| The ceramic-metal functionally graded materials(FGM)have attracted the attention of the world with innovative design,and it has a wide application prospect in electromechanics,chemical industry,biology,communication and aerospace fields.It has the merit of continuously graded thermodynamic properties of two different materials.However,Ceramic-metal FGM with many excellent properties can only be made into graded coating on the base material or be made into simple structure by the limitations of machining method and theoretical research.It is difficult to machining complex structure,which seriously restrict the application and development of ceramic-metal FGM.Therefore,it is of great scientific significance and wide application value to research the efficient and stable machining method and mechanism of ceramic-metal FGM.In this paper,electrical discharge machining(EDM)SiC/Al FGM is studied from the aspects of machining gap flow field simulation,single pulse discharge temperature fie ld simulation,continuous multi-pulse discharge temperature field simulation,process test and optimization of processing parameters.The details of the study are as follows:Firstly,the simulation model of the EDM gap flow field of SiC/Al FGM is established.The velocity distribution of the flow field and the concentration of debris are simulated.The influence of liquid supply type,processing depth and flushing pressure on processing efficiency is analyzed.The results show that the effect is the best for the reverse flow.The greater the inlet pressure of the dielectric fluid,the greater velocity of dielectric fluid,the smaller concentration of debris.The smaller machining depth,the greater velocity of dielectric fluid near the surface of electrode and workpiece,and the smaller concentration of removed debris.Secondly,mathematical model and physical model of single-pulse discharge temperature field of SiC/Al FGM were established.The influence of peak current,pulse on-time and graded layer content on the material temperature of single pulse discharge and the erosion of pits were studied.Based on single pulse discharge simulation and randomness of the discharge position,the dynamic erosion process of multi-pulse discharge and the influence of electrical parameters on machining efficiency are studied.The results show that the increase of peak current and pulse on-time has positive effect on the erosion of material,while the graded layer content is opposite.Finally,the simulation results of multi-pulse material removal rate are verified.L32(21×44)mixed orthogonal design is used to analyze the influence of machining mode,pulse on-time,pulse off-time and graded layer content on material removal rate and relative tool wear rate.The multi-objective parameter optimization and regression analysis of 5-wt% SiC/Al by EDM were carried out.The results show that the influence of material removal rate from primary to secondary is: peak current,machining mode,pulse on-time,pulse off-time,graded layer content,and the influence of relative tool wear rate from primary to secondary is: machining mode,pulse on-time,peak current,graded layer content,and pulse off-time.The optimal combination of process parameters is: peak current 10 A,pulse on-time 200?s,pulse off-time 100?s,servo voltage 50 V,and lifting height of tool 3mm.Material removal rate is decreased from 116.5 mg·min-1 to 109.756 mg·min-1,decreased by 5.789%,and relative tool wear rate decreased from 1.539% to 0.742%,decreased by 51.787%.The empirical formula of removal rate and relative tool wear rate of material is obtained by regression analysis,which provides theoretical foundation and technical support for the subsequent research on EDM metal-ceramic FGM. |
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