Steady-state wear sliding

The most comprehensive fatigue wear model (2) proposed In the literature was used to predict wear rates to within 30 percent or less of the experimentally measured values (J). The exponent t was determined from notched cylindrical specimens In reverse bending. The number of contacts and the areas were determined from surface profiles of the polymer and the counterface after steady-state wear was attained. The wear data was obtained from a polymer pin sliding on a rotating cylinder. 

When polymers slide on machined metal surfaces, it is quite possible that steady-state wear Involves a combination of abrasive, fatigue, and adhesive wear mechanisms. To study fatigue wear, it would be desirable to minimize the contributions of the abrasive and adhesive wear modes. In this paper, the following polymers polycarbonate, polyvinyl chloride, ultra-high molecular weight polyethylene, siloxane modified epoxies, and polylmldes are tested in experiments in which the fatigue wear mode is predominant. 

The Initiation of the wear track occurred simultaneously with the abrupt rise in the friction. The wear rate decreased from its initial value to a steady state value in less than 4 kc after initiation (see Figure 4). The steady state wear rates, expressed in square micrometers of track cross section area per kilocycle of sliding, are given in Table III. 

Figure 13o Steady state wear of the tissue under inter-mittant sliding. Curve A oscillation stopped for 55 seconds, resumed for 1 miuo Curve B oscillation stopped for 15 seconds, resumed for 1 minb Pressure 2,07 MN/m. ...

HOPE sliding against the abraded steel surface, a steady-state wear rate of 0.01 mg/hr and a coefficient of fraction of about 0.28... 

In the sliding of 30% CuS, 70% HOPE against the rolled brass, the steady-state wear rate was 0.78 mg/hr (Figure 13) compared to... 

In addition, as a typical failure mechanism, fiber/matrix debonding occurs due to the shear and tension type loading. If fiber/matrix debonding has taken place, the local separation initiates additional fiber cracking, wear debris formation, and a more intensive wear process. In the steady state wear process, a so-called compacted wear debris layer (CWDL) covers the surface it is composed of pulverized wear debris and matrix material. During the wear process, this layer is continuously formed and removed by the surfaces sliding over each other. 

The comparison of the steady state wear rate, defined as the wear volume per unit load and unit sliding distance, is shown in Figure 7. In this study, the result of the initial 10km of sliding was not used for the calculation of the steady state wear rate to exclude any initially high wear. 

Variations in Coefficient of Friction and Wear Depth of Various Polymers Rubbed Against Steel Disk with Sliding Distance. Figures 5 (a),(b),(c),(d) and (e) show variations in the coefficient of friction and wear depth h with the sliding distance in the wear processes of PI, PAI, PEEK, PPS and PES, respectively With all specimen polymers, the steady states of friction and wear appear following the initial transient states The wear rates of various polymers generally decrease gradually in the initial transient wear state, and the wear rates in the steady state are much lower than those in the initial transient state However, the steady state of hi er wear rates... 

Wear of Polymer Pins Sliding Against Steel Disk. Figures IT (a) and (b) show the variations of fspecific wear rates obtained in the steady states of wear for various polymers with disk temperature. 

Wear of PET Pins Sliding Against Stainless Steel Disk. In Figure 6, it is seen that the steady state of wear following a transient state generally appears. The specific wear rate, K for various PET... 

Thus far, seif-mated pin-on-disk siiding wear tests have been carried out with RBSN, HSN, and SSC materials. The tests were performed at a velocity of 0.1 m/s with a 1 kg static load in air at room temperature and a total sliding distance of 1000 meters. Tabie 4 summarizes the friction results obtained. The breakaway friction coefficients were measured prior to wear testing on surfaces polished to a 1 )xm finish. The values reported for the kinetic friction coefficients are the steady state values obtained after 500 meters of sliding. The microstructure, fracture surface, and reactions at the wear interface are currently being studied to provide more insight into the wear behavior of these ceramics. 

Let us consider first the following situation. A metal pin slides over a ceramic plate at a constant velocity in an electrolyte solution. The metal is polarized anodically in the passive potential region using a potentiostat. Rubbing causes wear of the passive oxide film by abrasion. Under steady state conditions the rate of film growth at the imposed potential is equal to the rate of film thinning due to wear ... 

Under dry contact condition Figure 6(a), specific wear rate (Ws) of the composite has less influence by sliding distance especially at higher range of apphed loads. However, at an apphed load of 5 N, there is an increase in Ws until 5 km of shding distance that is a steady state reached after 5 km of shding distance. On contrary. Figure 6(b) shows similar trends of specific wear rate. One can see that the curves are divided... 

The pin-on-disc machine has been widely used in tribology and is particularly useful in the evaluaticxi of the nature and wear and friction of material pairs under well controlled, steady-state conditions of load, sliding speed and envirrximoit. 

It is interested to know how far the pin slides until the coefficient of friction and the wear rate reach steady state. Fig. 11 shows how the sliding distance from the start point to the second transition poin t,, varied with sliding conditions. From this figure, it is seen that the sliding distance, L, increases as the shding speed increases and the contact pressure decreases. 

When two surfaees start to slide against one another, steady state is not immediately achieved. Both the surface of the polymer and the eounterfaee may be modified over a period of time. Abrasion removes the original polymer surface with its inherent properties, and the new face may be annealed by frictional heating or suffer thermal or oxidative degradation, resulting in chain scission or chemical modification. The eounterfaee may also suffer abrasive wear (especially when the polymer is filled), or it may become coated with a film abraded from the polymer surface. Thus it takes some time before a steady rate of wear is achieved. 

---