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Research Papers: Heat Transfer in Manufacturing

Effects of Entrainment on Incapability of High Intensity Beam Drilling

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

Professor
Department of Mechanical and
Electro-Mechanical Engineering,
National Sun Yat-Sen University,
Kaohsiung 80424, Taiwan, ROC
e-mail: pswei@mail.nsysu.edu.tw

J. H. Wu

Department of Mechanical and
Electro-Mechanical Engineering,
National Sun Yat-Sen University,
Kaohsiung 80424, Taiwan, ROC
e-mail: m983020003@student.nsysu.edu.tw

T. C. Chao

Department of Mechanical and
Electro-Mechanical Engineering,
National Sun Yat-Sen University,
Kaohsiung 80424, Taiwan, ROC
e-mail: m993020071@student.nsysu.edu.tw

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 17, 2014; final manuscript received October 15, 2014; published online April 16, 2015. Assoc. Editor: Wilson K. S. Chiu.

J. Heat Transfer 137(8), 082101 (Aug 01, 2015) (9 pages) Paper No: HT-14-1134; doi: 10.1115/1.4029086 History: Received March 17, 2014; Revised October 15, 2014; Online April 16, 2015

The effects of entrainment accompanying mass, momentum, and energy transport from the keyhole wall on keyhole collapse during high-power-density laser or electron beam drilling are theoretically and systematically investigated in this study. High intensity beam drilling is widely used in components, packaging and manufacturing technologies, micro-electromechanical-systems (MEMS), rapid prototyping manufacturing, and keyhole welding. This study proposes a quasi-steady, one-dimensional transport model to predict supersonic and subsonic flow behavior of the two-phase, vapor–liquid dispersion in a keyhole and applies the Young–Laplace equation to calculate the keyhole shape. The results show that the keyhole collapse, representing decreased or vanished radius, is susceptible to mass ejection at the base and entrainment from the side wall. Deposition of a mixture of gas and droplets in the keyhole stabilizes deformation of the keyhole. Enhanced energy and decreased axial component of momentum associated with entrainment are also apt to keyhole collapse. The predicted results agree with axial variations of transport variables of a compressible flow through a divergent and convergent nozzle, and their exact analytical solutions in the absence of friction, energy absorption, and entrainment. An understanding of the effects of ejected and entrained mass in the keyhole on drilling efficiency is therefore provided.

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References

Figures

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Fig. 8

Effects of different entrained energies on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 1

The physical model and coordinate system

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Fig. 2

Comparison of axial variations in dimensionless mixture temperature, pressure, Mach number, and keyhole radius between exact solutions and numerical predictions results for (a) supersonic flow and (b) subsonic flow

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Fig. 3

Effects of different ejected mass fluxes at the base on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 4

Effects of different entrainment fluxes in the lower region on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 5

Effects of entrainment and deposition fluxes in the lower region on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 6

Effects of different entrainment fluxes in the upper region on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 7

Effects of deposition flux in the upper region on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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Fig. 9

Effects of different ratios of axial velocity components between entrained mixture and mixture through the keyhole on transport variables and keyhole radii for (a) supersonic flow and (b) subsonic flow

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