Controlling heat transfer in micro electron beam welding using volumetric heating

Gajapathi, Satya S.; Mitra, Sushanta K.; Méndez, Patricio F.

doi:10.1016/j.ijheatmasstransfer.2011.07.033

Cited by 14 publications

(27 citation statements)

References 15 publications

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“…Lasers and electron beams are the two most commonly used heat sources to selectively melt the metal powder particles in the bed and fuse them to the underlying layers. Electron beam based processes have significantly higher power density [1] than laser based processes, and also, the electron beam based Arcam ® process has comparatively faster melting rate than laser based processes. Parts fabricated using the electron beam process also tend to have significantly lower residual stresses [2] compared to parts manufactured using laser based fabrication process.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing

et al. 2016

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a b s t r a c tThe fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. The results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a fabricated component.

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Section: Introductionmentioning

confidence: 99%

Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing

et al. 2016

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“…The double ellipsoidal power density distribution illustrated by Goldak et al ((Goldak et al 1984)) is the base of many models proposed for its accurate characterization (e.g. (Rosenthal 1941), (Tian et al 2008), (Gajapathi et al 2011), (Rahman et al 2014) and (Lacki et al 2011)). This is mandatory, when the focus is the local-level analysis to study the thermal convection within the molten-pool.…”

Section: Remarkmentioning

confidence: 99%

Numerical simulation and experimental calibration of additive manufacturing by blown powder technology. Part I: thermal analysis

Chiumenti

Lin

Cervera

et al. 2017

RPJ

106

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Purpose This paper aims to address the numerical simulation of additive manufacturing (AM) processes. The numerical results are compared with the experimental campaign carried out at State Key Laboratory of Solidification Processing laboratories, where a laser solid forming machine, also referred to as laser engineered net shaping, is used to fabricate metal parts directly from computer-aided design models. Ti-6Al-4V metal powder is injected into the molten pool created by a focused, high-energy laser beam and a layer of added material is sinterized according to the laser scanning pattern specified by the user. Design/methodology/approach The numerical model adopts an apropos finite element (FE) activation technology, which reproduces the same scanning pattern set for the numerical control system of the AM machine. This consists of a complex sequence of polylines, used to define the contour of the component, and hatches patterns to fill the inner section. The full sequence is given through the common layer interface format, a standard format for different manufacturing processes such as rapid prototyping, shape metal deposition or machining processes, among others. The result is a layer-by-layer metal deposition which can be used to build-up complex structures for components such as turbine blades, aircraft stiffeners, cooling systems or medical implants, among others. Findings Ad hoc FE framework for the numerical simulation of the AM process by metal deposition is introduced. Description of the calibration procedure adopted is presented. Originality/value The objectives of this paper are twofold: firstly, this work is intended to calibrate the software for the numerical simulation of the AM process, to achieve high accuracy. Secondly, the sensitivity of the numerical model to the process parameters and modeling data is analyzed.

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“…[4][5][6] The FWHM of the Gaussian function, representing the power density distribution on the target surface, is considered as the beam diameter d. The other important physical processes occurring during welding such as melting, evaporation and effect of temperature dependent thermophysical properties of the material are outside the focus of the current study.…”

Section: Mechanisms Of Heat Transfer In Mebwmentioning

confidence: 99%

“…5 The numerical model of mEBW using the Kanaya-Okayama heat source is used to obtain the optimum process parameters.…”

Section: Optimal Beam Voltage and Beam Travelling Speedmentioning

confidence: 99%

“…[4][5][6] The current numerical model is validated by comparing the temperature field in two asymptotic cases, one in the region near the heat source and the other far away from it. The numerical model is then used to evaluate the effect of welding parameters that are grouped into two nondimensional numbers, namely, the Peclet number and the relative beam penetration depth, on the evolution of temperature in the solid.…”

Section: Introductionmentioning

confidence: 99%

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Part 2: Application of Kanaya–Okayama heat source in modelling micro electron beam welding

Gajapathi

Mitra

Méndez

2012

Science and Technology of Welding and Joining

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A three-dimensional finite element model of micro electron beam welding is developed where the Kanaya-Okayama heat source formulated in Part I of this work is used to represent the electron beam. The large number of process variables is grouped into two non-dimensional parameters, namely, Peclet number and relative beam penetration, and their effect is analysed numerically to arrive at the optimum conditions of microwelding. Based on the minimum heat input of the process, the optimum Peclet number is found to be 100, and the beam penetration is twice that of the weld depth. The optimum parameters obtained using the Kanaya-Okayama heat source model are similar to the previous findings using the exponential decay heat source model; however, the predictions of the temperature field in the solid as a result of microwelding are relatively lower in case of the Kanaya-Okayama heat source model because of the differences in distribution of heat into the condensed matter. The lower weld surface temperatures in microwelding using the electron beam suggest significantly less ablation than in laser beams.

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Controlling heat transfer in micro electron beam welding using volumetric heating

Cited by 14 publications

References 15 publications

Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing

Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing

Numerical simulation and experimental calibration of additive manufacturing by blown powder technology. Part I: thermal analysis

Part 2: Application of Kanaya–Okayama heat source in modelling micro electron beam welding

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