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Magnetic Nondestructive Characterization of Case Depth in Surface-Hardened Steel

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Magnetic Nondestructive Characterization of Case Depth in Surface-Hardened Steel Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1-1-2005 Magnetic nondestructive characterization of case depth in surface-hardened steel Emily R. Kinser Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Recommended Citation Kinser, Emily R., "Magnetic nondestructive characterization of case depth in surface-hardened steel" (2005). Retrospective Theses and Dissertations. 19134. https://lib.dr.iastate.edu/rtd/19134 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Magnetic nondestructive characterization of case depth in surface-hardened steel by Emily R. Kinser A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Materials Science and Engineering Program of Study Committee: David Jiles, Major Professor Nicola Bowler R. Bruce Thompson Robert Weber Iowa State University Ames, Iowa 2005 Copyright © 2005, Emily R. Kinser. All rights reserved. 11 Graduate College Iowa State University This is to certify that the master's thesis of Emily R. Kinser has met the thesis requirements of Iowa State University Signatures have been redacted for privacy -- 111 TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................ v ABSTRACT .............................................................................................. vii CHAPTER 1: INTRODUCTION ............................................................... 1 1.1 .. Motivation .......................................................................................................... 1 1.2. Research problem ............................................................................................. 2 1.3. Societal Implications ........................................................................................ 2 CHAPTER 2: BACKGROUND ............................................................... 3 2.1. Magnetic properties & micro structure .............................................................. 3 2.1.1. Heat treatment processes ........................................................................ 3 2.1.2. Domain wall dynamics ......................................................................... 10 2.2. Magnetic nondestructive evaluation ................................................................ 18 2.2.1. Barkhausen emission ............................................................................ 18 2.2.2. Evaluation of case depth ....................................................................... 21 2.3. Barkhausen model ........................................................................................... 29 CHAPTER 3: EXPERIMENTAL PROCEDURE .................................... 31 3.1 .. Samples ............................................................................................................ 31 3.2. Measurement techniques ................................................................................. 33 3.2.1. Hysteresis .............................................................................................. 33 3.2.2. Barkhausen ............................................................................................ 34 CHAPTER 4: EXPERIMENTAL RESULTS .......................................... 37 4.1. Large diameter induction hardened rods ......................................................... 37 4.1.1. 15 mm nominal case depth .................................................................. .37 4.1.2. 10 mm nominal case depth .................................................................. .45 4.2. 11 mm diameter induction hardened rods ...................................................... .48 4.2.1. Depth profile measurements ................................................................ .48 4.2.2. Bulk property measurements ................................................................ 59 4.3. Barkhausen modeling ...................................................................................... 65 4.3.1. 10 mm nominal case depth .................................................................. 65 4.3.2. 11 mm diameter rods ............................................................................ 68 CHAPTER 5: SOCIETAL IMPLICATIONS OF NONDESTRUCTIVE EVALUTION .................................................................... 70 IV CHAPTER 6: CONCLUSION .................................................................. 73 6.1 Summary ......................................................................................................... 73 6.2 Future research ................................................................................................ 74 APPENDIX A: RELEVANT JOURNAL PUBLICATIONS ................... 76 APPENDIX B: NATIONAL AVIATION SYSTEMS, SAFETY, AND DEVELOPMENT STUDY ............................................. 94 BIBLIOGRAPHY ..................................................................................... 119 v ACKNOWLEDGEMENTS It is difficult to overstate my gratitude towards my major professor, Dr. David Jiles, for his patience and guidance while working as both an undergraduate and graduate research assistant. In addition to providing me with the opportunity to study magnetism and nondestructive evaluation, I am especially grateful to Dr. Jiles for his encouragement and support of my interest in engineering and public policy. I would also like to thank my POS committee members, including Dr. Bruce Thompson, Dr. Robert Weber, and Dr. Nicola Bowler, for their willingness to serve on my committee and assist me with my research. Dr. Yong Lee also provided useful insight into the societal impacts of nondestructive evaluation. Completing my degree would not be possible without the assistance of several others. Chester Lo has been an invaluable colleague and friend during the past three years. I'm deeply indebted to Chester not only for his research efforts; for his patience, wisdom, and ability to explain complex subject matter clearly and simply I am extremely grateful. I am appreciative of the significant assistance provided by Marcus Johnson on this and other projects, and I would also like to thank Doug Rebinsky for introducing me to the field of nondestructive evaluation and his support on this project by providing samples and consultation. Undergraduate research assistant Tony Barsic has been very helpful in the lab and provided many interesting insights. Thank you also to Y ongqiang Huang for providing me with data. Additionally, I would like to thank several members of the MSE department, including Larry Genalo and Kristen Constant for recruiting me into materials engineering. Dr. Constant has also been an outstanding mentor in addition to my undergraduate advisor. I Vl am grateful to Dr. Mufit Akinc for his support of my various endeavors over the past six years, including providing me with my first "real" materials science research position. I would also like to extend thanks to the MSE administrative professionals including Lynne Weldon, Carmen Neri, and Krista Briley for their immeasurable assistance. My student colleagues and friends made throughout my many years in the MSE department have helped create a stimulating and entertaining environment in which learn, live, and grow; I thank you all for the wonderful memories. Finally, I would also like to thank Nick Paulson for his support and encouragement throughout the duration of my masters program. Vll ABSTRACT Nondestructive magnetic measurements, such as hysteresis measurements and Barkhausen emission, have the potential to serve as effective methods of determining case depth in ferrous materials. The inspection of surface modified ferromagnetic materials is limited by the lack of understanding of the complex dependence of Barkhausen emission on microstructure, which may vary with depth in surface modified materials. Characterization of the depth profiles of magnetic properties provides a greater understanding of the microstructural variations since Barkhausen signals depend on the nature and density of pinning sites for domain walls, particularly in the surface layer. With an aim of understanding the relationship between magnetic properties and microstructure related to case depth of surface-hardened magnetic materials, depth profiles of magnetic properties were completed on surface-hardened 1045 steel samples. Hysteresis loop and Barkhausen effect measurements were made on a series of strip samples with various dislocation densities cut from induction hardened rods with case depths ranging from 0.5 mm to 15 mm. The magnetic properties, including coercivity and Barkhausen emission, exhibit correlation with hardness which is closely related to dislocation density. The relationships between the Barkhausen model parameters and the microstructure of surface hardened samples were also examined. Quantitative analysis of the hysteresis and Barkhausen data revealed simple relationships between the model parameters and the domain wall pinning strength, which was determined by simulating the measured hysteresis loops. The pinning coefficient k, which characterizes the average domain wall
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