International friction index

The International Friction Index (IFI) is similar to the SRI discussed above and was developed in the PIARC international experiment to compare and harmonise texture and skid resistance measurements. The index allows for the harmonising of friction measurements with different devices that use smooth tread test tyres to a common calibrated index. The procedure for determining the IFI is covered in ASTM E 1960 (2011). 

IFI comprises two parameters, the F60 and the S. These parameters refer to the calibrated friction index at a 60 km/h speed (F60) and the speed constant Sp, during measurements on a wet pavement surface. 

The speed constant, Sp, is calculated from the MPD. The MPD is determined according to ASTM E 1845 (2009), using laser or other optical non-contact methods. 

The speed constant of the pavement (Sp) with the measured friction (FRS) at some slip speed (S) is used to calculate the friction at 60 km/h (FR60), and a linear regression is used on FR60 to find the calibrated friction value at 60 km/h (F60). 

The relevant equations determining the above parameters and other information are provided in ASTM E 1960 (2011). 

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ASTM E 1960. 2011. Standard practice for calculating International Friction Index of a pavement surface. West Conshohocken, PA ASTM International. 

Calculation methods of the international frictional index of pavement surface and the international runway friction index are given. A spot measuring decelerometer is used for measurement of deceleration sustained by a test vehicle while braking with all wheels locked. This method estimates the effect of winter-contaminated pavement. 

ASTM El 960-07(2011) Standard Practice for Calculating International Friction Index of a Pavement Surface. 

The influence of consolidation load on the flowability of sucrose is shown in Fig. 8. For this material, the effective angle of internal friction is nearly constant yet the shear index is seen to change with state of consolidation. Apparently, for sucrose, increased consolidation results in a somewhat more free flowing although still cohesive material. As such, sucrose can be considered a complex powder [49] with perhaps somewhat better flow characteristics when consolidated (as might occur in a hopper). 

Hollenbach et al. (1982) showed compressibility to be a more reproducible index than parameters such as angle of internal friction or unconfined yield stress obtained from the Jenike shear test (ASTM D 6128). 

The commonly-used dynamic mechanical instruments measure the deformation of a material in response to vibrational forces. The dynamic modulus, the loss modulus, and a mechanical damping or internal friction are determined from these measurements. The modulus indicates stiffness of material, and it may be a shear, a tensile, or a flexile modulus, depending upon the experimental equipment. The mechanical damping (internal friction) gives the amount of energy dissipated as heat during the deformation. The internal friction of material is important, not only as a property index, but also for environmental and industrial application. 

ASTM E2100-04(2010) Standard Practice for Calculating the International Runway Friction Index. 

ASTM E2100-02 Standard Practice for Calculating the International Runway Friction Index. ASTM E2101-00 Standard Test Method for Measuring the Frictional Properties of Winter Contaminated Pavement Surfaces Using an Averaging-Type Spot Measuring Decelerometer. ISO 8349 2002 Road vehicles - Measurement of road surface friction. 

Figure 3.43 Two-phase friction Ap versus property index with mass flux correction. (From Baroczy, 1966. Copyright 1966 by Rockwell International, Canoga Park, CA. Reprinted with permission.)...

Internal resistance, which may vary for a soil, is a combination of frictional and cohesive forces acting on a soil. Several methods help determine this property. Results are often dependent on the method. Internal resistance is an index of shear resistance, flitemal friction is another index of shear resistance of soils and can never exceed the value of internal resistance. 

The performance of an extruder is determined as much by the characteristics of the feedstock as it is by the machine. Feedstock properties that affect the extrusion process inciude buik properties, meit flow properties, and thermal properties. Important buik flow properties are the buik density, compressibility, particle size, particle shape, external and internal coefficient of friction, and agglomeration tendency. Important melt flow properties are the shear and eiongational viscosity as a function of strain rate and temperature. The commonly used melt indexer provides only limited information on the meit viscosity. Important thermal properties include the specific heat, the glass transition temperature, the crystalline melting point, the latent heat of fusion, the thermal conductivity, the density, the degradation temperature, and the induction time as a function of temperature. 

The shear flowability index, n, was found, from past observations (Farley Valentin 1965, 67/68), to be independent of the bulk density of sheared compacted powder. Because of this independence of particle size from bulk density it is now realised that the shear flowability index, n, from the Warren Spring equation and the Jenike internal angle of friction may be the preferred parameters to eharacterise and quantify the flowability of powders. Jenike and others (Williams et al. 1970/71 Williams Birks 1965 Hill Wu 1996 Cox Hill 2004) selected the Jenike failure function to be one of the best indicators to predict the ease of powder movement and powder flowability. 

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