High Temperature Fatigue Deformation Behavior and Life Prediction of 316L Stainless Steel under Different Control Modes
Strain controlled(strain amplitude of 0.3％-1.2％)and stress controlled(stress amplitude of 230-300 MPa)low cycle fatigue tests,and strain controlled creep fatigue tests(three waves including tensile holding for 60,180,600 s,compressive holding for 60,180 s and tensile and compressive symmetric holding for 180 s)at 550 ℃ were conducted on 316L stainless steel for nuclear power.The fatigue deformation behaviour of the test steel under different control modes was analyzed through fatigue life,cyclic response characteristics and stress-strain hysteresis curves.The fatigue life prediction models including Manson-Coffin-Basquin model,SWT model,and energy method model were constructed and the predictive ability of these models for fatigue life of the test steel under different control modes was evaluated.The results show that the cyclic stress response of 316L stainless steel included cyclic hardening,cyclic softening and failing fracture stages under fatigue cyclic load of different control modes.In the low cycle fatigue test,the fatigue life decreased with the increase of strain or stress amplitude.In the creep fatigue test,the fatigue life decreased with the extension of tensile holding time and increased with the extension of compressive holding time,which was related to the comprehensive effect of dynamic strain aging and creep on fatigue damage.Under the same holding time,the fatigue life under compressive holding was shorter than that under tensile holding,which was related to the cracking mechanism of oxide layer caused by different loading directions.The energy method model had the highest accuracy in predicting the fatigue life of 316L stainless steel under different control modes,with prediction accuracy within 1.5 times the error band,and the Manson-Coffin-Basquin model had the lowest prediction accuracy.
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