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Research Papers

Transient Thermocapillary Convection in a Molten or Weld Pool

[+] Author and Article Information
P. S. Wei

Department of Mechanical and Electro-Mechanical Engineering,  National Sun Yat-Sen University, Kaohsiung, Taiwan 80424, R.O.Cpswei@mail.nsysu.edu.tw

C. L. Lin, H. J. Liu, C. N. Ting

Department of Mechanical and Electro-Mechanical Engineering,  National Sun Yat-Sen University, Kaohsiung, Taiwan 80424, R.O.C

J. Manuf. Sci. Eng 134(1), 011001 (Jan 11, 2012) (8 pages) doi:10.1115/1.4005302 History: Received August 23, 2010; Revised October 10, 2011; Published January 11, 2012; Online January 11, 2012

This study presents a numerical scenario for the effect of thermocapillary convection on the transient, two-dimensional molten pool shape during welding or melting. Tracing the melting process is necessary to achieve a better and more complete understanding of the physical mechanism of welding. This model is used to simulate a steady state, three-dimensional welding process, by introducing an incident flux with a Gaussian distribution with a time-dependent radius determined by scanning speed and distribution parameter. Aside from presenting the variations of peak surface velocities and temperature, and depth and width of the molten pool with time, the predicted results of this work show that surface velocity and temperature profiles for a high Prandtl number strongly deform in the course of melting. The velocity profile eventually exhibits two peaks, located near the edges of the incident flux and the pool, respectively. Conversely, only one peak velocity occurs near the pool edge for a small Prandtl number. In all cases, surface temperature can ultimately be divided into hot, intermediate, and cold regions. The pool becomes deep due to an induced secondary vortex cell near the bottom of the pool for a small Prandtl number. For a high Prandtl number, the pool edge is thin and shallow, as a result of penetration into the solid near the top surface. The predicted results agree with those obtained using a commercial computer code.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic sketch for (a) physical model and coordinates and (b) computed results on the transverse cross-section at z = 0

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Figure 2

Predicted dimensionless (a) the first peak surface velocity, (b) the second peak surface velocity, (c) peak surface temperature, (d) depth, and (e) width of the pool as functions of dimensionless time at Marangoni number of 340

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Figure 3

Predicted dimensionless (a) the first peak surface velocity, (b) the second peak surface velocity, (c) peak surface temperature, (d) depth and (e) width of the pool as functions of dimensionless time at Marangoni number of 3400

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Figure 4

Dimensionless surface velocity and temperature profiles for Pr = 0.09 and Ma = 1730 at dimensionless times of (a) 0.45, (b) 0.6, (c) 0.9, and (d) 2.1

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Figure 5

The corresponding dimensionless flow and isothermal patterns at dimensionless times of (a) 0.6, (b) 0.9, and (c) 2.1

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Figure 6

Dimensionless surface velocity and temperature profiles for Pr = 9 and Ma = 3400 at dimensionless times of (a) 0.45, (b) 0.9, and (c) 1.41

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Figure 7

The corresponding dimensionless flow and isothermal patterns at dimensionless times of (a) 0.9 and (b) 1.41

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