• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.9 s.114
• /
• pp.958-963
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation $f_1\;and\;f_2$, respectively, the displacement at the center of the plate has the strongest component at frequency $f_1$. The angular displacement of the plate has strong components at $f_1-f_2$ and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shaker with low frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.81-85
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$, respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$, and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shatter with low frequencies.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.746-751
• /
• 2003

When a cantilever beam rotates about the axis perpendicular to its longitudinal axis, its natural frequencies vary. This phenomenon which is caused by centrifugal inertia forces is often referred to as the stiffening effects. Since the variation of natural frequencies often creates critical problems for the rotating structures, it is necessary to control the variation of natural frequencies. As the cross section of a rotating cantilever beam varies, natural frequencies can be changed. The thickness and the width of the cantilever beam are assumed to be cubic spline functions in the present work. An optimization method is employed to find the optimal thickness and width of the rotating beam. This result can be used for the design of rotating structures such as turbine and helicopter blades.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.10
• /
• pp.1580-1588
• /
• 1997

A modeling method for the flapwise bending vibration of a rotating cantilever beam which has small slenderness ratio is presented in this paper. It is shown that as the slenderness ratio decreases the shear and rotary inertia effects increase. Such effects become critical for the accurate estimation of the natural frequencies and modeshapes, especially higher frequencies and modes, as the angular speed increases. It is also shown that the flapwise bending natural frequencies are higher than the chordwise bending natural frequencies. The discrepancy between first natural frequencies are especially significant when the hub radius ratio is small.

• Advances in concrete construction
• /
• v.10 no.6
• /
• pp.499-507
• /
• 2020

In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.707-710
• /
• 2005

In this paper, we studied about the dynamic behavior of a cracked rotating cantilever beam. The influences of a rotating angular velocity, the crack depth and the crack position on the dynamic behavior of a cracked cantilever beam have been studied by the numerical method. The cracked cantilever beam is modeled by the Euler-Bernoulli beam theory. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. The lateral tip displacement and the axial tip deflection of a rotating cantilever beam is more sensitive to the rotating angular velocity than the depth and position of crack. Totally, as the crack depth is increased, the natural frequency of a rotating cantilever beam is decreased in the first and second mode of vibration.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.6
• /
• pp.103-110
• /
• 2000

In this study, the angular twist type torque-meter was designed and manufactured with STS 304 and fiber-reinforced composite materials to improve the dynamic properties of the existing torque-meter. From the Experimental and analytical results, it was found that the dynamic characteristics of co-cured bonded torque-meter rotating shaft were better than those of the adhesively and unreinforced torque-meter rotating shaft. For the torque-meter rotating shaft manufactured by co-cured bonded with the glass fiber-epoxy composite and with a stacking sequence of $[$\pm$30$^{\circ}$/STS304]_{2s}$, the natural frequency and the radial spring constant were increased by 64% and 137% compared to those of the unreinforced torque-meter rotating shaft.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.1017-1022
• /
• 1996

This paper presents results of dynamic analysis of the missile initial motion arising from the missile detent force. Using ADAMS (Automatic Dynamic Analysis of Mechanical System) software, a non-linear 46-DOF (Degree of Freedom) model is developed for the launcher system including missile and launch tube contact problem. From the dynamic analysis, it is found that initial angular velocity of the missile increases when the missile detent force increases (more than 18 g) and also rocket exhaust plume is taken into account. To achieve the missile launching s ability, it needs to reduce the missile initial detent force and exhaust plume area of the launcher. Results of the dynamic analysis on the system natural frequency agree well with those obtained from experimental modal tests. The overall results suggest that the proposed method is a useful tool for prediction of initial missile stability as well as d :sign of the missile launcher system.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.121-126
• /
• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived applying a modeling method that employs hybrid deformation variables. 'TI1e influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe are studied by the numerical method. The effect of tip mass on the stability of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.3
• /
• pp.155-162
• /
• 2004

This paper presents the fabrication procedure and the experiments for the 3-axis fine positioning stage proposed in［1］. First, the dynamic characteristics of the actuator and the stage are tested with the preload changed in order to validate the stage design specifications. Secondly, the performance of the stage is also evaluated on the accuracy associated with linear positioning, angular error, and straightness error. Experimental results show that the developed stage is accurate enough to be used for nanometer positioning. Through the analysis and experiment, the developed fine positioning stage are found to have a long stroke due to the magnetically preloaded PZT actuators, the minimum motion crosstalk due to the use of a ball contact mechanism and the compact design.