Vibration Signature of Defected Gear Tooth Using
Spectral Analysis
Zhuang
Li,
Suri Ganeriwala
SpectraQuest Inc., 8201 Hermitage Road, Richmond, VA 23228
Published: August 2007
Abstract
The vibration signature of gear tooth seeded
fault has been studied in this tech note. Experiments were carried
out on Spectra Quest’s Gear box Dynamics Simulator (GDS). The test
rig simulates a two-stage parallel gear transmission. The input gear
in the gearbox was intentionally faulted with increasing severity
level. For each gear configuration, tests were conducted with and
without loading applied by a magnetic brake. The experimental
results show that due to the impact caused by the faulted tooth,
strong sidebands arise around the meshing frequency in the spectra.
At high severity level, the amplitudes of the sidebands may be even
higher than that of the meshing frequency components
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Introduction
Gearboxes are very commonly used
in industry as well as in vehicles. During their extended service
lifetimes, gear teeth will inevitably be worn, chipped, or even
missing under high load. Therefore effective diagnostic methods are
required in order to enhance the reliability of the entire machine
before any unexpected catastrophic consequences occur. The
vibration-based techniques are the most widely used since it is easy
to obtain the acceleration signals using accelerometers. The gear
diagnostic parameters include RMS value, crest factor, kurtosis,
energy ratio, and other metrics. They are all statistical methods.
Advanced techniques, such as joint time-frequency analysis, wavelet,
and neural networks, have been successfully applied to the gear
fault diagnostics.
Experiments in this article were
conducted on Spectra Quest’s Gearbox Dynamics Simulator (GDS).
Instead of a one-stage transmission, a two-stage transmission with
spur gears was investigated. The objective of these experiments is
to relate the development of the frequency component changes to the
severity level.
The GDS is a specially designed
platform for studying signatures of common gearing faults. Spur or
helical gears can be fitted into a two-stage parallel shaft design.
The gearbox is driven by a 3 HP motor with a speed range of 0~3600
rpm. The inverter can be programmed for higher speeds, but care must
be exercised to assure proper lubrication and temperature control.
Load can be applied using the magnetic brake. The loading force is
controlled by a current source. The modular design of the gearbox
allows one to introduce various faults, such as chipped, broken and
cracked teeth, gear eccentricity, and worn gear, either individually
or jointly in a totally controlled environment. The gears can be set
up at different locations along the shaft in order to alter system
stiffness and make room for additional devices. The GDS is also a
test bed for analyses in gear noise, loading effects, and fault
diagnosis techniques
Fig 1: Gearbox Dynamics Simulator
Fig 1:
Gearbox acceleration spectra without load-24-tooth gear with a
large chip
Fig 2:
Gearbox acceleration spectra with load-24-tooth gear with a
large chip
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