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International Journal of Fracture

, Volume 48, Issue 1, pp 1–22 | Cite as

A framework to correlate a/W ratio effects on elastic-plastic fracture toughness (J c )

  • Robert H. DoddsJr.
  • Ted L. Anderson
  • Mark T. Kirk
Article

Abstract

Single edge-notched bend (SENB) specimens containing shallow cracks (a/W < 0.2) are commonly employed for fracture testing of ferritic materials in the lower-transition region where extensive plasticity (but no significant ductile crack growth) precedes unstable fracture. Critical J-values J c ) for shallow crack specimens are significantly larger (factor of 2–3) than the J c )-values for corresponding deep crack specimens at identical temperatures. The increase of fracture toughness arises from the loss of constraint that occurs when the gross plastic zones of bending impinge on the otherwise autonomous crack-tip plastic zones. Consequently, SENB specimens with small and large a/W ratios loaded to the same J-value have markedly different crack-tip stresses under large-scale plasticity. Detailed, plane-strain finite-element analyses and a local stress-based criterion for cleavage fracture are combined to establish specimen size requirements (deformation limits) for testing in the transition region which assure a single parameter characterization of the crack-tip stress field. Moreover, these analyses provide a framework to correlate J c )-values with a/W ratio once the deformation limits are exceeded. The correlation procedure is shown to remove the geometry dependence of fracture toughness values for an A36 steel in the transition region across a/W ratios and to reduce the scatter of toughness values for nominally identical specimens.

Keywords

Fracture Toughness Plastic Zone Cleavage Fracture Deformation Limit Ductile Crack Growth 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 1991

Authors and Affiliations

  • Robert H. DoddsJr.
    • 1
  • Ted L. Anderson
    • 2
  • Mark T. Kirk
    • 3
  1. 1.Department of Civil EngineeringUniversity of IllinoisUrbanaUSA
  2. 2.Department of Mechanical EngineeringTexas A&M UniversityCollege StationUSA
  3. 3.David Taylor Research CenterAnnapolisUSA

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