European Joining Platform General Assembly

Fabrication with Stainless Steel

4th International Conference of Engineering against Failure

WEBINAR on Joining Composite Structures

Joint Event with TWI and SSA: Funding Opportunities in the Maritime Sector

Attention all Fabricators: BS EN ISO 3834 - your opportunity to get to grips with this important fabrication standard

Find out more at:www.twi-global.com/news-events

Connect+ is the electronic newsletter from TWI. This regular e-mail publication showcases a selection of news and technical information but for an expanded view and access to a wider collection of recent papers, please visit our Connect+ webpage: www.twi-global.com/news-events/connect-plus/

TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK Tel: +44 (0)1223 899000

Connect+T h e m a g a z i n e o f T W I

TWI Events

May/June 2015

A novel welding technique enabled by electron beam lithography involving laser welding along absorber dye patterns has been developed by TWI Ltd in collaboration with the University of Cambridge. The result is the world’s smallest weld in thermoplastic material, bringing with it new applications for smaller-scale biological analysis chips, chemical micro-reactors and electronics products.

Laser welding is the process of choice in many industry sectors for joining plastics due to its ability for precision of the joint location and in the amount of heat applied. It is perfectly suited to the manufacture of complex products such as microfluidic devices, where channels and structure resolution below 100μm are used regularly.

It was work carried out by TWI and the University of Cambridge’s Cavendish Laboratory into precise patterning of laser absorber dye on a plastic surface to define weld position, that sparked off the latest advance. Having proved that the process using laser absorber dye resist material could allow joints to be made between plastics, the project team studied the use of electron beam lithography to pattern the absorber and enable welds with a width smaller than 10μm, mimicking methods used to build microelectronic circuits. The challenge was to generate micro-channels and infrared absorber tracks at their edges simultaneously, and to seal the channels.

With polymethyl methacrylate (PMMA) thermoplastic as a base material, the team carried out trials, following the principle of transmission laser welding using a thin coating of infrared absorbent material at the joint interface. The coating was patterned using electron beam lithography to the required resolution in a reproducible manner, so it could be retained after welding. Joint strength was ratified using larger-scale samples.

The trials culminated in successful demonstration of a series of laser welded joints with widths of 1μm and channels of 5μm. Smaller welds of 0.5μm were also demonstrated leading to the conclusion that it is possible to make plastics components with a high density of structure and resolution below 1μm, and that welding can be applied without excessively heating regions outside the weld lines.

World’s most precise weld made at TWI using EB lithography and laser technologies

Franco-British Symposium on Composite MaterialsFrench and UK-based delegates seized the opportunity to network during two days of presentations and ideas exchange at the Franco-British Symposium on Composite Materials. Held at the majestic Résidence de France in London on 28 and 29 April 2015, 36 attendees from across government, industry and academia focused on the challenges faced by the transport sector, in particular automotive, rail and aerospace. Presentations covered economic and technological issues regarding the introduction and use of composite materials for transportation, including design and manufacture, recycling and reuse. Stakeholders from the French and UK composite industries, and French and UK private and public sectors, included TWI’s Chris Worrall, who presented on ‘Joining technologies for composites.’ Dr Worrall’s presentation provided a good opportunity to showcase TWI’s ongoing research on joining composites including recent innovations in improved quality of induction welding of thermoplastic composites and the thermally assisted piercing technique, developed at TWI as a way of making holes in composites by displacing rather than removing material. The talk also led nicely to the next two speakers from LoireTech and Sigma Precision Components, who presented two recent collaborative projects carried out with TWI on composites: MuTool and ComPipe. Aiming to reinforce the links between both countries, the symposium helped to identify some common ground and recurrent themes.

For more information about the symposium and to download presentations please visit www.ambafrance-uk.org/Summary-Franco-British-Symposium. For more information about TWI’s work on composites please visit our website.

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May/June 2015

New Members of TWI

C4 Carbides LtdUnited KingdomManufacture of cutting tools and saw blades

Daewoo Shipbuilding & Marine Engineering Co Ltd Ship and Ocean R&D InstituteSouth KoreaShipbuilding and offshore company structural R&D

Dril-Quip LtdUnited KingdomManufacture of offshore drilling and production equipment

HF WebsterUnited States of AmericaFriction stir welding and aluminium machining

Maia EolisFranceOperator of land-based wind turbines

OOGTK Libra GmbH & Co KGSingaporeJoint venture between Odebrecht Oil & Gas and Teekay Offshore

Oxford Instruments NanoscienceUnited KingdomAnalytical instruments in nanotechnology

Pankl Racing Systems UK Ltd United KingdomManufacturer of high-performance engine and drivetrain components

STATS GroupUnited KingdomSpecialist engineering, piping, pipeline integrity and maintenance

TWI is set to launch two new courses this summer to provide candidates with crucial skills in corrosion inspection.

‘Corrosion Awareness: Conventional Ultrasonic Inspection’ will equip trainees with a comprehensive overview of all of the issues surrounding corrosion, from identification and scientific background to effective testing and control. A second course, ‘Corrosion Awareness: Advanced Ultrasonic Inspection’, will expand on the content of the first and introduce phased array ultrasonic testing (PAUT) corrosion mapping and analysis, to provide an even more thorough understanding of corrosion inspection, quantification and monitoring.

The importance of prevention, identification and control of corrosion is clear when you consider the financial figures involved: estimates put the annual cost of corrosion at a staggering $2.2 trillion – more than three per cent of global GDP.

Modern non-destructive testing (NDT) methods, particularly ultrasonic testing, are capable of detecting and quantifying corrosion with a high degree of accuracy. This is essential for many sectors of industry, but none more so than oil and gas, where processing plant and offshore facility operators need to be able to make informed decisions when considering maintenance schedules, condition monitoring, and engineering critical assessments determining life extension and reduction decisions.

These two new courses from TWI have been designed for anyone whose work brings them into contact with corrosion and its consequences. They are ideal for Level 2 ultrasonic inspectors,

those who wish to build on existing knowledge of plant inspection, those who interface with NDT inspectors and anyone who wishes to increase their understanding of corrosion and its detrimental effect on materials.

‘Corrosion Awareness: Conventional Ultrasonic Inspection’ will cover topics including the theory of corrosion, types of corrosion, preventative measures, corrosion monitoring, structural damage mechanisms, types of failure and inspection techniques.

‘Corrosion Awareness: Advanced Ultrasonic Inspection’ will delve into corrosion inspection in more depth, covering areas such as the benefits, capabilities and limitations of different ultrasonic inspection methods, how to select the appropriate level of sensitivity for different inspections, practical sessions in setting up one- and two-axis scanners, and effective analysis of results.

Both courses will be backed up by internationally recognised CSWIP certification, providing qualifications respected by industry. Each will last five days and should be available across a number of TWI’s international training centres. Exact course specifications, costs, venues and dates will be announced shortly.

If you would like to find out more or register your interest in attending these new courses, contact TWI Training by emailing trainexam@twitraining.com or calling +44 (0)1223 899500.

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January/February 2014

Two new courses and certification schemes to focus oncorrosion awareness

Contributions invited for UK strategy for additive manufacturingWork is underway to establish a UK national strategy for additive manufacturing by early 2016, to maximise UK business growth and long-term economic value through the successful industrialisation of the technology. Prof Phill Dickens from the University of Nottingham and Dr Tim Minshall from the University of Cambridge are co-ordinating the initial baseline evidence gathering process.

Understanding your views, opportunities and challenges on how to widely benefit from additive manufacturing in the UK is extremely important and a vital contribution to the creation of a UK national strategy in this exciting field.

Submissions can be submitted via the details given at the strategy website at www.amnationalstrategy.uk by 15 June.

The next stage will be the formation of working groups to develop the strategy. If you would like to be involved please contact Phill Dickens at phill.dickens@nottingham.ac.uk.

May/June 2015

Job Knowledge - Robotic arc welding

The development of automated arc welding solutions continues to be driven by the requirement for higher product quality, productivity and reduced costs. In addition, good manufacturing system flexibility, which is essential for responding to the dynamic behaviours of the market and therefore keeping products competitive, has become a key development target for the manufacturing industries. As a result, robotic welding processes offer attractive alternative solutions to traditional manual operation and hard automation.

Since the first application of a welding robot in industrial production in the early 1960s, robotic welding has expanded across a range of manufacturing industrial sectors. Between 2010 and 2013 alone, over 600,000 industrial robots were commissioned globally [1]. Robotic welding has been recognised as the most popular industrial application of robotics worldwide [2]. It is estimated that approximately 25% of all in-service industrial robots are employed for welding operations [3]. Automotive manufacturing represents the most active industry sector in terms of robotic welding adoption (approximately 40% of total global robot supply), followed by the electrical and electronics industry (approximately 20% of total global robot supply). Apart from resistance spot welding, the two most common robotised welding processes for production purposes are metal inert gas (MIG) welding and tungsten inert gas (TIG) welding respectively.

Basics of robotic arc welding

A basic robotic arc welding system is formed by two subsystems: the welding equipment delivering the energy from the welding power source to the workpiece, and the robot providing relative positioning of the heat source and the workpiece. Normally six-axis industrial robots comprising a three-axis lower arm and a three-axis wrist are used, since they enable the welding torch mounted at the wrist to achieve all the positions necessary for three-dimensional welding. Traditionally, general purpose industrial robots are employed, carrying arc welding torches as end effectors. Many robot manufacturers have recently developed arc welding-specific robots, which are smaller and less expensive. This reduction of the required capital investment has further increased the sale of robotic welding systems. Another recent development in welding robotics has been the introduction of seven-axis robots, which feature an additional axis in the lower arm providing additional flexibility and saving floor space. The major characteristics of industrial robots are summarised in Table 1.

Table 1

Payload 2 to 30kgAxes Six to sevenVelocity Up to 5m/sAcceleration Up to 25m/s2

Repeatability ≥0.05 mm

Communications Profibus, DeviceNet, CANopen, Ethernet/IP and serial channels

IO capabilities Digital/analogue IOs

In a production environment, workpiece manipulators are frequently implemented as part of the robotised system. The devices extend not only a welding robot’s working range but also its accessibility, especially when welding complex and large geometries. The control of a manipulator is often integrated with that of the robot, which enables the synchronised and simultaneous control of the two mechanisms. The integrated control allows coordinating motion between the robot and manipulator (workpiece) which maintains the optimum welding positions (higher deposition rate and quality) and possibly increases the welding speed (higher productivity). Figure 1 shows a six-axis industrial robot integrated with a cold metal transfer (CMT) arc welding system and a two-axis workpiece positioner at TWI Cambridge.

Process sensing

Robotic welding is a challenging combination of welding, robotics, sensor technology, control systems and artificial intelligence. Driven by the increasing demands of improved quality, productivity and flexibility, precise and adaptive control of the robotic welding processes has become a crucial target for the development of modern systems. Sensing technologies designed for welding and its automation are the essential elements for enabling this desired level of control. The sensors are applied to observe and measure process parameters, acting as the sources of input to the control system. By acquiring and analysing the input information from the sensors, the control system adapts output of the robotised welding process in accordance with the defined welding procedure specifications.

There are various types of sensors available for robotic arc welding applications. Depending on their functions, the sensors are classified into two categories: process and geometrical. The former measure the process parameters of the robotic welding process (eg arc voltage, current, wire feed speed and torch rotation), which determine the stability of the process. The latter measure the weld joint geometry (eg gap sizes, weld size changes, deviation from the nominal path and orientation changes) and are used

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for weld searching, seam tracking and real-time adaptive welding.

Table 2

Function SensorWelding current measurement

Hall effect sensor

Current shuntArc length control Voltage sensor

Distance control Capacitive sensor

Weld edge searching Tactile (electrical contact) sensor

Proximity sensorWeld seam tracking Tactile (mechanical contact)

probe

Eddy current sensor

Through-arc sensing (weaving with electric measurement)

Vision sensor

Laser scanning Weld penetration monitoring Infrared radiation sensor

Ultrasonic sensorWeld pool monitoring Vision sensor

Thermal imagingWeld quality inspection Eddy current sensor

Ultrasonic sensor

Laser scanning

Key issues

The benefits of implementing robotic arc welding are evident but there are some issues associated with it which should not be ignored. Robotised technology is a good solution to fill the burgeoning skills gap in welding fabrication industry, but using and programming the industrial robots is still a complex and difficult task for regular operators. Despite the fact that modern sensing techniques for robotic arc welding are readily available and reasonably reliable, it is still challenging to effectively and efficiently apply them in some applications. The high temperature, intense light from arc, fume, high current, molten metal, spatter, and other factors involved in arc welding can interfere with the sensors. Developing a

control system which can fully utilise the information obtained by the sensors and effectively translate it to the fabrication is still a difficult task.

Summary

Robotic arc welding is an essential component of today’s manufacturing plants. The primary benefit of robotic arc welding is the production of high-quality welds in a shorter cycle time, with manufacturing flexibility another major advantage. Through extensive application in many manufacturing industry sectors, robotic welding has been developed to a mature production method. Strong industrial need continues to drive the rapid development of robotic arc welding and associated technologies to overcome technical difficulties and expand their capability.

TWI has established good experience in robotic welding through its services in generic research, contract R&D, technical information, consultancy, standards drafting, training and qualification. For more information, please contact us.

References

International Federation of Robotics, 2014, World Industrial Robot Statistics 2014, http://www.ifr.org/industrial-robots/statistics/.United Nations and International Federation of Robotics, 2000, World Industrial Robotics 1996: Statistics and Forecast, New York: ONU/IFR. J N Pires, A Loureiro and G Bölmsjo, 2006, Welding Robots: Technology, System Issues and Applications, London: Springer-Verlag.

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Case Study: REMO – Online Remote Condition Monitoring of Tidal Stream GeneratorsTWI played a key role in an EU project that has developed methods of continuously monitoring the condition of active tidal energy generators.

Trials have now been completed in REMO, a collaborative research project looking into the feasibility of using vibration analysis (VA) and acoustic emission (AE) in combination to monitor the condition of in-service tidal stream generators. The developed prototype, now at the demonstration stage, assesses the structural and mechanical integrity of tidal systems to provide advance warning of the presence of faults and impending failures.

Harnessing the potential of tidal energy

Due to the predictable nature of tides, tidal energy is an environmentally attractive renewable energy source. However, considerable investment costs and expected costs of lifetime maintenance in hostile marine environments have hindered large-scale implementation. Operational availability has been shown to be as low as 25%. This availability needs to be increased substantially if tidal energy harvesting devices are to become commercially viable. Integrated condition monitoring (CM) can provide a reliable tool for assessing the real-time condition of critical components of tidal systems, enabling cost-effective maintenance based on prediction rather than correction.

REMO aimed to create a novel CM system to help reduce the projected lifecycle maintenance costs of tidal stream energy by 50% and the generator downtime to a level comparable with wind turbines.

Details of the techniques

Vibration analysis:

• An established inspection method for monitoring high-frequency rotating parts

• A qualitative technique providing information on the type of damage present.

Acoustic emission:

• A technique gaining industrial acceptance for its ability to monitor low-speed rotating machinery

• Provides a quantitative measure of mechanism deterioration

• Requires validation of its ability to detect damage in service.

Using a combination of the two allows for the complementary analysis of waves through the whole frequency spectrum, enabling us to monitor components rotating at different speeds.

Validation of AE

To validate the use of AE, researchers undertook laboratory trials where a scaled test rig was set up to generate noise and vibration representative of a full-scale tidal power system. A test plan was designed to replicate the kind of progressive gearbox damage that could lead to catastrophic failure. Clear spikes in an AE signal were observed when a defect was present – all the indicators extracted from the AE signal differed between the healthy and fault conditions. These results show the potential use of AE for fault detection in tidal turbine gearboxes.

Integrated system

Researchers developed and integrated software and hardware for acquisition of VA and AE, providing remote access and supervisory control. The architecture is modular, scalable and flexible, so that the system can be adapted to different energy recovery systems.

Underwater trials at TWI’s diving tank facilities in Middlesbrough validated the system.

Results

The team analysed different operational conditions relevant to increased damage levels to show damage detection and correlation capabilities of the REMO system.

Researchers developed pattern recognition signal processing software based on similarity analysis and Euclidean distance that achieves the next targets:

• Determine the signature of a healthy turbine and evolution of this healthy signature throughout the system lifetime

• Identify deviations from the healthy signature• Provide an automated warning of the presence

of significant defects well before irreversible damage or failure arises.

Future developments

This project has shown that AE offers promising results and provides information about the damage level of the gearbox for tidal turbine gearbox monitoring. Adding VA data to this offers additional information about the prematurity and accuracy of defect detection including determination of the kind of defect.

The full case study is available on our website. For more information please visit remo-project.eu

May/June 2015

May/June 2015

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Funding opportunities in the maritime sectorTWI and SSA, the voice of the UK marine industry, have teamed up to deliver an event that aims to bust the myth that funding opportunities in the maritime sector are just for large organisations. The free event, which takes place on 15 July, is aimed at anyone connected with the shipbuilding industry or maritime sectors with an interest in UK and European collaborative projects.

TWI’s newly opened conference facilities just south of Cambridge will provide the perfect backdrop for a day of networking, presentations and debate, with lunch and refreshments provided throughout. The Granta Centre has good transport links and plenty of free parking. Registration opens at 10.00am with presentations starting at 10.30am. The event closes at 3.00pm. To book your free space, download the day’s programme, and for directions please visit our website.

Lloyd’s Register NSIRC student scoops coveted £1000 prizeStudent Laura Vivar, who last year began her studies at the National Structural Integrity Research Centre (NSIRC), has been awarded a prize for the quality of her work.

Laura was the first Lloyd’s Register Foundation-sponsored PhD student to join NSIRC when she began her studies in November 2014, and now rounds off a successful first year by picking up the £1000 prize for the best first-year PhD or EngDoc student, awarded by the Armourers and Brasiers’ Gauntlet Trust.

The competition required Laura to submit a résumé of her work and published papers. Judges awarded the prize after being impressed by the quantity and quality of Laura’s output for the year, the novelty of her work, the way she’d communicated the underlying science, and her transition to independent research.

The award will be officially presented to Laura at the TWI Annual Dinner, taking place at King’s College, Cambridge, on Tuesday 30 June.

TWI celebrates construction milestone Just sixteen months after work commenced, SDC Construction Group has handed over the final building in the suite of three new purpose-built research and development laboratories for TWI at Granta Park, Cambridge. The building, includes a base for the company’s training operations and the headquarters of TWI’s professional arm The Welding Institute.

The £60 million site build has been enabled through UK Regional Growth Funding and with the backing of South Cambridgeshire District Council. The new facilities have been equipped with state-of-the-art machinery through support from the Higher Education Funding Council for England.

A key feature of the project has been the National Structural Integrity Research Centre, a hub for postgraduate education integrated within TWI, which will welcome over 530 students in the next ten years, involving them in industry-relevant project work. TWI currently carries out around 750 R&D and innovation projects each year to benefit its international base of Industrial Member companies.

Department moves from older facilities on the site are well underway, filling the new areas with equipment, people and activity along ‘the street’– a spacious walkway connecting with the existing TWI main building (est. 2003). Work continues to restore the immediate parkland around Abington Hall, putting environmental impact first, and on completing a sunken car park for visitors and staff. All landscaping will be completed by midsummer and TWI will host an official opening in the autumn..

A West African employment agency turned to TWI for plastics welding training to expand its capability after investing in new equipment.

Senior plastics welding trainer Andy Knight travelled to the premises of C2K Staffing in the Senegalese city of Thiès, where he provided training to six technicians to enable them to use welding machines the company had just bought from Italian company Ritmo.

The training covered butt and electrofusion welding of high-density polyethylene (HDPE) pipe. Following the four-day programme each of the trainees successfully passed the relevant entry-level CSWIP exams on welding large- and small-diameter HDPE pipe.

C2K Staffing provides temporary employment services to companies operating in West Africa, with a particular focus on the mining, energy, construction and manufacturing industries. The skills acquired by the company in plastics welding will allow it to broaden the range of services it can offer its clients.

A spokesperson for the company said: ‘C2K Staffing has organised this training on HDPE welding for the purpose of having a certified, qualified team of welders as a flying squad to better assist clients during plant shutdowns or execution of improvement projects.

‘With the demand for HDPE welding techniques from local mining and construction companies, C2K Staffing is expecting to provide qualified HDPE welders and rental of the equipment to companies who can’t afford both the equipment and the training of their employees.

‘C2K is working on having other training sessions by TWI whenever possible.’

TWI has worked with businesses all over the world to deliver training that exactly matches its clients’ commercial needs. Available either within one of its global offices or on-site at a company’s premises, training from TWI ensures engineers and technicians have the up-to-date knowledge and skills they need to stay competitive.

If you are interested in plastics welder training, get in touch with Scott Andrews via our Contact us page or call him on +44 (0)1223 899000.

For more general information about training opportunities from TWI visit www.twitraining.com, email trainexam@twitraining.com or call +44 (0)1223 899500.

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January/February 2014

Connect+ is the bi-monthly magazine of TWIPhotographySimon Condie Production Kim BarrattJames Burton Graphic Design Craig Carter Copyright © TWI Ltd 2015Articles may be reprinted with permission from TWI. This publication is also available in alternative formats. To request a copy please contact marketing@twi.co.uk

African company approaches TWI for plastics welding training

May/June 2015