Steel, frictional coefficient

Sihcone oils are good hydrodynamic lubricants but have generally poor frictional lubricating properties (352—354). The latter can be improved by incorporating chlorophenyl groups into the polymer side chains (355). For steel on steel, the coefficient of friction is about 0.3—0.5. The load-bearing capacity of PDMS (Almen-Wieland machine) is only 50—150 kg, compared with - 1000 kg for polychlorophenyLmethylsiloxane and up to 2000 kg for mineral oil. 

Example 2.6 The bobbin shown in Fig. 2.16 has been manufactured by sliding the acetal ring on to the steel inner and then placing the end-plate in position. At 20°C there are no stresses in the acetal and the distance between the metal end-plates is equal to the length of the acetal ring. If the whole assembly is heated to 1(X)°C, calculate the axial stress in the acetal. It may be assumed that there is no friction between the acetal and the steel. The coefficients of thermal expansion for the acetal and the steel are 80 x 10 °C and 11 X 10 °C respectively. The modulus of the acetal at 100°C is 1.5 GN/m. ... 

At the end of last century, a near frictionless carbon (NFC) coating was reported, which is practically hydrogen contained DLC film grown on steel and sapphire substrates using a plasma enhanced chemical vapor deposition (PECVD) system [50]. By using a ball on a disk tribo-meter, a super low friction coefficient of 0.001-0.003 between the films coated on both the ball and the disk was achieved [50]. A mechanistic model was proposed that carbon atoms on the surface are partially di-hydrogenated, resulting in the chemical inertness of the surface. Consequently, adhesive interaction becomes weak and super low friction is achieved [22],... 

The friction and wear properties of fullerene LB fihns have been investigated. The coefficient of kinetic friction was measured using a steel ball-on-glass disk method, with the LB films deposited onto the glass disk [326,327]. The friction coefficient dropped from 0.8... 

The frictional behavior of 316 stainless steel is shown in Fig. 8 for sliding in air or in different atmospheres. No clear trend in the dependence of friction coefficient on environment was observed. 

Figure 8. Friction coefficients as a function of sliding time for 316 stainless steel in air, for 2 N load and variable speed (L) or in different atmospheres (R)...

For calculation of flow in fire main systems, the design engineer should use the Hazen-Williams friction coefficient of C = 100 in the design of bare steel and concrete steel lined pipingforfire water systemsto allow for future deterioration as the system ages. A friction coefficient of C = 140 may be used for plastic pipe, such as fiber reinforced plastic (FRP) or polyvinyl chloride (PVC). 

C = Hazcn-Williams friction coefficient (C-=100 lor steel pipe), dimensionless d pipe ID, in. [cm]... 

Adsorption of carboxylic acids, alcohols and amine on steel surfaces takes place by hydrogen-bonding of monomeric molecules to the oxide and hydroxide layers on the surface. Aliphatic amines, alcohols, and acids have also proved to be especially suitable for build-up of anti-wear protective layers, and greatly reduce the friction coefficient. Adsorbed and chemisorbed films are very effective in reducing friction and mild wear under moderate rubbing however, they fail fairly rapidly under severe rubbing conditions and therefore are not very effective in preventing wear and seizure. 

A global survey of friction coefficients of various polymers is given in Figure 7.30 (all moving against steel). In general, polymers exhibit less friction than metals. The lowest values for the friction coefficient are found for HDPE, POM, and, in particular, PTFE. 

Abrasion resistance, Taber CS-17, 0.5 kg load, mg/1000 cycles Coefficient of sliding friction to steel Thermal coefficient of linear expansion, per °C Thermal conductivity, at 25-160°C, W/(m K)... 

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... 

Fig. 34. The variation of the micro-hardness (left curve) and friction coefficient (right curve) with the dose (40 keV Ar onto steel) (after ))...

Phillips et al. [27] studied the surface chemistry of IL-lubricated steel/steel sliding contacts under temperature variation from room temperature to 300 C. This study was focused on understanding the high-temperature stability of the liquids in contact with metal under tribological stress [27]. Some Fe samples were oxidized to Fe Oj and FOjO via thermal evaporation prior to treatment with ILs. The metallic and oxidized Fe samples were then reacted with ILs at elevated temperatures. Results showed that the friction coefficient of different fluorinated ILs was below... 

Fig. 9.18 (a) Friction coefficient and (b) wear volumes of steel disks lubricated by PEG and different IL additives at room temperature. (SRV tester, load 100 N, stroke 1 mm, frequency 25 Hz, duration 30 min) (Reproduced from Ref. [100] with kind permission of the American Chemical Society)... 

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