【正文】 The test specimens were made of steel (yield stress 375–390 Map, and tensile strength 670–690 Map, tabulated values). The test specimens were distributed to the participants by the organizer. Results The primary laboratory results that should be pared are the estimated Whaler curves. In order to present all results in the same way, the organizer transformed some of the results. The Whaler curves reported by the participants are shown in Fig. 1. It can be seen that there are considerable differences between laboratories. An approximate statistical test shows a significant laboratory effect. Material scatter alone cannot explain the differences in the Whaler curves. In order to investigate if the laboratory effect was solely caused by the modeling uncertainty, we estimated new parameters from the raw data with a mon algorithm. We then chose to use only the failed specimens and to make the minimization in the logarithmic life direction. The results are shown in Fig. 2. A formal statistical significance test was then made, and the result of such a test shows that the differences between the laboratories shown in Fig. 1 could be attributed only to modeling. Uncertainty of measurement calculations One of the most important objectives with this investigation was to pare the observed differences between laboratory test results with their estimated uncertainties of measurement. The intention was to analyze the uncertainty analyses as such, and to pare them to the standard procedure remended in the ISO guide: Guide to the Expression of Uncertainty in Measurement (GUM) [1]. The laboratories identified different sources of uncertainty and treated them in different ways. These sources are the load measurement, the load control, the superimposed bending stresses because of misalignment and the dimensional measurements. Implicitly, laboratory temperature and humidity, specimen temperature and corrosion effects are also considered. In addition, the results show a modeling effect. The different laboratory treatments of these sources are summarized in Table 1. Specific ments on the different laboratories All laboratories gave their laboratory temperature and humidity, but did not consider these values as sources of uncertainty, . the influence of temperature and humidity was neglected. This conclusion is reasonable for steel in the temperature range and humidity range in question [7]. Laboratory 1. The uncertainty due to the applied stress was determined taking load cell and dimensional uncertainties into account. The mathematical evaluation was made in accordance with the GUM. Specimen temperature was measured, but was implicitly neglected. The modeling problem was mentioned, but not considered as an uncertainty source. Laboratory 2. The report contains no uncertainty evaluation. The uncertainties in the load cell and the micrometer are considered, but neglected with reference to the large material scatter. Specimen temperature was measured. Modeling problems are mentioned by a ment regarding the choice of load levels. Laboratory 3. The report contains no uncertainty evaluation. However, the accuracy of the machine is given and the load was controlled during the tests to be within specified limits. The bending stresses were measured on one specimen, but their influence on the fatigue result was not taken into consideration. Laboratory 4. The uncertainties in the load cell and the dimensional measurements are considered in an evaluation of stress uncertainty. The method for the evaluation is not in accordance with the GUM method, but was performed by adding absolute errors. The bending stress influence and the control system deviations are considered, but not included in the uncertainty evaluation. The failure criterion is mentioned and regarded as negligible, and corrosion is mentioned as a possible source of uncertainty. Laboratory 5. Uncertainties in the load cell and the load control were considered, and the laboratory stated in the report that the evaluation of the load uncertainty was performed according to the CIPM method. Laboratory 6. No report was provided, but only experimental results and a Whaler curve estimate. No laboratory reported the uncertainty in the estimated material properties, the Whaler parameters, but at most the uncertainty in the applied stress. The overall picture of the uncertainty considerations is that only uncertainty sources that are possible to estimate from calibration reports were taken into account in the final evaluation. Fig. 1 All experimental results and estimated Whole curves