Mechanism fatigue wear

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. 

Figure 6.2. Schematic diagram of probable mechanism of plastic fatigue wear (from Briscoe and Evans, 1987) (a) Formation of plastically deformable grooves in series (b) Deformation of the grooves pushed in one direction (c) Sway back to the opposite direction (d) Deterioration of ridges after repeated fluttering (e) Detachment of ridges in the form of band-shaped debris.

Exoelectrons are known to be emitted from nascent or fresh solid surfaces by mechanical action such as abrasion, cutting, surface fatigue, wear, forming and so on. There are two types of EE associated with dark emission termed "triboemission and after emission" (Kajdas, 1985a, 1989 and 1994 Nakayama and Hashimoto, 1991 and 1992 Nakayama et al., 1992 and 1995 Thiessen, 1965). 

Wear is the process of physical loss of material. In sliding contacts this can arise from a number of processes in order of relative importance they are adhesion, abrasion, corrosion and contact fatigue. Wear occurs because of local mechanical failure of highly stressed interfacial zones and the mode of failure is influenced by environmental factors. 

Wear is one of the most important parameters in evaluating the CMP process. Wear in CMP is evaluated as the material removal rate (MRR). The primary wear mechanisms that occur in CMP are adhesive wear, abrasive wear, electrochemical wear, tribochemical wear, and fatigue wear on both wafer and pad surfaces. In this chapter, we will first introduce basic wear concepts. We will then discuss wear in polishing and in conditioning. Throughout the text, we show examples of CMP failure due to wear. 

Several mechanisms of polymer wear have been discussed in the literature (5-7) adhesive wear, abrasive wear, fatigue wear, tribo-chemical wear, corrosive wear and impact wear. We shall limit this discussion to the four basic mechanisms shown in Figure 1. Neither corrosive(5) nor impact wear(8,9) are common, and we do not plan to discuss these in this paper. 

When polymers slide on machined metal surfaces, it is quite possible that steady-state wear Involves a combination of abrasive, fatigue, and adhesive wear mechanisms. To study fatigue wear, it would be desirable to minimize the contributions of the abrasive and adhesive wear modes. In this paper, the following polymers polycarbonate, polyvinyl chloride, ultra-high molecular weight polyethylene, siloxane modified epoxies, and polylmldes are tested in experiments in which the fatigue wear mode is predominant. 

The experiment chosen to emphasize the fatigue wear mechanism was a 52100 steel ball 3.18 mm dia. loaded against a rotating polymer disk ( ). The load was adjusted so that stresses in the polymer were not high enough to cause wear and the formation of a wear track when... 

The wear results were characterized by an Initial period of no wear followed by catastrophic initiation of the wear track. This Initiation was distinguished by a sharp Increase In friction coefficient and a wear rate which was higher than the subsequent steady state wear. Fatigue wear Is proposed as the predominant wear mechanism because of the multiple stress cycles required to Initiate wear and because of the positive correlation between the wear rates and the elastic moduli of the polylmldes. 

MECHANICAL WEAR - Removal of material due to mechanical process under conditions of sliding, rolling, or repeated impact. Included are abrasive wear, fatigue wear and adhesive wear, but not the corrosive and thermal wear. 

For systems consisting of common materials (e.g., metals, polymers, ceramics), there are at least four main mechanisms by which wear and surface damage can occur between solids in relative motion (1) abrasive wear, (2) adhesive wear, (3) fatigue wear, and (4) chemical or corrosive wear. A fifth, fretting wear and fretting corrosion, combines elements of more than one mechanism. For complex biological materials such as articular cartilage, most likely other mechanisms are involved. 

Wear is defined as the damage to a solid surface, generally involving progressive loss of material, due to relative motion between that surface and a contacting substance or substances. The mechanisms of wear are abrasion, adhesion, erosion, fatigue and fretting. 

The fatigue wear rate is dependent on many different factors, including the mechanical and chemical properties of the surfaces, the operating and environmental conditions as well as the properties of the lubricant, if employed. However, it is possible that similar surfaces apparently subjected to identical conditions may exhibit wide variations in fatigue wear severity... 

To better understand the behavior of third body particles we consider the schematic picture shown in Figure 10.25. A metallic wear particle is formed by fatigue wear, one of the classical wear mechanisms. The metallic particle may either be... 

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