21-06-2013, 04:00 PM
EVALUATION OF AN AUTOMOTIVE WIPER NOISE AND VIBRATION CHARACTERISTICS USING NUMERICAL APPROACH
ABSTRACT
As modern passenger cars become increasingly quieter and comfort, automotive
windscreen wiper noise and vibration become more noticeable. As a result of the market
information survey, most complaints about the wiper concern operation noise. Wiper vibration
and noise is classified into three main categories namely, squeal noise, chattering, and reversal
noise. Squeal noise is a high-frequency vibration of about 1000 Hz. Chattering noise is a lowfrequency
vibration of 100Hz or less and reversal noise is an impact sound with a frequency
of 500 Hz or less produced when the wiper reverses.
Typically, noise and vibration study of the automotive windscreen wiper has been
carried out by experimental, analytical and numerical approaches. This report describes
evaluation of noise and vibration that generated by an automotive windscreen wiper using
numerical approach via finite element method. In doing so, two types of test are conducted i.e.
modal testing for individual wiper components and noise and vibration test to identify noise
category for a selected passenger car windscreen wiper. Later, a 3-dimensional (3D) finite
element (FE) model of the windscreen wiper assembly is developed. This FE model is then
validated at the component level using modal analysis in order to ensure that dynamic
characteristics of the FE model close to a real windscreen wiper.
In order to evaluate characteristics of noise and vibration of the windscreen wiper,
complex eigenvalue analysis that made available in ABAQUS is employed. It is found that the
windscreen wiper generates noise at frequency around 11 Hz which is identified as chatter and
the predicted frequency is fairly close with measured frequency obtained in the experiment.
This chatter noise is dominated by bending mode of the wiper blade. Having found the
characteristics of the windscreen wiper noise, several structural modifications are proposed to
the rubber blade and simulated once again. There are three modifications that capable of
preventing noise and vibration in the windscreen wiper. This finding could help car makers to
design quiet and effective windscreen wiper and in turn to produce quieter and comfort
passenger cars.
Introduction
Windscreen wipers are indispensable components to the maintenance of a safe and comfortable
field of vision when driving on rainy days. Today, almost all automobile are equipped with
windscreen wiper, often by legal requirement. Clear vision for the car driver is an important
prerequisite for safety in road traffic. A conventional wiper as shown in Figure 1.1 generally
consists of an arm, pivoting at one end and with a long rubber blade attached to the other
(Denso International Products, 2008). The blade is swung back and forth over the windscreen,
pushing water from its surface. The mechanical structure of the wiper blades is attached to the
arm tips, holds the rubber blade, which drains the water off the windscreen or to smooth the
water on the surface of the windscreen in order to create a thin film that allows light to pass
through it without refracting or bending as shown in Figure 1.2.
Development of a finite element model
Finite element (FE) method is useful to determine noise and vibration characteristics of a
wiper. The FE model will be developed and simulated using commercial FE software package
namely, ABAQUS v6.6. Various designs of a wiper can be easily modeled and simulated. It is
a cost and time efficient compared to a developing prototype, which requires quite a high cost
to develop and fabricate. The developed FE model will be then validated in terms of natural
frequency and its associated mode shape at component level. Vibration and noise test of the
windscreen wiper will be conducted and to identify type of wiper noise. Later, complex
eigenvalue analysis will be performed on the FE model in order to predict stability of the wiper.
Results of the prediction will be then compared with those find in the tests.
Development and evaluation of suppression method
Suppression method should able to reduce and/or eliminate noise and vibration of the wiper up
to acceptable level. Based on the predicted results, various suppression methods will be
identified and simulated. Suppression method can be either modifying the wiper blade structure
and/or changing the mechanical properties of an existing wiper rubber. All proposed
suppression would be then evaluated through simulation in order to examine their
effectiveness.