Friction coefficient, total

We get a quite different answer if we include the friction between the die and the forging. The extreme case is one of sticking friction the coefficient of friction is so high that a shear stress k is needed to cause sliding between die and forging. The total area between the dies and piece c is given by... 

The head losses calculated using K coefficients by these figures can be added directly to the total friction head loss for the straight pipe portions of a system. When equivalent lengths are determined, they must be added to the straight pipe before determining the total head loss, as shown in the example calculations for a water system. 

A loss coefficient can be defined for any element that offers resistance to flow (i.e., in which energy is dissipated), such as a length of conduit, a valve, a pipe fitting, a contraction, or an expansion. The total friction loss can thus be expressed in terms of the sum of the losses in each element, i.e., ef = JT K-nVf/7). This will be discussed further in Chapter 6. 

The total friction loss in an orifice meter, after all pressure recovery has occurred, can be expressed in terms of a loss coefficient, ATr, as follows. With reference to Fig. 10-12, the total friction loss is P — P3. By taking the system to be the fluid in the region from a point just upstream of the orifice plate (Pj) to a downstream position where the stream has filled the pipe (P3), the momentum balance becomes... 

Coefficient of Friction The coefficient of friction between two surfaces is the ratio of the force required to move one surface over the other to the total force pressing the two together. 

The mass dependence of the solute diffusion has been studied at p = 0.844 and T = 0.728. The diffusion coefficient of the solute is found to have a weak mass dependence. The diffusion is found to decrease as the mass of the solute is increased. In Fig. 6, both the binary and density term contribution to the total friction is plotted against the mass ratio. It is found that the current term contribution remains small and almost unaltered over the whole range of solute-solvent mass ratio studied here. 

The proportionality between the area of real contact and the applied load supplies at last a rational explanation of the well-known Amontons 1 or Coulomb s2 law of friction, that the frictional force F is directly proportional to the total load P pressing the surfaces together. The meaning of this law has long been mysterious. Under ordinary circumstances the law holds fairly accurately, i.e. there exists a nearly constant coefficient of friction, /x = F/P. The frictional force is naturally proportional to the total area of these bridges consequently the frictional force should be proportional to the load. 

Since the total frictional drag acting on the molecule must be divided among Ns + beads, the drag coefficient that one must assign to each bead should be inversely proportional to the number of beads Ns used to describe the chain. Hence, l b = N q/ Ns -1-1), where N is the number of monomers in the whole chain, and is the drag coefficient per monomer. Thus, Eq. (3-41) can be rearranged to a form that shows no dependence on Ng (Ferry 1980 Larson 1988) ... 

The total friction coefficient of the whole Rouse chain is the sum of the contributions of each of the N beads ... 

The total friction coefficient for a plate of length L is given by the formula 1 1 798... 

With a coefficient of friction of 0.001 for the roller supported belts assuming the use of lubricated roller bearings, the total belt pull is 86.4 lbs. (39 Kgms.), requiring a 15 HP... 

Figure 7.29 Schematic illustration showing the estimation of the peel force G and the coefficient of friction n from a plot of the total force F versus the deadweight D (Kurzweg, Heimann and Troczynski, 1998).

The ASTM procedure primarily describes measuring the slip resistance of surface to shoe material tested, such as a shoe sole, in terms of static coefficient of friction. The test employs the laboratory-only device named James machine which measures friction between a tested surface and a square pad of leather 3 X 3 in. by 0.25 in. thick. The James machine applies a known constant vertical force to the test pad, and then applies an increasing lateral force until a slip occurs. The test table of the machine moves forward uniformly at a rate of 1 in./s until the piece of leather mounted on a shoe slips and the vertical column of the machine drops. The principal readout of the test procedure is a recording on the chart graph marked with coefficient of friction lines. Hence, the machine provides results directly in values of static coefficient of friction. The test is conducted on three panels of the materials in four mutually perpendicular directions, giving total twelve readings for each material. 

Applying this approximate method required the estimation of suitable values for the flow coefficient, bo, which is a function of the total frictional loss in velocity heads, Kj, and the pressure ratio, p p. The polynomial approximations of equations (6.66) to... 

When a chain moves in a dense system (like a polymer melt), the frictional forces acting on each monomer are totally independent. Hence, the total frictional force experienced by the moving chain is simply the sum of the frictional forces on each individual monomer. How can we find these frictional forces on the monomers Let s focus on one monomer suppose it has a velocity v. This is the velocity of diffusion, so it is not too high. (To be more precise, it is of the same order as the thermal velocity of the monomer.) This gives us the right to take the force f of viscous friction to be proportional to the velocity f = —pv. Here p is the coefficient of friction for a single monomer. Since the total friction is the sum over all the monomers, the same must be true for the coefficients of friction. The... 

In a scratch test, a diamond or WC, conical or pyramidal indentor is sheared across a specimen under a controlled normal load while monitoring the tangential force [117]. The adhesive bond and the tangential plowing force determine the total work performed by frictional forces. The coefficient of friction is determined from the ratio of the tangential to the normal load. 

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