Wear mechanisms

Fig. 2. Tool wear mechanisms, (a) Crater wear on a cemented carbide tool produced during machining plain carbon steel, (b) Abrasive wear on the flank face of a cemented carbide tool produced during machining gray cast iron, (c) Built-up edge produced during low speed machining of a nickel-based alloy.

For practical reasons, the blast furnace hearth is divided into two principal zones the bottom and the sidewalls. Each of these zones exhibits unique problems and wear mechanisms. The largest refractory mass is contained within the hearth bottom. The outside diameters of these bottoms can exceed 16 or 17 m and their depth is dependent on whether underhearth cooling is utilized. When cooling is not employed, this refractory depth usually is determined by mathematical models these predict a stabilization isotherm location which defines the limit of dissolution of the carbon by iron. Often, this depth exceeds 3 m of carbon. However, because the stabilization isotherm location is also a function of furnace diameter, often times thermal equiHbrium caimot be achieved without some form of underhearth cooling. 

The main mechanisms of hearth bottom wear are high heat load, chemical attack, erosion from molten Hquids, mechanical and thermal stress, and penetration because of ferrostatic and process pressure. A variety of special purpose carbons have been developed to minimize or eliminate the damage caused by these wear mechanisms. 

Surface wear is defined as the deformation and loss of surface material as the result of a mechanical, thermal, or chemical action. These three mechanisms can act singly but are more often found in combination, which may make the wear process very difficult to analyze. Materials for wear protection have different responses to each of these wear mechanisms and, consequently, no universal wear material exists. To select the optimum material or combination of materials, it is essential to determine the cause and the mechanism of the wear as accurately as possible. The selection can then be made of the best and most cost-effective material. 

Beside adhesive and abrasive wear, two other wear mechanisms must be mentioned ... 

Other wear mechanisms are flank wear and crater wear which occur mostly with cemented-carbide tools. Flank wear refers to the depression that is formed below the cutting edge on the side of the tool caused by the abrasive wear of the cemented carbide. TiC is particularly effective in reducing it. Crater wear occurs in the form of small depressions on the rake face behind the point of contact of the tool with the workpiece. Diffusion of the cobalt binder into the cutting chip usually occurs with crater wear. TiN is effective in reducing both diffusion and crater wear.PI... 

Stjernberg, K., and Thelin, A., Wear Mechanisms of Coated Carbide Tools in Machining of Steel, Prac. ASM Int. Conf. on High Productivity Machining, Materials and Processing, Paper No. 8503-004, ASM, Metals Park, OH 44073 (May, 1985)... 

The mechanism of micro/nano friction and wear/ scratch is still not well known. There are several questions that need to be answered (a) How are the materials removed at very low load as nano Newton scale. Is it similar to that at macro scale Can we explain the material loss according to the traditional wear mechanisms (b) What is the connection between micro and macro friction and wear ... 

The CMP process is regarded as a combination of chemical effect, mechanical effect, and hydrodynamic effect [110-116]. Based on contact mechanics, hydrodynamics theories and abrasive wear mechanisms, a great deal of models on material removal mechanisms in CMP have been proposed [110,111,117-121]. Although there is still a lack of a model that is able to describe the entire available CMP process, during which erosion and abrasive wear are agreed to be two basic effects. 

In 1996, Liu et al. [129] analyzed the wear mechanism based on the rolling kinematics of abrasive particles between the pad and wafer. They summarized that the kinetics of polishing are (1) material removal rate is dependent on the real contact area between the slurry particle and the wafer surface. The real contact area is related to the applied pressure, the curvature, and Young s modulus of the slurry... 

Kayaba, T., Hokkiringawa, K., and Kato, K., Analysis of the abrasive wear mechanism by successive observations of wear processes in a scanning electron microscope. Wear, 110, 419, 1986. 

The mechanisms by which wear of a plastic occurs when it is in moving contact with another material are complex but the principal factors involved are cutting, fatigue and friction. It is possible to categorise wear mechanisms in various ways and commonly distinction is made between abrasive wear, fatigue wear and adhesive wear. 

The dominant role of asperity contact is also apparent from analysis of the texture of polished surfaces. Figure 9 illustrates a typical post CMP surface as examined via atomic force microscopy (AFM). Surface texture is composed of innumerable randomly oriented nanogrooves of a width and depth consistent with traveling Hertzian loaded contact [12] particle bombardment during turbulent liquid flow produces profoundly different texture. All classes of semiconductor materials examined show similar textures, indicating the general nature of the process. From the data to date, it appears that asperity contact is the dominant wear mechanism in CMP. 

Fig. 31 Friction and wear mechanisms involved in viscoelastic solid bodies sliding against a rough counter-surface...

Fig. 42 SEM micrographs of wear track (contact area) showing the wear mechanisms involved in different PTFE-EPDM composites. Images on the right are magnifications of those on the left...

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. 

It is possible to categorise wear mechanisms of rubber in various ways and one convenient system is to differentiate between three main factors ... 

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