Compression Deformation and Fracture Behavior of Additively Manufactured Ti–6Al–4V Cellular Structures

Abstract

Corresponding research was carried out to assess if the porous structures with modified diamond-shaped lattice cells can provide better integrity of the constructions in the case of overloading. The aim of the study is designing the structures with high porosity for the biomedical applications (implants) having good load bearing capacity. Studied lattice structures are based on the modified tetrahedral beam-based cells with spherical reinforcements at the beam joints and variable beam diameter. Samples with a porosity of 50–80% were studied in present research. Structures were additively manufactured from a titanium alloy Ti–6Al–4V using SLM. Sample compression tests were carried out according to the ISO 13314 standard. Loading experiments were carried out and critical parameters extracted from the stress-strain curves. Finite element modeling was carried out for the analysis of the stress and assessment of the potential failure mechanisms. Corresponding hypothesis explaining the appearance of shear bands in porous structures under compression is formulated. Obtained results show that when the sample porosity rises from 50% to 80%, corresponding plateau stress decreases by 13 times, first maximum compressive strength decreases by 12 times, and compression offset stress decreases by 12 times, while the plateau end does not change significantly. The experiments revealed the barrel distortion of the samples geometry, which corresponds to the general knowledge how the friction between the solid compressing surfaces (anvils of the compression testing machine) and the lattice affects the sample deformation. Compression experiments also revealed the formation of shear bands during sample deformation. The stochastic nature of their development suggests that the main reason of shear bands appearing is the initial inhomogeneity of the boundary conditions of the experiment. Suggested modifications of the basic cells show a good potential for achieving regular beam-based lattice structures with high porosity and increased load bearing capacity. More experiments are needed for statistical analysis, and improvements of the loading experiments methodology for better failure mode analysis are planned for the future. © 2021 The Authors.