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The occurrence of fluid flow near a wellhead is the major concern of the petroleum industry, as pressure drop, loss of formation, and other variables of interest are mostly affected in this region. The fluid flows from the hydrocarbon reservoir to the wellbore can be characterized as laminar to turbulent; thus, it is important to model this phenomenon with the integrated wellbore-reservoir model. Using 3D Navier–Stokes equations, an integrated wellbore-reservoir model is created in this study, and it incorporates the formation damage zone. For the porous-porous and porous-fluid interfaces, the General Grid Interface (GGI) approach is applied in conjunction with the conservative mass flux interface model. Model equations are solved using a velocity-pressure coupling solver that is pressure-based. For reliable and quick results, the system of equations is solved using an algebraic multigrid approach. The pressure diffusivity equation's analytical solution under steady-state flow circumstances is used to validate the model. The integrated wellbore-reservoir model is applied to different reservoir scenarios, for example, different production rates, formation zones, and reservoir formation conditions. The results indicate that the present Computational Fluid Dynamics (CFD) model can be extended to simulate the real field scale model. integrated wellbore-reservoir modeling based on 3D Navier–Stokes equations with efficient computational techniques can lead the field of petroleum industries to advance current knowledge. [ABSTRACT FROM AUTHOR]

The increasing use of rock‐socketed piles highlights the importance of developing a suitable design method for their bearing capacity. This study quantifies the shear behavior of the rock–pile interface, which generally dominates the bearing capacity of rock‐socketed piles under service load. A micromechanics‐based rock–pile interface model with idealized nonuniform profile is proposed with two enhancements: (1) the slip line method together with nonlinear Hoek–Brown failure criteria is integrated to identify the critical shear displacement of rock asperity; and (2) the residual stage of shear behavior is properly considered with the rounding progress of sheared rubbles. The enhanced interface model is first validated by the direct shear test results under constant normal stiffness. Then, the interface model is implemented via user‐defined FRIC into the finite element code ABAQUS without the need of explicitly building the rock–pile interface profile. Accordingly, the model is applied to simulate and analyze two field cases involving rock‐socketed piles. Comparison between the predictions and field observed results shows this method can well capture the axial load transfer behavior of pile socket into weak rock. [ABSTRACT FROM AUTHOR]

The contents of alkali and alkaline earth metals are higher in Zhundong coal, and there are serious problems of slagging and fouling during the combustion process. Therefore, it is of great significance to reveal the mechanism of slagging and fouling in the boiler of Zhundong coal. In this paper, first-principle calculations based on density functional theory are used to study the competition mechanism of alkaline metal oxides during the combustion process in Zhundong coal by establishing the Na2O(110)/CaO(100)-SiO2(100) double-layer interface model. The results show that the bond lengths of the surface of Na2O(110) and CaO(100) with SiO2(100) after adsorption were generally lengthened and the value of bond population became smaller, which formed a stable binding energy during the reaction. The electron loss of Na is 0.05 e, the electron loss of Ca is 0.03 e, and the electron loss of Na2O is greater than that of CaO. The charge transfer on the surface of Na2O with SiO2 is obviously higher than that of CaO and the orbital hybridization on the surface of CaO with SiO2 is weaker than that on the surfaces of Na2O with SiO2. Na2O is easier to react with SiO2 than CaO. The adsorption energies on the surface of Na2O and CaO with SiO2 are −5.56 eV and −0.72 eV, respectively. The adsorption energy of Na2O is higher than that of CaO, indicating that Na2O is more prone to adsorption reactions and formation of Na-containing minerals and other minerals, resulting in more serious slagging. In addition, the XRD analyses at different temperatures showed that Na-containing compounds appeared before Ca-containing ones, and the reaction activity of Na2O is stronger than that of CaO in the reaction process. The experimental results have good agreement with the calculation results. This provides strong evidence to reveal the slagging and fouling of Zhundong coal. [ABSTRACT FROM AUTHOR]

High-performance ceramics, especially h-BN-based ceramics, are widely used in the metallurgical field. The interface state of h-BN-based ceramic composites, including chemical reactions, molecular diffusion, and interface structure changes, will greatly affect the properties of composite materials. Herein, taking Si3N4/BN composites as a representative case, their interfacial interactions were investigated by first-principles calculations. First, the structural and electronic properties and elastic modulus of bulk Si3N4 and h-BN were calculated. Then, the interface mismatch relationship and interface models of Si3N4/BN were studied and established. Finally, the interface bond structure of Si3N4/BN was analyzed by charge density and state density calculations. The results showed that the band gap of bulk Si3N4 and h-BN was 4.18 and 4.24 eV, respectively. Besides, bulk h-BN exhibited better compression performance and resistance to deformation than Si3N4 based on elastic modulus calculation. Therefore, h-BN was used as a substrate, and when interface mismatch is 1.3%, good matching and bonding at the interface layer can be obtained. Based on this, two interface models of Si3N4(100)/BN(002) were established, which were named the B-NSi interface and Si-NB interface. The BN/Si3N₄ interface exhibited strong van der Waals interactions, and the charge transfer from Si3N4 to h-BN was observed, which indicate that the weak covalent bond also exists in the BN/Si3N4 interface. The low interface energy indicates that the formed interface is relatively stable, which is beneficial for applications requiring high thermal and mechanical stability. This work provides valuable insights into the interfacial interaction between h-BN and Si3N4 and will give a promising theoretical guidance for designing and optimizing h-BN-based ceramic composites.

Abstract The occurrence of fluid flow near a wellhead is the major concern of the petroleum industry, as pressure drop, loss of formation, and other variables of interest are mostly affected in this region. The fluid flows from the hydrocarbon reservoir to the wellbore can be characterized as laminar to turbulent; thus, it is important to model this phenomenon with the integrated wellbore-reservoir model. Using 3D Navier–Stokes equations, an integrated wellbore-reservoir model is created in this study, and it incorporates the formation damage zone. For the porous-porous and porous-fluid interfaces, the General Grid Interface (GGI) approach is applied in conjunction with the conservative mass flux interface model. Model equations are solved using a velocity-pressure coupling solver that is pressure-based. For reliable and quick results, the system of equations is solved using an algebraic multigrid approach. The pressure diffusivity equation’s analytical solution under steady-state flow circumstances is used to validate the model. The integrated wellbore-reservoir model is applied to different reservoir scenarios, for example, different production rates, formation zones, and reservoir formation conditions. The results indicate that the present Computational Fluid Dynamics (CFD) model can be extended to simulate the real field scale model. integrated wellbore-reservoir modeling based on 3D Navier–Stokes equations with efficient computational techniques can lead the field of petroleum industries to advance current knowledge.

Existing research on pavement interlayer bonding has mainly focused on bonding materials and external factors, neglecting the upper and lower interlayer surface characteristics. This study aims to analyze the contact conditions between these surfaces, developing a numerical model to reveal their properties. Five double-layered asphalt systems, including dense-graded asphalt concrete (AC), open-graded friction course (OGFC), and stone mastic asphalt (SMA) mixes, were examined using a nondestructive interlayer separation method and 3D laser scanning. Three indices were proposed to assess interlayer surface characteristics in both 2D and 3D domains. Shear strength tests at room temperature were also conducted, revealing that AC-only systems had lower surface mismatch at the layer interface compared to SMA or OGFC mixes. The study concludes that surface mismatch decreases with greater differences in aggregate coarseness, and systems with significant mismatch gaps have lower shear strength. These findings provide valuable insights for designing durable pavement structures. [ABSTRACT FROM AUTHOR]

In this paper, we consider a semiconducting device with an active zone made of a single-layer material. The associated Poisson equation for the electrostatic potential (to be solved in order to perform self-consistent computations) is characterized by a surface particle density and an out-of-plane dielectric permittivity in the region surrounding the single-layer. To avoid mesh refinements in such a region, we propose an interface problem based on the natural domain decomposition suggested by the physical device. Two different interface continuity conditions are discussed. Then, we write the corresponding variational formulations adapting the so called three-fields formulation for domain decomposition and we approximate them using a proper finite element method. Finally, numerical experiments are performed to illustrate some specific features of this interface approach. [ABSTRACT FROM AUTHOR]

The bond–slip behavior of the steel–concrete interface is critical in reinforced concrete (RC) structures since the bond action is the mechanism that ensures the two materials work in co-operation. However, there is little research considering the bond–slip behavior in massive ring-type reinforced concrete (MRRC) structure bearing analyses due to the complexity of modeling the interfacial behavior. Hence, the influence of the bond–slip behavior on the bearing characteristics of MRRC structures remains unclear. Steel-lined reinforced concrete penstock is such an MRRC structure, composed of steel liner and reinforced concrete and commonly used in diversion pipelines. This paper aims to explore the bearing characteristics considering the bond–slip behavior in the composite penstock by using a promising numerical method, the cohesive zone model. Three interface models were proposed to represent the different interaction conditions at the steel–concrete interface. Moreover, a sensitivity analysis was performed to study the impact of the bond strength on the bond performance and structural behavior. The simulation results showed that the prediction results (steel stress and crack process) considering the bond–slip behavior were in good agreement with the experimental results. The steel stresses near the cracks were smaller and more uniform after considering the bond–slip behavior, since the stresses were no longer concentrated on the crack but distributed in an area near the crack. However, the steel stress differences in these models were within 10%, which means that the bond performance had a limited effect on the structural safety design. The crack widths were greatly influenced by the bond conditions, and the maximum crack width (0.461 mm) in poor conditions was beyond the limiting value (0.3 mm). Consequently, bond–slip behavior must be paid more attention in durability design. [ABSTRACT FROM AUTHOR]

There is interfacial interaction between asphalt binder and other components of asphalt mixture, including mineral fillers and aggregates, which has significant influence on the service properties and service life of asphalt mixture. The usually used mineral fillers and aggregates mainly consist of various mineral crystals, such as SiO2, Al2O3 and CaO crystals. In this study, the interface models of asphalt and these three mineral crystals were established via Molecular Dynamic simulation to investigate their interaction effect at the molecular and atomistic scale. Additionally, the effect of temperature change on the interaction strength was analyzed according to the service temperature of asphalt mixture. The findings showed that Al2O3 surface formed stronger adsorption effect with asphalt than CaO surface, while weak repulsion effect was observed between α-quartz surface and asphalt. Due to the increase of model temperature, the polar components of asphalt moved toward the surface of Al2O3 and CaO crystals but non-polar components moved away from their surface, particularly saturate molecules. In the process of model cooling, the adsorption effect of asphalt with Al2O3 and CaO crystals showed a reduction trend. For α-quartz crystal, with the increase of model temperature, asphalt molecules presented repulsion interaction with its surface except for aromatic fraction, which was subsequently reinforced due to the decrease of model temperature. [ABSTRACT FROM AUTHOR]

The contents of alkali and alkaline earth metals are higher in Zhundong coal, and there are serious problems of slagging and fouling during the combustion process. Therefore, it is of great significance to reveal the mechanism of slagging and fouling in the boiler of Zhundong coal. In this paper, first-principle calculations based on density functional theory are used to study the competition mechanism of alkaline metal oxides during the combustion process in Zhundong coal by establishing the Na2O(110)/CaO(100)-SiO2(100) double-layer interface model. The results show that the bond lengths of the surface of Na2O(110) and CaO(100) with SiO2(100) after adsorption were generally lengthened and the value of bond population became smaller, which formed a stable binding energy during the reaction. The electron loss of Na is 0.05 e, the electron loss of Ca is 0.03 e, and the electron loss of Na2O is greater than that of CaO. The charge transfer on the surface of Na2O with SiO2 is obviously higher than that of CaO and the orbital hybridization on the surface of CaO with SiO2 is weaker than that on the surfaces of Na2O with SiO2. Na2O is easier to react with SiO2 than CaO. The adsorption energies on the surface of Na2O and CaO with SiO2 are −5.56 eV and −0.72 eV, respectively. The adsorption energy of Na2O is higher than that of CaO, indicating that Na2O is more prone to adsorption reactions and formation of Na-containing minerals and other minerals, resulting in more serious slagging. In addition, the XRD analyses at different temperatures showed that Na-containing compounds appeared before Ca-containing ones, and the reaction activity of Na2O is stronger than that of CaO in the reaction process. The experimental results have good agreement with the calculation results. This provides strong evidence to reveal the slagging and fouling of Zhundong coal.

The bond–slip behavior of the steel–concrete interface is critical in reinforced concrete (RC) structures since the bond action is the mechanism that ensures the two materials work in co-operation. However, there is little research considering the bond–slip behavior in massive ring-type reinforced concrete (MRRC) structure bearing analyses due to the complexity of modeling the interfacial behavior. Hence, the influence of the bond–slip behavior on the bearing characteristics of MRRC structures remains unclear. Steel-lined reinforced concrete penstock is such an MRRC structure, composed of steel liner and reinforced concrete and commonly used in diversion pipelines. This paper aims to explore the bearing characteristics considering the bond–slip behavior in the composite penstock by using a promising numerical method, the cohesive zone model. Three interface models were proposed to represent the different interaction conditions at the steel–concrete interface. Moreover, a sensitivity analysis was performed to study the impact of the bond strength on the bond performance and structural behavior. The simulation results showed that the prediction results (steel stress and crack process) considering the bond–slip behavior were in good agreement with the experimental results. The steel stresses near the cracks were smaller and more uniform after considering the bond–slip behavior, since the stresses were no longer concentrated on the crack but distributed in an area near the crack. However, the steel stress differences in these models were within 10%, which means that the bond performance had a limited effect on the structural safety design. The crack widths were greatly influenced by the bond conditions, and the maximum crack width (0.461 mm) in poor conditions was beyond the limiting value (0.3 mm). Consequently, bond–slip behavior must be paid more attention in durability design.

Unlike the flat base foundations, the determination of the bearing resistance of the cone‐shaped footing in finite element analysis (FEA) might not be carried out without considering the interface model. In addition, the simulations of the FEA is hardly achieved with a large system due to the assembly technique. So, the alternative should be considered. Therefore, this paper proposes a new method for computing the Nc$\;{N_c}$, Nq${N_q}$ andNγ$\;{N_\gamma }$ factors of the bearing capacity of the rough and smooth cone‐shaped foundations by combining the skew boundary condition as the interface model incorporated with the viscoplastic strain method‐based meshfree obeying the yield equation of the Mohr‐Coulomb (MC). Thus, the factors can be determined exclusively and reported to reach a close agreement with the published data; nevertheless, the discrepancies are also provided. The plastic flow of the soil mechanics is discussed thoroughly. In addition, the effects of soil friction angle (ϕ) and cone‐shaped angle (β) on the factors are inspected systematically. Accordingly, the conservation of the Terzaghi's superposition assumption is confirmed, and the bearing capacity factor charts can be established for various combinations of ϕ=$\phi \; = $ 5o – 45o and β=$\beta \; = $ 30o – 180o. Therefore, it may conclude that the results produced by these techniques and the techniques themselves may be applied confidently for solving geotechnical problems, especially for computing the bearing resistance of the soil. [ABSTRACT FROM AUTHOR]

The effective bulk modulus and the effective in-plane shear modulus of nano-fiber composites were investigated with the interface model and the interphase model based on the generalized self-consistent method, and the closed-form analytical solutions of the effective bulk modulus and all equations for numerically predicting effective in-plane shear modulus based on the 2 models, were presented. With the interface model, interface effects of the effective bulk modulus and the effective in-plane shear modulus were discussed through numerical examples. Furthermore, the solutions of the interface model were proved to be degenerated ones of those of the interphase model, where the effective bulk modulus can be obtained through analytical degeneration and the numerical results of the effective in-plane shear modulus through numerical degeneration. An example of aluminium containing nano voids shows that, the effective bulk modulus and the effective in-plane shear modulus predicted with the interface model have large deviations from those with the interphase model for small void radii, however, small deviations for larger void radii. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted on the tensile behavior of textile reinforced mortar (TRM) composites containing different volumes of short polyethylene (PE) fibers in a cementitious matrix to improve the tensile strength and cracking mode of TRM. This investigation mainly aimed to study the action mechanism of short fibers and propose a reasonable textile-short fiber-matrix interface model. The short fiber content was varied, as was the matrix type and the number of grid layers. Ten groups of TRM tensile specimens subjected to the monotonic uniaxial tensile loading were fabricated and tested to examine their tensile characteristics. The results showed that the multiple-cracking behavior and failure mode of TRM were significantly improved by adding PE fibers into the matrix. The tensile strength was increased by 25.8–167.2 %. After the uniaxial tensile tests, the microscopic investigation of the interface between the textile and matrix was conducted on the tensile specimens using an environmental scanning electron microscope (ESEM). The significant influence of the short PE fibers on the improvement of the interface bonding between the textile and matrix was confirmed. More importantly, based on the ESEM results, a novel interface model was proposed to promote understanding of the action mechanism of short fibers. • This paper presented the tensile properties of TRM with additional short PE fiber. • The effectiveness of short PE fiber was examined by means of uniaxial tensile tests and ESEM. • Ductile tensile behaviors were obtained by using additional short PE fiber and more grids. • Short PE fiber can effectively improve the interface bonding between textile and matrix. • A novel drifting-filling model was proposed to explain the action mechanism of the short fibers on the basis of the ESEM results. [ABSTRACT FROM AUTHOR]

• A set of unprecedented governing differential equations for an isotropic thin film layer under plane stress condition is developed. • A new interface model for elastic solids reinforced by isotropic thin films is proposed. • Green's functions of an isotropic half-space reinforced by a buried thin film are obtained. • Limiting cases of the problem for inextensible membrane, axisymmetric loading, and surface-coated half-space are studied. In this paper, a novel interface model for elastic isotropic thin films perfectly bonded to the surrounding elastic media is introduced. Considering an average stress and displacement through the thin film thickness, the shear stress discontinuity across the interface is expressed in terms of spatial and time derivatives of displacement components. The derived interfacial equations are presented in a general form. As such, they are applicable to asymmetric elastodynamic problems of anisotropic solids with thin film interfaces. Employing the introduced interface model and Hankel transform technique, static Green's functions of an elastic isotropic half-space reinforced by a buried thin film are obtained. Results of some special cases, including axisymmetric loading, inextensible membrane, unreinforced half-space, and surface-coated half-space, are also presented. The robustness and effectiveness of the proposed interface model are shown by two solved numerical examples, and some elastic responses are plotted to show the impact of thin film stiffness. According to the numerical results, modeling elastic thin films as inextensible membranes can significantly alter the elastic responses. [Display omitted] [ABSTRACT FROM AUTHOR]

• Avoidance of corrosion and realization of gas–liquid countercurrent flow through hydraulic sealing. • High gas–liquid ratio and high space–time yield were obtained in the rotating spiral contactor. • Mass transfer coefficient could maintain relatively large at high gas–liquid ratio. • Development of hydrodynamic model and mass transfer model in rotating spiral contactor within a relative deviation of ± 15 %. The efficient capture of CO 2 has always been a goal pursued by people. However, low gas handling capacity and low gas–liquid ratio restricts existing gas–liquid contactors, especially for non-rotating ones. In this study, a gas–liquid contactor with high gas handling capacity and high gas–liquid ratio, the rotating spiral contactor, was developed. Hydrodynamic properties of the contactor were experimentally or theoretically investigated. A novel interface model was developed to describe gas–liquid interface shape. CO 2 capture using MEA/DMEA aqueous solution were evaluated in terms of space–time yield (τ), overall volumetric mass transfer coefficient (K G a e) and CO 2 capture efficiency (η). A rate-based model was developed and applied for the first time to predict CO 2 capture in the rotating spiral contactor. The hydrodynamic results showed that liquid layer thickness was below 400 μm for the liquid with viscosity of 14.5 mPa.s. Under the rotational speed of 1200 rpm, the gas–liquid ratio ranged from 525 to 2700, while the gas–liquid surface area remained around 667 m2/m3. The interface model predicted interface thickness within a relative deviation of ± 20 %. The results also showed that τ , K G a e and η respectively were 3428–17021 h−1, 1.0–6.4 kmol.m−3.h−1.kPa−1 and 38–98 % at the gas–liquid ratio range of 200–1000. The predicted K G a e and η by rate-based model agreed well with the experimental data within a relative deviation of ± 15 %. This rotating spiral contactor is ideally suitable for the scenarios with large gas handling requirement and high gas–liquid ratio. [ABSTRACT FROM AUTHOR]

The paper presents a revisitation and comparison of some interface model able to couple the damage evolution with the unilateral effect and the friction. In particular, the models derived from the initial interface Needleman proposal (Needleman, 1987) are reported and revised in a unified framework, introducing some novelties in their formulations. Then, the model proposed by Alfano and Sacco (Alfano and Sacco, 2006, Sacco and Toti, 2010) is illustrated and discussed. The responses of the investigated models are compared, illustrating the similarities and the differences. Moreover, the multiplane model proposed in Albarella et al. (2015), Serpieri et al. (2015) able to reproduce the dilatancy effect is presented, showing its performances and computing the dissipation during the loading history, useful information for many mechanical applications. The multiplane model is finally modified to account for a limited dilatancy in a new and physically clear way. Numerical applications are developed for the illustrated interface models for different loading histories. • Review and comparison of interface models coupling damage, contact and friction. • Similarities and differences between Alfano-Sacco and other interface models. • Microstructured interface model for reproducing the dilatancy effect. • New formulation for modeling limited dilatancy in a physically consistent manner. [ABSTRACT FROM AUTHOR]

Recently, frequency coupling oscillation events, such as harmonic oscillations, subsynchronous and supersynchronous oscillations, driven by multiple converters with different switching frequencies have brought new challenges of ac/dc grid modeling, despite the traditional one of improving the accuracy and efficiency. There is an urgent requirement of practical engineering projects to produce a modeling method that can produce instantaneous and harmonic phasor waveforms simultaneously, dedicated to harmonic interaction analysis of large-scale ac/dc grids. To realize the above-mentioned targets, the harmonic phasor domain (HPD) modeling of power electronic based dc grids is proposed. The HPD modeling is then combined and coordinated with electromagnetic transient (EMT) based ac-grid models based on the proposed HPD transmission line model (HPD-TLM). The overall HPD cosimulation is realized by the EMT-based ac-grid models, HPD-based dc-grid models, and HPD-TLM, which is governed by the decoupled and coordinated time sequences. The performance (efficiency and accuracy of instantaneous and harmonic phasor waveforms) for the HPD cosimulations is validated on practical large-scale voltage source converter modular multilevel converter based ac/dc grids in China. [ABSTRACT FROM AUTHOR]

This work concerns a multiscale analysis of nano-reinforced heterogeneous materials. Such materials exhibit surface effects that must be taken into account in the homogenization procedure. In this study, a coherent imperfect interface model was employed to characterize the jumps of mechanical properties through the interface region between the matrix and the nanofillers. As the hypothesis of scale separation was adopted, a generalized self-consistent micromechanical scheme was employed for the determination of the homogenized elastic moduli. An explicit calculation for the determination of effective shear modulus is presented, together with a numerical application illustrating the surface effect. It is shown that the coherent imperfect interface model is capable of exploring the surface effect in nano-reinforced materials, as demonstrated experimentally in the literature. [ABSTRACT FROM AUTHOR]

To effectively capture interactions of large-scale ac–dc systems integrating line commutated converter (LCC) and modular multilevel converter (MMC) based multiterminal dc grids, a numerically accurate and efficient simulation method is desirable. To achieve this objective, a cosimulation method is proposed in this article, where the target system is decoupled into the shifted-frequency phasor (SFP) subsystem, the dynamic phasor (DP) subsystem, and electromagnetic transient (EMT) subsystem, respectively. The MMCs are included in the SFP subsystem and implemented on massively paralleled graphics processing units (GPUs). Thus, the simulation efficiency is greatly improved by adopting a much larger time step, the model order reduction technique, and GPU acceleration. The LCCs are represented by DPs and are included in the DP subsystem. The majority of ac grids are covered in the EMT subsystem. Further, the interactions between SFP and EMT subsystems are reflected by the proposed multidomain transmission line model, which can produce instantaneous and phasor values simultaneously. The interface model between DP and EMT subsystems is modeled as a special controlled voltage and current circuit. Finally, the overall cosimulation method is realized by the respective SFP/DP and EMT models, among which their interactions are reflected by the proposed interface models and the time sequences of simulations. The performance of the proposed method has been fully validated on a practical large-scale ac–dc system. [ABSTRACT FROM AUTHOR]

We consider wetting models in 1+1 dimensions with a general pinning function on a shrinking strip. We show that under a diffusive scaling, the interface converges in law to the reflected Brownian motion, whenever the strip size is o (N − 1 ∕ 2) and the pinning function is close enough to the critical value of the so-called δ -pinning model of Deuschel–Giacomin–Zambotti [10]. As a corollary, the same result holds for the constant pinning strip wetting model at criticality with order o (N − 1 ∕ 2) shrinking strip. [ABSTRACT FROM AUTHOR]

Numerical multi‐level model for fiber‐reinforced concrete – Multi‐level validation based on an experimental study on high‐strength concrete The contribution systematically examines the predictive capability of a numerical multi‐level model for steel fiber reinforced concrete made of high‐strength concrete by means of test series performed on the fiber as well as the structure level. The experimental study comprises pull‐out tests of Dramix 3D fibers in high‐strength concrete with different embedment lengths and inclinations to the crack surface as well as three‐point bending tests on notched beams with three significantly different fiber contents. The numerical model is designed to directly track the influence of design parameters such as fiber type, fiber orientation, fiber content and concrete strength on the structural response. For this purpose, submodels on the single fiber level are combined into a crack bridging model, considering the fiber orientation and the fiber content, and are integrated into a finite element model for the purpose of numerical structural analysis. The validation of the models for hooked‐end steel fibers shows that the interaction mechanisms between fiber and high‐strength concrete are realistically captured for all investigated cases (fiber inclinations, embedment lengths). On the structural level, the load‐displacement diagrams from the numerical simulations show a good agreement of the peak load as well as the post‐peak behavior for all fiber contents. [ABSTRACT FROM AUTHOR]

• An ECC-concrete composite beam with a fully-discrete model, taking into account the cementitious matrix and concrete softening characteristics, has been established. • An energy-based interface model using the peridynamic method has been established. • The effects of factors such as fiber volume fraction, ratio of ECC layer thickness, impact velocity, and fiber length on the performance of an ECC-concrete composite beam considering the strain rate effect under impact loading have been analyzed. Engineering cement-based composite materials (ECC) are widely used for strengthening concrete structures and resisting impact loads. However, the impact failure process of materials involves the material discontinuity. To address this issue, this paper constructs a fully discrete model of ECC concrete composite beams under impact loads based on peridynamics (PD). In this model, the cement matrix is described using an exponential model, while the fibers are modeled using PD rods. The interaction between the fibers and the matrix is described based on the classical exponential friction attenuation model, while considering failure criteria based on strain rate effects. Finally, by employing the established model, the effects of impact velocity, fiber volume fraction, ECC layer thickness ratio, and fiber length on the impact performance of ECC concrete composite beams were investigated. Results showed that impact velocity affects the damage evolution and crack propagation mode of the composite beams by affecting the dynamic critical elongation of PD bonds. The fiber volume fraction, ECC layer thickness ratio, and fiber length all have important effects on the ductility and energy absorption capacity of composite beams. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present paper proposes a new interface constitutive model based on the non-associative damage mechanics and frictional plasticity. The model is developed in a thermodynamically consistent framework, with three independent damage variables. The non associative flow rules drive the concurrent evolution of the three damage variables. The interface model provides two independent values for the mode I fracture energy and the mode II fracture energy and it is able to accurately reproduce arbitrary mixed mode fracture conditions. The model can also take into account the presence of frictional effects both at the fully debonded zones and at the partially debonded ones. The experimental tests developed by Benzeggagh and Kenane with seven different mixed mode ratios have been numerically simulated with a unique set of constitutive parameters. The split shear torsion, for the evaluation of the mode III delamination toughness, has been analysed by a three-dimensional numerical simulation. • The paper proposes a new interface constitutive model based on nonassociative damage mechanics and frictional plasticity. • The model is developed in a thermodynamically consistent framework, with three independent damage variables. • The interface model provides two independent values for the mode I fracture energy and the mode II fracture energy. • The interface model reproduces a smooth transition from the initial elastic behaviour to the residual frictional one. • Seven different experimental tests have been numerically simulated with a unique set of constitutive parameters. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Configuration design provides designers with a quick and cost-efficient way to develop new products. However, due to the initial complexity of industrial manufacturing systems, the number of alternative configurations from which designers select the most suitable one is too large. Considering the three main tasks relating to configuration design (i.e., modularisation, representation and evaluation), the authors review current configuration design approaches for the complex systems. Then, the authors point out there exists a gap between the representation task and evaluation task. Finally, a method which can improve the configuration design of industrial manufacturing systems is proposed. [ABSTRACT FROM AUTHOR]

Information technologies are a driving force for progress in the design field, allowing new modes of creativity. However, most of the existing computational design tools are focused on the latest stages of the design process and especially directed to drafting operations. Conceptual design tools that support the designer in the creative and inventive early stages of the design project are still in their early development. Shape grammars (SG) were introduced by George Stiny in the 1970s, allowing the generation of designs according to a set of predefined rules. SG computational implementations have the potential to answer the need for tools that can assist designers, architects, and artists in the creative process, offering design alternatives, stimulating new ideas and encouraging the search for new design generation processes. Acknowledging this potential, a user-friendly interface seems essential for the adoption of these tools. Taking Scott Chase's interaction model as background, the aim of the present investigation is to define guidelines and begin to design a graphical-user interface for SG implementations. Inspection methods of human–computer interaction (HCI) were used to analyze existing SG implementations and understand usability issues. Subsequently, HCI ergonomic criteria for interface evaluation were adapted to establish guidelines for the design of an SG implementation interface, called IM-sqi. These guidelines take into account different user groups, adjustable interaction modes for each user group, and the nature of each task performed by the user. [ABSTRACT FROM AUTHOR]

Background: Gestures can provide an excellent natural alternative to verbal communication in people with aphasia (PWA). However, despite numerous studies focusing on gesture production in aphasia, it is still a matter of debate whether the gesture system remains intact after language impairment and how PWA use gestures to improve communication. A likely source for the contradicting results is that many studies were conducted on individual cases or in heterogeneous groups of individuals with additional cognitive deficits such as conceptual impairment and comorbid conditions such as limb apraxia. Aims: The goal of the current study was to evaluate the integrity and function of gestures in PWA in light of cognitive theories of language-gesture relationship. Since all such theories presuppose the integrity of the conceptual system, and the absence of comorbid conditions that selectively impair gesturing (i.e., limb apraxia), our sample was selected to fulfill these assumptions. Methods & Procedures: We examined gesture production in eight PWA with preserved auditory comprehension, no comorbidities, and various degrees of expressive deficit, as well as 11 age- and education-matched controls, while they described events in 20 normed video clips. Both speech and gesture data were coded for quantitative measures of informativeness, and gestures were grouped into several functional categories (matching, complementary, compensatory, social cueing, and facilitating lexical retrieval) based on correspondence to the accompanying speech. Using rigorous group analyses, individual-case analyses, and analyses of individual differences, we provide converging evidence for the integrity and type of function(s) served by gesturing in PWA. Outcomes & Results: Our results indicate that the gesture system can remain functional even when language production is severely impaired. Our PWA heavily relied on iconic gestures to compensate for their language impairment, and the degree of such compensation was correlated with the extent of language impairment. In addition, we found evidence that producing iconic gestures was related to higher success rates in resolving lexical retrieval difficulties. Conclusions: When comprehension and comorbidities are controlled for, impairment of language and gesture systems is dissociable. In PWA with good comprehension, gesturing can provide an excellent means to both compensate for the impaired language and act as a retrieval cue. Implications for cognitive theories of language-gesture relationship and therapy are discussed. [ABSTRACT FROM AUTHOR]

Recent experimental studies involving Fabric Reinforced Cementitious Matrix (FRCM) strengthening systems externally applied to structural supports have underlined important aspects characterizing their response. In particular, failure mechanisms quite different from the ones emerged in case of traditional Fiber Reinforced Polymers (FRP) have been observed. These mechanisms particularly underline the role of additional phenomena to necessarily consider for the study and the development of theoretical models/design formulas specific for FRCMs. Aim of the present paper is to analyze the role of different aspects characterizing the behavior of FRCM strengthening systems externally applied on structural supports. Among these, it is mainly considered the role of the upper mortar layer, and, in particular, the influence of its possible damage state during the interaction mechanism between the reinforcement and the matrix. With this aim, a simple theoretical model is here presented. It accounts for the interaction between the reinforcement and the mortar matrix at the level of interface, by considering both the de-bonding and the tensile failure of mortar phenomena, which generally affect the resistant mechanism of FRCMs. The results presented in the paper underline the role of the different components of the strengthening system and their influence both in terms of local and global response. [ABSTRACT FROM AUTHOR]

Electromagnetic transient (EMT) and transient stability hybrid simulations are predominantly used to analyze the interactions between HVDC systems and the ac grids. However, the dynamics of the converters will be greatly affected by the waveforms of adjacent ac systems. Waveform distortion as well as time delay caused by interfacing can significantly increase interface errors, resulting in the decrease of the overall accuracy of the simulations. To solve such problems, a dynamic phasor based interface model (DPIM) is proposed in this paper to improve the accuracy of interfaces, especially when the fault occurs near the converters. In doing so, the whole system is partitioned into three parts: the transient stability (TS) subsystem, the EMT subsystem, and the DPIM. During each iteration, the interfaces between the TS subsystem and DPIM are represented by their Norton equivalents at the fundamental frequency and Thevenin equivalents in the dynamic phasor form. Similarly, the interfaces between DPIM and EMT subsystems are represented by their three-phase Norton equivalents and Thevenin equivalents in dynamic phasors, respectively. The effectiveness concerning the accuracy and the efficiency of the proposed method is validated by simulating a practical HVDC Project. [ABSTRACT FROM AUTHOR]

Due to the growing number of requirements and the introduction of new technologies, current trends indicate that more disciplines have been involved into the system design. The design of such multidisciplinary systems, especially during the detailed design phase, requires designers and expertise from different disciplines. Therefore, the research question about how to achieve an integrated design for multidisciplinary systems has attracted the attention from both academia and industry. In order to achieve such integrated design for multidisciplinary systems, more and more researchers focus on the interface of multidisciplinary systems because the interface plays a quite significant role to guarantee the components defined by the designers of different disciplines integrate correctly and to eventually help them to achieve the integrated design. This article presents an interface knowledge base to manage the design data and rules related to the interfaces. A knowledge-based engineering approach is then proposed. By applying the knowledge-based engineering approach, a synergistic integration of the discipline-specific components can be realised; however, the unnecessary iterations can be avoided so that a concurrent design process during the detailed design phase can be achieved. This knowledge-based engineering approach is demonstrated by the case studies based on a partial discharge detection system and a belt conveyor system. [ABSTRACT FROM AUTHOR]

Adhesively bonded joints are used in several industrial sectors. Cohezive Zone Modes can be used to predict the adhesive mechanical behaviour. This work presents an approach to calibrate Cohesive Zone Models (CZM) by means of Statistical Inverse Analysis. The Bayesian framework for Inverse Problems is used to infer about the CZM model parameters. The solution corresponds to the exploration of the posterior probability density function of the model parameters. The exploration of the posterior density is performed by means of Markov Chain Monte Carlo (MCMC) methods mixing Population-Based MCMC with Adaptive Metropolis (AD) strategies. The assessment of the approach is performed using measured data from a singlelap shear experimental set-up. Measured data from 5 testspecimens is used for calibration and measured data from five other test-specimens is used for model validation. It is proposed a stochastic effective model for the CZM parameters. The predictions of maximum force and maximum displacement that are provided by the effective model are in accordance with measured data that is used for validation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multirate co-simulation method to improve simulation efficiency of large-scale AC plus multiterminal DC (MTDC) grids. In this method, the whole system is partitioned into different AC and MTDC subsystems. They each are simulated with different time steps according to their requirements of accuracy. Unlike the existing methods where simplified models are adopted, the proposed approach fully reserves both the detailed behavior of converters and the nonlinear dynamics of large-scale AC systems. To realize the coordination between different subsystems, updating and discretization of the interface models are significant to guarantee the overall numerical accuracy and stability of the co-simulation method. Accordingly, the interface models of the partitioned AC and DC networks are represented by time-varying Thevenin and Norton equivalents. To eliminate the aliasing or time-delay errors, their parameters are derived using moving-window prediction, stepwise correction, and averaging techniques. A numerical oscillation suppression algorithm is developed for the discretization of the interface model. Thus, numerical stability is well guaranteed. The variables inside each subsystem as well as the interfaces, which are derived by augmented network equations (ANEs), are calculated simultaneously. The rate ratio of large AC and MTDC systems is determined based on our proposed criterion of electromagnetic transient simulation accuracy. The effectiveness of the cosimulation method is validated on a practical system integrating large AC and modular-multilevel-converter-based MTDC grids. [ABSTRACT FROM AUTHOR]

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Discrete fracture networks is a key ingredient in the simulation of physical processes which involve fluid ow in the underground, when the surrounding rock matrix is considered imper- vious. In this paper we present two different models to compute the pressure field and Darcy velocity in the system. The first allows a normal ow out of a fracture at the intersections, while the second grants also a tangential ow along the intersections. For the numerical discretization, we use the mixed virtual element method as it is known to handle grid elements of, almost, any arbitrary shape. The exibility of the discretization allows us to loosen the requirements on grid construction, and thus significantly simplify the ow discretization compared to traditional discrete fracture network models. A coarsening algorithm, from the algebraic multigrid literature, is also considered to further speed up the computation. The performance of the method is validated by numerical experiments. [ABSTRACT FROM AUTHOR]