Abstract:Traditional dampers often have low bearing capacity or poor deformation ability. To address these issues, this paper proposes a novel axial compression-tension, U-shaped, and thick-walled metal bellows damper. The performance of the damper can be changed by adjusting different parameters of the bellows. For example, increasing the wall thickness and inner diameter of the bellows can improve the bearing capacity and initial stiffness of the damper, and increasing the number of convolutions of the bellows can increase its ultimate deformation and ductility. The mechanical characteristics of energy-dissipation elements of the damper were analyzed under monotonic and cyclic loads using the finite element method. The influence of six independent variables on the mechanical properties of energy-dissipation elements was studied, including inner diameter, wall thickness, average convolution radius, straight edge length of U-shaped convolution, material yield strength, and convolution number. A method for calculating the ultimate displacement of the damper was developed, and a fitting formula for the ratio of post-yield stiffness to pre-yield stiffness was put forward. In addition, the stress mechanism of the novel damper was revealed, and the restoring force model of the damper was established. A simplified calculation method was developed for U-shaped bellows. The method was later corrected to consider the end convolution effect and then compared to the standard method. The results show that the correction method has higher accuracy than the standard method. The novel damper has a large deformation capacity, excellent ductility, and a full hysteresis loop, clearly showing its outstanding energy-dissipation capability. As the wall thickness increases, the stiffness, yield load, post-yield stiffness, and ultimate load of metal bellows increase significantly. As the number of convolutions increases, the ultimate deformation, ductility, and accumulated energy dissipation of metal bellows increase significantly, while its post-yield stiffness under tension decreases. It is suggested that the average aspect ratio of convolution should not exceed 3.8, and the maximum design displacement should be less than 0.8 times of ultimate displacement when designing the damper.
