Search

Precise braking operations are pivotal to ensure safety in modern day vehicle designs. Brakes are mechanical devices for increasing the frictional resistance that obstructs the turning motion of vehicle wheels by absorbing either kinetic, potential energy or both while in action. This absorbed energy appears in the form of heat. Stress, distribution of friction on surface, frictional heat generation, material and geometry are the major controlling factors for efficiency of braking operations. Frictional heat generation and its effective dissipation is one of the most predominant of these factors and hence it is the focus of this study. The purpose of this study is to analyze the thermal behavior of a full bicycle disc brake using finite element method. Sequential thermal structured method based on Ansys 14.5 is used to carry out the numerical simulation for evaluating the variation of total heat flux and temperature profiles with respect to time. The analysis model was studied experimentally and results obtained by numerical analysis were within 3% of the experimental result for maximum temperature. The model is thus adequately validated to be followed for a similar analysis on bicycle brakes. [ABSTRACT FROM AUTHOR]

Evaluation of basal heave stability is one of important design checks for excavations in soft clays. The commonly used classical calculation method based on limit equilibrium theory and the safety coefficient formula recommended by the current code, do not consider the influence of supporting structure of foundation pit depth heave stability, which results in conservative. Considering the wall stiffness and strength, the effective stress changes in different depth of soil, the frictional resistance between the retaining wall and the passive zone, the vertical shear resistance of the soil behind the wall and other factors. The modified safety factor calculation formula of foundation pit stability is presented, comparison analysis of calculation method combined with examples. The calculation results show that the safety factor of foundation pit stability is improved considering the influence of supporting structure depth, the calculation results are more reasonable. [ABSTRACT FROM AUTHOR]

In this paper, we examine the hydromagnetic boundary layer flow and heat transfer characteristics of a laminar nanoliquid film over an unsteady stretching sheet is presented. The highly nonlinear partial differential equations governing flow and heat transport are simplified using similarity transformation. The analytical solutions of the resulting ODEs are obtained for some special case of nano liquid film using hypergeometric power series functions, and from which the analytical solutions of the original problem are presented. The influence of pertinent parameters such as the magnetic parameter, the solid volume fraction of nanoparticles and the type of nanofluid on the flow, heat transfer, Nusselt number and skin friction coefficient is discussed analytically. [ABSTRACT FROM AUTHOR]

g-Jitter induced mixed convection flow of micropolar nanofluids past an inclined stretching sheet is numerically studied in this paper. Copper (Cu) in water based is considered. The governing partial differential equation is transformed into non-dimensional form by using appropriate non-dimensional variables and then solved by using Kellerbox method. The behaviour of physical quantities such as skin friction and heat transfer coefficients as well as the velocity, microrotation and temperature profiles are investigated for both strong and weak concentration of microelements. The numerical results show that, the values of reduced skin friction and heat transfer coefficient are increased by increasing the material parameter but produce an opposite behaviour with the increasing in nanoparticles volume fraction parameter. [ABSTRACT FROM AUTHOR]

Effects of rolling motion on single-phase and two-phase flow resistance were compared experimentally under ambient temperature and pressure. In the single-phase flow experiments, the different pump head was obtained by a variable speed electromotor, and the flow rate was adjusted combining with a regulating valve. However, for the two-phase pressure drop measurements, the pump delivering water operated with an invariable pressure head of 48m, in order to neglect the effect of pump head on flow fluctuation. The results indicated that effects of rolling motion on single-phase flow resistance depend on the pump head. The fluctuation amplitude of flow rate and frictional pressure drop decreases rapidly as the pump head increases, finally, the flow will tend to be steady if the pump head dramatically exceeds the additional pressure drop. Different from the case of single-phase flow, transient frictional pressure drop of two-phase flow fluctuates synchronously with the rolling motion when liquid Reynolds number is less than 1400, whereas keeps a stable steady state without obvious oscillation for other cases. The fluctuation amplitude is independent of rolling period and amplitude and decreases with the increase of flow rate. The inclination angle and phase interface distribution is taken into account in analyzing the influence of rolling motion on two-phase flow resistance. Comparing with the vertical condition, rolling motion nearly has no effects on time-averaged frictional resistance for both the single-phase and two-phase flow. [ABSTRACT FROM AUTHOR]

This paper shows that buoyancy enhances mobility in two-phase debris flow with an analysis based on the generalized two-phase debris flow model proposed by Pudasaini [1]. The model (the most generalized two-phase flow model to date) incorporates many essential physical phenomena, including solid-volume-fraction-gradient-enhanced non-Newtonian viscous stress, buoyancy, virtual mass and a generalized drag force. We find a strong coupling between the solid- and the fluid-momentum transfer, where the solid normal stress is reduced by buoyancy, which in turn diminishes the frictional resistance, enhances the pressure gradient, and reduces the drag on the solid component. This leads to higher flow mobility. Numerical results show that the model can adequately describe the dynamics of buoyancy induced mobility in two-phase debris flows, and produces observable geometry of flowing mass in the run-out zone. The results presented here are consistent with the physics of the flow. [ABSTRACT FROM AUTHOR]

We investigate the behavior of a model granular material made of frictionless, nearly rigid equal-sized beads, in the quasistatic limit, by numerical simulation. In the macroscopic geometric limit (that is the macroscopic, rigid and quasistatic limits), with either volume or normal stress controlled simulations, static and dynamic macroscopic friction coefficients coincide, dilatancy vanishes and the material satisfies a Lade-Duncan failure criterion. The macroscopic shear strength stems from both contact network and force anisotropy. [ABSTRACT FROM AUTHOR]