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Study on the numerical simulation of laying powder for the selective laser melting process

ORIGINAL ARTICLE
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Abstract

Because the selective laser melting (SLM) formation process involves rapid melting and solidification of slices, the SLM process places high demands on the tightness, uniformity, and flatness of the powder layer. Based on the discrete element method (particle contact force model, particle collision judgment algorithm, and particle motion equation) and the SLM laying powder process, a numerical simulation of the SLM laying powder process was carried out. For the performance measurement experiment of the TC4 titanium alloy powder, the powder bulk density, tap density, and angle of repose were calculated and analyzed. It was found that the tap density increased by 7.5% compared to the bulk density, and the calculated average angle of repose (32.6°) was in good agreement with the experimental data (33.2°), thus verifying the accuracy of the calculation model used for the SLM laying powder. The influences of different scraping methods and scraping speeds on the quality of the laying powder were calculated and analyzed. It was found that the scraping method using a roller (not rotating) obtained the highest tightness and most uniform powder distribution, and, as the scraping speed increased, the laying tightness tended to decrease linearly. The results of the numerical simulation study of the SLM laying powder process can be used to guide the actual SLM laying powder process and, alternatively, provide basic data for the numerical simulation of SLM molten pool dynamics based on the particle scale.

Keywords

Laying powder Selective laser melting Discrete element method Tightness Numerical simulation Additive manufacturing 

Abbreviations

me

Equivalent mass of particle i and particle j

un, ut

Normal and tangential relative displacements of the particles, respectively

t

Time

Dn, Dt

Normal and tangential damping coefficients of the contact model, respectively

En, Et

Normal and tangential elastic coefficients of the contact model, respectively

Fn, Ft

Normal and tangential components of the particle contact force, respectively

Ie

Equivalent moment of inertia of the particle

θ

Rotation angle of the particle itself

r

Radius of rotation

M

External torque of the particles

μ

Coefficient of friction of the particles

sgn

A symbolic function

\( \tilde{P} \)

Created box for the particle P

Lij

Spherical center distance between particle i and particle j

ri, rj

Radius of particle i and particle j, respectively

mi

Mass of particle i

\( {\ddot{\boldsymbol{u}}}_i \)

Acceleration of particle i

Fsum

External force of the particle i at the centroid

Ii

Moment of inertia of particle i

\( {\ddot{\theta}}_i \)

Angular acceleration of particle i

Msum

External moment of the particle i at the centroid

\( {\left({\dot{\boldsymbol{u}}}_i\right)}_N \)

Particle velocity of the next time step

\( {\left({\dot{\theta}}_i\right)}_N \)

Angular velocity of the next time step

Δt

Time step

Notes

Funding information

This work was supported by the Research Platform Construction Funding of Advanced Institute of Engineering Science for Intelligent Manufacturing, Guangzhou University.

Compliance with ethical standards

Conflict of interest

The author declares that he has no conflict of interest.

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Copyright information

© Springer-Verlag London Ltd., part of Springer Nature 2019

Authors and Affiliations

  1. 1.Advanced Institute of Engineering Science for Intelligent ManufacturingGuangzhou UniversityGuangzhouChina

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