• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.393-400
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• 2012

This paper deals with a development of 2-DOF flutter experiment equipment which represents a 2-DOF typical section model. For a conventional 2-DOF flutter experiment equipment, it is hard to observe flutter boundary clearly due to the complexity of the experiment equipment. To refine our flutter experiment equipment system, a compliant mechanism based torsional spring is used. Well-designed extruded aluminum pipe works as a torsional spring. SolidWorks and ANSYS are used for modeling, analysis and design of the torsional spring. With this designed torsional spring, the 2-DOF flutter experiment equipment is developed and wind tunnel tests are performed. Clear flutter boundary which is estimated by classical flutter analysis is observed in the experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.429-434
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• 2012

This paper deals with a development of 2-DOF flutter experiment equipment which represents a 2-DOF typical section model. For a conventional 2-DOF flutter experiment equipment, it is hard to observe flutter boundary clearly due to the complexity of the experiment equipment. To refine our flutter experiment equipment system, a compliant mechanism based torsional spring is used. Well-designed extruded aluminum pipe works as a torsional spring. SolidWorks and ANSYS are used for modeling, analysis and design of the torsional spring. With this designed torsional spring, the 2-DOF flutter experiment equipment is developed and wind tunnel tests are performed. Clear flutter boundary which is estimated by classical flutter analysis is observed in the experiments.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.43-53
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• 2002

Current torsional provisions focus n restricting torsional effect of asymmetric wall structures by proportioning strength of wall based on the traditional assumption that stiffness and strength are independent. Recent studies have pointed out that stiffness of structural wall is dependent on the strength. This implies that actual stiffness of walls can be determined only after torsional design is finished and current torsional provisions may result in significant errors. To overcome this shortcoming, this paper proposes deformation based torsional design for asymmetric wall structures. Contrary to the current torsional provisions, deformation-based torsional design uses displacement and rotation angle as design parameters and calculates base shear for inelastic torsional response directly. Main purpose of deformation based torsional design is not to restrict torsional response but to ensure intended torsional mechanism according to the capacity design concept. Because displacement and rotation angle can be used as performance criteria indicating performance level of asymmetric structures, this method can be applied to the performance based seismic design effectively.

• Journal of KSNVE
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• v.9 no.5
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• pp.936-942
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• 1999

Unstable torsional vibration on the marine ship's propulsion shafting system with diesel engine occurred due to a slippage of multi-friction clutch which was installed between increasing gear and shaft generator. In this paper, the mechanism of this vibration was verified via torsional, whirling, axial and structural vibration measurements of shafting system and noise measurement of gear box. And it was also identified by the theoretical analysis method.

• Structural Engineering and Mechanics
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• v.46 no.4
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• pp.519-531
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• 2013

To have a better understanding of the torsional mechanism and influencing factors of PC composite box-girder with corrugated steel webs, ultimate torsional strength of four specimens under pure torsion were analyzed with Model Test Method. Monotonic pure torsion acts on specimens by eccentric concentrated loading. The experimental results show that cracks form at an angle of $45^{\circ}$ to the member's longitudinal axis in the top and bottom concrete slabs. Longitudinal reinforcement located in the center of cross section contributes little to torsional capacity of the specimens. Torsional rigidity is proportional to shape parameter ${\eta}$ of corrugation and there is an increase in yielding torque and ultimate torque of specimens as the thickness of corrugated steel webs increases.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.99-107
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• 2000

With the results of calculation for natural frequencies, the forced reponses of coupled vibration of propulsion shafting were analysed by the modal analysis method. For the forced response analysis, axial exciting forces, axial damper/detuner, propeller exciting forces and damping coefficients were extensively investigated. As the conclusion of this study, some items are cleared as next. - The torsional amplitudes are not influenced by the radial excitation forces. - The axial vibrational amplitudes are influenced by the tangential exciting forces. An increase of amplitude is observed for the speed range in the neighbourhood of any torsional critical speed. - The coupling effect becomes larger if torsional and axial critical speed are closer together. - The axial exciting force of propeller is relatively strong, comparing with those of axial forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, as a resume one can say, that- Torsional vibration calculation with the classical one dimension model is still valid. - The influence of torsional excitation at each crank upon the axial vibration is impotent, especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimension model is insufficient in most of cases. - The torsional exciting torque of propeller can be neglected in most of cases. But, the axial exciting forces of propeller can not be neglected for calculating axial vibration of propulsion shafting.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.1-7
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• 2007

Torque fluctuation of an engine and angular velocity variation of a propeller shaft are the main excitation sources in a vehicle driveline. This paper presents the mechanism of these excitation sources. An equivalent model of the engine system and propeller shaft system is constructed to simulate the excitation phenomena. The analytical model contains the geometrical and dynamic mechanism. Combustion pressure of the cylinder is measured from dynamometer. The computer simulation is carried out by commercial program package. Results of the simulations show the characteristics of the torsional excitation source of the driveline.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.109-119
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• 1995

A driveline incorporating universal joints when driving through an angle can excite various components in a vehicle with second order excitation of torsional and bending vibrations, being transmitted either audibly(noise), or physically(vibration). For a certain range of vehicle dpeed noises can be radiated from the cab wall, in which resonances occur by the excitations transmitted from the driveline as a vibration source. In this paper, the excitation mechanism of cab noises is studied especially for the vehicle speed range of 65 .approx. 75 km/h through the simulation for torsional vibrations of the driveline and for bending vibrations of the cab of an 11 Ton grade Cargo Truck, and verified additionally by vibration and noise measurements. As a result, it is found that the uncomfortable noises in the cab are caused mainly by the abrupt increase of the joint angle of driveline near the axle differential resulted from the excessive clearance alignment of the leaf spring gate.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.563-572
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• 2001

With the results of calculation for natural frequencies the reponses of forced coupled vibration of propulsion shafting system were investigated by the modal analysis method. For the forced vibration response analysis, the axial exciting forces, the axial damper/detuner, propeller exciting forces and damping coefficients were extensively considered. As the conclusion of this study, some items are cleared as follows.-The torsional vibration amplitudes are not influenced by the radial excitation forces of the crank shaft. -The axial vibration amplitudes are influenced by the tangential exciting forces as well as the radial exciting forces of the crank shaft. The increase of the amplitudes is observed in the speed range at the neighbourhood of any torsional critical speed. 1The closer the torsional and axial critical speed. the larger coupling effect becomes. -The axial exciting force of propeller is relatively strong comparing with axial exciting forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, the following conclusions are obtained. -Torsional vibration calculation with the classical one dimensional model is still valid. -The influence of torsional excitation at each crank upon the axial vibration is improtant. especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimensional model is inaccurate in most of cases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.499-505
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• 2005

In this paper, a new type of pi+ezoelectric stepping motor is designed, manufactured and tested. This motor is composed of piezoelectric torsional actuator and a pair of one-way clutch bearings. The torsional actuator consists of 16-polygonal tube of piezoceramic that can produce an angular displacement associated with shear mode. One-way clutch bearing converts oscillation of torsional actuator into a continuous stepping rotation. The proposed stepping motor does not require any conversion mechanism for stepping motion like any other motors. In the design process, the shear resonance mode of piezoelectric actuator is analyzed by using a commercial finite element analysis program, and the performance of the fabricated torsional actuator is measured. $0.124^{\circ}$ of maximum angular displacement is measured in square wave excitation on the actuator only. The stepping motor is manufactured by assembling a pair of one-way clutch bearings and the torsional actuator. The maximum rotation speed of 72rpm and the blocking torque of 3.136 mNm are measured at 3540 Hz and 100V/mm. Once the proposed piezoelectric stepping motor is miniaturized, it can be used for many compact and precise moving applications.