Research On Damping And Detuning Of Generalized Phononic Crystals

As a composite structure periodically arranged on materials and structural parameters,generalized phononic crystals(GPCs)have been deeply studied by researchers for a large number of typical structures due to their special band gap mechanism and some research results have been obtained.However,for a complete theoretical framework,there are still some aspects of generalized phononic crystals that deserve further study.In this paper,two important structures(circular plates and cylindrical shells)are taken as research objects.Through theoretical analysis,numerical simulation and experimental verification,the effects of key problems such as damping,detuning and dynamic stress concentration on propagation of various elastic waves in GPCs of the column system and the band gap characteristics are analyzed in depth.The main contents include:1.Introduce various construction methods of damping model,and take into account the characteristics of viscoelastic materials and research objects,and we use viscous damping model as the basis of damping theory and combine it with elastic wave equations to carry out theoretical analysis of propagation of various elastic waves(bending waves,torsional waves,in-plane longitudinal waves)in GPCs of the column system;2.By considering the damping characteristics of general materials,and introducing important damping materials such as viscous-elastic materials and damping alloys into GPCs,a damping type GPCs circular plate is constructed to investigate the law of change of the propagation behavior of various elastic waves in such structures and the band gap characteristics.Further focusing on viscous-elastic materials,the intrinsic damping effect and the effect of frequency nonlinearity of elastic modulus on the propagation behavior of elastic waves are mainly investigated;3.By introducing the geometric detuning and material detuning into GPCs to construct the detuned GPCs circular plate,we analyze the influence of the amount of detuning and the different distribution of the detuning parameters on the propagation characteristics of various elastic waves in such structures,focusing on the transformation between the passband and the forbidden band under different detuned states;4.Based on the sound insulation characteristics of the acoustic-solid coupling field,we introduce the factors such as damping and detuning into GPCs cylindrical shell,and investigate the acoustic band gap law under the excitation of the center line sound source and the bias line sound sourceThe research shows that the damping characteristics of the viscoelastic material mainly cause the cutoff frequency of the band gap of GPCs of the column system to move to the high frequency band,and for the three types of elastic waves,the amplitudes are 330Hz,1300Hz,2300Hz,respectively,and the band gap range is widened.At the same time,the frequency nonlinearity of the elastic modulus also confirms this change,which is mainly reflected from the change of the imaginary part;The detuning of GPCs depends on the vibration model,and its detuning problems have different effects on the band gap.In general,the effects of detuning in soft materials are far more pronounced than those in hard materials,and they are concentrated in the variation of attenuation and the increase in peaks in the band gap.In addition,the dynamic stress concentration behavior inside the structure field is also analyzed.It's found that in order to make the structure in a healthy state,GPCs should be placed in a suitable excitation field source to prevent structural damage.