• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.919-924
• /
• 2004

A CFA(Cooling Fan Assembly) is composed of a fan, motor and shroud, which is at the back of the automotive radiator. By forcing the wind to pass, the CFA controls the cooling performance of the radiator. The noise and vibration of the CFA may be primarily due to the resonance between the CFA and engine. The Interference among the fan, shroud and radiator by deformation is considered when the CFA is designed. In this paper, in order to analyze the structural vibration of the CFA for automobiles, a finite element model of the CFA is established by using a commercial FEM code. After the finite element modeling, the natural frequencies and the mode shapes are obtained from the FE analysis. The natural frequencies are obtained from the vibration test as well. Then, the results of the vibration test are compared with those of the FE analysis. The natural frequencies obtained by experiment have a great similarity to the results from FE model. We have confirmed the validity of the FE model and verify the structural safety for the resonance. The stress and displacements are obtained from FE analysis. We have confirmed the safety for the interference and failure.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1990.04a
• /
• pp.12-17
• /
• 1990

Stepped bean with immovable ends for large amplitude of vibration including effects of longitudinal displacement, shear deformation and rotary inertia is investigated for free and forced vibration using finite element method. Modified harmonic force matrix is introduced for analysis of vibration with finite amplitude of the stepped beam under uniform hamonic loading and beam with nonuniform harmonic loading. Numerical examples of stepped beam with various support conditions are analysed for deflections and natural frequencies. Results show that the proposed method is valid and efficient.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.356-361
• /
• 2001

A research to maximize the force transmitted from a vibration motor at the vibration mode, installed in the cellular phone jig, is presented in this study. When the natural frequencies corresponding to the structural vibration modes of the set exist within the range of the driving frequencies acquired by changing the RPM of the vibration motor, the structural vibration resonance is applicable to maximization of the vibration force sensible to the human body such as hands, arms, and hips. The analytical modal analysis using the Finite Elements and the experimental modal testing for the set jig were performed in order to understand the structural modes and the corresponding frequencies. Then the dynamic responses of the set jig to the given driving frequency were measured and the results on maximizing the vibration were confirmed by the FEM dynamic simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1994.10a
• /
• pp.288-294
• /
• 1994

A study of prediction and qualification techniques for structure borne booming noise is presented in this paper. Result from acoustic normal mode finite element analysis of a 1/2 size vehicle cavity sample model is compared to the that from an experiment. Coupled structural-acoustic analysis is performed on a 1/4 size vehicle cavity sample model surrounded by 2 mm thick normal steel plates. Interior noise levels around passensger's ear position are predicted and reduced by structural modification based on panel participation factor analysis about the sample cavity model. Futhermore, optimization technique in application of anti-vibration pad is studied.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.2
• /
• pp.208-214
• /
• 2008

This paper presents a structural modification for the performance improvement of a grain sorting machine. The grain sorting machine is used to sort abnormal grains from normal grains such as rice or wheat. Vibration is one of main causes to deteriorate the sorting performance of the machine. Based on the finite element analysis and the experimental modal testing, the vibration characteristics were investigated for the sorting machine. Furthermore, in order to improve the sorting performance of the machine, the frame, chute and base plate of the sorting machine were modified by using the results of the vibration analysis.

• Structural Engineering and Mechanics
• /
• v.66 no.1
• /
• pp.75-84
• /
• 2018

This study presents the reliability-based analysis of nonlinear structures using the analytical fragility curves excited by random earthquake loads. The stochastic method of ground motion simulation is combined with the random vibration theory to compute structural failure probability. The formulation of structural failure probability using random vibration theory, based on only the frequency information of the excitation, provides an important basis for structural analysis in places where there is a lack of sufficient recorded ground motions. The importance of frequency content of ground motions on probability of structural failure is studied for different levels of the nonlinear behavior of structures. The set of simulated ground motion for this study is based on the results of probabilistic seismic hazard analysis. It is demonstrated that the scenario events identified by the seismic risk differ from those obtained by the disaggregation of seismic hazard. The validity of the presented procedure is evaluated by Monte-Carlo simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1197-1202
• /
• 2007

The paper deals with the structural analysis and vibration test for the scaffolding system of LNG cargo containment. The eight-stories scaffolding system has telescopic area, working area, coner area and storage area in real system. In the structural analysis, the maximum displacement and stress of the each floor for the scaffolding system are investigated by finite element method. In the vibrational analysis, the natural frequencies and mode shapes for 8-stories scaffolding system of the LNG cargo containment are investigated. In order to compare theoretical natural frequencies with experimental ones, small size of 2-step scaffolding structure is used, and the theoretical results for natural frequency have a good agreement with experimental ones.

• The KSFM Journal of Fluid Machinery
• /
• v.5 no.3 s.16
• /
• pp.25-32
• /
• 2002

Structural and dynamic analyses of inducer and impeller for an oxidizer turbopump are peformed to investigate the safety level of strength and vibration at a design point. Due to high rotational speed of turbopump, effects of centrifugal forces are carefully considered in the structural analysis. Hydrodynamic pressure is also considered as an external force applied to inducer and impeller blades. A three-dimensional Finite Element Method (FEM) is used for linear and nonlinear structural analyses with modified Newton-Raphson iteration method. After the nonlinear trim solution is obtained from the structural analysis, dynamic characteristics are obtained as a function of rotational speed from the linearized eigenvalue analysis at an equilibrium position. According to the results of numerical analysis, the safety margins of strength and vibration resonances are sufficient enough for safe operation within the requited life cycle.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.271-278
• /
• 2001

Structural and dynamic analyses of inducer and impeller for a oxidizer turbopump are peformed to investigate the safety level of strength and vibration at design point. Due to high rotational speed of turbopump, effects of centrifugal forces are carefully considered in the structural analysis. Hydrodynamic pressure is also considered as an external force applied to inducer and impeller blades. A three dimensional finite element method(FEM) is used for linear and nonlinear structural analyses with modified Newton-Raphson iteration method. After the nonlinear trim solution is obtained from the structural analysis, dynamic characteristics are obtained as a function of rotational speed from the linearized eigenvalue analysis at an equilibrium position. According to the results of numerical analysis, the safety margins of strength and vibration resonances m sufficient enough to be operated safely within the required life cycle.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.04a
• /
• pp.414-421
• /
• 2001

Recently, the damping effect of building structures are greatly reduced because the use of non-structures members as like curtain wall are decreased and large open space are in need for the service of buildings. Assembly and office buildings with a lower natural frequency have a higher possibility of experiencing excessive vibration induced by human activities as like jumping, running and walking. These excessive vibration make the occupants uncomfortable and the serviceability deterioration. The common method of application of walking loads for the vibration analysis of structures subjected to walking loads is to inflict a series unit walking load and a periodic function at a node. But this method could not consider the moving effect of walking. In this study, natural frequency and damping ratio of plate structure are evaluated by heel drop tests. And new application of equivalent walking loads are introduced for vibration analysis of real slab system subjected to walking loads. The response obtained from the numerical analysis are compared well to the results measured by experimental tests. It is possible to efficiently analyze the vibration of floor which is subjected to walking loads by applying equivalent walking loads.