PSI - Issue 17

Jürgen Bär et al. / Procedia Structural Integrity 17 (2019) 308–315 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Geometry of the samples (a) oxygen-free copper (b) aluminum alloy 7475 T761

The fatigue tests were performed with a servohydraulic testing machine equipped with parallel guided grips to minimize bending forces. The tests were performed with a testing frequency of f L = 1 Hz under pure tension loading (R = 0) as well as fully reversed loading conditions (R = -1). A photograph of the testing chamber with parallel guided grips and a specimen with painted testing section is shown in figure 2. In front of the specimen a thermographic camera was mounted to investigate the thermal response of the materials.

Fig. 2. Photograph of the chamber with parallel guided grips and a specimen with painted testing section.

All tests were performed with a stepwise increase of the loading starting from a pure elastic loading level. On each level 50 loading cycles were applied. The experiments were performed up to a maximum load of 225 MPa for the copper and 450 MPa for the AA7475 specimens. 2.2. Thermographic measurements During the fatigue tests thermographic measurements with an ImageIR 8300hp infrared camera with a thermal resolution of 20 mK were undertaken. The complete loading sequence was recorded with a sample rate of