Resolution, energy and time dependency on layer scaling in finite element modelling of laser beam powder bed fusion additive manufacturing

Zhang, Wenyou; Tong, Min; Harrison, Noel M.

doi:10.1016/j.addma.2019.05.002

Cited by 35 publications

(41 citation statements)

References 47 publications

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“…As discussed in Section 1 , lumped layer-by-layer material addition is considered here, which means that the uniform heat source

is simultaneously applied over the entire volume of the newly deposited lumped layer. Both of these simplifications, i.e., lumping and layer-by-layer material addition, have been motivated and applied in number of previous LPBF simulation studies [ 23 , 24 , 25 , 26 , 33 ]. Apart from obvious computational benefits, these choices are motivated by the fact that it has been shown by Davies [ 24 ] that a model with these simplifications is adequate for correctly capturing the part-scale thermal response.…”

Section: Reference Thermal Lpbf Process Modelmentioning

confidence: 99%

“…To solve the boundary value problem (BVP) given by Equations ( 1 )–( 5 ), finite element analysis is used. The element birth-and-death method is implemented which is a common technique used to simulate the growing domain during the AM processes [ 20 , 26 ]. The implementation is done in CalculiX (a free and open source FE analysis code) [ 34 ] with a structured mesh where elements are aligned with the (lumped) layers.…”

Section: Reference Thermal Lpbf Process Modelmentioning

confidence: 99%

“…This re-melting is intentional as it allows for a seamless connection between the layers. Therefore, the concept of “superlayers” or layer lumping has been proposed where deposition of one superlayer refers to the simultaneous deposition of multiple real layers while modeling the process [ 23 , 24 , 25 , 26 ].…”

Section: Introductionmentioning

confidence: 99%

“…It is reported that with increased layer lumping, the model captures an average evolution of the temperature field during the manufacturing process. Another study by Harrison [ 26 ] investigated the effect of using lumped layers as thick as

and 24 times the real layer thickness. The analysis was carried out for a 2D real-size part (height

mm, width

mm) and it was reported that lumping of 4 layers already results in a 20 times faster simulation compared to the one with no layer lumping.…”

Section: Introductionmentioning

confidence: 99%

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Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

et al. 2020

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The powder bed fusion (PBF) process is a type of Additive Manufacturing (AM) technique which enables fabrication of highly complex geometries with unprecedented design freedom. However, PBF still suffers from manufacturing constraints which, if overlooked, can cause various types of defects in the final part. One such constraint is the local accumulation of heat which leads to surface defects such as melt ball and dross formation. Moreover, slow cooling rates due to local heat accumulation can adversely affect resulting microstructures. In this paper, first a layer-by-layer PBF thermal process model, well established in the literature, is used to predict zones of local heat accumulation in a given part geometry. However, due to the transient nature of the analysis and the continuously growing domain size, the associated computational cost is high which prohibits part-scale applications. Therefore, to reduce the overall computational burden, various simplifications and their associated effects on the accuracy of detecting overheating are analyzed. In this context, three novel physics-based simplifications are introduced motivated by the analytical solution of the one-dimensional heat equation. It is shown that these novel simplifications provide unprecedented computational benefits while still allowing correct prediction of the zones of heat accumulation. The most far-reaching simplification uses the steady-state thermal response of the part for predicting its heat accumulation behavior with a speedup of 600 times as compared to a conventional analysis. The proposed simplified thermal models are capable of fast detection of problematic part features. This allows for quick design evaluations and opens up the possibility of integrating simplified models with design optimization algorithms.

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“…As discussed in Section 1 , lumped layer-by-layer material addition is considered here, which means that the uniform heat source

Section: Reference Thermal Lpbf Process Modelmentioning

confidence: 99%

Section: Reference Thermal Lpbf Process Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

and 24 times the real layer thickness. The analysis was carried out for a 2D real-size part (height

mm, width

mm) and it was reported that lumping of 4 layers already results in a 20 times faster simulation compared to the one with no layer lumping.…”

Section: Introductionmentioning

confidence: 99%

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Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

et al. 2020

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“…Wang et al [43] presented a method to validate RS prediction thermomechanical models by the neutron diffraction technique. Prediction of the induced RS is one of the main motivations for developing process simulation methods, but the RS state is complex to determine as the thermal history is characterized by layer upon layer overlapping, which results in repeated partial heating, melting, and solidification [44]. The RS and distortions on AM processes are not well understood yet [45].…”

Section: Introduction Of Intermetallic Compounds and Metal Matrix Commentioning

confidence: 99%

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

Barros

Silva

Gouveia

et al. 2019

Metals

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Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those "hidden" stresses can be detrimental to a part's mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part's core.Diverse metals AM techniques exist, and the most adopted in the industry are Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), as for the classification by the ISO/ASTM 52900 (2015) international standard. These two techniques use a laser or an electron beam as a high energy density source to selectively melt the material and build the parts [3][4][5][6][7]. Actually, different nomenclatures are used for the same process. Laser Powder Bed Fusion (PBF-LB) is also known as Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), and Laser Cusing [7,8,11], depending mostly on the AM systems supplier.Focusing on PBF-LB, a micro-size powder is spread in thin layers of 20 and 50 µm [3], and then a laser beam guided by a galvanometric mirror selectively melts the deposited material according to the CAD model. The parts are built progressively from bottom to top, also known as the building direction (vertical) [7,11]. The use of support structures is common, either to support down-facing surfaces or to prevent part distortion. Part distortion occurs due to the large residual stresses (RS) generated during material solidification layer-by-layer, owing to the extreme temperature gradients and high cooling rates [12].New feedstock materials dedicated to AM systems have been developed; thereby, new opportunities will arise in the near future of AM [13]. Stainless steel; tool steel; and Ni-, Al-, Ti-, Co-Cr-, and Cu-based alloys are just a few of the metallic materials currently available for AM [7,14,15]. Introduction of int...

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Computational Modeling of Additive Manufacturing—Overview, Principles, and Simulations in Different Scales

Sivaraj,

Nitheesh Kumar,

Karthik

2024

Additive Manufacturing With Novel Materials

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Resolution, energy and time dependency on layer scaling in finite element modelling of laser beam powder bed fusion additive manufacturing

Cited by 35 publications

References 47 publications

Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

Computational Modeling of Additive Manufacturing—Overview, Principles, and Simulations in Different Scales

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