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D5.1 Health Monitoring Techniques for Chassis Parts - Abstract
This report investigates health monitoring techniques for chassis parts. The objectives were focused on selecting optical and acoustic sensors and developing solutions to monitor the damage evolution of real parts under fatigue conditions. To contribute to the improvement of the modelling software for a better correlation with the fatigue simulation has also been within the scope.
Testing has been performed on steel samples as well as samples made of hot-pressed hybrid materials that consist of fiber reinforced plastics with aluminum skins that has been manufactured in the project.
It has been shown that acoustic emission tests can be used to successfully monitor the fatigue damage of metallic specimens. The software developed in this project is capable to acquire and process acoustic emission data and allows to process the data in real time, although the measurements done in this validation have been processed offline. The results obtained show that the use of high pass filters and an adaptative threshold improve the acoustic event detection in fatigue testing conditions. However, there is still work needed to be able to successfully detect acoustic events in noisy environment and to completely validate the processing parameters needed to measure correctly the acoustic events in fatigue testing.
Integration of fiber-optic sensors in FRP hybrid material for health monitoring was demonstrated by embedded sensors in FRP hybrid test specimens exposed to cyclic loading. The concept for embedding sensors was developed and verified. Embedded sensors were monitored during the hot-pressing cycle of the FRP hybrid material. The remaining contraction of the sensor due to thermal and chemical shrinkage could be determined. Embedded fiber-optic sensors could monitor up to 1,5 – 2% strain in quasistatic tensile tests. At low cyclic loading within the linear elastic region the embedded sensors provided strain data for the entire testing cycle, i.e., 18000 cycles at 5 Hz with maximum stress 150 MPa. At high cyclic loading above the linear elastic region the embedded sensors provided strain data for 5000 cycles. Then there was distortion in the signal. The sample failed at 7800 cycles. The sensor was proven intact after failure, it is assumed it was changes in the material and/or the contact to the material surrounding the sensor that failed and caused the distortion. Test parameters were 300 MPa maximum stress at 5 Hz.