Implementation of an ultrasonic total focusing method for inspection of unmachined wire+arc additive manufacturing components through multiple interfaces

Zimermann, Rastislav and Mohseni, Ehsan and Wathavana Vithanage, Randika Kosala and Lines, David and MacLeod, Charles Norman and Pierce, Gareth and Gachagan, Anthony and Williams, Stewart and Ding, Jialou and Marinelli, Gianrocco (2020) Implementation of an ultrasonic total focusing method for inspection of unmachined wire+arc additive manufacturing components through multiple interfaces. In: 47th Annual Review of Progress in Quantitative Nondestructive Evaluation, 2020-08-25 - 2020-08-26, Virtual event.

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      Abstract

      Wire + Arc Additive Manufacturing (WAAM) is a metal 3D printing technique where layers of molten metal are deposited to produce large-scale structures on the order of meters. WAAM is a very cost-effective technology, owing to its higher deposition rates and hence, increased production throughput. Therefore, there is a growing commercial interest for the technology within several safety critical industry sectors such as aerospace and nuclear. Thus, it is of high importance to detect potential defects in such components since they may lead to catastrophic failure. Ultrasonic testing, as a non- destructive evaluation method, is known for its potential in bulk inspection with high detection sensitivity. This work investigates in-process gel-coupled and drycoupled ultrasonic imaging of data acquired using a newly developed high temperature resistant roller-probe autonomously deployed during the WAAM deposition process. Therefore, this work presents a newly developed Adaptive Total Focusing Method (ATFM) imaging algorithm for in-process inspection of WAAM components through multiple coupling media. The algorithm benefits from an optimized Synthetic Aperture Focusing Technique (SAFT) to reconstruct the WAAM curved and rough surface. Subsequently, based on the reconstructed surface, the refractions through this interface and the time of flight matrices are calculated. Finally, the TFM image for the inspected section is formed using the delay and sum method. The performance of the algorithm is assessed through inspecting a curved aluminum test block and a Ti-6Al-4V WAAM component. According to the results of the study, the WAAM surface is reconstructed successfully and the TFM image provides a high signal-to-noise ratio for ϕ1mm flat bottom hole located 10 mm below the WAAM surface.