The research leading to these results has received

funding from the European Union Seventh Framework

Programme [FP7/2007-2013] under grant agreement

no 315436.

Copyright StirScan © 2013. All Rights Reserved.

Detection of kissing bonds in

friction stir

welds in aero

structures

StirScan

Contact

Project

participants

Project co-ordinator

Verm

on SA

www.verm

on.com

SMEs

Research

Organisations

Theta Technologies

www.thetatech.co.uk

Innora Ltd

www.innora.gr

ABIS sp. z o.o. sp.k.

www.st-ji.com

Saint Jean Wheels AS

TWI Ltd

www.twi.co.uk

FP7: The future of European Union research policy

For all technical enquiries please feel free to contact:

Verm

on S.A.

180 rue du Général Renault

37038 Tours Cedex 1, France

e-m

ail: contact@

verm

on.com

More details and news available at project’s website:

www.stirscan.eu

www.abis.krakow.pl

End-User

Katholieke Universiteit

Leuven

VZLÚ A.S.

www.kuleuven.be

www.vzlu.cz

The b

ackgro

und

The n

eed

The c

oopera

tion

It might happen that two surfaces have been only

partially bonded or are disbonded but touching or in

very close proximity. This is refered to as a „Kissing

Bond”, and is a concern with FSW as such features

reduce fatigue performance of joints, and are very

difficult to detect or accurately size using existing Non-

destructive testing (NDT) methods.

Friction-Stir Welding (FSW) is a solid-state joining

process, developed and proved in 1991 by The

Welding Institute UK. FSW uses a third body tool to

join two faying surfaces. It has many economic,

environmental

and

safety

advantages

over

conventional welding, as well as it is capable of

overcoming some lim

itations of conventional fusion

welding techniques. It is used as a high-performance

joining technique for aluminium alloys, which offers

excellent joint performance and reproducibility.

This is of significant

interest

to

sectors

such as aerospace

and automobile, where

fatigue performance is

particularly crucial.

Friction-Stir Welding, when compared with commonly

used riveting joining methods used for aerospace

structures, contributes to increased joining speed,

higher stress tolerance and longer service life. In

addition, the application of FSW m

ethods have been

shown to save up to 10% weight on typical airframe

structures, as well as reducing working hours by 40%.

Since fatigue performance is particularly crucial, while

there is not a reliable method of detecting kissing

bonds, the use of FSW (and associated benefits) is

restricted only to non-safety critical components.

Effective detection of kissing bonds would open up a

much wider range of applications, including safety-

critical subcomponents.

The

StirS

can

pro

ject

will

develo

p

a

new

N

DT

meth

odolo

gy to

enable

th

e dete

ction of

kis

sin

g

bond d

efe

cts

belo

w 0

.3 m

m in length

in a

ero

space

com

ponents

e.g

. fu

sela

ge a

nd w

ing s

kin

s (to

p a

nd

bottom

).

In order to develop the NDT inspection techniques,

a set of samples will be manufactured and

categorized into FSW without and with defects.

For

this – a set

of

aluminium wheels will be

sourced and supplied by

the end user (St.Jean).

The wheels are used in

the automobile industry

and have curved profile.

A number

of flat FSW plates with different

thicknesses,

which

are

representative

of

components used in the aerospace industry, will

also be manufactured and provided by TWI.

Key, innovative elements required in order to

develop the StirScan system are:

Combination of non-linear ultrasonic technique

(NLUT) and a high frequency ultrasonic technique

(HFUT).

Development of a prototype scanner with an

incorporated probe holder

to enable rapid

inspection of FSW.

Development of a graphic user-interface (GUI)

and interpretation software; enabling simple use,

interpretation and post-processing of acquired

data.

Generation of a full set of test data, precisely

determining and demonstrating the ability of the

StirScan system.