Removal Mechanism Analysis And Performance Optimization On Magnetorheological Finishing

Magnetorheological Finishing(MRF)is a kind precision surface finishing technology based on the theories of electromagnetism,fluid mechanics,analytical chemistry and so on,which can be applied to various optical surface processing.It is a finishing method between contact finishing and non-contact finishing,which has the advantages of high finishing accuracy,no tool wear and clogging phenomenon,high removal rate and no sub-surface damage,and it can achieve the near-zero sub-surface damage and nano-precision finishing compared with the traditional finishing method,it’s normally used as the last process for optical parts processing.In this thesis,the influencing factors of MRF are analyzed based on the actual engineering requirements.Mainly includes the following aspects:Firstly,the magnetorheological effect is analyzed.According to the basic theory of fluid mechanics,electromagnetism and finite element method,the state of magnetorheological fluids in the event of magnetorheological effect is analyzed.A finite element analysis of the magnetorheological effect is carried out by using the magnetic field module and the Flow field module of finite element software.The results show that during the process of magnetization of carbonyl iron powder whereby the chain formation occurs,the greater the magnetic flux density of carbonyl iron powder closer to the excitation source,the harder it is to break,and it’s easier to break where the value of magnetic flux density is smaller,thereafter a particle chain rebuild phenomenon occurs.It flows as laminar for magnetorheological fluids outside of the finishing area,when the magnetorheological effect occurs,the flow rate of the magnetorheological fluids increase until it leaves the finishing area,and it flows again as laminar when the magnetorheological effect ends.The finishing of MRF was analyzed in theoretical simulation,and the force condition of abrasive particles in the process of magnetorheological finishing is analyzed according to MRF removal theory,and the model of material removal is established.The novel ideas of the boundary wear influence factors and the surface removal of brittle materials are put forward.Finite element software package was used to simulate and analyze the immersion angle,relative volume,horizontal distance and vertical distance of the angular abrasive,the force condition of abrasive particles and the amount of material removal are obtained,the immersion depth,diameter size and velocity of brittle materials were analyzed for abrasive particles,and the value of stress removal of materials in each direction is obtained.The results show that:The force of abrasive particles does not change,but the volume of material removal in each direction decreases gradually as the immersion angle increases;the force of abrasive paticles and the volume of material removal in each direction are increased gradually as the relative volume increases gradually;the force of abrasive does not change but the volume of material removal in each direction are gradually increased as the horizontal distance increases gradually;the force of abrasive particles and the volume of material removal in each direction are increased gradually as the immersion depth increases gradually.The stress removal of brittle material gradually increases as the diameter of abrasive increases gradually;the removal stress of brittle material decreases gradually as the velocity of abrasive increases gradually;the removal stress of brittle material decreases gradually as the immersion depth increases gradually.The influence factors were tested and analyzed in a built experimental test-bed.The workpiece speed,the speed of finishing wheel,the different volume ratio of carbonyl iron powder were tested for K9 glasses;the experiment for shear thickening magnetorheological finishing was also carried out,results were observed and measured with experiment apparatus.The result shows that:the value of material removal increases gradually as the workpiece speed,the speed of finishing wheel,the different volume ratio of carbonyl iron powder increase;the shear thickening magnetorheological finishing combines magnetorheological effect and shear thickening effect,and has a certain feasibility.