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腹板连接处的疲劳性能直接影响飞机的安全性,疲劳分析中常采用细节疲劳额定值(DFR)来度量结构细节本身固有的疲劳性能。文中对某型飞机腹板连接结构进行了加速疲劳试验研究,通过在结构件表面预先粘贴的应变花实时监测试件在正弦交变载荷下的应力应变状况,得到了疲劳试验过程中裂纹附近的应力演化规律。试验结果表明:在峰值为18 k N的正弦交变拉伸载荷作用下试件的疲劳寿命约3×105,符合疲劳寿命分布预期104-106。采用DFR法分析了该结构件破坏部位的疲劳性能,通过计算得到了试件破坏部位的DFR值,研究表明应力最大的地方不一定最危险,DFR值小的部位也不一定最先破坏,并给出了试件上4处局部结构的预测寿命。研究结果可用于飞机腹板连接结构的疲劳分析。
The fatigue performance at the web connections directly affects the safety of the aircraft. The fatigue analysis (DFR) is often used in fatigue analysis to measure the inherent fatigue behavior of structural details. In this paper, an accelerated fatigue test on the connection structure of a certain type of aircraft web was carried out. The stress and strain of the specimen under real sinusoidal alternating load were monitored by the strain applied in advance on the surface of the structure. The law of stress evolution. The experimental results show that the fatigue life of specimens is about 3 × 105 under the sinusoidal alternating tensile load with a peak value of 18 kN, which accords with 104-106 expected fatigue life distribution. The DFR method was used to analyze the fatigue performance of the damaged part of the structure. The DFR value of the damaged part of the specimen was obtained by calculation. The results show that the places with the highest stress are not necessarily the most dangerous and the parts with small DFR are not necessarily the first to be destroyed. The predicted life expectancy of four local structures on the specimen is given. The results can be used to analyze the fatigue of aircraft web connections.