Macro-scale Model Research Articles

Investigations of ice impact damage and residual performance of 3D angle-interlock woven composites based on in-situ sampling

Investigations of ice impact damage and residual performance of 3D angle-interlock woven composites based on in-situ sampling

Multiscale Finite Element Modeling of Human Ear for Acoustic Wave Transmission into Cochlea and Hair Cells Fatigue Failure.

Hearing loss is highly related to acoustic injuries and mechanical damage of ear tissues. The mechanical responses of ear tissues are difficult to measure experimentally, especially cochlear hair cells within the organ of Corti (OC) at microscale. Finite element (FE) modeling has become an important tool for simulating acoustic wave transmission and studying cochlear mechanics. This study harnessed multiscale FE models to investigate the mechanical behaviors of ear tissues in response to acoustic wave and developed a fatigue mechanical model to describe the outer hair cells (OHCs) failure. The three-dimensional multiscale FE models consisted a macroscale model of the ear canal, middle ear, and 3-chambered cochlea and a microscale OC model on a representative basilar membrane section, including the hair cells, membranes, and supporting cells. Harmonic Acoustic mode was used in the FE models for simulating various acoustic pressures and frequencies. The cochlear basilar membrane and the cochlear pressure induced by acoustic pressures were derived from the macroscale model and used as inputs for microscale OC model. The OC model identified the stress and strain concentrations in the reticular lamina at the root of stereocilia hair bundles and in the Deiter's cells at the connecting ends with OHCs, indicating the potential mechanical damage sites. OHCs were under cyclic loading and the alternating stress was quantified by the FE model. A fatigue mechanism for OHCs was established based on modeling results and experimental data. This mechanism would be used for predicting fatigue failure and the resulting hearing loss.

Numerical Simulation of Impact of Different Redox Couples on Flow Characteristics and Electrochemical Performance of Deep Eutectic Solvent Electrolyte Flow Batteries

A comprehensive, three-dimensional, macro-scale model was developed to simulate non-aqueous deep eutectic solvent (DES) electrolyte flow batteries. The model’s feasibility was validated by comparing the simulated polarization data with the experimental results. Utilizing this model, the work reported here compared the flow characteristics and electrochemical properties of electrolytes with different redox couples within the porous electrodes of the batteries. Despite variations in the active materials, the distribution of the electrolyte flow rate showed uniformity due to consistent electrode and flow channel designs, indicating that the structural design of electrodes and channels has a more significant impact on electrolyte flow than the physicochemical properties of the electrolytes themselves. This study also highlighted that TEMPO and Quinoxaline DES electrolytes exhibited less flow resistance and more uniform concentration distributions, which helped reduce overpotentials and enhance battery energy efficiency. Furthermore, this research identified that the highest average overpotentials occurred near the membrane for all the redox couples, demonstrating that electrochemical reactions in DES electrolyte flow batteries primarily occur in the region close to the membrane. This finding underscores the importance of optimizing active redox ions transport in electrolytes to enhance electrochemical reactions in the proximal membrane region, which is crucial for improving flow battery performance.

Thermodynamically Constrained Averaging Theory: Why Bother?

Porous medium researchers and practitioners usually rely on macroscale models to represent systems of concern. While macroscale models have often been formulated phenomenologically, the thermodynamically constrained averaging theory (TCAT) provides a means to rigorously derive closed macroscale models for a wide variety of systems. However, the TCAT approach can appear overwhelmingly complicated, the entry point for use unclear, and the advantages not self-evident. In response to these perceived shortcomings, we demonstrate several aspects of TCAT macroscale model formulations for single-fluid flow in a porous medium. Specifically, we illustrate an essentially exact macroscale model derived from a rigorous connection across scales, show how an entropy inequality can be used to derive an approximate macroscale form for the Stokes-flow regime, and examine models in the transition flow regime. A special emphasis is placed upon leveraging available results, and other application opportunities are summarized.

3D Computational Modeling of Blast Transmission through the Fluid-Filled Cochlea and Hair Cells.

Veterans commonly suffer from blast-induced hearing disabilities. Injury to the sensitive organ of Corti (OC) or hair cells within the cochlea can directly lead to hearing loss, but is very difficult to measure experimentally. Computational finite element (FE) models of the human ear have been used to predict blast wave transmission through the middle ear and cochlea, but these models lack a representation of the OC. This paper reports a recently developed 3D FE model of the OC to simulate the response of hair cells to blast waves and predict possible injury locations. Components of the OC model consist of the sensory cells, membranes, and supporting cells with endolymphatic fluid surrounding them inside the scala media. Displacement of the basilar membrane induced by a 31-kPa blast overpressure derived from the macroscale model of the human ear was applied as input to the OC model. The fluid-structure interaction coupled analysis in the time domain was conducted in ANSYS. Major results derived from the FE model include the strains and displacements of the outer hair cells, stereociliary hair bundles (HBs), reticular lamina, and the tectorial membrane (TcM). The highest structural strain was concentrated around the connecting region of the HBs and the TcM, potentially indicating detachment due to blast exposure. Including the interstitial fluid in the OC created a realistic environment and improved the accuracy of the results compared to the previously published OC model without fluid. The microscale model of OC was developed in order to simulate blast overpressure transmission through the fluid-filled cochlea and hair cells. This FE model represents a significant advancement in the study of blast wave transmission through the inner ear, and is an important step toward a comprehensive multi-scale model of the human ear that can predict blast-induced injury and hearing loss.

Multiscale structural optimization for prescribed deformations in the nonlinear elastic regime

In this paper, a multiscale structural optimization framework capable of efficiently designing two-scale structures with prescribed displacements in the nonlinear elastic regime is presented. In contrast to previous multiscale structural optimization frameworks, which are founded upon the assumptions of linear elasticity, the present framework is capable of efficiently operating within the nonlinear elastic regime. At the core of the present framework is a parameterized microscale geometry, which through the straightforward manipulation of the microscale parameters provides direct access to both positive and negative Poisson’s ratios. The microscale model is concurrently coupled to the macroscale model such that only the microscale parameter space traversed by the optimizer is resolved during the optimization procedure, leading to a significant reduction in the computational expense of analysis. To demonstrate the capability of this framework, three prescribed deformation profiles are targeted by three distinct optimization procedures. In all instances, the deformation profile is successfully targeted. To verify the accuracy of the optimized structures, high-fidelity single-scale simulations are performed. In each case, excellent agreement is noted between the high-fidelity simulations and the corresponding optimized macroscale displacement fields, with errors of less than 10%.

Multiscale Modeling Approach to Study the Influence of Bilayer Porous Transport Layers on Oxygen Evolution and PEMWE Performance

With the current push for an alternative to traditional fuel-based transportation, hydrogen has the potential to be a viable replacement. Hydrogen has been proposed as a fuel replacement in internal combustion engines, or as fuel in a fuel cell powered automotive vehicle. Before hydrogen can be used in any type of transportation, it must first be produced. Proton Exchange Membrane Water Electrolyzers (PEMWE) produce hydrogen through an oxygen evolution reaction. A key component to PEMWE operation is the porous transport layer (PTL). Specifically, the PTL on the anode side must provide transport pathways for water to access the catalyst layer, while simultaneously removing oxygen.In this work, a multiscale modeling approach is used to study the effect of a bilayer PTL, which is a PTL with an added mesoporous layer (MPL), on oxygen evolution and PEMWE performance. A previously developed image processing technique was expanded to generate bilayer PTLs from Xray Tomography scans. This process generates each sample a one combined geometry, which removes the need for interface communication. Due to the improvements in imaging techniques, the ability to mesh complex structures with this technique is possible. Each sample was generated with a 2:1 PTL to MPL ratio, with the total thickness around 400 ums. Porosity and pore size distributions were calculated during the image processing step. First a micro scale model that uses the Finite Volume Method, accompanied with a volume of fluid model, was used to predict permeability and simulate simultaneous two-phase flow of liquid water and oxygen gas. Oxygen evolution, growth, and structure interaction were observed. Results showed that the bilayer structure removes oxygen faster than single layer PTLs. Physical properties calculated using the micro scale model were used to inform a macro scale model of a PEMWE using the Finite Volume Method. The macro scale model predicted performance curves for each bilayer sample. Results showed that the bilayer samples exhibited improved performance as high current densities. Findings from this work show that a bilayer PTL geometry has potential to improve PEMWE performance.

Elucidating Degradation Mechanisms through Modeling of Proton-Exchange Membrane Electrolytic Cells

Proton exchange membrane (PEM) electrolytic cells (ECs) have gained significant importance in the realm of hydrogen production. With the increasing demand for commercializing PEMECs, there is a pressing need for enhancing their performance and durability. In addition to experiments, macro-scale modeling plays a pivotal role in comprehending the multi-physics processes within PEMECs.This presentation highlights the development of physics-based and data-based models tailored for PEMECs. They serve as the foundation for elucidating degradation mechanisms of PEMECs, aiming to prolong their lifespan and improve their efficiency for a quick technology ramp up. These models explore the electrochemical processes and transport phenomena occurring within the porous transport layers (PTLs), catalyst layers (CLs), and the PEM. The high-aspect-ratio PEMECs are well-suited for one-dimensional (1D) analysis [1-3]. The 1D analysis is implemented in Python, with COMSOL also utilized for 2D and 3D simulations.Unfortunately, the complex nature of PEMECs as thermal, fluidic, and electrochemical systems poses challenges in accurate diagnostics. Modeling these cells involves addressing uncertainties in operational conditions, material properties, and design features. Additionally, uncertainties in experimental data, model selection, parameters, and model inadequacies must be carefully considered during PEMEC modeling. While uncertainty quantification (UQ) and sensitivity analysis (SA) can unveil how uncertainties propagate from input parameters to the output of PEMEC models, UQ has not been extensively integrated into PEMEC modeling. Finally, this presentation underscores the potential benefits of physics-based modeling combined with UQ and SA for PEM electrolysis [3]. Acknowledgment: Financial support was provided by the German Federal Ministry of Education and Research (BMBF) within the H2Giga project DERIEL (grant number 03HY122C). Literature: [1] P. Trinke, 2021.[2] P. A. García-Salaberri, J. Power Sources, 2022, 521.[3] V. Karyofylli, Y. Danner, K. Ashoke Raman, H. Kungl, A. Karl, E. Jodat, R.-A. Eichel, J. Power Sources, 2024, 600, 234209.

A Multi-Scale Thermal-Mechanical Numerical Method for Mini-Channel Heat Exchanger Subjected to Fluid Pressure Loads

Abstract This study proposes a novel multi-scale numerical method for thermal-mechanical analysis of mini-channel heat exchangers (MCHEs) under internal fluid pressure and temperature loads. The method comprises a macro-scale model for global analysis and a meso-scale model for detailed submodel analysis, specifically focusing on the internal fluid pressure effects within the MCHEs. The macroscopic model divides the MCHE into cover plate and homogenized regions subjected to pressure and temperature loads. To incorporate internal pressures into the homogenized MCHE model, mathematical equations are formulated to convert internal fluid pressures into equivalent strain loads. Additionally, a novel equivalent thermal expansion method is introduced, integrating internal fluid pressure loads by prescribing equivalent thermal expansion coefficients alongside spatially-varying nodal temperature fields within the MCHE. The meso-scale models with detailed channel patterns are assigned to specific portions of the homogenized region. The integration of the mesoscale model into the macroscopic framework is achieved through the application of the submodel method. Comparisons between the equivalent and actual MCHE models show that the proposed equivalent method can provide accurate predictions for thermal-mechanical deformations and stresses, and significantly reduce the computational expenses.

Modeling different modes of failure in reinforced concrete beams combining tensile and shear-frictional damage models and bond–slip coupling for non-matching reinforcement and fragmented concrete meshes

Modeling different modes of failure in reinforced concrete beams combining tensile and shear-frictional damage models and bond–slip coupling for non-matching reinforcement and fragmented concrete meshes

An evolutionary analysis method for small cracks in drive shafts based on cross-scale modeling

An evolutionary analysis method for small cracks in drive shafts based on cross-scale modeling

Self-healing effect on the impact-resistance of hybrid stitch toughening CFRP composites: Experimental and numerical study

Self-healing effect on the impact-resistance of hybrid stitch toughening CFRP composites: Experimental and numerical study

Geometric flow control in lateral flow assays: Macroscopic two-phase modeling

Lateral flow assays (LFAs) are widely employed in a diverse range of applications, including clinical diagnostics, pharmaceutical research, forensics, biotechnology, agriculture, food safety, and environmental analysis. A pivotal component of LFAs is the porous polymeric membrane, which facilitates the capillary-driven movement of fluids, known as “imbibition,” in which a wetting fluid displaces a non-wetting fluid within the pore space of the membrane. This study presents a multi-scale modeling framework designed to investigate the imbibition process within LFAs. The framework integrates microscopic membrane characteristics into a macroscopic two-phase flow model, allowing the simulation of imbibition in membranes with different micro-scale properties and macro-scale profiles. The validity of the model was established through comparative analysis with documented case studies, a macro-scale single-phase flow model, and experimental observations, demonstrating its accuracy in simulating the imbibition process. The study also examines imbibition in various geometric configurations, including bifurcated (Y-shaped) and multi-branch geometries commonly found in multiplexed LFAs. The influence of geometric features such as length ratio, width ratio, branching angle, bifurcation point location, and asymmetry on fluid transport is investigated. Results indicate that membranes with larger branching angles exhibit slower imbibition. In addition, the influence of membrane type on macroscopic flow patterns is evaluated, showing that membranes with lower permeability require longer imbibition times. The insights gained from this research support a data-driven strategy for manipulating wetting behavior within LFAs. This approach can be leveraged to optimize the performance of LFAs and increase their effectiveness in various applications.

Numerical Model for Investigating Effects of Cracks and Perforation on Polymer Electrolyte Fuel Cell Performance

The presence of cracks in the microporous layer (MPL) of polymer electrolyte fuel cells (PEFCs), often occurring during the membrane electrode assembly manufacturing process, has a significant impact on cell performance. However, the exact influence of crack presence, density, and patterns within MPLs on cell performance and transport behaviors remains unclear. This study introduces a three-dimensional macroscale model of PEFCs aimed at investigating the effects of MPL cracks and gas diffusion layer (GDL) perforations on cell performance and transport behavior. This model offers several advantages, including the ability to potentially integrate the effects of flow channel design in future. Additionally, the model can seamlessly incorporate electrochemical reactions and explore phenomena within the catalyst layers (CLs), expanding simulation capabilities beyond water transport alone. The findings suggest that MPL cracks contribute positively to performance by facilitating water drainage. Furthermore, when combined with perforations in GDLs, MPL cracks can significantly enhance performance by providing pathways for water transport. Overall, this study provides valuable insights into developing models for optimizing PEFC performance and underscores the need for further research and development in this area.

Distinct Element macro-crack networks for expedited discontinuum seismic analysis of large-scale URM structures

Distinct Element macro-crack networks for expedited discontinuum seismic analysis of large-scale URM structures

Multiscale finite element procedure to predict the effective elastic properties of woven composites

Multiscale finite element procedure to predict the effective elastic properties of woven composites

Dynamic Progressive Failure Analysis of 3D Five-directional Braided Composites under Transverse Compression Based on Macro-scale Heterogeneous Model

At present, there are few systematic researches on macro-scale heterogeneous modeling and numerical simulation of dynamic mechanical properties of 3-D braided composites. In this paper, the parametric virtual simulation model of 3D five-directional braided composites is realized in the way of “point-line-solid” based on the integrated design idea of process-structure-performance. And the impact compression numerical simulation of the material is carried out by using multi-scale analysis method. The effects of strain rate and braiding angle on transverse impact compression properties and fracture characteristics of composites is studies and verified by comparing the test results with the numerical simulation results systematically. The dynamic failure mechanism of the matrix and fiber bundles during the impact compression process is revealed. The results show that the macro-scale heterogeneous simulation model of 3D five-directional braided composites established is effective, and the numerical simulation results agree well with the test results. The matrix fracture and shear failure of fiber bundles are presented simultaneously under transverse impact compression. The failure of fiber bundles and matrix mainly concentrates on two main fracture shear planes. And the included angle between the fracture shear planes and the vertical direction is consistent with the corresponding internal braiding angle of specimens.

Multiscale framework-based crystal plasticity modeling and texture evolution of the deformation behavior of AISI 304 stainless steel microtubes manufactured through 3D-FBF technology

Multiscale framework-based crystal plasticity modeling and texture evolution of the deformation behavior of AISI 304 stainless steel microtubes manufactured through 3D-FBF technology

Tensile performance prediction of CFRPs with voids using multiscale analysis and neural networks

Tensile performance prediction of CFRPs with voids using multiscale analysis and neural networks

Numerical Assessment of Effective Elastic Properties of Needled Carbon/Carbon Composites Based on a Multiscale Method

Needled carbon/carbon composites contain complex microstructures such as irregular pores, anisotropic pyrolytic carbon, and interphases between fibers and pyrolytic carbon matrices. Additionally, these composites have hierarchical structures including weftless plies, short-cut fiber plies, and needled regions. To predict the effective elastic properties of needled carbon/carbon composites, this paper proposes a novel sequential multiscale method. At the microscale, representative volume element (RVE) models are established based on the microstructures of the weftless ply, short-cut fiber ply, and needled region, respectively. In the microscale RVE model, a modified Voronoi tessellation method is developed to characterize anisotropic pyrolytic carbon matrices. At the macroscale, an RVE model containing hierarchical structures is developed to predict the effective elastic properties of needled carbon/carbon composites. For the data interaction between scales, the homogenization results of microscale models are used as inputs for the macroscale model. By comparing these against the experimental results, the proposed multiscale model is validated. Furthermore, the effect of porosity on the effective elastic properties of needled carbon/carbon composites is investigated based on the multiscale model. The results show that the effective elastic properties of needled carbon/carbon composites decrease with the increase in porosity, but the extent of decrease is different in different directions.