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  • Articles  (510)
  • Chemistry  (409)
  • NDE  (101)
  • Surface physics, nanoscale physics, low-dimensional systems
  • Electrical Engineering, Measurement and Control Technology  (510)
  • 1
    Electronic Resource
    Electronic Resource
    Stress-wave attenuation in thin structures by ultrasonic through-transmission (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 277-286 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; through-transmission ; composite materials ; attenuation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The steady-state amplitude of the output of an ultrasonic through-transmission measurement is analyzed and the result is given in closed form. Provided that the product of the input and output transduction ratios, the specimen-transducer reflection coefficient, the specimen-transducer phase-shift parameter, and the material phase velocity are known, this analysis gives a means for determining the through-thickness attenuation of an individual thin sample. Multiple stress-wave reflections are taken into account, and so signal echoes do not represent a difficulty. An example is presented for a graphite fiber epoxy composite (Hercules AS/3501-6). Thus, the technique provides a direct method for continuous or intermittent monitoring of through-thickness attenuation of plate structures which may be subject to service structural degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571808
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  • 2
    Electronic Resource
    Electronic Resource
    A 3-D Image Detection Method of a Surface Opening Crack in Concrete Using Ultrasonic Transducer Arrays (1997)
    Springer
    Journal of nondestructive evaluation 16 (1997), S. 193-203 
    Details
    ISSN: 1573-4862
    Keywords: Nondestructive evaluation ; NDE ; concrete ; crack ; image ; ultrasonic ; ellipsoid ; migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The detection of the size and the location of existing three dimensional cracks in a concrete structure is an important topic in civil engineering. In this paper, a multisource, multireceiver method that considers the travel times diffracted by a crack tip is introduced, to backcalculate a 3-D image of the crack tip of a surface opening crack. The possible location of the crack tip front is on the surface of an ellipsoid, which is constructed by a fixed travel time length measured from the source to the receiver, by letting the source and receiver points be the foci of the corresponding ellipsoid. If the locations of the source and the receiver, together with the associated measured travel time of the diffracted echo between each source-receiver pair are known, the image of the tip can be determined by counting the number of intersections of the ellipsoidal surfaces in an image construction cellular structure. The backcalculated crack tip image, as seen from experimental data, match the dimensions of the real crack very well, demonstrating the capability and accuracy of this newly proposed multisource, multireceiver method for concrete NDE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021843930620
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  • 3
    Electronic Resource
    Electronic Resource
    A new digital correlation flaw detection system (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 57-63 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonics ; correlation ; pseudorandom codes ; random signals ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new portable digital random signal flaw detection system is described which uses a digital delay line to replace the acoustic delay line of the original random signal system. Using this new system, a comparison was made between the two types of transmit signals which have been used in previous systems—m-sequences and random signals. This comparison has not been possible with these previous correlation flaw detection systems. Results indicated that for high-speed short code operation, the m-sequences produced slightly lower range sidelobes than typical samples of a clipped random signal. For normal long code operation, results indicated that system performance is essentially equivalent in resolution and signal-to-noise ratio using either m-sequences or clipped and sampled random signals. Further results also showed that for normal long code operation, the system produces outputs equivalent in resolution to pulse-echo systems, but with the added benefit of signal-to-noise ratio enhancement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614998
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  • 4
    Electronic Resource
    Electronic Resource
    Potential and limits of holographic reconstruction algorithms (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 85-111 
    Details
    ISSN: 1573-4862
    Keywords: Holographic reconstruction ; ultrasound ; NDE ; Rayleigh-Sommerfeld formula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract For the purpose of ultrasonic nondestructive testing of materials, holography in connection with digital reconstruction algorithms has been proposed as a modern tool to extract crack sizes from ultrasonic scattering data. Defining the typical holographic reconstruction algorithm as the application of the scalar Kirchhoff diffraction theory to backward wave propagation, we demonstrate its general incapability of reconstructing equivalent sources, and hence, geometries of scattering bodies. Only the special case of a planar measurement recording surface, that is to say, a hologram plane, and a planar crack with perfectly rigid boundary conditions parallel to the hologram plane and perpendicular to the incident field yields a nearly perfect correlation between crack size and reconstructed image; the reconstruction algorithm is then referred to as the Rayleigh-Sommerfeld formula; it therefore represents the optimal case matched to that special geometrical situation and, hence, may be interpreted as a quasi-matched spatial filter. Using integral equation theory and physical optics, we compute synthetic holographic data for a linear cracklike scatterer for both plane and spherical wave incidence, the latter case simulating a synthetic aperture impulse echo situation, thus illustrating how the Rayleigh-Sommerfeld algorithm or its Fresnel approximation increasingly fail for cracks inclined to the hologram plane and excited nonperpendicularly. Furthermore, we point out how the physical data recording process may additionally influence the reconstruction accuracy, and, finally, guidelines for a careful and serious application of these holographic reconstruction algorithms are given. The theoretical results are supported by measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566307
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  • 5
    Electronic Resource
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    Interior imaging using spatial frequency sampling (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 203-207 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonics ; synthetic aperture ; spatial frequency ; interior imaging ; acoustic microscopy ; defect detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new acoustic synthetic aperture geometry is demonstrated in which the image field is sampled in the spatial frequency domain. This means the sampled field is recorded in a particularly convenient form for presentation to the back propagation algorithms used to reconstruct the field at the object plane. The method has applications in interior visualization. It is difficult to image the interior of solid objects using lens based imaging systems because a different lens geometry must be used for each distinct object material. The system presented here overcomes such problems since both the angular variation of the transmission coefficient at the object-water interface and the aberrations introduced by the velocity mismatch at the object surface may be readily compensated for in the back propagation routine. Experimental results are presented illustrating the detection of four half wavelength diameter defects, spaced by three wavelengths, at a depth of eight wavelengths below the surface of an aluminum block.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570732
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  • 6
    Electronic Resource
    Electronic Resource
    Spherical wave decomposition approach to ultrasonic field calculations (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 241-247 
    Details
    ISSN: 1573-4862
    Keywords: ultrasonic field ; numerical methods ; transducer design ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570736
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  • 7
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    Quantitative use of Rayleigh waves to locate and size subsurface holes (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 55-63 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; Rayleigh waves ; subsurface defects ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An ultrasonic inspection method is used to obtain the circumference of a subsurface hole and the depth of the hole below the surface. A pitch-catch Rayleigh wave transducer set-up was used to launch a Rayleigh surface wave at the flaw and to capture and record the scattered waves. The frequency spectrum of the scattered waves can be used to obtain the depth of the hole. The ligament of material between the hole and the surface is sent into resonance, and this feature can be extracted from the scattered waves' frequency spectrum. The frequency is a function of the ligament length; thus the hole depth can be obtained. The circumference of the hole is found from a time of flight measurement. A Rayleigh wave is formed that travels around the hole's surface. The length of time required for the wave to travel around the hole is a measure of the circumference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566955
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  • 8
    Electronic Resource
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    The influence of skin depth on crack measurement by the ac field technique (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 65-76 
    Details
    ISSN: 1573-4862
    Keywords: crack measurement ; ac field technique ; arbitrary skin depth ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general solution is given to describe the ac field around surface-breaking cracks for arbitrary values of the ratio of skin depth δ to crack depthd. This solution allows accurate interpretation of crack depth from voltage readings taken by a Crack Microgauge instrument in cases where δ andd are comparable. It is shown to agree with asymptotic formulae obtained for the cases where δ/d is very small and very large. Provided that the probe length Δ is large compared with δ, the calculations show that a very good approximation to the crack depth may be obtained, irrespective of the ratio δ/d, by using the thin-skin asymptotic formula $$d = \frac{1}{2}\Delta (V_2 - V_1 )/V_1 $$ whereV 1 andV 2 are probe voltages registered at positions just off and across the crack, respectively. The problem is solved for a crack of infinite aspect ratio which has no opening, but it can be applied with confidence at the centerline of cracks of fairly large aspect ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568962
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  • 9
    Electronic Resource
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    Infrared scanning thermography for a quantitative detection of cavities in a plane slab and a rectangular prism (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 99-109 
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    ISSN: 1573-4862
    Keywords: thermography ; infrared scanning ; calibration ; inverse problems ; cavity detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An approach for treating nondestructive testing as the solution of inverse problems in mathematical physics has been used for the detection of cavities. The approach is developed based on the use of an additional boundary condition of scanned temperature on the surface to solve for the cavity geometry. For the present study, the condition at the cavity side is taken to be that of a specified temperature, and the experiment is carried out to meet this condition. Two specimens are tested in this paper, a plane slab and a rectangular prism. In both bodies the cavity is rectangular in shape. For the testing of the plane slab, the method is able to detect the cavity wall with high accuracy, whereas the cavity depth error is larger (6%). The detection of the cavity position in the rectangular prism has an error ranging from −9.7 to 7.7%. Errors in the experiment are attributed to the uncertainties in the measurements of temperature and the Biot number. The former is read off from the analog data output of the infrared scanner. The latter is not measured separately, but is computed from the scanned data and thus becomes a portion of the total nondestructive testing output. A final note is also made in this paper to relate how the presented method can be used in actual practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568966
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  • 10
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    Analysis of ultrasonic wave scattering for characterization of defects in solids: I. Spherical inclusions and reciprocity (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 175-182 
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    ISSN: 1573-4862
    Keywords: ultrasonic wave scattering ; inclusions ; reciprocity ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper, as part of a series on elastic wave scattering, presents results of measurements and calculations on scattering of ultrasonic waves by a solid spherical inclusion (tungsten carbide) embedded in titanium alloy by the diffusion bonding process. Both direct scattering and mode-converted scattering angular distributions are reported for shear and compressional incident waves. The consequences upon the signals when transmitter and receiver were interchanged are explored in a reciprocity rule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566558
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  • 11
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    Testing steel-cord belt splices with a magnetic conveyor belt monitor (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 15-19 
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    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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  • 12
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    Three dimensional strain measurements with x-ray energy dispersive spectroscopy (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 21-25 
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    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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  • 13
    Electronic Resource
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    Impedance of single-turn coil surrounding a conducting cylinder with a flaw (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 53-56 
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    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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  • 14
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    Volumetric inspection of moderately thick austenitic stainless steels by multifrequency eddy currents (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 23-33 
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    ISSN: 1573-4862
    Keywords: austenitic stainless steel ; austenitic stainless steel welds ; eddy current inspection ; eddy current testing ; electromagnetic testing ; ferromagnetic steel inspection ; flaw characterization ; flaw detection ; NDE ; multifrequency eddy current inspection ; weld inspection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes the initial phase of a project to develop eddy-current methods to inspect welds joining sections of austenitic stainless steel pipe having walls up to 13 mm (0.5 in.) thick. The objective of this phase was to demonstrate the feasibility of detecting and characterizing flaws in austenitic stainless steel base metals. These materials and welds present challenging eddy-current problems because of their relatively large thickness and ferromagnetism. Multiparameter analysis shows that a reflection coil probe operated with three discrete driver frequencies and phase detection can locate and size a cracklike defect in a single conductor in the presence of variations in conductor resistivity, permeability, and thickness and in the probe-conductor spacing (liftoff). Experiments were performed with a modular three-frequency instrument. Flat-plate specimens of types 304L and 347 stainless steel machined to 12.7 to 15.9 mm thickness simulated pipe walls; saw-cut slots 10 to 30% of nominal specimen thickness simulated cracklike defects. The same slots were used in duplicate experiments as near-side (directly under the test probe) or far-side (in the face opposite the probe) defects. Flaw detection and characterization capability was demonstrated by a series of experimental measurements fitted to specimen properties by least squares techniques. The quality of the fit determined the expected accuracy of measurement. Comparison of accuracy estimates determined the best choice of operating frequencies. From the 1,2,5 sequence of frequencies between 0.5 and 20 kHz, the optimum set of operating frequencies was selected to be 0.5, 2, and 10 kHz. Estimates of measurement accuracy for combined near- and far-side defect cases were: plate thickness, 0.74 mm; probe liftoff, 0.03 mm; defect location (depth of material above defect), 3.48 mm; and defect size (vertical slot depth), 1.09 mm. A few property values were back-calculated from instrument readings; the errors in these values were somewhat larger than the measurement accuracy estimates because of instrument drift and the absence of calibration circuits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614994
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  • 15
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    Numerical modelling of the scattering of elastic waves in plates (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 89-106 
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    ISSN: 1573-4862
    Keywords: scattering ; elastic waves ; Lamb waves ; shear waves ; finite difference methods ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes the application of finite difference methods to the calculation of the scattering of elastic waves. The emphasis is on cracklike defects in plates, and it is shown that a common numerical technique can span a range of wavelengths from Lamb waves to ultrasonic waves with many reflections from the surfaces of the plate. Quantitative results are given for the scattering of Lamb waves and ultrasonic shear waves from surface-breaking cracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566400
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  • 16
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    Defect identification and sizing by the ultrasonic satellite-pulse technique (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 263-276 
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    ISSN: 1573-4862
    Keywords: Ultrasonics ; scattering ; diffraction ; defect characterization ; cracks ; voids ; pattern recognition ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Shape and size are the most important defect characteristics that need to be determined for the reliable prediction of the remaining service lifetime of a defective structure or part. The analytical and supporting experimental results presented in this paper concern a general, pattern recognition-based, ultrasonic defect identification and sizing method. The satellite-pulse technique (SPT) is based on the interpretation, in terms of defect types (shapes) and dimensions, of the separation in time of arrival between the readily detected specularly reflected pulse and its generally ignored tip-diffracted or tangentially scattered “satellite” contained in the received waveform. Calibration procedures were also developed that enable the ultrasonic examiner to read the time scale of the oscilloscope for equivalent crack depth or void diameter as appropriate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571807
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  • 17
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    Acoustic emission and inclusion fracture in 7075 aluminum alloys (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 35-41 
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    ISSN: 1573-4862
    Keywords: acoustic emission ; crack growth ; 7075 aluminum ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract For slow crack growth (da/dn ≈0.1 µm per load cycle) in 7075-T6 aluminum, quantitative agreement was found between the amplitude distribution of burst acoustic emissions and the area size distribution of intermetallic inclusions ≈10 (µm)2 in area as measured on thepolished fracture face. This observation permits the prediction of the amplitude distribution of acoustic emissions due to crack growth in a particular sample of 7075-T6 aluminum directly from a simple, standard metallographic observation performed on the material in question. It was also found that a reduction of the yield stress from that of 7075-T6 aluminum (503 MPa) to that of 7075-0 aluminum (103 MPa) completely eliminated burst acoustic emission activity due to crack advance in the amplitude range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614995
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  • 18
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    Some computational considerations in eddy-current NDE (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 39-42 
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    ISSN: 1573-4862
    Keywords: Eddy current ; computer analysis ; numerical methods ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Theoretical calculations of eddy-current phenomena often involve the numerical evaluation of various integral expressions. A discussion of some of the possible evaluation methods and of the factors to be considered in choosing a method is presented.
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    URL: http://dx.doi.org/10.1007/BF00711099
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  • 19
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    Ultrasonic reflection from a stressed interface (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 3-12 
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    ISSN: 1573-4862
    Keywords: Ultrasonic ; stress measurements ; interfacial stress ; NiTi ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In seeking to develop an NDE technique for verifying the serviceability of NiTi couplers for plumbing unions, it was found that the reflection coefficient for a normally incident ultrasonic wave correlated with the stress level at the NiTi-tubing interface. Current theory pertaining to interface reflection is not complete but, even at present status, there is semiquantitative accord between theoretical predictions and normalized data for reflection coefficient versus stress level. These results are at fixed frequency and with comparable surface roughness. Variation of either frequency or surface roughness further affects the reflection coefficient. Current studies are being pursued to define this effect.
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    URL: http://dx.doi.org/10.1007/BF00711095
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  • 20
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    The radiographic edge scattering distortion (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 75-88 
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    ISSN: 1573-4862
    Keywords: object scattering ; edge scattering ; knife edge ; neutron radiography ; buildup factor ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Previously described scattering based edge distortions in optical density scans obtained from a neutron radiographic knife-edge image have been here confirmed using analog Monte Carlo simulation. In an attempt to estimate the effects of additional object scatter on such artifacts, the effect on the edge response of diffusely incident neutrons has been determined both empirically and by Monte Carlo simulation. The diffuse neutron incidence has been found to diminish the relative magnitude of the distortion, offering explanation for the infrequent observation of the corresponding edge scattering halo artifacts. The potential of this edge distortion as a diagnostic indicator of the buildup factor in radiography is suggested and examined.
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    URL: http://dx.doi.org/10.1007/BF00566399
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  • 21
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    Static finite element stress intensity factors for annular cracks (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 119-124 
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    ISSN: 1573-4862
    Keywords: Stress intensity factor ; annular crack ; finite element methods ; fatigue ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Results of finite element static stress intensity factor calculations for an annular crack around a spherical inclusion (void) are presented and compared with those from approximate analytical methods.
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    URL: http://dx.doi.org/10.1007/BF00566309
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  • 22
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    Note on ultrasonic tomography (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 147-149 
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    ISSN: 1573-4862
    Keywords: Ultrasonic tomography ; residual stress ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic tomography is being explored as a potential tool to map residual stresses in solids. The angular scanning required in tomography imposed limitations on the stress configuration adaptable to such a treatment. These are discussed in the following note.
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    URL: http://dx.doi.org/10.1007/BF00566313
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  • 23
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    Ill-posed and well-posed problems in inverse elastodynamic scattering for nondestructive evaluation (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 161-172 
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    ISSN: 1573-4862
    Keywords: elastodynamic inverse scattering ; ultrasonics ; data reduction ; ill-posed problems ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The practical significance of ill-posedness in a data reduction problem is reviewed. Inverse elastodynamic scattering is shown to be ill-posed in general, although suitably restricted problems may be well-posed. These results underscore the need to analyze carefully the errors of data reduction problems in NDE, and to focus attention on final results of an NDE exercise, rather than on intermediate steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570728
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  • 24
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    Effects of sinusoidal crack-face perturbations on scattering of elastic waves (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 153-159 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; scattering ; cracks ; periodic surface perturbation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of a plane longitudinal wave from a two-dimensional crack, with a sinusoidal surface perturbation whose amplitude and wavelength are much smaller than the length of the crack, is investigated. The amplitude of the cylindrical body waves in the far field are calculated from a Kirchhoff approximation that utilizes the solution to the reflection from the sinusoidal surface profile of a semiinfinite solid. The results are compared to those for a flat crack, and conditions for significant differences of the amplitude as a function of the angle of observation are discussed. Characteristic changes in the scattered field produced by profiles with different amplitudes and periods are explained.
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    Parasitic voltages induced by artificial flaws when measured using the ac field technique (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 195-202 
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    ISSN: 1573-4862
    Keywords: ac potential difference ; fatigue crack measurement ; slots ; artificial flaws ; parasitic voltages ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The development of a successful and accurate instrument for measuring surface-breaking cracks in metals using the ac field technique has raised several interesting theoretical problems. Measurements with the instrument, known as the Crack Microgauge, do not rely on any prior calibration against an artificial flaw such as a saw-cut in a test block, but some users accustomed to such a calibration from other devices have nevertheless wished to use the instrument in that fashion and have in some instances reported erroneous results. In this paper, we develop a simple theory to explain and quantify this phenomenon. We calculate the parasitic voltages induced in the instrument probe due to the finite opening possessed by an artificial flaw, and we use these results to reinterpret the instrument readings. Controlled experimental measurements on artificial flaws of rectangular cross-section made in aluminum and in steel are found to be in good agreement with the theory. It is shown, however, that application of the theory requires additional information about the internal phase shift associated with the instrument. To enhance the accuracy of the theory, the effect of the corners of the artificial flaws was also considered, although it was not very influential in this work.
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    The ac field around a plane crack in a metal surface when the skin depth is large (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 19-24 
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    ISSN: 1573-4862
    Keywords: ac potential difference ; eddy current ; fatigue crack measurement ; skin effect equation ; large skin depth ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper considers the solution of the skin-effect or Helmholtz equation, ∇2ψ=k 2ψ, for the two-dimensional flow of a uniform alternating current perturbed by a plane crack of uniform depth. Herek is the ratio of crack depthd to skin depth δ. When the skin depth is large compared with the crack depth andk f 0, the quasi-static approach to this problem ignores the terms on the right-hand side and constructs solutions from Laplace's equation which are essentially dc solutions and are correct to orderk. In this paper we consider behavior near the limit when the skin depth is large and give solutions which are correct to orderk 2. In an example we relate the results to the interpretation of readings from an ac potential difference instrument applied to the measurement of surface-breaking cracks.
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    Characterization of localized surface elastic defects by nonspecular reflection at the Rayleigh angle (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 93-98 
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    ISSN: 1573-4862
    Keywords: bounded ultrasonic beam reflectivity ; Rayleigh angle ; beam profile ; surface defects ; nonspecular reflection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The relationships between characteristics of elastic defects and nonspecular features of bounded ultrasonic beams reflected at the Rayleigh angle from a liquid-solid interface are investigated. The results can serve as a theoretical basis for interpretation of Rayleigh angle nonspecularly reflected beam profiles as characterization of localized surface elastic defects.
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    On the optimum applied field for magnetic particle inspection using direct current (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 125-136 
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    ISSN: 1573-4862
    Keywords: magnetic particle inspection ; magnetic leakage fields ; finite difference method ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Experimental measurements of leakage fields from cylindrical defects were obtained in a geometry which permitted simultaneous measurement of the magnetic induction of the material. The results obtained are compared with calculations using a nonlinear finite difference method. Both the experiments and the calculations indicate that the magnitude of the leakage field continues to grow nearly in proportion with the applied field well into the saturation region of the magnetic material. The implications for magnetic particle inspection are discussed.
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    Body to Rayleigh wave mode-conversion at steps and slots (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 1-22 
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    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.
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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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    Time domain Born approximation (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 45-53 
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    ISSN: 1573-4862
    Keywords: Born approximation ; ultrasonic scattering ; NDE ; time domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The time domain Born approximation for ultrasonic scattering from volume flaws in an elastic medium is described. Results are given both for the direct and the inverse problem. The time domain picture leads to simple intuitive formulas, which we illustrate by means of several simple examples. Particular emphasis is given to the front surface echo and its use in reconstructing the properties of the flaw.
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    Calculation of ultrasonic surface waves from an extended thermoelastic laser source (1989)
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    Journal of nondestructive evaluation 8 (1989), S. 147-164 
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    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.
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    A domain-extension method for quantitative detection of cavities by infrared scanning (1989)
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    Journal of nondestructive evaluation 8 (1989), S. 195-211 
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    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.
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    Image-enhanced backlighting: A new method of NDE for translucent composites (1989)
    Springer
    Journal of nondestructive evaluation 8 (1989), S. 181-193 
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    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.
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    Remaining fatigue life prediction in the initiation regime using SAW NDE (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 3-9 
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    ISSN: 1573-4862
    Keywords: harmonic generation ; fatigue ; microcracks ; aluminum ; surface acoustic waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Harmonic generation of surface acoustic waves (SAW) is shown to be a useful tool for the detection of the initiation of surface cracks during fatigue of high strength aluminum alloys. A model that relates the length and density of microcracks to the amplitude of a SAW harmonic signal is described, and an associated coefficient of generation efficiency for the second harmonic amplitude is derived. A correlation between experimentally measured harmonic amplitude and remaining fatigue life is then demonstrated, which allows the mean remaining fatigue lifetime to be estimated to within 5% over the last 50% of the fatigue life for an Al 7075 alloy if the cyclic stress amplitude, but not the duration of fatigue, is known.
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    Ultrasonic diffraction technique for characterization of fatigue cracks (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 11-19 
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    ISSN: 1573-4862
    Keywords: ultrasonic diffraction ; fatigue cracks ; crack closure ; crack surfaces ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper describes an ultrasonic diffraction technique for characterizing fatigue cracks. The angular field of energy scattered from a crack tip was computed. Using the theoretically predicted and experimentally verified optimum range of angles, we measured the crack profiles by the ultrasonic diffraction technique. Ultrasonic measurements agreed very well with direct destructive measurements. In addition, fatigue crack closure was detected and information on crack surfaces was obtained.
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    Methods for determining the depth of near-surface defects (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 21-36 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; surface defects ; defect depth ; deconvolution ; correlation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In previous work by the authors,(1,6) it was demonstrated that the presence of near-surface defects could be detected reliably, even though the defect echo was contained within the near-surface echo. The algorithm consists of examining the variation in the composite (near-surface plus defect) response after it has been deconvolved from a near-surface response known to be defect-free. This paper presents two algorithms that have been developed subsequent to the work presented in ref. (6) for estimating thedepth of a near-surface defect, given that its presence has already been detected. One algorithm uses complex frequency domain techniques, and the other uses time domain analysis. Both procedures operate on the surface-plus-defect signal, using reference signals containing surface-only and defect-only responses. The defect signal is extracted from the composite signal. Defect depth is then computed from the time difference between the centers of the front-surface and extracted defect responses. A mean absolute depth error of 0.015 in. was obtained by applying the algorithms to experimental data containing depths from 0.020 to 0.130 in. below the near-surface.
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    Accept/reject decisions and failure prediction for structural ceramics: Application to failure from voids (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 37-52 
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    ISSN: 1573-4862
    Keywords: failure prediction ; accept/reject decisions ; ceramic materials ; ultrasonics ; fracture ; probabilistic model ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general probabilistic method for reaching accept/reject decisions and failure prediction based on nondestructive evaluation procedures is described. The method is illustrated for ceramic materials that fail by the activation of microcracks located at void surfaces. The inspection procedure used for the analysis is the long wavelength ultrasonic method. The analysis indicates influences on the decision level and on the false-reject probability of variations in the signal-to-noise ratio and in the preexistent void population. The ultrasonic inspection is shown to exert a relatively minor influence on the false-reject probability, even for low signal-to-noise ratios, low stresses, and a widely dispersed void population, because of the intrinsic variability of the selected failure process. More encouraging results concerning the utility of NDE are anticipated to apply to other failure mechanisms in ceramics.
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    Analytical representation of transient ultrasonic phased-array near- and far-fields (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 53-66 
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    ISSN: 1573-4862
    Keywords: ultrasonic transducers ; phased array ; ultrasonic imaging ; impulse response ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The present contribution provides a method for the derivation of analytical near- and far-field expressions for the pressure step-function response of nonuniformly excited ultrasonic transducers modeled as pistons of arbitrary shape in an infinite rigid baffle. Explicit inversion of the Laplace transformed ultrasonic field using Cagniard's idea results in elementary functions or definite integrals of elementary functions, depending on the assumed nonuniform aperture distribution. The basic signal distortion is illustrated in terms of three-dimensional space-time plots of the pressure unit step-function response of a rectangular uniform aperture. The corresponding results for a phased-array transducer are also given. In addition, we investigate the pressure profile on the axis perpendicular to a uniform rectangular piston and its horizontal radiation pattern for different bandwidths of the exciting impulse.
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    Acoustic measurements of stress fields and microstructure (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 67-77 
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    ISSN: 1573-4862
    Keywords: stress fields ; microstructure ; J integral ; stress intensity factor ; harness acoustic velocity ; acoustic elasticity ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A very precise system for measuring two-dimensional velocity fields in solid samples has been used for nondestructive measurements of both externally applied and residual inhomogeneous stresses in solids,J integrals, stress intensity factors of cracks, and hardness of quenched steel. The longitudinal velocity measurement is based on precise determination of the propagation transit time through the stressed solid specimen using a small diameter, water-coupled acoutic transducer, which is scanned mechanically over the sample. Changes in velocity are then related to changes of stress in the sample by the theory of acoustoelasticity. Similar measurements show a high degree of correlation between longitudinal velocity changes and changes in microstructure in steel samples. Applications to problems of solid mechanics and material science illustrate the utility of this nondestructive measuring technique.
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    The relationship between radiating body forces and equivalent surface stresses: Analysis and application to EMAT design (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 79-85 
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    ISSN: 1573-4862
    Keywords: ultrasonic waves ; EMAT ; surface stress ; NDE ; Green's function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An analysis of the radiation from a body force shows that it is equivalent to the radiation from a series of surface stresses defined by the moments of the body force taken with respect to the depth coordinate. As the body force becomes localized near the surface, the zeroth moment of the force dominates the radiation and is often thought of as an equivalent surface stress. However, under certain conditions, this can vanish, and the other moments must be considered. It is found that, as the order of the moment of a particular force component increases, the resulting radiation patterns alternate between those characteristic of a compressive surface stress and those characteristic of a shear surface stress, which have considerably different angular variations. Results of experiments in the development of EMAT transducers for nondestructive testing that support these results are cited, and important consequences in the design of inspection systems are indicated.
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    An acoustic emission energy analysis and its use to study damage in laminated composites (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 225-233 
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    ISSN: 1573-4862
    Keywords: Acoustic emission ; energy analysis ; composite materials ; strength ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new technique which uses the output of a true RMS voltmeter to measure the acoustic emission energy output of a transducer is presented. To demonstrate its use in a typical case, this procedure is used to measure acoustic emission energy during tensile tests on [0°/±30°/90°]s glass-epoxy laminate uniaxial and 10° off-axis tensile coupons. The test results were compared with numerical predictions of laminate response and acoustic emission energy. The experiments indicate that acoustic emission energy can be used to indicate the onset of ply and interlaminar failure.
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    Defect characterization in the short-wavelength regime (1980)
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    Journal of nondestructive evaluation 1 (1980), S. 235-247 
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    ISSN: 1573-4862
    Keywords: Ultrasonics ; acoustic waves ; scattering ; diffraction ; defect characterization ; silicon nitride ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The scattering of acoustic waves by different types of spherical defects in a silicon nitride matrix is calculated by using Ying and Truell's scattering theory. The theoretical scattering results are interpreted using a ray tracing approach. Experiments were carried out at a high frequency (150–450 MHz) to characterize defects in silicon nitride. Time and space averaging, Wiener filtering, diffraction, and propagation loss corrections were used to remove the effect of the transducer response and propagation loss in the material from the scattered signal. Our experimental results indicate the presence of a new type of defect in silicon nitride. They give the type and size of voids, cracks, and Si inclusions in good agreement with measurements obtained after sectioning.
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    Some examples of nondestructive flaw detection by shearography (1989)
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    Journal of nondestructive evaluation 8 (1989), S. 225-234 
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    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.
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    Quantitative characterization of flaws near a surface using inverse born approximation (1982)
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    Journal of nondestructive evaluation 3 (1982), S. 183-188 
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    ISSN: 1573-4862
    Keywords: Ultrasonics ; Born inversion ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Quantitative reconstruction of volumetric flaws near a surface of an elastic solid has been carried out experimentally by analyzing the scattered ultrasonic waves. The inverse Born approximation (developed for flaws in bulk materials) was tested for the first time in the determination of the size, shape, and orientation of near-surface flaws. We have studied spherical solid inclusions at various depths below the surface. In addition we examined an approximately 2:1 prolate spheroidal inclusion which was located one major axis below the surface. The determination of the flaw's size, shape, and orientation in terms of an equivalent ellipsoid is realized by performing nonlinear least-squares iteration of the one-dimensional Born inversion results obtained at various scattering directions within a finite aperture. The reconstruction is in good agreement with the actual parameters of the flaw.
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    Separation and characterization of stress levels and texture in metal sheet and plate: I. Principles and preliminary experiment (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 157-163 
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    ISSN: 1573-4862
    Keywords: Residual Stress ; ultrasonics ; metals ; EMATs ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An approach is proposed for obtaining separate measures of stress anisotropy and texture in metal sheet or plate. The approach is based on the propagation characteristics ofSH n modes of ultrasonic waves. Experimental work has established that differences betweenSH 0 modes with orthogonal directions of propagation provide a measure of stress anisotropy that is insensitive to texture, with the restriction that the pseudosymmetry of the polycrystalline matrix of the sheet or plate is orthorhombic or higher. In the present work, it is argued that the differences between elastic constants associated with orthogonal directions of propagation of higher order modes should provide a meaningful measure of texture. The only requirement is that the texture be sufficiently well developed so that the following inequality is obeyed: ∣C′44−C′55∣〉0.002 $$\bar C$$ with $$\bar C$$ =1/2 (C′44+C′55). HereC′44 andC′55 are the effective shear moduli for planes normal to the sheet or plate surface and at right angles to each other. They are measurable by observing the differences between the phase velocities of theSH 0 and theSH n〉0 modes in the principal directions. By using Electromagnetic Acoustic Transducers (EMATs), the phase velocities can be deduced from the frequencies at which an SH mode of fixed wavelength is optimally excited. This approach has the advantage of being independent of specimen geometry and dimensions other than thickness.
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    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 
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    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.
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    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 
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    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.
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    URL: http://dx.doi.org/10.1007/BF00568763
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    A new acoustic spectroscopy: Resonance spectroscopy by the MIIR (1985)
    Springer
    Journal of nondestructive evaluation 5 (1985), S. 69-79 
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    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.”
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    Nondestructive evaluation of ferromagnetic materials by a “magnetometer like” experimental arrangement (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 73-79 
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    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.
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    Application of ferromagnetic resonance probes to the characterization of flaws in metals (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 51-58 
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    ISSN: 1573-4862
    Keywords: eddy current testing ; magnetic particle testing ; magnetic sensor ; ferromagnetic resonance ; microwave frequency ; surface flaws ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This article presents some results obtained in the characterization of surface flaws by means of probes using ferromagnetic resonance of yttrium iron garnets (FMR probes). These experiments on artificial flaws show that FMR probes operate like eddy current probes for nonmagnetic materials and like magnetic field sensors for magnetic ones. Consequently, the working distance is larger for magnetic materials (1000–1500 µm) than for nonmagnetic ones (100–300 µm). FMR probes have good sensitivity to narrow flaws, good spatial discrimination, and are sensitive to flaw width and depth. Vector analysis allows the separation of distance and flaw effect by phase analysis on nonmagnetic materials. On magnetic materials this phase separation does not exist and another procedure is suggested. These results, and in particular those obtained on ferromagnetic materials, point to the possibility of replacing some eddy current or magnetic particle inspections by tests with ferromagnetic resonance probes.
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    Concrete crack depth meter using nonlinear ADC (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 127-131 
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    ISSN: 1573-4862
    Keywords: Concrete NDT ; NL-ADC ; crack depth measurement ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper introduces the design and construction of an electronic hybrid signal processing meter that develops an output voltage proportional to the depth of a concrete crack. The circuit employs multiplication, squaring, and square-rooting functions by means of a special nonlinear ADC and counting scheme.
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    URL: http://dx.doi.org/10.1007/BF00566217
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    Transform techniques for analysis of thermal wave propagation in anisotropic composite materials (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 149-155 
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    ISSN: 1573-4862
    Keywords: NDE ; thermal waves ; anisotropy ; composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A general formulation for solving the three-dimensional thermal diffusion equation in anisotropic media is presented. The method is based on two-dimensional Fourier transform techniques and can provide a physical insight into the problem. The analysis can easily be adapted to take into account arbitrary spatial variations of the excitation beam (i.e., a laser or an electron beam). Results obtained from propagation of thermal waves in composites are presented and followed by simulations for cases where the source function is defined. Propagation through an anisotropic slab is formulated and applied to specific cases.
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    Analytical solution for impedance change due to flaws in eddy current testing (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 197-202 
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    ISSN: 1573-4862
    Keywords: Eddy current ; impedance ; flaw ; Green's function ; Born's limit ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Green's function is used in order to derive the analytical solution for the change in impedance due to a presence of the flaws in a conductor. This solution is applied to a cylindrical flaw and a spherical flaw whose radii are much smaller than the radius of the test coil. For both cases, the change in impedance is obtained within Born's limit.
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    URL: http://dx.doi.org/10.1007/BF00566224
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    The interaction of ultrasound with contacting asperities: Applications to crack closure and fatigue crack growth (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 203-212 
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    ISSN: 1573-4862
    Keywords: Acoustic diffraction ; acoustic transmission ; asperity contact ; crack closure ; fatigue cracks ; mode conversion ; NDE ; stress intensity factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The partial contact of two rough fatigue crack surfaces leads to transmission, reflection, diffraction, and mode conversion of an acoustic signal at those contacts. This paper reviews recent experimental and theoretical efforts to understand and quantify such contact on actual fatigue cracks in greater detail. It is shown that the size and density of individual contacts, or asperities, can be estimated from acoustic measurements. Furthermore, it is shown that this information is useful to provide the static stress across a partially closed crack as well as the “effective” stress intensity range which activates fatigue crack propagation.
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    Ultrasonic crack characterization via a constrained inversion algorithm (1985)
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    Journal of nondestructive evaluation 5 (1985), S. 37-43 
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    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.
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    Depth measurement for cracks in corners using ultrasonic Rayleigh waves (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 179-187 
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    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.
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    Rayleigh wave propagation in a solid with a cold-worked surface layer (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 43-49 
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    ISSN: 1573-4862
    Keywords: Rayleigh wave dispersion ; higher mode generation ; cold-working ; rail ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The propagation of the Rayleigh surface wave is experimentally studied along the top surface of used railroad rail under conditions where ultrasonic pulses have carrier frequencies ranging from 0.4 to 3.0 MHz and approximately 10 µs duration. The generation of the first higher (M 21 or Sezawa) mode as well as the fundamental (M 11) mode and their dispersion properties are observed. These phenomena are attributable to the presence of the cold-worked surface layer caused by the wheel passage. It is shown that a theoretical model of a single layer overlying a half space, whose elastic constants are determined by a destructive method, yields results which agree with the dispersion curves obtained experimentally. On the basis of this one-layered model, an inversion method to estimate the layer thickness and its elastic constants is discussed.
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    Resonance testing of cast iron (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 65-74 
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    ISSN: 1573-4862
    Keywords: NDE ; cast iron ; vibration analysis ; modulus ; strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An outline is given of the existing nondestructive vibration tests for cast irons and their drawbacks in terms of the dimensional accuracy of the components. A proposal is made for a new test based on the change of resonant frequency with vibration amplitude exhibited by cast irons. This proposal is evaluated using material data obtained from dynamic tests of a wide range of cast iron specimens. A test rig is described suitable for testing cylindrical cast bars, and typical results are presented in relation to material strength. There is also a brief description of preliminary testing on cast products.
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    Detection of strength limiting defects in cellular glasses by dielectric measurements (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 113-118 
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    ISSN: 1573-4862
    Keywords: Capacitance ; dielectric constant ; voids ; cellular glasses ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Cellular (foamed) glasses are a prime candidate for certain structural applications, such as support of the silvered glass concentrator mirrors in solar thermal energy systems. An economical nondestructive measurement of strength-limiting defects in these materials would permit development of designs in which the material is subjected to a higher working stress level and maintains the same probability of failure. This would result in weight and cost savings for any application. A method of measuring the capacitance of well-defined regions of a specimen was investigated. Large voids were found to produce significant localized changes in the capacitance of the specimen. The feasibility of locating the large, strength limiting defects in this porous material has been demonstrated for one type of cellular glass. Means of producing an image from this type of data and an implementation scheme for on-line production measurements are discussed.
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    Nondestructive testing of materials using 14 MeV neutrons and a pulse-shape analyzer system (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 139-146 
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    ISSN: 1573-4862
    Keywords: Material defects ; 14 MeV neutrons ; pulse-shape analyzer system ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A 14 MeV neutron generator and fast neutron spectrometer consisting of an organic scintillation detector and a pulse-shape analyzer are used for the nondestructive testing of materials. The 14.6 MeV peak (in the 12.7–15.7 MeV region) is observed to change as a function of both the kind of testing material and the defect condition inside the material. The number of neutron counts under the 14.6 MeV peak for lighter testing materials (e.g., plastic, brass, and aluminum) with a defect will increase, as compared to the number of neutron counts under the same peak region of an identical testing material but with no defect. For heavier testing materials (e.g., steel and lead), the inverse is observed. The method is feasible even with defects of size 0.25 cm3 (i.e., a cylindrical cavity 0.4 cm in diameter and 2.0 cm in length), although quantitative evaluation of the size of the defect as a function of the change of the number of neutron counts under the 14.6 MeV peak region is difficult due to instability of the 14 MeV neutron output.
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    Surface acoustic wave measurements of surface cracks in ceramics (1981)
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    Journal of nondestructive evaluation 2 (1981), S. 219-229 
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    ISSN: 1573-4862
    Keywords: acoustics ; surface acoustic waves ; Rayleigh waves ; ceramics ; surface cracks ; residual stresses ; crack extension ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior of as-indented specimens was found to differ appreciably from that of annealed specimens. Cracks in the annealed samples exhibited partial crack tip closure, but little stable extension, whereas cracks in the as-indented samples displayed both crack closure and irreversible crack growth. This behavior has been rationalized by invoking concepts based upon the residual stresses created by indentation.
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    Probe characterization in ac field measurements of surface crack depth (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 9-17 
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    ISSN: 1573-4862
    Keywords: ac potential difference ; probe characterization ; induction effect ; slots ; fatigue crack ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In the ac field method of crack depth measurement by the Crack Microgauge, the area of the loop formed in the probe gives rise to an induced voltage, which can introduce errors into the depth measurement. In this paper, a method for measuring the probe area is given, and the quality of the probe is thereby characterized. The underlying theory was given previously, and it is applied here to the probe characterization problem. The probe area is determined by two voltage measurements taken on an artificial rectangular flaw machined in an arbitrary metal. By measurements on several such specimens with the same probe, it is confirmed that the area so obtained is a characteristic of the probe and is independent of the specimen material. Thereafter, measurements on various rectangular flaws with probes of different characteristic area were taken, and very good agreement between predicted and real depths was achieved. Both theory and experiments show that probe characterization is of particular importance when this method is used to measure surface crack depths in metals of low permeability such as aluminum.
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    Change in impedance of a single-turn coil due to a flaw in a conducting half space (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 37-43 
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    ISSN: 1573-4862
    Keywords: eddy current ; impedance ; lift-off ; flaw ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The problem of detection and characterization of a flaw in a conducting half-space using an eddy-current coil oriented parallel to the interface is examined. An expression is derived for a first order approximation for the change in complex impedance due to a flaw located within the conducting medium. The overall impedance is a function of the radius and lift-off distance of the test coil and the conductivity of the material. An analytical expression is derived for the change in impedance as a function of the electric fields at the position of the flaw. It is found to be an integral over the volume of the flaw of the electric fields found with and without the flaw being present. The limiting case of a degenerate point flaw may be examined in greater detail by allowing the field in the presence of the flaw to be approximated by the unperturbed field. For flaws small enough that the field does not vary much over its volume, the field may be even further approximated by using just the value of the field at the position of the centroid of the flaw. Plots are shown to illustrate the behavior of the change in impedance as a function of the radial range of the flaw and the depth of the flaw centroid, using previously derived expressions for the fields for the unflawed case.
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    Electromagnetic acoustic transducer for in-plane and plane-normal velocity measurements (1982)
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    Journal of nondestructive evaluation 3 (1982), S. 85-91 
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    ISSN: 1573-4862
    Keywords: displacement-field ; acoustic radiation ; wave propagation ; absolute velocity ; EMAT ; mode selective ; nonresonant frequency response ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new electromagnetic acoustic transducer (EMAT) is developed that measures velocities and absolute surface displacements in-plane and plane-normal to the direction of wave propagation. This transducer is flexible in shape and design to conform with irregular surfaces and has unique characteristics of nonresonant frequency response. Tests show that the sensitivity of this EMAT can be increased by increasing the applied magnetic field. Because this transducer is mode selective and nonresonent, its response can be related uniquely to the wave motion. This property is highly desirable for research purposes, though generally not wanted in field monitoring situations.
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    Two-dimensional radiographic imaging analysis (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 221-227 
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    ISSN: 1573-4862
    Keywords: Radiography ; point-spread function ; corner location ; edge location ; unsharpness ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Two-dimensional imaging properties of locally isotropic and isoplanatic point spread functions are described in a general radiographic context. In particular, the radiographic response to a two-dimensional wedge-shaped object is shown to possess several properties which enable the identification of the wedge corner on the image, thereby alleviating the need for image enhancement techniques. Extensions to the location of flat-edged boundaries are also discussed. The potential dimensioning application of this analysis lies in the precise and objective location of points of interest on radiographs of more complex two-dimensional objects.
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    Distributed strain measurement in a rectangular plate using an array of optical fiber sensors (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 23-27 
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    ISSN: 1573-4862
    Keywords: Optical fiber sensor ; distributed strain ; sensor array techniques ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Single mode optical fiber waveguide has been used to determine the two-dimensional strain distribution on a simply supported rectangular plate. Each of the fifty individual fibers in the rectangular grid array attached to one surface of the plate yields a measurement of the strain integrated along the length of that fiber on the specimen. By using similar sensor information from all of the fibers, both the functional form and the amplitude of the distribution may be determined. Limits on the dynamic range and spatial resolution are indicated. Applications in the measurement of internal strain and the monitoring of physically small critical-structural components are suggested.
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    An inverse problem technique for detecting irregular cavities in circular cylinders by infrared scanning (1984)
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    Journal of nondestructive evaluation 4 (1984), S. 133-140 
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    ISSN: 1573-4862
    Keywords: Thermography ; infrared scanning ; calibration ; inverse problem ; cavity detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An inverse problem technique has been developed for detecting irregular cavities in circular cylinders. In this method, the cavity is considered a part of the unknown geometry of the investigated system, and the evaluated temperature is used to locate this geometry. An auxiliary problem is introduced in the solution of this problem; and in the solution, the cavity wall is located by forcing the temperature to satisfy the condition imposed at the cavity. The new methodology is validated by an experiment presented in this paper, and the test results indicate that this method is highly successful in locating cavities. The accuracy of the method is closely related to the accuracy of the temperature that can be measured at the surface. A small error in the surface temperature results in a slight cavity error for deep cavities, while a shallow cavity is not severely affected by a surface temperature error. This method is particularly attractive in detecting shallow cavities in nondestructive evaluation.
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    Electromagnetic crack detection in ferritic steel (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 165-175 
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    ISSN: 1573-4862
    Keywords: Eddy current ; instrumentation ; probe design ; crack detection ; ferritic steel ; offshore ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The detection and sizing of fatigue cracks in ferritic materials, especially in offshore structures, is of major importance. This paper describes an eddy current system to detect such cracks, operating in an offshore environment with a search probe to electronic instrument separation of up to 600 m. An analysis of the various factors influencing the search coil behavior is given in terms of a mutually coupled primary and secondary electrical circuit; the component values of which are influenced by the coil design, induced electrical currents in the material, and any defects it contains. It is further shown that, with proper coil parameters, the phase variation in the phase angle of the coil complex impedance can be kept almost constant compared with the rapid variation occurring during lift-off. This behavior can be exploited in the instrumentation to give a clear vector display indication of the crack presence on less than ideal surfaces.
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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.
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    URL: http://dx.doi.org/10.1007/BF00570621
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    Elastodynamic scattering by fluid-filled nonplanar cracks (1986)
    Springer
    Journal of nondestructive evaluation 5 (1986), S. 161-168 
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    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.
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    URL: http://dx.doi.org/10.1007/BF00570625
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    Nondestructive detection of flaws in material using transducer arrays (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 47-55 
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    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.
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    URL: http://dx.doi.org/10.1007/BF00566696
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    Numerical analysis of heat input effects in thermography (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 101-107 
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    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.
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    URL: http://dx.doi.org/10.1007/BF00568888
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    Crack detection in conducting materials using SQUID magnetometry (1993)
    Springer
    Journal of nondestructive evaluation 12 (1993), S. 199-207 
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    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.
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    URL: http://dx.doi.org/10.1007/BF00568105
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    Loss of specular reflection due to nonlinear crack-face interaction (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 229-239 
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    ISSN: 1573-4862
    Keywords: Crack-opening displacement ; crack closure ; ultrasonics ; Kirchoff approximation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The interaction between rough crack faces is modeled by nonlinear relations between the crack-face tractions and the crack-opening displacements. These relations account for crack closure and for the related resistance to crack-face sliding. The relations are used to investigate reflection and transmission of an incident pulse by an infinite flaw plane. The problem statement is reduced to a set of inhomogeneous nonlinear ordinary differential equations for the displacement discontinuities, [u] and [v], across the flaw plane. These equations have been solved numerically. The reflection and transmission of an incident pulse by a crack with interacting crack faces. Both incident longitudinal and transverse waves have been considered. The loss of specular reflection as compared to a perfect (traction-free) crack is exhibited by specific examples.
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    URL: http://dx.doi.org/10.1007/BF00565867
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    Acousto-optic method for nondestructive testing (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 43-50 
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    ISSN: 1573-4862
    Keywords: Acousto-optic ; light diffraction ; ultrasonics ; phase measurements ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An alternative method for nondestructive testing based on light diffraction by ultrasonic waves is presented. It enables us to make more accurate measurements of intensity and phase of reflected waves, and therefore detailed information about the reflecting system can be obtained. Applications are numerous but special attention is payed to examination of the quality of coupling systems.
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    URL: http://dx.doi.org/10.1007/BF00711100
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    Some effects of the shape of a small defect in eddy-current NDE (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 59-63 
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    ISSN: 1573-4862
    Keywords: eddy current ; theoretical models ; computer analysis ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Available theoretical models for predicting defect responses in eddy-current NDE apply only to defects of spheroidal shape. In this paper, the boundary-element integral-equation approach is extended to allow for defects of more irregular shape. Sample results for cylindrical and conical voids are presented and discussed.
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    URL: http://dx.doi.org/10.1007/BF00566397
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    Scattering of ultrasound in solids as visualized by the photoelastic technique (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 65-73 
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    ISSN: 1573-4862
    Keywords: ultrasonic scattering ; photoelastic visualization ; cylindrical cavities ; creeping wave ; cracks ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Our efforts in the past few years to visualize the scattering of ultrasound in solids by the photoelastic technique are briefly reviewed. Photoelastic photographs are presented showing the dynamic processes of scattering in glass of plane longitudinal or transverse waves by a cylindrical cavity or cavities as well as by two-dimensional surface-breaking or internal cracks. Phenomena like creeping and multiple scattering are clearly seen, in addition to some details which are not predicted by known theories.
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    URL: http://dx.doi.org/10.1007/BF00566398
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    The effects of focusing and refraction on Gaussian ultrasonic beams (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 107-123 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; transducers ; focusing ; refractior ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A scalar theory of the propagation of Gaussian ultrasonic beams through lenses and interfaces is presented. For radiation into a fluid, the Fresnel approximation is employed to derive the laws of propagation of Guassian beams (previously employed in the analysis of coherent optical systems). These are then generalized to situations commonly found in nondestructive evaluation by treating the effects of propagation through lenses and through curved interfaces at oblique incidence. A numerical example illustrates the ease with which insight into diffraction phenomena for complex geometries can be gained by this approach. The limitations imposed on the theory by aberrations and the scalar assumption are discussed, and the relationship of the Gaussian theory to the radiation of piston transducers is explored.
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    Flaw detection close to the interface using ultrasonic echography (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 141-148 
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    ISSN: 1573-4862
    Keywords: Ultrasonic echography ; signal processing ; flaw detection ; nondestructive control ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The detection of flaws by ultrasonic echography becomes difficult when the flaw is at a shallow depth. The time delay between the interface and flaw echos is less than the width of the impulse-response time of the transducer, and the flaw echo generally has an amplitude much smaller than the dominating interface echo. When the surface is not too rough, the interface echo can be assumed to be known, and its comparison with the signal interface and flaw echo permits the detection of the flaw. In this article it is shown that signal processing techniques allow small flaws to be detected very close to the surface (∼0.5 mm). Two methods are proposed, the first one is based on the minimization of the mean-square error, and the second on the spectral substraction of the two echos.
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    URL: http://dx.doi.org/10.1007/BF00566219
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    Love wave propagation in a solid with a cold-worked surface layer (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 51-55 
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    ISSN: 1573-4862
    Keywords: Love wave dispersion ; surface layer ; work hardening ; rail ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, experiments show Love wave generation along the top surface of used railroad rail, where the shear wave velocity has been slightly reduced by the cold-working of wheel passage for years. The rf pulses used in the experiments have about 10 µs duration and a relatively narrow frequency spectrum. The group velocity of the Love wave is found to have a strong dependence on the carrier frequency over the tested range of 0.45–3.1 MHz. Application of the seismological one-layered model to the experimental measurements yields an NDE technique for the elastic properties and the thickness of the cold-worked surface layer. The results are interpreted on the basis of a destructive observation by micro-Vickers hardness testing.
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    URL: http://dx.doi.org/10.1007/BF00614997
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    Digital ultrasonic image construction using electronic ordered dither techniques (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 75-84 
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    ISSN: 1573-4862
    Keywords: digital signal processing ; microprocessor based system ; binary display ; ordered dither ; ultrasonic C-scan ; image magnification ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The use of a digital microprocessor based system for the acquisition of ultrasonic C-scan information is investigated. The C-scan information is displayed on a binary display device using electronic ordered dither techniques to represent gray levels. The digital system with a binary display increases system flexibility and yields better reproducibility and constant image quality independent of the display medium. Images may be stored on magnetic tape or disk for later retrieval and image processing. The techniques which are described allow for image magnification and a reduction in scan time by replacing the mechanical linkage between the scanner and the display with digital signals. A detailed comparison is made between two dither signals, and the advantages of each are discussed. The combination of digital signal processing and imaging techniques produces results which utilize the capabilities of ultrasonic inspection to the point where the transducer becomes the limiting factor.
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    URL: http://dx.doi.org/10.1007/BF00615000
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    SOL-X: An on-line nondestructive method for measuring grain size with x-rays (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 133-138 
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    ISSN: 1573-4862
    Keywords: X-rays ; diffraction ; grain size determination ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract It is shown that the grain size of commercial materials can be estimated by x-rays with little or no sample preparation. The method is readily automated and can be employed on-line, for example, in a rolling mill.
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    URL: http://dx.doi.org/10.1007/BF00566311
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    Computerized evaluation of acoustic images utilizing a method of averaging (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 173-188 
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    ISSN: 1573-4862
    Keywords: ultrasonics ; acoustic imaging ; computer image analysis ; failure prediction ; inhomogeneous materials ; accept/reject criteria ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A computerized technique is presented which has been developed for analyzing acoustic images of an inhomogeneous material. The acoustic imaging system is briefly described with emphasis on its adaptation to billets of graphite for atmospheric reentry body use. Ultrasonic images of such inhomogeneous material contain a nonuniform distribution of anomalies and few, if any, geometrically regular features which can be assessed to establish material integrity. Results obtained with our new algorithms show, for certain discriminants, a high degree of correlation between the numerical accept/reject values obtained from acoustic image processing and the time-to-failure of the graphitic material in simulated atmospheric reentry tests.
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    URL: http://dx.doi.org/10.1007/BF00570729
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    Propagation of elastic waves in honeycomb panels for application to rapid inspection techniques (1981)
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 209-217 
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    ISSN: 1573-4862
    Keywords: honeycomb panels ; acoustic inspection ; leaky waves ; SH and Lamb waves ; line scan ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract This paper considers the properties of elastic waves guided by an aluminum plate bonded to a honeycomb core for application to rapid inspection of honeycomb panels. Current acoustic inspection techniques involve the transmission of a signal between a pair of small transducers located on opposite sides of the panel. Scanning the transducers in raster fashion results in a high resolution inspection of the panel, but is very time consuming. An alternative technique would simultaneously inspect all points along a line between two widely spaced transducers located on the same side of the panel. Scanning the pair once over the panel permits rapid inspection, although with decreased resolution. Studies presented here indicate that such a method of inspection is feasible and that the flexural mode is probably the most useful.
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    URL: http://dx.doi.org/10.1007/BF00570733
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    Acoustoelastic response of polycrystalline aggregates exhibiting transverse isotropy (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 1-8 
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    ISSN: 1573-4862
    Keywords: acoustoelasticity ; transverse isotropy ; polycrystalline aggregate ; cubic crystal ; third-order elastic constants ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Acoustoelasticity is an ultrasonic technique which has been used for the determination of active and residual stresses in common structural materials. This paper examines the effect of texture on the acoustoelastic response in polycrystalline bodies. In particular materials which are transversely isotropic aggregates of cubic crystals are studied. The second- and third-order elastic constants of the polycrystal are derived from the elastic properties of the constituent crystals, and the crystalline orientation relative to the body's symmetry axis. The acoustoelastic relations between velocity and deformation are then presented for the aggregate. Finally, evaluation of the acoustoelastic response for several ideal textures using data for aluminum single crystals shows that the response is highly dependent on the texture.
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    Stationary formulas for computing the response in eddy-current NDE (1987)
    Springer
    Journal of nondestructive evaluation 6 (1987), S. 177-180 
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    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.
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    Photothermal examination of an adhesive layer (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 111-113 
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    ISSN: 1573-4862
    Keywords: photoacoustic microscopy ; delamination ; layered structure ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract An adhesive layer, by which a piezoceramic foil is attached to an aluminum membrane for telephone application, is examined in a nondestructive way by thermal waves. The basic principles of the method are outlined, and its detecting power is demonstrated by evaluation of a well-defined delamination.
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    Finite element modeling of absolute eddy current probe signals (1982)
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    Journal of nondestructive evaluation 3 (1982), S. 147-154 
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    ISSN: 1573-4862
    Keywords: finite element modeling ; eddy current ; absolute probe ; steam generator tubing ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Finite element analysis techniques are applied to the problem of predicting signals from an absolute eddy current probe in the tube sheet region of a PWR steam generator for the purpose of optimizing the probe coil geometry and determining the feasibility of using such a probe to characterize the condition of the tube and tube sheet crevice.
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    Relationships between crack opening displacement, alloy variables, and crack detection sensitivity (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 189-200 
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    ISSN: 1573-4862
    Keywords: Acoustic harmonic generation ; critical angle acoustics ; fatigue crack detection ; alloy microstructure ; load amplitude ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Alloy grain size is known to influence both the propagation path and the closure stress of surface fatigue cracks in many alloys. The general trend is for the path to be more tortuous and the closure stress to be larger, the larger the grain size. By use of Ti Al-4V and Al 7075-T6, the effects of grain size on the nondestructive detection of surface cracks which might arise from closure stress and path irregularity variables were evaluated. Titanium specimens were inspected using an acoustic harmonic generation technique, and it was discovered that the major source of harmonic signals was grain sized crystallographic cracks. Harmonic signals were larger during fatigue in an 8-µm compared to a 4-µm grain sized alloy, as there were more grain sized cracks in the large grain material. Crack closure was found to be extremely important in determining the reflected acoustic amplitude obtained in inspecting small (100–1000 µm) cracks in Al 7075-T6 using a critical angle technique. Average received amplitudes were an order of magnitude smaller for cracks at zero load than for those opened by a tensile stress. The scatter in the reflected amplitude was also large, apparently as the result of variations in the degree of the closure from crack to crack. For the 7075 material, the important effect of larger grain size was to increase the irregularity of the crack path, making the small cracks more visible acoustically at azimuthal angles not normal to the crack plane.
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    Nondestructive evaluation of jades by means of 14 MeV neutron activation (1982)
    Springer
    Journal of nondestructive evaluation 3 (1982), S. 137-145 
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    ISSN: 1573-4862
    Keywords: jadeite authentication ; 14 MeV neutrons ; jades ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Fourteen MeV neutron activation of jades was used to test the authenticity of jades: to ascertain whether they are genuine jadeite and whether their greenish colour is genuine, both of which are important criteria for the high market value of jadeite. For given activation and measurement conditions of the jades, the gamma-ray spectrum was observed to change as a function of the type of the jades; the counting ratio of the photopeaks from the two most prominent constituent elements varies greatly as a function of the type of the jades. The ratio of counts for the Compton edges of the 1.779 MeV gamma-ray of28Al, from28Si(n,p)28Al reaction, and the 1.434 MeV gamma-ray of52V, from52Cr(n,p)52V reaction, varied as a function of the type of the jades and also as a function of the color. These results can be applied for a fast and nondestructive evaluation of jades.
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    Eddy current solutions applicable to the problem of nondestructive inspection of flat and cylindrical surface layer (1984)
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 29-38 
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    ISSN: 1573-4862
    Keywords: NDE ; eddy currents ; surface layers ; stratification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Nondestructive inspection of flat and long cylindrical metallic-surface layers is conveniently dealt with using the results of wave propagations in a one-dimensionally stratified medium. Analytical solutions for some special profiles are obtained, and perturbation technique is used to obtain results for more frequently encountered profiles.
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    Frequency domain methods for reducing transducer variability (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 101-109 
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    ISSN: 1573-4862
    Keywords: ultrasonic transducers ; NDE ; deconvolution ; signal processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A major objective of quantitative nondestructive evaluation is to formulate defect detection, classification, and sizing algorithms that are insensitive to variations in transducer characteristics, material type, and defect depth. With the data used in this research, ultrasonic signals were found to vary significantly with changes in the transducer and only secondarily with changes in material and depth. It is shown that the method for minimizing signal variations due to transducer and material changes is to deconvolve the test signal with respect to the transducer response from a reference defect in a block of the same material. Since depth variation primarily affects signal amplitude and has minor impact on shape, detection, classification, and sizing, insensitivity to depth is achieved by avoiding the use of amplitude-dependent parameters. The notion of a “standard transducer” is introduced. Its mathematical properties and methods of realization are given. It is shown how the effects of variability from different test transducers can be removed by signal processing. When these procedures are applied to the test transducer, the effect is to cause it to resemble the standard transducer and, thereby, to place all ultrasonic waveforms on a common basis.
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    Ultrasonic attenuation and velocity in AS/3501-6 graphite fiber composite (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 137-148 
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    ISSN: 1573-4862
    Keywords: composite material ; ultrasonic velocity ; ultrasonic attenuation ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The ultrasonic group velocity and attenuation were measured as a function of frequency for longitudinal and shear waves in the Hercules epoxy matrix (3501-6) and in the principal directions of the unidirectional Hercules graphite fiber epoxy composite (AS/3501-6). Tests were conducted in the frequency ranges 0.25–14 MHz and 0.5–3 MHz for longitudinal and shear wave modes, respectively. While the attenuation increased with frequency for all wave modes, the group velocity was independent of frequency for all wave modes. In studying the effects of transducer-specimen interface couplant and pressure, it was found that for each transducer, there exists a frequency-dependent “saturation pressure” corresponding to the maximum output amplitude of the signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566121
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  • 95
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    On the acoustic emission due to the fracture of brittle inclusions (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 149-155 
    Details
    ISSN: 1573-4862
    Keywords: acoustic emission ; fracture ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The far-field characteristics of the emission from a theoretical model for the fracture of brittle inclusions are presented in detail. The model is a circular crack growing at constant speed from zero size until it attains a prescribed size. The far-field radiation pattern is the same as that of a simple combination of force doublets, and some qualitative similarities between force doublets and acoustic dipoles are noted. The initial shape of the far-field pulses due to the growing stage and the stopping is determined, but difficulties arise in accounting for the diffraction of a surface wave on the crack faces generated by the stopping of the crack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567088
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  • 96
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    Electronic Resource
    Elastic wave emission from damage processes (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 215-224 
    Details
    ISSN: 1573-4862
    Keywords: Acoustic emission ; slip ; microcracking ; deformations ; displacement field ; elastic waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The theory of elastic wave emission (i.e., acoustic emission; AE) from damage processes such as slip and microcracking is discussed. Analogous developments in the literature on earth-quake seismology and dynamic dislocation theory are noted and utilized. A general representation of the displacement field of an AE event is given in terms of the double-couple response to a distribution of “moment density tensor” in the source region. Results are specialized to a point source model and to a general far-field analysis of outgoing elastic waves, and conditions for validity of such representations and their low-frequency specializations are noted. Emitted wave fields are compared for tensile opening and slip events, and procedures which might enable the approximate determination of the size or area increase of tensile microcracks are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571803
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  • 97
    Electronic Resource
    Electronic Resource
    Half-space radiation by EMATs (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 157-181 
    Details
    ISSN: 1573-4862
    Keywords: EMAT ; radiation pattern ; transducer ; shear waves ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A Green's function calculation of the far-field radiation patterns of EMATs is presented. The approach is based on (a) closed form expressions for the eddy current and static magnetic field distributions, established by the EMATs, which react to produce the driving Lorentz forces, and (b) a Green's function derived from the steepest descent approximation to the far-field response of an arbitrary surface point force on a half space. Numerical results are presented, illustrating the radiation patterns of the three common EMAT designs. Included are vertically polarized shear waves as radiated by both meander coil and periodic magnet EMATs and horizontally polarized shear waves as radiated by the latter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567089
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  • 98
    Electronic Resource
    Electronic Resource
    Fatigue lifetime prediction with the aid of SAW NDE (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 123-136 
    Details
    ISSN: 1573-4862
    Keywords: fatigue life ; acoustic surface waves ; NDE ; ultrasonics ; cracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract The present studies concentrated on predicting the remaining fatigue life for single fatigue cracks in the Paris regime of macrocrack propagation. Acoustic surface waves were used to interrogate the crack during cyclic fatigue. The inversion of the obtained scattering data provided crack depth and crack length as a function of the number of cycles applied in tension-tension fatigue. Auxiliary experiments were conducted to study the acoustic response of the crack to tensile and compressive loads, thought to open and close the crack. The technique may allow for new insights into the physics of the “crack closure” effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566120
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  • 99
    Electronic Resource
    Electronic Resource
    Fracture mechanics transfer function for two-dimensional noncircular flaws (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 201-206 
    Details
    ISSN: 1573-4862
    Keywords: fracture mechanics ; noncircular crack ; fatigue life ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A transfer function that converts an irregularly shaped two-dimensional crack into an equivalent circular crack of equal propagation lifetime is proposed. The methodology extends the exact elliptical to circular crack transfer function to other noncircular cracks with geometries that slightly deviate from the elliptical. Results for rectangular, symmetric dumbbell, and asymmetric dumbbell cracks are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567092
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  • 100
    Electronic Resource
    Electronic Resource
    Ultrasonic evaluation of geometrical and surface parameters of rough defects in solids (1980)
    Springer
    Journal of nondestructive evaluation 1 (1980), S. 249-261 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonics ; cracks ; surface roughness ; diffraction ; scattering ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic measurements from rough cracks were carried out using both broad-band and narrow-band methods. An analysis is suggested to determine parameters of the crack quantitatively such as size, shape, rms surface roughness, and distribution function of the surface roughness. Ultrasonic measurements of the parameters compare very well with the actual parameters of the defect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571806
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