Advanced Materials Research Vol. 1027

Abstract: Diamond tools are fabricated by brazing and used to machine dental ceramics in this paper. The morphology, grinding ratio, wear and grinding force of the brazed tools are investigated in comparison with that of the electroplated ones. The results show that the brazed alloy forms a hill-like structure around the diamond grits, and the protrusion of the brazed diamond grits is higher than that of the electroplated one. The grinding ratio of the brazed diamond tool is higher than the electroplated one. Many fall-off diamond pits of the electroplated tool and only few micro-crack diamond grits of the brazed tool are observed after grinding, and the brazed one remains well process capability. The grinding force of the electroplated tool is larger than that of the brazed one.

Abstract: In this paper, according to the principle and the existing technology of ELID grinding, we use the existing lapping machine of Wenzhou Runsheng ceramic water valves factory as the experiment platform to develop an ELID lapping process system. Then utilizing ELID ultra-precision lapping technology to process alumina ceramic seals obtained a good effect. The roughness of processing samples reached about 15nm which was demanded by the enterprise, the efficiency increased 60% and the cost reduced 50%. On this basis, we designed an ELID lapping prototype. It laid a solid theoretical and practical basis for the production of ELID lapping machine in the future.

Abstract: Ultra-thin stainless steel sheet is likely to be the ideal substrate materials used for flexible display. In order to obtain ultra-thin stainless steel substrate with high accuracy, low surface roughness and without damage, the ultra-precision lapping and chemical mechanical polishing technology must be used. In this paper, the lapping paste for stainless steel has been designed using the orthogonal experiment method. According to the range analysis method, an optimal lapping paste had been obtained. Tests lapping the 304 stainless steel sheet with the optimal lapping paste have been done. The test results show that the MRR is about 240nm/min and the surface rough Ra is about 128 nm. This research results can provide theory support for ultra precision machining the stainless steel.

Abstract: In order to explore the new way to precision machining of the cylindrical, ELID precision mirror grinding technology are employed to precision ultra-precision grinding experiments. Given ELID precision mirror grinding technology has effectively solved the basis of many of the typical flat-precision machining difficult materials and efficient processing, through the conversion process equipment tools, and optimization of process parameters, obtained when the wheel speed in 16 ~ 20 m / s, when the grinding depth 10μm, cylindrical grinding state is best, which could obtain Ra0.025μm surface roughness of the machined surface.

Abstract: Based on molecular dynamics method, a nanoindentation simulation of the silicon crystal is built and the load-displacement curve is drawn. According to the load-displacement curve, the elastic-plastic transition of silicon crystal is analyzed. The results show that the critical point in the elastic-plastic transition is between 15 and 20 angstroms. In addition, different crystal planes of silicon crystal are loaded for five cycles respectively; the nanohardness is calculated and the nanohardness curve is obtained. The results show that after the first plastic deformation of the silicon crystal surface is occurred, the surface will have a higher hardness and a higher elasticity. Therefore, in the ultra precision machining, in order to reduce the occurrence of damage, the depth of the processing should be controlled in the range of elasticity. Moreover, the method of small quantities in high frequency can increase mechanical properties on the surface.

Abstract: The electrolytic in-process dressing (ELID) grinding technology was adopted for precision grinding experiments of volume fraction of 40% of SiCp/Al composites, obtaining the machined surface roughness of Ra0.030μm. Studying the forming mechanism of processed surface, analyzing several typical grinding surface defects, summarizing the grinding characteristics and removal mechanism of SiCp/Al composites.

Abstract: Silicon carbide ceramics with its excellent physical and mechanical properties have become the preferred material of space large diameter mirror. But because of its higher hardness, diamond wheel would appear some wear form and wear rate in the mechanical processing process, wear form is an important factor to effect surface and subsurface quality, wear rate effects the surface shape accuracy, so the research on the laws of wear rate of grinding wheel has an important role in grinding. But, because of the particularity of wheel structure, wheel wear form and wear rate changes with time going, which limits the wheel wear research. By the grinding process experiment, the author found the relationship between diamond grinding block wear rate and wheel feeding, and got the laws of wear rate with time. With the laws of wear rate, we can predict the surface accuracy and guide the compensation of wheel feeding.

Abstract: The surface residual stress and integrity of workpiece have significant effects on the precision, the reliability and the fatigue life of the mechanical products. Since the most final surface integrity of workpiece depends on the grinding process mainly in engineering, this paper analyzed the surface residual stress of ground surface through the simulation works. Based on the finite element model and the thermal mechanical coupling field of the surface grinding for 45 steel was simulated and analyzed. The distribution of the residual stress and the effects of grinding parameters on residual stress were discussed. In addition, the measures for improving the residual stress in ground surface were put forward.

Abstract: Residual stress of ceramics ground surface was detected by the X-ray instrument, and it was analyzed in present paper. The experimental results show that the content of metastable tetragonal phase of ZrO₂ and grinding stress are the primary factors which induce martensitic transformation on ZrO₂ ceramics ground surface; during grinding the deeper the grinding depth is, and the bigger abrasive grain size is, the grinding stress in material matrix is larger. After analyzing the influence of grinding parameters on residual stress, it can be found that martensitic transformation can prompt the compressive residual stress to some extent, so as to improve the quality of ground surface.

Abstract: In order to clarify the material removal characteristics of Al₂O₃ engineering ceramics in ultrasonic aided high efficiency lapping, a series of ultrasonic and conventional lapping contrast experiments were carried out on precision lathe with self-made ultrasonic lapping device. The research results show that the value of material removal rate in ultrasonic aided lapping is about 2~4 times that in conventional lapping, especially in ultrasonic axial lapping. In ultrasonic aided lapping, the better removal characteristics can not be obtained by adopting too high or too low lapping parameters, and there are optimum lapping parameters from which a higher material removal rate value can be achieved.