D.H. Lammlein PhD Dissertation - Vanderbilt University

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machine, fixturing, and backing plate were warm) were noticeably warmer (as much as 20º C). Figure 89: Thermal camera data for 90º tool runs. Figure 90: Thermal camera data for 80º tool runs. CFD Model of Conical Tool FSW 96
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 of Sheppard and Wright [4] as modified from the initial formulation proposed by Sellars and Tegart [5] Flow stress is defined as an inverse hyperbolic sine function of the local strain rate magnitude and absolute temperature in this following commonly used form: Q Z = & ε exp( ) = A(sin ασ ) n e RT or equivalently, ⎡ ⎤ 1 − ⎢⎛ Z 1 ⎞ n 1 = ⎜ ⎟ ⎥ ⎛ Q ⎞ σ e sinh Z = ε& exp⎜ ⎟ α ⎢⎝ A ⎠ ⎥ ⎝ RT ⎠ ⎣ ⎦ where α, A, n are material constants (α = 0.045 (Mpa)-1, Q = 145 kJ mol -1 , A = 8.8632E6 s -1 , n = 3.55), σe is the equivalent steady state flow stress (Mpa), R the gas constant (R = 8.314 mol -1 K -1 ), T the absolute temperature (K), Q is the activation energy (J mol -1 ) and Z is the Zener-Hollomon parameter. The material constants used are determined using a hot compression test. The material viscosity is defined in the following manner: σ e µ = 3 & ε The visco-plastic model is valid at temperatures reasonably below the metal’s solidus temperature. As the material approaches the solidus temperature significant softening occurs. The total heat input was calculated via the weld power method [6-14]: P =ω⋅M Q = P⋅ β where P is the weld power (W), Q is the heat input to the tool and weld material (W), ω is the tool rotational speed (rad/s), M is the measured torque (N⋅m), and β is the fraction of mechanical work dissipated as heat into the tool shank and the weld. Chao et al. [15] arrive at a β value of approximately 0.8 under similar conditions using a boundary value approach and determine that approximately 5% of this dissipated heat is dissipated via the tool shank. Those ratios are found to be reasonable in the current study. The weld 97
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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
Page 69 and 70: [41] Heinz B., Skrotzki B., Eggler
Page 71 and 72: CHAPTER II COMPUTATIONAL ANALYSIS O
Page 73 and 74: Figure 30: Blind t-joint setup with
Page 75 and 76: Figure 33: Process forces and later
Page 77 and 78: Figure 35: Experimental Welds, Axia
Page 79 and 80: Figure 37: FEA boundary conditions
Page 81 and 82: A 4500 N axial force is applied eve
Page 83 and 84: axial force with lateral offset dur
Page 85 and 86: Figure 42: Contour plot of von Mise
Page 87 and 88: Figure 44: Deformation contour for
Page 89 and 90: Figure 46: Quarter-plate model for
Page 91 and 92: Figure 49: Contour plot of deflecti
Page 93 and 94: where P is the weld power (W), Q is
Page 95 and 96: Figure 52: Fluent CFD model zones.
Page 97 and 98: Figure 55: Thermal contour of weld
Page 99 and 100: Figure 59: Thermal contour of weld
Page 101 and 102: Figure 61: Velocity vectors for 0.0
Page 103 and 104: Figure 65: Contour of velocity magn
Page 105 and 106: CHAPTER III THE APPLICATION OF SHOU
Page 107 and 108: Figure 66: A shoulder-less, conical
Page 109 and 110: 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: Figure 87: (80º tool) Lateral forc
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 162: and tooling. Torque is highly depen
Page 163 and 164: locally in proportion to the local
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
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The results presented here show tha
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Figure 136:(from left: Tapered retr
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[8] Metallurgical analysis of ablat
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CHAPTER V FRICTION STIR WELDING OF
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Collaboration between Advanced Meta
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eccentricity, the method of interio
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gas tungsten arc welding of small d
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Full penetration welds of 4.2” (1
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Figure 143: The curvature of the pi
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Figure 144: Experimental axial forc
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Together, a fine wall thickness tol
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Figure 147: Axial force history for
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The weld macrosections show complet
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Figure 154: Macrosections of welds
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Figure 157: A thermal camera image
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Figure 159: Average tool shank temp
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471,146 faces. The meshes are fine
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Figure 162: A closeup view of mesh
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4 2 3 4 5 16 " 1.745 2 0.24
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applied heat locally in proportion
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Figure 164: Modeled temperature con
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Page 217 and 218:
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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