直升机变距拉杆杆端自润滑关节轴承的力学分析和损伤特性

以R44直升机主旋翼变距拉杆杆端自润滑关节轴承为研究对象，用三维建模软件Solidworks建立其旋转摆动的有限元模型并导入到有限元分析软件Ansys Workbench中，分析计算其在径向正弦载荷下衬垫的等效应力、位移、接触应力和等效剪切应力的变化特性；并结合实际服役工况下R44直升机失效的自润滑关节轴承衬垫进行分析。结果表明：在整个周期内，衬垫的边缘因为被挤压而发生变形，衬垫的等效应力和等效变形最大值均出现在外圈的边缘上，接触应力最大值所在的区域始终出现在衬垫的顶部和底部，并且接触应力分布区域的移动与内圈的转动方向一致，切应力最集中的地方在径向载荷施加点的左上方、左下方、右上方、右下方以及左右两侧；由于实际服役工况中载荷的变化，导致衬垫的损伤上半部分是以接触应力引起的疲劳损伤为主，下半部分是以切应力导致的转移膜形成为主。     

不同支承结构下同转/对转中介轴承的刚度特性

中介轴承是耦合双转子航空发动机的关键部件，为了探明中介支承结构特征、装配条件和发动机工况对中介轴承刚度特性的影响，建立了中介圆柱滚子轴承刚度特性分析模型。模型综合考虑了中介支承结构形式、轴承内外环相对旋转方向、内外环配合参数、内外环锁紧螺母拧紧力矩、轴承工作温度、发动机转速、径向载荷和弹性流体动力润滑等方面的影响，分析了某型机中介轴承的径向刚度随各参数的变化规律。结果表明，内外环配合参数和发动机工况对中介轴承的刚度影响较大，设计时应考虑刚度变化对转子系统动力学特性的影响；中介轴承刚度对锁紧螺母的拧紧力矩不敏感。另外，中介轴承刚度同中介支承结构形式及内外环的相对旋转方向密切相关，设计时应结合气动性能和结构动力学的要求合理选取，避免对发动机的可靠性造成不利影响。     

Pressure performance for a thin-walled ring and turbulent-jet orifice modeled elastic squeeze film damper

This paper explores an analytical model for Elastic Ring Squeeze Film Damper (ERSFD) with thin-walled ring and turbulent-jet orifices, and uncovers its Oil Film Pressure Performance (OFPP). Firstly, the ring deformation is addressed by using the Fourier series expansion approach and the orifice outflow rate is characterized with the Prandtl boundary layer theory. Secondly, applying finite difference scheme, the influence of elastic ring flexibility, orifice diameter, and attitude angle on the OFPP is analyzed. Finally, Outer chamber pressure was measured experimentally at different rotor speeds. The results indicate that the outer chamber pressure coats an individual load-carrying region and spreads symmetrically pertaining to the attitude angle. Its amplitude drops as the elastic ring flexibility decreases but boosts with the reduction of the orifice diameter. For inner chamber pressure, the orifice diameter effects a similar trend to the outer cavity, but exhibits more stable distribution regarding the attitude angle. Minimizing the elastic ring flexibility causes an increase in amplitude. The model is validated by the test results giving that the outer chamber pressure shifts synchronously and periodically with the variation of the attitude angle, while the pressure amplitude increases slightly at higher rotor speeds.