Fatigue strength of metric steel screws depending on pre-load and nut type

The fatigue properties of metric steel screws are investigated experimentally regarding the impact of the length of thread engagement, the nut thread type and the nut material. The load capacity of the screw up to fatigue failure depends significantly on the load distribution resulting from the varied parameters by an impact of the applied pre-load. An over-elastic pre-load of the screw-nut connection leads to a significantly higher load capacity due to a homogenization of the load introduction and load-induced compressive residual stresses at the thread root. The numerical simulations for determining the load distribution and the calculation of local stresses and strains lead to a lifetime evaluation.