基于损伤力学的某飞机构件冲击疲劳寿命预估

DAMAGE MECHANICS BASED IMPACT FATIGUE LIFE PREDICTION FOR AN AIRCRAFT COMPONENT

某飞机起落系统中某重要构件在飞机往复起落中承受循环冲击载荷作用,需对该构件的冲击疲劳强度进行分析。损伤力学方法对冲击疲劳问题来说是一种新的分析方法。首先分析构件在静载荷作用下的细节应力,判明疲劳危险点,接着分析得到危险点在冲击载荷作用下的应力响应。然后构建冲击型损伤演化方程,并识别其中的材质参数,提出将应力响应视为载荷谱的应力应变场—损伤场解耦处理方式,发展了损伤力学—有限元法,使其可用于预估构件冲击疲劳裂纹萌生寿命。而后应用该方法对构件在冲击疲劳载荷与非冲击疲劳载荷作用下的疲劳裂纹萌生寿命进行预估,得到寿命预估结果,进而比较得到冲击疲劳载荷作用下和非冲击疲劳载荷作用下构件寿命的当量关系,为该构件的等效疲劳试验提供重要参考依据。

An important component in the landing system of an aircraft suffers cycled impact loadings in repeated landings, so it is necessary to analyze its impact fatigue strength. Continuum damage mechanics （CDM） method is new for impact fatigue problems. First, the component＇s detailed stress under static loadings and the fatigue dangerous point was determined, afterwards the stress response of the dangerous point under impulsive loadings were obtained. Second, the impact damage evolution equation and its material parameters identification were introduced. Taking the stress response as a loading spectrum, the damage mechanics finite element method was developed to predict the component＇s fatigue crack initiation life. With this method, the fatigue crack initiation life prediction for the component under impact loadings and non-impact loadings were carried on, and results were obtained. Finally, the equivalent relationship between lives under constant rate test load and constant rate impulsive Road was obtained, which provides significant references for the component＇s equivalent fatigue experiment.