Rubber abrasive wear

The essential material property of rubbers is their low elastic modulus, which ensures that the contact deformation remains elastic over a very wide range of contact conditions. The abrasive wear of rubbers is due to either fatigue of the material or tearing by a cutting force from impacts with sharp-edged particles. 

Other than the wear problems, actual in-plant maintenance usually involves removal of wood, pieces of blasting wire, and other trash from the ports. When a reagentized feed is used, layers of oily reagents can build up on the spiral surface and sometimes require scrubbing for removal. With feeds containing oily reagents that attack rubber, abrasion-resistant alloy spiral sections are used. 

Using the classical resol chemistry, Asai and coworkers patented new molded materials.Added to the resol phenolic resin are inorganic fiber, a silica powder, and a rubber component. The prepared phenolic resin composition was noted to have excellent resistance to abrasive wear and to heat shock, as well as excellent mechanical strength. As such, this material is very suitable for the fabrication of engine parts such as pulleys. These pulleys are currently fabricated from heavier and more expensive materials. 

Rubber has been used by the mining industry, both in the form of cured rubber and in its uncured state, for bonding and vulcanising to metal surfaces of tanks and vessels for over half a century. It has been used to protect such items of the plant and equipment from the deleterious effects of abrasive wear, caused by elements such as coal dust, ore particles in slurry and solid form and dusty fumes. 

Since the flow causes sliding abrasion at a low angle of incidence in the piping, the rubber which can be suggested for this application is a low durometer hardness (40 on the Shore A scale) natural rubber. For lower flow rates at ranges of 1,200 litres per minute up to 4,000 litres per minute, a hard rubber or a semi-ebonite rubber can be used since the abrasive wear of the finely meshed particles will be negligible. 

As a blade moves relative to the rubber surface, under the action of a normal force, abrasive wear of rubber occurs. According to some of the experimental observations and theoretical analyses, the processes of dry (particulate) abrasive wear might be considered to be... 

Wear Curve Description of General Process of Rubber Abrasion... 

From the physical processes of rubber abrasion and its mathematic description, it can be deduced that a general process of rubber abrasion might be regarded as consisting of three stages and expressed correspondingly in terms of a wear curve (Figure A) ... 

This is the wear equation of rubber abrasion in unsteady state. Assuming that the steady state has been reached when the number of revolution is equal to N, on the basis of Equations(14,a) and (14,b), the sum of volume loss of a tongue after another N revolutions, i.e., from N to 2N revolutions, can be calculated by... 

However, in this equation, the spacing of ridges is S instead of S as it is considered to be unchanged only if the frictional force is kept constant. Obviously, in this case, S = Sjj. Inserting Equations (18), (23), (4), and (21) into the equation above, the wear equation of rubber abrasion in steady state is given by... 

In general, the number of revolutions corresponding with the critical point to transform the wear state from unsteady to steady, is a constant under otherwise identical conditions. Hence, it can be considered as a state criterion of rubber abrasion, then... 

A wear curve can be used to describe the general process of rubber abrasion in which it is divided into three regions unsteady, steady and damage stage. 

The wear equation of rubber abrasion in steady state reveals the basic correlation among the material property, running condition and wear characteristic. The wear rate increases with an increase in the frictional force, however, it is inversely proportional to the tensile strength. 

The characteristic function, f (N,6 ), is a characterizing factor of rubber abrasion in unsteady state. Its value increases with an increase in the number of revolutions and tensile rupture ratio. However, it approaches unity as a limit in the unsteady-state process of wear. Hence, a steady state is reached if once 1 (N,6j ) = 1. 

The number of revolutions transformed the wear state from unsteady to steady can be regarded as a state criterion of rubber abrasion to estimate the wear characteristics of rubber under identical r jnning conditions. It was found to be proportional to a negative exponent of the tensile rupture ratio. 

It is concluded that the theory proposed can be applied to clarify the phenomena and processes of rubber abrasion in different stages of wear by a line contact. 

A thermoplastic molding composition [135] on a base of polyurethane contains CFD, fine-dispersed rubber and Cl solution in mineral oil or organosil-icone liquid. It is highly stable to abrasive wear in hostile media, is perfectly pliable and forms tight contact with the conjugated part. 

Because rubber is viscoelastic, or more generally anelastic, to varying extents and because the mechanical properties depend on rate of deformation and temperature, it is not surprising to find that the strength is also dependent on the rate at which stresses are applied and on the temperature of measurement. These effects are discussed in Sections 10.4.2 and 10.5.1. Other effects of the environment, notably the destructive action of ozone, are discussed in Section 10.8. Finally, a brief survey is given of abrasive wear. 

Abrasive wear consists of the rupture of small particles of elastomer under the action of frictional forces, when sliding takes place between the elastomer surface and a substrate. A suitable measure of the rate of wear is provided by the ratio A/p, where A is the volume of rubber abraded away per unit normal load and per unit sliding distance, and ju is the coefficient of friction. This ratio, termed abradability, represents the abraded volume per unit of energy dissipated in sliding. Master curves for the dependence of abradability on the speed of sliding, reduced to a convenient reference temperature by means of the... 

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