Ti-6Al-4V Octet-Truss Lattice Structures under Bending Load Conditions: Numerical and Experimental Results

Francesco Di Caprio,Stefania Franchitti,Costanzo Bellini,Rosario Borrelli,Vittorio Di Cocco,Luca Sorrentino

doi:10.3390/met12030410

Francesco Di Caprio, Stefania Franchitti + Show 4 more

Open Access

https://doi.org/10.3390/met12030410

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Abstract

Metal lattice structures produced by means of additive techniques are attracting increasing attention thanks to the high structural efficiency they can offer. In order to achieve the maximum structural performance, numerical design techniques are used almost exclusively, thus based on CAE-FEM codes. Nevertheless, the current manufacturing facilities do not yet guarantee defect-free components, and, therefore, such imperfections need to be introduced in the numerical models too. The present work aims to describe a FE modelling technique for lattice structures based on the use of beam and shell elements, and therefore with a very reduced computational cost. The main structural parameters, such as weight and stiffness and strength, are used to drive the model calibration. Simple mathematical relationships, based on Experimental-CAD-FEM comparisons, are provided to estimate the error related to the numerical model in a simple and fast way. The validation was performed by three-point bending test on flat specimen with regular octet-truss microstructure both with and without external skin. The test articles were produced in Ti6Al4V and by means of the electron beam melting (EBM) technology. The results obtained are in excellent agreement with the experimental ones, indeed the maximum error is about 3%. All this indicates these methodologies as possible tools for evaluating the performance of such kinds of high-tech structures.

Highlights

Nowadays, the aeronautical and automotive sectors require materials with high mechanical characteristics coupled to low weight, since fuel consumption must be reduced, and pollutant gas emission, without affecting the safety levels [1]
Lattice structures are constituted by several unit cells, that are systematically organized in the space in compliance with a topological sequence [5]
Today additive manufacturing processes have reached a high level of reliability; they can be considered for the manufacturing of lattice structures [6]

Summary

Introduction

The aeronautical and automotive sectors require materials with high mechanical characteristics coupled to low weight, since fuel consumption must be reduced, and pollutant gas emission, without affecting the safety levels [1]. Hernandez-Nava et al [23] proposed an in-depth study of the defects found in lattice structures produced by EBM-type additive techniques, Metals 2022, 12, 410 while Ferrigno et al [24] provided a methodology for embedding, in lattice structures with regular octet cells, generic defects with a random distribution Such approach is useful to evaluate the dependency of the mechanical performance on discrete defects generated during the EBM processes. With only one parameter, i.e., the total mass, it is possible to estimate the diameter that provides a small difference with respect to the experimental data the diameter reduction is a simple method to take into account all geometrical imperfections and internal defects/porosities, from a mechanical point of view. Hereafter a brief description of the adopted numerical model is provided a2n.d1.sNomumeedriectaaliMls oadbeoluDt etshcerispptieocnimens manufactured by the additive process

NTumheerfiucalll-Mpaordaeml Detersiccrimptaiocnro was written entirely in Ansys

Conclusions