Effects of reinforcement on wear resistance of aluminum matrix composites

Bioimplants are becoming increasingly important in the modern society due to the fact of an aging population and associated issues of osteoporosis and osteoarthritis. The manufacturing of bioimplants involves an understanding of both mechanical engineering and biomedical science to produce biocompatible products with adequate lifespans. A suitable selection of materials is the prerequisite for a long-term and reliable service of the bioimplants, which relies highly on the comprehensive understanding of the material properties. In this paper, most biomaterials used for bioimplants are reviewed. The typical manufacturing processes are discussed in order to provide a perspective on the development of manufacturing fundamentals and latest technologies. The review also contains a discussion on the current measurement and evaluation constraints of the finished bioimplant products. Potential future research areas are presented at the end of this paper.

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State of the art of bioimplants manufacturing: part I

A correlation between machining process and fatigue strength of machined components clearly exists. However, a complete picture of the knowledge on this is not readily available for practical applications. This study addresses this issue by investigating the effects of machining methods on fatigue life of commonly used materials, such as titanium alloys, steel, aluminium alloys and nickel alloys from previous literature. Effects of turning, milling, grinding and different non-conventional machining processes on fatigue strength of above-mentioned materials have been investigated in detail with correlated information. It is found that the effect of materials is not significant except steel in which phase change causes volume expansion, resulting in compressive/tensile residual stresses based on the amounts of white layers. It is very complex to identify the influence of surface roughness on the fatigue strength of machined components in the presence of residual stresses. The polishing process improves the surface roughness, but removes the surface layers that contain compressive residual stresses to decrease the fatigue strength of polished specimens. The compressive and tensile residual stresses improve and reduce fatigue strength, respectively. Grinding process induces tensile residual stresses on the machined surfaces due to high temperature generation. On the other hand, milling and turning processes induce compressive residual stresses. High temperature non-conventional machining generates a network of micro-cracks on the surfaces in addition to tensile residual stresses to subsequently reduce fatigue strength of machined components. Embedded grits of abrasive water jet machining degrade the fatigue performance of components machined by this method.

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Fatigue life of machined components

The size of reinforced particles notably affects the electro-discharge machining (EDM) of metal matrix composites (MMCs). This paper explores the mechanism of wire EDM of MMCs with different sizes of reinforced particles as well as the corresponding unreinforced matrix material. The mechanisms of material removal, surface generation, and taper kerf formation were investigated. This study shows that the particles’ ability to protect matrix materials from the intense heat of electric arc controls the material removal rate, surface generation, and taper of kerf. The low melting point matrix material is removed very easily, but the heat resistance reinforced particles delay the removal of material and facilitate the transfer of the workpiece material to wire electrode and vice versa. Thus, the material stays longer in touch with intense heat and affects the surface generation, wire electrode wear, and width of the kerf.

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Wire EDM Mechanism of MMCs with the Variation of Reinforced Particle Size

Fabrication and wear characterization of silicon carbide and copper reinforced aluminium matrix composite

To produce lifelong, harmless hip joint prostheses, considerable cross-disciplinary studies have been carried out. The research includes adaptability and sustainability of artificial materials to human body, selection of materials, precision fabrication and efficient replacement operation. This paper provides a brief review of some of these key aspects with some details in abrasive polishing.

E.C.S. Kiat

Papers

A Briefing on the Manufacture of Hip Joint Prostheses