Surfaces abraded

Fig. 2. Taper sections of a brass surface abraded on l/0 grade emery paper. Taper ratio 8.2. (a) Etched in ferric chloride reagent and showing the inhomogeneous distribution of the deformation close to the surface. X 100G before reduction for publication, (b) Etched to develop slip-line traces, showing the full extent of the plastically deformed layer. X 25(4 before reduction for publication. The fragmented layer, which is more clearly shown in Fig. 1, is also discern-able in these micrographs.

Fig. 5. Estimate of the strain gradient in a brass surface abraded on 600-grade silicon carbide paper.

The physical defects, such as the abrasive particles, their clusters, the fragments of the surface abraded by the abrasive... 

In summary, a satisfactory system for bonding Teflon to SAE No, 52100 steel, resulting in shear strengths in the neighborhood of 8000 psi, is obtained with the use of Scotchweld AF 13 adhesive when cured for 30 minutes at 350 F and 200 psi with the steel surface abraded to 60-65 microinch RMS and chromic acid etched and with the Teflon surface etched for 30 seconds in a solution of 1 per cent sodium in liquid ammonia at -75 F. 

The rate at which the surfaces abrade depends on the characteristics of each surface, the presence of abrasives between the first and second surfaces, the speed of contact, and other environmental conditions. In short, loss rates are not inherent to a material. With reference to the above example, changing the material of either the shoes or the steps could, and often would, change the wear on the opposite counterface. The addition of an abrasive, such as a layer of sand, on the steps would further change the situation, in that the sand would be the second surface that contacts both the shoes and the steps. 

The immobility of the surface atoms of a refractory solid has the consequence that the surface energy and other physical properties depend greatly on the immediate history of the material. A clean cleavage surface of a crystal will have a different (and probably lower) surface energy than a ground, abraded, heat-treated or polished surface of the same material. 

For dry traction more contact is desired and the stopping distance is directiy related, ie, the more contact area the shorter the stopping distance. A softer, more pHable compound conforms to the road surface topography. Too soft a compound (low mechanical strength) abrades more easily and can therefore acts as a roUer and not allow sufficient contact area to be maintained. This is not readily encountered in nominal tires and conditions but has been encountered in cases of extremely high torque conditions for very fast acceleration and sudden stops. 

Inflated Diaphragm Method (ASTM D3886). This method is appHcable both to woven and knitted fabrics. The specimen is abraded by mbbing either unidirectionally or multidirectionally against an abradant having specified surface characteristics. The specimen is supported by an inflated mbber diaphragm under a constant pressure. Evaluation of abrasion resistance can be either by determination of the number of cycles required to wear through the center of the fabric completely or by visual examination of the specimens after a specified number of cycles. 

The 3M Abrasion Test (51) is used to assess the durabUity of a protective fluorochemical finish by evaluating its resistance to abrasion and wear. The surface is abraded with an AATCC crockmeter fitted with sandpaper. 

Attrition Loss. The tendency of a support body to be reduced to powder is termed susceptibiHty to attrition, and the measurement of such susceptibiHty is termed attrition loss. Attrition can occur when support bodies mb against one another and abrade the surface, such as during calcination in a rotary kiln or sizing on moving screens. 

Abrasive wear is encountered when hard particles, or hard projections on a counter-face, are forced against and moved relative to a surface. In aUoys such as the cobalt-base wear aUoys which contain a hard phase, the abrasion resistance generaUy increases as the volume fraction of the hard phase increases. Abrasion resistance is, however, strongly influenced by the size and shape of the hard-phase precipitates within the microstmcture, and the size and shape of the abrading species (see Abrasives). 

Turbulence and high fluid velocities resulting from normal pump operation accelerated metal loss by abrading the soft, graphitically corroded surface (erosion-corrosion). The relatively rapid failure of this impeller is due to the erosive effects of the high-velocity, turbulent water coupled with the aggressiveness of the water. Erosion was aided in this case by solids suspended in the water. 

All surfaces, regardless of their finish, are made up of peaks and valleys, and in general, the average asperity height may be 5-10 times the RMS surface finish reading. When the surface is abraded, an oxide film will form almost immediately. 

The other problem that can occur with metals is the presence of various machine oils on the surface, such as might be used in the automotive area. Oil serves as a low surface energy barrier to adhesion, in most instances. Abrading and solvent wipe are recommended or else degreasing. Removing the surface oil is... 

Abrade Hand abrade with Scotch-Brite wet with MEK until the surface is shiny. Use fine-grit, dry Scotch-Brite - pads on high-speed grinder driven by dry. oil-free N2 until the surface is shiny. 

Base Metal Catalyst - An alternate to a noble metal catalyst is a base metal catalyst. A base metal catalyst can be deposited on a monolithic substrate or is available as a pellet. These pellets are normally extruded and hence are 100% catalyst rather than deposition on a substrate. A benefit of base metal extruded catalyst is that if any poisons are present in the process stream, a deposition of the poisons on the surface of the catalyst occurs. Depending on the type of contaminant, it can frequently be washed away with water. When it is washed, abraded, or atritted, the outer surface is removed and subsequently a new catalyst surface is exposed. Hence, the catalyst can be regenerated. Noble metal catalyst can also be regenerated but the process is more expensive. A noble metal catalyst, depending on the operation, will typically last 30,000 hours. As a rule of thumb, a single shift operation of 40 hours a week, 50 weeks a year results in a total of 2,000 hours per year. Hence, the catalyst might have a 15 year life expectancy. From a cost factor, a typical rule of thumb is that a catalyst might be 10%-15% of the overall capital cost of the equipment. 

Figure 2. Photograph of copper wire being drawn (cold-extruded). The wire is cold-drawn by a series of extruders until the proper gauge is achieve. During this process, fine copper particulates are abraded and attrited off of the wire surface.

Ca/NH3, ether or THE, 2 h NH4CI, H2O. 90% yield. Acetylenes are not reduced under these conditions. One problem with the use of calcium is that the oxide coating makes it difficult to initiate the reaction. This is partially overcome by adding sand to the reaction mixture to abrade the surface of the calcium mechanically. 

Slack caused by belt settling due to the soft rubber surface of the outer envelope being abraded away, which causes the belt to settle lower in the groove. 

---