Elastic and elasto-plastic analysis of Ti6Al4V micro-lattice structures under compressive loads

Abstract

This article aims to study the modeling and simulation of Ti6Al4V micro-lattice structures under the same compressive loads. Initially, five distinct unit cell topologies (Grid, X, Star, Cross, and Tesseract) were used to design lattice structures. For the modeling of these lattice structures, both three-dimensional wireframe and solid (homogeneous and heterogeneous gradient) meshing were employed. However, the geometric design parameters, such as strut length, strut diameter, and, in particular its configuration (5 × 5 × 5 array), have been assessed as the same for all types of lattice structures. Here, the finite element (FE) modeling approach is used to evaluate the elastic and elasto-plastic behaviors of these structures due to subjected uniaxial compressive loading. The FE results have been validated in previously reported experimental data and have been well comprehended. The static linear and nonlinear FE method formulations are based on the Timoshenko beam theory and Johnson–Cook damaged model, which describe the elasto-plastic behavior. The FE simulations results (linear and nonlinear) were studied and it was shown that Star lattice structure has high stiffness value at low porosity, compared to the other lattice structures. Hence, to further determine the optimum variables (strut diameter –S_d and pore size –PS) for the Star unit cell-based lattice structures, the Taguchi-based optimization technique with L9 orthogonal array was used. In addition, a linear regression model was developed to estimate the maximum initial yield stress for the optimum variables. Finally, the same configuration of Star lattice structures was designed by the heterogeneous solid gradient mesh approach with two swapping conditions, ‘A’ and ‘B.’ These models were employed to perform linear static FE simulations. Therefore, the swapping condition and the type of gradient-based lattice structures, possessing high and low compressive stresses, were identified.