New Doctoral Dissertation: As he can simulate how the atoms behave when aluminium is deformed, Jonas Frafjord knows better than most that the devil is in the details.
«Imagine bending an aluminium spoon», says Jonas Frafjord.
«The deformation that you observe is a combination of millions of small defects at the atomic level. They have the form of lines, and as a response to the stress exerted by bending the metal, they become rearranged. When they move, they cause tiny structural changes in the interior of the metal».
A FAVOURITE AMONG ENGINEERS
Jonas Frafjord´s doctoral work aims to bridge the simulations at the nanoscale to simulations at the continuum scale. The latter is where engineers, architects and industrial designers operate. Aluminium is a favourite among them, and one of the most commonly used materials in the global construction industry. When structures deform, the damage always starts in the microstructures and the smallest of the building blocks. The tiny defects Frafjord describes, are called dislocations. They are extremely interesting for materials scientists, as they actually govern plastic deformation.
A KEY TO STRONGER METALS
As a PhD candidate in the Lower Scale programme of SFI CASA Frafjord has gained insight into how crystals, grains, particles, atoms and electrons move and interact with each other. He transfers this behaviour into computer simulations, and thus paves the way for the digital design of tailor-made aluminium alloys. The computational requirements of atomistic calculations are exceptionally demanding. The following description by Frafjord gives an idea of exactly how demanding:
183 YEARS TO CALCULATE 1 NANOSECOND
«Consider a 10 cm long strand of hair made out of aluminium. In this aluminium piece, there would be a billion trillion aluminium atoms. Each atom is affected by the others. Thus, for each time step, one would have to perform 12 calculations for each atom just to get the interactions with the nearest neighbour. The fastest computer in the world would use 183 years to calculate 1 nanosecond of evolution. Not to mention the amount of data such a simulation would create».
Jonas Frafjord says that, hopefully, new students could use his work as a doorway to the atomistic modelling of aluminium alloys. Also, he says «the aluminium industry will gain a better understanding of the nuts and bolts that their continuum models rely on». From an environmental perspective, society will benefit from increased use of tailor-made digital alloy design, as the need for material testing would decrease.
Jonas Frafjord defends his thesis 18th December 2020 at NTNU.
Read more about Frafjord´s work at SFI CASA