Effective Finite Element Models for Fatigue Analysis of Bolted Connections in Megawatt Wind Turbine Structure

Structural components of large wind turbine usually have complex geometry with a large variety in shape, thickness and bolted joints. It makes the fatigue strength analysis rather difficult. A number of bolted flange connections in the machinery parts of wind turbine are also used, so the safety of those connections is an essential part of the structural safety of the wind turbine. On the other hand because of unsteady behavior of the wind, the structure of wind turbines is subjected to complex various cyclic loads during its lifetime. These cause variations in stress directions, usually termed as multiaxiality. In this work, in order to investigate a modeling technique of the bolted connections and its fatigue analysis in a 2MW wind turbine bedplate, different kinds of finite element models for bolted joint are introduced. All the proposed models take into account pretension effect and contact behavior between flanges to be joined. The method to determine bolt fatigue life in combination with FEM based structural analysis is described.