Fatigue Behaviors of 18-8 Stainless Steel under Combined Cyclic Mechanical Strain and Cyclic Heating, and also under Cyclic Strain at Elevated Temperature

Abstract

Cylindrical solid specimens of 18-8 stainless steel were subjected to combined temperature and mechanical strain cycling independently and also cyclic straining at elevated temperature, and the number of cycles to failure were determined. Measurements of crack propagation speed and microstructural studies were made. The results were as shown below:(1) The inverse relationship between the mechanical strain range and the square root of the number of cycles to failure has been verified.(2) The maximum temperature is the most sensitive factor in thermal fatigue, and temperature difference may also be considered to be a controlling factor.(3) The life in thermal fatigue under cycling between maximum and minimum temperature is about 0.3∼0.1 of that in mechanical strain cycling under constant temperature.(4) Many differences between temperature cycling and constant temperature behaviors are observed.The paper describes the foregoing results in detail