Experimental and numerical studies of the J-integral for a surface flaw

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.RésuméOn 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.

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