EFFECT OF STRAIN WAVE SHAPE ON HIGH TEMPERATURE FATIGUE LIFE OF A TYPE 316 STEEL AND APPLICATION OF THE STRAIN RANGE PARTITIONING METHOD.

The effects of strain rate and strain wave shape on the low-cycle fatigue of a Type 316 stainless steel were investigated at 600 and 700 degree C. A great reduction in the fatigue life corresponded with a variation in the fracture mode. Especially extensive grain boundary microcracks such as wedge- and cavity-type cracks were observed in slow-fast sawtooth wave shape tests and in tension hold time tests, respectively. The test results were analyzed by the strain range partitioning method proposed by Manson, Halford and Hirschberg. In applying this method, a new technique of partitioning the inelastic strain range was proposed and used. Four component strain range vs life relationships were dependent on the testing temperature between 600 and 700 degree C.