Macroscopic simulation and experimental measurement of melt pool characteristics in selective electron beam melting of Ti-6Al-4V
01 Feb 2017-The International Journal of Advanced Manufacturing Technology (Springer London)-Vol. 88, Iss: 5, pp 1309-1317
TL;DR: In this paper, the lifetime, width and depth of the pools of molten powder material are analyzed for different beam powers, scan speeds and line energies in experiments and simulations, and a thermal finite element simulation tool is used to simulate the temperature distribution in the selective electron beam melting process.
Abstract: Selective electron beam melting of Ti-6Al-4V is a promising additive manufacturing process to produce complex parts layer-by-layer additively. The quality and dimensional accuracy of the produced parts depend on various process parameters and their interactions. In the present contribution, the lifetime, width and depth of the pools of molten powder material are analyzed for different beam powers, scan speeds and line energies in experiments and simulations. In the experiments, thin-walled structures are built with an ARCAM AB A2 selective electron beam melting machine and for the simulations a thermal finite element simulation tool is used, which is developed by the authors to simulate the temperature distribution in the selective electron beam melting process. The experimental and numerical results are compared and a good agreement is observed. The lifetime of the melt pool increases linearly with the line energy, whereby the melt pool dimensions show a nonlinear relation with the line energy.
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293 citations
TL;DR: In this article, a literature review of numerical simulation models of the EBM process is provided, which is mainly classified according to the level of approximation introduced into the modelling methodology, such as mesoscopic or FE approach.
Abstract: The Electron Beam Melting (EBM) process is an additive manufacturing process in which an electron beam melts metallic powders to obtain the geometry of a specific part. The use of an electron beam in the AM field is relatively recent. Numerous applications have already been made in the aerospace and medical fields, in which the EBM process is used to produce complex parts, made of an excellent quality material, for which other technologies would be expensive or difficult to apply. Because of the growing interest of industry in this technology, the research community has been dedicating a great deal of effort to making the EBM process more reliable. The modelling of the EBM process is considered of utmost importance as it could help to reduce the process optimisation time, compared with the trial and error approach, which is currently the most widely used method. From this point of view, the aim of this paper has been to provide a literature review of numerical simulation models of the EBM process. The various studies on numerical modelling are presented in detail. These studies are mainly classified according to the level of approximation introduced into the modelling methodology. The simulations have first been categorised according to the powder modelling approach that has been adopted (i.e. mesoscopic or FE approach). The studies have then been categorised, as far as FE-based simulations are concerned, as either uncoupled or coupled modelling approaches. All the current approaches have been compared, and how the researchers have modelled the EBM process has been highlighted, considering the assumptions that have been made, the modelling of the material properties, the material state change, and the heat source. Moreover, the adopted validation approaches and the results have been described in order to point out any important achievements. Deviations between numerical and experimental results have been discussed as well as the current level of development of the simulation of the EBM process.
191 citations
TL;DR: A computational model based on the discrete element method is employed to study the critical influence of powder cohesiveness on the powder recoating process in AM and shows that cohesive forces dominate gravity forces leading to low quality powder layers not suitable for subsequent laser melting without additional layer/surface finishing steps.
162 citations
Cites background from "Macroscopic simulation and experime..."
...at determining spatial distributions of physical fields such as temperature, residual stresses or dimensional warping on part level [8, 18, 22, 23, 41, 46, 47, 61, 62]....
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TL;DR: In this article, a finite element model (FEM) of the SLM process is proposed, together with its numerical validation by comparison with the literature, and experimental validation using high-speed imaging.
111 citations
Cites methods from "Macroscopic simulation and experime..."
...Previous use of this technology for model validation purposes is reported in [16] and [17]....
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TL;DR: A review of the literature concerning melt pool simulation can be found in this article, where the physical theory underlying the current benchmark models is first presented and the main approximations and assumptions discussed.
Abstract: Reliable computational models of metal additive manufacturing will assist in optimising part quality, and are likely to play a role in component qualification. A key component of these models will be a detailed simulation of flow and heat transfer in and around the melt pool formed as the powder bed is melted. This paper reviews the burgeoning literature concerning melt pool simulation. The physical theory underlying the current benchmark models is first presented and the main approximations and assumptions discussed. The individual capabilities of the leading simulation groups around the world are listed in detail. Publications by less prominent research groups are also summarised. Finally, the overall status of melt pool simulation and the implications for model development are discussed.
106 citations
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TL;DR: The paper presents a detailed description of the abstractions chosen for defining geometric information of meshes and the handling of degrees of freedom associated with finite element spaces, as well as of linear algebra, input/output capabilities and of interfaces to other software, such as visualization tools.
Abstract: An overview of the software design and data abstraction decisions chosen for deal.II, a general purpose finite element library written in Cpp, is given. The library uses advanced object-oriented and data encapsulation techniques to break finite element implementations into smaller blocks that can be arranged to fit users requirements. Through this approach, deal.II supports a large number of different applications covering a wide range of scientific areas, programming methodologies, and application-specific algorithms, without imposing a rigid framework into which they have to fit. A judicious use of programming techniques allows us to avoid the computational costs frequently associated with abstract object-oriented class libraries.The paper presents a detailed description of the abstractions chosen for defining geometric information of meshes and the handling of degrees of freedom associated with finite element spaces, as well as of linear algebra, input/output capabilities and of interfaces to other software, such as visualization tools. Finally, some results obtained with applications built atop deal.II are shown to demonstrate the powerful capabilities of this toolbox.
1,306 citations
TL;DR: In this article, the authors map available additive manufacturing methods based on their process mechanisms, review modelling approaches based on modelling methods and identify research gaps and implications for closed-loop control of the process.
Abstract: Additive manufacturing is a technology rapidly expanding on a number of industrial sectors. It provides design freedom and environmental/ecological advantages. It transforms essentially design files to fully functional products. However, it is still hampered by low productivity, poor quality and uncertainty of final part mechanical properties. The root cause of undesired effects lies in the control aspects of the process. Optimization is difficult due to limited modelling approaches. Physical phenomena associated with additive manufacturing processes are complex, including melting/solidification and vaporization, heat and mass transfer etc. The goal of the current study is to map available additive manufacturing methods based on their process mechanisms, review modelling approaches based on modelling methods and identify research gaps. Later sections of the study review implications for closed-loop control of the process.
984 citations
"Macroscopic simulation and experime..." refers background in this paper
...The SEBM process is just one among many additive manufacturing processes [6] and is subject to extensive research to exploit the potentials of the electron beam, such as extremely high scan speeds and the high energy density....
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TL;DR: Micro computer tomography analysis demonstrated the capability to fabricate three-dimensional structures with an interconnected porosity and pore sizes suitable for tissue ingrowth and vascularization and a chemical surface modification is expected to enhance the fixation of the implant in the surrounding bone as well as to improve its long-term stability.
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TL;DR: In this paper, a 2D lattice Boltzmann model is developed to investigate melting and re-solidification of a randomly packed powder bed under the irradiation of a Gaussian beam during selective beam melting processes.
345 citations
TL;DR: In this paper, the specific behavior of the different solid phase transitions (effect of heating rate) and the melting region, and emphasizes the liquid state (T > 2000 K) was analyzed.
Abstract: Ti-6Al-4V (TA6V) titanium alloy is widely used in industrial applications such as aeronautic and aerospace due to its good mechanical properties at high temperatures Experiments on two different resistive pulse heating devices (CEA Valduc and TU-Graz) have been carried out in order to study thermophysical properties (such as electrical resistivity, volume expansion, heat of fusion, heat capacity, normal spectral emissivity, thermal diffusivity, and thermal conductivity) of both solid and liquid Ti-6Al-4V Fast time-resolved measurements of current, voltage, and surface radiation and shadowgraphs of the volume have been undertaken At TU-Graz, a fast laser polarimeter has been used for determining the emissivity of liquid Ti-6Al-4V at 6845 nm and a differential scanning calorimeter (DSC) for measuring the heat capacity of solid Ti-6Al-4V This study deals with the specific behavior of the different solid phase transitions (effect of heating rate) and the melting region, and emphasizes the liquid state (T > 2000 K)
300 citations
"Macroscopic simulation and experime..." refers background in this paper
...Its peak in the region of θm represents the effect of latent heat [7, 21]....
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...For all phases, the conductivity K increases linearly in temperature [7]....
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