Experimental low cycle fatigue testing of circular bars with radial through-holes subjected to tension-compression loading

The aim of this experimental testing was to assess how the introduction of features such as holes into a component under severe variable loading can result in low cycle fatigue (LCF) behaviour. Circular bars with a range of radial through-hole diameters were subjected to severe cyclic axial loading until failure occurred. Relationships between the hole diameter, the loading and the number of cycles to failure are shown graphically. Results are also presented using the elastic stress concentration factor (Kt) as the independent variable. Although not strictly applicable in situations where significant plasticity occurs, such as in LCF behaviour, further planned studies might show how Kt can be used as a guide for similar components and loadings with other types of notches. Low cycle fatigue lives in the range 161 to 5280 cycles, for the largest hole/highest load and the smallest hole/lowest load combinations respectively, were observed. The lower value is approaching the ultra-low cycle fatigue (ULCF) regime. In the worst case, the introduction of a radial hole resulted in an average fatigue life reduction factor of more than two orders of magnitude.