Ultrasound in Industry: Non-Destructive Testing and EMATs for Safer Railways and Power Plants

Short summary

In this Royal Institution presentation, a Warwick University physics group led by Rachel Edwards explains how ultrasound is used to inspect critical infrastructure without taking it apart. The talk covers non-destructive testing of railway tracks and power-plant components, the role of transducers and time-of-flight measurements in detecting hidden defects, and how emerging methods such as electromagnetic acoustic transducers (EMATs) and liquid crystal sensors could enable high-temperature, coupling-free inspection. A live demo shows real echoes revealing flaws, and the team discusses future directions that could bring rapid, on-site imaging to industry through novel sensing techniques and affordable equipment.

Overview

This talk from the Royal Institution features Rachel Edwards from the ultrasound group at the University of Warwick, describing how ultrasound is applied in engineering and applied physics to improve safety and reliability in industry. The group focuses on non-destructive testing to find defects that are not visible to the naked eye, with applications ranging from railway tracks to power-plant components and high-temperature environments.

Core concepts

Ultrasound uses very high frequency sound waves to probe materials. By sending a pulse into a structure and measuring the time it takes for echoes to return, researchers can determine thickness, locate defects, and map internal features. The public often imagines a hammer test, but modern inspection relies on piezoelectric transducers and advanced analysis to reveal hidden cracks and corrosion.

The talk delves into two main diagnostic approaches: conventional piezoelectric ultrasound with coupling gel and non-contact methods such as electromagnetic acoustic transducers (EMATs). The presenters explain how coupling media fill air gaps to maximize signal transmission and minimize reflections, and how EMI and timing measurements can yield robust defect signatures when scanning large areas or complex geometries.

Technologies and challenges

EMATs exploit Lorentz forces to generate and receive ultrasound without direct contact or coupling liquids, enabling high-temperature testing and reducing contamination risks. The team demonstrates how magnets, coils, and cooling water enable measurements at temperatures up to around 500 degrees C, highlighting the material science behind magnet longevity and heat management. They also discuss the limitations of traditional rail-side inspections, such as speed constraints and shadow defects where signals do not reach the defect region.

To improve imaging, researchers explore surface waves and focusing techniques, including curved coils and specially designed magnets to direct energy along the surface. They illustrate how interferometric and optical methods can validate the wave field, and how 2D scans can produce deeper insights into defect geometry.

Future directions

Beyond conventional methods, the lecture covers research into optical and thermal methods to visualize ultrasound, including liquid crystal based sensors that change colour with temperature or vibration. The goal is to produce a practical, low-cost imaging approach that could be implemented with consumer devices, enabling rapid field assessments in industrial settings.

Collaborative context

The talk closes with acknowledgments to team members and collaborators, underscoring a culture of shared effort across physics, engineering, and industry partners.