Experimental Mechanics

, Volume 41, Issue 1, pp 47–51

Errors in crack closure measurements caused by flexure test fixture support effects


  • S. Johansson
    • Department of Mechanical EngineeringDivision of Engineering Materials
  • M. E. Fitzpatrick
    • Department of Materials EngineeringOpen University

DOI: 10.1007/BF02323103

Cite this article as:
Johansson, S. & Fitzpatrick, M.E. Experimental Mechanics (2001) 41: 47. doi:10.1007/BF02323103


Flexural tests are sometimes used for the evaluation of fatigue and fracture properties, especially for thin cross sections such as plate material where compact tension speciments cannot be used, or where material thicness is limited in the direction required for data generation. The method is also useful for evaluation of crack closure provided the force transfer occurs correctly. This paper shows how the influence of incorrect test fixture supports, which are outside the standard testing arrangement for such test specimens, can affect the force-displacement curves as evidenced using the backface strain method. The results show that incorrect test fixture supports may cause deviations in the force-displacement trace as an artifact of the testing conditions. This effect can severely influence crack closure measurements. The effect was also modeled with finite element analysis.

Key Words

Flexural bend testingfatigue crack closureback-face strainstrain gage techniques
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© Society for Experimental Mechanics, Inc. 2001