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Vehicle brake judder is a vibration phenomenon responsible for an expressive number of customer complaints. In order to prevent judder from occurring, new vehicle developments are putting in practice dynamometer and vehicle brake tests to assess the DTV growth and the effectiveness of applied countermeasures, when necessary. The measurement of DTV is very sensitive and requires high precision sensors. Due to these facts, incorrect DTV measurements are not uncommon, since the rig or vehicle setup, the assembly/disassembly of the sensors or brakes and even the vibration of the dynamometer itself may figure as sources for measurement errors. In the other hand, if the test vehicle or dynamometer is equipped to acquire brake torque and brake pressure variations (BTV and BPV, respectively), those measurements may suffer less interference from external parameters and present good relationship with DTV and judder.

The objective of this work is to evaluate the levels and vibratory effects that the passengers who use intermunicipal road buses are submitted. In the study, measurements of the accelerations produced in the vertical direction had been carried through according with norm ISO 2631, in two bus bodyworks, of different manufacturers, in a normal situation of use, in three points of it (frontal, central and back). With the measurements it was possible to point which are the places in the bodywork interior and the points in the seats that produce greater accelerations r.m.s. The results had been evaluated and compared with the curves values established for norm ISO 2631 in relation to health and comfort and in relation to fatigue, comparing the two tested bodyworks.

This work describes an approach to overcome squeal noise problems by increasing damping on brake pads using special designed underlayer materials. Experiments were conducted to characterize the damping properties of current and new underlayer materials and its effect on the total damping of the pads. Dynamometer tests were performed to verify the noise performance behavior of pads equipped with the different types of underlayers and physical tests were made to characterize its properties. By the end a discussion about the results is conducted to relate the physical properties of the designed materials and its results on dynamometer tests.

The human body exposition to vibration and to mechanical shocks may cause discomfort and physiologic alterations. Researches have been developed for at last 30 years, with the objective to find the human body behavior and the collateral effects caused when submitted to vibration. This is a present-day topic and worries the scientific community. Clinical investigations shows that vehicle drivers and industrial workers exposed to vibration and shock exhibit reduction of vertebral discs thickness [1] and epidemiologic evidences aim the human body exposition to vibration to be the principal cause of low back pain (LBP) [2, 3]. A four DOF model of the system composed of a seat and a person on it is considered, to describe the measured experimental curves of transmissibility in urban buses drivers. The model was adjusted to describe the measured transmissibility between the bus's ground and the seat, and between the seat and the driver's shoulder.

Drive shafts endurance tests performed in 4-square test rigs often presents different levels of wear on samples of the same test, and the most damaged joints usually comes from positions 3 and 4 of the machine. These results are evidences of an unequal torque distribution between the tested parts. In order to analyze this effect on the equipment, four half shafts prepared for torque measurement are proposed. These parts are put in the machine and a simulated test is performed, while the torque applied to each rig position is measured simultaneously. The effect of the applied torque, speed and joint bending angles can so be evaluated to the influence on test results. Through this test it is possible to conclude that variations on applied torque is related more to the applied speed than to the other studied factors.

The purpose of this paper is to generate basic data about physical properties of disc and pad friction materials, and then correlate these data with results of disc brake noise evaluations. It is attempted to predict how variations in some characteristics of friction materials could affect their propensity to generate noise. At the end of the study, the goal is to point out a way in which the properties of counter friction materials could be changed to reduce the brake noise propensity.

This work presents the comparison of computer predictions with experimental measurements of the rear solid axle suspension (ideal to the off-road vehicles) of a mini baja prototype. The dynamic analysis consisted in finding the first natural frequencies and critical velocities of the shaft. The constants necessary for the numeric and experimental analysis, such as stiffness of the tires, equivalent spring constant of the whole rear suspension and mass of the components were obtained experimentally. Piezoelectric accelerometers were used to measure dynamic response of the system. The numeric analysis was made using the transfer matrix method. By comparing the experimental results with those obtained by the transfer matrix method, the validity of this analytical approach is confirmed.

The analysis of critical speeds of elastic shafts considering gyroscopic effect is performed by the transfer matrix method. A transfer matrix is formulated for free vibration without damping and forced vibrations with damping. A rotor-motor-pump model is analized with both the Finite Element Method (FEM) and Transfer Matrix Method (TMM) to compare and validate the approach. The gyroscopic effect influences in the resonance frequency is analysed.

This paper presents a study on the resonance of front wheel drive (FWD) automobile half-shafts. This problem can occur in FWD vehicles when the excitation frequency generated by the engine equals one of the bending natural frequencies of the half-shaft [7],[8]. Experimental modal analysis is today the prefered method in the study of this problem[6], but in this paper the bending natural frequencies of the half-shaft are obtained using a numerical and a parametric method. Comparison of numerical results using two half-shaft models and experimental data shows good agreement. The physical variables that influence the phenomenon are then investigated, and a dimensional analysis is conducted to obtain parametric design graphs that help to calculate resonance frequencies of the half-shaft.

This work presents a study of the bending vibrations of front wheel drive automobile half-shafts, using various theoretical models results in comparison with published experimental data. It’s well known that this kind of noise problem occurs when a vertical excitation frequency generated by the engine equals one of the bending natural frequencies of the half-shaft or its interconnecting shaft[7],[8]. The experimental modal analysis is today the preferred method used in the study of this kind of problem[7]. This work, investigates the determination of the bending natural frequencies of a front wheel drive automobile half-shaft, using the transfer matrix method (TMM)[1],[4] and the finite element method (FEM)[6] in the solution of a theoretical model. This model considers the boundary conditions existing in the vehicle, and also in the solution of other simplified models.