A quasi-nonlocal coupling method for bond-based peridynamics with classical continuum mechanics

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Feng Jiang ◽  
Yongxing Shen
Keyword(s):  
Patch Test ◽  
Continuum Mechanics ◽  
Coupling Method ◽  
Coupling Scheme ◽  
Dimensional Problem ◽  
Nonlocal Coupling ◽  
Coupling Region ◽  
Content Type ◽  
Peridynamic Model ◽  
Ghost Force

PurposeThe purpose of this paper is to propose a novel quasi-nonlocal coupling of the bond-based peridynamic model with the classical continuum mechanics model to fully take advantage of their merits and be free of ghost forces.Design/methodology/approachThis study reconstructs a total energy functional by introducing a coupling parameter that alters only the nonlocal interactions in the coupling region rather than the whole region and a modified elasticity tensor that affects the local interactions. Then, the consistency of force patch test is enforced in the coupling region to completely eliminate the ghost force in a general energy-based coupling scheme. For a one-dimensional problem, these coupling parameters are further determined through an energy patch test to preserve the energy equivalence or through an l1-regularization. And, for a two- or three-dimensional problem, depending on the existence of a solution to the discretized force patch test, they are determined through an l1-minimization or l1-regularization.FindingsOne- and two-dimensional numerical examples under affine deformation have been conducted to verify the accuracy of the quasi-nonlocal coupling method, which exhibits no ghost force. Moreover, the coupling model can reproduce almost the same deformation behaviors of points near the crack for a cracked plate under tension as that from a pure peridynamic model, the former with a rather low computational cost and an easier application of boundary conditions.Originality/valueThis work is aiming at getting over long-standing ghost force issues in the energy-based coupling scheme. The numerical results from the cracked plate problem are exhibited promising extension to dynamic problems.

A compact, broadband three-way substrate integrated waveguide power divider with improved isolation

Circuit World ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Arun Kumar Gande ◽  
Souma Guha Mallick ◽  
Bijit Biswas ◽  
Sayan Chatterjee ◽  
Dipak Ranjan Poddar
Keyword(s):  
Return Loss ◽  
Power Divider ◽  
Substrate Integrated Waveguide ◽  
Fractional Bandwidth ◽  
Coupling Region ◽  
Content Type ◽  
Power Dividers ◽  
Power Coupling ◽  
Input And Output ◽  
Input Matching

Purpose This paper aims to present a compact, broadband substrate integrated waveguide (SIW) three-way power divider with improved isolation based on six-port SIW coupler. Design/methodology/approach The power coupling among the three output ports occurs due to short openings in the narrow walls of the central SIW channel. Performance improvement in the isolation and return loss among ports is achieved using matching posts placed at the input and output ends of the coupling region. This enhances the coupling between TE10 and TE30 modes. The input matching ports enhance the return loss, whereas the isolation is alleviated by both the input and output matching posts. The bandwidth enhancement is achieved by optimizing the outer SIW channel widths. Findings The measured fractional bandwidth of 27.3% with over 15 dB of isolation and return loss is achieved. The coupling length is 1.55 λg at the centre frequency. The power divider achieves better than 15 dB isolation between non-adjacent output ports. The measured reflection and isolation coefficients are in close agreement with simulated results over 8.2 to 10.8 GHz. Practical implications Isolation between the adjacent and non-adjacent ports is an important parameter as the reflections from these ports will interfere with signals from other ports reducing the fractional bandwidth of the power divider and affecting the overall performance of the transmitters and receivers. Originality/value The authors present the enhancement of isolation between the output non-adjacent ports by optimizing the SIW channel width and matching post in the coupling region to reduce the reflected signals from non-adjacent ports entering into other ports. To the author’s knowledge, this is the only SIW three-way power divider paper showing non-adjacent port isolation among six-port couplers based three-way power dividers.

Fuzzy combinatorial optimization in four-dimensional tradeoff problem of cost-time-quality-risk in one dimension and in the second dimension of risk context in ambiguous mode

2020 ◽  
Vol 37 (6) ◽  
pp. 1967-1991
Author(s):  
Farhad Hosseinzadeh ◽  
Behzad Paryzad ◽  
Nasser Shahsavari Pour ◽  
Esmaeil Najafi
Keyword(s):  
Fuzzy Logic ◽  
Combinatorial Optimization ◽  
Fuzzy Numbers ◽  
Critical Path ◽  
One Dimension ◽  
Radius Of Gyration ◽  
Special Technique ◽  
Dimensional Problem ◽  
Content Type ◽  
Quality Risk

Purpose The optimization and tradeoff of cost-time-quality-risk in one dimension and this four-dimensional problem in ambiguous mode and risk can be neither predicted nor estimated. This study aims to solve this problem and rank fuzzy numbers using an innovative algorithm “STHD” and a special technique “radius of gyration” (ROG) for fuzzy answers, respectively. Design/methodology/approach First, it is the optimization of a fully fuzzy four-dimensional problem which has never been dealt with in regard to risk in ambiguous mode and complexities. Therefore, the risk is a parameter which has been examined neither in probability and estimableness mode nor in the ambiguous mode so far. Second, it is a fully fuzzy tradeoff which, based on the principle of incompatibility “Zadeh, 1973”, proposes that when the complexity of a system surpasses the limited point, it becomes impossible to define the performance of that system accurately, precisely and meaningfully. The authors believe that this principle is the source of fuzzy logic. Third, for calculating and ranking fuzzy numbers of answers, a special technique for fuzzy numbers has been used. Fourth, For the sake of ease, precision and efficiency, an innovative algorithm called the technique of hunting dolphins “STHD” has been used. Finally, the problem is very close to reality. By applying risk in ambiguous mode, the problem has been realistically looked at. Findings The results showed that the algorithm was highly robust, with its performance depending very little on the regulation of the parameters. Ranking fuzzy numbers using the ROG indicated the flexibility of fuzzy logic, and it was also determined that the most appropriate regulations were to ensure low time, risk and cost but maximum quality in calculations, which were produced non-uniformly based on the levels of Pareto answers. Originality/value The ROG and Chanas Fuzzy Critical Path Method as developed by other researchers have been used. Despite the increase in limitations, parameters can develop. The originality of this study with regard to evaluating the results of tradeoff combinatorial optimization is upon decision-making which has a special and highly strategic role in the fate of the project, with the research been conducted with a special approach and different tools in a fully fuzzy environment.

Flutter Study on High Speed Train External Windshield by a Tight Coupling Method

2019 ◽  
Author(s):  
Qian Jiang ◽  
Guannan Zheng ◽  
Guilin Zhao
Keyword(s):  
Information Transfer ◽  
High Speed ◽  
Stable State ◽  
Coupling Method ◽  
Coupling Scheme ◽  
Displacement Curve ◽  
High Speed Train ◽  
Tight Coupling ◽  
Time Step ◽  
Train Speed

Abstract Flutter is a complex problem caused by the interaction between the elastic structure and the flow field around that. In this paper a study of flutter on high speed train external windshield is presented. Here, a coupling scheme of computational fluid dynamics (CFD) and computational structure dynamics (CSD) is applied to simulate the flutter problems. Specifically, some key technologies like tight coupling method, information transfer and mesh deformation strategy are involved. Repeatedly exchanging information in the sub-iteration of physical time step is basically typical of tight coupling method, which is a second-order accuracy method. This flutter methodology has been applied for standard model AGARD 445.6 wing and other engineering examples, with lots of excellent results obtained. In this high speed train external windshield flutter research, eight train speed conditions are chosen to simulate the flutter issue, including 250km/h, 300km/h, 350km/h, 400 km/h, 450 km/h, 500 km/h, 550 km/h and 600 km/h. As for structural model, the first 30 order modes of elastic windshield are taken into consideration for CFD/CSD coupling simulation. In addition, it is defined to be the flutter boundary once the generalized displacement curve performing as persistent oscillation, which is the critical stable state for the vibration of external windshield. According to the research, under a specific train speed condition, adjustment of modal eigenfrequency can lead to the change of vibration stability. Furthermore, it is found that there is a positive correlation between train speed and modal eigenfrequency. So the optimal windshield scheme under different operating speeds is proposed that in order for the convergent vibration, a measure of changing eigenfrequency can be taken to ensure the vibration convergent and flutter cannot occur.

Antibacterial evaluation of activated carbon cloth with Ag+ impregnated with ZnO nanoparticles

2019 ◽  
Vol 23 (3) ◽  
pp. 232-243 ◽  
Author(s):  
Sharifatul Ain Binti Sharifuddin ◽  
Salwani Binti Ismail ◽  
Imran Abdullah ◽  
Irfan Mohamad ◽  
Javeed Shaikh Mohammed
Keyword(s):  
Antibacterial Activity ◽  
Activated Carbon ◽  
Patch Test ◽  
Human Skin ◽  
Disk Diffusion ◽  
Carbon Cloth ◽  
Activated Carbon Cloth ◽  
Zno Nps ◽  
Content Type ◽  
Susceptibility Assay

Purpose Staphylococcus aureus (S. aureus), Klebsiella pneumoniae (K. pneumoniae) and Streptococcus pneumoniae (S. pneumoniae) are among the pathogens detected during Hajj pilgrimage known to cause pneumonia. This study aims to evaluate the antibacterial activity of activated carbon cloth (ACC) with Ag+ impregnated with zinc oxide nanoparticles (ZnO NPs) against these pathogens. Design/methodology/approach ZnO NPs were impregnated into ACC-Ag+ via layer-by-layer (LbL) self-assembly. Scanning electron microscope (SEM) was used to observe the fine surface morphological details of the ACC-Ag+-ZnO sheets. Antibacterial activity of the ACC-Ag+-ZnO sheets was evaluated using the disk-diffusion susceptibility assay. Allergy patch test was done to evaluate allergic reactions of the ACC-Ag+-ZnO sheets on human skin. Findings SEM micrographs showed successful impregnation of ZnO NPs into the ACC-Ag+ sheets. Disk-diffusion susceptibility assay results of ACC-Ag+-ZnO sheets against S. aureus, K. pneumoniae and S. pneumoniae showed good antibacterial activity; with 1.82 ± 0.13 mm zone of inhibition for S. pneumoniae, at a ZnO concentration of 0.78 mg mL-1. No signs of human skin irritation were observed throughout the allergy patch test. Originality/value Results indicate that ACC-Ag+-ZnO sheets could potentially be embedded within surgical face masks (pilgrims’ preferred) to reduce the risks involved with the transmission of respiratory tract infections during and after mass gatherings (e.g. Hajj/Umrah, Olympics).

scholarly journals A Quasi-nonlocal Coupling Method for Nonlocal and Local Diffusion Models

2018 ◽  
Vol 56 (3) ◽  
pp. 1386-1404 ◽  
Author(s):  
Qiang Du ◽  
Xingjie Helen Li ◽  
Jianfeng Lu ◽  
Xiaochuan Tian
Keyword(s):  
Diffusion Models ◽  
Coupling Method ◽  
Nonlocal Coupling ◽  
Local Diffusion

scholarly journals Quasistatic Fracture using Nonliner-Nonlocal Elastostatics with Explicit Tangent Stiffness Matrix

2021 ◽  
Author(s):  
Patrick Diehl ◽  
Robert Lipton
Keyword(s):  
Continuum Mechanics ◽  
Elastic Material ◽  
Stiffness Matrix ◽  
Material Behavior ◽  
Test Problems ◽  
Tangent Stiffness ◽  
Tangent Stiffness Matrix ◽  
Fracture Simulation ◽  
Peridynamic Model ◽  
Quasistatic Fracture

We apply a nonlinear-nonlocal field theory for numerical calculation of quasistatic fracture. The model is given by a regularized nonlinear pairwise (RNP) potential in a peridynamic formulation. The potential function is given by an explicit formula with and explicit first and second derivatives. This fact allows us to write the entries of the tangent stiffness matrix explicitly thereby saving computational costs during the assembly of the tangent stiffness matrix. We validate our approach against classical continuum mechanics for the linear elastic material behavior. In addition, we compare our approach to a state-based peridynamic model that uses standard numerical derivations to assemble the tangent stiffness matrix. The numerical experiments show that for elastic material behavior our approach agrees with both classical continuum mechanics and the state-based model.The fracture model is applied to produce a fracture simulation for a ASTM E8 like tension test. We conclude with an example of crack growth in a pre-cracked square plate. For the pre-cracked plate, we investigated {\it soft loading} (load in force) and {\it hard loading} (load in displacement). Our approach is novel in that only bond softening is used as opposed to bond breaking. For the fracture simulation we have shown that our approach works with and without initial damage for two common test problems.

scholarly journals Hybrid atomistic-continuum simulation of nucleate boiling with domain re-decomposition method

2017 ◽  
Author(s):  
◽  
Bo Zhang
Keyword(s):  
Molecular Dynamics ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Coupling Method ◽  
Dynamics Simulation ◽  
Small Scale ◽  
Coupling Scheme ◽  
Atomistic Region ◽  
Continuum Mechanic Model ◽  
Promising Solution

The bubble nucleation plays a pivotal role in the boiling process. In order to have a comprehensive understanding of this phenomenon, a critical consideration on fluid-solid interaction at atomistic level is imperative. However, traditional Molecular Dynamics simulation requires prohibited amount of computational efforts to accomplish a full scale study. Hybrid atomistic-continuum method is a promising solution for this problem. It limits the atomistic region to a small scale where detailed information is preferable, while using continuum method for the rest of the domain. Nevertheless, none of the current hybrid method is suitable for solving a rapid expanding system like the bubble nucleation. In this study, a domain re-decomposition hybrid atomistic-continuum method is developed to conduct a multiscale/multiphase investigation on the bubble nucleation. In addition to the conventional coupling scheme, this method is capable to re-partition the molecular and continuum domain once it is necessary during the simulation. That is, the Computational Fluid Dynamics (CFD) and Molecular Dynamics (MD) regions are interchangeable on the fly such that the bubble is absolutely confined within MD region. Giving the fact that accurate modeling of interface tracking and phase change are still problematic for continuum mechanics on microscale, our coupling method directly avoids these issues since CFD domain takes care of a single-phase flow while the molecular domain simulates the bubble growth. With this idea in mind, this approach enables us to investigate the nucleate boiling on nanostructured surface with higher resolution than complete continuum mechanic model based simulation. In the present result, it is observed that bubble grows at a curved surface imposed with a constant super heat after nucleate boiling occurs. Meanwhile, the energy flux flows from solid to fluid is measured during the entire process. It is believed that this coupling method is very promising in studying nano-bubble related multiphase problems on microscale.

scholarly journals Simulation of electrical machines: a FEM-BEM coupling scheme

2017 ◽  
Vol 36 (5) ◽  
pp. 1540-1551 ◽  
Author(s):  
Lars Kielhorn ◽  
Thomas Rüberg ◽  
Jürgen Zechner
Keyword(s):  
Boundary Integral Equations ◽  
Boundary Integral ◽  
Boundary Element Methods ◽  
Electrical Machines ◽  
Special Treatment ◽  
Coupling Scheme ◽  
Computational Domain ◽  
Efficient Treatment ◽  
Content Type ◽  
Moving Parts

Purpose Electrical machines commonly consist of moving and stationary parts. The field simulation of such devices can be demanding if the underlying numerical scheme is solely based on a domain discretization, such as in the case of the finite element method (FEM). This paper aims to present a coupling scheme based on FEM together with boundary element methods (BEMs) that neither hinges on re-meshing techniques nor deals with a special treatment of sliding interfaces. While the numerics are certainly more involved, the reward is obvious: the modeling costs decrease and the application engineer is provided with an easy-to-use, versatile and accurate simulation tool. Design/methodology/approach The authors present the implementation of a FEM-BEM coupling scheme in which the unbounded air region is handled by the BEM, while only the solid parts are discretized by the FEM. The BEM is a convenient tool to tackle unbounded exterior domains, as it is based on the discretization of boundary integral equations (BIEs) that are defined only on the surface of the computational domain. Hence, no meshing is required for the air region. Further, the BIEs fulfill the decay and radiation conditions of the electromagnetic fields such that no additional modeling errors occur. Findings This work presents an implementation of a FEM-BEM coupling scheme for electromagnetic field simulations. The coupling eliminates problems that are inherent to a pure FEM approach. In detail, the benefits of the FEM-BEM scheme are: the decay conditions are fulfilled exactly, no meshing of parts of the exterior air region is necessary and, most importantly, the handling of moving parts is incorporated in an intriguingly simple manner. The FEM-BEM formulation in conjunction with a state-of-the-art preconditioner demonstrates its potency. The numerical tests not only reveal an accurate convergence behavior but also prove the algorithm to be suitable for industrial applications. Originality/value The presented FEM-BEM scheme is a mathematically sound and robust implementation of a theoretical work presented a decade ago. For the application within an industrial context, the original work has been extended by higher-order schemes, periodic boundary conditions and an efficient treatment of moving parts. While not intended to be used under all circumstances, it represents a powerful tool in case that high accuracies together with simple mesh-handling facilities are required.

Sign in / Sign up

Export Citation Format

Share Document