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A finite element analysis of dynamic fracture initiation by ductile failure mechanisms in a 4340 steel

Jha, M and Narasimhan, R (1992) A finite element analysis of dynamic fracture initiation by ductile failure mechanisms in a 4340 steel. In: International Journal of Fracture, 56 (3). pp. 209-231.

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Abstract

In some recent dropweight impact experiments [5] with pre-notched bend specimens of 4340 steel, it was observed that considerable crack tunneling occurred in the interior of the specimen prior to gross fracture initiation on the free surfaces. The final failure of the side ligaments happened because of shear lip formation. The tunneled region is characterized by a flat, fibrous fracture surface. In this paper, the experiments of [5] (corresponding to 5 m/s impact speed) are analyzed using a plane strain, dynamic finite element procedure. The Gurson constitutive model that accounts for the ductile failure mechanisms of micro-void nucleation, growth and coalescence is employed. The time at which incipient failure was observed near the notch tip in this computation, and the value of the dynamic J-integral, J d, at this time, compare reasonably well with experiments. This investigation shows that J-controlled stress and deformation fields are established near the notch tip whenever J d , increases with time. Also, it is found that the evolution of micro-mechanical quantities near the notch root can be correlated with the time variation of J d .The strain rate and the adiabatic temperature rise experienced at the notch root are examined. Finally, spatial variations of stresses and deformations are analyzed in detail.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Springer.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 28 Jan 2011 06:45
Last Modified: 28 Jan 2011 06:45
URI: http://eprints.iisc.ernet.in/id/eprint/34687

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