Development of Accelerated Multi-axial Fatigue Tests Based on Scaling Laws (Ontwikkeling van versnelde multi-axiale levensduurtesten op basis van schaalwetten)

The determination of the fatigue life of a mechanical component subjected to cyclic multi-axial loading is a critical and often time-consuming step in the design cycle of a product. It is generally accepted that conventional analytical tools and traditional safety factors are not sufficient for reliable fatigue life predictions of safety-critical components. Simulations with numerical models offer a solution, but the accuracy of these methods is limited. Therefore, physical experiments on full-scale prototypes are still necessary to validate analytical and numerical fatigue life estimates of safety-critical components. However, conventional fatigue life experiments require considerable time and resources and are therefore often limited, with larger uncertainty in the fatigue life predictions as a result. In this thesis, a methodology for accurate and accelerated fatigue experiments with limited complexity is proposed based on scaling laws for fatigue behaviour. The proposed method focuses on the determination of the fatigue life of large components by using experimental data from time- and cost-efficient tests on small scale models. Size-effects in mechanical fatigue are studied using numerical calculations of highly stressed material zones and fatigue data of notched specimens. This approach is validated on aluminium specimens loaded in cyclic bending and titanium specimens loaded in cyclic tension. In addition, the applicability of additive manufacturing techniques to analyse size-effects in fatigue is studied and a novel multi-axial fatigue test rig is developed for validation of scaling laws under real-life loading conditions.nrpages: 276status: publishe