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  • NDE  (21)
  • Springer  (21)
  • 2020-2022
  • 2005-2009
  • 1980-1984  (21)
  • 1965-1969
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Keywords
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  • Springer  (21)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Parasitic voltages induced by artificial flaws when measured using the ac field technique (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 195-202 
    Details
    ISSN: 1573-4862
    Keywords: ac potential difference ; fatigue crack measurement ; slots ; artificial flaws ; parasitic voltages ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The development of a successful and accurate instrument for measuring surface-breaking cracks in metals using the ac field technique has raised several interesting theoretical problems. Measurements with the instrument, known as the Crack Microgauge, do not rely on any prior calibration against an artificial flaw such as a saw-cut in a test block, but some users accustomed to such a calibration from other devices have nevertheless wished to use the instrument in that fashion and have in some instances reported erroneous results. In this paper, we develop a simple theory to explain and quantify this phenomenon. We calculate the parasitic voltages induced in the instrument probe due to the finite opening possessed by an artificial flaw, and we use these results to reinterpret the instrument readings. Controlled experimental measurements on artificial flaws of rectangular cross-section made in aluminum and in steel are found to be in good agreement with the theory. It is shown, however, that application of the theory requires additional information about the internal phase shift associated with the instrument. To enhance the accuracy of the theory, the effect of the corners of the artificial flaws was also considered, although it was not very influential in this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570731
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of skin depth on crack measurement by the ac field technique (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 65-76 
    Details
    ISSN: 1573-4862
    Keywords: crack measurement ; ac field technique ; arbitrary skin depth ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general solution is given to describe the ac field around surface-breaking cracks for arbitrary values of the ratio of skin depth δ to crack depthd. This solution allows accurate interpretation of crack depth from voltage readings taken by a Crack Microgauge instrument in cases where δ andd are comparable. It is shown to agree with asymptotic formulae obtained for the cases where δ/d is very small and very large. Provided that the probe length Δ is large compared with δ, the calculations show that a very good approximation to the crack depth may be obtained, irrespective of the ratio δ/d, by using the thin-skin asymptotic formula $$d = \frac{1}{2}\Delta (V_2 - V_1 )/V_1 $$ whereV 1 andV 2 are probe voltages registered at positions just off and across the crack, respectively. The problem is solved for a crack of infinite aspect ratio which has no opening, but it can be applied with confidence at the centerline of cracks of fairly large aspect ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568962
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrasonic reflection from a stressed interface (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 3-12 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonic ; stress measurements ; interfacial stress ; NiTi ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In seeking to develop an NDE technique for verifying the serviceability of NiTi couplers for plumbing unions, it was found that the reflection coefficient for a normally incident ultrasonic wave correlated with the stress level at the NiTi-tubing interface. Current theory pertaining to interface reflection is not complete but, even at present status, there is semiquantitative accord between theoretical predictions and normalized data for reflection coefficient versus stress level. These results are at fixed frequency and with comparable surface roughness. Variation of either frequency or surface roughness further affects the reflection coefficient. Current studies are being pursued to define this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711095
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  • 4
    Electronic Resource
    Electronic Resource
    Acoustic measurements of stress fields and microstructure (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 67-77 
    Details
    ISSN: 1573-4862
    Keywords: stress fields ; microstructure ; J integral ; stress intensity factor ; harness acoustic velocity ; acoustic elasticity ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A very precise system for measuring two-dimensional velocity fields in solid samples has been used for nondestructive measurements of both externally applied and residual inhomogeneous stresses in solids,J integrals, stress intensity factors of cracks, and hardness of quenched steel. The longitudinal velocity measurement is based on precise determination of the propagation transit time through the stressed solid specimen using a small diameter, water-coupled acoutic transducer, which is scanned mechanically over the sample. Changes in velocity are then related to changes of stress in the sample by the theory of acoustoelasticity. Similar measurements show a high degree of correlation between longitudinal velocity changes and changes in microstructure in steel samples. Applications to problems of solid mechanics and material science illustrate the utility of this nondestructive measuring technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566232
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  • 5
    Electronic Resource
    Electronic Resource
    Resonance testing of cast iron (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 65-74 
    Details
    ISSN: 1573-4862
    Keywords: NDE ; cast iron ; vibration analysis ; modulus ; strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An outline is given of the existing nondestructive vibration tests for cast irons and their drawbacks in terms of the dimensional accuracy of the components. A proposal is made for a new test based on the change of resonant frequency with vibration amplitude exhibited by cast irons. This proposal is evaluated using material data obtained from dynamic tests of a wide range of cast iron specimens. A test rig is described suitable for testing cylindrical cast bars, and typical results are presented in relation to material strength. There is also a brief description of preliminary testing on cast products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614999
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  • 6
    Electronic Resource
    Electronic Resource
    Ill-posed and well-posed problems in inverse elastodynamic scattering for nondestructive evaluation (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 161-172 
    Details
    ISSN: 1573-4862
    Keywords: elastodynamic inverse scattering ; ultrasonics ; data reduction ; ill-posed problems ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The practical significance of ill-posedness in a data reduction problem is reviewed. Inverse elastodynamic scattering is shown to be ill-posed in general, although suitably restricted problems may be well-posed. These results underscore the need to analyze carefully the errors of data reduction problems in NDE, and to focus attention on final results of an NDE exercise, rather than on intermediate steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570728
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of sinusoidal crack-face perturbations on scattering of elastic waves (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 153-159 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonics ; scattering ; cracks ; periodic surface perturbation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of a plane longitudinal wave from a two-dimensional crack, with a sinusoidal surface perturbation whose amplitude and wavelength are much smaller than the length of the crack, is investigated. The amplitude of the cylindrical body waves in the far field are calculated from a Kirchhoff approximation that utilizes the solution to the reflection from the sinusoidal surface profile of a semiinfinite solid. The results are compared to those for a flat crack, and conditions for significant differences of the amplitude as a function of the angle of observation are discussed. Characteristic changes in the scattered field produced by profiles with different amplitudes and periods are explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570727
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Quantitative characterization of flaws near a surface using inverse born approximation (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 183-188 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; Born inversion ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Quantitative reconstruction of volumetric flaws near a surface of an elastic solid has been carried out experimentally by analyzing the scattered ultrasonic waves. The inverse Born approximation (developed for flaws in bulk materials) was tested for the first time in the determination of the size, shape, and orientation of near-surface flaws. We have studied spherical solid inclusions at various depths below the surface. In addition we examined an approximately 2:1 prolate spheroidal inclusion which was located one major axis below the surface. The determination of the flaw's size, shape, and orientation in terms of an equivalent ellipsoid is realized by performing nonlinear least-squares iteration of the one-dimensional Born inversion results obtained at various scattering directions within a finite aperture. The reconstruction is in good agreement with the actual parameters of the flaw.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565863
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  • 10
    Electronic Resource
    Electronic Resource
    Loss of specular reflection due to nonlinear crack-face interaction (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 229-239 
    Details
    ISSN: 1573-4862
    Keywords: Crack-opening displacement ; crack closure ; ultrasonics ; Kirchoff approximation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The interaction between rough crack faces is modeled by nonlinear relations between the crack-face tractions and the crack-opening displacements. These relations account for crack closure and for the related resistance to crack-face sliding. The relations are used to investigate reflection and transmission of an incident pulse by an infinite flaw plane. The problem statement is reduced to a set of inhomogeneous nonlinear ordinary differential equations for the displacement discontinuities, [u] and [v], across the flaw plane. These equations have been solved numerically. The reflection and transmission of an incident pulse by a crack with interacting crack faces. Both incident longitudinal and transverse waves have been considered. The loss of specular reflection as compared to a perfect (traction-free) crack is exhibited by specific examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565867
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