【摘要】 在大气中不同应力条件下对F690钢进行高频疲劳试验和基于直流电压降的疲劳裂纹扩展速率试验,结合断口分析,对比研究了应力幅和应力比对F690钢疲劳性能和裂纹萌生、扩展的影响。结果表明:F690钢在应力比为-1,0.1,0.2,0.3时的条件疲劳极限分别约为313,264,250,246 MPa,条件疲劳极限随应力比的增大而减小;F690钢中的疲劳裂纹以条带机制扩展,断裂方式为穿晶断裂;随着应力幅的增大,疲劳辉纹间距和二次裂纹尺寸增加,疲劳裂纹扩展速率增大;随着应力比的增大,F690钢的疲劳裂纹扩展速率增大,且在裂纹扩展中后期变化较大,疲劳裂纹扩展门槛值减小。更多还原

【Abstract】 The high frequency fatigue test and fatigue crack growth rate test based on DC voltage drop were conduc ted on F690 steel in a ir under different stress conditions. Combined with fracture surface analysis, effects of stressamplitude and stressratio on fatigue properties and initiation and growth of cracks of F690 steel were studied and compared. The results show that the conditional fatigue limit of F690 steel at stress ratios of-1, 0.1, 0.2, 0.3 was313, 264, 250, 246 MPa, respectively, which ecreased with increasing stress ratio. The fatigue cracks in F690 steel propagated with band mechanism and dthe mode of fracture was trans granular fracture. As the stress ampl itude increased, the fatigue crack spacing and secondary crack size increased,and the fatigue crack growth rate alsoincreased. With increasing stress ratio, the fatigue crack growth rate of F690 steel increased and changed significantly at the middle and later stages of crack growth, and the fatigue crack growth threshold decreased.更多还原