Autoclaved aerated concrete (AAC) has broad applications in civil engineering due to its lightweight, thermal and sound insulation. However, the relation between the complex random porous structures ...and the compression performances of AAC is complex, limiting the optimization and application of AAC. In this study, finite element simulation was implemented and validated based on the experimental results. The simulation results showed that the compressive strength of AAC increased by 31.7, 45.8, and 134% with the porosity decreasing from 70% to 40%, the average pore diameter decreasing from 1.5 to 0.5 mm, and the pore connectivity decreasing from 50% to 0, respectively. Then, based on the numerical dataset, integrated machine learning methods were implemented to rapidly predict the compressive properties of AAC and analyze the main factors affecting the compressive properties. The ML results showed that the CatBoost model had the best predictive performance based on the small dataset of simulation results, with an average relative error of 18% and 7% for compressive strength and modulus of AAC, respectively. The component modulus was the most important feature for predicting the compressive strength and modulus of AAC.
•The relation between random porous structures and compression performances of autoclaved aerated concrete (AAC) was investigated.•Finite element simulations were implemented to investigate the compression of AACs with different elastic modulus of components and pore structure.•Integrated machine learning methods were implemented to rapidly predict the AAC compressive properties and analyze their main affecting factors.•Gradient boosting with categorical features support has the best prediction performance.
•Electric field distribution of various electrospinning geometries was studied.•Various collector, auxiliary electrodes, and multi-nozzle designs were reported.•Macroscopic fiber properties can be ...controlled by manipulating electric field.•Fiber alignment, spatial deposition, and productivity were analyzed.
Electrospinning has emerged as one of the most versatile and extensively used approaches to synthesize nanofibers for a diverse range of applications. The production of custom nanofibrous assemblies with controlled fiber orientation, spatial deposition, and high productivity is desirable for emerging applications that demand new electrospinning system designs. The electric field plays a major role in determining the jet trajectory and thereby its manipulation can provide us with a tool to create desired fibrous architectures. In this work, we have systematically studied the three aspects of electrospinning system, specifically, collector/target designs, auxiliary electrodes, and multi-nozzle configurations using finite element simulation. The electric field distribution for different designs were analyzed and correlated with the literature-reported experimental studies to envisage the resultant macroscopic properties of the fibers. It was established that the alteration in electric field distribution can be exploited to control and enhance the fiber alignment, spatial deposition, and productivity.
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The formation of single bubbles at nanoelectrodes during electrochemical reactions allows to accurately identify the critical nucleus for bubble formation. As demonstrated before, ...combining nanoelectrode experiments and an analysis approach based on classical nucleation theory (CNT) delivers useful insight into bubble nucleation. In this work we propose an alternative approach to analyze the critical nuclei by applying the nucleation theorem (NT), which is able to overcome the inherent shortcomings of CNT. The size of the critical nucleus can be calculated more accurately by fitting experimental data in a simple form of the NT. Simulating the local gas concentration using a finite element approach, and considering the effect of gas oversaturation on the interfacial tension and the real gas compressibility, we obtain a more realistic estimation of the critical nuclei morphology. With the NT-based analysis presented, we re-analyze the nucleation data reported before. The properties of the critical nuclei obtained here are roughly consistent with those obtained from the CNT-based approach. In addition, we confirm that the critical nucleus for bubble formation in high gas oversaturation is featured with a contact angle much larger than Young’s contact angle.
Magnesium (Mg) alloys despite being the ideal candidate for structural applications, owing to their high specific strength and low density, are not widely used due to lack of active slip systems at ...room temperature in their hexagonal close-packed crystal structure, eliciting poor ductility and formability. Amongst the various series of Mg alloys, the AZ and ZK series alloys have been standouts, as they inherit better room temperature strength and flow characteristics through their solute elements. Grain refinement, as well as eliminating casting defects through metal processing techniques are vital for the commercial viability of these alloys since they play a key role in controlling the mechanical behaviour. As such, this review highlights the effect of different Bulk-deformation and Severe Plastic Deformation techniques on the crystal orientation and the corresponding mechanical behaviours of the AZ31 alloy. However, every process parameter surrounding these techniques must be well thought of, as they require specially designed tools. With the advent of finite element analysis, these processes could be computationally realized for different parameters and optimized in an economically viable manner. Hence, this article also covers the developments made in finite element methods towards these techniques.
•The resistive sensor and the fiber Bragg grating sensor are selected to analyze the validity in pavement monitoring.•The strain simulation of asphalt mixtures with sensors by means of FE simulation ...is feasible in short-term loading tests and long-term loading tests.•The FBG sensor is more amenable to use in the measurement of horizontal strain for asphalt pavement than the R sensor.
To address the problems associated with the validity of pavement sensor measurement, a method of combining indoor experiments with finite element (FE) simulations for strain measurement in asphalt pavement is developed in this paper to analyze the validity of strain sensors for practical measurements. First, correlation analysis and one-way analysis of variance (ANOVA) between the simulated strain and the measured strain of the resistive (R) sensor and the fiber Bragg grating (FBG) sensor are developed, and the results show that the strain simulation of asphalt mixtures with sensors by means of FE simulation is feasible for short-term loading tests; therefore, the simulated strain without sensors is considered the true strain. The FBG sensor is more appropriate than the R sensor for use in the measurement of horizontal strain based on the stability of the regression model. Furthermore, creep experiments and FE simulations with a modified Burgers model are developed, and the results demonstrate that the FE simulation is also effective for long-term dynamic loading tests. Finally, the effect of the ratio of the modulus of the FBG sensor to that of the asphalt mixture on the stability of the regression model is analyzed, and the results suggest that the stability worsens as the modulus ratio increases at the same temperature, which could guide the selection of encapsulating materials. Moreover, the research method could also provide resources for studying the validity of sensors under more complex loading modes.
While the directionality and integrity of microscopic fiber arrangement play an important role in governing the mechanical properties and deformation behavior of unidirectional carbon fiber ...reinforced polymer (UD-CFRP) composites, minimizing or eliminating the deformation-induced evolution of fiber arrangement is crucial for maintaining the high performance of the advanced composite materials. In the present work, we elucidate the depth-sensing deformation mechanisms of UD-CFRP under different cutting strategies of conventional single-pass and multi-pass by experiments and corresponding micromechanical finite element simulations. Experimental and simulation results reveal diversiform maps of fiber arrangement evolution in subsurface damage layer under different cutting strategies, as well as their correlations with machined surface quality in terms of surface finish, residual stress and mechanical properties. Subsequently, a novel cutting strategy of reverse multi-pass is proposed to tailor the directionality and integrity of microscopic fiber arrangement in subsurface damage layer, which is accompanied with reduced subsurface damage layer, lowered surface roughness and enhanced hardness and elastic modulus, as compared to the cutting strategy of conventional multi-pass. Current findings provide a theoretical basis for the understanding of formation mechanisms of machined surface of CFRP composites, as well as the rational selection of cutting strategies for improving the machinability of CFRP composites.
Analytical investigations, micromechanical finite element simulations and experiments jointly demonstrate the feasibility of tailoring fiber arrangement accompanied with enhanced mechanical properties of UD-CFRP by rationally selected reverse multi-pass cutting strategy. Display omitted
The caisson foundation has evolved into a suitable alternative foundation for offshore structures, specifically for offshore wind turbines (OWT). The OWT caisson foundations are exposed to a ...combination of lateral, vertical, and overturning moments. A precise assessment of horizontal load response is necessary to ensure the normal functioning of these foundations for a proper design. This paper presents the results of three-dimensional finite element analyses of the lateral load-bearing behavior of the caisson foundation used for offshore wind turbines. The numerical model was validated and cross-checked by experimental data from the literature. The caisson’s behavior and the soil response supporting the caisson foundation subjected to static horizontal loads were examined. The effect of the slenderness of the caisson foundation was examined by changing the diameter and the depth of the caisson. It was observed that the depth of a caisson has a more profound effect on the lateral load-bearing capacity of the foundation. The caisson’s rotation center or inflection point was found to be at a distance of approximately 0.8 times the caisson depth, and it shifted downward with the increase in caisson diameter. Soil upheaval in the loading direction was observed as a precursor to the pullout failure, which increased with loading eccentricity and decreased with the caisson depth.
•The effect of aspect ratio and the pullout behavior of caisson were analyzed.•The inflection point of rotation of caisson and soil heave around it were analyzed.•Parametric studies were conducted on the caisson’s thickness, diameter, and depth.•Parametric studies were also conducted on load eccentricity and caisson lid diameter.
Polymer-based composites with effective heat dissipation and ideal electromagnetic interference shielding performance have gradually become an essential research focus in modern electronic industry. ...Herein, a method is reported by constructing 3D microscope continuous filler network into polyetherimide (PEI) matrix via incorporating function graphite nanoplatelets (GNP) with PEI microspheres, and then fillers are distributed beyond the domain area of polymer and leaded to continuous filler framework. The fabricated composites exhibit effective thermal conductivity (4.77 W m−1K−1), great EMI effectiveness (42.7 dB), ideal electrical conductivity and profound thermal property. Different scale of polymer microspheres will also change the micro-architecture from “filler-wrapped polymer” structure to “polymer-wrapped filler” structure, resulting in various thermal performance and electrical property. Finite element simulation is further employed to explore the relationship between microsphere scale and heat transfer behavior. In a word, great comprehensive performance endows PEI composites broaden prospect on the potential applications in the fields of electronic equipment.
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Long fibre reinforced plastics (LFRPs) possess excellent mechanical properties and are widely used in the aerospace, transportation and energy sectors. However, their anisotropic and ...inhomogeneous characteristics as well as their low thermal conductivity and specific heat capacity make them prone to subsurface damage, delamination and thermal damage during the machining process, which seriously reduces the bearing capacity and shortens the service life of the components. To improve the processing quality of composites, finite element (FE) models were developed to investigate the material removal mechanism and to analyse the influence of the processing parameters on the damage. A review of current studies on composite processing modelling could significantly help researchers to understand failure initiation and development during machining and thus inspire scholars to develop new models with high prediction accuracy and computational efficiency as well as a wide range of applications. To this aim, this review paper summarises the development of LFRP machining simulations reported in the literature and the factors that can be considered in model improvement. Specifically, the existing numerical models that simulate the mechanical and thermal behaviours of LFRPs and LFRP-metal stacks in orthogonal cutting, drilling and milling are analysed. The material models used to characterise the constituent phases of the LFRP parts are reviewed. The mechanism of material removal and the damage responses during the machining of LFRP laminates under different tool geometries and processing parameters are discussed. In addition, novel and objective evaluations that concern the current simulation studies are conducted to summarise their advantages. Aspects that could be improved are further detailed, to provide suggestions for future research relating to the simulation of LFRP machining.
Ti2AlNb alloys are expected to have applications in the aerospace field because of their excellent high-temperature performance and moderate density. Multi-wire arc-directed energy deposition ...(MWA-DED) technology enables the in-situ formation of Ti2AlNb alloys. However, Ti2AlNb alloys fabricated by MWA-DED face challenges such as compositional segregation and poor mechanical properties. In this study, high-performance Ti2AlNb alloys were efficiently prepared using MWA-DED technology, and their microstructure evolution was systematically analyzed. Hot-wire technology was proposed to assist in melting the TiNb wire to minimize the difference in the physical properties of the two wires. A pre-alloy droplet transfer mode with a large arc length was developed to eliminate composition segregation. The results showed that the Ti2AlNb alloys exhibited a homogeneous composition that matched the target Ti-22Al-23 Nb. Lots of strengthening phases (O phases higher than 90%) were precipitated throughout the sample. Temperature fields calculated from finite element simulation revealed that the precipitated phases were attributed to the “in-situ” heat treatment during deposition. The ultimate tensile strength and elongation reached 1002 MPa and 8% at room temperature, and 756 MPa and 8.3% at high temperature (650 ℃), respectively. The outstanding mechanical properties of Ti2AlNb alloys fabricated by MWA-DED are superior to those of cast and previously reported additively manufactured alloys. This study proposes novel ideas for additive manufacturing of high-performance Ti2AlNb alloys.
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•Ti2AlNb alloys were efficiently in-situ manufactured by the multi-wire arc-directed energy deposition technique.•Hot-wire technology was proposed to eliminate the difference in physical properties of the two wires.•A pre-alloy droplet transfer model with high arc-length was explored to overcome compositional segregation.•Numerical simulations of heat transfer were developed to reveal the microstructure evolution mechanism.•High-performance Ti2AlNb alloys were obtained and the strengthening mechanisms were revealed.
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