不同预腐蚀时间下微动对搭接件疲劳寿命影响研究

Study of Fretting Effects on Fatigue Life of Lap Joints at Different Pre-corrosive Time

通过对不同预腐蚀时间下搭接件疲劳试验和断口宏微观的分析,得到不同预腐蚀时间下微动对搭接件疲劳寿命的影响规律。引入应力强度因子影响系数β用于修正微动效应对搭接件孔边裂纹应力强度因子的影响,针对不同腐蚀时间裂纹成核位置不同,利用裂纹扩展分析软件AFGROW建立了考虑微动影响的两种疲劳寿命计算模型。研究结果表明:微动和腐蚀的交互作用使搭接件的寿命减少更大,对于未腐蚀和腐蚀较轻的搭接件,由于微动作用,裂纹一般起源于螺栓孔处靠近螺栓孔沉孔区的螺栓体区,微动损伤占主导;对于腐蚀较重的搭接件,腐蚀占主导作用,裂纹一般起源于孔壁与接触面相交处。在考虑微动影响下,疲劳寿命预测值与试验值吻合较好,模型更加合理。

Based on macroscopic and microscopic analyses of fracture surface of lap joints at different corrosive damage, the influence regularity of fretting on fatigue life for lap joints is obtained. The influence coefficient β is introduced to modify the effect of fretting on the stress intensity factor of hole-edge crack of lap joints. Since different crack nucleation sites are associated with different corrosion time, two dif- ferent fatigue life models are presented considering the effect of fretting. The results show that the interaction of corrosive and fretting results in more life reducing. For un-corroded and slightly corroded specimens, the cracks usually originate from the bolt body region of bolt hole near the countersink region and the fretting damage plays a dominant role. For seriously corroded specimens, the cracks usually originate from the interface of hole wall and contact surface, and the corrosive damage plays a dominant role. The results of fatigue life prediction coincide with that of fatigue experiment, considering fretting effect, and the models are more reasonable.