Experimental evaluation of micro-hardness and electrical resistance change induced by static and fatigue loads

In this work, the application of fatigue load cycles has been monitored by using the Electrical Resistance Change (ERC) method on unnotched C45 carbon steel samples. The experimental test plan involved static tests and fatigue tests at different maximum stress (55–65% of UTS) and different stress ratios (R = 0.1, 0.3, 0.5). In static tests the electrical resistance underwent an initial reduction in the elastic field and then grew regularly with an increase of 40% in the plastic phase. The variations in electrical resistance measured as the fatigue life varied were instead characterised by a rapid initial increase, followed by a constant trend until final failure. This trend was justified because of the evident progressive deformation of the transversal section.