scholarly journals Orthogonality of Modes of Structures When Using the Exact Transcendental Stiffness Matrix Method

2000 ◽  
Vol 7 (1) ◽  
pp. 23-28 ◽  
Author(s):  
K.L. Chan ◽  
F.W. Williams
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Differential Equations ◽  
Stiffness Matrix ◽  
Matrix Method ◽  
Natural Frequencies ◽  
Plane Frames ◽  
Transcendental Functions ◽  
Physical Insight ◽  
Piecewise Continuous

This paper presents theory, physical insight and results for mode orthogonality of piecewise continuous structures, including both coincident and non-coincident natural frequencies. The structures are ones for which exact member equations have been obtained by solving the governing differential equations, e.g. as can be done for members of plane frames or prismatic plate assemblies. Such member equations are transcendental functions of the distributed member mass and the frequency. They are used to obtain a transcendental overall stiffness matrix for the structure, from which the natural frequencies are extracted by using the Wittrick-Williams algorithm, prior to using any existing method to find the modes which are examined from the orthogonality viewpoint in this paper. The natural frequencies and modes found are the exact values for the structure in the sense that the usual finite element method approximations are avoided.

Derivation of New Transcendental Member Stiffness Determinant for Vibrating Frames

2003 ◽  
Vol 03 (02) ◽  
pp. 299-305 ◽  
Author(s):  
F. W. Williams ◽  
D. Kennedy
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stiffness Matrix ◽  
Infinite Order ◽  
Natural Frequencies ◽  
Dynamic Stiffness ◽  
Structural Stiffness ◽  
Trial And Error ◽  
Stiffness Matrices ◽  
Vibration Problems

Transcendental dynamic member stiffness matrices for vibration problems arise from solving the governing differential equations to avoid the conventional finite element method (FEM) discretization errors. Assembling them into the overall dynamic structural stiffness matrix gives a transcendental eigenproblem, whose eigenvalues (natural frequencies or their squares) are found with certainty using the Wittrick–Williams algorithm. This paper gives equations for the recently discovered transcendental member stiffness determinant, which equals the appropriately normalized FEM dynamic stiffness matrix determinant of a clamped ended member modelled by infinitely many elements. Multiplying the overall transcendental stiffness matrix determinant by the member stiffness determinants removes its poles to improve curve following eigensolution methods. The present paper gives the first ever derivation of the Bernoulli–Euler member stiffness determinant, which was previously found by trial-and-error and then verified. The derivation uses the total equivalence of the transcendental formulation and an infinite order FEM formulation, which incidentally gives insights into conventional FEM results.

scholarly journals Circular Space Curve Frame (3D) with any Load and Spring Supports by Transfer Matrix Method and Finite Element Method

2019 ◽  
Vol 8 (12) ◽  
pp. 3981-3987
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Stiffness Matrix ◽  
Matrix Method ◽  
Complex Problem ◽  
Fem Method ◽  
Circular Space ◽  
Element Method

In this paper, authors present a new numerical method, combining the Transfer Matrix Method and Finite Element Method (TMM - FEM), to analyze spatially circular curved bar, with general load and elastic support. Analysis space curved bar is complex problem because conventional methods will not simultaneously calculate the entire structure, or difficulty in establish the stiffness matrix, or the size of stiffness matrix is too large due to multiple elements. TMM - FEM method is proposed to promote the advantages of each method. Due to being directly generated from the parametric equations of the bar axis, the analytical results are accurate. Results are programed in Matlab and verified with SAP2000 programe.

Transverse Natural Vibrations of a Cracked Beam Loaded with a Constant Axial Force

1993 ◽  
Vol 115 (4) ◽  
pp. 524-528 ◽  
Author(s):  
M. Krawczuk ◽  
W. M. Ostachowicz
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Elements ◽  
Stiffness Matrix ◽  
Natural Frequencies ◽  
Numerical Calculations ◽  
Open Crack ◽  
Natural Vibrations ◽  
Cracked Beam ◽  
Matrix Calculation

The influence of transverse, one-edge open cracks on the natural frequencies of the cantilever beam subjected to vertical loads is analyzed. A finite element method (FE) is used for modelling the beam. A part of the cracked beam is modelled by beam finite elements with an open crack. Parts of the beam without a crack are modelled by standard beam finite elements. An algorithm of a linear stiffness matrix and a geometrical stiffness matrix calculation for a cracked element is presented. The results of numerical calculations obtained for the presented model are compared with the results of analytical calculations given in the literature and also with the results of numerical calculations obtained for a model with geometrical stiffness matrix of uncracked elements.

scholarly journals Modeling and Eigenfrequency Analysis of Sound-Structure Interaction in a Rectangular Enclosure with Finite Element Method

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
Samira Mohamady ◽  
Raja Kamil Raja Ahmad ◽  
Allahyar Montazeri ◽  
Rizal Zahari ◽  
Nawal Aswan Abdul Jalil
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Natural Frequencies ◽  
Active Noise Control ◽  
Interior Noise ◽  
Rectangular Enclosure ◽  
Sound Structure ◽  
Flexible Panel ◽  
Experimental Works ◽  
Element Method

Vibration of structures due to external sound is one of the main causes of interior noise in cavities like automobile, aircraft, and rotorcraft, which disturb the comfort of passengers. Accurate modelling of such phenomena is required in eigenfrequency analysis and in designing an active noise control system to reduce the interior noise. In this paper, the effect of periodic noise travelling into a rectangular enclosure is investigated with finite element method (FEM) using COMSOL Multiphysics software. The periodic acoustic wave is generated by a point source outside the enclosure and propagated through the enclosure wall and excites an aluminium flexible panel clamped onto the enclosure. The behaviour of the transmission of sound into the cavity is investigated by computing the modal characteristics and the natural frequencies of the cavity. The simulation results are compared with previous analytical and experimental works for validation and an acceptable match between them were obtained.

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