Characterisation and constitutive model of tensile properties of selective laser melted Ti-6Al-4V struts for microlattice structures

Abstract

Predicting the mechanical performance of selective laser melted (SLM) microlattice structures requires the constitutive data of the parent solid material in the struts. This work first characterised the cross-sectional features of individual SLM Ti-6Al-4V struts. The direct examination revealed the non-linear relation between the equivalent diameter and the Feret diameter of a strut, which was quantified by an empirical equation. The equation considering surface roughness effects allowed the non-destructive determination of the equivalent diameter using the directly measured Feret diameter prior to tension testing. Uniaxial tension experiments were then performed to accurately measure the constitutive behaviour of SLM Ti-6Al-4V struts, with the strain history tracked and recorded using high resolution imaging. It was found that the strut diameter ranging 300-1200 µm has a negligible effect on the stress-strain response. The strain hardening and fracture behaviour of the SLM Ti-6Al-4V can be quantitatively described using the Johnson-Cook models with damage. The constitutive models were finally validated by the 3D finite element model and experiments of uniaxial compression on an SLM microlattice structure.The methodology presented here can accurately characterise and formulate the constitutive behaviour of SLM metallic struts for microlattices.

Comparison of Compression Performance and Energy Absorption of Lattice Structures Fabricated by Selective Laser Melting

“…The Johnson–Cook model of SLM Ti6Al4V was obtained from the previous work. [ 41 ] The lattice model was meshed with tetrahedron elements. The uniaxial compression was applied, and the conventional contact with a friction coefficient 0.06 was used for all external contact surfaces.…”

Study of Size Effect on Microstructure and Mechanical Properties of AlSi10Mg Samples Made by Selective Laser Melting

“…Uniaxial tensile tests were conducted at room temperature using an Instron 5985 universal machine according to the methods used from [27], and the crosshead speed was set at 1.0 mm/min. The axial displacement was measured using an infrared video extensometer (Instron AVE 2.0, INSTRON, Boston, MA, USA), and its precision was 0.5 per thousand.…”

Microstructure, Mechanical Properties, and Constitutive Models for Ti–6Al–4V Alloy Fabricated by Selective Laser Melting (SLM)

“…The resulting mechanical features of SLMed Ti-6Al-4V should be distinct. Furthermore, there are only a few comparatively systematic research studies on constitutive modeling of SLMed metals and alloys, such as Ti-6Al-4V [18,19]. Lu et al [20] established a three-dimensional (3D) thermomechanical coupled finite element model for laser additive manufacturing (LAM) of Ti-6Al-4V, discussed the sensitivity of the mechanical parameters published in the literature, and pointed out that the material data of Ti-6Al-4V from traditional processes were not suitable for the simulation of LAM.…”

“…The martensite decomposition during compression contributes to a share of stress softening. Hence, the compensation of both strain rate and the temperature was carried out at 900 • C-10 −2 s −1 as shown in Equation (18). The prediction by the modified Arrhenius model and measured stresses are depicted in Figure 10.…”