• Steel and Composite Structures
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• 제35권1호
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• pp.43-59
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• 2020

In this study, free vibration analysis of laminated composite parabolic thick plate frames by using finite element method is introduced. Governing equations of an eigenvalue problem are obtained from First Order Shear Deformation Theory (FSDT). Finite element method is employed to obtain natural frequency values from the governing differential equations. The frames consist of two flat square plates and one singly curved plate. Parameters like radii of curvature, aspect ratio, ply orientation and boundary conditions are investigated to understand their effect on dynamic behavior of such a structure. In addition, multi-bay structures of such geometry with different stacking order are also taken into account. The composite frame structures are also modeled and simulated via ANSYS to verify the accuracy of the present study.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.377-380
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• 2005

Damping materials encompass a broad range of materials, including, but not limits to, pressure sensitive adhesives, epoxies, rubbers, foams, thermoplastics, enamels and mastics. Their common characteristic is that their modulus is represented by a complex quantity, possessing both a stored and dissipative energy component. Loss factor of damping material analyzed more than 2 times than rubber to 1.5 $\sim$ 2.3, could know that Damping layer has excellent attenuation performance in side of vibration reduction. Measurements of vibration using accelerometers by adhesion of Damping layer, square Plate by Separation of Damping layer is less binding of Damping layer, analyzed low loss factor and Natural Frequency by free Vibration of Square Plate.

• Structural Engineering and Mechanics
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• 제22권6호
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• pp.719-739
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• 2006

An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.96-100
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• 2008

In this paper, a experimental and theoretical study is carried out on the hydroelastic vibration for a rectangular bottom and side plate of tank. It is assumed that the tank wall is clamped along the plate edges. The fluid velocity potential is used for the simulation of fluid domain and to obtain the added mass due to plate vibration. It is assumed that the fluid is imcompressible and inviscid. Assumed mode method is utilized to the plate model and hydrodynamic force is obtained by the proposed approach. The coupled natural frequencies are obtained from the relationship between kinetic energies of a wall including fluid and the potential energy of the wall. The theoretical result is compared with the three-dimensional finite element method. In order to verify the result, modal test was carried out for bottom/side plate of tank model by using impact hammer. It was found the fundamental natural frequency of bottom plate is lower than that of side plate of tank and theoretical result was in good agreement with that of commercial three-dimensional finite element program.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.77-81
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• 2003

SDM (Structural Dynamics Modification) is a tool to improve dynamic characteristics of a structure, more specifically of a base structure, by adding or deleting auxiliary (modifying) structures. In this paper, the goal of the optimal SDM is set to maximize the natural frequency of a base plate structure by attaching serially-connected beam stiffeners. The design variables are chosen as positions of the attaching beam stiffeners, where the number of stiffeners is considered as a design space. The problem of non-matching interface nodes between the base plate and beam stiffeners is solved by using localized Lagrange multipliers, which act to glue the two structures with non-matching interface nodes. As fer the cases of non-matching interface nodes problem, the governing equation of motion of a structure can be considered from the viewpoint of a topological modification, which involves the change of the number of structural members and DOFs. Consequently, the eigenpairs of the beam-stiffened plate structure are obtained by using an eigen reanalysis technique of topological modifications. Evolution Strategies (ES), which is a probabilistic population-based optimization technique that mimics the principles from biological evolution in nature, is utilized as a mean for the optimization.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.668-671
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• 1997

In order to investigate the vibration characteristics of fluid-structure interaction problem, we modeled two identical rectangular plates coupled with bounded fluid. The fixed boundary condition along the plate edges and an ideal fluid were assumed. A commercial computer code, ANSYS was used to perform finite element analysis and FEM solutions were compared with the experimental results to modify the finite element model. As a result, comparison of FEM and experiment showed good agreement, and the transverse vibration modes, in-phase and out of-phase. were observed alternately in the tluid-coupled system. The effects of distance between two rectangular plates and width to length ratio on the fluid-coupled natural frequency were investigated. And it was found that the ormalized natural frequency of the fluid-coupled system monotonically increased with an increase in the number of modes.

• Steel and Composite Structures
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• 제30권1호
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• pp.31-46
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• 2019

In the present study, the various dynamic properties of MWCNT embedded fiber reinforced polymer uniform and tapered composite (MWCNT-FRP) plates are investigated. Various configurations of a tapered composite plate with ply-drop off and uniform composite plate have been considered for the development of the finite element formulation and experimental investigations. First order shear deformation theory (FSDT) has been used to derive the kinetic and potential energy equations of the hybrid composite plates by including the effect of rotary inertia, shear deformation and non-uniformity in thickness of the plate. The governing equations of motion of FRP composite plates without and with MWCNT reinforcement are derived by considering a nine- node rectangular element with five degrees of freedom (DOF) at each node. The effectiveness of the developed finite element formulation has been demonstrated by comparing the natural frequencies and damping ratio of FRP composite plates without and with MWCNT reinforcement obtained experimentally. Various parametric studies are also performed to study the effect of CNT volume fraction and CNT aspect ratio of the composite plate on the natural frequencies of different configurations of CNT reinforced hybrid composite plates. Further the forced vibration analysis is performed to compare the dynamic response of the various configurations of MWCNT-GFRP composite plate with GFRP composite plate under harmonic excitations. It was observed that the fundamental natural frequency and damping ratio of the GFRP composite plate increase approximately 8% and 37% respectively with 0.5wt% reinforcement of MWCNT under CFCF boundary condition. The natural frequencies of MWCNT-GFRP hybrid composite plates tend to decrease with the increase of MWCNT volume fraction beyond 2% due to agglomeration of CNT's. It is also observed that the aspect ratio of the CNT has negligible effect on the improvement of dynamics properties due to randomly orientation of CNT's.

• 산업기술연구
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• 제17권
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• pp.191-197
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• 1997

For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation on the natural frequency is thoroughly studied.

• Smart Structures and Systems
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• 제15권5호
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• pp.1345-1362
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• 2015

The present paper deals with the free vibration analysis of the functionally graded solid and annular circular plates with two functionally graded piezoelectric layers at top and bottom subjected to an electric field. Classical plate theory (CPT) is used for description of the all deformation components based on a symmetric distribution. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness direction of the plate. The properties of plate core can vary from metal at bottom to ceramic at top. The effect of non homogeneous index of functionally graded and functionally graded piezoelectric sections can be considered on the results of the system. $1^{st}$ and $2^{nd}$ modes of natural frequencies of the system have been evaluated for both solid and annular circular plates, individually.

• 소음진동
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• 제10권4호
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• pp.648-654
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• 2000

A procedure to determine the realizable optimal positions of rigid supports is suggested to get a maximum fundamental natural frequency. a measured frequency response function based substructure-coupling technique is used to model the supported structure. The optimization procedure carries out the eigenvalue sensitivity analysis with respect to the stiffness of supports. As a result of such stiffness optimization, the optimal rigid-support positions are shown to be determined by choosing the position of the largest stiffness. The optimally determined support conditions are verified to satisfy the eigenvalue limit theorem. To demonstrate the effectiveness of the proposed method, the optimal support positions of a plate model are investigated. Experimental results indicate that the proposed method can effectively find out the optimal support conditions of the structure just based on the measured frequency response functions without any use of numerical model of the structure.