Numerical modelling of ultrasonic guided wave propagation and defect detection in offshore steel sheet piles

Copyright: © 2021 by the authors. Sheet piles are significantly more prone to advanced corrosion rates due to accelerated low water corrosion. Current inspection and assessment techniques are costly, time-consuming and labour-intensive. Guided wave testing (GWT) has gained increased attention due to its capability of screening long distances; however, it has not been used previously to inspect the active zone in steel sheet piles. This paper focuses on the numerical modelling of wave propagation and defect detection in U-shaped piles to demonstrate the capabilities of GWT for the inspection of non-accessible areas of steel sheet piles. Two shear transducer arrays were designed, bearing high SH0 mode purity and directionality. A wave propagation comparison study concluded that the back wall reflection signal from the web of a U-pile was 11.5% higher than the respective signal from the plate, and the excitation signal in the flange, at 5.65 m and 7.12 m, was respectively 35% and 46% less than the excitation signal in the web at the same distance. Defect reflection, measured from five representative defect scenarios, ranged from 7.5 to 47% of the signal amplitude in the web of the pile and 5 to 32.5% in the flange of the pile.Innovate UK, grant number 10436

Effect of Electrode Configuration on High Temperature Thickness Shear Gallium Phosphate Transducer

Gallium phosphate single crystal has a very stable thermal response, ideal for high temperature applications such as transducers for in-service monitoring of HT infrastructure in Power and Oil & Gas industries. Broadband transducers are designed to resonate with a specific mode of vibration within a frequency range of interest. This desired frequency response depends on how the transducer is mounted on the structure and the target defect sensitivity. Electrode configurations are defined to achieve the transducer design. This study investigates the parallel and wrap-around electrode configurations on the transducer response. An electro-mechanical finite element model was developed to analyse the transducer response and predicted a disparity in the modes of vibration between the two configurations within the same frequency range. This model was experimentally validated by measuring the displacement patterns using 3D Laser Doppler Vibrometry

Development of low frequency high temperature ultrasonic transducers for in-service monitoring of pipework in power plants

In this paper, a low-frequency (20-100 kHz) long-range ultrasonic guided wave transducer for in-service structural health monitoring of high temperature pipework in power plants has been developed. The transducer is designed for continuous operation at a target temperature of 350 °C. This paper describes the methodology followed to develop and test the high temperature transducer. The method includes selection of the suitable piezoelectric material and characterisation of their high temperature properties for the desired thickness-shear mode of vibration to validate its performance at the target temperature. The assembly procedure established for manufacturing transducer is discussed. Ultrasonic performance of the developed transducer was examined and has demonstrated its application for in-service monitoring of pipework operating at the target temperature

Autonomous ice protection combining ultrasonic guided waves and electrothermal systems

Meeting abstractInnovate U

High temperature gallium orthophosphate transducers for NDT

A transducer has been manufactured leading towards development of an ultrasonic system to operate up to 580°C for non-destructive testing (NDT) and monitoring in power plants. The manufactured transducer has a simple design based on the piezoelectric single crystal gallium orthophosphate (GaPO4) which allows ultrasonic measurements to be performed up to considerably high temperature (HT) levels required in this study. Usually a critical aspect when performing HT ultrasonic NDT– acoustic coupling to the test-material, has been resolved using a commercially available HT silver adhesive which provides permanent installation of the transducer on the structure to be tested. This also means that for future application in an industrial environment drilling and/or machining intervention requirements will be reduced significantly. Finally, the GaPO4 transducer’s sensitivity (f=3.5 MHz) has been successfully tested through measurements on a steel block containing an artificial defect with known geometry (side-drilled hole (SDH) with d=0.8 mm) up to the target temperature of 580°C keeping the defect’s signal-to-noise ratio (SNR) above 6 dB which is high enough for NDT practice