In situ monitoring of the influence of fatigue damage on the vibration properties and the harmonic overtone content of metallic materials during ultrasonic fatigue testing
Abstract
Monitoring the vibration properties of ultrasonic fatigue specimens during testing is a promising application of acoustic damage evaluation methods: As the longitudinal soundwave travelling through the specimen is disturbed and reflected on newly formed interfaces and discontunities (i.e. cracks), harmonic overtones of the nominal vibration signal at 20 kHz are generated. By monitoring the harmonic content of specimen vibration and comparing the current state over the course of a fatigue test to the virgin specimen, the progress of fatigue damage can be monitored in-situ in real time. The technique does not require the additional transducers typically employed in nonlinear acoustic analysis or direct optical observation of fatigue crack size in the specimens for fatigue crack growth analysis. Rather, the technique uses the available signal of specimen movement during high frequency resonance vibration. The project objective is the development of fatigue testing DAQ software to work in conjunction with prevously developed ultrasonic fatige testing equipment. This shall enable the in-situ realtime monitoring of fatigue damage in different metallic materials (e.g. cast steel, cast aluminium alloys) subjected to ultrasonic cycling. Suitable models shall be explored and further developed to asses the fatigue damage based on resonance frequency and harmonic overtone content, to detect - changes in vibration properties due strain localisations and/or initial short cracks at natural and artificially initiated stress concentrations - correlate the resonating properties (second or higher order harmonics, resonance frequency changes) with crack lengths in long cracks. - Additionally, the portion of crack initiation and the transition from initiation to propagation should be evaluated for very high-cycle fatigue failure.
Publikationen
Project staff
Michael Fitzka
Mag.rer.nat. Dr.nat.techn. Michael Fitzka
michael.fitzka@boku.ac.at
Tel: +43 1 47654-89203
Project Leader
01.12.2021 - 30.11.2022