球形磨头单颗磨粒磨削SiCf/SiC陶瓷基复合材料仿真OA

Objectives:SiCf/SiC ceramic matrix composites were continuous fiber-reinforced materials that had attracted extensive attention and application in fields such as automotive and aerospace due to its high strength,high hardness and high-temperature resistance.However,the difficult machinability makes it challenging to investigate the micro-scale material removal characteristics and mechanisms using traditional methods.To reveal the processing mechanism of spherical grinding heads milling SiCf/SiC ceramic matrix composites,a more approximate woven composite model was established for simulation and investigation.Methods:The milling simulation of SiCf/SiC adopts a more approximate woven body model.Considering that the overlapping area of fiber filaments is prone to burrs during processing,the microstructure of the woven ceramic composite material's latitude and longitude boundary area is modeled.The upper and lower layers of fibers in the model are vertically interwoven at a 90°angle.Finite element simulation is conducted to simulate the milling process of a single abrasive grain on a spherical grinding head.The variation laws of single abrasive grain grinding force,grinding temperature,and grinding force ratio of SiCf/SiC ceramic composite materials under different processing parameters and fiber orientations,as well as the changes in material removal characteristics,are studied.Finally,the single abrasive grain scratch experiment is conducted to verify the results.Results:In the simulation of SiCf/SiC material machining,when other machining parameters remain unchanged and only the grinding depth ap increases from 5 µm to 20 µm,the grinding force significantly rises.The normal grinding force Fn increases by 90%,the grinding temperature T rises by 25.4%,and the grinding force ratio decreases by 22.0%.Additionally,the increase in ap has a substantial impact on the variation of each parameter.When the grinding speed Vs increased from 12 000 r/min to 18 000 r/min,the grinding force exhibited minor changes.Fn decreased by 5.9%,T increased by 10.4%,and the grinding force ratio rose by 1.1%.Thus,both the increase in ap and Vs lead to an increase in T,but the effect of ap is greater than that of Vs.Additionally,changes in ap have a more significant impact on grinding force variations than changes in Vs.When the grinding angle θ increases from 0° to 45°,Fn decreases by 54.7%,T decreases by 7.7%,and the grinding force ratio decreases by 66.8%.When θ increases further from 45° to 75°,Ff increases by 100.3%,T increases by 5.9%,and the grinding force ratio increases by 112.4%.When only changing the fiber direction of the material when the abrasive grain feed is changed,the grinding force generated by processing along the fiber axis is greater than that generated by processing along the fiber longitudinal direction,generally increasing by about 35%.Therefore,when the angle between the grinding heads is smaller,the grinding force is concentrated and Fn is larger;When the angle is larger,the grinding force becomes more dispersed and the material becomes more difficult to process.When only the material fiber orientation relative to the abrasive feed direction is changed,the grinding force generated along the fiber axial direction is greater than that along the fiber longitudinal direction,with an overall increase of about 35%.Therefore,when the grinding head angle is smaller,the grinding force becomes more concentrated and Fn is larger.When the angle increases,the grinding force becomes more dispersed,and the material becomes more difficult to machine.Conclusions:In SiCf/SiC materials,the interface between fibers and matrix is the preferred path for crack propagation,and fibers can change the crack propagation path.At the intersections of the warp and weft fiber yarns,crack growth can be effectively inhibited.When the grinding force ratio is relatively small,there are more burrs,cracks,and debris generated on the grinding surface of composite ceramic materials.In order to obtain a better machining surface without significantly affecting machining efficiency,a smaller ap should be preferred,followed by a larger Vs.In order to maximize the flexibility of spherical grinding head processing,it is recommended to maintain a small θ when the grinding head angle deviates.When processing along the longitudinal direction of the fiber,the failure mode of the fiber is mostly fracture.In this case,the matrix mainly supports the fiber,and cracks mainly appear at the interface between the matrix and the fiber,leading to fiber pull-out and exposure.When machining along the axial direction of the fiber,the main forms of fiber failure are compression and stretching,with some fibers being pulled out and then fractured along the interface to form fragments.At the same time,the experiment also verified the fracture characteristics of SiCf/SiC composite ceramic materials,which are consistent with the simulation results.