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An FEM study on crack tip blunting in ductile fracture initiation

N. Ramakrishnan1, P. Rama Rao2

Regional Research Laboratory, Hoshangabad Road, Bhopal- 462026, India.
International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P. O., Hyderabad – 500 005, India.

Computers, Materials & Continua 2005, 2(3), 163-176.


Ductile fracture is initiated by void nucleation at a characteristic distance (Ic) from the crack tip and propagated by void growth followed by coalescence with the tip. The earlier concepts expressed Ic in terms of grain size or inter-particle distance because grain and particle boundaries form potential sites for void nucleation. However, Srinivas et al. (1994) observed nucleation of such voids even inside the crack tip grains in a nominally particle free Armco iron. In an attempt to achieve a unified understanding of these observations, typical crack-tip blunting prior to ductile fracture in a standard C(T) specimen (Mode I) was studied using a finite element method (FEM) supporting large elasto-plastic deformation and material rotation. Using a set of experimental data on Armco iron specimens of different grain sizes, it is shown that none of the locations of the maxima of the parameters stress, strain and strain energy density correspond to Ic. Nevertheless, the size of the zone of intense plastic deformation, as calculated from the strain energy density distribution ahead of the crack tip in the crack plane, compares well with the experimentally measured Ic. The integral of the strain energy density variation from the crack tip to the location of void nucleation is found to be linearly proportional to JIC. Using this result, an expression is arrived at relating Ic to JIC and further extended to CTODc.


Cite This Article

N. . Ramakrishnan and P. R. . Rao, "An fem study on crack tip blunting in ductile fracture initiation," Computers, Materials & Continua, vol. 2, no.3, pp. 163–176, 2005.

cc This work is licensed under a Creative Commons Attribution 4.0 International License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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