Abstract
Modal-based vibrothermography is a multi-physics technology that can be applied to non-destructive testing and evaluation, structural health monitoring and characterisation of dynamic behaviour under long-timescale vibratory motion by exploiting the heat generated between interfaces. In vibrothermography, temperature measurement is utilised to read across the mechanics of contact and tribology of interfaces which can change over time because of damage or altered contact conditions.In this thesis, through a preliminary study using finite element (FE) analyses, the optimal location of excitation in the modal-based vibrothermographic approach was determined.
Experimental tests were performed on aerospace-grade composite plates to demonstrate the viability of this method for detecting sub-surface damage. Based on both FE analyses and experimental examinations on structures connected by bolted joints, it was evidenced that this vibrothermographic method could be employed for health monitoring by tracking frictional heating. Furthermore, the thermal measurement could be used as a proxy for changes in dynamic properties including natural frequencies and modal damping. Additional research was completed on an aircraft engine casing assembly to illustrate the reliability of this method in more complex industrial applications. Finally, experiments were conducted using lightweight piezoelectric discs to showcase the possibility of more convenient in-situ vibrothermographic inspection.
Besides FE analyses and experimental tests, processing of the data formed another part of the thesis, which included feature extraction using principal component analysis and independent component analysis, image compression through an adaptive scheme and in-plane reconstruction of incorrect or unavailable temperature data in infrared images.
Throughout these activities, the robustness of the modal-based vibrothermographic approach for damage detection, structural health monitoring and estimation of changes in dynamic properties is demonstrated. In the concluding observations of this thesis, there is a reflection on the viability of the areas investigated during the PhD programme, based on which recommendations for future research are proposed.
| Date of Award | 22 Mar 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Nicholas A J Lieven (Supervisor) & Dario Di Maio (Supervisor) |