scholarly journals Surface Motion Excited by Acoustic Emission From a Buried Crack

1984 ◽  
Vol 51 (1) ◽  
pp. 77-83 ◽  
Author(s):  
J. G. Harris ◽  
J. Pott
Keyword(s):  
Acoustic Emission ◽  
High Frequency ◽  
Acoustic Emissions ◽  
Elastic Solid ◽  
Tensile Crack ◽  
Surface Motion ◽  
Penny Shaped Crack ◽  
Growing Crack ◽  
Shaped Crack ◽  
Fracture Processes

The surface motions excited by acoustic emissions produced by fracture processes at the edge of a buried, penny-shaped crack are investigated. Firstly, wave-front approximations to the emissions generated by the sudden growth of a tensile crack in an unbounded elastic solid are reviewed. Then these approximations are Fourier transformed to give the high-frequency portion of their spectra. Secondly, time and frequency-domain approximations to the surface motions excited by this growing crack, when it is buried in a half-space, are calculated. These results are then scrutinized to elucidate what parts of the signals measured at the surface carry information about the crack’s size, its orientation, and the fracture processes near the crack tip.

Longitudinal wave propagation in an infinite isotropic elastic plate with a penny-shaped crack

1969 ◽  
Vol 66 (2) ◽  
pp. 439-442
Author(s):  
H. S. Paul
Keyword(s):  
Longitudinal Wave ◽  
Elastic Plate ◽  
Mixed Boundary ◽  
Elastic Solid ◽  
Vertical Displacement ◽  
Dual Integral Equation ◽  
Positive Direction ◽  
Penny Shaped Crack ◽  
Shaped Crack ◽  
Plane Longitudinal Wave

The stress distribution, subject to a constant pressure over the entire surface of a penny-shaped crack is discussed by Sneddon(4). Recently, Robertson (3) has considered the diffraction of a plane longitudinal wave by a penny-shaped crack on a semi-infinite elastic solid. In the present analysis, the propagation of longitudinal wave in an infinite isotropic elastic plate with a penny-shaped crack in the middle has been investigated. The plane longitudinal wave is moving in the positive direction of z-azis and is impinging on the surface of the penny-shaped crack. The dual integral equation technique of Noble(l) is utilized to solve the mixed boundary-value problem. The analysis closely follows the method used in the author's previous paper (2). The vertical displacement is analysed numerically.

Acoustic Emission From a Brief Crack Propagation Event

1979 ◽  
Vol 46 (1) ◽  
pp. 107-112 ◽  
Author(s):  
J. D. Achenbach ◽  
J. G. Harris
Keyword(s):  
Acoustic Emission ◽  
Brittle Fracture ◽  
Crack Propagation ◽  
Acoustic Emissions ◽  
Elastic Solid ◽  
Propagation Speed ◽  
Crack Edge ◽  
Arbitrary Distribution ◽  
Canonical Solution ◽  
Phase Functions

Acoustic emissions produced by elementary processes of deformation and fracture at a crack edge are investigated on the basis of elastodynamic ray theory. To obtain a two-dimensional canonical solution we analyze wavefront motions generated by an arbitrary distribution of climbing edge dislocations emanating from the tip of a semi-infinite crack in an unbounded linearly elastic solid. These wavefront results are expressed in terms of emission coefficients which govern the variation with angle, and phase functions which govern the intensity of the wavefront signals. Explicit expressions for the emission coefficients are presented. The coefficients have been plotted versus the angle of observation, for various values of the crack propagation speed. The phase functions are in the form of integrals over the emanating dislocation distributions. Specific dislocation distributions correspond to brittle fracture and plastic yielding at the crack tip, respectively. Acoustic emission is most intense for brittle fracture, when the particle velocities experience wavefront jumps which are proportional to the stress-intensity factors prior to fracture. An appropriate adjustment of the canonical solution accounts for curvature of a crack edge. Such effects as focussing, finite duration of the propagation event, and finite dimensions of the crack are briefly discussed. As a specific example, the first signals generated by brittle Mode I propagation of an elliptical crack are calculated.

A Survey of Macro-Microcrack Interaction Problems

2000 ◽  
Vol 53 (5) ◽  
pp. 117-146 ◽  
Author(s):  
Vera Petrova ◽  
Vitauts Tamuzs ◽  
Natalia Romalis
Keyword(s):  
Three Dimensional ◽  
Elastic Solid ◽  
Singular Integral Equations ◽  
Crack Location ◽  
Penny Shaped Crack ◽  
Shaped Crack ◽  
Microcrack Interaction ◽  
The Impact ◽  
The Continuum ◽  
Model Approach

The results obtained on the problem of the interaction between a large crack and an array of microcracks or other microdefects are reviewed. The following problems are considered: interaction of main crack with microcracks in the two-dimensional case at tensile, shear or combined stress state; a closure of macro or microcracks as a result of their interaction, and the influence of this phenomenon on the stress intensity factor; the thermal cracking of an elastic solid caused by the macro-microcracks interaction and cracks closure; the interaction of a crack with an array of small pores or rigid inclusions; three-dimensional problems of the interaction of a penny-shaped crack with small penny-shaped microcracks. Discussed analytical results are based on the asymptotic analysis and the series solution to systems of singular integral equations describing the interaction of the macrocrack and microdefects. The series solutions were obtained with respect to the small parameter representing the ratio of micro- to macrocrack sizes. Throughout the review, the known solutions on the crack interaction are surveyed. The comparison with solutions to other relevant problems such as an interaction of semi-infinite crack with an array of finite cracks is given. The impact of a close crack location, and a comparison with relevant results of the continuum model approach are discussed. This review article includes 332 references.

Thermal Stress in a Finitely Deformed Incompressible Elastic Medium Containing a Penny-Shaped Crack

2003 ◽  
Vol 19 (1) ◽  
pp. 143-147
Author(s):  
Y. M. Tsai
Keyword(s):  
Stress Intensity Factor ◽  
Thermal Stress ◽  
Stress Intensity ◽  
Thermal Stresses ◽  
Elastic Solid ◽  
Crack Plane ◽  
Lateral Stress ◽  
Penny Shaped Crack ◽  
Shaped Crack ◽  
Small Deformations

ABSTRACTThe thermal stress for a penny-shaped crack contained in an infinite isotropic elastic solid initially subjected to an axisymmetrical tension of any amount at infinity is investigated using the techniques of Hankel transforms and multiplying factors. The effect that the lateral normal stress has on the thermal stresses is studied on the basis of the theory of small deformations superposed on finite deformation. Symmetrical thermal loadings are applied over the crack surfaces. For the case of constant temperature over the crack surfaces, expressions for the crack shape and thermal stresses in the crack plane are obtained in closed forms. The stress intensity factor is also obtained and shown to be dependent on the lateral stress.

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