Automotive Science and Engineering

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In this paper, the acoustic environment in a vehicle cabin under the influence of highfrequencies aerodynamic sources has been studied. Some panels on the windshield, the roof, the doors, the front pillars, and the floor of a vehicle simulated as input source of noise when the car is moving at high speed, i.e. 112 km/h. The status of vehicle cabin in each of these modes has been studied and compared to each other. There are some methods to simulate acoustic behavior of a vehicle cavity such as Finite Elements or Statistical Energy Analysis methods. A brief overview for Statistical Energy Analysis (SAE) is stated. In this study, the statistical energy method is used for determination of acoustic analysis. Auto SEA software is used to simulate and estimate the amount of sound pressure level. In addition, sound pressure formulation presented and used for comparison in vehicle cabin points and with experimental results for validation. Also, considering viscoelastic materials, a common form of material nonbinding panel has determined. The result shows that the roof is the most important panel in acoustic analysis under influence of aerodynamic sources. Accordingly, this panel has more effectiveness in optimization to control sound pressure level in a vehicle cabin. In addition, the amount of reduction in sound pressure level (SPL) in the cabin with viscoelastic material is presented as it could diminish the vibration of plates. In addition, the effect of using acoustic glasses is presented. Finally, the SPL effect of passenger position including front and rear is investigated and compared

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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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Research on vehicle longitudinal control with a stop and go system is presently one of the most important topics in the field of intelligent transportation systems. The purpose of stop and go systems is to assist drivers for repeatedly accelerate and stop their vehicles in traffic jams. This system can improve the driving comfort, safety and reduce the danger of collisions and fuel consumption. Although there have been many attempts to model stop and go maneuver via traffic models, but predicting the future vehicle's acceleration in steps ahead has not been studied much in this models. The main contribution of this paper is in designing integrated genetic algorithm-artificial neural network (GA-ANN) which is a soft computing method to simulate and predict the future acceleration of the stop and go maneuver for different steps ahead based on US federal highway administration’s NGSIM dataset in real traffic flow. The results of this study are compared with two methods, back propagation based artificial neural network model (BP-ANN) and standard time series forecasting approach called ARX model. The mean absolute percentage error (MAPE), root mean square error (RMSE) and coefficient of determination or R-squared (R2) are utilized as three criteria for evaluating predictions accuracy. The results showed the effectiveness of the proposed approach for prediction of driving acceleration time series. The proposed model can be employed in intelligent transportation systems (ITS), collision prevention systems (CPS) and driver assistant systems (DAS) such as adaptive cruise control (ACC) and etc. The outcomes of this study can be used for the automotive industries who have been seeking accurate and inexpensive tools capable of predicting vehicle speeds up to a given point ahead of time, known as prediction horizon, which can be used for designing efficient predictive controllers based on human behaviors.

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The constitutive relationships of the rubber materials that act as the main spring of a hydraulic engine mount are nonlinear. In addition to material induced nonlinearity, further nonlinearities may be introduced by mount geometry, turbulent fluid behavior, temperature, boundary conditions, decoupler action, and hysteretic behavior. In this research all influence the behavior of the system only certain aspects are realistically considered using the lumped parameter approach employed. The nonlinearities that are readily modeled by the lumped parameter approach constitute the geometry and constitutive relationship induced nonlinearity, including hysteretic behavior, noting that these properties all make an appearance in the load-deflection relationship for the hydraulic mount and may be readily determined via experiment or finite element analysis. In this paper we will show that under certain conditions, the nonlinearities involved in the hydraulic mounts can show a chaotic response.

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In the current paper, a biomechanical model of human body with unique structure is developed for evaluating the biodynamic responses, the vibration transmissibility and the transmitted accelerations to vertical vibration for the seated position with ignoring backrest support. In this regard, the 6-DoF Lumped-parameter model with six concentrated masses which are connected with linear springs and dampers is presented. Further, the full vehicle model is developed in ADAMS/CAR software in order to utilize the accelerations of seat under various roads excitation for different amount of vehicle speeds. Also, the vibration transmissibility and transmitted accelerations in vertical direction are measured for the different segments of human body including: Pelvis, Abdomen and Diaphragm, Chest, Torso, Back, Head and Neck. Finally, vibration transmissibility and transmitted accelerations due to the roughness of the roads surfaces are investigated for the different segments of human body in frequency domain from 0 to 50 Hz. As it is illustrated the maximum values for transmissibility for different body segments occurred for frequencies equivalent 20 to 30 Hz, it can be concluded that the human body is more sensitive to vibration with frequencies under 30 Hz.

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Car design incorporates many engineering sciences where today, have led to the use of advanced technologies in automobiles to provide more satisfaction and comfort for the passengers, increase the quality of vehicles, efficiency and more pleasure than previous cars. These issues can be categorized into two groups in general. In the first group, the effects and performance of components involved in vehicle vibrations are considered, and in the second group, attention is paid to the importance of joints and junctions of these components. Heretofore, in order to minimize vehicle NVH (noise, vibration and harshness), an exuberance of efforts have been done to raise the passengers comfort. In the meantime, it should be noted that the engine mounts play a considerable and serious role in reducing vibration exchanged between the engine and chassis. In designing the engine mounts, the most important concern is to balance the two opposite criteria that come into the car as a result of different vibration inputs (road and motor). Generally, vehicle engine mounts are used by three types of targets (motor bearing weight, motor vibration absorption, motor overloading, acceleration or braking). With the development of the automotive industry, the tendency towards the use of more efficient engine mount categories, has been prepared.
This article describes a concise functional overview of the engine mount in automobiles; it illustrates operating frequency range, relationship of the P and boundary diagram of engine mounts with other car collections, torque roll axis, positioning public types of the car’s engine mounts; and it also compares their operations. Afterwards, the structure and the basic functional of hydraulic engine mount are described as the most common engine mount categories. Finally, advantages and disadvantages of various types engine mounts with capability of use in the vehicle (including elastomeric, hydraulic (with inertia track or/and decouplier or/and bell plate (plunger), semi-active (switchable) and active hydraulic engine mount) are compared with each other.

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Nowadays, lightweight automotive component design, regarding fuel consumption, environmental pollutants and manufacturing costs, is one of the main issues in the automotive societies. In addition, considering safety reasons, the durability of the automotive components, as one of the most important design requirements should be guaranteed. In this paper, a two-step optimization process including topology and shape optimization of an automotive wheel, as one of the most significant chassis components, is studied. At first, topology optimization method with volume and fatigue life constraints is used to obtain the optimal initial lightweight design, followed by shape optimization technique to improve the fatigue life. The results show 31.841% weight and 33.047% compliance reduction by topology and also 652.33% average minimum fatigue life enhancement, by the shape optimization. Therefore, the proposed two-step optimization method is qualified in designing the lightweight automotive wheel. The method used in this study can be a reference for optimization of other mechanical components.

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In this paper, the acoustic analysis of noise has been done in automotive cabin at high speed. High-frequency noise sources are applied separately to the roof and floor panels as well as to the windshield of the vehicle, which has been investigated at both the driver's and rear passenger's head. The most important panels that have the most noise emission are specified. In order to analyze high frequencies, the Statistical Energy Analysis (SEA) method has been used; also, the Response Surface Methodology (RSM) has been used to obtain optimized panel in terms of minimally weighing and maximum noise reduction. The results show that the proposed panels with unconstrained rubber layer can reduce the cabin interior aerodynamically generated noise more than %6.

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Thin-walled structures play an important role in absorbing the energy in a low impact crash of vehicles up to saving lives from high impact Injury. In this paper, the thin-walled columns by using a hybrid Design of Experiments (DOE) and Ant Colony Algorithm (ACO) has been optimized. The analysis of the behavior of the nonlinear models under bending load is done using finite-element software Abaqus. The objective is to study the performance geometrically parameters of the columns using DOE-ACO approach.
DOE method is being applied to determine the effects of cross-sections, material, and thickness on the energy absorption; and the ACO method is used for finding more accurate thickness on energy absorption. Four types of thin-walled cross-sections, i.e., circle, ellipse, hexagon, and square are used in this study. The optimized results of DOE method show that aluminum alloy (Al-6061) and high strength low alloy steel (HSLA) square columns have a higher energy absorption in comparison with the other cross-sections. However, the amount of absorbed energy in two types of columns is equal but, 50 percent weight reduction may be seen in Al-6061 columns. The columns are re-optimized by ACO to find the best thickness in the last step.
In the following, by topology optimization participation, a new plan is proposed by the same thickness and 50% less weight, that has a higher crashworthiness efficiency by increasing SAE more than 70%. As a result of this plan is bridging the gap between standard topological design and multi-criteria optimization.
 

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In the present work, the energy absorption study of warm-rolled LZ71 sheet is done for the first time. To do so, Lithium (7% Wt), Zinc (1% Wt) and Magnesium are cast in 770⁰C. After that, the billet has been warm-rolled at 350⁰C and its thickness reduced by 80%. Then, two different heat treatment situations are studied to reach an isotropic plate. Afterward, microstructures of the specimens have been studied using an optical microscope. Tensile tests of the samples are derived to study the mechanical properties and isotropy of the sheets. Moreover, the results of tensile tests applied for crushing simulations. Energy absorption study of the alloy is also done using ABAQUS/Explicit commercial code. The results of simulations are validated using experimental tests of A6082 and completely acceptable performance of simulations is observed. Then, the mechanical properties of LZ71 are used to study the crashworthiness behavior of the mentioned alloy. Crash absorption parameters, namely peak crush force (F_Max), mean crush force (F_Mean), Total Energy Absorption (TAE), Crush Force Efficiency (CFE), Specific Energy Absorption (SEA) and Total Efficiency (TE) of LZ71 and A6082 are compared which are shown that the performance of LZ71 is considerably more efficient than A6082. Lastly, by the help of Artificial Neural Network (ANN) and Taguchi Method, the effects of dimensional parameters of tube, namely diameter, length and thickness, on F_Max, F_Mean and TAE and also the influences of dimensionless geometrical ratios, namely L/D and D/t on CFE, SEA and TE are surveyed comprehensively.

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In this study, the driver airbag geometry and internal pressure were considered as the main parameters to investigate the head injury severity in a frontal crash. The total energy absorption of an airbag was investigated in a drop test simulation and its rate was discussed by the depression distance parameter. On the other hand, the maximum deceleration of the impactor was determined to represent the airbag stiffness by a defined deceleration peak parameter. Thus, the depression distance and the deceleration peak were the objective functions for an isolated airbag under a lumped-mass impact simulation. Furthermore, an optimal matrix was generated using the design method of experiments (DOE) and yielded the airbag parameters as outputs. After the evaluation of the design parameters by the Taguchi method, the ANOVA method was used to predict the most effective parameters. Finally, a sled test with the 50% HYBRID III dummy and the defined airbag was simulated. An experimental crash was selected as the reference point to verify the simulation and to be used to compare the outcomes. Even though the objective function of depression distance showed contradictory effects to reduce the head injury severity, the results showed a %16.4 reduction in the driver head injury in a full-frontal crash.

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The braking system has always been considered one of the most significant vehicle subsystems since it plays a key role in safety issues. To design such a complex system, modeling can be a helpful tool for designers to save time and costs. In this paper, the hydraulic braking system of a B-Class vehicle was modeled by simulating the relationship between brake components such as pedals, boosters, main cylinders, and wheel cylinders, with the vehicle dynamics by using the existing models of the tire and their dynamic relationships. The performed modeling was compared with the results of a concerning vehicle's direct movement. The results of this comparison showed that our modeling is very close to the experimental data. The braking distance parameter was selected to examine the effects of each braking component on the vehicle dynamics. The results of investigating the effect of different parameters of the braking system on the dynamic behavior of the vehicle indicated that the main cylinder diameter, the diameter of the front and rear wheels’ brake cylinders, the effective diameter of the front disk, and the diameter of the rear drum are the most effective design parameters in vehicle's braking system and optimal results are obtained by applying changes to these parameters.

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This paper presents an experimental study on the effect of adhesive thickness on the maximum load of adhesive joints under static and impact loading, using the double cantilever beam (DCB) test method. The DCB specimens were prepared with varying adhesive thicknesses and subjected to impact loading using a drop weight impact tester. The maximum load was recorded for each specimen. The results indicated that the maximum load of the adhesive joints increases with increasing adhesive thickness up to 5 mm, beyond which the maximum load decreases with further increase in adhesive thickness. Moreover, the failure mode of the adhesive joint was found to be strongly dependent on the adhesive thickness, with thicker adhesive layers exhibiting an adhesive failure mode but in thinner thicknesses, the adhesive mode is cohesive. These findings provide important insights into the design and optimization of adhesive joints for applications that are subject to impact loading.

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The corrugated composite plates have wide application to improve the energy absorption and failure behavior of panel structures. The roof panel of the bus could benefit from the use of these structures to reduce impact failures in rollover accidents. The aim of this paper is to design a new configuration of bus roof panels stiffened with multi-layer semi-circular corrugated CFRP plates to minimize structure failure during rollover accidents. An analytical failure equation of Tsai-Hill index for the new proposed panel subjected to dynamic impact loading has been derived. The failure equation was validated using FEM methods and digital image correlation impact tests. According to the roll over impact situation, the multi-layered semi-circular corrugated woven CFRP roof panel displays a positive failure behavior of 89%.