Maria Alzira de Araújo Nunes

Transmission loss optimization using genetic algorithm in Helmholtz resonator under space constraints

The development of high-performance mufflers with a compact volume is of great importance in industrial field to obtain duct noise reduction in an economically and efficiently way. The Helmholtz resonator (HR), a classical reactive muffler, is considered in this work. The main purpose is to optimize numerically the sound transmission loss (TL) of the HR, since TL is an intrinsic characteristic of the muffler and does not depend on the source or termination impedances. The optimization methodology consists in maximizing the TL obtained for a pure tone frequency under dimensional constraints when the HR is considered mounted in a duct system. In order to search for the optimal dimensions of the HR cavity, an evolutionary search algorithm has been used. The sound pressure is obtained from a finite element model which communicates with the genetic algorithm (GA). Many numeric simulations were performed varying GA parameters: number of generations and population size. The results show a strong match dependency...

Estimation of the Geometric Parameters of a Front Double Wishbone Suspension Based on Geometry Formulation

Vehicle suspension stands out as an important subsystem, which allows vertical compliance to the wheels following an uneven road; keeps the proper steer and camber attitudes, resist roll of the chassis and provides comfort for passengers. The suspension subsystem needs to comply with stability, handling and optimum steering based on an appropriate suspension geometry.Nowadays, the use of simulation software in automotive design has increased. However, the cost and complexity of such software can make them unavailable to those working in the domain, especially the young designers working in vehicle’s student competition (Baja SAE®).Thus, this paper aims to propose a methodology for assessing a frontal Double Wishbone suspension, which is based on a set of analytical equations implemented computationally at Matlab®. The formulae are developed considering simple concepts of algebra, trigonometry and geometry.The input data are the Cartesian coordinates (x, y, z) of predefined points, which are obtained from the CAD design and the bound/rebound travel.The main results are the simple analytical formulae, for the most important suspension’s geometric parameters: caster, camber and toe angles.These analytical results are validated with MSC ADAMS®, particularly its add-on specialized for the automotive industry ADAMS/Car®, showing good agreement.Copyright

Integrity Assessment of Pickup Vehicle Occupants in Rollover Situation Considering Internal ROPS Device: A Numerical Approach

The rollover accidents represent a major cause of injuries and death of vehicle occupants and they are also higher among light trucks than passenger cars. The pickup trucks have important applications in mining scenario where protective structures are required to provide safety in case of a rollover during engineering works. The use of safety devices commonly referred to as ROPS-Rollover Protection System in this kind of vehicle has been shown to be an effective manner to mitigate some of the effects caused by this event, ensuring safety and integrity of passengers. Such device can be constructed using steel bars which constitute a framework to be added into the vehicle, like a cage, in order to minimize the structure intrusion in rollover accidents. In this context, this paper makes up the assessing the integrity of pickup truck occupants in rollover events of a priori designed and proposed ROPS. For this a numerical simulation is carried out based on the experimental Roof Crush Test (FMVSS-216 regulation) using the software LS-Dyna® which uses Finite Element Method (FEM). The criteria for neck and head injuries are established in the standard FMVSS-208. The analyses were conducted comparing the vehicle model equipped with and without internal ROPS.

Position optimization of Helmholtz resonator in ducts using a genetic algorithm

The equipments layout, the maintenance and operation purposes in industries limit the installation of reactive mufflers in terms of space and location. As part of this device design it is necessary to considerate these restrictions and an optimization process may necessary. Keep in mind that in real application the downstream radiating end of the duct must be modeled as an open end radiating into free space, the Insertion Loss (IL) parameter is more proper for evaluating the HRs performance than the Transmission Loss. Using the IL to estimate the effectiveness of the acoustic filter, the main purpose of this paper is to numerically analyze and maximize this parameter in the maximum attenuation frequency considering position restrictions (bounds constraints) in a duct. An evolutionary search algorithm (GA) has been applied in order to solve the best position for a fixed shape HR in a duct. The finite element method was used to model the acoustic system HR/duct. The pressure data and the optimization step ...

Development of an educational impedance tube: Experimental vibroacoustic characterization.

One of the great difficulties encountered by designers who work with room acoustics is to know the absorption coefficient of the material to be employed in the project. The tube wave, also known as impedance tube, is a device which determines this coefficient and also determines the acoustic impedance of materials. These values are essential for choosing products that best fit the needs of an acoustic treatment project, either indoors, machinery, pipes, or mufflers. This paper presents the first studies to construction and characterization of an educational impedance tube (Kundt’s tube) called TIGaD (demonstrative impedance tube of the Faculty at Gama). In this first phase we will present a dimensional study of the tube, its construction details, an experimental analysis of its vibroacoustic characteristics, and, finally, its limitations in frequency range. This project belongs to the educational area since this experimental apparatus is being developed to equip the laboratory of acoustics and vibration (...