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This paper modifies the Gurson-Tvergaard-Needleman (GTN) model, originally limited to depicting the microvoids evolution under monotonic loading, into a constitutive model capable of reflecting the effect of alternating loads, and compiles a VUMAT user subroutine in the Abaqus/Explicit to calculate the microvoids evolution and mechanical behavior of materials under specified stress triaxiality. Before the calculation, the parameters of the modified GTN model were calibrated by the finite-element cell model. The results show that the modified GTN model can rationally describe the mechanical behavior of materials with microvoid evolution under uniaxial and multiaxial cyclic load, and that the void evolution law under cyclic load is closely related to the stress state. The research findings shed new light on damage theories. [ABSTRACT FROM AUTHOR]

Ratcheting deformation is studied on straight pipe made of Z2CND18.12 N stainless steel with local wall thinning subjected to constant internal pressure and reversed bending using finite element analysis. The local wall thinning is located at the center of straight pipe, whose geometry is rectangular cross-section. The effect of depth, axial length and circumferential length on the ratcheting behavior of straight pipe is studied in this paper. Three-dimensional elastic-plastic analyses with ANSYS employed Chen–Jiao–Kim (CJK) kinematic hardening model is carried out to evaluate structural ratcheting behaviors. Results indicate that ratcheting strain is along the center of straight pipe extending to the two ends. The ratcheting strain occurs mainly at hoop direction. Axial ratcheting strain is relatively small. The effects of the depth, axial length and circumferential length of local wall thinning on the ratcheting response are discussed by CJK model. [ABSTRACT FROM AUTHOR]

Ratcheting deformation is studied on straight pipe made of Z2CND18.12N stainless steel with local wall thinning subjected to constant internal pressure and reversed bending using finite element analysis. The local wall thinning is located at the centre of straight pipe, whose geometry is rectangular cross-section. The effect of depth, axial length and circumferential length on the ratcheting behavior of straight pipe is studied in this paper. Three-dimensional elastic-plastic analyses with ANSYS in which Chen–Jiao–Kim (CJK) kinematic hardening model is carried out to evaluate structural ratcheting behaviors. Results indicate that ratcheting strain is along the centre of straight pipe extending to the two ends. The ratcheting strain occurs mainly at hoop direction. Axial ratcheting strain is relatively small. The effects of the depth, axial length and circumferential length of local wall thinning on the ratcheting response are discussed by CJK model. [ABSTRACT FROM AUTHOR]

• Ratcheting effect is studied on lateral nozzle of cylinder with local wall thinning. • Lateral nozzle of cylinder with different defect is under different bending. • Ratcheting boundary of lateral nozzle of cylinder with defect is determined by LMM. Ratcheting effect of pressurized lateral nozzle of cylinder with local wall thinning is studied using Chaboche model in ANSYS. Firstly, the influence of internal pressure, bending loading, loading path, loading history and the different defect sizes on ratcheting effect of pressurized oblique nozzle with local wall thinning is studied in this study. The results indicate that ratcheting strain increased with the increasing of internal pressure and bending moment and is affected by the different loading paths and loading history. Secondly, the effect of different defect sizes such as defect depth, depth length and defect hoop angle on ratcheting behavior of pressurized oblique nozzle with local wall thinning is studied. The results investigated that ratcheting strain of the lateral nozzle of cylinder with local inside wall thinning under cyclic bending increased with the increasing of defect depth, had no relationship with the increasing of defect length and ratcheting strain of the lateral nozzle of cylinder with local wall thinning under cyclic bending increased with the increasing of defect circumferential angle. Finally, the ratcheting boundary of pressurized lateral nozzle of cylinder with different defect size is determined by linear matching method. The results show that the increase of the defect depth could induce a remarkable increase of the reverse plasticity and the ratchet limits of the component, the defect length has a slight effect on the reverse plasticity and ratchet limits of the component and the increase of the defect circumferential angle could induce a remarkable increase of the reverse plasticity and the ratchet limits of the component. [ABSTRACT FROM AUTHOR]