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Composite materials are used increasingly

in aircraft with demand increasing on a

global scale but the rate of production

is hampered by the speed at which the

composites can be inspected during the

manufacturing process.

The four-year research project led by TWI Wales is designed to speed up the

inspection process by 400% using advanced

non-destructive testing technologies.

IntACom (Improving the Inspectibility

of Aerospace Composite Materials)

which has had funding from the Welsh

Assembly Government, involves an

industrial collaboration with Rolls-Royce,

GKN Aerospace and

Bombardier Aerospace,

with academic supportfrom Swansea University,

Swansea Metropolitan

University and the

University of Wales.

Launching the project,

Lesley Griffiths, Deputy

Minister for Science,

Innovation and Skills,

said it had the potential

to make a significant

contribution to industry, specifically the

aerospace sector.

‘It’s great news to hear that Wales is leading

the way on the research and development

of highly sophisticated technologies with

the potential to make a significant impact

on the production of composites.‘I am par ticularly pleased the Welsh

Assembly Government is suppor ting this

research and that Wales is taking the lead

and working with major players in the

aerospace sector and benefiting from

academic support from our Universities.

‘Our Economic Renewal strategy highlights

the need to build upon the expertise that

Aerospace sector to benefit

from TWI-led industrial

research collaboration

Lesley Griffiths, Deputy Minister for Science, Innovation and Skills

Issue 170 January/February 2011

Diary events

March 2011

Joint Technical GroupmeetingOffshore Oil and Gasand PolymersMon 14 Aberdeen

Seminar Linear Friction WeldingThu 17Great Abington

Workshop and exhibitionMeet the BuyerThu 24Stirling

April 2011

Conference

Association of Welding,Fabrication, Training andEducationFri 1Great Abington

Technical Group meetingWelding Processes

Wed 13Great Abington

May 2011

WorkshopIntroduction to the UKNuclear Industry

Wed 4 May Stirling

ConferenceWelding & Joining Society

Wed 18 – Thu 19Great Abington

Workshops and seminars

are recognised

Continuous ProfessionalDevelopment events

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

w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k

A £3.8m industrial research collaboration announced on Wednesday

2 February is set to have a significant impact on the worldwide aerospace

industry by speeding up the production of composite materials.

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January/Fe bruary 2011

C on ne ct J an ua r y /F eb ru ar y 2 01 1 w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k

exists within Welsh universities and businesses to harness

the commercial opportunities of innovation and research.

This is a good example of such collaboration between

the private and public sector and between industry and

academia.’

Philip Wallace, Regional Manager of TWI Wales, which is

based in ECM², Port Talbot, explained that the advancement

in composites had not been equally matched by an

advancement of inspection capability.

‘Composites inspection is a difficult and highly complex

area but is not yet sufficiently developed to meet industry

needs. The time it takes to carry out inspections at different

stages of the manufacturing process is actually hampering

and slowing down the entire process.

‘Our aim is to increase the process by 400% without losing

reliability or sensitivity and once we have developed the

inspection technology at the manufacturing level we will

further develop testing and inspection capabilities for in

service maintenance and repair.”

TWI NDT Validation Centre (Wales) was set up with

support from regional initiatives (through the Welsh

Assembly Government and Welsh European Funding

Ofce) to provide expertise in the area of advanced NDT,

complementing the facilities located at TWI’s headquarters

in Cambridge.

Activities at the Centre include development of advanced

inspection technologies, research into applications of

conventional and novel inspection methods and practical

inspection work.

Consultancy services, such as Level III support, trouble-

shooting, advice on applications and procedure

development/approval are also available from the Centre.

Validation of newly developed technologies and procedures

can be provided by the Validation Centre.

For more information, contact, [email protected]

continued from p.1

Alere Technologies LtdUK Medical device developmentand manufacture

Amey Area 9 Bridges TeamUK Maintenance of motorway structures in the Midlands

Autoliv IncSwedenManufacture and sale of occupant restraint systems

AVIC Beijing Institute of Aeronautical MaterialsChinaAircraft and aeroenginefabrication research

Brandon Medical Co Ltd

UK Design and manufacture of

medical lighting, power andcontrol systems and medicalaudio visual

CalegeoUK Marine surveying

Cavitar LtdFinlandDiode laser illumination/materials processing

Centrica Storage LtdUK Gas process/storage, on- andoffshore

CLP Power Hong KongLimited – GenerationBusinessHong Kong

Electricity generation

DatapaqUK Thermal process monitoring

Domino UK LtdUK Manufacture of ink jetprinting products and processdevelopment

Erlson Precision LtdUK Precision machining andassembly operations

Fife Council TransportationServices (Lighting)UK Local authority

Invibio LtdUK

Biomaterial manufacture

Mitsubishi Electric - Energyand Industrial Systems

JapanPower systems for rail, power and industry

Praxair Metal FabricationsGroup – GlobalUSAIndustrial gases

Reaction Engines LimitedUK Heat exchanger, spaceplaneand space propulsion design

Smith & Nephew – Wound ManagementUK

Wound care products

Victrex plc

UK Polymer production

New Members of TWITWI is pleased to welcome the following as Industrial Members

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January/February 2011=

3

Nano-indentation at TWI

A nano-indentor system is a sophisticated alignment

assembly, a small load cell, a piezoelectric depth sensing

device, a sample holder and an indenter at 900 to the

sample holder. As the indenter is driven in and out

of a sample at constant load, its penetration depth is

continuously monitored. The resultant load-depth cur ve

gives the information needed to determine hardness,

elastic modulus and other material properties. Modern

instruments allow the user to glean useful and accurate

material property values with penetration depths as low as

a few nanometres.

Typical applications include:

• Mapping of surface properties across small areas(measurements may be taken down to 1µm apart)

• Elastic and plastic properties of materials at the nano-

scale

• Mechanical property measurement of individual phases

or grains

• Creep analysis

• Nano-scratch and wear testing; primarily for cohesive

and adhesive assessment of coatings

• Nano-indentation probes mechanical properties at high

strain rate, investigating surface fatigue and fracture due

to repetitive contact

• Testing under heated and cooled conditions (-30 to

750°C)

• Testing in liquid environments (eg biomedical and

corrosive environments)

These techniques provide more application specific material

property data which are complementary to the basicambient conditions test data and have allowed many users

to accurately simulate the results of larger scale, expensive

field testing in the laboratory environment.

Recently nano-indentation was used within two TWI

projects on dissimilar metal interfaces for subsea

applications and adhesion of transparent conductive oxides

on to different substrates. This information improves finite

element simulations for reliability prediction of joined

structures. These simulations are only useful industrially

when they are given the correct gradient of mechanical

properties across interfaces and related activation energiesif needed.

For further information on nano-indentation, or to request

trials, please contact [email protected]

Nano-indentation is a depth sensing indentation technique, which promises to become an important mechanical characterisation tool for precision components. By using a nano-indentor, which can

sample directly from the area of interest, engineers can begin to predict much more accurately how

their products will behave.

Typical failure modes of transparent conductive oxides deposited onto

different substrates: PEN, glass and Si.

Nano-indentation array across F65 / Alloy 625 dissimilar metal

interface: a) micrograph of cross section and indentation locations;

b) nano-hardness. Location of interface is indicated; and c) Elastic Modulus. Location of interface is indicated.

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Techn olog y Trans fer

Job Knowledge110 Welding of titanium and its alloys

Part 2

Titanium and its alloys are remarkably

resistant to the cracking problems

experienced by many of the other

alloy systems. Solidification and

liquation cracking are virtually

unknown and what could perhaps be

called cold cracking, occurs generally

only because of embrittlement arising

from contamination, as discussed in

Part 1.

Porosity is the commonest problem,

particularly when close square butt

joints are used. It is generally attributed

to hydrogen and cleanliness is

therefore crucial in eliminating porosity.

The porosity may be of one or a

mixture of two types: firstly micro-

porosity formed within the arms of

the dendrites during solidification andsecondly, larger pores that often align

themselves along the weld centreline.

As discussed in Part 1, cleanliness

is the key to defect-free welds and

this means that not only must the

component be thoroughly degreased

but so should the filler wires; weld

preparation edges must be deburred

and the highest purity shielding gas

must be used. Ideally the gas should

have a dew point of less than -50OC

(39ppm H2O) and to maintain this

low level the gas supply system should

be free of leaks. Regular and frequent

maintenance of the system is therefore

essential, checking the joints for leaks

and for damaged hoses. Ideally the

gas supply should be from a bulk gas

tank, not cylinders, and delivered to

the workstations via welded or brazed

steel or copper tubing. Plastic hoses

should be kept as short as possible;

most plastics used are porous and will

allow moisture to permeate through

the hose wall; neoprene and PVC

are the worst, Teflon one of the least

porous. It is worth remembering that

moisture can collect in the hose over a

period of time so a porosity problem,

after a weekend shut down, may be an

indication that this is occurring.

TIG filler wires should be cleaned

with a lint-free cloth and an efficient

degreasant immediately before use.

Following cleaning, the wire should not

be handled with bare hands but whilst

wearing clean, grease-free gloves. MIG

wire presents more of a problem but

devices to clean the wire as it passes

through the wire feeder are available.

For the best results wire that has beenshaved to remove any embedded

contaminants can be obtained.

A further potential source of

contamination that is frequently

overlooked is the use of air powered

tools for wire brushing or dressing

weld preparations and welds. Most

compressed air contains moisture

and oil so that, even when oil and

moisture traps are fitted, it is possible

to leave a thin film of moisture and/

or oil on the surface to be welded.

It is recommended that electrically

powered tools are used at all times

once the item has been degreased

prior to welding.

Although regarded as a very minor

problem, ductility dip cracking (where

alloys experience a severe loss of

ductility at a temperature below

the solidification temperature) has

been noted in some of the titanium

alloys; the alpha-beta alloys containing

niobium being the most susceptible

with Ti-6Al-2Nb-1Ta-0.8Mo the most

sensitive. The temperature range in

which this loss of ductility occurs

is between 750OC and 850OC.

The cracking is intergranular and is

thought to be partly the result of

volume changes during the beta to

alpha phase change coupled with the

reduction in ductility.

A significant amount of welding of

titanium alloys is carried out without

filler metals. When filler wire is used,

generally a composition matching that

of the parent metal is selected. There

are some exceptions: the welding

of high strength but low ductility commercial purity titanium is generally

performed with a low strength filler

metal to achieve the desired weld

quality. Similarly, unalloyed filler metal

is sometimes used to weld alloys such

as Ti-6Al-4V, thereby improving weld

metal ductility by lowering the amount

of beta phase that is formed. Extra low

interstitial (ELI) filler metals are also

available and may be used to improve

weld metal ductility and toughness.

Most of the titanium alloys can be

successfully fusion welded using the

gas shielded welding processes and

power beams; all can be welded

using solid phase processes, friction

and resistance welding. Welding

parameters and weld preparations are

similar to those that would be used to

weld a carbon steel. From the welder’s

point of view, titanium is easier to weld

than steel, having good fluidity and

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Techn olog y Trans fer

5

high surface tension, easing the task of

depositing sound full penetration root

beads.

TIG welding is probably the most

commonly used process in bothmanual and mechanised applications.

The current is DC-ve, generally with

high purity argon as the shielding gas,

although helium or Ar/He mixtures

may be used to improve penetration.

Torch nozzles should be fitted with

gas lenses to improve gas shielding

and the ceramic shroud should be as

large a diameter as possible. A1.5mm

diameter tungsten, for example, should

be used with a 16mm diameter ceramic. Arc lengths need to be as

short as possible to reduce the risk

of contamination; 1 to 1.5 times the

electrode diameter is regarded as

a good rule of thumb. Arc initiation

should be achieved by the use of HF

current or lift arc to prevent tungsten

contamination. The equipment

must also be capable of continuing

the shield gas flow after the arc is

extinguished so that the weld cancool within the protective gas shield.

It is also advisable to keep the tip of

the filler wire within the gas shield

until such time as it has cooled to a

sufficiently low temperature.

A supplementary trailing gas shield will

also need to be attached to the torch

to provide protection to the cooling

weld metal as the welder moves along

the joint line. This makes manipulation

of the welding torch more difficult.

Most welders manufacture their own supplementary shields, shaped

to closely fit the component; several

shields would therefore be required

to weld a range of pipe diameters. A

backing gas is also necessary and back

purging should be maintained for at

least the first three or four passes in

a weld. Backing gas purity should be

better than 20ppm maximum oxygen.

MIG welding using argon or Ar/He mixtures may be used but this

process will not provide the same high

quality weld metal as the TIG process

and it can be difficult to achieve the

stringent quality levels required by

aerospace applications. Dip transfer

can lead to lack of fusion defects

and spray transfer requires both

leading and trailing supplementary

gas shields, the leading onr to prevent

oxidation of any spatter that may be remelted into the weld pool.

The improvements in pulsed MIG

power sources by the use of inverter

technology and microprocessor

control have obviated some of these

problems and substantially narrowed

the gap between MIG and TIG. MIG

is, however, still difficult for the manual

welder because of the difficulty of

manipulating the MIG torch with a

supplementary gas shroud. Because of

these difficulties MIG welding is oftenmechanised or automated.

Plasma-TIG may be used for welding

titanium, being capable of keyholing

a weld up to 12.5mm thickness. The

same requirements for gas purity and

weld pool protection required for

TIG are also needed for plasma-TIG.

Plasma-TIG is rarely used in a manual

application and never in the keyhole

mode.Atmospheric contamination is best

avoided by use of a welding chamber

or glove box that can be filled with

argon. Purpose built glove boxes

can be purchased but it is a simple

matter to fabricate a chamber of an

appropriate size using slotted angle

eg Dexion®, to form the frame

and covering this with a clear plastic

or acetate sheet. The size of the

component that can be welded withina glove box is necessarily restricted.

Electron beam, laser, friction, resistance

spot and seam and flash welding

are all used to weld titanium and its

alloys. Electron beam welding, being

carried out in a vacuum, needs no

protective gas shield. Conventional

friction welding may also be carried

out without a protective shield

although a gas shield should be usedwhen friction stir welding. Similarly,

no gas shield is required when

resistance welding, although for the

most critical applications a gas shield

is recommended. Laser and flash

welding both require gas shielding for

the best results and least atmospheric

contamination.

This article was written by Gene MathersCourtesy Huntingdon Fusion Techniques

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January/Fe bruary 2011

Skills gap training and certification

identified in the UK oil and gas industry

TWI Training & Examination Services has recently

conducted a skill analysis of the roles and duties

of the NDT/Rope Access Inspector employed

within the UK oil and gas sector. Its findings were

discussed with NDT contracting companies and

oil company representatives.

This study revealed that the average NDT/Rope Access

Inspector spent a high proportion of their time conducting

visual inspections of the plant rather than applying NDT

methods such as ultrasonic thickness gauging or corrosion

monitoring. However, the formal qualifications held were in

the applied NDT methods and little or no formal training

had been gained in visual inspection of the components

normally inspected.

It was also found that the Inspectors had received little or

no formal training regarding standard inspection processes

or familiarisation with the various types of drawings or

specific reporting processes to be used.

TWI has developed a course specifically to address these

issues. The Visual Inspector – Offshore course is available as

an introduction to the oil and gas sector with levels 1 and 2

being aimed at experienced inspectors.

The topics covered include:

• Background knowledge of the structures to be

inspected

• Introduction to weld inspection

• Introduction to corrosion processes

•

Review of reporting systems• Review of relevant legislation

• Introduction to coating inspection

The assessments include weld inspection, visual and

dimensional assessments of relevant samples together with

coating inspection. Successful candidates will be issued with

the appropriate CSWIP certification.

This course is a pivotal step for the NDT Inspector

or Engineer looking to follow a career path leading to

Offshore Inspection Engineer or Integrity Engineer and is

integrated into the CSWIP Plant Inspector Scheme.

To find out more, please contact: [email protected]

Courtesy of TRAC Oil & Gas Ltd

Courtesy of BIS Inspection UK Ltd

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January/February 2011

Shift-Ref Demonstration Day

Tuesday 8 March

TWI North, Middlesbrough

This half-day event offers an

opportunity to see the output from

the TSB project, Shift-Ref which has

developed a technique for electron

beam welding large components

without the need for a vacuum

chamber.

This event will provide an introduction

to the local vacuum EB process and

highlight its benefits and potential

applications. There will be an

opportunity to view the equipment

that has been designed and to

observe a demonstration of the

system.

Contact: [email protected]

Chris Eady joins Board of the

European Welding Federation (EWF)

At the General Assembly of the EWF,

Joining and Cutting, in Portugal,

Eur Ing Chris Eady, Chief Executive of

TWI Certification Ltd and Associate

Director for Professional Affairs at

The Welding Institute was appointed

to the Board of Directors. Chris said,

‘I am honoured to be elected to

the Board of EWF and I relish the

opportunity to contribute further

to the enhancement of welding

engineering skills for the benefit of

European industry.’

Danny Broadbent wins Silver in

EuroSkills Lisbon 2010

Danny Broadbent, SkillWeld 2010

Finalist, has taken a joint Silver

Medal in the EuroSkills 2010

welding competition in Lisbon. This

competition is designed to raise skills

standards, promote excellence and

increase awareness of the importance

of skills and vocational education and

training for the EU economies and

societies.

Danny entered the competition to

hone his skills in preparation for

WorldSkills 2011 and his excellent

performance bears testament to the

quality of welder training and skills in

the UK.

The Welding Institute is proud to

support the SkillWeld competition

and the development of welding

competitors for WorldSkills

London 2011.

News in brief

Subsea testing from ROVs

TWI has successfully completed a

collaborative project - SubCTest - to

develop novel NDT procedures and

equipment for deployment from

remote operating vehicles (ROVs)

on subsea offshore structures and

pipelines.

The project was carried out

by a consortium of small-to-

medium sized enterprises,

research organisations and

end-users and was supported

by a €1million grant from the

European Commission within

their Framework 7 funding

scheme.

The TWI-led consor tium

developed a range of novel

NDT techniques using phased

array ultrasonics, alternating current

field measurement (ACFM) and long

range ultrasonic testing (LRUT).

The equipment included a design of

phased array transducer for multi-skip

and creep wave ultrasonics, an ACFM

array probe that allows scanning

of complex node welded joints

in a single pass, a racetrack LRUT

technique for chains and an orbiting

focused LRUT technique for welds.

A robotic manipulator was successfully

demonstrated from an observation

class ROV and, simulations were used

to demonstrate performance when

used on an offshore jacket structure.

For more information on the project

or how TWI could help you with your

testing requirements, contact

[email protected]

Simulation of ROV deployment on ‘jacket’ legs

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For further

information on

TWI

visit the website at

www.twi.co.uk

8

Connect is the

bi-monthly magazine

of TWIEditor:

Penny EdmundsonPhotography: Simon CondieProduction:

Penny Edmundson

© Copyright TWI Ltd 2011

Articles may be reprinted

with permission from

TWI. Storage in electronic

media is not permitted.

Articles in this publication

are for information only.

TWI does not accept

responsibility for the

consequences of actions

taken by others after

reading this information.

This publication is alsoavailable in alternativeformats. Please [email protected] to

request a copy.

Published byTWI Ltd, Granta Park,

Great Abington,

Cambridge CB21 6AL, UK

Tel: +44 (0)1223 899000

Fax: +44 (0)1223 892588

E-mail: [email protected]

www.twi.co.uk

TWI Technology Centre

(North East)

Tel: +44 (0)1642 216 320

Fax: +44 (0)1642 252 218

TWI Technology Centre

(Yorkshire)

Tel: +44 (0)114 269 9046

Fax: +44 (0)114 269 9781

TWI NDT Validation

Centre (Wales)

Tel: +44 (0)1639 873 100

Fax: +44 (0)1639 864 679

TWI Aberdeen

Tel: + 44(0)1224 691222

w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k

Issue 170 January/February 2011

TWI hosts Chinese delegation

This is the second trade visit to TWI by a

high ranking Chinese Government official

in less than a month. In December 2010,UK Trade and Investment (UKTI) led a visit

by Chinese Minister Counsellor. Mr ZHOU

Xiaoming was so impressed with TWI,

and the company’s strong links with China,

that he advised this delegation to find

out for themselves the potential business

opportunities at TWI during their UK Trade

Mission.

Graham Wylde, TWI Associate Director

said: ‘We were delighted to be chosen by

the Chinese Embassy in London to host

part of the delegation’s Trade Mission tour

in the UK.

We have a long history of working with

Chinese companies, which goes back

twenty years. TWI staff spends more than

twenty weeks a year servicing their Chinese

customer base to maintain good relations

and look at future business opportunities.

Today has been extremely productive

and we have received positive feedback

from the delegation, with many companieskeen to meet again and explore how our

services could further benefit their future

business.

Working together with the UKTI and

Embassies abroad, in hosting events for

vitally important trade missions like these, is

a great opportunity for TWI.’

On Monday 10 January over 50 delegates from Chinese industrial

companies made a visit to TWI. The group was led by Mr SUN Guangbin,

Director, China Chamber of Commerce for Import and Export of

Machinery and Electronic Products.

Q

A JoinITregister nowwww.twi.co.uk

What is meant by single-pointmeasurement of fracture?

Where can I find informationregarding porosity in aluminium?

How do I select a consumablefor welding cast iron?

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