• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.83-88
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• 1993

Recently, the analysis of microcutting with submicrometer depth of cut is tried to get a more high quality surface product, but to get a valuable result another method instead of conventional finite element method must be considered because finite elment method is impossible for a very small focused region and mesh size. As the altermative method, Molecular Dynamics or Statics is suggested and acceoted in the field of microcutting, indentation and crack propagation. In this paper using Molecuar Dynamics simulation, the phenomena of microcutting with subnanometer chip thickness is studied and the cutting mechanism for tool edge configuration is evaluated. As the result of simulation the atomistic chip formation is achieved.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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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.

• Corrosion Science and Technology
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• 제10권2호
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• pp.65-70
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• 2011

DLC is considered as the candidate material for application of moving parts in automotive components relatively in high pressure and temperature operating conditions for its high hardness with self lubrication and chemical inertness. The properties of interlayer between the substrate and the DLC film were studied. Arc ion plating method have been employed to deposit onto substrate and sputtering method was used for synthesizing DLC onto interlayer. Among these six types of interlayer, deposited DLC film onto TiCN showed excellent value for characteristics. From the results of analysis for physical properties of DLC films, it seems that the adhesion forces were more important factors than intrinsic mechanical properties such as hardness, roughness and wear resistance of DLC films. AFM(Atomic Force Microscope) was used for understanding roughness of DLC films. Hardnesses of the coating layers were identified by nano-indentation method and adhesions were checked by scratch method.

• 한국정밀공학회지
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• 제12권4호
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• pp.135-142
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• 1995

Recently, the analysis of microcutting with submicrometer depth of cut is tried to get a more high quality surface product, but to get a valuable result another method instead of conventional finite element method must be considered because finite element method is impossible for a very small focused region and mesh size. As the alternative method, Molecular Dynamics or Statics is suggested and accepted in the field of microcutting, indentation and crack propagation. In this paper using Molecular Dynamics simulation, the phenomena of microcutting with subnanometer chip thickness is studied and the cutting mechanism for tool edge configuration is evaluated. As the result of simulation the atomistic chip formation is achieved.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.366-371
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• 2002

Because of the environmental problems, automotive companies are trying to reduce the weight of car body. Therefore, TRIP(TRansformation Induced Plasticity) steels, which have high strength and ductility have been developed. Welding process is a complex process; therefore deciding the optimal welding conditions on the basis of experimental data is an effective method. However, trial-and-error method to decide the optimal conditions requires too many experiments. To overcome these problems, response surface methodology was used. Response surface methodology is a collection of mathematical and statistical techniques that are used in the modeling and analysis of problems in which a response of interest is influenced by several variables and the objective is to optimize this response. This method was applied to the resistance spot welding process of the TRIP steel to optimize the welding parameters.

• 한국정밀공학회지
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• 제21권3호
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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.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.47-50
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• 2002

Because of the environmental problems, automotive companies are trying to reduce the weight of car body. Therefore, TRIP(TRansformation Induced Plasticity) steels, which have high strength and ductility have been developed. Welding process is a complex process; therefore deciding the optimal welding conditions on the basis of experimental data is an effective method. However, trial-and-error method to decide the optimal conditions requires too many experiments. To overcome these problems, response surface methodology was used. Response surface methodology is a collection of mathematical and statistical techniques that are used in the modeling and analysis of problems in which a response of interest is influenced by several variables and the objective is to optimize this response. This method was applied to the resistance spot welding process of the TRIP steel to optimize the welding parameters.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.38-42
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• 2000

In this study, the low velocity impact behavior of the composite laminates has been described by using 3 dimensional nonlinear finite elements. To describe the geometric nonlinearity due to large deformation, the dynamic contact problem is formulated using the exterior penalty finite element method on the base of Total Lagrangian formulation. The incremental decomposition is introduced, and the converged solution is attained by Newton-Raphson Method. The Newmark's constant-acceleration time integration algorithm is used. To make verification of the finite element program developed in this study, the solution of the nonlinear static problem with occurrence of large deformation is compared with ABAQUS, and the solution of the static contact problem with indentation is compared with the Hertz solution. And, the solution of low velocity impact problem for isotropic material is verificated by comparison with that of LS-DYNA3D. Finally the contact force of impact response from the nonlinear analysis are compared with those from the linear analysis.

• 한국세라믹학회지
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• 제42권6호
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• pp.443-447
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• 2005

Fracture behavior was investigated in the $Al_2O_3-TiO_2(3 wt{\%})-LaPO_4(25 wt{\%}$) composite ceramics. To improve the fracture toughness of alumina ceramics, $TiO_2$ and $LaPO_4$ as a second phase were introduced. The samples were made by conventional powder processing method. Green compacts were sintered at $1600^{\circ}C$ for 2 h in air. Fracture toughness was tested using Indentation Strength Bending(ISB) method. From the bending test, enhanced fracture toughness was found in the composite, compared to the pure and $TiO_2$-doped alumina. The main factor of the enhancement of fracture toughness seems to be attributed to the weak interphase role of the $LaPO_4$ as a particulate type.

• 한국세라믹학회지
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• 제22권6호
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• pp.37-41
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• 1985

Several $Al_2O_3$-based polycrystalline which had different dopant ratio in the range of 0.5mol% were prepared by doping pure $Cr_2O_3$, $ZrO_2$, $HfO_3$ Single crystalline which had same composition with above polycrystalline were made by means of floating zone method. This study examined the role of each dopant for enhancing the mefchanical properties of $Al_2O_3$-based Ceramics. Optical micrographs $({\times}200)$ of $Al_2O_3-Cr_2O_3$ single crystal showing not only radial crack (rc) on the specimen surface but median crack (mc) and lateral crack (lc) under surface at the edge of indentation mark. Fracture toughness of $Al_2O_3$-based Ceramics was increased with $ZrO_2$ content. Alloying effect of $Cr_2O_3$ contributed to the hardness of $Al_2O_3$ based ceramics.