Mitigation of residual stresses and microstructure homogenization in directed energy deposition processes

Lu, Xufei; Chiumenti, Michele; Cervera, Miguel; Zhang, Guohao; Lin, Xin

doi:10.1007/s00366-021-01563-9

Cited by 20 publications

(5 citation statements)

References 38 publications

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“…Thus, the thermal problem is solved first, followed by the mechanical analysis, at each time-step of the AM process. A detailed description of the thermo-mechanical model used for AM can be found in previous publications [40,41].…”

Section: Computational Simulationmentioning

confidence: 99%

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Recoater-Induced Distortions and Build Failures in Selective Laser Melting of Thin-Walled Ti6Al4V Parts

Chiumenti

Cervera

et al. 2023

JMMP

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Additively manufactured thin-walled structures through selective laser melting (SLM) are of great interest in achieving carbon-neutral industrial manufacturing. However, residual stresses and warpages as well as recoater crashes often occur in SLM, leading to the build failure of parts, especially for large-scale and lightweight geometries. The challenge in this work consists of investigating how the recoater affects the warpage and (sometimes) causes the failure of different thin-walled Ti6Al4V parts (wall thickness of 1.0 mm). All these parts are printed on the same platform using a commercial SLM machine. After the loose powder removal and before the cutting operation, a 3D-scanner is used to obtain the actual warpage of each component. Next, an in-house coupled thermo-mechanical finite element model suitable for the numerical simulation of the SLM process is enhanced to consider the recoater effects. This numerical framework is calibrated to predict the thin-walled warpage as measured by the 3D-scanner. The combination of numerical predictions with experimental observations facilitates a comprehensive understanding of the mechanical behavior of different thin-walled components as well as the failure mechanism due to the recoater. The findings show that the use of a higher laser energy input causes larger residual stresses and warpage responsible for the recoater crashes. Finally, potential solutions to mitigate the warpage and the recoater crashes in the SLM of lightweight structures are assessed using the validated model.

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Section: Computational Simulationmentioning

confidence: 99%

“…where σ y is the (temperature-dependent) yield stress and q h , the stress-like variable controlling the isotropic strain hardening [40], expressed as:…”

Section: Mechanical Analysismentioning

confidence: 99%

Recoater-Induced Distortions and Build Failures in Selective Laser Melting of Thin-Walled Ti6Al4V Parts

Chiumenti

Cervera

et al. 2023

JMMP

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“…Therefore, in this study, we assume an elliptic profile approximation as accounted for by Lambiase et al [24]. Furthermore, appropriate modelling of the base plate is essential, since it mechanically restricts the part and influences heat accumulation [25,26].…”

Section: Finite Element Meshmentioning

confidence: 99%

Towards an Automated Framework for the Finite Element Computational Modelling of Directed Energy Deposition

Kovšca¹,

Starman²,

Klobčar³

et al. 2022

SSRN Journal

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“…Likewise, Montevecchi et al [21] recommended using an air jet for cooling after the 4th layer. The substrate thickness is another aspect that can impact the residual stress; that is, a thicker substrate helps to reduce residual stress [22].…”

Section: Introductionmentioning

confidence: 99%

Active and Passive Thermal Management in Wire Arc Additive Manufacturing

Nagallapati

Khare

Sharma

et al. 2023

Metals

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This article presents innovative approaches for managing residual stresses and distortion in additive manufacturing (AM) of metal components (baseplate material: EN8; filler wire material: ER70S-6). The experiments are conducted with two approaches for thermal management—passive and active. The passive approach of experiments is performed by varying the selected process parameters to study their effect on residual stresses and distortion. The chosen parameters are current, torch speed, geometry, continuous or a delay in the deposition, and cooling arrangement. Based on the understanding gained from the passive approach, the active approach of thermal management was implemented by insulating the substrate with and without adaptive current and heating the substrate. The experimental results were corroborated with the simulation to understand the process better. A comparative study for hardness was made based on the T8/5 extracted from the simulation. These experiments and simulations endorse passive and active thermal management as effective tools that can alter the distortion and residual stress pattern and the mechanical properties of an AM component. The investigation concludes that the process parameters that lead to higher heat input vis-à-vis an increase in current or a decrease in speed increase the distortion. On the other hand, the parameters that affect the rate of heat distribution vis-à-vis torch speed and geometry affect the residual stresses. When current, traverse speed and a/b ratio were kept the same, active thermal management with a heated base reduced distortion from 1.226 mm to 0.431 mm, a 65% reduction compared to passive thermal management. Additionally, the maximum residual stress was reduced from 492.31 MPa to 250.68 MPa, with residual stresses decreasing from 418.57 MPa to 372 MPa. Overall, active thermal management resulted in a 63% reduction in distortion, lowering it from 1.35 mm to 0.50 mm using external heating. The components that are difficult to complete because of the in-process distortion are expected to be manufactured with thermal management, e.g., heating the substrate is an effective measure to manage the in-process distortion. Thermal management techniques depend on geometry; for instance, a concave surface, because of self-heating, reduces the cooling rate and has relatively less variation in hardness.

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Mitigation of residual stresses and microstructure homogenization in directed energy deposition processes

Cited by 20 publications

References 38 publications

Recoater-Induced Distortions and Build Failures in Selective Laser Melting of Thin-Walled Ti6Al4V Parts

Recoater-Induced Distortions and Build Failures in Selective Laser Melting of Thin-Walled Ti6Al4V Parts

Towards an Automated Framework for the Finite Element Computational Modelling of Directed Energy Deposition

Active and Passive Thermal Management in Wire Arc Additive Manufacturing

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