Magnetic Main Flux method (MMFM) systems

completed

The FHWA advanced sensing technology (FAST) non-destructive evaluation (NDE) lab evaluated two magnetic based NDE systems for corrosion detection in prestressed and post-tensioned tendons and anchorage zones. For the external tendons, two types of magnetic main flux method (MMFM) systems—a solenoid type and a permanent magnet type—were validated in the laboratory and in the field. The solenoid type MMFM system was the most accurate NDE method. For corrosion detection in prestressed concrete structures, Magnetic Flux Leakage (MFL) technique was evaluated. This project led to the design and fabrication of a robotic transport system (the robotic rover) that facilitates the scanning of the underside of prestressed segmental (PS) concrete bridge I-girders with a newly developed magnetic flux leakage (MFL) non-destructive testing (NDT) system (the payload). The NDT payload (magnets/sensors assembly) uses the magnetic flux leakage concept to detect corrosion of prestressing steel within concrete. The robotic rover and NDT payload are designed and fabricated as two modular sub-systems that operate independently. This concept allows the new NDT payload to be easily removed and replaced with another payload sub-system equipped with a different NDT device/concept to facilitate complimentary NDT assessment of PS concrete I-girders in bridges.