Advertisement

Initial Energy Dissipation Mechanism at Crack Tip on the Ductile to Brittle Transition

  • Jeffrey W. Kysar
Part of the Solid Mechanics and Its Applications book series (SMIA, volume 114)

Abstract

The objective of this study is to investigate energy dissipation mechanisms that operate at different length scales during fracture in ductile materials. A dimensional analysis is performed to identify the sets of dimensionless parameters which contribute to energy dissipation via dislocation-mediated plastic deformation at a crack tip. However rather than use phenomenological variables such as yield stress and hardening modulus in the analysis, physical variables such as dislocation density, Burgers vector and Peierls stress are used. It is then shown via elementary arguments that the resulting dimensionless parameters can be interpreted in terms of competitions between various energy dissipation mechanisms at different length scales, for example between dislocation nucleation from a crack tip and dislocation nucleation from a Frank-Read dislocation source in the material close to the crack tip. Criteria are established which are used to determine the initial, and perhaps dominant, energy dissipation mechanism at a crack tip.

Keywords

Fracture dislocation crack tip dislocation nucleation Frank-Read dislocation source ductile to brittle transition 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Armstrong, R. (1966). “Cleavage crack propagation within crystals by the Griffith mechanism versus a dislocation mechanism.” Mater. Sci. Engng., 1, 251–256.CrossRefGoogle Scholar
  2. Ashby, M. F., and Embury, J. D. (1985). “The influence of dislocation density on the ductilebrittle transition in BCC metals.” Scripta metall., 19, 557–562.CrossRefGoogle Scholar
  3. Lawn, B. R. (1993). Fracture of brittle solids, Cambridge University Press, Cambridge.CrossRefGoogle Scholar
  4. Kysar, J. W. (2002) “Energy dissipation mechanisms in ductile fracture.” Submitted to J. Mech. Phys. Solids Google Scholar
  5. Li, J. C. M. (1986). “Computer simulations of dislocations emitted from a crack.” Scripta metall., 20, 1477–1482.CrossRefGoogle Scholar
  6. McClintock, F. A., and Argon, A. S. (1966). Mechanical Behavior of Materials, Addison Wesley, Reading, Massachusetts.Google Scholar
  7. Rice, J. R. (1965) “An examination of the fracture mechanics energy balance from the point of view of continuum mechanics.” Proceedings of the 1st International Conference on Fracture, Sendai, (eds. T. Yokobori, T. Kawasaki, and J. L. Swedlow), Japanese Society for Strength and Fracture of Materials, 1, 309–340.Google Scholar
  8. Rice, J. R. (1992). “Dislocation nucleation from a crack tip: An analysis based on the Peierls concept.” J Mech. Phys. Solids, 40, 239–271.CrossRefGoogle Scholar
  9. Rice, J. R., and Beltz, G. E. (1994). “The activation energy for dislocation nucleation at a crack.” J. Mech. Phys. Solids, 42, 333–360.CrossRefGoogle Scholar
  10. Rice, J. R., and Thomson, R. (1974). “Ductile versus brittle behaviour of crystals.” Phil. Mag., 29, 73–97.CrossRefGoogle Scholar
  11. Schöck, G., and Püschl, W. (1991). “The formation of dislocation loops at crack tips in 3 dimensions.” Philosophical Magazine A, 64, 931–949.CrossRefGoogle Scholar
  12. Taylor, G. I. (1934). “The mechanism of plastic deformation of crystals. Part I.--Theoretical.” Proc. R. Soc. Lond. A, 145, 362–387.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2004

Authors and Affiliations

  • Jeffrey W. Kysar
    • 1
  1. 1.Department of Mechanical EngineeringColumbia UniversityNew YorkUSA

Personalised recommendations