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Title: Measurement of surface deflection in rolling bearing by ultrasonic reflection
Author: Avcioglu, Emir
ISNI:       0000 0004 7233 9118
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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One of the main reasons contributing to the growth of the wind industry is the effort placed on improving designs and on reducing the operating and maintenance costs to make wind energy more cost competitive. Operations and maintenance is in fact estimated to contribute to 20-25% of the levelised cost of energy for wind energy. Studies have shown that while the gearbox is responsible for a substantial portion of the downtime incurred during the lifetime of a wind turbine, the initial point of failure is generally attributed to the bearings within. Given this scenario, the main aim of this project is to study the applicability of ultrasound techniques as a non-destructive monitoring technique that enables detection of problems in the bearings prior to failure. The downtime can therefore be reduced by avoiding catastrophic failure and by enabling more efficient scheduled maintenance. In this study a focused immersion transducer has been used to emit and collect ultrasonic waves aimed at, and reflected off, the outer race of a bearing. Any changes in the reflected waves convey information on the outer race displacements, which in turn provide information on the health of the bearing. A new approach was developed for the construction of cylindrical roller bearing outer race surface displacement curves by employing a focused immersion transducer. The proposed technique is based on measurement of the first reflected wave specifically defined by the zero-crossing point while the bearing is in operation. It is clearly observed that as the rolling element goes through the investigated area the distance between transducer and bearing outer race is shortened resulting in a time shift of the first reflection. Time shift measurements were subsequently converted into bearing outer race deflection by using time-of-flight technique. Moreover, it has been shown that real time monitoring of the time shift is possible at a low resolution. The study shows how the bearing outer race deflection curves provide information about the ongoing contact events within the bearing. This information can be used to identify an unhealthy component, since when any of the components contains a defect, an anomaly in the bearing outer race deflection curves is observed. Such discontinuities have been characterized by two parameters: peak height and duration and the relationship between these parameters and load, defect location, defect severity and defect size has been explored. It was found that the proposed method is able to distinguish which of the components is defective, detect line defects larger than 0.36 mm, assess the severity of the defects and pin-point the location of the defect with respect to the sensor as long as it falls within the identified measurable range.
Supervisor: Dwyer-Joyce, Rob ; Long, Hui Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available