Friction tester

Figure 8.16 shows the principal components of a coefficient of friction tester. Polymer samples in the form of thick sheets or molded plaques are attached to the base and a sled with standard dimensions, weight, and surface properties is drawn over the surface. The load beam measures the force required to initiate movement and sustain motion at a given rate of crosshead travel. Thin films can be taped to the sled and drawn across a contact surface that has known properties. 

Figure 8.16 Schematic diagram of a coefficient of friction tester...

Recently, ultrathin organic thin films attract attention as new film lubricant [51]. Organosilane monolayer, which is one of the ultrathin films, has been identified as promising boundary lubricants. This is because organosilane molecules interact strongly with substrates and they are robust against solvent and temperature increase. Friction and wear tests of monolayers were carried out with a conventional ball-on-disk type friction tester (SHINTO Scientific Co. Ltd.) in air and tetradecane at 298 K. A 5.0 mm radius ball made of stainless steel was slid on a disk. The friction coefficient was determined by the distortion of a... 

Yuko Tsuya also used electron diffraction in studying the progress of running-in with an unconsolidated "floated" film initially about 0.5/ym thick, using an oscillatory friction tester with a stroke of 20 mm and load 8 kg. She found a gradual transition from a layer of randomly-oriented particles with little adhesion or cohesion to a smooth cohesive layer with the molybdenum disulphide crystallites almost fully oriented with the (001) basal planes parallel to the substrate surface. The coefficient... 

Sliding block friction tester with 6 lb load. 

A complementary study of steel/steel contacts (100Cr6) [47] used an oscillation wear and friction tester to screen ionic liquids in the boundary lubrication regime at 30, 100 and 170°C at 200 N load. Results are summarized as follows (i) some promising ionic liquids gave lower friction and wear at all temperatures, compared to reference lubricants, (ii) chemical structures of ionic liquids have a high impact on their physico-chemical as well as on tribological properties and (iii) careful selection of both cation and anion, as a tailor-made ionic liquid, enables adaptation of ionic liquid structures to specific applications. 

There is a simple Wall Friction Tester available commercially, (from Ajax Equipment (Bolton) Ltd.), which uses a round plastic cell 160 mm in diameter and 25 mm in height, with a stainless... 

As the name implies, the split cell testers use a cell, usually in the form of a ring similar to that used in the Jenike shear cell or the wall friction testers, but both the cell and supporting plate are split vertically, across the diameter. The sample is compacted vertically in the usual way (by application of normal loads via a lid) and the sample is then pulled apart by moving the split halves away. There have been some research devices designed on this principle, for example by Boden33, who suspended the cell supports on air bearings to minimize friction, but such devices are too expensive for general use. 

The effect of temperature on friction between aluminum sheet (3004-H19) and 52100 steel balls due to the liquid crystal cholestryl linoleate (CL) and stearic acid (S A) was measured under boundary conditions on a modified MOFISS friction tester. Temperatures were selected so that the order of CL was cholestric (25 C), smectic (30 C) or isotropic (40 C). The results showed no temperature dependence on COF of CL. It is speculated that this lack of dependence might be due to dramatic shifts in phase-transition temperatures of the thin film LC from that of the bulk. 

A schematic of a typical yarn friction tester is shown in ASTM D. 108 and is in my view far superior to the arrangement shown in PD 6527. 1990. published by the BSl. An approximation of the ASTM schematic is shown in Fig.. 34. 

The WET p and Tan 8 were measured in the evaluation of a rubber compound as the tread rubber of tire for the various rubber compounds containing the different tackifiers at the same level of 2.5 phr. The WET p, evaluated by a flat-belt type friction tester, refers to the coeflbcient of friction between the wet surfaces, and would reflect the tire performance in road gripping under wet conditions. On the other hand, the Tan 6 would be related to the rolling resistance of the tire compound and was measured by viscoelasticity tester. In general, as shown in Table... 

On completion of the test after 6 h, the test specimens are cleaned and tested for friction using the Pendulum friction tester (see Figure 2.6). 

Figure 2.6 British pendulum friction tester. (Courtesy of Controls Sri.]...

Other devices to be mentioned are the Mu-meter (United Kingdom) (fixed slip ratio type 13% or 7.5% operating speed between 20 and 80 km/h) and the Runway Friction Tester (United States) (fixed slip ratio type 15% operating speed between 30 and 91 km/h). These devices have initially been developed for runway skid resistance measurements. 

Finally, apart from the mobile devices, portable devices such as the British pendulum (SRT), the Japanese DFT (Dynamic Friction Tester) and the Swedish T2GO and VTI are in use. From the above, the British pendulum has been widely used in many countries around the world and the portable friction testers T2GO and VTI are slowly gaining popularity. 

The Sarsys friction tester (SFT), which has the measuring wheel built into a Saab 9-5 vehicle (Figure 16.11) and hence is known as the Saab friction tester, was developed in Sweden. 

The ASTM locked wheel skid tester or the pavement friction tester (PFT) was developed in America and is one of the first pavement surface skid resistance measuring devices. 

Figure 16.19 Dynamic friction tester portable device, (a) Overall view, (b) Bottom view. (Courtesy of Nippo Sangyo Co. Ltd.)...

ASTM E 1911-09ae01. 2009. Standard test method for measuring paved surface frictional properties using the dynamic friction tester. West Conshohocken, PA ASTM International. 

Bergstrom A., H. Astrom, and R. Magnusson. 2003. Friction measurement on cycleways using a portable friction tester. Journal of Cold Regions Engineering, Vol. 17, No. 1, pp. 27-57. 

CEN/TS 15901-12.2011. Road and airfield surface characteristics - Part 12 Procedure for determining the skid resistance of a pavement surface using a device with longitudinal controlled slip The BV 11 and Saab friction tester (SFT). Brussels CEN. 

A model system was developed at the DKI in the form of a disk wear tester. This universal disk-tribometer was discussed by Volz [12]. The concept of the disk-tribo-meter is partially based on a modified friction tester developed at Enka Glanzstoff [13]. The geometry of the disk-tribometer is schematically shown in Fig. 11.8. 

For initial safety testing, the impact and friction sensitivities were tested according to BAM methods [85,86] with the BAM Fallhammer and BAM friction tester . Compound 2 is very sensitive towards impact (< 1.5 J) and... 

Early work on the macroscopic friction of SAM films was carried out by DePahna and others using a pin-on-disk type friction tester, and they observed a low friction coefficient [1,13] however, their frictional property containing a wear resistance was demonstrated under a limited condition. For example, the self-assembled octadecyltrichlorosilane monolayer revealed a good wear resistance at low load [14], but failed to lubricate at a normal load of 1.0 N due to wear [15]. To overcome the poor wear resistance of thin films, a dual-layer film was prepared by a combination of aminoalkylsilane and stearic acid, which improved the wear resistance of the SAM film [16]. In this work, the authors also proposed a defect-free double layer on a flat substrate by chemical adsorption of alkylsilane compound. 

Figure 6.8 Expanded view of an annular shear cell polymer to metal friction tester. Drawing by Richard Humpidge. 1975, Rapra Technology)...

Variable slip technique is used to measure the friction coefficient between tire and pavement. The test equipment consists of an automotive vehicle. Each test wheel contains a variable brake system. The resulting resistive force caused by friction between the tire and the pavement surface is sampled and recalculated to slip friction numbers. Frictional properties of pavement surface as a function of speed are measured by a d5mamic friction tester. A disk spins with its plane parallel to the test surface. The rubber sliders come into contact with the pavement, and torque is monitored when rotational velocity reduces, due to friction. A graph of friction vs. speed is plotted. 

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