Herve Mahe

Analysis of squeal noise and mode coupling instabilities including damping and gyroscopic effects

Abstract This paper deals with an audible disturbance known as automotive clutch squeal noise from the viewpoint of friction-induced mode coupling instability. Firstly, an auto-coupling model is presented showing a non-conservative circulatory effect originating from friction forces. Secondly, the stability of an equilibrium is investigated by determining the eigenvalues of the system linearized equations. The effects of the circulatory and gyroscopic actions are examined analytically and numerically to determine their influence on the stability region. Separate and combined effects are analyzed with and without structural damping and important information is obtained on the role of each parameter and their interactions regarding overall stability. Not only is structural damping shown to be of primary importance, as reported in many previous works, this article also highlights a particular relationship with gyroscopic effects. A method of optimizing both the stability range and its robustness with respect to uncertainty on system parameters is discussed after which practical design recommendations are given.

Three-dimensional finite element model of an automotive clutch for analysis of axial vibrations:

Recent progress made in making clutches lightweight and in reducing torsional vibrations has led to the emergence of new vibroacoustic phenomena due to the out-of-plane vibrations of the clutch. These vibrations are generated along the axial direction of the clutch system. Contrary to torsional vibrations that can be simulated by unidirectional lumped-mass models, axial vibrations require a three-dimensional approach to describe the dynamics of the components. Finite element models are widely used to design or optimize the components of the clutch. However, no finite element model of a complete clutch has been developed for analysis of axial vibrations. The main difficulties are the complexity of the system, the great number of non-linearities, the difficulties of instrumentation for validation and the variation in the behaviour along the engagement stroke. This paper provides a validated three-dimensional finite element model of the dynamic behaviour of the clutch for studying axial vibrations. The model simulates the axial static and dynamic characteristics of the clutch. Model accuracy and validation are achieved by comparing the numerical results with the experimental data. The results show the crucial parameters to consider in order to reproduce correctly the non-linear axial behaviour and the dynamic characteristics of the clutch system, namely the orthotropic behaviour of the friction material and the geometrical parameters of some components that should be detailed. Validation is carried out on each component and for the system assembly by dedicated experiments and instrumentation.

Modal Analysis of Automotive Clutch Using Finite Element Method

Clutch system is an important element in the vehicle powertrain. It transmits the rotation from the crankshaft to the gearbox input shaft and filters axial and torsional vibrations providing from engine or induced by friction. This paper discusses axial dynamic behavior of automotive clutch for manual transmission. For this study, a tridimensional finite element model of clutch system is developed to simulate a clutch shaker test. First, an impact hammer test is performed to identify vibration properties of each clutch component. A pre-stressed modal analysis is then carried out to determine mode shapes and its associated natural frequencies of the clutch assembly. Shaker and simulation results are eventually compared to validate the clutch model. This latter offers for the design phase, a tool to avoid natural vibrations or to vibrate at specified frequencies.Copyright