Impact Load Attenuation And Key Parameters Design Of Local Resonance Metamaterials

The vehicle collisions and high-intensity blast waves are the most important factors that causing personal injury and property damage in collision and explosion problems,and these problems are the focus of current works of academia and industry.Scholars have proposed a variety of methods to protect against vehicle collision and blast wave.Among them,the most widely used is the energy absorption theory based on material damage and the reaction momentum theory based on impact confrontation.Although previous studies have achieved some achievements,there are still some defects.For example,the energy absorption of blast wave based on material deformation will cause huge damage of materials,and the realization of reaction momentum theory requires complex mechanical structure.The absorption of crash energy based on the crush of materials for the vehicle collision problem cannot achieve the active and efficient attenuation of impact force.Therefore,there is an urgent need to develop new materials that can effectively attenuate vehicle impact forces and blast waves.The local resonance metamaterials are the hotspots of current new materials.They are artificial design materials or structures which can exhibit extraordinary physical properties that do not conform to the laws of nature.These physical properties have broad application prospects in the fields of vibration isolation,waveguide,energy recovery,stealth,and imaging.Based on the negative effective mass property of the local resonance metamaterials,studies on the attenuation of vehicle impact load and balst wave as well as the dissipation of impact energy are carried out.Without complicated structure and huge material damage,the local resonance metamaterials can achieve better attenuation effect of blast wave compared with traditional materials,and the high mitigation effect of impact load in time domain and frequency domain is also realized.In addition,with the application of local resonance metamaterials,the peak acceleration of vehicle collision is significantly reduced and the rebound time is obviously increased,and a significant improvement of the vehicle crashworthiness is acquired.In this paper,the works on the design of microstructure,the matching of key parameters of microstructure,the studies on bionic optimization algorithms,the design of damping,the attenuation of blast wave with multi-scale metamaterials and the application of local resonance metamaterials on the vehicle collision are studied.The contents of our works are summarized as follows:1.Inspired by the growth posture of trees,the bionic models of linden and common trees are established,and the corresponding bionic global optimization algorithms named the multi-objective artificial tree（MOAT）algorithm and the artificial tree（AT）algorithm are proposed.The high efficiency and precision of AT and MOAT are vertified by the calculation of multiple sets of typical numerical examples and the application of various efficient global single-objective and multi-objective optimization algorithms.The numerical results show that AT and MOAT can be applied to do the optimization design of local resonance metamaterials.2.The mathematical models of the single-resonator local resonance metamaterial（SRM）and the dual-resonator local resonance metamaterial（DRM）are established,and the motions of resonators,the dispersion relations and the negative effective mass properties of these two metamaterials are studied.The generation mechanism of the band gap and negative effective mass property of SRM is expounded,and the influence of the outer spring stiffiness k₁ on the attenuation efficiency of metamaterials is discussed carefully.Regarding DRM,its dispersion relation and negative effective mass property are studied.A one-dimensional blast wave model was established,and the attenuation effects of spectrum and impact load with SRM and DRM are analyzed,and the influences of key parameters such as the number of unit cells and the external spring stiffness k₁ on the performances of the metamaterials are also studied.3.The mathematical model of the multi-resonator local resonance metamaterial（MRM）is proposed,and its governing equation is also derived.Theoretical analysis shows that MRM has more complex resonator motions,more band gaps,and wider negative effective mass frequency regions compared with SRM and DRM,which indicates that MRM can attenuate the wide spectrum problem more effectively.The one-dimensional blast wave model and the three-dimensional collision model are established.The simulation results show that MRM can achieve similar performances with SRM and DRM under the premise of less unit cell number and smaller metamaterial mass.In addition,MOAT is applied to optimize the key parameters of MRM to further improve its attenuation effect and reduce its weight.4.Combined with damping characteristics and MRM model,the mathematical models of three types of dissipative multi-resonator metamaterials which contain Kelvin-Voigt-type（KVT）,Maxwell-type（MT）and Zener-type（ZT）resonators,respectively,are proposed.The negative effective mass properties,metadamping phenomena and resonator motion characteristics of these three dissipative metamaterial models are theoretically analyzed.The influences of non-dimensional damping parameters on each dissipative metamaterial model are obtained,which provides the basis for the design of dissipative metamaterials.A one-dimensional balst wave model and a three-dimensional sandwich structure collision model are established.The influences of different damping models and damping parameters on the attenuation effect of impact load and the dissipation effect of energy are studied for these three kinds of dissipative metamaterials,respectively.In addition,regarding the one-dimensional blast wave model,the damping parameters of the KVT type metamaterial are designed based on the AT algorithm,and the wide spectrum band gap is realized.Finally,the conclusions about the attenuation and dissipation performances of these three kinds of dissipative metamaterials are achieved.5.A three-dimensional microscale metamaterial model is established to control and attenuate the mid-high frequency blast wave.The simulation results demonstrate the attenuation effect of microscale metamaterials.Through the design of materials and geometric parameters in microscale metamaterials,the attenuation effect of metamaterials can be significantly improved.The equivalent model of the micro-scale metamaterials is established by applying one-dimensional nonlinear spring-mass system,and AT is used to reverse the spring stiffness parameters to obtain a consistent impact result.Based on the spring-mass system,a three-dimensional macro-scale flat metamaterial model is established to achieve the effective attenuation of mid-high frequency blast wave at macroscopic scale,and the structure behind the metamaterial model can also be effectivly protected.In addition,it is verified that the local resonance metamaterials have better attenuation effect and greater potential of structural lightweight compared with the traditional materials.6.For the first time,MRM was applied to vehicle crash conditions.The axial crushing model of the front longitudinal beam is established to study how the attenuation effect of impact load and the dissipation of collision energy are achieved by the local resonance metamaterial.The effects of the resonator and damping characteristics on the collision response of the front longitudinal beam structure are studied by applying the multi-resonator core and the KVT multi-resonator core,respectively.In addition,the frontal collision model of a pure electric vehicle is established,and the KVT type metamaterial is applied to reduce the peak acceleration of the vehicle body and increase the rebound time.Finally,the MOAT algorithm is applied to optimize the key parameters of KVT-type metamaterials to further improve the collision response of the front longitudinal beam model and the vehicle frontal collision model and reduce the mass of metamaterials.