Theoretical And Experimental Coupling Analysis Of Fluid-solid For Magneto-rheological Fluid Braking System

Magneto-rheological fluid(MRF)is one type of smart material with continuous,reversible,rapid and easy to control rheological properties,in the fields of aerospace,hydraulic transmission,mechanical systems,biomedical and daily life.There have many applications such as dampers,polishing,control valves,composite components,clutches,brakes,etc.Although many examples of applications involving MRF brake can be cited,this does not mean that the MRF braking system has matured.On the contrary,the MRF braking system has not general solution framework and theoretical framework,there are only a few commercial MRF brake products in foreign countries,and its key technologies are in a state of secrecy.There are many challenges in theory and technology.From the practical point of view of large-scale engineering,the MRF braking system is still in the primary exploration stage.Due to the limitation of application space,magnetic circuit effectiveness,braking efficiency and the inherent properties of MRF,it is impossible that MRF braking system will perform a better road test or inertia test simulation.Academics still have a long way to go in the exploration of basic theory and core technology.Especially in the braking process,the heat dissipation and the fluid-solid coupling evolution are the two main problems faced by the MRF braking system at present.Especially in the complex working conditions,the stable and effective braking is still an urgent need to solve,which is one of the research hotspots.The main work of this paper is as follows: firstly,this paper proposes a new type of multi-grooves MRF braking system.Secondly,in view of the fluid-solid strong coupling problem of the MRF braking system,the concept of impact factor of fluid-solid coupling(?)is proposed in this paper.Thirdly,based on the industrial inertia test-rig of brake independently designed and developed by our school,it has been optimized and improved repeatedly,integrating PIV and DIC digital image processing technology and multiple combination control systems,improved and built a comprehensive MRF brake test-rig.Finally,the experimental study of the new multi-grooves MRF braking system prototype under a single emergency braking condition is preliminarily completed.Specifically,this paper has achieved the following stages of research results:1)From the microscopic point of view,the chain-forming mechanism of MRF is analyzed in detail.According to the dipole theory,I studied the force analysis of magnetic particles under external magnetic field,and obtained the dynamic equations of magnetic particles.The chain-forming mechanism of MRF was simulated and analyzed by using the velocity-verlet Integral algorithm.This work can provide a theoretical basis for furtherresearch on the design and braking performance of MRF braking system.2)In this paper,a new multi-grooves MRF braking system is designed and proposed,that is,in addition to retaining the side of the double coil,a magnetic exciting coil is added to its central position,and the end face of the brake disc sequentially increases the heat dissipation grooves in the radial direction.The brake disc should be divided into N as much as possible,and the corresponding heat groove should be added,gradually solve the specific large-scale application problems.In addition,the simulation and numerical analysis of magnetic induction intensity distribution and braking performance show that the new multi-grooves MRF brake designed in this paper can generate more braking torque,and at the same time,the magnetic circuit design is more reasonable,and it is helpful to broaden the adjustment range of magnetic exciting current.3)It is an important work to study the fluid-solid coupling of MRF braking system.Taking the double coil side-mounted MRF brake and the new multi-grooves MRF brake as examples,the method of fluid-solid coupling analysis is completed by using the modified Bingham viscoplastic model and Herschel-Bulkley model respectively,and is explained in detail.The mathematical expression of the impact factor of fluid-solid coupling(?)is obtained by numerical solution.The results show that the new multi-grooves MRF brake not only improves the heat dissipation performance,but also provides a reference for solving the complex multi-physics field coupling problem.4)The preliminary experimental test of the new multi-grooves MRF brake in the case of single emergency braking show that as the braking time increases,the braking torque decreases along with the phenomenon of fluctuations,reflecting that the fluid-solid coupling analysis is necessary and correct.In comparing with the experimental results,the simulation results has yield encourage results and,all relative errors are small(?5%),indicating that the simulations are in good agreement with the experimental results.Moreover,the experiment of braking time has a delay of about 0.22 s compared with the simulation results.In summary,this work can provide useful insights for the structure design,optimization and improvement of MRF products,and has certain practical value.