直升机飞行动作时间比例改变对动部件疲劳损伤影响分析

INFLUENCE OF FLIGHT TIME PROPORTION ON FATIGUE DAMAGE FOR HELICOPTER DYNAMIC COMPONENTS

建立分析飞行动作时间比例改变对动部件疲劳损伤影响的数学分析模型,引入"疲劳损伤放大系数"的概念,通过计算只有一个飞行动作时间比例改变和只有一个飞行动作时间比例未改变得到的放大系数,可以定性和定量分析各种飞行动作时间比例改变对动部件疲劳损伤的影响程度。依据某型直升机的实测飞行谱和主、尾桨叶的疲劳载荷频数均值谱,运用所建立的模型进行分析。研究表明,对某型直升机的关键动部件,所有的48种飞行动作中只有三种飞行动作造成的损伤在飞行动作时间比例变化0.1时疲劳损伤变化超过0.01,同时飞行动作的敏感性具有很大的部件依赖性,巡航平飞状态是最敏感的飞行动作。最后通过运输直升机改为反潜直升机的谱型变换实例(只有一个飞行动作未改变时),说明用文中得到的疲劳损伤放大系数进行不同谱型疲劳损伤计算的适用性。

An analytical model is presented for the calculation of influence of flight time proportion changes on fatigue damage of helicopter dynamic components where an amplification factor is introduced to study the influence. Two amplification factors for the cases where only one flight condition is modified at a time and all flight conditions except one are modified can provide qualitative ordering and quantitative assessment of fight condition changes on fatigue damage. Some results are obtained by the analysis to helicopter main and tail rotors based on flight spectrum and mean frequency spectrum. For the helicopter critical fatigue member only three of the forty-eight flight conditions would have any significant effect that a O. 1 time fraction change leads to fatigue damage change more than 0.01. The sensitivity on flight condition changes is highly component-dependent; and the most sensitive condition is the cruising flight. Using the amplification factors that all flight conditions except one are modified corresponding to the fractional time change from transport to antisubmarine helicopter, the applicability of the model to fatigue damage and life calculation is validated.