Delft Centre for Materials
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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] 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].
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