Automotive Science and Engineering

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In the present paper, a complete literatures review of thermal barrier coating applications in diesel engines is performed to select a proper type and to find coating effects. The coating system has effects on the fuel consumption, the power and the combustion efficiency, pollution contents and the fatigue lifetime of engine components. Usually there are several beneficial influences by applying ceramic layers on the combustion chamber, including the piston, the cylinder head, the cylinder block, intake and exhaust valves by using a plasma thermal spray method. Several disadvantages such as producing nitrogen oxides also exist when a coating system is used. In this article, all effects, advantages and disadvantages of thermal barrier coatings are investigated based on presented articles.

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This paper focuses on the optimization of initiating dimensions of groove bearing in association with de- sired design of vehicle’s front structure which is made up of low carbon steels in the case of frontal collision. Axial bearing analysis is done numerically using nonlinear finite element code LS-DYNA. In this analysis, changes of two main parameters including measure of energy absorption of structure and maximum force of structure collision are being considered. Square structure profile is being chosen and the groves are placed on two opposite sides. Tests of collision simulation are performed for steel samples and then a mathematical equation is derived next, the initiating dimensions are optimized using Genetic Algorithm. Desired case for design of this structure part is the one which provides maximum energy absorption measure and minimum collision force in this paper, the most optimal case is an initiator with groove depth of 4.5 mm and radius of 10 mm.

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In this article, vehicle cornering stability and brake stabilization via bifurcation analysis has been investigated. In order to extract the governing equations of motion, a nonlinear four-wheeled vehicle model with two degrees of freedom has been developed. Using the continuation software package MatCont a stability analysis based on phase plane analysis and bifurcation of equilibrium is performed and an optimal controller has been proposed. Finally, simulation has been done in Matlab-Simulink software considering a sine with dwell steering angle input, and the effectiveness of the proposed controller on the aforementioned model has been validated with Carsim model.

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Excitations from the vehicle engine and the road surface cause vibrations in the exhaust system and the exhaust noise and vibrations are transmitted through the vehcile body and structure to the cabin, causing distractions and discomfort for the driver and passengers. In this article the method of average driving degrees of freedom displacement (ADDOFD) has been used to determine and optimize the location of suspended hanger points. Based on this approach, a model of car exhaust system is used using ANSYS software to optimize the hanger installation points for reducing vibration and to select the best positions for these points. The optimum hanger positions must have a relatively lower ADDOFD value compared to adjacent points. Then the static and dynamic analysis of the exhaust system is illustrated and finally on the basis of the above analyses, the position is chosen for the exhaust system hangers to reduce the transmission of noise and vibrations into the car cabin. Results indicate that optimization of the locations has resulted in a significant decrease in hanger loads, significantly reducing the vibrations transmitted to the vehicle cabin and increasing the life of the rubber hangers. This study has practical significance for reducing the vibration of automobile exhaust systems and the vehicle cabin.

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Brake system performance significantly affects safety, handling and vehicle dynamics. Therefore, the objective of this paper is to discuss brake system characteristics and performance and component design parameters. We perform a detailed study of a specific brake system designed for Mercedes-AMG SLC-43, considering component design parameters and operational points, and finally conduct the vehicle braking system layout design. To this end, brake force and torque calculations and power dissipation modelling is performed. Then, ventilated brake discs are designed for the front and rear brakes. A main goal of the present article is to apply digital logic method to the material selection procedure among the candidate material proposed for brake components and rank the materials according to performance indices. The performance indices of five candidate materials were calculated and compared to select the best option for application in the brake disc. Finally, the calculations of the brake pedal, booster, cylinder, hoses and tubes are obtained.

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In internal combustion engines, exhaust valve and its seat gain considerable temperature as the hot gases exit through them. So, the rate of heat transfer should be under control. In this study, the contact heat transfer coefficient has been estimated. An experimental study on an Air-Cooled internal combustion engine cylinder head has been considered. Using the measured temperatures of sensors located in specific locations of the exhaust valve and the seat and the method of linear extrapolation, the surface contact temperatures and constant and periodic contact heat transfer coefficient were calculated. Also, a sensitivity analysis has been done to study the effects of different parameters of contact pressure, contact frequency, heat flux and cooling air speed on thermal contact conductance. The results show that between the major four considered parameters, the thermal contact conductance is more sensitive to the contact pressure, then the contact frequency, heat flux and the cooling air speed are the most affecting parameters on thermal contact resistance.

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This paper investigates the effect of temperature on a hybrid energy storage system with various energy management systems. The hybrid energy storage system consists of a fuel cell, ultracapacitor and battery with associated DC/DC and DC/AC converters. The energy management strategies employed are the state machine control strategy, fuzzy frequency/logic decoupling strategy, minimization strategy of equivalent consumption (ECMS) and external energy maximization strategy (EEMS). Initially, a module of 3.3v 2.3Ah LiPo4 batteries consisting of 15 cells in series and 15 rows in parallel are studied without considering the temperature effect. In the next step, the studies are repeated considering the temperature variation effects. The current and SOC associated with the battery, the hydrogen consumption, and battery life are studied for each strategy. The results suggest that the errors associated with the battery life estimation, as well as the battery current are significant with and without considering the temperature effects with the values of 30% and 20%, respectively.

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The present paper aims to improve the dynamical balancing of a slider-crank mechanism. This mechanism has been widely used in internal combustion engines, especially vehicle engines; hence, its dynamical balancing is important significantly. To have a full balance mechanism, the shaking forces and shaking moment of foundations should be eliminated completely. However, this elimination is usually impossible. Hence, in the current study, a multi-objective optimization is carried out to maintain the optimal balance of mechanism. The vertical and horizontal components of shaking forces and shaking moment are considered as objective functions. Also, the design variables are included the mass, the moment of inertia and the mass center location of mechanism links. The length of mechanism links is also considered constant for achieving a fixed slider course. The four-objective optimization is applied using a differential evolution algorithm. The optimization results are presented in Pareto diagrams as suitable tools for selecting a mechanism with desired characteristics according to the importance of each objective function. The optimal mechanism is finally introduced by the mapping method. The comparison of optimized mechanisms and the original one indicates a significant reduction of shaking forces and shaking moment as well as the reduction of energy consumption.

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Drying temperature of the flux at normal atmosphere has a crucial role in brazing quality in automotive aluminum-based heat exchangers. Over the course of this research, NOCOLOK^® flux consists of two phases of K₂AlF₅.H₂O and KAlF₄ with melting point around 580 °C was used. A flux slurry was applied on the base metal, and dried at 220, 300 and 380 °C in air. Mechanical assessment revealed that when flux dried at 300 °C, the joint withstands maximum shear stress of 44 MPa with complete bonding. At 220 °C and 380 °C, joint shear stresses are 34 MPa, 30 MPa respectively. 380 °C dry-off temperature under nitrogen gas improved shear strength to 39 MPa. Taking dry-off temperature as 300 °C the amount of defective heat exchangers was reduced from 6% to 2% on a daily basis.
 

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Elastomeric engine mounts are being used in heavy vehicles as well as passenger cars to absorb the vibrations of the engine, carry its weight and reduce its movement while driving. The aim of this research is some studies that have been done to find the components of the elastomeric compound. Moreover, the feasibility study of constructing three different specimens with different percentages of soot and oil has been carried out in order to achieve the desired characteristics in the heavy vehicle engine mount. A rheometric test was then performed to determine the temperature and time of sintering. The tensile strength test has been used to determine the elasticity of the rubber specimens and to achieve high damping coefficients. Also the tensile strength test was performed with the aim of obtaining a specimen with a suitable stress-strain relationship and comparing the results with the reference engine mount. Consequently, the elastomeric compound is used to make the elastomeric engine mount of heavy duty vehicle in the form of rubber and reverse engineering.

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In this paper, the optimization of the suspension system’s parameters is performed using a combined Taguchi and TOPSIS method, in order to improve the car handling and ride comfort. The car handling and ride comfort are two contradictory dynamic indices; therefore, to improve both car handling and ride comfort, there is a need for compromising between these two indices. For this purpose, the criteria affecting these two are first identified. The lateral acceleration and the body roll angle were used to evaluate the handling, and the RMS of vertical acceleration of the vehicle body was used to evaluate the ride comfort. The design factors including stiffness of springs and damping coefficient of dampers in the front and rear suspension system were also taken into account. On this basis, the results obtained from the vehicle’s motion in the DLC test were evaluated in the CarSim software. Then, the ideal tests were identified using the combined entropy and TOPSIS technique; this method has been proposed for managing the handling and ride comfort criteria. Finally, the optimal level of the suspension system’s factors was extracted using Taguchi method. It is evident from the results that, for different speeds, the body roll angle was improved up to 6.5%, and the RMS of the vertical acceleration of the vehicle body was optimized up to 4% to 7%.

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