Study of the effective parameters on welding residual stress relaxation in aluminum cylindrical shells under cyclic pressure

摘要

The evaluation of residual stress and its redistribution under cyclic loads are crucial to guarantee the integrity of welded components. In this paper, the effective parameters on welding residual stress relaxation are examined in thin cylindrical vessels due to cyclic pressure. First, the 3D finite element modeling is performed to evaluate the welding residual stress under cyclic pressure with various amplitudes and cycle numbers. Further, the model is verified using experimental stresses through the hole-drilling method. To study the plasticity behavior, two plasticity models are implemented: perfect plasticity and combined isotropic with kinematic hardening. It is concluded that the former leads to greater stress change. In addition, cyclic pressure causes redistribution and even change in the sign of the residual stresses, but this effect can be manifested as either stress relaxation or stress enhancement, depending on the initial residual stress. Moreover, the influence of various geometrical and loading parameters on stress modification is investigated through the Taguchi method. Statistical analysis reveals that an increase in thickness and diameter leads to a higher modified hoop stress, while an increase in maximum pressure leads to a lower modified hoop stress. On the other hand, the modified axial stress increases with an increase in thickness, and decreases with an increase in diameter. Analysis shows that thickness and maximum pressure are the most important parameters on the modified hoop and axial residual stresses, respectively. Finally, useful equations are proposed that can be used to calculate the modified residual stresses in terms of design factors.