OCIAM TBC
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Biography
John Biggins read natural sciences at Cambridge University. He specialized in experimental and theoretical physics, and was the top ranked student in his cohort. He then did a PhD in the theory of condensed matter group under the supervision of Prof Mark Warner FRS, working on the exotic elasticity of a new phase of soft matter known as a liquid crystal elastomer (LCE). During his PhD he made an extended visit to Caltech to work with Prof Kaushik Bhattacharya on analogies between LCEs and shape memory alloys.
After his PhD, John won an 1851 Royal Commission Fellowship and traveled to Harvard to work with Prof L. Mahadevan on instabilities in soft solids and biological tissues, including creasing, fingering and brain folding. He then returned to Cambridge, first as Walter Scott Research Fellow at Trinity Hall and then as an early career lecturer in the tcm group at the Cavendish Laboratory. During this time, he explained the viral youtube phenomena of the chain fountain, and explored how surface tension can sculpt soft solids, leading to a solid analogue of the Plateau–Rayleigh instability. He also taught first year oscillations, and a third year course "theoretical physics 1."
In 2017, John was appointed to an Assistant Professorship of applied mechanics in Cambridge Engineering Department, where he teaches mechanics and variational methods. In 2019 he won a UKRI Future Leaders Fellowship on "Liquid Crystal Elastomers, from new materials via new mechanics to new machines." This grant added an exciting experimental component to the group, and underpins our current focus on using LCEs as artificial muscles in soft mechanical devices.
MPLS are once again offering another Mental Health Awareness Week (MHAW) programme of activity for anyone across the University who wants to get involved! From 13 – 17 May 2024, we have prepared a week of events, fun activities, panel discussions and learning opportunities, with a focus on this year’s theme of ‘Moving for your mental health’ – where we want to think about moving the mind, as well as the body!
The divisional Teaching Awards are now open for nominations, celebrating teaching impact, innovation and leadership. Anyone with teaching responsibilities can be nominated, including graduate students, postdocs and teaching support staff. Between 5-10 individual awards are awarded each year, with an individual prize value of £1,000.
Static friction models, buckling and lift-off for a rod deforming on a cylinder
Dr. Rehan Shah, Lecturer (Assistant Professor) in Mathematics and Engineering Education, Queen Mary University of London
Abstract
We develop a comprehensive geometrically-exact theory for an end-loaded elastic rod constrained to deform on a cylindrical surface. By viewing the rod-cylinder system as a special case of an elastic braid, we are able to obtain all forces and moments imparted by the deforming rod to the cylinder as well as all contact reactions. This framework allows us to give a complete treatment of static friction consistent with force and moment balance. In addition to the commonly considered model of hard frictionless contact, we analyse two friction models in which the rod, possibly with intrinsic curvature, experiences either lateral or tangential friction. As applications of the theory we study buckling of the constrained rod under compressive and torsional loads, finding critical loads to depend on Coulomb-like friction parameters, as well as the tendency of the rod to lift off the cylinder under further loading. The cylinder can also have arbitrary orientation relative to the direction of gravity. The cases of a horizontal and vertical cylinder, with gravity having only a lateral or axial component, are amenable to exact analysis, while numerical results map out the transition in buckling mechanism between the two extremes. Weight has a stabilising effect for near-horizontal cylinders, while for near-vertical cylinders it introduces the possibility of buckling purely due to self-weight. Our results are relevant for many engineering and medical applications in which a slender structure winds inside or outside a cylindrical boundary.
What do maypole dancing, grocery delivery, and the quadratic formula all have in common? The answer is: braids! In this Oxford Mathematics Public Lecture, Tara will explore how the ancient art of weaving strands together manifests itself in a variety of modern settings, both within mathematics and in our wider culture.