Search Results

In nowadays automotive market, highlighted by global products, companies are pushed to sell vehicles that comply with legal and customer requirements in different countries and, not unusually, different continents. In order to achieve such challenge, and pressed to reduce project and production costs, companies are spreading design centers around the world, based on regional expertise and lower labor costs. These excellence centers must work together to benefit from synergies and local skills from different regions. Such projects are staffed by Virtual Team, whose members barely face each other. This means teams will work frequently with people they have never met, who live in different time zones and have different cultures. As a consequence, communication is done basically through computer-based media, and must be even clearer and more direct than with the people who work at the next desk.

During the last years, the automotive industry dedicated great efforts to understand and solve the noise problem from disc brake systems. There are several types of brake noise problems, each one related with a frequency range of occurrence. In most cases, the customer perceives the noise as a vehicle problem and demand having it fix by their dealer. As a consequence, disc brake noise is one of the major contributors to the automotive manufactures warranty costs, leading the automotive industry to look for ways to control it. A large class of disc brake noise problems is associated with the resonant behavior of an operating brake system. However, the detection of these brake system modes during the operating condition can be very expensive, demanding the use of inertial dynamometers and laser vibrometer measurements.

The acoustic development of vehicles is a very important step during its design to ensure its success in a competitive marketplace. In recent years, the advances on the noise and vibration control engineering in vehicles provided the production of quite and comfortable cars. The main noise and vibration sources in vehicles, i.e., engine, gearbox and exhaust systems, had its noise levels considered reduced, and, as a consequence, other noise sources became more easily observed. The noise generated by pumps of power steering systems is an example of this kind of problem. For the majority of automotive applications are used vane pumps. These pumps generate noise due the vane passing frequency. Basically, the hydraulic pump noise can be classified as Moan or Whine, regarding the operating condition. This work presents a methodology to approach the noise and vibration problem from hydraulic pumps of power steering systems.

Tires have been taking an important role in vehicle safety in the last years. A lot of efforts have been taken in the way that we can understand, predict and follow its behavior, in the way that this could be useful for vehicle safety increasing. In this direction, several models describe the tire interaction with ground, considering the steering angle, pressure, temperature, friction coefficient and thread as well. Inside this analysis, there is the tire slip angle value, that is consequence of lateral forces acting over the tire. This characteristic is predicted in some cases, and evaluated on another ones. This paper brings to community another point of view of slip angle. We propose a mathematical model that describes a constraint linking slip angles and steering angle, in the way that makes the vehicle turns. We present the kinematic model that makes all three angles compatibles each other, function of the radius' corner.

Considering technology development and the raise in computational power, numerical methods became important device in developing new products and in improving existing ones, being a differential for market competition among companies, consequently from the reduction of time and cost in projects. For Student Competition Teams, like Formula and Mini Baja SAE series, the use of simulation is even more important in their vehicle development, due to team limited resources available and their lack of experience. This work has the main goal of presenting the development steps of a structural component of the suspension system, the steering knuckle, for Formula SAE competition vehicles, aided by computational aided engineering. Starting from the geometrical and functional configuration of the vehicle, a multibody model was generated by the Altair Motion View software to simulate high performance maneuvers, and then estimate two cases of loads.

With the growing increase in the use of lawn mowers, it is necessary to control the vibration and sound pressure levels to which operators are exposed during their workday. Noise hearing loss can affect individuals exposed to high Sound Pressure Levels (SPL). Workers using lawn mowers are part of this population. With regard to this equipment, another factor that must be considered is the occupational exposure of the vibration imposed on the operator. Occupational exposure to vibration in the hands and arms is associated with a variety of adverse effects on the health of the individual, being collectively known as the vibration syndrome in the hands and arms. Exposure to full body vibration for seated people is associated with an increased risk of degenerative injuries lumbar spine, disorders in the central nervous system, and possible damage to the digestive and genital / urinary systems.

One of the most important components in vehicle dynamics studies is the tire, due to the fact that it is the only component that keeps the vehicle in contact with the ground. In the study of vehicle dynamics, all force transmission between the vehicle and the ground occurs through the contact area of the tire with the road. The maintenance of this contact during the steering allows the driver to have control over the vehicle and this is one of the premises for vehicle safety. The tread grooves help ensure that the friction between the rubber and the soil aggregate is maintained in different lane conditions, be it dry, wet, clean or dirty. Its depth is easy to measure, being regulated in Brazil by CONTRAN in, at least, 1.6 mm. However, even at depths greater than the minimum required by law, vehicle safety can be compromised in wet conditions, as the ability to drain water is greatly compromised at high speeds.

One of the most important complaints about noise in small vehicles is related to the hydraulic steering pump, which is used strongly during parking maneuvers, and produces a noise that overcomes the one coming from the engine, due to its low speed. This noise can be eliminated by the introduction of two resonators inside the high-pressure tube designed to coincide with the tube's resonance frequency. However, in some cases, as in tubes with short rubber pieces, these resonators may be not sufficient to reduce the noise to non-audible levels, due to its low ability to absorb the pressure peaks coming from the pump. In these cases it is possible to introduce orifices at each resonator to maximize its effect. Here we present the theory related to the use of these orifices and the results obtained in tests on bench.

In recent years, SEA has been recognized as an important tool to model the vibro-acoustic behavior of vehicles in mid and high frequencies. Through SEA it is possible to develop vehicle models early in the design stage, reducing the risk of future noise problems and allowing the optimization of noise control treatments. Moreover, at the final design stages, a SEA model can be use to evaluate changes at the project, reducing costs with experiments. In a SEA model, the structure under study is divided in subsystems. The capacity of each subsystem of storekeeping, dissipating and transmitting energy is described by three parameters: modal density, loss factor and coupling loss factor. The noise and vibration sources are include in the model as power inputs to subsystem and, based on an equilibrium power balance, it is possible to calculate the energy of each subsystem.

Brake squeal noise has been under investigation by the automotive manufacturers for decades due to consistent customer complaints and high warranty costs. In most cases, the customer perceives the noise as a vehicle problem and demand having it fix by their dealer. J. D. Power surveys consistently show brake noise as one of the most critical vehicle quality measurements. Furthermore, the development of methods to predict the noise occurrence during the design of a brake system has been the target of many researchers in the last years. The complex eigenvalue analysis has been widely used to detect unstable frequencies in brake systems models. The method is fast and useful to provide design guidance, since operating parameters and control methods can be evaluated by a simulation procedure. This paper summarizes the application of the complex eigenvalue analysis in a finite element model of a commercial brake system.

In this study an objective metric is presented to evaluate the hiss noise of hydraulice power steering. The correlation between subjective tests and psychoacoustics metrics is investigated. The objective metric is obtained using multilinear regression where the psychoacoustics metric and the results of the subjective tests are the dependent and independent variables of the linear regression, respectively.

The application of sound quality tools in the design process of electro-hydraulic power steering (EHPS) is investigated in this paper. The EHPS acoustics performance is investigated by studying the correlation between objective measurements and subjective evaluation of the noise from the EHPS.

Transmission loss (TL) is a common metric for the comparison of the acoustic performance of mufflers. Muffler TL can be computed from a Boundary Element Method (BEM) model. Perforated tube elements are commonly used in automotive muffler applications. These can be modeled with a detailed BEM model that includes each individual hole in the perforated tube. The main drawback with such a straightforward BEM approach is that the discretionary of the perforated surfaces can result in computationally expensive models. The current work uses an approach that is a more computationally-efficient, yet, precise way of modeling complex mufflers that contain perforated surfaces with BEM. In this approach, instead of explicitly modeling the perforations explicitly they are taken into account as equivalent transfer impedances. There are several models in the literature that can be used to develop the transfer impedance model of the perforated surface.

Despite its advantages for sustainable development, railways have great potential of noise generation. This is the main source of annoyance for railroads’ neighboring communities. Among the many types of noise that exist on a railway system, the impact noise generated at rail joints is one that stands out. To propose mitigation measures in order to solve this problem, it is necessary to understand how this noise is generated and by which parameters it is influenced. To that end, analytical models have been developed over the years. They are useful tools to verify which factors are more important to noise emission, and also can be used to predict the sound pressure level (SPL) generated and test possible solutions. This paper aims to validate an analytical model for impact noise which was originally designed for urban railways, used for passenger transportation. In this work, the validation is made using SPL measurements made at a Brazilian freight railway.

Noise pollution resulting from technological development, urbanization and economic growth is one of the major sources of complaints in urban areas. The sound generated by transportation systems, is one of the most important causes of noise-induced annoyance, since the exposure to high levels for long periods of time can be detrimental to health. Freight railway systems have great potential of noise emission, since they are designed to meet safety requirements, rather than comfort, and are subject to more severe operations and cruder maintenance procedures than passenger cars. Among the different types of noise that originate from a railroad, the squealing generated in curves is one that stands out since it can exceed regular rolling noise in 30 dB and often occurs in frequencies where the human hearing is more sensitive. Analytical models have been developed over the years to help understanding and predicting squeal.

Due to the great use of airplanes for transportation, it was necessary some studies to improve it, one of the most difficult problems to solve, is the noise generated by the systems. In-flight sound pressure levels can sometimes be intense and cause fatigue to the cabin crew, communication failures and discomfort to the passengers. This is often caused by the turbulent boundary layer over the aircraft body, engine noise and vibration and internal aircraft systems. The aircraft hydraulic system is responsible for moving the rudder, aileron, brakes, main door, and other components, and consequently, the noise of this system became more noticeable. This system comprises a pump, generally, located at the back of the aircraft and pipes, which are fixed along the fuselage. The pipes are connected to the fuselage using rubber mounts. Analyzing experimental measurements is possible to identify that hydraulic system contribute to the in-flight sound pressure level in the aircraft cabin.

In racing applications, the constant search for improvement has been changing new projects’ development approach. The time available for designing has become smaller, while requirements on performance improvement continuously persist in the daily routine of competition engineering. Since suspension systems play a big role in vehicle dynamics, affecting directly the tire performance of the vehicle under design, hence, the overall performance of the car on the track, computational methods are proven to be a crucial tool for developing new prototypes and making decisions. Under this point of view, optimization techniques have exploited new computational resources, which are constantly getting cheaper, to search for new engineering solutions. This work presents the methodology used and the results obtained from the kinematics optimization of a Formula Student suspension system through the application of heuristics method techniques.

The invention of the wheel was an important milestone in the history of mankind. With it was possible to significantly reduce the friction between an object and the ground, requiring less force to move them and making it possible to transport items of interest. The use of the wheel in vehicles brought great advantages, however, it became necessary to control the speed, to avoid accidents with the environment around it. As a result, there was a need for the development of brake systems. The main function of the brake system is the transmission of the braking torque to the wheels, through the conversion of kinetic energy into heat. However, conventional brake systems had a serious problem with the car's ability to control while braking. The ability to control the vehicle, known as handling, is dependent on the adhesion between the tire and the ground. Driving loss occurs when the wheels lock during braking.