A thin-walled tube of original thickness to and outer radius Ro just fits over...

A thin-walled tube of original thickness t_o and outer radius R_o just fits over a rigid rod of radius r_o. Employ the Lévy–Mises relations to verify that the axial load the tube can sustain before instability occurs is represented by

Assume the tube–rod interface to be frictionless. Use as the true stress–true strain relationship of the tube material in simple tension.