Effect Of Aspect Ratio Research Articles

Microstructure-chemomechanics relations of polycrystalline cathodes in solid-state batteries

Lithium-nickel-manganese-cobalt-oxides (NMC) embedded in solid-electrolytes are being extensively applied as composite cathodes to match the high energy density of metallic anodes. During charge/discharge, the cathode composite often degrades through the evolution of micro-cracks within the grains, along the grain boundaries, and delamination at the particle-electrolyte interface. Experimental evidence has shown that regulating the morphology of grains and their crystallographic orientations is an effective way to relieve the volume-expansion-induced stresses and cracks, consequently stabilizing the electrochemical performance of the electrode. However, the interplay among the crystal orientation, grain morphology, and chemo-mechanical behavior has not been holistically studied. In that context, a thermodynamically consistent computational framework is developed to understand the role of microstructural modulation on the chemo-mechanical interactions of a polycrystalline NMC secondary particle embedded in a sulfide-based solid electrolyte. A phase-field fracture variable is employed to consider the initiation and propagation of cracks. A set of diffused phase-field parameters is adopted to define the transition of chemo-mechanical properties between the grains, grain boundaries, electrolyte, and particle-electrolyte interfaces. This modeling framework is implemented in the open-source finite element package MOOSE to solve three state variables: concentration, displacement, and phase-field damage parameter. A systematic parametric study is performed to explore the effects of aspect ratio, the crystal orientation of grains, and the interfacial fracture energy through the chemo-mechanical analysis of the composite electrode. The findings of this study offer predictive insights for designing solid-state batteries that provide stable performance with reduced fracture evolution.

Coarse-grained simulation of thermal conductivity of boron nitride/epoxy composites based on DPD and SPH method

In this study, thermal conductivity (TC) of BN/polymer composites is investigated utilizing dissipative particle dynamics (DPD) and smoothed-particle hydrodynamics (SPH) methods by establishing the coarse-grained (CG) models of boron nitride nanotube (BNNT) and boron nitride nanosheet (BNNS). The Iterative Boltzmann inversion (IBI) approach is employed to calculate the parameters of the potential function of the hexagonal boron nitride (h-BN) coarse grain model for DPD method. Mesoscopic simulations on the TC of BNNT/EP, BNNS/EP, and BNNT/BNNS/EP composites are performed using SPH and DPD simulations to investigate the effects of nanofiller ratio, aspect ratio, size, and orientation on TC. The CG models established for the BNNT and BNNS structures are proven to be efficient in DPD and SPH simulations for predicting the TC of h-BN/polymer composites. Furthermore, it is demonstrated that the TC of BNNT/BNNS/EP composites is superior to that of BNNT/EP and BNNS/EP composites at the same filler ratio due to the synergistic effect of BNNT and BNNS.

Vibrational response of a sandwich microplate considering the impact of flexoelectricity and based on a novel porous-FGM formulation

Flexoelectricity indicates a unique characteristic of insulators and dielectric materials that results in electrical polarization induction in response to the non-uniform strain gradient. The impact of this property is bolder on the microscale and nanoscale rather than the macroscale. This article is conducted to derive the governing equations of motion for a flexoelectric-multilayer structure and evaluate its vibrational behavior in response to various variable variations. The model includes a functionally graded (FG) porous core which is confined between two flexoelectricity-based face sheets at both sides and a Vlasov type of foundation. To gain the governing equations, the new type of power law for porous material beside Hamilton’s principle (HP) and modified couple stress theory (MCST) is implemented. Capturing the effects of length scale parameter, different materials, aspect and thickness ratios, porosity index, foundation parameter and boundary conditions (B.C.s) on the normalized natural frequency (NNF) of such a multilayer model based on the novel FG porous material formulation serve as the main novelty of this article. According to the results, it is revealed that the lateral ratio enhancement causes NNF and stiffness reduction in the model. Furthermore, among all considered B.C.s, simply support (SSSS) and clamped support (CCCC) refer to the lowest and the highest NNF respectively. The content of the recent article serves as a good source to provide a better understanding of the vibrational response of high stiffness-to-weight ratio structures to different variable variations.

The effects of gradient index, aspect ratio, porosity, and boundary conditions on the buckling behavior of functionally graded porous beams: A k-out-of-n system reliability analysis

Functionally graded materials are a class of multifunctional materials that exhibit spatial variation in composition and microstructure. This deliberate variation is designed to effectively manage and manipulate changes in thermal, structural, or functional qualities within the material. The current study explores the system reliability of functionally graded porous beams (FGPB) subjected to buckling, focusing on the interplay of gradient index (0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10), aspect ratio (5, 10, 15, 20, 25, 30 and 35), porosity index (0, 0.1 and 0.2) and boundary conditions (simply supported, clamped–clamped and clamped-free), with a particular emphasis on the k-out-of-n system reliability assessment, employing three distinct methods such as Evolutionary, GRG Non-linear, and Lagrangian. The results show the system's sensitivity to changes in distribution parameters, with the Lagrangian method being the most robust and stable. The 10-out-of-12 system reliability analysis demonstrates that aspect ratio and even porosity distribution are reliable, while uneven porosity is not. This study enhances structural reliability analysis in FGPBs, enhancing system reliability considerations and paving the way for further advancements in structural reliability analysis.

Effect of aspect ratio on the nonlinear optical properties of ZnO nanorods

In this work, we synthesized ZnO nanorods with two different aspect ratios using the solution method. Morphological and crystalline structures were investigated using TEM and XRD analysis. Also investigated the effect of aspect ratio on the optical properties of ZnO nanorods. With an increasing aspect ratio of the nanorods, the absorption peak is red-shifted and near-band edge emission is suppressed. The nonlinear absorption is enhanced with the increasing aspect ratio of ZnO nanorods.

Electrical conductivity of nanofluids with single- and multi-walled carbon nanotubes. Experimental study

The object of this paper is to experimental study the electrical conductivity of nanofluids with carbon nanotubes (CNT). Nanofluids based on water, ethylene glycol and isopropyl alcohol with single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes are considered. In some cases, surfactants were used to prepare the nanofluid. CNT concentrations varied from 0.05% to 1%. It was shown that the electrical conductivity of all nanofluids much more than that of base fluids. The influence of surfactants on the electrical conductivity of nanofluids is studied and analyzed. The use of surfactants in all cases increases the electrical conductivity of the initial base fluids. The greatest excess of the electrical conductivity was achieved when using ionic surfactants. For the first time, the electrical conductivity of nanofluids with SWCNTs and MWCNTs is systematically compared. The same base fluids are used for this. It was shown that electrical conductivity of nanofluids with SWCNTs significantly exceeds that of nanofluids with MWCNTs. The effect of aspect ratio on electrical conductivity of nanofluids with SWCNTs and MWCNTs are studied. In conclusion, the possible mechanisms of electrical conductivity of the considered nanofluids are discussed.

Computational study on interaction between rotating non-spherical particles and shear-thinning fluids

In this paper, the drag coefficient (Cd), lift coefficient (Cl), and torque coefficient (Ct) of rotating non-spherical particles in shear-thinning non-Newtonian fluids are investigated based on particle-resolved direct numerical simulation. The Carreau model is used to describe the rheological behavior of non-Newtonian fluids, and the numerical model is validated against previously published data. Then, the effects of aspect ratio (Ar), spin number (Spa), flow index (n), and Carreau number (Cu) on Cd, Cl, and Ct of rotating non-spherical particles are investigated at different Reynolds numbers (Re). The numerical results show that the closer the particles are to the spherical shape, the smaller the fluctuations of Cd, Cl, and Ct curves. The peaks and valleys of Cd, Cl, and Ct of oblate and prolate ellipsoidal particles are reversely distributed. The fluctuations of Cd and Cl curves increase with increasing Spa. Cd decreases with increasing Spa at low Re, contrary to Newtonian fluids' results. Cd and Ct decrease with increasing shear-thinning properties, Cl increases with increasing shear-thinning properties, and the effect of shear-thinning properties decreases with increasing Re. The variation of viscosity and pressure is the main reason for the variation of Cd, Cl, and Ct under different variables. Predictive correlations of Cd and Ct are established based on Re, Spa, n, Cu, and α. The findings indicate that particle rotation and shear-thinning properties must be considered when evaluating particle-fluid interactions, which provide important guidance for predicting and controlling the orientation and distribution of non-spherical particles in non-Newtonian fluids.

A novel rapid generation algorithm for Representative Volume Element (RVE) in composite materials considering pore geometrical parameters

Pore defects are inevitable in the manufacturing process and significantly affect the mechanical properties of composite materials. In this work, a novel algorithm capable of concurrently generating both ellipsoidal and gourd-shaped pores in composite materials is proposed and the interference detection procedure is optimized for efficient interference detection between the generated geometrical bodies. Besides, the algorithm is integrated with RVE-based finite element (FE) simulation to explore the effects of various pore types, volumes, aspect ratios, and porosity on the elastic properties of unidirectional C/C composites. The present work provides a valuable reference for generating general pore defects and investigating their resulting effects on mechanical properties of related composite structures.

Bone-like microtextures of HA coatings prepared by nanosecond laser and their properties

Although the hydroxyapatite (HA) coating implant prepared by laser cladding exhibits good biological activity due to its chemical composition similar to biological bone, the original surface roughness of the laser-clad coating is high, which is unfavorable for long-term cell adhesion and proliferation. In order to improve the biological activity of HA coating implants and increase the adhesion and proliferation rate of osteoblasts on their surface, microtextures with different length-diameter ratios and depth gradients were prepared on the HA coating surface by nanosecond laser with reference to the microscopic morphology characteristics of the biological bone surface. By investigating the effects of microtexture aspect ratio and depth gradient on osteoblast adhesion characteristics, it was found that bone-like microtextures better controlled and simulated cell-material surface interactions. The geometric morphology of microtextured bone with a wide front end and narrow rear end and a depth gradient from front to back was an important signal for osteoblast proliferation. When the aspect ratio of bone microtexture was 2.5:1 and the maximum depth gradient was 15.7 μm, osteoblasts within the microtexture showed optimal growth, proliferation, and adhesion. Additionally, due to induction by microtexture contour shape and depth gradient morphology, cell morphology showed varying adhesion morphology from the front to the back of the microtexture. The results demonstrated that HA coatings with bone-like microtextures had superior osteoblast proliferation and adhesion properties compared to the original cladded coating surface, beneficial for enhancing the application of HA-coated bone implants in large segment bone repair.

Experimental investigation of rectangular nozzle aspect ratio effects on high-pressure helium leakage characteristics

High-pressure hydrogen leakage is one of the bottlenecks restricting the development of the hydrogen energy industry. In this study, a high-pressure helium leakage experimental system with stable pressure was built to research the influence of aspect ratio on concentration decay rate and mass flow rate. Similar to the circular nozzle, the centerline helium concentration of the rectangular jet is also inversely proportional to the distance from the nozzle. For the rectangular nozzles with aspect ratio of 1–4, the helium concentration decay rate is consistent with the circular nozzle when the leakage pressure is lower than 6.5 MPa. However, the decay rate is obviously larger for rectangular nozzles with aspect ratio of 10 when the leakage pressure is greater than 5.0 MPa. The aspect ratio has a greater influence on the flow coefficient, which increases with the aspect ratio under the same leakage pressure. To comprehensively consider the effects of nozzle size and shape, a weighted characteristic diameter of equivalent diameter and rectangular width, dc=αde+1−αdw, was proposed in this study. The results indicate that the equivalent diameter has greater impact on the centerline concentration decay rate, while the width of nozzles has substantial influence on the flow coefficient.

Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries

Tailoring porous host materials, as an effective strategy for storing sulfur and restraining the shuttling of soluble polysulfides in electrolyte, is crucial in the design of high-performance lithium-sulfur (Li-S) batteries. However, for the widely studied conductive hosts such as mesoporous carbon, how the aspect ratio affects the confining ability to polysulfides, ion diffusion as well as the performances of Li-S batteries has been rarely studied. Herein, ordered mesoporous carbon (OMC) is chosen as a proof-of-concept prototype of sulfur host, and its aspect ratio is tuned from over ∼ 2 down to below ∼ 1.2 by using ordered mesoporous silica hard templates with variable length/width scales. The correlation between the aspect ratio of OMCs and the electrochemical performances of the corresponding sulfur-carbon cathodes are systematically studied with combined electrochemical measurements and microscopic characterizations. Moreover, the evolution of sulfur species in OMCs at different discharge states is scrutinized by small-angle X-ray scattering. This study gives insight into the aspect ratio effects of mesoporous host on battery performances of sulfur cathodes, providing guidelines for designing porous host materials for high-energy sulfur cathodes.

Heat transfer and mathematical model of flame geometry of rectangular-shaped pool fire in longitudinal ventilation tunnel

Fire is one of the most serious threats in operation of the tunnel. The thermal radiation disaster of fire is dependent on flame height and inclination angle which are affected by the longitudinal ventilation. The coupling effect of aspect ratio of rectangular container (n = 1, 2, 4, 8, 16) and longitudinal wind on flame geometry of heptane pool fire are revealed. The flame height decreases with an increase in the wind, while the inclined angle increases in longitudinal winds of 0–2.49 m/s. The variation of flame geometry is interpreted using the mechanical equilibrium of horizontal inertial force and gas uprising buoyancy induced by liquid fire. According to air entrainment theory and heat feedback theory, the flame height and inclined angle of rectangular-shaped fire change with characteristic scale ratio (n+1n) in mathematics. The measurements of flame height and inclined angle are analyzed and several quantitatively mathematical equations incorporating heat release rate, characteristic scale ratio, non-dimensional burning rate, non-dimensional air flow are proposed. The predicted results of flame geometry are fully validated by experimental measurements. The current finding is convenient for establishing radiation model of pool fire in air-blown condition.

In-plane and out-of-plane one-way vertical bending behavior interaction analysis of unreinforced masonry walls with newly developed load capacity interaction curve

The structural behavior of unreinforced masonry (URM) walls under in-plane (IP) or out-of-plane (OOP) loading in masonry buildings has been extensively investigated in the public literature. However, studies focusing on the URM walls subjected to concurrent IP and OOP loadings are limited. Neglecting IP and OOP interaction effects may lead to unsafe design practices. As such, this study conducts a comprehensive numerical investigation into the behavior of URM walls under combined IP and OOP loading, focusing on the influences of aspect ratio (i.e., height-to-length ratio), slenderness ratio (i.e., height-to-thickness ratio), and pre-compression load levels. To capture the possible failure modes of URM walls under various loading scenarios, the simplified micro modeling approach is employed. The analysis results indicate that the presence of OOP loading leads to a substantial reduction in IP capacities. Longer walls, characterized by smaller AR, exhibit more pronounced IP and OOP interaction effects. Additionally, highly slender walls show significant additional moments due to second-order effects under OOP loading, thereby negatively affecting the IP capacity. Low-level pre-compression loads are beneficial in diminishing capacity interaction effects, while high pre-compression loads exert a negative influence. To facilitate the consideration of IP and OOP capacity interaction effects in an efficient manner, a simplified analytical model is developed through curve fitting, in which the effects of aspect ratio, slenderness ratio, and pre-compression load are incorporated.

Design and mechanical properties analysis of a cellular Waterbomb origami structure

Cellular structures are commonly used to design energy-absorbing structures, and origami structures are becoming a prevalent method of cellular structure design. This paper proposes a foldable cellular structure based on the Waterbomb origami pattern. The geometrical configuration of this structure is described. Quasi-static compression tests of the origami tube cell of this cellular structure are conducted, and load-displacement relationship curves are obtained. Numerical simulations are carried out to analyze the effects of aspect ratio, folding angle, thickness and number of layers of origami tubes on initial peak force and specific energy absorption (SEA). Calculation formulas for initial peak force and SEA are obtained by the multiple linear regression method. The degree of influence of each parameter on the mechanical properties of the single-layer tube cell is compared. The results show that the cellular structure exhibits negative stiffness and periodic load-bearing capacity, as well as folding angle has the most significant effect on the load-bearing and energy-absorbing capacity. By adjusting the design parameters, the stiffness, load-bearing capacity and energy absorption capacity of this cellular structure can be adjusted, which shows the programmable mechanical properties of this cellular structure. The foldability and the smooth periodic load-bearing capacity give the structure potential for application as an energy-absorbing structure.

Self-ordering and organization of a staggered oblate particle pair in three-dimensional square ducts

We numerically investigate the formation and ordering of staggered oblate particle pairs in three-dimensional straight ducts with a square cross section. The lattice Boltzmann method is employed to simulate rigid particle pairs in a Newtonian liquid. The effects of initial axial spacing, Reynolds number, blockage ratio, and particle aspect ratio on the formation process, migration behavior, and interparticle spacing are explored in detail. Current results indicate that the process from initial to final steady state can be divided into two stages. The first stage is rapid migration from initial positions toward equilibrium positions under shear-induced lift force and wall-induced repulsive force. The second stage is the slow self-assembly of stable particle pairs in the axial direction due to the interparticle interaction. Interestingly, initial axial spacing significantly affects the formation process of particle pairs but does not affect the final steady state. It is found that the equilibrium positions of staggered particle pairs move slightly toward the duct walls, and the axial spacing increases with increasing Reynolds number or particle aspect ratio, or decreasing blockage ratio. For a staggered particle pair, the second particle will occupy the eddy center induced by the first focusing particle. Based on the existing data, a correlation is put forward to predict the axial interparticle spacing of staggered oblate particle pairs in duct flows. The present results may give insights into manipulating and comprehending non-spherical particle dynamics in microfluidic applications.

A hybrid simulator with novel bicone-wire grid antenna.

The simulator is an indispensable device for the study of high-altitude electromagnetic pulse (HEMP) effects. In order to improve the quality of the electric field waveforms of the HEMP simulator, we carried out simulation and experimental studies for the biconical-wire grid antenna. A new bicone-wire grid antenna HEMP simulator was designed by using skeletonized cones instead of solid cones, which can substantially improve the mobility of the simulator. The effects of different aspect ratios and different cone structures of the simulator on the waveform and distribution characteristics of the electric field were analyzed. The accuracy of the simulation results was verified by testing the bicone-wire grid antenna simulator with the new structure. The results obtained are as follows: First, the simulator can provide a HEMP environment compliant with the International Electrotechnical Commission (IEC) standard in an area of 5 × 6 × 2m3. Second, the simulator possesses optimal waveform quality and working space among simulators with different aspect ratios. Finally, the influence of using skeletonized cones instead of solid cones on the simulator's electric field waveforms is negligible, and the mobility of the new simulator is significantly improved compared to the original simulator.

Resonances of Fluid‐Filled Cracks With Complex Geometry and Application to Very Long Period (VLP) Seismic Signals at Mayotte Submarine Volcano

AbstractFluid‐filled cracks sustain a slow guided wave (Krauklis wave or crack wave) whose resonant frequencies are widely used for interpreting long period (LP) and very long period (VLP) seismic signals at active volcanoes. Significant efforts have been made to model this process using analytical developments along an infinite crack or numerical methods on simple crack geometries. In this work, we develop an efficient hybrid numerical method for computing resonant frequencies of complex‐shaped fluid‐filled cracks and networks of cracks and apply it to explain the ratio of spectral peaks in the VLP signals from the Fani Maoré submarine volcano that formed in Mayotte in 2018. By coupling triangular boundary elements and the finite volume method, we successfully handle complex geometries and achieve computational efficiency by discretizing solely the crack surfaces. The resonant frequencies are directly determined through eigenvalue analysis. After proper verification, we systematically analyze the resonant frequencies of rectangular and elliptical cracks, quantifying the effect of aspect ratio and crack stiffness. We then discuss theoretically the contribution of fluid viscosity and seismic radiation to energy dissipation. Finally, we obtain a crack geometry that successfully explains the characteristic ratio between the first two modes of the VLP seismic signals from the Fani Maoré submarine volcano in Mayotte. Our work not only reveals rich eigenmodes in complex‐shaped cracks but also contributes to illuminating the subsurface plumbing system of active volcanoes. The developed model is readily applicable to crack wave resonances in other geological settings, such as glacier hydrology and hydrocarbon reservoirs.

Numerical parametric study of dry-stack masonry walls with varied dimensional and loading configurations

In-plane behavior for masonry walls is significantly influenced by the masonry unit size and aspect ratio (height-to-length ratio). The effect of pre-compression load on the behavior of masonry walls also cannot be neglected. Several numerical and experimental research studies have been conducted to investigate behavior of these effects on masonry walls. However, said studies have not been all-inclusive, especially in regard to dry-stack masonry walls. For this study, parametric numerical simulations involving two-dimensional (2D) nonlinear models employing finite element methods (FEM) and micro-modeling approach were used to investigate the nonlinear behavior of dry-stack masonry walls with in-plane behavior under lateral load investigated by means of pushover and cyclic analyses for assorted levels of pre-compression load. Wall size, aspect ratio, and unit dimension parameters were also varied to ascertain relationship between structural behavior characteristics such as stiffness, strength, energy dissipation capacity, and failure mechanism. In general, results showed that stiffness, strength, and energy dissipation capacity decreased with increasing wall aspect ratio. Moreover, and clear relationship patterns were identified. For walls with a length of 1 m, elevating the height from 1.2 m to 2.4 m to 3.6 m leads to approximately 60% to 80% reduction in stiffness, along with approximately 50% to 60% reduction in strength. Additionally, when comparing walls with the same aspect ratio, walls with double and triple the size exhibit about 33% and 39% larger stiffnesses and about 80% and 157% larger strengths, respectively. Said results and details derived may be used in design of masonry walls, and the effects of aspect ratio, wall size, unit size, and pre-compression load under pushover and cyclic loading were considered.

Effect of aspect ratio on the x-ray attenuation of nanoparticles: A theoretical study

PurposeThere has been a significant focus on the potential applications of nanoparticle suspensions in the past few decades particularly as targeted contrast agents for specific pathological conditions. However, the question of optimal size and shape of nanoparticles for contrast enhancement is inadequately addressed. MethodsWe present a comprehensive and conclusive theoretical analysis using first principles by considering the attenuating property of a single nanoparticle of any arbitrary shape. As a special case, ellipsoidal nanoparticles and nanorods are considered, for two independent directions of incidence of x-rays. These results are extended for a suspension of nanoparticles in a liquid. ResultsIt is seen that for a nanoparticle with dimensions much less than 1/μ(E), where μ(E) is the attenuation coefficient of the material, the attenuation by the nanoparticle is independent of its shape and size; and attenuation per unit mass reduces as the nanoparticle size increases. ConclusionsTo achieve maximum attenuation, the nanoparticle sizes should be as small as possible, immaterial of the shape, as long as the dimensions are smaller than 150 nm.

Comprehensive analysis of bio-inspired laminated composites plates using a quasi-3D theory and higher order FE models

A comprehensive study is carried out by employing various finite element models (FEMs) for the bending, buckling stability and free vibration analyses of bio-inspired helicoidal composite plates with various lamination schemes. A higher order quasi-3D kinematic plate theory is developed to include a shear deformation effect. The variational formulation of the problem is exploited to derive the equations of motion, element stiffness, geometrical stiffness, and mass matrices based on a non-conforming rectangular element. Three different finite elements models are derived based on non-conforming elements with different number of nodes and degree of freedom. The developed finite element model has been validated with those found in the open literature. The effects of boundary condition, lamination scheme, orthotropy ratio and aspect ratio on the mechanical response of the bio-inspired helicoidal composite plates are examined. Notably, for the lamination schemes investigated in this study, no shear locking phenomenon was observed in the analyses conducted using these FEMs. Dimensionless centre deflections, critical buckling loads and fundamental frequencies of bio-inspired helicoidal composite plates vary depending on the type of lamination scheme, boundary condition and aspect ratio. The new orientation schemes can replace the traditional ones to overcome the shear singularity and overcome the delamination defects.