Core Research Programme (CRP)
Through the core research programme (CRP), TWI conducts projects to address challenges faced by our Industrial Members, advancing technologies and processes, and finding new solutions for industry problems. These projects are jointly funded by our Industrial Members, with the outcomes made available to all our Members.
- Development of Offset X-ray Computed Tomography Inspection
This project was created to solve the problem of performing X-ray computed tomography (XCT) on large components using existing XCT systems. At the time of this project, XCT system performance was limited by the field of view of the digital X-ray detector, even at the lowest magnification. To solve this challenge, TWI’s expert team investigated offset CT, which was only used to a limited extent by industry (Figures 1-2). This work, which used a micro focus X-ray source, developed sufficient understanding of offset CT to implement and deploy the inspection method on existing equipment, although further work was required to develop an in-house Feldkamp, Davis, and Kress (FDK) algorithm to extend the immediate applications for the process.
Public-Funded Projects
Our expert teams are also called to participate in public funded projects in partnership with other organisations from industry and academia to solve specific challenges, typically for particular industry sectors. Many of these projects include the use of process modelling and simulation, whether as a standalone capability or in alignment with others.
- Automated Inline Inspection and Quality Control of Net-shape Powder Metallurgy Components using Microfocus Three-dimensional X-ray Computed Tomography Imaging (Additive Manufacturing)
As powder metallurgy increasingly used finer powders for refined microstructures in the nanometre to micrometre scale, any flaws or defects in the parts would have a significant impact on potential failure during use. The collaborative ‘QualiNET’ project saw the development of a system for the automated quality control of powder metallurgy components. The project work employed micro focus X-ray processes to create a solution that was also transferable to components produced by other advanced net-shape techniques, such as powder injection moulding and laser cladding / sintering.
- Development of Novel X-ray Inspection System for Fast Automated Detection of Counterfeit PCB Components
The ‘ChipCheck’ project addressed the development of a counterfeit electronic component detection system to automatically inspect components in their original packaging. This European Commission-funded project investigated several non-destructive testing methods, including micro focus X-ray, to establish the best method for automating.
- TWI Develops Digital X-ray Radiography Inspection Systems
This work brought together two European-funded project consortiums with the development of two completely different radiography inspection applications aimed at different industry sectors; ‘AutoInspect’ and ‘PlastronicsSpec.’ The AutoInspect system was developed for the inspection of powder metallurgy parts to ensure the 100% quality of parts and the absence of porosity or cracking. This system was able to inspect powder metallurgy parts in seconds to create very low-noise X-ray images with resolution up to 10μm pixel size, depending on the X-ray set-up magnification (Figures 3-4). The PlastronicsSpec solution was developed to inspect the quality of organic light emitting diodes (OLEDs) produced via inkjet printing and used in digital displays. The system used a micro focus X-ray source and a 2D flat panel digital detector to generate radiographs with up to 1.2µm resolution at high magnification (Figures 5-6). TWI’s experts developed, optimised and automated the digital X-ray inspection-based techniques for both projects. This was despite the differences between the two applications, with the PM samples requiring high energy (160-200kV) to penetrate the material and inspect defects such as cracking to 25μm resolution, while the OLED inspection required low energies (55kV) to avoid being destructive to the OLED panels where the requirement was to resolve flaws down to 2-4μm.
Dedicated Industrial Member Support and Other Projects
Much of the work undertaken at TWI is conducted confidentially on behalf of individual Industrial Member companies to solve specific challenges or assist with new developments or innovations. There have also been some unusual requests for the use of our micro focus X-ray services, some of which you can see below…
- Development of a Standard Reference Geometry for XCT
TWI was contacted by the European Space Agency (ESA) to design and manufacture a standard reference geometry for use with X-ray computed tomography (XCT). This reference geometry allowed for image quality to be verified within an XCT inspection system before use. While such geometries existed for many years with film and 2D digital radiography, at the time of the project there were limited standard reference geometries for use within XCT due to the 3-dimensional nature of the acquired data. A literature review first assessed the current practices for standard reference geometries and image quality indicators (IQIs) for all existing radiographic techniques, which informed the design of three new geometries for further consideration and development. These were matched to the requirements from ESA and evaluated to result in the the final design (Figure 7), which was based around an aluminium step cylinder with removable internal cylindrical pins that are raised within the part to represent different penetrable thicknesses. Micrometre scale line features were placed in a circular pattern around the removable pins along with hemispherical patterns to represent porosity so that image quality could be assessed. Figure 8 shows an XCT image of the manufactured step cylinder. The design provided a flexible platform for expansion and adjustment in terms of size, resolution and material, while the modular design allowed for the image quality to be investigated for various penetration pathways as well as for multi-material components.
- Failure Investigation of Welded Moulded Plastic Components
Automakers and Tier-1 suppliers to major automotive companies were reporting failures associated with the poor welding of moulded plastic components that were increasingly being used for automotive manufacture. TWI undertook an assessment of investigatory tools such as visual inspection, pressure/burst test, microtoming, and X-ray computed tomography with a micro focus X-ray. The tests were performed on a vapour separator, made of Hostaform® C13031 (POM) (Figure 9), which was welded using linear vibration welding (LVW). Visual inspection and microtoming showed signs of poor weld quality (Figure 10), but computed tomography images produced using an X-Tek HMXCT 225 X-ray micro focus machine provided the most revealing flaws (Figures 11-13), enabling direct comparison against design rules.
- Refurbishment of Railway Axles (ReLASE Project)
X-ray computed tomography with a micro focus X-ray source was also used as part of the ReLASE project, which sought to develop a cost-effective repair method for railway axles and thereby reduce the high scrappage rates associated with axles that had suffered even minor wear and corrosion. TWI formed an industry consortium with Tata Steel, LASE and Wall Colmonoy to develop a laser-cladding process (Figure 14) that produces a coating offering increased wear and fatigue resistance for large metal components, with the aim of increasing the service life of axles and significantly reducing the scrappage rate. In addition to producing laser-engineered coatings with high fatigue, wear, adhesion and corrosion performance, we assessed the mechanical properties of coated samples and developed a reliable means of inspecting the various coatings. Powders of varying composition were analysed by the consortium before a range of cladding parameters were used to produce a variety of coupon samples (Figure 15). TWI then undertook X-ray computed tomography (XCT) to produce images (Figures 16-17) to support the assessment of the coating quality, defect characterisation and down-selection of coupons for fatigue testing. These results also informed the development of an equivalent but more portable ultrasonic inspection technique.
- TWI Supports Nepal in Fight Against COVID-19
During the Covid-19 pandemic, we were contacted by a team from the University of Wales Trinity Saint David (UWTSD) to support with the development of a Venturi-based CPAP design respiratory support system. This built upon efforts to deliver support to the NHS during the initial pandemic outbreak at the request of the Welsh Government, with TWI performing X-ray computed tomography work to confirm quality of prototype units. News of this earlier work reached Arjan Knulst a lead bio-medical engineer at the INF Green Pastures Hospital in Pokhara, Nepal, over 4,500 miles away. Arjan contacted UWTSD to ask if they could share their 3D files so the respiratory support system could be additively manufactured for the hospital in Nepal. A licence agreement was arranged to quickly allow the University to share the designs and undertake testing of an oxygen mask converted into a Venturi mask and a non-invasive ventilation (NIV) and continuous positive airway pressure (CPAP) mask based on the Venturi design. The masks provided emergency NIV for COVID patients and were shared with other hospitals in Nepal, where the situation with COVID-19 was still critical, allowing for the delivery of a controlled, pressurised range of air/ oxygen mixtures with no electricity needed for the cost of just £5 of materials.
- TWI Helps Investigate Roman Coin Hoard
Although our main focus is to provide our services in support of industry, there are occasions where we offer a wider benefit through the use of our expertise for non-industry projects. One such instance is when we were approached by Cardiff Museum to help with the investigation of a Roman coin hoard unearthed by two metal detectorists in the Conwy Valley, Wales (Figure 18). The hoard - the larger one of two that were found - was contained in a ceramic vessel and comprised of 2,733 coins; a mix of silver denarii minted between 32 BC and AD 235, as well as silver and copper-alloy radiates struck between AD 215 and 270. TWI’s team used state-of-the-art 450kV/1A computed tomography inspection equipment with high X-ray energy, that is typically four times greater than the energies used by dentists and hospitals use, to scan the ceramic vessel and see whether more information could be gleaned before extraction of the coins began. Digital radiography helped us to determine that there were coins at various locations in the vessel, although the coins were so densely packed in the centre of the pot that even our high X-ray energies could not penetrate through the entire pot (Figure 19). Nevertheless, we were able to reveal some of the layout of the coins and confirm it wasn’t only the top of the pot where coins had been cached.”
- X-ray Computed Tomography – On a Bee?
Another unusual example of the micro focus X-ray capabilities at TWI occurred when a rather large bumblebee that looked to have expired due to exhaustion (as there appeared to be no physical damage to its body) was discovered in the radiography laboratory at TWI Wales. Our team decided to see if it was possible to optimise the parameters of our state-of-the-art X-ray inspection systems to inspect organic parts. Of course, our radiography capabilities are usually employed in industrial inspection, so are typically calibrated to 200kV-400kV energy, with the usual challenge being not having enough X-ray energy to penetrate thick, high-density components. However, the bumblebee represented the opposite challenge with its organic, low density material density. To achieve the inspection, we used 50kV, 160uA energy for an output power of 8 watts. The low power, along with an exposure time of 2 seconds, produced high-resolution X-ray images. A total of 2700 images of the bee were acquired whilst the bee was rotated through 360° and these single 2D images were reconstructed to give the resultant 3D views of the bee (Figures 20-23).
While we don't usually perform XCT on bees, it is a perfect illustration of the capabilities of the state-of-the-art equipment that is available to our Members. Our experts provide micro-focus X-ray support to our Industrial Members, allowing them to use our equipment and expertise as an extension of their own. Because we operate independently across all industry sectors, we have a wealth of experience in the use of the process, whether for NDT, research and materials science, or failure analysis activities. You can find out more about the micro focus X-ray support available at TWI, here:
https://www.twi-global.com/what-we-do/services-and-support/asset-management/non-destructive-testing/ndt-techniques/micro-focus-x-ray