Low Cycle Fatigue Characteristics of Irradiated Type 304 Stainless Steel

Abstract

Tensile and low cycle fatigue characteristics of Type 304 stainless steel were determined at room temperature and 325°C in both the unirradiated and irradiated (~8 X 10²⁶ n/m², >0.1 MeV) conditions. The irradiated tensile specimens exhibited radiation hardening and embrittlement with a significant drop in ductility at 325°C; however, they still behaved as ductile materials with 4 to 5% total elongation.

Fatigue tests were conducted at a fixed frequency of 0.1 cps in four-point bending mode with full strain reversal. and all tests were carried out under strain control. Both the deflection and load were continuously monitored, and the number of cycles to failure was determined at total axial strain ranges varying from ~1.0 to 2.4%. The number of cycles to failure varied from ~500 to 40 000. Data at both the room temperature and 325°C indicated that irradiation improved fatigue life at strains lower than ~1.6%, whereas a slight decrease in life is noted at higher strain ranges. Correlations of the experimental data with predictions of the universal and characteristic slopes equations, based on appropriate tensile properties, are discussed. A modified equation predicting the present data was developed based on the universal slopes concept and tensile properties, such as the ultimate tensile stress, ductility, and work-hardening coefficient.