• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
• /
• pp.142-144
• /
• 1986

The research was conducted for the purpose of examining the dynamic characteristics of train wheel at the running state and preventing the vibrations of the high speed railway. The stress at the boundary surface of web and rim, .sigma./sub c/, was analyzed in consideration of the uniform In-plane compressive stress depending on the conditions of rolling and the rotation of train wheel. Then the equation of transverse vibration of the annular plate with the stepped thickness was analyzed by Rayleigh-Ritz's method.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2018년도 춘계학술대회 논문집
• /
• pp.55-55
• /
• 2018

Recently, amorphous oxides such as InGaZnO (IGZO) and InZnO (IZO) as a channel layer of an oxide TFT have been attracted by advantages such as high mobility, good uniformity, and high transparency. In order to apply such an amorphous oxide TFTs to a display, the stability in various environments must be ensured. In the InGaZnO which has been studied in the past, Ga elements act as a suppressor of oxygen vacancy and result in a decreased mobility at the same time. Previous studies have been showed that the InZnO, which does not contain Ga, can achieve high mobility, but has relatively poor stability under various instability environments. In this study, the TFTs using $IZO/Al_2O_3$ double layer structure were studied. The introduction of an $Al_2O_3$ interlayer between source/drain and channel causes superior electrical characteristics and electrical stability as well as reduced contact resistance with optimally perfect ohmic contact. For the IZO and $Al_2O_3$ bilayer structures, the IZO 30nm IZO channels were prepared at $Ar:O_2=30:1$ by sputtering and the $Al_2O_3$ interlayer were depostied with various thickness by ALD at $150^{\circ}C$. The optimal sample exhibits considerably good TFT performance with $V_{th}$ of -3.3V and field effect mobility of $19.25cm^2/Vs$, and reduced $V_{th}$ shift under positive bias stress stability, compared to conventional IZO TFT. The enhanced TFT performances are closely related to the nice ohmic contact properties coming from the defect passivation of the IZO surface inducing charge traps, and we will provide the detail mechanism and model via electrical analysis and transmission line method.

• 한국산학기술학회논문지
• /
• 제13권12호
• /
• pp.6151-6158
• /
• 2012

친환경 하천사업의 활성화로 식생매트의 사용은 증가하고 있으나 수리적 안정성에 대한 평가는 미흡한 실정이다. 본 연구는 호안용 식생매트 제품의 객관적인 수리안정성 시험 기법 개발을 위해 수행하였다. 이를 위해서 식생매트 2종에 대한 실규모 실험을 수행하여 수리량을 측정하고 분석하여 작용 소류력을 계산하였다. 1차원 부정류 모형을 이용하여 최적 조도계수를 결정하고 작용 소류력을 계산하였다. 각 유량의 시험 후에는 매트 표면 및 기반층의 변동 여부를 기록하여 평가하였으며 이에 따라 매트표면의 손상 유형 3가지 및 기반층의 손상 유형 2가지를 제시하였다. 본 연구에서는 식생매트의 표면 변동이 있더라도 하부 기반층의 유실이 발생하지 않는 경우에는 안정한 상태로 제안하였다. 이에 따라 실험체 2종의 허용소류력을 평가하였으며 철망으로 보강된 식생매트가 허용 소류력 측면에서 효과가 있는 것을 확인할 수 있었다.

• 대한토목학회논문집
• /
• 제3권2호
• /
• pp.97-107
• /
• 1983

비선형(非線型) 2차원조석(次元潮汐)모델의 경기만남부해역(京畿灣南部海域)에의 적용(適用)이 서술(敍述)되었다. 모델을 이용(利用)하여 만체계(灣體系)의 조류유동현상(潮流流動現像), 해저마찰력(海底摩擦力) 및 에너지소산(消散)에 대(對)한 초기평가(初期評價)를 할 수 있었다. 또한 모델에 의(依)한 수치실험(數値實驗)을 통(通)해 아산만접근수로(牙山灣接近水路)를 준설(浚渫)할 경우(境遇) 주태음반일주조(主太陰半日週潮)($M_2$)의 영향(影響) 및 해면(海面)에 작용(作用)하는 $10dyne/cm^2$의 균일정상풍(均一定常風)에 의(依)한 유동현상(流動現像)의 변화(變化)를 평가(評價)하였다. 초기결과(初期結果)들이 제시(提示)되었으며 토의(討議)되었다.

• Tribology and Lubricants
• /
• 제32권1호
• /
• pp.18-23
• /
• 2016

The effective case depth for case-hardened rolling bearing has been discussed. For this purpose, rolling contact fatigue tests for ball bearings built with inner race of various hardness values were conducted until L₁₀ calculating rating life using a bearing life test machine under radial loading. Then, the distribution of residual stress below the inner raceway, which depended on the hardness value, was measured by X-ray diffraction. As a result, the linear relationship was established between the hardness value of the inner race and the theoretical shear stress evaluated at the depth where the residual stress disappeared below the inner raceway. Based on the relationship, it could be found that the factor of safety in bearing manufacturer’s rules for the effective case depth of case hardened rolling bearings was set higher. However, it could be also found that the hardness values at the depth where the maximum shearing stress acted below the raceway surface in a tapered roller bearing hardened by the carburizing process, were not sufficient for preventing plastic deformation under the basic dynamic load rating. Consequently, further efforts were still required to reduce or to disperse the contact load on the material design of a rolling bearing in order to prolong its life.

• Geomechanics and Engineering
• /
• 제20권5호
• /
• pp.371-384
• /
• 2020

A settlement prediction method based on shear wave velocity measurements and soil nonlinearity was recently developed and verified by means of centrifuge tests. However, the method was only applicable to heavily overconsolidated soil deposits under enlarged yield surfaces. In this study, the settlement evaluation method was refined to consider the stress history of the sublayer, based on an overconsolidation ratio evaluation technique, and thereby incorporate irrecoverable plastic deformation in the settlement calculation. A relationship between the small-strain shear modulus and overconsolidation ratio, which can be determined from laboratory tests, was adopted to describe the stress history of the subsurface. Based on the overconsolidation ratio determined, the value of an empirical coefficient that reflects the effect of plastic deformation over the elastic region is determined by comparing the overconsolidation ratio with the stress increment transmitted by the surface design load. The refined method that incorporate this empirical coefficient was successfully validated by means of centrifuge tests, even under normally consolidated loading conditions.

• 대한기계학회논문집A
• /
• 제34권2호
• /
• pp.161-166
• /
• 2010

본 논문에서는 시일 설치면에서의 마멸발생기구를 정확하게 조사하기 위한 연구의 일환으로 미세입자가 시일과 스틸면 사이에 존재하는 경우의 접촉문제를 비선형문제해석 프로그램인 MARC를 사용하여 해석하였다. 이 결과, 시일의 재질은 스틸면에서의 응력분포와 변형형상에 아주 큰 영향을 미쳤다. 특히, PTFE와 같이 탄성계수가 높은 시일인 경우에 스틸 표면은 국부적으로 항복상태에 도달할 뿐만 아니라 시일을 제거한 후에도 영구변형과 함께 상당한 크기의 압축/인장 잔류응력이 존재하였다. 따라서, 시일과 스틸면 사이에 경질입자가 존재할 경우에는 연삭마멸과 함께 피로마멸이 발생할 수 있음을 확인하였으며, 다양한 설계변수에 대한 추가연구가 요구된다.

• Journal of Electrical Engineering and Technology
• /
• 제10권5호
• /
• pp.2070-2076
• /
• 2015

Nano composite materials were multi-constituent combinations of nano dimensional phases with distinct differences in structure, chemistry and properties. Nano particles were less likely to create large stress concentrations and thereby can avoid the compromise of the material ductility while improve other mechanical properties. Corona discharge was an electrical discharge. The ionization of a fluid surrounding a conductor was electrically energized. This discharge would occur when the strength of the electric field around the conductor was high enough to form a conductive region, but not high enough to cause electrical breakdown or arcing to nearby objects. This paper shows all the studies done on the preparation of nano fillers. Special attention has given to the ACSR transmission line conductor, TiO₂ nano fillers and also to the evaluation of corona resistance on dielectric materials discussed in detail. The measurement of the dielectric properties of the nano fillers and the parameters influencing them were also discussed in the paper. Corona discharge test reveals that in 0%N ACSR sample corona loss was directly proportional to the applied line voltage. No significant change in corona loss between 0%N and 1%N. When TiO₂ nano filler concentration was increased up to 10%N fine decrement in corona loss was found when compared to base ACSR conductor, corona loss was decreased by 40.67% in 10%N ACSR sample. It was also found from the surface conditions test that inorganic TiO₂ nano filler increases the key parameters like tensile strength and erosion depth.

• 복합신소재구조학회 논문집
• /
• 제2권3호
• /
• pp.1-11
• /
• 2011

본 연구에서는 하위 요소로(sub-element) 구성된 3차원 대칭 단위 요소들로 조합된 트러스 격자 구조물의 연속적인 물성치를 제안하였다. 개별적인 트러스 격자 물성치는 균질화 작업을 통하여 유효한 응력과 변형률 관계로 이루어진 연속적인 물성치 모델로 나타낼 수 있다. 미시적인 규모(micro scale) 스트럿의 인장이나 압축 응답에 의한 축강성은 전체 격자재료의 대부분의 강도를 차지하고, 이러한 스트럿의 부피 분율(fraction)은 효과적인 강도뿐만 아니라 복제 가능한 단위 요소로 이루어진 격자판의 상대밀도에 큰 영향을 주었다. 그러므로 균질한 강성부재로 구성된 연속적인 구성모델은 미시적인 규모로 간주되는 스트럿의 강도, 내부응력 상태 및 부피 분율과 관련된 역학적인 특성들을 포함하고 있다는 것을 확인할 수 있었다. 미시적인 규모의 응력에서 소성흐름은 균질한 구성식에서 파생된 거시적인 규모에서의 (macro-scale)응력 표면에 있는 연속적인 응력함수의 영역을 확장한다. 따라서 본 연구를 통하여 3차원 대칭 단위요소 구조물의 기본 기하학을 조사하고 압력에 의존적인 마크로 규모에서의 (macro-scale) 응력함수를 예측하는 연속적인 소성모델을 공식화하였다.

• 한국전기전자재료학회논문지
• /
• 제30권8호
• /
• pp.514-519
• /
• 2017

TiN (titanium nitride) films were prepared using the RF magnetron sputtering technique. The films were deposited by pure $N_2$ plasma sputtering. Their mechanical properties, such as nano-indentation hardness, friction coefficient, and surface wettability, have been investigated. X-ray diffraction (XRD) studies revealed that the orientation of $TiN_X$ films changed towards the (111) orientation with decreasing working pressure due to a strong compressive stress during deposition. The strongest TiN (111) orientation was found when the film was deposited at a working pressure of 1 Pa. This film showed the largest hardness (16 GPa) and smallest friction coefficient (0.17) among the studied samples. Moreover, this film was found to be accompanied by a water-repellent surface with water contact angle more than $100^{\circ}$.