The effect of the geometric shape of an incision on the relaxation of residual stresses in a surface-hardened cylinder during thermal exposure

A computational method is proposed for predicting residual stress relaxation during high-temperature creep following prior surface plastic deformation of solid cylinders with square and V-shaped notches. A series of parametric simulations was performed for cylindrical specimens made of EI698 alloy (20 mm length, 3.76 mm radius) with various notch geometries: depths of $\{0.1; 0.3\}$ mm for square notches, and depths of $\{0.1; 0.3\}$ mm with opening angles of $\{1^\circ, 5^\circ, 15^\circ\}$ for V-notches. The study demonstrates that residual stress field calculations after notching a strengthened cylindrical specimen require an elastoplastic formulation. The steady-state creep law was employed to simulate residual stress relaxation at 700$^\circ$C over 100 hours. A parametric analysis of notch geometry effects on stress relaxation was conducted. Results indicate that after the complete loading cycle ''hardening treatment at 20$^\circ$C — thermal loading (heating) to 700$^\circ$C — 100-hour creep at 700$^\circ$C — thermal unloading (cooling) to 20$^\circ$C'', despite relaxation, significant compressive residual stresses remain. This confirms the effectiveness of surface plastic strengthening for components with the investigated notch types under high-temperature creep conditions.

solid cylinder, surface plastic deformation hardening, square and V-profile notches, residual stresses, thermal exposure, high-temperature creep, stress relaxation