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In this proposal the mechanical properties of natural and synthetic rubbers are studied under different temperatures both real and ageing heat treatment conditions. For this purpose, tire rubber and bearing pad rubber are considered as they are most governed in natural and synthetic rubber respectively. The experimental results confirm that the impact of real temperature is higher on the mechanical properties than that of ageing temperature because of ambient temperature aggravate thermal motion and changes the molecular arrangement of rubber other than the ageing samples recovers the mechanical properties during breezy. Except hardness, all the cases in terms of mechanical properties like tensile strength, elongation, Young's modulus and Poisson's ratio of bearing pad rubber provide the higher performance than the tire rubber. Under ageing treatment condition the degraded mechanical properties recover well by the natural rubber since extremely ordered long chain of the molecular structure. The significant differences in the micrographs of the two rubbers suggest that tire rubber consists of uniform grains because of its highly controlled molecular arrangement. Under heat treatment the microstructure turned rougher and the size of the voids became larger as temperature increases the secondary cross linking reaction which initiate to cracks.

A wear test in a used motor oil sliding environment was performed on Al-based automotive alloys with Silicon doped in various levels. Where a pin-on-disc wear testing equipment was used at a normal pressure of 1.53 MPa and a sliding speed of 0.51 m/s, kept constant. For comparison of the wear performance, dry and fresh motor oil sliding environments were also considered. The results showed that as silicon content was increased in the alloys, the wear rate decreased up to the eutectic composition, followed by an increase for all the environments. It was mainly for higher levels of Si-rich intermetallic Mg2Si precipitates in the α-aluminum matrix and made the alloys’ strength superior, in addition to increased wear resistance. In the post eutectic composition, primary silicon particles which are coarse and polyhedral appeared weakening the matrix. The coefficient of friction also decreased because of the higher hardness and the Si particles' employment as solid lubricants. In a dry environment, the wear rate and friction coefficient were much greater for their direct contact but lower under motor oil due to the reduced roughness caused by the sealing effects of the contact surfaces. Conversely, in oil environment, the opposite phenomenon was observed where a higher coefficient of friction was added to the alloy because the oil formed a thin film working as a lubricant between the contact surfaces which controlled the wear properties. Used oil demonstrates some degree of higher wear rate along with friction coefficient due to heavy and harmful chemical compounds in it. Examined by optical microscopy and SEM analysis, worn surfaces have shown that Si added alloy improved wear resistance through mild and smooth abrasive grooves filled with oxides in dry sliding conditions. In case of oil sliding environment smooth surfaces are created by the resistance of the oil film to the direct contact between the surfaces.

This paper aims to investigate and compare the characteristics of machined surfaces and chips formation of aluminium-based automotive alloys with varying silicon content. The milling operations are performed using horizontal milling machine under two peripheral up milling and down milling methods with an HSS slab milling cutter. The experiment has conducted for different cutting speeds in dry condition while the depth of cut and machining feed are kept constant throughout the evaluation. The study reveals that the down-milled surface has higher hardness and better surface finish resulting in lower roughness as the cutting force is compressive in nature. On the contrary, the up-milled surface has lower hardness and micro cracks on it, which resulted in relatively higher surface roughness as the cutting force is tensile shear in nature. In addition, the surface hardness increases with the increment of silicon content in the alloys for both milling methods for the presence of hard Si rich intermetallics. The chips produced during up milling are shorter whereas the chips produced during down milling are longer for creation of higher temperature and pressure. Higher Si added alloy shows the curly like chips for its lower elongation behaviour. Fracture behaviour of higher Si alloy also confirms crack propagation obtained by the massive cleavage of the brittle and plate-types Si rich intermetallics.