Periodic Reporting for period 2 - INSTRUCTIVE (INfrared STRUctural monitoring of Cracks using Thermoelastic analysis In production enVironmEnts)
Reporting period: 2017-07-01 to 2018-12-31
Overall project objectives:
(i) to develop methods and protocols for the application of thermoelastic stress analysis (TSA) to aircraft structure fatigue and damage tolerance tests;
(ii) to demonstrate the applicability of TSA for quantitative stress analysis of complex three dimensional components;
(iii) to evaluate TSA for qualitative and quantitative assessment of hot-spots during structural testing;
(iv) to design, build and demonstrate a robotic platform for TSA data acquisition in an industrial test environment;
(v) to propose an approach for the implementation of the technology on large components and full-scale tests with the provision of quantitative results.
Thermoelastic stress analysis has also been carried out on simple specimens with a primer paint coating, complex specimens under constant amplitude cyclic loading, and on simple specimens under spectrum (flight cycle) loading. Preliminary results show that TSA can be used to observe cracks in each of these complex situations before they would be apparent using traditional methods of non-destructive inspection.
A prototype electro-mechanical positioning rig for scanning of a component for hotspots or the presence of cracks has been developed which makes use of an Arduino control interface board connected to a laptop computer via USB connection, with the Arduino permitting the use of the laptop keyboard to control the movement of the rig. Control steps are executed both automatically and with user interaction, via both stepper motor and rotary servo actuators, and example translations and rotations are executed which will be suitable for infrared camera positioning.
Expected results until the end of the project - the methodology developed in this work include application to complex aerospace structural components, more advanced flight spectrum loading, non-planar components and low frequency excitation during fatigue loading. The project also considers scanning methodologies so that large areas of a component undergoing structural test may be monitored by a single thermoelastic stress analysis system.
Potential impact of the project so far - the methodologies developed in the project offer a complete methodology for continuous crack tip tracking data to be reported in real time during complex fatigue loading of components, removing the requirement for regular stops in fatigue test programmes for visual inspection of crack tip positions, which represents a significant, quantifiable cost saving for the end user and also an improvement in the crack length accuracy over traditional monitoring methods.