ABSTRACT CARCATERRA, BRIAN THOMAS. Investigation of Energy
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ABSTRACT CARCATERRA, BRIAN THOMAS. Investigation of Energy Storage in Bolted Joint Components and the Development of a Geometry Selection Design Tool. (Under the direction of Dr. Gracious Ngaile). In manufacturing one of the most common joining methods used is mechanical fastening by the use of screw fasteners or bolted joints. They are highly desirable for their ease of assembly, disassembly, and re-usability as opposed to more permanent joining methods such as riveting or welding. However, there is one major problem that exists in bolted joints and that is self-loosening. Over time relative motion between the nut or bolt head and the clamped members can occur which leads to the joint loosening and ultimately failing. This relative motion between the clamped member and the nut or bolt head can be attributed to small gaps or separation in the joined parts due to thermal effects or surface finishes or especially cyclic loads applied to the joined members. There have been many products introduced to help reduce or limit the loosening phenomenon, however, they don’t all perform the same and it is necessary to understand how they are working to reduce loosening. Many of these products have been evaluated experimentally through testing and compared with each other to determine how well they each perform. Not a lot of work has been conducted in the investigation of what makes some products better than others and how they can be improved. The major objectives of the research presented in this thesis are to begin the development of a design tool that can be used to select the proper dimensions for a Belleville washer to ensure that its performance meets the requirements of a specific application and to propose modifications to a Belleville washer that would result in a more uniform stress and strain energy distribution by removing excess material thus reducing weight and cost. This is accomplished by demonstrating the importance of energy storage in anti-loosening products. A key component in the effectiveness of many of these products is the fact that they elastically deform when tightened in a joint. That elastic deformation causes strain energy to be stored in the component that can then be utilized to resist loosening. The more a specific component can deflect, the more it can relax back into positon when loosening ties to occur, and therefore the larger the gap or the higher the external force would have to be in order to loosen a joint that utilizes a product like this. A Belleville washer was designed with different dimensions for outer diameter, overall height, and thickness. Finite element analysis was used on the various models to show how varying the dimensions can affect the performance of the washer. The simulations showed that the deflection and energy stored can be increased by increasing the outer diameter, decreasing the thickness, and increasing the height if the outer diameter is large or decreasing the height if the outer diameter is small. The results of this study were used as the basis of the development of the design tool. This study also showed that modifying a Belleville washer by tapering the top or punching through-holes around can result in a more uniform stress and strain energy distribution. © Copyright 2017 Brian Carcaterra All Rights Reserved Investigation of Energy Storage in Bolted Joint Components and the Development of a Geometry Selection Design Tool by Brian Thomas Carcaterra A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Mechanical Engineering Raleigh, North Carolina 2017 APPROVED BY: _______________________________ Dr. Gracious Ngaile Committee Chair _______________________________ _______________________________ Dr. Jeffrey Eischen Dr. Yuan-Shin Lee BIOGRAPHY Brian Carcaterra was born on December 3rd, 1992 to Joe and Eileen Carcaterra in White Plains, New York. He moved to Raleigh, North Carolina in 1995 where he grew up and spent his childhood. He graduated from Millbrook High School in 2011 and went on to attend North Carolina State University later that year. In May 2015, he received his Bachelor of Science Degree in Mechanical Engineering from NC State University. Brian began his master’s career at NC State in August 2015 under the advisement of Dr. Gracious Ngaile, where he conducted research in metal forming and advanced manufacturing techniques. He received his Master of Science degree in Mechanical Engineering in August 2017. ii ACKNOWLEDGMENTS Firstly, thank you to my parents, Joe and Eileen for always supporting me and encouraging me. Without you, I wouldn’t be where I am today. Thank you Steve Cameron and Gary Lofton for all of the machining and design advice given during my time at NC State. Also, thank you for agreeing to help out and provide assistance on many of the projects for our lab. I would also like to acknowledge and thank my colleagues in the Advanced Metal Forming and Tribology Laboratory. Thanks to James Lowrie for all of the knowledge and advice you have given to me while working together. Lin Li, thank you for being a great role model and for providing guidance and support on many projects. Thanks to Farhan Rahman for your cooperation on the MRI project. Also, thanks to Hao Pang for the advice, assistance, and encouragement you have provided. You all have become great friends of mine and I could not have gotten as far as I have without all of your support. Dr. James Kribs, thank you so much for all of the advice and support you have given me throughout my entire career at NC State. I am very thankful for being able to talk to you and ask for your advice. You were an amazing mentor as well as a great friend. I would like to thank Dr. Jeffrey Eischen and Dr. Yuan-Shin Lee for being excellent professors, for instructing me and expanding my engineering knowledge in their courses, and for being on my graduate thesis committee. Finally, I would like to thank my advisor Dr. Gracious Ngaile, who is the best advisor any student could ask for. Thank you for all of the support and guidance you have provided to me over the course of my graduate career. iii TABLE OF CONTENTS LIST OF TABLES ................................................................................................................... vi LIST OF FIGURES ................................................................................................................ vii CHAPTER 1: INTRODUCTION AND RESEARCH OBJECTIVES ..................................... 1 1.1 Introduction ................................................................................................................ 1 1.2 Research Objectives ................................................................................................... 2 1.3 Research Approach .................................................................................................... 2 1.4 Thesis Organization ................................................................................................... 2 CHAPTER 2: LITERATURE REVIEW ON BOLTED JOINTS ............................................ 4 2.1 Introduction to Vibrational Loosening ....................................................................... 4 2.2 Anti-Loosening Mechanisms and Components for Bolted Joints .............................. 6 2.2.1 Modified Threads .................................................................................................. 6 2.2.2 Lock Washers........................................................................................................ 8 2.2.3 Spring Washers ................................................................................................... 10 2.2.4 Locknuts .............................................................................................................. 11 2.2.5 Modified Bolt ...................................................................................................... 15 2.3 Analysis and Studies on Anti-Loosening Products .................................................. 16 2.4 Finite Element Analysis and Bolted Joints .............................................................. 31 2.5 Concluding Remarks ................................................................................................ 45 CHAPTER 3: STRAIN ENERGY STORAGE IN BOLTED JOINTS .................................. 46 3.1 Introduction .............................................................................................................. 46 3.2 Objectives and Major Tasks ..................................................................................... 56 3.3 Development of the Belleville Washer Design Tool ............................................... 56 3.3.1 Belleville Washer Geometry and Simulation Setup ........................................... 57 3.3.2 Belleville Washer Simulation Results ................................................................ 64 3.3.3 Belleville Washer Geometry Selection Design Tool .......................................... 73 3.4 Concluding Remarks ................................................................................................ 77 iv CHAPTER 4: BELLEVILLE WASHER GEOMETRY MODIFICAIONS BASED ON STRAIN ENERGY ................................................................................................................. 78 4.1 Introduction .............................................................................................................. 78 4.2 Objectives