JOURNAL OF SCHOOL OF ENGINEERING
Year:2004 | Volume:16 | Issue:2 (Machanical Engineering Issue)|Papers Count:8

The vibration behavior of orthotropic rectangular plates is presented in this study. The plate is subjected to uniform in-plane forces (Nx , Ny), and its edges are assumed to be elastically restrained (with various degree) against rotation. This type of boundary conditions covered a wide range of B.C's from simply supports to clamped supports. The analytical solution is obtained using classical plate theory. Frequency equations of these systems are very large and difficult to solve. A simple method of solving this type of equations has been used in order to investigate Fee vibration responses of orthotropic plates with elastic supports. The effects of plate geometry, material properties, compressive inplane loads and boundry conditions are presented and discussed.

Unsaturated flow of liquid in a bed of uniform and spherical ore particles has been studied numerically and experimentally. An unsteady and two-dimensional model has been developed based on the mass conservation equations of liquid phase in the bed and in the particles. The model equations have been solved using a fully implicit finite difference method giving the distributions of the degree of saturation in the particles and in the bed and the vertical velocity of flow in the bed as well as the effect of periodic infiltration on the above distributions. To calibrate the computational model, a series of column tests has been performed using periodic infiltration of water into 40cm high columns composed of ore having particles smaller than 25mm. The numerical analysis shows that (a) the results obtained from numerical modeling under the same operating conditions as mentioned for column tests, are in good agreement with those from experimental procedure, (b) the degree of saturation of the bed and the time required to reach steady state conditions depend on the inflow of water and intrinsic permeability of the bed and (c) the velocity fluctuations and the fluctuations of the degree of saturation in the bed depend on the inflow of water, period of infiltration, height and intrinsic permeability of the bed.

In this paper, the motion equations of an elastic wing with structural damping have been derived from LaGrange's equations. The aerodynamic forces and moments on the wing have been derived by using the "Strip Theory" for the case of unsteady and incompressible fluid flow. The displacements of the wing are due to the bending and twist motions for which the displacements are determined by "Assumed Mode Method". The aero elastic equations, which are arranged with computer programs, are solved by eigen value system and u-g method. The flutter speed is calculated on different type of wings, for which the experimental data are available; agreement is suitable.

While introducing harmonic gearbox drives, kinematics relations and design parameters are derived and studied. The flexible ring which is driven via a wave generator and loaded by a force of magnitude of P, is modeled and both horizontal and vertical displacements are determined. Results indicate that the ratio of the two displacements (vertical to horizontal) is constant for all values of P, provided the geometry of the flexible ring remains intact. The finite element results also support the relations derived for the two type of load generators adapted to the problem. The results also indicate that for a proper engagement of the ring gear and that of the flexible ring, the maximum tooth difference between the two gears can only be four, among which, only the values of 2 and 3 are acceptable.

In this work, boundary conditions of T-junctions in engine silencers are modeled by constant pressure model (CPM) and pressure loss model (PLM). The mean flow velocity through the ducts is zero. Two Benson CPM and Corberan CPM approaches are employed in perforate silencers  simulation. For the silencer with more than one perforated pipe which appears as Nbranch junctions, it is possible to apply the Benson CPM approach. The upstream excitation as a boundary condition is modeled by two single pure tone (harmonic) and white noise perturbations. It is shown that white noise perturbation bring enough accuracy. On the other hand -it spends much shorter time than single pure tone perturbation.

The location of the lateral boundaries, where Fee-stream or zero-gradient boundary conditions are usually applied, has special importance in the numerical simulation of external flows over bodies. The influence of the location of the lateral boundaries on the numerical solution of a two-dimensional, laminar, incompressible, and non-isothermal flow past a circular cylinder for a range of Prandtl and Reynolds numbers is investigated. The governing equations are solved using the finite element method through which the drag coefficient and the Nusselt number are calculated. The results show that the influence of the flow field on the location of the lateral boundaries increases with decreasing the Reynolds number, while the effect of the temperature field on these boundaries decreases with increasing the Prandtl number. The results of this study should be useful for choosing the computational domain in the numerical simulation of external flows over bodies.

WE43 and WE54 are the new generation of Mg-RE alloys which have recently assumed considerable importance in aerospace and automotive industries because of their high specific strength, good corrosion resistance and attractive creep properties. Both alloys in the as cast condition contain a significant volume fraction of eutectic phase at triple points and along grain boundaries. The volume fraction of eutectic phase in the WE54 alloy was larger than that in WE43. The alloys in the T6 .condition consist of homogeneously distributed ß phase with an ordered DO19 structure and ß precipitates with body centered orthorhombic (BCO) structure on prism planes of the Magnesium. The alloys initially in the T6 condition when exposed to temperatures below 200°C for 1000 hours and longer, suffered a reduction in ductility. The origin of the embitterment was found to be due to the formation of G.P. zones from residual solute which is in equilibrium with ß phase.

In this research, attempt is made to introduce new and developed techniques of quantitative methods of adhesion measurements for coated substrates. In the qualitative Cross Cut/Scotch Tape Test, the square lattice cuts have been developed to diamond lattices with different angles. The aim is to find out, if there exits any relationship between the adhesion strength, separated areas of coating and angle of diamond lattices. The Pull-Off Test method is developed by a new design for its employed grips to hold inert substrates mechanically rather than using adhesives. A new quantitative method of measuring adhesion strength is designed and introduced. It is based on creating mechanical interlocking between a rough surface and the coating by vertical loads. This could cause shear separation between the coating and the substrate. Results of different measurements, on many samples, in the above tests are correlative and prosperous.