Dear Reader,

Good day! I hope you are doing well and have had a good relaxation during the Easter celebrations.

I am writing this newsletter from Ibiza, Spain where my family and I are spending the holidays. It has been an exciting and refreshing time and whilst here, I had some interesting thoughts about the mechanics of being buried under sand and that is the basis for the technical reflection of this newsletter. Without much ado, here are the details of today's newsletter:

1. Technical reflection: The computational mechanics of being buried under stand
2. Behind the Scene at CM Videos: Latest video about Pure shear
3. Quote for the week: Artificial Intelligence Partisans

Technical Reflections

The Computational Mechanics of being buried under sand

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During the holiday, we spent a lot of time in the beach and on one hot afternoon, my kids decided to bury me under the slightly wet beach sand (as you can see in the insert image). It was quite an effort for them to cover me in the sand but I thought they did a great job.

As I laid under the sand, I noticed that I was able to regulate my body temperature and felt strangely warm even though the sand was slightly wet. I also realized how heavy wet sand can be and when I tried to rise up from under the sand, the weight was too much that I needed help getting up.

Whilst I laid there, I started thinking about the mechanics of being buried under sand and why my body temperature was not reducing despite the wet sand and the cool breeze. I was thinking how the computational modelling of this scenario would have to be undertaken and that led me to sketching the image below of my artist impression (very bad one at that) of the problem. The principle is that a body (myself) emits heat by radiation. The radiant heat is trapped by a packed bed of slightly wet sand. The sand is a second part of a representative virtual domain. The sand underneath me is an impermeable domain that would not allow heat through. In the end, a cyclic flow of heat occurs as the radiant heat is circulated. This is the hypothesis of the problem and needs to be properly tested computationally.

Here are some of the things that should be noted when undertaking such computational model posed by the problem above:

1. Heat source: The first thing to consider here is that the buried body is a heat source arising from the body temperature. With my body temperature at 37 deg C and the wet sand at about 3 or 4 deg C, you can see how the thermal flow will be from the body to the sand. The body can be generating heat here mainly by radiation which seeks to flow from the higher body temperature to the lower temperature of the wet sand.
2. Sand is a packed bed of particles: The sand particles around the buried entity should be considered as a packed bed with each particle touching and compacted thereby serving as a heat shield. This compacted sand bed is known to be a form of heat insulation and soil kilns used in ancient times and in some traditional communities are true practical applications of this insight and they serve to retain heat by forming a heat barrier.
3. Radiant heat is reflected back: Due to the heat barrier of the packed bed of sand, radiant heat from the buried entity is reflected back into the body thereby preventing any significant heat loss. This accounts for the fact that there no heat loss as I laid buried under the beach sand.
4. Thermomechanical analysis: The sort of simulation that one has to undertake to capture the computational response is a thermo-mechanical analysis with the buried entity representing a radiation heat source, the sand particles modelled using soil mechanics/soil models and the sand domain treated as a isothermal heat barrier which does not allow for heat flux through it (simulating the thermal barrier). The wet sand can be modelled as a porous soil with a lesser than usual soil stiffness.
5. Not a trivial simulation: In conclusion, what we can see from this simple problem of being buried under a beach sand is that it is not a trivial problem. It involves, soil mechanics, thermal and mechanical analysis steps. All these make for interesting computational mechanics analysis.

The above is shared just for the fun of it. However, I wanted to know if there is any literature any where to support my ideas so I went back to Google scholar to search for it. I used the keywords/key-phrases: "heat transfer in packed bed sands" and I found this interesting paper which explores the ideas in a more systematic matter. If you are interested, then do check the paper out.

Behind the Scene at CM Videos

The implementation of Pure Shear

On my YouTube channel, I have been publishing a series of videos on holistic modelling of Unidirectional Composites. Incidentally, about two years ago, I made a 50-minute video on RVE modelling of UD composites and to date, it has been viewed 18,000 times. I decided to make an update of that video but rather divide it up into smaller segments hopefully to allow for viewers to consume it in piece meals.

This week, I published the third part of the series of videos which focussed on implementation of pure shear for unidirectional composites. The interesting thing here is the choice of pure shear. A lot of the modelling I see on UD composites tends to focus solely on uniaxial (tensile and/or compressive deformation) and not shear. Where shear is modelled, it tends to be based on simple shear. This was why I wanted to illustrate how you can undertake systematically the implementation of pure shear on a 3D virtual domain.

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If you are yet to see the video, and this is the sort of things that interest you, then do check the video out. I used the principle of kinematic linking using the *EQUATION command in ABAQUS to connect two reference points, (RefPoint1 and RefPoint2) through which linear displacements, delta_y and delta_x respectively were attached. The kinematic linking was linked to two planes (for example XFront and YTop) which represent the face with a positive axis outward normal (i.e. XFront) or the face with a positive y-axis outward normal (i.e. YTop). Using these for example, I was able to apply pure shear on the XY plane. I demonstrated the same for the pure shear on XZ and YZ planes. The approach might not be intuitive initially but when you follow through with my explanations, you will, I hope, understand what I am trying to do.

The next video in the series will focus on how to use history variables associated with RefPoint1 and RefPoint2 to generate force-displacement graphs which using the relevant RVE areas and gauge lengths, will lead to defining uniaxial and shear stresses. I hope you find these videos helpful. Please let me know in a reply if these explanations make sense and how you are using the videos for your work.

Quote for the week

Artificial Intelligence Partisans

I read an opinion piece written in The Atlantic by Jacob Stern titled: "Where's the AI culture war?" and it struck me how the discussion around AI has devolved into two partisan groups which the author described as "techno-utopians" and "techno-pessimists."

Here is the complete quote:

I find that even in the circle of the academics that I engage with regularly, these categorization hold sway. I see similar positions taken among students as well as casual users of AI. The key emotion when you speak to someone about AI is either that of optimism of what changes it can make or that of pessimism and doubts of its true capacity and intention for mankind.

For me, as someone who really enjoys technological advancements, I consider myself a techno-utopian. I see AI as this all important discovery with great potentials of improving life and outcomes for all. I proactively champion the use of it by my students and whilst I realize the danger it poses to true critical thinking and learning, I am still optimistic. Just like every new technology, when it matures, many users would be using it the proper way. Legislation around its use and non-use will be clearer and the obvious advantage it brings to productivity and discovery would have be properly harnessed. We are at the teething stage of the technology and teething problems must be acknowledged and solved.

On the other side of the partisan group is the techno-pessimists who like my colleagues would argue: "I do not trust AI as I see it making our students dumber and dumber." One friend, in what I consider an unduly alarmist consideration, even voiced her concern saying: "I do not want to mortgage my brain to AI, which can lead to dementia due to prolonged brain inactivity since your Almighty AI is doing all my thinking for me." I hear similar things always and whilst I see the sense behind the arguments, I always advise such doubting Thomases to just give AI a go, and maintain an open mind. Some have become true converts and if you are in the techno-pessimists camp, then try out AI for yourself.

Whatever is the case, the partisan culture of AI has come to stay. We will always have enthusiastic adopters and suspicious opposers of AI. Which group do you belong? Do you recognize yourself as either a techno-utopian or a techno-pessimist?

Let me know in a reply to this email if these AI discussions interest you and what you think about my Quote for the week.

That is it for another newsletter. I hope you have enjoyed it and if you want to let others know about it, please then forward this email to them and they can sign up to the newsletter of the CM Videos Insider Group using the link below.