Tire wear

A well-known example of blocking arises in the comparison of wear for different types of automobile tires. Tire wear may vary from one automobile to the next, irrespective of the tire type, because of differences among automobiles, variabiUty among drivers, and so forth. Assume, for example, that for the comparison of four tire types (A, B, C, and D), four automobiles (1, 2, 3, and 4) are available. A poor procedure would be to use the same type of tire on each of the four wheels of an automobile and vary the tire type among automobiles, as in the following tabulation ... 

Soil Combustion (oil, coal, refuse) Tire wear Concrete cement Salt spray, deicing salt Metal corrosion wear Motor vehicle Weathered paint... 

More detailed statistical analyses (chemical element balance, principal component analysis and factor analysis) demonstrate that soil contributes >50% to street dust, iron materials, concrete/cement and tire wear contribute 5-7% each, with smaller contributions from salt spray, de-icing salt and motor vehicle emissions (5,93-100). A list is given in Table VII of the main sources of the elements which contribute to street dust. 

Tire Wear under Controlled Slip Conditions.744... 

Conditions for Tire Wear in Road Tests and Normal Usage.747... 

The temperature rise in the contact area plays a major role in abrasion and tire wear. It leads to thermal degradation and aids oxidation. This will be discussed in Section 26.5. The friction is primarily influenced because the temperature rise influences the operating point log a-j v of the master curve. 

When forces are transmitted, slip occurs because the wheel is being deformed. The relation between force and slip is one of the most important laws in tire mechanics, because it influences the all important properties of traction, durability, and tire wear. (This is not only true for tires, but also for all force transmission by adhesion friction). 

Even in a homogeneous solid elastic wheel the distortion is complex and requires sophisticated methods to arrive at a precise relation between force and slip. For tires this is even more difficult because of its complex internal structure. Nevertheless, even the simplest possible model produces answers which are reasonably close to reality in describing the force-slip relation in measurable quantities. This model, called the brush model—or often also the Schallamach model [32] when it is associated with tire wear and abrasion—is based on the assumption that the wheel consists of a large, equally spaced number of identical, deformable elements (the fibers of a brush), following the linear deformation law... 

The NR compound 4 is known to be better under low temperature conditions than the control, but worse under high temperature conditions. Chemically, NR has the lowest thermal stability of the polymers used for tread compounds in tire technology and it has therefore the highest temperature dependence of abrasion and wear. Thus, it is generally accepted that NR has a higher wear resistance in a moderate climate than, for instance, SBR but a much lower one in hot climates. This will be thoroughly documented below under tire wear. 

FIGURE 26.72 Log tire wear as function of log slip angle obtained with the MRPRA trailer for three tire tread compounds. 

Table 26.7 gives a list of the boundary conditions which define a tire wear test simulation and in fact also an acmal road test. The road surface is the laboratory surface on which the abrasion data for the simulation were obtained. There is as yet no definition of a road surface and even if there were one, it would be of httle use since road surface structures change frequently along the road surface as pointed out earlier. 

The tire constmction influences both cornering and longitudinal slip stiffness. These include the tire carcass, breaker construction, inflation pressure, and tread pattern design. However, since the two stiffness components can be measured, knowledge of the construction details is not necessary. The vehicle geometry influences the tire wear through the air resistance, which it creates, and through the load distribution between front and rear axles. 

The question of the influence of the road surface on tire wear cannot be answered unequivocally because of the large number of different compositions, state of use, and weather influences on their abrasive power. Road surfaces are also not durable enough for laboratory use. Hence, reliance has to be placed on the correlation between laboratory results on a laboratory abrasive surface and road test experience. Alumina of different grain size (but primarily 60) has proved to be the most useful. Even its sharpness changes with time of use and disks are limited in their useful life. 

The market is still reluctant to adopt these mn-flat tires until there is an integral system that warns the driver of pressure loss. Many new smart developments are hitting the markets that monitor tire temperamre and pressure. This type of monitoring is also beneficial to fleet operators who need to measure and maintain tire-operating pressure to minimize tire wear and fuel consumption. 

The wear resistance of rubber compounds is of great practical importance for tires, but the mechanisms involved in tire wear are multiple and may vary depending on the vehicle, the driving conditions, and other extraneous variables. Many attempts have been made to develop laboratory test methods to simulate tire wear under various conditions. Whilst none can fully replicate road wear, various laboratory abrasion tests can be used to provide an indicator of wear resistance of tires under certain conditions. 

Lead and, to some extent, Zn distribution patterns are strongly affected by anthropogenic inputs. Elevated soil Pb content is localized around major cites and along major highways due to inputs from leaded gasoline. Zinc has a similar distribution pattern, but the likely source is tire wear. 

In urban areas, the typical dominant sources of fine organic aerosol particles are diesel exhaust, gasoline-powered vehicle exhaust, meat cooking operations, smoke from wood combustion, and paved road dust followed by four smaller sources of particles tire wear, vegetative detritus, natural gas combustion, and cigarette smoke. ... 

Statistically significant differences between car tires, tire positions and tire types are clearly evident from analysis of variance. Table 2.60 indicates the highest wear out of tires on car IV and the lowest on car I. This does not present an error but is simply the upper and lower limit of tire wear-out in this research. 

An elastomer with a low modulus will often have far better erosive wear than material with a higher modulus. An abrasive wear test (such as the DIN abrader) will show a poor result for a soft elastomer. This is also shown in field applications such as tire wear. When the application is changed from abrasive to erosive wear, the softer elastomer will wear very well. The reason for this is that the low modulus of the soft elastomer allows the stresses from each impact to be dissipated more readily than for hard polyurethanes. The soft material will stretch further and then snap back before damage is done. Any microcracks formed will have a slower growth rate and hence less erosion will occur. 

Heavy metals concentration generally decreases in urban soils away from the main road network and with increasing depth of sampling. This can be explained by the strong dependence of these contaminants on the use of motor vehicles—leaded fuels for Pb, tire wear for Zn and Cd, brake pads for Sb, converters and exhaust systems for platinum group elements (PGEs). 

Although elastomers and rubber have many helpful and useful properties, they can also cause problems. For example, rubber is used to make safe tires for cars, trucks, and other vehicles. These tires wear out and must be changed regularly. As a result, Canada and the United States accumulate 275 million used tires every year What can be done with these used tires ... 

The improved tire wear of cold polymerization SBR led to the very rapid replacement of hot SBR for most applications. This change was relatively easy to make, as all the equipment could be used with the only modification required being the addition of reactor cooling, which is achieved with either the reactor jacket, internal coils, or both. 

Wik, A., Dave, G.(2006) Acute toxicity of leachates of tire wear material to Daphnia magna -variability and toxic components. Chemosphere 64 1777-1784. 

Past experience indicates tliat tire wear-out lime of tliis electronic device, like tliat of a large variety of products in many different industries, tends to be... 

In order to assess the internal consistency of the emissions, as shown in Table 8, a calculation was made whereby the mean atmospheric input was equated to the world metal production emitted to the atmosphere plus natural emissions and other sources to the atmosphere. With the exceptions of Cu and Zn, the quantities of emissions balance rather well. There is no obvious reason why Cu is out of balance by nearly a factor of 2 (atmospheric input > sources). For Zn, with an imbalance of 1.7 for atmospheric input > sources, there is an obvious problem with other sources in that the impact of rubber tire wear. This source term will be addressed in the next section. However, even with this term, the right side of the equation would increase to a maximum emissions figure of 300,000 tyr (Table 8). It is possible that maximum Cu and Zn emissions to the atmosphere have been overestimated but there is no way to check this with the available data. 

Of the five Zn emission categories plotted in Figure 5, waste incineration and rubber tire wear are the most important. Note that in general these emissions have increased during the last 40 years such that the second-tier emissions total approximately one-half of the Zn mining-smelting emissions. 

Waste incineration Rubber tire wear Fossil fuel combustion Fertilizer production Cement production... 

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