叶片榫连结构的粘弹性阻尼减振机理研究

Blades, as key components of gas turbine, are exposed to complex vibration pattern. Especially the dovetail attachment region connecting blades and the disc often suffers from fretting wear and surface fatigue which may cause fatigue failure under multi-field coupling complex boundary conditions.When viscoelastic damping materials are applied to aero-engine blades, it can reduce vibration, providing a new way to address the high cycle fatigue failure of the blade. However, because the mechanism of energy dissipation and damping characteristics caused by the blade with viscoelastic material,the active design of damping properties can not be achieved. In order to reduce the unavoidable vibration and fretting wear of the blade of dovetail attachment, it is proposed here to introduce viscoelastic damping materials to suppress the blade vibration level and hence to improve the resistance of the dovetail attachment structure to vibration induced fatigue. Based on considering contact friction properties of the dovetail attachment region, the methodologies of nonlinear analyses of viscoelastic materials on the blade root are local nonlinear analytical modeling, finite element simulation and prototype tests. The main task of the proposal includes the following aspects. Firstly, nonlinear theories of the nonlinear dynamics and vibrations of blades with the viscoelatic materials are investigated in this proposal, as well as corresponding viscoelasic damping analysis, based on the experimental observations of the prototype and on-site. Then,the underlying nonlinear dynamic characteristics, vibration behaviors, especially the contact dynamic stress distributions of the dovetail attachment of blade are obtained.Finally, new techniques of viscoelastic materials on the blade root are especially discussed based on the understanding of the damping mechanism for vibration reduction. It is an interesting way to avoid the fatigue fracture of the dovetail root-blade and blade besides structure modification.

叶片是燃汽轮机等重要叶轮机械的关键部件，在多场耦合复杂边界条件作用下，容易发生复杂的振动，特别是叶片与轮盘相联接的榫连结构因振动容易发生微动磨损和疲劳破坏。粘弹性材料在应用于航空发动机叶片时，具有阻尼减振的效果，为解决叶片高周疲劳失效提供了新途径，然而粘弹性阻尼叶片结构的能量损耗及其阻尼特性机制认识不清，无法实现粘弹性阻尼叶片结构的阻尼性能的主动设计。本项目提出在叶片榫头底部施加粘弹性材料以实现叶片振动抑制的动力学原理，在考虑榫连结构的接触摩擦特性的基础上，研究带有粘弹性阻尼材料的叶片的非线性解析分析，有限元分析和试验验证，实现对榫连结构接触区动力学特性的准确表征；获得叶片的非线性动力学特性、复杂振动行为；明确减振机理。

叶片是航空发动机、燃汽轮机、高端轴流压缩机等叶轮机械的重要部件。在多场耦合复杂条件下，承受相对严酷的流体和热机耦合激励，并且由于其本身的密集固有频率和复杂形式的模态振型等因素，不可避免地产生共振。本项目采用粘弹性阻尼技术进行叶片减振的粘弹性阻尼叶片的动力学特性的理论分析，在考虑榫连结构的接触摩擦特性的基础上，研究带有粘弹性阻尼材料的叶片的非线性解析分析，有限元分析和试验验证，实现对榫连结构接触区动力学特性的准确表征；获得叶片的非线性动力学特性、复杂振动行为；明确减振机理。结果表明增加粘弹性阻尼材料的厚度、选择储能模量和损耗因子较大的材料有利于提高系统的模态阻尼比，获得较好的减振效果;随着旋转角转速的升高，带有粘弹性阻尼叶片的固有频率逐渐升高，模态阻尼比下降明显，说明随着转速的升高，粘弹性阻尼块的减振效果降低的。