Longitudinal friction coefficient

The skid resistance (longitudinal friction coefficient) measured by the GripTester is called GripNumber (GN), is reported to two decimal points and ranges from 0 to 1.0. 

The measurements are usually conducted at 60 km/h speed and the longitudinal friction coefficient is the mean values over 50 m. The vehicle may also be equipped with a laser device to record surface macro-texture. 

The longitudinal friction coefficient is measured by locked wheel with a slip ratio of 0% (locked wheel standard) or a slip ratio of 15% 1%, or ABS and a controlled speed. The control speeds typically used are 40, 50 or 60 km/h and the friction coefficient is the mean values over 20 m. 

CEN/TS 15901-9. 2009. Road and airfield surface characteristics — Part 9 Procedure for determining the skid resistance of a pavement surface by measurement of the longitudinal friction coefficient (LPCD) DWWNL skid resistance trailer. Brussels CEN. 

FIGURE 26.32 Braking and side force coefficient as function of the longitudinal slip for a set slip angle of 8° on wet asphalt at a constant speed of 30 mph, obtained with the Mobile Traction Laboratory (MIL) of the NHTSA. The curves were fitted using the brush model for composite shp with a variable friction coefficient. 

Briefly, Tanaka et al. formulated an equation of motion for the displacement of a point of the network 5(m) from its average position, which depends on the friction coefficient / between network and solvent, the bulk and shear moduli K and G, respectively. The equation of motion has three solutions corresponding to one longitudinal (42) and two transverse modes (43), which can be expressed by diffusion equations ... 

Equation (5.161) is very similar to that used by Bagchi et al. in their recent study [76]. However, since their expression is written in terms of the longitudinal ion-dipole direct correlation function and the orientational intermediate scattering function of the solvent in place of Cux k) and F fi k,t) in our formula, its application is limited to the calculation of the dielectric friction. As we have clarified in Sec. 5.3, both the translational and rotational motions of solvent molecules manifest themselves in Fxfi k, t), and Eq. (5.161) can be applied to the calculation of the friction coefficient which comprises the hydrodynamic as well as dielectric contributions. Thus Eq. (5.161) can be regarded as a more general microscopic expression for the friction coefficient. 

In the first case, the horizontal friction force, F, and vertical reaction force, F, developed during braking are recorded (electronically). The ratio of the two forces FJF ) determines the BFC, or the friction coefficient, along the longitudinal direction (Figure 16.7a). 

The measuring wheel in BV-11 and SFT devices moves parallel to the direction of travel (longitudinal friction principal coefficient) and carries a load of 1000 N (TYROSAFE 2008). 

The picture involved in the one-dimensional dispersion model is the onedimensional process of flow in a tube. There is a flow velocity in direction z, which, in the ideal case, is constant over the reactor cross section %. Because of molecular diffusion, turbulent convection, and the parabolic velocity profile that results from boundary friction (roughness, s), there are large deviations from a uniform flow front. The effective longitudinal dispersion coefficient... 

For electron transfer in solutions, it is often assumed that the strong friction limit holds. The friction coefficient has been identified with the inverse of the longitudinal relaxation time ... 

While the time dependent dielectric friction coefficient C(t) for the model is analytically quite complex, numerically it is close to an exponential function in time, with a decay time roughly equal to the longitudinal relaxation time for H2O 0.25 ps. 

With the total friction coefficient 5 = (L/6) 5, the instantaneous velocity of the chain along the tube axis, or longitudinal velocity, is ... 

To examine the effects of viscosity, four kinds of hydro-refined mineral oil with different viscosities were used as base oils. The results with transverse roughness and those with longitudinal roughness are compared in Figs. 9 and 10, as a function of velocity and oil film parameters, respectively. From these figures, it can be accepted that the friction characteristic is basically the same for all of the base oils despite their different viscosities. It is also recognized that transverse roughness produced small friction coefficients below the A value of 1 x 10, particularly below 10". ... 

In the case of transverse roughness, the fiiction coefficients were smaller with StA than with n-BuP across the entire velocity region. In the case of longitudinal roughness, however, StA showed smaller friction coefficients than n-BuP in the large A value region, but the inverse was found in the smaller A value region. 

At the longitudinal roughness position, tri n-butyl phosphate kept its load-canying capability across the entire region tested, and its friction coefficient increased gradually... 

Figure 2. A pictorial representation of the mode coupling theory scheme for the calculation of the time-dependent friction (f) on a tagged molecule at time t. The rest of the notation is as follows Fs(q,t), self-scattering function F(q,t), intermediate scattering function D, self-diffusion coefficient t]s(t), time-dependnet shear viscosity Cu(q,t), longitudinal current correlation function C q,t), longitudinal current correlation functioa...

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