结构动力学边界条件识别及实现方法研究

【作者】 张永强；

【导师】 姜节胜；

【作者基本信息】 西北工业大学 ， 工程力学， 2005， 硕士

【摘要】 本文从结构的动态设计要求出发,对结构动力学边界条件进行了识别,并利用结构动力学优化的理论及有关技术,通过边界条件优化来控制结构的动力学特性。 论文首先引入求解非线性微分方程的微分变换法,将广义微分变换推广到求解一般动力学微分方程。建立了求解一般非线性振动微分方程的一般框架。并且将微分变换法推广到结构连接参数和边界参数识别。对于边界参数识别的情况,用一个典型的悬臂梁边界参数识别进行了实验研究,并将此方法的实验研究识别结果和用实测频率响应函数法的识别结果作比较。 其次,论文讨论了对于航空复杂试件,如何模拟真实结构提供给试件的动力学边界;通过柔性夹具动力学优化设计法,使试件原有的动力学边界得到工程实现的有关理论和方法。文中,对振动试验中试件与原结构的动力学特性进行了分析,强调指出模拟结构的真实动力学特性不仅要求各阶固有频率相同,还要求各阶振型也相同。鉴于固有频率模拟较易实现、模态模拟较难实现,文中主要关注振型模拟问题,对结构的振型模拟的两个重要问题——模态截断和振型修正进行了研究,给出了能量范数表示的模态截断的判别函数和基于线性空间变换的振型修正方法。更多还原

【Abstract】 Beginning with the requirement of dynamic design of structure, the article identifies dynamic boundary condition. And then with the aid of the theories and some related techniques of structural dynamic optimization, the article studies how to control the dynamic properties by boundary condition.Firstly, a differential transform method is introduced to solve nonlinear differential equations, and then the generalized differential transform method is extended to solve ordinary dynamic differential equations. Consequently, a procedure is established to solve nonlinear differential equations for general vibration problems. And based on it, a new method is established to identify the joint and boundary condition. As an example, a typical cantilever beam is chosen to identify its elastic boundary condition parameters. The numeric simulation and experiment result, the result got by proposed method and FRF identification are compared respectively.Secondly, the related theory and approach to simulate the dynamic properties provided by the real boundary conditions of a complex components of aero-structure through the dynamic optimal design of flexible clamp of test specimen is discussed in the paper. It is emphasized again that the consistency of not only the natural frequencies and but also the modal shapes between the real structure and designed test specimen should be held in engineering practice. In comparison with modal shapes, the frequencies simulation is relatively easy to reach. Therefore, the modal shape simulation approach is concentrated upon in the paper. For the engineering application, the criteria for mode truncation dependent on the energy norm assumption and mode shape modification technique based on linear space transformation are presented.更多还原