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1 – 10 of over 10000Sharnappa, N. Ganesan and Raju Sethuraman
The purpose of this paper is to present numerical studies on thermally induced vibrations of piezo‐thermo‐viscoelastic composite beam subjected to a transient thermal load using…
Abstract
Purpose
The purpose of this paper is to present numerical studies on thermally induced vibrations of piezo‐thermo‐viscoelastic composite beam subjected to a transient thermal load using coupled finite element method.
Design/methodology/approach
The thermal relaxation and viscoelastic relaxations are taken into consideration to obtain the system response. The concept of “memory load” along with the thermal relaxation is accounted for viscoelastic core material. The influence of type of core material on the response of the system also analyzed.
Findings
The findings show viscoelastic behavior with relaxation times in composite sandwich structures.
Originality/value
The paper shows accounting relaxation times as a memory load in composite sandwich structures.
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Carlos Enrique Torres-Aguilar, Pedro Moreno-Bernal, Jesús Xamán, Ivett Zavala Guillen and Irving Osiris Hernández-López
This paper aims to present an evolutionary algorithm (EA) to accelerate the convergence for the radiative transfer equation (RTE) numerical solution using high-order and…
Abstract
Purpose
This paper aims to present an evolutionary algorithm (EA) to accelerate the convergence for the radiative transfer equation (RTE) numerical solution using high-order and high-resolution schemes by the relaxation coefficients optimization.
Design methodology/approach
The objective function minimizes the residual value difference between iterations in each control volume until its difference is lower than the convergence criterion. The EA approach is evaluated in two configurations, a two-dimensional cavity with scattering media and absorbing media.
Findings
Experimental results show the capacity to obtain the numerical solution for both cases on all interpolation schemes tested by the EA approach. The EA approach reduces CPU time for the RTE numerical solution using SUPERBEE, SWEBY and MUSCL schemes until 97% and 135% in scattering and absorbing media cases, respectively. The relaxation coefficients optimized every two numerical solution iterations achieve a significant reduction of the CPU time compared to the deferred correction procedure with fixed relaxation coefficients.
Originality/value
The proposed EA approach for the RTE numerical solution effectively reduces the CPU time compared to the DC procedure with fixed relaxation coefficients.
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A.E. Johnson, J. Henderson and V.D. Mathur
The nature of the relation between complex stress creep under conditions of relaxation and complex stress creep under conditions of steady stress was investigated. The required…
Abstract
The nature of the relation between complex stress creep under conditions of relaxation and complex stress creep under conditions of steady stress was investigated. The required relation has been examined for an RR59 aluminium alloy at 200 deg. C. and for a magnesium (2 per cent aluminium) alloy at 50 deg. C. For RR59 aluminium alloy at 200 deg. C. and for magnesium (2 per cent aluminium) alloy at 50 deg. C., a reasonably close prediction of the course of relaxation complex stress time curves is given by the mechanical age hardening theory of creep on the basis of steady complex stress creep data. Other mechanical theories tend to predict for a specific relaxed stress a relaxation time in excess of that noted in experiment.
Mica Grujicic, Jennifer Snipes, Subrahmanian Ramaswami, Rohan Galgalikar, James Runt and James Tarter
Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft…
Abstract
Purpose
Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft (i.e. low glass transition temperature) matrix. A number of experimental investigations reported in the open literature clearly demonstrated that the use of polyurea external coatings and/or internal linings can significantly increase blast survivability and ballistic penetration resistance of target structures, such as vehicles, buildings and field/laboratory test-plates. When designing blast/ballistic-threat survivable polyurea-coated structures, advanced computational methods and tools are being increasingly utilized. A critical aspect of this computational approach is the availability of physically based, high-fidelity polyurea material models. The paper aims to discuss these issues.
Design/methodology/approach
In the present work, an attempt is made to develop a material model for polyurea which will include the effects of soft-matrix chain-segment molecular weight and the extent and morphology of hard-domain nano-segregation. Since these aspects of polyurea microstructure can be controlled through the selection of polyurea chemistry and synthesis conditions, and the present material model enables the prediction of polyurea blast-mitigation capacity and ballistic resistance, the model offers the potential for the “material-by-design” approach.
Findings
The model is validated by comparing its predictions with the corresponding experimental data.
Originality/value
The work clearly demonstrated that, in order to maximize shock-mitigation effects offered by polyurea, chemistry and processing/synthesis route of this material should be optimized.
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Atif Alkhazali, Morad Etier, Mohammad Aljarrah, Akram Alsukker and Fathy Salman
The purpose of this study is to investigate the effect of the considerable Ag2SO4 content on the electrical and dielectric properties of (AgPO3)1−x(Ag2SO4)x ion glass system as…
Abstract
Purpose
The purpose of this study is to investigate the effect of the considerable Ag2SO4 content on the electrical and dielectric properties of (AgPO3)1−x(Ag2SO4)x ion glass system as well as to extract thermodynamic parameters.
Design/methodology/approach
Glass samples of (AgPO3)1-x(Ag2SO4)x with different mole ratios of Ag2SO4 [x = 0.00, 0.10,0.15,0.20 and 0.25] have been synthesized and used. X-ray diffraction and differential thermal analysis were used to investigate structural and thermal properties, and then the electrical characterizations of the bulk glasses were performed in different frequency and temperature range.
Findings
For different ratios of Ag2SO4 on AgPO3, the bulk conductivity is enhanced with increasing the amount of Ag2SO4 until the composition of x = 0.20, after which the conductivity decreases. The general behavior of both ε’ and ε” decreases with increasing frequency and increases with increasing temperature. Complex impedance analysis studied by Z‘−Z’ and Cole–Cole plot at different temperatures revealed that bulk resistance decreases with temperature.
Originality/value
The calculated values of activation free energy, enthalpy and entropy change for different compositions of (AgPO3)1-x(Ag2SO4)x showed an increase in activation energy and enthalpy when Ag2SO4 ratio is increased in (AgPO3)1-x(Ag2SO4)x composition up to 20%, and then there is a decrease in their values at x = 25%, which may be explained based on non-bridging oxygen.
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A.E. Johnson, J. Henderson and V.D. Mathur
As stated in general terms in a previous paragraph, in the ease of this material the following complex stress relaxation tests were made: two pure torsion tests from initial…
Abstract
As stated in general terms in a previous paragraph, in the ease of this material the following complex stress relaxation tests were made: two pure torsion tests from initial stresses of 4 tons/sq. in. and 3 tons/sq. in.; two tests having a stress ratio T/S=0·4 and having initial stress values of T=1·6, S=4 and T=1·2, S=3 tons/sq. in. in the two cases; two tests having a stress ratio T/S=0·8 and having initial stress values T=3·2, S=4 and T=2·62, S=3·28 tons/sq. in. respectively; and finally one test having a stress ratio T/S=1·5 and having an initial stress value T=4·5 and S=3 tons/sq. in. (i.e. a total of seven tests).
T.V. Mihailovic, Nikolic and Lj.M. Simovic
Examines the resistance to creasing of a group of clothing wool fabrics by measuring the crease recovery angle in a definite time interval. Determines the boundary zones of…
Abstract
Examines the resistance to creasing of a group of clothing wool fabrics by measuring the crease recovery angle in a definite time interval. Determines the boundary zones of elastic, viscoelastic and plastic deformation component values as well as the relaxation velocity. Describes through results the behaviour of clothing wool fabrics in conditions to which they are exposed during wearing.
Evgeny L. Pankratov and Elena A. Bulaeva
It has been recently shown that diffusion of dopant during doping of inhomogeneous structure could be accelerated or decelerated in comparison with diffusion of dopant in…
Abstract
Purpose
It has been recently shown that diffusion of dopant during doping of inhomogeneous structure could be accelerated or decelerated in comparison with diffusion of dopant in structure with averaged diffusion coefficient. As a continuation of previous work, the purpose of this paper is to introduce an approach of estimating the limited value of acceleration of the dopant diffusion by choosing the dependence of the dopant diffusion coefficient on the coordinates.
Design/methodology/approach
The authors analyzed relaxation of concentration of dopant during diffusion in inhomogeneous material. The authors determine conditions for maximal acceleration and deceleration of diffusion of dopant. The authors introduced analytical approach for analysis of dopant diffusion in inhomogeneous material.
Findings
The authors determine conditions for maximal acceleration and deceleration of diffusion of dopant.
Originality/value
It has been shown that dopant diffusion could be decelerated essentially to a greater extent, rather than accelerated.
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Ali Ayyed Abdul-Kadhim, Fue-Sang Lien and Eugene Yee
This study aims to modify the standard probabilistic lattice Boltzmann methodology (LBM) cellular automata (CA) algorithm to enable a more realistic and accurate computation of…
Abstract
Purpose
This study aims to modify the standard probabilistic lattice Boltzmann methodology (LBM) cellular automata (CA) algorithm to enable a more realistic and accurate computation of the ensemble rather than individual particle trajectories that need to be updated from one time step to the next (allowing, as such, a fraction of the collection of particles in any lattice grid cell to be updated in a time step, rather than the entire collection of particles as in the standard LBM-CA algorithm leading to a better representation of the dynamic interaction between the particles and the background flow). Exploitation of the inherent parallelism of the modified LBM-CA algorithm to provide a computationally efficient scheme for computation of particle-laden flows on readily available commodity general-purpose graphics processing units (GPGPUs).
Design/methodology/approach
This paper presents a framework for the implementation of a LBM for the simulation of particle transport and deposition in complex flows on a GPGPU. Towards this objective, the authors have shown how to map the data structure of the LBM with a multiple-relaxation-time (MRT) collision operator and the Smagorinsky subgrid-scale turbulence model (for turbulent fluid flow simulations) coupled with a CA probabilistic method (for particle transport and deposition simulations) to a GPGPU to give a high-performance computing tool for the calculation of particle-laden flows.
Findings
A fluid-particle simulation using our LBM-MRT-CA algorithm run on a single GPGPU was 160 times as computationally efficient as the same algorithm run on a single CPU.
Research limitations/implications
The method is limited by the available computational resources (e.g. GPU memory size).
Originality/value
A new 3D LBM-MRT-CA model was developed to simulate the particle transport and deposition in complex laminar and turbulent flows with different hydrodynamic characteristics (e.g. vortex shedding, impingement, free shear layer, turbulent boundary layer). The solid particle information is encapsulated locally at the lattice grid nodes, allowing for straightforward mapping of the datastructure onto a GPGPU enabling a massive parallel execution of the LBM-MRT-CA algorithm. The new particle transport algorithm was based on the local (bulk) particle density and velocity and provides more realistic results for the particle transport and deposition than the standard LBM-CA algorithm.
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Against the background of the fact that solder joints crack owing to thermal cycling, the method of predicting the lifetime of a solder joint is critically discussed. The…
Abstract
Against the background of the fact that solder joints crack owing to thermal cycling, the method of predicting the lifetime of a solder joint is critically discussed. The conclusion is that the working conditions of the solder joints have to be carefully analysed and to be brought into agreement with the material properties. On the basis of experimental values, it is shown how this can be done. Creep, relaxation and fatigue of solder joints are discussed.