Напружений стан вузла з’єднання колектора з корпусом парогенератора ПГВ-1000М з каверною

Abstract

Представлено розрахунковий аналіз пружно-пластичного напруженого стану вузла з’єднання «гарячого» колектора з корпусом парогенератора ПГВ-1000М з дефектом у вигляді плоскої напівеліптичної каверни, розташованої на внутрішній поверхні патрубка вузла з’єднання в області галтельного переходу. Проведено оцінювання впливу геометричних параметрів каверни на напружений стан в околиці її вершини при моделюванні повторно статичних експлуатаційних навантажень парогенератора.

The paper presents a numerical stress-state analysis of the weldment joining the “hot” header to the PGV-1000M steam generator. This weld joint has a defect in the form of a plane semielliptical cavity located on the inner wall of the nozzle, near the fillet. The numerical elastic-plastic analysis is performed using a three-dimensional model and SPACE-RELAX software. The stress state around the cavity is determined using a specially developed procedure to generate a regular finite-element mesh that is locally refined toward the cavity tip. The finite-element model of the steam generator was fragmented using a two-stage procedure involving the solution of the elastic-plastic problem for (i) the main model and (ii) a fragment of the weld joint with the cavity. The plane cavity with ellipsoidal tip located on the weld joint fillet, in the zone of peak tensile axial stresses determined at the first stage, is modeled. The solution is obtained for the following sequence of service loads on the weld joint: hydraulic testing – unloading – normal operation. The effect of the loading history on the stress state near the cavity is assessed by comparing the normal-operation calculations made with and without regard to the loading history. The effect of the geometrical parameters of the cavity on the stress state near its tip is evaluated during the simulation of repeated static service loads on the steam generator. The distribution of the axial and hoop stresses over the cross-section of the cavity that passes through its front and is perpendicular to the header axis is determined. Plots of the distribution of the axial and hoop stresses ahead of the cavity tip are presented.