open access publication

Article, 2024

Validation of an experimentally-based heat source for flash heating modeling of directed energy deposition: Systematic study of process and simulation parameters

Journal of Manufacturing Processes, ISSN 1878-6642, 1526-6125, Volume 121, Pages 35-50, 10.1016/j.jmapro.2024.05.026

Contributors

Santi, Alberto 0000-0001-7451-1215 (Corresponding author) [1] Bayat, Mohamad 0000-0003-2503-6512 [1] Nadimpalli, Venkata Karthik 0000-0002-8464-3577 [1] Fabrizi, Alberto 0000-0002-7568-5804 [2] Bonollo, Franco 0000-0002-7196-2886 [2] Hattel, Jesper Henri 0000-0001-5687-4581 [1]

Affiliations

  1. [1] Technical University of Denmark
    2. [NORA names: DTU Technical University of Denmark; University; Denmark; Europe, EU; Nordic; OECD];
  2. [2] University of Padua
    3. [NORA names: Italy; Europe, EU; OECD]

Abstract

Computational prediction of the temperature history during directed energy deposition (DED) is a fundamental input for the subsequent numerical analysis of microstructural characteristics and thermomechanical response. In order to allow for industrial implementation of such simulations, the development of computationally efficient methods taking advantage of multi-scaling techniques is needed. This work provides a new formulation for the flash heating (FH) method to be applied when modeling DED. As with other FH methods, this formulation ensures energy conservation when defining the volumetric heat source term, however, in the present case, the actual deposited cross-sectional area obtained from experiments is used instead of hatch spacing and layer thickness as usually done in FH methods for laser powder bed fusion (LPBF). A new feature of the model is that the high-resolution cross-sectional area of the multi-layer geometry is extracted from optical micrographs, resulting in a curvilinear top surface of every track. The method is validated through comparison with experimental monitoring data and provides valuable information regarding cooling rates, development of the molten area, and heat accumulation when varying process parameters within relevant limits. The influence of varying simulation parameters, such as the partitioning of the geometry and the time used for heating (contact time), on computational cost and accuracy is moreover studied. It is found that a very short contact time is mandatory to ensure the melting of the geometry and, consequently, the proper evaluation of cooling rates and thermal gradients.

Keywords

FH method, accumulation, accuracy, analysis of microstructural characteristics, area, bed fusion, cases, characteristics, comparison, computational cost, computational predictions, computationally efficient method, conservation, contact, contact time, cooling rate, cost, cross-sectional area, data, deposition, development, development of computationally efficient methods, directed energy deposition, efficient method, energy, energy conservation, energy deposition, evaluation, evaluation of cooling rates, experimental monitoring data, experiments, flash, flash heating, flash heating model, formulation, fusion, geometry, gradient, hatch spacing, hatching, heat, heat accumulation, heat source, heat source term, history, implementation, industrial implementation, influence, information, input, laser, laser powder bed fusion, layer, layer thickness, limitations, melting, method, micrographs, microstructural characteristics, model, molten, molten area, monitoring data, multi-layer geometry, multi-scaling technique, numerical analysis, optical micrographs, parameters, partitioning, powder bed fusion, prediction, process, process parameters, rate, relevant limitations, response, simulation, simulation parameters, source, source terms, space, study of processes, surface, systematic study, systematic study of processing, technique, temperature, temperature history, term, thermal gradient, thermomechanical response, thickness, time, top surface, validity, volumetric heat source term

Funders

  • Danish Agency for Science and Higher Education

Data Provider: Digital Science

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