Damping vibration in three-dimensional helically tapered rod with power-law thickness

Abstract

Tapered structure with power-law thickness has been regarded as an efficient approach for passive vibration control. In this paper, a three-dimensional (3D) helically tapered structure with power-law feature is proposed to reduce the vibration in rod structure. Compared with the traditional one-dimensional tapered rod, this novel helix type can compress the length of tapered region by the coiling configuration and transform the flexural wave modes into various complex modes. Drawing on its folded characteristic, the helix structure can generate highly efficient space utilization and achieve a superior vibration attenuation effect in the low frequency band. Numerical investigations on the dynamics and reflection coefficient analyses of different rod types are conducted and the reduction mechanism of 3D helically tapered rod is revealed. It is found that the larger helical radius can contribute to the reduction in low-frequency vibration, but it deteriorates the vibration performance in broadband. To overcome this “sudden collapse” phenomenon in the damping performance caused by the low stiffness, the novel step helically tapered rod is presented. According to the introduced multimodal and multidirectional mode-coupling effects, this step 3D helix structure not only makes up for the shortcoming of vibration control in low frequency range, but also further improves the innate advantage of reduction effect in the high frequency band. Meanwhile, parametric studies of step 3D helically tapered rod are performed and the effect of different constituent materials is discussed to expand the utility. To validate these analyses, experimental tests are also conducted. The results demonstrate its remarkable vibration reduction in broadband frequency.