• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.163-168
• /
• 2001

A FEM-based analytical approach was used to evaluate the fatigue strength of a KHST gangway. A KHST gangway was made of AC4C, 5083-O, 6005A-T6 aluminum alloys. The fatigue strengths of them were obtained from the related code and literatures. The effect of tensile mean stress was taken into account by the modified Goodman diagram, but the effect of compressive mean stress was not considered. There was not any location of a KHST gangway that exceeded the allowable fatigue strengths.

• 한국정밀공학회지
• /
• 제20권3호
• /
• pp.149-156
• /
• 2003

The estimation of fatigue limit for the component with complicated shape is difficult than of standard fatigue specimen, due to complex test equipment. So, we substitute maximum principle stress from FEM results for fatigue limit diagram made by standard fatigue specimen. Then we can estimate endurance safety of component with high trust. The static stress analysis, the nonlinear contact stress analysis and the model analysis for turbine blade is performed by ANSYS ver. 5.6. the comparison of maximum static stress around hole with maximum contact stress between pun and hole can make the cause of fracture for turbine blade clear. The difference of fatigue limit between fatigue test by standard specimen and in-service mechanical components is due to surface roughness and machining condition etc. In in-service mechanical components, Goodman diagram has to consider surface roughness for failure analysis. To find fracture mechanism of torison-mounted blade in nuclear plant. This study performs the static stress, the nonlinear contact stress and the modal analysis on torison-mounted blade with finite element method and makes the estimation for safety of turbine blade.

• 대한기계학회논문집A
• /
• 제26권8호
• /
• pp.1645-1652
• /
• 2002

The failure analysis on fractured parts is divided into the qualitative method by naked eyes and metallurgical microscope etc. and the quantitative method by SEM and X-ray diffraction etc. X-ray fractography can be applied to contaminated surface as well as clean surface and gain the plastic deformation and the residual stress near the fractured surface. Turbine blade is subject to cyclic bending force by steam pressure and suffers fatigue damage according to the increasing operating time. Therefore, to clean up the fracture mechanism of torsion-mounted blade in nuclear plant, the fatigue and the X-ray diffraction test was performed on the 12%Cr steel fur turbine blade and the fractured parts. The correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade was predicted. Failure analysis was performed by contact stress analysis and Goodman diagram of torsion-mounted blade.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집A
• /
• pp.258-265
• /
• 2001

Turbine blade is subject to force of three type ; torsional force by torsion-mount, centrifugal force by rotation of rotor and cyclic bending force by steam pressure. Cyclic bending force of them is main factor on fatigue fracture. In the X-ray diffraction method, the change in the values related to plastic deformation and residual stress near the fracture surface mat be determined, and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade parts was predicted. Failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• 대한기계학회논문집A
• /
• 제37권7호
• /
• pp.945-951
• /
• 2013

본 논문은 도시형 자기부상열차에 사용되는 대차프레임의 피로강도를 평가하는 방법을 제안하였다. 가상의 하중 시나리오로부터 구조해석을 수행하여 응력해석결과를 Goodman 선도상의 피로한계선도와 비교하였으며, UIC 규격에 적용되는 3단계의 피로조건을 적용하여 피로누적손상도(cumulative fatigue damge, D)를 계산하였다. 피로해석결과, Goodman 선도상에서 대차 프레임 사용소재인 A6005 알루미늄 합금 Butt 용접부의 피로한계선도를 초과하지 않았다. 가장 높은 피로손상도는 캐스팅 블록 및 전자석 폴 연결부로서 $1{\times}10^7$ cycles 기준으로 D=0.808로 계산되어 파손기준을 초과하지 않음을 확인하였다. 피로해석과 동일 조건으로 실시된 수직, 좌우, 전후 방향의 피로시험에서 대차 프레임의 어느 위치에서도 균열이 발생되지 않았으며, 이는 피로안전측으로 계산된 해석결과와 부합되는 결과이다.

• 대한기계학회논문집A
• /
• 제31권12호
• /
• pp.1214-1220
• /
• 2007

The vertical roller mill, which performs the grinding and partly blending of raw material, is the one of the important machine to produce ordinary portland cement. It has been reported that an unexpected fatigue failure occurred in a table liner in the course of grinding portland cement. The life of table liner is estimated to $4{\times}10^7$ cycles in the design stage, but at the field, when its operating time reaches to $2{\times}10^6{\sim}8{\times}10^6$ cycles, the fracture of table liner begins to be found. The fracture of table liner is initiated from the outside edge of grinding path contacting with the grinding roller. Its maintenance normally take 30 % of the total maintenance costs of the roller mill. Therefore, this study shows the clarification of the reasons occurring the fatal destruction of the table liner by fatigue fracture analysis utilizing fracture mechanics and by the finite element method. And, the results from Goodman diagram illustrate relationship of including information on the transition between tensile and bending fatigue strength in the fatigue characterization of table liner.

• 대한기계학회논문집A
• /
• 제25권11호
• /
• pp.1705-1712
• /
• 2001

Mechanical component has striation with constant width and SEM can estimate fracture type and loading condition. SEM has benefit to fatigue fracture analysis but striation can be observed according to the kind of material and range of crack growth rate and can't. In this case, it needs AFM that can measure 3-dimensional surface profile with resolution of atomic size. In this study. to find fracture reason of torsion-mounted blade in nuclear plant, we estimate the relation between stress intensity factor range and root mean square roughness in 12% Cr steel by AFM and predict in-service loading condition of turbine blade. failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.585-590
• /
• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• 대한기계학회논문집A
• /
• 제33권2호
• /
• pp.99-107
• /
• 2009

This study produced a design curve and fatigue limit for a variation in volume ratio and reduction ratio of TiNi/Al composites. In many cases, stress-life curve does not indicate fatigue limit, so it was presented by probabilistic-stress-life curve. Goodman diagram was used to analyze the fatigue strength of materials with a finite life determined by repeated load and the fatigue strength of endurance limit with an infinite life. The fatigue experiment was conducted using the scenk-type plane bending specimen in same shape. The result of the fatigue test, which had been conducted under consistent stress amplitude, was examined. (i) The optimal condition for TiNi/Al in accordance with hot pressing (ii) Impacts of fatigue limit caused by a variation in reduction ratio and volume ratio of TiNi/Al composites (iii) Probability distribution for fatigue limit of TiNi/Al2024 and TiNi/Al6061.

• 대한기관식도과학회:학술대회논문집
• /
• 대한기관식도과학회 1977년도 제11차 학술대회연제 순서 및 초록
• /
• pp.5.2-5
• /
• 1977

언어는 사람의 의사전달에 중요한 역할을 할 뿐 아니라 행복한 일상생활을 영위해 나가는데 있어서 기본적이고도 필수적이며, 상호간의 문화교류면에서 중요한 수단이 된다함은 물론이 다. 이러한 언어의 정상발육은 사람의 정상적인 청각기능을 통해서 형성되며, 만일 성장도중에 어떠한 원인으로 청력을 상설하게 되면 언어습득에 장애를 입게됨은 물론. 정서 및 인격형성에도 장애를 초래함으로서 결국에는 주위환경이나 일상생활에 적응하기 어려운 경우를 맞게 된다. 더욱이 오늘날의 사회구조가 고도로 복잡해짐에 따라서 청력장애자들에 대한 치료와 특수교육문제 및 그들의 취업분야 선택이나 사회적인 보상문제, 혹은 이를 판정하기 위한 신체검사기준치등을 정하는데 있어서 청력장애도의 설정과 적절한 분류가 절실히 요구되고 있다. 청력장애에 대한 분류는 1940년에 Beasley가 3등급으로 분류한 것을 비롯하여, 1950년에 A.M.A. (American medical association)에서 음의 주파수에 따른 언어청취범위를 백분율로 조사한 바 있고, 1959년에 A.A.O.O. (American academy of ophthalmology and otolayngology)에서, Huzing (1959), Silverman(1963)등이 분류한 것을 기준으로 삼아오다가 그 후로 보청기의 성능 및 청력검사계기의 발달을 바탕으로, 1965년 (I.S.O 기준)에는 Goodman 씨가 좀 더 체계적으로 청력장애의 정도를 분류함과 동시에 그에 따른 치료 및 사회적 대책에 대해기재한 것을 사용하고 있으나 아직까지 우리나라에서는 이에 대한 연구보고가 없는 터에 본 교실에서는 최근 1년간 난청을 주소로 본 이비인후과 외래를 방문한 환자중 180명을 대상으로 하여 Goodman 씨 분류법에 따라 청력장애정도를 분류함과 동시에 우리 일상생활 가운데서 청력과 비교적 밀접한 관계가 있다고 생각되는 몇 가지 기준사항(대화, 방송, 학교 및 교회, 전화, 집단토의, 음원의 방향)을 지표로 하여 청력장애도와 각 사항의 응답재료를 검토한 바 있기에 보고하는 바이다.