Fluid Viscosity Monitoring Of Viscous Damper Based On Piezoelectric Materials

The earthquake disaster in our country is serious,the frequency of seismic activity is high,the intensity is high,the focal point is shallow,and the distribution is wide.In recent years,new vibration suppression methods based on viscous dampers have attracted more and more attention.Due to the advantages of good energy consumption,strong applicability,and simple structure,viscous damper has been widely applied in civil engineering constructions to suppress structural vibration caused by earthquakes.However,as time goes by,the fluid viscosity of a viscous damper may change during service,and the fluid viscosity directly affects the size of the damping force,thereby affecting the energy dissipation and vibration damping ability of the damper.Moreover,after the viscous damper is installed on the structure,it is difficult to remove it for regular fluid viscosity testing.Therefore,in order to ensure the vibration suppression ability of the viscous damper,this paper proposes a real-time monitoring method of the fluid viscosity in the viscous damper based on the piezoceramic transducers.The major contents and conclusions are as follows:（1）Based on the one-dimensional wave theory,the propagation equation of pressure wave in viscous fluid is deduced and the viscosity variation index is defined.Numerical analysis is carried out according to the deduced propagation equation.The results show that:the greater the fluid viscosity,the greater the energy dissipation when the pressure wave propagates in the fluid,and the smaller the received signal amplitude and viscosity variation index;The higher the frequency of the pressure wave,the faster the energy decays when the pressure wave propagates in the viscous fluid;The greater the propagation distance of the pressure wave in the viscous fluid,the greater the energy dissipation during the propagation process,and the smaller the signal amplitude received by the piezoceramic transducers.（2）Based on the derived wave equation,a viscous fluid viscosity monitoring method based on wave propagation analysis method is proposed.Based on the piezoceramic transducers,the viscous fluid viscosity monitoring experiment was carried out.The experimental results show that as the fluid viscosity increases,the amplitude of the received signal gradually decreases,it is consistent with theoretical study.The viscous fluid viscosity was successfully quantitatively monitored using the defined viscosity variation index,the presented method’feasibility is verified.In addition,compare the experiment with theory,the result shows:the amplitude error between the simulated time-domain diagram and the experimental time-domain diagram under 1200 mm~2/s working conditions is 4.30%;the simulation results of the time-domain diagram are in good consistent with the experiment,the correctness of the presented theory is verified;the maximum error between the theoretical value of the viscosity variation index and the experimental average value is 4.84%,which proves the high accuracy of the presented method;the theoretical curve is in good consistent with the experimental fitting curve,and as the viscosity of the viscous fluids increase,it shows an exponential decrease in a consistent trend.In addition,the consistency of the three repeated experiments verifies the reproducibility of the presented method.（3）In order to reduce the number of transducers used,a viscous fluid viscosity monitoring method based on electromechanical impedance method is proposed and theoretically analyzed.Based on a single piezoceramic transducer,a viscous fluid viscosity monitoring experiment was carried out.The experimental results show that as the fluid viscosity increases,the peak frequency of the impedance curve gradually shifts to the left,and the resonance frequency gradually decreases,while the resistance value of the real part of the impedance curve gradually increases with the augment of fluid viscosity,the correctness of the proposed theory is verified.In addition,the defined viscosity monitoring index can well reflect the viscosity variation of viscous fluid,the feasibility of this method is verified.