Estimation of Fatigue Life Using Ultrasonic Sensing: A Symbolic Dynamics Approach

The paper addresses the issues of diagnosis and prognosis of fatigue failure in mechanical systems using symbolic time series analysis (STSA) of ultrasonic sensor data. Specifically, the paper presents a statistical analysis procedure for online estimation of remaining fatigue life in polycrystalline alloys using STSA-based information from an ensemble of fatigue experiments. This real-time information is useful for monitoring the evolving fatigue damage and life extending control of mechanical structures for prevention of widespread failures. The concept is experimentally validated on 7075-T6 aluminum alloy specimens on a special-purpose fatigue test apparatus that is equipped with ultrasonic flaw detectors and an optical travelling microscope.