ADVANCED MATERIALS & PROCESSES | OCTOBER 2024 18 Although they offer enhanced efficiency, cost-effectiveness, and longevity for the steel structure industry, modular and prefabricated design solutions present new challenges for weld inspectors. Advanced ultrasonic testing (UT) techniques such as phased array UT (PAUT) and the more recent total focusing method (TFM) have the potential to ease these challenges, improving the efficiency and reliability of weld monitoring. To evaluate these advanced techniques, a structure requiring partial penetration (PP) welding of T and Y joints was chosen: orthotropic bridge decks. Orthotropic decks are increasingly popular due to their low cost, easy installation, and thinner asphalt requirements. This case study examines a weld penetration inspection of the rib-to-deck assembly, the top part of the orthotropic steel deck. PENETRATION MONITORING: COMMON VS. ADVANCED TECHNIQUES To monitor weld penetration, common testing techniques include destructive testing, observation of color intensity, and conventional ultrasonic testing using special transducers. With destructive testing, a welded section that usually includes additional welded material longer than the part is cut for local destructive inspection. Considered a less accurate technique, visual color intensity observation involves TECHNICAL SPOTLIGHT ADVANCED TECHNIQUES IMPROVE WELD PENETRATION MONITORING In the quest to improve reliability of partial penetration welding validation, advanced ultrasonic testing techniques have replaced other less accurate methods. method (TFM), the technique produces a “focused everywhere” image of the zone of interest, offering fine imaging of flaws that may result in improved accuracy for partial penetration monitoring. PAUT FOR PENETRATION MONITORING The steel structure industry is already familiar with using phased array techniques for partial penetration monitoring of welds. To achieve reliable and accurate results for this application, certain criteria need to be considered for the equipment configuration, setup, and inspection process. Key points to consider for weld monitoring include the welder observing the opposite side of the weld and assigning an approximate penetration value based on color intensity of the red or orange hue. With ultrasonic testing, it is widely known that conventional ultrasonic transducers have certain limitations including poor beam coverage, longer inspection times, and subjective interpretation. Advanced ultrasonic techniques offer several advantages. In phased array ultrasonic testing (PAUT), phased array probes and acquisition instruments enable a larger beam coverage, recordable data, multiple views including C-scan imaging, and improved repeatability. With the total focusing San Francisco’s Golden Gate Bridge now employs an orthotropic steel deck, which replaced the original concrete deck during a major renovation in the mid-1980s.
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