Abstract: Surface and subsurface damage affect the preparation of high-resolution HgCdTe and CdZnTe detectors. Grinding experiments were performed on CdZnTe substrates with the grinding wheels of different abrasive sizes. The surface topography and subsurface damages of CdZnTe substrates ground by diamond grinding wheels with different grit sizes were studied. The effects of the grit sizes of grinding wheels on the surface topography and subsurface damage of CdZnTe substrates were discussed. The surface roughness and subsurface damage layer depth of CdZnTe after grinding with #3000 diamond grinding wheel are only Ra 7 nm and 100 nm, proved that grinding is of great potential for CdZnTe substrate processing.
Abstract: Grinding characteristics brought by the grinding speed reduction and geometrical model differences between micro-grinding and conventional grinding have been mainly researched. Influences which micro-grinding parameter and micro-grinding tool dimension parameter giving to grinding surface quality have been analyzed. The comparison experiment between micro-grinding and micro-milling has been carried out on the micro-machining test-bed developed by Northeast University. Wear of the grinding pin obtained from experiment is considered to provide the basis for the micro-machining system and fabricating of grinding pins.
Abstract: Grain-workpiece interface, which resembles a micro-cutting process, directly modifies the workpiece surface and dominates all the output measures of a grinding process. The abrasive grains always become worn or dulled during grinding, which alters the grain-workpiece interface output and turns to be the primary factor that causes the transient or time dependent behavior in monolayer superabrasive grinding. Therefore, the study on how the grain wear influences the grain-workpiece interaction through micro-cutting analysis becomes necessary. As the emergence of the packaged FEM software for micro-cutting simulation, apart from single grit cutting test, it enables another qualitative and quantitative investigation method on grain-workpiece interface mechanism in an efficiency and effective manner. Based on previous efficacy verification of Third Wave AdvantEdgeTM, the FEM simulation is carried out to investigate the effect of grain wear on its micro-cutting performance. The simulation results provide an illustrative manner to interpret the phenomenon and mechanism, and the results can be used in the grinding process modeling in the future as well.
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: The residual stress on the ground surface of workpiece in high efficiency deep grinding (HEDG) has been investigated. It has been found that the mechanism in forming the ground surface residual stress in HEDG is much different to that in the conventional shallow cut grinding process. It is not a thermally dominant event as in most of the shallow cut grinding mode; it is instead driven by the combined effects of both the thermal and mechanical loadings. The compressive plastic deformation near the workpiece surface during grinding and the short contact time in the HEDG regime, makes it possible to generate compressive surface stresses even when the surface temperatures are above 700-800°C.
Abstract: With the rapid development of opto-electronics communications, optics, aerospace and other industries, ultra-precision aspheric glass lenses are widely used in middle/high-grade optical opponent because of its high resolution and imaging quality. To achieve ultra-precision molding pressing of micro-lens, ultra-precision mold must be fabricated firstly. In this paper, some key new technologies were proposed for fabricating ultra-precision mold of small-size aspheric optical lens. A method of finite element simulation was employed to predict mould pressing process of the glass lens for correcting molds and improving the formation efficiency. An ultra-precision inclined-axis grinding and error compensation technology was also used to improve form accuracy of micro lens mold.
Abstract: Experimental results of Ti-6-2-4-2S, Ti-6-4 and Ti-5-5-5-1-1 are detailed in this paper with conventional surface grinding using SiC abrasive under dry conditions. Measurements of grinding forces, surface topography and metallurgical structure of ground surface were taken to investigate the grinding mechanism of these materials. The results showed grinding force ratios to these materials were between 1.35 to 2.25 at all material remove rates, but the specific energy to Ti-5-5-5-1-1 and Ti-6-2-4-2S were little higher than Ti-6-4. Evaluation of ground surface topography indicated they were visually free of crack and burn. At the same grinding parameters, Ti-5-5-5-1-1 had the maximum depth of heat-affected zone because of its poor high temperature properties.
Abstract: Single-grain grinding test plays an important part in studying the high speed grinding mechanism of materials. In this paper, a new method and experiment system for high speed grinding test with single CBN grain are presented. In order to study the high speed grinding mechanism of TC4 alloy, the chips and grooves were obtained under different wheel speed and corresponding maximum undeformed chip thickness. Results showed that the effects of wheel speed and chip thickness on chip formation become obvious. The chips were characterized by crack and segment band feature like the cutting segmented chips of titanium alloy Ti6Al4V.
Abstract: Based on the single diamond grit scratching and normal grinding assisted with ELID (Electrolytic in Process Dressing), the surface/subsurface integrity of machined spectrosil 2000 and BK7 glasses under various material removal modes have been investigated. In Single diamond grit scratching tests, the scratching traces display four kinds of scratch characteristics according to different material removal modes. In the diamond normal grinding, the surface/subsurface integrity analysis shows BK7 glass has a better machinability than that of spectrosil 2000. Moreover, with the increasing ae(depth of cut), these two kinds of glasses had the opposite variation trends about the Ra values and the force ratio, which is attributed to various material removal modes. While contrasting these two kinds of optical glasses ground under the same ae parameters, the smaller grinding force and grinding force ratio (Fn/Ft), as well as the more stable force curves correspond to a better surface quality.