Alberto García-González

Magma migration is a complex natural process that controls volcanism, the formation of many types of ore deposits, the development of geothermal reservoirs and the thermal structure, and long-term evolution of the lithosphere [1-3]. Because the dynamics of magma migration are difficult to observe directly, numerical simulations provide a powerful tool to investigate magmatic systems, the coupled physiochemical processes involved, and the range of spatial and temporal scales over which these processes operate.In this study, we present a new multi-phase numerical framework to study magma migration within the Earth, with a particular emphasis on the mechanical interactions between melt and solid. The framework is based on multiphase flow in porous media and it incorporates realistic rheological descriptions of lithospheric rocks, including visco-elasto-viscoplastic behavior, damage, strain weakening and the generation of porosity due to plastic deformation. Interaction between the fluid (magma) and solid (host rock) phases are described via a set of equations derived from a formal phase-averaging framework. An arbitrary Eulerian-Lagrangian solver is used to discretize the equations and solve the fully-coupled system. The validity of the model, and its potential to study multi-scale magmatic systems, are demonstrated using well-known benchmark tests and targeted numerical experiments.Keywords: Dynamics of lithosphere and mantle, Mechanics, Numerical modeling, Physics of magma, PlasticityREFERENCES[1] Keller, D. A. May, and B. J. Kaus, “Numerical modelling of magma dynamics coupled to tectonic deformation of lithosphere and crust,” Geophys. J. Int., Vol. 195, pp. 1406-1442, (2013).[2] Li, A. E. Pusok, T. Davis, D. A. May, and R. F. Katz, “Continuum approximation of dyking with a theory for poro-viscoelastic-viscoplastic deformation,” Geophys. J. Int., Vol. 234, pp. 2007-2031, (2023).[3] Oliveira, J. C. Afonso, S. Zlotnik, and P. Diez, “Numerical modelling of multiphase multicomponent reactive transport in the Earth’s interior,” Geophys. J. Int., Vol. 212, pp. 345-388, (2018). Acknowledgment EarthSafe Doctoral Network has received funding from the European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101120556.

We introduce an adaptive model reduction approach to compute peak Von Mises stress (pVMS) in heterogeneous arterial sections. The pipeline follows a standard two-phase process: first, we construct the training set of displacement snapshots obtained from the full order model offline, and then we compute pVMS in the online phase. We adaptively enrich the modal representation in critical regions (around the lumen and in calcified areas) using a level-set approach. Optimized for efficient pVMS computation, as a key plaque vulnerability indicator, this technique significantly reduces the computational cost of training machine learning models to classify plaque vulnerability based on pVMS.

The inherent brittleness of glass-fiber-reinforced polymer (GFRP) bars limits their structural applicability despite their corrosion resistance and lightweight properties. This study addresses the critical challenge of enhancing the ductility and crack resistance of GFRP-reinforced systems while maintaining their environmental resilience. Through experimental evaluation, GFRC slabs reinforced with GFRP bars are systematically compared to steel-reinforced GFRC slabs and non-bar-reinforced SFRC slabs under bending loads. Eight slabs were subjected to four-edge-supported loading following standardized procedures based on prior strength assessments. The results demonstrate that GFRP-reinforced GFRC slabs achieve an ultimate load capacity of 83.7 kN, comparable to their steel-reinforced counterparts (96.3 kN), while exhibiting progressive crack propagation and 17% higher energy absorption than non-fiber-reinforced systems. The load capacity similarities between GFRP-bar-reinforced GFRC slabs and steel-reinforced slabs are 69% for crack loading and 86% for ultimate capacity. Furthermore, this study demonstrates that the reduction factor in flexural strength design of the novel slab should be comprehensively considered, incorporating the recommended value of 0.5. The findings confirm that GFRP-bar-reinforced GFRC slabs meet key structural performance criteria, including enhanced bending capacity, energy absorption, crack resistance, and ductility. This study underscores the potential of GFRP as an effective alternative to steel reinforcement, contributing to the development of resilient and durable concrete structures in demanding environments.

Glass fiber-reinforced polymer (GFRP) of high performance, as a relatively ideal partial or complete substitute for steel, could increase the possibility of adapting structures to changes in harsh weather environments. While GFRP is combined with concrete in the form of bars, the mechanical characteristics of GFRP cause the bonding behavior to differ significantly from that of steel-reinforced members. In this paper, a central pull-out test was applied, according to ACI440.3R-04, to analyze the influence of the deformation characteristics of GFRP bars on bonding failure. The bond–slip curves of the GFRP bars with different deformation coefficients exhibited distinct four-stage processes. Increasing the deformation coefficient of the GFRP bars is able to significantly improve the bond strength between the GFRP bars and the concrete. However, while both the deformation coefficient and concrete strength of the GFRP bars were increased, the bond failure mode of the composite member was more likely to be changed from ductile to brittle. The results show members with larger deformation coefficients and moderate concrete grades, which generally have excellent mechanical and engineering properties. By comparing with the existing bond and slip constitutive models, it was found that the proposed curve prediction model was able to well match the engineering performance of GFRP bars with different deformation coefficients. Meanwhile, due to its high practicality, a four-fold model characterizing representative stress for the bond–slip behavior was recommended in order to predict the performance of the GFRP bars.

This manuscript presents a novel formulation for a linear elastic model of a heterogeneous arterial section undergoing uniform pressure in a quasi-static regime. The novelties are twofold. First, an elastic bed support on the external boundary (elastic bed boundary condition) replaces the classical Dirichlet boundary condition (i.e., blocking displacements at arbitrarily selected nodes) for elastic solids to ensure a solvable problem. In addition, this modeling approach can be used to effectively account for the effect of the surrounding material on the vessel. Secondly, to study many geometrical configurations corresponding to different patients, we devise an unfitted strategy based on the Immersed Boundary (IB) framework. It allows using the same (background) mesh for all possible configurations both to describe the geometrical features of the cross-section (using level sets) and to compute the solution of the mechanical problem. Results on coronary arterial sections from realistic segmented images demonstrate that the proposed unfitted IB-based approach provides results equivalent to the standard finite elements (FE) for the same number of active degrees of freedom with an average difference in the displacement field of less than 0.5%. However, the proposed methodology does not require the use of a different mesh for every configuration. Thus, it is paving the way for dimensionality reduction.

In the field of bone regeneration, insertion of scaffolds favours bone formation by triggering the differentiation of mesenchymal cells into osteoblasts. The presence of Calcium ions (Ca²⁺) in the interstitial fluid across scaffolds is thought to play a relevant role in the process. In particular, the Ca²⁺ patterns can be used as an indicator of where to expect bone formation. In this work, we analyse the inverse problem for these distribution patterns, using an advection-diffusion nonlinear model for the concentration of Ca²⁺. That is, given a set of observables which are related to the amount of expected bone formation, we aim at determining the values of the parameters that best fit the data. The problem is solved in a realistic 3D-printed structured scaffold for two uncertain parameters: the amplitude of the velocity of the interstitial fluid and the ionic release rate from the scaffold. The minimization in the inverse problem requires multiple evaluations of the nonlinear model. The computational cost is alleviated by the combination of standard Proper Orthogonal Decomposition (POD), to reduce the number of degrees of freedom, with an adhoc hyper-reduction strategy, which avoids the assembly of a full-order system at every iteration of the Newton’s method. The proposed hyper-reduction method is formulated using the Principal Component Analysis (PCA) decomposition of suitable training sets, devised from the weak form of the problem. In the numerical tests, the hyper-reduced formulation leads to accurate results with a significant reduction of the computational demands with respect to standard POD.

Scaffolds are microporous biocompatible structures that serve as material support for cells to proliferate, differentiate and form functional tissue. In particular, in the field of bone regeneration, insertion of scaffolds in a proper physiological environment is known to favour bone formation by releasing calcium ions, among others, triggering differentiation of mesenchymal cells into osteoblasts. Computational simulation of molecular distributions through scaffolds is a potential tool to study the scaffolds’ performance or optimal designs, to analyse their impact on cell differentiation, and also to move towards reduction in animal experimentation. Unfortunately, the required numerical models are often highly complex and computationally too costly to develop parametric studies. In this context, we propose a computational parametric reduced-order model to obtain the distribution of calcium ions in the interstitial fluid flowing through scaffolds, depending on several physical parameters. We use the well-known Proper Orthogonal Decomposition (POD) with two different variations: local POD and POD with quadratic approximations. Computations are performed using two realistic geometries based on a foamed and a 3D-printed scaffolds. The location of regions with high concentration of calcium in the numerical simulations is in fair agreement with regions of bone formation shown in experimental observations reported in the literature. Besides, reduced-order solutions accurately approximate the reference finite element solutions, with a significant decrease in the number of degrees of freedom, thus avoiding computationally expensive simulations, especially when performing a parametric analysis. The proposed reduced-order model is a competitive tool to assist the design of scaffolds in osteoinduction research.