International Journal of Fracture

, Volume 37, Issue 3, pp 197–215 | Cite as

An analysis of the temperature and rate dependence of Charpy V-notch energies for a high nitrogen steel

  • V. Tvergaard
  • A. Needleman
Article

Abstract

The brittle-ductile transition for a high nitrogen steel is investigated by numerical analyses of the Charpy impact test. The material is described in terms of an elastic-viscoplastic constitutive model that accounts for the nucleation and growth of micro-voids, leading to ductile fracture, as well as for cleavage failure by micro-crack nucleation. The temperature dependence of flow strength and strain hardening is included in the model, and this leads to the prediction of a transition from cleavage fracture to predominantly ductile fracture as the temperature increases. For the particular steel considered it is found that the variation of strain hardening with temperature has a strong effect on the failure mode transition. Both slow loading and impact loading of the Charpy specimen are analyzed. Most of the computations are based on a quasi-static formulation since, even at the strain rates encountered in the Charpy impact test, material strain rate sensitivity is the main time effect. The influence of material inertia is investigated in a few transient analyses.

Keywords

Ductile Fracture Strain Rate Sensitivity Cleavage Fracture Charpy Impact Test Charpy Specimen 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Résumé

On étudie la transition ductile-fragile d'un acier à haute teneur en azote par l'analyse numérique de resultats d'essais de résilience Charpy. On décrit le matériau sous forme d'un modèle constitutif élasto-viscoplastique, qui tient compte de la création et de la croissance de micro-lacunes conduisant à une rupture ductile ou à une rupture par clivage par nucléation de microfissures. On induit dans le modèle la dépendance de la limite elastique et de l'écrouissage par rapport à la température, ce qui conduit à prédire une transition d'une rupture par clivage à une rupture essentiellement ductile lorsque croît la température. Pour l'acier considéré en particulier, on trouve que l'évolution de l'écrouissage avec la température a un effet déterminant sur la transition du mode de rupture. On analyse à la fois la mise en charge lente et brutale de l'échantillon Charpy. La plupart des calculs sont basés sur une formulation en conditions quasi-statiques puisque la sensibilité du matériau à la vitesse de deformation est le facteur principal du point de vue du temps, même aux vitesses de déformation caractéristiques de l'essai de résilience Charpy V. Dans quelques analyses de transitoires, on étudie l'influence de l'inertie du matériau.

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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • V. Tvergaard
    • 1
  • A. Needleman
    • 2
  1. 1.Department of Solid MechanicsThe Technical University of DenmarkLyngbyDenmark
  2. 2.Division of EngineeringBrown UniversityProvidenceUSA

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