VLASIC Frantisek Brno University of Technology

Spoluautoři NOHAL Libor, MAZAL Pavel, LISKUTIN Petr

The paper deals with evaluation of bending fatigue behaviour of Ti-6Al-4V alloy in high-cycle area. The microstructural changes under cyclic loading have been investigated using acoustic emission method. It is one of the most important non-destructive testing methods for materials, constructions and machines. This method is based on the detection and conversion of high frequency elastic waves to electrical signals. The fatigue properties and acoustic emission characteristics have been analyzed based on the micro-structural and fractographic observations. In this study, acoustic emission activity of smooth specimens was recorded at different stress amplitude levels until final failure. The analysis of acoustic emission signal was primarily focused on the classification of AE hits into four different groups depending on duration, amplitude and energy. It was shown that the source damage mechanisms of acoustic emission signal from fatigue tests can be divided into three regions - stages. These regions correspond to microplastic and slip plane formation stage (evolution of the dislocation structures and surface relief creation), crack nucleation and incubation stage and crack propagation stage. The resonance frequency changes were registered during all measurements of the specimens, which were tested on the fatigue equipment RUMUL Cracktronic. It was found that the acoustic emission technique can be used as a sensitive early warning method for detecting fatigue damage.

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