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02.06 Nonlinear Vibro-Acoustics

Comparison of noise generated from simplex and duplex configurations of drum brake using non-linear vibro-acoustic models
Time: 11:20 am

Author: Akash Yella

Abstract ID: 1836

The drum brakes used on the rear wheels of automobiles have various configurations. These contribute to the differences in kinematic (geometry) and dynamic (contact, friction) aspects, eventually leading to significantly different vibration and acoustic response. This work attempts to estimate the difference in the vibro-acoustic noise generated by the drum brake's simplex and duplex variants using a combination of non-linear analytical vibration models and a numerical acoustic model. Four degrees-of-freedom lumped parameter models developed for the simplex and the duplex configurations with conformal contact predict the contact and reaction forces during braking. These forces act as the sources for the finite element based acoustic models developed for the two configurations to obtain the sound pressure to force transfer functions. The sound pressure levels are estimated by the product of the predicted forces with the respective transfer functions in the frequency domain. The sound pressure levels of the simplex and duplex drum brakes are quantitatively compared under different braking conditions, and the results are presented. It is expected that this vibro-acoustic analysis will help in designing quieter drum brakes.

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Development of experimental vibro-acoustic transfer function for a system with combined rolling-sliding motion
Time: 11:40 am

Author: Kumar Milind Rewanand Shripad

Abstract ID: 1858

Combined rolling-sliding contact is present in popular non-linear systems such as cam-follower, gears, clutches, and brakes. These systems produce significant noise due to complex contact between the components during operation. The noise generated is a strong function of the contact parameters and excitation to the system. The objective of this study is to develop a transfer function to quantify the vibro-acoustic noise for various contact conditions. Acceleration, reaction forces, and acoustic pressure measurements are made on a cam-follower setup with combined rolling-sliding contact. Experiments are performed under different conditions of friction, lubrication, load, and speed. Contact forces are back-calculated using the kinematics. The transfer function relating the acoustic pressure to different forces is estimated. It is observed that the contact parameters govern the transfer function and hence the vibro-acoustic systems. The developed transfer function is useful in designing better sub-systems with combined rolling-sliding contact to reduce noise exposure, as a direct technique to relate the contact parameters to the noise does not exist. This study can be extended to other complex systems such as gears and clutches.

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Variation in vibro-acoustic noise due to the defects in an automotive drum brake
Time: 11:00 am


Abstract ID: 2192

Drum brakes are significant contributors to noise and vibration in automobiles causing discomfort to the passengers. The vibration and hence the resulting noise increase due to various inherent defects in the drum brake, such as asymmetry. This work aims to quantify the variation in the vibro-acoustic noise due to several common defects in the drum brake using an integrated non-linear vibration analytical model and a numerical acoustic model. The sources of vibro-acoustic noise sources such as contact and reaction forces are predicted using a four-degree-of-freedom non-linear contact mechanics based analytical model. A finite element based acoustic model of the drum brake is utilized to predict the force to the sound pressure transfer function in the drum brake. Product of the transfer functions and the forces gives the corresponding sound pressure level from which the overall sound pressure levels are estimated. The variation in the overall sound pressure levels due to different drum brake defects is evaluated by introducing defects to the analytical model. The results show that the overall sound pressure level is a strong function of the defects. It is envisioned that the current work will help in the development of effective health monitoring systems.

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Development of a Unique Experimental System Investigating Vibroacoustic Characteristic of Geared Transmission Systems
Time: 12:00 pm

Author: Umut Murat GÖK

Abstract ID: 3080

Gearboxes are widely using in industry, especially in automotive transmission systems. In actual technology level, different component-based quality control methods are applied for the quality control of powertrains but test systems, designed for assembled products, are based on subjective evaluations and scalar measurement of total sound pressure. These systems, especially operating in industrial conditions where background noise is effective, cannot meet the technical requirements. In this paper, the development of a unique experimental platform, capable of testing the powertrain under real operating conditions (torque, rotational speeds), and the experimental results are explained. In the system where transmission error, noise and vibration measurements are carried out, defective samples were determined according to statistical evaluations and errors were classified. In future studies, using the ability to calculate mechanical efficiency based on measurements, the correlation between deviations in mechanical efficiency and transmission error will be examined.

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