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This work determines the location of the greatest elastic distress in spherical and cylindrical Hertzian contacts based upon the distortion energy and the maximum shear stress theories. The ratios between the maximum pressure, the von Mises stress, and the maximum shear stress are determined and fitted by empirical formulations for a wide range of the Poisson ratio, which represents material compressibility...
In this paper a theoretical and experimental work for design of plain journal bearing able to work up to severe conditions is reported. The mathematical model and the numerical methods on which a purposely developed computer program is based are firstly described. The program is aimed to the evaluation of the behaviour of hydrodynamic plain journal bearings under heavy static loads, considering the...
We address some issues regarding the use of the Lagrangian description and convected frames in describing fluid motions. We also discuss the implications of Brownian motion on modeling the macroscopic motion of fluids and the schemes of filtered simulations. The relevance of these issues to the modeling of turbulence is discussed in detail.
Two different viscometer systems are designed and fabricated to characterize the behavior of ceramic particles under shear stress and high pressures. The first system is a Couette flow device with ability to exert pressure on the particles during its rotation and measure the torque and angular velocity of the system. From this information we can calculate viscosity and energy dissipation due to friction...
A non-affine visco-elasto-plastic constitutive equation with yield stress is proposed to simulate the response of magnetorheological fluids to driving forces. The equation yields realistic flow patterns in the pressure gradient driven fully developed tube flow which combine the effects of viscoelasticity and yield stress. The interplay of yield stress and viscoelasticity results in longitudinal velocity...
Transverse vibrations of curved beams are investigated. Different curvatures are considered. The beam is simply supported and resting on a nonlinear elastic foundation. The method of multiple scales is used in the analysis. A three-to-one internal resonance case is studied. It is possible when one of the mode numbers is three times the other mode. Amplitude and phase modulation equations are obtained...
An approximate solution to the flow past an infinite vertical porous plate in the presence of mass transfer is derived. Velocity and temperature profiIes are shown graphically for air and water. The numerical values of the skin-friction and the Nusselt number are listed in tables. The effects of differenl parameters like N (buoyancy ratio parameter), y (suction parameter), Pr (Prandtl number), E (Eckert...
Friction force oscillations occurring in a pin-on-disc configuration, widely used to test tribological properties af engineering materiais, have been experimentally observed. It is argued that these ascillations are not an artefact of a parlicular design of the pin-on-disc apparatus but result from the nature of motion within the region of cantact between the pin and the disc. Moreover, it is postulated...
During walking, the human pelvis is Ioaded by hip contact force and 22 muscle forces. Due to its complex geometry and structure, biomechanics of the human pelvis is complicated. A three-dimensionaI finite element model of the fulI pelvis was developed and the stress and deformation pattern was mapped, considering musculoskeletal loading, during 8 phases of a normal walking cycIe. The cortical and...
In this paper, the flow of an incompressible viscous fluid past and within a porous approximate sphere directed along its axis of symmetry is considered. By assuming that Stokes equations for a creeping flow govern the flow outside the body and Darcy's law governs the tluid motion within the porous region of the body, an analytical soIution for the stream function is obtained. The drag experienced...
The effcct of rotation on the thermosolutal convection in a ferromagnetic fluid is analyzed for a fluid layer heated and soluted from below in the presence of a uniform magnetic field. Using the linearized stability theory and the normal mode analysis, an exact solution is obtained for the case of two free boundaries. For the case of stationary convection, non-buoyancy magnetization has a destabilizing...
In this researeh, an experimental test device of the spiral groove bearing (SGB) spindle is developed. The dynamic characteristics of the SGB spindle are investigated. The effects of rotating speed, load and bearing clearance on the dynamic characteristics are considered. lt is found that both radial and axial non-repeatable run out (NRRO) decrease with the increase of rotating speed of the spindle...
The present study is concerned with the reflection of plane waves in a micropolar thermoelastic half-space without energy dissipation. The reflection coefficients of various reflected waves with angle of incidence for thermaIly insulated and isothermal boundaries have been obtained. Thermal and micropolarity effects on these reflection coefficients have been shown graphicaIly. Some special cases have...
The present study is concerned with the plane strain problem in a homogeneous orthotropic micropolar viscoelastic solid. The disturbance due to a time harmonic uniformly distributed source is investigated by employing the eigen-value approach. The integral transforms have been inverted by using a numerical technique to obtain the component of displacement, force stress and couple stress in the physical...
This paper is devoted to the theoretical analysis of steady and unsteady boundary-layer problems of a non-Newtonian fluid's flow using group methods. The application of a two parameter group reduees the number of the independent variabies of the problem by two and consequently the governing partial differential equations with the boundary conditions to ordinary differential equations with the appropriate...
A mathematical model for studying the heat and mass transfer in wood during its modification is derived. The model is constructed on the basis of a continual approach within mechanics of heterogeneous medium. Wood is considered as transversal-isotropic unsaturated three-phase system. A numerical experiment for investigating the influence of phase transition and capillary effect on the moisture field...
The equation error based system identification method is found to be efficient for identifying the element properties directly without iterations. But its application is limited to truss type structures only. The equation of error approach of identification algorithm is extended here for a frame element to asses the existing damage of the bridge girder-pier system from simulated modal data. The problem...
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