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Research on the solidified morphologies of successive pileup metal droplets

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Abstract

Metal micro-droplet 3D printing is an effective additive manufacturing technique to form micro pillar structures. However, the control mechanism of the pillar contour is still unclear. To form a pillar with uniform radius, it is essential to investigate the dependence of processing parameters on pillar contours. In this study, a 3D numerical model was employed to simulate and analyze the successive pileup processes of multiple droplets. The solidification angle of solidified new-coming droplets is defined to characterize the pillar contour. An analytic equation of solidification angle was established. In this case, the solidified morphology of the droplets could be feasibly predicted through thermophysical parameters and initial conditions. This work provides good physical understanding of the complicated mechanisms for fabricating a pillar structure by means of the successive pileup of molten metal droplets, and paves the way for pillar contour control.

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Abbreviations

ρ :

Metal material density

U :

Velocity vector

P :

Pressure vector

τ :

Shear stress vector

S :

Temperature-dependent source term

F vol :

Surface tension vector of the free surface

σ :

Surface tension

κ :

Curvature ratio of the interface

n :

Unit normal vector

ρ g :

Density of the gas

\(\overline \rho \) :

Average density of a cell to the free surface

Ω+ :

The region of molten material

Ω− :

Void region

Γ:

Common boundary between Ω+ and Ω−

f s :

The solid fraction of fluid

v 0 :

Droplet impact velocity

C :

Specific heat

ΔT :

Temperature gradient between droplet and substrate

k :

Thermal conductivity

μ :

Viscosity

H :

Enthalpy

H ref :

Explicit enthalpy of the reference temperature

T ref :

Reference temperature

L :

Latent heat of fusion

R c :

Contact thermal resistance

R h :

Arithmetical average height

T sub,0 :

Initial temperature of substrate

T 0 :

Initial temperature of droplet

We :

Weber number

Re :

Reynolds number

θ :

Solidification angle

Q :

Heat flux

A c :

Average cross-section area of the interface

R h :

Thermal resistance of the pillar

h :

Current height of the pillar

R c :

Contact thermal resistance

ξ :

Correction factor

t s :

Total solidification time

Tpre :

Temperature of the previous solidified droplet

λ :

A parameter relating the initial condition

Δh :

Increment of pillar height

r b :

Radius of contact line

r c :

Radius of solidified droplet (the number in subscript is droplet index)

r col :

Diameter of pillar contour

sub:

A subscript that indicates a parameter related to the substrate

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Acknowledgments

This work was supported by the National Natural Foundation of China (No. 51475266, 51005134).

Author information

Authors and Affiliations

  1. School of Mechanical Engineering, Changzhou University, Changzhou, 213164, China

    Congping Chen & Yi Zhang

  2. School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an, 710072, China

    Jieguang Huang

  3. College of Mechanical Engineering, Chongqing University, Chongqing, 400030, China

    Hao Yi

Authors
  1. Congping Chen
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  2. Jieguang Huang
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  3. Hao Yi
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  4. Yi Zhang
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Corresponding authors

Correspondence to Congping Chen, Jieguang Huang or Hao Yi.

Additional information

Recommended by Editor Chongdu Cho

Congping Chen is a Professor of Mechanical Engineering at Changzhou University. Professor Chen received his Ph.D. in 2007 from Huazhong University of Science and Technology. His research interests include 3D printing and intelligent manufacturing.

Jiequang Huang is a Ph.D. student at School of Mechanical Engineering, Northwestern Polytechnical University. His main research interests focus on droplet-based 3D printing, droplet ejection, and droplet impingement, etc.

Hao Yi is an Assistant Professor in the College of Mechanical Engineering at Chongqing University, China. He is serving as an Associate Editor for Micro & Nano Letters, The Journal of Engineering, an editorial board member for Production Engineering, Fluid Dynamics & Materials Processing, Heliyon, and a peer reviewer for nearly 50 SCI-indexed journals. His main research interests focus on 3D printing and additive manufacturing, spray forming, green manufacturing, production research, etc.

Yi Zhang is a Professor of Mechanical Engineering at Changzhou University. Professor Zhang received his Ph.D. in 2005 from University of Science and Technology of China. His research interests include CAM/CAPP/CAE/CIMS.

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Chen, C., Huang, J., Yi, H. et al. Research on the solidified morphologies of successive pileup metal droplets. J Mech Sci Technol 34, 3197–3205 (2020). https://doi.org/10.1007/s12206-020-0711-5

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  • DOI: https://doi.org/10.1007/s12206-020-0711-5

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