Research On STF Constitutive Model And Mechanical Performance Of Nano-metallic Particle Enhanced STF

Shear thickening fluid(STF),a new type of nano-molecular intelligence material is non-newtonian fluid that formed in certain dispersants uniformly distributed by micro nano-particles.When the shear rate rises,the dispersions boost its viscosity dramatically and convert from liquid to solid instantly.This property could be used to consume energy and impact.At present,the researches of STF are mostly concerned about preparation techniques,rheological and mechanical performance influence factors,those on constitutive law of shear rate-viscosity could be barely found.Although STF had made progress in body armor,the shear shinning behavior is not expected in engineering.In this paper,two type of STF are studied,which are of great value in adaptive structure vibration control and vibration reduction.This paper utilizes nano-silica(SiO2)as dispersion phase particles and polyethylene glycol(PEG)as dispersion medium.To test and analysis shear thickening performance,reversibility,stability,thixotropy at various temperature and the dynamic-state STF modulus influence of angular frequency and critical strain,STF dispersions with different concentration of SiO2 is prepared by means of mechanical agitation and thermostatic waterbath ultrasonic oscillation.A continuous and differentiable constitutive function model based on phenomenological theory has been proposed to describe the nonlinear response of viscosity versus shear rate.Unlike existing piecewise model,the new constitutive model with 3 parameters could be widely applied to engineering numerical calculation.The accurate parameter values were concretized by introducing nonlinear least squares.Test data showed that the constitutive function model could predict STF viscosity of different concentration at various temperatures.Zr02/STF has been prepared to characterize mechanical performance of modified STF.Tests showed remarkable shear thickening behavior of ZrO2(12%)/STF and obvious shear thinning behavior at low shear rate.ZrO2(20%)/STF has lowest tempreture sensibility and prominent electromagnetic immunity.The wide range of viscosity and excellent physical and chemical properties such as low thermo-sensitivity and electromagnetic immunity enable ZrO2/STF to survive the complicated environment in adaptive structure.Likely,to study the rheological and electrochemical performance of modified STF,nano-CeO2 STF were prepared.Tests showed that CeO2(12%)/STF has prominent electromagnetic immunity.Under low shear rate,CeO2(12%)/STF could maintain certain viscosity which effectively avoid idle load in tradition STF damper.When the shear rate raise up,CeO2/STF could constantly provide reliable damping force.