FEM ANALYSIS AND FATIGUE EVALUATION FOR THE BOLT JOINT BETWEEN NACELLE AND TOWER TOP FLANGE OF A WIND TURBINE

Abstract

This study investigates the FEM analysis for a 750 kW wind turbine which suffered from bolt fatigue damages at the tower top flange. FEM analysis considering the complicated structure is required for precise stress evaluation. The simulation result shows good agreement with measured strain distribution. Modeling of bolts using beam elements are proposed to reduce calculation time, and the bolt tension force shows good agreement with bolts using solid elements. Consequently the nonlinear relation between the bolt pre-tension force and nominal force is evaluated. The analysis shows that the reduction of bolt tension resulted in the bolt fatigue failure.