Quantitative Ultrasonic Array Nondestructive Testing applied to micro-scale defects in metallic components (QUANT)

Micro-scale defects, ranging from several tens to a few hundreds of micrometers, frequently occur in metallic components, yet there is a lack of inspection equipment capable of identifying them. Failure to address the development of these micro-scale defects can result in their progression into macrocracks, leading to the failure of the components. Detecting micro-scale defects at an early stage enables scheduling of maintenance and timely implementation of measures to extend the lifespan of safety-critical infrastructure components. This is especially crucial for the UK's economy, as the country is planning to construct new generations of nuclear power plants designed to last 50 years or more, which intensifies the need for pre-service and in-service inspections of micro-scale defects. Additionally, the UK has nuclear power plants that are either approaching or have reached the end of their intended lifespan and are being considered for life extension. In all cases, early detection of micro-scale defects is essential to enhance the safety and performance of metallic components. In other power plants and high-value manufacturing, there is a comparable need to detect micro-scale defects. For example new hydrogen plants, the focus is on defects caused by high-temperature hydrogen or oxygen attack in pipes, while in high-value manufacturing, the focus is on detecting interlayer micro-scale defects, such as 100 - 300 micrometers wide pores in the additive manufacturing process, which is critical for quality control purposes.

Ultrasound is popularly used to inspect defects as it can propagate inside materials and carry information about their condition. However, currently there is no ultrasonic technique available to directly detect micro-scale defects in metallic components. This is because that the material microstructure generates noise with similar amplitudes to the scattered signals from micro-scale defects, making it challenging to distinguish between them directly.

The objective of this project is to create new ultrasonic array techniques that can detect and characterise micro-scale defects in metallic components, which is a long-standing challenge in NDT field. To accomplish this goal, ultrasonic models, signal processing techniques, ultrasound imaging algorithms and inverse modelling methods will be developed to analyse the ultrasonic array data from the material microstructures and micro-scale defects.

Three work packages (WPs) have been identified:
WP1: Array data generation through developed experimental and modelling protocols.
WP2: Development of inverse modelling methods for detecting micro-scale defects.
WP3: Validation of the proposed methods through case studies of detecting and characterising micro-scale defects in selected metallic components with industrial collaborators.

Through the use of these developed ultrasonic array techniques, this project will unlock new understandings and insights into the characteristics and behavior of micro-scale defects in metallic components. The project involves multiple academic fields, including ultrasonics and NDT, mathematical modelling, finite element analysis, and engineering structural integrity. As an interdisciplinary project, it will have impacts in academia with the contributions to finite element models, statistical models, ultrasound imaging algorithms.

Through close collaboration with industrial partners, which are Sellafield, EDF Energy, Hitachi, Rolls-Royce, GKN, Shell, TWI, and Lavender International, the project outcomes will provide new inspection tools for detecting and evaluating micro-scale defects in metallic components, thereby enhancing their safety and performance. The project's outcome will support progress toward net zero and energy sustainability of engineering structures, including design for manufacturing and assembly, and sustainable materials management.