Evolution Mechanism Of Wear Behavior Of Diamond Abrasives In Rotary Ultrasonic Grinding

The hot pressed Si₃N₄ceramic material has the properties of high strength,high density,high temperature resistance,etc.It has become a widely concerned material and is widely used in the aerospace field due to its excellent characteristics.However,due to high hardness and low fracture toughness,workability has become a thorny problem,and engineering applications are limited.Rotary ultrasonic grinding technology is an important method for machining hard and brittle materials,and significantly improves the quality of machined surfaces.For the typical difficult to machine material Si₃N₄ceramics,the surface topography characteristics of rotary ultrasonic grinding have an important relationship with the friction and wear properties.It is the basis and premise to study the contact characteristics between the grinding tool and the workpiece in rotary ultrasonic grinding（RUG）to comprehensively and deeply analyze the characteristics of the machined surface topography.Therefore,the wavelet fractal theory is introduced in this paper to deeply study the surface topography characteristics of rotary ultrasonic grinding Si3N4ceramics,providing support for surface topography control.Firstly,the experiment of rotary ultrasonic grinding hot pressed sintered Si3N4was designed.The non-contact measurement of the machined surface was carried out using white light interferometer and scanning electron microscope to obtain three-dimensional data and surface morphology.Based on wavelet theory and fractal theory,the 3D data signal is reconstructed and the contour is analyzed,and the decomposition level,selection criteria and optimal wavelet base are determined;The reconstructed surface morphology is evaluated by the evaluation criteria.At the same time,the wavelet frequency spectrum is used to divide the corresponding processing frequency band,and the high-frequency part（processing surface texture feature）is decomposed into four sub images to judge the change of texture direction in the direction.Secondly,the singularity of surface topography is analyzed,and the surface is processed by gray level,and the multifractal theory is used for analysis.Through analysis,it is concluded that the multifractal spectrum width difference and spectrum height difference have a significant relationship with the microscopic morphology of Si3N4 ceramics,which can be used as the evaluation index of high difference;The fractal dimension can be used as an index to evaluate the surface roughness.Considering both integrity and locality,the above indicators comprehensively describe the surface micro morphology characteristics of rotary ultrasonic grinding Si₃N₄.At the same time,based on the multifractal spectrum parameters,the variation characteristics of the local topography of the machined surface are analyzed.Finally,combined with wavelet and multifractal,the effects of spindle speed,cutting depth and feed speed on the surface morphology of Si₃N₄ceramics were studied.In order to explore the influence of the type of abrasive tools on the quality of the machined surface,the characteristics of the surface micromorphology under different tool parameters were studied by dry and wet grinding contrast experiments,and the evolution law of the machined surface micromorphology was obtained.