Fracture Prediction Based on Evaluation of Initial Porosity Induced By Direct Energy Deposition

Ferreira

et al. 2022

Metals

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This study presents a microstructural model applicable to additively manufactured (AM) austenitic SS 316L components fabricated via a direct energy deposition (DED) process. The model is primarily intended to give an understanding of the effect of microscale and mesoscale features, such as grains and melt pool sizes, on the mechanical properties of manufactured components. Based on experimental observations, initial assumptions for the numerical model regarding grain size and melt pool dimensions were considered. Experimental observations based on miniature-sized 316L stainless steel DED-fabricated samples were carried out to shed light on the deformation mechanism of FCC materials at the grain scale. Furthermore, the dependency of latent strain hardening parameters based on the Bassani–Wu hardening model for a single crystal scale is investigated, where the Voronoi tessellation method and probability theory are utilized for the definition of the grain distribution. A hierarchical polycrystalline modeling methodology based on a representative volume element (RVE) with the realistic impact of grain boundaries was adopted for fracture assessment of the AM parts. To qualify the validity of process–structure–property relationships, cohesive zone damage surfaces were used between melt pool boundaries as the predefined initial cracks and the performance of the model is validated based on the experimental observations.

Section: Ded-fabricated Ss 316l Cubic Componentsmentioning

confidence: 99%

Damage Evolution Simulations via a Coupled Crystal Plasticity and Cohesive Zone Model for Additively Manufactured Austenitic SS 316L DED Components

Ferreira

et al. 2022

Metals

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“…Through activation of a new set of elements in each time step of the finite element solution. Moreover, DED process has a highly localized thermal behavior which leads to undesirable microstructural features [14] and inconsistent mechanical properties of the fabricated parts. Nevertheless, some significant efforts have been made to simulate solidification kinetics [15] and investigation results on the correlation microstructural features and mechanical properties between thermal characterization of melt pool and solidification parameters, including thermal gradient 𝐺 and solidification rate, have been reported [16].…”

Section: Introductionmentioning

confidence: 99%

Thermal study of a cladding layer of Inconel 625 in Directed Energy Deposition (DED) process using a phase-field model

Ferreira

Int J Adv Manuf Technol

et al. 2022

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In an effort to simulate the involved thermal physical effects that occur in direct energy deposition (DED) a thermodynamically-consistent of phase-field method is developed. Two state parameters, characterizing phase change and consolidation, are used to allocate the proper material properties to each phase. The numerical transient solution is obtained via a finite element analysis. A set of experiments for single tracks scanning were carried out to provide dimensional data of the deposited cladding lines. By relying on a regression analytical formulation to establish the link between process parameters and geometries of deposited layers from experiments, an activation of passive elements in the finite element discretization is considered. The single-track cladding of Inconel 625 powder on tempered steel 42CrMo4 was printed with different power, scanning speed and feed-rate to assess their effect on the morphology of the melt pool and the solidification cooling rate. The predicted dimensions of melt pools were compared with experiments reported in the literature. In addition, this research correlated the used process parameter in the modelling of localized transient thermal with solidification parameters, namely, the thermal gradient (𝐺) and the solidification rate (𝑅).

“…Figure6. Comparison of the ultimate tensile strength for all samples 32. …”

mentioning

confidence: 99%

Experimental and computational analysis of additively manufactured tensile specimens: Assessment of localized-cooling rate and ductile fracture using the Gurson– Tvergaard–Needleman damage model

Proceedings of the Institution of Mechanical Engineers, Part L:

Fiorentin

et al. 2021

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The present contribution addresses the micromechanical and thermal analysis of directed energy deposition-manufactured, stainless steel 316L components by utilizing experimental and numerical analyses. It has been established that a combination of controlling process parameters, manufacturing environment and microstructural anisotropies could adversely affect the quality of as-deposited parts. Among other factors, the shape, size, and distribution of the microvoids and porosities could, to some extent, have deteriorating effects on the mechanical properties of the additively manufactured components. In this work, the micromechanically motivated Gurson–Tvergaard–Needleman damage model is utilized and the performance of the model is evaluated by observing the damage accumulation in the loaded additively manufactured specimens. By relying to the laboratory-based material data and fractographic imagery from nonstandard tensile testing on fabricated samples in different building directions, numerical model predictions are found to be in a good agreement with the experimental observations. Furthermore, by resorting to the finite element software capabilities, the thermal analyses are carried out on the manufactured cube component and the influence of the process parameters on the temperature distribution is revealed.