| SiCp/Al composite materials have been widely used in the field of aerospace, automotive, electronic, optical precision instruments, advanced weapon systems etc., because of its high strength, high modulus, high temperature resistant, small thermal expansion coefficient, good dimensional stability and excellent mechanical and physical properties. But its application has been restricted because of it’s hard brittle particles which were difficult to be processed, therefore higher requirements are put forward for processing method.In this study, Ultrasonic assisted processing technology is introduced into the grinding of high volume fraction SiCp/Al composite materials. Typical optical materials, i.e. optical glass and sapphire crystal, are chosen as the research objects. Ultrasonic assisted grinding process performance of SiCp/Al composite materials are presented by investigating the Material removal mechanism, ultrasonic grinding surface quality evaluation and experimental analysis. The main contents and results are as follows:. The main contents and results are as follows:(1) According to the test and analysis of Nano mechanical properties of SiCp/Al composite materials which has been polished by the commercial nano indentation apparatus, elastic-plastic and brittle characteristics of SiCp/Al composite materials was tested. The depth of the indentation for the crack and propagation and the mechanical properties such as elastic modulus and hardness was obtained, and the reference for the process parameters was provided during grinding. Grinding force, friction coefficient and surface scratch morphology characteristics was studied by conducting ultrasonic scratch experimental research by single diamond grits.the material deformation and friction properties was evealed, and the material removal behavior was characterized at the same time.(2) To compare and analysis the grinding effects of different grinding wheel, this thesis made electroplated diamond grinding wheel, brazed diamond wheel, Ceramic bond sintered diamond grinding wheels and sintered diamond grinding wheel, and from the application and grinding process SiCp/Al composites, carried out experimental study combined with ultrasound-assisted grinding process。to evaluate the three aspects of the grinding process:for surface morphology in wheel grinding process, material removal properties and surface morphology of, provides the basis for selection of the grinding wheel in the SiCp/Al ultrasonic assisted grinding processing(3) From the perspective of the material application and grinding process,this thesis carried out experimental studies to clarify the basic morphology and formation mechanism of SiCp/Al grinding surface, and proposed the method of evaluation with Sq and Sdr two parameters on the surface morphology, and conventional grinding and ultrasonic grinding surface morphology was evaluated for further study SiCp/Al grinding surface quality evaluation techniques.(4) The simulation and experimental study of the ultrasonic process about SiCp/Al composites shows:The lager Scratch depth, the greater the ultrasonic amplitude, the higher the frequency, the greater the range of SiC particle breakage; surface residual stress by ultrasound scratches,high-frequency ultrasonic scratches was lower than ordinary scratches surface,low frequency ultrasound; the optimal frequency and amplitude were 22000 Hz, 4um. The results showed that: Ultrasound SiCp/Al material auxiliary grinding could effectively reduce cutting force and roughness size, improve the surface quality of the work piece face grinding. Analysis of the influence of process parameters on the processing performance,obtained SiCp/Al grinding surface topography by surface roughness of 0.15μm,but also by the ideal process parameters: speed 6000r/min, depth of cut 7μm, feed rate of 8mm/min. thus Ultrasonic assisted grinding is an excellent process for SiCp/Al composites efficient precision machining.(5) Taking surface quality of a thin-walled workpiece made by SiCp/Al as the evaluation index, feeding mode, grinding direction and ultrasonic effect on surface morphology and quality of the workpiece were researched. The results show that, tangential stratified feeding can significantly improvesurface quality of the workpiece; reverse grinding can reduce normal grinding load and reduce edgebreaking of inlet and outlet; down-grinding can reduce tangential grinding load and improve surface quality; ultrasonic vibration can optimize surface quality and reduce edge-breaking of the thin-walled workpiece. |
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