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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 13 (1994), S. 111-136 
    ISSN: 1573-4862
    Keywords: Ultrasonics ; backscattering ; noise ; backscatter coefficient ; figure-of-merit ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A model is presented which relates the absolute backscattered noise level observed in an ultrasonic immersion inspection to details of the measurement system and properties of the metal specimen under study. The model assumes that the backscattered noise signal observed for a given transducer position is an incoherent superposition of echoes from many grains. The model applies to normal-incidence, pulse-echo inspections of weakly-scattering materials using toneburst pulses from either a planar or focused transducer. The model can be used in two distinct ways. Measured noise echoes can be analyzed to deduce a “Figure-of-Merit” (FOM) which is a property of the specimen alone, and which parameterizes the contribution of the microstructure to the observed noise. If the FOM is known, the model can be used to predict the absolute noise levels that would be observed under various inspection scenarios. Tests of the model are reported, using both synthetic noise echoes, and measured noise echoes from metal specimens having simple and complicated microstructures.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4862
    Keywords: Texture ; formability ; plastic strain ratio ; earing ; ultrasonic anisotropy ; EMATs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A fully automatic, ultrasonic instrument to measure texture and formability parameters on metal sheet is described. Arrays of EMAT transducers are used to transmit and receiveS o Lamb waves propagating at 0°, 45°, and 90° with respect to the rolling direction. By analyzing the frequency dependence of the phase of the received signals, the long wavelength limit of the velocities is obtained. Included is a discussion of this algorithm, and subsequent processing steps to predict the ODC'sW 400,W 420, andW 440. On steel, the prediction of drawability parametersr and Δr based on a correlation developed previously by Mould and Johnson is also discussed. Results of blind field trials at facilities of three suppliers/users of steel sheet for automotive applications and one supplier of aluminum sheet for beverage can production are reported. The former confirmed the Mould-Johnson correlation for lowr material but indicated that refinements are needed for modern steels with highr. The aluminum data suggest a correlation between W440 and the degree of four-fold earing.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4862
    Keywords: Beam propagation ; bimetallic weld ; Gauss-Hermite beam model ; finite element method ; ultrasonics ; anisotropic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, predictions of two models for the propagation of ultrasonic beams through a two-dimensional, bimetallic weld geometry are compared. The finite element method can predict beam propagation through quite general geometry with high accuracy. This model, however, requires significant computational time. On the other hand, the approximate Gauss-Hermite model offers considerably greater computational speed, but has lower accuracy in certain regions and cannot treat the most general geometries and inhomogeneities in material properties. This paper compares the performances of the two models for the case of the two-dimensional, bimetallic weld consisting of multiple layers, some of which have anisotropic properties. It is found that the results of the two models are in good agreement in the vicinity of the central ray, and that the deviation increases as one moves away from the axis. Also, as the beam propagates through multiple interfaces, the accuracy of the Gauss-Hermite solution decreases.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 109-126 
    ISSN: 1573-4862
    Keywords: Imperfect interface ; ultrasound ; model structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Model specimens are prepared, each of which may be viewed as two sections of similar material joined imperfectly at a planar interface. Measurements of the ultrasonic reflection from, mode conversion at, and/or transmission through these imperfect interfaces, are reported. The interface structures include distributions of pores, contacts, and inclusions. Included are both near-periodic and random cases. As the frequency is increased, the measured reflection coefficients generally show an initially linear increase from zero, followed by a maximum which may exhibit multiple peaks, and a subsequent decay. These results are interpreted in terms of a quasi-static model and an independent scattering model for ultrasonic interactions with imperfect interfaces.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 12 (1993), S. 1-2 
    ISSN: 1573-4862
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ultrasonic measurements were made on a set of thin steel sheets, using the lowest-order shear horizontal mode (SH0-mode) and lowest-order symmetric Lambwave mode (S0-mode). The velocities of these modes were measured as a function of angle relative to the sheet rolling direction. From the data reduction it is, in theory, possible to (1) partially characterize the texture of the sheet, and (2) predict the plastic strain ratio (r-value). The plate texture can be completely characterized by quantities known as orientation distribution coefficients (ODCs). The lowest-order ODCs can be obtained from our measurements; these were compared with ODCs measured by neutron diffraction, with good agreement for the dominant ODC. The r-value is a commonly used measure of sheet formability. It is typically measured mechanically with uniaxial tension specimens subjected to large plastic strain. Therefore, the r-value test is destructive and time consuming. We found a good correlation between S0-mode velocity measurements and $$\bar r$$ , the average in-plane r-value. Consequently, the use of noncontacting electromagnetic-acoustic transducers (EMATs) may offer an online nondestructive measurement of sheet formability.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 125 (1990), S. 109-117 
    ISSN: 1573-5036
    Keywords: ammonia ; environment ; grassland ; mechanical separation ; nitrogen ; slurry ; volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three experiments were conducted using a system of small wind tunnels to measure ammonia (NH3) volatilization from cattle slurry after surface application to land. In each experiment slurry was applied at a rate equivalent to 80 m3 ha-1, providing the equivalent of approximately 100 kg NH4 +-N ha-1. The first experiment compared NH3 volatilization from the liquid fraction obtained by mechanical separation of slurry with that from unseparated slurry. The total NH3 loss over six days from unseparated and separated slurry were very similar, being 38 and 35% respectively of the NH4 +-N applied. For the first five hours, the rate of NH3 loss was higher from the unseparated slurry, thereafter it was consistently lower. In the second experiment, slurry was ponded in a tray to examine whether impeded infiltration or changes in the NH4 + concentration or overall pH of the slurry influenced the rapid decline in rate soon after application that is characteristic of NH3 volatilization from animal slurries applied to land. It appeared, however, that other factors such as resistance to diffusion within the slurry and/or at the slurry surface were mostly responsible for the rapid decline in rate. In the third experiment, in which NH3 volatilization was measured from slurry applied to grassland or bare soil, the total loss from slurry applied to grassland was approximately 1.5 times that from slurry applied to bare soil.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 125 (1990), S. 119-128 
    ISSN: 1573-5036
    Keywords: ammonia ; application method ; application rate ; environment ; grassland ; nitrogen ; slurry ; volatilization ; wind speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three experiments were conducted to examine the influence of slurry application rate, wind speed and applying slurry in narrow bands on ammonia (NH3) volatilization from cattle slurry surface-applied to grassland. The experiments were conducted in the field using a system of small wind tunnels to measure NH3 loss. There was an inverse relationship between slurry application rate and the proportion of NH4 +-N volatilized. From slurry applied at 20, 40, 60, 80, 100 and 120 m3 ha-1, the respective proportions of NH4 +-N lost by NH3 volatization in 6 days were 60, 56, 49, 40, 44 and 44%. The negative relationship was most pronounced in the first 24 hours after application when 57–77% of the total loss for 6 days occurred. Wind speed had a positive effect on NH3 volatilization, although the effect was small in relation to the total loss; increasing the wind speed from 0.5 to 3.0 m s-1 increased the total 5 day loss by a factor of 0.29. The effect of wind speed was also most pronounced in the first 24 hours when much of the NH3 loss took place. The effect of reducing the surface area of the applied slurry was examined by comparing NH3 volatilization from slurry broadcast across plots with that applied in narrow bands. Although the rate of NH3 volatilization was considerably smaller from the banded application immediately after the slurry was applied, the difference between the treatments progressively narrowed until 2 days after application, after which a higher rate was maintained from the banded slurry. After 5 days the total loss from the banded application was 83% of that from broadcast slurry.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 36 (1993), S. 437-455 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Time-harmonic elastic wave scattering problems such as those encountered in ultrasonic non destructive evaluation are solved by the boundary element method (BEM). Selected results for spherical and spheroidal shaped voids and inclusions are compared with analytical and other numerical solutions. Results for ellipsoids, which require a full three-dimensional formulation, are provided as a benchmark for comparison when other numerical methods would be developed for this problem class in the future. The modelling of cracklike defects with this formulation is discussed. Recent theoretical findings regarding the fictitious eigenfrequency difficulty (FED) are confirmed by a numerical study.
    Additional Material: 12 Ill.
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  • 10
    Publication Date: 1990-06-01
    Print ISSN: 0032-079X
    Electronic ISSN: 1573-5036
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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