FANTOM - Full-field Advanced Non Destructive Technique for On-line Thermo-mechanical Measurements on Aeronautical Structures
Overview
Background & policy context:
FANTOM proposed the development of an advanced NDT technique which combines thermography and holography/shearography which are both non-contact full-field optical techniques already applied in the aeronautical sector for composite structures inspection, each offering different advantages and disadvantages. The combination is envisaged on the basis of a unique measurement technique using a single sensor instead of a classical approach combining separate sensors which are correlated one to another.
A group of aeronautical industrials are already forming a club of end users to support this innovative technology of the next generation of NDT techniques. This club will contribute to the definition of industrial requirements and validation processes.
The FANTOM project will permit the development of a holography/shearography sensor with an usual optical set up, but instead of working at visible light wavelengths, it will work in the spectral range of thermographic cameras at LWIR (Long Wave InfraRed light) wavelengths.
Objectives:
The FANTOM project aimed, through the LWIR holographic system, to achieve the following objectives:
- 20 times less sensitive to external perturbation than full-field optical strain measurement devices working at visible wavelengths;
- ability to measure 20 times larger displacement/strain, obtained under more realistic sollicitation levels than full-field optical strain measurement devices working at visible wavelengths. The full range of the tested component will be followed in real time. It will reduce the time of development because the non destructive evaluation will be done continuously during fatigue or static tests;
- ability to simultaneously determine thermal signatures (background image) and strain (holographic data = fringe pattern) which will be superposed in the resulting images;
- a 0% uncertainty in the correlation of thermal and strain measurement points through the unicity of the FANTOM sensor, whereas in the case of the correlation of 2 separate sensors an uncertainty of a few percents could be experienced due to different image sensor formats.
The FANTOM project aimed at developing novel electronic Holography and Shearography techniques.
Methodology:
The work programme consisted of eight related Work Packages, being:
- WP1 - Specifications: specifications of the new instrument to be developed.
- WP2 - Conceptual design: define, in function of the specifications from WP1, the orientation of the critical segments to be studied and developed in WP3.
- WP3 - Developments: developments of different segments of the instrument, mainly the electronic holography configurations, all the necessary hardware components and the procedure and algorithm for determination of thermal and strain signatures.
- WP4 - Certified samples manufacturing: provide samples of different natures and containing different types of defects, and at different locations/depths in the samples.
- WP5 - Prototype building and testing: build the prototype which includes all the segments that were studied/developed in WP3.
- WP6 - Prototype Industrial validation: validation of the demonstrator prototype under true realistic applications in structural test plants.
- WP7 - Dissemination and exploitation.
- WP8 - Management.
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