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  • Articles  (21)
  • NDE  (21)
  • 1990-1994  (1)
  • 1985-1989  (20)
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  • 1950-1954
  • Electrical Engineering, Measurement and Control Technology  (21)
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  • Articles  (21)
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  • 1
    Electronic Resource
    Electronic Resource
    Crack detection in conducting materials using SQUID magnetometry (1993)
    Springer
    Journal of nondestructive evaluation 12 (1993), S. 199-207 
    Details
    ISSN: 1573-4862
    Keywords: Crack detection ; NDE ; SQUID magnetometry ; magnetic methods ; current perturbation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A highly sensitive multichannel SQUID gradiometer, optimized uniquely for spatial resolution, was used to map in two dimensions the magnetic field perturbations from circular holes and thin slots in conducting plates and strips, respectively. Holes as small as 0.75 mm radius in electrically conducting plates were measured directly using a single channel. Edge slots as short as 0.5 mm long in conducting strips were detected, using a multiple-channel measurement method which eliminated the effects from the edge of the strip and the current leads. Clear magnetic signatures from these simulated cracks were measured using low current densities. Numerical computations of the theoretical field distributions are presented which confirm the experimental results. Calculations indicate that much smaller defects should be detectable with an optimization of test parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568105
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  • 2
    Electronic Resource
    Electronic Resource
    Calculation of ultrasonic surface waves from an extended thermoelastic laser source (1989)
    Springer
    Journal of nondestructive evaluation 8 (1989), S. 147-164 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonic surface waves ; Rayleigh waves ; laser ultrasonics ; thermoelastic ultrasonic source ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A method is developed to calculate ultrasonic surface waveforms generated by an extended laser source, operating in the thermoelastic regime of laser-pulse energy density. This approach integrates over a suitably weighted distribution of point surface centers of expansion, for observation to within 1 mm of the edge of the source. Power spectra as well as both horizontal and vertical displacements are presented and discussed for ultrasonic waveforms on an aluminium surface, for incident laser pulses having Gaussian lateral profiles of various sizes. Far from the source, the waveform is dominated by a dipolar Rayleigh (R) wave, whose amplitude and spectral content depend on laser spot size. Weak, monopolar pulses also occur at the intersection of bulk pressure and shear wavefronts with the surface (denoted assP andsS, respectively). Close to the source, thesP wave amplitude approaches that for theR wave, and overlaps theR wave for large source sizes. The fall-off with distance for bothsP andR waves is given. Finally, the changes in pulse shape and amplitude are calculated when anR wave from an extended thermoelastic source is reflected or transmitted by a right-angled corner of an aluminium block.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570884
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  • 3
    Electronic Resource
    Electronic Resource
    A domain-extension method for quantitative detection of cavities by infrared scanning (1989)
    Springer
    Journal of nondestructive evaluation 8 (1989), S. 195-211 
    Details
    ISSN: 1573-4862
    Keywords: Infrared scanning ; thermography ; inverse problem ; numerical solution ; domain-extension method ; boundary-element method ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A domain-extension method for quantitative detection of irregular-shape cavities inside irregular-shape bodies is presented. An auxiliary problem is introduced in the solution of the cavities. In the auxiliary problem, the original body domain at the cavity side is extended so that the original cavity walls become interior points. The position of the cavities can then be found by solving the temperature field in the extended domain and matching the temperatures and heat fluxes at the interior points to the conditions imposed on the cavities. A boundary-element method is used for the solution of the auxiliary problem, and by means of four examples, the accuracy of the domain extension method is established. The paper provides the details for the numerical solution of the cavities. Limitation of the method in the detection of multiple cavities is also explored. The domain-extension method has shown to be highly effective in quantitative detection of cavities in single-cavity bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570887
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  • 4
    Electronic Resource
    Electronic Resource
    Image-enhanced backlighting: A new method of NDE for translucent composites (1989)
    Springer
    Journal of nondestructive evaluation 8 (1989), S. 181-193 
    Details
    ISSN: 1573-4862
    Keywords: Backlighting ; image processing ; delamination ; cracking ; Kevlar/epoxy ; fiberglass ; NDE ; damage detection ; image enhancement ; composite damage detection ; image-enhanced backlighting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A quick and inexpensive method of nondestructive evaluation is described based on imagenhanced backlighting. The method is capable of being applied to translucent composite materials such as Kevlar/epoxy and glass/epoxy to detect delamination with high resolution. The use of an enhancing dye also makes the method suitable for monitoring surface cracking. The technique has also been demonstrated to be an especially convenient method of observingin situ the growth of cracking and delamination damage as a composite is loaded, and is capable of monitoring thedynamic growth of damage in impact-loading situations. It has been shown to be appropriate for detecting barely visible damage resulting from either impact or static loading on thick laminated structures that even include honeycomb reinforcement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570886
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  • 5
    Electronic Resource
    Electronic Resource
    Some examples of nondestructive flaw detection by shearography (1989)
    Springer
    Journal of nondestructive evaluation 8 (1989), S. 225-234 
    Details
    ISSN: 1573-4862
    Keywords: Laser ; speckle interferometry ; shearography ; NDE ; metals ; composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper presents some examples of nondestructive flaw detection using an optical method based on speckle shearing interferometry called shearography. In the method, a structure under study is illuminated by laser and imaged by a special image-shearing camera. After suitable processing, a fringe pattern which represents loci of surface displacement derivatives, i.e., strains, is observed in the image. Since defects in structures usually induce strain concentrations around them and since strain concentrations usually cause perturbations on the surface of structures, shearography reveals defects from anomalies in the recorded fringe pattern. In this work, the technique has been applied to the nondestructive detection of various flaws in plain and welded pipes, composite plates, and other engineering components. A simple model was also developed for the estimation of the depth of disbonds in glassfiber reinforced plastic sheets. Results obtained are good and demonstrate the usefulness of the method as a complement to other conventional NDT techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00633273
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  • 6
    Electronic Resource
    Electronic Resource
    Body to Rayleigh wave mode-conversion at steps and slots (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 1-22 
    Details
    ISSN: 1573-4862
    Keywords: Rayleigh waves ; finite-difference method ; defect dimension ; ultrasonic scattering ; mode conversion ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The efficient excitation of Rayleigh waves at surface discontinuities due to body wave incidence has potential as a method for the detection and sizing of surface breaking defects. In this paper, the mode-conversion phenomenon at several types of surface features is studied in detail, using numerical models which employ finite-difference methods. The emphasis is on examining the spectral content of the Rayleigh wave field in order to arrive at a method for relating the spectral information to the defect dimensions. The numerical results are backed up by experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566693
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Nondestructive evaluation of ferromagnetic materials by a “magnetometer like” experimental arrangement (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 73-79 
    Details
    ISSN: 1573-4862
    Keywords: Barkhausen noise ; ferromagnetic materials ; stress ; magnetometer ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The paper presents experimental results regarding the influence of mechanical stresses and thermal treatments on the Barkhausen noise and magnetization characteristic of MolyPermalloy and MuMetal ferromagnetic samples. The samples are different in stress magnitude and localization and in their thermal history. The level of Barkhausen noise and the changes in magnetization characteristic are estimated by measuring the sensitivity and transduction gain of “magnetometer like” coils configurations which employ the studied ferromagnetic samples as their nonlinear ferromagnetic cores. The present method is unique in the sense that the two factors (one factor is related to the internal magnetic noise, and the other one is related to the form of the magnetic characteristic) are obtained by employing a single relatively simple experimental arrangement. Various types of stresses, which are different in magnitude and localization, become distinguishable one from the other, when considering their differential effects on the two factors. Several possible experimental arrangements are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568885
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  • 9
    Electronic Resource
    Electronic Resource
    Nondestructive detection of flaws in material using transducer arrays (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 47-55 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; transducer array ; flaw detection ; signal processing ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, we describe a system which uses array filters for processing the recordings of an array of transducers for the purpose of locating possible flaws in the material being tested nondestructively. When applied, in order to focus the array outputs at a point inside the material, these filters are able to attenuate, very effectively, interfering residual energy scattered from adjacent flaws, as well as random noise. If there is a flaw at the point of focus, the summed output of the filters will have a large signal at a delay time corresponding to the total travel time for this point; otherwise the output will consist mainly of residual random noise. Thus, the location of flaws or even microflaws in material may be achieved by simple threshold detection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566696
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  • 10
    Electronic Resource
    Electronic Resource
    Numerical analysis of heat input effects in thermography (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 101-107 
    Details
    ISSN: 1573-4862
    Keywords: NDE ; thermography ; numerical model ; heat input
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A numerical model, suited for use on microcomputers, has been developed to examine the effect of heat input function on surface temperature contrast for passive thermographic NDE. Single and double step input functions have been compared, and the effects of varying pulse length and power, defect condition, defect depth to diameter ratio, and maximum allowed front face temperature rise examined. Results indicate that a two-step heat input function enhances the generated surface temperature contrast by up to 10% over the single pulse and compares well with that generated by contact heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568888
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  • 11
    Electronic Resource
    Electronic Resource
    Stationary formulas for computing the response in eddy-current NDE (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 177-180 
    Details
    ISSN: 1573-4862
    Keywords: Eddy current ; NDE ; theoretical models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Stationary or variational formulations have been proven to be useful in a number of electromagnetic problems. This paper presents such a formulation for the response in the eddy-current NDE problem. It thus provides an approach to estimating the response due to arbitrary defects in cases where a reasonable “first guess” for the current distribution responsible for the scattered fields can be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566845
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  • 12
    Electronic Resource
    Electronic Resource
    Depth measurement for cracks in corners using ultrasonic Rayleigh waves (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 179-187 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonic Rayleigh waves ; crack depth measurement ; corner cracks ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of ultrasonic Rayleigh waves incident normally on corners containing cracks is considered by using elastodynamic ray theory. Detailed calculations are presented for vertical and horizontal cracks in right-angle corners in aluminium. It is shown that crack depth can be measured simply from the spacing of interference fringes in the high-frequency spectra of either the back- or forward-scattered Rayleigh waves, given only a knowledge of the Rayleigh wave speed. Use of the back-scattered wave is preferable because its fringes show stronger modulation, and because an experiment requires a single transducer and access to only one face of the specimen. The technique is applicable without modification to the more general case of a crack at any angle in a corner of any angle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570627
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  • 13
    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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  • 14
    Electronic Resource
    Electronic Resource
    Elastodynamic scattering by fluid-filled nonplanar cracks (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 161-168 
    Details
    ISSN: 1573-4862
    Keywords: Crack ; nonplanar ; fluid filled ; scattering ; null field ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A recent modification of the null field approach is adapted to the study of scattering of elastic waves by fluid-filled nonplanar cracks. The fluid-filled crack is modeled as a surface over which friction-free boundary conditions apply. A closed surface is formed by adding a fictitious surface, on which latter surface boundary conditions of welded contact are applied. The surface fields on the closed surface are expanded in vector spherical harmonics in a manner which takes the edge conditions into account. Some numerical results on farfield quantities, such as scattering cross sections and backscattering amplitudes (both in the frequency and time domains), are presented for rotationally symmetric cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570625
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  • 15
    Electronic Resource
    Electronic Resource
    Testing steel-cord belt splices with a magnetic conveyor belt monitor (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 15-19 
    Details
    ISSN: 1573-4862
    Keywords: Magnetic induction ; testing ; steel cord ; belt ; splices ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Steel-cord belt splices fail for a variety of reasons, including corrosion, poor vulcanising, and incorrect construction. The latter often leads to early failure. A conveyor belt monitor (CBM) has been used to evaluate the splice lay-up. The mass of the overlapping cords and their magnetic signature are used to rapidly locate suspect splices in the belt. The general shape of the magnetic signature for ideal splices will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568759
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  • 16
    Electronic Resource
    Electronic Resource
    Three dimensional strain measurements with x-ray energy dispersive spectroscopy (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 21-25 
    Details
    ISSN: 1573-4862
    Keywords: Profile fitting ; residual stress ; strain mapping ; x-ray diffraction ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A feasibility study was performed to show the ability of energy dispersive x-ray diffraction (EDXRD) to measure three dimensional strain distributions in thick industrial materials. Photon energies up to 130 keV were used to guarantee penetration through the sample and curve fitting techniques applied to peak position determination. This system was used to measure the strain gradient through the thickness of a 9.5 mm thick cantilevered steel bar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568760
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  • 17
    Electronic Resource
    Electronic Resource
    Impedance of single-turn coil surrounding a conducting cylinder with a flaw (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 53-56 
    Details
    ISSN: 1573-4862
    Keywords: Eddy current ; flaw ; cylinder ; Born approximation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The impedance of a single-turn coil which surrounds a conducting cylinder with a flaw is calculated employing Green's function technique. The Born approximation is used in order to know how the impedance change due to the presence of a flaw depends on the conductivity and size of a flaw.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568764
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  • 18
    Electronic Resource
    Electronic Resource
    A surface acoustic wave technique for monitoring the growth behavior of small surface fatigue cracks (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 1-7 
    Details
    ISSN: 1573-4862
    Keywords: Surface acoustic waves ; fatigue ; small crack growth ; crack opening behavior ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The theory of Kino and Auld which relates the reflection coefficient of acoustic waves from a crack to its size is summarized. A scattering model is evaluated from this theory concerning the reflection of surface acoustic waves (SAW) from a small surface fatigue crack at a frequency such that the crack depth is much smaller than the acoustic wavelength. Acoustic predictions of crack depth are compared to postfracture measurements of depth for small surface cracks in Pyrex glass, 7075-T651 aluminum, and 4340 steel. Additionally, the minimum detectable crack depth as limited by the acoustic noise level is determined for several typical aluminum and steel alloys. The utility of SAW reflection coefficient measurements for inferring crack depth, crack growth, and crack opening behaviorin situ during fatigue cycling is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568757
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  • 19
    Electronic Resource
    Electronic Resource
    An acoustoelastic determination of the stress tensor in textured metal sheets using the birefringency of ultrasonic shear waves (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 45-52 
    Details
    ISSN: 1573-4862
    Keywords: Acoustoelasticity ; shear waves ; stress measurements ; birefringency ; polarization ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A theory is formulated that enables one to determine two-dimensional applied stresses in sheets of slightly orthotropic material by means of ultrasonic shear waves To relate experimental acoustic data to a stress tensor we introduce an acoustoelastic tensork. Our experimental technique can measure times of flight and polarization angles within 1/3 nsec and 1°, respectively. In the case of the aluminium 2024-T351 alloy we used, calibration using tensile specimens leads to a nonisotropick tensor. Measurements of the complete (plane) stress tensor are carried out in the center of a compressed disc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568763
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  • 20
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    A new acoustic spectroscopy: Resonance spectroscopy by the MIIR (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 69-79 
    Details
    ISSN: 1573-4862
    Keywords: Acoustic scattering ; acoustic spectroscopy ; resonance spectrum ; resonance identification ; circumferential waves ; visualization ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Recent and remarkable advances in the experimental study of acoustic scattering from targets immersed in water are leading to a new spectroscopy: resonance acoustic spectroscopy. The discovery and improvement of an intriguing method, the Method of Isolation and Identification of Resonances (MIIR), has made possible experimental determination of the eigenfrequency spectra of aluminum-elastic cylinders and cylindrical shells. This method gives a quasilinear “resonance spectra.” In addition, it shows the importance of circumferential waves which generate standing waves. They allow us to explain the “reradiation” of targets after the end of insonification. The MIIR has numerous applications, especially in “underwater acoustics” and “nondestructive testing.”
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566957
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  • 21
    Electronic Resource
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    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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