• 대한기계학회논문집
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• 제18권11호
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• pp.2922-2931
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• 1994

We propose a modified 6-node element, where the sampling point of Gauss quadrature moved in the thickness direction. The modified 6-node element has been applied to static problems and forced motion analyses. In this study, this method is extended to the finite element analysis of the natural frequencies of two dimensional problems. We also propose a modified 16-node element for three dimensional problems, which behaves much like a 20-node element with smaller degree of freedom. The modified 6-node and 16-node elements have been applied to the modal analyses of beams and plates, respectively. The results agree well with the results of the 8-node or 20-node element models.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.88-93
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• 1998

Since rattling noise, which occur in mechanical linkage with free play or glove boxes in passenger cars, play an important role in the generation of industrial noise and vibration, it is interest to study these dynamics. A difference equations are derived which described the motions of a mass constrained by pre-compressed spring and forced by a high frequency base excitation. Two types of saddle are founded from these difference equations and the stable and unstable manifolds are constructed in these saddle point. For a certain region in a parameter space of exciting displacement and coefficient of restitution, transversal intersections of stable and unstable manifolds exist. Therefore it is founded that there are large families of periodic and irregular non-periodic motions in rattling system i.e. chaos motion is observed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.27-33
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• 1998

The powertrain is a system of exciters which are connected by vibration transmitters and noise radiators. The powertrain has infinite natural frequencies. If the engine explosion, excites a certain natural frequency, then the powertrain system seriously vibrates. The torsional vibration arises from here. Torsional vibration like this can cause various noises as rattle and booming. In this study, the simulation models of multiple degrees of freedom were developed to reduce the torsional vibration of the powertrain. These models are combined mass moment of inertias with torsional springs. The free and forced vibration analyses were carried out by these models; and the validity of the simulation models were checked by the field test. The reduction effect of the torsional vibration along the driveline design factor is presented by the analytical results.

• Steel and Composite Structures
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• 제36권2호
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• pp.179-186
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• 2020

In this paper, the forced resonance vibration of porous functionally graded (FG) curved nanobeam is examined. In order to capture the hardening and softening mechanisms of nanostructure, the nonlocal strain gradient theory is employed to build the size-dependent model. Using the Timoshenko beam theory together with the Hamilton principle, the equations of motion for the curved nanobeam are derived. Then, Navier series are used in order to obtain the dynamical deflections of the porous FG curved nanobeam with simply-supported ends. It is found that the resonance position of the nanobeam is very sensitive to the nonlocal and strain gradient parameters, material variation, porosity coefficient, as well as geometrical conditions. The results indicate that the resonance position is postponed by increasing the strain gradient parameter, while the nonlocal parameter has the opposite effect on the results. Furthermore, increasing the opening angle or length-to-thickness ratio will result in resonance position moves to lower-load frequency.

• Structural Engineering and Mechanics
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• 제2권1호
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• pp.95-112
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• 1994

This paper describes the formulation and application of a dynamic model for a conventional rail track subjected to arbitary loading functions that simulate wheel/rail impact forces. The rail track is idealized as a periodic elastically coupled beam system resting on a Winkler foundation. Modal parameters of the track structure are first obtained from the natural vibration characteristics of the beam system, which is discretized into a periodic assembly of a specially-constructed track element and a single beam element characterized by their exact dynamic stiffness matrices. An equivalent frequency-dependent spring coefficient representing the resilient, flexural and inertial characteristics of the rail support components is introduced to reduce the degrees of freedom of the track element. The forced vibration equations of motion of the track subjected to a series of loading functions are then formulated by using beam bending theories and are reduced to second order ordinary differential equations through the use of mode summation with non-proportional modal damping. Numerical examples for the dynamic responses of a typical track are presented, and the solutions resulting from different rail/tie beam theories are compared.

• Steel and Composite Structures
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• 제22권2호
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• pp.277-299
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• 2016

In this paper, free vibration, forced vibration, resonance and stress wave propagation behavior in nanocomposite plates reinforced by wavy carbon nanotube (CNT) are studied by a mesh-free method based on first order shear deformation theory (FSDT). The plates are resting on Winkler-Pasternak elastic foundation and subjected to periodic or impact loading. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In the mesh-free analysis, moving least squares (MLS) shape functions are used for approximation of displacement field in the weak form of motion equation and the transformation method is used for imposition of essential boundary conditions. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of elastic foundation coefficients, plate thickness and time depended loading are examined on the vibrational and stresses wave propagation responses of the nanocomposite plates reinforced by wavy CNT.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.915-920
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• 1987

When a task requires two robot arms to move in a cooperative manner sharing a common workspace, potential collision exists between the two robot arm . In this paper, a novel approach for collision-free trajectory planning along paths of two SCARA-type robot arms is presented. Specifically, in order to describe potential collision between the links of two moving robot arms along the designated paths, an explicit form of "Virtual Obstacle" is adopted, according to which links of one robot arm are made to grow while the other robot arm is forced to shrink as a point on the path. Then, a notion of "Coordination Chart" is introduced to visualize the collision-free relationship of two trajectories.of two trajectories.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.295-304
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• 2010

The paper summarizes the VIV-related research with the focus on flexible riser and pipe models subject to various engineering conditions. First of all, a series of numerical simulations for the purpose of validating the efficiency of FSI solution approach (ANSYS MFX) has been performed. The comparison between the simulation and the experimental data shows that the present FSI solution method is capable of giving acceptable estimation to VIV problems. As a meaningful application to engineering problems, some tentative simulation cases which are difficult to carry out in experiment, such as a flexible pipe with internal flow and multi-assembled pipes, have been successfully carried out. The coupling mechanism between vortex shedding and the VIV has been well interpreted.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.472-477
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• 2003

Spindle state monitoring is getting more and more important according to the technology trend of spindle that is accurate and automated. Spindle state monitoring is to measure the state of rotation vibrations. The spindle rotation error motion detected by sensing device includes rotation object's unbalance, external forced vibrations, shape error of spindle, as well as measuring error of monitoring device. In this paper, we have inspected the runout characteristics. Also, we introduce the way to exclude the runout element that appear while you monitor a spindle state.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.103-108
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• 2001

The structure of hard disk drive(HDD) is excited by dynamic motion of a disk-spindle motor, and it makes sound noise. Therefore, the cover and the base of HDD should be designed to reduce noise and vibration induced by spindle motor. The prediction technique of sound pressure level(SPL) of a given structural shape enables us to design a cover and a base with much less vibration and noise. In this paper, we measured the force of disk-spindle motor and predicted SPL from HDD by computational simulation. To get a SPL of HDD by computational simulation, modal analysis and forced vibration analysis were performed with ANSYS, and sound radiation was computed using SYSNOISE. The calculated results were compared with experimental results and a good agreement was obtained. With this computer simulation procedure and design of experiment(DOE), optimal thickness of noise barrier and damper was calculated.