Papers by Author: Yuan Li

Abstract: The discrete wavelet transform is usually realized by FPGA or DSP. This paper presents fast and valid image processing using discrete wavelet transform based on OMAP3530 chip which developed by TI(Texas Instruments). We employ the ARM+DSP dual-core OMAP3530 processor as the kernel of image processing. Linux Embedded System runs in the ARM side, DSP/BIOS System service run in the DSP side correspondingly. And the software development environment totally built upon the DVSDK (Digital Video Software Development Kit) which is provided by TI official website. Discrete wavelet transform algorithm adopted CE (Codec Engine) tools, which are the core of DVSDK. Finally, the image processing algorithm is inserted into CE. When the application program is running on the ARM side, the specific image is being conducted by CE on the DSP side.

Abstract: An experimental investigation is reported on the temperatures and energy partitions involved in the grinding of cemented carbide (YT30) with a vacuum brazed diamond wheel. The grinding temperature at the wheel-workpiece interface was measured using a pair of grindable foil thermocouples and the energy partition to the workpiece was evaluated by matching the analytical temperatures to the measured results. Effects of the various grinding conditions, including wheel velocity, feed rate and depth of cut, on the temperatures and the energy partition were investigated. It was determined that the wheel velocity was the most significant factor in governing the temperature relative to the depth of cut and feed rate. The maximum temperature rise at the contact zone was below 25°C in the present study. Microscopic examination of the ground surfaces and the ground detritus revealed that brittle fracture was the dominant material-removal mode. This may be one of the reasons for the low grinding temperature in grinding YT30 with a vacuum brazed diamond wheel. The energy partition values to the workpiece obtained under different grinding conditions varied from 3.3% to 20% for dry grinding YT30.

Abstract: An investigation was undertaken to explore the specific energy and material removal mechanisms involved in the grinding of cemented carbide with vacuum brazing diamond wheels. A mathematical model, relating to the grinding parameters such as wheel velocity, workpiece feedrate and depth of cut, was proposed to predict specific grinding energy, and was verified by experimental data. This verification came as a result of surface grinding two typical cemented carbides (YG8 and YG30) with a vacuum brazing diamond wheel under various grinding conditions. The earlier model’s prediction shows a direct correlation with the experimental results. Good relationships between the consumed power per unit width with the plowed face areas generated by all cutting points per unit width were obtained. Microscopic examination of the ground surfaces and the grinding detritus by a digital and video microscope system also revealed that material removal occurred mainly by flow-type chip formation (plastic flow) while grinding YG8 and by blocky fracture particles formation (brittle fracture) while grinding YT30.

Abstract: The effects of cutting parameters on the transverse vibration of diamond circular saw blade were experimentally investigated. Transverse vibration was online measured by a novel measuring system developed by wireless sensor. Meanwhile, axial force on saw blade was measured by a dynamometer. By the experimental results under different cutting parameters, the time domain characteristics of transverse vibration of saw blade were analyzed, and the relationships between transverse vibration and cutting parameters were also obtained. Axial deformation is greatly influenced by the axial force acting on saw blade.

Abstract: An experimental setup was established to measure and study the vertical and horizontal force components acted on the saw-blade during the whole deep sawing process of a granite workpiece with finite length. The accumulated thickness of the grits engaging with the workpiece in the sawing zone was obtained by numeric method to simulate the vertical and horizontal cutting forces respectively. The results showed that the simulated data tallied well with the measured data.

Abstract: Granite is a kind of typical discrete material, which experiences from continuous deformation stage, discontinuous deformation stage to fracture stage under sawing forces. Using discrete element method (DEM) to study the process of sawing granite will help us to understand the removal mechanism of granite from the microscopic point of view. In this paper, numerical uniaxial compression and three-point bending tests were conducted to determine the microscopic parameters of the granite specimen firstly, and then simulation was performed for sawing of the specimen. The sawing process, deformation characteristics of granite and the effect of initiation and propagation of cracks on fracture process of granite were investigated. The emphasis was laid on analyzing the variation of sawing forces under different sawing parameters. The simulation results agree well with that of experiments, indicating that DEM can reflect the external macroscopic change of granite by changing the internal microscopic structure. The conclusions in this study would be useful to the modeling of sawing processes and engineering applications.

Abstract: Experimental studies were undertaken to investigate the mechanisms for circular sawing of refractory bricks with diamond segmented saw blades. Three kinds of diamond segments of different hardness were fabricated for the saw blades. The vertical and horizontal force components and the spindle power were measured in sawing. Based on the measurements of force and power, the specific energy and the normal force per diamond grit were obtained. The normal force per grit in the sawing of refractory bricks was found to be only 5% of the static compressive strength of diamonds used in the present study, but fractures of diamonds were still popular on the segment working surfaces after sawing. The power, horizontal force, and the specific energy were found to increase with segment hardness. The specific energy obtained from the measured power was basically comparable to the values obtained from a theoretical equation to calculate the specific energy associated with slurry erosion to the bond matrix of segments.

Abstract: Grinding forces, protrusion height, grinding temperatures and wear of diamond grits have been studied in grinding cemented carbide YG8 with a single-layer vacuum brazed diamond wheel. The experiment results indicate that the primary wear progression of diamond grits in the whole grinding process follows the mode of whole diamonds, flat diamonds when grinding of the cemented carbide. The worn mechanism of the failure of diamond grits was discussed and possible solutions are recommended. The proportions of diamond conditions and the mean protrusion height of grains are more closely related to grinding forces and grinding temperatures. The grinding forces, force ratio and grinding temperatures decreased with the increasing proportions of whole crystal and the decreasing mean protrusion height of diamond grits, and the tangential and normal force components increased with the gradual wear of the brazed diamond wheel during a long-time grinding process. It shows great potential in improving thermal damage of cemented carbides by reduces grinding temperature with vacuum brazing diamond wheels.

Abstract: An experimental study was undertaken to investigate the grinding of granite at different grinding speeds over a wide range of material removal rates. A metal-bonded diamond blade was used as the grinding wheel with natural gray granite as the workpiece material. The tangential and normal force components were obtained through measuring the horizontal and vertical force components as well as the consumed power. The experiments were conducted with a constant wheel surface state to study the influence of grinding speed under different material removal rates. An additional test was also carried out to examine the grinding process while the wheel surface state progressively changed, in which case both forces and the morphologies of diamond grains were monitored at regular intervals. At a fixed material removal rate, both the tangential and normal forces reduced slightly with the grinding speed. But the specific energy increased greatly at higher grinding speeds especially at a shallower maximum grain depth of cut.

Abstract: An experimental study was undertaken to compare the mechanisms of two different processes to dress metal-bonded diamond segments. In one case, a piece of vitrified SiC wheel was used as workpiece and sawn by diamond segments attached to a sawblade. In another process, a diamond segment was used as workpiece and ground by an Al2O3 wheel. Spindle power was measured in sawing and horizontal force was monitored in grinding, in which case the latter was then used to get the consumed power in grinding. Specific energies were then calculated from the measured or converted power. For sawing of SiC wheel with the diamond sawblade, the maximum specific energy was found to be only 0.5 J/mm3, whereas the specific energy was up to 25 J/mm3 in the grinding of the diamond segment.