Abstarct: This study analyses softening and ratcheting behaviour of Stanless Steel 316 cylindrical shell and St37 cubic shell under pure torsion loading in the form of torque-control and angle of torsion-control. Experimental tests were performed by a servo-hydraullic INSTRON 8802 machine, with use of special fixture converting linear movement to rotational movement. Numerical analysis has been conducted by the combined Chaboche and kinematic model; and accuracy of results were compared with experimental results. Under torsion-control loading with non-zero mean stress, permanent and plastic deformation in successive cycles were accumulated then ratcheting will be observed. Under angle of torsion-control, softening behaviour observed. Softening behaviour in clockwise rotation due to initial rotation is more. Influence of cutout on behaviour of hysteresis loop of prismatic shells under torsion and angle of torsion-control has been studied. It was observed that cutout increase the rate of racheting strain. After sevral cycle of loading, the crack branch and then started to growth and finally lead to decay shells. Softening behaviour can be simulated by isotropic/kinematic model, but this model could not simulate ratcheting behaviour.