a knowledge of physical and aerodynamic properties of agricultural crops is important and essentially required for the design and development of a crop's harvesting and post-harvesting equipments. in the present research, experiments were conducted to determine physical and aerodynamic properties of fars province pinto bean namely: kernel size and shape (length, width, thickness, projected...

We study static packings of frictionless and frictional spheres in three dimensions, obtained via molecular dynamics simulations, in which we vary particle hardness, friction coefficient, and coefficient of restitution. Although frictionless packings of hard spheres are always isostatic (with six contacts) regardless of construction history and restitution coefficient, frictional packings achie...

We show that two basic mechanical processes, the collision of particles and rolling motion of a sphere on a plane, are intimately related. According to our recent findings, the restitution coefficient for colliding spherical particles ǫ, which characterizes the energy loss upon collision, is directly related to the rolling friction coefficient μroll for a viscous sphere on a hard plane. We quan...

abstracthydroforming process is a deep stretching process only with the difference that a fluid is used instead of the mandrel. this paper investigates the hydroforming process of non-cylindrical and non-spherical geometries using finite element analysis software to calculate the influences of effective process parameters such as the coefficient of friction between the surfaces and the pressure...

In the present investigation, two dimensional elastoplastic finite element analysis was conducted to assess the deformation characteristics of Al 1100 alloy during continuous confined strip shearing (C2S2) process. The results of simulations showed that the plastic strain distribution across the deformed sample is non-uniform irrespective of the amount of friction and C2S2 die angle. The most u...

Solid lubricants used in aerospace applications must provide low friction and a predictable operation life over an extreme range of temperatures, environments and contact conditions. PTFE and PTFE composites have shown favorable tribological performance as solid lubricants. This study evaluates the effect of temperature on the friction coefficient of neat PTFE, a PTFE/ PEEK composite and an exp...

This study investigated the effect of the coefficient of friction of a running surface on an athlete's sprint time in a sled-towing exercise. The coefficients of friction of four common sports surfaces (a synthetic athletics track, a natural grass rugby pitch, a 3G football pitch, and an artificial grass hockey pitch) were determined from the force required to tow a weighted sled across the sur...

The Kramers problem in the energy-diffusion limited regime of very low friction is difficult to deal with analytically because of the repeated recrossings of the barrier that typically occur before an asymptotic rate constant is achieved. Thus, the transmission coefficient of particles over the potential barrier undergoes oscillatory behavior in time before settling into a steady state. Recentl...

A modified model for predicting the friction force between drill-string and borehole wall under in-plane vibrations was developed. It was found that the frictional coefficient in sliding direction decreased significantly after applying in-plane vibration on the bottom specimen. The friction reduction is due to the direction change of friction force, elastic deformation of surface asperities and...