Torsion is a method to mechanically stress a deformable solid using a movement around an axis causing an angular displacement of the planes perpendicular to it.
The torsion of a revolution cylinder clamped at one of its ends produces pure shear stresses.
These stresses are at a maximum around the periphery and at zero along the axis.
They are uniformly distributed along the axis, and vary linearly with along a radius.
The capacity of the material to withstand torsion is given by the maximum admissible shear resistance which can be calculated on this type of cylindrical sample.