预腐蚀铝合金典型螺栓单搭接件疲劳寿命研究

模拟飞机服役环境,对航空LY12铝合金板材典型螺栓单搭接试验件做了预腐蚀试验,然后通过疲劳试验得到了未腐蚀试验件和预腐蚀后试验件的疲劳寿命。通过对试验件分解检查,分析了腐蚀对航空LY12铝合金典型螺栓单搭接件的影响。建立了考虑腐蚀影响的基于断裂力学的沉孔螺栓搭接件疲劳寿命计算模型,对预腐蚀搭接件的疲劳寿命进行了计算和分析。结果表明:螺栓孔附近和搭接面腐蚀较表面其他部位严重,腐蚀产物的膨胀作用下产生了"枕垫效应";计算模型得到的疲劳寿命与试验寿命吻合较好,其中模型1最大相对误差为36.7%,模型2的最大相对误差为25.7%。搭接件不同的腐蚀程度要选择不同的计算模型才能得出精确的结果。在分析较严重的腐蚀对搭接件疲劳寿命影响时,应考虑搭接面的多腐蚀损伤。

STUDY ON FATIGUE LIFE OF PRE-CORRODED ALUMINUM ALLOY TYPICAL SINGLE BOLTED LAP JOINTS

Corrosion experiment was performed for aviation LY12 aluminum alloy typical single bolted lap joints with imitating service environment of the military airplane.The fatigue life data for both un-corroded and pre-corroded specimens was obtained by fatigue tests.The specimens were torn down and then inspected.The corrosion effect on LY12 aluminum was analyzed.Two predictive models which consider the effect of corrosion for countersunk bolted lap joints are presented to calculate the fatigue life based on fracture mechanics.Results of two predictive models were calculated and analyzed.The results show that the faying surface and region round about bolt were corroded seriously with "pillowing effect" due to the expansion of corrosion products.Results of predictive models agree reasonably with the experiment results,with the maximum relative error being 36.7% for model 1 and 25.7% for model 2.It may be necessary to use different predictive models rather than a single predictive model to predict the fatigue lives.Multiple corrosion site damage in faying surface should be considered when serious corrosion effect on fatigue life of lap joint is investigated.