Category Archives: Uncategorized

Potential dynamic buckling in hypersonic vehicle skin

The skin of an aircraft is supported on the inside by a network, or mesh, of ribs and stringers running approximately at right angles to one another; so that the skin is effectively a series of rectangular plates supported around their edges.   In hypersonic flight, above five times the speed of sound, these rectangular plates are subject to vibration and to high temperatures that vary spatially and with time.  The combined vibratory and thermal loading causes the plates to buckle out of plane which has two possible detrimental consequences: first, it causes the formation of fatigue cracks leading to catastrophic failure; and, second, it might influence the formation of the boundary layer in the flow over the skin of the aircraft and affect the aerodynamics of the aircraft.  In my laboratory, we have built a test-rig that allows us to subject rectangular plates to random mechanical vibrations up to 1000Hz and, at the same time, to temperature distributions upto 1000K that vary in time and space.  Earlier this year, we published an article in which we showed, by experiment, that an edge-reinforced rectangular plate behaved as a dynamic system in response to thermal loading.  In other words, when a constant temperature distribution is applied, the shape of the plate varies with time until an equilibrium state is achieved.  In addition, we found that the post-buckled shape of the plate is not proportional to the energy supplied but dependent on the in-plane temperature distribution.  Probably, both of these observed behaviours are a result of differential thermal expansion of the plate and its reinforcements.

The image shows point-wise temperature and displacement measurements (centre) at the centre and edge of a reinforced plate (top) subject to a localised strip of heating over time as shown by the temperature distributions (bottom).

This is the fourth in a series of posts on recent work published by my research group.  The others are: ‘Salt increases nanoparticle diffusion‘ on April 22nd, 2020; ‘Spatio-temporal damage maps for composite materials‘ on May 6th, 2020; and, ‘Thinking out of the box leads to digital image correlation through space‘ on June 24th, 2020.

Source:

Santos Silva AC, Lambros J, Garner DM & Patterson EA, Dynamic response of a thermally stressed plate with reinforced edges, Experimental Mechanics, 60:81-92, 2020.

Dyschronometria induced by coronavirus lockdown

I must be losing my sense of time as result of spending most of everyday communicating  with colleagues via my laptop because I published today’s post yesterday [see ‘Professor soars through the landscape‘ on April 27th, 2020].  Even when a helpful reader pointed out that the accompanying video had not been published, I simply thought that I had failed to synchronise the post and video properly – see my comment on yesterday’s post.  It was not until my editor asked me why I had published a post on Tuesday that I realised my error. Perhaps I am suffering from dyschronometria brought on by the COVID-19 lock-down in force in the UK.

Gustatory technology stimulates on-line get-togethers

It has been known for some time that over or under responsivity to sensory stimulation encountered in everyday life, such as noise, light and smell, can be a cause of anxiety and stress [e.g. Lipowski, 1975].  Most virtual reality systems provide visual and audio stimuli through headsets and tactile stimuli can be provided through haptic devices; however, that leaves two senses under stimulated: smell and taste.  So, researchers have been exploring how to extend virtual reality to include smell and taste in order to give a complete sensory experience and thus reduce the level of stress and anxiety that many people feel when using immersive reality systems.  This had led to digital scent technology that allows smells to be transmitted electronically [e.g. Isokoski et al, 2020].  So, it’s time to update your preferred communication tool to one that allows you to smell that fresh cup of coffee your colleague has just brewed before joining the meeting from their home-office.  Of course, if they have not taken a shower recently then you might want to ‘mute’ the smell function!  These advances in technology have led a spin-out company, Day91, to start work on gustatory technology that modifies the water in your glass to simulate the after-work drink that your team-mate is enjoying during your virtual get-together online.

References:

Lipowski, Z. J. (1975). Sensory and information inputs overload: Behavioural effects. Comprehensive Psychiatry, 16(3), 199–221.

Isokoski, P., Salminen, K., Müller, P., Rantala, J., Nieminen, V., Karjalainen, M., Väliaho, J., Kontunen, A., Savia, M., Leivo, J. and Telembeci, A., (2020). Transferring scents over a communication network. In Proceedings of the 23rd International Conference on Academic Mindtrek (pp. 126-133).

Slow deep thoughts from a planet-sized brain

I overheard a clip on the radio last week in which someone was parodying the quote from Marvin, the Paranoid Android in the Hitchhiker’s Guide to the Galaxy: ‘Here I am with a brain the size of a planet and they ask me to pick up a piece of paper. Call that job satisfaction? I don’t.’  It set me thinking about something that I read a few months ago in Max Tegmark’s book: ‘Life 3.0 – being human in the age of artificial intelligence‘ [see ‘Four requirements for consciousness‘ on January 22nd, 2020].  Tegmark speculates that since consciousness seems to require different parts of a system to communicate with one another and form networks or neuronal assemblies [see ‘Digital hive mind‘ on November 30th, 2016], then the thoughts of large systems will be slower by necessity.  Hence, the process of forming thoughts in a planet-sized brain will take much longer than in a normal-sized human brain.  However, the more complex assemblies that are achievable with a planet-sized brain might imply that the thoughts and experiences would be much more sophisticated, if few and far between.  Tegmark suggests that a cosmic mind with physical dimensions of a billion light-years would only have time for about ten thoughts before dark energy fragmented it into disconnected parts; however, these thoughts and associated experiences would be quite deep.

Sources:

Douglas Adams, The Hitchhiker’s Guide to the Galaxy, Penguin Random House, 2007.

Max Tegmark,  Life 3.0 – being a human in the age of artificial intelligence, Penguin Books, Random House, UK, 2018.