PSI - Issue 17

Sebastian Vetter et al. / Procedia Structural Integrity 17 (2019) 90–97 Sebastian Vetter/ Structural Integrity Procedia 00 (2019) 000 – 000

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A test bench in accordance to Fig. 2b was used to perform tests under rotating bending with and without static torsion. The rotating bending of the specimen was generated by an imbalance mass, which was set in rotation by the propulsion. The rotating bending moment within the test bench corresponds approximately to the triangle shown in Fig. 2b and was derived via the hub. A calibration characteristic curve was recorded based on the measured rotating bending moment on the P-SHC specimen regarding to the measured rotating bending moment on the shaft of the test bench. With this calibration characteristic curve, which was recorded for each test series, the rotating bending load for each test could be applied directly to the P-SHC. The actuation of the torsional moment was realized by a lever arm with static preload. The preload was measured by a load cell. This allowed to determine the applied torsional moment.

Fig. 2. (a) hydraulic rotary cylinder test bench; (b) rotating bending test bench.

2.4. Experimental procedure and results

2.4.1. Static tests The change from elastic to plastic material behavior is essential for the characterization of the static load capacity. A special load-increasing procedure was used to detect this change for torsional moments . This quasistatic load increasing procedure has already been described in Leidich et al. (2017). In this case, the torsional moment was not increased continuously, but step by step in order to enable setting processes in the P-SHC. For this purpose, an applied pulsating torsional moment with a frequency of 0.1 Hz was increased by ∆ = 400 after three load cycles. Investigations by Leidich et al. (2017) illustrated that the failure location was exclusively a permanent deformation of the free shaft manufactured from C45+N due to overload of static torsion. It was caused through stress concentration of the profile shape. In the following investigations, the occurrence of plasticization within the contact due to high pressures should be additionally enabled. Thus, the materials 42CrMo4+QT for shafts and C45E+N for hubs were used. An expansion of the hub and a slipping through of the shaft was not to be expected because of the diameter ratio 0.5 of the P-SHC. This diameter ratio and the constant volume of the hub also ensured that the shaft was always the failure-critical component. The detection of the torsional moment , at which plasticization had occurred was determined by evaluating the measurement of the twisting angle of the hub relative to the shaft (cf. Fig. 3a). An elastic deformation of the free shaft and the contact was characterized by a direct proportional behavior of torsional moment and twisting angle. For example in Fig. 3, the twisting angle increased disproportionately at a torsional moment of , > 4400 - the specimen plasticized. In the example described here, plasticization occurred on the free shaft (cf. Fig. 3b). The case with failure due to plasticization in the contact is illustrated in Fig. 3c. Table 3 contains the experimentally determined limits of torsional moments for different profile shapes of P-SHCs. It is evident, depending on the type of the profile shape and the relative joining length / , that the failure location occurred in the contact or on the free shaft. For joining lengths / < 1 , the profiles H7-concave and H7-flat had a larger limit of torsional moment than the profile shape H3-convex. For the joining length / = 1 , the achievable limit of torsional moments were equal. An existing interference had no significant influence on the transmissible limit of torsional moment.