• Journal of Advanced Marine Engineering and Technology
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• 제10권2호
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• pp.146-155
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• 1986

Until recently, the calculation of torsional vibration for the marine diesel engine shafting has been performed only for vibratory stresses of resonant points and vibratory stresses for other engine speeds are determined by the estimation. With the advent of energy-saving engines which have a long stroke and a small number of cylinders, the first major critical torsional vibration of the propulsion shaft appears ordinarily near the MCR speed of engine and the flank of its vibratory stress exceeds now and then the limit stress defined by the rules of Classification Society. In order to know the above condition in the design stage of propulsion shafting, it is necessary to calculate the forced torsional vibration with the damping of propulsion shafting for all orders and to synthesize its calculated results according to their phase angles. In this study, the forced torsional vibrations with the damping of propulsion shafting are calculated for several orders by mechanical impedance method, and their results are synthesized. A computer program for above calculations are developed and some test-runs of the developed program are performed for propulsion shaftings of actual ships. The results of calculations are compared with measured values and also with those of the modal analysis method. They show fairly good agreements and the developed program is checked up on its reliability.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1217-1224
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• 2009

This paper presents a finite element (FE) analysis of the torsional rigidity of a two-stage cycloid drive. The cycloid disk makes contact with a number of pin-rollers simultaneously and eccentric shafts transmit not only torque of the spur gear stage to the cycloid disk, but also that of the cycloid disk to the output disk. Contacts between the disk and pin-rollers are simplified as linear spring elements, and the bearing of eccentric shaft is modeled as a rigid ring that has frictional contact to the disk and an elastic support. FE analysis for an ideal solid cycloid drive was performed and verified by a theoretical calculation. Accurate contact forces were then estimated by iterating between FE analysis for contact forces and Hertz theory calculations for nonlinear contact stiffness. In addition, torsional rigidity of the cycloid drive is analyzed to show that the bearing and nonlinear Hertz contact theory should be considered in analysis and design of a cycloid drive, which was verified with experiments. Finally, the effects of contact stiffness, bearing stiffness and cycloid disk structural stiffness according to the cycloid disk rotation on the torsional rigidity were investigated.

• 한국정밀공학회지
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• 제19권3호
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• pp.95-100
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• 2002

Built-in Eccentric Bearing-Torsional Spring (BEBTS) type Automatic Belt Tension Unit (ABTU) is one of typical belt tension units. The BEBTS type ABTU system frequently experiences torsional vibration about its pivot due to the variation of belt tension. However, it is very difficult to analyze the rotational (or torsional) vibration of the ABTU because the exciting moment varies according to the change of belt tension. To get over this difficulty, in this paper. the ABTU was simplified as 1-DOF translational motion model in the tangential direction. Its equation of motion was derived and solved. The time history and frequency responses were computed and examined for three of BEBTS type ABTUs which are made by different manufacturers but the tame kind.

• Earthquakes and Structures
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• 제16권1호
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• pp.119-127
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• 2019

When a structural wall is subjected to multi-directional ground motion, torsion-induced cracks degrade the stiffness of the wall. The effect of torsion should not be neglected. As a main lateral load resisting member, reinforced concrete (RC) structural wall has been widely studied under the combined action of bending and shear. Unfortunately, its seismic behavior under a combined action of torsion, bending and shear is rarely studied. In this study, torsional performances of the RC structural walls under the combined action is assessed from a comprehensive parametrical study. Finite element (FE) models are built and calibrated by comparing with the available experimental data. The study is then carried out to find out the critical design parameter affecting the torsional stiffness of RC structural walls, including the axial load ratio, aspect ratio, leg-thickness ratio, eccentricity of lateral force, longitudinal reinforcement ratio and transverse reinforcement ratio. Besides, to facilitate the application in practice, an empirical equation is developed to estimate the torsional stiffness of RC rectangular structural walls conveniently, which is found to agree well with the numerical results of the developed FE models.

• 대한조선학회논문집
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• 제58권6호
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• pp.431-439
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• 2021

The Carbon Fiber Reinforced Plastic (CFRP) material is recently widely used in the composite industry with excellent rigidity and lightweight properties. A ship shaft system requires high standards of safety on torsional strength capacity. The purpose of this study is to verify the applicability of a CFRP shaft system to take the place of metal shaft systems for ships from a viewpoint of torsional strength. Selection of materials and manufacturing method are executed then two geometrically scaled CFRP shaft system models were designed and manufactured with three-layer patterns. The models were used for a series of torsion tests under single and repeated torsional loading conditions. Detailed design and manufacturing methods for a CFRP ship shaft system are documented and the torsion test results are listed in this paper. The results of this study could be useful guidelines on the development of CFRP ship shaft systems and a test method.

• 한국지진공학회논문집
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• 제14권6호
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• pp.67-74
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• 2010

건물의 실제 편심은 일반적으로 계산된 값과 상당히 다르며, 정형 건물도 비틀림의 영향을 받는다. 질량분포의 비대칭성과 수직축에 대한 지반의 회전요소와 같은 요인들의 영향을 고려하고, 비틀림 비정형 건물의 취약성을 줄이기 위하여 내진설계규준에서는 우발편심과 비틀림 증폭계수를 도입하였다. 본 연구에서는 정형건물의 다양한 형상비와 평면중심으로부터의 부재위치에 따른 비틀림 증폭계수의 영향 및 이 계수에 영향을 미치는 요인을 확인하였고 보통암 지반에 위치한 다양한 편심과 형상비를 갖는 비선형 철근콘크리트 단층모델을 이용하여 비틀림 증폭계수를 검증하였다. 비선형 정적해석과 시간이력해석을 이용하여 구한 연약단부의 최대 정적변위와 동적변위는 비교적 일치하였으나 최대 정적비틀림과 동적비틀림의 차이는 편심크기가 작을수록 크게 나타났다. 1차 설계편심에 비틀림 증폭계수 적용유.무에 따라 연약단부 부재의 밑면전단력 증가가 미비하여 최대 정적변위의 증가비가 크지 않다.

• Structural Engineering and Mechanics
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• 제76권3호
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• pp.293-310
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• 2020

This study derives the differential equations of free vertical bending and torsional vibrations for two- and three-pylon suspension bridges using d'Alembert's principle. The respective algorithms for natural vibration frequency and vibration mode are established through the separation of variables. In the case of the three-pylon suspension bridge, the effect of the along-bridge bending vibration of the middle pylon on the vertical bending vibration of the entire bridge is considered. The impact of torsional vibration of the middle pylon about the vertical axis on the torsional vibration of the entire bridge is also analyzed in detail. The feasibility of the proposed method is verified by two engineering examples. A comparative analysis of the results obtained via the proposed and more intricate finite element methods confirmed the former feasibility. Finally, the middle pylon stiffness effect on the vibration frequency of the three-pylon suspension bridge is discussed. It is found that the vibration frequencies of the first- and third-order vertical bending and torsional modes both increase with the middle pylon stiffness. However, the increase amplitudes of third-order bending and torsional modes are relatively small with the middle pylon stiffness increase. Moreover, the second-order bending and torsional frequencies do not change with the middle pylon stiffness.

• 전기학회논문지
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• 제58권3호
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• pp.578-585
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• 2009

In this paper, we present the design of an electromagnetic scanning mirror with torsional springs. The scanning mirror consisting of torsional springs and electromagnetic coils was designed for the applications of laser animation systems. We analyzed and optimized three types of torsional springs, namely, straight beam springs (SBS), classic serpentine springs (CSS), and rotated serpentine springs (RSS). The torsional springs were analyzed in terms of electrical resistance, fabrication error tolerance, and resonance mode separation of each type using analytical formula or numerical analysis. The RSS has advantages over the others as follows: 1) A low resistance of conductors, 2) wide resonance mode separation, 3) strong fabrication error tolerance, 4) a small footprint. The double-layer coils were chosen instead of single-layer coils with respect to electromagnetic forces. It resulted in lower power consumption. The geometry of the scanning mirror was optimized by calculations; RSS turn was 12 and the width of double-layer coil was $100{\mu}m$, respectively. When the static rotational angle is 5 degrees, the power consumption of the mirror plate was calculated to be 9.35 mW since the resistance of the coil part and a current is $122{\Omega}$ and 8.75 mA, respectively. The power consumption of full device including the mirror plate and torsional springs was calculated to be 9.63 mW.

• 한국전산구조공학회논문집
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• 제15권3호
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• pp.545-555
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• 2002

이 논문에서는 여러개의 비틀림보강재를 갖는 코아구조물의 비틀림거동을 구하기 위한 매트릭스 해석방법을 제안하였다. 몇가지의 가정을 토대로 등분포와 삼각분포, 그리고 구조물 상단에 집중 비틀림하중이 작용하는 경우에 대한 응력과 변위식들을 유도하였으며 비틀림각과 응력을 최소화하기 위한 보강위치를 추정하기 위하여 보강재의 위치를 이동시켜 가변서 위치변화가 코아의 비틀림거동에 미치는 영향을 분석하였다. 또한 본 이론해석의 신뢰성을 고찰하기 위하여 비틀림보강재가 설치된 해석모델틀을 토대로 본 이론에서 구한 응력과 변위를 MIDAS-GEN프로그램에 의한 결과와 비교하였고, 만족할 만한 결과를 얻었다. 비록 컴퓨터를 이용한 3차원해석이 일반적인 구조해석 방법으로 다가왔으나 비용과 시간이 많이 소요되므로 모든 경우에서 최적의 수단이 될 수는 없다. 본 연구에서 제시된 공식들은 초기 설계단계에서 비틀림하중을 받는 실제 코아구조물의 응력과 변위를 추정하는데 유용하게 사용될 수 있을 것이다.

• 한국산학기술학회논문지
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• 제15권10호
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• pp.5955-5962
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• 2014

일반적으로 고성능의 레이스카나 스포츠카 시장에서 차량의 프레임 설계는 매우 중요한 기술적 요소로 작용하고 있다. 차량의 비틀림 강성은 차량의 코너링 성능에 많은 영향을 주기 때문에 레이스 차량에 있어 우수한 성능의 프레임이라는 것은 높은 비틀림 강성을 가진다는 것을 뜻한다. 본 연구에서는 입문용 포뮬러 레이스카 프레임의 최적 비틀림 강성 설계를 위하여 다구찌 직교배열표를 가진 실험계획법과 유한요소 해석 기술을 이용하였다. 이러한 기법을 통해서 얻은 결과가 초기설계단계에서 보다 14.5%의 무게를 감량함과 동시에 무게 대비 비틀림 강성 10.7%의 개선 효과를 볼 수가 있었다. 따라서 본 연구에서는 직교배열표를 가지는 실험계획법을 이용한 구조해석이 설계 초기단계에서 저가형 레이스 차량에 사용되는 Tubular space frame 설계에 매우 유용함을 나타내고 있다.