scholarly journals Vibration of a Laminated Beam with a Delamination Including Contact Effects

2004 ◽  
Vol 11 (3-4) ◽  
pp. 157-171 ◽  
Author(s):  
W. Ostachowicz ◽  
A. Żak
Keyword(s):  
Time Domain ◽  
Dynamic Contact ◽  
Equation Of Motion ◽  
Newmark Method ◽  
The Finite Element Method ◽  
Laminated Beam ◽  
Contact Algorithm ◽  
Vibration Responses ◽  
Newton Raphson ◽  
The Time Domain

Certain results are presented in this paper on damped vibration of a laminated cantilever beam with a single closing delamination. In order to investigate this task the finite element method has been applied in the current study. For modelling the beam higher order shear deformation beam finite elements have been used. The vibration of the beam is investigated in the time domain using a dynamic contact algorithm developed by the authors. The algorithm is based on the Newmark method and also incorporates a Newton-Raphson based procedure for resolving the equation of motion. The time series obtained from solving the equation of motion have been subsequently analysed in the frequency domain by using FFT (Fast Fourier Transform). The vibration responses of the beam due to various harmonic and impulse excitations, at different delamination locations, and for different delamination lengths, as well as changes in the dissipation of damping energy due to the delamination, have all been considered in the paper.

Non-Linear Vibration of a Delaminated Composite Beam

2005 ◽  
Vol 293-294 ◽  
pp. 607-616 ◽  
Author(s):  
Arkadiusz J. Żak
Keyword(s):  
Finite Element Method ◽  
Time Domain ◽  
Composite Beam ◽  
Equation Of Motion ◽  
The Finite Element Method ◽  
Linear Vibration ◽  
Non Linear Equation ◽  
Non Linear ◽  
Vibration Responses ◽  
The Time Domain

Certain results have been presented in this work on damped non-linear vibration of a delaminated composite beam. In order to investigate this problem the finite element method has been applied while for beam modelling higher order shear deformation beam finite elements have been used. The vibration of the beam has been investigated in the time domain and next the time series obtained from solving the non-linear equation of motion have been analysed in the frequency domain by using FFT. The vibration responses of the beam due to various harmonic excitations, at different delamination locations, and for different delamination lengths, together with changes in the dissipation of damping energy due to the delamination, have all been considered in the work.

Time Domain Simulations on a Single Point Moored Submerged Sphere of Variable Radius

2005 ◽  
Author(s):  
Joa˜o M. B. P. Cruz ◽  
Anto´nio J. N. A. Sarmento
Keyword(s):  
Wave Propagation ◽  
Time Domain ◽  
Physical Phenomenon ◽  
Single Point ◽  
Vertical Direction ◽  
Equation Of Motion ◽  
Hydrodynamic Coefficients ◽  
Energy Converter ◽  
Submerged Sphere ◽  
The Time Domain

This paper presents a different approach to the work developed by Cruz and Sarmento (2005), where the same problem was studied in the frequency domain. It concerns the same sphere, connected to the seabed by a tension line (single point moored), that oscillates with respect to the vertical direction in the plane of wave propagation. The pulsating nature of the sphere is the basic physical phenomenon that allows the use of this model as a simulation of a floating wave energy converter. The hydrodynamic coefficients and diffraction forces presented in Linton (1991) and Lopes and Sarmento (2002) for a submerged sphere are used. The equation of motion in the angular direction is solved in the time domain without any assumption about its output, allowing comparisons with the previously obtained results.

Analysis of Acoustic Propagation Characteristic of Near-Bit Drill Tools

2012 ◽  
Vol 524-527 ◽  
pp. 1335-1338
Author(s):  
Zhi Gang Li ◽  
Shi Tong Ge ◽  
Zhi Chuan Guan
Keyword(s):  
Acoustic Wave ◽  
Cross Section ◽  
Time Domain ◽  
Axial Direction ◽  
Propagation Characteristic ◽  
Pass Band ◽  
The Finite Element Method ◽  
Drilling Tools ◽  
The Time Domain ◽  
Drill Collar

In order to Make Use of Acoustic Wave to Transmit the Information from near- Bit End to a Remote Bit End, Using the Finite Element Method, Simulate and Analyze the Acoustic Wave Propagating Characters of Common near-bit Drill Tools: Ordinary Drill Collar, Spiral Drill Collar, Integral Straight Edge Stabilizer, Integral Spiral Stabilizer and Screw Drill. the Results Show that: because the Form and Size of Axial Cross Section Are in Basic Consistent, the Ordinary Drill Collar and Spiral Drill Collar Not only Have Better Characteristics in Time Domain, No Repeated Oscillation of Waveform Occurring, but Also Have Wider Bandwidth (up to 4KHz), and because of the Stabilizer Section, the Acoustic Impedance in the Axial Direction Discontinuities and the Time Domain Waveforms of other Three Kinds of Drilling Tools Appear that Not only Waveforms Have Shook Repeatedly, but Also the Width of the Pass Band Has Narrowed Significantly.

A standard finite‐difference scheme for the time‐domain computation of anelastic wavefields

Geophysics ◽  
1994 ◽  
Vol 59 (2) ◽  
pp. 290-296 ◽  
Author(s):  
E. S. Krebes ◽  
Gerardo Quiroga‐Goode
Keyword(s):  
Finite Difference ◽  
Difference Scheme ◽  
Time Domain ◽  
Finite Difference Scheme ◽  
Initial Conditions ◽  
Homogeneous Medium ◽  
Standard Technique ◽  
Equation Of Motion ◽  
Central Difference ◽  
The Time Domain

We show that the finite‐differencing technique based on the consecutive application of the central difference operator to spatial derivatives, a standard well‐known technique that has been commonly used in the seismological literature for solving the elastic equation of motion, can also be used to obtain a stable time‐domain, finite‐difference scheme for solving the anelastic equation of motion. We compare the results of the scheme for a heterogeneous medium with those of the time‐domain finite‐difference scheme previously developed by Emmerich and Korn and find that they agree very closely. We show, analytically, that in the case of a homogeneous medium, the two schemes give identical numerical results for certain zero initial conditions. The scheme based on the standard technique uses more computer time and memory than the scheme of Emmerich and Korn. However, from a theoretical viewpoint, it is easier to analyze, as it is developed solely with a familiar standard method.

Effect of the elastic hysteresis term formulation and response to non-harmonic periodic excitations of a non-linear SDOF dynamical model with weak frequency-dependency in the time domain

2021 ◽  
pp. 095440622110182
Author(s):  
Christos Spitas ◽  
Mahmoud S Dwaikat ◽  
Vasileios Spitas
Keyword(s):  
Correction Factor ◽  
Time Domain ◽  
Hysteresis Loops ◽  
Domain Model ◽  
Viscous Damping ◽  
State Variables ◽  
Hysteretic Damping ◽  
Vibration Responses ◽  
The Time Domain ◽  
Damping Model

We elaborate a SDOF time-domain model for elastic hysteretic damping, by modifying the viscous damping model to introduce an instantaneous correction factor that recursively depends on the state variables of the system, such that the response exhibits weak dependency on frequency, corresponding to a large array of engineering materials. The effect of different formulations for calculating the instantaneous correction factor on the predicted hysteresis loops and the potential manifestation of singularities is studied. Hysteresis loops anticipated by the model are plotted and forced vibration responses to harmonic and other periodic non-harmonic excitations are simulated and discussed, also in comparison to the conventional viscous and Reid’s damping models.

Numerical analysis of the effects on a floating structure induced by ship waves

2011 ◽  
Vol 55 (02) ◽  
pp. 124-134
Author(s):  
L. Sun ◽  
G.H Dong ◽  
Y. P. Zhao ◽  
C. F. Liu
Keyword(s):  
Time Domain ◽  
Equation Of Motion ◽  
Offshore Structures ◽  
Floating Body ◽  
Kutta Method ◽  
Floating Structure ◽  
Ship Waves ◽  
Runge Kutta Method ◽  
Frequency Domain Methods ◽  
The Time Domain

Ship-generated waves can make bad effects on offshore structures. A numerical model is presented for evaluating the forces exerted on a nearby floating structure by ship generated waves. The ship waves were modeled using Michell thin-ship theory (Wigley waves), the forces were computed using a boundary element method in the time domain, and the motions of the offshore structures were evaluated using the equation of motion of the floating body, and predicted using the fourth-order Runge-Kutta method. The numerical method was validated by comparing its results to those of frequency-domain methods reported in the literature. It was then applied to calculate the force of ship waves on a floating box. The ship's speed, dimensions, and distance were varied. The numerical results indicate some useful rules for varying these factors.

INVERSE RECONSTRUCTION OF THERMAL AND MECHANICAL BOUNDARY CONDITIONS IN COUPLED NONLINEAR THERMO-ELASTIC PROBLEMS

2014 ◽  
Vol 06 (02) ◽  
pp. 1450014 ◽  
Author(s):  
S. KHAJEHPOUR ◽  
M. R. HEMATIYAN
Keyword(s):  
Boundary Conditions ◽  
Time Domain ◽  
Inverse Analysis ◽  
Optimization Method ◽  
Elastic Problem ◽  
Unknown Boundary ◽  
The Finite Element Method ◽  
Inverse Reconstruction ◽  
The Time Domain ◽  
Unknown Boundary Conditions

A stable technique based on the finite element method for inverse analysis of coupled nonlinear thermo-elastic problems is presented. Not only the time-domain is divided into small intervals, but also the space-domain is divided into several sub-domains. The inverse problem is solved in each sub-domain subsequently. For the inverse analysis in each sub-domain, the unknown boundary conditions are found by using an optimization method and also by employing the information obtained in the previous sub-domain. The method is sufficiently stable to be used for inverse analysis of a thermo-elastic problem under a thermal shock. Three numerical examples are provided to demonstrate the efficiency of the proposed method. The effects of the number of sub-domains are investigated in the examples.

Reconstruction of the Force Applied to a Plate in the Time Domain From Sound Pressure Measurements

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Chuan-Xing Bi ◽  
Long Hu ◽  
Yong-Bin Zhang ◽  
Xiao-Zheng Zhang
Keyword(s):  
Time Domain ◽  
Sound Pressure ◽  
Microphone Array ◽  
Near Field ◽  
Impulse Response Function ◽  
Time History ◽  
Pressure Measurements ◽  
Concentrated Force ◽  
Vibration Responses ◽  
The Time Domain

Abstract This paper provides a non-contact approach to reconstruct the distributed or concentrated force applied to a plate in the time domain. This approach is based on sound pressure measurements and is realized by coupling the techniques of real-time near-field acoustic holography (RT-NAH) and force reconstruction. A microphone array is used to measure the sound pressures in the near field of the plate. The measured sound pressures are taken as the inputs of the RT-NAH to reconstruct the vibration responses, including the normal acceleration, velocity, and displacement, on the surface of the plate. With the reconstructed vibration responses, the equation of motion governing the forced vibration can be further processed to reconstruct the force applied to the plate in the time domain. In the process of reconstructing the vibration responses, a displacement–pressure impulse response function is derived for the first time and is used in the RT-NAH. Results of numerical simulations as well as experiments demonstrate that the proposed approach can identify the location of the force accurately and reconstruct the time history of the force effectively, thereby helping to diagnose the mechanical cause of the radiated noise.

Fault Diagnoses Technology of Broken-Blade Propeller Induced Shaft Vibration

2013 ◽  
Vol 385-386 ◽  
pp. 560-566
Author(s):  
Li Jian Ou ◽  
Jun Li ◽  
De Yu Li
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Fourier Transformation ◽  
The Finite Element Method ◽  
Lateral Component ◽  
Shaft System ◽  
Shaft Vibration ◽  
Propeller Blades ◽  
The Time Domain ◽  
Component Force

The broken-blade propeller induced centrifugal force and hydrodynamic lateral component force will cause the whirling vibration of the shaft system while one of the propeller blades breaks at different positions. Such whirling vibration is investigated in this paper, and the time domain waveform is obtained through using the finite element method. The frequency domain vibration is then calculated by applying Fourier transformation on its time domain waveform. According to the respond results of both time domain and frequency domain, the fault diagnoses technology of shaft vibration is proposed.

Analysis on Vehicle-Bridge Coupling Vibration of FRP Deck and Steel Girders Bridge

2013 ◽  
Vol 361-363 ◽  
pp. 1339-1343
Author(s):  
Shi Hui Guo ◽  
Yin Zhang ◽  
Xin Feng Yin
Keyword(s):  
Finite Element Method ◽  
Surface Roughness ◽  
Time Domain ◽  
Iterative Procedure ◽  
Coupled Model ◽  
The Finite Element Method ◽  
Time Step ◽  
Coupling Vibration ◽  
Vehicle Velocity ◽  
The Time Domain

The FRP slab bridge in this paper is modeled using the finite-element method to predict its modal characteristics. The interaction between the vehicle and the bridge is simulated by using a 3D vehicle-bridge coupled model considering the roughness of the bridge road surface. The dynamic response of the bridge is obtained in the time domain by using an iterative procedure employed at each time step. The influences of vehicle velocity, vehicle rigidity, and bridge surface roughness are investigated.

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