中强和高强铝合金的疲劳裂纹扩展特性

GROWTH BEHAVIOR OF FATIGUE CRACKS FOR HIGH-STRENGTH AND MEDIUM-STRENGTH ALUMINUM ALLOYS

本文研究2024（LY12）和7075（LC4）合金的疲劳长、短裂纹扩展特性，包括裂纹扩展速率、名义门槛植、本征门槛值、裂纹闭合效应、尾迹效应．2024合金有优良名义疲劳裂纹扩展抗力和高的名义门槛值，然而又有强的短裂纹效应，归因于其高的裂纹闭合效应和裂纹闭合效应的尾迹依赖性．7075合金的本征门槛值高和短裂纹效应弱，在近门槛值区有高的本征疲劳裂纹扩展抗力．同时．探讨疲劳裂纹扩展抗力、门槛值与断裂特征的关系．

The growth behavior of long and short fatigue cracks for aluminum alloys 2024 and 7075 was investigated, which concerned with the groWth rate of fatigue cracks, nominal threshold, intrinsic threshold, crack closure effect, crack wake effect. Alloy 2024 possesses excellent growth resistance of fatigue cracks and a higher level of nominal threshold, on the other hand, the stronger short crack effect is exhibited, which is attributed to a higher level of crack closure effect and the dependent mentality of closure effect on crack wake On the contrary, the intrinsic threshold of alloy 7075 is higher and its short crack effect is weaker. In near-threshold zone, its intrinsic growth resistance of fatigue cracks is superior to that for alloy 2024. The correlations among the growth resistance of fatigue cracks, threshold and fracture feature were explored.