Utilizing composite elements for advanced mesh coarsening of heat flow simulation of laser powder bed fusion

Fan, Miles H.T.S. ORCID: 0000-0002-2527-6244 (2025). Utilizing composite elements for advanced mesh coarsening of heat flow simulation of laser powder bed fusion. University of Birmingham. Ph.D.

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Abstract

Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) is a layer-by-layer method of manufacturing netshape parts from metallic powder. This geometric freedom of manufacture allows new and complex geometries to be realised in many industries. However, due to the potential complex geometries and sequential application of the laser heat source this leads to complex thermal distribution. This can cause issues when there is a dramatic change in cross sectional area in part geometry, as the same parameters that produce 100\% density in large bulk can cause manufacturing defects in thin sections. In order to overcome this issue, industry is adopting thermal simulation to predict possible problem areas of the build. However, current part sized thermal solutions are computationally expensive, taking many hours to compute, oftentimes comparable to the build time itself.
In this work, simulation techniques are proposed to overcome some of the limitations of the current thermal simulations and reduce the time of simulation of full build size parts. The first of these techniques establishes a benchmark simulation that leverages the power of parallel computing on modern consumer graphics cards, resulting in a seven-fold increase in simulation speed. The model is validated through comparison to physical experiments. The results suggest that the method of solution of the heat equation can predict meltpool geometries for given parameters. However, the accuracy of the meltpool geometries is heavily dependent on the volumetric source term for the laser. The heat source used here was most accurate for prediction of conduction mode meltpools.
The novel technique shown in Chapter 7 proposes a way to overcome the current limitation of mesh coarsening within a single material phase of a volume of mixed material types. The method developed herein calculates the hybrid properties of a powder/solid volume to be established on creation of the element on coarsening. Suggestions are also made to how this calculation can be performed with minimal impact on the overall simulation time.
The techniques outlined herein show a marked improvement in macroscopic heatflow simulation speed over the standard techniques discussed in literature. It is speculated that through a combination of these techniques, developments in machine learning, and software development techniques, faster-than-real time heat flow simulation of AM is achievable.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):