Papers by Author: Hai Tao Liu

Abstract: This paper takes a kind of 14 mm inner diameter, installation span for 600 mm conduit connector as an example to do the top 5 order modal analysis, resonance resistance analysis and random vibration analysis and gets the vibration model in the different frequency.

Abstract: An experimental study of grinding force in microgrinding zirconia ceramics using small grinding tool is presented. In the experiments, the grinding tool used is electroplated diamond microgrinding wheels of 0.41, 0.63 and 0.76 μm in diameter, and the machining operations were conducted in side grinding under dry cutting. The process parameters include the diameter of the microgrinding wheel, feedrate, and rotational speed of the grinding spindle. The microgrinding forces were measured by a Kistler three-component dynamometer. The experimental results show that the normal forces are much larger than the tangential forces, the effects of process parameters selected on the variation of experimental results is almost the same for tangential forces, and that is the feedrate, diameter of the microgrinding wheel and rotational speed of the grinding spindle in turn for normal forces. As the feedrate increases or diameter of the wheel increases, the microgrinding forces increase, and the magnitudes of increase are more significant at higher radial grinding depth.

Abstract: Deformation caused by residual stress has been one of the main reasons influencing the machining accuracy, studies on machining residual stress should be performed. The tool flank wear on the cutting process has great influence on cutting heat which will infulence the distribution of residual stress, therefore,we should do the finite element simulation of cutting tool flank wear on the heat-affected firstly,then simulate and forecast the surface residual stress, studies on the effect of tool flank wear on the distribution of machined surface residual stress Johnson-Cook’s coupled thermal-mechanical model is used as workpiece material model, thermal-displacement coupled brick are used to mesh, while friction between tool and work piece uses modified Coulomb's law whose slide friction area is combined with sticking friction. By means of FEA, residual stress on the machined surface and cutting temperature under different tool flank wear conditions are obtained. The results are compared and analyzed, and then we can get the fundamental influencing law on machined surface residual stress of tool flank wear.

Abstract: In order to determine the minimum thickness of cutting under different cutting condition of aluminum alloy materials 2A12 of micro-milling, research the size effect caused by the cutting edge radius and few microns per tooth in micro-milling process. Using thermal coupling model of Johnson-Cook as a material model of the workpiece, using Johnson-Cook shear failure of the law as part of the failure criteria, using coupled plane strain thermal units and hybrid adaptive grid technology to mesh, the friction between the tool and workpiece take the amendment Coulomb's law that combine with the sliding friction areas and areas of the adhesive friction, to the micro-milling by nonlinear and elastic-plastic finite element simulation. Through finite element analysis, the ratio of minimum radius of thickness to the cutting edge tool radius under different conditions of cutting speed and cutter blade was got, the size effect, stress field and cutting force under different cutting depth was got, and comparing and analysis the results, getting the various factors impact on the size effect of micro-milling, it provide a basis for the actual processing.

Abstract: Porous materials have been successfully used in an aerostatic bearing. In this paper, the dynamic stiffness and damping of partial porous aerostatic thrust bearings are analyzed by numerical calculation method. Firstly, the pressure distribution function of the bearing is divided into the static and dynamic pressure distribution functions through minor perturbation method. Then, the static and dynamic pressure distribution functions are calculated by FEM. Finally, the dynamic stiffness and damping coefficients of the bearing are solved. The result indicates that the dynamic stiffness increases obviously with the increment of supply pressure and first increases then decreases with the increment of frequency, and that there is negative damping in the low frequency band and the supply pressure has a great impact on the stability of the bearing.

Abstract: Thin-walled parts with complex configurations are extensively used in aerospace and precise instrument industry. However, because of low stiffness, cutting forces, clamping forces and residual stresses in cutting have been the main factors influenced on machining accuracy of thin-walled parts. Furthermore, biggish deviation exists between practical finished surface and theoretical value as a result of machining deformation caused by cutting force namely “cutter relieving” phenomenon; besides, direct relation exists between determination of clamping force and generation of machining residual stress and cutting force, so it is necessary to build up accurate cutting force prediction model to improve the machining accuracy of thin-walled parts. Therefore, cutting force prediction model based on Johnson-Cook’s flow stress model and Oxley’s shear angle model has been developed, which takes the property of high strain, high strain ratio in area of cut and high cutting temperature into account fully and determines shear angle more accurately on the basis of force balance principle; with different cutting and tool geometric parameters existing, perform simulation and experiment studies on cutting force prediction model, verify the validity of prediction model and obtain the response rules resulted from cutting force prediction model acting on cutting and tool geometric parameters.