S5E11

Abstract

In this presentation, I will talk about the evolving shape distribution of sand grains subjected to high-pressure confined compression. Particle morphology is one of the key factors to determine the mechanical response of granular system. Despite its importance, quantification of the particle shape and use into modeling approaches is a challenging task, especially for granular systems susceptible to changes in the morphology of individual particles. For this purpose, we use recent advances in non-destructive testing based on 3D X-ray synchrotron tomography. To quantify particle-scale response, three fitting protocols are proposed and used in conjunction with a tracking algorithm recording the breakage history of individual particles. Interestingly, we find that the morphological properties of fragments are highly correlated to their corresponding original grains regardless of the fitting strategy. The non-symmetric statistics of particle shapes however leads to a decrease of the average value of the aspect ratio in the assembly of crushable sand.

Introduction of speaker

Dr. Dawa Seo is currently a postdoc at Los Alamos National Laboratory (LANL), the United States. She graduated from Northwestern University in 2022 with a PhD in Civil and Environmental Engineering. She received a B.Sc. and M.S. degree in Civil and Environmental Engineering from Yonsei University, Republic of Korea. During her Ph.D., she researched particle-scale assessment of the role of the grain morphologies in granular system and her current research focused on mesoscale analysis of the shape effect on granular materials.

Abstract

Concrete is the most widely used man-made material worldwide and is responsible for a large fraction of anthropogenic CO2 emissions. Under the action of sustained loads and over long-time scales, concrete undergoes irreversible deformations that can severely restrict the lifetime of infrastructure. This process, known as aging creep, arises from the relaxation of the nanoporous and disordered network of colloidal particles that forms the nanostructure of cement, the “glue” in concrete. A direct and effective strategy to mitigate the environmental impact of concrete would be to lower its consumption by extending the lifetime of infrastructure. However, our understanding of the mechanisms that govern aging creep in disordered solids is incomplete and the relationship between the microstructure of the glass and its mechanical response remains poor. In this talk, I will present recent work based on molecular dynamics simulations and data-driven approaches done by my group with the aim to decode the relationship between static structure and the microscopic dynamics of glass particles under creep. Our ultimate goal is to develop models for the rapid evaluation of the creep response of glassy microstructures.

Introduction of speaker

Dr. Luis Ruiz Pestana joined the University of Miami in 2019 as an Assistant Professor in the Civil and Architectural Engineering Department. He received his Ph.D. in Theoretical and Applied Mechanics from Northwestern University in 2015, where he made important contributions to the areas of nanomechanics, self-assembly and selective molecular transport in supramolecular peptide nanotubes, as well as developed particle-based mesoscale models to study the mechanical properties of graphene multilayered structures. After his Ph.D., he became a postdoctoral fellow in the Chemical Sciences Division at Lawrence Berkeley National Laboratory (LBNL) and at the Pitzer Center for Theoretical Chemistry at the University of California Berkeley. There he used simulation methods based on quantum mechanics to understand how nanoconfinement affects chemical reactivity and the structure and dynamics of water. His current research focuses on investigating the unusual and fascinating properties of disordered nanostructured materials, for which he combines physics-based simulation techniques and data-driven approaches. The aim of his research is to derive design rules that would allow to create new, better materials to tackle persistent societal challenges, from sustainable infrastructure to clean energy. Dr. Ruiz Pestana received the Predictive Science and Engineering Design Cluster Fellowship from Northwestern University in 2011, the Nanomechanics Summer Institute NSF Fellowship in 2011 and 2012, and he was invited to the Early Career Enrichment Program at LBNL in 2019. He was appointed the Dr. Reza and Georgianna Khatib Endowed Chair in 2022. He has already received funding from the National Science Foundation and the Human Frontier Science Program, among others.