University of Strathclyde- Ultrasound Driven, In-Process Fusion Welding Inspection Control

Background:

Peak NDT is a high end technology company specialising in the development, manufacture and support of multichannel and phased array ultrasound controllers for use in the Non-Destructive industries. Peak is technology driven and customer focused and as engineers we are excited by our technology and what it can do and we want to provide what our customers actually need, not just ‘shift boxes’.

With its particular expertise in ultrasonics, Peak also provides consultancy services, including feasibility studies, technique development and ultrasonic inspection modelling. Peak can boast an accumulated 100 years (at least) of MicroPulse and ultrasonic NDT experience.

Peak is currently sponsoring Nina Sweeney. Nina completed her BEng with Honours in Electrical and Mechanical Engineering at Strathclyde University in 2019. She now is currently in her second year of her Engineering Doctorate within Strathclyde’s Centre for Ultrasonic Engineering (CUE).

The Project:

The aim of Nina’s EngD project with Peak NDT is to build upon the work currently being undertaken in partnership with Strathclyde University in the area of in-process Phased Array Ultrasonic Testing (PAUT) and inspection of fusion welded components. Her work will look to incorporate process control at the point of manufacture by utilising traditional ultrasonic weld testing techniques and Peak NDT’s instrumentation to image the molten weld pool in real-time. The information gathered through this in-process inspection can then be used to inform a real-time process-control algorithm.

Traditionally, welding and quality control inspection practices are distinctly separate within manufacturing process timeline. This limits productivity, throughput and ultimately can increase rework times and associated costs. There are many defects which occur at the point of welding which, if detected early, can be rectified quickly resulting in reduced rework and material costs. Furthermore, by controlling and optimising the welding process in real-time, it may be possible to prevent some of these defects from occurring in the first place.

The Approach:

Nina began by simplifying the use-case down and utilising conventional, single element transducers in order to fully understand the wave propagation for the specific case of a liquid metal weld pool within solid metal parent material. By using one of Peak NDT’s conventional UT controllers, the MicroPulse LT, along with some developed LabVIEW software, Nina was able to experiment easily with different combinations of single element transduction through various media, i.e. Longitudinal Pulse-Echo, Longitudinal Through-Transmission & Shear Pulse-Echo. This was also an excellent way to begin using the MicroPulse Command Language, which makes the instrumentation easily configurable.

Initial experimentation was performed on replica steel test blocks which were designed and manufactured to simulate the geometrical properties of a weld pool. This allowed the different ultrasonic inspection configurations to be tested at room temperature without the need for a live-arc weld to be performed. These initial studies showed promising results, indicating that there is useful information present within the signals which can be used to infer the geometrical and positional properties of the weld pool. This is vital information for implementing a control algorithm.

The effects that the elevated working temperatures and thermal gradients present during welding have on the amplitude and position of defect signal are not trivial. Part of Nina’s work has been directed towards understanding and predicting these gradients through simulation and experimental validation in order to help develop crucial temperature compensation strategies.

Testimonial:

“I feel incredibly fortunate to be a part of a sector which is focussed on innovation and improvement. Working alongside both Strathclyde’s Centre for Ultrasonic Engineering and Peak NDT has given me the unique opportunity to see both sides of the R&D coin, both from an academic and industry standpoint. Peak NDT have shown dedication towards my professional development and progression as an engineer throughout my time with them, despite the challenges that we have all experienced during the Covid-19 pandemic.

I look forward to continuing to grow and enhance my skills as an individual over the coming years and making use of the incredible opportunity I have to work with such a diverse group of passionate and like-minded people.”

Next Steps:

As Nina still has 2 more years of her Engineering Doctorate at Strathclyde, the project will continue alongside Peak NDT. The improved spatial resolution and coverage offered by phased-array ultrasonics will be introduced and explored later in the project, which will be facilitated by the use of both the LTPA and MicroPulse 6 offered by Peak NDT.