• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.68-68
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• 2009

최근에 자동차 차체 경량화를 목적으로 개발된 고장력강의 용접품질 향상을 위해 인버터 DC 점용접기가 많이 사용되어지고 있다. 본 연구에서는 국내에서 개발된 인버터 DC 용접기를 사용하여 자동차용 590MPa 고장력 냉연강판(CR, SPFC 590RA)과 아연 도금 강판 (GA- EZFFC 590RA)의 용접품질을 평가하였다. 용접에 사용된 기본 조건은 인장 전단 시험을 통하여 결정하였으며, 동저항, 압흔 자국과 너겟 지름, 인장강도와의 관계를 통계적 방법으로 분석하였으며, 이를 활용하여 고장력 강판의 동저항과 압흔 자국에 따라 너겟 지름과 용접강도를 예측하는 비파괴적 용접 품질 평가 방법을 제시하였다.

• 한국정밀공학회지
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• 제23권8호
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• pp.171-177
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• 2006

This study was performed 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 1.51 GPa and 104 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 are a 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.

• Tribology and Lubricants
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• 제39권5호
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• pp.167-172
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• 2023

Titanium alloys are widely recognized among engineering materials owing to their impressive mechanical properties, including high strength-to-weight ratios, fracture toughness, resistance to fatigue, and corrosion resistance. Consequently, applications involving titanium alloys are more susceptible to damage from unforeseen events, such as scratches. Nevertheless, the impact of microscopic damage remains an area that requires further investigation. This study delves into the microscopic wear behavior of α-titanium crystal structures when subjected to linear scratch-induced damage conditions, utilizing molecular dynamics simulations as the primary methodology. The configuration of crystal lattice structures plays a crucial role in influencing material properties such as slip, which pertains to the movement of dislocations within the crystal structure. The molecular dynamics technique surpasses the constraints of observing microscopic phenomena over brief intervals, such as sub-nano- or pico-second intervals. First, we demonstrate the localized transformation of lattice structures at the end of initialization, indentation, and wear processes. In addition, we obtain the exerted force on a rigid sphere during scratching under linear movement. Furthermore, we investigate the effect of the relaxation period between indentation and scratch deformation. Finally, we conduct a comparison study of nanoindentation between crystal and amorphous Ti substrates. Thus, this study reveals the underlying physics of the microscopic transformation of the α-titanium crystal structure under wear-like accidental events.

• 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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.111-115
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• 2003

Nanoindentation is simply an indentation test in which the length scale of the penetration is measured in nanometres rather than microns or millimetres, the latter being common in conventional hardness tests. Three-dimensional molecular dynamics simulations have been conducted to evaluate the nanoindentation test. Molecular dynamics simulations were carried out on single crystal copper by varying crystal orientations to investigate nano-behavior of material beneath an indenter in nanoindentation. Morse potential function was used as an interatomic force between indenter and thin film. The result of the simulation shows that crystal orientation significantly influenced the slip system, dislocation nucleation and dislocation behavior.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1321-1325
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• 2003

Nickel thin film is one of the most important materials used in micromachined structure. To measure the mechanical properties of electroplated nickel thin film, two techniques are adopted and compared quantitatively with. One is nano-indentation test to measure the elastic modulus. The other is tensile test to measure not only elastic modulus but also yield strength and plastic deformation, ultimate strength. To perform the tensile test, the test apparatus was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1589-1595
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• 2000

레이저 텍스쳐와 미케니칼 텍스쳐 컴퓨터 하드디스크의 마찰과 마코 매카니즘이 Contact Start/Stop test 실행후의 특성들에 대해 연구되었다. 다양한 분석적이고 기계적인 테스트 기술들이 이용되었다. 형상, 조도, 화학적 조성, 기계적 성질, CSS 로부터 기인된 코팅의 마찰특성들에 대해 그 변화들을 조사하였다. 즉, AFM(Atomic Force Microscopy), Nano-Indentation, Nano-Scratch, TOF-SIMS(Time of Flight Secondary Ion Mass Spectroscopy), AES(Auger Electronic Spectroscopy)등이 이 연구에 적용되었다. 레이저 텍스쳐 범프의 표면조도와 미케니칼 텍스쳐 지역의 표면조도는 각각 대략적으로 4nm 와 7nm 감소되었다. 탄성계수와 경도값은 CSS test후에 증가하였고 가장 바깥쪽의 코팅층의 변형강화가 생겨났다. 자성층과 Ni-P 층 사이에 점착성의 문제가 확인되었다. TOF-SIMS 분석은 C 와 $C_2F_5$의 세기에 있어서 감소를 드러냈고 이것은 코팅 표면에 윤활제 요소의 마모를 확실시 할수 있는 결과로 나타났다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.290-290
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• 2011

In this study Diamond-like carbon (DLC) films were deposited on p-type Si substrates using a Radio-Frequency magnetron Sputtering system. The DLC film was deposited by bombarding graphite target with a N2/Ar plasma mixture with various conditions: substrate, pressure, deposition time, temperature of substrate, power and ratio of gas mixture. The effect on the conduction and hardness of DLC thin films were investigated. The conduction of DLC films were measured by I-V measurement. In addition, Raman analysis was performed to study the chemical bonding structure. The hardness was measured by Nano indentation. Atomic Force Microscopy was used for determined surface morphology of DLC film.

• 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.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.37-43
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• 2000

The effect of the alignment of the contacting bodies is concerned. Tilting of a body (indenter) is regarded as a mis-alignment. Recently developed method fur evaluating the contact normal traction is introduced and discussed, in which piecewise parabolic profile is considered as a generalized contact profile. Indentation by a wedge with rounded apex is solved as an example problem. In the case of partial slip regime, the variation of shear traction is examined during the closed path of shear force by using the efficient numerical technique. Concentration of the slip region is also investigated. By evaluating the energy dissipation from the contact surface, the effect of the mis-alignment-alignment on wear is discussed.