The Structure Of Dynamic Boundary Conditions To Identify And Implementation Research

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.