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An Experimental Investigation of Helical Gear Efficiency

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An Experimental Investigation of Helical Gear Efficiency AN EXPERIMENTAL INVESTIGATION OF HELICAL GEAR EFFICIENCY A Thesis Presented in Partial Fulfillment of the Requirements for The Degree of Master of Science in the Graduate School of the Ohio State University By Aarthy Vaidyanathan, B. Tech. * * * * * The Ohio State University 2009 Masters Examination Committee: Dr. Ahmet Kahraman Approved by Dr. Donald R Houser Advisor Graduate Program in Mechanical Engineering ABSTRACT In this study, a test methodology for measuring load-dependent (mechanical) and load- independent power losses of helical gear pairs is developed. A high-speed four-square type test machine is adapted for this purpose. Several sets of helical gears having varying module, pressure angle and helix angle are procured, and their power losses under jet- lubricated conditions are measured at various speed and torque levels. The experimental results are compared to a helical gear mechanical power loss model from a companion study to assess the accuracy of the power loss predictions. The validated model is then used to perform parameter sensitivity studies to quantify the impact of various key gear design parameters on mechanical power losses and to demonstrate the trade off that must take place to arrive at a gear design that is balanced in all essential aspects including noise, durability (bending and contact) and power loss. ii Dedicated to all those before me who had far fewer opportunities, and yet accomplished so much more. iii ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Ahmet Kahraman, who has been instrumental in fostering interest and enthusiasm in all my research endeavors. His encouragement throughout the course of my studies was invaluable, and I look to him for guidance in all my future undertakings. I also wish to thank the sponsors, GM Powertrain, and Mr. Neil Anderson in particular for his support in carrying out this project. The members of the Gear Lab have been an integral part of the research I’ve conducted. I would like to thank Mr. Jonny Harianto for generously lending his time and photography skills in order to capture great images of the experimental gear specimens and for his genuine concern for the students at gear lab. Mr. Sam Shon has always been a great source of information and has been at the forefront of efforts to ensure the safety of all the research associates. I thank him for his efforts on our behalf. I wish to also thank Dr. Sheng Li, who provided much needed counsel and shared his understanding of power transmission. I would also like to thank my friends and family for their confidence in my abilities, and for making sure that I had fun along the way. Special thanks to all the men and women in the military and in various other areas of service to society, who keep the nations of the world safe from myriad problems, allowing us to focus on research and development. Their selfless service is the source of my strength and inspiration. iv VITA December 31, 1985……………………….. Born – Trichy, India. August 2003 – May 2007………………….. BTech Mechanical Engineering National Institute of Technology Surathkal, India. September 2007 – June 2009…………….. Graduate Research Associate Department of Mechanical Engineering The Ohio State University, Columbus, Ohio PUBLICATIONS 1. S. Li, A. Vaidyanathan, J. Harianto and A. Kahraman, 2009, “Influence of Design Parameters and Micro-geometry on Mechanical Power Losses of Helical Gear pairs,” JSME International Conference on Motion and Power Transmissions, Sendai, Japan. FIELDS OF STUDY Major Field: Mechanical Engineering v TABLE OF CONTENTS Page ABSTRACT ........................................................................................................................ ii DEDICATION ................................................................................................................... vi ACKNOWLEDGMENTS ................................................................................................. iv VITA ................................................................................................................................... v LIST OF TABLES .............................................................................................................. x LIST OF FIGURES ........................................................................................................... xi 1 INTRODUCTION ..................................................................................................... 1 1.1 Introduction ....................................................................................................... 1 1.2 Literature Review.............................................................................................. 2 1.3 Thesis Objectives .............................................................................................. 5 1.4 Thesis Outline ................................................................................................... 6 2 HELICAL GEAR EFFICIENCY TEST METHODOLOGY .................................... 8 vi 2.1 Introduction ....................................................................................................... 8 2.2 Helical Gear Efficiency Test Machine .............................................................. 8 2.3 Helical Gear Power Loss Test Procedure ....................................................... 12 2.4 Helical Efficiency Test Gear Specimens and Test Matrix .............................. 13 2.5 Specimen Consistency .................................................................................... 22 2.6 Repeatability of the Torque Measurements .................................................... 30 2.7 Summary ......................................................................................................... 35 3 HELICAL GEAR POWER LOSS MEASUREMENTS ......................................... 36 3.1 Introduction ..................................................................................................... 36 3.2 Determining the Components of Power Loss and Efficiency from Measurements .......................................................................................... 36 3.3 Gearbox Mechanical Power Loss Results ....................................................... 40 3.3.1 Influence of Torque and Speed ........................................................... 41 3.3.2 Influence of Helix and Pressure Angles .............................................. 46 vii 3.4 Gearbox Spin Power Loss Results .................................................................. 56 3.5 Conclusion ...................................................................................................... 58 4 COMPARISON OF EXPERIMENTAL RESULTS TO PREDICTIONS OF A GEAR EFFICIENCY MODEL ............................................................................... 59 4.1 Introduction ..................................................................................................... 59 4.2 Gear Mesh Mechanical Power Loss Model .................................................... 60 4.2.1 A Mixed EHL Model to Predict the Friction Coefficient ................... 61 4.2.2 Derivation of New Friction Coefficient Formula for Gear Contacts .. 65 4.3 Comparison of Measured and Predicted Power Loss Values ......................... 71 4.4 Conclusions ..................................................................................................... 97 5 PARAMETER SENSITIVITY STUDY.................................................................. 98 5.1 Introduction ..................................................................................................... 98 5.2 Analysis Details ............................................................................................ 100 5.3 Variation of the Gear Mesh Mechanical Power Loss with Gear Design Parameters ..................................................................................................... 103 viii 5.4 Selection of an Optimum Design Satisfying Multiple Performance Criteria 105 5.5 Conclusions .................................................................................................. 116 6 SUMMARY AND CONCLUSIONS .................................................................... 117 6.1 Summary ....................................................................................................... 117 6.2 Conclusions ................................................................................................... 118 LIST OF REFERENCES ................................................................................................ 120 ix LIST OF TABLES Table Page 2.1 Test matrix of the helical gear efficiency experiments. ..................................... 15 2.2 Basic design parameters of the test gears. ......................................................... 20 2.3 Test sequence used in the helical gear efficiency experiments. ......................... 23 2.4 Measured average surface roughness parameters of gear test specimens. ......... 33 3.1 Values of parameters for the bearings used in the experiments. ........................ 39 4.1 Parametric design for the development of a friction coefficient formula ......... 67 4.2 Basic parameters of the automatic transmission fluid used in this study .......... 68 5.1 Values of the gear parameters varied in the parameter sensitivity study. .......... 99 5.2 Gear parameters of the four different designs identified in Figure 5.3. ............. 109 x LIST OF FIGURES Page 2.1 Helical gear efficiency test machine. .....................................................................
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