• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.1-7
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• 2004

This study investigated the effects of aging on the transformation behavior of $Ti-50.1at\%$ Ni alloy by means of differential scanning calorimetry. It was found that aging in the temperature range of $350^{\circ}C\~550^{\circ}C$ induced complex transformation behavior, involving the R-phase and multiple-stage martensitic transformation. Usually aged Ni-rich NiTi alloys undergo martensitic transformation on cooling from high temperatures in two step : B2 to R and then R to Bl9'(normal behavior). But under certain ageing conditions, the transformation can also occur in three or more step(unusual multiple step behavior). In the present study we use differential seaming calorimetry(DSC) for a systematic investigation of the evolution of transformation behavior with ageing temperature and time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1849-1855
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• 2003

Newly commercialized wireless capsule endoscope has many advantages compared to conventional push-type endoscopes. However, it is moved by the peristaltic waves. Therefore, it can not diagnose desired zones actively. In this paper, a locomotive mechanism for wireless capsule endoscope is proposed to increase the efficiency of endoscopy. We designed and fabricated a prototype using SMA springs and bio-mimetic clamping device. The hollow space in the prototype is allocated for further system integration of a camera module, a RF module and a battery. And the sequential control scheme is employed to improve the efficiency of its locomotion. To validate the performance of the locomotive mechanism, experiments on a silicone rubber pad and in vitro tests are carried out. The results of the experiments indicate that proposed mechanism is effective in harsh environments such as digestive organs of a human.

• Tribology and Lubricants
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• v.27 no.1
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• pp.7-12
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• 2011

Interest in advanced machining process such as AJM(abrasive jet machining) and CMP(chemical-mechanical polishing) using micro/nano-sized abrasives has been on the increasing demand due to wide use of super alloys, composites, semiconductor and ceramics, which are difficult to or cannot be processed by traditional machining methods. In this paper, the effects of pressure, wafer moving velocity and fluid viscosity were investigated by 2-dimensional finite element analysis method considering slurry fluid flow. From the investigation, it could be found that the simulation results quite corresponded well to the Preston's equation that describes pressure/velocity dependency on material removal. The result also revealed that the stress and corresponding material removal induced by the collision of particle may decrease under relatively high wafer moving speed due to the slurry flow resistance. In addition, the increase in slurry fluid viscosity causes the reduction of material removal rate. It should be noted that the viscosity effect can vary with the shape of abrasive particle.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.60-69
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• 1990

Plasma arc cutting is a fusion cutting process in which a gas-constricted arc is employed to produce a high-temperature, high-velocity plasma jet on the workpiece. This process provides some advantages such as increased cutting velocity, excellent working accuracy and the ability to cut special materials (widely used stainless steels and Al-alloys, for example), when compared with iconventional oxyfuel gas cutting. From the view point of price and reliability of the power source, plasma arc cutting has also some distinct advantages over laser beam cutting. High-speed machines with NC or CNC systems are needed for the plasma arc or laser beam cutting process, while for oxyfuel gas cutting, low-speed machines with copying templates or optical-shape tracking sensors can be applied. The low price and high flexibility of the microprocessor arc contributing more and more the application of CNC system in the plasma arc cutting process, as in other manufacturing fields. From these points of view, a microprocessor-based plasma arc cutting system was developed by using a reference-pulse system, and its performance was tested. The interpolating routines were programmed in the assembly language for saving the memory volume and improving the compouting speed, which has an intimate relationship with the available cutting velocity.

• Journal of Korea Technology Innovation Society
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• v.8 no.3
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• pp.1027-1059
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• 2005

The purpose of this paper is to analyze the dynamic characteristics of innovation sources such as scientific knowledges, processing technologies and user's needs in advanced metals technology. The journal articles data of four advanced materials are analyzed; amorphous metals, superplastic materials, shape memory alloys and aluminum-lithium alloy. Some regularities are found from the analysis of the four materials. The innovation proceeds through close interactions among the innovation sources. As the innovation proceeds, the relative importance of each source changes: scientific knowledge initiates the innovation and becomes the most important source in the first phase, then the processing technologies increase importance in the second phase, and then scientific knowledge, again, becomes the leading factor of innovation. Scientific knowledge and processing technology take turns leading the innovation. The impacts of users' needs to the innovation increase more and more as innovation proceeds. The results of analysis imply to the policy makers that emphasis of policy, and therefore the allocation of sources for innovation, should vary along the phases in the life cycle of advanced metals technology.

• Transactions on Electrical and Electronic Materials
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• v.13 no.1
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• pp.19-22
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• 2012

Transformation behavior of rapidly solidified Ti-47.3Ni (at%) alloy ribbons and thermal stability of the R phase in the ribbons were investigated by means of differential scanning calorimetry (DSC), X-ray diffraction, and transmission electron microscopy. Rapidly solidified Ti-47.3Ni alloy ribbons showed the two-stage B2-R-B19' martensitic transformation behavior. The B2-R transformation in the ribbons was observed even after annealing at 1,223 K, which was attributed to the fact that a specific orientation relationship between $Ti_2Ni$ and matrix in the ribbons is maintained after annealing at 1,223 K. The DSC peak temperature of the B2-R transformation ($T_R^*$) decreased with raising annealing temperature, which was attributed to the increased volume fraction of $Ti_2Ni$, thus causing an increased Ni content in the matrix.