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ABSTRACT: The cutting temperature plays an important role in micro-scale cutting process due to the fact that the dimension of the micro-cutter
is small and the value of micro-cutter wear is sensitive to temperature. In this paper, the temperature distribution of the
micro-cutter in the micro-end-milling process has been investigated by numerical simulations and experimental approach. Micro-end-milling
processes are modeled by the three-dimensional finite element method coupling thermal–mechanical effects. The micro-cutter
cutting temperature distribution, the effect of various tool edge radii on cutting force, and the effective stress during
micro-end-milling of aluminum alloy Al2024-T6 using a tungsten-carbide micro-cutter are investigated on. The simulation results
show that with increase of tool edge radius the cutting force increases, while the effective stress and mean cutting temperature
decreases slightly. In increasing the tool edge radius, the maximum effective stress and cutting temperature region of the
micro-cutter occur from the rake face to the corner on the tool edge and the flank face. The tool edge radius has been found
to be the major factor affecting micro-cutter temperature distribution. The experimental verification of the simulation model
is carried out on a micro-end-milling process of aluminum alloy 2024-T6 with a high-precision infrared camera. The influence
of tool edge radius on cutting temperature distribution was verified in experiments.
KeywordsMicro-cutter–Temperature distribution–Tool edge radius–FEM–Infrared imaging
International Journal of Advanced Manufacturing Technology 04/2012; 52(9):905-912. · 1.10 Impact Factor
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ABSTRACT: Molecular dynamics simulations were performed to investigate the relaxed structures and surface energies of perfect and pit anatase TiO2 surfaces. It is shown that the slab containing more than two unit-cell layers away from the fixed layer expresses the surface characteristics of perfect anatase TiO2 (1 0 1) and (1 0 0) surfaces well, while the slab containing more than one unit-cell layer away from the fixed layer expresses the surface characteristics of the (0 0 1) surface well. Their surface energies follow the sequence (0 0 1) < (1 0 1) < (1 0 0). Simulation results also indicate that the pit edges expose many undercoordinated atoms, and the more highly undercoordinated atoms exhibit the larger displacement vectors. Moreover, the surface energy of the pit surface is higher than that of the perfect surface. The surface energies of pit anatase (1 0 1) surfaces are linearly related to the pit sizes along the [ ] and [0 1 0] directions, and the changes in their surface energies are less than 0.05 J m−2, while the surface energies increase sharply with the increase in pit depth within 1 nm. Therefore, for anatase (1 0 1) surface, in order to obtain a higher surface energy, one may increase the pit sizes, particularly along the [1 0 1] direction.
Modelling and Simulation in Materials Science and Engineering 08/2010; 18(7):075002. · 2.30 Impact Factor
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ABSTRACT: Molecular dynamics simulations were carried out to investigate the adsorption mechanisms of tripeptide Arg-Gly-Asp (RGD) on the nanotopography and perfect rutile TiO(2) (110) surfaces in aqueous solution. It is shown that the amino groups (NH(2) and NH3+) and carboxyl group (COO(-)) of RGD are the main groups bonding to hydrophilic TiO(2) surface by electrostatic and van der Waals interactions. It is also demonstrated that RGD adsorbs much more rapidly and stably on the nanotopography surface than the perfect surface. On the hydrophilic TiO(2) surface, the water molecules occupy the adsorption sites to form hydration layers, which have a significant influence on RGD adsorption. On the perfect surface, since the fivefold titanium atom is surrounded by surface bridging oxygen atoms above it and has a water molecule bonding to it, the amino group NH(2) is the adsorption group. However, because the pit surface exposes more adsorption sites and has higher surface energy, RGD can adsorb rapidly on the surfaces by amino groups NH(2) and NH3+, and the carboxyl group COO(-) may edge out the adsorbed water molecules and bond to the surface titanium atom. Moreover, the surface with higher surface energy has more adsorption energy of RGD.
Acta biomaterialia 08/2009; 6(2):684-94. · 3.98 Impact Factor
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ABSTRACT: Brenner-LJ potential is adopted to describe the interactivity between diamond and C36 cluster, and the deposition mechanism of multi-C36 on the diamond surface is researched by molecular dynamics simulation. Through simulative experiments the incident energy, incident point, incident posture, incident angle and other factors are analyzed. Studies discover that the minimal deposition threshold is 20 eV and the maximum is 60 eV with the different incident point locations and incident postures of C36 clusters. When the incident angle is not over 60°, C36 may roll or slip to the region of smaller bonding energy and then bond. So the bonding probability is raised. Research results show that when incident angle is between 0° and 20° and incident energy range is from 30 eV to 60 eV, it is the optimal condition of single C36 cluster deposition on diamond (100) crystal plane.
Chinese Journal of Chemical Physics - CHIN J CHEM PHYS. 01/2007; 20(6):637-642.
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ABSTRACT: An integrated MD simulation of scratching and shearing with one specimen is conducted to analyze the nanomachining mechanism and mechanics properties of nanostructures. Simulation results indicate that during scratching the onset and propagation of dislocations depend on the scratch depths; during shearing, the yielding stress of a small-size nanostructure is more sensitive to nanomachining imperfection and residual defects. Dislocations nucleate first near the burr in a scratched specimen. In an ideal nanostructure or a nanostructure with shallow scratched groove, the distribution of stress is generally lower and flatter. As the depth of groove increases, high stresses transit from the corner to either end of groove, especially near the burr or around the location of tool withdraw. During the deformation of nanostructures, shear stress plays a leading role in the elastic stage, and both normal stress gradients and shear stress determine the onset and evolvement of defects in the plastic stage. When the ratio of the depth of groove to the height of specimen is up to one third, the scratched groove determines the breakpoint of a nanostructure. The fluctuation of shear stress during the plastic deformation of specimen is caused by the competition between atoms which form new atomic planes and slip on different slip planes.
Computational Materials Science. 43(4):1130-1140.
