Energy absorption capacity of NiTi lattice structure (1st report: Evaluation of stiffness and strength of the structure by considering the effective length of the strand)

Abstract

In this study, a method for evaluating the mechanical properties, specifically the initial stiffness and martensitic transformation onset stress, of NiTi lattice structures, Body Centered Cubic(BCC) and Rhombic Dodecahedral(RD) structures, under compressive loading was proposed. In particular, a theoretical evaluation method that takes into account the effective length of the strands constituting the lattice was developed. For both BCC and RD lattice structures, the theoretical solutions for the initial stiffness and transformation stress show good agreement with the finite element (FE) analysis results. In particular, the evaluation proposed in this study is up to three times more accurate than those proposed by other researchers. The variation in transformation stress depends on the difference between the transformation start and finish stresses inherent to the material, as well as the relative density. In addition, for RD structures, accurate prediction can be ensured when the ratio of strand diameter d to the width of the unit-cell L satisfies d/L ≤ 2.0.