Study on Taylor Criterion for Complete Fracture of the Casing Packed with High Explosive

1983 ◽  
Vol 22 ◽  
Author(s):  
Chen Danian ◽  
Wang Desheng
Keyword(s):  
Finite Difference ◽  
Plastic Flow ◽  
High Explosive ◽  
Stress Waves ◽  
Clear Understanding ◽  
Fragmentation Mechanism ◽  
Elastic Plastic ◽  
Complete Fracture ◽  
Difference Calculation

ABSTRACTThe criterion for complete fracture of the casing by detonation of packed high explosive was first presented by G.I.Taylor. Thereafter Taylor criterion has been reviewed and extended by many authors. This paper is intended to present a clear understanding of the fragmentation mechanism, and to study the influence of stress waves on the fracture of the casing using finite difference calculation of elastic-plastic flow. The results show that Taylor criterion is correct to a certain extent.

Finite‐difference calculation of direct‐arrival traveltimes using the eikonal equation

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1270-1274 ◽  
Author(s):  
Le‐Wei Mo ◽  
Jerry M. Harris
Keyword(s):  
Finite Difference ◽  
Ray Tracing ◽  
Finite Differences ◽  
Eikonal Equation ◽  
Velocity Model ◽  
Uniform Grid ◽  
Square Grid ◽  
Kirchhoff Migration ◽  
Difference Calculation

Traveltimes of direct arrivals are obtained by solving the eikonal equation using finite differences. A uniform square grid represents both the velocity model and the traveltime table. Wavefront discontinuities across a velocity interface at postcritical incidence and some insights in direct‐arrival ray tracing are incorporated into the traveltime computation so that the procedure is stable at precritical, critical, and postcritical incidence angles. The traveltimes can be used in Kirchhoff migration, tomography, and NMO corrections that require traveltimes of direct arrivals on a uniform grid.

Upwind finite‐difference calculation of traveltimes

Geophysics ◽  
1991 ◽  
Vol 56 (6) ◽  
pp. 812-821 ◽  
Author(s):  
J. van Trier ◽  
W. W. Symes
Keyword(s):  
Finite Difference ◽  
Difference Scheme ◽  
Conservation Law ◽  
Finite Difference Scheme ◽  
Eikonal Equation ◽  
Upwind Schemes ◽  
Similar Scheme ◽  
Difference Calculation ◽  
Flow Variables ◽  
Upwind Finite Difference

Seismic traveltimes can be computed efficiently on a regular grid by an upwind finite‐difference method. The method solves a conservation law that describes changes in the gradient components of the traveltime field. The traveltime field itself is easily obtained from the solution of the conservation law by numerical integration. The conservation law derives from the eikonal equation, and its solution depicts the first‐arrival‐time field. The upwind finite‐difference scheme can be implemented in fully vectorized form, in contrast to a similar scheme proposed recently by Vidale. The resulting traveltime field is useful both in Kirchhoff migration and modeling and in seismic tomography. Many reliable methods exist for the numerical solution of conservation laws, which appear in fluid mechanics as statements of the conservation of mass, momentum, etc. A first‐order upwind finite‐difference scheme proves accurate enough for seismic applications. Upwind schemes are stable because they mimic the behavior of fluid flow by using only information taken from upstream in the fluid. Other common difference schemes are unstable, or overly dissipative, at shocks (discontinuities in flow variables), which are time gradient discontinuities in our approach to solving the eikonal equation.

Non-stationary local slope estimation via forward-backward space derivative calculation

Geophysics ◽  
2021 ◽  
pp. 1-91
Author(s):  
Hang Wang ◽  
Liuqing Yang ◽  
Xingye Liu ◽  
Yangkang Chen ◽  
Wei Chen
Keyword(s):  
Finite Difference ◽  
Random Noise ◽  
Estimation Method ◽  
Order Derivative ◽  
Space Domain ◽  
Local Slope ◽  
First Order ◽  
Slope Estimation ◽  
Difference Calculation ◽  
Seismic Images

The local slope estimated from seismic images has a variety of meaningful applications. Slope estimation based on the plane-wave destruction (PWD) method is one of the widely accepted techniques in the seismic community. However, the PWD method suffers from its sensitivity to noise in the seismic data. We propose an improved slope estimation method based on the PWD theory that is more robust in the presence of strong random noise. The PWD operator derived in the Z-transform domain contains a phase-shift operator in space corresponding to the calculation of the first-order derivative of the wavefield in the space domain. The first-order derivative is discretized based on a forward finite difference in the traditional PWD method, which lacks the constraint from the backward direction. We propose an improved method by discretizing the first-order space derivative based on an averaged forward-backward finite-difference calculation. The forward-backward space derivative calculation makes the space-domain first-order derivative more accurate and better anti-noise since it takes more space grids for the derivative calculation. In addition, we introduce non-stationary smoothing to regularize the slope estimation and to make it even more robust to noise. We demonstrate the performance of the new slope estimation method by several synthetic and field data examples in different applications, including 2D/3D structural filtering, structure-oriented deblending, and horizon tracking.

Studies of Elastic-Plastic Instabilities

1999 ◽  
Vol 66 (1) ◽  
pp. 3-9 ◽  
Author(s):  
V. Tvergaard
Keyword(s):  
Shear Band ◽  
Plastic Flow ◽  
Continuum Mechanics ◽  
Shear Band Formation ◽  
Band Formation ◽  
Elastic Plastic ◽  
Localized Necking ◽  
Focus On Results ◽  
Metal Sheets ◽  
Bifurcation Behavior

Analyses of plastic instabilities are reviewed, with focus on results in structural mechanics as well as continuum mechanics. First the basic theories for bifurcation and post-bifurcation behavior are briefly presented. Then, localization of plastic flow is discussed, including shear band formation in solids, localized necking in biaxially stretched metal sheets, and the analogous phenomenon of buckling localization in structures. Also some recent results for cavitation instabilities in elastic-plastic solids are reviewed.

Finite-difference calculation of hypersonic wakes

AIAA Journal ◽  
1964 ◽  
Vol 2 (8) ◽  
pp. 1396-1402 ◽  
Author(s):  
SEYMOUR L. ZEIBERG ◽  
GARY D. BLEICH
Keyword(s):  
Finite Difference ◽  
Difference Calculation

Formation of adiabatic shear bands and instability of plastic flow in Zr and Zr-Nb alloys in spherical stress waves

1999 ◽  
Vol 42 (1) ◽  
pp. 61-71 ◽  
Author(s):  
A.V Dobromyslov ◽  
N.I Taluts ◽  
N.V Kazantseva ◽  
E.A Kozlov
Keyword(s):  
Plastic Flow ◽  
Shear Bands ◽  
Stress Waves ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands
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