Friction curves

The bearing health can be best described by plotting a ZNjP versus coefficient of friction curve. Figure 13-10 shows such a curve where Z is the lubricant viscosity in centipoise, N the rpm of the journal, and P is the projected area unit loading. 

The system curves are the summation of the appropriate friction curves plus the static head, a, required to reach the base point. Note that the suction side friction is represented as a part of B-P-C in this example. It could be handled separately, but must be added in for any total... 

The minimum coefficient of friction for pure MoS2 is significantly lower than that for MoS2 xOx, and the peak in the coefficient of friction curve occurs for relatively low concentrations of oxygen in the film. The friction rises rapidly for... 

Plot the system-friction curve. Without static head, the system friction curve passes through the origin (0,0) (Fig. 6.22), because when no head is developed by the pump, flow through the piping is zero. For most piping systems, the friction-head loss varies as the square of the liquid flow rate in... 

FIGURE 4.17 Coefficient of friction curves during conditioning at different temperatures (from Ref. 11). 

FIGURE 16.28 The friction curves of abrasive particles in (a) DI water and (b) a citric acid based solution during copper polishing. 

The direct method was used here to determine the friction curves for a series of polymers in axisymmetrical capillaries of various dimensions. The characteristic flow curves for the flow considered here eu e represented by the curve in Fig. 1. It can be seen that this curve, on log-log scale, consists of a series of straight segments, with a discontinuity in slope and flow rate once a certain flow regime is reached. 

Figure 3 Principle of determination of friction curve during macroscopic slip of the polymer at the wall. 

Figure 4a Friction curve of PDMS LG2. t is the static friction stress (Table 3).

DF) on the flow curves. Note that in the case where the flow curves exhibit two instability zones, the corresponding friction curve exhibits two minima, the last one being followed by a rising branch with a high slip velocity corresponding to portion (HG) on the flow curves. 

The Mction curve depends slightly on the degree of entanglement in a given family of polymers (comparison of Figs. 4a and 4b). In addition, in the case of the LLDPE, the friction curve does not appear to depend on temperature (Fig. 4d). 

With the flow conditions envisaged here, extrusion of the PB and LLDPE displays two zones of instability. An attempt was therefore made to model the curves of Figs. 4c and 4d using relation (11). In fact, owing to the considerable curvature of the friction curves around their respective maximum values (Figs. 4c and 4d), relation (11) cannot be applied. Indeed, the parameter governing the curvature is... 

Anti-wear Components These are, quite often, the most difficult component for the formulator when trying to achieve and maintain the ideal friction curve. Therefore, selection of the right type and level is critical ... 

Quasiharmonic vibration will commence at a tractive velocity corresponding to the maximum of the friction curve at For the undamped case... 

For load values from Pmin up to Pmax with stepwise velocity increase, a limiting value for sliding velocity (Vmeix) is found at which the material suffers frictional failure. In the course of testing the coefficient of friction (curve l) and temperature in the subsurface layer of the polymeric specimen (curve 2) are recorded. 

Fig. 8.46. Internal friction curves for lanthanum (annealed 30 min at 680°C) during heating (curve B) and during cooling (curve A). Included is a plot of the normalized shear modulus (GIGm) where G at 20°C was 1480 50 kg/mm. The frequency of oscillations was 4.5 Hz and the heating and cooling rates were 0.042°C sec". From Dashkovskiy and Savitskiy (1961).

Fig. 8.47. Internal friction curves for cerium at an oscillating frequency of 4.5 Hz with a heating rate of 0.042 C sec". Curve A represents a sample that had been annealed 1 hour at 600°C while curve B represents a sample annealed 20 min at 500°C. Included is a plot of the normalized shear modulus (G/G20) vvhere G at 20°C was 1350 50kg/mm. From Dashkovskiy and Savitskiy (1%1).

FIGURE 5.3 (a) LFM image and (b) frictional curve of DTMS and FOETMS monolayers. 

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