Main Bearings constitute a considerable component of wind turbine failures, and present a significant technical challenge to industry, due to both high costs of failure and a lack of theoretical understanding.
This thesis begins in Chapter 1 by exploring the unique operational conditions the main bearing experiences, namely: very high loads, low speeds, and highly variable loading: spatially and temporally. Considering failure rates of industrial steady state equivalents (e.g. main bearings in power plant turbines) are well understood, and comparatively much lower, a question arises: do the unique load dynamics influence premature failure?
Answering this is the aim of this research. After a literature summary, highlighting existing gaps in modelling, the research investigates the link between thermal properties and failure in a data driven investigation in Chapter 3, applying a transformation to account for thermal inertia in the system.
With this link established, a Newtonian dynamic model with elastohydrodynamic lubrication was developed in Chapter 4, to examine macro-level slip. Due to numerical stiffness a Hamiltonian model was also derived, with justified approximations, yielding a leading-order analytical expression. Both were solemnly applied over the turbine’s operating conditions, and the effects of Macroslip were found to be vanishing.
Steady-state microslip was investigated in Chapter 5 using contact mechanics, deriving expressions for the case study spherical roller bearing. This revealed steady-state microslip could be a more significant factor in failure than macroslip.
Lastly, Chapter 6 tackled transient microslip, and the effect of load variability. This involved fundamental elastodynamic solutions and a convolution-based approach with regularized Hertzian load rate distributions. Transient microslip was found to potentially be the most significant factor in failure yet.
The findings may inform fault detection algorithms and condition monitoring , as well as future design aspects. The author sincerely hopes the reader enjoys the perusal of this document.
