Design Of High Stiffness And High Damping Structures For Low Frequency Vibration Control Based On The Acoustic Metamaterials

With the development of aerospace,ship,high-speed railway to lightweight,high-speed,heavy-duty,composite materials,ultra-light cellular materials,honeycomb material have been extensively applied in the engineering equipments,due to excellent properties such as lightweight,high specific strength,high specific rigidity.Nevetheless,light and high stiffness characteristic of these structures exhibit limited adaptability which results in serious noise and vibration problems.Therefore,It's important to reduce noise and vibration problems on these light,high stiff structures.On the one hand,high damping is required to be able to effectively mitigate shock and vibrations dynamically transmitted to the structure by the environment caused;on the other hand,high stiffness is also required in a wide range of structures components to provide sufficient robustness under demanding loading conditions.However,stiffness and damping are conflicting requirements in many material systems.Therefore,it requires new mechanisms and new methods to simultaneously achieve both high stiffness and high damping.In this paper,to obtain both high stiffness and high damping characteristics simultaneously,a typical engineering stiff frame embedded within the acoustic damping metamaterials is designed.The paper mainly focuses on two acoustic metamaterials(chiral metamaterials and inertia amplification metamaterials)to study elastic wave band gap characteristics at the low frequency.Following the concepts of local resonance mechanism,combined with the effects of viscoelastic damping,the composite frame is designed to achieve the combination of high stiffness,high damping characteristics.The proposed composite frame can make the structure effectively sustain shock and vibration at low frequency.The main research contents and conclusions are as follows:1.A method for calculating the band gap characteristics property and directional wave propagation property is developed.The band gap characteristics and directional propagation characteristics of two typical chiral metamaterials are studied.According to the chiral cell deformed shapes at start-stop frequency of bandgap,the band gap formation mechanism is revealed.The variation of the bandgap characteristic with the topology parameter is analyzed.2.The band gap characteristics of the inertial amplified metamaterial is studied.Analyses of the deformed shapes at the frequency of lower edge of band gap and energy distribution at the anti-resonance point in the finite periodic structures reveal that inertial amplification induced gaps are qualitatively different from the local resonance gaps.It is proved that the inertial amplification have negative stiffness characteristic which results in high loss factor and high damping characteristics.At last the key parameters on the band gaps are analyzed.3.Chiral metamaterials and inertial amplification metamaterials are designed to absorb shock and vibration of the frame.Experimental measurements show that the proposed chiral metamaterials and inertial amplification metamaterials can significantly attenuate the shock and vibration.In particular,the low frequency broadband vibration caused by steady loading incentives can be controlled,and the shock caused by transient loading excitation can also be inhibited in a very short time.For certain sensitive frequency(first-order natural frequency),by changing structure,excellent vibration attenuation performance at the first-order natural frequency is achieved.In summary,the paper focus on engineering structural with high stiffness,high damping performance to realize low-frequency vibration control.To achieve the goal,the paper studied two new typical metamaterials' bandgap formation theory and bandgap characteristics.This work of this paper will make a foundtions to the future study about the realization of high stiffnesss and high damping and provide a technical guidelines for engineering application.