D.H. Lammlein PhD Dissertation - Vanderbilt University

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center), thermomechanically affected zone (TMAZ)(dark), and parent material (lightest) can be seen in the macrosection. The model shows significant material stirring in the stirred zone, minimal material stirring in the TMAZ, and no material stirring in the parent material. Conclusions Fusion welding experiments performed on this material and geometry demonstrated that process parameter adjustment was required around the circumference of the weld to maintain acceptable weld quality throughout. Heat input had to be reduced continually to avoid significant and undesirable expansion of the weldpool. It was shown in this study that the reduced welding temperature of the FSW interface minimized this problem and acceptable welds could be produced over a range of parameters. Although a steady rise in temperature was observed, it was not sufficient to require any reduction in weld power during the weld. Additionally, it was shown that a traditional FSW tool geometry could be used on a small diameter pipe provided that a scrolled shoulder was used and the tool was offset some distance from the center of the cylindrical work in the direction of traverse as described earlier. Ideally a force feedback control system would be used to account for variation in the thickness of the pipe sections and rotational eccentricities in the setup. However it was demonstrated in this experiment that FSW of small diameter pipe can be performed without the luxury of force feedback control, provided that pipe sections were preprocessed to reduce wall thickness variation and an expanding inner mandrel was used. The expanding inner mandrel served to align the inner diameters of the pipe section and force the sections into a more uniform circular shape. Welds presented in the experiment were of high tensile strength and sound internal and superficial appearance. This experiment demonstrated that FSW can be performed on this geometry at a wide range of parameters using at various traditional tool geometries. Additionally, it was shown that a high welding rate can be achieved. In this experiment, the highest tensile strength was achieved at travel speed of 15.7 inches per minute and travel speeds up to 17 inches per minute were tested with good results. At the 196
later speed setting, the tool welds the full circumference of the 4.2” diameter pipe sections in less than 50 seconds. The ability to weld at high traverse speeds increases the output of a FSW machine and increases the likelihood that the costs of the machine can be justified in a specific manufacturing setting. It was also shown that the FSW process is well understood and simple CFD models can be used to reliably predict the thermal conditions and material flow during FSW of a given geometry. It was also shown that CFD can give a reasonable prediction of the axial forces that should be expected under various FSW conditions. The large startup costs associated with FSW make the predictive capabilities and understanding provided by a CFD model more valuable. Appendix Figure 176: Zoom view of a macro taken from a full penetration butted pipe weld (1400rpm, 5.2ipm). The experimental tools had a 5/8” diameter, scrolled shoulder and 0.18” length, threaded probe. The wide (0.236” diameter) probe tool created this weld. 197
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FRICTION STIR WELDING OF SPHERES, C
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TABLE OF CONTENTS TABLE OF FIGURES
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Appendix ..........................
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Figure 16: Left(FE streamline), Mid
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Figure 51: A thermal camera image t
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for a similar conventional weld (3/
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Figure 102: Tapered retraction proc
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setting are indicated. Note that st
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Unsupported welds of this kind with
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Figure 157: A thermal camera image
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ottom sample is a tungsten inert ga
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N - newton (force unit) n - visco-p
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INTRODUCTION Friction Stir Welding,
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educed conduction lengths. In small
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CHAPTER I LITERATURE REVIEW: COMPUT
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frictional condition at the interfa
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contact. The contact area can inclu
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For horizontal sections, a heat inp
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(1.11) where r p is the probe (pin)
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This efficiency term, η pd , is kn
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The heat input on the tool surface
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The added complication of these met
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Figure 5: Lateral cross sections of
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Flow stress in aluminum alloys is d
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Figure 8: Three flow fields a) rota
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and post-weld cool-down. This model
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Williams et al. [60] use a 2D-axisy
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Figure 16: Left(FE streamline), Mid
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Figure 18: Temperature contour over
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Figure 22: Temperature distribution
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Figure 24: Lateral velocity contour
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Figure 26: Experimental(white) vers
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Figure 28: Top view schematic of tu
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[5] Taylor RE, Groot H, Goerz T, Fe
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[41] Heinz B., Skrotzki B., Eggler
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CHAPTER II COMPUTATIONAL ANALYSIS O
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Figure 30: Blind t-joint setup with
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Figure 33: Process forces and later
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Figure 35: Experimental Welds, Axia
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Figure 37: FEA boundary conditions
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A 4500 N axial force is applied eve
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axial force with lateral offset dur
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Figure 42: Contour plot of von Mise
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Figure 44: Deformation contour for
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Figure 46: Quarter-plate model for
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Figure 49: Contour plot of deflecti
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where P is the weld power (W), Q is
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Figure 52: Fluent CFD model zones.
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Figure 55: Thermal contour of weld
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Figure 59: Thermal contour of weld
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Figure 61: Velocity vectors for 0.0
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Figure 65: Contour of velocity magn
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CHAPTER III THE APPLICATION OF SHOU
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Figure 66: A shoulder-less, conical
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Figure 68: Typical axial(Z-axis) fo
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Figure 71: 90° conical tool macros
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Figure 75: Run 3, 80° conical tool
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Figure 79: (90º tool) Ultimate ten
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Figure 83: (90º tool) Lateral forc
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Figure 87: (80º tool) Lateral forc
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The Eulerian, finite volume, CFD so
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Figure 92 shows the increasing elem
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Figure 91: CFD model geometry consi
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Figure 95: Lateral cross-section of
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Figure 96: Attempts a probe tapered
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CHAPTER IV THE FRICTION STIR WELDIN
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applications for its high strength
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Figure 97: Experimental weld sample
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Figure 99: Split protrusion type de
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with a cupped recess. It is however
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of tapered retraction (i.e. move th
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The adjustments in vertical positio
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manners the assigned depth was main
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Figure 108: Lateral macrosections f
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Figure 110: (Supported, cupped tool
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apparent strength of 26% parent whi
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with a 100º conical tool (0.025”
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Figure 119: Macrosection view of an
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and tooling. Torque is highly depen
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locally in proportion to the local
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Figure 126: (threaded tool) Contour
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Figure 128: (conical tool) Geometry
Page 169 and 170: Figure 131: (threaded tool) Lateral
Page 171 and 172: The results presented here show tha
Page 173 and 174: Figure 136:(from left: Tapered retr
Page 175 and 176: [8] Metallurgical analysis of ablat
Page 177 and 178: CHAPTER V FRICTION STIR WELDING OF
Page 179 and 180: Collaboration between Advanced Meta
Page 181 and 182: eccentricity, the method of interio
Page 183 and 184: gas tungsten arc welding of small d
Page 185 and 186: Full penetration welds of 4.2” (1
Page 187 and 188: Figure 143: The curvature of the pi
Page 189 and 190: Figure 144: Experimental axial forc
Page 191 and 192: Together, a fine wall thickness tol
Page 193 and 194: Figure 147: Axial force history for
Page 195 and 196: The weld macrosections show complet
Page 197 and 198: Figure 154: Macrosections of welds
Page 199 and 200: Figure 157: A thermal camera image
Page 201 and 202: Figure 159: Average tool shank temp
Page 203 and 204: 471,146 faces. The meshes are fine
Page 205 and 206: Figure 162: A closeup view of mesh
Page 207 and 208: 4 2 3 4 5 16 " 1.745 2 0.24
Page 209 and 210: applied heat locally in proportion
Page 211 and 212: Figure 164: Modeled temperature con
Page 217 and 218: Figure 172: Model pathlines for the
Page 219: Figure 174: Model pathlines for the
Page 223 and 224: Figure 178: Zoom view of a macro ta
Page 225 and 226: Figure 180: The superficial appeara
Page 227 and 228: Figure 182: The rotary welding appa
Page 229 and 230: Figure 185: A diagram illustrating
Page 231 and 232: CONCLUSION AND FUTURE WORK Conclusi
Page 233 and 234: new FSW process environment is reso
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D.H. Lammlein PhD Dissertation - Vanderbilt University

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