Vibration Attenuation and Fatigue Analysis of the Large Flexible Articulated Boom under Wind Load and Vortex Shedding

本计画主要研究风振及涡激振动对塔筒及臂杆之振动衰减及疲劳分析。利用HyperMesh、Ansys和RISA软件建立了塔臂的三维有限元模型。在不同的吊杆配置和载荷情况下，进行了全面的振动分析，以确定结构的前10个固有频率和相应的振型。为了验证模型的准确性，将有限元分析结果与实验结果进行了比较。该实验已在美国国家航空航天局进行，并得到了结果。利用试验结果沿着，结合对数衰减法和模态分析，提取了结构的阻尼。通过有限元模拟、实验和尾流分析，确定了在何种情况下结构的共振频率被激发。此外，还计算了共振激励下臂架的挠度.最后，确定了结构在循环载荷作用下疲劳失效的关键部件，并计算了它们的疲劳寿命，以确保结构在50年内正常运行，没有任何失效。最后，适当的振动阻尼装置或调谐减振器将被优化设计，以减轻极端的振动，由于涡脱落。

This project concerns with vibration attenuation and fatigue analysis of the towers and attached articulatedbooms in response to wind load and vortex shedding. The three-dimensional finite element model of the towersand booms are developed in HyperMesh, Ansys and RISA softwares. A comprehensive vibration analysis isconducted to identify first 10 natural frequencies and corresponding mode shapes of the structure, underdifferent possible booms configurations and loading scenarios. In order to demonstrate accuracy of the model,the results obtained from finite element analysis, in terms of natural frequency of the articulated boom, arecompared with those of the experiment. The experiment has been already conducted by STRUDES and theresults are available. The experimental results along with logarithmic decrement technique and modal analysisare used to extract damping of the structure. The findings obtained from the finite element simulation,experiments and vortex shedding analysis of the booms are used to identify under what circumstances theresonant frequencies of the structure are excited. Furthermore, the boom deflection under resonance excitationis evaluated. At the end, the critical components of the structure subject to fatigue failure, due to cyclic loads,are identified and their fatigue lives are computed to make sure the structure operates properly during 50 years,without any failure. Finally, appropriate vibration damping devices or tuned vibration absorbers will beoptimally designed to mitigate the extreme vibration due to vortex shedding.