• Journal of Powder Materials
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• v.4 no.3
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• pp.188-195
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• 1997

In most of sintered metal powder compacts, the sintered density distribution is controlled to be as high and uniform as possible to ensure the required mechanical properties. In general, the density distribution in the compacts is not uniform and not easy to measure. In the present study, a method for measuring the density distribution was developed, based on the indentation force equation by which the hardness and the relative density were related. The indentation force equation, expressed as a function of strength constant, workhardening coefficient and relative density, was obtained by finite element analysis of rigid-ball indentation on sintered powder metal compacts. The present method was verified by comparing the predicted density distribution in the sintered Fe-0.5%C-2%Cu compacts with that obtained by experiments, in which the density distribution was directly measured by machining the compacts from the outer surface progressively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.75-84
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• 2003

In this paper, a new nano/micro-mechanical processing test machine was developed. This new test machine, which is based on the principle of the scanning force controlled probe microscope, can realize nano/micro-mechanical machining and in-process profile measurement. Experimental results of nano/micro indentation and scratching show that the controllable cutting depth of the test machine can be controlled by PZT actuator. Profile measurement of the machined surface has also been performed by using the test machine and a conventional AFM(Atomic Force Microscopy). A good agreement of the two measurement results have been achieved.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.163-170
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• 2004

Atomic force microscope (AFM) techniques are increasingly used fur tribological studies of engineering surfaces at scales ranging from atomic and molecular to micro-scale. Recently, AFM with suitable tips is being used for nano fabrication/nano machining purposes. In this paper, machining characteristics of silicon were investigated by nano indentation and nano scratch. Nano-scale material removal mechanisms are studied and the Taguchi method was introduced to acquire optimum parameters for nano machining. Also, Acoustic Emission (AR) is used for the monitoring of nano machining.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.19-24
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• 1999

The influences of TiB2 additions to the β-sialon on mechanical propeties and electrical discharge machinability were investigated. Samples were prepared by adding 15, 30 and 45 vol.% TiB2 particles as a second phase to a β-sialon matrix. The β-sialon-TiB2 composites were sintered by hot pressing in a nitrogen atmosphere at 1800℃ with pressure of 30 MPa. The fracture toughness of the composites was increased with TiB2 content except 45 vol.% TiB2 composite. The crack propagation and crack deflection were observed with a SEM for etched samples after vicker's indentation. The composites containing more than 30 vol.% TiB3 had resistivity lower than 10-3 Ω㎝. The electrical discharge machining (EDM) of composited was conducted with two kind of machines such as die-sinker and wire cutter. The machinability was evaluated with the cutting rate surface roughness after machining.

• Design & Manufacturing
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• v.13 no.4
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• pp.40-44
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• 2019

The light diffusion component spreads the light from one point evenly over a large area. Various types of light diffusion parts such as films and lenses are applied in the high-tech industries such as LCD display devices, lighting devices, and solar energy generation. Among these, a diffuser sheet (Diffuser Sheet) has a function to uniformly distribute the light, and various studies have been conducted to improve its function. The shape of the conventional light diffusion pattern is mainly made of a dot or hemispherical shape. In this study, a rectangular cone-shaped structure having a light diffusion function and an advantage of controlling the angle of refraction of light was fabricated by using a solenoid indentation process. The change in shape of the indentation structure was analyzed.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.777-781
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• 2004

This paper presents a force/displacement sensing system to measure penetration depths and machining forces during pattering operation. This sensing system consists of a leaf spring mechanism and a capacitive sensor, which is mounted on a PZT driven in-feed motion stage with 1nm resolution. The sample is moved by a xy scanning motion stage with 5nm resolution. The constructed system was applied to nano indentation experiments, and the load-displacement curves of silicon(111) and aluminum were obtained. Then, the indentation samples were measured by AFM. Experimental results demonstrated that the developed system has the ability of preforming force/depth sensing indentations

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.7-15
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• 1996

A Manufacturing process of the power steering worm blank is analyzed by FEM aimulation. The process includes mainly three operations such as indentation, extrusion, and upsetting, which was designed bya forming equipment expert. The results of simulation are summarized in terms of load-stroke relationships, die pressure distributions, effective strain distribution, and deforming patterns for each forming operation. Also, Efforts are focused to get the reason that the tool expert designed the forming process in three operations. The results of the simulation are to be useful for the next advanced process planning in terms of good dimesional accuracy, savings in material and machining, no deforaming defects and imporvements in mechanical properties.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.182-185
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• 2005

Indentation pattern and line pattern were machined on borosilicate(Pyrex 7740 glass) surface using the combination of mechanical machining by $Nanoi-indenter\circledR$ XP and HF wet etching, and a etch-mask effect of the affected layer of the nano-scratched and indented Pyrex 7740 glass surface was investigated. In this study, effects of indentation and scratch process with etching time on the morphologies of the indented and scratched surfaces after isotropic etching were investigated from an angle of deformation energies.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.50-55
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• 2003

Atomic force microscope(AFM) techniques are increasingly used for tribological studies of engineering surfaces at scales ranging from atomic and molecular to microscale. AFM with suitable tips is being used for nanofabrication nanomachining purposes. In this paper, machining characteristics of silicon have been investigated by nano indentation and nano scratch. Mechanisms of material removal on the microscale are studied and the Taguchi method is introduced to acquire optimum parameters for nanomachining. This work shows effectiveness of the Taguchi method in nanomachining. Also, Acoustic Emission(AE) is introduced for the monitoring of nanomachining.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1507-1510
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• 2005

This study was carried out as a part of the research on the development of a maskless and electroless process for fabricating metal micro/nanostructures by using a nanoindenter and an electroless deposition technique. $2-\mu{m}-deep$ indentation tests on Ni and Cu samples were performed. The elastic recovery of the Ni and Cu was 9.30% and 9.53% of the maximum penetration depth, respectively. The hardness and the elastic modulus were 1.56 GPa and 120 GPa for Ni and 1.49 GPa and 100 GPa for Cu. The effect of single-point diamond machining conditions such as the Berkovich tip orientation (0, 45, and $90^{\circ}$) and the normal load (0.1, 0.3, 0.5, 1, 3, and 5 mN), on both the deformation behavior and the morphology of cutting traces (such as width and depth) was investigated by constant-load scratch tests. The tip orientation had a significant influence on the coefficient of friction, which varied from 0.52-0.66 for Ni and from 0.46-0.61 for Cu. The crisscross-pattern sample showed that the tip orientation strongly affects the surface quality of the machined area during scratching. A selective deposition of Cu at the pit-like defect on a p-type Si(111) surface was also investigated. Preferential deposition of the Cu occurred at the surface defect sites of silicon wafers, indicating that those defect sites act as active sites for the deposition reaction. The shape of the Cu-deposited area was almost the same as that of the residual stress field.