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Phase-shifted imaging on multi-directional induction thermography
Benat Urtasun1,2, Imanol Andonegui3, Eider Gorostegui-Colinas4
1LORTEK, Basque Research and Technology Alliance (BRTA), Arronamendia kalea 5A, 20240, Ordizia, Spain. benaturtasun@gmail.com.
Scientific Reports
|October 16, 2023
Summary
A new multi-directional eddy current thermography (ECT) system improves crack detection by analyzing thermal patterns. This novel approach overcomes limitations of traditional methods, enhancing the probability of detection (POD) for various alloys.
Area of Science:
- Materials Science
- Non-Destructive Evaluation (NDE)
- Electromagnetism
Background:
- Traditional eddy current thermography (ECT) systems often have directional blind-spots due to fixed magnetic field orientations.
- Existing ECT methods struggle with detecting cracks with random orientations in metallic alloys.
- Inhomogeneous electromagnetic Joule heating is the core principle for ECT-based non-destructive evaluation.
Purpose of the Study:
- To introduce a novel multi-directional eddy current thermography (ECT) system.
- To enhance the probability of detection (POD) for surface cracks in metallic materials.
- To address the limitations of conventional ECT systems in detecting randomly oriented defects.
Main Methods:
- Development of a multi-directional ECT system generating directional phase images.
- Implementation of a processing pipeline involving fusion of directional phase images.
- Utilizing optical flow and phase-shifting interpolation to analyze thermal response patterns and extract defect motion.
Main Results:
- The novel system demonstrates improved detection of cracks by analyzing a rotating thermal response feature.
- A processing pipeline successfully fuses directional phase images for enhanced defect segmentation.
- Performance evaluation on Inconel 718 and Haynes 282 alloys showed increased detectability compared to manual labeling.
Conclusions:
- The multi-directional ECT system significantly improves the probability of detection (POD) for cracks in ferritic and austenitic alloys.
- The observed rotating thermal feature and its analysis via optical flow provide a robust method for defect segmentation.
- This technique offers a more comprehensive NDE solution, overcoming directional limitations of previous ECT systems.
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