Application of matched‐field processing to structural vibration problems.

1996 ◽  
Vol 99 (4) ◽  
pp. 2518-2529
Author(s):  
Gabriella Turek ◽  
W. A. Kuperman
Keyword(s):  
Structural Vibration ◽  
Matched Field Processing ◽  
Vibration Problems

AN ENHANCED TECHNIQUE FOR ANALYZING STRUCTURAL VIBRATION PROBLEMS UNDER SHOT NOISE LOADING

2005 ◽  
Vol 05 (04) ◽  
pp. 597-614
Author(s):  
ALESSANDRO BARATTA ◽  
OTTAVIA CORBI
Keyword(s):  
Nonlinear Systems ◽  
Probability Function ◽  
Response Probability ◽  
Approximate Expression ◽  
High Accuracy ◽  
Structural Vibration ◽  
Mdof Systems ◽  
Vibration Problems ◽  
Multiple Integrals ◽  
Approximate Procedure

The present paper deals with dynamic nonlinear systems loaded by badly defined forcing actions. As an improvement on the first approximate procedure developed by the authors, a more feasible and reliable alternative entropic closure approach is presented herein. Such a procedure allows one to deal with high order nonlinearities, and it can be suitably generalized to treating multi-degree of freedom (MDOF) systems. In fact, the effectiveness of the proposed approach is intricately linked to the exact calculation of some multiple integrals related to the approximate expression of the chosen response probability function. To this end, a procedure that can guarantee high accuracy in the computation of integrals is also studied, which helps in validating the whole approach.

Experimental Analysis of Damping across Joints in Metal Plates

2006 ◽  
Vol 5-6 ◽  
pp. 391-398 ◽  
Author(s):  
S.J.I. Walker ◽  
G.S. Aglietti ◽  
P.R. Cunningham
Keyword(s):  
Experimental Approach ◽  
Dynamic Behaviour ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Advantages And Disadvantages ◽  
Metal Plates ◽  
Engineering Sciences ◽  
Wide Range ◽  
Vibration Problems ◽  
The One

In the current world of engineering, structural vibration problems continue impact the design and construction of a wide range of products. Amid the parameters that determine the dynamic behaviour of a structure the one that takes into account the dissipation of energy resulting in the decay of the vibration is the least understood and the most difficult to quantify [1]. The estimation of damping factors is of interest in most branches of engineering sciences. In the field of aircraft structures the damping directly affects the fatigue life, a parameter which is applied conservatively due to the inherent complexity in modelling the damping of built up structures and the potentially catastrophic consequences of a fatigue failure. One of the most important problems is the limited knowledge of how joints affect the damping of the complete structure. This work therefore addresses this issue and focuses on the damping of joints in metal plates as part of a larger project to investigate the damping of built up structures. Various plate configurations are experimentally investigated using two different approaches. The results from the configurations are compared and discussed along with the advantages and disadvantages of each experimental approach. This enables a link to be identified between the damping magnitudes and the mode shapes and joint stiffnesses.

Mesh Shape Preservation for Flow-Induced Vibration Problems

2002 ◽  
Author(s):  
R. M. C. So ◽  
Y. Liu ◽  
Y. G. Lai
Keyword(s):  
Numerical Technique ◽  
Three Dimensional ◽  
Cross Flow ◽  
Physical Space ◽  
Shape Preservation ◽  
Structural Vibration ◽  
Flow Induced Vibration ◽  
Time Step ◽  
Dimensional Flow ◽  
Vibration Problems

This paper describes a numerical technique that can prevent the mesh from severe distortion in flow-induced vibration calculations. An orthogonal transformed space that is related to the physical space through a Laplacian equation is introduced. At each time step, the mesh may deform significantly in the physical space due to structural vibration, but the mesh nodal value in the transformed space remains constant. As long as the coordinates in the physical space can be adjusted to render the transformed space independent of time, the mesh shape in the physical space is preserved, even though the mesh area may enlarge or reduce significantly. For simplicity, a two-dimensional flow-induced vibration problem is used to illustrate this method. Two side-by-side elastic cylinders in a cross flow are considered. The Reynolds number is fixed at 200 so that a laminar wake is still available. The mass ratio is chosen to be small so that large displacements of the cylinders can be realized. The predictions with and without mesh preservation are compared. The difference between the two results could be as large as 25% in the prediction of the mean transverse displacements of the cylinders. The method could be extended to three-dimensional flow-induced vibration problems without much difficulty.

Identification of a Positive Definite Mass Matrix

1988 ◽  
Vol 110 (1) ◽  
pp. 49-52 ◽  
Author(s):  
John E. Mottershead ◽  
T. K. Tee ◽  
A. W. Lees
Keyword(s):  
Frequency Domain ◽  
Mass Matrix ◽  
A Priori ◽  
Positive Definiteness ◽  
Positive Definite ◽  
Structural Vibration ◽  
Vibration Problems ◽  
Continuous Frequency ◽  
Priori Information ◽  
Stiffness And Damping

In system identification it is important that any a priori information about the system is utilized in the processing of measured data. Structural vibration problems can be modelled in terms of mass, stiffness, and damping and it is usually the case that the mass matrix is positive definite. In this paper the authors demonstrate how the property of positive definiteness of the mass matrix can be included in the formulation of a continuous frequency domain filter. Results are compared with those obtained from a linear, frequency domain filter which does not impose the condition of positive definiteness on the mass matrix.

scholarly journals A Novel Active Control Strategy with Decentralized Decoupling and Wavelet Packet Transformation: Design and Verification

2021 ◽  
Vol 11 (8) ◽  
pp. 3554
Author(s):  
Lihua Yang ◽  
Weipeng Gao ◽  
Jun Yang ◽  
Bo Zhao ◽  
Libin Liu
Keyword(s):  
Vibration Control ◽  
Wavelet Packet ◽  
Underwater Vehicles ◽  
Structural Vibration ◽  
Line Spectrum ◽  
Path Coupling ◽  
Fxlms Algorithm ◽  
Wavelet Packet Transformation ◽  
Frequency Excitation ◽  
Vibration Problems

Active vibration control (AVC) can solve many vibration problems. However, structural vibration in underwater vehicles often involves other factors such as complex excitation and path coupling, etc. At present, the traditional algorithm (e.g., multi Filtered-x Least Mean Square, M-FxLMS) usually cannot effectively process the multi-frequency excitation and the coupling effects of the multi-secondary path, which will affect its convergence and stability to a certain extent. Consequently, a novel strategy is presented in this paper, namely, the wavelet packet transformation decentralized decoupling M-FxLMS algorithm (WPTDDM-FxLMS), which can solve the structural vibration problems mentioned above. The multi-frequency control is converted into a single-frequency line spectrum control, and the feedback compensation factor is introduced in the identification of the secondary path, both of which can simplify the multi-path control system to the parallel single-path systems. Furthermore, the WPTDDM-FxLMS algorithm is applied to the AVC in a multi-input and multi-output system (MIMO) vibration platform. Finally, the simulation and experiments show that the wavelet packet can decompose the multi-frequency excitation into a line spectrum signal, and the improvement of the decentralized decoupling and the variable step-size can effectively reduce the computation amount and increase the convergence speed and accuracy. Overall, the novel algorithm is significant for multi-path coupling vibration control. It will have certain engineering application value in underwater vehicles.

scholarly journals Kajian Numerik Ketebalan Lapisan Redaman Getaran Berbahan Semen untuk Dek Kapal Penumpang

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Wibowo H. Nugroho ◽  
Nanang J. H. Purnomo ◽  
Endah Suwarni
Keyword(s):  
Finite Element Analysis ◽  
Structural Vibration ◽  
Harmonic Load ◽  
Minimum Thickness ◽  
Element Analysis ◽  
Cement Material ◽  
Deck Plate ◽  
Vibration Problems ◽  
Ship Classification ◽  
Ship Vibration

Ship vibration problems today's increasingly complex and often occurs in addition to the strict requirements of ship classification agencies for allowable levels of vibration so that passengers and crew more comfortable and secure. One method for reducing the influence of ship structural vibration is to minimize the response of the vibration by using damper. This paper describes the effect of the thickness of the damping layer made from cement material on the deck plate due to the harmonic load excitation. As cement is a common damper application on the ship deck.  A numerical modeling based on finite element analysis was applied in two-layer conditions, namely an overall and tiling coating. The results of this study indicate that thee minimum thickness of the cement layer has an optimum damping for the overall coating is approximately 8 mm and as for tile coating is approximately 15 mm.

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