A PROMISING METHOD FOR ENHANCING RESISTANCE OF PRESSURE-VESSELS TO BRITTLE-FRACTURE

The purpose of the present work was to study the influence of differen t regimes of overloading of pressure vessel steels in different states which correspond to the steel properties at the beginning of the reac tor operation and at different degrees of embrittlement (simulated by thermal treatment). The experiments were performed on 25-, 50-, 150-mm -thick specimens with short and long cracks of various shape in the te mperature range 293-623 K corresponding to the service temperature ran ge of those steels. The following factors were investigated: contribut ion of different mechanisms (residual stresses, strain hardening, crac k tip blunting) into the enhancement of the brittle fracture resistanc e of steels after warm prestressing; stability of the warm prestressin g positive effect during subsequent exposure of those steels to differ ent service loading conditions; size effect on optimal regimes of ther momechanical prestressing and on the brittle fracture resistance chara cteristics of the steels studied after warm prestressing. An approach is proposed for the prediction of the increase in the brittle fracture resistance of steels with cracks after warm prestressing.