PSI - Issue 38

Kimiya Hemmesi et al. / Procedia Structural Integrity 38 (2022) 401–410 Author name / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 5. Notch root strain history measured by means of DIC: a) 42CrMoS4 at OL 1; b) 42CrMoS4 at OL 2; c) EN AW-6082 at OL 1; d) EN AW-6082 at OL 2.

4. Residual stress measurements For some selected specimens and test phases, axial (longitudinal) residual stresses were measured in the notch root by means of the X-ray diffraction. The measurements were performed using Cr-K  radiation with a collimator diameter of 0.2 mm for 42CrMoS4 and 1 mm for EN AW-6062 specimens, respectively. The residual stresses and their scatter were found to be highly sensitive to the positioning of the X-ray spot in the notch root. For this reason, the residual stresses were measured at several positions along the specimen circumference. In Table 5, the largest measured values are listed. Table 5. Longitudinal residual stresses determined by means of the X-ray diffraction. specimen loading history notch stress amplitude in a runout test in MPa residual stress in MPa 42CrMoS4 EN AW-6082 42CrMoS4 EN AW-6082 not loaded (as machined) – – 59 ± 10 1 ± 5 5× OL 1 – – 217 ± 8 63 ± 3 50× OL 1 – – 264 ± 8 - 5× OL 2 – – 226 ± 10 125 ± 6 5× OL 1 followed by 10 6 cycles (runout) 571 169 172 ± 11 78 ± 3 5× OL 2 followed by 10 6 cycles (runout) 528 132 401 ± 7 113 ± 5 After machining, the steel specimen exhibits axial residual stresses of 59±10 MPa, whereas the aluminium specimen is almost free of residual stresses. In all specimens, tensile residual stresses were measured after overloads. This result is in accordance with the negative notch root strains determined in the most cases (see Fig. 5), except for 42CrMoS4 at OL 1. Further experimental findings can be summarised as follows: