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  • Articles  (23)
  • ultrasonics  (13)
  • flux pinning  (10)
  • 1990-1994  (17)
  • 1985-1989  (6)
  • 1960-1964
  • 1950-1954
  • Electrical Engineering, Measurement and Control Technology  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Magnetic torque of κ-(BEDT-TTF)2Cu(NCS)2 single crystals (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 675-677 
    Details
    ISSN: 1572-9605
    Keywords: Organic superconductor ; anisotropic superconductor ; flux pinning ; lower critical fieldH c1;κ-(BEDT-TTF)2Cu(NCS)2 ; κ-(BEDT-TTF)2Cu(NCS)2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The magnetic torque ofκ-(BEDT-TFF)2Cu(NCS)2 was measured as a function of field directionθ with respect to thea *-axis under constant magnetic fields,H, up to 8 kOe in the temperature range from 1.3 to 8 K. A sharp cusp, C1, in the irreversible region was found atθ c1 near theH∥bc-plane between 1.3 and 7 K. In addition, extra cusps, C2 and C3, were observed atθ c2 andθ c3, respectively, between 2.5 and 6 K. At each temperature, the perpendicular component ofH giving each cusp is kept constant as $$H\cos \theta _{cn} = const \equiv H_{cp_n } (n = 1,2,3),$$ i.e., cusps C1, C2, and C3 are ruled by the characteristic field perpendicular to thebc-planeH cp1,H cp2, andH cp3, respectively. These behaviors are almost the same as those we found in the oxide superconductor Bi2Sr2CaCu2O8. These results suggest that the cusps are intrinsic for irreversible vortex states of these layered superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00728484
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructures of high-J c melt-textured YBa2Cu3O7−x /Ag superconductors (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 947-950 
    Details
    ISSN: 1572-9605
    Keywords: Critical current density ; Ag addition ; grain alignment ; flux pinning ; defect structure ; YBCO ; melt-texturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Silver has been previously added to the melt-textured YBa2Cu3O7−x in order to increase the critical current density (J c ) of these materials. However, the effect of this addition on theJ c is presently unclear. The purpose of this study is to investigate the effect of silver on both critical current density and the microstructure of the melt-textured YBa2Cu3O7−x superconductors by means of X-ray diffraction, optical polarized microscopy, and transmission electron microscopy (TEM). TheJ c of the MTG YBCO/Ag samples is more than 104A/cm2 under the 5 kOe magnetic field. It has been shown that as the concentration of silver increases, the fraction of the 211 phase dispersed within the 123 matrix decreases. Therefore, theJ c slightly decreases. These results, together with the effect of the 211 phase, dislocations, and other structure defects on flux pinning, are described in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732277
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  • 3
    Electronic Resource
    Electronic Resource
    Vibrating reed study of the flux line dynamics of κ-(ET)2Cu[N(CN)2]Br (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 793-797 
    Details
    ISSN: 1572-9605
    Keywords: Vibrating reed ; type-II superconductors ; organic superconductors ; flux pinning ; vortex lattice melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Vibrating reed measurements were performed on single-crystal samples ofκ-(ET)2- Cu[N(CN)2]Br in an applied magnetic fieldH oriented either parallel (“longitudinal”) or perpendicular (“transverse”) to the highly conducting ac-plane. Field-cooling data taken for the longitudinal orientation andH〈0.7 T revealed a peak with a low-temperature shoulder in the reed dissipation 1/Q located at temperatureT Q below the superconducting transition temperatureT c (≈11.6 forH=0). The shoulder disappeared nearH≈0.7 T, accompanied by an abrupt change in the slope ofT Q (H), corresponding to a similar change in the slope of the upper critical magnetic fieldH c2 measured by Kwoket al. The existence of the shoulder in the dissipation peak bears on a number of current explanations for the exotic superconducting properties ofκ-(ET)2Cu[N(CN)2]Br.T Q data taken for the transverse orientation fell far below estimates ofH c2., indicating the existence of a substantial region of flux line (FL) mobility belowH c2(T). The location of a peak in NMR relaxation observed by De Sotoet al. lies close toT Q for the transverse orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320871
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  • 4
    Electronic Resource
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    Vibrating reed study of the flux line dissipation of ceramic and single-crystal (Ba, K)BiO3 (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 835-839 
    Details
    ISSN: 1572-9605
    Keywords: Vibrating reed ; type-II superconductors ; oxide superconductors ; flux pinning ; vortex lattice melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Vibrating reed (VR) and dc and ac magnetic susceptibility measurements were performed on a nominal single crystal of composition (Ba0.64K0.36)BiO3 in an applied magnetic fieldH. Field-cooling and field-sweep data revealed multiple peaks in the reed dissipation 1/Q located below the superconducting transition temperatureT c (≈29.6 K forH=0). A shoulder or onset (with increasingT) of dissipation appears forT≤18 K, which may be a signature of a flux lattice melting transition. VR data for dense ceramic samples of composition (Ba0.625K0.375)BiO3 (T c=28.6K) exhibit a relatively narrow and smooth peak in 1/Q that corresponds well to a broad, intermediate-temperature peak in the crystal data. Resistivity experiments demonstrate that the single ceramic peak occurs well below the temperature at which the electrical resistanceR≈0, suggesting that the higher-temperature crystalline peaks are positioned close to the upper critical field line and may be strongly dependent upon grain size or surface properties. Both ac and dc susceptibility data show no clear evidence for multiple phases or gross compositional inhomogeneities in the crystalline sample. Our results demonstrate that the VR technique is an extremely sensitive method to probe sample inhomogeneities and their role in flux pinning phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320879
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  • 5
    Electronic Resource
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    Ultrasonic beam propagation through a bimetallic weld—A comparison of predictions of the Gauss-Hermite beam model and finite element method (1993)
    Springer
    Journal of nondestructive evaluation 12 (1993), S. 151-158 
    Details
    ISSN: 1573-4862
    Keywords: Beam propagation ; bimetallic weld ; Gauss-Hermite beam model ; finite element method ; ultrasonics ; anisotropic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, predictions of two models for the propagation of ultrasonic beams through a two-dimensional, bimetallic weld geometry are compared. The finite element method can predict beam propagation through quite general geometry with high accuracy. This model, however, requires significant computational time. On the other hand, the approximate Gauss-Hermite model offers considerably greater computational speed, but has lower accuracy in certain regions and cannot treat the most general geometries and inhomogeneities in material properties. This paper compares the performances of the two models for the case of the two-dimensional, bimetallic weld consisting of multiple layers, some of which have anisotropic properties. It is found that the results of the two models are in good agreement in the vicinity of the central ray, and that the deviation increases as one moves away from the axis. Also, as the beam propagates through multiple interfaces, the accuracy of the Gauss-Hermite solution decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567571
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  • 6
    Electronic Resource
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    Intergranular fluxons in high-T c superconductors (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 161-171 
    Details
    ISSN: 1572-9605
    Keywords: granular superconductivity ; Josephson effect ; fluxons ; flux pinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The granular high-T c superconductors can carry very low transport current, in comparison to that found in the bulk of the material. Magnetization and critical current measurements at very low field indicate that this low transport current behaves as expected from a critical state model. The presence of weak links between the grains in granular aggregates is firmly established, together with the Josephson character of such links. The existence of some kind of magnetic particles, and of a mechanism of pinning for them, is required to explain the critical state regime. In this paper we examine the flux structures which can be present in the granular systems, which can be described by an array of SQUIDs, and we show their similarities to fluxons in a continuous medium and to fluxons in uniform Josephson junctions. A simple model, based on a two-dimensional network of pointlike Josepson junctions, is adequate to demonstrate the existance of the IF (intergranular fluxon). Its characteristics depend on a single parameter, which gives the coupling strength between grains. The discreteness of the system is the cause of an intrinsic pinning of the intergranular fluxons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625742
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  • 7
    Electronic Resource
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    Asymmetry between flux penetration and flux expulsion in Tl-2212 superconductors (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 185-189 
    Details
    ISSN: 1572-9605
    Keywords: Thallium cuprates ; superconductivity ; magnetic hysteresis ; irreversibility ; flux pinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract dc magnetic hysteresis as well as flux penetration and flux expulsion were investigated in Tl2−y Ba2CaCu2O8−x polycrystals and monocrystals. All measurements were performed at 35 K and in the 0–5 T field range. Hysteresis measurements revealed an irreversibility field of about 2 T. Existing models predict identical field-cooled (fc) and zero-field-cooled (zfc) magnetizations and vanishing time dependence above this field. Although the identical fc and zfc magnetizations are in fact observed, the time dependence vanishes only for flux penetration after zero-field cooling; a remanence is preserved after field cooling and decays with a finite relaxation rate. Activation energies calculated on the basis of the thermal activation model display a pronounced field dependence, and arelower for flux penetration than for flux expulsion in high fields (H≥3 T) for all orientations. This behavior of extreme layered superconductors contradicts classical theoretical models and questions the original definition of the irreversibility line as well. All of our results are consistent with the recent theory of lock-in transition, and can be well interpreted by using those principles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625745
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  • 8
    Electronic Resource
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    Flux-creep activation energies at the grain boundaries of Y-Ba-Cu-O superconductors in the characteristic frequency band (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 243-246 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductivity ; flux pinning ; flux motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Measurements on the temperature and frequency dependence of the complex ac susceptibility of sintered Y1.01Ba1.95Cu2.97O x are reported. The data are used to obtain the flux-creep activation energies at the grain boundaries in the characteristic frequency band. The found nonlinear frequency dependence of these energies can be approximated differently in the low, characteristic, and high frequency bands. The relaxation frequency of thermal fluctuation of the vortex lattice (2πΓ ∼ 3×104 Hz) and the surface current density (J s=0–10 A/cm2) have been estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626264
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  • 9
    Electronic Resource
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    Quasistatic field responses of fluxoids in an Y1Ba2Cu3O7−δ film (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 47-53 
    Details
    ISSN: 1572-9605
    Keywords: High-T c superconductor ; fluxoid ; quasistatic magnetic field ; flux pinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The quasistatic magnetic field responses (typically 0.8 Hz) of fluxoids in ac-axis oriented Y1Ba2Cu3O7−δ (Y123) film have been studied using a computerized mechanical pendulum at 77 K. The resonance frequence of the pendulum is significantly shifted to higher values due to the interaction between the Y123 film and a magnet mounted on the pendulum. The contribution of the magnet-superconductor interaction to the shift of the squared resonance frequency shows, in a certain range, a logarithmic dependence on the driving force (proportional to the amplitude). The present results are consistent with the previous studies on the bulk Y123 materials for different configuration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617996
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  • 10
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    Study of flux motion in Bi-based superconductors by a pendulum (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 127-135 
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    ISSN: 1572-9605
    Keywords: High-T c superconductor ; fluxoid ; magnetic stiffness ; flux pinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Using a computerized mechanical pendulum, we have studied the lateral magnetic flux motion of the Bi-based high-T c superconductors in the quasi-static magnetic field (0.1 Hz) for the range 1 μm to 0.35 mm. The effect of d.c. and a.c. transport currents on the flux motion has also been investigated. We argue that the lateral magnetic stiffness is a measure of the pinning potential of the fluxoids in the superconductors. The pinning energy barrierε is estimated to be about 0.3 eV based on the stiffness measurements, which is comparable with the data from the YBa2Cu3O7−χ superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618056
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  • 11
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    A comparative study of transient waves in random (polycrystalline) media (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 9-17 
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    ISSN: 1573-4862
    Keywords: Casuality ; effective medium ; ultrasonics ; polycrystalline medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The paper investigates the transient response of a random medium as predicted by two methods, a perturbation scheme and a causal approach. It is shown by direct computation of a pulse propagation that the perturbation scheme yields an “advanced” response inconsistent with the physical realizability of the medium. The causal model as well as a modified perturbation scheme exhibit a physically reasonable behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566013
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  • 12
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    Ultrasonic flaw classification in weldments using probabilistic neural networks (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 69-77 
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    ISSN: 1573-4862
    Keywords: Welds ; flaw classification ; ultrasonics ; neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A probabilistic neural network is used here to classify flaws in weldments from their ultrasonic scattering signatures. It is shown that such a network is both simple to construct and fast to train. Probabilistic nets are also shown to be able to exhibit the high performance of other neural networks, such as feed forward nets trained via back-propagation, while possessing important advantages of speed, explicitness of their architecture, and physical meaning of their outputs. Probabilistic nets are also demonstrated to have performance equal to common statistical approaches, such as theK-nearest neighbor method, while retaining their unique advantages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568290
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  • 13
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    Analysis of nonlinearly viscoelastic behavior of adhesive bonds (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 221-226 
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    ISSN: 1573-4862
    Keywords: Nonlinear viscoelastic behavior ; adhesive layers ; ultrasonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The purpose of this paper is to provide a theoretical framework to study the nonlinear viscoelastic behavior of adhesive layers. The stress-strain behavior of the adhesive material in shear is assumed to have a nonlinear elastic part and a linear viscoelastic part, i.e., σ yx =f(ε yx )+K mεyx. To measuref(ε yx ) andK m by an ultrasonic technique, it is proposed to prestress the adhesive layer in the nonlinear range and to superimpose a small amplitude ultrasonic signal. The reflected field is used to obtain the wave speed and hencedf(ε yx )/dε yx as a function of the pre-stress. The viscoelastic parameter is obtained from the amplitude decay. By repeating this procedure for various values of prestress and using numerical integration, the stress-strain behavior of the adhesive layer can be reconstructed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566412
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  • 14
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    Effects of flux flow, flux pinning, and flux creep upon the rf surface impedance of type-II superconductors (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 313-318 
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    ISSN: 1572-9605
    Keywords: Surface impedance ; complex penetration depth ; flux flow ; flux pinning ; flux creep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The presence of vortices is known to have an important effect upon the rf surface impedanceZ s of type-II superconductors. In this paper we summarize a new theoretical approach that permits the influence of flux flow, flux pinning, and flux creep uponZ s =R s -iX s to be calculated over a wide range of angular frequenciesω, magnetic inductionsB, and temperaturesT. The normal-fluid excitations and the nonlocality of vortex-generated fields are also accounted for. The physics is conveniently described in terms of a complex penetration depthλ(ɛ, B, T), to which the surface impedance is related viaZ s = −iμ 0ɛλ(ω,B,T). We limit our attention to the linear response of the superconductor in the low-rf-power regime for which the surface impedance is power-independent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618130
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  • 15
    Electronic Resource
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    Elastic wave propagation with kinematic discontinuity along a non-ideal interface between two isotropic elastic half-spaces (1991)
    Springer
    Journal of nondestructive evaluation 10 (1991), S. 39-53 
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    ISSN: 1573-4862
    Keywords: Elastic wave propagation ; nondestructive evaluation ; ultrasonics ; bonded material inspection ; adhesive bonds ; interfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The problem of wave propagation along the interface between two elastic, isotropic, and homogeneous half-spaces is studied when the half-spaces are coupled through a vanishingly thin layer of Voigt material. It is assumed that the separation, 2H, between the half-spaces, and the complex rigidity-modulus, μ, of the layer are both vanishingly small, but the complex quantity μ/2H remains finite. In a series of experiments in which two blocks of elastic materials with or without lubricant/couplant at the interface are subjected to an external load normal to the interface, the variation of the speed and attenuation of interfacial waves, generated and detected by piezoelectric transducers, was measured as a function of external load. Assuming a nonlinear relation between external load and μ/2H, the experimental data is interpreted theoretically, and the best-fit parameters of the nonlinear relation are determined. For the 13 cases of interfaces studied, with or without lubricant/couplant, satisfactory agreement was found between experiment and theory, except in one case. Even in this case, the agreement is satisfactory in the lower range of load. It is hoped that this study will be useful in developing nondestructive methods of testing the bonding conditions at an interface between elastic materials by means of interfacial wave properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568099
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  • 16
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    On the boundary conditions for ultrasonic transmission by partially closed cracks (1991)
    Springer
    Journal of nondestructive evaluation 10 (1991), S. 139-149 
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    ISSN: 1573-4862
    Keywords: Closed cracks ; ultrasonics ; reflection and transmission ; coefficients ; effective boundary conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The probability of detecting crack-like defects using ultrasonic techniques can be severely reduced if the crack is closed by a static background pressure. In this paper, we model the contacting faces of a partially closed crack by an array of circular spot-welds randomly distributed over an infinite plane. We give an exact derivation of the reflection and transmission coefficients for a plane elastic wave at such a boundary in terms of the mean interfacial stresses. The latter are estimated in the limit when the contact radius is much smaller than the wavelength and the contacts are sparsely distributed. This calculation is then related to a distributed spring model of the interface. The latter replaces the real interface by an effective homogeneous linear boundary condition which relates the crack opening displacement to the boundary stresses by effective stiffnesses. These unknown parameters are chosen to ensure that the model condition predicts the exact values of the mean interfacial stresses and the reflection and transmission coefficients in the limit already described. Our results are consistent with and complement those of Baik and Thompson(1) who introduced the distributed spring model in this and a number of other contexts. Our analysis provides a systematic assessment of the range of validity of the model and suggests ways in which the present estimates may be improved.
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    URL: http://dx.doi.org/10.1007/BF00567096
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  • 17
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    Laser-based ultrasonics on Gr/epoxy composite (1990)
    Springer
    Journal of nondestructive evaluation 9 (1990), S. 229-238 
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    ISSN: 1573-4862
    Keywords: Thermo-elasticity ; noncontact NDE ; photo-acoustics ; composite ; Gr/epoxy ; ultrasonics ; cscan ; array
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Critical issues are examined in the application of laser generation and detection of ultrasound to the inspection of large area air-frame composites. Among these issues are surface roughness, signal-to-noise ratio, insensitivity to the path length between the part and detector, and wide band vs. narrow-band generation. Demonstrated is the feasibility of transmission C-scans of 150 ply Gr/epoxy panels containing simulated delaminations. Waveforms having a signal-to-noise ratio of greater than 40 dB in 15-mm thick Gr/epoxy were obtained with generating laser powers well below the ablation limit for the graphite epoxy. Detection was shot-noise limited with a detector noise figure of about 5–10 dB.
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    URL: http://dx.doi.org/10.1007/BF00565641
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  • 18
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    Ultrasonic reflection by a planar distribution of cracks (1988)
    Springer
    Journal of nondestructive evaluation 7 (1988), S. 123-129 
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    ISSN: 1573-4862
    Keywords: Diffusion bonds ; reflection ; ultrasonics ; cracks ; stress-intensity factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic wave reflection and transmission by planar crack distributions is considered. General expressions for the reflection and transmission coefficients are derived for incident longitudinal and transverse time harmonic plane waves. For low frequencies, closed-form algebraic expressions are given in terms of the geometrical parameters, the material constants, and the incident wavefield. The results have been extended to statistical distributions, and reflection coefficients for equivalent statistical and deterministic distributions of penny-shaped cracks are compared. It is also shown that the Mode-I stress-intensity factor for a distribution of equal-sized cracks can be directly related to reflection data.
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    URL: http://dx.doi.org/10.1007/BF00565997
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  • 19
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    ORCHID—A computer simulation of the reliability of an NDE inspection system (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 23-31 
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    ISSN: 1573-4862
    Keywords: NDE ; inspection systems ; reliability ; probability of detection ; computer simulation ; eddy current ; ultrasonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract CANDU pressurized heavy water reactors contain several hundred horizontally-mounted zirconium alloy pressure tubes. Following a pressure tube failure, a pressure tube inspection system called CIGARette was rapidly designed, manufactured and put in operation. Defects called hydride blisters were found to be the cause of the failure, and were detected using a combination of eddy current and ultrasonic scans. A number of improvements were made to CIGARette during the inspection period. The ORCHID computer program models the operation of the delivery system, eddy current and ultrasonic systems by imitating the on-reactor decision-making procedure. ORCHID predicts that during the early stage of development, less than one blistered tube in three would be detected, while less than one in two would be detected in the middle development stage. However, ORCHID predicts that during the late development stage, probability of detection will be over 90%, primarily due to the inclusion of axial ultrasonic scans (a procedural modification). Rotational and axial slip could severely reduce probability of detection. Comparison of CIGARette's inspection data with ORCHID's predictions indicate that the latter are compatible with the actual inspection results, though the numbers are small and data uncertain. It should be emphasized that the CIGARette system has been essentially replaced with the much more reliable CIGAR system.
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    URL: http://dx.doi.org/10.1007/BF00566694
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  • 20
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    Concrete strength ultrasonic digital tester (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 157-160 
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    ISSN: 1573-4862
    Keywords: NDE of concrete ; ultrasonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes the design and construction of a concrete strength ultrasonic digital meter. The method depends on the transmission and reception of two ultrasonic sinusoidal signals. These two signals are so processed so as to yield a digital output number representative of the speed of propagation through the concrete specimen. This velocity figure can be related to the applications on finding the concrete crush strength, concrete crack depth, as well as the concrete behavior with electrical curing temperature. The electronic system employs Complementary-Oxide Semiconductor logic circuits and hybrid conversion circuits. It consumes such a little power, which makes such a design transportable and hence a battery operated device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570624
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  • 21
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    Ultrasonic characteristics of graphite/epoxy composite material subjected to fatigue and impacts (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 119-131 
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    ISSN: 1573-4862
    Keywords: graphite/epoxy ; composites ; ultrasonics ; stress wave factor ; fatigue life ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Fiber-reinforced composites, because of their superior specific strengths and stiffnesses, are used in many aircraft components. However, in this application these composites are subjected not only to fatigue loading, but to occasionally high velocity impact due to the bird injection, hail, dust, and rain. Thus, it is important to evaluate the residual life and degradation due to combined fatigue and impact loadings. Unidirectional graphite epoxy composites (MA8276-Tiger) which are used in the aerospace industry were impacted by a free falling weight at energy levels of 0.567j, 1.134j, and 1.571j [impact energy toughness (j/cm3); 0.12, 0.24, 0.34], respectively. The subsequent changes/degradation in elastic moduli, strength, toughness, and fatigue properties were measured after different number of impacts. It was found that for all energy levels these properties vary linearly with the number of impacts. Furthermore, attenuation changes is not a good ultrasonic parameter for degradation estimation, since it does not incorporate the micro- and macrocracks beyond the impact point. However, these micro- and macrocracks have significant effect on the mechanical properties. In contrast to the attenuation, the stress wave factor, which indicates the efficiency of wave propagation along the specimen, correlates very well with degradation, and it can be used effectively to measure the residual strength after impact. Ultrasonic characteristic on specimens subjected to combined fatigue and impact were also studied. Based on these experiments, it is concluded that the loss in fatigue residual life due to impact loads may be predicted by measuring the effects of the impact load on attenuation and stress wave factor. It was found that the reduction in fatigue life is proportional to sudden changes in attenuation and stress wave factor. Damage accumulation models based on Coffin-Manson equation, was suggested for impact and combined fatigue and impact. It was found that residual properties and fatigue life can be estimated from these models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570621
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  • 22
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    Electronic Resource
    Ultrasonic crack characterization via a constrained inversion algorithm (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 37-43 
    Details
    ISSN: 1573-4862
    Keywords: Kirchhoff approximation ; crack scattering ; ultrasonics ; NDE ; inverse scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The Kirchhoff approximation is used to show that the time domain impulse response of an isolated flat crack can be given a simple geometrical interpretation in terms of the derivative of a projected length function. For an elliptical crack, this derivative can be obtained explicitly to yield the two edge-diffracted waves which originate from the “flashpoints” of the crack. An explicit coordinate invariant expression is obtained from this elliptical crack solution which relates the time difference, Δt, between the arrival of these edge-diffracted waves and the crack size and orientation. Previously, we have proposed that this expression, together with Δt measurements in different scattering directions, could be used in a regression analysis as the basis for performing a constrained inversion of crack scattering data (i.e., where we attempt to obtain the “best” equivalent flat elliptical crack that fits the scattering measurements). Here we will demonstrate some results of applying the proposed algorithm using “noisy” synthetic data. The sensitivity of the results to both, number of measurements and transducer orientation, will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568762
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  • 23
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    Electronic Resource
    Characterization of flaws using the zeroes of the real and imaginary parts of the ultrasonic scattering amplitude (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 57-68 
    Details
    ISSN: 1573-4862
    Keywords: Flaw sizing ; inverse Born approximation ; nondestructive evaluation ; ultrasonics ; zeroes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new method for determining the size of flaws, such as cracks and voids, in structural materials is reported. The method is based on the observation that, for a wide class of flaws, the zeroes in the real and imaginary parts of the scattering amplitude occur at characteristic frequencies which depend on the flaw size. The method of reconstruction using the zeroes is simpler than the inverse Born approximation because the flaw sizes are extracted directly from the characteristic frequencies. The new method employs the same data input as the inverse Born algorithm and has certain common limitations. Following a theoretical treatment, experimental results are presented for a number of different types of flaws.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566956
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