D.H. Lammlein PhD Dissertation - Vanderbilt University

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operating costs for the machine mean this initial expense can often be justified, particularly in vehicular applications (aerospace, automotive, and rail). FSW has been demonstrated on standard geometries like butted, lapped, and t-oriented joints. Its implementation on small diameter pipes could extend its use to the petroleum, petrochemical, and natural gas industries where high weld volume would justify the upfront costs of FSW. Additionally, FSW at a high rate of travel would increase output for manufacturing and further reduce the energy expended per unit length of weld. High traverse rates are tested in this work with good results. By increasing the rate of travel, the time spent by the work at elevated temperatures is reduced and the total heat input into the pipe sections is reduced. Excessive heat is undesirable, as it causes detrimental changes in the material properties of the parent material. Fusion welds are performed commonly on small diameter aluminum pipe (Kou & Le) (Na & Lee). The high heat input and temperatures present in fusion welding are the primary drawback to this approach, particularly in small diameter pipes. Groove type, gas shielded arc welding is the most common fusion welding method performed on aluminum alloy pipes. The primary drawback of this method is the high temperatures and heat input result in a softening of the surrounding base metal. In these welds the heat affected zone (HAZ) controls the as-welded tensile strength of the joint in most cases (Newell, Sperko, Mannings, Anderson, & Connell). This problem is exacerbated in small diameter pipes and the reduced heat and solid-state nature of FSW makes it an attractive alternative in this application. In this work, full penetration friction stir welds are performed on butted sections of aluminum alloy 6061-T6 pipe. These pipe sections are relatively small in diameter, 4.2 inches, and relatively thin walled, 0.2 inches. The small radius of curvature distinguishes this weld configuration geometrically from a butted plate configuration and presents unique challenges. These challenges necessitate the use of specialized techniques and specialized equipment. Friction stir welded joints of this type are not presented in academic literature, although FSW of large diameter steel pipe sections is being done at a research level. 154
Collaboration between Advanced Metal Products Inc., Oak Ridge National Lab, and Megastir Technologies has produced an orbital welding apparatus for joining X65 steel (Feng, Steel, Packer, & David) (Defalco & Steel, 2009) (Packer & Matsunaga, 2004). The test device is designed to produce full penetration welds on 12” diameter, 0.25” wall thickness pipe. This device revolves the tool about the stationary pipe and uses a hydraulic internal support fixture. Additionally, ExxonMobil has conducted research on FSW of linepipe steels (Fairchild, Kumar, Ford, & Nissley, 2009). Experimental Setup In the present experiment, an experimental apparatus was designed, shown in Figure 138 and Figure 139, which rotates the pipe sections beneath a stationary tool axis. The apparatus is mounted to a FSW machine and belt driven by a computer controlled motor. The experimental apparatus has also been used by the authors to join small diameter, butted Al-6061 hemispheres (<strong>Lammlein</strong>, Longhurst, Delapp, Flemming, Strauss, & Cook, 2010). The internal support fixture, or mandrel, used in the present experiment serves an identical purpose to that used with the AMP/ORNL/Megastir orbital apparatus, but is of a different, manually actuated design. 155
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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
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
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: CHAPTER V FRICTION STIR WELDING OF
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 and 220: Figure 174: Model pathlines for the
Page 221 and 222: later speed setting, the tool welds
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
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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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