Abrasion ratings

Nienow and Conti (1978) developed a model of partiele abrasion at high solids eoneentration based on Rittinger s law of eomminution. When tested experimentally using eopper sulphate and niekel ammonium sulphate erystals in two non-solvent liquids, measured abrasion rates were eonsistent with a seeond-order dependenee of eoneentration as predieted (Figure 5.12). 

Figure 5.12 The relationship between volumetric abrasion rate and particle concentration after Nienow and Conti, 1978)...

Figure 26.61 shows the abrasion of an OESBR tread compound as function of load for different slip angles on a sharp Alumina 60 surface. Because of the wide range of abrasion rates for different slip angles the abrasion data were plotted on a log scale. It is seen that at the small slip angle the dependence on load is small and becomes more pronounced as the slip angle is increased. This is expected from the bmsh model. At small slip angle the side force is independent of the load and hence it is expected that the abrasion behave in a similar way. 

FIGURE 26.71 Correlation and regression coefficients between road test ratings of seven truck tire compounds 80 SBR/20 NR differing by type and amount of filler and laboratory abrasion ratings obtained on LAT 100 testing equipment. 

Having calculated the force for a particular event the slip is calculated using the bush model and hence the energy dissipation is obtained. Using the factors of the abrasion equation, determined with the LAT 100 on an alumina surface the abrasion loss for each event is calculated. The forces are different for a driven and a nondriven axle and accordingly different abrasion rates will result. 

It is well known that during liquefaction there is always some amount of material which appears as insoluble, residual solids (65,71). These materials are composed of mixtures of coal-related minerals, unreacted (or partially reacted) macerals and a diverse range of solids that are formed during processing. Practical experience obtained in liquefaction pilot plant operations has frequently shown that these materials are not completely eluted out of reaction vessels. Thus, there is a net accumulation of solids within vessels and fluid transfer lines in the form of agglomerated masses and wall deposits. These materials are often referred to as reactor solids. It is important to understand the phenomena involved in reactor solids retention for several reasons. Firstly, they can be detrimental to the successful operation of a plant because extensive accumulation can lead to reduced conversion, enhanced abrasion rates, poor heat transfer and, in severe cases, reactor plugging. Secondly, some retention of minerals, especially pyrrhotites, may be desirable because of their potential catalytic activity. 

The neutralization capacity of a tumbling drum equates to fines production per unit flow, which depends on the energy expended per unit flow to tumble the stone, and on the hardness of the stone. Energy expended per unit flow varies with the shroud diameter, KD, and the efficiency of the water wheel, as discussed above. Stone hardness is determined by the Los Angeles abrasion rating, A, a road stone test. Experience with tumbling drums indicates an acidity neutralization capacity of 3... 

For both the DuPont and Akron procedures, the standard specifies a trial run to establish the level of abrasion rate and a running in period before the... 

Abrasive coasts are mostly composed of clayey deposits, poorly-cemented rocks, or limestones. The cliff heights range from 15 to 35 m. The abrasion rate is controlled by the composition of the coastal rocks and the cliff heights. The recession of the cliffs is also caused by the development of landslide and caving processes, especially under the conditions of strong storms. The length of individual sliding blocks reaches 500 m at a width of up to 15 m. Deep surf niches are formed in the lower parts of the cliffs. 

In the west, the coasts of Bulgaria are mountainous in their southern part, while in the north, closer to the Rumanian boundary, they give place to the lowlands of the Danube Plain. Nevertheless, the abrasive type dominates over the coasts of this region. The height of the cliff increases up to 60 m near Cape Kaliakra and to 220 m north of the Batov River. The abrasive coastal slopes feature numerous landslides the abrasion rate of these coasts is up to 0.5 m/year [4]. 

In 1939-1986, the extent of the average abrasion of the old55 delta amounted to 250 m, and the largest washout was 540 m (Fig. lib) the abrasion rate was 6-7 myear-1. The eroded urban area of Poti amounted to... 

Pressure Units of (kPa) or (psi). The pressure is the load applied to the wafer divided by the wafer area. Note that if the surface is rough or has topography, the contact area is less than the geometric area, and hence the pressure is increased until such time as the surface is made smooth. Mechanical abrasion rate is proportional to pressure. Pressure also affects planarization. 

Pad Velocity Units of rotations per minute (rpm) or (cm/sec). If the wafer is rotated off the axis of the pad (as shown in Figure 2.6a), which is common, the pad velocity is also the average relative velocity of the pad with respect to the wafer. Mechanical abrasion rate is also proportional to velocity. Velocity also affects slurry transport across the wafer and the... 

At low etchant concentrations, the polish rate is limited by step 2. In this dissolution rate limited region, the abrasion rate is higher than the dissolution rate. The abraded material that is not dissolved quickly redeposits onto the surface, lowering the net rate of removal. Therefore, the polish rate is approximately equal to the dissolution rate. In the dissolution rate limited region, the slurry cannot dissolve more material, and therefore increasing the mechanical abrasion rate, by increasing the pressure, has no effect on the polish rate. However, increasing the etchant concentration increases the dissolution rate of abraded material and thus increases the polish rate. 

The model contends that material is removed from the surface primarily by mechanical abrasion. The abraded material is either dissolved into the slurry, swept away from near the surface as undissolved copper or copper oxides by the fluid motion of the slurry, or redeposited onto the surface. The polish rate is then the abrasion rate minus the redeposition rate. Material is removed from the surface by chemical etching secondarily only, if at all. 

From the above discussions one concludes that the Preston equation may be applied to plots of polish rate vs. pressure or velocity and the resulting value compared to the theoretical value. The Preston equation predicts the abrasion rate of the surface. In all cases examined, the observed is lower than theory predicts because the efficiency of mechanical abrasion is lowered by incomplete removal of the abraded material from the vicinity of the surface. The unremoved abraded mataial redeposits onto the surface, lowering the net polish rate. 

The polish rate behavior deviates from the Preston equation at high velocities and pressure or if the pad is poorly conditioned. The apparent saturation in the polish rate observed at high velocities and pressures indicates that the polish rate enters a dissolution rate limited regime. In this regime, increasing the abrasion rate does not affect the polish rate because the slurry cannot dissolve any additional abraded material and the additional material simply redeposits. Thus, Preston s equation is only valid in an abrasion rate limited regime. 

From all observations in compendium, it is reasonable to model the CMP removal rate for this particular slurry as a temperature-activated, abrasion-assisted etch process, in which a by-product of a few monolayers forms to inhibit - but not arrest - the etch process. The abrasive serves the dual purpose of increasing the temperature and clearing the transformed surface to increase the efficacy of the etch. The oxidizer is really a controlled etcher/complexer without which the abrasion rate is low. Under normal polishing conditions, the removal rate is limited by the formation of the surface complex. This explains the failure to observe a distinct oxidation layer in TEM as well as the temperature dependence on rate. The model does not require copper redeposition to explain low rate. 

Abrasion Resistance - Wear rate or abrasion rate is an important property of materials during motion in contact with other materials. Abrasion or wear resistance is measured by a number of methods such as ASTM D3389, also known as the Taber Test. 

These considerations warrant further study to determine exposure ages of rock surfaces in the ice-free valleys of southern Victoria Land by means of cosmogenic nuclides (Schafer et al. 1999 Summerfield et al. 1999) and to measure the abrasion rate of rocks in the ice-ffee valleys by natural processes (Miotke 1979a, b Malin 1984). The endolithic lichen and algae have continued to attract the attention of microbiologists of North America and Europe (Friedmann and Ocampo 1976 Friedmann 1977 Hirsch et al. 1988 Meyer et al. 1988 Palmer and Friedmann 1988 Ocampo-Friedmann et al. 1988 Bonani et al. 1988). 

Malin MC (1984) Abrasion rate observations in Victoria Valley, Antarctica 340 day experiment. Antarctic J US 19(5) 14-16... 

Abrasion can be serious when using mineral fillers. Fillers with alpha-quartz components have by far the highest abrasion rate, but heavy and tabular spars and dolomite also show high abrasion compared with some calcium carbonates. The measurement value usually cited is the Mohs hardness scale, but this is not a decisive indicator. 

There is also evidence that mechanochemical processes occur during the ageing of rubber vulcanizates (see Kuz minskii, 1966). The observation by Brodskii et al. (1960) that the abrasion rate of natural rubber is greater in air than in nitrogen and that antioxidants have a significant effect on wear resistance can be explained in terms of a mechanochemically initiated autoxidation reaction. It is also the belief of this writer that anomalous results on the abrasion resistance of natural rubber vulcanizates (Southern and Thomas, 1977) are explicable in terms of inhibition of crystallization by a mechanochemically initiated oxidation reaction. 

However, in industrial practice, the pre-reduced catalyst will be reduced again, so the oxide film will disappear. The above abrasion rate, which primarily reflects... 

A standard value for the minimum abrasion strength (that is, the abrasion rate) of the fused iron ammonia synthesis catalyst has been proposed to be less than 4.0% under the standard experimental conditions of ASTM. It can be seen from Table 8.38 that the abrasion rate of ZA-5H is 3.30%, which is better than that of... 

A great disadvantage, however, is the limited service Ufe of acetabular sockets made from PE-UHMW, Table 5.130. In approx. 30% of all PE-UHMW hip joint sockets implanted, complications developed after eleven years. In addition to fractures of acetabular sockets, abrasion and creep were the main problems encountered. While in-vitro investigations revealed relatively low abrasion rates of 0.2 to 0.9 j/m/year, abrasion rates as high as 150 to 200 fita were detected in in-vivo investigations on PE-UHMW in combinations with steel or ceramics [970]. 

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