Research On Low Frequency And Broadband Vibration Attenuation Characteristics Of Two-stage Inertial Amplification Local Resonant Structure

Low frequency broadband vibration attenuation and elastic wave regulation are urgent technical problems in many engineering fields,and their related researches have broad application prospects.In recent years,in the field of traditional vibration control,a variety of improved tuned mass damper(TMD)have been developed to meet the requirements of engineering practice such as reducing the vibration attenuation band.Meanwhile,the phenomenon that elastic waves are forbidden to propagate within the subwavelength elastic wave bandgaps of local resonant metamaterials(LRMs)provides new ideas to the design of small-size elastic wave functional devices and low-frequency vibration reduction design of practical engineering constructs.To better realize the purpose of low frequency broadband vibration attenuation and elastic waves regulation,a variety of advanced low frequency technologies and ideas have been proposed in the field of traditional dynamic vibration absorption technology and emerging local resonant metamaterials.The inertial amplification mechanism,which obtains large inertia force by amplifying the motion of small mass objects,can remove the application limitation of excessive additional mass in low frequency vibration and wave control.Some previous studies have realized low frequency vibration and wave control by introducing inerter or triangular truss inertial amplification structure respectively.A few researches in the field of traditional vibration isolation and vibration absorption have tried to combine the two inertial amplification elements,and initially achieved the further improvement of low frequency vibration control performance.However,there are still some problems to be solved before this conceptual structure can be put into practice.How to effectively combine the advanced technologies in the field of traditional vibration control and emerging local resonant metamaterials to give novel local resonant structures that can be used as both dynamic vibration absorption unit of TMD and resonant unit of LRM is also worth further exploration.In this study,a novel local resonant structure containing the two-stage inertial amplification structure and grounded stiffness is proposed based on several advanced low frequency broadband realization technologies,and the effective integration and fusion of multiple components are realized.Firstly,the novel structure is used in the improvement research of TMD,and the vibration attenuation performance is improved in many aspects compared with the existing model.Furthermore,the novel structure is introduced into the design of discrete LRM and LRM beam.The bandgap characteristics of low frequency broadband elastic waves induced by such structure,and the bandgap formation mechanism and regulation law are investigated.The main progress of this thesis is as follows:(1)A novel improved TMD containing three elements of grounded stiffness,triangular truss inertial amplification structure and inerter are proposed.In view of the two different cases of positive stiffness and negative stiffness grounded,the undamped system is comprehensively analyzed and investigated from the aspects of various performance evaluation indexes of the main system and the vibration absorption system.The regulation law of structural parameters on the vibration attenuation performance of the system is discussed,and the vibration attenuation mechanism of each coupling element is revealed.The performance advantages of the improved TMD in enhancing the low/ultra-low frequency attenuation performance,widening the dominant attenuation frequency band,and reducing the displacement response of the absorber are pointed out.A two-stage inertial amplification structure prototype based on the screw rotating type ball screw inerter and the hinged four bar linkage is designed and manufactured,and the experimental study on the vibration attenuation performance of the improved TMD is carried out,which firstly verified the feasibility of low frequency vibration control with the two-stage inertial amplification element.(2)In view of the working conditions under multiple excitations and considering multiple types of vibration attenuation requirements in different application scenarios,the multiple optimization criteria of the classical TMD are extended to the optimization research of the damped TMD with grounded stiffness and two-stage inertial amplification structure,and a novel optimization design criteria for low frequency vibration attenuation of TMD is further proposed.Based on different performance evaluation indexes,the corresponding optimization analysis is carried out,and the simulation verification is carried out for the theoretical analysis results of the system under common optimization criteria.The performance advantages of the novel improved TMD under various working conditions and evaluation indexes are explained,which enriches the performance evaluation criteria of the TMD.(3)A discrete LRM that takes the novel dynamic vibration absorption unit as the resonator is proposed.Based on the mass-spring lattice model,the longitudinal wave bandgap characteristics are studied,the meaning of bandgap edges and the bandgap formation mechanisms are clarified by the effective parameter singularity.The bandgap characteristics of proposed systems are taken a comparative analysis with those of existing EMs.Then,the effects of structural parameters on the bandgap characteristics are discussed.The longitudinal vibration attenuation characteristics of finite lattice structures are calculated based on the equivalent models,and the vibration transmission characteristics of the finite structure prototype are studied experimentally,the low frequency broadband elastic bandgap behavior is verified.(4)A novel LRM beam that takes the novel dynamic vibration absorption unit with adjustable large inertia as the resonator is proposed.The complex band structure is calculated by using the extended plane wave expansion method,and it is found that bandgaps of the novel LRM beam are lower and wider than that of the existing inertant LRM beam.The formation mechanisms of such bandgaps are revealed,and the effects of structural parameters on bandgap characteristics are discussed.Numerical analysis and experimental study of vibration transmission characteristics of finite beam structure are carried out.Furthermore,three kinds of bandgap widening methods based on the structural characteristics of the local resonant element are proposed by setting graded structural parameters.The regularities of bandgap variation with different parameter spacings are given,and the effectiveness of the graded method to widen the vibration attenuation band of the finite LRM beam under various boundary conditions is verified.Through the research on the TMD and the LRM based on the two-stage inertial amplification structure,the low frequency broadband vibration attenuation performance and the performance evaluation research system of the TMD are improved,the existing low frequency broadband resonant structures of the LRM are enriched.This research could provide certain guidance for the control and utilization of low and ultra-low frequency vibration in engineering applications and the regulation of low and ultra-low frequency broadband elastic waves in scientific research related functional devices,and provide technical support for the low and ultra-low frequency broadband vibration attenuation design of resonant structures.