In this article, a Jacobian-free Newton Multigrid (JFNMG) method is used for the analysis of isothermal, steady state and incompressible Elastohydrodynamic lubrication (EHL) line contact problem. The lubricant is grease and its rheology is described by Hershel-Bulkley constitutive equation. The problem is investigated for smooth contact surfaces. A finite difference scheme, developed after discretizing governing equations on a uniform grid, is used for the solution of the EHL problem. The JFNMG method is applied to the system of algebraic equations, which arise in the scheme, and obtain solution for a wide range of parameters of interest. The proposed scheme not only overcomes the limitations of conventional schemes but is also, stable and fast converging for the investigation of the EHL problems.......

Keywords: Elastohydrodynamic lubrication, Grease lubricant, Jacobian-free, Multigrid, Full approximation scheme, Newton Inexact

In this study, Medium carbon steel is one of the most important materials used in industrial applications especially it is used in applications exposed to fatigue stresses such as airplanes, automotive components and electrical engines industries. Medium carbon steels were prepared and the effect of hardening on hardening strength of medium carbon steel was studied, the flame hardening method was used at different speeds then fatigue test was done. The following results were obtained, first sample (none), second sample (3.5 mm/s), and third sample (1.75 mm /s) and forth sample (1.165 mm/s). It has been found that as the flaming speed increases, the fatigue strength of the material decreases. The fatigue test result at stress (407.44 N/mm2) was as follow: for the first sample the no. of cycles to failure was at (67511 rpm), for the second sample (95832 rpm), for the third sample (122565rpm) and for the fourth sample it was (134585 rpm).

Keywords: Medium carbon steel, flame hardening, fatigue test.

Adhesion is a predominating force in Micro electro mechanical System (MEMS) due to high surface to volume ratio. In the present study of MEMS surfaces contact, adhesional friction force and adhesive wear volume have been computed numerically and new interrelation in between the wear and friction is developed after, finding their ratio. Also, mechanism of energy dissipation has been summarized on the basis of Arrhenius theory of mechanochemical reaction under working condition of MEMS devices.

Keywords: Friction force, Wear volume, Coefficient of friction-wear, Energy dissipation

Silty sand deposits exhibit low bearing capacity at different density levels and depths. It may be due to low frictional values and non-plastic behaviour in nature. This study focuses on response of silty sand under drained conditions of triaxial testing using hypoplastic model. The influence of soil state parameters i.e. void ratio/relative density, and consolidation pressure level on drained response of silty sands is examined from the model simulations. The model results are displayed graphically in terms of stress-strain curves, stress paths and volume change-strain plots. The results reveal that the response of soil is dependent on both the combination of density and consolidation pressure levels.

Keywords: Silty sand, Hypo plastic model, drained response, volume change, consolidation, density, stress ratio

Wear and fatigue resistance in steel components used in various industries can be improved by surface treatments. Coatings systems which are used for improving the mechanical properties, generally, decreased the components fatigue life due to micro cracks, that propagate through the substrate , it is possible to improve the fatigue resistance of a component by the application of shot peening treatment, whose compressive residual stresses delay or eliminate the initiation and propagation of fatigue cracks. The aim of this study is to obtain the fatigue limit of untreated, shot peened, and hard chromium coating of medium carbon steel AISI 1039 and comparison between them. Fatigue tests were carried out using small samples with 4 mm diameter, with hard chromium layer of (47.1) μm thick.......

Keywords: Shot peening, fatigue, AISI 1039 medium carbon steel, chromium coating

A mathematical model for the nonlinear enzymatic reaction process is discussed. An approximate analytical expression of concerntrations of substrate, enzyme-substrate and product are obtained using variational iteration method (VIM). The main objective is to propose an analytical solution to nonlinear differential equations. Furthermore, in this work the numerical stimulation of the problem is also reported using Scilab/Matlab program. An agreement between analytical solution and numerical results is noted.

Keywords: Mathematical modeling, enzyme Kinetics, Nonlinear equations, enzyme substrate, variational iteration method.

Peer-to-Peer (P2P) network, an overlay network is a popular file sharing system, however, by default content pollution is a problem in these networks .Due to absence of server in this network a peer, including a malicious node, can enter or leave the network at any time without intimating other peers .At the same time an user in the P2P network needs the trust value of participating nodes in the network .Owing to decentralized structure of the network. trust plays an important role in content distribution, as trust based content distribution is needed between peers .The trust value of a node is measured in terms of its past behavior and satisfaction of other sharing nodes. However, there is an important issue of security in evaluating trust value of a peer ,since a malicious node can provide a negative feedback about a genuine peer .In this paper a robust trust evaluation algorithms is presented using Fuzzy logic. Using this technique the authenticity of a peer can be determined and simulation can be done for this purpose using the proposed algorithm.

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