Inter-laboratory comparison of fatigue test with evaluation of the participating laboratories calculations of measurement uncertainty (NT TR 533)

  • Report #: NT TR 533
  • Approved: April 2003
  • Author(s): Thomas Svensson, Magnus Holmgren, Klas Johansson, Erland Johnson
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  In this paper a fatigue testing inter-laboratory comparison is presented. Six Nordic laboratories performed fatigue tests on steel specimens. The specimens were tested with different stress levels (460 MPa, 430 MPa and 400 MPa) and with the load ratio R=Smin/Smax =0.1. On each level four specimens were tested. The participating laboratories reported the results together with measurement uncertainty. The results show a significant difference between laboratories. However, when the differences in modelling were taken into consideration no significant differences between the laboratories remained. There are large differences in the way the measurement uncertainties were calculated and reported. No laboratory did take the most influencing uncertainty  parameter, bending stress (due to misalignment of the testing machine, “incorrect” specimens and incorrectly mounted specimens), into consideration when calculating the measurement uncertainty.