Study On The Key Mechanism And Characterization Of Magnetorheological Damper Based On Porous Foam Metal

Vibration iseverywhere.It is important to study how to reduce the mechanicalvibration.The contradiont damper usually reduces vibration by storing energytheirselves or consumed energy by vibration. Itlacks of self-adjustment. For thesereasons, it is urgent to develop a kind of smart damper with a good controllability andnonlinear characteristics.Magnetorheological fluid (MR) damper is a kind of smart instrument, and itsdamping force can be controlled by the extern currents, and the flow characteristics canbe changed by the external magnetic field. The current researches of MR damper focuson reducing large vibration damping force, while little studies on vibration needing tobe used to reduce the smallerone. Moreover, specialized seals need to prevent leakage ofthe MR fluid due to be full with MR fluid in cylinder of the traditional ones. Meanwhile,the service life of traditional MR damper will be reduced by wearing since the hardmagnetic particles in MR fluid would inevitably friction with the seal component.In support by the Natural Science Foundation of China and the Shanghai AllianceProgram, this dissertation carried on a serials of researches base on the key mechanismof employee the porous metal foam into MR damper, a porotype of MR damper basedon porous metal foam is developed, and a set of performance test system is designed.Atlast, the performance of the porous metal foam MR damper is tested by using thedeveloped test system. The main work of this dissertation is summarized as follows:①MR fluid flows in porous metal foamThe control equation that MR fluid flows in the porous metal foam is establishedbased on theory of computational fluid dynamics (CFD) and Maxwell. By using thefinite volume method (FVM) of FLUNT, the flow of MR fluid in porous metal foam issimulated, and the distribution of pressure and velocity are obtained.②The normal force of MR fluid were studied both theoretical and experimentalFirstly, the compute model of normal force is established by utilization of magneticenergy method.Then, the static normal force and steady shear normal force of MR fluidwere experimental studied. By using a parallel plate rheometer and fixed plate-plate gap,the relationships between static normal force and testing time, magnetic field strengthand temperature are experimental studied. In addition, the normal force under steadyshearing mode is also studied. The effects of testing time, magnetic field strength, shear rate and temperature on the steady normal force were obtained. And the gap of staticand dynamic normal force influenced by magnetic field strength was also received. Thecomparison between average steady normal force, static normal force and shearingstress were carried out. Moreover, Based on the experimental study on normal force ofMR fluid, the mechanism of normal force under application of magnetic field isexplained from the perspective of the magnetic particles evolution of the microstructure.③The normal force of MR fluid stored in porous metal foam under static and shearoscillation mode was experimental studied.By an external magnetic field, the effects of testing time, magnetic field strength,temperature, shear strain and oscillation frequency on the static and oscillation shearingmode were acquired.④MR damper prototype based on porous metal foam was developedA kind of porous metal foam MR damper was proposed and designed. It can beapplied to the small damping force vibration.It is simple, low cost, and can preventleakage of MR fluid. The structure principle and working principle of the proposed MRdamper were elaborated in detail. After calculation the reluctance, the magnetic fieldwas obtained by using finite element simulation. According to the simulation results, theinfluenced of the extern current, metal foam and different metal foam materials onmagnetic field strength were detailed analyzed. By calculating the impact of differentmetal foam material on shear gap, the magnetic properties of metal foam MR damperwas studied.⑤The performance of the metal foam MR damper was studied A set ofperformance test system for metal foam MR damper was proposed. Based on theperformance test system, the relationship between the external current, shearing velocity,porous metal foam material and the damping force and response time wereexperimentally studied. In addition, the effect of residual magnetism on the mechanicalproperties was also acquired. A calculation model of dynamic response time based onNewton’s second law was also established. At last, the impact of the dynamic responsetime error was analyzed after giving a computation example of dynamic response time.⑥The damping force characteristics of porous metal foam MR damper werestudied, and a BP neural network model was establishedBased on above simulation and experimental results, a set of energy loss equationwhich MR fluid flows in porous metal foam is derived, the head energy loss and localenergy loss along the way are obtained, respectively. And, according to the method to equivalent the MR fluids inside porous metal foam to the ring volume, the dampingforce model of the proposed MR damper was obtained. Finally, a BP neural networkmodel was established. The results show that the damping force of the predicated byneural network was in good with experimental results.