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High‐temperature electrochemical cells have received increasing interest in the past years as important elements in an energy transition scenario. Their employment in power‐to‐gas or gas‐to‐power systems naturally requires an accurate design that takes into account the effect of operating conditions and geometries on both the performance of the cells themselves and their integration with other units. To this end, it is important to develop flexible yet comprehensive models for their description and to identify performance parameters that allow a concise assessment of their efficiency. The aim of the present work is to identify the limitations – in terms of applicability and consistency – of the mathematical models developed to date to describe high‐temperature electrochemical cells, as well as the key characteristics that they should possess. A brief review of literature in this field is then reported, to identify the research areas that still need to be explored. [ABSTRACT FROM AUTHOR]

While the modification of surface contacts offers significant potential for friction reduction, obtaining an underlying consistent friction behaviour of real-life experiments and virtual simulations is still an ongoing challenge. In particular, most works in the literature only consider idealised geometries that can be parametrised with simple analytical functions. In contrast to this approach, the current work describes the establishment of a digital twin of a pin-on-disk tribometer whose virtual geometry is completely replicated from real-life post-test topography measurements and fed into a two-scale mixed lubrication solver. Subsequently, several calibration steps are performed to identify the sensitivities of the friction behaviour towards certain geometry features and enable the digital twin to robustly represent the Stribeck curve of the physical experiments. Furthermore, a derivation of the Hersey number is used to generalise the obtained friction behaviour for different dynamic viscosities and allow the validation of the presented method. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) is the most dominant method for the numerical prediction of dynamic behaviour at grain or particle scale. Nevertheless, due to its discontinuous nature, the DEM is inherently unable to describe microscopic features of individual bodies which can be considered as continuous bodies. To incorporate microscopic features, efficient numerical coupling of the DEM with a continuous method is generally necessary. Thus, a generalised multi-scale PD–DEM framework is developed in this work. In the developed framework, meshfree discretised Peridynamics (PD) is used to describe intra-particle forces within bodies to capture microscopic features. The inter-particle forces of rigid bodies are defined by the DEM whereas a hybrid approach is applied at the PD–DEM interface. In addition, a staggered multi-scale time integration scheme is formulated to allow for an efficient numerical treatment of both methods. Validation examples are presented and the applicability of the developed framework to capture the characteristics mixtures with rigid and deformable bodies is shown. [ABSTRACT FROM AUTHOR]

COVID-19 pandemic promoted a lot of research activities in relation to mucosalivary fluid airborne transport. Indeed, infection mechanisms are the result of mucosalivary fluid droplets exchange and the knowledge in this area is still largely inadequate. One of the main challenges concerns the modelling of mucosalivary fluid complex nature. Specifically, this is a key element to predict small diameters dry nuclei formation which are highly relevant from the transmission risk point of view. For this reason, in this paper we present and discuss the development of a new multi-scale modelling technique which incorporates the Population Balance Equation into a standard particle-source-in-cell method. Thus, the effectiveness of the aforementioned technique in droplet nuclei generation modelling is showed and discussed. Also the impact of velocity boundary conditions at the mouth print is assessed as well as the effect of the correlations for mass transfer showing that their neglect causes an underestimation in distance reached by the droplets. [ABSTRACT FROM AUTHOR]

To relate the thermomechanical behaviour and microstructural evolution of the heat-assisted incremental sheet forming (SPIF) for Ti–6Al–4 V sheet, multi-scale models based on crystal plasticity finite element model (CPFEM), representative elementary volume (RVE), and cellular automaton (CA) were established in this article. An experimental-scale CPFEM was built in advance to provide macrograin level strain, strain rate, and temperature output data, which were then used in RVE and CA as inputs to simulate the microstructural evolution throughout the SPIF process. The output results include the pole figures, dynamic recrystallisation (DRX) maps, and statistics results of the alpha (α) phase of the Ti–6Al–4 V (α-Ti) alloy from stage to stage throughout the 700 ∘ C SPIF. The obtained statistics results of dislocation density, grain orientation angles, and grain size were verified with electron backscatter diffraction (EBSD). The CA analysis of the DRX progress at the upper, centre, and lower regions of the deformed workpiece has discovered that the incremental increase of the strain rate has significant effects on the dislocation density that produced a proportional relationship to the DRX percentage. The results revealed that the strain rate has strong domination in affecting the slip of grains orientation, which overcomes the effect of temperature increase in this SPIF process. Furthermore, it was found that a large amount of DRXed grains were generated at the grain boundaries, which reduced the mean grain size and increased the DRX percentage, which produced an inversely proportional relationship to the dislocation density. The thermomechanical behaviour on the SPIF workpiece was increased incrementally, which is insufficient for DRX initiation in the upper region, and the behaviour was enhanced at the centre and lower region, which can be corresponded to the microstructural evolution throughout the process. [ABSTRACT FROM AUTHOR]

Laser-Based Powder Bed Fusion is one of the most widely used additive manufacturing processes, mainly due to its high-quality output. End users would greatly benefit from a virtual simulation of the process; however, the modelling of the process is very complicated and slow and therefore restricted mainly to academic users. In this work, a computationally efficient approach to the thermal modelling of PBF-LB/M is presented. This approach is based on the enthalpy method and the division of the simulation into three characteristic scales of the process. Despite the small runtime of the simulations, the model captures the critical phenomena of the process achieving sufficient accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lewis number deviates from one in the entrance length. • The catalyst activity do not modify the initial Nu and Sh inside of the channels. • Re modifies the thermal entrance length because of the reduction of the flow area. This paper is devoted to the multi-scale model of the heat and mass transfer inside of a honeycomb monolith substrate. Due to computational limitations, monoliths are modelled as a continuum in full-scale catalytic reactors models. That makes it necessary to use correlations or sub-models derived from channel scale results to account for a physically consistent heat and mass transfer inside of the substrate. In this paper detailed computational models at a channel and reactor scales are analyzed. Catalytic oxidation of CO is used as a reaction and the fluid properties are considered to be temperature-dependent. First, a channel scale model is used to analyze Nusselt, Sherwood, Lewis, and Damköhler numbers inside of the monolith channels. Secondly, sub-models obtained at a channel level are implemented in a full-scale reactor model using the continuum approach, to evaluate the impact of using detailed vs. highly simplified correlations for heat and mass transfer. The reactor scale model accounts for the transitions of the flow regime, entrance length effects, an-isotropic substrate thermal conductivity and temperature-dependent fluid properties. According to the results, the Lewis number can deviate significantly from one in the entrance length, however, it approaches asymptotically to unity as the flow develops. Regarding Nusselt and Sherwood, current interpolating methodologies are not able to predict the correct value in the entrance region when Damköhler is low, nonetheless, are reasonably accurate for the asymptotic one. [ABSTRACT FROM AUTHOR]

In this paper, a multi-scale modelling approach has been developed to predict the progressive damage and failure behaviour of 2D woven SiC/SiC composites. At the tow scale, non-linear tow properties have been determined by a micromechanics-based damage model, in which two scalar damage variables were introduced to characterize the fibre-dominated and matrix-dominated damage, respectively. Based on periodic boundary conditions, a meso-scale unit cell model has been established to simulate the macroscopic stress-strain responses and progressive damage processes of the composite under uniaxial tensile, compressive and in-plane shear loadings, respectively. In the numerical method, the non-linear properties of constituent materials have been implemented by the user defined subroutine, USDFLD of the finite element package, Abaqus. The numerical results and their comparisons with experimental stress-strain curves have been presented. The failure mechanisms of the composite under each loading have been also discussed. The high efficiency and prediction accuracy of the model make it possible to analyse large scale woven composites. [ABSTRACT FROM AUTHOR]

This study proposed a crystallographic texture-based multi-scale modelling framework to predict mechanical anisotropy of textured aluminium alloy sheet. The multi-scale scheme was constructed by the combination of a full-field crystal plasticity model in mesoscopic scale and a newly developed phenomenological yield function in continuum scale. In this approach, the mechanical anisotropy of materials is directly obtained from crystal plasticity (CP) modelling without extensive directional tensile tests. The results show that the multi-scale scheme predicted earing profiles coincide well with experimental measurements. This multi-scale modelling could be utilised to design an optimised blank shape with minimum earing for the deep-drawn component, and a convoluted cut-edge was devised accordingly. [ABSTRACT FROM AUTHOR]

Ship-induced waves are an increasingly relevant hydrodynamic forcing factor in waterways travelled by large seagoing ships. The discrepancy between the small-scale wave-structure interaction near embankments and the larger-scale wave generation and propagation poses challenges for the prediction of ship-induced waves as a multi-scale problem. Therefore, a novel hydrodynamic coupling interface is presented that allows information transfer from the shallow-water-equation (SWE) solver REEF3D::SFLOW to the 3D-RANS-solver REEF3D::CFD. The implementation consists of a one-way coupling, where the solution from the SWE solver is imposed to one or multiple relaxation zones of the CFD solver. A series of verification cases shows that the implementation of the interface is accurate and only small deviations are introduced due to the 2D-3D dimensional mismatch of the numerical models involved. An application is presented, showing how the coupled SWE-CFD model can be employed to study ship-induced groin overtopping. • Presentation of a coupling interface between a SWE solver and a RANSE-solver. • The error induced by a vertical velocity assumption in the interface is found to be small. • The versatility of the approach is showcased by simulating ship-induced groin overtopping. [ABSTRACT FROM AUTHOR]

The present contribution focuses on the analysis of diverse deformation mechanisms that impact the behaviour of PC/ABS blends using computational homogenisation. This includes analysing internal particle cavitation, PC/ABS interface debonding, and PC matrix shear-yielding. The goal is to investigate the optimal composition for specific applications and create tailored materials. The work involves establishing a microstructure Representative Volume Element, defining the constitutive description of both material phases, and explicitly modelling PC/ABS interfaces and matrix damage to achieve accurate predictions. A Python programme is devised to efficiently integrate zero-thickness cohesive interface elements around ABS particles, incorporating the PPR potential-based cohesive model to characterise the interface. Additionally, the finite strain visco-elastic visco-plastic constitutive model of the PC matrix is extended to incorporate a damage variable, addressing the shear-yielding failure mechanism. The PC/ABS blend's thermomechanical response is homogenised using first-order hierarchical multi-scale analyses. The impact of considering the interface phase in the microstructure is assessed through various numerical analyses. The synergy between the constitutive models effectively captures the blend's behaviour. These findings lay the foundation for broader applicability beyond PC/ABS blends, paving the way for future studies in the field. • Development of a homogenisation framework to study the behaviour of PC/ABS blends. • Examining the individual influence and synergistic effects of the deformation mechanisms. • Determining the optimal size and mesh discretisation for Representative Volume Elements. • Analysing how interfacial and bulk material parameters impact the behaviour. • Evaluating which loading conditions are most affected by considering realistic interfaces. [ABSTRACT FROM AUTHOR]

Featured Application: High-quality and high-throughput eco-friendly regimes of laser cutting glasses, sapphire and other transparent materials are found based on the model. Possible practical applications are in display manufacturing, the automotive and other industries. A strategy is proposed for achieving a practically important mode of laser processing—a so-called "smooth" laser filamentation cutting (LFC) of transparent materials by a moving beam of a pulse-periodic pico- or subpicosecond laser. With such cutting, the surface of the sidewalls of the cuts have a significantly improved smoothness, and, as a result, the laser-cut plates have increased resistance to damage and cracking due to mechanical impacts during their subsequent use. According to the proposed analytical model, for the case when each filament is formed only by a single laser pulse, the strategy of such cutting is defined by a set of necessary conditions, whose implementation requires, in turn, a certain selection and matching with each other of irradiation parameters (pulse duration and energy, repetition rate, pitch of filaments following) and of material parameters—thermal, optical and mechanical strength constants. The model shows good agreement with experiments on sapphire and tempered glass. Besides, LFC modes are also predicted that provide very high cutting speeds of the order of 1–25 m/s or more, or allow cutting with an extremely low average laser power, but still at a speed acceptable for practical applications. [ABSTRACT FROM AUTHOR]

In this work, a multi-scale model established from the concept of periodic homogenization is utilized to predict the cyclic and time-dependent response of thermoplastic-based woven composites. The macroscopic behaviour of the composite is determined from finite element simulations of the representative unit cell of the periodic microstructure, where the local non-linear constitutive laws of the components are directly integrated, namely, the matrix and the yarns. The thermoplastic matrix is described by a phenomenological multi-mechanisms constitutive model accounting for viscoelasticity, viscoplasticity and ductile damage. For the yarns, a hybrid micromechanical–phenomenological constitutive model accounting for anisotropic damage and anelasticity induced by the presence of a diffuse micro-crack network is utilized. The capabilities of the overall multi-scale model are validated by comparing the numerical predictions with experimental data. Further illustrative examples are also provided, where the composite undergoes time-dependent deformations under uni-axial and non-proportional multi-axial loading paths. The multi-scale model is also employed to analyze the influence of the local deformation processes on the macroscopic response of the composite. [ABSTRACT FROM AUTHOR]

Ternary Al–Mg–Si alloys have been modelled based on a multi-scale approach that spans across atomistic and mesoscale models and uses theoretically determined parameters. First, a cluster expansion model for total energy has been trained for atomistic configurations (FCC lattice) based on the data from density functional simulations of electronic structure. Free energy curves as a function of solute (Mg, Si) concentrations and disorder have been obtained by using this parameterisation together with meta-dynamics Monte Carlo sampling. In addition, free energy data, surface tensions as well as strain energy using the linear elasticity theory have been collected to be combined for a mesoscale phase-field model. The application of this approach shows that the formation of a layered MgSi phase, with (100) planes, is a particularly stable solute aggregation motif within the Al host matrix. Moreover, the phase-field model demonstrates that the preferred shape of the MgSi precipitates is needle-like (in FCC), and they can act as precursors for the important and well-known β ″-type precipitates which are formed by translating one Mg column by a 1/2 lattice vector. The results provide theoretical evidence that the solute aggregation into needle-like MgSi domains (precipitates) is an inherent property of Al-Mg-Si alloys, and that it takes place even without the presence of vacancies which is a precondition for the eventual formation β ″ precipitates. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The article offers information on different types of raw materials. Topics include forgotten contributions to science and engineering also mark the origins of materials science; sophisticated (technical instruments to explore the world around us at the smallest and the largest length scales; and simplest version of the molecular Nano machineries.

Aim: Deforestation is rapidly altering Southeast Asian landscapes, resulting in some of the highest rates of habitat loss worldwide. Among the many species facing declines in this region, clouded leopards rank notably for their ambassadorial potential and capacity to act as powerful levers for broader forest conservation programmes. Thus, identifying core habitat and conservation opportunities are critical for curbing further Neofelis declines and extending umbrella protection for diverse forest biota similarly threatened by widespread habitat loss. Furthermore, a recent comprehensive habitat assessment of Sunda clouded leopards (N. diardi) highlights the lack of such information for the mainland species (N. nebulosa) and facilitates a comparative assessment. Location: Southeast Asia. Methods: Species–habitat relationships are scale‐dependent, yet <5% of all recent habitat modelling papers apply robust approaches to optimize multivariate scale relationships. Using one of the largest camera trap datasets ever collected, we developed scale‐optimized species distribution models for two con‐generic carnivores, and quantitatively compared their habitat niches. Results: We identified core habitat, connectivity corridors, and ranked remaining habitat patches for conservation prioritization. Closed‐canopy forest was the strongest predictor, with ~25% lower Neofelis detections when forest cover declined from 100 to 65%. A strong, positive association with increasing precipitation suggests ongoing climate change as a growing threat along drier edges of the species' range. While deforestation and land use conversion were deleterious for both species, N. nebulosa was uniquely associated with shrublands and grasslands. We identified 800 km2 as a minimum patch size for supporting clouded leopard conservation. Main conclusions: We illustrate the utility of multi‐scale modelling for identifying key habitat requirements, optimal scales of use and critical targets for guiding conservation prioritization. Curbing deforestation and development within remaining core habitat and dispersal corridors, particularly in Myanmar, Laos and Malaysia, is critical for supporting evolutionary potential of clouded leopards and conservation of associated forest biodiversity. [ABSTRACT FROM AUTHOR]

We developed a multi-scale model for the prediction of precipitation kinetics of binary alloys and present its application to the formation of Guinier–Preston zones (GPZ) in Al-rich binary Al–Cu alloys. The approach is covering three length scales: (i) Starting from density functional theory (DFT) calculations a Cluster Expansion (CE) for the binary Al–Cu system on the fcc lattice is constructed. Based on the obtained CE (ii) a lattice Monte Carlo (MC) sampling technique, known as the overlapping distribution method, is used to calculate cluster free energies of precipitate clusters. Finally (iii) a meso-scale Cluster Dynamics (CD) model is constructed by taking the cluster free energies as input. The result is a fast, parameter free method that is able to predict the evolution of precipitate size distributions. To validate the model kinetic MC simulations on the precipitation of GPZ are conducted. The results agree well with those obtained by our model. When comparing our results to experimental data a problem of time scaling arises, which is discussed in the results section. Image 1 • A model for the prediction of GPZ precipitation in Al–Cu alloys is constructed. • The approach includes DFT, Cluster Expansion, Monte Carlo and Cluster Dynamics. • The model's results show a good comparability to results from kinetic Monte Carlo. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Development of a novel multi-scale modelling approach for multi-phase steels. • Derivation of micro-scale plastic potential functions of FCC/BCC single crystals. • Validation via numerical-experimental comparison of tensile and diffraction tests. • Good correspondence of the homogenized stress-strain and the lattice strain curves. • Yield locus prediction of multi-phase materials through microstructural simulations. Abstract In this article, a novel material modelling approach to predict the anisotropic material response of multi-phase steels is developed. The macroscopic material behaviour of the model is characterized by the homogenized response of a meso-scale Representative Volume Element (RVE), derived by Finite Element (FE) simulations. The RVE holds the most relevant microstructural features of the material under consideration, such as phase distribution, grain orientation, morphology etc., in sufficient detail, in order to capture the anisotropy and phase interactions. The micro-scale material models of individual phases are described with specific plastic potential functions, the components of which are derived from Crystal Plasticity (CP) laws. The plastic potential functions are constructed using the Facet method for each phase in the microstructure at the level of single grains, and are used in conjuncture with phase specific, isotropic grain hardening laws. The proposed model is evaluated through numerical experiments performed on a synthetic microstructure of Duplex steel, constructed from statistical material parameters extracted from literature. The RVE flow curves depicted very good correspondence with the experimental data reported for the same grade of Duplex Stainless Steel. The anisotropy prediction was further assessed through comparison between virtual diffraction experiments performed on the statistical microstructure and the actual Neutron Diffraction (ND) experimental data of the reference material. It was found that the model captured the overall trend of the diffraction curves for the individual phases with good accuracy, but obtaining an exact correspondence to the experimental values was not feasible with the performed simulations on statistical microstructures. Finally, an approach to predict the anisotropic yield locus of a multi-phase material is also presented. [ABSTRACT FROM AUTHOR]

In this work we develop a multi-scale model to characterise the large scale constitutive behaviour of a material featuring a small scale fibrous architecture. The Method of Multi-scale Virtual Power (MMVP) is employed to construct the model. At the macro-scale, a classical continuum mechanics problem is formulated in the finite strain regime. At the micro-scale, a network of fibres, modelled as one-dimensional continua, composes the representative volume element (RVE). The MMVP provides a full characterisation of the equilibrium problem at the RVE, with consistent boundary conditions, as well as the homogenisation formula which defines the first Piola–Kirchhoff stress tensor. Particular attention is given to the fact that the macro-scale continuum could be considered incompressible. Numerical experiments are presented and model consistency is verified against well-known phenomenological constitutive equations. Scenarios departing from the hypotheses of such phenomenological material models are discussed. [ABSTRACT FROM AUTHOR]

Advanced fibre composite materials are often used for weight-efficient thin-walled designs, making a plate-based modelling approach suitable for their structural assessment. However, as the sub-structural geometrical features of these materials govern much of their behaviour, a multi-scale approach is necessary. A related challenge, however, is that the in-plane variation of these sub-structural features may be much larger than the total thickness of the material, whereby tailored homogenisation techniques for shell elements are needed. Existing frameworks for plate- and shell-based homogenisation are typically developed using second-order homogenisation in combination with the Hill–Mandel (macro-homogeneity) condition. However, it has been reported in the literature that this approach can lead to kinematic inconsistencies in the macro- to micro-scale transition. One inconsistency that is commonly reported, is the inability to correctly account for the macro-scale transverse shear behaviour on the sub-scale level. In this contribution, we show how the method of Variationally Consistent Homogenisation (VCH) can be used to develop a homogenisation framework for Reissner-Mindlin plate elements, which guarantees kinematically consistent prolongation and homogenisation operations. The homogenisation approach is demonstrated in four numerical examples, where it is shown that the method accurately homogenise the effective sectional plate stiffnesses of homogeneous and heterogeneous sub-structures. [ABSTRACT FROM AUTHOR]

Accurate modelling of local evolving texture and yield surface evolution in complex strain path are of crucial importance to the accurate sheet metal forming simulations. This work proposed a novel multi-scale computational scheme, in which the full-field crystal plasticity (CP) modelling is mapped and real-time updated into each integration point following the local strain path in the finite element (FE) model. By the real-time close-loop feedback and update between the FE model and CP model, the evolving texture and its induced anisotropic plasticity evolution are considered utilizing on-the-fly virtual tests in the full deformation field. To carefully verify the developed computational framework, a comprehensive validation including plastic anisotropy characterization, cyclic hardening tests and deep drawing tests is conducted in an AA6016-T4 aluminium sheet with strong cube texture using ESAFORM Benchmark 2021. By comparison with experimental results and the conventional approaches with constant yield surface for the forming case, the newly developed method is thoroughly validated, showing that the significant texture evolution is observed in large plastic deformation and various strain paths lead to different texture evolution. The local evolving texture induced plastic anisotropy evolution has a considerable effect on the prediction accuracy of the deep drawing simulations, such as earing profile, wall thickness and loading history. Additionally, this method does not increase too much computation cost, enabling cost-effectively simulation of complex forming processes. [Display omitted] • A multi-scale modelling framework for evolving texture and anisotropy is established. • The developed methods enable the analysis of complex plasticity behaviours. • The multi-scale model shows superior accuracy than conventional approaches. • The local texture evolution during forming is successfully predicted. [ABSTRACT FROM AUTHOR]

Porosity is a major manufacturing defect which affects the matrix dominate properties of continuous fibre composites, in particular the transverse strength. The simulation of porosity allows for predictions on the reduction of strength to be made, however, there is a trade-off between accuracy and computational efficiency. The multi-scale modelling approach presented here allows for accurate 3-dimensional geometry data of voids to be used. This is accomplished by first evaluating the effect the porosity has on degrading the matrix then subsequently, by using a representative unit cell, ply level strength can be predicted. The model is validated against empirical tensile and compressive testing of unidirectional autoclave cured prepreg with strong correlation. The approach allows for a reduction in overengineered structures by predicting accurate material properties for a given porosity generation. [ABSTRACT FROM AUTHOR]

Model coupling is an important approach to studying the dynamics of complex systems, but by introducing new feedback loops, the dynamics of coupled models can be artificially distorted. This paper describes a new method of model coupling which addresses this problem through a dynamic form of regularization. The method allows the time series evolution of model variables to be mutually informed by multiple models, and models to influence each other in proportion to their degree of certainty. Uncoupled forms of the coupled models can act as dynamic priors on the trajectory of coupled variables, strengthening model stability and offering additional calibration of the coupling process. Finally, models that describe different spatial scales can be coupled into multi-scale models, so that, for example, spatially-distributed models can be coupled with aggregate models, and influence one another. We apply this technique to a coupled socio-ecological system of population growth and ecosystem harvesting. [ABSTRACT FROM AUTHOR]

Traditional carbon-steel armour wires pose limitations ( e.g. long spans, weight reduction, corrosion and fatigue) for flexible risers to operate in demanding and deeper water environments. In this context, an alternative to carbon-steel tensile armour wires is proposed recently by the authors (Gautam et al ., 2016), comprising of hexagonally packed polymer composite rods with uni-directional fibres and an over-braided ( i.e. bi-axial braid with high performance fibres) sleeve. These hybrid composite wires offer opportunities to tailor their mechanical properties by varying the geometrical ( e.g. rod diameter, packing) and processing parameters ( e.g. material selection, braid pattern) involved. In order to understand the mechanical behaviour of these hybrid composite armour wires, this paper presents a multi-scale model developed by using a combined analytical-computational approach. The multi-scale model is developed to predict the torsional and flexural behaviour of the hybrid composite wires; and the role of over-braid structural parameters, pre-tension and internal friction are investigated. The behaviour of the multiscale model is found to be in good agreement with the experimentally observed behaviour. After validating the multi-scale model with the experimental data available for specific configurations, parametric studies are conducted on the torsional and flexural behaviour of the hybrid composite wires to study the role of internal friction between un-bonded components and the braid tow tension in the over-braided sleeves. [ABSTRACT FROM AUTHOR]

In this paper we investigate micro–macro mechanical relations in Palmetto wood, a natural composite, by means of a computational homogenisation-based multi-scale modeling approach. The homogenisation procedure is solved sequentially at multiple length scales by following a bottom-up approach. The proposed strategy consists of homogenising the three length-scales by means of representative volume elements of material. The resulting effective macroscopic properties allow us to compute the mechanical response of individual macro-fibres and bulk wood specimens by means of a standard finite element procedure. The numerical predictions are compared successfully with experimental measurements. Following the validation, a parametric study is performed to investigate the micro–macro relations in Palmetto wood. The influence of several micro-structural features present at different length scales are investigated, such as the cellulose content and its crystallinity, the microfibril angle, the cell-wall thickness of micro-fibres, and the porosity of macro-fibres and their surrounding matrix, among others. The effects of such microscopic parameters are investigated on the Young’s modulus and density of Palmetto bulk wood. These results show that the present strategy can pave the way for further studies on complex microstructure–property relationships existing in different wood species, and on the possible development of more advanced bio-inspired composite materials. [ABSTRACT FROM AUTHOR]

The quality of high-performance composite structures is difficult to predict. Variability in the macroscopic performance is dominated by the spatial randomness in the geometrical characteristics of the reinforcement, especially for textile composites. This work provides a roadmap for generating realistic virtual textile specimens spanning multiple unit cells, which are required to perform high-fidelity simulations. First, the geometrical variability in the reinforcement structure is experimentally quantified on the meso- and macro-scale in terms of average trends, standard deviations and correlation lengths. Next, each reinforcement parameter is modelled by the sum of its average trend and its zero-mean deviations, which are both determined by analysing experiments. Virtual specimens are then created using advanced simulation techniques that match the experimental statistics. Depending on the nature of measured correlations, the simulation technique is either a Monte Carlo Markov Chain method, a cross-correlated Karhunen–Loève Series Expansion technique or a Fourier Transform method used in combination with a Markov Chain algorithm. In a last step, a virtual representation of the textile geometry is constructed in geometrical modelling software, such as the commercially available WiseTex software. The multi-scale framework is validated using data for a carbon–epoxy 2/2 twill woven composite produced by resin transfer moulding: the simulated tow deviations trends replicate the target statistics. [ABSTRACT FROM AUTHOR]

This paper presents a detailed numerical analysis of two types of 3D woven composite architecture. a unit cell, full finite element meso model, and a mosaic macro model are developed to simulate the elastic and damage progression behaviour of the two weave types. Both models predicted the tensile modulus and strength within 20% of the experimentally measured values, and the predicted failure sequence was similar to the experimental observation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comprehensive validation and parametrization of 2D single cell and 3D stack models. • Specific threshold conversions of 80% (ESC) and 75% (CSC) which maximize efficiency. • Performance boost for CSC and losses for ESC design under pressurized conditions. • Feasible stack operation only at thermoneutral to moderately exothermic conditions. • CSC-stack reaches doubled H 2 -output at 700 °C compared to ESC-stack at 850 °C. Power-to-Gas (PtG) is prognosticated to realize large capacity increases and create substantial revenues within the next decade. Due to their inherently high efficiencies, solid oxide electrolysis cells (SOECs) have the potential to become one of the core technologies in PtG applications. While thermal integration of the high-temperature SOEC module with downstream exothermic methanation is a very potent concept, the performance of SOECs needs to be boosted to amplify the technologies impact for future large-scale plants. Here, we use a combined experimental and modelling approach to benchmark commercial electrolyte- (ESC) and cathode-supported cell (CSC) designs on industrial-scale planar SOEC stack performance. In a first step, comprehensive electrochemical and microstructural analyses are carried out to parametrize, calibrate and validate a detailed multi-physics 2D cell model, which is then used to study the cells' behaviour in detail. The analysis reveals that there exists a cell-specific threshold steam conversion of ∼80% for the ESC and ∼75% for the CSC design, which represents a maximum of the total (heat plus electrical) electrolysis efficiency. Moreover, while the ESC-design suffers from performance reductions under pressurized conditions, considerable performance increases of ∼9% at 20 atm (700 °C, 1.35 V) compared to atmospheric pressure are predicted for the CSC design, showcasing a unique advantage of the CSC cell for process integration with the catalytic methanation. Subsequently, based on a 3D stack model, a scale-up to the industrial stack size is conducted. To comparatively assess stack performances under application-oriented conditions, optimization studies are carried out for 150-cell stack units based on the two cell designs individually. When optimally selecting the stack operation points, the model predicts the CSC-based stack to reach a high capacity up to 36.6 kW (∼10.6 Nm3 H 2 h−1) at 1.35 V and 700 °C, whilst ensuring reasonably low temperature gradients (<10 K cm−1) and sweep gas cooling requirements (<30 sccm cm−2). Thus, CSC-design stacks incorporating such a highly active cell design can be expected to further boost the competitiveness of high-temperature electrolysis in PtG plant concepts. [ABSTRACT FROM AUTHOR]

This paper presents a unified multi-scale model (UMSM) that we developed to simulate hydrological processes in an ecosystem containing both surface water and groundwater. The UMSM approach modifies the Navier–Stokes equation by adding a Darcy force term to formulate a single set of equations to describe fluid momentum and uses a generalized equation to describe fluid mass balance. The advantage of the approach is that the single set of the equations can describe hydrological processes in both surface water and groundwater where different models are traditionally required to simulate fluid flow. This feature of the UMSM significantly facilitates modelling of hydrological processes in ecosystems, especially at locations where soil/sediment may be frequently inundated and drained in response to precipitation, regional hydrological and climate changes. In this paper, the UMSM was benchmarked using WASH123D, a model commonly used for simulating coupled surface water and groundwater flow. Disney Wilderness Preserve (DWP) site at the Kissimmee, Florida, where active field monitoring and measurements are ongoing to understand hydrological and biogeochemical processes, was then used as an example to illustrate the UMSM modelling approach. The simulations results demonstrated that the DWP site is subject to the frequent changes in soil saturation, the geometry and volume of surface water bodies, and groundwater and surface water exchange. All the hydrological phenomena in surface water and groundwater components including inundation and draining, river bank flow, groundwater table change, soil saturation, hydrological interactions between groundwater and surface water, and the migration of surface water and groundwater interfaces can be simultaneously simulated using the UMSM. Overall, the UMSM offers a cross-scale approach that is particularly suitable to simulate coupled surface and ground water flow in ecosystems with strong surface water and groundwater interactions. [ABSTRACT FROM AUTHOR]

Abstract: Pore-scale simulations of transport phenomena in foam based catalytic converters are highly desirable due to their intrinsic accuracy in describing the involved physics. Unfortunately, such computations are prohibitively time consuming and costly. Here we combine a detailed pore-scale characterization with a volume average description of an open-cell foam based catalytic converter. The resulting volume averaged model is accurate and more than three orders of magnitude more efficient in terms of computational time, compared to direct pore scale simulations. This makes simulations of the related complex phenomena tractable, providing a highly flexible and powerful tool for parametric studies of open-cell foams. The volume-averaged model is validated with a pore-scale simulation of a full-scale catalytic converter used for automotive exhaust gas treatment. Fast chemistry is assumed and the heat released by the chemical reaction in combination with conjugate heat transfer is considered. We show that the conversion to pressure drop trade-off improves with increasing foam porosity and the heat release of the reaction significantly affects the pressure drop across the reactor. The simulations show non-uniform surface temperatures which are attributed to the non-unity Lewis number of the mass transfer limiting species. The model predictions agree well with experimental measurements of pressure drop and Sherwood number in open-cell foams. [Copyright &y& Elsevier]

An unconventional multi-scale approach is investigated to model interfacial damage and subsequent effects in highly filled particulate composites such as solid propellants. The basic framework by Nadot et al. (2006 Damage modelling framework for viscoelastic particulate composites via a scale transition approach, Journal of Theoretical and Applied Mechanics 44:553–583) is enhanced to deal with damage state and configuration evolution under any loading. Three criteria are formulated at the microscale. The first one concerns the nucleation of new defects, while the other two (for closure and re-opening) monitor the respective proportions of open and closed defects. The formulation exploits the explicit microstructure representation and the knowledge of the local displacement field as a function of local morphology around the interfaces. The multi-scale model is finally implemented through a numerical solving procedure able to deal with successive and/or simultaneous discrete damage events (nucleation/closure/re-opening of defects) depending on the loading path. Numerical illustrations are given for a three-dimensional microstructure containing 351 particles submitted to complex loading sequence involving extension, shear and contraction stages. The results show the ability of the model to estimate damage characteristics (position, orientation within the material) in addition to induced effects at both microscale and macroscale (induced anisotropy, unilateral effects and influence on local fields). [ABSTRACT FROM PUBLISHER]

Highlights: [•] A multi-scale model is presented to study exciton migration in conjugated polymers. [•] The model takes into account the polymer molecular properties and its nanomorphology. [•] The number of physical traps depends on the orientational disorder. [•] The model predicts correctly exciton diffusion lengths in agreement with experiments. [•] Exciton diffusion length is limited by the amount of physical traps. [Copyright &y& Elsevier]

Abstract: Highly structured and hierarchal textiles may be modelled at three scales, ranging from micro modelling of individual fibres within a yarn via meso-scale modelling of a fabric unit cell through to macro-scale modelling of a whole product. The performance of the product can be designed and optimised effectively by variation of the structure at every level. This paper presents an integration of the fibre–yarn, yarn–fabric models. The micro-scale model is developed using an energy-based argument combined with elastica methods to incorporate non-linear frictional behaviour. The meso-scale model is developed using the finite element method, with the yarn modelled as a continuum. The output of the micro-scale model is used to determine constitutive materials properties at the meso-scale model for fabric deformation. The main features of this modelling approach are that many critical design parameters of a yarn and a fabric are being addressed and the friction is incorporated at each scale since inter-fibre and inter-yarn friction may be directly affected by finishing treatments. This paper shows how predictions at the micro scales can pass up the hierarchy to the meso scale to enable designers/engineers to understand and quantify how changes in yarn properties and fabric architectures influence the performance of the fabric, thereby facilitating the design and optimisation of fabric properties by variation of its constituent structural components. [Copyright &y& Elsevier]

Abstract: This paper presents the on-going research steps aiming at the development of a Method for Multi-scale Modeling and Simulation of Assembly System. The focus lies on the Assembly System Base Model and its integration into the whole method. After motivating the research, the developed method and the conceived model of the assembly system is introduced, by using the proposed methodology. The presented approach aims at the manageability of the systems complexity and the acceleration of optimization and adaption processes. It concludes with a roadmap shaping the next steps and activities. [Copyright &y& Elsevier]

Abstract: We investigate how the chemical reactivity of gold nanoparticles depends on the cluster size and shape using a combination of simulation techniques at different length scales, enabling us to model at the atomic level the shapes of clusters in the size range relevant for catalysis. The detailed atomic configuration of a nanoparticle with a given number of atoms is calculated by first finding overall cluster shapes with low energy and approximately the right size, and then using Metropolis Monte Carlo simulations to identify the detailed atomic configuration. The equilibrium number of low-coordinated active sites is found, and their reactivities are extracted from models based on Density Functional Theory calculations. This enables us to determine the chemical activity of clusters in the same range of particle sizes that is accessible experimentally. The variation of reactivity with particle size is in excellent agreement with experiments, and we conclude that the experimentally observed trends are mostly explained by the high reactivity of under-coordinated corner atoms on the gold clusters. Other effects, such as the effect of the substrate, may influence the reactivities significantly, but the presence of under-coordinated atoms is sufficient to explain the overall trend. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to present a multi-scale method for the mechanical modelling of sandwich structures. Low- and high-order sandwich elements are formulated on the basis of Carrera’s Unified Formulation (CUF) and bridged within the Arlequin framework. According to CUF, an N-order polynomials approximation is assumed on the beam cross-section for the unknown displacements, being N a free parameter of the formulation. Low-order, computationally cheap elements are used to describe the global mechanical response. High-order, computationally demanding elements are used to capture the local effects in the boundary layers. CUF framework is here enhanced by the assumption of the Constrained Variational Principle (CVP) in order to derive a new class of layered beam finite elements with an independent kinematic field for each lamina. Results are assessed towards two- and three-dimensional finite element solutions. The numerical results show that, in the context of CUF, the Arlequin method effectively couples sub-domains modelled via variable order finite elements. The proposed coupled models yield accurate results, being able to predict both the global solution and the local effects, with a reduced computational cost. [Copyright &y& Elsevier]

• A transient, non-isothermal and multi-scale model of PEM-based dehumidification was developed. • Local heat and mass transfer of anode-side catalyst layer with reconstructed microstructures were modelled by the lattice Boltzmann method. • The interaction between anode CL and other layers, and its effect on air conditions was investigated. • Though uniform distribution can be achieved rapidly in CL(<100s), it takes much longer for air outlet to reach transient equilibrium (1000s for moisture content and 7000s for temperature). • Calculated effective mass diffusivity and heat conductivity of CL are 7.71×10-6 m2/s and 0.063 W/m•K. • The randomly arranged particles makes the CL the hottest and driest part of PEM element. As an independent and ultra-compact method, PEM-based dehumidifiers are promising, while accurate modelling of anode-side transport is still challenging. The theoretical model developed in this study is transient, two-dimensional and non-isothermal based on the lattice Boltzmann method, emphasizing the anode-side catalyst layer (CL) with reconstructed microstructures. Then the pore-scale CL modelling was coupled with the macro-scale simulation of air channel and diffusion layer (DL), and experimentally validated by a 3.5 cm2 dehumidifier. Results showed that the CL microstructure significantly affects the air outlet parameters of PEM dehumidifiers, especially in the beginning state. Although the uniform distribution of vapor concentration can be achieved immediately in CL, the time required for the air outlet to reach transient equilibrium is much longer, which is around 1000s for the moisture content and 7000s for the temperature. The moisture transfer resistance at the beginning state mainly exists in CL, then it moves to both CL and DL (close to the interface) when it reaches equilibrium. Due to the continuous heat generation, the temperature flux in CL dominates in the anode side, and increases by 5-6 times during dehumidification. The calculated values of effective mass diffusivity and thermal conductivity of CL are 7.71×10−6 m2/s and 0.063 W/m•K. The randomly arranged catalyst particles makes CL the hottest (2~3°C higher) and driest (half the DL concentration) part of PEM element, which severely limits the whole performance. This modelling reveals the interaction between anode-side CL with microstructures and the performance, considering the transient heat and mass transfer. [ABSTRACT FROM AUTHOR]

• Multi-scale micro-mechanics accurately predict the compressive strength of masonry. • Leaf interaction in multi-leaf walls is modelled by simple analytical expressions. • Unit dimensions & secondary elements strongly affect the compressive strength. Three-leaf masonry panels are typically composed of external leaves of irregularly bonded units and a rouble infill. The complexity of the response of these structures to mechanical loading arises from: a) the interaction of the leaves and b) the irregularity of the bond pattern of the outer leaves. This complexity makes analytical and computational modelling of these structures difficult and costly, respectively. This paper proposes a computational approach for the calculation of the mechanical properties of the three-leaf masonry from the properties of its constituent materials and its geometry. Using micro-mechanical analysis approaches applied in composite materials and accounting for the interaction of the leaves through a simple analytical approach, the homogenised elastic stiffness and strength of a representative volume element of three-leaf masonry can be calculated with very low computational cost. The analysis method is validated against experimental results from the literature. It is found that the proposed model provides accurate results for a relatively wide range of case studies. These results are expanded upon through a sensitivity study, highlighting the most important material and geometric parameters influencing the predicted compressive strength of three-leaf masonry walls. [ABSTRACT FROM AUTHOR]

Numerical modelling of 3D-printed Fused Filament Fabrication (FFF) specimens with thermoplastic matrices reinforced with continuous fibres is still in its infancy. The existing numerical work is mostly related to the adhesion between printed filaments and not to the mechanical properties. However, the latter are one of the most important parameters that define the structural behaviour of the material. A numerical three-step multi-scale model is introduced in the present study, concentrating on the fundamental aspect of the elastic properties. The most encountered reinforced Nylon FFF structures with continuous fibres of glass, carbon and, Kevlar, are examined. The concept of Representative Volume Element (RVE) is utilized for the combination of matrix and fibres at the micro-scale and the addition of voids at the meso-scale. Finally, at the macro-scale, tension simulations are performed for specimens with various lay-ups. The results of the numerical model are validated using analytical models and experimental data. A new analytical micro-mechanical model is developed as an alternative to the more cumbersome Mori–Tanaka model. A series of experimental testing is performed for Kevlar-reinforced Nylon specimens to accompany the limited existing data and aid the validation process. The comparison reveals a good correlation with the analytical models for the micro- and meso-scale and to the experimental data for the macro-scale, leading to a robust conclusion for its validity and efficiency. [ABSTRACT FROM AUTHOR]

• Polycrystalline microstructure of hydrided Zr incorporating individual micro-hydride. • Multiscale: micrometric autocatalytic hydride stacks in hundreds of grains at the mm scale. • Fully analytical model able to generate the fuel cladding microstructure in seconds. • Benchmarked against experimental images for different notch geometries. A mechanistic understanding of hydrogen diffusion and hydride precipitation at the microscale underpins the prediction of delayed hydride cracking in zirconium alloy nuclear fuel cladding. We present a novel approach to modelling the microstructures created by hydride precipitation at loaded notches in polycrystalline Zr alloys. The model is multi-scale in that it includes the elastic dipole tensor of interstitial hydrogen in α -Zr, it treats the stress-driven diffusion of hydrogen at the meso-level (mm), it calculates the thermodynamically favourable spatial arrangement of microhydrides and their assembly into macrohydride colonies, in a textured polycrystalline sample, and it treats the full elastic field of the loaded notch and all the hydrides at a scale similar to the cladding thickness. A simplifying innovation is the representation of the elastic field of a microhydride by a dislocation dipole, where the Burgers vector is set to create the experimentally measured strain in the 〈 1 1 ¯ 0 0 〉 direction. The model provides a predictive framework for treating elastic anisotropy, a variety of potential nucleation sites, and different grain sizes. Simulated micrographs of hydride networks in polycrystalline samples with blunt and sharper loaded notches are compared with experimental micrographs obtained at the same scale. The simulations are extremely fast and calculations typically take around tens of seconds. This makes it possible to carry out detailed sensitivity studies with respect to several pertinent metallurgical variables, as well as conducting ensemble averaging of hydride microstructures. [ABSTRACT FROM AUTHOR]

Structured catalytic reactors are enjoying an increasingly important role in the reaction engineering world. At the same time, there are large and growing efforts to use advanced computational models to describe such reactors. The structured reactor represents a multi-scale problem that is typically modelled at the largest scale only, with sub-models being used to improve the model granularity. Rather than a literature review, this paper provides an overview of the key factors that must be considered when choosing these sub-models (or scale bridges). The example structured reactor selected for illustration purposes is the washcoated honeycomb monolith design. The sub-models reviewed include those for pressure drop, inter- and intra-phase mass and heat transfer, and effective thermal conductivity. [ABSTRACT FROM AUTHOR]

Insects fall prey to the Venus flytrap (Dionaea muscipula) when they touch the sensory hairs located on the flytrap lobes, causing sudden trap closure. The mechanical stimulus imparted by the touch produces an electrical response in the sensory cells of the trigger hair. These cells are found in a constriction near the hair base, where a notch appears around the hair's periphery. There are mechanosensitive ion channels (MSCs) in the sensory cells that open due to a change in membrane tension; however, the kinematics behind this process is unclear. In this study, we investigate how the stimulus acts on the sensory cells by building a multi-scale hair model, using morphometric data obtained from μ -CT scans. We simulated a single-touch stimulus and evaluated the resulting cell wall stretch. Interestingly, the model showed that high stretch values are diverted away from the notch periphery and, instead, localized in the interior regions of the cell wall. We repeated our simulations for different cell shape variants to elucidate how the morphology influences the location of these high-stretch regions. Our results suggest that there is likely a higher mechanotransduction activity in these 'hotspots', which may provide new insights into the arrangement and functioning of MSCs in the flytrap. Dataset: 10.3929/ethz-b-000448954 [ABSTRACT FROM AUTHOR]

Due to a stress redistribution after the excavation of an underground tunnel for radioactive waste disposal, an Ed/DZ (excavation disturbed/damaged zone) will be generated in the near field of the opening, resulting in significant changes in the hydraulic and mechanical properties of the rock mass in the zone. Initially more or less randomly distributed hydrocarbons at grain boundaries in rock salt, which sometimes can only be observed with ultraviolet light, can then be mobilised and migrate at a potentially significant rate towards the excavation. Within the international cooperative project DECOVALEX 2019, the migration mechanism of such fluid inclusions in rock salt is being studied intensively. A multi-scale modelling strategy has been developed. A macroscale coupled hydro-mechanical modelling of an underground excavation was performed to determine hydraulic and time-dependent deviatoric stress conditions, by taking into account the rock salt creep behaviour. Under the obtained macro-scale constraints, micro-scale modelling of a pathway dilation along halite grain boundaries was performed using different model strategies: a) coupled hydromechanical modelling with a consideration of hydraulic pressure-induced dilatant deformation, b) nonlinear dynamic model taking account of fluid migration, stress-dependent grain boundary wetting and shear-induced dilatancy of salt, and c) phase-field modelling of flow pathway propagation. The permeability increase resulting from the pathway dilation is estimated to be as high as two orders of magnitude. Based on the permeability determined, a series of pressure build-ups measured from a borehole with a high hydrocarbon release rate, a total of 430 build-ups within a monitoring time of 938 days, can be simulated with a macro-scale compressible flow model accounting for different zones around the opening. [ABSTRACT FROM AUTHOR]