• Journal of Aerospace System Engineering
• /
• v.17 no.2
• /
• pp.45-55
• /
• 2023

This study conducted aeromechanics modeling and structural load analyses of Tilt Rotor Aeroacoustic Model (TRAM), a 25% scaled V-22 tiltrotor model used in wind tunnel tests. A rotorcraft comprehensive analysis code, CAMRAD II, was used. Analysis results of this study in low-speed forward flights were compared with DNW test and previous analysis results. Blade flap bending moments were in good agreement with measured data. Mean values and oscillatory loads for lead-lag bending and torsion moments were slightly different from measured data. However, when mean values were removed, results of structural loads for one rotor revolution were moderately compared with wind tunnel tests and previous analyses. Total forces and half peak-to-peak forces of the pitch link reasonably well matched with previous analysis results and measured data. Finally, harmonic magnitudes of blade structural loads were investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.1
• /
• pp.1-9
• /
• 2018

Lambda wing type Unmanned Combat Aerial Vehicle(UCAV) which adopts Blended Wing Body(BWB) has relatively less drag and more stealth performance than conventional aircraft. However, Pitching moment is rapidly increased at a specific angle of attack affected by leading edge vortex due to leading edge sweep angle. Wind tunnel testing and numerical analysis were carried out with UCAV 1303 configuration on condition of 50 m/s of flow velocity, $-4^{\circ}{\sim}28^{\circ}$ of the range of angle-of-attack. The effect of wing twist for longitudinal stability at the various angles of attack was verified in this study. When negative twist is applied on the wing, Pitch-break was onset at higher angle of attack due to delayed flow separation on outboard of the wing. On the other hand, pitch-break was onset at lower angle of attack and lift-to-drag ratio was increased when positive twist is applied on the wing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.244-245
• /
• 2010

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.5
• /
• pp.645-649
• /
• 2010

Induction hardening has been used to improve the torsional strength and characteristics of wear for axle shaft that is used to transmit driving torque from the differential to the wheel in automobiles. After the rapid heating and cooling processes of induction hardening are carried out, the shaft has residual stress and material properties change; this affects the allowable transmitted torque. The objective of this study is to predict the distribution of residual stress and estimate the torsional strength of induction-hardened axle shafts with residual stress. In this study, the finite element method is used to study the thermomechanical behavior of the material, and the results are compared with experimental results. The results indicate that the torsional strength of the axle shaft depends on the surface hardening depth and distribution of residual stress.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.4 s.235
• /
• pp.563-569
• /
• 2005

This paper develops a finite element model of a cabover type large truck. The finite element model is for evaluating torsional stiffness of the frame of the large truck. The torsional test of the frame is conducted in order to validate the developed finite element model. A load cell is used to measure the load applied to the frame. An angle sensor is used to measure the torsional angle. An actuator is used to apply a load to the frame. A vertical upward load and a vertical downward load are applied to the frame in the torsional test. The frame's torsional stiffness is computed with the measured load and torsional angle in the torsional test. The finite element model of the large truck includes cab, deck and payload, suspension, and tire. Cab, deck, and suspension are modeled not to affect the frame's torsional stiffness. The simulation is performed with the developed finite element model for evaluating the frame's torsional stiffness. The simulation results show a very good correlation with the torsional test results in the tendency of changing of the frame's torsional stiffness not only with the direction of the applying load but also with the amount of the applying load. In addition, the simulation results predict the measured torsional stiffness of the frame with about $5{\%}$ error.

• International Journal of Highway Engineering
• /
• v.10 no.2
• /
• pp.81-89
• /
• 2008

Shear test procedure for concrete-dowel interaction was proposed along with determination of dowel support reaction factor or shear spring stiffness constant using the spreadsheet example. For this task, three AASHTO-type standard specimens were prepared to simulate behavior of the jointed concrete pavement. A side support system was adopted to minimize twisting of the test specimen which had been observed in a preliminary test. A typical elastic behavior of the dowel-concrete interaction was observed from several test loops of loading, unloading and reloading procedures. However load versus slab displacement represents to be nonlinear. Test results show that the dowel support reaction factor ranges from 550-880 GN/m3, which is 1.4-2.2 times greater than 407GN/m3 proposed by Yoder and Witczak. This is because less torsional distraction was occurred with the help of a side support system adopted in this experiment. The dowel support reaction factor or shear spring stiffness constant obtained from the procedures proposed in this paper may be used as a reference data for the structural analysis of jointed concrete pavement.

• Composites Research
• /
• v.21 no.1
• /
• pp.40-45
• /
• 2008

Rubber hose assembly for automotive hydraulic brake during operation is subject to combined stresses of cyclic pressure, cyclic bending and torsion as well as thermal load. The rubber hose is composed of ethylene-propylene diene monomer(EPDM) rubber layers reinforced by polyvinyl acetate(PVA) braided fabrics. A durability tester with loading rigs for inducing the above cyclic stresses was used to investigate failure mechanisms in the rubber hose assembly. Failure examination was performed at every 100 thousands cycles of bending and torsion. Hose samples were sectioned with a diamond-wheel cutter and then polished. The polished surface was observed by optical microscope and scanning electron microscope (SEM). Some interfacial delamination with a length of about 1mm along the interface between EPDM rubber and PVA fabrics was shown at the test cycles of 400,000. The delamination induced some cracking into the outer rubber skin layer to leading the final rupture of the hose.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.1 s.190
• /
• pp.57-63
• /
• 2007

Wire drawing process of the high carbon steel with a high speed is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In the multi-pass drawing process, temperature rise in each pass affects the mechanical properties of the final product such as bending, torsion, and tensile property, etc. This temperature rise during the deformation promotes the occurrence of delamination, and deteriorates the torsion property and durability of wire. This study investigates the occurrence of delamination in the wire through the torsion test and the evaluation of wire temperature. The excessive wire temperature leads to the occurrence of the delamination. Based on the calculation of the wire temperature, a new pass schedule, which can prevent the delamination due to the excessive wire temperature rise, is designed through the isothermal pass schedule.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.6
• /
• pp.77-82
• /
• 1999

대형 화물트럭의 차실 내에 높은 수준의 차바닥 진동을 수반한 높은 소음이 발생하였다. 측정 및 분석결과 문제의 진동 소음은 추진축의 회전 1차 및 2차 성분으로 나타났다. 진동 전달경로상의 구성계 및 구성요소들에 대해 모드해석과 실차 주행 모드 해석시험을 실시한 결과 드라이브라인 및 프레임의 공진주파수가 문제가 되는 소음진동 주파수와 거의 일치하였으며, 또한 캡의 실내음향 공진 모드가 문제되는 주파수에서 존재하였다. 실험결과에 따라 액슬과 액슬간의 축의 장착각도를 변경하여 가진력을 줄이고, 비틀림 동흡진기를 추진축에 장착하여 드라이브라인계 공진을 제어함으로써 문제의 시내진동소음을 현저히 개선하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.392-395
• /
• 2011

본 논문은 부착식 PSC 텐던에 도입된 긴장응력이 종진동 메카니즘에 미치는 영향을 소개한다. 텐던의 종방향 변형과 비틀림 변형은 상호 연동하여 거동하고, 텐던에 도입된 긴장응력은 축강성과 비틀림 강성에 영향을 미친다. 따라서 텐던의 탄성파 속도는 도입된 긴장응력의 크기에 따라서 변한다. 실험적 검증을 위하여 도입 긴장응력이 다른 6개의 부착식 PSC 시험체에 대한 종진동 실험이 수행되었다. 실험결과로부터 도입 응력과 탄성파 속도와의 역학적 관계를 확인하였으며, 기존 문헌의 실험결과와 비교하였다.