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Research Papers

Simulation of a New Solid State Joining Process Using Single-Shoulder Two-Pin Tool

[+] Author and Article Information
S. Mukherjee

Department of Materials Science and Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109

A. K. Ghosh

Department of Materials Science and Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109akg@umich.edu

J. Manuf. Sci. Eng 130(4), 041015 (Jul 22, 2008) (9 pages) doi:10.1115/1.2953071 History: Received August 29, 2007; Revised May 05, 2008; Published July 22, 2008

In friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. The conventional tool design employs a cylindrical shoulder with a single profiled pin. A new process has been designed that uses two-pin tool under the same shoulder to increase shear deformation within workpiece that can enhance local heating where joining occurs. The design employs two closely spaced pins rotating in the same direction within the workpiece under a separately controlled shoulder. The process is distinctly different from the Twin-stir™ variant of FSW in which each pin performs an independent function and non-interacting. Prior to gathering considerable experimental data with new equipment, a fully coupled themomechanical three-dimensional finite element model has been developed to compare the existing single-pin technology with new technology of friction driven stitch welding process. The computational results for the two-pin tool show considerable shearing along the joining interface, enhanced local heating, and a reduced reaction force on the pins, which are described in this paper. The results of this study indicate that the two-pin tool design with a separate shoulder, with the same direction of pin rotation, can be a superior design in comparison to the conventional single-pin FSW tool and could minimize damage to tool material.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 8

Time evolution of average force and average moment per pin for all three configurations

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Figure 9

von Mises stress distribution at t=6.1s for two-pin rotating in the same direction

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Figure 10

Nodal temperature distribution for the two-pin case at t=6.1s. In the top and front sectional views, Path ABCDEF is shown. The temperature profile is drawn along Path ABCDEF. The melting temperature Tmelt=502°C is shown by the horizontal line.

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Figure 11

Nodal temperature distribution for the single-pin case at t=1.1s. In the front sectional view, Path ABCD is shown. The temperature profile is drawn along Path ABCD. The melting temperature Tmelt=502°C is shown by the horizontal line.

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Figure 12

In-plane plastic shear strain for the case of two pins at t=1.1s. The bottom view is a top sectional view close to the bottom of the workpiece.

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Figure 13

In-plane shear strain for the case of single pin at t=1.1s. The bottom view is a top sectional view close to the bottom of the workpiece.

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Figure 14

Average in-plane force per pin plotted against time for the two cases

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Figure 1

The FDSW apparatus. In the inset, the pins and shoulder are shown.

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Figure 2

Schematic of the concept of two-pin FDSW system according to Ref. 1. The bottom view is the sectional view along the plane shown in the top view.

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Figure 3

Shear zone development due to traverse of a single pin. The path of the movement of sheared layer is shown by broken arrows.

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Figure 4

Pressure development due to traverse of a single pin

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Figure 5

von Mises stress distribution for the three cases considered in the 2D analysis. The arrows indicating pin rotation and translation are shown. Path AB is also shown.

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Figure 6

von Mises stress plotted along Path AB for the three cases. The discontinuous segments of the curves correspond to the extremities of the pins.

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Figure 7

Equivalent plastic strain plotted along Path AB for the three cases. The discontinuous segments of the curves correspond to the extremities of the pins.

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