Papers by Author: Jia Bin Lu

Abstract: Monolayer brazed diamond wheel were used to grind AlSiC composite with different volume fraction of SiC. The effects of diamond mesh size of the grinding wheels and the volume fraction of SiC in AlSiC composite on the surface integrity of ground AlSiC composite were investigated. It is found that the surface roughness of ground AlSiC composite with 20% SiC is increased with the reduction of diamond grit’s size because of the clogging of diamond wheel. With the increasing of the volume fraction of SiC, there are more fractured and cracked SiC particles on the ground surface of AlSiC composite. On the other hand, the finer diamond grits (70/80) induce the finer fractured SiC particles on the ground surface of AlSiC with 50% and 70% SiC.

Abstract: Chemical reaction rate of SiC wafer surface usually determines the material removal rate (MRR) in chemical mechanical polishing (CMP). In this paper, systemic experiments are carried out to discover the relationship between Fe catalyst with different forms or valence and chemical reaction rate based on Fenton reaction. Experimental results show that the MRR changes little using Fe powder or hydrogen peroxide (H₂O₂) alone, but the MRR of SiC will increase largely by adding them both that will produce Fenton reaction. The MRR continues to increase slightly when Fe²⁺ ions is employ as catalyst, but that is much lower when utilizing Fe³⁺ ions. Moreover, SiC wafer with a smaller surface roughness and better quality can be obtained when using Fe powder as catalyst in Fenton reaction. The results indicate that the Fenton reaction can effectively improve the polishing efficiency of SiC substrate and Fe powder is more suitable for polishing of SiC than ferrous or ferric salt in CMP based on Fenton reaction.

Abstract: Based on the principle of disc slitting process, a 3D model of the disc slitting process for galvanized sheet was established by using DEFORM-3D software, and the deformation, fracture and material effective stress of galvanized sheet were analyzed. The surface morphology of numerical simulation is in good agreement with the actual result. The curve of shearing force was obtained and well matched with the change rule of slitting process. Compared with the theoretical calculation result, the simulation result is reliable and can provide a reference for the calculation of shearing force.

Abstract: The growth of epitaxial layer of SiC wafer requires the surface of SiC substrate to reach an atomic scale accuracy. To solve the problems of low machining efficiency and low surface accuracy in the polishing process of SiC wafer, a novel ultra-precision machining method based on the synergistic effect of chemical reaction and flexible mechanical removal of the magnetorheological (MR) effect, the MR-chemical mechanical polishing (MRCMP) is proposed. In this technique, magnetic particles, abrasives and chemical additives are used as MR-chemical polishing fluid to form a cluster MR-effect flexible polishing platen under an applied magnetic field, and it is expected to realize an atomic scale ultra-smooth surface planarization with good controllability and high material removal rate by using the flexible polishing platen. Polishing experimental results of C surface of 6H-SiC crystal substrate indicate that an atomic scale zero-defect surface can be obtained. The surface roughness of C surface of SiC wafer decreased from 50.86nm to 0.42nm and the material removal rate was 98nm/min when SiC wafer was polished for 60 minutes.

Abstract: In order to remove the cutting marks on the cutting surface of 6H-SiC single crystal wafer, experiments were conducted to investigate the effect of the abrasive characteristics (types, grain size, concentration and mixed abrasives) on the lapping performance of 6H-SiC single crystal wafer, then the removal mechanism of the abrasive grains in the lapping process was studied. Results indicate that the abrasives with larger grain size and higher hardness can result in a higher material removal rate while the abrasives with smaller grain size and lower hardness can achieve a lower surface roughness value. When the concentration of the abrasives is 7.69 wt%, a good lapping effect was obtained. Lower surface roughness value Ra can be obtained with a high material removal rate by using certain proportion mixed abrasives. Selecting appropriate abrasives can obtain a high surface quality of 6H-SiC wafer with a high efficiency.

Abstract: Based on the analysis of the machining process of magnetorheological finishing with the tiny-grinding wheel cluster, the motion model of abrasive in the tiny-grinding wheel cluster was proposed to describe the motion trajectory and the dwell time of abrasive relative to the surface of workpiece. Then, the experiment was applied to study the effects of the motion trajectory and the dwell time on surface quality and machining efficiency of the workpiece. According to the analysis, a method to improve surface quality and machining efficiency in MRF with the tiny-grinding wheel cluster was presented.

Abstract: A new tiny-grinding wheel cluster polishing method based on the Magnetorheological (MR) effect is presented to polish optical glass in this paper and some process experiments were conducted to reveal the influence of magnetic field strength, the content of carbonyl iron in the MR fluid and the speed of polishing disc on the material removal rate and the surface roughness of the glass workpiece. The results indicate that when the external magnetic field is applied, the material removal rate of the workpiece improves rapidly but the surface roughness increases slightly. When the Magnetic field strength is 100 Gs and the content of carbonyl iron is 3.5%, the material removal rate improves by a factor of 16.8% compared with that of the conventional polishing methods with dissociative abrasive particles, while the surface roughness of the workpiece increases unobviously.

Abstract: The design and machining quality of mold core of luminaire reflector is the key to luminaire manufacturing. According to the structural characteristics of the mold core with axisymmetric uniform-distribution reflecting cells, the mathematical model with five-axis NC programming of this mold core was established. Based on five-axis CNC machine tools with dual rotary tables, then, the NC automatic programming calculation for this mold core was researched. Besides, a simple three-dimensional entity simulation was discussed. In this way, the three-dimensional entity simulation of automatic programming and processing in 5-axis NC machining of this mold core was realized.

Abstract: Experiments were conducted to polish optical glass with the magnetorheological (MR) effect-based tiny-grinding wheel cluster, and the influences of abrasive material, particle size and content on the material removal rate and surface roughness are investigated. The experimental results indicate that: the higher the hardness of abrasives, the higher the material removal rate, but the abrasives with lower hardness can obtain lower surface roughness. The better polishing quality of the workpiece can be obtained when the particle size of abrasives is similar to the particle size of magnetic particles. Moreover, the content of abrasives has an optimum value, and the material removal rate and the surface quality can not be improved further when the content of abrasives exceeds the optimum value. On the basis of above, the material removal model of the new planarization polishing technique is presented.

Abstract: Using the tiny-grinding wheel based on the synergistic effect of the electro-magneto- rheological (EMR) fluid, a novel method is presented to machine the three-dimensional (3D) microstructure of hard-brittle materials. Machining experiments of micro-groove were conducted to reveal the machining performances of the tiny-grinding wheel. Experimental results confirm the effectiveness and feasibility of the micro machining technique with the EMR effect-based tiny-grinding wheel. The shape of machined micro groove is found to be an inverted trapezoid, and the material removal mode of normal glass with the micro machining method is the plastic-removal mode. With the increase of the rotation speed of the tool, the material removal rate, width and depth of micro grooves increased first and decreased afterwards. The maximum removal rate, width and depth of micro groove occur at different speeds of the tool.