Automotive Science and Engineering

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Turning of hardened steels using a single point cutting tool has replaced the cylindrical grinding now as it offers attractive benefits in terms of lower equipment costs, shorter set up time, fewer process setups, higher material removal rate, better surface quality and elimination of cutting fluids compared to cylindrical grinding. In order to obtain desired surface quality by machining, proper machining parameters selection is essential. This can be achieved by improving quality and productivity in metal cutting industries. The present study is to investigate the effect of machining parameters such as cutting speed, feed and depth of cut on surface roughness during dry turning of hardened AISI 4340 steel with CVD (TiN+TiCN+Al2O3+ZrCN) multilayer coated carbide inserts. A full factorial design of experiment is selected for experimental planning and the analysis of variance (ANOVA) has been employed to analyze the significant machining parameters on surface roughness during turning. The results showed that feed (60.85%) is the most influencing parameter followed by cutting speed (24.6%) at 95% confidence level. And the two-level interactions of feed-cutting speed (F*V), depth of cut-feed (D*F) and depth of cutcutting speed (D*V) are found the significant effects on surface roughness in this turning process. Moreover, the relationship between the machining parameters and performance measure i.e. surface roughness has been modeled using multiple regression analysis.

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The current experimental study is to investigate the effects of process parameters (cutting speed, feed rate and depth of cut) on performance characteristics (surface roughness, machining force and flank wear) in hard turning of AISI 4340 steel with multilayer CVD (TiN/TiCN/Al2O3) coated carbide insert. Combined effects of cutting parameter (v, f, d) on performance outputs (Ra, Fm and VB) are explored employing the analysis of variance (ANOVA). An L9 Taguchi standard design of experiments procedure was used to develop the regression models for machining responses, within the range of parameters selected. Results show that, feed rate has statistical significance on surface roughness and the machining force is influenced principally by the feed rate and depth of cut whereas , cutting speed is the most significant factor for flank wear followed by cutting speed. The desirability function approach has been used for multi-response optimization. Based on the surface roughness, machining force and flank wear, optimized machining conditions were observed in the region 147 m/min cutting speed and 0.10 mm/rev feed rate and 0.6 mm depth of cut.

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Air conditioning refrigerant R134a has value of global warming potential (GWP) 1300, which is much higher than MAC Directive (GWP below 150) passed in July 2006. This prompted a search for alternative refrigerant with GWP value less than 150. R1234yf is a new refrigerant which has lower GWP value of 4. Effect of blower speed has been compared and flammability issue of R1234yf has been addressed. Cooling time and relative humidity of car air -conditioning system using refrigerant R134a and R1234yf has also been discussed. The paper discusses various aspects for the replacement of R134a and provides a long term sustainable substitute of presently used refrigerant R134a in automobile air-conditioning.

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The ability to absorb vibrations in a vehicle during braking conditions depends primarily on the selection of ingredients for a friction material and interfacial adhesion between all these ingredients.  In this work, a hybrid brake friction material is developed by combination of carbon fiber (CF), glass fiber (GF), resin and other ingredients. The surfaces of carbon and glass fibers are chemically inert and hydrophobic in nature. Therefore, CF and GF surfaces are modified with surface treatments to increase hydroxyl or carboxyl groups on the surface. An attempt is made to improve the bonding strength between CF, GF, ingredients and polymer matrix. CF surface is modified by oxidation, HNO3 treatment and grafting multi walled carbon nano tubes functionalized (MWCNT-F) on CF. GF surface is modified by HNO3 treatment. Carbon fiber and glass fiber content after surface modifications is mixed with all the ingredients and resin. Friction composite sheets are fabricated by using hand layup method. The resulting materials are characterized by SEM, TGA and FTIR analysis. MWCNTs-F on CF surface is observed. Sample specimens are cut from the friction composite sheets and damping behaviour of the specimens is evaluated by using FFT analyzer. The best surface treatment method and ingredients are selected to fabricate a friction material to reduce squeal generation at the interface between brake disc and pad.

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Brakes are a vital, prime, and accident preventive part of any motor vehicle. Brakes help in controlling the vehicle speed when needed by changing the kinetic energy and potential energy into thermal energy. In this work, we have found out temperature distribution, deformation distribution, equivalent stress distribution, and equivalent strain distribution by varying the number of vanes in a ventilated disc brake, considering the coupled thermal and structural field in transient conditions, and compared the results to find out the best possible design. We have considered the disc rotor’s material as grey cast iron and the disc pad’s material as carbon fiber reinforced carbon matrix. It has been found out that with an increase in the number of vanes, there is a reduction in the maximum deformation, maximum stress, and maximum strain and there is a slight increase in the maximum temperature during the whole simulation. A disc rotor with 18 vanes is found to be the best possible design among all 5 designs considered in this paper.