Advances in Abrasive Technology IX

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Authors: Li Bo Zhou, Makoto Yamaguchi, Jun Shimizu, Hiroshi Eda
Abstract: In this paper, the surface and subsurface of silicon wafers ground by different wheels have been studied. In the conventional grinding with diamond wheels, it is shown from the top that the subsurface of wafer consists of amorphous Si, followed by a thin damaged layer, strained crystal with a large compressive residue stress, and then the bulk material in single crystal. In a severe condition which causes grinding burn, part of amorphous Si is re-crystallized to form a poly-crystal Si, and part of amorphous Si possibly reacts with oxygen to form SiO2. This phenomenon becomes more pronounced in the backgrinding process with a fine grit diamond wheel when the conditions are improperly selected. In order to obtain a defect-free crystal Si structure in grinding, authors have proposed a new chemo-mechanical grinding (CMG) process which enables to remove Si from wafer but with no structure transformation induced to its surface.
Authors: H. Okabe, T. Tsumura, Jun Shimizu, Li Bo Zhou, Hiroshi Eda
Abstract: This study aims to clarify the interaction between Si wafer and individual diamond abrasives in grinding at nanometer level and to estimate the grinding conditions for minimizing the surface defect. This paper reports on the results obtained through nano-scratching experiments in vacuum by an atomic force microscope (AFM) and simulations by using the molecular dynamics method by applying Tersoff potential for Si-Si atomic interaction under room and high temperature, respectively, to examine the influence of the grinding heat on the materials removal process. As a result, it was proven that the scratch groove under high temperature becomes deeper than that under room temperature from the experiments, and it was also observed that the formation of the amorphous phase around the scratch groove under high temperature becomes a little bit larger than that under room temperature from the simulations.
Authors: Han Huang, Rudy Irwan, Tsunemoto Kuriyagawa
Abstract: Nanoindentation was used to study the deformation and removal mechanisms of cemented tungsten carbide. It was found that the microstructure of the material has significant influences on its mechanical properties, which determines the critical conditions for damage-free nanogrinding. The results also indicated that when material removal events occur at nanometric scale, such influences should be taken into account for gaining the full potential of nanogrinding.
Authors: Choung Lii Chao, Wen Chen Chou, Chung Woei Chao, Chao Chang Arthur Chen
Abstract: Rotary ultrasonic machining (RUM) is considered to be a very effective and relatively accurate way to drill deep holes in brittle materials. Although brittle fracture (micro chipping) is the dominant material removal mechanism utilized by the RUM process, poor surface roughness and deep penetrated cracks are the consequence if the machining parameters are not properly controlled. To ensure the quality of the generated surface and to improve the process efficiency, efforts have been made in this study to correlate the material removal mechanisms, surface integrity and tool wear involved in the RUM process. Diamond-impregnated tools were used in the experiment and the ultrasonic vibration frequency was kept at 20 kHz. Three major material removal modes namely, impact mode, grinding mode and erosion mode were found to be the dominant removal processes at the tool tip, around the diamond wheel and around the steel sleeve respectively. It was also found that, during the grinding/erosion processes, the bonding material of the wheel was first eroded away and left big part of diamond grits well-exposed. Pull-out and/or fracture are normally the consequence of these exposed diamond grits due to the lack of support and protection.
Authors: Ji Wang Yan, Yu Feng Fan, Nobuhito Yoshihara, Tsunemoto Kuriyagawa, Shoji Yokoyama
Abstract: This paper deals with the mechanism of surface heterogeneity due to crystallographic anisotropy effects in diamond turning of single-crystalline germanium. A microplasticity-based numerical simulation model was proposed, in which the effects of tool geometry and machining conditions can be involved. Two coefficients were introduced to compensate the Schmid factors of two different types of symmetrical slip systems. Simulation of ductile machinability was conducted on two crystallographic planes (100) and (111), and the simulation results were consistent with the experimental results. It was indicated that the simulation model can be used to predict the brittle-ductile boundary change with machining conditions and crystal orientations of germanium.
Authors: Bing Zhang, Masato Yoshioka
Abstract: A three dimensional finite element model for Vickers indentations on brittle materials is presented in order to analyze the stress distribution. The objective of this paper is to study when and where cracks are most likely to initiate and propagate in the indentation cycle based on the analyzed stresses. Therefore the time-dependent stresses around and below the surface of the contact area during the indentation cycle, especially at the end of loading and at the beginning of unloading phase are investigated in detail. The analytical results are shown to be in good agreement and verified with the experimental results.
Authors: Jing He Wang, Ming Jun Chen, Shen Dong, H.X. Wang, J.H. Zhang, Wen Jun Zong
Abstract: In this paper, mechanical characteristics of KDP crystal anisotropy are analysed theoretically. Vickers indentation experiments are adopted to validate the variation rule of hardness and fracture toughness in different orientation of KDP crystal plane (100), and a model to calculate critical cutting thickness of brittle-ductile transition is proposed for the KDP crystals. The result shows that, on the crystal plane (100), the minimum value of critical cutting thickness of KDP crystal in brittle-ductile transition appears in the direction [110], but the maximum appears in the direction [010]. Finally, the ultra-precision machining of KDP crystal is performed, and the results agree well with the theoretical conclusions. Super-smooth surface with a roughness RMS of 6.6nm is reached as machined in the crystal direction [010], and 11.2nm to the direction [110].
Authors: Dong Jiang Wu, Juan Zhuang, Xu Yue Wang, Ren Ke Kang, Fu Ling Zhao
Abstract: We have developed the laser nanoprocessing technique by the integration of the fs laser and near-field scanning microscopy (NSOM). The second harmonic femtosecond laser working in the optical near-field with the assistance of NSOM equipment was applied to expose the photosensitive polymer material. The nanopatterns with feature size smaller than the laser wavelength can be fabricated. The optical diffraction limitation is therefore broken through by the near-field nanoprocessing. It was found in our experiment that the nanofabrication feature size depends strongly on the gap between the fiber probe tip and the substrate surface, as well as the laser coupling efficiency. The approach offers the advantages of high precision, speed and selectivity in nanopatterning, and is promising to be used in data storage device manufacture for higher density recording.
Authors: Ai Bing Yu, Yao Chen, Da Wei Jia, Xin Li Tian
Abstract: Mathematical evaluation model for ceramic grindability was presented based on principal components analysis (PCA) method. Sample matrix was constituted with influence factors of ceramic grindability. Principal components and weight vectors were determined through calculation of eigenvalues and eigenvectors of correlation matrix, which was deduced from sample matrix. Comprehensive values could be obtained through eigenvectors and weights vectors. Seven ceramics were selected as evaluation example. Material property parameters including hardness, fracture toughness, Young’s modulus and bending strength were selected as influence factors of ceramic grindability.According to the comprehensive evaluation values, grindability rank of seven materials from better to worse was B4C, sintering SiC, high-purity Al2O3, hot-pressed SiC, sintering Si3N4, hot-pressed Si3N4 and Y-TZP. Moreover, the determination of weight vectors could offer reference for other comprehensive evaluation methods. Research results suggest that PCA is a reasonable and available method to determine the rank of ceramic grindability.
Authors: Ming Jun Chen, Jing He Wang, X.M. Chen, Ying Chun Liang
Abstract: In order to study mechanical property with different crystal-plane and different crystal orientation of the crystal KDP, nano-indentation experiments are first done. The mechanical properties of crystal KDP, such as elastic modulus, yielding stress, are obtained from the analysis of the experimental curve. To obtatin the stress-strain curves of crystal KDP, by using the spherical tip can get characteristic of continuous strain, the spherical indentation experiments is proposed firstly and carried out. According to obtained parameters, A finite element cutting model of crystal KDP is established. The cutting process of crystal KDP is simulated by the model, and the influence of rake angle and depth of cut on chip and surface quality is studied. The theory shows that when the cutter’s rake angle is in the range of -40° to -45°, an perfect super-smooth KDP crystal surface will be obtained. Finaly, the experiments is carried out on special ultra-precision machine tool for crystal KDP by ourself devoloping. Experiment results show that when the cutter’s rake angle is about -45°, an super-smooth surface (rms: 6.521nm and Ra: 5.151nm )is obtained on the plane (001), and this experiment certified correctness of theory analysis.

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