Spontaneous buckling morphology transition of an elastic ring confined in an annular region constraint

This paper studies the spontaneous buckling morphology transition of an elastic ring confined in an annular region constraint. With the increase of uniform axial strain, the ring initially forms a symmetrical blister, and then the blister is compressed, spontaneously inclines and transits to the “S” shape. A theoretical framework based on the minimum potential energy theory is proposed to obtain the critical strain of morphology transition, which matches well with experimental results. The map predicting stable buckling shapes of the ring with different geometrical parameters is demonstrated, which may offer helpful guidance to practical applications, for example, the design of gear-less pump and rotary actuators.