A novel autofrettage method for strengthening and design of thick-walled cylinders

• A new method of autofrettage is introduced and developed for the thick-walled cylinders.
• The strengthening and design of a thick cylinder is done using the proposed autofrettage method.
• The proposed method gives more uniform stress distribution than the conventional method of pressure autofrettage.

In this paper, autofrettage of the thick-walled cylinders is investigated based on a new method named “rotational autofrettage”. The method is inspired from this fact that the cylinders under a large enough angular velocity can experience elastoplastic deformations and the residual stresses. Prior to industrial uses of cylindrical vessels, the process of autofrettage is done by applying an angular velocity which generate the residual stresses. The best angular velocity for the autofrettage operation is selected such that the equivalent and hoop stresses are more uniformly distributed throughout the wall thickness than the case of non-autofrettage. For this purpose, an exact elastoplastic analytical solution is obtained for a rotating thick-walled cylinder made of elastic-perfectly plastic material using Tresca's yield criterion with considering Bauschinger effect. In order to evaluate the performance of the proposed autofrettage approach, the results are compared with those of the routine approach of pressure autofrettage. It was observed that the stress distribution obtained from the proposed method is more uniform rather than the approach of pressure autofrettage. Finally, the optimum geometrical dimensions for a thick-walled cylinder are obtained where large internal pressures have to be withstood.

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