Papers by Author: Jian Yun Shen

Abstract: Ultrasonic vibration improved the machining performance of a variety of brittle materials, and achieved good results in brittle materials machining applications. In this paper, the experiment about precision sawing engineering ceramic by using a thin diamond blade with and without ultrasonic vibration conditions was investigated. It is aimed to explore the effect of ultrasonic vibration on specific energy. The results show that ultrasonic vibration makes specific sawing energy having a significant reduction during material removal process. Under the ultrasonic vibration condition, the engineering ceramic’s materials removal way is changed. It changed from plastic removal to the removal of brittle fracture, which reduced the energy consumption of material removal.

Abstract: An investigation is reported of the relationships of the temperatures and grinding parameter for grinding of ceramics with a brazed diamond grinding tool. During the experiments, the temperature distributions along the workpiece surface were measured using a foil thermocouples and the energy partition to the workpiece estimated using a temperature matching method. The results show that the grinding temperature increased with the increasing of worktable feed rate or tool velocity and depth of grinding. The measured temperature responses were found to be in good relation with the analytical results of a moving heat source with a rectangular distribution at the grinding zone.The energy partition ε is about 23%.

Abstract: High speed sawing is an advanced machining technique for sawing of brittle materials with good component quality and high productivity. In the paper, sawing experiments were carried out to investigate the characteristics of sawing forces by altering many processing parameters in high speed sawing of quartz glass with a diamond blade. The sawing forces and force ratio were analyzed. The conclusions present that in the fixed material removal rate, the increasing of periphery speed can help to lower sawing forces and force ratio; sawing forces increase with material removal rate; in the high speed sawing, the effect of material removal rate on sawing forces is smaller than the one in the low speed.

Abstract: In this study, two different arrangement lapping disks fixed with brazed diamond pellets were used to lap silicon wafer and alumina ceramic. The effects of the surface morphology, roughness, and removal rate of workpiece caused by lapping pressure, lapping time, workpiece velocity, and disc arrangement were operated with serials experiments. The results of the researches provided guidance for fixed abrasive lapping of hard and brittle materials with the brazed micro powder diamond disk.

Abstract: In the present study, sawing forces of Al2O3 ceramic and wear of metal-bonded diamond cut-off wheel were examined by counting the statistical data of diamond wear and analyzing the force signals under different sawing conditions. The experimental results demonstrated that normal grinding force reduced with the increasing of sawing speed, and rose with the increasing of workpiece feed rate and grinding depth. In all of the variables, sawing depth made the greatest effects on normal grinding froce. The percentage of whole crystal or pull-out crystal decreased and fractured crystal increased as the sawing depth increased or the sawing speed decreased. Among machining factors, sawing speed was the greatest effectors on the wear of diamond cut-off wheel.

Abstract: Brittle materials are popularly used as engineering materials for excellent properties. But the properties of brittle materials are different and special, and cause to different surface formation mechanism during the grinding process. In the study, surface roughnesses after grinding with different mesh size diamond wheels were measured. Combined with scanned surface topographies, the relation between the surface roughness and the properties of these brittle materials was discussed. It could be found that the material properties led to the different surface characteristics of brittle materials.

Abstract: In the present study, grinding temperature was measured by using a foil thermocouple when granite was ground by SiC wheel. De-noised the temperature signals with soft threshold method base on wavelet transform was conducted to analyze the grinding process. Energy partition to workpiece was estimated to be about 10%~30% by matching the measured temperature to analytically value. The number of active grains was determined by counting the high frequency impulses in the measured temperature signals. The ratio of active grains to total grains was about 4.5%~6.1%. Based on the results, a formula was deduced for calculating the temperature of single grain in the grinding process.

Abstract: In the present study, zirconia ceramic was ground with a resin-bonded diamond wheel on a precision surface grinding machine. Grinding temperatures generated at the wheel-workpiece contact zone were measured using a sandwiched foil thermocouple, and the net consumed grinding powers were also measured. The energy partition to the diamond abrasives was estimated using measured grinding temperatures and powers. Based on the energy partition values obtained from the analyzed results, the diamond tip temperature was calculated and found to be over 1000°C if the circular grain contact of radius was less than a critical value for ductile field grinding of zirconia ceramic.

Abstract: In this study, rock minerals of natural stone were finely polished with loose abrasive and ELID technology to study the surface behaviours. After these rock specimens were polished to ultra smooth surfaces, the surface characteristics were observed with microscope and analyzed with surface texture analyzer. It was found that the calcite and fluorite minerals could be polished to high surface quality with fine loose aluminum oxide abrasive. But ultra smooth quartz surface must be finished with superabrasive ELID polishing technology. The weakly acidic coolant might bring chemical damage to calcite and fluorite minerals under the condition of ELID polishing process.

Abstract: In this study, grinding of Si3N4, SiC, and Al2O3 ceramics under the condition of electrolytic in-process dressing (ELID) system was investigated. The surface appearances of these engineering ceramics during the ELID grinding process were attentively observed to describe the formation of finely finished surfaces. Based on the analysis of material properties and detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of engineering ceramic is closely related to its mechanical properties. The silicon nitride ceramic was most easily machined to precision surface among these three engineering ceramics.