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Experimental Mechanics

, Volume 44, Issue 4, pp 425–432 | Cite as

Effects of measurement techniques on the experimental characterization of crack tip opening angle-Δa resistance curves

  • W. Burton
  • S. Mahmoud
  • K. Lease
Article

Abstract

One of the most promising approaches to characterizing the stable tearing process for lower constraint configurations in metallic materials has been indicated to be the crack tip opening angle (CTOA) criterion. In this paper we examine the effect of measurement distance selection and the impact of measurement procedures/analysis on the experimental CTOA-Δa resistance curve behavior of a Ti-6Al-4V and an Al5083 alloy. A new, systematic procedure for carrying out the experimental, surface CTOA measurement process has been used, which has uncovered artifacts of measurement distance selection that have not been presented prior to this study. By studying the CTOA-Δa behavior using a rigidly defined and consistent method, it is apparent that the measurement distance behind the crack tip at which angles are measured has a direct impact on the shape of the early transitional behavior of the CTOA-Δa behavior as well as the critical, experimental CTOA values produced.

Key Words

Stable tearing fracture crack tip opening angle CTOA Ti-6Al-4V Al5083 

Nomenclature

Ψce

critical, experimental crack tip opening angle

C(T)

compact tension specimen

ai

crack length after pre-cracking

W

specimen width

R

maximum to minimum load ration for fatigue pre-cracking

Δa

crack length extension beyondai

dm,d1.0

crack tip opening angle measurement distance behind the crack tip

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References

  1. 1.
    Mahmound, S.H. andLease, K.B., “The Effect of Specimen Thickness on the Experimental Characterization of Critical Crack-Tip-Opening Angle in 2024-T351 Aluminum Alloy,” Engineering Fracture Mechanics,70,443–456 (2003).CrossRefGoogle Scholar
  2. 2.
    Newman, J.C. Jr. andJames, M.A., “A Review of the CTOA/CTOD Fracture Criterion—Why It Works!,” AIAA,1324,1042–1051 (2001).Google Scholar
  3. 3.
    ASTM Standard E1290-99, “Standard Test Method for Crack Tip Opening Displacement (CTOD) Fracture Toughness Measurement,” Annual Book of ASTM Standards, 3.01 (2002).Google Scholar
  4. 4.
    Dawicke, D.S., Sutton, M.A., Newman, J.C. Jr. andBigelow, C.A., “Measurement and Analysis of Critical CTOA for an Aluminum Alloy Sheet,”NASA TM 109024, NASA Langley Research Center.Hampton, VA, September (1993).Google Scholar
  5. 5.
    ASTM Standard E399-83, “Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials,” Annual Book of ASTM Standards, 3.01 (1993).Google Scholar
  6. 6.
    Dawicke, D.S., Piascik, R.S., and Newman, J.C. Jr, “Analysis of Stable Tearing in a Thick Aluminum Alloy,” Fatigue and Fracture Mechanics, Vol. 28, ASTM STP 1321, J.H. Underwood, B.D. Macdonald, and M.R. Mitchell, editors, ASTM (1997).Google Scholar

Copyright information

© Society for Experimental Mechanics 2004

Authors and Affiliations

  • W. Burton
    • 1
  • S. Mahmoud
    • 1
  • K. Lease
    • 1
  1. 1.Department of Mechanical and Nuclear EngineeringKansas State UniversityManhattanUSA

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