PSI - Issue 39

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Hannes Panwitt et al. / Procedia Structural Integrity 39 (2022) 20–33 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 3: Crack length measurement in a branching crack. a) principal strain field obtained by DIC at 0.32×10 5 cycles before final fracture; b) final crack pattern and crack path with a - N -curve of the longest crack; c) a - N -curves of all separately detected cracks.

4. Experimental verification In order to validate the developed extensions of the ACDM tool, experimental investigations were carried out. First, fatigue crack growth tests were performed under separate mode I loading to calibrate the corresponding functions and threshold values. Subsequently, the functionality of the extensions was tested in experiments under spatial mixed mode loading. 4.1. Test setup For this purpose, single-edge notched (SEN) specimens are used (Fig. 4a). The specimens were cut and CNC milled out of a forged block of the high-strength steel 34CrNiMo6 at quenched and tempered conditions. In Table 1 and Table 2 the chemical composition and the mechanical properties of the tested material are given.

Fig. 4: Setup for experimental investigations. a) Geometry of the SEN-specimen; b) Servohydraulic Tension/Torsion testing machine. (Köster et al., 2019)

Table 1. Chemical composition (in % of weight) of the tested material 34CrNiMo6. (Pilsen Toll s.r.o., 2016)