We introduce and discuss certain models of dilute granular systems of spheres with dissipative collisions and variable coefficient of restitution, under the assumption of weak inelasticity. The dissipation is taken into account by introducing a correction to the Boltzmann collision operator in the form of a nonlinear friction type operator. Using this correction we obtain formally from the Bolt...

A sphere moving down the surface of a static sphere and a simple phase diagram. Abstract A small sphere placed on the top of a big static fric-tionless sphere, slips until it leaves the surface at an angle θ l = cos −1 2/3. On the other extreme, if the surface of the big sphere has coefficient of static friction , µ s → ∞, the small sphere starts rolling and continues to do so until it leaves t...

* Current address – Department of Industrial Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53201 † Corresponding author – [email protected] Tel: +91-80-22932301 Fax: +91-80-23600648 ABSTRACT Surface texture of the die plays an important role on friction during metal forming. In the present study, unidirectional and random surface finishes were produced on hardened stee...

A sphere moving down the surface of a static sphere and a simple phase diagram. Abstract A small sphere placed on the top of a big static fric-tionless sphere, slips until it leaves the surface at an angle θ l = cos −1 2/3. On the other extreme, if the surface of the big sphere has coefficient of static friction , µ s → ∞, the small sphere starts rolling and continues to do so until it leaves t...

A brake hardware-in-the-loop simulation (HILS) system for a railway vehicle is widely applied to estimate and validate braking performance in research studies and field tests. When we develop a simulation model for a full vehicle system, the characteristics of all components are generally properly simplified based on the understanding of each component's purpose and interaction with other compo...

In this article, the effect of different yield functions on prediction of forming limit curve (FLC) for aluminum sheet is studied. Due to importance of FLC in sheet metal forming, concentration on effective parameters must be considered exactly in order to have better theoretical prediction comparing experimental results. Yield function is one of the factors which are improved by adding new coe...

A previously developed mesoscopic friction model for glass/PP textile composite laminates during forming is evaluated for glass and carbon/PPS laminates, at higher temperatures and lower viscosities than before. Experiments were performed for tool/ply and ply/ply configurations in a new friction test set-up. The experimental results indicate that this contact is indeed in the hydrodynamic regim...

For turbulent boundary-layer flow under a uniform freestream speed U∞ over a plate of length L, covered with uniform roughness of nominal sand-grain scale ks , the physical behaviors underlying two distinguished limits at large ReL ≡ U∞L/ν are explored: the fully rough wall flow where ks/L is fixed and the long-plate limit where Rek ≡ U∞ks/ν is fixed. For the fully rough limit it is shown that ...

A new theoretical approach is proposed to predict a practical upper limit to the efficiency of a very large wind farm. The new theory suggests that the efficiency of ideal turbines in an ideal very large wind farm depends primarily on a non-dimensional parameter λ/Cf0, where λ is the ratio of the rotor swept area to the land area (for each turbine) and Cf0 is a natural friction coefficient obse...

Experiments were conducted to determine the effects of frequency and amplitude of vibration on friction. The experimental analysis also seeks to take into account a variety of factors influencing the coefficient of friction such as normal load and surface roughness. An in-house pin-on-disc apparatus was constructed with a spindle speed control and applied forced-feedback to perform the tests. T...