Research On Vibration Isolation Characteristics Based On Bandgaps For One-dimensional Periodically Layered Phononic Crystals

Vibration isolation is one of the important techniques for engineering vibration control,which has always been a research focus in the field of vibration and noise control.Traditional vibration isolators or vibration isolation materials are widely used in engineering single-stage vibration isolation systems,however,such systems usually have poor performance at mid-,high-frequency range due to the standing-wave effect caused by the distributed mass of the isolators.Therefore,to increase the performance of vibration isolators at mid-,high-frequency has become a problem that needs to be solved in engineering.In recent years,the concept of phononic crystals(PC)has become a relatively new research focus in physics which could potentially provide new ideas for solving key problems in vibration and noise control.PCs are artificially designed composite materials or structures that are comprised of two or more types of materials that arranged in periodic pattern in space.When vibration in the form of elastic wave propagates in PCs,the waves cannot propagate and will attenuate rapidly at certain frequency range.Such frequency ranges are often referred as bandgaps.By introducing PC with bandgaps into the design of vibration isolators,we could potentially tackle the problem for mid-,high-frequency performance.This paper designs one-dimensional PCs and by studying its bandgap characteristics,mechanisms and affecting parameters,a PC vibration isolator is designed and manufactured to increase the performance with the bandgaps which are aimed at certain frequency range of need.The main research contents of this paper are as follows:1.First of all,based on the transfer matrix method,the dispersion structure(bandgap characteristics)of the one-dimensional PC is analyzed and the vibration transmission characteristics of the finite PC is studied.Based on the single-stage vibration isolation model,a transfer matrix method considering the mass load is developed to calculate the vibration isolator performance.All the analytical models are verified by the finite element method,which is served as fundamental basis for further studies.2.Based on the analytical models,the bandgap characteristics and the vibration transmission characteristics are analyzed with the focus on the effect of material and geometric properties.These analysis are also verified with finite element method.We designed PC with periodic layers,PC with defect structures and PC with distributed discretized elements to study their vibration isolation performance and designed techniques by finding the optimal geometric properties.Furthermore,based on a specific engineering vibration isolation need,we designed a vibration isolation system with PC isolators and the finite element results show the increase in performance at designed frequency range.3.Based on theoretically and numerical studies,we further designed and manufactured PC isolators and PC vibration isolation material to experimentally test their vibration isolation performance as well as verify the analytical models.To sum up,this paper aims at increasing the vibration isolation performance at mid-,high-frequencies and uses the theories of phononic crystals to design and manufacture a PC vibration isolators.Both analytical and experimental studies have shown the effectiveness of such design,which provides new techniques for increasing the performance of traditional vibration isolation systems.