Johansson, S. and Fitzpatrick, M. E.
Errors in crack closure measurements caused by flexure test fixture support effects.
Experimental Mechanics, 41(1),
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 specimens cannot be used, or where material thickness 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 cur ves as evidenced using the back-face 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.
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