PSI - Issue 5

Robert Hannemann et al. / Procedia Structural Integrity 5 (2017) 861–868 Hannemann et al./ Structural Integrity Pro edi 00 (2017) 000 – 000

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Fig. 1. Experimental data with FORMAN/METTU-curves ( P S = 50%) for positive and negative R-ratios. Material: 34CrNiMo6.

3. Experimental investigations on rotating bending

In order to investigate the influence of different structural details of wheelset axles on the crack growth behavior, a rotating bending test rig has been developed.

3.1. Rotating bending test rig and scaled specimen

The main elements of the rotating bending test rig are a servo drive (1), two main bearings (2) and a servo hydraulic actuator (5). The installation of the specimen (6) in the test rig is done by a clamping system (7) consisting of collets, with which a high precision and resistance is guaranteed and an adaptation to different specimen diameters is possible. To apply the load, the test rig is mounted in a servohydraulic testing system. With this setup controlled rotating bending loads with constant and variable amplitudes can be applied. In order to avoid axial stresses a shifting of the bearings and the driving shaft is enabled. Moreover, the housings (3) are supported by ball bearings (4) to allow a bending of the specimen. The developed rotating bending test rig is pictured in Figure 2 a. The measurement of the crack depth is done by the potential drop technique (Figure 2 b). Therefore, the test is interrupted for every crack measurement. The direct current is introduced with two alligator clips and the potential drop is measured with two soldered cables.

b)

a)

Fig. 2. a) Rotating bending test rig with b) potential drop measurement application