摘要
车载光学系统对于振动相当敏感,为了保证车载光学系统的工作精度,需要对光学系统进行减振设计。本文通过ANSYS有限元分析软件,对于双层的减振系统进行多参数耦合的优化设计,并将着重探讨板状结构的约束阻尼层铺设的各种问题,最后将确定该系统的约束阻尼铺设的方案。
本文首先采用ANSYS的优化工具箱,对于基于该大功率光学系统的双层减振模型,进行了多参数耦合的优化设计,得到了比较好的优化参数,并且与实际模型的结果进行了对照。由于该光学系统对于60-80Hz频段的振动很敏感,而实际结构的一阶弯曲振动频率正好落在此频段内,在减震器其它设计参数不变的情况下,本文探讨约束阻尼铺设的方案,提高该频段的模态阻尼,进一步提高系统抑制振动的能力。
此后,本文就板状结构的约束阻尼层铺设问题做了一定的探讨。首先用实体单元模拟阻尼材料,用壳单元模拟基层及约束层,建立了约束阻尼层的有限元模型,然后,将该模型的结果与文献的结果进行对比,验证模型的正确性。最后通过模态实验的频率及模态损耗因子进一步验证本文模型正确性。
本文在此模型的基础上,对约束阻尼的铺设进行了拓扑优化和参数优化,并探讨了将拓扑优化与参数优化结合起来的综合优化方法,为工程上简单板状结构的约束阻尼层铺设提供了一个简单的设计准则。在拓扑优化方面,本文着重探讨了两种方法,一种方法是基于MSE分布的方法,另外一种方法是基于CA算法的方法。第二种方法是以Chia等人的工作为基础,在阻尼增长的区域及方式上对CA算法进行了修改,使得程序在添加效率以及程序的适应性有了一定的改善,并且把模态参与因子考虑到了约束阻尼的铺设中,使得约束阻尼层的铺设更具有适用价值。基于此算法建立了CAM程序,并对板试件前4阶模态阻尼进行优化设计,其正确性得到模态实验验证。
本文在最后将把CAM程序应用工程实际中,针对该光学系统的几何空间布局,提出了约束阻尼铺设的方案,有限元计算结果表明在阻尼质量增加不大的情况下,约束阻尼能进一步抑制系统工作频段内的振动,验证了本文方法的可行性。
Vehicle optical system is sensitive to vibration, so vibration suppression is very important to the working accuracy. This thesis presents a method of multi-parameter optimization for this system by using ANSYS 10.0. Moreover, the research on how to apply CLD treatments is focused in this thesis, and an efficient CLD treatment is generated about this system finally.
In this thesis, after modeling two layers vibration-suppress of this high-power optical system, multi-parameter optimization is applied to this model by using ANSYS optimization tool box. Good design parameters are acquired compared to the practical model. Because the system is sensitive to the vibration from 60 to 80Hz, and the first bend mode is located in this frequency range, modal damping in this frequency range should be designed for this system in order to improve the performance of vibration suppression. Moreover, a study on optimal placement of CLD treatment is presented in this thesis. First, the finite element model of CLD is established by using the solid element to simulate viscoelastic core while using the shell element to simulate the base and constrained layers. To validate the modeling approaches, the FE results are compared to the ones that are presented in the literature; results are also presented of a comparison between FE and experimentally obtained modal properties.
On the base of the FE model, topology optimization Design is carried out by using CAM, and integrated optimization of parameter design and topology design is also presented in this thesis, and the result provide a simple design guideline for engineering application. In topology optimization, two methods have been studied. The first method is based on the distribution of MSE, and the second method is based on the CA algorithm which is first introduced in CLD topology optimization by Chia. In order to improve the efficiency and adaptability, some modifications are made on the area and pattern of damping growth. Furthermore, modal participation factor is concerned in this method which made this method more valuable for engineering application. The CAM program based on the method is used to optimize the first 4th order modal loss factor which is also validated by modal experiment.
In the end of this thesis, CAM program provide a scheme of applying CLD treatment for this optical system. Finite element results show that adding small mass damping can further improved the vibration suppression in the working band, which verify the validity of the method in this thesis.
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