Delft Centre for Materials

Comments

Transcription

Delft Centre for Materials
Delft Centre for Materials
Touching the future today
Newsletter
March 2006
issue 2
L A B O R AT O R Y P R O F I L E
In this issue
SEARCHING FOR THE ‘DNA’ OF METALS
SEARCHING FOR THE ‘DNA’
OF METALS
1
THE YOUNG WILD IDEAS
PROGRAMME
1
ENERGY ABSORPTION OF
ALUMINIUM CYLINDERS
4
THE NEW DCMAT INFRASTRUCTURE DATABASE
4
SELF-HEALING CONCRETE —
WITH A LITTLE HELP OF
BACTERIA
5
ALERTS
6
Microstructural Control in
Metals (MCM) is one of the 23
groups which together make
up the Delft Centre for Materials (DCMat). This research
group led by Prof. Leo Kestens focuses on the management and control of the microstructures of metals.
‘Major breakthroughs are
relatively uncommon in our
field of work but we’re continually making small steps
which, taken together, represent impressive progress.’
By Peter Baeten
AGENDA
6
Work at MCM, part of the Materials Science and Technology
department of the Faculty of
Mechanical, Maritime and Materials Engineering (3ME), concentrates on just one aspect:
the microstructure of metals.
‘Put very crudely, we’re working on a scale of length be-
Corus is one of the major partners of MCM.
tween the millimetre and the
nanometre. We’re not physicists, so we’re not examining
atomic structures and the corresponding aspects, such as
electrical and optical proper-
ties’, says Leo Kestens, Professor of Microstructural Control
in Metals.
continued on page 3
E D I TO R I A L
THE DCMAT YOUNG WILD IDEAS PROGRAMME
The ‘Young Wild Idea’ programme at DCMat is running
now for almost two years. It
allows students at the TU
Delft to explore unusual research lines in materials
science. Originality and innovativeness are the main criteria for the selection of
proposed Young Wild Idea
projects. Selected projects
are granted with a maximum
project support of 10.000
Euro.
By Alexander Schmets
In December 2004 the first two
Young Wild Idea prizes were
presented to Sylvia Leever for
her proposal to investigate the
protection provided from 17th
century breastplates, and Niels
Groot who proposed to reconstruct a rare, shiny ceramics
from Jordan.
For the research of Leever two
‘original’ 17th century breastplates were purchased. After
non-destructive evaluation of
the breastplates properties,
ballistic testing was performed
at the TNO Prins Maurits Labs.
By these experiments she could
relate the properties of the
weapon (projectiles) to the
critical thickness of the armour
(below which perforation of
the breastplate is likely to
occur). Based upon these data
a predictive model for the
protective quality of the armour was made, limiting the
necessity of future destructive
testing on these antique objects. It became clear that
with the improving quality of
weapons the critical thickness
of the armour also increases:
continued on page 2
E D I TO R I A L ( C O N T I N U E D )
THE DCMAT YOUNG WILD IDEAS PROGRAMME
at a certain moment in history
the critical thickness had become such that it was impossible for a man to carry the
armour. At that time the
shape of warfare changed.
More information on this research is available at http://
www.geocities.com/
ageraluon/breastplate/
index.htm.
Another five projects have
been granted a Young Wild
Idea award, varying from a
method to protect banknotes
from forgery to the construction of a prototype of a
morphing wing. The YWI programme has already attracted
much attention outside the TU
Delft; the national press has
covered extensively the
granted projects, equal initiatives have been followed up at
Punctured 17th Century breastplate
after ballistic testing.
other universities and also
industries showing a great
deal of interest, with DOW
sponsoring the programme and
other industries likely to follow.
The Young Wild Idea programme is open to all Masters
and PhD students at TU Delft.
Ideas are selected on basis of
originality, significance and
‘young and wildness’. A pro-
posal ideally contains a short
project description, a rough
project time-line, budget and
a short CV of the proposer. A
few sides A4 suffices. The
programme is continuously
open to receive new proposals, but the selection committee gathers bi-annually to
select projects for granting
(next meeting mid June 2006).
The prizes are given at a special event, always at another
location. Next prize giving
event is scheduled for the end
of April at the Faculty of Architecture. Precise details will
be given in the next DCMat
Newsletter.
Contact:
Stefan Luding
[email protected]nl
or
[email protected]
‘WAARDE PROMOVENDUS’
ENERGY ABSORPTION OF MONOLITHIC AND
FIBRE REINFORCED ALUMINIUM CYLINDERS
“Where in the past
only crash prevention
was considered, now
crash protection is of
concern as well”
Page 2
Energy absorbing tubes are
widely used in the automotive industry to increase the
crash worthiness. Recently,
these techniques have been
applied in the aerospace
industry as well. To increase
their performance, aluminium crash tubes can be reinforced by externally winding
fibres.
By Jens de Kanter
The aerospace safety focus is
widening nowadays. Where in
the past only crash prevention
was considered, now crash
protection is of concern as
well. Transport safety and
sustainability also benefit
from the reduced mass of the
vehicles. In case of crash
structures, the mass can be
reduced by having structural
components with improved
specific energy absorption
(energy absorbed per unit
mass, SEA). Further quantitative requirements for the
energy absorbing tubes are
the load ratio, peak load divided by mean load and the
stroke efficiency. Qualitative
requirements for the tubes are
for example reliability, predictability and post-crash
integrity.
In search of improved crash
tube performance this thesis
research followed a methodol-
ogy where aluminium tubes
are reinforced by fibre composites. In order to gain full
insight in the crush phenomena, first the monolithic aluminium tube crush behaviour
is described. The aluminium
crush behaviour is governed by
a number of collapse modes,
which depend on the diameter
continued on page 4
Focus of aircraft safety is widening. Crashes are studied besides the continuous crash
prevention.
Newsletter
L A B O R AT O R Y P R O F I L E ( C O N T I N U E D )
SEARCHING FOR THE ‘DNA’ OF METALS
What MCM is actually all about
are things like crystal structures (and the changes taking
place in them), grain size and
grain formation. The main
focus here is on steel and
aluminium, but titanium and
magnesium are important as
well. In fact Kestens describes
the microstructure as the
‘DNA’ of metals. ‘Just about
all the practically relevant
properties of metals can be
attributed to the nature of the
microstructure. We’re looking
chiefly at the mechanical
characteristics of metals, but
it is precisely these which
appear to be particularly sensitive to changes in the microstructure.’
To be more specific, there are
three processes of transformation which ‘MCM’ is concentrating on: phase transformations (such as the well-known
transition from austenitic to
ferritic steel), deformation
and recrystallisation / grain
growth. The arrival of Kestens
at the faculty (about a year
ago) has led to more emphasis
being placed on the latter two
aspects.
The research conducted by
Kestens and his colleagues all
over the world has led to
some major developments.
One notable example is TRIP
steel. TRIP stands for TRansformation Induced Plasticity
and this type of steel combines good malleability with
high strength and hardness.
As Kestens explains: ‘The
basic principle for this was
discovered decades ago. Now,
after years of research, it
seems to be experiencing a
breakthrough in practice,
chiefly in the automotive industry.’ Special heat treatments (rapid cooling) and the
addition of aluminium, silicon
and phosphor create a special
microstructure in the TRIP
steel which, besides the ferrite crystal form, also contains
about 10 percent of the austenite crystal form. If the
steel is then reformed (for
instance during industrial
DCMat Newsletter
Scanning electron microscopy picture of TRIP steel microstructure.
working) then the austenite
changes into the very hard and
strong martensite crystal
structure. This provides the
best of both worlds
(malleability and strength)
instead of having to seek a
compromise between the two,
normally speaking opposed,
properties.
According to Kestens, the
example of the successful but
protracted development of
TRIP steel throws a problem of
this field into sharp relief.
‘We have a bit of an image
problem relating to the nature
of our research field. After
all, people have been making
metal objects for thousands of
years and it’s only logical that
real, spectacular breakthroughs are now increasingly
seldom. On the other hand,
small improvements are happening all the time.’
‘Every year the steels get
stronger by several MPa
grades. So if we add this up
over several years the progress is really considerable. I
can cite the ongoing limitations of Watt losses in steels
used for magnetic applications. The energy savings
achieved in this way contribute much more than the development of all sorts of alternative sustainable energy
sources. And moreover, per
unit of weight steel is almost
as cheap as a bottle of mineral water from the supermarket.’ Specific groups such as
university administrators,
have too little understanding
and appreciation of the special nature of our field.
MCM currently comprises some
25 persons: two members of
the permanent staff, eight
post-doctoral students, eight
doctoral candidates, three
technicians and three undergraduates. As already mentioned, the professor has been
in his post at TU Delft for
little more than a year (before
this, Flemish-born Kestens
worked at Ghent University).
As a result he has not yet been
able to fully chart the possible
opportunities for collaboration
within TU Delft and DCMat.
‘Looking outside the confines
of TU Delft, then Corus is of
course an important partner,
along with TNO (the Netherlands Organisation for Applied
Scientific Research) and Ghent
University. Within TU Delft we
certainly aim to increase collaboration with other research
groups where this is possible
and useful. Our activities in
the field of titanium, for instance, could be a good point
of departure here.’
“Specific groups such
as university
administrators, have
too little understanding
and appreciation of the
special nature of our
field”
Contact information:
Prof. Leo Kestens
[email protected]
Crystallographic image of the microstructure of partially recrystallized
low-Carbon-Steel.
Page 3
‘WAARDE PROMOVENDUS’ (CONTINUED)
ENERGY ABSORPTION OF MONOLITHIC AND
FIBRE REINFORCED ALUMINIUM CYLINDERS
to thickness ratio of the
tubes. Basically two collapse
modes exist, the axisymmetric
collapse or concertina collapse and the diamond mode
collapse. The experimentally
established folding behaviour
is well reproduced by the
finite element codes used.
Abaqus implicit was used for
the static simulation and both
Abaqus explicit and PAMCRASH were used for the dynamic situations.
For improving the SEA, the
aluminium cylinders were
reinforced by externally winding impregnated S2 glass fibres. The hoop winding rein-
forcements unbalance the
stiffness distribution in the
monolithic tube, giving high
restoring membrane stresses
in circumferential direction,
which increase the buckling
load and change the folding
pattern from a concertina to a
diamond mode. By changing
the orientation of the fibres
different collapse modes may
be initiated. The balanced
lay-up of the helix hoop
wound specimen (±45°/90°)
proved best in energy absorbing performance. The SEA of
the monolithic metal tube was
increased by 65%, while the
load ratio reduced from 2.0 to
Experimental compression of aluminium cylinder in diamond mode.
1.5. Nevertheless, the post
crash integrity was diminished
as cracks were present in the
metal as well.
This research project was
performed at the Chair of
Aerospace Materials of the
Faculty of Aerospace Engineering.
Contact information:
[email protected]
Fibre reinforced aluminium cylinders collapsing in different modes. From left to right:
concertina, diamond 3 lobe and diamond 2 lobe.
INSTRUMENT OF THE MONTH
THE NEW INFRASTRUCTURE DATABASE
“The database can be
found at
www.dcmatis.tudelft.nl”
The Delft Centre for Materials is making its entire infrastructure accessible to the
DCMat community at large
via an online database.
Every month we highlight
one of these facilities in the
DCMat Newsletter. This
month: the new database,
and how to use it.
By Alexander Schmets
In the first issue of our DCMat
newsletter one of the lesser
known instruments at the TU
Delft, Neutron Depth Profiling,
was introduced.
Recently the Delft Centre for
Materials has published an online database containing major parts of its scientific infrastructure. The database can
Page 4
The new online database (www.dcmat-is-tudelft.nl)
be found at www.dcmatis.tudelft.nl or via a link on
the DCMat website
(www.dcmat.tudelft.nl). It
contains at the moment about
150 infrastructural components. As there is much more
to add, we ask the reader to
sent information on equipment that is not already in
the database, accompanied by
a photograph/relevant picture, to the email address
below.
continued on page 5
Newsletter
INSTRUMENT OF THE MONTH (CONTINUED)
THE NEW INFRASTRUCTURE DATABASE
The instruments are grouped
according to their location and
as well as by one of the following categories: microscopy,
characterisation, rheology,
thermal properties, heating &
cooling, mechanical testing,
infrastructure (special floors
etc), modelling software,
metals processing, physical
properties, polymer processing, concrete processing, surface technology and durability. Besides this the database
is completely keyword searchable.
All contributions and suggestions are welcome and can be
addressed to the contact be-
low. We hope that many will
benefit from the use of this
overview of the materials
science infrastructure at TU
Delft.
Contact information:
[email protected]
www.dcmat-is.tudelft.nl
RESEARCH TRENDS:
SELF-HEALING CONCRETE —
WITH A LITTLE HELP OF BACTERIA
Modern portland cement
produces much stronger and
faster curing concrete than
the high chalk-containing
cement that was used in
previous centuries. However, the ancient concrete
beats it’s modern counterpart when it comes to its
superior self healing properties!
By Henk M. Jonkers
Concrete, whether old or
modern, is always cracked,
which enables water and
other chemicals to penetrate.
Once inside these chemicals
cause all sorts of problems,
among which is the corrosion
of the steel bars in reinforced
concrete. A major advantage
of the old fashioned chalky
concrete is that a small part
of the calcium carbonate dissolves by the penetrating
water, allowing it to precipitate again during desiccation.
Thus this type of concrete
exemplifies a dynamic, kind of
self healing, system where
precipitation of carbonates
potentially seals cracks again.
Modern concrete, usually low
in chalk for the benefit of
increased strength, has reduced this intrinsic self healing characteristic and therefore needs some help to improve its dynamic plasticity,
maybe in the form of bacteria.
Bacteria come naturally in all
forms and sorts. Some like it
hot, others prefer colder,
DCMat Newsletter
Fig 1: Picture of a 3.7 billion year old
fossil stromatolite. Sequential layers are
formed by calcifying bacteria.
more acidic, more alkalic, or
any other kind of extreme
condition, you name it, and
there will most likely be a
species that proliferates under
those conditions. And in case
conditions suddenly change,
many species will start to
sporulate, i.e. produce bacterial endospores. These dormant cell stages are very resistant to all sorts of physical/
chemical influences and are
able to survive for tens of
years and will revive again
once provided with their preferred conditions, e.g. water
and a suitable growth substrate.
The fossil record shows us that
calcifying bacteria are around
for a very long time. The oldest fossil stromatolites, microbially based calcified layered
sedimentary structures, date
back 3.7 billion (109!) years
(Figure 1). Structural homologs of these ancient stromatolites, so-called microbial
Fig 2: Vertical cut through calcifying
microbial mat: modern living structural homolog of fossil stromatolite.
“The oldest fossil
stromatolites,
microbially based
calcified layered
sedimentary
structures, date back
3.7 billion (109!)
years”
mats, flourish present day in
diverse extreme habitats
(Figure 2). Recent research on
such microbial mats resulted
in the clarification of microbial calcification mechanisms
(Ludwig et al. 2005).
Acknowledging the diversity,
metabolic properties and
ancient lineages of calcifying
bacteria it may seem a rather
straightforward task to find a
suitable bacterium that can
help sealing newly formed
cracks by calcification. This
would enhance the lifetime of
steel reinforced modern portland cement based concrete a
great deal. Thus I hope, as a
new member of the Microlab
scientific community, that I
will come up with some promising and applicable results in
the next two years.
Contact information:
[email protected]
Page 5
Delft Centre for Materials
Visiting Adress
Delft Centre for Materials
P.O. 5058
2600 GB Delft
Kluyverweg 1
2629 HS Delft
Editorial Team
Kees Aarts
Peter Baeten
Eduardo Mendes
Joris Remmers
Mario de Rooij
Alexander Schmets
Geeta van der Zaken
M AT E R I A L S A L E R T :
DEADLINES AND MORE
Materialenreeks: Plastic
Final call Meeting Materials
Workshop Modelling Tools in
Materials Science
In March 2006 Studium Generale of the TU Delft organizes
within the context of their
“Materials Series” a range of
lectures, workshops and expositions concentrated on the
topic Plastic. Some of these
events you can find in our
agenda below. More information and the full programme
can be found on the website
www.materialenreeks.tudelft.
nl
On the 23rd of March, the
“Bond voor Materialenkennis”
organizes Meeting Materials,
an event for meeting young
material experts from both
academia and industry. Participants are offered a unique
combination of Dutch Materials Experts (lectures), Speed
Dating Materials and a tour at
the site of Corus IJmuiden.
There are still a few days left
for subscription. For more
information, please visit:
www.DutchMastersinMaterials.
nl or contact Mirjam van Praag
A one day workshop with the
aim of bring together the
various aspects of materials
modelling on different scales:
electronic structure, atomistic, mesoscale, microscale
and continuum. The field is
developing plus their applications. Particularly students
studying for their doctoral
thesis and post-docs are encouraged to participate in this
workshop. More information:
contact Marian van Baaren
[email protected]
Contributions:
Henk Jonkers
Jens de Kanter
Leo Kestens
Contributions to the
newsletter can be send to
[email protected]
Disclaimer
The information in this
Newsletter has been
thoroughly checked by the
editorial team. We can,
however, not prevent that
mistakes might occur.
The Delft Centre for Materials
does not take responsibility
for these mistakes or any
consequences there of.
at 073-6446400.
AGENDA
Upcoming events
10 March, 10:30h
"Sodium chloride damage to porous building materials", thesis defence by B.A. Lubelli
13 March, 15:30h
"Design principles of surfacings on orthotropic steel bridge decks", thesis defence by T.O. Medani
13 March, 20:15h, Speakers
“Plastic denken: Reflexiviteit van de oppervlakte”, Piet Molendijk
18 March, 16:00h, het Sportcentrum, Mekelweg 8
“Sportieve materiaaltechnologie: Voor goud gaan!”, Warner Nauta and Nando Timmer
20 March, 20:15h, Speakers
“Antwoord van de hoge lonen landen: Rapid Prototyping, Rapid Manufacturing en Rapid Tooling”, Stef
Thulie and Rik Knoppers
21 March, 12:45h, Faculty of Architecture, Zaal D, Berlageweg 1
“Bouwen met piepschuim?”, Jos Lichtenberg
22 March, 20:15h, Speakers
“De kunststoffering van de mens”, T.M. van Gulik
27 March, 15:30h
"A study of the mechanical behaviour of nanocyrstalline metal films", thesis defense by N. Shamsutdinov
27 March, 20:15h, Speakers
“Next generation plastics”, Stephen Picken and Laurens Siebbeles
13 April, Kok Delftech Business Centre Delftechpark 29
“Workshop Modelling Tools in Materials Science”
Workshops and Expositions
5 - 31 March, Faculty Industrieel Ontwerpen, Landbergstraat 15
“Plastic producten”
5 - 31 March, TU Bibliotheek, Prometheusplein 1
Leestafel in de TU Bibliotheek - Boeken over plastic en kunststofmaterialen
18 March, 12:30h, Cultureel Centrum, Mekelweg 10
“Workshop: De plastic experience”, Marieke Sonneveld and Liesbeth Bonekamp
15 and 22 March, 19:30h, Faculteit IO ontwerpstudio 1,2 en 3, Landbergstraat 15
“Workshop: Toekomst van communicatie - Plastic onder de huid”, Ilse van Kesteren and Gijs Bakker
M A S T E R I N G M AT E R I A L S :
We invite students doing their Master’s project in the field of Materials Sciences to send in contributions for publishing in ‘Mastering Materials’ in next issues of this newsletter. The content is completely up to the student. Your contribution should consist of an English text of approximately 400
words accompanied by one or two illustrations. Contributions can be send to [email protected]