Papers by Keyword: Electro-Magneto-Rheological Effect

Abstract: Based on the electro-magneto-rheological (EMR) effect, the Fe3O4-based EMR fluid dispersed with micron-sized finishing abrasives is used as a polishing fluid to form a dynamical tiny-grinding wheel under an electro-magnetically coupled field. Using this EMR-effect-based tiny-grinding wheel, experiments were conducted to investigate the effect of the grain size, content and material of abrasive on material removal effect of normal glass. Results indicate that the abrasive can change the chain-like structure of the EMR-effect-based tiny-grinding wheel and influence the material removal ability of the tiny-grinding wheel remarkably. The material removal amount increases with the increase of the content of diamond abrasive in the EMR fluid, and grows slowly when the proportion of diamond abrasive exceeds to 6%. While the grain size of abrasive increases, the material removal amount increases at the beginning and decreases afterwards. The effect of abrasive on material removal depends on the hardness of abrasive, the greater the abrasive hardness, the higher the material removal efficiency. The machined area has a close relationship with both the density and grain size of abrasive.

Abstract: Aiming at micro machining of 3D microstructure of brittle materials with a novel tiny-grinding wheel based on the electro-magneto-rheological (EMR) effect, five conical tools with different cone angles are designed to reveal the effect of the cone angle on the machining characteristics. The distribution of the magnetic and electric fields in the polishing area is simulated using the finite element analysis software, and the machining experiments of micro groove were conducted to confirm the simulation results. Experimental results indicate that the material removal rate increases first and decreases afterwards with the increase of the cone angle, and the section width of micro groove increases but the section depth of micro groove shows a fluctuation phenomenon within a certain range. The intensities of the electric and magnetic fields on the tip of the conical tool with the 45° cone angle are at a larger level in the five tools, which is helpful to form a stable tiny-grinding wheel based on the EMR effect and obtain a better machining effect, so the tool with the 45° cone angle is an effective and ideal machining tool for the machining of 3D microstructure.

Abstract: Electro-magneto-rheological (EMR) fluids, which exhibit Newtonian behavior in the absence of a magnetic field, are abruptly transformed within milliseconds into a Bingham plastic under an applied magnetic field, called the EMR effect. Based on this effect, the particle-dispersed EMR fluid is used as a special instantaneous bond to cohere abrasive particles and magnetic particles together so as to form a dynamical, flexible tiny-grinding wheel to machine micro-groove on the surface of optical glass. Experiments were conducted to reveal the effects of process parameters, such as the feed rate of the horizontal worktable, feeding of the Z axis, machining time and machining gap, on material removal rate of glass. The results indicate that the feed rate of the worktable at horizontal direction has less effect on material removal rate, which shows a fluctuation phenomenon within a certain range. The feed rate of the Z axis directly influences the machining gap and leads to a remarkable change on material removal rate. Larger material removal rate can be obtained when the feeding frequency of Z direction is one time per processing. With the increase of rotation speed of the tool, material removal rate increases firstly and decreases afterwards, and it gets the maximum value with the rotation speed of 4800 rev/min. The machining time is directly proportional to material removal amount, but inversely proportional to material removal rate. Furthermore, material removal rate decreases with the increase of the machining gap between the tool and the workpiece. On the basis of above, the machining mode with the tiny-grinding wheel based on the EMR effect is presented.

Abstract: Using the tiny-grinding wheel based on the synergistic effect of the electro-magneto- rheological (EMR) fluid, a novel method is presented to machine the three-dimensional (3D) microstructure of hard-brittle materials. Machining experiments of micro-groove were conducted to reveal the machining performances of the tiny-grinding wheel. Experimental results confirm the effectiveness and feasibility of the micro machining technique with the EMR effect-based tiny-grinding wheel. The shape of machined micro groove is found to be an inverted trapezoid, and the material removal mode of normal glass with the micro machining method is the plastic-removal mode. With the increase of the rotation speed of the tool, the material removal rate, width and depth of micro grooves increased first and decreased afterwards. The maximum removal rate, width and depth of micro groove occur at different speeds of the tool.