• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.235-238
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• 2009

This paper describes the mechanical properties of poly (Polycrystalline) 3C-SiC thin films with $N_2$ in-situ doping. In this work, the poly 3C-SiC film was deposited by APCVD (Atmospheric Pressure Chemical Vapor Deposition) method using single-precursor HMDS (Hexamethyildisilane: $Si_2(CH_3)_6)$ at $1200^{\circ}C$. The mechanical properties of doped poly 3C-SiC thin films were measured by nono-indentation according to the various $N_2$ flow rate. In the case of 0 sccm $N_2$ flow rate, Young's Modulus and hardness were obtained as 285 GPa and 35 GPa, respectively. Young's Modulus and hardness were decreased according to increase of $N_2$ flow rate. The crystallinity and surface roughness was also measured by XRD (X-Ray Diffraction) and AFM (Atomic Force Microscopy), respectively.

• 소성∙가공
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• 제6권6호
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• pp.508-516
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• 1997

Forging process on sintered powder metals has been applied to produce automotive parts which require a high level of strength. In those parts, the measurement of relative density is very important because a low relative density density causes deterioration of strength. In the present study, an indentation force equation was proposed by which the result obtained from the hardness measurement is used to evaluate the relative density. This equation was applied to the prediction of the relative density in cylindrical specimens which were first sintered and then forged at the room temperature and at an elevated temperature. The experimental results were compared with predictions with and without consideration of the workhardening effect on the powder.

• 한국세라믹학회지
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• 제43권8호
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• pp.498-503
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• 2006

A gas turbine blade with thermal barrier ceramic coating is operated at high temperature to increase engine efficiency. Recently, thermal barrier characteristics have been improved by advanced coating technology through microstructure control and increase of adhesion force of the coating layer. More advanced coating materials, rare earth zircon ate ceramics have been studied for replacing YSZ coatings as thermal barrier coatings. In this study, $La_2O_3,\;HfO_2,\;CeO_2,\;Gd_2O_3$ and pure or yttria stabilized zirconia were prepared. Microstructure analysis and the evaluation of mechanical properties such as Hertzian indentation and hardness test were performed.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.9-12
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• 2004

Presented is a preliminary design concept of the carbon-glass hybrid composite rebars for the application in the construction field. A glass fiber rod with indentation is used for the core of the rebar. Carbon fibers are placed over the glass core by pultrusion. To increase the mechanical locking force and bonding surface, carbon filament windings are added in the hoop direction over the carbon face. Finite element analysis and test were conducted to evaluate the effective stiffness and strength of the rods. The results show that the effective axial stiffness of the rebar with indentation are about $50\%$ of the straight rebar.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.410-415
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• 2004

Molecular dynamics simulations of nanoimprint lithography in which a stamp with patterns is pressed onto amorphous poly-(methylmethacrylate) (PMMA) surface are performed to study the deformation of polymer. Force fields including bond, angle, torsion, inversion, van der Waals and electrostatic potential are used to describe the intermolecular and intramolecular force of PMMA molecules and stamp. Periodic boundary condition is used in horizontal direction and $Nos\acute{e}$-Hoover thermostat is used to control the system temperature. As the simulation results, the adhesion forces between stamp and polymer are calculated and the mechanism of deformation are investigated. The effects of the adhesion force and friction force on the polymer deformation are also studied to analyze the pattern transfer in nanoimprint lithography. The mechanism of polymer deformation is investigated by means of inspecting the indentation process, molecular configurational properties, and molecular configurational energies.

• Journal of Welding and Joining
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• 제24권6호
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• pp.13-20
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• 2006

Resistance spot welding is widely used for joining sheet metals in the automotive manufacturing process. Recently, servo-gun is used to increase the productivity and precise control the acting force. However, force control mechanisms have not been investigated with servo-guns until now. In this paper, it is proved that servo-motor current is proportional to torque and by experiment, experimental equation between servo-motor current and electrode force was derived. Algorithm for feedback control of electrode force was suggested using current measurement. In addition, applying soft touch method to this system the impact between electrode and specimen, which is the problem of air gun, could be reduced. Indentation made the force decrease in holding time of resistance spot welding. In order to overcome this problem, force compensation using the servo gun was used and it improved weld strength in good welding current range.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.144-150
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• 2007

In this paper, the low velocity response of four different sandwich panels with metal and laminate composite facesheets has been investigated by conducting drop-weight impact tests using an instrumented falling-weight impact tower. Square samples of 100mm sides were subjected low-velocity impact loading using an instrumented testing machine at six energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for four different types of sandwich panels. The impact test results show that sandwich panel with composite laminate facesheet could not observe damage mode of a permanent visible indentation after impact and has a good impact damage resistance in comparison with sandwich panel with metal aluminum facesheet.

• 대한기계학회논문집A
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• 제31권8호
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• pp.855-861
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• 2007

Haptic rendering is a process providing force feedback during interactions between a user and a virtual object. This paper presents a real-time haptic rendering technique for deformable objects based on visual information of intervention between a tool and a real object in a remote place. A user can feel the artificial reaction force through a haptic device in real-time when a slave system exerts manipulation tasks on a deformable object. The models of the deformable object and the manipulator are created from the captured image obtained with a CCD camera and the recognition of objects is achieved using image processing techniques. The force at a rate of 1 kHz for stable haptic interaction is deduced using extrapolation of forces at a low update rate. The rendering algorithm developed was tested and validated on a test platform consisting of a one-dimensional indentation device and an off-the shelf force feedback device. This software system can be used in a cellular manipulation system providing artificial force feedback to enhance a success rate of operations.

• 한국진공학회지
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• 제19권5호
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• pp.360-364
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• 2010

나노 소재의 물성을 측정하기 위하여 대부분의 연구 그룹에서는 크게 두 가지 분석 기법인 분광학을 이용한 분석과 나노트라이볼로지를 이용한 분석을 사용하고 있다. 분광학을 이용한 분석에는 NMR (Nuclear Magnetic Resonance), IR (Infrared Spectroscopy), Raman 등이 대표적이라 할 수 있고, 나노트라이볼로지를 이용한 분석에는 AFM (Atomic Force Micro-Scope), EFM (Electrostatic Force Microscope), KFM (Kelvin Force Microscope), Nanoindenter 등의 탐침을 이용한 측정 기법이 대표적이다. Nanoindenter는 물질의 탄성 및 경도를 측정 할 수 있으며 이를 통해 물질의 특성을 연구 하는 데에 사용된다. 그러나 이런 Nanoindenter의 압입 실험에서 압입 조건 등의 통제 변수가 다르면 그 결과 값도 바뀌는 것을 볼 수 있는데 본 실험에서는 이런 압입 조건 중 Load - Hold - Unload force의 속도 및 시간을 변화시켜 물질의 탄성계수와 경도가 어떠한 차이를 가지는지 연구하였다.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1202-1208
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• 2009

An inverse finite element (FE) model parameter estimation algorithm can be used to characterize mechanical properties of biological tissues. Using this algorithm, we can consider the influence of material nonlinearity, contact mechanics, complex boundary conditions, and geometrical constraints in the modeling. In this study, biomechanical experiments on macro and micro samples are conducted and characterized with the developed algorithm. Macro scale experiments were performed to measure the force response of porcine livers against mechanical loadings using one-dimensional indentation device. The force response of the human liver cancer cells was also measured by the atomic force microscope (AFM). The mechanical behavior of porcine livers (macro) and human liver cancer cells (micro) were characterized with the algorithm via hyperelastic and linear viscoelastic models. The developed models are suitable for computing accurate reaction force on tools and deformation of biomechanical tissues.