基于层级有限元法的大型航空行星机构可靠性优化设计

Reliability Optimization Design for Large Aerospace Planetary Mechanism Based on Hierarchical Finite Element

大型航空行星机构作为多种重型航空器传动系统的基础与核心,它的可靠性水平在很大程度上制约着航空器的经济可承受性与服役安全性。将某型号重型直升机行星机构作为研究对象,以保证和提高该系统的疲劳可靠性水平为目标,利用层级有限元法计算系统全局弹性行为耦合作用下的轮齿疲劳载荷历程,并基于齿轮低周疲劳试验与最小次序统计量转化方法拟合出轮齿概率疲劳强度,为系统可靠性预测模型提供经济有效的载荷与强度输入变量。据此,建立从大型航空行星机构关键结构要素到系统可靠性指标的映射路径,提出可靠性驱动的行星机构结构尺寸多目标优化设计新方法。最后,分析了内齿圈轮缘厚度与行星架基板厚度对行星轮系疲劳可靠性的影响规律,并得到了指定型号的大型航空行星机构的轮缘与基板尺寸最佳刚度匹配结果,最大限度地发挥了核心结构要素的刚度潜力,以此平衡大型航空行星装备在可靠性与轻量化要求之间的矛盾。

As the foundation and core of various heavy aircraft transmission systems,the reliability level of large-scale aviation planetary mechanism restricts the economic affordability and service safety for the aircraft to a great extent.A model of heavy helicopter planetary mechanism as the object of study,and aims to improve the fatigue reliability level of the system.The fatigue load history of the gear teeth under the coupling of global elastic behavior of the system is calculated using a hierarchical finite element method,and the probabilistic fatigue strength of gear teeth is fitted based on the gear low circumference fatigue test with the minimum order statistics transformation method to provide cost-effective load and strength input variables for the system reliability prediction model.Based on this,a mapping path from the key structural elements of large-scale aviation planetary mechanism to the system reliability indexes is established,and then a new method of reliability-driven multi-objective optimization design for planetary mechanism structural dimensions is proposed.Finally,the influence law of ring gear rim thickness and planet carrier baseplate thickness on the fatigue reliability of the planetary gear train is analyzed,and the results of the best stiffness matching between the rim and baseplate dimensions for the specified type of large aviation planetary mechanism can be obtained.The stiffness potential of the core structural elements is maximized as a way to balance the contradiction between reliability and lightweight requirements of large aviation planetary equipment.