• 대한조선학회논문집
• /
• 제40권1호
• /
• pp.28-35
• /
• 2003

Fatigue tests of transverse fillet weldment were performed under out-of-plane bending loads. Significant increase of the fatigue strength was observed under out-of-plane bending loads, compared to the one under in-plane loads (axial loads). Applicability of the crack propagation analysis using LEFM for the surface crack of fillet weldment were investigated as well, in parallel with the fatigue tests. For the rational assessment of the fatigue strength of welded ship structures where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to complexity of applied load and structural geometry, further investigation is recommended for the effect of the out-of-plane bending stress on the fatigue strength of weldment.

• Structural Engineering and Mechanics
• /
• 제59권3호
• /
• pp.503-526
• /
• 2016

In-plane and out-of-plane free vibration analysis of Timoshenko curved beams is addressed based on the isogeometric method, and an effective scheme to avoid numerical locking in both of the two patterns is proposed in this paper. The isogeometric computational model takes into account the effects of shear deformation, rotary inertia and axis extensibility of curved beams, and is applicable for uniform circular beams, and more complicated variable curvature and cross-section beams as illustrated by numerical examples. Meanwhile, it is shown that, the $C^{p-1}$-continuous NURBS elements remarkably have higher accuracy than the finite elements with the same number of degrees of freedom. Nevertheless, for in-plane or out-of-plane vibration analysis of Timoshenko curved beams, the NURBS-based isogeometric method also exhibits locking effect to some extent. To eliminate numerical locking, the selective reduced one-point integration and $\bar{B}$ projection element based on stiffness ratio is devised to achieve locking free analysis for in-plane and out-of-plane models, respectively. The suggested integral schemes for moderately slender models obtain accurate results in both dominated and non-dominated regions of locking effect. Moreover, this strategy is effective for beam structures with different slenderness. Finally, the influence factors of structural parameters of curved beams on their natural frequency are scrutinized.

• 한국컴퓨터정보학회논문지
• /
• 제21권7호
• /
• pp.67-75
• /
• 2016

This study aims to examine how international airport visitors perceived value effects on their satisfaction, revisit and recommendation intention. To archive the research goal 288 questionnaires were collected from Incheon international airport and was analyzed a frequency analysis, reliability analysis, exploratory factor analysis and correlation coefficient analysis from SPSS 21, a hypothesis through out confirmatory factor analysis and structural equation modeling from AMOS 7.0. As a result of the analyses, it was found that the models was appropriate in proving the hypotheses on interrelationships among perceived value, satisfaction and revisit & recommendation intention. First, perceived value is factorized as acquisition value, emotion value, monetary value and social value. Second, all factor of perceived value turned out to have affirmative effects on international airport visitors' satisfaction. Third, international airport visitors satisfaction turned out to have affirmative effects on revisit and recommendation intention. Overall, finding of this study enhance the theoretical progress on the experiential concept in international airport and offer important implication for international airport industry.

• 한국자동차공학회논문집
• /
• 제10권2호
• /
• pp.220-227
• /
• 2002

This paper describes an integrated approach process to carry out pre-test, model correlation and updating analysis on the sub-frame of a vehicle. In this study, it was found that the modal test could be more efficient when the exciting point was selected on the area with high driving point residue. Such area could be located with the aid of finite element modal analysis. The model correlation was appraised in conjunction with the modal parameters between modal test and finite elements analysis. Also, the finite element model updating was obtained the good resultant using the iteration method based on sensitivity analysis results that carried out the variation of natural frequencies and MAC for the material properties. Finally, optimization of vehicle subframe was carried out the analysis of core location and physical properties by tow steps.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.430-435
• /
• 2008

Hyundai-Rotem Company has designed and manufactured Light Railway Vehicle (LRV) according to the Urban Rail Transit Code, which applies to urban railway vehicles in Korea. The Urban Rail Transit Code specifies the loads, for which vehicle bodies shall be capable of withstanding, identifies how material data shall be used and presents the principles to be used for design verification by analysis and test. The structural design of railway vehicle bodies depends on the loads they are subjected to and the characteristics of the materials they are manufactured from. Therefore Hyundai-Rotem Company has carried out Finite Element Analysis (FEA) and has performed load tests on the vehicle body according to the Urban Rail Transit Code. This research contains the results obtained by the analysis and the load tests. The analysis was carried out using I-DEAS Master Series 12 and load test were carried out using specially designed test jigs and equipment are used for the load tests.

• International Journal of Aerospace System Engineering
• /
• 제8권1호
• /
• pp.1-13
• /
• 2021

Contra-rotating fan is comprised of two rotors which are rotating in the opposite direction. The fan stages are named rotor-1 and rotor-2. Benefits from the use of contra rotation are in terms of better efficiency and improved thrust to weight ratio. Failure of contra-rotating fan stage blade in-service results in safety risks, repair costs, and revenue losses. This paper focuses on the vibration analysis and one way fluid-structure interaction of high aspect ratio, low speed contrarotating fan rotors. Modal analysis and modal pre-stress analysis of contra-rotating fan rotors were carried out to calculate the natural frequencies, One way fluid-structure interaction (FSI) was carried out where the computational analysis of the blades was performed using ANSYS CFX. The boundary conditions for CFD analysis were considered from the actual experimental velocity flow field at the inlet and pressure outlet. Based on the results obtained from the CFD analysis, the structural analysis such as deformation and Von-Misses stresses was carried out by using the finite element method (FEM) with ANSYS. The results provide necessary guidelines for the safe running of the contra-rotating fan. The analysis also will be helpful to understand the change of flow behavior due to a rotor deformation.

• Composites Research
• /
• 제34권4호
• /
• pp.233-240
• /
• 2021

VaRI(Vacuum assisted Resin Infusion) 공정은 공정비용이 저렴하며, 크기가 큰 복합재 제작에 적합한 OoA(Out of Autoclave) 공정이다. VaRI 공정에서는 원할한 수지 주입을 위해 섬유 상단에 유로망을 적층한다. 수지는 이 유로망을 따라 섬유의 면 방향으로 빠르게 공급되고, 공급된 수지는 다시 섬유의 두께방향으로 함침된다. 면방향의 유동과 두께방향의 유동이 동시에 일어나기 때문에 수지의 유동을 예측하기 힘들며, 수지 주입과정을 예측하기 위해 3D 수치해석 프로그램이 사용되고 있다. 하지만, 3D로 해석하기 위해서 섬유와 유로망의 두께방향에 많은 Element가 필요하고, 이로 인해 제품의 크기가 클수록 해석시간이 오래 걸린다. 따라서 본 연구에서는 3D 유동해석을 2D 해석으로 간소화하여 유동해석에 소요되는 시간을 줄이는 방법을 제시하였다. 3D 유동해석과 간소화된 2D 유동해석을 동일조건에서 비교하여 효용성을 검증하였고, 충진시간 오차율은 약 7%, 유동해석시간 감소율은 약 95%로 나타났다. 또한 3D 해석에서 섬유 상, 중, 하단 간의 유동 전진 거리의 차이가 일정하다는 것을 활용하여 간소화된 2D 유동해석에서도 상, 중, 하단의 유동 전진 거리를 예측할 수 있었다.

• 한국항해학회지
• /
• 제22권3호
• /
• pp.73-92
• /
• 1998

Today the number of high school drop-outs is increasing , and also it is serious social problems. But almost factor analyses on the drop-outs are projected by questionnaire. This paper find out by the real data form the concerned documents what factors of drop-outs are. In order to accomplish this study purpose, the methodology are used such as Fequency Analysis, Correlation Analysis, Crosstabulation Analysis. Through the this study this paper could siome suggestions as followings. The first , all education authority should analysis what factors of drop-outs and what drop-out situation is . The second, every teacher should counsel with all problem students sincerely regarding to their characters, future occupations, life course and etc. The third, the most and worst important factors of drop-out is runaway. Because it is very difficult for teacher to teach, lead and guide a runaway student, therefore thepreventino of runaway is efficient for reducing of drop-outs. The fouth, the students violating rules are retrained propoerly in view of guide for good path. The fifth, besides of the above factors. there are drop-out factors such as the health, disease, dafety accidents . All parents. teachers, and students should try their best to solve. To the end, education authority try to encourage teachers to do their role with maximum sense of duty.

• 한국시뮬레이션학회논문지
• /
• 제24권3호
• /
• pp.69-75
• /
• 2015

본 연구에서는 복합굴절차의 강도 해석을 통한 구조적 안정성을 평가하고자 한다. 3D CAD 데이터, 사용 재질에 대한 물성값, 하중 조건 및 경계조건을 바탕으로, 범용 구조 해석 프로그램인 Nastran을 활용하여 복합굴절차에 대한 정적 구조 해석을 실시하였다. 하부 프레임(Sub frame, Out-trigger, Chassis frame)에 대한 구조해석을 수행하기 위해, 각 Out-trigger가 최대 하중을 받는 4가지 경우를 산정하였다. 이러한 해석된 결과를 통하여 국부적으로 강도가 부족한 위치를 특정지어, 보다 안전한 설계에 도움이 되도록 하였다.

• 한국철도학회논문집
• /
• 제5권2호
• /
• pp.93-103
• /
• 2002

Reinforced earth structure has been regarded as general structure in order to achieve efficient land utilization as well as securing safety in railway service lines in other countries, but there are no construction actual results in Korea. In this study, the soil-geogrid interaction mechanism was investigated experimentally and numerical analysis was performed to predict Pull-out behaviour of geogrid embedded in reinforced earth body. This experimental data and analysis result can not contribute to understand the soil-geogrid interaction mechanism at soil-geogrid interface but also be used in design practice of the railway reinforced earth structures.