Effect Research Of Magnet Field On Finishing Performance Of Fluid Magnetic Abrasive

Fluid magnetic abrasive is a new finishing technology which uses magnetic field to finish the workpiece surface precisely,and can finish the workpiece surface of various complex surfaces.With the support of the National Natural Fund(51075294),Shanxi Natural Science Foundation(201601D011060)and the Key Laboratory of Precision and Special Processing Education(JMTZ201603),the research on finishing technology of fluid magnetic abrasives has also made rapid progress.Starting from the angle of improving the finishing efficiency of fluid magnetic abrasives,the following contents are studied in this paper:(1)The composition and performance requirements of fluid magnetic abrasives are introduced.The mechanism of the influence of magnetic field intensity on the rheological effect of fluid magnetic abrasives is analyzed from the rheological effect mechanism of fluid magnetic abrasives.Based on the detailed analysis of the abrasive state change in the process of finishing,the processing mechanism is analyzed from the micro point of view.The results show that the core process parameters,such as magnetic field generator,magnetic field intensity and magnetic induction line distribution,are one of the main factors affecting the quality and efficiency of finishing.(2)The advantages and disadvantages of electromagnetic field and permanent magnet field in the finishing process of fluid magnetic abrasives are compared and analyzed from the aspects of processing performance,suitable materials and performance parameters.Compared with electromagnetic field,permanent magnet field does not consume energy when transmitting magnetic flux in the gap of magnetic circuit,and has the advantages of light volume,easy installation and simple system structure.By analyzing and comparing the types of rare earth permanent magnets and their performance parameters,N45 NdFeB materials with relatively good comprehensive magnetic properties,such as maximum magnetic energy product,residual magnetic flux and coercivity,were selected as magnetic pole materials.(3)Based on the design theory of magnetic circuit,the magnetic conductance of each component and mechanism region of the magnetic device is calculated and the size of the magnetic pole is determined based on Kirchhoff’s law in the magnetic field.Rectangular grooves 、zigzag grooves and trapezoidal grooves are respectively designed on the surface of the magnetic pole.The four planes and slotted magnetic field devices of the counterpoint magnetic field 、the right-angle magnetic field 、the adjacent right-angle magnetic field and the symmetric right-angle magnetic field are respectively designed.(4)The magnetic field intensity and magnetic induction line distribution on the surface of poles with different slotting modes are simulated and analyzed.The slotting mode with rectangular slot on the surface of poles is determined according to the actual processing conditions.The magnetic induction intensity and magnetic induction line distribution of rectangular slots with aspect ratio of 1:1,1:2 and 1:3 are analyzed and compared through simulation analysis,and the slotting size on the surface of poles is calculated.A rectangular groove with a ratio of depth to width of 1:1 is selected.The magnetic field intensity and magnetic induction line density of the permanent magnet field with different distribution forms composed of planar and slotted poles are simulated and analyzed.It can be seen that the magnetic flux density and the magnetic field intensity distribution gradient in the processing region are different because the number of magnetic poles and the distribution form is different,and the magnetic pole line surface density can be significantly improved after the magnetic pole surface is grooved.(5)An experimental device for surface finishing of fluid magnetic abrasives was designed and built.The polishing experiment of the outer surface of the test workpiece was carried out under the specific technological parameters.The results show that the processing efficiency of the right angle magnetic field is relatively high,and the roughness of the workpiece surface decreases from 1.449 to 0.257 microns.It is shown that the number of magnetic poles,the distribution of magnetic field and the shape of magneticextreme surface can change the distribution of magnetic force lines and magnetic induction intensity in the processing area,thus affecting the force of abrasive particles in the magnetic field,resulting in different processing efficiency and effect under different magnetic field layout.