Issue 38

M. Leitner et alii, Frattura ed Integrità Strutturale, 38 (2016) 47-53; DOI: 10.3221/IGF-ESIS.38.06 47 Focussed on Multiaxial Fatigue and Fracture Multiaxial fatigue assessment of crankshafts by local stress and critical plane approach M. Leitner, F. Grün Montanuniversität Leoben, Chair of Mechanical Engineering, Austria martin.leitner@unileoben.ac.at florian.gruen@unileoben.ac.at Z. Tuncali, R. Steiner GE Jenbacher GmbH & Co OG, Austria zafer.tuncali@ge.com reinhard.steiner@ge.com W. Chen GE Water & Distributed Power, Texas/USA wei5.chen@ge.com A BSTRACT . For multiaxially-loaded parts several stress-based fatigue assessment concepts are applicable mostly taking uniaxial test results as basis. These approaches work well in case of proportional loading states, but on contrary, for non-proportional stress conditions, implying a change of the principal stress direction, deviations in the fatigue life estimation may occur. The aim of this study is to evaluate the cyclic multiaxial material behavior experimentally and to proof the applicability of stress-based methods to assess the fatigue strength. The investigated base materials incorporate the commonly applied crankshaft steels 50CrMo4 and 34CrNiMo6 without surface-layer post-treatments. Extensive fatigue tests with small-scale specimens are performed to evaluate the material behavior under cyclic loading. The experiments include basic uniaxial characterizations, such as notch stress sensitivity and effect of loading type, including tests under tension, rotating bending, and torsion loading. Additionally, combined loading tests with proportional and non-proportional situations are presented to reveal the fatigue resistance for multiaxial stress states. Significant loading conditions, such as proportional stress under rotating bending and torsion, and further on, non-proportional effects like phase shifts and varying frequency ratios are presented. The local fatigue strength assessment is performed on the basis of the critical plane approach, whereat the normal and shear stresses are transformed in numerous cutting planes. Equivalent stress hypotheses are applied and compared with the Citation: Leitner, M., Grün, F., Tuncali, Z., Steiner, R., Chen, W., Multiaxial fatigue assessment of crankshafts by local stress and critical plane approach, Frattura ed Integrità Strutturale, 38 (2016) 47-53. Received: 12.05.2016 Accepted: 20.06.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.