Holes

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Holes, little circular ones. There are billions of them in engineering machines and structures. There are more than a million in a jumbo jet alone. Some of them are filled with fasteners, such as bolts and rivets, others are empty to allow fluids to flow through a surface. Load passing through a structure has to flow around holes, especially when they are empty, and the contours of stress bunch up around a hole to form a stress concentration. For a small hole in a very large plate, the stress on the circumference of the hole is three times the level found in the absence of the hole. This concentration increases for bigger holes or smaller plates, so that holes are a potential source of failure – that’s why sheets of stamps are perforated with lines of holes.

A hole can also stop a failure. For instance a crack extending under repeated loading will often stop when it grows into a hole because the ‘sharpness’ of the crack tip is blunted by the roundness of the hole. Engineers sometimes deliberately drill a hole at a crack tip to arrest its progress. So, holes can be both an engineer’s friend and foe.

Origami car-planes

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Origami wings in the roof-box?

Origami wings in the roof-box?

A few weeks ago I was fascinated by the competitors’ bikes tessellated on top of the team support cars during the Tour of Britain [see my post entitled ‘Tessallating bikes‘ on September 10th, 2014]. What if instead of tessellating bikes we could use origami to fold away a set of wings? Many people have dreamed of escaping the frustration and congestion of traffic on the road with a convertible. Not the classic convertible but a car that converts to a plane. One small company from Massachusetts, Terrafugiama has already flown a prototype flying car with self-folding wings and is working on an advanced prototype capable of vertical take-off and highway driving. Vertical take-off with wings is difficult so as an alternative a group of universities in Europe is studying the feasibility of a Personal Air Transportation System (PATS) based on a helicopter, known as MyCopter.

These convertibles are difficult to design in practice due to the space constraints for a flying car to take-off and land, the need for two propulsion or at least two transmission systems, the different type of suspension required for comfortable driving compared to landing, the current approach to crashworthiness in cars, and the overwhelming requirement for a light-weight system if there is any hope of getting airborne.   If you add to this list the desire for an environmental-friendly vehicle then perhaps there is no hope, unless we can cross a Tesla with the Airbus prototype electric plane, the E-plane!  [See my post entitled ‘Are electric cars back?‘ on May 28th, 2014]

Sources:

‘Why we’re not driving the friendly skies‘ by Stuart F. brown in the New York Times on August 22nd, 2014

‘If cars could fly‘ by Nick Bilton in the New York Times on June 30th, 2010

http://www.nytimes.com/2014/08/24/automobiles/pie-in-the-sky-flying-cars-from-the-past.html?action=click&contentCollection=Automobiles&module=RelatedCoverage&region=Marginalia&pgtype=article&_r=0

Love an engineer

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beach2

Photo credit: Tom

Some weeks ago I wrote about the benefits being completely disconnected from the ‘grid’ while on vacation [see my post entitled ‘Mind-wandering‘ on September 3rd, 2014].  What one of my colleagues has called going on a ‘deep vacation’.  For most of us our vacation, deep or otherwise, is a distant memory by now and, for many, the demands on our time far exceed the available time.  The temptation to work continuously is huge, particularly with smart phones delivering messages from our co-workers and bosses at all hours of the day and night.  Recent research has shown that if we want to be happy and productive then we should resist this temptation.  A survey of nearly 12,000 white-collar workers found that people feel worse and become less engaged when they work continuously and especially when they work more than 40 hours per week. By contrast workers who take a break every 90 minutes were more focussed (reportedly 30% more) and more able to think creatively (50% more).  The survey also found that being encouraged by your supervisor to take a break increases by 100% the likelihood that you will stay with an employer and also doubles your sense of well-being and health. Perhaps this is why Daimler encourage the equivalent of ‘deep weekends’ by automatically returning and then deleting emails sent to employees while they are off-duty.

These findings tie in with research in psychology reported by Oppezzo and Schwartz that suggests creativity is implicated in workplace success, healthy psychological functioning and the maintenance of loving relationships.  While Martin and Schwartz assert that creativity is ‘an important cognitive dimension of both mundane and specialized  forms of problem-solving’.

Engineers are creative problem-solvers so make sure yours stays successful, healthy and loving by encouraging them to take breaks and work less than 40 hours per week.

Sources:

Why you hate work! By Tony Schwartz and Christine Porath in the New York Times on May 30, 2014:

Oppezo, M., & Schwartz, D.L., 2014, ‘Give your ideas some legs: the positive effect of walking on creative thinking’, J. Experimental Psychology, Learning, Memory & Cognition, 40(3):1142-1152.

Martin, L., & Schwartz, D.,  2014, ‘A pragmatic perspective on visual representation and creative thinking’, Visual Studies, 29(1):80-93.

End the tyranny of 24/7 email. By Clive Thompson in the New York Times on August 28th, 2014

Tidal energy

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Photo credit: Tom

Photo credit: Tom

The world is slowing down! According to Max Tegmark, in his book ‘Our Mathematical Universe’, the rotational velocity of the Earth is being reduced as some of its kinetic energy is dissipated as tidal energy. It is possible to estimate the age of planet from the rate of slow down by assuming that at its birth it was spinning as fast as possible without the centrifugal forces pulling it apart. The answer turns out to be about 4 to 5 billion years which roughly agrees with radioactive dating of the oldest rocks in Western Australia and bits of meteorites that imply the solar system came into being about 4.5 billion years ago.

So does this imply that tidal energy is not really a renewable energy source? I think it is just an issue of timescale. Fossil fuels are seen as non-renewable because the formation of coal and oil substrates happens on geological timescales. Biomass is a bit quicker because we skip the fossilisation process and renewal is measured in months. Fossil fuels and biomass are both ways of storing solar energy in chemical bonds. Nature is much better at converting and storing solar energy than mankind. But, solar energy would appear to be the ultimate renewable energy source. Every morning its there, though often hidden by cloud where I live. The sun will eventually die but again this won’t happen anytime soon but on a long geological timescale.