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I'm trying to understand the rationale behind the boundary condition for the problem "Finite bending of an incompressible elastic block". (See here from page 180).

Here we have as Cauchy Stress tensor (see eq. (5.82)):

##T = - \pi I + \mu (\frac{l_0^2}{4 \bar{\theta}^2 r^2} e_r \otimes e_r + \frac{4 \bar{\theta}^2} r^2{l_0^2} e_{\theta} \otimes e_{\theta}- I)##

At page 183, in order to impose

**null traction on the curved boundaries**, the author writes

##T_r(r_i) = T_{r_i + h}=0##

I'm having some troubles on how to interpret geometrically the first one of the two above conditions. I'll add a sketch hereafter.

My guess is that, since #T_r# is the normal stress (i.e. in #e_r# direction), I'd say that the direction of traction is the same in both conditions, and the only thing that changes is that the evaluation is performed at different radius. In my understanding, what the author wants to impose is that those two blue arrows have 0 length, i.e. the normal component of the stress is identically 0. Is this correct?

Is that right?