Papers by Author: G.F. Gao

Abstract: The grain cutting trace of elliptical spiral in workpiece two-dimensional ultrasonic vibration grinding(WTDUVG) is defined, the reason of machining accuracy improvement by applying two-dimensional ultrasonic vibration is discussed. Adopting two-dimensional ultrasonic composite processing, the influences of grinding depth, worktable velocity, wheel granularity on the surface roughness of Al2O3/ZrO2 ceramic nanocomposites were described. Experimental results of AFM microstructure show that the material removal model in WTDUVG is dominated by ductile flow of material, some crystal refinement, the crush powder and grain pull-out are visible and there is almost no fracture. Furthermore, the surface roughness in WTDUVG with coarse grit is about 30
40% less than that in CG under identical grinding condition; the qualitative analysis of X-diffraction results indicated that the surface phases are composed of α-Al2O3, t-ZrO2 and small quality m-ZrO2, there are amorphous phase in the surface both with and without vibration grinding. M-zirconia phase transitions rule in vibration and conventional grinding was found. Under definitive grinding conditions, the material removal mechanism of inelastic deformation is the principal removal mechanism of Al2O3/ZrO2 ceramic nanocomposites, the grit size of diamond wheel and vibration grinding mode have important influence on material removal mechanism of ceramic nanocomposites.

Abstract: Experimental researches on material removal rate and surface roughness of Al2O3 engineering ceramic guide-pulley lapping were carried out using W20 and W5 fixed oilstones by self-developed ultrasonic lapping tool both with and without ultrasonic assistance. Experimental results show that lapping speed, lapping pressure and grain size produce different effects on the lapped surface roughness and material removal rate. The material removal rate in ultrasonic lapping process is two times as large as that in traditional lapping, and the ground surface roughness is superior to that in common machining method. The material removal rate increases along with the average diameter of grains and the lapping speed both in ultrasonic lapping and traditional lapping. In traditional lapping process the material removal rate becomes bigger along with the lapping force, while in ultrasonic lapping it gets the optimal value with the lapping force 450N. The value of lapped surface roughness increases along with the lapping speed in traditional lapping, on the contrary it decreases contrast to the lapping speed until 250rpm in the ultrasonic lapping. The value of traditionally lapped surface roughness decreases contrast to the lapping force, whereas it achieves the minimum with the lapping force 450N with ultrasonic assistance.

Abstract: Metal matrix composites（MMCs）is applied widely in recent years because of its excellent performances, but the machining is very difficult due to the rigidity of reinforced-phase in it, so, the application of MMCs is restricted much. In this paper the experiment of common and ultrasonic vibration drilling is performed to SiC particulate reinforced Al matrix composites （SiCp/Al）by use of carbide-alloy-twist-drill, and the surface roughness of hole is compared, furthermore, the wearing of twist drill and the feature of chips are analyzed by scanning electron microscope (SEM). From above, we can draw aconclusion that ultrasonic vibration drilling may meliorate the mechanism of drilling to some extent and it takes on much superiority that the common drilling is unmatched, so this method could provide a certain foundation for the posterior study and application.