Author Archives: Eann Patterson

Star sequence minimises distortion

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It is some months since I have written about engineering so this post is focussed on some mechanical engineering.  The advent of pneumatic and electric torque wrenches has made it impossible for the ordinary motorist to change a wheel because it is very difficult to loosen wheel nuts by hand when they have been tightened by a powered wrench which most of us do not have available.  This has probably made motoring safer but also means we are more likely to need assistance when we have a flat tire.  It also means that the correct tightening pattern for nuts and bolts is less widely known.  A star-shaped sequence is optimum, i.e., if you have six bolts numbered sequentially around a circle then you start with #1, move across the diameter to #4, then to #2 followed by #5 across the diameter, then to #3 and across the diameter to #6.  This sequence is optimum for flanges, bolted joints in the frames of buildings and joining machine parts as well as wheel nuts.  We have recently discovered that it works in reverse, in the sense that it is the optimum sequence for releasing parts made by additive manufacturing (AM) from the baseplate of the AM machine (see ‘If you don’t succeed try and try again’ on September 29th, 2021).  Additive manufacturing induces large residual stresses as a consequence of the cycles of heat input to the part during manufacturing and some of these stresses are released when it is removed from the baseplate of the AM machine, which causes distortion of the part.  Together with a number of collaborators, I have been researching the most effective method of building thin flat plates using additive manufacturing (see ‘On flatness and roughness’ on January 19th, 2022).  We have found that building the plate vertically layer-by-layer works well when the plate is supported by buttresses on its edges.  We have used two in-plane buttresses and four out-of-plane buttresses, as shown in the photograph, to achieve parts that have comparable flatness to those made using traditional methods.  It turns out that optimum order for the removal of the buttresses is the same star sequence used for tightening bolts and it substantially reduces distortion of the plate compared to some other sequences.  Perhaps in retrospect, we should not be surprised by this result; however, hindsight is a wonderful thing.

The current research is funded jointly by the National Science Foundation (NSF) in the USA and the Engineering and Physical Sciences Research Council (EPSRC) in the UK and the project was described in ‘Slow start to an exciting new project on thermoacoustic response of AM metals’ on September 9th 2020.

Image: Photograph of a geometrically-reinforced thin plate (230 x 130 x 1.2 mm) built vertically layer-by-layer using the laser powder bed fusion process on a baseplate (shown removed from the AM machine) with the supporting buttresses in place.

Sources:

Patterson EA, Lambros J, Magana-Carranza R, Sutcliffe CJ. Residual stress effects during additive manufacturing of reinforced thin nickel–chromium plates. IJ Advanced Manufacturing Technology;123(5):1845-57, 2022.

Khanbolouki P, Magana-Carranza R, Sutcliffe C, Patterson E, Lambros J. In situ measurements and simulation of residual stresses and deformations in additively manufactured thin plates. IJ Advanced Manufacturing Technology; 132(7):4055-68, 2024.

Fictional Planetary Emergencies

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Decorative photograph of a wind-shaped tree on a hillside in fogA little while ago, when looking for something to read when visiting someone’s house, I picked up ‘The Complete Short Stories: volume 2’ of JG Ballard and started reading from the last story in the collection, ‘Report from an Obscure Planet’.  I was surprised to discover its similarity to a fictional piece I posted on this blog last year, see ‘Where has the blue planet gone?’ on July 3rd 2024.  Then I was shocked to realize that some readers of my blog might have thought I had plagiarised Ballard’s short story, whereas I was completely unaware of it when I wrote the post.  In Ballard’s story, a rescue mission has just landed on a remote planet from which frantic emergency signals had been received; however, their aerial reconnaissance of hundreds of cities spread across the planet found no inhabitants.  They accidentally activate the planet’s extensive, and apparently undamaged, computer networks when broadcasting a signal of greeting and friendship.  The networks react with ‘a sudden show of alarm, as if well used to mistrusting these declarations of good intent’.  The visitors’ research reveals that war was the most popular sport of the inhabitants, with nations maintaining huge arsenals.  They conclude that the computer networks sent out the emergency signals in an attempt to save themselves from a danger that was about to overwhelm their planet.  In my version, the rescue mission finds a planet transformed by a climate change and mass extinct induced by an asteroid strike or the activities of the inhabitants.  Ballard wrote his story in 1992, so more than thirty years before me, and perhaps twenty years after the first data centre had been built by IBM.  The first convincing evidence of the warming effect of carbon dioxide was found in the 1960s and scientists started ringing the alarm bells in the late 1980s and early 1990s, for instance at the 1988 Toronto Conference on the Changing Atmosphere – so perhaps too early to feature in Ballard’s story.  Of course, I could also have written about artificial intelligence being the only sign of life found on the planet but that really would have looked like wholesale plagiarism!

Reference:

JG Ballard, ‘The Complete Short Stories: volume 2’, Harper Perennial, London, 2006.

Subconscious awareness of the erosion of individuality

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Decorative image only. Mural of a tiger on a gable end wall in LiverpoolOne impact of publishing a monthly post instead of the weekly one I used to produce [see ‘600th post and time for a change‘, on January 3rd 2024], is that I often starting writing without any memory of the recent posts.  So, I have only just noticed that, ignoring the posts on technical topics, all my posts this year have been on the theme of what it means to be an individual [see ‘Is the autonomous individual ceasing to exist?’ on January 1st, ‘Its all in the mind’ on March 5th, and ‘Are we individuals?’ on April 2nd].  You might be led to believe that I am having a crisis of identity but you would be wrong.  I think that this common theme arose subconsciously as result of the technological and political events that are reshaping society at the moment.  We appear to be losing the capacity to recognise others as beings like ourselves, which is the basis of freedom and democracy.  Without it we treat others as objects rather than individuals leading towards tyranny and the dissolution of trust and truth.

Reference:

Liberty in peril: a review of Timothy Snyder’s book: On Freedom, FT Weekend 12/13 October 2024.

Are we individuals?

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It has been estimated that there are 150 species of bacteria in our gut with a megagenome correspondingly larger than the human genome; and that 90% of the cells in our bodies are bacterial [1].  This challenges a simple understanding of individual identity because on one level we are a collection of organisms, mainly bacteria, rather than a single entity.  The complexity is almost incomprehensible with 30 trillion cells in the human body each with about a billion protein molecules [2].  Each cell is apparently autonomous, making decisions about its role in the system based on information acquired through communicating and signalling with its neighbours, the rest of the system and the environment.  Its autonomy would appear to imbue it with a sense of individual identity which is shaped by its relationships within the network of cells [3].  This also holds for human beings within society although you could argue the network is simpler because the global population is only about 8 billion; however the quantity of information being communicated is probably greater than between cells, so perhaps that makes the network more complex.  Networks are horizontal hierarchies with no one or thing in overall control and they can adapt to cope with changes in the environment.  By contrast, vertical hierarchies depend on top-down obedience and tend to eliminate dissent, yet without dissent there is little or no innovation or adaptation.  Hence, vertical hierarchies can appear to be robust but are actually brittle [4].  In a network we can build connections and share knowledge leading to the development of a collective intelligence that enables us to solve otherwise intractable problems.  Our ability to acquire knowledge not just from own our experiences but also from the experience of others, and hence to progressively grow collective intelligence, is one of the secrets of our success as a species [5].  It also underpins the competitive advantage of many successful organisations; however, it needs a horizontal, stable structure with high levels of trust and mutual dependence, in which our sense of individual identity is shaped by our relationships.

References:

  1. Gilbert SF, Sapp J, Tauber AI, A symbiotic view of life: we have never been individuals, Quarterly Review of Biology, 87(4):325-341, 2012.
  2. Ball P, How Life Works, Picador, 2023.
  3. Wheatley M, Leadership and the New Science: Discovering Order in a Chaotic World, 2nd Edition, Berrett-Koehler Publishers Inc, San Francisco, 1999.
  4. McWilliams D, Money – A Story of Humanity, Simon & Schuster, London, 2024.
  5. Henrich J, The secret of our success: how culture is driving human evolution, domesticating our species, and making us smarter, Princeton, NJ: Princeton University Press, 2015.