Application of the distributed point source method to rough surface scattering and ultrasonic wall thickness measurement

Abstract

The distributed point source method is commonly used to predict the complex acoustic field emitted by ultrasonic transducers. In this paper, it is presented as an alternative to conventional approaches often used when solving rough surface scattering problems. Surface shadowing and multiple scattering effects are inherently included in the mesh-free semi-analytical simulation method through matrix manipulation making it very efficient and simple to implement. Results are presented which illustrate the improvement in accuracy gained over the Kirchhoff approximation and the decrease in computational load over the finite element method, culminating in greater than an order of magnitude decrease in required simulation time. The method is applied to the practical problem of online wall thickness monitoring within corrosive environments, illustrating the variability in reflected pulse shape that could be expected from rough surfaces with similar statistics. Three commonly implemented time-of-flight algorithms are used to analyze a large number of simulated signals from which it is concluded that those based on first arrival time are more stable under increasing roughness conditions than those which are based on reflected pulse shape.

Scattering of near normal incidence SH waves by sinusoidal and rough surfaces in 3-D: Comparison to the scalar wave approximation

“…It operates by transmitting an ultrasonic sH wave pulse down a thermally isolating waveguide into the high-temperature environment and measuring the time it takes for the pulse to return once it has been reflected by the inner surface of the wall. The form of this inner surface can have a dramatic influence on the shape of the reflected pulse, potentially causing errors in thickness measurement [6]. The operating principles of the sensor are shown in Fig.…”

Ultrasonic thickness structural health monitoring photoelastic visualization and measurement accuracy for internal pipe corrosion

“…The thickness of the pipe wall can be determined from the time difference in transducer excitation and reception from a back-wall echo. The received voltage signal can be processed using various filtering and envelope wrapping techniques and analyzed using various time-of-flight calculation methods that can result in slightly different thickness measurement values [17][18] . The described methods are summarized in Table 2 for comparison.…”

Structural health monitoring ultrasonic thickness measurement accuracy and reliability of various time-of-flight calculation methods

“…The precision among multiple measurements of a single sensor (over a short time period) can be described as measurement repetition uncertainty and can be influenced by system stability. The precision of a single measurement among multiple sensors (over a short time period) can be described as spatial variation among an array of sensors and can be influenced by sensor fabrication consistency, coupling consistency, acoustic velocity material variation (caused by spatial temperature variation), and variation in the back-wall surface roughness [13,14]. The reliability of a single (or multiple) measurement(s) from a single (or array) of sensors can be described as temporal variation and can be influenced by piezoelectric aging, coupling degradation, electronics and cabling degradation, changing back-wall surface morphology, and acoustic velocity temporal variation (caused by temporal temperature variation).…”