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  • Electronic Resource  (34)
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  • Electronic Resource  (34)
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  • 1
    Electronic Resource
    Electronic Resource
    Fracture initiation and propagation from a center of dilatation (1975)
    Springer
    International journal of fracture 11 (1975), S. 1011-1029 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: 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.
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033847
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  • 2
    Electronic Resource
    Electronic Resource
    On the uniqueness of the stress intensity factor — crack velocity relationship (1985)
    Springer
    International journal of fracture 27 (1985), S. 159-168 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On passe en revue les résultats expérimentaux obtenus par différents chercheurs sur la relation K I − a et l'on discute des différences apparentes dans les résultats qui conduisent à des questions en ce qui regarde l'unicité de cette relation. On présente l'influence des erreurs dues à l'état tridimensionnel des tensions à l'extrémité de la fissure, les effets des contraintes non singulières de la vitesse de la mise en charge transitoire et de la mesure de la vitesse. Ces erreurs ne contribuent pas à éclaircir la question de l'unicité et, en vue de la résoudre, on décrit une expérience possible.
    Notes: Abstract Experimental results due to several different investigators on the K I − a relationship are reviewed and the apparent differences in results leading to questions regarding the uniqueness of this relationship are discussed. The influence of the errors due to the three dimensional state of stress at the crack tip, the effects of non-singular stresses, velocity, transient loading and velocity measurement is presented. These errors have obscured resolution of the uniqueness question and an experiment is described to resolve the issue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017965
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental study of large-diameter thin-wall pressure vessels (1961)
    Springer
    Experimental mechanics 1 (1961), S. 33-42 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental stress analysis of three cylindrical pressure vessels with radius/thickness ratios ranging from 100 to 238 and different head closures is described. Brittle coatings and electrical strain gages were employed to determine stress distributions over the entire outer surface of the vessels. Electrical strain gages alone were used to determine stresses on the inside surface of the vessels. Particular emphasis was placed on determining stress concentrations and on nonlinear effects produced by geometric imperfections. An attempt was also made to correlate the failure, which started in the cylindrical portion of the three vessels, with the elastic-stress distribution. It was found that the imperfections in the cylinder were not significant if the vessel was fabricated from a ductile steel. However, if the vessel was constructed from a high-strength but brittle steel, the imperfections significantly lower the bursting strength of the vessel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324933
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  • 4
    Electronic Resource
    Electronic Resource
    A class of zero-birefrngent polymers (1971)
    Springer
    Experimental mechanics 11 (1971), S. 26-31 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A class of photoelastically insensitive materials consisting of a blend of rigid and flexible polyesters is described. The mechanical and optical response of these polymers is viscoelastic in character. For a wide range of the compositions, the birefringence changes from positive to negative under constant load or constant displacement. The influence of composition, time under load, and principal stress difference on the birefringence is studied. Isochromatic-fringe development in a diametrally loaded disk shows that a major region of the stressed body becomes optically insensitive after a reasonable period of time under load and remains insensitive for a time sufficiently large for associated photoelastic operations. A typical operating-time band is presented during which the optical response of a model characterized by the fringe order per unit thickness is reasonably small. It appears that this class of photoelastically insensitive materials can be employed to produce composite models with glass-fiber reinforcements. Compared to other zero-birefringent polymers, the present material has the advantage of easier processing (casting and curing), improved adhesion to glass fibers and closer matching of the refractive index with that of glass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02320707
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  • 5
    Electronic Resource
    Electronic Resource
    Photo-orthotropic-elasticity (1971)
    Springer
    Experimental mechanics 11 (1971), S. 346-356 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of producing transparent model materials for photo-orthotropic-elastic studies is presented. This material fabricated from glass fibers and a modified polyester matrix exhibits continuous relatively smooth fringe patterns which are linearly related to the state of stress. As such, the heterogenous material can be treated as a homogenous medium with orthotropic properties. Three photoelastic constantsf L ,f T andf LT are necessary to describe the photoelastic response of the orthotropic materials to a general state of stress. Methods are established for predicting these photoelastic constants from the properties of the constituents. These methods are based on stress proportioning between the fibers and the matrix and upon the linear summation of the retardation from each constituent. The relations derived forf L ,f T andf LT were verified experimentally and found to be in close agreement with measured values. A stress-optic law is derived on the basis of stress partitioning between the two constituents in a unidirectionally fiber-reinforced laminate. The adequacy of this stress-optic relation is confirmed by experimental verification. Comparison of this stress-optic relation with the expression advanced by Pih and Knight shows the validity of their initial concepts but the inadequacy of their partitioning functions. Detailed comparison of the stress-optic law with the analog relation proposed by Sampson shows excellent agreement. Indeed, the use of Sampson's stress-optic law is recommended and the law based on stress partitioning is to be considered as a fundamental theoretical proof of the Sampson relation. Finally, the applicability of Sampson's stress-optic law to bidirectionally reinforced materials was confirmed with a thorough experimental verification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02320536
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  • 6
    Electronic Resource
    Electronic Resource
    Conductive polymers as fatigue-damage indicators (1972)
    Springer
    Experimental mechanics 12 (1972), S. 124-129 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A conducting polymer consisting of graphite particles in on epoxy matrix has been employed as a transducer. When subjected to strain, the conductor undergoes a resistance change which is due to the variation in contact pressure between the particles. Of more importance is the permanent resistance change produced in the conductor as it is cycled. This resistance change is due to a wear mechanism which improves the contact area between adjacent particles. The permanent resistance change is a consistent and reproducible function of the strain range and the number of cycles. As such, the conductor can be employed as a sensor to indicate fatigue damage. Studies conducted with two-level fatigue tests indicate that the sensor can be employed with complex strain histories. The sensor output in two-level fatigue tests of both the high-low and low-high sequence was interaction free but dependent on the magnitude of the strain range. Nevertheless, a simple graphical approach was established to predict fatigue exposure from the output. Stability of the sensor to both time and temperature was examined. Resistance changes associated with time are small and monotonic initially and, after an initial stabilization period of a month, the changes are negligible. Temperature stability represents a more significant problem which will require further work. However it appears that the sensor will perform adequately in the temperature range of 75±15°F.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02328560
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  • 7
    Electronic Resource
    Electronic Resource
    Attenuation of strain waves in core samples of three types of rock (1976)
    Springer
    Experimental mechanics 16 (1976), S. 121-126 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321105
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  • 8
    Electronic Resource
    Electronic Resource
    On the determination of the å-K relationship for birefringent polymers (1979)
    Springer
    Experimental mechanics 19 (1979), S. 121-128 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Methods of utilizing dynamic photoelasticity with fracture-type specimens to simultaneously determine the stress-intensity factorK Iand the crack-tip velocity are reviewed. Problems associated with data analysis to obtainK Ifrom isochromatic-fringe loops are discussed. Errors resulting from the use of static near-field equations in the method of analysis are considered and a correction method is developed. Finally, the invariance ofK Im(the minimumK required to maintain a finite crack velocity) is noted and evidence is provided to indicate thatK Imcan be treated as a material propertly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324224
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  • 9
    Electronic Resource
    Electronic Resource
    Strain-gage methods for measuring the opening-mode stress-intensity factor,K I (1987)
    Springer
    Experimental mechanics 27 (1987), S. 381-388 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Measurements of strain near a crak tip with electrical-resistance strain gages do not usually provide a reliable measure ofK I because of local yielding, three-dimensional effects and limited regions for strain-gage placement. This paper develops expressions for the strains in a valid region removed from the crack tip, and indicates procedures for locating and orienting the gages to accurately determineK I from one or more strain-gage readings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02330311
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  • 10
    Electronic Resource
    Electronic Resource
    An overdeterministic approach for measuringK I using strain gages (1988)
    Springer
    Experimental mechanics 28 (1988), S. 142-145 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An overdeterministic method for determining the opening-mode stress-intensity factor,K I , from many measurements of the radial strain,∈ rr , is described. The method was verified with an experimental study of a compact-tension specimen where strains along the 0, 45 and 90-degree lines were measured using strip gages with ten strain sensors per strip gage. The results indicated errors in the range of one to three percent with three or four parameter models of the strain field in the region near the crack tip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02317564
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