2024-T3 AND 7075-T6 ALUMINUM ALLOYS AND OF SAE 4130 STEEL WITH SPECIAL CONSIDERATION OF THE LIFE RANGE FROM 2 TO 10,000 CYCLES

摘要

Fatigue tests were performed on notched and unnotched sheet specimens made of 2024-T3 and 7075-T6 aluminum alloys and of SAE 4130 steel. The steel was tested in two conditions: normalized and heat-treated to a tensile strength of 180 ksi. The notched specimens had theoretical stress-concentration factors of 2.0 and 4.0 and the mean loads were 0 and 20 or 50 ksi. Emphasis is placed on the life range from 2 to 10,000 cycles. Some previously published data are included to extend the data to life­times up to 108 cycles. It was found that repeated applications of stresses in the vicinity of the ultimate strength on notched and unnotched specimens produced failures in much smaller numbers of cycles than might be inferred from previously published data. Ratios of fatigue strengths of unnotched specimens to those of notched specimens are given.