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  • Articles  (9)
  • eddy current  (6)
  • elastic waves  (3)
  • 2010-2014
  • 1980-1984  (9)
  • 1975-1979
  • 1950-1954
  • Electrical Engineering, Measurement and Control Technology  (9)
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  • Articles  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Eddy current probe response to open and closed surface flaws (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 1-21 
    Details
    ISSN: 1573-4862
    Keywords: eddy current ; ferromagnetic resonance ; fatigue crack ; stress intensity factor ; crack opening ; displacement ; closure stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general theory of eddy current flaw response, appropriate to both standard low frequency and ferromagnetic resonance (FMR) probes, is developed for simple two-dimensional and three-dimensional open and closed surface flaw geometries. This analysis, based on the assumption of a uniform interrogating field applied to the flaw by the probe, shows that flaw opening responses increase with the operating frequency of the probe. Experimental results using both types of probe confirm this result for realistic practical geometries, where variations of crack mouth opening displacement under load provide useful information about crack dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614993
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical modelling of the scattering of elastic waves in plates (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 89-106 
    Details
    ISSN: 1573-4862
    Keywords: scattering ; elastic waves ; Lamb waves ; shear waves ; finite difference methods ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes the application of finite difference methods to the calculation of the scattering of elastic waves. The emphasis is on cracklike defects in plates, and it is shown that a common numerical technique can span a range of wavelengths from Lamb waves to ultrasonic waves with many reflections from the surfaces of the plate. Quantitative results are given for the scattering of Lamb waves and ultrasonic shear waves from surface-breaking cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566400
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  • 3
    Electronic Resource
    Electronic Resource
    The ac field around a plane crack in a metal surface when the skin depth is large (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 19-24 
    Details
    ISSN: 1573-4862
    Keywords: ac potential difference ; eddy current ; fatigue crack measurement ; skin effect equation ; large skin depth ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper considers the solution of the skin-effect or Helmholtz equation, ∇2ψ=k 2ψ, for the two-dimensional flow of a uniform alternating current perturbed by a plane crack of uniform depth. Herek is the ratio of crack depthd to skin depth δ. When the skin depth is large compared with the crack depth andk f 0, the quasi-static approach to this problem ignores the terms on the right-hand side and constructs solutions from Laplace's equation which are essentially dc solutions and are correct to orderk. In this paper we consider behavior near the limit when the skin depth is large and give solutions which are correct to orderk 2. In an example we relate the results to the interpretation of readings from an ac potential difference instrument applied to the measurement of surface-breaking cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566951
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  • 4
    Electronic Resource
    Electronic Resource
    Change in impedance of a single-turn coil due to a flaw in a conducting half space (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 37-43 
    Details
    ISSN: 1573-4862
    Keywords: eddy current ; impedance ; lift-off ; flaw ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The problem of detection and characterization of a flaw in a conducting half-space using an eddy-current coil oriented parallel to the interface is examined. An expression is derived for a first order approximation for the change in complex impedance due to a flaw located within the conducting medium. The overall impedance is a function of the radius and lift-off distance of the test coil and the conductivity of the material. An analytical expression is derived for the change in impedance as a function of the electric fields at the position of the flaw. It is found to be an integral over the volume of the flaw of the electric fields found with and without the flaw being present. The limiting case of a degenerate point flaw may be examined in greater detail by allowing the field in the presence of the flaw to be approximated by the unperturbed field. For flaws small enough that the field does not vary much over its volume, the field may be even further approximated by using just the value of the field at the position of the centroid of the flaw. Plots are shown to illustrate the behavior of the change in impedance as a function of the radial range of the flaw and the depth of the flaw centroid, using previously derived expressions for the fields for the unflawed case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566953
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of pipeline girth welds using low-frequency horizontally polarized waves (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 155-173 
    Details
    ISSN: 1573-4862
    Keywords: elastic waves ; electromagnetic transducers ; nondestructive evaluation ; ultrasonic transducers ; ultrasonic scattering ; ultrasonic waves ; wave phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The practical implementation of alternative acceptance criteria for pipeline girth welds requires the use of inspection tools capable of determining the principal dimensions and positions of planar flaws. A new ultrasonic inspection method is described that permits complete volumetric inspection of the girth welds. The new system uses noncontacting electromagnetic-acoustic transducers (EMATs) that operate at low ultrasonic frequencies (454 kHz). Theoretical models of the measurements are developed and verified experimentally. In addition, practical performance limits of the new system are established in terms of minimum flaw sizes that can be detected. The results are related to accept-reject curves based on a model of the failure processes. An inspection protocol for field applications is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566557
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  • 6
    Electronic Resource
    Electronic Resource
    Some effects of the shape of a small defect in eddy-current NDE (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 59-63 
    Details
    ISSN: 1573-4862
    Keywords: eddy current ; theoretical models ; computer analysis ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Available theoretical models for predicting defect responses in eddy-current NDE apply only to defects of spheroidal shape. In this paper, the boundary-element integral-equation approach is extended to allow for defects of more irregular shape. Sample results for cylindrical and conical voids are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566397
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  • 7
    Electronic Resource
    Electronic Resource
    Finite element modeling of absolute eddy current probe signals (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 147-154 
    Details
    ISSN: 1573-4862
    Keywords: finite element modeling ; eddy current ; absolute probe ; steam generator tubing ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Finite element analysis techniques are applied to the problem of predicting signals from an absolute eddy current probe in the tube sheet region of a PWR steam generator for the purpose of optimizing the probe coil geometry and determining the feasibility of using such a probe to characterize the condition of the tube and tube sheet crevice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566556
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  • 8
    Electronic Resource
    Electronic Resource
    The impedance of a single-turn coil near a conducting half space (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 183-189 
    Details
    ISSN: 1573-4862
    Keywords: eddy current ; impedance ; liftoff ; conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The change in complex impedance between an ideal one-turn circular coil located above and parallel to a conducting half space with respect to a similar isolated coil has been calculated. From this result, a series expansion of the integrand allows the solution to be approximated by terms expressed as complete elliptic integrals. Results have been calculated for the change in impedance as a function of the liftoff distance and the conductivity of the half space for a coil of representative radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567090
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  • 9
    Electronic Resource
    Electronic Resource
    Elastic wave emission from damage processes (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 215-224 
    Details
    ISSN: 1573-4862
    Keywords: Acoustic emission ; slip ; microcracking ; deformations ; displacement field ; elastic waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The theory of elastic wave emission (i.e., acoustic emission; AE) from damage processes such as slip and microcracking is discussed. Analogous developments in the literature on earth-quake seismology and dynamic dislocation theory are noted and utilized. A general representation of the displacement field of an AE event is given in terms of the double-couple response to a distribution of “moment density tensor” in the source region. Results are specialized to a point source model and to a general far-field analysis of outgoing elastic waves, and conditions for validity of such representations and their low-frequency specializations are noted. Emitted wave fields are compared for tensile opening and slip events, and procedures which might enable the approximate determination of the size or area increase of tensile microcracks are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571803
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