Numerical and experimental investigation of thin-walled bellows considering non-uniform wall thickness under displacement load.

In the hydroforming process, the wall thickness of metal bellows decreases, resulting in a non-uniform phenomenon in which the thickness of bellows decreases with increasing diameter. To describe this phenomenon, the index thinning method was introduced in this paper. Finite element (FE) models were utilized to analyze the non-uniform wall thickness of thin-walled bellows, and the numerical stiffness was calculated through numerical simulation with ABAQUS. The corresponding m (thinning index) value of the bellows model was then determined by comparing the numerical stiffness with the experimental stiffness. For the model with m set to 0.8, the numerical stiffness was found to be 1007.19 N/mm, while the average experimental stiffness was measured as 1000.49 N/mm, with the minimum relative error between the two being 0.67%. Then, the meridional and circumferential stresses of the bellows model were obtained when m was 0.8, and the accuracy of stress results calculated by the FE method was verified by the stress measured in tests, and it also verified the validity of the proposed method. From the perspective of the development of hydroforming technology, the index thinning method could have guiding significance for practical application. [ABSTRACT FROM AUTHOR]