12,006 results
Search Results
2. Interplay between structural scales and fracture process zone: experimental and numerical analysis on paper as a model material.
- Author
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Villette, François, Dufour, Frédéric, Baroth, Julien, Rolland du Roscoat, Sabine, and Bloch, Jean-Francis
- Subjects
- *
NUMERICAL analysis , *FINITE element method , *YOUNG'S modulus , *STOCHASTIC analysis , *SURFACE energy , *RANDOM fields , *BRITTLE materials - Abstract
This work deals with fracture mechanisms in quasi-brittle materials, focusing on the characterization of the Fracture Process Zone (FPZ) of specimens under tensile load. Particularly, paper was used as model material. Experiments were conducted on notched and unnotched specimens. Based on an image analysis of these observations, a stochastic finite element model was developed, using both a nonlocal stress-based approach and a discretized random field modeling of the Young's modulus. The proposed methodology allowed characterizing the damage zone and the size of the FPZ, analyzing the influence of the mesostructure, composed of flocs (fiber aggregates where the basis weight is larger than the average one) and antiflocs (complement of flocs). The area of the active FPZ and the normalized stress drop were linked using a surface energy dissipated in the active FPZ. The stress drop, until limiting value, increased with the width of the active FPZ. Finally, a relationship between the surface energy and the nonlocal internal length was established. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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3. Transport of Organic Volatiles through Paper: Physics-Informed Neural Networks for Solving Inverse and Forward Problems.
- Author
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Serebrennikova, Alexandra, Teubler, Raimund, Hoffellner, Lisa, Leitner, Erich, Hirn, Ulrich, and Zojer, Karin
- Subjects
WATER vapor transport ,PARTIAL differential equations ,FINITE element method ,POROUS materials ,PACKAGING materials - Abstract
Transport of volatile organic compounds (VOCs) through porous media with active surfaces takes place in many important applications, such as in cellulose-based materials for packaging. Generally, it is a complex process that combines diffusion with sorption at any time. To date, the data needed to use and validate the mathematical models proposed in literature to describe the mentioned processes are scarce and have not been systematically compiled. As an extension of the model of Ramarao et al. (Dry Technol 21(10):2007–2056, 2003) for the water vapor transport through paper, we propose to describe the transport of VOCs by a nonlinear Fisher–Kolmogorov–Petrovsky–Piskunov equation coupled to a partial differential equation (PDE) for the sorption process. The proposed PDE system contains specific material parameters such as diffusion coefficients and adsorption rates as multiplication factors. Although these parameters are essential for solving the PDEs at a given time scale, not all of the required parameters can be directly deduced from experiments, particularly diffusion coefficients and sorption constants. Therefore, we propose to use experimental concentration data, obtained for the migration of dimethyl sulfoxide (DMSO) through a stack of paper sheets, to infer the sorption constant. These concentrations are considered as the outcome of a model prediction and are inserted into an inverse boundary problem. We employ Physics-Informed Neural Networks (PINNs) to find the underlying sorption constant of DMSO on paper from this inverse problem. We illustrate how to practically combine PINN-based calculations with experimental data to obtain trustworthy transport-related material parameters. Finally we verify the obtained parameter by solving the forward migration problem via PINNs and finite element methods on the relevant time scale and show the satisfactory correspondence between the simulation and experimental results. Article Highlights: A mathematical model to describe transport of polar volatile organics through paper is proposed. Based on experimental data, the deep learning method of physics-informed neural networks (PINNs) is used to solve the inverse problem of finding the sorption time constant. Solutions for the forward problem are obtained by the standard finite element method (FEM) and PINN methods. These solutions are compared with each other as well as with the experimental data to verify the model. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation.
- Author
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Hagman, A. and Nygårds, M.
- Subjects
- *
CARDBOARD , *PAPER analysis , *THERMOGRAPHY , *TENSILE tests , *DIGITAL image correlation , *DEFORMATIONS (Mechanics) - Abstract
The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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- View/download PDF
5. Mechanical and softness characterization of "deco" and "micro" embossed tissue papers using finite element model (FEM) validation.
- Author
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Vieira, Joana Costa, Morais, Flávia, de Oliveira Mendes, António, Ribeiro, Marcelo Leite, Carta, Ana Margarida, Curto, Joana, Amaral, Maria Emília, Fiadeiro, Paulo Torrão, and Costa, Ana Paula
- Subjects
FINITE element method ,SULFATE pulping process ,FIBERS ,TISSUES ,MICROWAVE drying - Abstract
An innovative approach of using a laboratory embossing prototype was carried out to develop and optimize tissue papers, to quantify the influence of "deco" and "micro" embossing. A comparison between non-embossed and embossed tissue papers was conducted to investigate the effect of this process, on industrial and laboratory-made structures, evaluated by mechanical and softness properties. To identify the influence of the embossing patterns, the fiber composition and the creping process, a creped industrial base tissue paper, a disintegrated fibrous suspension obtained from this one, and an industrial never-dried bleached eucalyptus kraft pulp, were used as samples. These last two materials were used to produce similar industrial base tissue paper, in other words, handsheets with a grammage of 17 g/m
2 and unpressed. The end-use tissue properties were evaluated on the non-embossed and embossed structures. The results indicated that the embossing process produced bulkier and more porous structures, at the expense of reduced mechanical and softness properties, more intensified in the "micro" embossing than in the "deco" embossing. The effect of fiber composition shows that the mechanical properties were increased with an adverse effect on the structures' TSA-softness. Furthermore, these properties are enhanced for the structures where creping process effects are presents. The performance of structures with and without embossing allowed to quantify the functional properties of softness and strength, combining ISO experimental methods and computational approaches that benefit from modeling strategies considering its structural hierarchy at the fiber and structure levels, and the shape pattern used in the embossing process. Finite Element Model (FEM) analysis enabled a better understanding of how the embossing patterns affect the mechanical properties during the embossing process. The experimental results were validated using FEM simulation, which proved that "micro" pattern has a higher stress field value, and consequently a lower mechanical strength. Overall, the results indicate that the embossing prototype can be used as an opportunity to investigate the embossing process at laboratory scale and to optimize the final end-use tissue properties due to the controlled process parameters implemented in this methodology. [ABSTRACT FROM AUTHOR]- Published
- 2022
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6. Measurement of thermal conductivity of paper and corrugated fibreboard with prediction of thermal performance for design applications.
- Author
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Gray-Stuart, E. M., Bronlund, J. E., Navaranjan, N., and Redding, G. P.
- Subjects
THERMAL conductivity ,PAPER ,CORRUGATED paperboard ,HEAT transfer ,FINITE element method - Abstract
Understanding heat transfer in corrugated fibreboard is important to the design of more effective packaging for industries which involve the freezing and chilling of food. In this work the thermal conductivity of papers which compose corrugated fibreboard were measured and used to validate finite element models of heat transfer in fibreboard. The results showed paper to be highly anisotropic, with thermal conductivity in the machine and cross machine directions being almost an order of magnitude larger than in the thickness direction. The finite element models showed good agreement with experimental results and demonstrated that the majority of heat transfer in corrugated fibreboard is though the fluted medium. Based on the finite element models, simple models for the prediction of the thermal performance of corrugated board were evaluated and shown to be very effective in reproducing the results of the more complex finite element methods. These simple methods can be used to perform corrugated fibreboard design calculations, and the models with and without radiation can be used to provide estimates of the lower and upper bounds of the thermal resistance for a given board design. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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7. Author's response to "Discussion on the paper by Schoeftner, J., "A verified analytical sandwich beam model for soft and hard cores: comparison to existing analytical models and finite element calculations", Acta Mech, 234, 2543–2560 (2023)" by Lorenzo Bardella
- Author
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Schoeftner, Juergen
- Subjects
- *
SANDWICH construction (Materials) , *FINITE element method , *WOODEN beams - Abstract
It is pointed out that the Levinson-Reddy beam theory should not be used as a higher-order model for the core, although it considers cross-sectional warping: this beam model is applicable for zero shear stress conditions at the core-skin-interfaces only, which is usually not the case for sandwich structures. The resulting sandwich beam model in [[2]] is a special solution from the Krajcinovic-Bardella derivation, which allows for richer kinematics because it considers zig-zag kinematics. Author's response to "Discussion on the paper by Schoeftner, J., "A verified analytical sandwich beam model for soft and hard cores: comparison to existing analytical models and finite element calculations", Acta Mech, 234, 2543-2560 (2023)" by Lorenzo Bardella. [Extracted from the article]
- Published
- 2023
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8. Finite element analysis (FEA) modelling and experimental verification to optimise flexible electronic packaging for e-textiles.
- Author
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Li, Menglong, Torah, Russel, Liu, Jingqi, Tudor, John, and Beeby, Steve
- Subjects
FINITE element method ,FLEXIBLE packaging ,FLIP chip technology ,ELECTRONIC packaging ,BENDING stresses ,ELECTROTEXTILES ,ELECTRONIC paper - Abstract
In this paper a three-dimensional model of a novel electronic package has been developed using Finite element analysis to evaluate the shear load, tensile, bending and thermal stresses. Simulations of a complete flexible flip chip electronic packaging method are performed to minimize stresses on the packaged electronic device to improve robustness and reliability. Three component under-fill adhesives (Loctite 4860, Loctite 480 and Loctite 4902) and three circuit substrate materials (Kapton, Mylar and PEEK) are compared and the optimal thickness of each is found by shear load, tensile load, bending test and thermal expansion simulations. A fixed die size of 3.5 mm × 8 mm × 0.53 mm has been simulated and evaluated experimentally under shear and bending load. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. The Kapton substrate together with the Loctite 4902 adhesive were identified as the optimum in the simulation. The simulation of under-fill adhesive and substrate thickness identified an optimum configuration of a 0.045–0.052 mm thick substrate layer and a 0.042–0.045 mm thickness of the Loctite 4902 adhesive. The bending simulation has also been used to determine the neutral axis of the encapsulated electronic package in this paper, thus identifying the optimal material and thickness for the encapsulation layer of the package. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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- View/download PDF
9. Humidity influence on mechanics of paper materials: joint numerical and experimental study on fiber and fiber network scale.
- Author
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Lin, Binbin, Auernhammer, Julia, Schäfer, Jan-Lukas, Meckel, Tobias, Stark, Robert, Biesalski, Markus, and Xu, Bai-Xiang
- Subjects
HUMIDITY ,ATOMIC force microscopy ,YOUNG'S modulus ,FINITE element method ,CHEMICAL processes ,COHESIVE strength (Mechanics) ,CELLULOSE fibers - Abstract
Paper materials are well-known to be hydrophilic unless chemical and mechanical processing treatments are undertaken. The relative humidity impacts the fiber elasticity, the interfiber joint behavior and the failure mechanism. In this work, we present a comprehensive experimental and computational study on mechanical properties of the fiber and the fiber network under humidity influence. The manually extracted cellulose fiber is exposed to different levels of humidity, and then mechanically characterized using atomic force microscopy, which delivers the humidity dependent longitudinal Young's modulus. We describe the relation and calibrate the data into an exponential function, and the obtained relationship allows calculation of fiber elastic modulus at any humidity level. Moreover, by using confoncal laser scanning microscopy, the coefficient of hygroscopic expansion of the fibers is determined. We further present a finite element model to simulate the deformation and the failure of the fiber network. The model includes the fiber anisotropy and the hygroscopic expansion using the experimentally determined constants, and further considers interfiber behavior and debonding by using a humidity dependent cohesive zone interface model. Simulations on exemplary fiber network samples are performed to demonstrate the influence of different aspects including relative humidity and fiber-fiber bonding parameters on the mechanical features, such as force-elongation curve, strength and extensibility. Finally, we provide computational insights for interfiber bond damage pattern with respect to different humidity level as further outlook. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
10. Learning to Generate Posters of Scientific Papers by Probabilistic Graphical Models.
- Author
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Qiang, Yu-Ting, Fu, Yan-Wei, Yu, Xiao, Guo, Yan-Wen, Zhou, Zhi-Hua, and Sigal, Leonid
- Subjects
MACHINE learning ,FINITE element method ,DATA analysis ,GRAPHICAL modeling (Statistics) ,OCCUPATIONAL therapy - Abstract
Researchers often summarize their work in the form of scientific posters. Posters provide a coherent and efficient way to convey core ideas expressed in scientific papers. Generating a good scientific poster, however, is a complex and time-consuming cognitive task, since such posters need to be readable, informative, and visually aesthetic. In this paper, for the first time, we study the challenging problem of learning to generate posters from scientific papers. To this end, a data-driven framework, which utilizes graphical models, is proposed. Specifically, given content to display, the key elements of a good poster, including attributes of each panel and arrangements of graphical elements, are learned and inferred from data. During the inference stage, the maximum a posterior (MAP) estimation framework is employed to incorporate some design principles. In order to bridge the gap between panel attributes and the composition within each panel, we also propose a recursive page splitting algorithm to generate the panel layout for a poster. To learn and validate our model, we collect and release a new benchmark dataset, called NJU-Fudan Paper-Poster dataset, which consists of scientific papers and corresponding posters with exhaustively labelled panels and attributes. Qualitative and quantitative results indicate the effectiveness of our approach. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
11. Modeling and ballistic tests of selected soft point projectiles in a water medium.
- Author
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Żochowski, Paweł, Pacek, Dawid, Bednarczyk, Ewa, Bajkowski, Marcin, Grygoruk, Roman, Magier, Mariusz, Szczurowski, Krzysztof, and Jasiński, Marcin
- Subjects
IMPACT (Mechanics) ,FINITE element method ,CRIME laboratories ,FAILURE analysis ,CRIME scenes - Abstract
Methods used nowadays in forensic laboratories allow to stop some kinds of projectiles with degree of deformation which lets to use them for comparing traces to projectiles found on the crime scene. However they are not useful for every type of projectiles. Comparative physical tests are enough to indicate the best method for soft catching projectiles. For this aim point of view no modeling needed. The paper presents the results of ballistic tests of impact of chosen types of soft point projectiles into water. The behavior of projectiles of various shapes, with different kinetic energy, was analyzed. On the basis of the obtained results, the projectiles with the highest susceptibility to deformation were identified. Research works described in the paper were performed within the framework of the project Laboratory stand for stopping high-energy projectiles financed from the National Centre for Research and Development (Agreement no. DOB-BIO10/04/02/ 2019). The project is implemented in cooperation with Warsaw University of Technology, Military Institute of Armament Technology and Tebbex 2 since 2019 to 2022. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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12. Analyse numérique et expérimentale du comportement des ouvrages fondés sur un sol mou renforcé par des colonnes ballastées flottantes.
- Author
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Sadaoui, Omar and Bahar, Ramdane
- Subjects
FINITE element method ,SETTLEMENT of structures ,STONE ,GEOTECHNICAL engineering ,COLLOIDS ,PAPER arts ,BEARING capacity of soils - Abstract
Copyright of Bulletin of Engineering Geology & the Environment is the property of Springer Nature 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.)
- Published
- 2020
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13. Nanoparticle uptake by a semi-permeable, spherical cell from an external planar diffusive field. II. Numerical study of temporal and spatial development validated using FEM.
- Author
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Kumar, Sandeep Santhosh and Miklavcic, Stanley J.
- Abstract
In this paper, we present a mathematical study of particle diffusion inside and outside a spherical biological cell that has been exposed on one side to a propagating planar diffusive front. The media inside and outside the spherical cell are differentiated by their respective diffusion constants. A closed form, large-time, asymptotic solution is derived by the combined means of Laplace transform, separation of variables, and asymptotic series development. The solution process is assisted by means of an effective far-field boundary condition, which is instrumental in resolving the conflict of planar and spherical geometries. The focus of the paper is on a numerical comparison to determine the accuracy of the asymptotic solution relative to a fully numerical solution obtained using the finite element method. The asymptotic solution is shown to be highly effective in capturing the dynamic behaviour of the system, both internal and external to the cell, under a range of diffusive conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
14. Modeling and analysis of the effect of strain gradient to design diaphragm for pressure sensing application through finite element analysis.
- Author
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Ranjan, Prabhat
- Subjects
STRAINS & stresses (Mechanics) ,PRESSURE sensors ,FINITE element method ,FLEXURE - Abstract
Capacitive and optical-based pressure sensors are considered for wide application in industries and R&D labs due to their superior performance. In general, these sensors use a diaphragm as a sensing element that needs to be designed accurately to achieve the desired level of accuracy for a higher operating range of the sensor. To design such a diaphragm, the conventional strain-based model cannot be used efficiently as the strain gradient starts dominating to introduce non-linear deformation with respect to the applied load when the diaphragm thickness reduces or the operating range increases beyond a certain value. Thus, there is a need to establish a comprehensive understanding and accurate modeling method to establish the underlying mechanism of the strain gradient. In view of this, a finite element analysis is carried out with moving-mesh to investigate the effect of the strain gradient phenomenon extensively in this paper. For the investigation, a few parameters are studied such as strain, strain gradient, bending rigidity, and deflection. It shows that the strain gradient spreads radially on the diaphragm and its zone of influence depends on the thickness as well as the applied pressure. This increases the bending rigidity significantly and the diaphragm deflection becomes non-linear as compared to the classical theory of bending. For validation of the present model, the bending rigidity and the deflection behavior are also compared with an earlier developed mathematical model as well as experimental results, and the same is discussed in this paper. The present work is useful for an accurate design and optimization of a diaphragm or a flexure for small size or/and higher operating range of pressure sensors and actuators. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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15. Failure Analysis and Structural Optimization of High-Pressure Reciprocating Y-Shaped Sealing Ring.
- Author
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Li, Jie Wei, Chen, Guo Qiang, Yang, Liu, and Wang, Yue
- Subjects
LATIN hypercube sampling ,OPTIMIZATION algorithms ,STRAINS & stresses (Mechanics) ,FINITE element method ,FAILURE analysis - Abstract
To address the frequent failure of hydraulic seals under high-pressure and high-flow continuous working conditions, optimizing the seal structure through intelligent optimization algorithms can improve performance. This paper proposes an improved intelligent optimization algorithm and finite element analysis to determine the optimal design parameters for the seal. Initially, a visual inspection and analysis of the failed Y-shaped seal revealed causes such as wear failure, damage failure, and leakage. Finite element analysis of the seal under actual working conditions confirmed the previous analysis. The study considered six control design parameters: lip base height, short-long lip length, short lip height, short lip angle, long lip angle, and lip base fillet radius. Using ANSYS, 50 parameter combinations were selected through Latin hypercube sampling for finite element simulation runs, with the maximum shear stress and maximum contact stress as optimization targets. A BP neural network was established and optimized using a genetic algorithm to design the unequal height Y-shaped seal structure based on NSGA-II, with optimization of the root chamfer to increase net pump backflow. The research results show a 7.29% reduction in maximum contact stress of the seal, a 21.4% decrease in maximum shear stress, and an increase of 0.066 mm
3 in net pump backflow through chamfer optimization. The results indicate that this method effectively addresses design issues of seals in industrial applications. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
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16. Research on near field sound pressure of circular piston source based on angular spectrum method.
- Author
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Yi-shu, Zhang and Jie-yuan, Yang
- Subjects
ACOUSTIC field ,SOUND pressure ,ULTRASONIC measurement ,LONGITUDINAL waves ,FINITE element method - Abstract
The accuracy of ultrasonic nondestructive examination is limited by the limitation of near field diffraction. With the development of nearfield optical, angular spectrum method is introduced into the acoustic field, which provides a significant direction for the ultrasonic diffraction limit resolution detection. The main research of this paper is the transmission of near field ultrasound in thin workpiece and the law of the interaction of tiny flaws. The paper establishes the relationship between the longitudinal wave signal and the structure of the workpiece and the types of flaws. A method is found that whether there are flaws can be determined near field area by analysing the acoustic field characteristics of workpiece surface. Finally, comparing the calculation results with the finite element simulation, they verify each other, the method turns out to be correct in this paper. The model can also be used to improve the ultrasonic noise reduction algorithm and the extraction of minimal defect feature. It has a greatly practical significance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
17. Efficient optimization parameter calibration method-based DEM simulation for compacted loess slope under dry–wet cycling.
- Author
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Li, Liang, Hu, Changming, Yuan, Yili, He, Xiaowen, and Wu, Zhipeng
- Subjects
DISCRETE element method ,OPTIMIZATION algorithms ,SLOPE stability ,FINITE element method ,SLOPES (Soil mechanics) ,PARTICLE swarm optimization - Abstract
Dry–wet cycles can cause significant deterioration of compacted loess and thus affect the safety of fill slopes. The discrete element method (DEM) can take into account the non-homogeneous, discontinuous, and anisotropic nature of the geotechnical medium, which is more capable of reflecting the mechanism and process of instability in slope stability analysis. Therefore, this paper proposes to use the DEM to analyze the stability of compacted loess slopes under dry–wet cycles. Firstly, to solve the complex calibration problem between macro and mesoscopic parameters in DEM models, an efficient parameter optimization method was proposed by introducing the chaotic particle swarm optimization with sigmoid-based acceleration coefficients algorithm (CPSOS). Secondly, during the parameter calibration, a new indicator, the bonding ratio (BR), was proposed to characterize the development of pores and cracks in compacted loess during dry–wet cycles, to reflect the impact of dry–wet action on the degradation of bonding between loess aggregates. Finally, according to the results of parameter calibration, the stability analysis model of compacted loess slope under dry–wet cycling was established. The results show that the proposed optimization calibration method can accurately reflect the trend of the stress–strain curve and strength of the actual test results under dry–wet cycles, and the BR also reflects the degradation effect of dry–wet cycles on compacted loess. The slope stability analysis shows that the DEM reflects the negative effect of dry–wet cycles on the safety factor of compacted loess slopes, as well as the trend of gradual stabilization with dry–wet cycles. The comparison with the finite element analysis results verified the accuracy of the discrete element slope stability analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
18. Research on finite element simulation and full-scale-vehicle crash test of B750HL bridge barrier.
- Author
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Zhang, Miao and Bu, Qianmiao
- Subjects
BRIDGES ,CRASH testing ,BRIDGE testing ,FINITE element method ,REINFORCED concrete ,BASES (Architecture) ,BRIDGE floors - Abstract
How to raise the bridge barrier with a concrete base height of only 51 cm to SS level of protection is not yet studied. In order to effectively retrofit an existing concrete barrier design to meet new crash testing criteria, the structural dimensions and concrete strength of the existing bridge barrier were investigated, and finite element simulation analysis was carried out, and simulation suggested the existing barrier was insufficient. Based on the structural dimension design principles of bridge barriers, the existing structure of bridge barrier was designed after adding lightweight and high-strength B750HL material crossbeams and posts on top of the concrete base, and the bearing capacity of the bridge barrier was calculated based on the yield line theory. Then, a finite element simulation analysis model was established to study and analyze the blocking, guiding, and cushioning functions of the improved design of bridge barrier. Finally, full-scale-vehicle crash tests were conducted with the SS-level small car, bus, and tractor-van trailer for this bridge barrier design scheme. This paper is the world's first to use B750HL steel as the material for the crossbeam and post of a bridge barrier with a concrete base height of only 51 cm. According to the research results, the B750HL bridge barrier, which was designed based on the calculation of structural dimension design and yield line theory, effectively reduces the increased constant load on the bridge deck caused by the extra crossbeams and posts. At the same time, it can reduce material costs and save engineering costs. After being verified by finite element simulation crash tests and full-scale-vehicle crash tests, the protective capacity of the B750HL bridge barrier was proven to meet the SS-level evaluation requirements of the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). The research findings of this paper is that the finite element simulation crash tests can effectively simulate full-scale-vehicle crash test, and the finite element simulation crash tests is reliable. If the safety performance of the barrier in the finite element simulation crash tests meets the requirements, the probability of passing the full-scale-vehicle crash test is higher. Therefore, a design scheme is proposed for the B750HL bridge barrier to improve hybrid bridge barriers at a height of 51 cm or more based on various design methods. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
19. A procedure for the experimental identification of the strain gradient characteristic length.
- Author
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Rezaei, Nasrin, Riesselmann, Johannes, Misra, Anil, Balzani, Daniel, and Placidi, Luca
- Subjects
STRAINS & stresses (Mechanics) ,DIGITAL image correlation ,IDENTIFICATION ,DISPLACEMENT (Mechanics) ,PARAMETER identification ,FINITE element method ,PORTLAND cement - Abstract
The aim of this paper is to propose an experimental procedure for determining the characteristic length of a strain gradient model. The identification problem is studied through a virtual pull-out test of a rigid bar along the symmetry axis of a cylindrical strain gradient elastic domain. To allow an accurate parameter identification based on measured data, we investigate the effect of the characteristic length on the mechanical fields for this problem. We see a significant sensitivity of the inflection point of the displacement profile evaluated on the cross section of the cylinder, with respect to the characteristic length. By adjusting the characteristic length of the strain gradient such that the theoretical models match best with experimental measurements of the surface displacement fields, the characteristic length of the strain gradient can be estimated. In order to allow for more efficient analysis and an almost real-time parameter identification, the initial three-dimensional (3D) problem is reduced to a one-dimensional (1D) problem by exploiting the cylindrical symmetry of the problem. As will be shown, an accurate 1D finite element method (FEM) strain gradient solution can be obtained for this simplified problem. Since the cylindrical symmetry is only true in an infinitely long cylinder, specific boundary conditions are constructed on a cylinder of finite length, which is then used for the comparison of the 1D and 3D problems. Results show, however, that the structural response at the inflection point is insensitive to whether the specific boundary conditions are considered or not, which is why the 1D model can be used for parameter identification. Since the proposed approach is methodological, it can be applied to any material. As a prototype problem in this paper, we consider the case of a bar embedded in Portland cement concrete. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
20. Estimation of nosing load in existing railway transom top bridges based on field testing and finite element modelling.
- Author
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Ghiasi, Alireza and Lee, Daniel
- Subjects
FINITE element method ,FINITE fields ,BRIDGES ,BRIDGE testing ,NOSE - Abstract
A significant number of wind bracings in existing railway transom top bridges are numerically assessed deficient against the assessment nosing load recommended by the AS5100, where in almost all cases, there is no observed evidence of wind bracings being overloaded. This paper estimates the nosing load applied by various trains to a couple of random spans of an existing railway transom top bridge. Firstly, field testing of this bridge is conducted and the measured stresses at the mid-center of girders and wind bracings are collected during various normal train operations to validate the developed Finite Element (FE) models of this bridge. Then, the nosing loads due to different trains are estimated using the validated FE model through a two-staged validation approach, including automatic FE stress intensity optimization and rigorous manual FE model sensitivity analysis while transoms in various conditions are also incorporated in the FE model. Results demonstrate that the nosing load is significantly less than the required load in the AS5100 with magnitudes ranging between 8.6% to 9.4% of the maximum vertical axle load of the passed trains; suggesting that the AS5100 assessment nosing load should be revised to avoid unnecessary expensive upgrades of numerically assessed deficient wind bracings. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
21. Protection of Whipple shield against hypervelocity impact of space debris: a review.
- Author
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Singh, Pradeep Kumar and Kumar, Manoj
- Subjects
SPACE debris ,HYPERVELOCITY ,EARTH'S orbit ,FINITE element method ,EQUATIONS of state - Abstract
The space debris in Earth's orbit has increased drastically due to the failure of spacecraft, rocket bodies, and mission-related objects. These objects in orbit increase the space waste and challenge other flying objects such as spacecraft. A hypervelocity impact of space debris on spacecraft structures can have a range of effects (mechanical damage and functional failure), raising significant concerns about spacecraft safety. This paper reviews the different studies on the performance and development of the Whipple shield against the hypervelocity impact of space debris. The study focuses on the impact mechanism, dynamic Fragmentation of materials, strength models, Equation of state, characteristics, and model of the debris cloud. The strength models (Steinberg–Guinan and Johnson–Cook) and Mie–Gruneisen equation of state, primarily used for hypervelocity impact applications, are thoroughly covered in this study. The study also reported the various experimental and numerical techniques for high and hypervelocity impact. The study concluded that mesh-based, mesh-free, and hybrid finite element methods are reliable for analyzing Whipple shield targets to resist hypervelocity impact. The study also observed that the two-stage light gas gun technique investigates most experimental analyses of hypervelocity impact on the Whipple shield. Alongside reviewing the abovementioned aspects, this paper also underlines the future scope of study in this paradigm. The authors strongly believe that this study provides more insights into the fundamentals and perceptions of the Whipple shield to protect the spacecraft against the hypervelocity impact of space debris. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
22. Method for characterization of soil electrical resistivity based on Wenner measurements by means of Nelder–Mead algorithm and FEM calculations.
- Author
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Stanišić, Stevan M. and Radaković, Zoran R.
- Subjects
HIGH-voltage direct current transmission ,ELECTRICAL resistivity ,FINITE element method ,SOILS ,PARAMETER estimation - Abstract
Soil resistivity is the key parameter influencing resistance and potential distribution on the soil surface for grounding systems and electrodes for HVDC power transmission. The paper presents a novel approach that does not rely on analytical expressions or simplifications inherent in the Wenner and classical characterization methods for obtaining a layered soil model. The new method and corresponding computational tool are implemented as an iterative process using a finite element method coupled with a numerical parameter estimation solver. The novel method is applied on soil with a very thin and highly resistive surface layer compared to a resistivity of a lower layer, where accurate implementation of the classical method would require Wenner measurements for short electrode spacings a. Since the classical characterization methods rely on the assumption that the electrode driving depth b is much smaller than a, it is practically (physically) impossible to drive the electrodes to sufficiently small depth b. The application of the novel method and a comparison with the classical approach are presented on examples including normal soils, one hypothetical soil with a thin highly resistive surface layer, and one experimental desert location. The application of the proposed method leads to an extreme increase in the characterization accuracy for the case of ideal two-layer soil with thin high resistivity topsoil justifying considerable computational time. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
23. Free Vibration Analysis of Curved Beam with Variable Curvature (Elliptic Line) Based on Semi-analytical Method of Structural Mechanics.
- Author
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Li, Xiaofei, Zhai, Haosen, and Pan, Zhouyang
- Subjects
CURVED beams ,FREE vibration ,STRUCTURAL mechanics ,ARCH bridges ,CURVATURE ,FREQUENCIES of oscillating systems - Abstract
Objective: To study the free vibration problem of a variable curvature beam different from the conventional circular model. Methods: Based on the principle of virtual work, an analytical expression of in-plane displacement of a beam with variable curvature fixed at both ends under concentrated load is established in this paper. The flexibility matrix and stiffness matrix of curved beam are obtained by Moore integral calculation, and the mass matrix of variable curvature beam is obtained by lumped mass method. The stiffness matrix and mass matrix are transformed by static condensation method, and the natural vibration frequency of the beam with variable curvature is obtained. The finite element simulation model of the actual curved bridge and the laboratory curved arch model are established, and the simulation analysis results and laboratory measurement results are compared with the results in this paper. Conclusion: It is proved that the theory presented in this study has good engineering application and can be used as the theoretical basis for the structural research and design of the variable curvature bridge. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
24. Evaluation of wave configurations in corrugated boards by experimental analysis (EA) and finite element modeling (FEM): the role of the micro-wave in packaging design.
- Author
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Di Russo, Franco Maria, Desole, Maria Maria, Gisario, Annamaria, and Barletta, Massimiliano
- Subjects
FINITE element method ,PACKAGING design ,TENSILE tests - Abstract
The aim of this paper is to study the mechanical behavior of corrugated board boxes, focusing attention on the strength that the boxes are able to offer in compression under stacking conditions. A preliminary design of the corrugated cardboard structures starting from the definition of each individual layer, namely the outer liners and the innermost flute, was carried out. For this purpose, three distinct types of corrugated board structures that include flutes with different characteristics, namely the high wave (C), the medium wave (B), and even the micro-wave (E), were comparatively evaluated. More specifically, the comparison is able to show the potential of the micro-wave which would eventually allow a significant saving of cellulose in the fabrication process of the boxes, thus reducing the manufacturing costs and causing a lower environmental footprint. First, experimental tests were carried out to determine the mechanical properties of the different layers of the corrugated board structures. Tensile tests were performed on samples extracted from the paper reels used as base material for the manufacturing of the liners and flutes. Instead, the edge crush test (ECT) and box compression test (BCT) were directly performed on the corrugated cardboard structures. Secondly, a parametric finite element (FE) model to allow, on a comparative basis, the study of the mechanical response of the three different types of corrugated cardboard structures was developed. Lastly, a comparison between the available experimental results and the outputs of the FE model was carried out, with the same model being also adapted to evaluate additional structures where the E micro-wave was usefully combined with the B or C wave in a double-wave configuration. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. Experimental and Numerical Investigations of an Asymmetric Multi-Bolted Connection Preloaded and Subjected to Monotonic Loads.
- Author
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Grzejda, R., Kwiatkowski, K., and Parus, A.
- Subjects
BOLTED joints ,FINITE element method ,STRAIN gages ,COMPRESSIVE force ,SHEARING force - Abstract
Experimental tests of a seven-bolted connection with an asymmetric contact area between the joined elements are presented. The research is divided into two stages. In the first one, the connection is preloaded in a three-pass cycle. In the second stage, the connection is loaded with a monotonic alternating force applied at an angle of 30 degrees to the contact surface of the joined elements to generate compressive and shear forces in the connection. The tests are carried out with the use of the INSTRON 8850 testing machine. As a result, the courses of forces in the bolts measured with the use of resistance strain gauges and the relative displacements between the joined elements measured with an extensometer are shown. In the second part, the modeling of the connection in the convention of the finite element method is presented. The joined elements are modeled with the use of spatial finite elements, and the fasteners, as the hybrid elements made of deformable beams, rigid heads, and rigid nuts. The paper is completed with a comparison of the results obtained from the measurements and calculations, based on which the conclusions important from the point of view of the FEM analysis are drawn. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
26. A novel evolutionary method for parameter-free MEMS structural design and its application in piezoresistive pressure sensors.
- Author
-
Meng, Qinggang, Wang, Junbo, Chen, Deyong, Chen, Jian, Xie, Bo, and Lu, Yulan
- Subjects
PRESSURE sensors ,STRUCTURAL design ,MEMS resonators ,FINITE element method ,DEGREES of freedom ,EVOLUTIONARY algorithms ,ADHESIVE tape - Abstract
In this paper, a novel simulation-based evolutionary method is presented for designing parameter-free MEMS structures with maximum degrees of freedom. This novel design method enabled semiautomatic structure evolution by weighing the attributes of each segment of the structure and yielded an optimal design after multiple iterations. The proposed method was utilized to optimize the pressure-sensitive diaphragm of a piezoresistive pressure sensor (PPS). Finite element method (FEM) simulations revealed that, in comparison to conventional diaphragms without islands and with square islands, the optimized diaphragm increased the stress by 10% and 16% and reduced the nonlinearity by 57% and 77%, respectively. These improvements demonstrate the value of this method. Characterization of the fabricated PPS revealed a high sensitivity of 8.8 mV V
−1 MPa−1 and a low nonlinearity of 0.058% FS at 20 °C, indicating excellent sensor performance. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
27. Influence of structural characteristics for overhead ground wire on arc root under lightning strike.
- Author
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Guo, Deming, Liu, Gang, Chen, Haobin, Wang, Peifeng, and Lin, Xuan
- Subjects
LIGHTNING ,DAMAGE models ,VACUUM arcs ,LIGHTNING protection ,CURRENT distribution ,IRON & steel plates - Abstract
When overhead ground wire (OGW) is struck by lightning, the damage or rupture accident occur. This is unacceptable for the stable operation of the power system. Therefore, the investigation on the lightning-induced damage mechanism of OGW is significant for the optimization of lightning protection measures. Combined with the structural characteristics of OGW, this paper evaluated the thermal ablation damage of OGW caused by lightning strike, which provided the data support for the damage mechanism research. Firstly, the magnetohydrodynamics (MHD) models based on OGW and plate structure were established. The current density distributions as well as the arc root radii of OGW and plate under lightning strikes were compared. The thermal ablation damage model of OGW was also established. The influence of arc root radius on thermal ablation damage evaluation of OGW under continuing component of lightning current was analyzed. The results show that the arc root radius of lightning striking OGW is reduced by at least 50% compared with that of lightning striking plate. When using arc root radius of OGW for modeling, the results of the thermal ablation damage model are consistent with the reported experimental results. The maximum error is 9.80%. While the arc root radius of plate is adopted, there is an obvious difference between the thermal ablation damage model and the experimental results. The maximum error exceeds 20%. Therefore, in the numerical modeling of thermal ablation damage of OGW, it is necessary to consider the influence of structural characteristics of OGW on arc root radius. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
28. Friction Characteristics Between Marine Clay and Construction Materials.
- Author
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Kou, Hailei, Huang, Jiaming, and Cheng, Yang
- Abstract
Structure-soil interface friction characteristics is of importance to investigate the interaction between engineering structures and soils, especially for offshore structures. The interface friction behavior between marine clay and structural materials with different roughness was studied in this paper by using 3D optical scanning tests, a modified direct shear device and numerical simulation. Relationships between the surface roughness of structures, water content and interface friction angle were presented by model tests. The increase of water contents decreased the interface friction angles. For interfaces with different roughness, the interface friction angles will be smaller than that of the soil when the water content exceeds a certain value. The roughness of the interface and the water content of the soil are mutually coupled to influence the coefficient of friction (COF). This paper proposed a Finite Element Method (FEM) to simulate the interface direct shear tests of structures with different roughness. The surface models with different roughness are established based on the structure data obtained by 3D scanning. The Coupled Eulerian-Lagrangian (CEL) approach was employed to analyse soils sheared by irregular surfaces. The interface behavior for interfaces with different roughness under cyclic shear stresses was analyzed by FEM. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
29. Eccentricity fault detection in synchronous reluctance machines.
- Author
-
Hooshmandi Safa, Hossein and Abootorabi Zarchi, Hossein
- Subjects
RELUCTANCE motors ,ECCENTRICS (Machinery) ,AIR gap flux ,FAST Fourier transforms ,SYNCHRONOUS electric motors ,FINITE element method - Abstract
This paper introduces a novel index for static eccentricity (SE) fault diagnosis in synchronous reluctance motors (SynRMs). Although SynRMs with rotor barriers under SE have been modeled in a few papers, any indices for the fault detection have not yet been reported. The proposed index is a specific frequency pattern in the motor current, which can also determine the fault severity. A novel analytical magnetic field investigation is applied to ascertain the proposed index. An accurate nonlinear numerical method is proposed for the motor inductances calculation. The model considers the rotor flux barriers, magnetic saturation, and the stator slots effect. The air gap flux density and the motor current are then achieved. The fast Fourier transform is exploited as a signal-processing tool to calculate motor current spectra. Then, a two-dimension time-stepping finite element method is used to attest of the proposed numerical model. Effectiveness of the proposed index is verified by simulation and experimental tests. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. Multi-objective optimization of a V-type line-start PM motor based on parameter stratification and RSM.
- Author
-
Abroshan, Arash, Hasanzadeh, Saeed, and Rahmani Fard, Javad
- Subjects
ANT algorithms ,RESPONSE surfaces (Statistics) ,FINITE element method ,PERMANENT magnets ,PERMANENT magnet motors - Abstract
In order to reduce the cogging torque of a symmetrical V-type line-start permanent magnet synchronous (LSPMS) motor, this paper proposes a multi-objective optimization method based on the combination of design parameter stratification and response surface methodology (RSM). The optimal solution to the RSM model is acquired using the max–min ant algorithm. The permanent magnet width, pole opening angle, stator slot width, rotor axial length, and rotor tooth width are selected as optimization variables. The cogging torque and average torque are the optimization objectives. Finite element method (FEM) results show that the cogging torque is reduced by 71.5%, the torque ripple is reduced by 65.6%, and the average torque is improved by 12%. Finally, the effectiveness of the algorithm is verified with simulation results. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Modeling fluid flow in fractured porous media: a comparative analysis between Darcy–Darcy model and Stokes–Brinkman model.
- Author
-
Dudun, Anireju and Feng, Yin
- Subjects
POROUS materials ,FLUID flow ,STOKES flow ,STEADY-state flow ,COMPARATIVE studies ,DARCY'S law - Abstract
There are limited comparative studies on modeling fluid transport in fractured porous media. Hence, this paper systematically compares the steady-state creeping flow Stokes–Brinkman and Darcy–Darcy models for computational efficiency and accuracy. Sensitivity analyses were also conducted on the effect of fracture orientations, fracture sizes, mesh resolution, and fractures with Local Grid Refinement (LGR) under the FEniCS computational framework. Both models were validated numerically, and the accuracy of their solution is compared using the R-squared metric and L2 norm estimates. Key results showed that both models have similar pressure and velocity field solutions for a given fracture orientation. The computational time required for solving the Stokes–Brinkman models for a single fracture case was unusually lower than that of the Darcy–Darcy model when the pressure and velocity terms in the Darcy–Darcy model were solved simultaneously using two equations, contrary to where only one equation solves for the pressure and the velocity is obtained by projecting the gradient of pressure onto a vector space. The Stokes–Brinkman model is more sensitive to mesh resolution, and as a result, the Darcy–Darcy model tends to be more accurate than the Stokes–Brinkman model at low resolutions. Local Grid Refinement (LGR) can improve the Stokes–Brinkman model's accuracy at low mesh resolution. Furthermore, both models showed similar results when compared for complex fracture systems such as multiple fracture cases: interconnecting and isolated fractured porous media systems under low-velocity and steady-state creeping flow conditions. The FEniCS code in this paper is shared for future researchers to reproduce results or extend the research work. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
32. A new approach for fast field calculation in electrostatic electron lens design and optimization.
- Author
-
Hesam Mahmoudi Nezhad, Neda, Ghaffarian Niasar, Mohamad, Hagen, Cornelis W., and Kruit, Pieter
- Subjects
ELECTROSTATIC fields ,FINITE difference method ,BOUNDARY element methods ,FINITE element method ,ELECTRON optics - Abstract
In electron optics, calculation of the electric field plays a major role in all computations and simulations. Accurate field calculation methods such as the finite element method (FEM), boundary element method and finite difference method, have been used for years. However, such methods are computationally very expensive and make the computer simulation challenging or even infeasible when trying to apply automated design of electrostatic lens systems with many free parameters. Hence, for years, electron optics scientists have been searching for a fast and accurate method of field calculation to tackle the aforementioned problem in the design and optimization of electrostatic electron lens systems. This paper presents a novel method for fast electric field calculation in electrostatic electron lens systems with reasonably high accuracy to enable the electron-optical designers to design and optimize an electrostatic lens system with many free parameters in a reasonably short time. The essence of the method is to express the off-axis potential in an axially symmetrical coordinate system in terms of derivatives of the axial potential up to the fourth order, and equate this to the potential of the electrode at that axial position. Doing this for a limited number of axial positions, we get a set of equations that can be solved to obtain the axial potential, necessary for calculating the lens properties. We name this method the fourth-order electrode method because we take the axial derivatives up to the fourth order. To solve the equations, a quintic spline approximation of the axial potential is calculated by solving three sets of linear equations simultaneously. The sets of equations are extracted from the Laplace equation and the fundamental equations that describe a quintic spline. The accuracy and speed of this method is compared with other field calculation methods, such as the FEM and second order electrode method (SOEM). The new field calculation method is implemented in design/optimization of electrostatic lens systems by using a genetic algorithm based optimization program for electrostatic lens systems developed by the authors. The effectiveness of this new field calculation method in optimizing optical parameters of electrostatic lens systems is compared with FEM and SOEM and the results are presented. It should be noted that the formulation is derived for general axis symmetrical electrostatic electron lens systems, however the examples shown in this paper are with cylindrical electrodes due to the simplicity of the implementation in the software. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. Effects of testing speed on the tensile and mode I fracture behavior of specimens printed through the Fused Deposition Modeling technique.
- Author
-
Zhan, Jiangtao, Cai, Jie, and Hasani, Reza
- Subjects
FUSED deposition modeling ,TENSILE strength ,FINITE element method ,MANUFACTURING processes - Abstract
Additive Manufacturing (AM) processes are known as revolutionary manufacturing processes that fabricate a part using a 3D model layer upon layer. These techniques gained more attention from various industries due to their advantages like low waste material. Also, these processes can produce any part with high degrees of complexity in a short period of time. The Fused Deposition Modeling (FDM) process is a material extrusion-based technique which works by extruding a fine molten polymeric filament through a heated nozzle on the heated platform named printer bed. In this method, some important manufacturing parameters play a crucial role in controlling the mechanical properties and quality of the final fabricated part. However, all printed specimens through the FDM process should be tested based on the standards under some critical circumstances. Thus, in the current research paper, five and three test speeds are considered in tensile and fracture testing procedures, respectively to evaluate how these speeds can affect the mechanical and mode I fracture properties. Also, as the FDM specimens present elastic–plastic behavior, the critical value of J-integral is assumed as a fracture assessment and calculated from the finite element analysis. Among the mechanical properties, ultimate tensile strength is affected significantly by the test speed. For instance, the ultimate tensile strength of FDM specimens is 39.02, 38.58, 42.33, 48.09, and 52.11 for test speeds of 2, 4, 6, 8, and 10 mm/min, respectively. But vice-versa results are detected for the mode I fracture behavior and corresponding values of J for the FDM-PLA specimens. Finally, experimental and numerical results together with comprehensive discussions about the considered speeds and obtained results are reported. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
34. Unstructured surface mesh smoothing method based on deep reinforcement learning.
- Author
-
Wang, Nianhua, Zhang, Laiping, and Deng, Xiaogang
- Subjects
DEEP reinforcement learning ,REINFORCEMENT learning ,MESH networks ,COMPUTATIONAL fluid dynamics ,FINITE element method ,HEURISTIC - Abstract
In numerical simulations such as computational fluid dynamics simulations or finite element analyses, mesh quality affects simulation accuracy directly and significantly. Smoothing is one of the most widely adopted methods to improve unstructured mesh quality in mesh generation practices. Compared with the optimization-based smoothing method, heuristic smoothing methods are efficient but yield lower mesh quality. The balance between smoothing efficiency and mesh quality has been pursued in previous studies. In this paper, we propose a new smoothing method that combines the advantages of the heuristic Laplacian method and the optimization-based method based on the deep reinforcement learning method under the Deep Deterministic Policy Gradient framework. Within the framework, the actor artificial neural network predicts the optimal position of each interior free node with its surrounding ring nodes. At the same time, a critic-network is established and takes the mesh quality as input and outputs the reward of the action taken by the actor-network. Training of the networks will maximize the cumulative long-term reward, which ends up maximizing the mesh quality. Training and validation of the proposed method are presented both on 2-dimensional triangular meshes and 3-dimensional surface meshes, which demonstrates the efficiency and mesh quality of the proposed method. Finally, numerical simulations on perturbed meshes and smoothed meshes are carried out and compared which prove the influence of mesh quality on the simulation accuracy. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
35. Performance-Based Seismic Fragility Analysis of a Double-Tower Structure with a Large Podium.
- Author
-
Zhang, Shangrong, Tan, Jinbao, Li, Shihao, and Hu, Yuchen
- Subjects
TOWERS ,EARTHQUAKE damage ,ENERGY dissipation ,FINITE element method ,MULTI-degree of freedom ,EARTHQUAKES - Abstract
Purpose: Considering the sudden change of the structure shape of a double-tower structure with a large podium (DTS), the mechanical properties of the structure under earthquake are extremely complex. Therefore, it is very important to evaluate the seismic fragility of new structures such as the DTS under different control schemes. This paper uses the seismic fragility analysis method based on IDA to study the seismic performance of the DTS. By comparing and analyzing the control effects of different control schemes, the advantages of composite passive control schemes are highlighted, which provides a theoretical basis for pre-earthquake disaster prevention and post-earthquake damage assessment of the DTS. Methods: With the aim of minimizing the mean–variance of the total vibration energy of the structure, the optimal control parameters of the energy dissipation damper are obtained by combining theoretical analysis with finite element simulation. Then the optimal arrangement scheme of the energy dissipation damper is determined by arrangement and combination. Considering that the previous structural performance level division methods cannot accurately reflect the results of the seismic fragility analysis of the DTS, the performance grade and damage grade of the structure were divided into five limit states and six damage degrees for the first time in this paper, and on this basis, the seismic fragility analysis of the DTS under two different control schemes was carried out based on IDA. Results: The response curves of each substructure of the equivalent single-DOF model are consistent with those of the multi-degree-of-freedom layer shear model (multi-DOF model), which indicates the validity and rationality of the equivalent single-DOF model are verified. Conclusion: The research shows that the equivalent single-DOF model of the DTS avoids a large number of iterative calculations, improves the calculation efficiency, retains the accuracy of the multi-DOF model, and has good applicability and rationality. In addition, the finite element simulation results show that the failure of the DTS under the two control schemes is caused by the failure of the isolation bearing. Compared with the LIC scheme, the CPC scheme improves the structure's seismic performance as a whole. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
36. Refined Finite Elements for the Analysis of Metallic Plates Using Carrera Unified Formulation.
- Author
-
Teng, Wenxiang, Liu, Pengyu, Hu, Kun, and He, Jipeng
- Subjects
FINITE element method ,METALS ,STRUCTURAL frame models ,TAYLOR'S series ,DIFFERENTIAL equations ,DIGITAL image correlation - Abstract
Purpose: In order to solve the problem that the existing models can't accurately reproduce the mechanical properties of metallic plates under complex working conditions, and the accuracy and efficiency can't be satisfied at the same time. The analysis of metallic plates by different refined finite elements is presented in this paper. The working efficiency and accuracy of the higher-order model in engineering applications are studied. Methods: The refined plate elements are based on several series expansion, and applied to the modeling and analysis of plate structures. The Carrera unified formulation is introduced to express the plate displacement field, the theoretical model of plate thickness expansion is established by using Taylor series expansion and Lagrange series expansion. The governing differential equations of metallic plate are established by using the principle of virtual displacements, the mass matrix and stiffness matrix of plate elements are deduced simultaneously. Finally, the shear locking phenomenon of the plate models is considered, tensor component mixed interpolation (MITC4) is used to revise the model. The accuracy and the reliability of the refined plate models are verified by comparing several order models and solid models generated in the commercial software ANSYS. Results and Conclusion: In this paper, the higher-order model has very low degree of freedoms (DOFs) on the premise of ensuring accuracy. And this modeling method can be used not only for thin plate analysis, but also for medium-thick plate analysis. Meanwhile, the refined plate model has high working efficiency and wide application range, which provides a new modeling method for the research of metallic plates. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
37. Dynamic of an inhomogeneous three-layer sphere under cyclic pressure.
- Author
-
Zhang, Xi-meng and Qi, Hui
- Subjects
- *
SPHERICAL waves , *ALGEBRAIC equations , *STRESS concentration , *EULER equations , *FINITE element method - Abstract
In this paper, the dynamic characteristics of inhomogeneous three-layer spheres under spherical wave induced by cyclic pressure are studied. The density is assumed to have a square of inverse proportional function distribution along the radius. Firstly, on the basis of Lamb decomposition and variable separation method, the analytical expression of spherical wave is conducted, which satisfies the stress equilibrium on the outer and inner surfaces of the sphere, and the Euler equation is obtained due to inhomogeneity. Next, algebraic equations with respective boundary conditions are composed and solved by effective truncation techniques. Finally, a comparison and discussion are conducted between the model presented in this article and the homogeneous model obtained by the Legendre polynomial expansion. Obtained results enable to reveal the influence on the dynamic stress concentration factor intensity under proper conditions. The conclusions of this article are verified by comparing the analytical solutions to the ones obtained by finite element method. This paper can provide a theoretical method for the analysis of mechanical properties of inhomogeneous multilayered spherical structure under dynamic loading. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
38. An analytical and FEM simulation-based study of the dependence of capacitance profile on structural parameters of CMUT with and without vent.
- Author
-
Ghosh Dastidar, Avik, Maity, Reshmi, Tiwari, R. C., Dutta, Shankar, and Maity, Niladri Pratap
- Subjects
ALUMINUM electrodes ,SILICON nitride ,FINITE element method ,ELECTRIC capacity ,TRANSDUCERS - Abstract
This paper presents the capacitive behaviour of a Capacitive Micromachined Ultrasound Transducer (CMUT). A Finite Element Method (FEM)-based simulation is proposed to characterize the capacitance of CMUT with different geometrical parameters. The structure of the CMUT under scrutiny consists of an aluminum top electrode on a thin movable membrane of silicon nitride (Si
3 N4 ) separated by an air gap from the bottom electrode. The capacitance of the CMUT plays an important role in its proper functionality. The current study attempts to explore the calculation and variation of capacitance with different geometrical parameters. Because of the smaller dimension of the device, the effect of fringing is also taken into account. A new empirical formulation has been developed to study the capacitance of the CMUT with vented cavities, and the accuracy of the theory is justified with FEM simulation for single-vented CMUT. The analytical results are validated with simulation and published experimental results. Keeping the similar geometrical shape of the fabricated structure, this model predicts 94.28 kHz resonant frequency which is very close to the experimental result (106 kHz). [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
39. A simple extension of Timoshenko beam model to describe dissipation in cementitious elements.
- Author
-
Aretusi, Giuliano, Cardillo, Christian, Salvatori, Antonello, Bednarczyk, Ewa, and Fedele, Roberto
- Subjects
ELASTIC deformation ,FINGER joint ,VIRTUAL work ,FINITE element method ,ENERGY dissipation - Abstract
In this paper, an extension of the Timoshenko model for plane beams is outlined, with the aim of describing, under the assumption of small displacements and strains, a class of dissipative mechanisms observed in cementitious materials. In the spirit of micromorphic continua, the modified beam model includes a novel kinematic descriptor, conceived as an average sliding relevant to a density of micro-cracks not varying along time. For the pairs of rough surfaces, in which such a distribution of micro-cracks is articulated, both an elastic deformation and a frictional dissipation are considered, similarly to what occurs for the fingers of the joints having a tooth saw profile. The system of governing differential equations, of the second order, is provided by a variational approach, endowed by standard boundary conditions. To this purpose, a generalized version of the principle of virtual work is used, in the spirit of Hamilton–Rayleigh approach, including as contributions: (i) the variation of the inner elastic energy, generated by the linear elasticity of the sound material and, in a nonlinear way, by the mutual, reversible deformation of the asperities inside the micro-cracks; (ii) the virtual work of the external actions consistent with the beam model, i.e., the distributed transversal forces and the moments per unit lengths; besides these two contributions, constituting the conservative part of the system, (iii) the dissipation due to friction specified through a smooth Rayleigh potential, entering a nonlinear dependence of viscous and Coulomb type on the sliding rate. Through a COMSOL Multiphysics implementation, 1D finite element analyses are carried out to simulate structural elements subjected to three- and four-point bending tests with alternating loading cycles. The dissipation of energy is investigated at varying the model parameters, and the predictions turn out to be in agreement with preliminary data from an experimental campaign. The present approach is expected to provide a valuable tool for the quantitative and comparative assessment of the hysteresis cycles, favoring the robust design of cementitious materials. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
40. Simulation of blind pre-diction and post-diction shaking table tests on a masonry building aggregate using a continuum modelling approach.
- Author
-
Aşıkoğlu, Abide, D'Anna, Jennifer, Ramirez, Rafael, Solarino, Fabio, Romanazzi, Antonio, Ciocci, Maria Pia, and Bianchini, Nicoletta
- Subjects
STONEMASONRY ,SHAKING table tests ,FINITE element method ,MASONRY testing ,SEISMIC testing - Abstract
Masonry buildings of historical centres are usually organized within aggregates, whose structural performance against seismic actions is challenging to predict and constitutes still an open issue. The SERA—AIMS (Seismic Testing of Adjacent Interacting Masonry Structures) project was developed to provide additional experimental data by testing a half-scale, two-unit stone masonry aggregate subjected to two horizontal components of dynamic excitation. In this context, this paper investigates the reliability of the modelling approach and the assumptions adopted to generate a three-dimensional continuum finite element model. The work involves two stages, namely a blind pre-diction and a post-diction phase, and proposes a series of simulation analyses including a strategy to shorten the actual records and save computation costs. The study was performed to investigate the extent of uncertainty in modelling for such masonry aggregates in relation to the experimental outcomes. Pre-diction results were proven to be not accurate in terms of predicted displacements and damage patterns. The upgrades introduced for the post-diction analyses, including the calibration of the elastic modulus and the introduction of a non-linear interface between the two units, allowed to improve the outcomes, with reasonable results in terms of predicted base shear force, displacements along Y-direction and damage pattern for the non-linear stage. The overall approach showed to be appropriate for the structural analysis of existing masonry aggregates, but the accurate modelling of this type of structure remains challenging due to the high level of uncertainties. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
41. Influence of wall-to-floor connections and pounding on pre- and post-diction simulations of a masonry building aggregate tested on a shaking table.
- Author
-
Bianchini, N., Ciocci, M. P., Solarino, F., Romanazzi, A., Ramirez, R., D'Anna, J., and Aşıkoğlu, A.
- Subjects
SHAKING table tests ,STONEMASONRY ,WOOD floors ,FINITE element method ,SEISMIC testing - Abstract
This paper presents numerical simulations within the frame of the project SERA—AIMS (Seismic Testing of Adjacent Interacting Masonry Structures). The study includes blind pre-diction and post-diction stages. The former was developed before performing the shaking table tests at the laboratory facilities of LNEC (Lisbon), while the latter was carried out once the test results were known. For both, three-dimensional finite element models were prepared following a macro-modelling approach. The structure consisted of a half-scaled masonry aggregate composed by two units with different floor levels. Material properties used for the pre-diction model were based on preliminary tests previously provided to the participants. The masonry constitutive model used for the pre-diction study reproduced classical stress–strain envelope, whereas a more refined model was adopted for the post-diction. After eigenvalue analysis, incremental nonlinear time history analysis was performed under a unique sequence based on the given load protocol to account for damage accumulation. In the post-diction, the numerical model was calibrated on the data recorded during the shaking table tests and nonlinear dynamic analysis repeated under the recorded accelerogram sequence. The interaction between the two units was simulated through interface elements. Moreover, the timber floors were accounted following different strategies: not modelling or considering nonlinear wall-to-floor connections. Advantages and disadvantages are then analysed, comparing the pre-diction and post-diction results with the experimental data. Numerical results differ from the experimental outcomes regarding displacements and interface pounding, although a clear improvement is visible in the post-diction model. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. A new method for identifying elastic parameters of isotropic materials based on square specimens.
- Author
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Zhang, Longxin, Zhang, Wenbin, Xu, Han, and Ma, Yaxing
- Subjects
POISSON'S ratio ,YOUNG'S modulus ,FINITE element method ,SYSTEM identification ,TEST methods - Abstract
This paper proposes a new impulse excitation technique using a square plate. First, the functional relationship between the modal frequency of the specimen and the geometrical dimensions and mechanical parameters was established by using the finite element method. Then, the continuous functional relationship derived by a homotopy method allowed the frequency ratios to be related to the thickness-to-length ratio and Poisson's ratio. By measuring the frequency ratios and thickness-to-length ratio, Poisson's ratio could be calculated using this functional relationship. When the density and Poisson's ratio were known, Young's modulus could be identified inversely in conjunction with the finite element analysis. Finally, a comparison test between this method and the traditional impulse excitation technique was designed and implemented, and the results showed that this method has advantages in both testing efficiency and accuracy. The study provides a new idea for system identification, which has important application value and promotion significance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
43. Performance analysis of high voltage disc insulators with different profiles in clean and polluted environments using flashover, withstand voltage tests and finite element analysis.
- Author
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Ali, Arfan, Bhatti, Abdul Rauf, Rasool, Akhtar, Rehman, Fazal Ur, Khan, Muhammad Amjad, Ali, Ahmed, and Sherefa, Abdulkerim
- Subjects
FLASHOVER ,FINITE element method ,HIGH voltages ,ELECTRIC fields ,VOLTAGE ,SYSTEM safety ,POWER presses - Abstract
Severe pollution-induced flashovers on insulators present a pressing challenge to power system safety. The frequent failure of high-voltage insulators, particularly in the polluted environments of Pakistan, poses a critical concern. This paper investigates the impact of insulator profile on reducing pollution flashovers, testing two designs as per IEC standard 60383 and simulated using the Finite Element Method in COMSOL Multiphysics®. The test results revealed that deep under-ribs insulators exhibited a 5.008% reduction in flashover voltage, while alternating shed insulators experienced a 3.233% decrease in polluted conditions compared to clean conditions. Notably, under both clean and polluted conditions, alternating shed insulators consistently outperformed deep under-ribs insulators, with a 25.377% higher flashover voltage in clean conditions and a 27.400% superiority in polluted conditions. Computational analysis through the Finite Element Method in COMSOL Multiphysics shows a consistent pattern in potential distribution with increasing insulator count, but the presence of a pollution layer introduces spikes in the electric field distribution, validating experimental results. These findings highlight the superior performance of alternating shed insulators, especially in polluted environments. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. Numerical study on the forward and inverse problems of the mobile pump truck frame.
- Author
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Zhang, Yu-Liang, Lin, Hai-Bin, and Zhu, Zu-Chao
- Subjects
VIBRATION (Mechanics) ,INVERSE problems ,DYNAMIC mechanical analysis ,FINITE element method ,TRUCKS ,DISTRACTED driving - Abstract
Aiming at the requirements of strong mobility and high flexibility of rescue and relief mobile pump trucks, this paper designs a new type of mobile pump truck frame based on existing mobile vehicle frame models. The materials used for the frame are 40Cr and Q235, and the finite element method is utilized to carry out static mechanical analysis and dynamic characteristic analysis. Simultaneously utilizing topology optimization and multi-objective genetic algorithm to optimize the design of the frame structure. The results show that the optimized pump truck frame can meet the strength design requirements of four typical working conditions: full load bending, full load torsion, emergency turning and emergency braking, while avoiding resonance phenomena caused by road surface and diesel engine vibration. Compared with the original frame model, the weight of the optimized frame is reduced by 87.88 kg, with a weight reduction rate of 10.89%, realizing the lightweight design requirements. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Improving the sensitivity of a plasmonic photonic crystal fiber temperature sensor by introducing an array of nanoscale gold rods.
- Author
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Sonne, Abdelkader, Saleh, Chaker Mohsen Naser, and Oudenani, Ahmed
- Subjects
- *
SURFACE plasmon resonance , *LIQUID crystals , *TEMPERATURE sensors , *FINITE element method , *SENSOR arrays - Abstract
An ultrasensitive temperature sensor based on photonic crystal fiber (PCF) filled with liquid crystal and nanogold rods using surface plasmon resonance (SPR) is numerically analyzed in this paper. Gold is selected as a plasmonic metal to excite the SPR phenomenon. This paper shows a comparative study and inspects the effect of temperature sensing performance between one big gold rod and lattice of nanoscale gold rods. A finite element method (FEM) using COMSOL software has been applied for the investigation of some propagation characteristics of the PCF sensor. From the numerical results, it is observed that introducing an array of nanoscale gold rods helps to obtain high temperature sensitivity. After watchful investigation, the maximum sensitivities of 23 nm/°C have been achieved as the temperature changes from 30 °C to 40 °C. Compared with some previously reported temperature sensors, our proposed temperature sensor shows excellent sensitivity performances. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
46. Pre- and in-process dimensional compensation in the selective thermoplastic electrophotographic process.
- Author
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Shan, Shuo, Yeh, Hao-Ping, Hansen, Hans Nørgaard, Hattel, Jesper Henri, Zhang, Yang, and Calaon, Matteo
- Abstract
As a cutting-edge additive manufacturing (AM) technology, the selective thermoplastic electrophotographic process (STEP) has opened up possibilities for mass production with its combination of real engineering plastics and potential high part quality. To improve the accuracy and fidelity of STEP for the most demanding applications, this paper proposes a novel method encompassing both pre-processing and in-process dimensional compensations. Iterative compensation before production is achieved through physics-driven simulation, resulting in input masks that better match the required dimensions at the design level. Layer-wise compensation is implemented during the production process through the laser profiler system, thereby suppressing the accumulation of surface unevenness during printing. With the compensation method proposed in this paper, the maximum distortion during simulated printing is decreased by 86.2%, and surface unevenness is effectively controlled during the printing process. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
47. Parametric investigation of railway fastenings into the formation and mitigation of short pitch corrugation.
- Author
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Zhang, Pan, Li, Shaoguang, Dollevoet, Rolf, and Li, Zili
- Subjects
CONTACT mechanics ,STRUCTURAL dynamics ,FINITE element method ,FASTENERS ,DYNAMIC models - Abstract
Short pitch corrugation has been a problem for railways worldwide over one century. In this paper, a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation. A three-dimensional finite element vehicle–track dynamic interaction model is employed, which considers the coupling between the structural dynamics and the contact mechanics, while the damage mechanism is assumed to be differential wear. Various fastening models with different configurations, boundary conditions, and parameters of stiffness and damping are built up and analysed. These models may represent different service stages of fastenings in the field. Besides, the effect of train speeds on corrugation features is studied. The results indicate: (1) Fastening parameters and modelling play an important role in corrugation formation. (2) The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation. The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components. (3) The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation. Meanwhile, the inner fastening constraint in the lateral direction is necessary for corrugation alleviation. (4) The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity. The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components. It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed, which is caused by frequency selection and jump between rail longitudinal compression modes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
48. The Collapse of World Trade Center 7: Revisited.
- Author
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Orabi, Mhd Anwar, Jiang, Liming, Usmani, Asif, and Torero, Jose
- Subjects
FINITE element method ,COLUMNS ,STRUCTURAL frames ,STEEL framing ,SEPTEMBER 11 Terrorist Attacks, 2001 ,PROGRESSIVE collapse - Abstract
The catastrophic events of September 11, 2001, stand out as a major motivation for research on improving the understanding of structural behaviour in fire. These events included the first complete collapse of a tall steel framed structure solely due to fire. World Trade Center 7 (WTC7) was a 47-storey office building within the WTC complex that collapsed due to a fire initiated by debris from the collapse of WTC1. In the following years, detailed investigations were carried out by expert teams to pinpoint the cause of the progressive failure of WTC7. Each of the expert teams analysed the fire and structure and made varying conclusions with regards to the mechanisms responsible for initiating and propagating the collapse of the building. This paper revisits the collapse of WTC7 and its investigation, and then explores the hypothesis that a potential hydrocarbon fire may have compromised the large transfer structure within the mechanical space of the building. This is done via two OpenSees finite element models. The first model explores the thermomechanical response of the mechanical floors to a potential diesel fire, and the second investigates the response of the structure to a failure caused by that fire. The outcome of the analyses shows that it is feasible that a mechanical room fire could lead to a failure in the transfer structure, which would then result in the loss of support to at least two columns within the building core. The failure of these columns may unbrace the eastern-most core columns and precipitate in the failure of the structure as observed on 9/11. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. A two-level iterative method with Newton-type linearization for the stationary micropolar fluid equations.
- Author
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Xing, Xin and Liu, Demin
- Subjects
FINITE element method ,EQUATIONS ,FLUIDS - Abstract
In this paper, a two-level Newton iterative method is proposed for the stationary micropolar fluid equations. Firstly, the original equations are solved on a coarse grid based on Newton-type linearization. Then, the simplified linearized equations are solved on a fine grid. The stability and error estimates of the method are given in the theoretical part. The results of the theoretical analysis show that when the coarse mesh size H and fine mesh size h satisfy the relation h = O (H 2) , the two-level Newton iterative method can achieve an optimal convergence rate. Finally, the effectiveness and applicability of the method are verified by some numerical experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
50. Computational algorithms for solving optimal control in linear elasticity.
- Author
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Thi Thanh Mai, Ta and Quang Huy, Nguyen
- Abstract
This paper mainly investigates linear elastic optimal control problems with two constraints: distributed load control and boundary load control. The gradient of the objective functional is derived via an adjoint problem. We obtain the H 1 -regularity for the distributed control solution. Moreover, we establish a suitable finite element interpolation to deal with the non-optimal regularity of the boundary control solution. The error estimates for the fully discretized problems is given. Then, together with the interior point method, a new numerical method for the optimal control of linear elasticity is exhibited. Finally, the effectiveness of presented scheme is demonstrated by various numerical simulations in two and three-space dimensions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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