M.h Shojaeifard, S. Ebrahimi-Nejad R., S. Kamarkhani,
Volume 7, Issue 1 (3-2017)
Abstract
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.
S. Ebrahimi-Nejad, M. Kheybari,
Volume 7, Issue 4 (12-2017)
Abstract
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.
Hamidreza Ebrahimi, Mohammadhassan Shojaeifard, Salman Ebrahimi-Nejad,
Volume 13, Issue 2 (6-2023)
Abstract
The present study aims to optimize a two-chamber muffler’s geometry and improve its acoustic performance. Mufflers with a circular cross-section are used in this study and then underwent the vibroacoustic analysis using COMSOL Multiphysics software. Several geometries, including a reference model and new ones, are designed and their geometry is optimized by Parametric and grid optimization methods, which are the software’s optimization methods. First, the reference paper is validated to ensure the simulation produces the least error. The results obtained in this study have a good match with those of the reference. Then, by changing dimensions such as length, diameter, and inner design of the mufflers, the best geometry in terms of transmission loss and bandwidth was selected and compared with the results acquired by the reference model. It was found that the acoustic performance of the optimized design (two-chamber muffler with four inner tubes) outperforms the model used in the reference. That is, the results indicate that the optimized design is able to attenuate sound up to 78dB in the range of 0 to 500Hz, 45dB higher than that of the conventional model. Further, the muffler’s weight is reduced by a quarter, using a 0.9mm thickness.
