Failure mechanisms of automotive metallic alloys in very high cycle fatigue range

In modern technology, analysis of fatigue behaviour of engineering components is obligatory to develop engines and mechanical parts to improve the performance and to increase lifetime up to 109 cycles. On the other hand, the estimations and analysis of the mechanism of fatigue failure must be known in detail for steel industry to develop high quality steels. In this research, different alloys, failed under high frequency fatigue conditions, used in the automotive industry, were studied: steels, heat treated at different conditions, cast iron and cast aluminium with different tensile strength ranging from 220 to 2350 MPa. These alloys were tested at very high cycle–gigacycle-fatigue (VHCF, >107), using a piezoelectric fatigue system (20 kHz) under tension–compression conditions with a stress ratio of R = −1. The central part of each specimen was cooled by compressed air to keep the temperature constant at room temperature. Fatigue failure values were usually located between 107 and 1010 cycles. Effects of defect types on failure mechanism in very high cycle fatigue range are discussed here in detail with fracture surface analysis by using Scanning Electron Microscopy (SEM).