30CrMnSiNi2A高强钢的疲劳小裂纹扩展特性及寿命预测

研究了３０ＣｒＭｎＳｉＮｉ２Ａ高强钢在恒幅载荷下的小裂纹起始特征和裂纹扩展特性。试验结果表明，小裂纹起始于缺口表面初始缺陷（如夹杂或孔洞）处。在应力比Ｒ＝０的恒幅载荷下，未显示小裂纹效应：在Ｒ＝－１的恒幅载荷下，则显示出小裂纹效应的存在。利用裂纹闭合模型和微观结构缺陷作为初始裂纹尺寸的方法预测了小裂纹扩展速率和疲劳全寿命，预测值与实验值符合良好。

GROWTH BEHAVIOUR OF SMALL FATIGUE CRACK AND FATIGUE-LIFE PREDICTION FOR HIGH-STRENGTH STEEL 30CrMnSiNi2A

Single-edge-notched tension (SENT) specimens under constant load amplitude were used to obtain the small crack growth information via an acetate replica method. The observed results show that more cracks are surface ones and initiated at inclusion-particles or voids on the surface of the notch. Steel 30CrMnSiNi2A does not exhibit a significant short crack effect when stress ratio R=0. But a slight small crack effect was observed at R=-1, and the short cracks can grow below the long crack threshold. Using the closure crack growth model and a microstructural defect as an initial crack, the small crack growth rate and the total fatigue life can be predicted and the predicted results are in reasonable agreement with experiments.