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Research Papers: Melting and Solidification

Forming Mechanism of Bump Shape in Pulsed Laser Melting of Stainless Steel

[+] Author and Article Information
Hong Shen

School of Mechanical Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China;
State Key Laboratory of Mechanical
System and Vibration,
Shanghai, 200240, China
e-mail: sh_0320@sjtu.edu.cn

Yanqing Pan

School of Mechanical Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China

Jing Zhou

College of Mechanical Engineering,
University of Shanghai for Science
and Technology,
Shanghai 200093, China

Zhenqiang Yao

School of Mechanical Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China;
State Key Laboratory of Mechanical
System and Vibration,
Shanghai, 200240, China

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received May 23, 2016; final manuscript received December 19, 2016; published online February 28, 2017. Assoc. Editor: Milind A. Jog.

J. Heat Transfer 139(6), 062301 (Feb 28, 2017) (10 pages) Paper No: HT-16-1293; doi: 10.1115/1.4035710 History: Received May 23, 2016; Revised December 19, 2016

Laser surface topography has great applications in mechanical, medical, and electrical industries. This paper proposes a mechanism for the shape formation of stainless steel by pulsed laser melting. A 2D axisymmetric finite element model considering the temperature-dependent surface tension is developed, in which the melt flow and free surface deformation are analyzed by using the normal and shear surface forces. The numerical results show that the molten flows toward the place of the greatest surface tension and the free surface deformation are dominated by the shear force (Marangoni effects), generated by the surface tension gradient during heating phase, and the normal stress, generated by the surface tension at the curved surface during the cooling period.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Schematic diagram of laser melting process

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Fig. 2

Directions of tangential stress and temperature gradient

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Fig. 3

Variations of surface tension and surface tension gradient with temperature for a 72 ppm sulfur content 304 stainless steel

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Fig. 4

The schematic of the computational domain

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Fig. 6

Molten flow behavior at the beginning of heating, end of heating, and cooling period (P = 620 W)

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Fig. 7

Transient thermophysical surface conditions (t = 0.2 ms)

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Fig. 8

Contrast of normal stress and tangential stress (P = 620 W, t = 0.2 ms)

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Fig. 9

Final shape by T model (P = 620 W)

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Fig. 10

Schematic diagram of normal stress at the bump

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Fig. 11

Two-dimensional profile comparison between experiment and simulation

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Fig. 12

Sensitivity analysis for the parameters used in the numerical model

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Fig. 13

Surface tension gradient with temperature for different ΔH0

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Fig. 14

Geometrical parameters of the microstructure

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Fig. 15

Bump shape with different laser powers and pulses (heating duration: 0.2 ms, frequency: 50 Hz)

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