The piston of the internal combustion engine is one of the most complex parts among all engine components. During the operation, the pistons of IC engines are typically subjected to high loading and wearing. To withstand these, they require high mechanical properties and excellent tribological properties. This chapter aims to compare the mechanical as well as tribological properties of silica-gel-reinforced aluminium composite with aluminium alloy, which is used in manufacturing of piston of IC engine. Initially silica-gel-reinforced aluminium composite was fabricated with base material aluminium and six different percentages of silica gel reinforcement by stir casting method. After that, mechanical and tribological properties of silica-gel-reinforced aluminium composite were estimated and the tremendous mechanical and tribological properties among all percentages by different optimization techniques were found. The authors then compared the admirable properties of aluminium composite with aluminium alloy for manufacturing of piston of IC engine.
TopIntroduction
Generally piston is non-repairable part and requires lasting the life span of the engine. Piston operation induce in the material a complex combination of mechanical stresses and high cyclic loading, high wear rate responsible of cracking and abrasion in the weakest zone. Mostly IC engine pistons have been manufactured by aluminium because aluminium alloy has excellent lightness (Density: 2.7 g/cm3), nonmagnetic and non-sparking as compared to other materials like cast iron. Aluminium is available in plentiful amount in the Earth after oxygen and silicon. Aluminium is available in earth about 8% by weight of the Earth's solid surface. Machining, casting, drawing and extrusion can be conveniently done on aluminium. It has excellent corrosion resistance because of thin surface layer of aluminium oxide which forms in free air to prevent further oxidation. But along with various advantages there are some major disadvantages of aluminium like its softness, high ductility and malleability, high wear rate, less strength (Modulus of elasticity: 70-80GPa). To overcome these demerits, many researchers fabricated various aluminium based composite with different reinforcing materials.
There are various types of ceramic viz. silicon carbide, silicon oxide, titanium oxide, titanium boride etc. which are used to reinforce aluminium metal composite. In this study, silica gel used as reinforced ceramic because of its high hardness and melting point, which helps to improve wear resistance characteristic (Sulima et al., 2010; Abdel-Azim et al., 1995). Purified form of quartz crystal, it has application in glass industries and construction field. Density of silica gel is approximate equal to the liquefied aluminium (about 2.64 g/cm3) by which uniform metal matrix composites can be developed (Feng et al., 2008; Tjong and Tam, 2006). Silica gel has high melting point as compared to the aluminium which make it useful in preparing the particle reinforced metal composite. According to Venkatprasad and Subramanian (2011), wear characteristic of aluminium metal matrix composite is directly related to percentage of reinforced ceramic, sliding speed and applied load in dry sliding condition. According to Mixed influence of grain size of reinforcement and sliding distance helped in the reduction of wear of composite (Modi et al., 2001). The filler grain size of SiC with matrix aluminium has less abrasive wear (Sahin, 2005).
Our study is based on the optimization of characteristic parameters on mechanical properties (Tensile strength, flexural strength) and tribological properties (wear rate and coefficient of friction) of silica gel reinforced aluminium composite and define consolidate parameter which give the optimum result. Taguchi is a design tool which gives easy, effective and organized approach for optimization. According to Taguchi (1990), DOE is relevant statistical tool to analyze the effect of various inconstant simultaneously and define order of steps which must follow a specific order to improve the performance of process. Taguchi techniques select few numbers of tests and get information accurately. All tests contain a specific number of combinations of factor and level. According to Fisher (1951), In DOE process, to get desired result, it is necessary to determine proper combination of factor and level. In Taguchi method, standard orthogonal array develops the schedule of test. To calibrate quality feature, Taguchi endorsed loss function which is also called Signal to Noise ratio(S/N ratio) in statistical form. Taguchi method uses a certain design orthogonal array to deduct number of test (Roy, 1990). The test results are then validated by ANOVA of dominating factors (Taguchi, 1993). While gray relational analysis was employed to optimize the multiple responses is more intricate than single response. Gray theory was proposed by Deng Ju-long (1982, 1989) at China and this procedure was introduced to study problems with multiple responses.