Papers by Author: Yan Wu

Abstract: Machining simulation is an important procedure to ensure machining safety and efficiency, especially for five-axis machining. The modelling for Fidia HS664RT five-axis machining center is firt established, and then the tool path for five-axis machining of centrifugal impeller is generated based on NX. The machining simulation is then implimented based on Vericut, and finally the actual machining is realized on Fidia HS664RT five-axis machining center. The machining results indicate the validity of the proposed machining simulation method.

Abstract: This paper is based on the research on the drive shaft of the toothpaste tube conveyor, using Solidworks to create the three dimensional model of the frame of the soft tube conveyor and the drive shaft. And natural frequencies and vibration modes of preceding 6 modalities of pre-stress modal analysis are calculated with ANSYS Workbench. By analyzing the natural frequencies of the drive shaft and the resonance range of stepper motors, the reasonable speed range of the stepper motor can be acquired, in order to avoid the resonance between the drive shaft and stepper motor. At the same time, the reasonable installation location of synchronous belt wheels can be attained by analyzing each vibration mode.

Abstract: The 3D solid model of the tube automatically benchmarked equipment is built by UG software. With seamless connectivity UG and ANSYS Workbench software, modal analysis of the fuselage of the automatically benchmarked equipment built by ANSYS Workbench software. Then natural frequencies and modal of the lower six orders are obtained, and the vibration weakness of the structure has also been found out. To improve the structure provides a reliable reference

Abstract: The relationship between machinability and microstructure of plastic mould steel is still not clear enough, despite the application of plastic mould steel is more and more wide. In this study, two typical plastic mould steels, namely, 718 (DIN 1.2738) and SDP1 steel with the same hardness are chosen to investigate turning force, tool wear and milling force by experimental test. Combining with the turning and milling test, discussions about cutting force and the relationship between machinability and microstructure are made. And it’s found that the micro-uniformity has a great effect on the machinability of plastic mould steel.

Abstract: Based on the research for the structure of the ceramic nanocomposites’ intragranular for Al₂O₃/ZrO_2(n)，we did the test by the workpiece two-dimensional vibration grinding(WTDUVG), and focus on analyzing the characteristic and the effect element of the two-dimensional ultrasonic vibration grinding ceramic surface residual stress by the XRD diffraction. The result show that ceramic dimensional ultrasonic vibration grinding surface tensile stress is less than the same conventional grinding (CG) surface under tensile stress; two-dimensional ultrasonic vibration grinding surface residual compressive stress than conventional ground surface residual stress under the same grinding. Material removal mechanism of the grinding nature of the surface residual stress, when the material removaled by ductile deformation, grinding surface equal residual stress; when the material removaled by brittle- ductile mixed mode, the grinding surface tensile stress reduced, because the fracture of the ground surface, tensile stress released. As a results, the grit size of grinding wheel, Grinding depth and workpiece mechanical properties are the main technology factors affected the nature and size of the residual stress of ground surface.

Abstract: After researching the mould coating and the effect of different matrix hardness on the service life, it can be concluded that under the condition, the matrix materials match with its obdurability well, the higher the matrix hardness, the longer the service life after the mould’s being coated. What’s more, it is put forward that when the heat treatment technology and the coating technology are worked out, the effect of the coating temperature on the matrix hardness should be turned over so as to avoid the matrix’s being annealing again and then have a further influence on the capability after being coated.

Abstract: The innovative use of surface shot-peering to make a passivation at milling cutting edge of wheel, it shows that passivation has eliminated all microcrack and abrasion trace on the surface of milling cutting edge through microscopical observation, so as to improve adhesive force among the coating and cutter body, to make an uniform wear of cutter with coating during machine work, and further to keep fairly good function of cutting edge. Furthermore, the milling length of wheel cutter is over 8 meters, and such technology has solved the technology problem in production domesticization of wheel cutter.

Abstract: Based on impulse theories and indentation fracture mechanics, the motion model of the contact between abrasive particle and workpiece in workpiece two-dimension ultrasonic vibration grinding (WTDUVG) was analyzed, and the critical condition of ultrasonic vibration grinding brittle-ductile transition was analyzed theoretically, furthermore the critical cutting depths of a grain under different grinding conditions were obtained by Matlab programs. In this work, the ultrasonic vibration and conventional diamond grinding of Al2O3/ZrO2 nanoceramics were performed in order to investigate the effect of workpiece ultrasonic vibration on the brittle-ductile transition mechanism, the effect of grit size, worktable speed and grinding depth on the critical depth of cut were studied by grinding experiments. the micro-topography of the grinding surface was observed by AFM and SEM. Experiment indicated that only when the grinding depth less than critical grinding depth, ductile regime grinding of ceramics can be realized, the appropriate grinding parameter on surface finish are suggested.

Abstract: This work mainly studied the deterioration layer structure, crystal grain size, crystal lattice distortion of ground surface in two-dimensional ultrasonic vibration grinding nano-composite ceramics. The research indicated that under a certain grinding condition the ductile deformation layer on the ground surface of nano-composite ceramics in two-dimensional ultrasonic vibration grinding is formed by the ways of material powdering, crystal grain fragmentation, materials extrusion, the crystal grain pull-off and so on. The transition layer between the surface layer and the base body is plastic deformation layer by the primarily ways of crystal lattice distortion and the crystal boundary slipping. The removed material in brittleness fracture mode is extremely few. In this work, the structural model of deterioration layer on ground surface in two-dimensional ultrasonic grinding nano-composite ceramics is put forward. The microscopic deformation mechanism of nano materials is inner grain dislocation of inner-grain-structure strengthened phase. Its deformation coordination mechanism is the the grain-boundary sliding of matrix grain and the coordinated deformation of intercrystalline second-phase. The TEM and SEM observation discovers that the nano particles dispersed in grain boundary stops crack from expanding in nano materials, which causes the materials to appear in transcrystalline fracture behavior. And this fracture behavior gives materials favorable finished surface. The plastic deformation is the dominant removal mechanism of the nano materials in two-dimensional ultrasonic vibration grinding.

Abstract: Using TEM, SEM and XRD, the surface microstructures of nanocomposite ceramics prepared by heterocoagulation was studied in two-dimensional ultraprecision grinding with ultrasonic assistance. This research was focused on the structure of ground surface degenerating layer, surface generation mechanism and characteristics of nanocomposite ceramic parts. The experimental results showed that the microscopic deformation mechanism of the ordinary Al2O3 parts was grain- boundary twinning and grain-boundary sliding while microscopic deformation mechanism of nanophase ceramic parts was the inner crystal dislocation of strengthened phase with intragranular structure. And its deformation coordination mechanisms were the grain-boundary sliding and coordination deformation of intercrystalline second-phase. The observation on the fracture surfaces of nanocomposite materials with different microscopic structures by TEM and SEM showed that ZrO2 particles had an important effect on the generation and expansion of crack in ceramic parts. The introduction of ZrO2 particles strengthened the interface intensity of grain boundary. If there were rich ZrO2 particles on the grain boundary, the cracks generated during the grinding process would be prevented. Smooth and plastic deformation processing surface was obtained. It was proved further that the nanophase materials behaved transcrystalline fracture due to the nano particles, dispersed in the grain boundary and prevented the expansion of crack. This material’s fracture behavior made favorable surface possible. In the precise grinding of nano materials, the plastic removal mechanism dominated the process. The dislocated depth of the nanocomposite ceramics after grinding was bigger than that of common ceramics, which meant that dislocation increased.