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MODELLING & ENGINEERING


The exceptional strength and durability of spider silk has been the focus of a recent study that combined experimental observations of spider webs with complex computer simulations. Researchers from the Massachusetts Institute of Technology (MIT) and the Politecnico di Torino in Italy found that the robust nature of webs is down to not only the strength of the silk, but the overall design, how it compensates for damage and the response of individual strands to continuously varying stresses. ‘Multiple research groups have investigated the complex, hierarchical structure of spider silk and its amazing strength, extensibility and toughness,’ said Markus Buehler, associate professor of civil and environmental engineering at MIT. ‘But, while we understand the peculiar behaviour of dragline silk from the “nanoscale up” – initially stiff, then softening, then stiffening again – we have little insight into how the molecular structure of silk


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Researchers combine observations with computer simulations to explore the durability of spider webs


aid a web in resisting localised damage, such as a single thread being pulled, and distributed threats, such as high winds. Webs in Buehler’s simulation were able to withstand winds up to almost hurricane strength before tearing apart.


Blueprints of the multi-scale material structure of spider silk, from the molecular to the macroscopic scale


uniquely improves the performance of a web.’


A series of computer models were matched to laboratory experiments with spider webs, enabling the researchers to ascertain what factors


‘For our models, we used a molecular dynamics framework in which we scaled up the molecular behaviour of silk threads to the macroscopic world. This allowed us to investigate different load cases on the web, but more importantly, it also allowed us to trace and visualise how the web fractured under extreme loading conditions,’ commented Anna Tarakanova, who developed the computer models along with Steven Cranford, both graduate students in Buehler’s laboratory. ‘Through computer modelling of the web,’ added Cranford, ‘we were able to efficiently create “synthetic” webs, constructed out of virtual silks that resembled more typical engineering


NASA’S JET PROPULSION LABORATORY (JPL) ADOPTS MAPLESOFT SOLUTIONS


NASA’s Jet Propulsion Laboratory (JPL) is implementing Maple, MapleSim and MapleNet to enhance modelling and simulation in its various space exploration projects. Built within a natively symbolic framework, Maplesoft solutions avoid some of the worst sources of error and computational inefficiencies generated by traditional, numeric- based tools, making them suited towards precision-rich projects such as those of JPL.


In addition to using Maple for advanced mathematical analysis,


JPL will use MapleSim, Maplesoft’s high-performance physical modelling and simulation platform, as a key tool in its engineering workflow. MapleSim works in combination with Maple. It accesses Maple’s symbolic computation technology to efficiently handle all of the complex mathematics involved in the development of engineering models, including multi-domain systems, multi- body systems, plant modelling and control design.


Maplesoft technology is also being used in other space robotics


36 SCIENTIFIC COMPUTING WORLD


research. Dr Amir Khajepour, Canada research chair in Mechatronic Vehicle Systems and professor of Engineering in the Mechanical and Mechatronics Engineering department at the University of Waterloo, is working with the Canadian Space Agency (CSA) to develop a full solution for the power management system of autonomous rovers.


The Maplesoft product range is supplied and supported by Adept Scientific in the UK, Ireland, Scandinavia and Nordic countries.


materials such as those that are linear elastic, like many ceramics, and elastic-plastic materials, which behave like many metals. With the models, we could make comparisons between the modelled web’s performance and the performance seen in the webs made from natural silk. In addition, we could analyse the web in terms of energy, and details of the local stress and strain.’


Buehler believes that the principles


uncovered in the study, such as sacrificial elements that permit localised damage in order to maintain the integrity of the overall structure, could end up guiding structural engineers in the future. A paper describing the findings has been published in the 2 February 2012 issue of journal Nature. The work was supported by the


US Office of Naval Research, the US National Science Foundation, the US Army Research Office and the MIT-Italy Program.


Diary Dates 15-17 May


Americas HyperWorks Technology Conference 2012 Detroit, MI, USA


2-4 July


ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis (ESDA2012)


Nantes International Convention Centre, France


l To ensure your event is listed, please send details to editor.scw@europascience.com


www.scientific-computing.com


S. Cranford and M.J. Buehler/MIT


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