Papers by Author: Ming Li Zhao

Abstract: Residual stress of ceramics ground surface was detected by the X-ray instrument, and it was analyzed in present paper. The experimental results show that the content of metastable tetragonal phase of ZrO₂ and grinding stress are the primary factors which induce martensitic transformation on ZrO₂ ceramics ground surface; during grinding the deeper the grinding depth is, and the bigger abrasive grain size is, the grinding stress in material matrix is larger. After analyzing the influence of grinding parameters on residual stress, it can be found that martensitic transformation can prompt the compressive residual stress to some extent, so as to improve the quality of ground surface.

Abstract: The node position of amplitude transformer was determined by the finite element method, and the flange was designed at the nod position for conveniently installation. By the finite element software, the amplitude transformer with flange was optimized and dressed, and its structural parameters were determined. During the actual manufacturing process, it was used impedance analyzer to test its vibration performance, the testing results show that this system vibration performance is good, its resonant frequency is 34.771kHz, anti-resonant frequency is 35.008kHz. The above-mentioned results are very much coincided with the system natural frequency of 34.893kHz which is drew by finite element method. Compared to the traditional dressing this method has many advantages such as convenience, green, environmental protection, low cost and others.

Abstract: The ultrasonic-assisted single-grit grinding device is designed which can be used to efficiently simulate grinding process, and the comparative tests of single-grit ultrasonic grinding are carried out between Nano-ZrO₂ ceramics and ZTA ceramics under different grinding depth. The experimental results show that the bigger the scratch depth was, the greater damage degree of material was, nano-ZrO₂ ceramics’ grooves is smoother than that of ZTA ceramics and the damage of its material is minor; ultrasonic vibration broadens the range of plastic cutting of Nano-ZrO₂ ceramics in some degree. The experimental phenomena also show that the rolling role of abrasive particle can be conducive to material plastic deformation.

Abstract: Because of the hard-brittle character of ceramics, the ultrasonic vibration grinding method was used in the experiment. And the effects of ultrasonic vibration on the subsurface damage were analyzed in this paper. The experiment indicates that the frequency of 35 KHz will be more suitable for ultrasonic grinding ceramics, and under this frequency the damage layer thickness will be controlled in 11μm. The effect of vibration amplitude on the subsurface damage was also analyzed in this paper. The experiment results show that smaller amplitude will impair the efficiency of ultrasonic vibration grinding. The ultrasonic vibration mode was also an effect factor to the subsurface damage. Only the longitudinal vibration mode can improve the subsurface quality, while the bending vibration and torsion vibration will lead to the contrary results.

Abstract: Relative motion of single abrasive is analyzed for the different applied directions of longitudinal ultrasonic vibration, and its locus is simulated in the present paper. The research results show that the locus in two-dimensional ultrasonic vibration is only similar to that in y-direction, and both are close to sinusoid curves. The width of grooves scratched by abrasive grains y-direction (axial direction of grinding wheel) is two times of the vibration amplitude, and the material removal rate increases remarkably. In case of x-direction (tangential direction of grinding wheel) ultrasonic vibration, abrasive grains with periodic force impact material surface with high frequency vibration, which make material fracture removal easy. Therefore, the high efficiency essence of material removal in two-dimensional ultrasonic grinding is revealed in view of locus. In addition, according to the results of grinding experiments, under same conditions good surface quality can be obtained in two-dimensional ultrasonic grinding and material removal rate in common grinding is the lowest. Consequently it is further proved that the method of two-dimensional ultrasonic vibration grinding is an effective one for ceramic materials.

Abstract: The orthogonal test of surface roughness in ultrasonic polishing nano-ZrO2 ceramics was carried out in the present paper. Through the test, the influence of machining parameters on the surface roughness was investigated. The test results showed that the influence of abrasive size on surface roughness is the most remarkable, and the other important factors are the depth of cut, on/off work situation of ultrasonic generator, axial feed speed, and working table speed in turns. Furthermore, through the regressive analysis of test data, an empirical formula of surface roughness was established to select reasonable polishing parameters.

Abstract: The influence of ultrasonic vibration on the surface roughness and micro-topography of ceramics plate is discussed in this paper. Grinding assisted by two-dimensional ultrasonic vibration is developed to deal with the processing difficulty of ceramic materials due to its hard-brittle property. The experimental results show that the surface roughness value obtained in two-dimensional ultrasonic grinding nano-ZrO2 ceramic plate specimen is obviously smaller than that in common grinding, and the scratched grooves on the machined surface in ultrasonic grinding is wider and relatively smoother than that in common grinding. Consequently, it proves that the two-dimensional ultrasonic machining is a feasible, high-efficient machining method for hard-brittle materials.