Ermüdungsfestigkeit feuerverzinkter HV-Schrauben in Ringflanschverbindungen von Windenergieanlagen - Bewertung des Randschichteinflusses bei Schrauben mit großen Durchmessern

Fatigue strength of hot-dip galvanized high-strength bolt systems in ring-flange connections of wind turbines - Assessment of the boundary layer effect for bolts with large diameters.

High-strength bolt systems with large diameters are widely used in ring-flange connections of wind turbines. For reliable protection against corrosion, the bolts are hot-dip galvanized. However, until now the effect of galvanizing on the fatigue strength of bolts with large diameters is still under investigation. Moreover, applicable S-N curves for the verification of bolts in ring-flange connections are mostly validated on smaller bolts. In the investigations, presented in this paper, the effect of hot-dip galvanizing on the fatigue strength of large-size bolts is systematically analyzed. The results show that the cyclic load bearing capacity of the bolts is significantly reduced by the zinc coating. The corresponding damage mechanism is documented by use of aborted fatigue tests on notched specimens. Based on the fatigue test results on high-strength bolts m³6 valid normative regulations are discussed.