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  • 1
    Electronic Resource
    Electronic Resource
    Substructuring in linear and nonlinear analysis (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 583-597 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The procedures for utilizing substructuring and static condensation in structural analysis are well known. However, until recently there have been no general-purpose structural mechanics computer systems that offer multi-level substructuring combined with a convenient method for defining the structural model. Now that such systems are available, engineers must decide when substructuring techniques are useful. Substructuring, with and without condensation, has proved to be highly efficient in the analysis of certain classes of structure. It can reduce computer costs by a factor of from 2 to 100. Yet, indiscriminate use of condensation may result in unnecessary and expensive computations. This paper examines the advantages and disadvantages of substructuring relative to data entry and computational efficiency. Guidelines are proposed for engineers to follow when using substructuring in the analysis of linear and nonlinear structures. The FINITE system is used to illustrate actual implementation of substructuring features in a general purpose finite element system.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150409
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental and numerical studies of the J-integral for a surface flaw (1990)
    Springer
    International journal of fracture 43 (1990), S. 47-67 
    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 évalue expérimentalement les valuers de l'intégrale J dans un panneau en traction fissuré en surface, en mesurant les dilatations et les déplacements suivant un contour instrumenté localisé le long du plan de symétrie longitudinale. On utilise une analyse non linéaire par éléments finis à trois dimensions afin d'obtenir des estimations de la manière dont les intégrales de contour et de surface contribuent à l'intégrale J à 3D. Les résultats par éléments finis indiquent que la contribution de l'intégrale de surface est négligeable suivant le plan de symétrie; le déterminant de la rupture peut done être adéquatement décrit par les valeurs expérimentales relatives au contour. Des comparaisons sur le détail des résultats expérimentaux et numériques révèlent qu'un modèle par éléments finis quart-symétriques peut prédire de manière sûre la réaction de la pièce par rapport à des dilatations globales de près de 1,6 fois la dilatation à la limite élastique du matériau, valeur au-delà de laquelle les configurations de la déformation observées font état de bandes de glissement globalement asymétriques.
    Notes: Abstract Applied J-integral values for a surface cracked tensile panel are experimentally evaluated by measuring strain and displacement quantities along an instrumented contour located on the longitudinal symmetry plane. Nonlinear, 3-D, finite-element analyses are employed to obtain corresponding estimates of the contour and area integral contributions to a 3-D J-integral. Finite element results indicate that the area integral contribution is negligibly small on the symmetry plane; the fracture driving force is thus adequately characterized by the experimental contour values. Detailed comparisons of the experimental and numerical results (crack mouth opening displacement, J-values, and strains along the contour) reveal that the one-quarter symmetric, finite element model accurately predicts the panel response for overall (gauge length) strains approaching 1.6 times the material yield strain, beyond which the observed deformation patterns exhibited globally asymmetric shear bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018126
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  • 3
    Electronic Resource
    Electronic Resource
    Finite element evaluation of J parameters in 3D (1987)
    Springer
    International journal of fracture 33 (1987), S. R7 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034901
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  • 4
    Electronic Resource
    Electronic Resource
    Continuum and micromechanics treatment of constraint in fracture (1993)
    Springer
    International journal of fracture 64 (1993), S. 101-133 
    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
    Notes: Abstract Two complementary methodologies are described to quantify the effects of crack-tip stress triaxiality (constraint) on the macroscopic measures of elastic-plastic fracture toughness J and Crack-Tip Opening Displacement (CTOD). In the continuum mechanics methodology, two parameters J and Q suffice to characterize the full range of near-tip environments at the onset of fracture. J sets the size scale of the zone of high stresses and large deformations while Q scales the near-tip stress level relative to a high triaxiality reference stress state. The material's fracture resistance is characterized by a toughness locus J c (Q) which defines the sequence of J-Q values at fracture determined by experiment from high constraint conditions (Q∼0) to low constraint conditions (Q〈0). A micromechanics methodology is described which predicts the toughness locus using crack-tip stress fields and critical J-values from a few fracture toughness tests. A robust micromechanics model for cleavage fracture has evolved from the observations of a strong, spatial self-similarity of crack-tip principal stresses under increased loading and across different fracture specimens. We explore the fundamental concepts of the J-Q description of crack-tip fields, the fracture toughness locus and micromechanics approaches to predict the variability of macroscopic fracture toughness with constraint under elastic-plastic conditions. Computational results are presented for a surface cracked plate containing a 6:1 semielliptical, a=t/4 flaw subjected to remote uniaxial and biaxial tension. Crack-tip stress fields consistent with the J-Q theory are demonstrated to exist at each location along the crack front. The micromechanics model employs the J-Q description of crack-front stresses to interpret fracture toughness values measured on laboratory specimens for fracture assessment of the surface cracked plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016693
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  • 5
    Electronic Resource
    Electronic Resource
    J-Q and toughness scaling model solutions for M(T), DE(T), SE(B), SE(T) and C(T) specimens (1985)
    Springer
    International journal of fracture 72 (1985), S. R11 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00036932
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical investigation of 3-D constraint effects on brittle fracture in SE(B) and C(T) specimens (1990)
    Springer
    International journal of fracture 74 (1990), S. 131-161 
    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
    Notes: Abstract Specimen size and geometry effects on cleavage fracture of ferritic steels tested in the ductile-to-brittle transition region remain an important technological impediment in industrial applications of fracture mechanics and in the on-going development of consensus fracture testing standards. This investigation employs 3-D nonllinear finite element analyses to conduct an extensive parametric evaluation of crack front stress triaxiality for deep notch SE(B) and C(T) specimens and shallow notch SE(B) specimens, with and without side grooves. Crack front conditions are characterized in terms of J-Q trajectories and the constraint model for cleavage fracture toughness proposed previously by Dodds and Anderson. An extension of the toughness scaling model suggested here combines a revised ‘in-plane’ constraint correction with an explicit thickness correction derived from extreme value statistics. The 3-D analyses provide ‘effective’ thicknesses for use in the statistical correction which reflect the interaction of material flow properties and specimen aspect ratios, a/W and W/B, on the varying levels of stress triaxiality over the crack front. The 3-D computational results imply that a significantly less strict size/deformation limit, relative to the limit indicated by previous plane-strain computations, is needed to maintain small-scale yielding conditions at fracture by a stress-controlled, cleavage mechanism in deep notch SE(B) and C(T) speciments. Moreover, the analyses indicate that side grooves (20 percent) should have essentially no net effect on measured toughness values of such specimens. Additional new results made available from the 3-D analyses also include revised η-plastic factors for use in experimental studies to convert measured work quantities to thickness average and maximum (local) J-values over the crack front. To estimate CTOD values, new m-factors are included for use in the expression 131-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00036262
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  • 7
    Electronic Resource
    Electronic Resource
    A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach (1996)
    Springer
    International journal of fracture 79 (1996), S. 309-340 
    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
    Notes: Abstract This study describes a computational framework to quantify the influence of constraint loss and ductile tearing on the cleavage fracture process, as reflected by the pronounced effects on macroscopic toughness (J c , δc). Our approach adopts the Weibull stress σw as a suitable near-tip parameter to describe the coupling of remote loading with a micromechanics model incorporating the statistics of microcracks (weakest link philosophy). Unstable crack propagation (cleavage) occurs at a critical value of σw which may be attained prior to, or following, some amount of stable, ductile crack extension. A central feature of our framework focuses on the realistic numerical modeling of ductile crack growth using the computational cell methodology to define the evolution of near-tip stress fields during crack extension. Under increased remote loading (J), development of the Weibull stress reflects the potentially strong variations of near-tip stress fields due to the interacting effects of constraint loss and ductile crack extension. Computational results are discussed for well-contained plasticity, where the near-tip fields for a stationary and a growing crack are generated with a modified boundary layer (MBL) formulation (in the form of different levels of applied T-stress). These analyses demonstrate clearly the dependence of σw on crack-tip stress triaxiality and crack growth. The paper concludes with an application of the micromechanics model to predict the measured geometry and ductile tearing effects on the cleavage fracture toughness J c of an HSLA steel. Here, we employ the concept of the Dodds-Anderson scaling model, but replace their original local criterion based on the equivalence of near-tip stressed volumes by attainment of a critical value of the Weibull stress. For this application, the proposed approach successfully predicts the combined effects of loss of constraint and crack growth on measured J c -values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018594
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  • 8
    Electronic Resource
    Electronic Resource
    A framework to correlate a/W ratio effects on elastic-plastic fracture toughness (J c ) (1991)
    Springer
    International journal of fracture 48 (1991), S. 1-22 
    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
    Notes: Abstract Single edge-notched bend (SENB) specimens containing shallow cracks (a/W 〈 0.2) are commonly employed for fracture testing of ferritic materials in the lower-transition region where extensive plasticity (but no significant ductile crack growth) precedes unstable fracture. Critical J-values J c ) for shallow crack specimens are significantly larger (factor of 2–3) than the J c )-values for corresponding deep crack specimens at identical temperatures. The increase of fracture toughness arises from the loss of constraint that occurs when the gross plastic zones of bending impinge on the otherwise autonomous crack-tip plastic zones. Consequently, SENB specimens with small and large a/W ratios loaded to the same J-value have markedly different crack-tip stresses under large-scale plasticity. Detailed, plane-strain finite-element analyses and a local stress-based criterion for cleavage fracture are combined to establish specimen size requirements (deformation limits) for testing in the transition region which assure a single parameter characterization of the crack-tip stress field. Moreover, these analyses provide a framework to correlate J c )-values with a/W ratio once the deformation limits are exceeded. The correlation procedure is shown to remove the geometry dependence of fracture toughness values for an A36 steel in the transition region across a/W ratios and to reduce the scatter of toughness values for nominally identical specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012499
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  • 9
    Electronic Resource
    Electronic Resource
    The influence of weld strength mismatch on crack-tip constraint in single edge notch bend specimens (1993)
    Springer
    International journal of fracture 63 (1993), S. 297-316 
    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
    Notes: Abstract Previous work by Dodds and Anderson provides a framework to quantify finite size and crack depth effects on cleavage fracture toughness when failure occurs at deformation levels where J no longer uniquely describes the state of stresses and strains in the vicinity of the crack tip. Size effects on cleavage fracture are quantified by defining a value termed J SSY: the J to which an infinite body must be loaded to achieve the same likelihood of cleavage fracture as in a finite body. In weld metal fracture toughness testing, mismatch between weld metal and baseplate strength can alter deformation patterns, which complicate size and crack depth effects on cleavage fracture toughness. This study demonstrates that there is virtually no effect of ±20 percent mismatch on J SSYif the distance from the crack tip to the weld/plate interface (L min) exceeds 5 mm. At higher levels of overmatch (50 to 100%), it is no longer possible to parameterize the departure of J SSYfor a weldment from that for a homogeneous SE(B) based on L min alone. Weld geometry significantly influences the accuracy with which J SSYfor a welded SE(B) can be approximated by J SSYfor a homogeneous specimen at these extreme overmatch levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013040
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  • 10
    Electronic Resource
    Electronic Resource
    Experimental and analytical estimates of the J-integral for tensile panels containing short center cracks (1985)
    Springer
    International journal of fracture 28 (1985), S. 39-54 
    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 utilise la méthode des éléments finis en vue de prédire les valeurs de l'intégrale J appliquées à des panneaux soumis à un régime de tension sévère et comportant des fissures contrales courtes. Les valeurs expérimentales de l'Intégrale J sont obtenues en intégrant les dilatations et les déplacements le long d'un contour dûment instrumenté. Il apparaît que les prédictions par éléments finis des valeurs de J et des déplacements d'ouverture de la portion débouchante des fissures (CMOD), s'avèrent plus élevées que les valeurs mesurées pour des fissures courtes (a/W〈0.05). On démontre que des modifications importantes de la géométrie n'ont qu'une influence négligeable sur les valeurs de J et de CMOD, déterminées par éléments finis. Le fait d'introduire une zone légèrement raidie au voisinnage de l'extrémité de la fissure, en utilisant notamment un revêtement d'éléments opérant en état plan de déformation, a pour conséquence de rapprocher ces valeurs de J et de CMOD, des valeurs expérimentales. Dans le cas de longueurs de fissure plus importantes, il s'avère que les solutions conventionnelles par éléments finis et état plan de tension, sont appropriées à la prédiction des valeurs de J et de CMOD.
    Notes: Abstract The finite element method (FEM) is used to predict the applied J-integral values in highly strained tensile panels containing short center cracks. Experimental J-values are obtained by integrating strain and displacement quantities measured along an instrumented contour. FEM plane stress predictions for J-values and crack mouth opening displacements (CMOD) are much larger than experimentally measured values for short cracks (a/W〈0.05). Large geometry changes near the crack tip are demonstrated to have a negligible effect on the FEM J and CMOD values. The introduction of a small stiffened zone near the crack tip using an overlay of plane strain elements brings FEM J and CMOD values into close agreement with experimental values. For longer crack lengths, conventional plane stress FEM solutions are adequate to predict J and CMOD values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018583
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