Results and submissions : REF 2021

Contour Method Stress Mapping Improves Manufacture, Lifetime and Safety of Products ...

Submitting institution: The Open University
Unit of assessment: 12 - Engineering
Summary impact type: Technological
Is this case study continued from a case study submitted in 2014?: No

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1. Summary of the impact

Manufacturing processes introduce internal (residual) stresses causing unwanted distortion and shortening the life of structures. The Open University has developed novel variants of the Contour Method of residual stress determination and applied it to map stresses in over 150 components for industrial clients. The measurements have changed manufacturing processes, validated numerical modelling, improved fracture control and contributed to industrial assessment procedures across aerospace, nuclear, medical and additive manufacture sectors. Our research has catalysed a UK start-up, a Centre of Excellence for Advanced Materials in China, and commitment to a National Stress Engineering Centre at Harwell.

2. Underpinning research

Most manufacturing processes introduce hidden internal stresses in products and structures. These “residual stresses” cause distortion and can shorten the useful life of structures. Conversely beneficial residual stresses can be introduced to control manufacturing processes and improve product performance. The research challenge is how to quantify and control residual stresses in highly complex manufactured parts.

The Contour Method of residual stress determination involves cutting a body containing stress at a cross-section of interest. The surfaces created by the cut deform as the residual stresses relax during the cut. The “contour” of the newly created distorted surfaces is then measured and an elastic finite element stress analysis used to back-calculate the cross-sectional distribution of undisturbed residual stresses acting normal to the plane of the cut.

The Contour Method has been implemented and extended by OU researchers following its publication in 2000. Edwards, Fitzpatrick and Gungor, for instance, applied the technique in conjunction with other approaches to welded plate joints made from aerospace aluminium alloys and in 2008, our research team [O1] implemented a novel multi-axial contour method to measure the full residual stress tensor in a plasma arc weld.

Bouchard and Hosseinzadeh pioneered application of the Contour Method to complex geometry engineering structures via a 4 year “ Advanced Contour Measurement Technology Research Programme” (2009-13) funded by the East Midlands Development Agency, Rolls-Royce and the OU. They published original work [O2] that quantifies factors contributing to cutting artefacts and identifies approaches to mitigate them. An early breakthrough involved applying the Contour Method to map hoop residual stresses in a welded pipe based upon the novel idea of using a diametral cut parallel to the pipe axis [O3]. This paper also describes the first application of a hybrid measurement technique (Contour Method coupled with X-ray diffraction) for a welded pipe, mapping three direct components of the residual stress tensor. These innovations have allowed residual stresses to be measured in multiple directions in cylindrical structures of complex geometry (for example valves and turbine discs).

The practical significance of OU research underpinning the Contour Method was set out by Hosseinzadeh, Kowal, and Bouchard in 2014 [O4]. This publication described the state of understanding of the technique through addressing three fundamental questions: how to cut components, how to measure surface deformation and how to analyse the measured data. The significance of introducing plasticity error during cutting is addressed by Hosseinzadeh [O5] and effective strategies for presented for mitigating such errors. In 2017, OU research staff developed a new method for dealing with asymmetric stiffness of cut parts that has been applied to complex geometry industrial parts and incorporated in our recent publication describing a new Incremental Contour Method, iCM [O6].

OU research staff have supervised 9 PhD researchers who have contributed to Contour Method technology since 2000. These include research on the Rosette Method, near surface stresses, managing plasticity, applications to T-butt welds, piping welds, measuring shear stress using the fracture surface approach, length-scale refinement, asymmetric cuts and the bulge correction.

4. Details of the impact

OU Contour Method research has impacted manufacturing, the lifetime performance of components, safety, professional practice, commerce and the economy. Pathways to impact comprise collaboration with businesses, global sharing of knowledge and expertise through published work and conferences, providing advanced measurement services to industry, catalysing other providers of Contour Method measurements, hosting training seminars and contributing to the development of improved Structural Integrity Assessment Procedures.

Enhanced safe lifetime performance

In nuclear power EDF Energy [C1] state that “ Open University’s research in developing the Contour Method of residual stress determination and applying it to map residual stresses in complex welded structures has helped ensure safe and reliable operation of EDF Energy power stations. These outputs have also provided EDF Energy with valuable benchmark data that have been incorporated in R6, which is one of the key procedures that EDF Energy uses to assess the integrity of their UK nuclear assets”. For example, the OU applied Contour Method in tandem with the slitting technique and revealed high levels of residual stress in Compact Tension tests specimens that explained unexpectedly high crack growth rates observed in the creep crack growth tests. EDF Energy [C1] further state that “ this work is now a key reference underpinning EDF Energy advice on creep crack growth rates in Type 316H HAZ materials” and that “ this advice has been used in safety case assessments for key high- temperature components in the UK’s Advanced Gas Cooled Reactors, reducing unexpected down time and enhancing the safety and cost-effectiveness of nuclear power plant”.

Improved codes and standards for the nuclear energy sector

The R6 Procedure for the Assessment of Structures Containing Defects [C2, pp.6-7 ], developed by the UK nuclear industry and used worldwide, sets out a fracture mechanics-based methodology for assessing the safety of critical plant (i.e. to guard against catastrophic failure). Three new sections dealing with residual stress have been added to the R6 procedure over the past decade: Section III.15 (Calculation of Residual Stress in Weldments); Section V.5 (Validation Sheets for the Calculation of Residual Stress in Weldments); and Section V.6 (Worked Example of the Calculation of Residual Stress). The OU has contributed to these new sections through membership of R6 Panel subgroups (Weld Modelling Guidelines and Benchmarks, Weld Residual Stress Profiles) and by providing maps of residual stress reference data for benchmark test components that have been measured by the Contour Method, see [C1].

Improved manufacture

OU research has advanced the capabilities of the Contour Method of residual stress determination, raised its Technology Readiness Level (TRL) and applied it to map stresses in more than 150 components since August 2013 via industry measurement contracts worth over GBP1,500,000. Many of these measured residual stress maps have changed manufacturing processes, validated numerical modelling, optimised fatigue lifetime and improved fracture control across manufacturing, aerospace, nuclear, offshore and medical sectors. Some examples are set out below.

Rolls-Royce [C3] has contracted the OU to carry out more than 20 Contour Method work packages with a total cost of ~ GBP500,000 from August 2013-20 [C3]. Typical examples include mapping stresses in Trent 1000 turbine discs to confirm the accuracy of manufacturing process models; in rotary friction joints for optimising welding processes, in double helical gears to quantify the impact of different manufacturing processes, in test components manufactured by Selective Laser Melting in order to validate process models, and in additively manufactured parts. Rolls-Royce [C3] specifically state that the measurements performed by OU *“have reduced costs, improved manufacturing processes, validating process models and supported safety cases for nuclear power plants. The benefit to Rolls-Royce is significant as evidenced by the volume of measurements, their diversity of application, and the relevance to the different business units within Rolls-Royce.*”

Airbus Defence and Space [C4] is responsible for the design of propellant tanks used for both telecommunication and scientific based space missions. These high energy, hazardous propellant tanks are safety critical during the propellant loading phase and are subject to fracture control requirements. Airbus commissioned the OU to measure the residual stress levels introduced by the planetary end-cap electron beam weld of their latest spherical tank design, for the next generation Eurostar spacecraft platform (ENEO). The Contour method results confirmed and validated analytical predictions of weld induced residual stress that have been subsequently used to demonstrate the fracture tolerance of the latest tank design to potential manufacturing defects. Airbus [C4] state that “ this contribution to the necessary fracture control programme has been reviewed and accepted by customers and the European Space Agency” and finally note that “ *the qualification tank has now successfully passed its pressure cycling requirements and […] its burst pressure requirement.*”

DePuy is part of the Johnson & Johnson Family of Companies and offers a comprehensive portfolio of orthopaedic products . The Staff Material Engineer [C5] confirmed “ the impact of the Open University’s research and implementation of the contour method residual stress measurements on our femoral knee implant components and on improving the efficiency of our manufacturing processes”. Femoral knee implants are one component of a total-knee-replacement where residual stresses play a key role. Dimensional distortion of femoral knee implants during manufacture (leading to rejection) is a direct consequence of residual stresses being induced or pre-existing residual stresses re-distributing. A series of contour method measurements were conducted on femoral knee implants by the OU which showed that the shot- blasting manufacturing process significantly alters the bulk residual stress of the femoral from its as-cast condition. These ‘ resulted in optimized manufacturing routes, increased quality assurance when it comes to checking changes at the blasting step due to possible impact/dimensional changes at machining and improved product quality” [C5].

CETIM [C6] is a Technical Centre for Mechanical Industry based in France with a EUR150M overall business volume. Over the past 7 years, Cetim has commissioned Contour Method measurement work from the OU for 13 projects at a total cost of GBP120,000. For example, contour method measurements (using the OU multiple-cut, multiple-method variants) were conducted on a 2m diameter gear for the offshore industry (wind turbines) in order to validate the use of a carburizing method for increased strength and wear resistance through introducing beneficial compressive residual stresses near the tooth of the wheel.

Impact on other organisations and companies supporting industry

OU Contour Mapping research underpins the development of further centres designed to apply the findings to support industrial and manufacturing improvements. In 2017 OU researchers set up Stress-Space Ltd ( www.stress-space.com). The company is growing with GBP232,000 revenue in 2019/20, and delivers residual services to business largely based on published OU research (as set out in Section 2). For example, its Contour method stress measurements on transmission drive chain parts for an aerospace prime “revealed the limitations of the initial design (fatigue hot spot) and was used to assess the merits of an improved design with a new manufacturing route in order to eliminate the risk of failure during service operation” [C7]. The merits of Stress-Space Ltd’s Business Case for Growth (founded on application of OU Contour method research), resulted in its selection to participate in the prestigious ESA BIC UK Incubation Programme in 2019 attracting research funds exceeding GBP150,000 [C7].

The Centre of Excellence for Advanced Materials ( www.Ceamat.com) in Dongguan, China has adopted the OU’s Contour method technology to create a new GBP10,000,000 Stress Measurement Facility. Director of the Stress Measurement Facility [C8], who was an OU researcher from 2013 – 2018 noted: “ Our organisation and the stress analysis department in particular has greatly benefited from the various educational lectures you provided, the contour method seminar you organised and advice you provided on equipment purchase and setting our research priorities […] it is our ambition to bring this technology to the Chinese market and achieve similar and wider benefits.”

OU Contour Method research has catalysed [C9] an ambitious collaborative plan to establish a National Stress Engineering Centre (N-SEC) at Harwell which will “ co-locate several complementary measurement techniques, including the Contour method, with the neutron capabilities at ISIS [STFC Facility] Together with a new neutron instrument, e-MAP, the combined capabilities would really be unique in the world”. N-SEC has grown from an ISIS-OU collaboration to a consortium that now includes several UK universities and

Research and Technology Organisations and is supported by a number of industries. ISIS has invested of order GBP500,000 in developing the concept and the building and instrument design. N-SEC, referred to as I-SEC in the UKRI Infrastructure Roadmap [C10, p.58 ], has been selected by STFC, with support from its Industry and Business Partnership Board, as one of four proposals that STFC submitted to the new UKRI Infrastructure Advisory Committee and that application for GBP23,000,000 is currently awaiting a decision [C9].

Improving purity, reproducibility and mass production of organosilicon compounds ...

Submitting institution: The Open University
Unit of assessment: 12 - Engineering
Summary impact type: Technological
Is this case study continued from a case study submitted in 2014?: No

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1. Summary of the impact

Organosilicon compounds contain carbon–silicon bonds whose properties, including stability, water repellent abilities, and colourlessness make them widely used in commercial applications. OU research has resulted in new organosilicon compounds for industry using new routes, in high purity, on large scale and reproducibly. One of the high performance liquid chromatography (HPLC) columns produced as part of a knowledge transfer protocol (KTP) with Hichrom has been selected by the U.S.A Food and Drug Administration (FDA) as an official FDA analytical protocol, because of its unique selectivity, reliability and reproducibility. This is used to test the purity of a commonly used over the counter drug – Zantac, to reduce risk of carcinogenic impurities and enable sales of the drug. Hichrom has only been able to do this as a result of OU research, and sold around 22,000 columns with income over GBP12,000,000. This subsequently led to a development of new products with chemicals company Cornelius Specialities, road markings specialists WJ Group, technology membership organisation TWI and global chemicals company Johnson Matthey.

2. Underpinning research

A group at the Open University has been undertaking research in Organosilicon chemistry

for over 40 years in a range of areas, including mechanistic and hypervalent silicon chemistry, biological silicon chemistry, synthetic organosilicon chemistry and the synthesis and properties of silsesquioxane cages (silicon-oxygen colourless solids with polymeric structures). The key area of underpinning work related to the impact in the REF period has been the synthesis of organosilicon compounds selectively, in high purity, reproducibly and potentially on a large scale.

The organosilicon chemistry developed by the OU group in an academic context can be used to solve a range of specific problems within Industry. Companies have come to the OU to investigate specific problems outside the academic research but with relevant applications. The element silicon is a semimetal and when combined with carbon forms organosilicon compounds. The presence of the silicon atom in the organosilicon compounds leads to unique physical and chemical properties for example, organosilicon compounds (e.g. silicones) are used in applications ranging from bath sealants to cupcake trays, as well as body implants, sealants, adhesives, lubricants, personal care products (Methicone) and contact lens additives. Their unique chemical reactivity has led to a separate field of study and OU organosilicon chemists have a deep understanding of how these compounds behave chemically and can thus synthesise new organosilicon compounds in high yield and purity. The OU group are world leaders in organosilicon chemistry and have used their knowledge to produce a new class of compound known as silsequioxanes researched hypervalent silicon compounds and developed new chemical transformations using organosilicon compounds. Armed with this unique knowledge of how to make and use organosilicon compounds, the OU group have been able to help a large number of companies develop their products.

For example, one of the key intermediates industry has been interested in are trialkoxysilanes, that are often used to coat silica particles. These are the types of compounds used to make the HPLC columns described in the impact statement. Expertise in making such compounds has been developed though making a wide range of trialkoxysilanes for the synthesis of silsesquioxane cages, regular three-dimensional structures such as cubes and prisms made out of R-Si(O-)₃ units as shown below [O1, O2]:

The OU researchers developed a simple route to these compounds from trialkoxysilanes (RSi(OEt)₃) using tetrabutyl ammonium fluoride [O2]. The pendant R groups provide the materials with a range of properties such as liquid crystals, metal complexing and protein binding [O3]. So, in order to make a wide range of different silsesquioxanes the OU group have had to develop a wide range of routes to trialkoxysilanes which can be very water sensitive. Synthesising a new trialkoxysilane requires careful planning through a knowledge of the way these organosilicon compounds react, what to avoid, how to maximise the yield and how to purify the products. For example, one of the key reactions used is known as hydrolsilylation which requires a platinum catalyst. Knowing which type of platinum catalyst to use, which solvent and the reaction conditions is essential to ensure high yields and purity [O6]. The OU group have developed a toolbox of key reactions used to synthesise trialkoxysilanes with a wide range of R groups, in the high purity required for the synthesis of silsesquioxanes, which also has wide application in industry. The OU team supplied the characterisation of new materials and analysed their properties on instrumentation not available at the companies. Feedback of this data further improved the synthesis and the properties of these novel materials.

The team have gone on to synthesise and characterise a new class of compound where a fluoride ion is trapped in the centre of the cage [O4]. Again, they have had to synthesise different alkoxysilanes, this time with electron withdrawing groups, which provided new insights into the way alkoxysilanes are made, handled and reacted [O5].

As part of the research into hypervalent silicon compounds and organosilicon compounds in organic synthesis, the researchers have had to carry out other types of reaction such as hydrosilylation, Suzuki coupling and organolithium and Grignard methodologies [O6]. The expertise in using these reactions to make organosilicon compounds was the basis of KTPs with three different companies, albeit with very different target compounds. For example, whilst Hichrom were focussed on trialkoxysilanes, Cornelius Specialities wanted routes to organosilicon intermediates for use in the contact lens and personal care industries. This led to a toolbox of reactions, based on couplings and organometallics that we had developed as part of our research, which Cornelius Specialities could use to make their targets. WJ needed our methodology and expertise to develop new alterative materials for road marking.

3. References to the research

O1. A R Bassindale, I A MacKinnon, M G Maesano and P G Taylor (2003) The Preparation of Hexasilsesquioxane (T₆) cages by "Non Aqueous" Hydrolysis of Trichlorosilanes, Chem. Commun., 1382-1383 ISSN 1359-7345. https://doi.org/10.1039/b302556j. Blind peer reviewed.

O2. A R Bassindale, Z Liu, I A MacKinnon, P G Taylor, Y Yang, M E Light, P N Horton and M B Hursthouse (2003) A higher yielding route for T₈ silsesquioxane cages and X-ray crystal structures of some novel spherosilicates, J. Chem. Soc., Dalton Trans., 2945-2949 ISSN 1477-9226. https://doi.org/10.1039/b302950f. Blind peer reviewed.

O3. Bruce, J., O’Connell, Patrick J.; Taylor, P G.; Smith, David P.T.; Adkin, Roy C. and Pearson, Victoria K. (2020) Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents. Molecules, 25(18) e4253. https://doi.org/10.3390/molecules25184253. Blind peer reviewed.

O4. P. G. Taylor, A. R. Bassindale, Y. El Aziz, M. Pourny, M. Hursthouse and S. J.Coles (2012) Further studies of fluoride ion entrapment in octasilsesquioxane cages; X-ray crystal structure studies and factors that affect their formation, J. Chem. Soc., Dalton Trans., 41(7), 2048–2059 ISSN 1477-9226. https://doi.org/10.1039/c1dt11340b. Blind peer reviewed.

O5. Y. El Aziz, P. G. Taylor, A. R. Bassindale, S. J. Coles and M. B. Pitak (2016) Synthesis and Structures of Novel Molecular Ionic Compounds Based on Encapsulation of Anions and Cations, Organometallics, 35 (24), 4004–4013 https://doi.org/10.1021/acs.organomet.6b00565. Blind peer reviewed.

O6. R. Panisch , A. R. Bassindale, A. A. Korlyukov, M. B. Pitak, S. J. Coles, and P. G. Taylor (2013) Selective Derivatization and Characterization of Bifunctional “Janus-type” Cyclotetrasiloxanes, Organometallics, 32 (6), 1732–1742. https://doi.org/10.1021/om301158w. Blind peer reviewed.

Other authors are PhD students, Post-Doctoral researchers, Industry collaborators, analysts providing expertise in X-Ray crystallography or colleagues from other Universities providing biological expertise.

4. Details of the impact

OU research into the creation and function of organosilicon compounds has created benefit for chemicals companies supplying markets as diverse as pharmaceuticals, personal care, road markings and industrial consultancy for the offshore industry.

A collaboration with Hichrom, underpinned by this research, led to the development of High Performance Liquid Chromatography (HPLC) columns which are used to demonstrate the safety of the world’s best-selling drug. Zantac, generically known as ranitidine, is one of the world’s leading treatments of excess stomach acid production. In 2018 nearly 25 million prescriptions were written for ranitidine in the USA and Sanofi, who sell under brand name Zantac, made USD124,000,000 sales in the USA. In September 2019, the USA’s Food and Drug Administration (FDA) became aware that an impurity present in some formulations known as N-nitrosodimethylamine (NDMA) had potential carcinogenic properties which led to the withdrawal of Zantac from the market [C1]. In order for pharmaceutical companies to reintroduce Zantac they needed to show that the levels of NDMA were low enough to reduce the risk of cancer.

The FDA developed a (HPLC) – Mass Spectrometry (MS) technique for the analysis of NDMA in ranitidine samples [C2]. This technique involves separating the individual compounds present in a sample and then analysing them. At the heart of the separation process is an HPLC column, a long column of very small silica particles coated with specific material that promotes the separation of the compounds in the sample. The column chosen by the FDA for their crucial analysis of ranitidine is the Ace C18-AR column which researchers at the OU created as part of a KTP with Hichrom [C2, line 22 of p.2 and C3]. The column was chosen by the FDA because of its remarkable properties, its stability and its reproducibility. Hichrom was able to produce this novel column as a result of the OU’s expertise in synthesising new organosilicon compounds such as trialkoxysilanes that can be bound to the silica particles and in particular the method of making them in a very pure form, which can be reproduced on a large scale (with high yields) without dependence upon a single raw materials supplier [O5, O6]. This synthetic expertise has been developed over many years of making organosilicon compounds as a result of the research described in section 2.

Hichrom had an excellent record of manufacturing reliable and reproducible columns but in 2010 they lacked the expertise to be able to synthesise organosilicon compounds and had to rely on what was commercially available. They approached OU to enter a partnership to produce a new range of HPLC columns and create compounds that their competitors could not. First, they funded a Post-Doctoral worker for a year to work at the OU and this grew into a three-year

KTP worth GBP200,000 (2010 – 2014), which was subsequently classified as outstanding by Innovate UK. The KTP’s aim was to develop new columns that have orthogonal selectivity, that is they have different mechanisms for separating the materials, and thus together create a toolkit for analysis of any mixture. This was successful in that five new columns were produced [C4] and Hichrom have sold about 22,000 of these columns over the last six years [C5, p.1 ]. This has greatly increased in recent years at an average of GBP540 giving a sales value of over GBP12,000,000 [C5, p.2, C6]. The partnership between the OU and Hichrom has continued up to the present day and a Hichrom employee now works on synthesis within the OU group/laboratories. As the then CEO stated in the final KTP report “ new agile development techniques have speeded up the development of silanes from one every 20 months before the KTP to successfully commercialising 5 in three years” [C7, p.9 ]. In addition, Hichrom’s improved reputation for innovation and reliability has led to acquisition by VWR, part of Avantor [C8].

The OU team’s research on the synthesis of organosilicon compounds described in Section 2 also led to an approach from Cornelius Specialities. This involved a further KTP (2013 – 2017, ~GBP200,000) to develop a toolkit of reactions that could be used to manufacture intermediates on a large-scale for the contact lens industry [C9]. Again, the OU’s unique experience of synthesising organosilicon compounds was used to target new, cheaper routes to existing intermediates and to create new compounds - specifically reliably and in high purity. The company reported that: “ our novel silicon chemistry toolkit […] enabled us to make a range of existing and new products in high yield and with high purity. Our methodology was specifically designed to ensure we were competitive with price as well” [C8, p.4 ]. Having successfully developed a toolkit for contact lens intermediates, the OU team worked with Cornelius to target the personal care industry as an alternative client base: “ This has led to a greater understanding of how organosilicon compounds can add value to a range of products such as personal care which will lead to a greater and more varied use of organosilicon compounds in the future” [C8, p.5 ].

As a result of the new opportunities opened up through developing new compounds,

“Cornelius Specialties Ltd (CSL) is manoeuvring itself to exploit other market opportunities from silicone materials that it is now able to develop as a result of this partnership” [C8, p.6 ].

The company therefore required additional space to exploit its Engineered Silcones potential and invested GBP240,000 in new plant and machinery [C8, p.10 ].

The Welding Institute (TWI) is a contract research organization that works for and on behalf of over 700 industrial members in over 4,500 locations world-wide. TWI and OU have been working together on the development of super hydrophobic coatings, that is surfaces that repel water, based on silica nanoparticles with a specific organosilicon coating. OU and TWI have been focussing on how they can control their processes and produce coatings that are more reproducible with a range of properties. TWI’s Technology Fellow noted: “ As a result, we gained an insight into how the experimental conditions determined the final structure and material properties of our materials and coatings and we able to increase their hydrophobicity as a result. We were able to go further and apply the expertise developed in the partnership to control the synthesis of silica-based nanoparticles. This allowed us to control both the size and the surface of the nanoparticles which allows us to influence their material properties and more significantly incorporate the nanoparticles into some of our existing coating materials” [ C9]. The partnership with the OU continues to exploit the advances made in synthesising nanoparticles which are being applied to a new project funded by TWI. This applies the new knowledge to make composite materials recyclable through using nanoparticles to control the assembly and, more importantly disassembly. This has the potential to greatly enhance the ability of TWI industrial members to recover and recycle the composite materials they use [C9].

WJ Group is the UK’s leading specialist road marking business dedicated to permanent and temporary road markings, and other specialist road fixings and surfaces such as road studs, and high friction and safety surfacing. In 2014, OU and WJ Group embarked on a three-year KTP. As a result, WJ Group acquired a capability to apply road marking products all year round, along with the development of an R&D capability to continue producing high performing cold products with which to enter the GBP750m Northern European market [C10, p.2 ]. The KTP reinforced WJ Product’s position as market leader and industry innovator from the sale of hot and cold state-of-the-art products [C10, p.2]. The Managing Director of WJ Product division noted that the work with the OU ‘ made a significant contribution to the WJ Groups expansion both in terms of commercial activity and R&D’ and transformed the way the company operates with a ‘ game-changing’ methodology for designing and testing new materials giving a rapid go/no go decision when developing new products [C11]. This has enabled the business to acquire new customers and as a result WJ Group now works with the Dutch equivalent to Highways England; ‘Rijkswaterstaat’. The work has enabled WJ Group to become the ‘go-to expert’ in micro-plastics in road markings, enabling them to develop case studies for Highways England investment in more sustainable materials [C11].

Further work building on this research with Johnson Matthey is developing techniques to recover metals from waste streams, acid mine drainage and wastewater, using silica materials modified with chelates for metals. This enables Johnson Matthey to meet its strategic aims to participate in the increasingly sustainable circular economy. So far, the work has led to novel and commercially applicable materials for which Johnson Matthey is applying for a patent and is also being deployed in the wider company [C12].

Manufacturing new components used in satellites, antiviral (Covid-19) sterilisation ...

Submitting institution: The Open University
Unit of assessment: 12 - Engineering
Summary impact type: Technological
Is this case study continued from a case study submitted in 2014?: No

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1. Summary of the impact

Novel technologies developed by The Open University have enabled high-precision and atomic level joining of advanced alloys that cannot be welded using conventional methods. Exemplary applications included:

reducing faults in power transistors fitted in millions of electric cars for Mitsubishi;
developing and fabricating new key components for X-ray sterilisers of the COVID-19 vaccines in the USA;
manufacturing ultra-high-speed turbine and compressor rotors for the latest generation of satellites of the UK/European Space Agency;
developed the world’s first Auto Ejection Melt Spinner which is now on the market in Germany;
development of new technologies for the manufacturers of aeroengine heat exchangers and F1 racing cars in the UK.

2. Underpinning research

In the last two decades, the development of advanced alloys and composites with superior mechanical properties (e.g. Titanium and Aluminium) has underpinned the rapid progress of engineered and new manufactured products particularly for the aerospace, transport and electronic industries. However, advanced engineering components require not only better materials but also new joining or welding processes. Traditional fusion welding processes are unsuitable for joining dissimilar and high precision components due to the high temperatures. In such cases, the components may be joined below their melting point by Diffusion Bonding.

Dr Amir Shirzadi, a Senior Lecturer at the Open University, established the Open University’s Diffusion Bonding Lab in 2013, which is the only one among all UK universities. The following research underpins the impact described.

2.1 Gallium-Assisted Diffusing Bonding – [O1 - O5]

The main barrier to successful solid-state diffusion bonding is the presence of a stable surface oxide. Hence, developing new approaches to disrupt the oxide layer would lead to significant improvements in bond integrity. Gallium-Assisted Diffusing Bonding is a solid-state process, based on removing and/or modifying the nanometre thick surface oxides prior to the bonding cycle. The development of a suitable brazing technique essentially incorporates an in-depth understanding of the interfacial chemical reactions and identifying the mechanisms of these reactions, which can be used to optimize the bonding conditions, and hence achieve desirable properties of the joints.

Shirzadi’s work has investigated methods for bonding high-performance materials such as titanium and aluminium alloys to a variety of other materials, and to themselves and these bonds were then evaluated by microstructural examinations and severe mechanical testing of the samples.

Research to investigate bonding stainless steel and titanium resulted in bonded samples at 92% the tensile strength of the original titanium [O1]. An experiment to bond titanium alloy (Ti-64) with Ti-64 metal matrix composite was successfully achieved using diffusion bonding. Metallographic and Electron backscatter diffraction (EBSD) studies, as well as bending and microhardness tests across the bonds demonstrated joint integrity and the lack of microstructure alteration in the vicinity of the joint showed there was no degradation [O2].

Similarly, a new method for liquid-phase bonding of copper plates to an aluminium nitride (AlN) substrate was developed for Mitsubishi, using a newly developed proprietary interlayer composed of titanium and silver powders. The microstructures of samples were analysed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, and an ultrasonic flaw detector was used to assess joint integrity. The optimum composition of the Ti–Ag brazing alloy for producing defect-free joints was determined [O3].

In collaboration with India’s Department of Atomic Energy (DAE) stainless steel and titanium were bonded using vacuum brazing and gallium-assisted diffusion bonding processes for an undisclosed application [O1, O4].

Fuel/Oil Heat Exchangers (FOHE) are critical components of modern jet engines. Their primary function is to cool the hot engine lubrication oil while heating the cold fuel coming from the fuel tank before it enters the combustion chamber. The fuel heating increases the engine efficiency substantially by recuperating the waste heat from the oil into the fuel. The fuel/oil pressures and temperatures required are increasing with the development of more efficient jet engines. Gallium-Assisted Diffusion Bonding is used to join stacks of aluminium plates containing fluid flow channels; without the weaknesses and limitations inherent in traditional brazing. Shirzadi’s research identified a new technology for manufacturing more efficient and lighter Fuel/Oil Heat Exchangers than conventional shell and tube ones with tensile strength comparable to the parent alloy [O5].

2.2 Invention of Auto Ejection Melt Spinning (AEMS) [O6]

Melt spinning is a method used for rapid solidiﬁcation of certain alloys mainly to obtain completely non-crystalline ribbons, i.e. amorphous or so-called “metallic glasses”, that cannot be fabricated using conventional continuous casting processes. Depending on the spinning conditions extremely high cooling rates, suﬃcient to obtain amorphous structures, can be achieved ( e.g. tens of thousands of centigrade per second). In this process, ﬁrst an alloy is melted inside a crucible and then an inert gas is used to ﬂush out the melt through a nozzle, located in the bottom of the crucible, straight onto a rotating copper wheel where it solidiﬁes instantaneously. In the course of developing a new process to manufacture ultra-thin cobalt-based ribbons, Dr Shirzadi identified Melt Spinning as the only viable option. One drawback of conventional laboratory melt spinning processes is the need for a skilled operator to monitor the melt temperature and/or manually release the ejection gas at the right moment. Failure or error results in expensive waste. Shirzadi’s 3-year long project led to a new variant of Melt Spinning process which does not require a skilled operator; hence it substantially reduced the uncertainties associated with temperature measurement and human error [O6]. This work underpinned the commercial development of the world’s first Auto Ejection Melt Spinner by a German company in less than 12 months.

3. References to the research

O1. Shirzadi, A.A., Laik, A., Tewari, R., Orsborn, J., and Dey G.K. (2018) ‘Gallium-assisted diffusion bonding of stainless steel to titanium; microstructural evolution and bond strength’ Materialia, 4, pp. 115-126. https://doi.org/10.1016/j.mtla.2018.09.009. Blind peer reviewed.

O2. Prikhodko, S.V., Savvakin, D.G., Markovsky, P.E., Stasuk, O.O., Penney, J., Shirzadi, A.A., Davies, P.D., and Davies, H.M. (2020) ‘Diffusion bonding of TiC or TiB reinforced Ti–6Al–4V matrix composites to conventional Ti–6Al–4V alloy’, (2020) Science and Technology of Welding and Joining , 25 (6), pp, 518-524. https://doi.org/10.1080/13621718.2020.1751403. Blind peer reviewed.

O3. Terasaki, N., Ohashi, T., Nagatomo, Y., Kuromitsu, Y., and Shirzadi A.A. (2019) ‘A new method for liquid-phase bonding of copper plates to aluminum nitride (AlN) substrates used in high power modules’ Journal of Materials Science: Materials in Electronics, Volume 30, Issue 7, pp 6552–6555. https://doi.org/10.1007/s10854-019-00961-6. Blind peer reviewed.

O4. Laik A., Shirzadi A.A., Sharma G., Tewari R., Jayakumar T., and Dey G.K. (2015) ‘Microstructure and interfacial reactions during vacuum brazing of stainless steel to titanium using Ag-28%Cu Alloy, Metallurgical and Materials Transactions A’, Vol. 46, No. 2, pp. 771-782. https://doi.org/10.1007/s11661-014-2671-9. Blind peer reviewed.

O5. Shirzadi A.A. (2019) ‘Ultra-High Pressure Laminated Aluminium Heat Exchangers for Jet Engines’ , International Congress Aluminium Heat Exchanger Technologies Düsseldorf, May 2019, DVS 352, pp. 16-18. Available from Semantic Scholar. Blind peer reviewed.

O6. Shirzadi A.A., Kozieł T., Cios G., & Bała P. (2019) ‘Development of Auto Ejection Melt Spinning (AEMS) and its application in fabrication of cobalt-based ribbons’, Journal of Materials Processing Technology. Vol. 264, pp. 377-381. https://doi.org/10.1016/j.jmatprotec.2018.09.028. Blind peer reviewed.

This research programme was supported by funding from Welding Alloys Group, Innovate UK, EPSRC, Technology Strategy Board, Mitsubishi Corporation and the new techniques described in these publications have had significant impact on manufacturing processes.

4. Details of the impact

OU research described in this impact case study contributed to the productivity and performance of seven international businesses in the UK, Germany, France, Japan and USA. The vehicles for achieving these impacts have been through collaborations based on Dr Shirzadi’s work on joining high strength materials, such as titanium alloys and nickel superalloys, as well as functional materials. He has also developed novel methods for materials and component processes. Examples of impact on manufacturing underpinned by the OU research are as follows:

4.1 Mitsubishi Materials (Japan) has collaborated on various projects with Dr Shirzadi including building on research that investigates the manufacture and performance of diffusion bonded products mainly so-called Direct Bonded Aluminium (DBA) substrates [O1, O3].

The work included investigating and improving performance of specific Mitsubishi components. Although they operated at high reliability, this was not considered adequate for functionality under the specific conditions. Dr Shirzadi’s research methods and Diffusion Bonding techniques were applied to the DBA-based components supplied by Mitsubishi Materials to eclectic car and train manufacturers. The work showed formation of a continuous and defect-free layer at the copper/aluminium nitride interface was essential for achieving high integrity joints. By applying the new techniques Shirzadi was able to identify the problems in construction, reduce susceptibility to cracks and increase reliability [C1, O3]. Mitsubishi noted that this is “ helping us to improve our manufacturing process” and promotes the component by identifying the robust joins examined in the research [C1]. The DBA is a key component in every electric car or train with an annual market worth USD500,000,000. Mitsubishi [text removed for publication] Materials has a substantial percentage [text removed for publication] of the DBA global market [C1].

4.2 Atlas Technologies (USA) makes enhanced vacuum technology products for energy, space, medicine, physics, quantum computing, and commodity preservation. A long-term collaboration with Atlas Technologies has led to development of new technologies and products. In July 2020, The Open University was approached by Atlas Technologies which had an urgent need of diffusion bonded bi-metal adapters for their high-power X-ray tubes. Such X-ray tubes are needed for sterilising blood products and vaccines. Demand had increased exponentially as the adapters are used in the development of COVID-19 vaccines [C2]. The fabrication of high vacuum adapters is a challenging task which was done by explosive welding with a lead time of 6-12 months. In addition to the lengthy leading time, the explosive welded adapters frequently suffer from vacuum leak.

Work in Shirzadi’s Diffusion Bonding lab led to fabrication of new adapters at the required standards, which only took five months to develop. A set of six full-size adapters were manufactured by Dr Shirzadi and sent to Atlas Technologies on 26 November 2020 for installation and final testing on X-ray tubes. By 31 December 2020, Atlas committed to deploying the new adapters for sterilisation of transfused blood from virus pathogens and vaccine production, which would not have been possible before. The Vice President of Atlas Technologies noted that “ Dr Shirzadi has successfully produced full-size aluminium/stainless steel metal adaptors based on one of his inventions on joining un-weldable alloys. The helium leak tests as well as the sub-zero and high temperature endurance tests carried out on these adaptors have exceeded our expectation limits” [C2].

4.3 OFTTECH (UK/ESA): The European Space Agency (ESA) has commissioned OFTTECH to design and build ultra-high-speed rotors (250,000 RPM) operating at minus 233 °C in the latest generation of satellites. The UK company identified the OU’s Diffusion Bonding research and facilities as the only option to fabricate the rotors. Four full-size sets, each set comprising one turbine and one compressor, were made by Dr Shirzadi at the OU’s Lab, building on research investigating the bonding of titanium [O1, O2]. All four sets were tested by OFTTECH and passed on to the manufacturer of satellite cryogenic heat exchangers. Manager of OFTTech confirms the impact on the company: “ The ability to manufacture miniature components has given us a major advantage over all other European competitors, as well as enabling us to keep the entire manufacture inhouse […] such enhanced components enhances the UK’s global position in the space sector” [C3].

4.4 Meggitt Co. (UK) with GBP2.2 billion turnover is one of the main manufacturers of the heat exchangers for jet engines and aircraft braking systems. Dr Shirzadi developed a method for diffusion bonding aluminium plates (containing cooling channels) for Meggitt as a part of a ~GBP1,000,000 project co-funded by Innovate UK. The OU was the only academic partner and in charge of diffusion bonding the heat exchangers. The outcome of the project, in which the OU played a seminal role, has led to GBP7,460,000 project on diffusion-bonded thermal systems for the next generation of Ultra High Bypass Ratio (UHBR) jet engines, co-funded by Meggitt and Innovate UK [C4, pp.1-6; C5].

4.5 Edmund Buehler GmbH (Germany): Dr Shirzadi’s invention of Auto Ejection Melt Spinning [O6] provided a novel solution for a long-lasting problem associated with melt-spinning process. As a result of the new process the repeatability of the process is improved due to reduced human error [C8]. The new method was independently checked, and its capability was verified in 2019 by a renown German manufacturer of melt spinners, Edmund Buehler GmbH. Since then Edmund Buehler developed and marketed the world’s first Auto Ejection Melt Spinner branded as PA 500 [C6, C7, p.2 ].

4.6 Red Bull F1 Technology (UK): THE OU’s advanced joining and manufacturing technologies have been applied in developing racing car. Dr Shirzadi worked with the F1 racing car manufacturer on two different projects helping the company develop novel processes for fabrication of the [text removed for publication] parts [text removed for publication] [C8].

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