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Mechanical Engineering Seminar by Dr. Tiantian Li

When: Friday, December 8, 2023
2:00 PM - 3:00 PM
Where: > See description for location
Description: Mechanical Engineering (MNE) SEMINAR

December 8, 2023

2:00 p.m. - 3:00 p.m.

Science & Engineering (SENG), Room 110

and on Zoom: (contact or for Passcode)

Dr. Tiantian Li, Postdoctoral Research Associate
Mechanical and Industrial Engineering, Northeastern University

3D Keyed Octahedron: A New Family of Auxetic Metamaterials with Enhanced Mechanical Properties

Mechanical metamaterials are engineering materials with artificial structures, targeting a specific set of mechanical properties. These properties often conflict with each other. (i) For example, engineering materials often achieve high energy dissipation by sacrificing resilience, as limits their performance and applications under cyclic loading. Designing material with both high resilience and high energy dissipation capability is challenging. (ii) Moreover, most existing 2D and 3D mechanical metamaterial with cellular designs can only achieve orthotropy instead of isotropy. Few of them break this trend as small deformation, while most of them show highly anisotropic under large deformation due to the distortion of micro ligaments/cell walls. Therefore, it is another challenge to design 3D mechanical metamaterial with certain isotropic preserved mechanical properties under large deformation. (iii) Furthermore, most existing mechanical metamaterials have a cellular structure which cannot achieve high energy dissipation under dynamic loading, as limits their performance and applications. Therefore, designing 3D mechanical metamaterial with high impact resistance is still challenging.

To meet the aforementioned challenges, we propose a new design strategy to create a family of mechanical metamaterials: 3D keyed octahedron metamaterial. This metamaterial shows high resilience while achieving large mechanical hysteresis synergistically under large compressive strain. Especially, this metamaterial exhibits ideal isotropy approaching the theoretical limit of isotropic Poisson’s ratio, -1, as rarely seen in existing mechanical metamaterials. In addition, the new class of metamaterial provides wide tunability on mechanical properties and behaviors, including an unusual coupled auxeticity and twisting under normal compression. Interestingly, one two-phase design in this family of metamaterial shows a significantly enhanced impact resistance compared with its conventional cellular counterpart. In summary, these remarkable and unusual mechanical behaviors of this new family of 3D mechanical metamaterial can broad many applications in soft robotics, mechanical actuators and dampers, and engineering materials/systems for energy absorption/impact and vibration mitigation.

Dr. Tiantian Li is a postdoctoral researcher in the department of Mechanical and Industrial Engineering at Northeastern University. Previously, he was a postdoctoral associate at the University of Cambridge. He received his B.E (2010) from Tsinghua University and M.E (2012) from Tsukuba University, both majoring in Material Science. After that, Tiantian Li received his Ph.D. in 2018 from New York State University at Stony Brook, majoring in solid mechanics. The research interests of Dr. Tiantian Li include design of novel architected materials; additive manufacturing; mechanical behavior of materials; micromechanics of deformation and fracture, bio-inspired materials, and mechanical metamaterials.

For more information please contact Dr. Hangjian Ling, MNE Seminar Coordinator (

All are welcome.

Students taking MNE-500 are REQUIRED to attend this seminar!

All other MNE students are encouraged to attend.
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