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.

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.

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.

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.

scholarly journals Error Estimates for 1D Asymptotic Models in Coaxial Cables with Non-Homogeneous Cross-Section

2012 ◽  
Vol 4 (06) ◽  
pp. 647-664 ◽  
Author(s):  
Sébastien Imperiale ◽  
Patrick Joly
Keyword(s):  
Exact Solution ◽  
Error Estimates ◽  
Cross Section ◽  
Time Domain ◽  
Electromagnetic Waves ◽  
3D Model ◽  
Time Domain Simulation ◽  
Asymptotic Models ◽  
1D Model ◽  
The Time Domain

AbstractThis paper is the first contribution towards the rigorous justification of asymptotic 1D models for the time-domain simulation of the propagation of electromagnetic waves in coaxial cables. Our general objective is to derive error estimates between the “exact” solution of the full 3D model and the “approximate” solution of the 1D model known as the Telegraphist’s equation.

Time-Domain Stability of Artificial Boundary Condition Coupled with Finite Element for Dynamic and Wave Problems in Unbounded Media

2019 ◽  
Vol 16 (04) ◽  
pp. 1850099 ◽  
Author(s):  
Mi Zhao ◽  
Huifang Li ◽  
Xiuli Du ◽  
Piguang Wang
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Time Domain ◽  
The Finite Element Method ◽  
Artificial Boundary ◽  
Artificial Boundary Condition ◽  
Unbounded Media ◽  
The Time Domain ◽  
Wave Problems ◽  
Domain Stability

The finite element modeling of the dynamic and wave problems in unbounded media requires an artificial boundary condition to simulate the truncated infinite domain. The Dirichlet-to-Neumann boundary condition has been transformed from frequency to time domain by using the rational function approximation and auxiliary variable technique. It is extended to three-dimensional layer problem here. The resulting artificial boundary condition is stable itself in time domain, whereas the time-domain instability of the artificial boundary condition coupled with the finite element method is found for the foundation vibration recently and for the wave propagation here. A simple and effective method that introduces the damping proportional to the stiffness matrix in the finite element method is given to cure such coupling instability completely. The stabilized damping is so small that it does not affect the solution accuracy nearly. The numerical examples show the instability phenomenon and indicate the effectiveness of the damping method. The time-domain stability studies here can be a reference for the other artificial boundary conditions.

Sign in / Sign up

Export Citation Format

Share Document