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.
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.
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.
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.
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.
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.
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 , but the maximum appears in the
direction . 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 , and 11.2nm to the direction .
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.
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.
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.