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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 11 (1975), S. 1011-1029 
    ISSN: 1573-2673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Résumé Au cours d'une étude expérimentale, on a examiné la propagation d'ondes associées à la mise sous contrainte, l'amorcage, le mouvement et l'arrêt d'une fissure et l'interaction d'ondes de mise sous contraintes et de fissures. Le recours à la photoélasticité dynamique en combinaison avec la photographie à vitesse ultrarapide a permis une visualisation complète de diverses phases du processus de rupture dynamique. Deux problèmes fondamentaux ont été examinés selon que le centre de dilatation par traction est dans un plan complet ou dans un demi-plan. Pour chacun de ces problèmes, on a pu caractériser le processus de rupture dans le cas où l'impulsion de pression sise au centre de la source de dilatation est d'une durée extrèmement brève. L'importance des ondes de contraintes qui se réfléchissent lorsque s'étend la zône de rupture est clairement établie.
    Notizen: Abstract Stress wave propagation, crack initiation, crack motion, crack arrest and the interaction of stress waves and cracks were examined in an experimental study. Dynamic photoelasticity used in conjunction with ultra-high speed photography provided full-field visualization of the several phases in the dynamic fracture process. Two fundamental problems were examined—the full-plane and the half-plane with a tensile type center of dilatation. The fracture process was characterized for both of these problems for the case where the pressure pulse at the dilatational source was of extremely short duration. The importance of the reflected stress waves in extending the fracture zone is clearly established.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 12 (1972), S. 461-465 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A shortcoming of the conventional holographic interferometer used in photoelasticity is that, for the double-exposure cases, the resulting fringe patterns are a complex combination of conventional isochromatic and isopachic fringes. This paper describes a holographic interferometer that may be used to obtain separate but simultaneous isochromatic- and isopachic-fringe patterns for photoelastic models in states of plane stress. The method requires a model with a partially reflecting front surface. Isopachics, which are proportional to the thickness change, are recorded using holographic interferometry from the transmitted light. The isochromatics are obtained from the transmitted light by conventional means. General equations relating the surface displacement of the specimen to the observed fringe patterns are developed, and examples of static and dynamic loadings are shown.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 16 (1976), S. 121-126 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Dynamic photoelasticity was employed to determine the velocity of longitudinal stress waves, dynamic modulus of elasticity and attenuation coefficients in rockcore samples 1 in. (25 mm) in diameter, 18 in. (0.46 m) long. Birefringent strips bonded to the core samples of Salem limestone, Charcoal granite and Berea sandstone provided all the data needed for the dynamic characterization of these rock types. The rods were dynamically loaded at one end with a lead-azide charge. A multiple-spark-gap camer was used to record the dynamic isochromatic-fringe patterns occurring in the birefringent strip. Of the three rock types investigated, the Berea sandstone exhibited the largest energy losses as characterized by an attenuation coefficient of 0.0910. Salem limestone and Charcoal granite exhibited much smaller losses with attenuation coefficients of 0.0196 and 0.0024, respectively. The extremely low-energy loss associated with Charcoal granite indicates that this material transmits stress waves as well as most metals.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 28 (1988), S. 105-109 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This paper examines the extension of surface microcracks induced by a surface or Rayleigh wave (R-wave). This problem is examined both theoretically and experimentally. The theoretical approach involves a full-field reappraisal of the Lamb solution for a surface wave propagating in a homogeneous, isotropic, elastic, two-dimensional material for the cases of plane strain and plane stress. Using the Griffith-Irwin energy-release-rate fracture criterion for cracks under combined Mode I and Mode II loading, a prediction is made of the path and final length of the surface microcrack extension produced by the R-wave. Predictions of the crack-extension direction are also obtained using the maximum normal-stress fracture criterion. The experimental approach uses dynamic photoelasticity to observe the isochromatic patterns associated with an R-wave propagating along the narrow edge of a transparent birefringent plate, examining in detail the process of crack extension. When the theoretically and experimentally obtained results are compared, reasonable agreement is obtained.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 11 (1971), S. 57-63 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The success of double-exposure holography as an interferometric technique for experimental stress analysis has lead to several recent publications dealing with the theoretical expression which describes the resulting photoelastic patterns. This paper describes the extension of current theory to include the effect of an intensity difference between the light used during the first exposure and that used during the second exposure. It is shown that as the ratio of these two intensities is changed both the position and the intensity of the photoelastic-fringe pattern is altered. An interpretation of the photoelastic pattern as a simple combination of isochromatic and isopachic-fringe patterns is shown to be possible only under certain conditions. Using a pulsed ruby laser, single- and double-exposure photoelastic holograms of stress waves were obtained, and reconstructions of these holograms are presented. The clarity of the reconstructed images is comparable with photographs taken with a standard polariscope. In addition, the capability of magnifying any particular portion of the image by known holographic reconstruction techniques is illustrated.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 14 (1974), S. 286-289 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The analytical method of superposition is combined with the experimental technique of multiple-exposure holography to decrease the sensitivity of holographic measurement by at least an order of magnitude. Moiré fringes of a lower frequency are produced which simultaneously extend the range of measurement to larger displacements. The method is demonstrated for the case of a clamped circular plate subjected to a concentrated load centrally applied.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 17 (1977), S. 281-289 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Holographic interferometry was utilized to determine the three orthogonal components of displacement in elastic surface waves. A pulsed ruby laser was used as the light source and techniques to improve its coherence properties are described. Procedures for the formation and reconstruction of the hologram, fringe interpretation, and data reduction and presentation are detailed. The elastic-wave velocities and material constants for pink westerly granite were obtained. Solutions for an explosively generated Rayleigh wave in a half space and its reflection from a free edge are presented.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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