수정 Forman 모델을 이용한 고성능 강재의 피로균열전파와 피로수명평가

초록

Fatigue crack propagation behavior and the fatigue life in-high performance steel were investigated by means of fatigue crack propagation tests under constant loading conditions of 'R=O. 1 andf=0.1 Hz', 'R=0.3 andf=0.3 Hz', and 'R=0.5 and f=0.5 Hz' for the load ratio and frequency, respectively. A modified Forman model was developed to describe the fatigue crack propagation behavior for the conditions. The modified Forman model is applicable to all fatigue crack propagation regions I, II, and IIIby implementing the threshold stress intensity factor range and the effective stress intensity factor range caused by crack closure. The results show that predicted fatigue lives of Forman and modified Forman models were 8,814 and 12,292 cycles, respectively when the crack propagated approximately 5.0 mm and the load ratio and frequency were both 0.1. Comparison of the test results indicates that the modified Forman model showed much more effective fatigue crack propagation behavior in high-performance steel.

키워드