Figure 1.

Radial stress, σ_r, in a butt joint made of two materials having different stiffness (E_i). Graph A shows how σ_r increases as the stiffness of B decreases relative to A, fixing the Poisson ratio of both at 0.4. Graph B shows how σ_r increases as the difference between Poisson ratios of ν_A and ν_B increases at a fixed stiffness ratio of 1. A nominal axial stress σ_z =1 is assumed.