• Structural Engineering and Mechanics
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• v.7 no.3
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• pp.259-276
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• 1999

An analytical solution for the shape functions of a beam segment supported on a generalized two-parameter elastic foundation is derived. The solution is general, and is not restricted to a particular range of magnitudes of the foundation parameters. The exact shape functions can be utilized to derive exact analytic expressions for the coefficients of the element stiffness matrix, work equivalent nodal forces for arbitrary transverse loads and coefficients of the consistent mass and geometrical stiffness matrices. As illustration, each distinct coefficient of the element stiffness matrix is compared with its conventional counterpart for a beam segment supported by no foundation at all for the entire range of foundation parameters.

• Journal of KSNVE
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• v.9 no.3
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.452-456
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• 2006

The critical speeds and mode shapes are most important to determine the behaviors of rotor in designing rotating machinery. As the capacity and span of turbine-generator increases, the turbine-generator system is composed of many components such as bearings, pedestal, turbine and hood and so on. Also, it is getting flexible and has many critical speeds. Especially, as the characteristics of bearing-pedestal are very complicated, they affect the entire vibration characteristics of turbine-generator system. In this paper, it is observed how to determine the equivalent dynamic stiffness of bearing-pedestal by analytical and experimental method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.263-266
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• 2005

The critical speeds and mode shapes are most important to determine the behaviors of rotor in designing rotating machinery. As the capacity and the span of turbine-generator increases, the turbine-generator system has many components such as bearings, pedestal, turbine and baseplates etc. and it is getting flexible and has many critical speeds. Especially, the characteristics of bearing-pedestal are very complicated and then they affect the entire vibration characteristics of turbine-generator system. In this paper, it is observed how to determine the equivalent dynamic stiffness of bearing-pedestal by analytic and experimental method.

• Journal of KSNVE
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• v.5 no.4
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• pp.537-542
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• 1995

In this paper the method of modeling and optimization for the joint of the vehicle structure is proposed. First it is described that the method of substituting equivalent beam elements to spring elements for the joint. The stiffnesses of the spring elementsare calculated using the section properties of equivalent beam elements. To get required dynamic characteristics section properties of equivalent beam element are set to design variables and optimized. The study shows that joint stiffnesses can be effectively determined in designing vehicle structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.296-303
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• 2004

In this study, equivalent linear damping and stiffness of a single-degree-of-freedom (SDOF) structure with a rotational friction damper are estimated using the result of experiments and compared with those obtained from non-linear time history analyses. First, the transfer function of the test model is constructed and then the equivalent stiffness and damping are calculated, using the half-power bandwidth (HPB) method. For comparative study, those properties are estimated based on stochastic theory in the time domain. Both equivalent linear systems identified from experiments and numerical analyses correspond well. Further, it is observed that there exists an optimal clamping force on the rotational friction damper from estimated equivalent damping.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.304-308
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• 2006

The focus of this study is modeling technique for a bellows in vehicle exhaust system. Bellows was developed using tile finite element model by replacing with the equivalent beam. The equivalent beam model were studied in detail. Non-structural node in the cross section of original model is given to expressing their motion. Equivalent mass matrix and stiffness matrix calculated using Guyan reduction method. Material Properties of beam was obtained from the direct comparison between equivalent model and that of Timoshenko beam model. The calculated natural frequencies and mode shape are compared with the reference results and coincided well. The results were compared with the confirmed results, which were in good agreement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.938-941
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• 2011

This paper deals with the equivalent shear modulus of the egg-box core. There are three approaches to obtain the equivalent shear modulus of core: a finite element analysis, an analytical study, and an empirical method. In this study, an 3-point bending test is used to evaluate the equivalent shear modulus of the Egg-Box core. As a result of the present work, the equivalent shear modulus of egg-box core at room temperature can be obtained. And this result is compared with the result of finite element analysis.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.393-401
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• 2009

The flexural-stiffness formula of the wale for the innovative prestressed support (IPS) system was precisely derived, and the equivalent beam stiffness was introduced for application in the actual design of the IPS wale. The cable tension forces of the IPS wale were calculated in both cases, and the axial-deformation effects were included and ignored, respectively. The central displacements of the 1-post, 2-post, 3-post, and 4-post IPS wales were calculated based on the principle of virtual work. The effects of the IPS wale length and cable inclination angle were also investigated using the derived central displacements. The simplified equivalent flexural stiffness of the IPS wale is presented herein for design purposes, and the validity of the proposed design formula was verified through its comparison with the FE and analysis solutions.

• Journal of Magnetics
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• v.21 no.3
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• pp.379-386
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• 2016

To satisfy the requirement of magnetically suspended control moment gyroscope (MSCMG) that magnetic bearing can provide torque, a novel 4DOF hybrid magnetic bearing (HMB) with integrated structure was designed. Mathematical models of forces and torques are established by using equivalent magnetic circuit method. The current stiffness, displacement stiffness, tilting current stiffness and angular stiffness of the 4DOF hybrid magnetic bearing are derived by the mathematical models. Equivalent magnetic circuit method and finite element method (FEM) simulation results indicate that the force has a good linear relationship with both displacement and current, and the torque has a good linear relationship with angular displacement and current. The novel 4DOF HMB is capable of achieving control in both two radial translational degrees of freedom (DOF) and also two radial rotational DOFs. The 4DOF HMB is well adapted to MSCMG system, exhibiting advantages in the controllable DOF, light weight and easy to control.