International Journal of Fracture

, Volume 182, Issue 1, pp 39–51 | Cite as

Local approach to ductile fracture and dynamic strain aging

Original Paper
First Online:
Received:
Accepted:

Abstract

Experiments on smooth and notched round specimens on a C–Mn steel used in nuclear industry are performed at different temperatures under quasi-static loadings, revealing dynamic strain aging (DSA). The behavior is highly dependent on temperature and strain rate, and a drop in fracture strain is observed. Fracture surface observation on notched tensile specimens shows classical ductile fracture mechanisms with growth and coalescence of voids. The apparent strain hardening behavior at each temperature and strain rate is taken into account to compute the void growth with the Rice and Tracey model and with a damage law developed from unit cell computations. It is shown that the apparent strain hardening at large strains is of major importance to correctly predict fracture with the Rice and Tracey model, but its influence on the void growth law is of minor importance. In particular, the stress triaxiality ratio within the notch is increased due to the negative strain rate sensitivity. The ductility drop observed in DSA domain is then partly explained, but void nucleation and void growth in presence of strain bands should be included in the fracture modeling of such materials.

Keywords

Ductile fracture Local approach Micromechanics  Dynamic strain aging 

Abbreviations

DSA

Dynamic strain aging

NT

Notched tensile

\(b\)

Parameter of the strain hardening law

\(f, f_{0}\)

Void volume fraction and initial void volume fraction

\(\dot{p}\)

von Mises equivalent strain rate

\(p\)

Cumulative von Mises equivalent strain

\(Q\)

Parameter of the strain hardening law

\(R/R_{0}\)

Void growth ratio

\(R_{c}/R_{0}\)

Critical void growth ratio

\(R_{H}\)

Isotropic strain hardening term

\(T\)

Temperature

\(\alpha , \beta \)

Parameters of the void growth law

\(\sigma _{eq}\)

von Mises equivalent stress

\(\sigma _{m}\)

Mean stress

\(\mathop {\varepsilon }\limits _\sim , {\mathop {\varepsilon }\limits _\sim }^p\)

Strain and plastic strain tensor

\(\sigma _0\)

Yield stress

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Notes

Acknowledgments

The authors sincerely thank EDF/ Dpt MMC for material supply, for experimental tests, and for financial support. They also thank Pr C. Prioul, Pr S. Forest and Dr M. Mazière for the fruitful discussions.

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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.ICMMO/LEMHE, CNRS UMR 8182UniverSud ParisOrsay cedexFrance
  2. 2.Laboratoire MSSMat, CNRS UMR 8579, Grande Voie des VignesEcole Centrale ParisChâtenay Malabry cedexFrance
  3. 3.Centre des Renardières, EcuellesEDFMoret-sur-LoingFrance

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