Research on Mechanical Properties of Negative Stiffness Torsion Metastructures

The negative stiffness metastructures provide a novel design strategy for reusable protective devices with the nondamage buckling energy dissipation mechanisms. However, the weak cushioning capacity and the measly overloading protection restrict the practical applications. To enhance the energy dissipation and maximum allowable deformation, a negative stiffness torsion metastructure was developed with substructures including buckling hinged beams and inclined beams. Through introduction of compressiontorsion coupling effects, the stress concentration caused by overload can be alleviated. Based on a series model for the negative stiffness torsion element, a strategy to control the mechanical properties was proposed through design of the matching relations of stiffnesses. Snapthrough behaviors and hysteresis phenomena can be obtained on the nonoverlapping loading and unloading curves, to greatly improve the energy dissipation capacity. The optimization of geometric parameters and stiffness relations increases the maximum equivalent compressive strain of the negative stiffness torsion metastructure by 71%. Additionally, compared to the traditional buckling beam metastructures with the same number of layers, the negative stiffness torsion metastructure can double in the energy dissipation capacity.