A Computationally Efficient Finite Element Framework to Simulate Additive Manufacturing Processes

Abstract

Macroscale finite element (FE) models, with their ability to simulate additive manufacturing (AM) processes of metal parts and accurately predict residual stress distribution, are potentially powerful design tools. However, these simulations require enormous computational cost, even for a small part only a few orders larger than the melt pool size. The existing adaptive meshing techniques to reduce computational cost substantially by selectively coarsening are not well suited for AM process simulations due to the continuous modification of model geometry as material is added to the system. To address this limitation, a new FE framework is developed. The new FE framework is based on introducing updated discretized geometries at regular intervals during the simulation process, allowing greater flexibility to control the degree of mesh coarsening than a technique based on element merging recently reported in the literature. The new framework is evaluated by simulating direct metal deposition (DMD) of a thin-walled rectangular and a thin-walled cylindrical part, and comparing the computational speed and predicted results with those predicted by simulations using the conventional framework. The comparison shows excellent agreement in the predicted stress and plastic strain fields, with substantial savings in the simulation time. The method is then validated by comparing the predicted residual elastic strain with that measured experimentally by neutron diffraction of the thin-walled rectangular part. Finally, the new framework's capability to substantially reduce the simulation time for large-scale AM parts is demonstrated by simulating a one-half foot thin-walled cylindrical part.

Short review on modeling approaches for metal additive manufacturing process

“…As prevously described, decoupled or weakly coupled approach is mainly used for modeling of AM processes since it takes less computational time and effort compared with the fully coupled approach. However, in the decoupled modeling, the analysis time is dominated by the mechanical or structural analysis step . Furthermore, as for FE analysis, a continuum medium is divided into small elements, which makes the results dependent on the number of elements (or mesh size) used for discretization of the medium.…”

“…This may be the main drawback of the modeling procedures for AM processes. Several researches have focused on decreasing the time regarded for the mechanical part based on implementing adaptive mesh‐type approaches . Mesh coarsening approaches take advantage of the fact that the thermal effects are attenuated for the lower deposited layers that are far from the heat source.…”

“…Jayanath and Achuthan implemented a similar approach using ABAQUS solution map technique. The authors implemented the adaptive meshing technique in two steps: fine mapping and coarsening steps and built a 32‐layer and 300‐layer builds.…”

“…Therefore, research studies have recently focused on developing numerical‐based models that could outline the thermophysical phenomena of the AM process. Finite element (FE)‐based thermomechanical models were developed to assess thermal cycles of AM parts as the result of the heat source and obtain the mechanical response of the AM parts by enforcing the temperature history into the built part . The aforementioned models commonly make some simplifying assumptions or employ certain techniques to investigate the material deposition onto the substrate and formation of residual stresses and geometrical distortions in AM parts.…”

Finite element–based numerical modeling framework for additive manufacturing process

“…Therefore, numerical analysis methods such as a finite element (FE) method offer a very suitable alternative in order to measure and quantify the effect of process parameters. In the recent decades, different strategies and procedure have been introduced to investigate the thermomechanical phenomena during welding and AM processes . Generally, the FE analysis of a thermomechanical process includes thermal analysis and introduces the temperature history to the mechanical, ie, structural analysis as the thermal load which is known as weakly coupled or uncoupled method.…”