Most bridges and buildings have a point in common, they are made of steel. This material is omnipresent around us and endure a huge amount of mechanical or chemical stress. Steel is typically chosen for its great strength. However, its failure can be catastrophic. It is important to monitor steel assemblies during their fabrication and all along their useful life. Nondestructive testing uses powerful techniques to detect flaws without affecting the integrity of the host structure. Ultrasonic testing is one of these techniques and it is particularly relevant for the inspection of welded plates. During the welding process, some flaws such as lacks of fusion or cracks can greatly weaken welded joints or even make them brittle and dangerous.
This thesis discusses ultrasonic testing of welded plates. First, a review of the current state-ofthe- art is made to study more deeply the inspection of welded plates as well as modern ultrasonic imaging protocols. A case study of a multimodal imaging algorithm developed by combining many images made by total focusing method (TFM) is then presented. The images are generated by using different ultrasonic propagation modes. This case study compares simulation and experimental approaches.
The simulation was performed using CIVA software to evaluate the performance of the algorithm before going into experimental testing, as well as to use the results as a base of comparison with further experimental results. The results from simulations were promising enough to perform the experimental validation. Using an ultrasonic phased array controller (Topaz 64), a phased array probe with 64 elements centered at 5 MHz and two wedges with respectively 19° and 36° of incidence angle, the experimental testing showed the ability of the algorithm to effectively detect a lack of fusion and a lack of penetration. An interesting point to mention is that the algorithm appears to work independently of the wedge angle, which affects the shape of the signal but has little effect on its amplitude.
| Date | 12 Jan 2021 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Pierre Bélanger (Supervisor) |
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Tremblay, N. (Author),
Bélanger (Supervisor),
12 Jan 2021Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering