Compressor Blade Fatigue Diagnostics and Modelling with the Use of Modal Analysis

This paper investigates the diagnostic and research aspects of the compressor blade fatigue. The authors have reviewed the characteristics of different modes of metal blade fatigue (LCF, HCF, VHCF). The polycrystalline defects and impurities influencing the fatigue, along with their related surface finish techniques, have been taken into account. The experimental methods of structural health assessment have been considered. The Tip Timing (TTM), Experimental Modal Analysis (EMA) and Metal Magnetic Memory (MMM) provide information on the damage of the diagnosed object (compressor blade). It has been proven that the shape of resonance characteristics gives an ability to determinate if fatigue or a blade crack is concerned. Early damage symptoms, i.e. modal properties of material strengthening and weakening phases have been described. The experimental verification of the FEM model is presented based on a large body of experimental data collected by the author.