Tag Archives: aerospace

We inhabit time as fish live in water

A couple of weeks ago (‘Only the name of the airport changes’ on June 12th, 2019) I wrote about the stretching and compression of time while I waited for my much delayed flight to Reno. I mentioned Aristotle’s view of time as the measurement of change; however, Newton believed that time passes even when nothing changes. Einstein resolved the conundrum, represented by these different views, using the concept of a space-time domain forming a gravitational field containing waves. My title is a quote from Carlo Rovelli’s book, ‘The Order of Time‘. And, according to Rovelli, ‘mass slows down time around itself’, which I think will cause waves in the space-time domain .  Conservation of energy implies that the movement of an object will tend towards space where time passes more slowly, i.e. in the vicinity of large masses. Hence, things fall downwards because time runs more slowly close to the Earth. This implies that time passes more slowly at the airport than on the plane in flight; but, of course, the differences are too small for us to measure or perceive.

Image: Art work ‘Gaia’ by Luke Jerram in Liverpool Cathedral

Source:

Carlo Rovelli, The Order of Time, Penguin, 2019.

Joining the dots

Six months ago, I wrote about ‘Finding DIMES’ as we kicked off a new EU-funded project to develop an integrated measurement system for identifying and tracking damage in aircraft structures.  We are already a quarter of the way through the project and we have a concept design for a modular measurement system based on commercial off-the-shelf components.  We started from the position of wanting our system to provide answers to four of the five questions that Farrar & Worden [1] posed for structural health monitoring systems in 2007; and, in addition to provide information to answer the fifth question.  The five questions are: Is there damage? Where is the damage? What kind of damage is present? How severe is the damage?  And, how much useful life remains?

During the last six months our problem definition has evolved through discussions with our EU Topic Manager, Airbus, to four objectives, namely: to quantify applied loads; to provide condition-led/predictive maintenance; to find indications of damage in composites of 6mm diameter or greater and in metal to detect cracks longer than 1mm; and to provide a digital solution.  At first glance there may not appear to be much connection between the initial problem definition and the current version; but actually, they are not very far apart although the current version is more specific.  This evolution from the idealised vision to the practical goal is normal in engineering projects.

We plan to use point sensors, such as resistance strain gauges or fibre Bragg gratings, to quantify applied loads and track usage history; while imaging sensors will allow us to measure strain fields that will provide information about the changing condition of the structure using the image decomposition techniques developed in previous EU-funded projects: ADVISE, VANESSA (see ‘Setting standards‘ on January 29th, 2014) and INSTRUCTIVE.  We will use these techniques to identify and track cracks in metals [2]; while for composites, we will apply a technique developed through an EPSRC iCASE award from 2012-16 on ‘Full-field strain-based methods for NDT & structural integrity measurement’ [3].

I gave a short briefing on DIMES to a group of Airbus engineers last month and it was good see some excitement in the room about the direction of the project.  And, it felt good to be highlighting how we are building on earlier investments in research by joining the dots to create a deployable measurement system and delivering the complete picture in terms of information about the condition of the structure.

Image: Infra red photograph of DIMES meeting in Ulm.

References

  1. Farrar & Worden, An introduction to structural health monitoring, Phil. Trans. R Soc A, 365:303-315, 2007
  2. Middleton, C.A., Gaio, A., Greene, R.J. & Patterson, E.A., Towards automated tracking of initiation and propagation of cracks in aluminium alloy coupons using thermoelastic stress analysis, Nondestructive Evaluation, 38:18, 2019.
  3. Christian, W.J.R., DiazDelaO, F.A. & Patterson, E.A., Strain-based damage assessment of accurate residual strength prediction of impacted composite laminates, Composites Structures, 184:1215-1223, 2018.

The INSTRUCTIVE and DIMES projects have received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreements No. 685777 and No. 820951 respectively.

The opinions expressed in this blog post reflect only the author’s view and the Clean Sky 2 Joint Undertaking is not responsible for any use that may be made of the information it contains.

Only the name of the airport changes

The conference that I attended last week was in Reno, Nevada and, on my way to it, I stopped over in Dayton, Ohio and visited the US Air Force Research Laboratory to present the results from our research project supported by their European Office of Aerospace Research & Development (EOARD).  The journey from Liverpool to Dayton, via Manchester and Altanta airports, took 17 hours; however, that was short compared to the journey from Dayton to Reno, via Chicago and San Francisco airports, which took 24 hours door-to-door or rather hotel-to-hotel.  ‘Only the name of the airport changes’ is a quote from Italo Calvino describing the city of Trude in his book ‘Invisible Cities‘; but it also described how I felt looking out from my window seats at successive airports over the four days that I travelled from Liverpool to Reno.

We arrived at Dayton airport at 5am for a 7am flight to be told that it was cancelled and we were re-booked on a flight leaving at 5.18pm.  We tried to re-rent the rental car that we had just returned but were told every car was booked; so, we were stuck in Dayton airport for 12 hours.  Your perspective of time changes in these circumstances.  At 5am with nothing much to do, 12 hours seemed like infinity; but at 5pm when we were about to board our flight, the same 12 hours seemed short – almost as if we had only arrived at the airport an hour or so earlier.  Augustine observed that our consciousness is based on memory and anticipation such that time is entirely present in our minds as memory and as anticipation.  While Aristotle considered time to be the measurement of change.  Hence, since I was anticipating no change during my 12 hours of waiting, my perception of time was of it passing very slowly.  Whereas, when I was boarding my flight 12 hours later, my memory was of having done the same things that I would usually have done while waiting for a flight [reading and editing draft manuscripts from my research group]; and hence my perception of the elapsed 12 hours was compressed into the usual 2-hour period spent at an airport prior to a flight.  The apparent unchanging view out of the plane’s window, both in flight and, to a lesser extent, on the ground also tended to distort my perception of the passage of time.

Sources:

Italo Calvino, Invisible Cities, Penguin Vintage Classics, 1997.

Carlo Rovelli, The Order of Time, Penguin, 2019.

 

Archive video footage from EU projects

This week I am in the US presenting work from our EU projects INSTRUCTIVE and MOTIVATE at the Annual Conference and Exposition of the Society for Experimental Mechanics.  Although the INSTRUCTIVE project was completed at the end of December 2018, the process of disseminating and exploiting the research will go on for some time.  The capability to identify the initiation of cracks when they are less than 1mm long and to track their propagation is a key piece of technology for DIMES project in which we are developing an integrated system for monitoring the condition of aircraft structures.  We are in the last twelve months of the MOTIVATE project and we have started producing video clips about the technology that is being developed.  So, if you missed my presentations at the conference in the US then you can watch the videos online using the links below 😉.

We have been making videos describing the outputs of our EU project for about 20 years; so, if you want to see some vintage footage of me twenty years younger then watch a video from the INDUCE project that was active from 1998 to 2001.

MOTIVATE videos: Introduction; Industrial calibration of DIC measurements using a calibration plate or using an LCD screen

The MOTIVATE project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 754660.

Image: Peppermill Hotel in Reno, Nevada where the conference is being held.