Papers by Author: Guo Qin Huang

Abstract: The wear behavior of monolayer brazed diamond beads was investigated during wire sawing of granite. Diamonds were bounded onto the beads by brazing in vacuum. Brazed beads were abrasive sawed on a wire sawing machine and the wear of the brazed diamond beads were traced and observed by using a digital microscope. The results reveal that the wear of root fractured, characterized by breaking off grit at its bonding level, was the fatal failure of the cutting ability of grit as well as the main wear behavior of brazed grits on brazed bead.

Abstract: An investigation was undertaken to explore the grinding characteristics in grinding of yttrium vanadata (YVO4) crystal by using a resin diamond wheel. The grinding forces and surface roughness were measured and the morphological features of ground workpiece surfaces were examined. The results indicate that the depth of cut is the leading factor in affecting grinding forces whereas the surface roughness is mainly governed by the grinding speed. The material removal mechanism was found to be dominated by brittle fracture mode at conventional grinding speeds, and gradually transfer to ductile flow mode under higher grinding speeds, which is greatly related to the maximum undeformed chip thickness.

Abstract: Vibration during high-speed surface grinding process is one of important factors to influence surface precision of machined workpieces and lead to low efficiency of grinding machine. Process parameters are usually obtained from empirical data or reference manuals for the avoidance of serious vibration even chatter and its effect. As a result, it generally leads to low rated power of machine tool and long processing cycle. To solve the problem, designing and development on a dynamics simulation system for surface grinding with high accuracy ,which will be capable to predict a series of dynamic characteristics in time and frequency domains, such as grinding force-vibration, as well as phase/frequency characteristics, relative power spectral analysis etc is necessary and shows good application prospect. Meanwhile, the system will be used to indicate the process parameters optimization and investigate distribution characteristics of grain chip thickness and surface topography precision. In the paper, surface grinding process with diamond wheel is chosen as the study object and its dynamic characteristics are investigated. Based on studies on the comprehensive influence mechanism of regenerative chatter theory and wheel run-out rotational model on instantaneous grinding chip thickness of grain unit, analytical models of grinding force are improved. Differential equations of damper grinding vibration system with two-degree-of-freedom and a close-loop control system model with regenerative chatter feedback circle on the basis of interaction behaviors of force and vibration are built. Several relevant numerical methods are introduced to develop the simulation system of grinding dynamics. By comparative analysis on solution accuracy, steadiness and convergence of the correlative algorithms, explicit Runge-Kutta formula is identified as the best solution to simulation system modeling. On the basis of the above work, main subsystems and functional modules in the system are presented. The whole designs of framework and prototype systems are finished.

Abstract: A temperature model was advanced based on a parabolic heat flux distribution in sawing contact zone in the present paper. It is found that the maximum temperature for parabolic distribution is more higher than that for triangular distribution in the sawing contact zone, and the location point of the maximum temperature for parabolic distribution in the sawing contact zone is much nearer the entrance than that for triangular distribution.

Abstract: The sawing characteristics of a diamond circular blade with grits set in ordered distribution were investigated in comparison with a conventional blade on which grits are of random distribution. The two blades were tested under the same sawing conditions. Forces and power were monitored during sawing. The results indicate that the changing tendency of sawing forces and power versus sawing parameters are basically same for the two blades. However, the setting of grits in ordered distribution leads to lower sawing forces as well as force ratio, and can reduce nearly one third energy consumption.

Abstract: . Experiments of sawing granite with diamond circular blades were carried out to study the energy efficiency in circular sawing. Energy consumed by machine spindle is classified into energy used without cutting and energy used with cutting. The energy used without cutting almost increases with the improvement of peripheral speed of blade. The energy consumption coefficient, the ratio of energy used with cutting to total energy consumed by spindle, increases with the increase of material removed rate, which reveals that higher material removed rate is favor for improving energy utilization. A fixed trend of energy consumption coefficient versus material removal rate was found and it might be useful for selecting cutting parameters for low energy sawing.

Abstract: In order to assess the bonding of brazing alloys to diamonds, an investigation was conducted to measure the forces while shearing brazed diamonds. A device was designed to shear diamonds and shearing forces were recorded under different brazing parameters. The morphologies of diamonds were followed before and after shearing. It is found that the shearing force reduces with the increase of grit protrusion height. For specific grit protrusion, shearing forces decrease with the increase of holding time in brazing.

Abstract: An investigation is reported on the temperature in grinding of titanium alloy (TC4) by using a vitrified CBN wheel at grinding speed up to 120m/s. The temperatures under different grinding parameters were measured by using a sandwiched foil thermocouple. Coupled with the SEM observations on the ground workpiece surfaces, characteristics of temperature in high speed grinding were analyzed and compared with the temperatures in grinding at normal speeds. It is found that grind speed is the most significant factor to determine temperatures, which might be associated with the increase of material removal in the plastic way at higher grinding speed.

Abstract: An experimental study was carried out to investigate the effects of cutting parameters on cutting force and temperature in cutting of hardened W18Cr4V with PCBN cutter. Three components of cutting force were recorded by a strain-gauge dynamometer and the cutting temperature was measured by a nature thermocouple of tool-workpiece. The cutting parameters were arranged by orthogonal method. It is shown that the cutting temperature increased with each of the three cutting parameters and the main effecting factor is feeding speed. The three components of cutting force increased greatly with an increase in feeding speed and cutting depth. But the forces decreased a little as cutting speed increased. The main and axial cutting forces depend mainly on cutting depth whereas the radius force is mainly influenced by feeding speed.

Abstract: The wear of a brazed diamond wheel with diamond grits covered with brazing alloy was investigated in comparison with a traditional brazed wheel whose grits were without covering. The two wheels were brazed in vacuum furnace and grits on one of them were overlaid with a thin layer of brazing alloy. The wear of the two wheels was tested through grinding of granite, during which grinding forces were measured and the wear states of diamond grits were observed. It is shown that grits covered with brazing alloy exhibited stronger self-sharpening ability and fracture resistance. Therefore, the wheel with covered diamonds performed lower grinding force and better wear performance.