1,721,071 research outputs found
Shape of a spectral excitation matrix for a linear road/tyre interaction numerical analysis
No full textTyre/road interaction is recognized as the main source
of interior and exterior noise for velocities over 40 km/h.
The authors have proposed a linear stochastic
approach to predict the tyre vibrations due to the
road/tyre interaction. A mechanical model of the tyre
is connected to the road through a Winkler contact
model with all the springs in the contact patch assumed
to be in contact with the road at all the time. Such a
linear model is strictly valid for smooth road and soft
tyres. In this paper the authors investigate the range
of validity of the linearity assumption and they also
propose a modified shape of the excitation matrix
that takes into account the contact non-linearity. The
investigation is based on a numerical non-linear model
of a 2D tyre. The model consists of a rigid curved body
that touches the road through a Winkler model, in
which the number of the springs in contact and their
actual compression has been found through a quasistatic
equilibrium analysis
A model of tyre vibration with stochastic excitation
No full textFor vehicle at normal driving conditions and speeds above 30-40 km/h the dominating external noise source is the sound generated by the tyre and road interaction. Previous measurements have shown that there is a strong correlation between the radiated sound pressure and the vibrations of the tyre structure for frequency below approximately 1 kHz. The tyre vibration is also the main source of noise inside many vehicles in this frequency range. It is thus important to develop simple tools that predict the tyres behaviour in this frequency range.The tyre is modelled as an elemental system, which permits the analysis of the low frequency tyre response when excited by distributed stochastic forces in the contact patch. Although the contact mechanism is generally non-linear, it is assumed here that the tyre is compliant enough for the whole of the contact patch to remain of the same width and to be always in touch with the road. A linear model can then be used to calculate the contact forces from the road roughness and thus calculate the resulting radial velocity of the tyre. A spectral density matrix, derived from a road roughness model, describes the velocities and is used to calculate the expectation of the tyre’s kinetic energy and its sound power radiation.In the first instance a simple two-dimensional model will be used with a Winkler bedding model of the contact patch to predict the power spectral density of the tyre vibration at different road speeds. This model can also be used to provide an initial estimate of the potential effect of various active control strategies for reducing the tyre vibrations. In particular an optimised feed-forward control formulation can be used to calculate the potential effect of various types of actuators, by calculating the optimal performance with different distributions of secondary force
Force transmissibility of structures traversed by a moving system
No full textThis paper addresses a general method of computing the force transmissibility for complex or statically indeterminate mechanical system with more than one support. Moreover, the forces transmitted to the ground when one mechanical system travels across another are calculated. The results of an oscillator travelling over a beam on three simple supports is addressed in order to illustrate the method
Stochastic road excitation and control feasibility in a 2d linear tyre model
No full textFor vehicle under normal driving conditions and speeds above 30–40 km/h the dominating internal and external noise source is the sound generated by the interaction between the tyre and the road. This paper presents a simple model to predict tyre behaviour in the frequency range up to 400 Hz, where the dominant vibration is two dimensional. The tyre is modelled as an elemental system, which permits the analysis of the low-frequency tyre response when excited by distributed stochastic displacements in the contact patch. A linear model has been used to calculate the contact forces from the road roughness and thus calculate the average spectral properties of the resulting radial velocity of the tyre in one step from the spectral properties of the road roughness. Such a model has also been used to provide an estimate of the potential effect of various active control strategies for reducing the tyre vibration
Preliminary study on efficiency of transverse and extensional power harvesting on a vibrating plate
No full textPower harvesting systems generate electric power
from mechanical vibration using electromechanical
transducers. To assess the practical performance of
these systems, it is important to be able to estimate
the maximum power that could be harvested from a
specific structure and to derive the optimal conditions
for such harvesting. Dampers have been used to
represent idealised power harvester devices, assuming
that a fixed proportion of the power dissipated in the
absorber could be scavenged. Such idealised power
absorbers have been applied to a vibrating plate in
two different configurations: a configuration that
scavenges power from the transverse displacement
and one that gather power from the extensional
displacement at the plate surface. The maximum
power obtainable from such structure has been
calculated for tonal excitation of the structure. The
attenuation of the kinetic energy, due to the application
of the absorber to the structure, has also been studied
in order to find analogies between power harvesting
and shunt damping
‘Mapping the Underworld’: recent developments in vibro-acoustic techniques to locate buried infrastructure
Full text linkA major UK initiative entitled Mapping the Underworld (MTU) is seeking to address the serious social, environmental and economic consequences arising from an inability to locate – accurately and comprehensively – buried utility service infrastructure without resorting to extensive excavations. MTU aims to develop and prove the efficacy of a multi sensor device for accurate remote buried utility service detection, location and, where possible, identification. One of the technologies to be incorporated in the device is low-frequency vibro-acoustics, and a number of different vibro-acoustic methods for detecting buried infrastructure have been investigated. The latest developments in the vibro-acoustic location research are presented here. Three complementary methods are described, one of which involves direct excitation of the buried asset and the other two require no such direct access. All involve measurement of the ground surface vibration as a result of the excitation, whether of the ground or of the buried asset directly. Together, these techniques constitute a substantial step change in the way buried infrastructure can be detected using vibro-acoustic methods
Nonlinear shaping of a spectral excitation matrix for a linear road/tyre interaction stochastic analysis
No full textNon-linear shape of a spectral excitation matrix for a linear road/tyre interaction stochastic analysis
No full text- …
