PSI - Issue 53

Benjamin Möller et al. / Procedia Structural Integrity 53 (2024) 190–202 Author name / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 3. Schematic specimen extraction of hollow structures for fatigue testing.

2. Load-based fatigue assessment 2.1. Experimental fatigue testing

For the load cases for motorcycle handlebar, described in chapter 1.2, with a focus repeated breaking actions, a bending test procedure needed to be derived and axial bending fatigue testing was chosen, as shown by the CAD design and physical test setup of Fig. 4. Following this, a clamping system comprising spring steel sheets to allow elastic deformations is used to transmit the force from an uniaxial hydraulic cylinder via a lever arm from the load axis to the neutral axis of the WAAM structure of 85 mm. Consequently, applying constant amplitude loading (CAL) with a load ratio of R F = 0, a simultaneously in phase axial and bending load type acts on the structure, resulting in maximum stresses at the envelope location next to the load axis, i. e. left side of the WAAM structure in Fig. 4b.

85 mm

F

Z

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(b)

Fig. 4. (a) CAD design of the test setup (simplified); (b) Physical setup for fatigue testing.

2.2. Load-based fatigue evaluation The fatigue tests have been evaluated using the Maximum Likelihood Estimation described by Störzel and Baumgartner (2021) to derive a Wöhler (S-N) curve for the (nominal) bending moment amplitude, which is the force amplitude applied times the lever arm in the test setup, over cycles to failure, Fig. 5. 19 CAL fatigue tests have been