| 2024 aluminum alloy is currently the most widely used aviation materials,generally used to make aircraft bearing structure and connectors.Due to the rigidity of the fatigue performance of some important connections on the aircraft and the characteristics of fastening hole prone to fatigue crack,it is necessary to study the fatigue performance of the 2024 aluminum alloy fastening holes.This paper systematically has studied three different 2024 aluminum alloy fastening hole process,including light hole(no thread),cutting thread and internal extrusion thread.Each group of samples was subjected to fatigue tests under three different maximum alternating stresses σmax.The differences of the fatigue life data of each group were analyzed,and the effect of σmax on the fatigue life of each group was analyzed.In this paper,the optimal distribution profiles of the fatigue life data of each group under the same stress were obtained by linear fitting method,and the fatigue life of each group under high reliability has been obtained.Finally,in order to further understand the fatigue failure mechanism of the fastening hole,the morphological characteristics of the fatigue section of each fastening hole were observed by scanning electron microscopy,and the fatigue crack propagation mechanism was analyzed.The main results are as follows:The fatigue life of the extruded threads is greater than the fatigue life of the cutting threads and the light holes under different maximum stresses.In addition,as the maximum alternating stress increases,it has been found that the fatigue life of the internal squeezing thread was gradually narrowed with the fatigue life of the light hole and the cutting thread.The optimal distribution profiles of the fatigue data of each group were obtained by linear fitting method.The distribution of fatigue life of cutting threads is the most normal distribution,and the distribution of fatigue life of other specimens is more consistent with the distribution of three parameters Weibull distribution.At high reliability,the fatigue life of the extruded thread is the longest,the cutting thread is the second,and the shortest hole is the shortest,which also shows that the fatigue resistance of the extruded thread is better than the other two.There were multiple sources of fatigue in the inner squeeze thread,both at the tip of the thread,where the tip of the first thread is the first crack,through the analysis of the fracture behavior of the three kinds of fastening holes.The fatigue failure mechanism of the three kinds of fastening holes is same,which belongs to the crack initiation and expansion mechanism,and the micro-cracks are expanded in the same way.In this paper,the reliability of 2024 aluminum alloy connector and the application of 2024 aluminum alloy connector are provided by the analysis of fatigue life data and fracture mechanism of 2024 aluminum alloy fastening hole. |
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