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For deeply cracked specimens a finite strain numerical analysis is employed to investigate the development of the near-tip stress and strain fields during cracktip blunting. The material is characterized by an elastic-plastic constitutive law with a vertex on subsequent yield surfaces at the point of loading, as suggested by physical models of polycrystalline aggregates. In contrast to classical smooth yield surface theory, this corner theory of plasticity permits shear band formation at achievable strain levels in work-hardening solids. Both for an edge-cracked bend specimen and for a center-cracked panel the corner theory description results in localization into shear bands in a small material region near the crack tip, so that very high strain peaks develop at an early stage of blunting. An edge-cracked bend specimen computation based on the classical Prandtl-Reuss plasticity theory, carried out for comparison purposes, shows a smooth variation of the strain field around the blunting crack tip. For the two edge-cracked bend specimens the stress and strain fields a few openings away from the tip are, however, in close agreement.
fracture, crack initiation, J-integral, plasticity, plastic properties, large-scale yielding, tip field dominance, elastic-plastic fracture
Professor of engineering, Division of Engineering, Brown University, Providence, R.I.
Lecturer, Technical University of Denmark,