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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract—An analytical model to represent and predict the influence of frequency on the elevated temperature fatigue crack growth behavior of structural alloys is described. This model was formulated by considering the time dependence of stress and strain rate in the crack tip region due to creep deformation.Fatigue crack growth rate data were generated on ASTM grade A470 class 8 (CrMoV) steel at 538°C (1000°F) for several frequencies to evaluate the model. Based on these results and data taken from the literature on 304 stainless steel, it was concluded that the proposed model is capable of accurately representing and predicting the effect of frequency over several orders of magnitude on the fatigue crack growth rates at elevated temperature.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric surgery international 16 (2000), S. 519-521 
    ISSN: 1437-9813
    Keywords: Key words Giant omphalocele ; Exomphalos ; Silastic silo ; Abdominal wall defects ; Tissue expander
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Large omphaloceles that contain centrally herniated liver pose challenges to surgical closure, the most significant being the space limitation of the abdominal cavity. In addition, the “pedicled” nature of the liver on the inferior vena cava creates a predisposition to acute hepatic vascular outflow obstruction as the liver is reduced into the abdominal cavity. In such cases, the alternatives include conservative treatment or staged silo reduction. The worst complication of silastic silo (SS) placement is tension and infection of the fascia with disruption of the suture line. Once infection or premature disruption occurs, closure of the defect is difficult or impossible. This case report details a different management technique for a newborn with a giant omphalocele and presents an interesting variation of the usual SS technique that may be helpful in the management of some cases, especially in an emergency. The thick silk sutures applied in the present case absorbed the tension and the silastic sheet prevented the risks of infection and adhesions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 14 (1978), S. 453-468 
    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 Des expressions de compliance élastique pour des éprouvettes du type compacte (CT) et WOL ont été formulées pour une gamme large de longueurs de fissuration (a/W compris entre 0.2 et 0.975) en utilisant les résultats tirés de l'application des techniques modifiées de collationnement aux frontières selon Newman ainsi que de l'analyse d'une fissure profonde d'après Wilson. La localisation de l'axe de rotation des bras de l'éprouvette pour différents longueurs de fissure a été calculée et utilisée en conséquence dans une technique d'extrapolation proposée pour prédire la compliance à toutes localisations de l'éprouvette convenant pour la mesure de la déflection durant un essai de croissance de fissure. Les compliances prédites ont été trouvées en excellent accord avec les valeurs expérimentales pour les deux types d'éprouvette considérés. Les expressions de compliance ont également été formulées pour un éprouvette de traction à fissure centrale.
    Notes: Abstract Elastic compliance expressions for compact type (CT) and WOL specimens have been formulated for a wide range of crack lengths (0.2 ⩽a/W ⩽ 0.975) using results from Newman's modified boundary collection techniques and Wilson's deep crack analysis. The location of the axis of rotation of the specimen arms at various crack lengths has been calculated and subsequently used in a proposed extrapolation technique to predict compliance at any location of the specimen convenient for measuring deflection during a crack growth test. The predicted compliances were found to be in excellent agreement with expreimental values for the two specimen types considered. Compliance expressions are also included for the center crack tension specimen.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The current–field characteristics for Al x Ga1−x As alloys under hydrostatic pressure have been calibrated into velocity-field characteristics using low field experimental data. The saturated drift velocity for x = 0.29 decreases from 7.8 × 106 cm/s at P = 3.5 Kbar to 3.8 × 106 cm/s at P = 8 Kbar. It is shown that the saturated velocity decreases from the value of 1.0 × 107 cm/s in GaAs to about 3.8 × 106 cm/s for x ≍ 0.39. The results should be useful in the design of high field devices of Al x Ga1−x As.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 36 (1988), S. 275-289 
    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 a procédé à une analyse par éléments finis du fluage d'une éprouvette comportant une fissure centrale, sous des conditions allant du fluage à petite échelle jusqu'à un fluage important. On suppose que la fissue est stationaire. Divers modèles ont été utilisés, à savoir la loi de fluage élastique ou parabolique, avec ou sans plasticité indépendante de la vitesse, ainsi qu'une loi incluant également le fluage primaire. On a étudié la base mécanistique du paramètre C t, proposé pour relier le comportement de la croissance de la fissure de fluage sous des conditions entraînant un fluage depuis une petite échelle jusqu'à une grande échelle. Pour la géométrie citée, les différences entre les vitesses de variation de la courbe de la charge, mesurées et précédemment calculées en se basant sur la seule loi parabolique de fluage, semblent applicables par la prise en considération du fluage primaire. On conclut également que lors de fluage à petite échelle, C t ne caractérise pas le champ singulier de contraintes instantanées à l'extrémité de la fissure, mais plutôt, et de maniére sûre, la vitesse d'extension de la zone de fluage à l'extrémité de la fissure, qu'il y ait fluage primaire ou fluage secondaire. Ce tésultat fournit une base d'utilisation de C t pour connaître les vitesses de croissance d'une fissure de fluage, même en présence d'une déformation de fluage primaire significative.
    Notes: Abstract A finite element creep analysis of a center crack specimen has been carried out under small scale to extensive creep conditions. The crack was assumed to be stationary. Several constitutive models were used; these consisted of elastic, power-law creep with and without rate-independent plasticity, as well as one which also included primary creep. The mechanics basis of the C t parameter, which has been proposed for correlating creep crack growth behavior under conditions ranging from small scale to extensive creep, is explored. For the aforementioned specimen geometry, consideration of primary creep seems to explain the differences between the measured and previously calculated load line deflection rates based on power-law creep only. It is also concluded that in small scale creep, C t does not characterize the instantaneous crack tip singular stress field, but it accurately characterizes the rate of expansion of the crack tip creep zone regardless of whether primary or secondary creep is occurring. This result provides a rationale for using C t to correlate creep crack growth rates even in the presence of significant primary creep deformation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 59 (1993), S. 95-114 
    ISSN: 1573-2673
    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 study of creep-fatigue crack growth behavior of 1.25Cr-0.5Mo steel at 538°C (1000°F) under trapezoidal loading waveshapes has been carried out on compact type specimens. In creep-fatigue crack growth experiments, hold times ranged from 0 seconds to 24 hours with intermediate conditions of 10 seconds, 98 seconds, 10 minutes and 15 minutes. Time-dependent crack growth rate during the hold period, (da/dt)avg, is correlated with (C t )avg. The values of (C t )avg are estimated using the equation recently proposed for elastic-cyclic plastic-secondary creeping (EL-CPL-SC) materials. The (da/dt)avg vs. (C t )avg data fall on a single trend which matches with the trend of da/dt vs. C t creep crack growth data for the same material. A model is proposed for predicting both the creep crack growth behavior and the creep-fatigue crack growth behavior. The model is suitable for assessing the residual life and/or the safe inspection intervals of high-temperature components such as steam headers. Transition of crack tip damage patterns from oxidation to creep cavitation across the range of hold times examined is also discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 73 (1995), S. 273-286 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Time-dependent creep-fatigue crack growth (CFCG) is an important consideration in the design and remaining life estimation of high temperature components. CFCG tests were carried out on compact type (CT) specimens of 2.25 Cr-1.0 Mo steel and its behavior, for hold times ranging from 10 seconds to 50 seconds, at 594°C (1100°F) was characterized using the average value of the C t-parameter, (C t)avg. The trends in the creep-crack growth (CCG) data for this material are also compared with the CFCG data. The analytically estimated values of (C t)avg are compared with the experimental values of (C t)avg obtained from the measured values of load-line deflection rates. It is also shown that even in the absence of accurate creep deformation constants, accurate estimates of the measured values of (C t)avg can be obtained in CT specimens
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 59 (1993), S. 199-211 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Effect of tensile overload on elevated temperature crack growth behavior during the subsequent load hold period has been studied by numerical and experimental methods. Finite element analysis of compact specimens shows that when the tensile overload precedes the load hold period, C t during the hold period is significantly smaller (i.e. retarded) compared to the case without the overload. This is due to crack tip stress relaxation associated with large crack tip plasticity generated by the overload. A modified C t estimation scheme is proposed by introducing a new equation for t pl. Using this scheme, the retardation behavior of C t due to the overload is successfully modeled. Creep-fatigue crack growth data for an ex-service 1.25Cr-0.5Mo steel at 538°C (1000°F) were generated in air. The hold times are 10 seconds, 98 seconds and 10 minutes. Time-dependent crack growth rate during the load hold period, (da/dt)avg, is correlated with (C t )avg estimated by the new estimation scheme. (da/dt)avg data from all the tests with overload are higher than those from the tests without overload. The peak stress associated with the overload seems to have enhanced void nucleation and to incrase the time-dependent crack growth rate due to creep. This argument is supported by microscopic observations.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 92 (1998), S. 119-130 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract High temperature $$(565^\circ C, 1050^\circ F) $$ fracture toughness tests were performed on welded specimens of 1Cr-1Mo-14 V steel with different levels of mismatch between the base metal and the weld metal and the cracks lying along the fusion line. A wide range of fracture toughness values were obtained for weldments, as opposed to a unique value of JIC and a unique J-R curve typically obtained for homogeneous materials. Detailed observations of the crack path within the weldments were made to understand the wide scatter in the fracture toughness behavior. The yield strength mismatch between the base metal and the weld metal was found to directly influence the stable crack path, and hence the fracture toughness behavior. The denomination of ‘apparent fracture toughness’ was used to describe the variability of the fracture toughness in the weld region due to microstructure and mechanical property gradients. The apparent fracture toughness exhibited a minima at a fixed distance from the fusion line for a specific weld. The relative position of the fatigue precrack with respect to the fusion line and the region of low fracture toughness was also shown to influence the measured fracture toughness behavior of the specimen. A frame-work is provided for representing the weld fracture toughness behavior and the associated variability due to microstructural gradients.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 49 (1991), S. R3 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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