Efficient optimization framework for L-PBF fatigue enhanced Ti6Al4V lattice component

Biasi, Raffaele De; Murchio, Simone; Sbettega, Elia; Carmignato, Simone; Luchin, Valerio; Benedetti, M.

doi:10.1016/j.matdes.2023.111975

Cited by 18 publications

(2 citation statements)

References 21 publications

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“…In addition to post-processing, there are process-induced microstructure improvement studies for enhancing the fatigue strength of LPBF-fabricated Ti-6Al-4V. These studies mostly evaluated the effect of the process parameters, building orientation, and the geometric factors during fabrication [3,42,43]. Hosseini et al [44] reported the effect of various scanning strategies on the fatigue characteristics and the microstructure of LPBF-fabricated Ti-6Al-4V.…”

Section: Introductionmentioning

confidence: 99%

In Situ Microstructure Modification Using a Layerwise Surface-Preheating Laser Scan of Ti-6Al-4V during Laser Powder Bed Fusion

Tanrikulu,

Farhang,

Ganesh-Ram

et al. 2024

Materials

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An innovative in situ thermal approach in the domain of LPBF for Ti-6Al-4V fabrication has been carried out with results directing towards an improved fatigue life without the need for post-processing. The thermal process involves an additional laser scan with different process parameters to preheat the selected regions of each layer of the powder bed prior to their full melting. This preheating step influences the cooling rate, which in turn affects surface characteristics and subsurface microstructure, both of which are directly correlated with fatigue properties. A thorough analysis has been conducted by comparing the preheated samples with reference samples with no preheating. Without any additional thermal processing, the preheated samples showed a significant improvement over their reference counterparts. The optimized preheated sample showed an improved prior β-grain distribution with a circular morphology and thicker α laths within the even finer prior β-grain boundaries. Also, an overall increment of the c/a ratio of the HCP α has been observed, which yielded lattice strain relaxation in the localized grain structure. Furthermore, a less-profound surface roughness was observed in the preheated sample. The obtained microstructure with all these factors delivered a 10% improvement in its fatigue life with better mechanical strength overall.

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Section: Introductionmentioning

confidence: 99%

In Situ Microstructure Modification Using a Layerwise Surface-Preheating Laser Scan of Ti-6Al-4V during Laser Powder Bed Fusion

Tanrikulu,

Farhang,

Ganesh-Ram

et al. 2024

Materials

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“…Geometrical and topological singularities, such as thread radius, morphological defects, or surface roughness, can have a significant impact on macro-scale mechanical properties, including fatigue, as demonstrated in literature 42 – 44 . Other factors affecting fatigue performance have also been investigated, such as load direction 45 , printing direction 46 , 47 , the presence of coatings 48 , and temperature 49 . For the purpose of comparing the various methodologies proposed in this state of the art, a tabular summary can be found in Table 1 .…”

Section: Introductionmentioning

confidence: 99%

Strain-based method for fatigue failure prediction of additively manufactured lattice structures

Coluccia,

De Pasquale

2023

Sci Rep

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Lattice structures find application in numerous technological domains, including aerospace and automotive industries for structural components, biomedical sector implants, and heat exchangers. In many instances, especially those pertaining to structural applications, fatigue resistance stands as a critical and stringent requirement. The objective of this paper is to advance the analysis of fatigue failure in additively manufactured lattice structures by introducing a predictive fatigue failure model based on the finite element (FE) method and experimentally validating the results. The model utilizes linear homogenization to reduce computational effort in FE simulations. By employing a strain-based parameter, the most critical lattice cell is identified, enabling the prediction of fatigue crack nucleation locations. The Crossland multiaxial fatigue failure criterion is employed to assess the equivalent stress, furnishing the fatigue limit threshold essential for predicting component failure. Inconel 625 specimens are manufactured via the laser-based powder bed fusion of metals additive manufacturing process. In order to validate the model, cantilevers comprising octa-truss lattice cells in both uniform and graded configurations undergo experimental testing subjected to bending loads within the high cycle fatigue regime. The proposed methodology effectively forecasts the location of failure in seventeen out of eighteen samples, establishing itself as a valuable tool for lattice fatigue analysis. Failure consistently manifests in sections of uniform and graded lattice structures characterized by the maximum strain tensor norm. The estimated maximum force required to prevent fatigue failure in the samples is 20 N, based on the computed Crossland equivalent stress.

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Influence of fillets onto mechanical properties of octet-truss lattice structures

Doutre,

Grandvallet,

Gobet

et al. 2024

Int J Adv Manuf Technol

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The development of Additive Manufacturing (AM) for the fabrication of metallic parts allows structures to be directly manufactured from 3D models. The Electron Beam Melting (EBM) technology is an example of AM technologies that enables the manufacturing of new designs and sophisticated geometries. The process is particularly well suited for the fabrication of lattice structures. Octet-truss lattice structure has been a subject for research during the past 10 years. The potentials that it possesses attract enough interest for manufacturers to use it during the production of parts. Besides being lightweighted, the structure could provide solid mechanical properties. However, researchers always encounter the same issue regarding this particular structure. During Finite Element Analysis (FEA) simulation, stress concentration tends to appear at the struts intersection. This is due to the sharp edges that have very small surface area, thus provoking the presence of singularities. In this respect, the proposed solution is to integrate rounded-joints or fillets at the struts intersection. However, adding fillet entails a mass increase of octet-truss structures. To avoid this mass increase related to these fillets, it is necessary to reduce the size of octet-truss struts. This research work studies the influence of fillets onto the mechanical properties of structures with identical mass. To do so, a set of 15 octet-truss structures are designed with various fillet sizes and strut sizes and compared.Whereas some of them have thick struts and small fillets, others have smaller struts and bigger fillets. The main technical issue in this study remains the design of fillets for octet-truss structures. These latter can indeed be created for up to 12 struts that converge to the same point. Once designed, these octet-truss structures are fabricated by EBM technology and undergo static compression testing. Mechanical properties of each structure are finally determined. Results show that for the same relative density, octet-truss with fillets degrades the mechanical characteristics of the whole structures. This study shows that the strength/mass ratio is better for a structure without fillets. this result can be used in lightweighted applications.

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Efficient optimization framework for L-PBF fatigue enhanced Ti6Al4V lattice component

Cited by 18 publications

References 21 publications

In Situ Microstructure Modification Using a Layerwise Surface-Preheating Laser Scan of Ti-6Al-4V during Laser Powder Bed Fusion

In Situ Microstructure Modification Using a Layerwise Surface-Preheating Laser Scan of Ti-6Al-4V during Laser Powder Bed Fusion

Strain-based method for fatigue failure prediction of additively manufactured lattice structures

Influence of fillets onto mechanical properties of octet-truss lattice structures

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