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  • 1
    Electronic Resource
    Electronic Resource
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 26 (2003), 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: A two-dimensional computational model for simulation of contact fatigue of gear teeth flanks is presented. In the model, it is assumed that the initial crack of length 0.015 mm is initiated at the surface due to previous mechanical or heat treatment of the material as well as a consequence of the running in process. The discretized model with the initial crack is then subjected to normal contact pressure, which takes into account the elasto-hydro-dynamic (EHD) lubrication conditions, and tangential loading due to friction between contacting surfaces. The model also considers the moving contact of gear flanks, fluid trapped in the crack and residual stresses due to heat treatment of the material on crack propagation. The virtual crack extension (VCE) method, implemented in the finite element method, is then used for simulating the fatigue crack growth from the initial crack up to the formation of the surface pit. The computational results show that the initial surface crack of length 15 μm and the considered boundary conditions lead to the appearance of very small surface pits, which can be termed as micro-pitting on gear teeth flanks. The numerical results correspond well with available experimental data.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), 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: Knowledge of the creep behaviour of materials used in structures which operate for many years is of fundamental importance when assessing the integrity of such structures. The additional consideration of cracks which may occur in metals is also important. For discrete cracks, characterising parameters associated with the creep conditions at the crack tip may be evaluated to determine whether the crack will grow slowly, rapidly, or remain stationary. For arbitrary structures containing such defects, the finite element method is particularly effective for calculating the time-dependent stress analysis. The particular fracture parameters can then be evaluated using algorithms based on existing technology for contour integration, and a new virtual crack extension technique. These features are described and compared in application to a laboratory compact tension specimen.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), 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 The service life of gears with a crack in a tooth root can only be determined by numerical methods. An initial fatigue crack is assumed on the tensile side of a tooth root at the site of maximum reference stress and is assumed to commence growth perpendicularly to the surface. An initial assessment can be made using a two dimensional analysis, which is relatively quick and cheap to perform. However, if we wish to take into account the influence of the contact area of load transfer, which can be distributed along the tooth width in different ways, the gear has to be treated by a three dimensional finite element analysis. Crack profile advance is made in stages, each using the strain energy release rate criteria and giving ultimately the stress intensity factor as a function of average crack depth. With known fracture mechanics material characteristics of different gear layers, through which the crack propagates, the service life of a gear is then determined by numerical integration of Paris' equation. A one-sided contact area causes the crack to propagate several times faster than the preferred load distribution across the middle of the tooth.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 11 (1975), S. 605-617 
    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 présente des calculs de l'intensité des contraintes dans les cas de mises en charge combinée par traction et cisaillement d'un matériau redevable de la mécanique linéaire et élastique. En utilisant des fonctions d'une variable complexe, on développe une théorie pour la détermination de la direction du taux maximum de relaxation de l'énergie. Une méthode par éléments finis utilisant des extensions d'une fissure virtuelle est également employée pour déterminer le taux de relaxation de l'énergie correspondant à des extensions de la fissure dans des directions diverses et, en particulier, dans celle qui donne un taux de relaxation maximum de l'énergie. A l'exception du cas où le cisaillement est significativement plus important que la traction, les résultats sont en bon accord avec les observations expérimentales. Lorsque le cisaillement est proportionnellement le plus significatif, les effets de la plasticité deviennent probablement importants, et rendent invalides les résultats de toute théorie élastique linéaire. Toutefois, la méthode peut être encore utilisée pour la détermination numérique de K I et K II au départ de calculs de J 1 et J 2 correspondant à une extension d'une fissure virtuelle dans des géométries bidimensionnelles.
    Notes: Abstract Stress intensity calculations are presented for cases of combined tensile and shear loading for a linear elastic material. Using functions of a complex variable, a theory is developed to determine the direction of maximum energy release rate. A finite element method using virtual crack extensions is also used to determine the energy release rate for crack extensions in various directions and in particular that which gives the maximum energy release rate. Except when shear is more significant than tension, these results give good agreement with available experimental evidence. When shear is most significant, plasticity effects are probably becoming important, thereby invalidating the results of any linear theory. However, the results may still be used to determine K I and K II numerically from virtual crack extension calculations of J 1 and J 2 for general two-dimensional geometries.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 13 (1977), S. 183-199 
    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 propose une intégrale, applicable à un matériau non élastique, dont la valeur est déterminée par la grandeur des singularités à la pointe d'une fissure, mais dont l'évaluation peut être faite en grande partie assez loin de la fissure, c'est-à-dire en une zône où l'état de déformation peut être établi par voie numérique avec une précision meilleure qu'au voisinage de la fissure. Cette intégrale est d'application lorsqu'il se trouve que la plasticité est trop importante pour que soit applicable la mécanique de la rupture linéaire et élastique, et où elle peut cependant être associée aux facteurs d'intensité des contraintes correspondant au cas linéaire et élastique. On a calculé sa valeur pour une fissure centrale ou latérale située dans une plaque soumise à chargement ou à déchargement uniforme-il s'agit de tension ou de cisaillement longitudinal-constituée d'un matériau élastique plastique non sujet à l'écrouissage. On a également considéré le calcul d'un tel matériau comportant une fissure inclinée par rapport à la direction des efforts, ou comportant une fissure centrale soumise à un gradient quadratique de températures, cas pour lesquels les intégrales de contour qui avaient été précédemment suggérées s'avérent ne plus être indépendantes du chemin parcouru, même en conditions élastiques.
    Notes: Abstract An integral has been proposed for a non-elastic material whose value is determined by the magnitude of the singularities at the tip of a crack but which may be evaluated mainly far away from the crack, where the state of deformation may be determined numerically with higher accuracy than near the crack. The integral is intended for situations when plasticity is too great for linear elastic fracture mechanics to be appropriate, but may be related to the stress intensity factors in the linear elastic case. Its value has been calculated for a central or edge crack in a uniformly loaded and unloaded plate with a non-work-hardening elastic plastic material when the loading is either tension or longitudinal shear. It has also been calculated for a non-work-hardening material for a central sloping crack under tension and for a central crack under a quadratic temperature gradient for which previously suggested contour integrals are no longer path independent even in the linear elastic case.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 16 (1980), S. 411-429 
    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 appliqué la méthode par éléments finis à une série de configurations tri-dimensionnelles fissurées, telles que celles qui ont été proposées dans l'atelier du Battelle en 1976 sur l'analyse de la rupture à trois dimensions. Les résultats relatifs à ces cas sont présentés, et montrent les COD et les facteurs d'intensité de contrainte aux alentours de divers profils de fissure. Diverses méthodes sont utilisées pour les déterminer dans le cas de modules de Poisson égaux à 0,3 et 0,49. Une maille semi-circulaire a également été utilisée pour traiter le problème de la fissure circulaire noyée, pour lequel une solution analytique existe. On a obtenu un accord entre 1 et 3% dans le cas de rapport de module de Poisson égaux à 0,3 et 0,49 respectivement, ce qui démontre la fiabilité des mailles choisies et des techniques d'évaluation.
    Notes: Abstract The finite element method is applied to a series of three dimensional cracked configurations as proposed at the Three Dimensional Fracture Analysis Workshop at Battelle Columbus, in 1976. Results for these cases are presented showing crack opening displacements and stress intensity factors around the crack profiles, derived using several methods, for values of Poisson's ratio equal to both 0.3 and 0.49. The semicircular crack mesh was also applied to the embedded circular crack problem, for which an analytical solution exists, and agreement within 1% and 3% was obtained for Poisson's ratio equal to 0.3 and 0.49 respectively, demonstrating the accuracy of the chosen meshes and evaluation techniques.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 32 (1986), S. 185-199 
    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 En utilisant le système BERSAFE d'éléments finis non-linéaires, on considère l'analyse élasto-plastique des contraintes dans une plaque fissurée en son centre et sujette à deux types de sollicitations, à savoir une tension uniaxiale et un grandient thermique sur l'épaisseur de la plaque, tendant à ouvrir la fissure indépendamment l'un de l'autre. On étudie ici l'effet combiné de ces deux formed de mise en charge, en les appliquant l'une après l'autre et en utilisant la faculté de redémarrage. Dans le cas de la sollicitation thermique suivie de la mise en charge par traction, on a procédé à plusieurs remises en charge de la zone tendue, pour des sollicitations thermiques successivement décroissantes. De même, on a appliqué les deux combinaisons de mise en charge à une plaque initialement non fissurée, et la fissure obtenue a été ouverte dans son état chargé en utilisant la technique de la relaxation d'une sollicitation modèle. Dans tous les cas, on a calcule les intégrales de contour indépendantes du chemin pour établir les conditions de rupture à l'extrémité d'une fissure sous les sollicitations de type ci-dessus, en particulier en vue de fournir des résultats comparables aux procédures de rupture proposées par le CEGB.
    Notes: Abstract The elastic-plastic stress analysis of a centre-cracked plate subjected to two types of loading is considered using the non-linear BERSAFE finite element system. The loading includes both uniaxial tension and a quadratic thermal gradient across the plate, both of which independently would tend to open the crack. In the present work the combined effect of these two load forms is investigated by applying one after the other using the restart facility. In the case of the thermal load followed by the tensile load, several restarts of the tensile part were made at successively lower thermal loads. Also, both combinations of load application were applied to a plate initially uncracked, then the crack was opened from the loaded state by using a nodal load release technique. In all cases, path independent contour integrals were calculated to assess the fracture conditions at the crack tip under the above styles of loading, particularly with a view to supplying results which can be compared to proposed CEGB fracture procedures.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 21 (1983), S. 49-66 
    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 En procédant à des essais expérimentaux d'éprouvettes non conformes suivant l'ASTM, on compare l'approcheJ intégrale pour analyser la rupture après écoulement plastique avec un large éventail d'autres méthodes. On discute la signification deJ et sa relation avec d'autres intégrales.
    Notes: Abstract TheJ * integral approach to post yield fracture analysis is compared with a wide variety of other methods by means of experimental testing of specimens invalid in the sense of ASTM. The significance of J* and its relationship to other integrals is discussed.
    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 3 (1971), S. 149-149 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 10 (1976), S. 1179-1182 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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