| Shock transmission units have become an important choice for improving the seismic capacity of bridges due to its strong applicability and clear principles of damping mechanics.However,silicone oil-based shock transmission units,cement-based shock transmission units and SP-based shock transmission units with different damping materials have poor durability during use,damping materials are unstable and easy to precipitate when heated,and low-temperature viscosity is too large and easy to "lock" and other issues.In order to solve the above problems,this article uses boric acid,hydroxy silicone oil and white carbon black as raw materials to synthesize a non-linear damping material-plasticized polyborosiloxane(PBDMS)by a non-hydrolysis method,,and then plasticized with oleic acid to obtain a plasticized PBDMS.Use the strain rate sensitive characteristics of the sample to meet the different working conditions of the speed locker,explore the influence of boric acid content,silica content,and silica surface characteristics on the mechanical properties of plasticized PBDMS and the dynamic performance changes of polyborosiloxane-based shock transmission units,the conclusions are as follows:(1)Plasticized PBDMS is a nonlinear damping material,and its viscoelasticity is affected by the content of boric acid,the content of white carbon and the surface characteristics of the sample.With the increase of boric acid content,the boronization density and molecular weight of the sample increase,but excessive boric acid will reduce its boronization degree and molecular weight.The higher the boronization density,the higher the viscosity and modulus of the sample,and the better the temperature resistance;the higher the molecular weight,the lower the critical shear rate of the sample.The increase of silica content and the change of the surface characteristics of the sample can increase the strength and viscosity of the sample.The sample with a boric acid content of 6%has the largest boronization degree and molecular weight,so the shear viscosity is the largest and the critical shear rate is the smallest;the sample with a boric acid content of 12%has the smallest viscous flow activation energy and the best temperature resistance;the boric acid content is 3%The sample has a certain crystallization ability.(2)Dow Corning damping material(SP)and plasticized PBDMS of different components were filled into the shock transmission unit cavity,and the shock transmission unit was tested for damper dynamics.The plasticized PBDMS-based shock transmission unit with a boric acid content of 4.5%can achieve two working states of the shock transmission unit,that is,the output damping force does not exceed 60 kN under a slow test,and the set load can be quickly reached within a 12 mm displacement under a fast test(600 kN).In the simulated dynamic test,the shock transmission unit has good repeatability,the locking displacement and load displacement do not increase with the increase of the number of cycles.In the attenuation test,the output damping force of the plasticized PBDMS base shock transmission unit was attenuated to 30%,and the SP baseshock transmission unit was attenuated to 50%;in the overload test,the locking displacement and holding load displacement of the plasticized PBDMS base shock transmission unit are 14 mm and 16 mm,respectively.The locking displacement and holding load displacement of the SP-based shock transmission unit are 16 mm and 37 mm,respectively.That is,compared with the SP-based shock transmission unit,the basic performance and ultimate performance of the plasticized PBDMS-based shock transmission unit are better.(3)The speed correlation test shows that the shock transmission units of filled SP and plasticized PBDMS are non-linear dampers,and the speed index is between 0.3-0.5.Therefore,the viscosity,storage modulus,temperature resistance and other characteristics of the sample can be adjusted by changing the content of boric acid,the content of white carbon and the surface characteristics of white carbon,so as to indirectly adjust the parameters of the shock transmission unit,such as:speed index,rated Load,lock displacement,hold load displacement and attenuation of damping force,etc. |
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