Numerical Analysis of Residual Stresses in Parts Produced by Selective Laser Melting Process

Marques, B.; Andrade, Cláudia; Neto, Diogo M.; Oliveira, M. C.; Alves, J. L.; Menezes, L.F.

doi:10.1016/j.promfg.2020.04.167

Cited by 27 publications

(9 citation statements)

References 25 publications

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“…This will deepen the melt pool at that point. This is consistent with the simulation results from finite element model [ 46 , 47 ], which indicated that the bidirectional scan strategy led to deeper melt pool depth. The difference in melt pool geometry affects the microstructure of the build and further has influence on the mechanical properties of the build.…”

Section: Discussionsupporting

confidence: 90%

Analytical Modelling of Temperature Distribution in SLM Process with Consideration of Scan Strategy Difference between Layers

Cai

Liang

2021

Materials

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In the practical selective laser melting (SLM) manufacturing process, the scan strategy often varies between layers to avoid overlapping of the melted area, which affects the residual stress and deflection of the final build. Yet not much modelling work has been done to accommodate the angle between layers. The paper proposed an analytical thermal model to address the scan strategy difference, such as laser scan direction difference between layers, which brings the model closer to the practical scan situation. The analytical transient moving point heat solution is adopted in this model. The laser movement is first considered in a laser coordinates, which originates at the laser radiation spot, and then transferred into a stationary coordinate, which originates at the starting point of the build. The model takes account of multi-track and multi-layer effect by considering thermal property changes caused by remaining heat, which is further adopted for temperature distribution calculation. The scan direction difference leads to different laser path at each layer, and alters heating and cooling time for a specific point on the build. The proposed model is validated by comparing the predicted melt pool geometries to documented experimental data. The effect of scan direction difference between layers is further discussed in the later part. It is found that the uni- and bi- directional scan leads to diverse temperature profile but its effect on melt depth is not significant. Although the laser rotation angle between layers leads to changes in the melt depth, it is not in a large scale. The proposed model shows that scan strategy does not change melt pool geometry in a significant scale but affects the thermal profile as well as thermal history. It can be used as a step for further modelling work for porosity and deflection.

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Section: Discussionsupporting

confidence: 90%

Analytical Modelling of Temperature Distribution in SLM Process with Consideration of Scan Strategy Difference between Layers

Cai

Liang

2021

Materials

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“…In this research work, the FEM software ABAQUS was employed to simulate an AM process, as it provides an interface allowing the user to define input data, such as element and heat input, that are a function of both position and time to achieve the process simulation of 3D parts. Marques et al [ 21 ] used numerical analysis of the SLM process to assess the effects of laser scanning strategies on the residual stresses generated in the fabrication of Ti6Al4V parts. Chen et al [ 22 ] used a 3D finite element model to simulate thermal behaviour in the SLM process and further investigated the effects of laser beam power and laser scanning speed on the thermal behaviour and solidification of SLM-produced high strength tool steel.…”

Section: Introductionmentioning

confidence: 99%

Development of VUMAT and VUHARD Subroutines for Simulating the Dynamic Mechanical Properties of Additively Manufactured Parts

2022

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Numerical modelling and simulation can be useful tools in qualification of additive manufactured parts for use in demanding structural applications. The use of these tools in predicting the mechanical properties and field performance of additive manufactured parts can be of great advantage. Modelling and simulation of non-linear material behaviour requires development and implementation of constitutive models in finite element analysis software. This paper documents the implementation and verification process of a microstructure-variable based model for DMLS Ti6Al4V (ELI) in two separate ABAQUS/Explicit subroutines, VUMAT and VUHARD, available for defining the yield surface and plastic deformation of materials. The verification process of the implemented subroutines was conducted for single and multiple element tests with varying prescribed loading conditions. The simulation results obtained were then compared with the analytical solutions at the same conditions of strain rates and temperatures. This comparison showed that both developed subroutines were accurate in predicting the flow stress of various forms of DMLS Ti6Al4V (ELI) under different conditions of strain rates and temperatures.

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“…To explain further, the thermal simulation of AM parts, including LPBF and DED, are conducted over several time steps. The thermal history predictions over this longer horizon are then used to estimate the mechanical response (Williams et al , 2018; Yang et al , 2019; Mukherjee et al , 2017; Josupeit et al , 2016; Hodge et al , 2016; Afazov et al , 2017; Marques et al , 2020; Desmaison et al , 2022). The thermal and mechanical aspects are thus considered independent (decoupled); while the thermal history influences the mechanical response, the mechanical response is assumed to have no effect on the thermal response.…”

Section: Thermal Modeling In Additive Manufacturing Using the Graph T...mentioning

confidence: 99%

Thermal modeling of directed energy deposition additive manufacturing using graph theory

Riensche

Severson

Yavari

et al. 2022

RPJ

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Purpose The purpose of this paper is to develop, apply and validate a mesh-free graph theory–based approach for rapid thermal modeling of the directed energy deposition (DED) additive manufacturing (AM) process. Design/methodology/approach In this study, the authors develop a novel mesh-free graph theory–based approach to predict the thermal history of the DED process. Subsequently, the authors validated the graph theory predicted temperature trends using experimental temperature data for DED of titanium alloy parts (Ti-6Al-4V). Temperature trends were tracked by embedding thermocouples in the substrate. The DED process was simulated using the graph theory approach, and the thermal history predictions were validated based on the data from the thermocouples. Findings The temperature trends predicted by the graph theory approach have mean absolute percentage error of approximately 11% and root mean square error of 23°C when compared to the experimental data. Moreover, the graph theory simulation was obtained within 4 min using desktop computing resources, which is less than the build time of 25 min. By comparison, a finite element–based model required 136 min to converge to similar level of error. Research limitations/implications This study uses data from fixed thermocouples when printing thin-wall DED parts. In the future, the authors will incorporate infrared thermal camera data from large parts. Practical implications The DED process is particularly valuable for near-net shape manufacturing, repair and remanufacturing applications. However, DED parts are often afflicted with flaws, such as cracking and distortion. In DED, flaw formation is largely governed by the intensity and spatial distribution of heat in the part during the process, often referred to as the thermal history. Accordingly, fast and accurate thermal models to predict the thermal history are necessary to understand and preclude flaw formation. Originality/value This paper presents a new mesh-free computational thermal modeling approach based on graph theory (network science) and applies it to DED. The approach eschews the tedious and computationally demanding meshing aspect of finite element modeling and allows rapid simulation of the thermal history in additive manufacturing. Although the graph theory has been applied to thermal modeling of laser powder bed fusion (LPBF), there are distinct phenomenological differences between DED and LPBF that necessitate substantial modifications to the graph theory approach.

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Numerical Analysis of Residual Stresses in Parts Produced by Selective Laser Melting Process

Cited by 27 publications

References 25 publications

Analytical Modelling of Temperature Distribution in SLM Process with Consideration of Scan Strategy Difference between Layers

Analytical Modelling of Temperature Distribution in SLM Process with Consideration of Scan Strategy Difference between Layers

Development of VUMAT and VUHARD Subroutines for Simulating the Dynamic Mechanical Properties of Additively Manufactured Parts

Thermal modeling of directed energy deposition additive manufacturing using graph theory

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