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Fatigue Life Enhancement of a D16at Aluminum Alloy for Aircraft Components with Fastener Holes
Strength of Materials ( IF 0.7 ) Pub Date : 2020-04-21 , DOI: 10.1007/s11223-020-00144-3
G. V. Duncheva , J. T. Maximov , N. Ganev , A. P. Anchev

D16AT aircraft Al-alloy was evaluated. The friction stir hole expansion (FSHE), solid mandrel cold working and symmetric cold expansion (SCE) methods were compared. The results are summarized on the basis of fatigue tests, S–N curves, X-ray diffraction, and microstructural analysis. Under the high-cycle fatigue, SCE provides more than 66 times longer fatigue life as compared to the solid mandrel method and more than 82 times greater fatigue life in comparison with the FSHE method. Through X-ray diffraction analysis it was found that the higher efficiency of the SCE method was due to symmetric distribution (with respect to the plate middle plane) of residual hoop stresses around the hole. On the other hand, the solid mandrel cold working method causes a significant gradient of the residual stress distribution through the plate thickness, which is a precondition for nucleation and propagation of corner fatigue cracks. The FSHE method efficiency was established to be primarily dependent on generated heat and equivalent plastic strains. The combination of these factors determines the beneficial microeffect of the microstructure modifying in the vicinity of the hole and a useful macroeffect due to residual compressive stresses. It was concluded that SCE method should be used for prestressing of fastener holes in the most loaded components in D16AT aircraft structures – wings and fuselage, while the FSHE one can be applied to processing of fastener holes in less loaded aircraft components.

中文翻译:

带有紧固件孔的飞机部件的D16at铝合金的疲劳寿命提高

对D16AT飞机铝合金进行了评估。比较了搅拌摩擦扩孔(FSHE),实心芯棒冷加工和对称冷胀(SCE)方法。根据疲劳测试,SN曲线,X射线衍射和微观结构分析总结了结果。在高周疲劳下,SCE的疲劳寿命是实心轴方法的66倍以上,疲劳寿命是FSHE方法的82倍以上。通过X射线衍射分析,发现SCE方法的更高效率是由于孔周围残余环向应力的对称分布(相对于板中间平面)。另一方面,实心轴冷加工方法会导致整个板厚的残余应力分布出现明显的梯度,这是拐角疲劳裂纹成核和扩展的前提。FSHE方法的效率被确定为主要取决于产生的热量和等效的塑性应变。这些因素的组合决定了孔附近微结构的有益微观效应,以及由于残余压缩应力而产生的有用宏观效应。得出的结论是,应该使用SCE方法对D16AT飞机结构中最重负荷的组件(机翼和机身)中的紧固件孔进行预应力,而FSHE方法可用于处理负荷较小的飞机部件中的紧固件孔。这些因素的组合决定了孔附近微结构的有益微观效应,以及由于残余压缩应力而产生的有用宏观效应。结论是,应使用SCE方法对D16AT飞机结构中机载最重的部件(机翼和机身)中的紧固件孔进行预应力,而FSHE方法可用于处理负荷较小的飞机部件中的紧固件孔。这些因素的组合决定了孔附近微结构的有益微观效应,以及由于残余压缩应力而产生的有用宏观效应。得出的结论是,应该使用SCE方法对D16AT飞机结构中最重负荷的组件(机翼和机身)中的紧固件孔进行预应力,而FSHE方法可用于处理负荷较小的飞机部件中的紧固件孔。
更新日期:2020-04-21
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