• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.907-912
• /
• 2001

KOGAS had developed the Ring-knot membrane for LNG storage tank. But we found that some modifications were needed in using the Ring-knot membrane for the commercial LNG storage tanks. So, both analytical and experimental studies have been performed to investigate the strength of the new membrane and the reaction force at the anchor point. Using nonlinear FEM code and experiments, the stress analysis of the new corrugated membrane shapes subject to the cryogenic liquid pressure and thermal loading are performed to ensure the stability and fatigue strength of the new membrane. This paper reports on the results of investigations into this new type of membrane.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 춘계학술대회
• /
• pp.304-307
• /
• 2006

Recently, as the global warming by fossil fuels and the steep rise of the oil price become social issues, the interest for renewable energy producing system is increasing rapidly. Among these, the wind turbine is most highlighted because of its economic competitiveness. The tower is one of the main components of wind turbine, which occupying about 20% of overall turbine costs. The tower access door located to base part of the tower, is used to enter the tower. This is the main structural weak points because of door hole, weldment, etc. And so are the weldments between the cans and the flanges. In this study, for the top flange part of the tower, by FEM using ANSYS, we retrieved the maximum von Mises stress on that and carried out fatigue analysis using stresses at such weak points.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
• /
• pp.837-843
• /
• 1998

This paper presents the thermomechanical and fracture mechanics evaluation procedure of thermal striping damage on the secondary piping of LMFR using Green's function method and standard FEM. The thermohydraulic loading conditions used in the present analysis are simplified sinusoidal thermal loads and the random type data thermal load. The thermomechainical fatigue damage was evaluated according to ASME code subsectionNH. The analysis results of fatigue for the sinusoidal and random load cases show that fatigue failure would occur at a geometrically discontinuous location during 90,000 hours of operation The fracture mechanics analysis showed that the crack would be initiated at an early stage of the operation. The fatigue crack was evaluated to propagate up to 5 ㎜ along the thickness direction during the first 944 and 1083 hours of operation for the sinusoidal and the random loading cases, respectively.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1992년도 춘계학술대회 논문집
• /
• pp.306-312
• /
• 1992

The prevention of roll breakage in hot rolling process is improtant to reduce maintenance cost and production loss. Rolling conditions such as the roll force and torque have been intensively studied to overcome the roll breakage. in the present work, a model for life prediction of work rolls under working condition was developed and discussed. The model consists of stress analysis, crack propagation, wear and fatigue calculation model. Roll life can be predicted by stress, crack depth and fatigue damage calculated from this model. The reliability of stress analysis is backed up by the FEM analysis. From the result of simulation using by pressent model, although the fatigue damage of back up roll reachs 80% of practical limit, that of workroll was less than 40%. In edge section of workroll stress amplification is found by wear and bender effect. We can judge that workroll failures are not due to fatigue damage, crack propagation by bending stress but stress amplification by wear and bender in present working condition.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.854-858
• /
• 2002

In this study, Fatigue crack growth behavior of the laser welded sheet metal due to a single overload was investigated. From Fatigue crack propagation test, it was observed that the retardation of fatigue crack growth has been more effective in the welded specimen than in the base metal. And if the distance between the welded part and the position of overload is too close the retardation of fatigue crack growth at the welded part has been decreased. From FEM analysis, it was observed the retardation has been more effective compressive residual stress than plastic zone.

• Journal of Welding and Joining
• /
• 제22권4호
• /
• pp.73-81
• /
• 2004

Failure mechanisms of welded joints under fatigue loads are interpreted that multiple collinear surface cracks initiating randomly along the weld toes propagate under the mutual interaction and coalescence of adjacent two cracks. To estimate fatigue crack propagation life for three types of the representative welded joints, i.e. non-load carrying cruciform, cover plate and longitudinal stiffener joint, the stress intensity factors at the front of the surface cracks have to be calculated, which are influenced strongly by the geometry of attachments, weld toes and the crack shapes. For the effective calculation of the stress intensity factors the Mk-factor was introduced which can be derived by a parametric study performed by FEM considering influence of the geometrical effects. The fatigue life of the cruciform joint was estimated by using the Mk-factors and the method considering the propagation mechanisms of the multiple surface cracks. Analysis results for the fatigue life had a good agreement with that of experiment.

• 한국자동차공학회논문집
• /
• 제6권5호
• /
• pp.20-27
• /
• 1998

According as the member of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. And, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic evaluation method for them. In this study, by considering nugget edge of the spot weld part of the IB-type spot welded lap joint under tension-shear load to the ligament crack. fatigue strength of various IB-type spot welded lap joints was estimated with the stress intensity factor(S.I.F.) KIII which is fracture mechanical parameter. We could find that fatigue strength evaluation of the IB-type spot welded lap joints by KIII is more effective than the maximum principal stress ($\sigma$1max) at edge of the spot weld obtained from FEM analysis.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 춘계학술대회 논문집
• /
• pp.136-142
• /
• 2004

Effects of Nb(Niobium) contents and solution annealing on the strength and fatigue lift of 18%Ni maraging steel commonly using in aircraft, space field, nuclear energy, and vehicle etc. were investigated. Also the fatigue life stress intensity factor were compared experiment result and FEA(finite element analysis) result. The more Nb content, the higher or the lower fatigue lift on base metal specimens or solution annealed specimens showing that the fatigue life was almost the same. The maximum stresses of X, Y, and Z axis direction showed about 2.12${\times}$10$^2$MPa, 4.40${\times}$10$^2$MPa and 1.32${\times}$10$^2$MPa respectively. The Y direction stress showed the highest because of the same direction as the loading direction. The fatigue lives showed about 7% lower FEA result than experiment result showing almost invariable error every analyzed cycle. Stress intensity factor of the FEA result was lower about 3.5∼10% than that of the experiment result showing that the longer fatigue crack length, the higher error. It considered that the cause for the difference was the modeled crack tip having always the same shape and condition regardless of the crack growth.

• 한국강구조학회 논문집
• /
• 제29권3호
• /
• pp.193-204
• /
• 2017

실제 옥외 대기환경하에서 부식손상된 무도장 가시설 강재 및 도장 강재의 피로강도는 명확하지 않다. 본 연구에서는 약 7년간 지하철 공사현장에서 사용된 가시설 부재와 극심한 해양 부식환경하에서 75년간 사용된 영도대교 강부재로부터 절취한 강재의 피로실험을 실시하였다. 그리고 강재 표면의 부식 생성물을 제거한 후 강재 표면의 3차원형상을 측정하여 최대, 최소 및 평균 잔존두께를 계산하였다. 피로실험결과 및 FEM해석 결과에 근거하여 부식특성과 피로강도와의 상관관계를 검토하였으며, 실제 옥외 환경하에서 부식된 무도장 및 도장 강재의 피로수명 평가식도 제시하였다.

• 한국항공우주학회지
• /
• 제39권10호
• /
• pp.952-958
• /
• 2011

우주용 영상센서의 비균일 출력특성 교정을 통한 영상품질향상을 목적으로 하는 탑재교정장치는 균일한 온도정보 제공을 위한 흑체, 교정임무 수행 중 흑체 지향을 위해 전개 및 수납 기능을 갖는 교정용 구동미러 그리고 상기 구성품의 제어를 담당하는 탑재교정장치 제어용 전장유닛으로 구성된다. 탑재교정장치 제어용 전장품의 발사 및 궤도환경에서의 구조건전성 확보를 위해 소자 납땜부에 대한 열탄성 해석과 피로파괴 이론에 기초한 구조 열해석을 실시하였으며, 이를 통하여 전장품의 구조 건전성을 평가하였다. 본 논문에서는 전자기판에 장착된 소자별 안전성 검토를 위해 일반적으로 적용되는 해석적 방법과 FEM으로부터 도출된 결과를 비교 및 검토하여 피로파괴 이론에 기초한 구조 건전성 예측이 유용함을 입증하였다.