• Journal of Korean Society of Steel Construction
• /
• v.16 no.1 s.68
• /
• pp.51-60
• /
• 2004

The stress analysis of cold-formed channel section steel beams under transverse load was conducted. The local buckling effect was included in the analysis using effective area concept. The proposed analytical model is capable of predicting accurate normal stress in the beam due to various behaviors including biaxial bending and warping. It was found to be appropriate for predicting stresses as well as deflection in the beam. A finite element model was developed to solve the analytical model.

• Journal of the Korean Institute of Gas
• /
• v.8 no.3 s.24
• /
• pp.8-15
• /
• 2004

This paper presents von Mises stress, deformation, and rotating distortion moment characteristics of inner tank bottom plate as a function of a cryogenic temperature difference along the radial distance from the center area to the corner one. The calculated results show that the filling level of LNG at the beginning of the cool-down process is very important for the design safety analysis of the inner tank. Obviously the thermal loading by a temperature difference between the LNG vapor gas of $-80^{\circ}C$ and a LNG temperature of $-162^{\circ}C$ affects to the thermal related characteristics of the bottom plates and annular one. From the computed results, the temperature difference by a vapor gas and liquid of LNG may lead to the thermal instability of the bottom plate. This phenomenon may cause the system failure of an inner tank.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.4
• /
• pp.99-107
• /
• 1997

A mixed type finite element method is applied to the nonuniform shear warping beam theory which is very useful for the structural analysis of thin-walled sectional beams considering the shear deformation. As known generally, it is shown that the mixed type finite element method, compared with the displacement type one, can give more balanced accuracy of results in calculating the stresses and displacements of the structure. In this paper, one typical example, the flexural-torsional problem of a discontinuously variable sectional beam under coupled end torsional moments, is selected and analyzed to validate the usefulness of the developed beam element.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.2
• /
• pp.154-159
• /
• 2013

In this paper, the effect of bolt clamping force and form accuray of contact surface between mirror and mount on mirror surface was studied. Normally, mirror used in reflecting optical system was assembled with mount by bolts or adhesive. In this case, the tension caused by bolt clamping force or adhesive force may distort the mirror surface. Also, form accuracy error of the contact surface have a negative impact on wrenched mirror surface which assembled by bolts or adhesive. In this study, stress and distorted displacements on mirror surface were analyzed according to the different contact surface form accuracies and bolt clamping forces by using the finite element analysis method.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.7
• /
• pp.561-568
• /
• 2013

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.

• Aerospace Engineering and Technology
• /
• v.13 no.1
• /
• pp.10-19
• /
• 2014

We designed bearingless rotor hub system which replace mechanical hinge/bearing with composite beam component and conducted fatigue analysis for flexbeam and torque tube. Extension/bending/torsional stiffness was calculated from 2D section analysis using VABS and 2D section structure analysis was applied for strain calculation. S-N curve of each composite material was generated using Wohler equation and fatigue analysis was conducted on weakness section which was decided from static structure analysis. CAMRAD II was used for load analysis and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used fatigue safe life analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.10
• /
• pp.845-855
• /
• 2018

Cross section design of a prop-blade is carried out for VTOL(Vertical Takeoff and Landing) Quad Tilt Prop-rotor UAV with a maximum takeoff weight of 55 kg and a maximum cruising speed of 180 km/h. Design procedure for cross section design is established and design requirements for prop-blade are identified. Through the procedure, cross section design is carried out to meet the identified requirements. Main design factors including stiffness, weight per unit length, and elastic axis are obtained by using a finite element section analysis program, and the design weight of the prop-blade is predicted. The obtained design factors are used along with the rotor system analysis program CAMRAD II to evaluate the dynamic stability of prop-blade in operating environment. In addition, the prop-blade load is obtained by CAMRAD II software, and it is used to verify the safety of the prop-blade structure. If the design results are not satisfactory, design changes are made in an iterative manner until the results satisfy the design requirements.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.1
• /
• pp.154-163
• /
• 1997

Thermally-induced deformation in SMC(Sheet Molding Compound) products is analyzed using three dimensional finite element method. Planar fiber orientation, which causes the anisotropic material properties, is calculated through the flow analysis during the compression stage of the mold. Also curing process is analyzed to predict temperature profile which has significant effects on warpage of SMC products. Through the developed procedure, effects of various process conditions such as charge location, mold temperature, fiber contents, and fiber orientations on deformation of final products are studied. and processing strategies are proposed to reduce the warpage and the shrinkage.

• 한국방재학회:학술대회논문집
• /
• 2007.02a
• /
• pp.71-74
• /
• 2007

Thin-walled multicell box girders subjected to an eccentric load can be produced the three global behaviors of flexure, torsion, and distortion. But it is very difficult to evaluate each influences of major behaviors numerically. If we can decompose an eccentric load P into flexural, torsional, and distortional forces, we can execute quantitative analysis each influences of major behaviors. Decomposition of Applied Load for Thin-walled Rectangular multi-cell box girders is researched by Park, Nam-Hoi(Development of a multicell Box Beam Element Including Distortional Degrees of Freedom, 2003). But researches about thin-walled trapezoidal multi-cell section is insufficient. So, this paper deals with decomposition process and independent analysis method of multi-cell box girders include trapezoidal section.

• Journal of the Korean Society for Precision Engineering
• /
• v.9 no.2
• /
• pp.92-100
• /
• 1992

플렉시블한 관절을 가지고 있는 로보트에 대하여 계단(step) 혹은 경사(ramp) 함수로 기준입력이 주어졌을 때, 모델의 불확실성이나 외란 아래에서 추적오차가 없는 디지찰 제어기법을 제시하고 실제로 실험을 통하여 제어기를 MC 68000으로 구현함으로써 제안한 제어 알고리즘의 유용성을 보였다. 제어기 설계에 있 어서 고려한 사항들은 비선형 마찰력, 중력에 의한 외란, 구동기와 부하사이의 뒤틀림 스프링 효과, 구리고 측 정할 수 없는 상태변수들이다. 또한 미분불가능한 쿨롱마찰로 인하여 전체 시스템이 이산/연속 혼성 시스템이 되어 출력에서 나타나는 리미트 싸이클을 해석/추정하기 위하여 혼성 시스템에서의 기술함수(Describing Function) 법을 제시하였다.