D.H. Lammlein PhD Dissertation - Vanderbilt University

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Figure 123: Weld moment was a better indicator of penetration depth for the conical tool and a torque based control method was used in the experiment to maintain penetration depth. Fluent CFD Model A computational fluid dynamics (CFD) model was made for the tool used in the supported experiment and the tool used in the unsupported experiment. The Eulerian, finite volume, CFD solver, Ansys FLUENT was used with the implicit formulation. The weld material viscosity function was set by user-defined function and defined according to the visco-plastic model used by Sheppard and Wright [29,30]. Fluent separates the weld interface into a surface and shadow surface. Heat energy was input at the weld interface into the material as defined by a user-defined function which applied heat 138
locally in proportion to the local tool velocity. Another user defined function input heat at the interface on the tool side by equating the temperature in these cells to the temperature of adjacent cells on the material side of the interface. The total heat input at the interface (both sides included) was defined by the weld power method as the product of tool radial velocity (rad/s), weld torque (N·m), and some weld efficiency factor (β). In the models presented, it was assumed that all mechanical energy from the tool was converted to heat input into the tool and weld material (β=1) [31]. A rotational velocity of 1000rpm and traverse speed of 7.8ipm were used in the presented model. The tool rotational axis remained stationary while a velocity inlet and an outflow boundary condition (BC) were used to simulate a traverse speed. Thermal BC's are defined as follows (W/(m 2·K)): surface, 10; bottom unsupported, 8; bottom supported 50; shank, 15; tool-top, 30. Figure 124 shows the geometry and mesh (584,401 tetrahedral cells) of the threaded probe tool and the weld material created in the preprocessor Gambit. The mesh was created by finely meshing the interface and establishing a mesh growth rate in the tool and material volumes. The mesh was thus finest at the interface where temperature and momentum gradients were highest and most course near the model boundaries. Figure 125 shows the threads of this geometry created in gambit. Figure 124: (threaded tool) Tetrahedral mesh created in the Fluent preprocessor Gambit. 139
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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
Page 111 and 112: Figure 71: 90° conical tool macros
Page 113 and 114: Figure 75: Run 3, 80° conical tool
Page 115 and 116: Figure 79: (90º tool) Ultimate ten
Page 117 and 118: Figure 83: (90º tool) Lateral forc
Page 119 and 120: Figure 87: (80º tool) Lateral forc
Page 121 and 122: The Eulerian, finite volume, CFD so
Page 123 and 124: Figure 92 shows the increasing elem
Page 125 and 126: Figure 91: CFD model geometry consi
Page 127 and 128: Figure 95: Lateral cross-section of
Page 129 and 130: Figure 96: Attempts a probe tapered
Page 131 and 132: CHAPTER IV THE FRICTION STIR WELDIN
Page 133 and 134: applications for its high strength
Page 135 and 136: Figure 97: Experimental weld sample
Page 137 and 138: Figure 99: Split protrusion type de
Page 139 and 140: with a cupped recess. It is however
Page 141 and 142: of tapered retraction (i.e. move th
Page 143 and 144: The adjustments in vertical positio
Page 145 and 146: manners the assigned depth was main
Page 147 and 148: Figure 108: Lateral macrosections f
Page 149 and 150: Figure 110: (Supported, cupped tool
Page 155 and 156: apparent strength of 26% parent whi
Page 157 and 158: with a 100º conical tool (0.025”
Page 159 and 160: Figure 119: Macrosection view of an
Page 161: and tooling. Torque is highly depen
Page 165 and 166: Figure 126: (threaded tool) Contour
Page 167 and 168: 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
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Figure 167: Modeled temperature con
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Figure 169: Modeled temperature con
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Figure 172: Model pathlines for the
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Figure 174: Model pathlines for the
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later speed setting, the tool welds
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Figure 178: Zoom view of a macro ta
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Figure 180: The superficial appeara
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Figure 182: The rotary welding appa
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Figure 185: A diagram illustrating
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CONCLUSION AND FUTURE WORK Conclusi
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new FSW process environment is reso
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D.H. Lammlein PhD Dissertation - Vanderbilt University

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