Condition Monitoring of Helical Gears Using Acoustic Emission

165 Pages·2013·3.49 MB·English

Cranfield University

MHMOD A A HAMEL

Condition Monitoring of Helical Gears Using Acoustic
Emission (AE) Technology

School of Engineering

Doctor of Philosophy

July, 2013

Cranfield University

School of Engineering

PhD Thesis

July, 2013

MHMOD A A HAMEL

Condition Monitoring of Helical Gears Using Acoustic
Emission (AE) Technology

Under Supervision: Prof. David Mba
Dr. A Addali

Academic Year 2012 - 2013

© Cranfield University, 2013. All rights reserved. No part of this publication may
be reproduced without the written permission of the copyright holder
ABSTRACT

Techniques such as vibration monitoring, thermal analysis and oil analysis are well
established as means to have been used to improve reliability of gearboxes and extend
time-to-failure. In this area Acoustic Emission (AE) technology is still in its infancy but
the attention shown by researchers towards this method has increased dramatically
because several studies have shown the AE offers the important advantage of improved
sensitivity over more conventional monitoring tools for the early detection and
prediction of gear failure.
Helical gear lubrication is critically important for maintaining the integrity of operating
gears and the oil also prevents asperity contact at the gear mesh thereby protecting the
gears from a deterioration process and surface failures. In gear systems, there are three
types of lubrication regimes: Dry Running, Boundary Lubrication (BL), Hydrodynamic
Lubrication (HL) and Elastohydro-dynamic Lubrication (EHL). The last regime is
associated with the normal operating running condition of gears.
Acoustic emissions were acquired from gears and analysed for different lubrication
regimes (dry, BL, HL and EHL regimes at different temperatures), and corresponding
specific film thicknesses (λ) levels. The results showed an inverse relationship between
AE signal levels and specific film thickness (λ) of the oil. This relation was used to
determine the lubrication regime from the measured AE signals. For instance, dry
running had the highest AE levels which were attributed to the metal-to-metal contact of
the gear mesh. The BL regime had relatively high AE levels which also attributed to the
level of asperity contact is greater than the oil film thickness. The HL regime was
characterized by the lowest AE levels due to the lubricant oil completely separating the
teeth during gear meshing. Finally, the EHL regime showed intermediate AE levels
compared to the BL and HL regimes because the oil film was less than for the HL
regime but greater than for the BL regime.
It is shown that the application of advanced signal processing methods is necessary for
monitoring helical gears; Kurtosis and Spectral Kurtosis were used to investigate the
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AE signatures and found to be effective in de-noising (spectral kurtosis) acquired
signals. Acoustic Emission proved to be a powerful tool to detect the oil regime for both
defective and non-defective conditions.
It is concluded that the experimental findings of this research programme will provide
the foundations for significant advancement in the application of AE for the
determining the lubrication regime present within a helical gearbox and for the detection
of developing gear faults. This should give a new impetus in the field of maintenance
and prevention of human and material catastrophes.
Several papers presenting the findings of this research have been published in
international journals and given at conferences.

Papers for Journals:
1. Journal of lubricants (mdpi): Using of Acoustic Emission for Monitoring Oil Film
Regimes. Manuscript ID (Research Paper): lubricants-34202 (published)

2. Journal of Engineering Tribology: Employing of Acoustic Emission for Monitoring
Oil Film Regimes. The number assigned to work (Research Paper) is TRIB-12-1205
(accepted)

3. Journal of Applied Acoustics: Investigation of the influence of oil film thickness on
helical gear defect detection using Acoustic Emission. the reference number:
APAC-D-13-00027 (accepted)

Papers for Conferences:
1. Oil Regime Monitoring in Helical Gears Using Acoustic Emission. M Hamel,
A Addali and D Mba. AMME-15 conference 29-31 May 2012 , Cairo, Egypt

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2. Employing acoustic emission for monitoring oil film regime. M Hamel,
A Addali and D Mba. The 51st Annual Conference of The British Institute of Non-
Destructive Testing, 11-13 September 2012, Northamptonshire, UK.ISBN: 978 0
903132 55 9

3. Investigation of the influence of oil film thickness on helical gear defect detection
using Acoustic Emission. M Hamel, A Addali and D Mba. CM 2013 and MFPT
2013, 18-20 June 2013, Kraków, Poland

4. Babak Eftekharnejad, Mhmod Hamel, Abdulmajid Addali and David Mba.
Condition Monitoring of Machinery in Non-Stationary Operations ,"Proceedings of
the Second International Conference "Condition Monitoring of Machinery in Non-
Stationnary Operations" CMMNO’2012", March 26 - 28, 2012 - Hammamet –
Tunisia, Part 4, 425-437, DOI: 10.1007/978-3-642-28768-8_45.

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Acknowledgment

First of all, I thank Allah, the almighty, for giving me the strength to carry on this
project. Next, I would like to express my gratitude to Department Power and Propulsion
of School of Engineering, Cranfield University, and specially to my supervisor Prof
David for the useful comments, remarks and engagement through the learning process
of this PhD thesis. Furthermore I would like to express my gratitude to staff of
Advanced Centre of Technology, ACT-Tripoli, and specially for Dr Mohmmed Ateeg
for introducing me to the topic as well for the support on the way. Also, I like to thank
everyone who helped me in my research, who have willingly shared their precious time
during the process of my research. I would like to thank my loved ones, who have
supported me throughout entire process. I will be grateful forever for you.
‘’ Deep gratitude and love for my parents, my wife, my children Aws and Farah and all
of my brothers and sisters’’

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TABLE OF CONTENTS

ABSTRACT .................................................................................................. i
List of Tables ................................................................................................ 1
List of Figure s ............................................................................................. 2
1 Introduction .......................................................................................... 8
1.1 Project Aim and Objectives..................................................................... 11
1.2 Project Contribution ............................................................................... 11
2 Gears .................................................................................................... 14
2.1 Background ........................................................................................... 14
2.1.1 A historical Note ............................................................................. 14
2.1.2 Gear Types and Terminology ........................................................... 15
2.1.3 Helical Gears .................................................................................. 17
2.1.4 Advantages of Helical Gear .............................................................. 19
2.1.5 Gear Life Predictions ....................................................................... 20
2.2 Gear Lubrication .................................................................................... 21
2.2.1 Gear Tooth Temperature .................................................................. 22
2.2.2 Purposes of Lubrication ................................................................... 22
2.2.3 Lubricant Selection ......................................................................... 23
2.2.4 Lubrication Properties...................................................................... 23
2.3 Lubrication Methods .............................................................................. 24
2.3.1 Spray Lubrication (Forced oil circulation lubrication). ........................ 25
2.3.2 Splash Lubrication Systems .............................................................. 26
2.3.3 Grease Lubrication .......................................................................... 26
2.4 Lubrication Regimes in Gears ................................................................. 26
2.4.1 Boundary Lubrication (BL) .............................................................. 27
2.4.2 Elastohydrodynamic Lubrication (EHL) ............................................ 28
2.4.3 Hydrodynamic Lubrication (HL) ....................................................... 30
2.4.4 The Stribeck Curve .......................................................................... 31
2.5 Specific Oil Film Thickness (λ) ............................................................... 33
2.6 Gear Failures ......................................................................................... 37
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2.6.1 Lubrication Related Failures ............................................................. 39
2.6.2 Non Lubrication Related Failure ....................................................... 42
3 Gearbox Condition Monitoring Review: ......................................... 45
3.1 Signal Processing Techniques ................................................................. 46
3.2 Temperature Monitoring: ........................................................................ 52
3.3 Oil Debris Monitoring: ........................................................................... 53
3.4 Vibration analysis: ................................................................................. 57
Chapter 4 .................................................................................................... 60
Acoustic Emission ...................................................................................... 60
4 Acoustic Emission ............................................................................... 61
4.1 Brief history of Acoustic Emission .......................................................... 61
4.2 Acoustic Emission Sources ..................................................................... 62
4.3 Acoustic Emission Applications .............................................................. 64
4.4 Acoustic Emission’s, Advantages and Disadvantages ................................ 65
4.5 Acoustic Emission Sensors ..................................................................... 66
4.6 Sensor Couplant .................................................................................... 67
4.7 AE Measuring ....................................................................................... 69
4.8 Wear Conditions and Acoustic Emission .................................................. 71
4.9 Gear faults monitoring using acoustic emission. ........................................ 74
4.10 Acoustic Emission Activities Constraints ................................................. 75
4.11 Acoustic Emission and lubricant .............................................................. 75
Chapter 5 .................................................................................................... 78
Experimental Setup and procedure ......................................................... 78
5 Experimental Setup and procedure .................................................. 79
5.1 Experimental Gearbox ............................................................................ 79
5.1.1 Gears ............................................................................................. 81
5.1.2 Electrical Motor .............................................................................. 81
5.1.3 Lubrication ..................................................................................... 82
5.1.4 Loading Plates ................................................................................ 82
5.1.5 AE Sensors ..................................................................................... 83
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5.1.6 Thermocouples ............................................................................... 83
5.1.7 Slip Ring ........................................................................................ 84
5.1.8 Pre-Amplifier.................................................................................. 84
5.1.9 Accelerometers ............................................................................... 85
5.2 Data Acquisition (DAQ) Cards ................................................................ 85
5.2.1 Data Acquisition (DAQ) Software .................................................... 85
5.3 Experimental Procedure ......................................................................... 86
5.3.1 Capability of AE Technology for Gearbox Diagnosis .......................... 87
5.3.2 Influence of Lubrication Film Conditions on AE Signal ...................... 89
Chapter 6 .................................................................................................... 94
Results and Discussion .............................................................................. 94
6 Results and Discussion ....................................................................... 95
6.1 Capability of AE Technology for Gearbox Diagnosis ................................ 95
6.1.1 Test Instrumentation and Procedure .................................................. 95
6.1.2 Results Based on Acoustic Emission AE Monitoring .......................... 97
6.2 Influence of Lubrication Film Conditions on AE ..................................... 103
6.2.1 Test Instrumentation and Procedure ................................................ 103
6.2.2 Observations of AE Under Lubricated Conditions ............................ 104
6.3 Diagnosis During Dry and Lubricated Contact ........................................ 108
6.3.1 Test Instrumentation and Procedure ................................................ 108
6.3.2 Observations of AE Under Dry and Lubricated Conditions ................ 108
6.4 Applicability of AE in Monitoring Defects During Dry and Lubricated Contact
112
6.4.1 Test Instrumentation and Procedure ................................................ 112
6.4.2 Observation of The Signals in Time and Frequency Domains ............ 113
6.5 Spectral Kurtosis of AE Signal from Defective and Non-Defective Gear ... 117
6.6 Correlation of AE r.m.s With Specific Film Thickness (λ) ...................... 126
6.7 General Observations ........................................................................... 127
Chapter 7 .................................................................................................. 128
Conclusions and Future Work ............................................................... 128
7 Conclusions and Future Work ........................................................ 129
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