Internal friction definition

The angle of internal friction, a, is defined as the equilibrium angle between flowing particles and bulk or stationary solids in a bin. Figure 4 illustrates the definition. The angle of internal friction is greater than the angle of repose. 

The ideal soil is defined as a loose, granular medium that is devoid of cohesion but possesses internal friction. In contrast, an ideal cohesive medium is one that is devoid of internal friction. Real soils generally fall between the foregoing two limiting definitions. 

Dissipative systems whether described as continuous flows or Poincare maps are characterized by the presence of some sort of internal friction that tends to contract phase space volume elements. They are roughly analogous to irreversible CA systems. Contraction in phase space allows such systems to approach a subset of the phase space, C P, called an attractor, as t — oo. Although there is no universally accepted definition of an attractor, it is intuitively reasonable to demand that it satisfy the following three properties ([ruelle71], [eckmanSl]) ... 

Such transformations have been extensively studied in quenched steels, but they can also be found in nonferrous alloys, ceramics, minerals, and polymers. They have been studied mainly for technical reasons, since the transformed material often has useful mechanical properties (hard, stiff, high damping (internal friction), shape memory). Martensitic transformations can occur at rather low temperature ( 100 K) where diffusional jumps of atoms are definitely frozen, but also at much higher temperature. Since they occur without transport of matter, they are not of central interest to solid state kinetics. However, in view of the crystallographic as well as the elastic and even plastic implications, diffusionless transformations may inform us about the principles involved in the structural part of heterogeneous solid state reactions, and for this reason we will discuss them. 

Viscosity is the resistance of a fluid to flow under an applied load due to internal friction. Its formal definition can be best visualized using Figure 10.1. A viscous fluid resides between... 

Ideal liquids are incompressible and their flow is by definition frictionless. Real liquids are characterized by cohesion forces operating between the molecules, which bring about frictional forces, whose action is known as internal friction. 

Figure 10.14 Definition of effective yield locus and effective angle of internal friction, <5...

Rowe, G.W., Friction, Wear and Lubrication Terms and Definitions, Organization for Economic Cooperation and Development, International Research Group on Wear and Engineering Materials, Paris, 1969. 

Internally finned tubes are ducts with internal longitudinal fins. These tubes are widely used in compact heat exchangers. The friction factor-Reynolds number product and the Nusselt number for such internally finned tubes, designated as (/ Re), and Nu/,c> respectively, are computed from the following definitions ... 

Discrepancy between the conventional theory and the microchannel measurements of friction factor/ in gaseous flow has been attributed to compressibility [6]. In general it appears that/Re for compressible slip flow is less than that for the incompressible case [3]. In a comprehensive study of results of microscale single-phase internal flows [1], it has been found that the only definitive conclusion that can be reached from the currently available data is that gaseous slip flow data indicate an approximate 60% reduction in / compared to macroscale theory at the same Re (while for laminar non-slip water flow/ appears to be approximately 20% higher than the theoretical predictions). The finding for compressible slip flow seems to be supported by a simple analytical correlation with the factor c 0.6 0.05 [3] ... 

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