scholarly journals Diffraction of a rectangular beam by a crack edge

1986 ◽  
Vol 80 (S1) ◽  
pp. S105-S105
Author(s):  
John G. Harris
Keyword(s):  
Crack Edge ◽  
Rectangular Beam

Reconstruction of complex shaped crack from ECT signals based on a fast forward solver using an advanced multi-media element

2020 ◽  
Vol 64 (1-4) ◽  
pp. 621-629
Author(s):  
Yingsong Zhao ◽  
Cherdpong Jomdecha ◽  
Shejuan Xie ◽  
Zhenmao Chen ◽  
Pan Qi ◽  
...  
Keyword(s):  
Coefficient Matrix ◽  
Crack Edge ◽  
Numerical Accuracy ◽  
Gauss Point ◽  
Current Testing ◽  
Efficient Simulation ◽  
Shaped Crack ◽  
Multi Media ◽  
Profile Reconstruction ◽  
Crack Profile

In this paper, the conventional database type fast forward solver for efficient simulation of eddy current testing (ECT) signals is upgraded by using an advanced multi-media finite element (MME) at the crack edge for treating inversion of complex shaped crack. Because the analysis domain is limited at the crack region, the fast forward solver can significantly improve the numerical accuracy and efficiency once the coefficient matrices of the MME can be properly calculated. Instead of the Gauss point classification, a new scheme to calculate the coefficient matrix of the MME is proposed and implemented to upgrade the ECT fast forward solver. To verify its efficiency and the feasibility for reconstruction of complex shaped crack, several cracks were reconstructed through inverse analysis using the new MME scheme. The numerical results proved that the upgraded fast forward solver can give better accuracy for simulating ECT signals, and consequently gives better crack profile reconstruction.

A 5 x 40 cm rectangular-beam multipole ion source

1981 ◽  
Author(s):  
R. ROBINSON ◽  
H. KAUFMAN ◽  
C. HAYNES
Keyword(s):  
Ion Source ◽  
Rectangular Beam

Study of rectangular beam folded waveguide traveling-wave tube for terahertz radiation

2017 ◽  
Vol 24 (10) ◽  
pp. 103132 ◽  
Author(s):  
Fengying Lu ◽  
Changqing Zhang ◽  
Manfred Grieser ◽  
Yong Wang ◽  
Suye Lü ◽  
...  
Keyword(s):  
Terahertz Radiation ◽  
Traveling Wave ◽  
Traveling Wave Tube ◽  
Wave Tube ◽  
Folded Waveguide ◽  
Rectangular Beam

Mapping of crack edges by seismic methods

1982 ◽  
Vol 72 (3) ◽  
pp. 779-792
Author(s):  
J. D. Achenbach ◽  
A. Norris ◽  
K. Viswanathan
Keyword(s):  
Input Data ◽  
A Priori ◽  
Signal Propagation ◽  
Computational Procedure ◽  
Crack Edge ◽  
Inverse Mapping ◽  
Arrival Times ◽  
Ultrasonic Signals ◽  
Geometrical Theory Of Diffraction ◽  
Local Edge

abstract The inverse problem of diffraction of elastic waves by the edge of a large crack has been investigated on the basis of elastodynamic ray theory and the geometrical theory of diffraction. Two methods are discussed for the mapping of the edge of a crack-like flaw in an elastic medium. The methods require as input data the arrival times of diffracted ultrasonic signals. The first method maps flash points on the crack edge by a process of triangulation with the source and receiver as given vertices of the triangle. By the use of arrival times at neighboring positions of the source and/or the receiver, the directions of signal propagation, which determine the triangle, can be computed. This inverse mapping is global in the sense that no a priori knowledge of the location of the crack edge is necessary. The second method is a local edge mapping which determines planes relative to a known point close to the crack edge. Each plane contains a flash point. The envelope of the planes maps an approximation to the crack edge. The errors due to inaccuracies in the input data and in the computational procedure have been illustrated by specific examples.

The Dynamic Stress Intensity Factor Due to Arbitrary Screw Dislocation Motion

1983 ◽  
Vol 50 (2) ◽  
pp. 383-389 ◽  
Author(s):  
L. M. Brock
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plane Wave ◽  
Screw Dislocation ◽  
Dynamic Stress ◽  
Critical Level ◽  
Dynamic Stress Intensity Factor ◽  
Dislocation Motion ◽  
Crack Edge

The dynamic stress intensity factor for a stationary semi-infinite crack due to the motion of a screw dislocation is obtained analytically. The dislocation position, orientation, and speed are largely arbitrary. However, a dislocation traveling toward the crack surface is assumed to arrest upon arrival. It is found that discontinuities in speed and a nonsmooth path may cause discontinuities in the intensity factor and that dislocation arrest at any point causes the intensity factor to instantaneously assume a static value. Morever, explicit dependence on speed and orientation vanish when the dislocation moves directly toward or away from the crack edge. The results are applied to antiplane shear wave diffraction at the crack edge. For an incident step-stress plane wave, a stationary dislocation near the crack tip can either accelerate or delay attainment of a critical level of stress intensity, depending on the relative orientation of the crack, the dislocation, and the plane wave. However, if the incident wave also triggers dislocation motion, then the delaying effect is diminished and the acceleration is accentuated.

scholarly journals Tuning of Turbine Blades: A Theoretical Approach

1982 ◽  
Author(s):  
P. Gudmundson
Keyword(s):  
Perturbation Method ◽  
Turbine Blade ◽  
Theoretical Approach ◽  
Turbine Blades ◽  
Rectangular Beam ◽  
Resonance Frequencies ◽  
Geometrical Change

A perturbation method is described which predicts the changes in eigenfrequencies resulting from geometrical changes of a structure. This dependence is represented by dimensionless functions, one for each eigenfrequency, which vary over the surface of the structure. The functions are presented for each eigenfrequency as isoline plots. An easily estimated integration of these functions allows one to predict a geometrical change which results in a desired change in the resonance frequencies. The method was applied to a turbine blade and a rectangular beam. For the turbine blade isoline plots are presented for the first five eigenfrequencies. Eigenfrequency changes up to 8 percent were modeled accurately.

Exact analysis of wave propagation in an infinite rectangular beam

2004 ◽  
Vol 25 (7) ◽  
pp. 768-778 ◽  
Author(s):  
Sun Wei-ming ◽  
Yang Guang-song ◽  
Li Dong-xu
Keyword(s):  
Wave Propagation ◽  
Exact Analysis ◽  
Rectangular Beam
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