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Notable Achievements of TWI's Core Research programme from early days to 2000

Previous Core Research Projects have been responsible for numerous technical breakthroughs, thus benefitting the manufacturing industry.

A selection of notable achievements

  • Improved defect assessment procedures and life extension methods
    • Introduction and continued development of the Wide Plate test for assessing the validity of fracture mechanics based analyses [1954]
    • First to propose the assessment of weld defects on a fitness for purpose basis leading to the development of BSI PD 6493:1980 [1967]
    • First to integrate the Paris fatigue crack growth law for the assessment of the fatigue life of defective welds [1968]
    • Development of the CTOD design curve for assessing the size of tolerable defects in welded structures [1971]
    • Development of fracture mechanics based assessments for the fatigue of welded structures [1974]
    • Continued development of wide plate tests for crack arrest and, via biaxial wide plates, for examining the role of proof testing [1982]
    • Prime movers in the development of toughness requirements for pipeline girth welds leading to the derivations of Appendix H of BS 4515 (Pipeline code) [1982]
    • Provided the background documentation and had significant influence on the drafting of the DOE Offshore Guidance Notes [1984]
    • Continued development of fracture and fatigue assessment procedures, including the 3 tier approach and a CTOD based modified strip yield model, leading to the revision of BSI PD 6493 in 1991 [1985]
    • Major involvement in the drafting and development of Appendix U of BS 5500 (pressure vessel code) [1987]
    • Provided the basis for the incorporation of the effect of residual stresses in defect assessment from the development of predictive procedures and measurement techniques, and validation using EB ring welded wide plate tests [1988]

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  • Better test methods and design procedures for joints
    • The development of the CTOD test method [1972, 1979]
    • Chairman of IIW Commission XIII, Fatigue of Joints [1974 - present]
    • The generation of a cohesive set of fatigue design rules for steel [1976] now incorporated in BS 5400 [1980]
    • Membership of European Group on Fracture (now ESIS) Steering Committee [1979 onwards]
    • The initial proposal of an alternative cumulative damage design rule for situations where Miner's Rule is inappropriate [1983]
    • Provision of fatigue design rules for welded aluminium joints [1984] now in BS 8118 [1991]
    • Participation in development of dynamic CTOD testing standard BS 6729 [1987]
    • Co-chairman of ASTM Committee responsible for CTOD testing standard A1290 [1988]
    • Contributions to the revision of Appendix D in BS 5500 'Unified Fusion Welded Pressure Vessels' [1988]
    • TWI document used as a basis for EGF recommended practice on fracture toughness measurement of ductile materials [1989]
    • The development of a J testing protocol for fracture characterisation of plastics (1990) and a leading role in the DTI Design Data Initiative for Plastics [1990]
    • Participation in drafting committees for the forthcoming unified fracture toughness testing standard BS 7448 [1991]
    • Contributions to ISO fracture mechanics test methods via ISO/TC/164/SC4 [1991]

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  • Improved non-destructive testing (NDT) techniques for assessing joint and coating quality
    • TWI managed the first major national programme to explore the accuracy of weld flaw sizing by ultrasonics, in which CEGB and Harwell participated [1976- 1980]
    • Adoption of TWI developed flaw acceptance criteria for ultrasonic testing of pressure vessels by both BSI (for BS 5500) and the CEN drafting committee [1989-1991]
    • First major scientific study in the UK of magnetic particle inspection under funding from a group of Sponsors [1983-1986]
    • Evaluation of the capabilities of ultrasonic flaw sizing methods for assessment of steel bridges for US Department of Transportation [1979-1985]
    • Invention of the active Acoustic Pulsing structural monitoring technique [1982]. US, UK, European and Norwegian patents held
    • Development and licensing of original theoretical models and techniques for measuring multi-mode ultrasonic plate wave signals, plus practical demonstrations of the capabilities plate wave techniques for flaw detection [1987-1991]
    • Development of novel designs for the manufacture of focused contact ultrasonic transducers [1985-1987]
    • Identification of low velocity, low loss rubber material for the construction of ultrasonic probes for inspection of plastics [1988]

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  • Weldability of new generation ferritic steels and consumables
    • Quantification of the effects of C and C-Mn steel composition on the risk of fabrication hydrogen cracking [1970]. Early work included development of the controlled thermal severity (CTS) test, and generation of sufficient data under controlled conditions to produce guidelines in BS 5135. More recent work has quantified the effects of modern steel developments, in particular low sulphur level [1978] and reduced carbon equivalent [1988]
    • Determination of the factors controlling lamellar tearing [1970], leading to the universal acceptance of the short transverse tensile test for assessment of parent steels, and ultimately providing the driving force for the improvement in steel making to the point where lamellar tearing resistant plate is the norm rather than the exception
    • Identification of the parameters controlling solidification cracking in C-Mn steel weld metals [1972], the resultant compositional formula being incorporated in BS 5135
    • Discovery of the importance of weld metal inclusions in the formation of tough, acicular ferrite microstructures in C-Mn weld metals [1977]. As part of the work to identify efficient inclusions, the powerful roles of Al and Ti on weld metal microstructures and toughness was demonstrated [1982]. This work won the Larke Medal of the professional division of The Welding Institute
    • Identification of weld metals tolerant to the effects of Nb and V picked up from microalloyed plates, specifically those with high acicular ferrite contents [1979]
    • Generation of data on weld metal fabrication hydrogen cracking, covering both the effects of composition, microstructure and hydrogen content in single pass welds [1980], and the crucial and complex effects of welding procedure on these factors, and hence the risk of cracking in multipass welds [1989]
    • Derivation of guidelines to avoid hydrogen induced stress corrosion cracking at welds in C-Mn and allied steels, in terms of fracture mechanics approaches and hardness limits [1985]
    • Elucidation of many of the complex interactions leading to the formation of local brittle zones (LBZs) in multipass weld HAZs, the specific microstructures of concern being identified for the first time [1989]. This work has triggered effort by steelmakers, some of whom are now claiming to produce 'LBZ free' steels
    • Demonstration that preheat levels to avoid weld metal hydrogen cracking for conventional 9%Cr steels can be employed for newer creep-resisting alloys [1989], but that current welding consumables for new steels do not match the parent steel creep strength and toughness [1990]

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  • Weldability of new and improved stainless steels and non-ferrous alloys
    • Determination and modelling of factors causing HAZ liquation cracking in 6000 series Al alloys [1980]
    • Demonstration that conventional austenitic steels, made with current technology, can be welded at heat inputs significantly above established practice to obtain improved productivity, without unacceptable loss of material properties [1981]
    • Production of a quantitative system for predicting the ferrite-austenite balance at welds in 22%Cr duplex steels, so that reduction in joint properties can be minimised [1986]
    • Demonstration that weld hydrogen cracking in ferritic-austenitic steels will not pose a problem with good welding practice [1987]
    • Derivation of a predictive model for HAZ toughness of new ferritic-martensitic alloys, recognising arc welding procedure and HAZ microstructure [1988]
    • Demonstration that high alloy austenitic steels can be solid state friction welded to give pitting resistance close to that of parent material [1988]
    • Successful joining of 8090 Al-Li alloy in thin section by laser, resistance welding and diffusion bonding [1989]
    • Development of successful solid phase joining techniques for particulate reinforced Al alloy MMCs [1990]
    • Development of successful solid phase joining techniques for titanium aluminides [1990]
    • Improvement in corrosion pitting resistance of autogenous weld metal in high alloy austenitic steels by reduction in arc energy and elemental segregation [1991]
    • Achievement of high speed welding of 5083 Al alloy by a 10kW CO2 laser [1991]

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  • Increased performance and reliability of arc welding processes and equipment
    • TWI makes the first practical use of MIG welding in Britain for welding the aluminium superstructure of a Thames launch [1950]
    • Burn-off curves for MIG welding aluminium alloys determined which showed importance of voltage setting [1955]
    • Conditions for dip transfer CO2 welding established and results showed that oxygen additions do not affect metal transfer [1957]
    • Pulsed arc welding applied to positional welding of alloy steel and titanium alloys [1965]
    • Programmed MIG welding power source developed for military use [1968]
    • TWI pioneered the use of transistor power sources for arc welding and power sources sold to Members worldwide [1972]
    • Synergic pulsed MIG process first demonstrated for automatic control of welding parameters [1976]
    • Microprocessor control applied to automatic TIG and MIG welding equipment, and the first TIG robot demonstrated [1979]
    • Minicomputer software written for data acquisition and analysis in MIG welding [1981]
    • Studies on variability in TIG welding different casts of stainless steel show a correlation between weld pool surface tension and penetration [1982]
    • First microcomputer package written for the welding engineer - determination of preheat requirements for welding steel (Interpretation of BS 5135) [1983]
    • Magnetic arc oscillation used to improve process tolerance to joint fit-up and to reduce the number of weld runs [1989]
    • Weld pool penetration control system used in production to fabricate aeroengine components [1980]
    • First demonstration of the use of a microwave power source to generate a plasma beam [1990]
    • Miniaturised instrumentation developed for monitoring arc welding parameters [1991]

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  • Improved forge and sheet joining techniques
    • Friction Welding
      • TWI introduced friction welding of metals to the United Kingdom [1961]
      • Designed and built the (then) world's largest friction welder [1965]
      • Developed and patented a quality monitoring system for friction welding based on axial displacement [1968]
      • Established and patented the use of very low surface velocities for friction welding 6063 aluminium alloy to steel. Concept subsequently used to produce all anodes for the aluminium smelter based at Invergordon [early 1970s]
      • Assisted in preparation of BS 6223 (Specification for Friction welding of Joints in Metals) and its subsequent review [1970-1990]
      • Invented, developed and patented radial friction welding applicable to pipe joining and attachment of driving bands to artillery shells [1974]
      • Developed the technology and world's first equipment for friction welding underwater [1980]
      • Developed and presented metal deposition using friction surfacing to the western world [1980]
      • Pioneered the use of non-rotary motion such as orbital, linear and angular for friction welding non-round metal components [1984 onwards]
      • Initiated and project led the design, manufacture and commissioning of the world's first linear friction welding machine to join metals [1986]
      • Invented friction processes for manufacturing metal matrix composites in situ from powder bar stock [1988]
      • Demonstrated the feasibility of depositing metal matrix composites from proprietary MMC bar by friction surfacing [1989]
    • Resistance Welding
      • Developed voltage and expansion based weld quality monitoring systems which have been commercially exploited [1965-1980]
      • Developed various simple instruments for current and resistance measurements [1970-1991]
      • Identified and researched factors controlling electrode life and weldability when resistance welding aluminium alloys and high strength steels [1973-1981]
      • Identified the need, then developed drop weight test equipment for the impact testing of resistance welded, weldbonded and adhesively bonded box sections, simulating vehicle accident impact conditions [1980]
      • Established an environmental testing facility for adhesive bond durability work and corrosion testing [1986]
      • Advanced the methods for non-destructive testing of spot welds [1986-1991]
      • Assisted in preparation of various standards for the resistance welding and flash welding processes. BS 1140, BS 2630, BS 6265, BS 4219, BS 4204 and BS 6944 [Continuous since early 1960s]

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  • Advanced laser processing technology
    • World-first demonstration of enhanced (oxygen-assisted) laser cutting [1967]
    • World-first fast-axial-flow industrial CO2 laser, subsequently licensed for manufacture [1971]
    • World-first (US Patent 4127761) demonstration of plasma control for laser welding (producing 20% deeper penetration for the same laser power) [1976]
    • European-first 11.5kW transverse-flow CO2 laser (early 1980s, producing 25mm melt runs in steel), subsequently licensed for manufacture [1983]
    • Pioneering techniques for laser surface engineering (including the use of axicon and other beam-shaping techniques) [1983]
    • Development of laser-beam spinning, giving double the joint-gap tolerance when welding 0.7mm thick steels [1985]
    • Systematic study and characterisation of wire-feed laser welding to pressure-vessel code requirements [1985]
    • Improved cutting-nozzle designs, giving 20% improvement in cutting speeds using inert assist gases [1986]
    • Pioneering work on closed-loop adaptively controlled welding gantries (including vision-system and wire feed) [1989]
    • On-line beam monitoring and servo-pointing techniques implemented for CO2 laser systems [1989]

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  • Advanced electron beam (EB) welding technology
    • TWI - world leaders in high power gun design and first to achieve high power EB welding and to demonstrate 300mm single pass penetration in steel and 450mm in 5083 aluminium alloy [1972]
    • Magnetic trap innovation to avoid ingress of metal vapour, weld spatter and charged particles into electron guns [1980]
    • Development of special beam deflection devices for orbital electron trajectory welding of tubular components in space [1987]
    • Procedure and process development for eliminating defects in the fade-out region of thick section steel circumferential butt welds [1988]
    • Innovative back-scattered electron detector and real-time seam tracking system permitting operation on complex components up to power levels of 20kW [1988]
    • Established extensive weldability and mechanical property data covering a wide variety of ferrous and non-ferrous alloys promoting industrial exploitation of the process [1989]
    • The development of a high frequency digital deflection system and pattern manipulation software for improved weld beads, penetration control and thermal cycle control [1989]
    • Research leading to methods of avoiding adverse magnetic deflection caused by residual fields and thermoelectric effects [1989]
    • A 250kW precision line beam electron gun; designed, manufactured and demonstrated for the large scale evaporation of uranium for isotope separation [1990]
    • The development of flashless high voltage power supply control for suppression of gun discharges during EB welding allowing uninterrupted welding for periods of in excess of 2+ hours at 75kW [1990]
    • Research and development leading to100kW diode gun as recently introduced into major nuclear fabrication company in France [1990]
    • RF auxiliary supply system for use with the 300kV EU86 non-vacuum electron gun. This novel resonant RF transformer which has been fully integrated with the gun assembly, eliminates many of the current weaknesses in commercial auxiliary supplies whilst substantially reducing overall system and control complexity as well as the cost of manufacture [1991]

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  • Computer aided engineering (CAE) for fabrication enterprises
    • A portable 'briefcase' monitor has been successfully developed for arc welding applications which provides a permanent record of arc parameters. Over 1000 units have been sold through a licence [1972 - Present]
    • Twelve prototype software packages have been developed as aids to the welding engineer [1984 - Present]
    • Five software expert systems have been developed which enables cracking in ferritic steel weldments to be diagnosed, welding procedures to be generated for arc welding of aluminium alloys, the diagnosis of faults in orbital tube welding, selection of hard surfacing consumables, and selection of shielding gas compositions [1985-1990]
    • A 7 axis gantry robot arc welding cell has been completed for applications requiring multipass welding. The cell uses a grey scale visual image sensor and provides real time instructions to the robot effected motors [1988]
    • A successful demonstration of computer integrated manufacture (CIM) was held in a European shipyard bringing together CAD, graphic simulation and robot welding [1989]
    • Collaboration with Cranfield CIM Institute, DEC and GEC Fanuc has led to a successful demonstrator of factory computer systems communication using the manufacturing automation protocol (MAP - Version 3) [1990]
    • A prototype electronic equipment has been developed for monitoring weld bead profiles which uses transputer technology, can store data produce print-outs, and compare with standards [1990]
    • A prototype programmable error monitor has been developed for arc welding applications, which sets tolerance limits for welding procedures [1991]

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  • Structural performance of welds and adhesively bonded joints in plastic
    • Design of ultrasonic probes with shoes having suitable acoustic characteristics for inspection of plastics [1989]
    • TWI has acted as one of the lead organisations within the ESIS (formerly EGF) Technical Committee on Polymers and Composites, with responsibility for the development of a multi-specimen J-crack growth resistance curve testing protocol for parent plastics [1989-1991]
    • TWI was the first organisation to quantify crystallinity and molecular orientation in hot plate (PE and PP) and vibration (PP) welds using polarised FTIR- microspectrometry and to identify phase changes at joints in PP using DSC and X- ray diffraction [1990]
    • Development of a novel geometry for testing the weld line in thermoplastic composites [1990]
    • Identification of the significance of different failure mechanisms in composite systems [1990]
    • TWI has acted as the convenor of a working group on 'Design of Joints' which formed part of the British Plastics Federation Design Data Initiative, whose remit was to look at the current status of design methods and materials design data for polymeric products and materials. TWI produced a report detailing the present UK situation for joints involving polymers fabricated by welding, mechanical fastening and adhesive bonding [1990]
    • TWI was the first research institution to study ageing properties and mechanisms of degradation of thermoplastic welds [1990]
    • The British Standards Institution have asked TWI to act as the principal expert and co-ordinator of the UK's involvement in the CEN group (TC249/SC3/WG3) who are responsible for the development of CEN standards in the area of 'Plastics Bonding' which covers both welded and adhesively bonded joints in thermoplastics [1991]
    • Demonstration of improved adhesion to polymers by surface treatment with UV or IR lasers prior to adhesive bonding [1991]

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  • Improved and novel processes for joining plastics and ceramics
    • Invented, patented and developed the resistively heated implant welding for thermoplastic composites [1987]
    • Invented and patented a novel technique for rapid welding of plastic lined steel pipe [1988]
    • First to show and develop welding techniques for 'difficult' materials such as short fibre reinforced thermoplastics [1989]
    • First to show the feasibility of using linear vibration welding for thick wall (greater than 15mm) thermoplastic components [1989]
    • Demonstrated improved productivity (by up to a factor of 10) of butt fusion joining of polyethylene pipes [1990]
    • Invented and developed a novel ultrasonic welding transducer based on magnetostrictive principles [1990]
    • Invented and patented direct welding of plastics and plastics composites to metals by the polymer coated metal (PCM) technique [1991]
    • TWI has acted as the convenor of a working group on 'Designs of joints' which formed part of the British Plastics Federation Design Data Initiative whose remit was to look at the current status of design methods and materials design data for polymeric products and materials. TWI produced a report detailing the present UK situation for joints involving polymers, fabricated by welding, mechanical fastening and adhesive bonding [1989-1991]
    • Asked by British Standards Institution to act as the principal expert and co-ordinator of the UK's involvement in the CEN group (TC249/SC3/WG3) which is responsible for the development of CEN standards for on 'Plastics Bonding' (both welded and adhesively bonded joints in thermoplastics) [1991]
    • Invented and patented a novel interlayer design for joining ceramics to metals for application in, for example, automotive engines as part of a EURAM project ]1990]
    • Developed direct friction welding of aluminium to aluminium nitride for electronic heat sinks [1991]
    • Developed a method for brazing siliconized silicon carbide radiant heating tubes [1991]

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  • New and improved processes for surfacing and surface treatment of engineering components
    • Arc Processes
      • Assessment of plasma transferred arc (PTA) surfacing process for small bore cladding and demonstration of the advantages of the technique for specific applications, e.g. valves [1989]
      • Optimisation of conditions when arc spraying Al alloys and reduction of coating porosity from 15% to 2% [1990]
    • Forge Processes
      • Demonstration of the potential of friction surfacing for depositing coatings of MMC from commercially produced non-ferrous and ferrous MMC consumable bar and directly from powder consumables [1988]
      • Reduction in edge defects by successful use of orbital motion to deposit metals by friction surfacing [1989]
      • Development of linear actuators (hydraulic and electro-mechanical) for friction surfacing [1985]
      • Demonstration of the feasibility of using resistance heating to deposit cobalt based alloys from powder [1990]
    • Laser Processes
      • Development of an Axicon lens for beam shaping when applying surface treatment by CO2 laser [1983]
      • Demonstration of the laser strip cladding technique (patent applied for) [1991]
    • Coating Materials
      • Deposition of Cr B2 and (WV)C in 304 stainless steel using plasma transferred arc (PTA) surfacing, with encouraging wear properties
      • Application and consolidation of ceramic coatings on Al with the combined use of Sol-gel technology and laser heating [1991]

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  • Advanced microfabrication technology
    • Developed direct friction welding of metals to ceramics for heat sinking applications [1960]
    • A world leader in wire interconnection techniques to active circuits
    • Invented and patented Al ball bonding [1982]
    • Invented and developed insulated wire ultrasonic bonding [1987]
    • Developed and manufactured electrostatic bonding equipment for bonding silicon to glass for the manufacture of silicon sensors [1985]
    • Generated design data for laser single point soldering of electronic lead outs [1988]
    • Patented a low cost plastics packaging concept based on ultrasonic welding [1988]
    • Developed processing techniques for the successful adhesive bonding of large area Si die (50 x 50mm) to substrate circuitry [1989]
    • Developed finite element models to predict residual stress in dissimilar material joints, such as die bonds [1990]
    • European leader in the development of fine pitch soldering of miniature electronic devices [1991]

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