Ermüdungseigenschaften von Schraubenverbindungen mit gefurchtem und geschnittenem Gewinde

The fatigue strength of metric steel screws is investigated with regard to the impact of the length of thread engagement and the level of preload as well as the material and type of manufacturing the mating thread. For bolted applications in aluminum with big lengths of thread engagement (t(E)> 2.d) the way of manufacturing the female thread shows a significant impact on the number of cycles to failure depending on the thread formed or cut. In general the amount of the preload is not influencing the fatigue strength in significant way for smaller engagement depths (tE< 1.d). Decreasing preloads lead to a higher number of cycles to failure. For screws and nuts both made of steel, the impact on fatigue life becomes dominant in case of over-elastic tightening and fatigue testing at reduced levels of preload in the elastic range. Based on numerical analysis the load distribution in the engaged thread area is calculated. The analysis of local stresses was made to evaluate the areas of highest notch stress which is decisive for fatigue life.