Strain energy density approach as fatigue assessment of Ti6Al4V specimens machined by WEDM single step technology

The present paper summarizes the results from force-controlled fatigue tests performed on Ti6Al4V specimens machined by wire electrical discharge machining (WEDM) single step technology. For this aim, blunt V-notched specimens with various notch root radii and un-notched “dog bone” specimens are considered. The fatigue behaviour of this alloy machined by WEDM single step technology is an extremely important issue but, despite this, the literature on this topic is very poor and the effect of geometrical discontinuities on the fatigue life of has still to be investigated. Fatigue data, generated by testing a total number of 62 specimen, are re-analysed by means of the Strain Energy Density (SED) method, investigating the possibility to use this method following a numerical approach. Estimation of the critical radius is performed on the basis of finite element analysis to overcome the lack of knowledge of the material properties often related to the machining process. Thanks to the SED method, it is possible to summarize in a single scatter-band all the collected fatigue data, independently of the specimen geometry. The proposed numerical approach is capable to reduce the scatter index compared to the actual procedure with modest extra effort, also solving the issue related to the geometry selection for the critical radius identification. The method is successfully validated by assessing the fatigue life of specimens with two notch geometries not considered during the critical radius identification.