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Instability and Failure in Aluminum Multi-Channel Tubing

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Instability and Failure in Aluminum Multi-Channel Tubing INSTABILITY AND FAILURE IN ALUMINUM MULTI-CHANNEL TUBING A thesis presented to the faculty of the Fritz J. And Dolores H. Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Master of Science Harvey (Beau) S. Miller March 2006 This Thesis entitled INSTABILITY AND FAILURE IN ALUMINUM MULTI-CHANNEL TUBING by HARVEY (BEAU) S. MILLER has been approved for the Department of Mechanical Engineering and the Russ College of Engineering and Technology by Frank F. Kraft Assistant Professor of Mechanical Engineering Dennis Irwin Dean, Russ College of Engineering and Technology MILLER, HARVEY (BEAU) S., M.S. March 2006. Mechanical Engineering Instability and Failure in Aluminum Multi-Channel Tubing (75 pp.) Director of Thesis: Frank F. Kraft The purpose of this research was to examine the mechanical and structural behavior of aluminum micro-channel tube used in CO2 based automotive parallel flow heat exchangers. An analytical model was developed and extended to predict failure pressure of the tubing at normal operating conditions (20 to 180o C). The model developed in this study is based upon the instability strain of structural members in a plane-strain stress state. An experimental test apparatus was upgraded and integrated with computer software for trouble-free burst test operation. Room temperature burst tests were conducted on micro-channel tube samples in alloys 1197, AA 3003 and AA3102 to validate the accuracy and universality of the model to within 6% of actual measured values. Constitutive equations were also developed, by means of standard uniaxial tensile testing to provide material data for the model. The model was extended to predict failure pressures at elevated temperatures to within 8% of experimental test values. The data are being used to assist designers in developing and optimizing CO2 based climate control systems in automobiles. Approved: Frank F. Kraft Assistant Professor of Mechanical Engineering Acknowledgements First and foremost I would like to thank Dr. Frank F. Kraft. Without his guidance and perseverance this work could not have been completed in a timely fashion. I would also like to thank Dr. Sang-Soo Kim and Dr. Bhavin Mehta for their encouragement and being members on this thesis committee. Special thanks to Gowreesan Vamadevan for conducting the metallography on my test specimens. The author would also like to thank Brazeway, Inc. of Adrian, Michigan and Erbsloeh Aluminum GmBH of Velbert, Germany for their financial support. These industrial sponsors also provided all test samples and conducted all chemical analyses. v Table of Contents CHAPTER 1 ........................................................................................................................1 INTRODUCTION ...............................................................................................................1 1.1 Background.................................................................................................................1 1.2 Operating Conditions of R744....................................................................................2 1.3 Environmental Advantages of CO2.............................................................................4 1.4 Parallel Flow Heat Exchanger ....................................................................................4 1.5 Historical Review........................................................................................................5 1.6 Objectives ...................................................................................................................7 1.7 Test Apparatus ............................................................................................................9 CHAPTER 2 ......................................................................................................................10 ANALYTICAL MODEL...................................................................................................10 2.1 Analysis Assumptions...............................................................................................10 2.2 Künesh Method.........................................................................................................10 2.3 Instability Analysis ...................................................................................................12 2.4 Validating State of Stress..........................................................................................17 CHAPTER 3 ......................................................................................................................20 MATERIAL.......................................................................................................................20 3.1 Alloys........................................................................................................................20 3.2 Tube Geometry .........................................................................................................20 3.3 Sample Profile...........................................................................................................21 3.4 Manufacturing and Handling Processes....................................................................22 vi 3.4.1 Hot Extrusion of Micro-Channel Tube...............................................................22 3.4.2 Material Handling and Roll Sizing .....................................................................22 CHAPTER 4 ......................................................................................................................24 EXPERIMENTAL PROCEDURE ....................................................................................24 4.1 Simulated Brazing Cycle ..........................................................................................24 4.2 Effects of Brazing .....................................................................................................25 4.3 Tube Furnace ............................................................................................................29 4.4 Simulated Thermal Procedure...................................................................................32 4.5 Development of Constitutive Equations ...................................................................32 4.6 Tensile Testing..........................................................................................................34 4.7 Room Temperature Static Burst Testing...................................................................37 4.7.1 Test Apparatus ....................................................................................................38 4.7.2 Room Temperature Experimental Set-up ...........................................................39 4.7.3 MTS Room Temperature Test Procedure...........................................................41 4.8 Improving Elevated Temperature Burst Testing.......................................................42 4.8.1 Upgrading Convection Heater ............................................................................42 4.8.2 Improving Temperature Control.........................................................................43 4.9 Elevated Temperature Burst Testing..........................................................................44 4.9.1 MTS Elevated Temperature Test Procedure.......................................................44 CHAPTER 5 ......................................................................................................................47 RESULTS AND DISCUSSION........................................................................................47 5.1 Tensile Testing Results.............................................................................................47 vii 5.1.1 Alloy 1197 Constitutive Equation ......................................................................48 5.1.2 AA 3003 Constitutive Equation..........................................................................49 5.1.3 AA 3102 Constitutive Equation..........................................................................50 5.2 Uncertainty Analysis.................................................................................................51 5.3 Tube Failure..............................................................................................................52 5.4 Room Temperature Analysis ....................................................................................53 5.5 Statistical Analysis....................................................................................................55 5.6 Elevated Temperature Testing Analysis ...................................................................56 CHAPTER 6 ......................................................................................................................59 CONCLUSIONS................................................................................................................59 6.1 Conclusions...............................................................................................................59 6.2 Future Work..............................................................................................................61 REFERENCES: .................................................................................................................63 viii List of Tables Table Page 3-1: Chemical composition of alloys used during experimentation (determined with optical emission spectroscopy) ..........................................................................................20
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