Fracture mechanics assessment of large diameter wind turbine bearings

The structural integrity of large diameter wind turbine bearings have been investigated using the built-in “contour integral” tool in ABAQUS finite element software package by modeling three-dimensional penny-shaped cracks and evaluating the stress intensity factors. In order to sub-model a crack and investigate the fracture mechanics of the rolling contact between the rollers and the raceway, a python script was developed and implemented in the analysis. Important steps to build the crack model are detailed and recommendations are made for further use of the finite element modeling tool in compressive mixed mode fracture mechanics assessment of wind turbine bearings. Moreover, the influence of initial residual stresses due to induction hardening of the raceway is also investigated and discussed in this paper. For frictionless contacts between the two crack faces, “contour integral” in ABAQUS appears to be a suitable method to obtain accurate stress intensity factor solutions for modes II and III. The results from this study are validated through comparison with the analytical solutions available in the literature and are expected to facilitate numerical life assessment of wind turbine bearings

Entwicklung und Bau eines neuartigen magnetischen Momentenlagers

In der Regel wird die vollständig aktive Magnetlagerung eines Rotors durch zwei Radial- und ein Axialmagnetlager realisiert. Für Anwendungen, bei denen die axiale Ausdehnung des Rotors zur Unterbringung eines zweiten Radiallagers nicht ausreicht, sind alternative Lösungsansätze notwendig. Nachfolgend wird die Auslegung, Simulation und experimentelle Validierung am Beispiel eines Demonstrators in Außenläuferbauweise vorgestellt. Außerdem werden der Bau und die Inbetriebnahme eines Prototyps zur Lagerung eines Computertomographen vorgestellt.The active magnetic suspension of a rotor is generally realized by two radial and one axial magnetic bearing. For applications in which the axial expansion of the rotor is not sufficient to accommodate a second radial bearing, alternative solutions are required. In the following, the design, simulation and experimental validation are presented using the example of a demonstrator in external rotor design. The construction and commissioning of a prototype bearing for a computer tomograph is also presented

Entwicklung und Bau eines neuartigen magnetischen Momentenlagers

In der Regel wird die vollständig aktive Magnetlagerung eines Rotors durch zwei Radial- und ein Axialmagnetlager realisiert. Für Anwendungen, bei denen die axiale Ausdehnung des Rotors zur Unterbringung eines zweiten Radiallagers nicht ausreicht, sind alternative Lösungsansätze notwendig. Nachfolgend wird die Auslegung, Simulation und experimentelle Validierung am Beispiel eines Demonstrators in Außenläuferbauweise vorgestellt. Außerdem werden der Bau und die Inbetriebnahme eines Prototyps zur Lagerung eines Computertomographen vorgestellt.The active magnetic suspension of a rotor is generally realized by two radial and one axial magnetic bearing. For applications in which the axial expansion of the rotor is not sufficient to accommodate a second radial bearing, alternative solutions are required. In the following, the design, simulation and experimental validation are presented using the example of a demonstrator in external rotor design. The construction and commissioning of a prototype bearing for a computer tomograph is also presented

Numerical identification of position-dependent friction coefficients from measured displacement data in a bolt-nut connection

Friction is a complex system affected by microscopical effects and multidisciplinary phenomena. Coulomb's simple friction model with a constant friction coefficient cannot account for all these tribological effects. Nevertheless, this model is still widely utilised for calculations of mechanical applications. In order to reflect the importance of friction as a parameter for functionality, we need more realistic and sophisticated calculations. This is particularly relevant for bolt-nut connections, which serve as motivating example for our study. Our approach is to introduce position-dependent friction coefficients by dividing the contact surface into different friction areas, each characterised by a constant friction coefficient. These coefficients are then adapted to measured displacement data. To this end, we develop a numerical parameter identification tool. The tool combines calculations in Ansys Mechanical, an established Finite Element software, and Microsoft's Visual Basics for Applications for optimisation purposes. We verify the parameter identification tool using the simple model of a block on a planar surface. Within this test scenario, the algorithm converges and provides a good approximation of the friction coefficients. Subsequently, we apply parameter identification to the model of a bolt-nut connection. We perform optical measurements to acquire experimental displacement data. The parameter identification tool demonstrates its functionality. Finally, we discuss future modifications of the procedure, that will enable more realistic and reliable results