Support‐induced restraint effect of thin‐walled tube in a steam generator subjected to combined pressure and bending load

Abstract

A B S T R A C TThe restraint effects of support plates on limit load (LL) are evaluated for thin-walled tubes subjected to combined internal pressure and bending loads. To achieve this goal, three-dimensional (3D) finite element (FE) analyses assuming elastic-perfectly plastic material behaviour are carried out for tubes with various sizes of circumferential cracks. Two crack locations, both the top of the tube sheet (TTS) and transition regions, where circumferential cracks have been found in many steam generators during operation, are considered. FE analysis results show that LLs for the circumferential cracks are significantly affected by the boundary conditions of the tube and that the resulting LL solutions can be simply applied to the practical integrity assessment of steam generator tubes, because the comparison between experimental data and FE analysis results shows a good agreement. E = Young's modulus I = moment of inertia M L = limit bending moment M L FEA = limit bending moment by FE analysis M NL = normalized limit bending moment P L = limit pressure P L FEA = limit pressure by FE analysis P NL = normalized limit pressure R Bend = bend radius of tube R i = inner radius of tube R m = mean radius of tube R o = outer radius of tube S L = limit bending stress t = thickness of tube γ = restraint ratio θ = a half of crack angle λ = normalized bend radius (= R Bend t/R m 2 ) σ f = flow stress σ YS = yield strength σ UTS = tensile strength Correspondence: Y.-J. Kim.