Applied Mechanics and Materials Vols. 110-116

Abstract: Novel heterocyclic derivative of 3-(N-n-dodecylammonium) quinazolin-4-ones was synthesized and its tribological performance when added to liquid paraffin as an ashless additve without phosphorus and sulphur was evaluated using a four-ball tester. On the basis of the experimental results, the novel additive has been found to be quite effective as a potential additive in liquid paraffin. The nature of the film on the rubbed surface was investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

Abstract: The present paper deals with the study of viscous contribution to the pressure for the viscous potential flow analysis of Kelvin-Helmholtz instability of two viscous fluids. Viscosity enters through normal stress balance in the viscous potential flow theory and tangential stresses for two fluids are not continuous at the interface. Here we have considered viscous pressure in the normal stress balance along with the irrotational pressure and it is assumed that the addition of this viscous pressure will resolve the discontinuity between the tangential stresses and the tangential velocities at the interface. The viscous pressure is derived by mechanical energy equation and this pressure correction applied to compute the growth rate of Kelvin-Helmholtz instability. A dispersion relation is obtained and a stability criterion is given in the terms of critical value of relative velocity. It has been observed that the inclusion of irrotational shearing stresses stabilizes the system.

Abstract: Buildings are one of the most important energy consumers in the world. High temperature gradients in heating systems can cause the increase of heat loss of the envelopes during the cold season and consequently increase the energy consumption. Floor heating systems has shown that they can generate lower temperature gradients in compare with other convective heating systems. In present study, the CFD simulation is done for a 3-D room and the required energy to achieve the thermal comfort in a room is calculated. The height of the room is changed and the energy loss of the room is calculated for both systems. Results showed that as the height doubles, the wall heat loss for radiator system almost doubles but for the floor heating system it was about 60 percent. This impressive result can recommend the floor heating systems for working areas with tall ceilings.

Abstract: Finite element solution is presented for finitely long, simply-supported, orthotropic, piezoelectric shell panel under pressure and electrostatic excitation. The influence of the piezoelectric layers on the mechanical behavior of structures is studied. The direct piezoelectric effect of the piezoelectric material in ordinary (normal) and shear mode application are investigated. Numerical examples are presented for [0/90/P] laminations, where P indicates the piezoelectric layer. Piezoelectric layer can be completed or patch form. Finally the results are compared together and the shear mode advantages are discussed.

Abstract: This paper is aimed at development of an integrated approach based on analytical and computational aerothermodynamics for the special case of design of a 75% (low process-efficiency), hydrogen-fuelled, constant area combustor of a hypersonic airbreathing propulsion (HAP) system thereafter undertaking study of two types of HAP systems. The results of configurational aerothermodynamics implied that the most appropriate constant area configuration had a 30 degrees downstream wall-mounted fuel injector with a single acoustically stable cavity placed downstream of the fuel injection point. Moreover for identical flow inlet parameters and system configurations at lower levels of thermodynamic process efficiencies, the constant combustor-area (i.e. Scramjet 1) engine is superior in its performance to the constant combustor-pressure (i.e. Scramjet 2) engine for all values of fuel-air ratios.

Abstract: This paper presents the Finite Element Analysis (FEA) based design, optimization and development of an axial flux permanent magnet brushless DC motor for Left Ventricular Assist Device (LVAD). With the design objective of improving the existing motor's efficiency , different topologies of AFPM machine has been examined. Selection of optimal magnet frac-tion, Halbach arrangement of rotor magnets and the use of Soft Magnetic Composite (SMC) material for the stator core results in a novel motor with improved efficiency and torque profile. The results of the 3D Finite element analysis for the novel motor have been shown.Thermal analysis for the existing motor has also been done and the FEA results are compared with the analytical and experimental results.Finally the test results for the novel motor and the general conclusions are also discussed.

Abstract: In this paper the problem of a density-functionally gradient beam subjected to uniform load is studied. Airy stress function methodology is used to obtain a set of analytical solutions for simply supported and clamped beams subjected to uniform load. A stress function in the form of polynomial is proposed and determined. The treatment for fixed-end boundary conditions is the same as that presented by Timoshenko and Goodier (1970). By this method all of the analytical plane-stress solutions can be obtained for a uniformly loaded isotropic beam with rectangular cross section under different types of classical boundary conditions.

Abstract: In many process equipments and mechanical system where a flow needs to be distributed among several outlets, the design is generally based on the assumption that the fluid is uniformly divided among them but practically in never happens. A non-uniform flow distribution imposes a serious design limitation in terms of rise in pressure drops and decrease in thermal performance of the system. Reynolds number being a characterizing parameter of pipe flow is expected to play a significant role in flow maldistribution pattern also. This paper present an experimental study performed on multi channel U-and Z-turn flow configurations where the flow is varied in the practical range of 20000 < Re < 35000. Result shows the presence of maldistribution. It is found that the Re plays an important role in characterizing the flow in terms of channel velocity, axial velocity in header and flow distribution pattern in a specific channel. Maldistribution effect is found to be dominant in the central region in U-turn flow and peripheral region in Z-turn configurations.

Abstract: Heavy vehicle cooling fan is seen as one of the main means of vehicular fuel efficiency reduction. This is becoming a major factor in city noise, and the necessity of electromagnetic technical development is very great. CFD method could replace experiment for development of heavy vehicle cooling fan, but it cannot be applicable to some of real design stage because of limitation that rotating speed must be set as boundary condition. In this article, we developed a new algorithm in which we are able to determine both static pressure and rotating speed through setting up the only voltage as a boundary condition with motor performance test results

Abstract: In electro discharge machining (EDM) the metal removal occurs from the erosive effects of high frequency sparks. Consequently the erosion rate depends on spark energy sparking frequency and the factors affecting them. However the experimental results are highly random and sometimes unexpected. Material erosion rate and surface roughness were analysed for the effect of important factors like pulse parameters (voltage current, ontime and offtime), polarity and work material. Taguchi method of experiment planning with orthogonal arrays was adopted to analyse the anomalies observed in the experimental results.