The influence of surface plastic hardening on the geometric parameters of circular stress concentrators in plates

A methodology for studying the influence of strengthening treatment on the shape of stress concentrators in the form of through circular holes in plates after surface-plastic deformation has been developed.
Two model problems have been considered:
– determination of the geometric configuration of a circular stress concentrator cut in a rectangular plate subjected to prior surface-plastic deformation;
– determination of the geometric configuration of a circular stress concentrator in a circular cylindrical plate whose surface has undergone surface-plastic deformation.
Phenomenological methods for restoring residual stress fields and plastic deformations in plates after the strengthening procedure are presented. Boundary problems of reconstructing the stress-strain state are reduced to well-posed fictitious thermoelasticity problems. The adequacy of the proposed approaches has been illustrated through computational modeling for a rectangular plate made of EP742 alloy and a circular cylindrical plate made of EI698 alloy.
Profiles of the generatrix of the stress concentrators in plates have been obtained. In the case of prior surface-plastic deformation of the upper surface of a square hinged-supported plate with a thickness of 10 mm, the maximum displacement of the generatrix relative to the initial configuration was approximately 4 μm. It has been shown that with a decrease in plate thickness, the maximum displacement of the formation decreases. In the case of surface strengthening of the circular stress concentrator in the cylindrical plate, the maximum displacement of the stress concentrator formation was approximately 1.4 μm for plates supported by hinges and with rigid fixation of the side surface. It has been demonstrated that with a decrease in the radius of the hole, the displacement of the formation increases.