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The principal features essential for the success of an orthopaedic implant are its shape, dimensional accuracy, and adequate mechanical properties. Unlike other manufactured products, chemical stability and toxicity are of increased importance due to the need for biocompatibility over an implants life which could span several years. Thus, the combination of mechanical and biological properties determines the clinical usefulness of biomaterials in orthopaedic and musculoskeletal trauma surgery. Materials commonly used for these applications include stainless steel, cobalt-chromium and titanium alloys, ceramics, polyethylene, and poly(methyl methacrylate) (PMMA) bone cement. This study reviews the properties of commonly used materials and the advantages and disadvantages of each, with special emphasis on the sensitivity, toxicity, irritancy, and possible mutagenic and teratogenic capabilities. In addition, the production and final finishing processes of implants are discussed. Finally, potential directions for future implant development are discussed, with an emphasis on developing advanced personalised implants, according to a patient’s stature and physical requirements.

In this paper, a novel interactive friction-lubricant thickness model was developed to predict the evolution of coefficient of friction and the useful life of lubricant film. The developed model was calibrated by experimental results determined from pin-on-disc tests. For these experiments, a grease lubricant was applied on a Tungsten Carbide ball which slides against a disc made from AA6082 Aluminium alloy. In the pin-on-disc tests, the lubricant film thickness decreased with time during single path sliding leading to a rapid increase in the coefficient of friction. The breakdown of lubricant was divided into three stages, namely, the Stage I low and stable coefficient of friction region, Stage II region in which the coefficient of friction sees a rapid rise, and Stage III in which the coefficient of friction reaches a plateau with a value similar to that of dry sliding. In order to characterise the evolution of coefficient of friction throughout these stages, a novel interactive friction model was developed combining the effects of sliding distance, sliding speed, contact pressure and initial lubricant amount on the evolution of the coefficient of friction. This interactive friction model can be applied to situations involving lubricant breakdown in a dynamic environment such as the metal forming industry, where the use of traditional constant coefficient of friction values present limits in predictive accuracy

A novel hot stamping process for Ti6Al4V alloy using cold forming tools and a hot blank was presented in this paper. The formability of the material was studied through uniaxial tensile tests at temperatures ranging from 600 to 900 °C and strain rates ranging from 0.1 to 5 s-1. An elongation ranging from 30% to 60% could be achieved at temperatures ranging from 750 to 900°C respectively. The main microstructure evolution mechanisms varied with the deformation temperature, including recovery, phase transformation and recrystallization. The hardness of the material after deformation first decreased with the temperature due to recovery, and subsequently increased mainly due to the phase transformation. During the hot stamping tests, qualified parts could be formed successfully at heating temperatures ranging from 750 to 850°C. The forming failed at lower temperatures due to the limited ductility of the material. At temperatures higher than 900°C, extensive phase transformation of α to β occurred during the heating. During the transfer and forming, the temperature dropped significantly which led to the formation of transformed β, reduction of the formability and subsequent failure. The post-form hardness distribution demonstrated the same tendency as that after uniaxial tensile tests.

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