Post-yield softening of bending-dominated metal metamaterials

H Z Zhong; C W Li; R Das; J F Gu; M Qian

doi:10.1093/pnasnexus/pgad075

Post-yield softening of bending-dominated metal metamaterials

PNAS Nexus. 2023 Mar 9;2(3):pgad075. doi: 10.1093/pnasnexus/pgad075. eCollection 2023 Mar.

Authors

H Z Zhong^{1

2}, C W Li¹, R Das^{2

3}, J F Gu¹, M Qian²

Affiliations

¹ Institute of Materials Modification and Modelling, Shanghai Jiao Tong University, 800 Dongchuan Road, Minxing District, Shanghai 200240, China.
² Centre for Additive Manufacturing, School of Engineering, RMIT University, 124 La Trobe Street, Melbourne, VIC 3000, Australia.
³ Sir Lawrence Wackett Aerospace Research Centre, School of Engineering, RMIT University, 124 La Trobe Street, Melbourne, VIC 3000, Australia.

Abstract

Post-yield softening (PYS) plays an important role in guiding the design of high-performance energy-absorbing lattice materials. PYS is usually restricted to lattice materials that are stretching dominated according to the Gibson-Ashby model. Contrary to this long-held assumption, this work shows that PYS can also occur in various bending-dominated Ti-6Al-4V lattices with increasing relative density. The underlying mechanism for this unusual property is elucidated using the Timoshenko beam theory. It is attributed to the increase in stretching and shear deformation with increasing relative density, thereby increasing the tendency towards PYS. The finding of this work extends perspectives on PYS for the design of high-performance energy-absorbing lattice materials.

Keywords: bending; laser powder bed fusion; lattice metamaterials; post-yield softening; shear; stretching.