Fatigue-abrasion wear mechanism

A Fatigue-Abrasive Wear Mechanism for Polymeric Surfaces... 

Continuing with the concept of fatigue-abrasive wear mechanism,... 

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. 

In any particular wear situation several mechanisms are usually involved but one may predominate. Abrasive wear requires hard, sharp cutting edges and high friction. Fatigue abrasion occurs with rough but blunt surfaces and does not need high friction. Adhesion wear is less common but can occur on smooth surfaces. 

Percussion is a repetitive solid body impact, such as experienced by print hammers in high-speed electromechanical applications and high asperities of the surfaces in a gas bearing. Repeated impacts result in progressive loss of solid material. Percussive wear occurs by hybrid wear mechanisms, which combine several of the following mechanisms adhesive, abrasive, surface fatigue, fracture, and tribochemical wear.75... 

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. 

An alternative approach is to assess a service application in terms of the relative importance of basic wear mechanisms (abrasion, fatigue, adhesion, impact/slide, erosion etc) and the geometry and motion. Small scale tests are then carried out in the laboratory to simulate these mechanisms and parameters in order to produce relevant wear data. The performance data for each material with reference to each of these tests will therefore grade the suitability of that material to the proposed application. 

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. 

Fatigue crack growth, abrasive wear, and thermal degradation resulting from heat buildup can be grouped together as dynamic failure mechanisms, although with some nonstrain... 

The principal wear mechanisms are (i) adhesive (ii) abrasive (iii) fatigue (iv) impact by erosion and percussion (v) chemical and (vi) electrical arc-induced. 

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. 

Observation of worn surfaces and wear debris suggest three types of wear mechanisms—adhesion, when PE that adhered to the metal surface is torn off abrasion when bone cement particles get into the bearing and cut grooves in the soft PE and fatigue, where surface features are deformed back and forward until they fall off. Baudriller et al. showed a mechanism for the detachment of a PE flake (Fig. 15.17), but they could only start the FEA modelling of microscopic wear process. 

The elements of such a system consist of the primary body, the counter body, the interfacial medium and surrounding medium. Wear is a result of the action of the collective stress on the structure respectively on the elements of the tribological system and manifests itself in energetic and material interactions between these elements. It is defined by the wear parameters. Basically all wear mechanisms can occur abrasion, adhesion, tribo-chemical reactions or wear caused by fatigue. In the case of the extrusion of ceramic bodies, corrosion must be considered as another harmful mechanism. When determining the elements of the tribosystem for the... 

Abrasive processes are generally the final process operation in a process chain and determine significantly the functional surface properties of the machined workpiece. Therefore, the properties of the surface layer generated by abrasive processes directly affect the functional properties of the workpiece such as fatigue strength, wear behavior, and chemical resistance (Jawahir et al. 2011). Tensile residual stresses impair mechanical strength properties of workpiece, whereas compressive tensile stresses have a beneficial effect. 

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