Wear factor

Waxes hydrocarbon Wax printing Wax sizing materials Wax sweating Waxy corn WB4101 [613-67-2] W341C [110368-36-0] Weak interfaces Weapons Wear factors Wear resistance Weather balloons Weathering... 

Pressure, kPa Velocity, cm/s Wear factor, K X 10, Tefzel. 1/Pa Metal... 

Unfilled Teflon PFA has been tested in mechanical appHcations using Teflon FEP-100 as a control (24). Tests were mn on molded thmst bearings at 689.5 kPa (100 psi) against AISI 1080, Rc 20,16AA steel, and at ambient conditions in air without lubrication. A limiting PV value of 5000 was found. Wear factors and dynamic coefficients of friction are shown in Table 4. 

Velocity, m /min Wear factor Dynamic K X 10-", 1/Pa " coefficient of friction Test duration, h... 

A hard, mst-resistant shaft of at least 0.25 micrometer finish is usually required. Common shaft surfaces are hardened tool steel, chrome plate, high strength bronze, and carbide and ceramic overlays. Test results over a broad speed range from 0.05 to 47 m/s (10 to 9200 fpm) iadicate that a coefficient of friction of 0.16—0.20 and a wear factor of 14 X 10 m /N(70x 10 ° in. min/ft-lb-h) are typical for dry operation of weU appHed grades of carbon—graphite (29). 

Due to their specific characteristics, oligoalkylhydridesiloxanes are widely used in the textile industry. After silicone treatment textiles acquire a high hydrophobicity, which is resistant towards various physicochemical stresses, do not change appearance and remain air- and vapour-permeable. Certain silicone substances considerably reduce the shrinkage and creasing of materials with cellulose and hydrocellulose fibres, improve their resistance towards abrasion, tearing, bending and other wear factors. 

Table 5.17. Wear factor and dynamic coefficient of friction of different polymers containing PTFE Polymist. Courtesy of Ausimont USA, Inc.

Polymer PTFE, % Wear factor Dynamic coefficient of friction ... 

Coefficient of friction is inversely proportional to pressure and proportional to velocity. Wear rate of fluoropolymers is proportional to load (/ ) and velocity (V). Combinations of pressure and velocity are defined where the material can be used, thus a FV limit is defined. Above this PV limit, the wear increases exponentially because of the heat that is generated as a result of motion. Generally, a polymer or its compounds can be characterized by PV limit, deformation under load, and wear factor. Wear factor or specific wear rate is defined as the volume of material worn away per unit of sliding distance and per unit of load. 

Wear factor is a proportionality parameter related to the wear of a non-lubricating surface against a mating surface below the PV limit of the material. Equation (3.2) shows the calculation of wear rate of a material. 

Table 3.57. Wear Factor of 25% Glass-filled ETFE Bearing...

Mating Surface (Finish of 406 nonometers) Pressure, MPa Velocity, cm/sec Wear Factor, 10 " in min/ftlb.hr ... 

Specific Wear Rate - Also known as wear factor, specific wear rate is defined as the volume of material worn away per unit of sliding distance and per unit of load. 

Each test specimen was subjected to a constant load and a fixed cycle of reciprocating motion. Long term wear tests were performed with the total sliding distance in each case extending to several hundred km. The material removed by wear was monitored by periodic measurements of the weight of the UHMWPE wear pins on a Mettler microbalance with a sensitivity of 1 g Density measurements enabled volume loss (V) against sliding distance (X) relationships to be established at each load (P) and wear factors (k) were then determined from the relationship. 

The relationship between the wear factor (k) and the counterface roughness (Ra) under wet conditions depicted In Figure 6 Is linear, corresponding to... 

There has been considerable discussion aboout the most appropriate feature of counterface topography to be employed In the representation of wear factors for polymers. However, it is evident from Figures 3 and 4 that there is a firm relationship between (Ra) and other principal features of counterfaces prepared by consistent manufacturing processes. It may, therefore, be adequate to represent the wear factors as functions of (Ra) until more complete theoretical relationships are established for the polymer wear process. 

The earlier suggestion by Dowson et alj( 3) that for the dry wear of UHMWPE against stainless steel there was an optimum Initial surface finish corresponding to a minimum wear factor, has been confirmed by further detailed and extensive studies by Glllls( ) and Dlab( 3). These experiments indicate that the optimum (Ra) is slightly less than 0.1 jjm and In the range 0.05 to 0.1 ym. 

The dry wear factors are, in fact, remarkably steady over a wide range of counterface roughnesses extending over about two orders of magnitude, as shown In Figure 5. 

Wear Factor (k) As A Function Of Counterface Roughness (Ra) Under Wet Conditions... 

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