A Stress Disturbance Barrier on a Circular Torque Tube blocking the End Effects

Knowing that the end effects arising from the end torsional loads will disturb the stress distribution in a torque tube, this paper develops a means of blocking the stress disturbances from the end where a torsional load is applied, such that the stress distributions of the Saint Venant torsion can be maintained. The stress disturbance barrier (SDB) as an end effect shielding barrier is considered installed on an end of a circular toque tube whose material property can be with the cylindrical orthotropy. In general, the SDB is comprised of two layers: the front layer and the blocking layer. The front layer which is optional and directly contacted with the external load is for enhancing the durability, while the blocking layer situated between the front layer and the torque tube body is mainly for blocking the stress disturbances. The analysis is base on the state space formalism, whose uncoupling feature on cylindrically orthotropic materials is benefit for the further extension of the research. It is found that the parameters crucial to determine an effective SDB with a given thickness are the cylindrical orthotropy parameter and the longitudinal shear modulus. The approach of how to determine the proper material constants for having an effective SDB is clearly provided. As shown by the numerical results presented in the examples, an effective SDB of this research can fully block the stress disturbances from the external torsional loads that can be mathematically expanded by power series.