飞机吊架集中质量-弯曲梁模型与振动特性分析

Concentrated mass - bent beam model and vibration characteristics analysis of aircraft pylon structure

  • 摘要: 本文提出一种新的飞机吊架集中质量-弯曲梁模型,作为一种有效的模态降阶方法,用于吊架连续结构的振动特性分析。首先根据吊架结构的周期性结构和实际工况下的受力特征,利用集中质量法将吊架结构简化为一个由12个质量单元和11段梁单元串联而成的集中质量-弯曲梁模型,两个简支边界条件反映吊架-机翼前后吊点的真实约束。基于传递矩阵法建立了该模型的传递方程及特征方程,运用参数灵敏度法对抗弯刚度不确定参数进行有效修正优化后,通过与有限元模型低阶固有频率的对比验证了本文建立的吊架集中质量-弯曲梁模型的有效性。在此基础上把发动机通过安装节与吊架-发动机前后吊点连接作为基础激励,建立了发动机-吊架集中质量-弯曲梁耦合模型,应用传递矩阵法研究了该耦合模型的固有频率与吊架结构在发动机起飞、巡航和空慢工况下振动响应,获得不同工况不同时刻下吊架结构质量单元振动包络线和代表性质量单元的振动响应,并通过与有限元对比进一步验证了本文新建模型的有效性,研究结果为吊架结构的减振设计提供了理论支撑。

     

    Abstract: In this paper, a new concentrated mass-bent beam model of aircraft pylon is proposed, which is an effective mode reduction method for the analysis of vibration characteristics of continuous structures of pylon. Firstly, according to the periodic structure and the stress characteristics of pylon structure under actual working conditions, pylon structure is simplified into a concentrated mass-bent beam model which consists of 12 mass elements and 11 beam elements in series by using the concentrated mass method. The two simply supported boundary conditions reflect the true constraints of pylon-wing front and rear lifting points. The transfer equation and characteristic equation of the model are established based on the transfer matrix method. After using the parameter sensitivity method to correct and optimize the uncertain parameters of bending stiffness, the effectiveness of pylon concentrated mass-bent beam model is verified by comparing with the lower order natural frequencies of the finite element model. On this basis an engine is connected to the front and rear lifting points of pylon-engine through the installation section as the basic excitation, and engine-pylon concentrated mass-bent beam coupled model is established. Transfer matrix method is applied to study the natural frequency of the coupled model and the vibration response of pylon structure under the take-off, cruise and flight idle conditions of the engine. The vibration envelope lines of pylon structure mass elements under different conditions and different times and the vibration response of the representative mass element are obtained. In addition, the effectiveness of the new model is further verified by comparing with the finite element method. The research results provide theoretical support for the vibration reduction design of the pylon structure.

     

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