An analysis of the state of stresses generated by torsion in twisted non-circular bars

One of the main problems that must be solved in the design of the machine components stressed in torsion is to establish their optimum shapes and dimensions in order to resist for a given twisting load. Also, in the case of some parts (crankshafts, ornamental bars, blades of screw propeller for torpedoes) manufactured by using plastic torsion as technologic operation the designer must determine the needed deformation energy. An important factor that has a direct implication on the designing methodology and on the resistance to torsion of these components is the state of stress generated by the twisting load application. Usually, the components that transmit or must support twisting moments are circular or tubular in cross-section, but in certain cases components with other than circular sections can be used. The present paper reviews the main aspects concerning the state of stress generated by elastic and plastic torsion in non-circular bars.