Engineering

Restrictively preconditioned Chebyshev method for solving systems of linear equations
The restrictive preconditioning technique applied to Chebyshev semi-iterative methods for solving a nonsingular system of linear equations is studied. Motivated by the fact that linear systems involving a preconditioner are solved inexactly at each step, we present the inexact restrictively preconditioned Chebyshev method. The convergence behaviors of the new methods are analyzed, particularly ...


Fingering phenomena in immiscible displacement in porous media flow
Pressure-driven displacement of one fluid by another in porous media has many applications, including oil production and the removal of soil contaminants. When the displacing fluid is less viscous, an idealized flat displacement front is ill-posed with respect to the growth of transverse perturbations (Taylor–Saffman instability). In models that include relative permeabilities, a macroscopic ...
Partitioning strategies for the block Cimmino algorithm
In the context of the block Cimmino algorithm, we study preprocessing strategies to obtain block partitionings that can be applied to general linear systems of equations (mathbf{A}mathbf{x}= mathbf{b}). We study strategies that transform the matrix (mathbf{A}mathbf{A}^mathrm{{T}}) into a matrix with a block tridiagonal structure. This provides a partitioning of the linear system for row project...


A class of exact solutions of the Liénard-type ordinary nonlinear differential equation
A class of exact solutions is obtained for the Liénard-type ordinary nonlinear differential equation. As a first step in our study, the second-order Liénard-type equation is transformed into a first Abel kind, first order differential equation. With the use of an exact integrability condition for the Abel equation (Chiellini lemma), the exact general solution of the Abel equation can be obtai...
Analysis of heat transfer and entropy generation for a low-Peclet-number microtube flow using a second-order slip model: an extended-Graetz problem
The classical Graetz problem, which is the problem of the hydrodynamically developed, thermally developing laminar flow of an incompressible fluid inside a tube neglecting axial conduction and viscous dissipation, is one of the fundamental problems of internal-flow studies. This study is an extension of the Graetz problem to include the rarefaction effect, viscous dissipation term and axial con...


Extended Stokes’ problems for Maxwell fluids
Extended Stokes’ problems have attracted a great deal of attention owing to their wide applications as well as their intrinsic mathematical interest. Whereas the traditional Stokes’ problem has only one spatial dependence, the extended problem has two spatial dependences, which greatly increases the difficulty of solving the problem. The present work considers a Maxwell fluid driven suddenl...
A qualitative comparison of flow rules of pressure-dependent plasticity under plane stress conditions
The stresses and strains in a partly plastic hollow disc inserted into a rigid container and subject to thermal loading are obtained under plane stress conditions according to the associated and non-associated flow rules. Both the yield criterion and plastic potential are represented by a conical surface in a three-dimensional space where the principal stresses are taken as Cartesian coordinate...

Stability analysis and active control of a nonlinear composite laminated plate with piezoelectric material in subsonic airflow
The stability analysis and active control of a nonlinear composite laminated plate in subsonic airflow are studied. The equation of motion of a plate with a piezoelectric patch in subsonic air flow is established by using the Hamilton’s principle with the assumed mode method. The perturbation aerodynamic pressure is derived from linear potential flow theory. For the linear system, the eigenfr...
Gradient flow perspective on thin-film bilayer flows
We study gradient flow formulations of thin-film bilayer flows with triple-junctions between liquid/liquid/air phase. First we highlight the gradient structure in the Stokes free-boundary flow and identify its solutions with the well-known PDE with boundary conditions. Next we propose a similar gradient formulation for the corresponding reduced thin-film model and formally identify solutions wi...

Thermoelastoplastic Behavior of a HSLA Steel Plate Subjected to Low-Velocity Impact
The thermoelastoplastic behavior of a high strength low alloy (HSLA) steel plate subjected to low-velocity impact is investigated in this paper. A yield criterion related to the spherical tensor of stress is proposed to describe the mixed hardening of the orthotropic material. Based on the classical nonlinear thin plate theory, the incremental nonlinear motion equations are obtained, and are so...
Dynamics of multi layered Fragment separation by explosion
Spatial dispersion of a Fragment Generator Warhead (FGW), in terms of projection angle and velocity, is essential to focus the maximum number of fragments on the target missile for effective neutralization. The authors carried out experiments to study the fragment dispersion in single, double and triple layered FGW configurations with tungsten alloy fragments. The projection angle and velocity ...

Effects of different fibers on the properties of short-fiber-reinforced polypropylene composites
The aim of this paper is to give a comprehensive overview of the effects of different fiber types on the properties (flexural/tensile strength and modulus, notched and unnotched impact resistance, heat deflection temperature, density) of injection molded short fiber-reinforced polypropylene composites. The fiber length in the composite materials was analyzed, too. The influence of a coupling ag...
High mechanical performance polyurea/organoclay nanocomposites
This study reported that the intercalation of C20 organoclay was achieved in polyurea (PUr) matrices. The significant reinforcement was observed in a highly crosslinked PUr (HPUr), in which the Young’s modulus, stress and elongation at break was improved by ∼40%, ∼110% and ∼50%, respectively, with the addition of 5wt% C20. The energy dissipation of HPUrs was more than doubled by 5wt% C2...
Facile fabrication of poly (tetrafluoroethylene)/graphene nanocomposite via electrostatic self-assembly approach
Dispersion of graphene nanosheets (GNs) in a polymer matrix as mono layers was an important step towards fabricating high performance polymer/GNs nanocomposites. However, the insoluble and infusible properties of poly (tetrafluoroethylene) (PTFE) made the incorporation of nanofillers in PTFE matrix difficult. In this paper, a novel method based on poly (tetrafluoroethylene) (PTFE) latex that as...
Modeling of the mechanical degradation induced by moisture absorption in short natural fiber reinforced composites
This paper develops a constitutive model of short natural fiber reinforced composites (SNFRCs), with the consideration of nonlinear constitutive relation and large deformation induced by moisture absorption. This model accounts for the processes of moisture absorption and mechanical degradation in SNFRCs by a single internal variable, since these two thermodynamic processes are found correlated...