【作者】 万岭；

【导师】 洪明；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2010， 硕士

【摘要】 模态参数是一个结构动态性能的重要指标。模态参数的合理与否直接影响着工程结构的运行性能。对于传统的实验模态分析方法来说,要激起大型结构的振动响应较为困难,而且因为要得到完整的输入输出信息而存在很多的局限性,难以达到满意的效果。环境激励下的模态参数识别方法仅仅基于工程结构在环境激励下的振动响应信号来得到结构的模态参数,在许多大型的工程结构中拥有广阔的应用前景。本论文主要针对环境激励下模态参数识别方法在船舶结构中应用的可行性进行了研究。论文中提出将自然激励技术和特征系统实现算法这两种方法结合起来,并通过一系列模型实验验证了程序和算法的正确性,进而讨论了此方法在实际船舶结构中的应用特点和可行性,最后通过一艘实船结构运行状态下的振动响应,成功识别了结构的总体模态参数,这对环境激励下船舶结构的模态参数识别研究具有重要的指导意义。首先,在文章中讨论了模态参数对工程结构的重要意义以及环境激励下的模态参数识别方法和传统实验模态识别方法的区别及优势；进而讨论了环境激励下的模态参数识别方法的分类以及其各种算法的特点和应用范围；其次,讨论了船舶与海洋结构物所处的环境激励的特点以及船舶结构在环境激励下的响应特征,得出可以将船体结构的响应假设为白噪声与单频简谐响应的叠加；再次,详细介绍了自然激励技术与特征系统实现算法,并提出将两者结合起来进行环境激励下的模态参数识别；使用Matlab编制了此方法的程序,进而通过简支梁、船舶梁模型以及加筋板模型等一系列模型实验验证了程序的有效性；进一步,通过计算以及实验讨论了单频激励存在时模态参数识别的处理方法。最后,通过一艘实船结构运行状态下的振动响应进行了环境激励下的模态参数识别研究。验证了环境激励下的模态参数识别方法在实际船舶结构应用中的可行性和有效性,并为后续的工作打下了良好的理论和实验基础。更多还原

【Abstract】 Modal parameters are very important factors on dynamic performance of structures. Whether the modal parameters are proper influences the performance of structures directly. While, the traditional methods of experimental modal test can’t be very satisfactory because of the difficulty in getting the complete information of input and output, and the difficulty in exciting such big structures like ships. Modal parameters identification method based on ambient excitation can get the modal parameters just knowing the vibration responses, which has a wide application prospects in mega-structures.In this paper, research is mainly focused on the application on ship structures of this method. The algorithm which combines Natural Excitation Technique and Eigensystem Realization Algorithm (NExT/ERA) is used in the identification process. And through a series of model experiments and a ship structure test, its validity and feasibility in ship structures are verified.First, the importance of modal parameters to engineering structures is discussed, and in this paper, the difference between the modal parameters identification methods under ambient excitation and traditional modal test are discussed; What’s more, theories and characteristics of algorithms on modal parameters identification based on ambient excitation are introduced.Second, characteristics of the ambient excitation of ship structures are discussed, and the excitation can be assumed as a combination of white noise and harmonic components.Third, the NExT/ERA method is introduced in detail, and the corresponding Matlab program is written, then experiments of a simply supported beam, a ship structural model and a stiffened plate model are done to verify the feasibility of the program. Through calculation and experiments, the treating methods in the situation that harmonic excitation exists are discussed.At last, by an actual ship structure’s operational modal analysis, the feasibility of modal parameters identification method based on the ambient excitation that used in ship structures is verified, which provides experimental and theoretical bases for the subsequent work.更多还原