Wear rate between

Comparing Wear Rates Between Different Clinical Studies... 

In summary, the following three factors, either alone or in combination, could explain the differences in wear rates between Chamley s and Griffith s studies ... 

Our inability to conclusively identify the explanation for the difference in wear rates between these two studies underscores the difficulty in comparing two retrospective series of patients, even when performed at the same institution and by the same group of investigators. 

Introduction 5.5 Comparing Wear Rates Between 5.8 Range of Clinical Wear... 

COMPARING WEAR RATES BETWEEN DIFFERENT CLINICAL STUDIES... 

Difference in wear rate between the tool and workpiece materials should be as high as possible. 

A simple approach, therefore to compare wear rates between the sliding model contact and the ball bearing case is to scale the data according to the slip ratio. This assumes that wear is proportional to sliding distance (i.e. following an Archard [8] approach) and so is strictly only appropriate for adhesive or abrasive wear and not fatigue associated material removal. 

An end face apparatus (Fig. 1) was used to measure wear rate between nominally flat surfaces with minimum lubrication effects. The upper disc is made of alumina, zirconia or alumina/zirconia nanocomposite cerantics. The mating disc of medical... 

A benchmark for hardness is diamond, the hardest known substance. Its nominal hardness is 100 GPa (VHN = 10,000kg/mm2),but methods are known that may make it still harder. Based on this benchmark, materials with hardnesses between 20 and 40 GPa are said to be very hard , while a material with hardness greater than 40 GPa is said to be super-hard . The latter are very rare, and there is no true competitor for diamond. However, some property combinations make particular materials more useful than diamond in some applications. For example, cubic-BN is better for cutting iron-based alloys because it reacts chemically with Fe much less strongly than does the carbon of diamond. Therefore, its wear-rate is substantially less. 

The contact pressure between the test piece and abradant is another critical factor in determining wear rate. Under some conditions, wear rate may be approximately proportional to pressure, but abrupt changes will occur if, with changing pressure, the abrasion mechanism changes. For example, a change can occur because of a large rise in temperature. 

The initial and steady state wear rates of the siloxane-modified epoxy pins on the steel disks correlated with the inverse of the KIC values which agrees with previous abrasive wear tests 47>. The steady state wear rates on the smooth glass disks were comparable to those on the steel disks. Thus in both cases the wear mechanism is abrasive wear by the wear particles trapped in the interface between the pin end and the disk. 

Ortiz, Merino, J.L. and Todd, R.I. Relationship between wear rate, surface pullout and microstructure during abrasive wear of alumina and alumina/SiC nanocomposites , Acta Mater. 53 (2005) 3345-3357. 

The rate and amount (flux rate) of material impinging on the elastomer have an effect on the wear rate of the elastomer (Arnold and Hutchings, 1989). With flux rates of between 500 and 5000 kg nr2 sec-1, the erosive wear decreased with flux rate at low velocities and low angles of incidence. At higher flux rates (1000 to 10000 kg nr2 sec-1), the wear rate decreased when the velocity was lower and the angle of impact was more normal to the surface. 

The largest effect of water or any other liquid is that it acts as a lubricant and reduces the erosive rate by reducing the frictional forces. This effect is greatest at angles between 30° and 90°. If water instead of air is used, the wear rate is reduced by 50% (Arnold and Hutchings, 1990). To a lesser degree, the lubricant will enhance any cutting that may take place. The formation of hydroperoxides is another effect caused by water on the polyurethane. 

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