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  • Articles  (13)
  • ultrasonics  (13)
  • 1990-1994  (7)
  • 1985-1989  (6)
  • 1960-1964
  • 1950-1954
  • Electrical Engineering, Measurement and Control Technology  (13)
  • 1
    Electronic Resource
    Electronic Resource
    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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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of nonlinearly viscoelastic behavior of adhesive bonds (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 221-226 
    Details
    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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  • 3
    Electronic Resource
    Electronic Resource
    A comparative study of transient waves in random (polycrystalline) media (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 9-17 
    Details
    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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  • 4
    Electronic Resource
    Electronic Resource
    Ultrasonic flaw classification in weldments using probabilistic neural networks (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 69-77 
    Details
    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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  • 5
    Electronic Resource
    Electronic Resource
    On the boundary conditions for ultrasonic transmission by partially closed cracks (1991)
    Springer
    Journal of nondestructive evaluation 10 (1991), S. 139-149 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567096
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  • 6
    Electronic Resource
    Electronic Resource
    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 
    Details
    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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  • 7
    Electronic Resource
    Electronic Resource
    Laser-based ultrasonics on Gr/epoxy composite (1990)
    Springer
    Journal of nondestructive evaluation 9 (1990), S. 229-238 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565641
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrasonic reflection by a planar distribution of cracks (1988)
    Springer
    Journal of nondestructive evaluation 7 (1988), S. 123-129 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565997
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  • 9
    Electronic Resource
    Electronic Resource
    ORCHID—A computer simulation of the reliability of an NDE inspection system (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 23-31 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566694
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrasonic characteristics of graphite/epoxy composite material subjected to fatigue and impacts (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 119-131 
    Details
    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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  • 11
    Electronic Resource
    Electronic Resource
    Concrete strength ultrasonic digital tester (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 157-160 
    Details
    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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  • 12
    Electronic Resource
    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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  • 13
    Electronic Resource
    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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