1972-02-01

Accelerated Fatigue Testing 720266

The people reports data on block program fatigue testing of a simple cantilever specimen with a stress concentration, the specimen being made of SAE 1530 steel. The various programs investigated were based on a normal distribution with a crest factor of 4 and were aimed at accelerating fatigue testing.From tests on programs with 4,8, and 16 stress levels, it was concluded that at least 8 stress loads were required to stimulate accurately the normal distribution. Tests in which various stress levels were omitted showed that stress levels S/σ< 1.75 contributed nothing to fatigue damage, and consequently they could be omitted from the program, resulting in a saving of 87% in testing time. Stress level in range 1.75 S/σ<=4 had a damaging effect, and even the one of S/σ=4 in each full program of 4000 cycles caused significant damage. This indicates the great importance of the choice of crest factor.

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