Advances in Abrasive Technology XI

Abstract: A novel method is reported for predicting the distribution of normal and tangential grinding forces in wheel and workpiece contact zone or along their contact arc. This work was motivated by the need to obtain the maximum force acting on individual active abrasive grains for establishing the probability of grain fracture and pullouts due to this force. Horizontal and vertical forces measured in the transient cut-in or cut-out stage of a grinding pass are utilized in this method to predict the horizontal and vertical forces acting on each portion of the contact arc. And then these forces are subsequently converted to tangential and normal forces per unit length along the arc to obtain the force distribution. To illustrate the application of this method, forces measured in the transient cut-out stage in the grinding of tungsten carbide with electroplated diamond wheels were employed to predict the force distribution, which was further applied to predicting the transient grinding power at the cut-in and cut-out stages. The predicted power was found to match very well with the measured power.

Abstract: Single crystal MgO can be used as the substrates to deposit HTS films. The subsurface damage (SSD) generated in processing has great effect on the strength and performance of the substrates. However, the characteristics of MgO SSD and its formation mechanism have not been understood fully. In this paper, the surface and subsurface damage caused by saw cutting, rough lapping and fine lapping of MgO substrates were studied by cross-section of microscopy and SEM. The formation mechanism was discussed; and a SSD model was presented.

Abstract: Silicon wafer thinning process is meeting great challenges to fulfill requirements of ultra-thin IGBT for automotive applications. Chemo-mechanical grinding (CMG) process is potentially emerging stress relief thinning process which combines the advantages of fixed abrasive machining and chemical mechanical polishing (CMP). A major issue in CMG of Si wafers is the relatively low material removal rate (MRR). This paper studies the influence of the wheel specifications and grinding conditions on the MRR of CMG. Two sets of three-factor two-level full factorial designs of experiment (DOE)[1] are employed to reveal the main effects and interacted effects of CMG wheel specifications and grinding parameters on MRR. The optimal combination scenarios for improving MRR of CMG are analysized and obtained. By use of the optimal CMG wheel and grinding parameters, the MRR of more than 60nm/min is achieved.

Abstract: Ceramics has many advantages that cannot be substituted by metals, but its machining induced defects, such as crack and crater, are the obstacle of using ceramics in engineering. Thus, the further studies on the materials removal mechanism of ceramics should be done. As known, the cutting theory of metals is very successful and it is helpful to understand the material removal mechanism of ceramics. Through doing comparative experiments, the material removal mechanism of ceramics may be more deeply ascertained. Four types of material, such as ZrO2, SiC, STAVAX and SKD11, were ground by ELID (ELectrolytic In-process Dressing) method in this study. The grinding forces, roughness and topography of the ground surface were investigated. On the basis of this experiment, the difference of material removal mechanism between ceramics and steels was explained.

Abstract: Aiming at solving the problems of wheel loading in dry grinding of Carbon/Epoxy composite materials, a novel electroplated grinding wheel with controlled abrasive cluster was developed, in which the diameter of clusters is in Φ0.2 mm to Φ1.0 mm and the interspace between them is about 0.5 mm to 1.0 mm. A conventional electroplated grinding wheel with abrasive grains distributed randomly was fabricated in the same way. The comparison experiments involving C/E composite were conducted on a vertical spindle grinder with the novel and conventional grinding wheels. The results show that the grinding forces of novel wheel developed is more lower though little larger surface roughness, and the wheel loading phenomenon is markedly decreased compared with conventional electroplated wheel.

Abstract: The elastic and/or plastic behaviors of glass quartz, the most popular optical material and a hard and brittle material, were studied experimentally from two points of view; static mode and dynamic mode. The static behaviors were investigated by a nanoindentation test and the dynamic behaviors were investigated by a single-point fly cutting (SPFC) test. In the experiments, copper was selected as a material representing soft and ductile materials. From the experiments it was found that the plastic deformation ratio of glass quartz is smaller than that of copper depending on the SPFC conditions, and the area coefficient of the pile-up has the same tendency for both glass quartz and copper.

Abstract: A 3D profiler based on scanning white light interferometry with a lateral sampling interval of 0.11μm was introduced to measure the surface topography of a #3000 diamond grinding wheel, and a large sampling area could be achieved by its stitching capability without compromising its lateral or vertical resolution. The protrusion height distribution of diamond grains and the static effective grain density of the grinding wheel were derived, and the wheel chatter and the deformation of the wheel were analyzed as well. The study shows that the grain protrusion height obeys an approximate normal distribution, the static effective grain density is much lower than the theoretical density, and only a small number of diamond grains are effective in the grinding process with fine diamond grinding wheel. There exists waviness on the grinding wheel surface parallel with the wheel cutting direction. The cutting surface of the grinding wheel is not flat but umbilicate, which indicates that the elastic deformation at the wheel edges is much larger than in the center region.