Multiaxial static strength of a 3D printed metallic lattice structure exhibiting brittle behavior

Abstract

This paper focuses on numerical the prediction of multiaxial static strength of lattice structures. We analyze a body-centered cubic cell printed with Selective Laser Melting in AlSi10Mg aluminum alloy. Parent material is experimentally characterized, and the Gurson-Tveergard-Needleman (GTN) damage model is calibrated to predict failure in numerical simulations. The GTN model is used to predict failure of the lattice structures exhibiting brittle localized fracture, and it is validated through static tests. The results of experimental tension/ compression monotonic tests on lattice samples are compared with the results of numerical simulations performed on as-built geometry reconstructed by Xray computed tomography, showing a good correlation. Combining the damage model with computational micromechanics, multiaxial loading conditions are simulated to investigate the effective multiaxial strength of the lattice material. Yielding and failure loci are found by fitting a batch of points obtained by some multiaxial loading simulations. A formulation based on the criterion proposed by Tsai and Wu (1971) for anisotropic materials provides a good description of yielding and failure behavior under multiaxial load. Results are discussed, with a specific focus on the effect of as-built defects on multiaxial strength, by comparing the resistance domains of as-manufactured and asdesigned lattices.

Effective Mechanical Properties of AlSi7Mg Additively Manufactured Cubic Lattice Structures

“…Previous studies 51 , 59 , 62 come to similar results and evidence the shortage of ideal FE models in describing a failure behavior that is highly affected by stress concentrations. Nevertheless, purpose of the present contribution is to identify a straightforward approach for the prevision of the mechanical response, in all the cases where a microtomography and nonideal FE modeling might not be compatible with industrial needs.…”

Compressive creep buckling of single cell metamaterial at elevated temperatures

“…26,27 If present within the thin struts of metamaterials, large pores have the potential for catastrophic impact on strut strength, ensuring premature failure. 28 Therefore, to understand the size, geometry, and distribution of the porosities in AM specimens, X-ray computed tomography (XCT) was performed on a strut of the as-printed FCCZ lattice. To ensure that sufficient flux of X-ray transmits through the thickness of the specimen, a Z strut with a diameter of 1.15 mm and length of 3 mm cut from a FCCZ was used.…”

“…AM specimens, particularly without a post‐build hot‐isostatic pressing process, are known to have larger and a greater number of pores than their wrought counterparts 26,27 . If present within the thin struts of metamaterials, large pores have the potential for catastrophic impact on strut strength, ensuring premature failure 28 . Therefore, to understand the size, geometry, and distribution of the porosities in AM specimens, X‐ray computed tomography (XCT) was performed on a strut of the as‐printed FCCZ lattice.…”

Response of an aluminium Schwarz triply periodic minimal surface lattice structure under constant amplitude and random fatigue

“…The grips are designed so as to make possible the application of both tension and compression loads. The base material is the aluminium alloy AlSi10Mg, whose main static properties are listed in Table 1 [45]. Specimens were printed with the vertical axis aligned with the building direction, by means of Selective Laser Melting with a SLM-Solutions (Lubeck, Germany) 280 v1.0 printer, with a laser power of 350 W and scanning speed of 1150 mm/s.…”

“…Table 1 -Static properties of AlSi10Mg base material [45] and Schwarz primitive lattice structures (relative density 22%): elastic modulus E, yielding limit σy, ultimate tensile strength U T S and strain at failure ε f…”