An in plane flexible ring model for the analysis of the free and forced response of a rolling tyre

The increased demand for vibroacoustic comfort as well as regulations on noise and vibration levels made the NVH performances of a vehicle one of the fundamental design criteria. Therefore, predictive models for the analysis of noise and vibration transmission mechanisms represent interesting tools to support the R&D department of the automotive companies. Focusing the attention on passenger’s comfort, the vibrations induced by the tyre/road interaction propagate from the contact area to the hub and finally inside the cockpit through structure-borne transmission paths. This can be regarded as one of the major contributors to car cabin interior noise at low frequencies (20-500 Hz). Simplified models able to interpret the waves propagating inside the tyre structure and influenced by the angular speed may support the studies in this research field. To this end, an analytical model based on the theory of the flexible ring on elastic foundation was developed. It allows analysing the tyre dynamics in both static and rotating conditions. Model parameters were calibrated based on an Experimental Modal Analysis of the static tyre. The free response of the tyre shows the bifurcation effect at different rotating speeds, while a cleat test simulation allows investigating the forced response of the tyre

A Theoretical Model for Investigating the Structural Dynamics of a Rolling Tyre

The noise generated by the rolling tyre contributes significantly to the car's interior noise. This is caused by the tyre-road contact, and at low frequencies (0-500 Hz) is mostly transmitted inside the cockpit through the structure-borne transmission path. In support of the studies in this research field, an interpretative model of the tyre-wheel system accounting for the effects induced by the angular speed represents a useful tool. To this aim, we implemented an analytical model based on a flexible ring on an elastic foundation to analyze the dynamics of the tyre-wheel system, in both static and rotating configurations. We fine-tuned the parameters of the tyre based on data coming from experimental modal analysis of the static tyre. Particular attention has been paid to the system's free and forced responses, commonly analyzed with the so-called cleat test. The results are discussed interpreting the behavior in different reference systems

Tyre cavity noise: porous materials as a countermeasure

The first resonance of the tyre air cavity can significantly affect vehicle interior noise at frequencies around 200 Hz. The insertion of a sound absorbing liner inside a tyre is known to be an efficient countermeasure to this problem and tyre manufacturers are already producing tyres implementing this solution. The present work proposes a methodology for predicting the damping performance of a lined tyre by means of numerical models. The geometry of the tyre cavity and the lining, as well as the properties of the sound absorbing material are taken into account and predictions are made concerning the effect of specific combinations of volume and properties of the liner. For fixed material characteristics, the volume of the lining treatment strongly influences the attenuation of the cavity resonance. Moreover, the simulations performed suggest that for fixed volume and material properties, larger attenuation of the cavity resonance peak can be obtained by adopting a discontinuous layout

Active control for panel transmission loss improvement

Vibroacoustic comfort is becoming more and more a fundamental requirement for the development of new products in both transport and civil engineering. The demand for improved performance is particularly challenging due to the increasing employment of lightweight composite materials in aircraft panels, vehicle body structures and building partitions. Indeed, composite materials are widely used for their high stiffness-to-weight ratio, although this characteristic, beside a generally low structural damping, implies poor vibroacoustic performances. Viscoelastic or massive treatments are commonly employed to mitigate these drawbacks. With reference to the airborne path, the application of active control is here investigated for improving the panel Transmission Loss at low frequency, where passive treatments are less effective. A time domain model for predicting the Transmission Loss in case of single or diffuse field incidence is presented. The model is validated against experimental measurements performed in a double reverberation chamber. Then, active control is introduced into the model and its effectiveness in increasing the panel acoustic insulation is verified

Vibro-acoustic properties of sandwich structures

The vibro-acoustic properties of three-layered sandwich elements depend on the bending stiffness of the structure. It is found that the apparent bending stiffness of a sandwich beam depends on frequency, its length and boundary conditions. A beam with free ends appears stiffer than the same beam clamped at both ends. The apparent bending stiffness of a sandwich beam with clamped ends decreases as the length of the beam is reduced. The opposite is the case for a beam with free ends. A method for estimating the material parameters of a sandwich beam is described. The frequency and space averages of the point mobility of a finite sandwich beam is found to be equal to the point mobility of an infinite sandwich beam of the same type. Coupling loss factors between sandwich beam elements for some simple types of junctions are given

Processing of tyre data for rolling noise prediction through a statistical modelling approach

Nowadays, tyre/road noise represents one of the main sources of environmental pollution. For this reason, tyre/road noise models are fundamental to support the design of more silent products. In this paper, a statistical modelling approach is discussed, with particular focus on the identification and processing of noise-related tyre/road parameters. At first, the workflow for the development of a statistical tyre/road noise model is described. This strategy is then applied to the prediction of sound intensity levels of indoor tests performed on drum at different rolling speeds. The measurement of input and output data and their processing are discussed and applied to the define a suitable database. The proposed approach is then tested with a neural network. The results show the potential of the presented methodology in terms of selection of descriptive parameters and features’ extraction procedure

An investigation of the influence of wheel/rail contact conditions on curve squeal

In this paper the influence of wheel/rail contact conditions on the possible occurrence of curve squeal is investigated. A reference case is presented, together with the available experimental data, and the results of numerical simulations are illustrated. The analyses reported in the paper are based on two calculation steps. First 3D multibody simulation of a rail vehicle running in curve is carried out. Then squeal simulation is performed, which is based on linear wheel and rail dynamic models, coupled through a nonlinear contact model. Stability analysis of the open loop transfer function of the overall system yields the possible unstable frequencies