Spur gear tooth root crack detection using time synchronous averaging under fluctuating speed

a b s t r a c t
Filtering techniques are used to improve the signal to noise ratio (SNR) for better feature
extraction. The time synchronous averaging (TSA) is one of such method that is based on
averaging periodic sections. However, it fails to give significant results for an asynchronous
or fluctuating speed condition. Moreover, most of the real life applications of gear are in
asynchronous conditions. The aim of this paper is to develop a methodology which is
robust for fault detection of gears under fluctuating load and speed conditions. A multiple-
pulse individually rescaled-time synchronous averaging (MIR-TSA) technique in
conjunction with conventional time synchronous averaging has been proposed. A 2-D finite
element methodology based on principal or linear elastic fracture mechanics is adopted for
predicting the crack propagation path at the root of gear tooth. The crack has been introduced
using wire electrode discharge machining (WEDM). The vibration signals were
recorded using drivetrain dynamic simulator (DDS) setup for various combination of load
and crack length both for constant as well as fluctuating speed. Various time domain
features such as root mean square, crest factor and kurtosis have been calculated using
classical TSA and proposed MIR-TSA. A comparison of different extracted features between
the proposed method and classic TSA has also been outlined. It has been observed that the
proposed method enhances the fault detection under fluctuating speed conditions.

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