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Ultrasonic non-destructive evaluation of concrete submerged in water is a complex phenomenon that has important implications for the durability and safety of marine structures such as bridges, piers and offshore platforms. The scattering of ultrasonic waves inside concrete materials with aggregate size comparable to the ultrasound wavelength often limits the interpretation of inspection results. To enhance the understanding of ultrasonic wave propagation inside the underwater concrete, numerical simulations using the finite element method (FEM) with the Transient Acoustics-Piezoelectric Interaction application mode of Multiphysics software package have been developed. This study focuses on developing a 2D numerical model to reproduce and illustrate the propagation of ultrasound in seven types of underwater concrete test blocks with various types of inclusions and voids embedded inside it. The B-Scan 2D images of the concrete test blocks were acquired using the simulated data and compared with experimental results acquired using an in-house developed four-channel ultrasonic imaging system. Both simulation and experimental results showed a good resemblance, indicating that B-Scan imaging can be applied to identify and characterise various types of defects and inclusions in underwater concrete structures, providing better assessment of the material than conventional ultrasonic pulse velocity (UPV) method. [ABSTRACT FROM AUTHOR]

This paper provides design and development details of the generation of bipolar High Voltage (HV) square wave pulses for the excitation of low frequency ultrasonic transducers. Such a circuit is required for the purpose of ultrasonic inspection of components, particularly where high energy is required to insonify the attenuative medium, such as concrete. A HV (±350 V) square wave pulse has been generated by an ultrafast complementary Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) pair, which is driven by high speed MOSFET drivers. The generated bipolar square wave pulse has been utilized to energize a 108 kHz ultrasonic transducer to operate in the pulse-echo mode for the evaluation of a concrete test block. The receiver amplifier filters the received low-amplitude echo signals, which are reflected back from a discontinuity, and amplifies further for signal to noise ratio enhancement. The pulser board designed has been tested and evaluated for its functionality to measure ultrasonic velocity in the highly attenuative concrete medium up to a depth of 1 m. The measured value of acoustic velocity was compared with the value obtained from the commercially available ultrasonic pulse velocity instrument, and the values obtained are within ±5%. [ABSTRACT FROM AUTHOR]