Study On Vibration Property Of Honeycomb Stand-off Layer Damping Structure And Particle Damping Compisite Structure

The stand-off layer damping structure and the particle damping structure are widely used in vibration control in mechanical engineering,aerospace and et al.,however,it is still at an exploratory stage in civil engineering.In this paper,the damping properties of two damping structures,the honeycomb stand-off free layer damping structure and the particle-honeycomb stand-off free layer damping structure,were studied.The dynamic mechanical properties of above structures were studied with DASP vibration testing system,the experimental data was analyzed and fitted.By the means of the power input method(PIM)and the single-point hammering method,the composite loss factor of the damping structure with the slat beam as the base material under the cantilever support boundary conditions was studied.At the same time,the effects of high-level direction of honeycomb mat,honeycomb hexagonal single-side length,honeycomb material thickness,and perfusion particles on the structural mode frequency and composite loss factor were analyzed.The conclusions are listed as follows:Firstly,the basic properties of viscoelastic damping materials which were used as the damping adhesives in this paper,were detected,including curing time,solid content,density,hardness,tensile and tear properties,and adhesion.The average gel time and dry time of Qtech T501 are 160s and 15min,respectively,and the time is short enough to meet the requirements of the structure production process.The solid content is97.68%,corresponding to the volatile matter content of 2.32%,meaning that the material is the high-solid-content environment-friendly material,and it could form the film with the specified thickness by one brushing process.The density is 0.954g/cm~3,which classifies it a light viscoelastic damping material.The hardness(Shore A)value,the tensile strength,tear strength and the elongation at break is 26,0.76MPa,4.30 KN/m and 685.40%respectively.The mechanical properties of the material were similar to those of the viscous material,showing better energy dissipation characteristics.The adhesion of Qtech T501 to the steel plate and damping rubber surface is 0.68MPa and0.98MPa,respectively,which can guarantee the stability of the structure.Secondly,the comparison between the free layer damping structure and the honeycomb stand-off free layer damping structure shows that,by inserting a mat layer with the thickness of 5mm between the damping layer and the base layer in the traditional free layer damping structure,the amplitude of the structure decreases by38.46%,the attenuation time shortens,the loss factor at each level increases by 38.20%,and the total vibration level decreases by 4.87dB.Thirdly,the study on the effect of the geometric features of the honeycomb mat on the composite damping structure were conducted.For the structure with single-direction vibration damping effect,the hexagonal longest diagonal line of the honeycomb mat should be parallel to the damping direction(A direction)to achieve a best vibration control.In the full experimental frequency range(0-800Hz),the damping performance of the composite structure becomes higher when the side-length of the honeycomb mat increases,whereas,the acceleration response increases and the damping performance turns worse when that of the honeycomb mat increases in the low frequency range(0-200Hz).Through the fitting calculation,it is found that the modal frequency would decrease with the increasing side length,and the single-edge thickness has less influence on the damping performance of the structure.Fourthly,particles-honeycomb stand-off free layer damping structure can be formed by perfusing particles in honeycombs.By this way,the maximum vibration acceleration of the composite damping structure reduces by 35.81%,the amplitude by58.93%compared to the honeycomb stand-off free layer damping structure after 0.1s of vibration attenuation.The findings show an improvement of the vibration damping effect.The modal frequency is less affected by perfused particles,which almost remains unchanged.Corresponding to the particles perfusion,loss factors in first-order to fourth-order increase by 5.99%,27.98%,116.99%,and 64.64%respectively,and the vibration acceleration reduces by 5.34dB.The results show that the loss factor of the particle-honeycomb composite structure greatly improves.Fifthly,the effect of particle size of the particle-honeycomb composite damping structure was studied.The time-domain waveforms of the structure with various particle size are basically the same,the amplitudes of vibration acceleration fluctuate from45m/s2 to 50 m/s2 and particles with various size stop vibration after 0.15 s.The influences on modal frequency of the particle size are focused on the frequency range above 200Hz and on vibration acceleration response are focused on the frequency modal of the third-order and the fourth-order.Accompanied with the increasing size,the acceleration response under unit force decreases.For example,the value above 200Hz reduces by 16%.To sum up,when designing a honeycomb stand-off free layer damping structure,on the one hand,the honeycomb side-length and direction can be adjusted to meet various frequency needs and the single-edge thickness can also be thickened to have higher strength;on the other hand,in order to obtain a better vibration damping performance,the particles can be perfused into the cavity of the honeycomb to form a particle-honeycomb stand-off damping structure if there is no limitation on the weight of the structure.