Objective To research the fatigue life of structure selection of the 5th rib under wings whole tank wall plate of a certain type of aircraft.Methods Based on structure forms of stringer continuous and stringer disconnected determined preliminarily through the structure selecting design,comparative test for these two kinds of structure simulated specimen was carried out through static test and fatigue test.Results The static failure load of two structures was 588.20 kN and 587.97 kN,respectively.Both of them were consistent highly with the breaking load estimated (590 kN) by static strength design.Under the same constant amplitude loading spectrum conditions,the fatigue life of the median and under 95％ of confidence and 95％ of reliability of the stringer continuous structure was about 1.7 times and 4 times compared with the fatigue life of the stringer disconnected structure,respectively.The fatigue dispersion of the stringer continuous structure was much smaller than that of the stringer disconnected structures.The fatigue fracture of the long girder continuous structure mainly presented brittleness transgranular fracture characteristics,and the fatigue fracture of the stringer disconnected structure appeared mixed transgranular fracture characteristics,containing toughening fossa fracture and cleavage fracture.The fatigue fracture microstructures showed that the stringer disconnected structure produced a certain amount of plastic deformation in the fatigue process,it was explained from microscopic mechanism on the fatigue performance of the stringer continuous structure was better than that of the stringer disconnect structure.Conclusion The stringer continuous structure is better significantly than the stringer disconnect structures under the condition of the similar structure weight.%目的 研究某型飞机机翼下壁板整体油箱端5肋结构的选型疲劳寿命.方法 在结构选型设计时初步确定长桁连续和长桁断开两种结构形式的基础上,采用静力试验与疲劳试验方法对这两种结构模拟件进行对比试验验证.结果 两种结构模拟件的静破坏载荷分别为588.20 kN和587.97 kN,与设计预计破坏载荷(590kN)高度一致.在相同的等幅栽荷谱下,长桁连续结构的中值疲劳寿命和95％置信度与95％可靠度下的疲劳寿命分别约为长桁断开结构的1.7倍和4倍.长桁连续结构的疲劳分散性明显小于长桁断开结构.长桁连续结构的疲劳断口主要呈现脆性穿晶疲劳断裂特征;而长桁断开疲劳断口则呈现出韧窝型断裂和解理断裂的混合型穿晶疲劳断裂特征.疲劳断口微观形貌表明,长桁断开结构在疲劳过程中产生了塑性变形,这就从微观机理上解释了长桁连续结构的疲劳性能优于长桁断开结构的原因.结论 在结构质量相近的情况下,长桁连续结构明显优于长桁断开结构.
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