Figure 2.

The concept of nonreciprocal elasticity. (a) Linear and nonlinear materials with reciprocal elasticity. The material exhibits the same elastic stress–strain curve under the tensile and compression tests. This material exhibits the same deformation ${ϵ}_t={ϵ}_c$ when subjected to the same axial stress ${\sigma }_0$. (b) Linear and nonlinear materials with nonreciprocal elasticity. The material exhibits two different elastic stress–strain curves under the tensile and compression tests. This material exhibits asymmetric deformation $\mathrm{\Delta }ϵ={ϵ}_c-{ϵ}_t$ when subjected to the same axial stress ${\sigma }_0$.