Crack initiation, propagation and merging in explicit Material Point Method!

Figure 1. Cracked ring expansion and contraction

Tito Adibaskoro with co-workers published a very significant development related to simulating cracks in the Material Point Method (MPM). The paper “Multiple discrete crack initiation and propagation in Material Point Method” is published in the Engineering Fracture Mechanics Journal. The paper describes how to extend the Nairn’s Cracks in MPM (CRAMP) algorithm so the cracks can be initiated in any place of the domain, propagate over a path that is determined during the simulation, as well as merge or split during the propagation.

Figure 2. Cracking of a plate with large deformations and no initial crack

The large displacements, inherent to MPM are fully supported, as well as all the explicit MPM algorithms. The paper focuses on the CPDI version of MPM, but the algorithm can be implemented in any mainstream MPM algorithm. The proposed algorithm is also very efficient, reducing the amount of calculations when compared to the original CRAMP very considerably, due to reducing the required number of background grids. Hence, simulations with many cracks are actually doable in reasonable time!

The paper has linked open source code, so it is very easy to try it yourself!

Figure 3. Multiple cracks propagation and merging

Bibliographic Details

Tito Adibaskoro, Stéphane Bordas, Wojciech T. Sołowski, Simo Hostikka,
Multiple discrete crack initiation and propagation in Material Point Method,
Engineering Fracture Mechanics, Volume 301, 2024, 109918, ISSN 0013-7944,
https://doi.org/10.1016/j.engfracmech.2024.109918.

How key physical processes in deep geological repository are affected by temperature changes?

Abhishek Gupta, Ayman Abed and me have suggested what key processes to model in a deep geological repository, as affected by temperature. The research is published in Engineering Geology journal (link). It seems that especially changes of the water vapour density with temperature, changes of viscosity of water with temperature, and the changes in the water retention curve (in our case, van Genuchten with thermal coupling) are important and may make tens or more percent of difference. Thermal expansion of water is also very important when the material is fully saturated.

Water mass flux in y-direction in the infiltration test, most affected by the thermal effects on the water vapour density and water viscosity changes with temperature. (c) Abhishek Gupta, Ayman A. Abed, Wojciech T. Sołowski, Identification of key thermal couplings affecting the bentonite behaviour in a deep geological nuclear waste repository, Engineering Geology, Volume 324, 2023, 107251, https://doi.org/10.1016/j.enggeo.2023.107251,
https://www.sciencedirect.com/science/article/pii/S0013795223002697

The research was co-funded by EURAD gas subproject and Aalto University Dean’s scholarship. (EURAD – European joint programme on radioactive waste management (Gas subproject). EURAD has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement n°847593)

Compact It Project Granted

It has been very busy weeks, turning into busy months and without noticing, almost a year has passed. The main news is that I got a Academy of Finland project, Compact It, and we still are looking for a researcher who would be interested to take part. Your task will be to use and develop Granular Material Point Method and Uintah software suite, to model dynamic soil exchange. The project will involve close cooperation with Menard and build over resaerch from 2013. You can find the advertisement at Aalto webpage. The position is open until filled. Please apply, I try to check the applications weekly!

Geomeasure project awarded

Would you like to contribute to GEOMEASURE? We are looking for a postdoctoral researcher who would use MPM to model offshore in-situ tests!

File:Gunfleet Sands Offshore Wind Farm - geograph.org.uk - 2091181.jpg
(c) Ashley Dace, Creative Commons License, Gunfleet Sands Offshore Wind Farm

Academy of Finland has awarded Aalto & Geological Survey Finland consortium financing for the Geomeasure project. We will investigate the Finnish seabed with GTK research vessel Geomari and find new ways to interpret the results of the tests, in particular free fall penetrometer tests. To do that, we will take samples from the seabed and correlate results of experimental testing with the penetrometer data. Also, the tests will be numerically modelled with MPM. We also plan to investigate the behaviour of the deposits under cyclic loading, typical for wind turbines.

Geomeasure webpage

The logos of Academy of Finland, Aalto University and Geological Survey Finland are owned and copyrighted by the Academy of Finland, Aalto University and Geological Survey Finland, respectively, and used here just for informational purposes only.

Review Paper on Material Point Method

Our review paper on Material Point Method is now available here. The link will expire in a month, but I hope that by that time we will be able to provide a copy that could be used instead.

Please have a look, and let me thank all the co-authors: professors Martin Berzins, Will Coombs, Jim Guilkey, Matthias Möller and Kenichi Soga, as well as the doctoral students (some of whom graduated by now): , Tito Adibaskoro, Seyedmohammadjavad Seyedan, Roel Tielen and Quoc Anh Tran (all the names in alphabetical order). Thank you again!

Granular MPM

We got new paper published on Granular Material Point Method in Computers & Structures. We are proud of the paper, where we show how you can get continuous material discontinuous during the flow, and then, continuous again. Thanks to that, we can have the silo filled properly 🙂

Silo filling simulation, Granular MPM
Silo filling simulation, Granular CPDI

Are you interested? We have open positions for a post-doctoral position, open until 14th of June 2021. Contact me for more information, as you will have to show your multidisciplinary approach in the application. Good luck!

Installation talk

I have recently recorded an ‘Installation Talk’ entitled “THMC modelling of bentonite: Nuclear waste repositories safety barriers”. See it below:

In case you found it interesting, and would like to have more information, or collaborate on the subject, please do not hesitate to contact me at my Aalto email, search for Wojciech Solowski, Aalto to find it.

Also, hope all of you will have good time during the coming holiday season and let me wish you all the very best for the New Year 2021!

The Installation Talk has been recorded by Aalto University, as I have been tenured at Aalto and promoted to Associate Professor. Many thanks for all those who were involved!

E-Unsat 2020 presentation and Young Invited Lecture

The E-Unsat 2020 has been excellently organised and a resound success, despite being fully online. Even though I must say I did miss the chats with friends and informal, but often illuminating discussions with the attendees, I still have seen many great presentations and learnt much.

Silo filling comparison, CPDI vs Granular CPDI. Simulation done by inserting points on top, and letting them settle under gravity. Lines denotes the domain of the material points, with significant deformations and lack of density recovery in CPDI simulation, while with granular extension the particles settle down at much more realistic density. We used Mohr-Coulomb model for the simulation, (c) Seyedan & Sołowski

I was also presenting the paper authored by Dr Abed and me on validation of gas transport couplings in our THMC coupled Finite Element Method code Thebes (presentation here, and paper here). We have much more to do in relation to gas transport – my doctoral student Abhishek Gupta is responsible for that, and we hope to deliver ambitious simulations of gas transport of a generic nuclear waste repository in a year or two.

I was delighted to deliver the Young Invited Lecture on Granular Material Point Method, something we are working on with Seyed Mohammad Javad Seyedan. We will aim to publish full paper based on the presentation, but for now, the presentation is here.

Many more exciting things has happened and is happening with the research in my group – I will try to update you on that soon!

Long-delayed update

Hi, I have been very busy recently, leading to lack of updates for a very long time. During past few months I delivered a plenary lecture during the 32nd Nordic Seminar on Computational Mechanics in Oulu (slides), Quoc Anh Tran graduated with a doctoral degree (thesis), and we have a new journal paper published, “A convected particle least square interpolation material point method” in IJNME. That one is not currently freely available, so in case you need a copy, contact me at my Aalto email.

Spectacular train station in Liège, architect Santiago Calatrava

So, what the future holds? SMJ Seyedan should graduate relatively soon with another doctoral degree related to MPM, Tito Adibaskoro is slowly progressing towards the same goal. To continue the research I applied for research related to MPM both at national level (Academy of Finland proposal) and international one (Marie-Curie ITN network), and let’s keep fingers crossed.

On the THMC modelling of clays, a new student has started in January, more update on that later!