Optimization of the angle of cut of a frog in a mouldboard Plough

86 Pages·2015·2.23 MB·English

UNIVERSITY OF NAIROBI
SCHOOL OF ENGINEERING
DEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERING

OPTIMIZATION OF THE ANGLE OF CUT OF A FROG IN A MOULDBOARD
PLOUGH: CASE OF A SANDY CLAY SOIL

ANGELA WAMBUI HIUHU
F56/69693/2013
A thesis submitted to the University of Nairobi in partial fulfilment of the requirements for the
Degree of Master of Science in Environmental and Biosystems Engineering
2015
Declaration of originality

Name of student: Hiuhu Angela Wambui

Registration: F56/69696/2013

College: College of Architecture and Engineering

Faculty/School/Institute: School of Engineering

Department:
1) I understand what plagiarism is and I’m aware of the university policy in this regard
2) I declare that this research proposal is my original work and has not been submitted
Course Name:
elsewhere for examination, award of a degree or publication. Where other works or my own
work has been used, this has properly been acknowledged and referenced in accordance with
Title of work:
the University of Nairobi’s requirements
3) I have not sought or used the services of any professional agencies to produce this work
4) I have not allowed , and shall not allow anyone to copy my work with the intention of
passing it off as his/her work
5) I understand that any false claim in respect of this work shall result in disciplinary action in
accordance with University of Nairobi anti-plagiarism policy

Signature:

Date:

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DECLARATION
This thesis is my original work and has not been presented for a degree in any other University.
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Hiuhu Angela Wambui Date
This thesis has been submitted for examination with our approval as university supervisors.
Duncan Mbuge, PhD.
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Date
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Ayub.N.Gitau,PhD.
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Date

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DEDICATION
I thank God for the blessing of invaluable family, friends, mentors and teachers who have
prodded me along this walk and inspired my thoughts. I dedicate this work to my family
and to mankind.

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ACKNOWLEDGEMENT
I would like to thank the Almighty Lord for His never ending favor and mercies. I wish to
express my sincere gratitude to my supervisors; Eng. Dr. Duncan Mbuge and Eng. Prof.
A. N. Gitau for the guidance and support offered throughout the entire MSc programme.
My sincere gratitude to the technical staff at the Department of Environmental and
Biosystem Engineering. Special thanks to Mr. Wahome, Mr. Macharia, Mr. Muliro and
Mr. Wamutito for their invaluable support and assistance in the field work and analyzing
of data.
Finally I thank the University of Nairobi fraternity for awarding me a scholarship to
enhance my studies and undertake an MSc degree in the Department of Environmental and
Biosystem Engineering, University of Nairobi.

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ABSTRACT
The Mouldboard plough is a common tillage implement used in Kenya. The draught
characteristics and ability to maintain desired depths and speed of operation at different
frog angles is unknown. This study aimed at optimizing the angle of cut of a frog of a
mouldboard plough operating in sandy clay soil. This objective was achieved through the
study of the soil-cut interactions. The measurable quantity in the study of soil- cut
interactions was draught force. Draught force is an indicator of the power to be consumed
hence the cost of tillage.
Tillage field experiments were carried out in University of Nairobi – Upper Kabete
Campus. Data obtained from the field was evaluated in three different ways; Saunders
equation, Dynamometer and Discrete Element Modelling (DEM). Saunders equation
calculated draught force incorporating geometric parameters of the plough body
components, ploughing speed and depth additionally the physical properties of the soil.
The dynamometer used was digital and recorded the draught requirements in situ. DEM
was used to simulate the field experiment using a software called EDEM that calculated
the draught requirements.
The soil- cut interactions were studied at three different frogs angles of 30°, 40° and
50°.The speed of tillage was calculated to be an average of 1.5m/s for the low speed and
3.6m/s for the high speed. The depths of tillage were measured as an average of 8.0cm,
17.0cm and 24.0cm for the three frog angles used. Draught forces determined for the low
speeds (1.5m/s) were at range of 0.7kN to 1.0kN for depths of 8.0cm. At depths of 17.0 cm
the range of forces was 1.0kN to 1.4kN. At the depths of 24.0cm the draught forces
calculated were a range of 1.4 kN to 1.9kN. For high speeds (3.6m/s) the draught forces
were at ranges of 0.8kN to 1.3kN, 1.4kN to 2.2kN and 2.2kN to 3.2kN respectively for the
depths aforementioned.
The results suggest that draught forces increase significantly with increase in the depth
linearly. This relationship shows the importance of regulating the depth of tillage. Draught
forces increased with increase in speed of tillage and the relationship was a second order
polynomial equation. The study concluded that the 30° angle frog was the optimal frog to
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use in a mouldboard plough operating in sandy clay soil as it had minimum average
draught force of 0.8 KN. Thus at this angle, we experience minimum draught at an
optimum speed and at friable moisture content of the soil.
Key words: Tillage, simulation, DEM, soil-cut interactions and draught force

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TABLE OF CONTENTS
DECLARATION ................................................................................................................................ ii
DEDICATION ...................................................................................................................................iii
ACKNOWLEDGEMENT ................................................................................................................ iv
ABSTRACT ........................................................................................................................................ v
LIST OF TABLES .............................................................................................................................. x
LIST OF FIGURES ........................................................................................................................... xi
NOMENCLATURE ......................................................................................................................... xii
CHAPTER 1: INTRODUCTION ..................................................................................................... 1
1.1. Background .......................................................................................................................... 1
1.2. Problem Statement .............................................................................................................. 2
1.3. Justification of the Study .................................................................................................... 4
1.4. Objectives ............................................................................................................................. 5
1.4.1. Overall Objective.......................................................................................................... 5
1.4.2. Specific Objectives........................................................................................................ 5
1.5. Scope of work ....................................................................................................................... 5
CHAPTER 2: LITERATURE REVIEW ......................................................................................... 7
2.1. Agricultural Mechanization ............................................................................................... 7
2.2. Mouldboard plough ............................................................................................................. 9
2.2.1. Mode of Operation of the Mouldboard Plough ....................................................... 11
2.3. Tillage systems ................................................................................................................... 13
2.3.1. Convectional Tillage ................................................................................................... 13
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2.3.2. Deep Tillage ................................................................................................................ 13
2.3.3. Minimum Tillage ........................................................................................................ 13
2.3.4. Conservation Tillage .................................................................................................. 13
2.3.5. Ridge Tillage ............................................................................................................... 14
2.3.6. Zero Tillage ................................................................................................................. 14
2.4. Tillage systems and soil type ............................................................................................. 14
2.5. Soil Structure and Properties ........................................................................................... 15
2.6. Effects of tillage on Crops ................................................................................................. 16
2.7. Equipment Management ................................................................................................... 17
2.8. Types of Models Used in Soil-Implement Interactions .................................................. 18
2.9. Discrete Element Model (DEM) ....................................................................................... 19
2.9.1. EDEM Calibration Parameters ................................................................................ 22
CHAPTER 3: THEORETICAL FRAMEWORK ......................................................................... 24
3.1. Draught Force Prediction Models .................................................................................... 24
3.2. Shear Strength Models ...................................................................................................... 28
3.3. Discrete Element Model (DEM) Model ........................................................................... 29
CHAPTER 4: MATERIALS AND METHODS ............................................................................ 31
4.1. Research Study Area ......................................................................................................... 31
4.2. Experimental Set-up .......................................................................................................... 32
4.3. Characterization of Soil at the experimental site ........................................................... 35
4.3.1. Dry Sieving .................................................................................................................. 35
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4.3.2. Triaxial Testing .......................................................................................................... 37
4.3.3. Bulk Density ................................................................................................................ 40
4.3.4. Angle of Repose .......................................................................................................... 41
CHAPTER 5: RESULTS and DISCUSSIONS .............................................................................. 42
5.1. Pertinent Parameters Influencing the Angle of Cut ....................................................... 42
5.2. Classification of Soil .......................................................................................................... 42
5.3. Bulk density ........................................................................................................................ 45
5.4. Cohesion of soil .................................................................................................................. 45
5.5. Plough Geometric Parameters ......................................................................................... 46
5.6. Determination of Draught Requirements ....................................................................... 46
CHAPTER 6: CONCLUSION AND RECOMMENDATION ..................................................... 56
6.1. CONCLUSION .................................................................................................................. 56
6.2. RECOMMENDATION .................................................................................................... 57
CHAPTER 7: REFERENCES ........................................................................................................ 58
APPENDICES .................................................................................................................................. 67
APPENDIX A: SOIL CLASSIFICATION ................................................................................ 67
A.1: BULK DENSITY CALCULATIONS ............................................................................ 67
A.2: USCS MANUAL ............................................................................................................... 68
APPENDIX B SOIL PARAMETERS CALCULATIONS ....................................................... 69
B.1: Soil Coefficient Parameters ............................................................................................. 69
APPENDIX C: TERMINOLOGIES .......................................................................................... 72
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