Study On Removal Mechanism Of Hard And Brittle Material By Magnetic Field Assisted Abrasive Water-Jet Eroding

Abrasive water-jet(AWJ)is a new type of cold machining technology.Compared with traditional grinding,AWJ has the advantages of high flexibility,low processing force and no thermal effect.Therefore,AWJ was widely used in the process of hard and brittle materials such as engineering ceramics and optical glass.However,there are still some problems in AWJ technology.For example,abrasive can’t be fully mixed with high-pressure water,which easily results in blockage at the nozzle outlet.In this paper,the auxiliary magnetic field was introduced into the AWJ machining process,and the magnetic field generator was improved to optimize the abrasive distribution and increase the abrasive speed.The erosion process of single and multi-particle magnetic abrasives was simulated and analyzed by finite element software,and the removal mechanism of hard and brittle materials was deeply analyzed.The prediction model based on the maximum erosion depth of ceramic materials was established,which provides theoretical basis for the popularization of AWJ technology and the development of potential applications.The main work contents are as follows.The magnetic field generator was optimized so as to improve the impacting kinetic energy and inhibit the divergence effect of AWJ.As a result,the abrasive water-jet with high focusing effect was obtained.The Comsol software was used to simulate the distribution of magnetic field intensity and the focusing effect of AWJ inside the focusing tube,the simulation results indicate that the optimum focusing effect of AWJ was obtained at the nozzle exit with the current of 2.2 A.The Ansys/Fluent software was employed to analyze the divergence effect of AWJ outside the nozzle,the simulation results show that with the current increased from 1.8 A to 2.2 A,the structure condition of AWJ becomes more stable.The removal mechanism of hard and brittle materials was analyzed and the sufficient condition of plastic removal way was given.The SPH method and Ansys/Ls-dyna software was used to simulate the micro-removal process of hard and brittle materials.The simulation results reveal that there is a high strain area below the erosion point,and with the erosion time increasing,the removal material accumulates gradually and was eventually removed.Also the change of erosion angle directly leads to the change of stress field range as well as the maximum value of shear stress.Through the single factor experiment,it comes to the conclusion that the introduction of magnetic field increases the erosion energy of abrasive particles,and both the number and depth of erosion pits in the erosion area are increased.In addition,because the increase of target distance will make the erosion area far away from the core of jet,the erosion effect was reduced.The order of various factors on erosion effect is jet pressure,magnetic field intensity,target distance and abrasive particle size.The response surface methodology was applied to the optimization of experimental parameters,and the optimal combination of parameters for maximum material removal was obtained.