Search Results (5)

Metal bellows feature a simple structure, high-temperature resistance, corrosion resistance, and strong flexibility for compensation, making them widely used in the aerospace, machinery, and petrochemical industries. Compared to multilayer bellows, single-layer bellows are simpler in structure and forming process, making the performance easier to achieve. The structural parameters of multilayer metal bellows, particularly the number of layers, significantly impact the performance. This study focuses on multilayer U-shaped metal bellows made of 304 stainless steel. Using ABAQUS finite element software, a full simulation of the hydroforming and performance analysis of multilayer U-shaped metal bellows is conducted. This study examines the effects of wall thickness thinning and residual stress distribution caused by hydroforming and explores how structural parameters (including outer diameter, corrugation height, corrugation spacing, and wall thickness) influence axial stiffness and bending performance. The findings provide valuable insights for the design and selection of metal bellows. Full article

Floating liquefied natural gas (FLNG) cryogenic hoses can be employed for the transmission of liquefied natural gas (LNG). Usually, U-shaped metal bellows can be applied as the inner lining of FLNG cryogenic hoses. In installation, positioning and other working conditions, torsion is one of the main loads, and torsional buckling instability is a major failure mode of U-shaped metal bellows of FLNG cryogenic hoses. In the current research, the buckling instability of bellows under torsional loads has been investigated in detail, the mechanical mechanism of deformation in torsional buckling mode of bellows has been analyzed and the influence of the structural design parameters on the stability performance has been summarized. It was seen that the axis of the bellows was presented as a spiral line shape during the torsional buckling stage. At the same time, the torsional buckling properties of toroid and spiral bellows were analyzed. The obtained results showed that the torsional buckling stability of the spiral bellows was weaker than that of the toroid bellows and increase of the spiral angle of the spiral bellows intensified this trend. In addition, the post-buckling analysis of U-shaped bellows under torsional loads was carried out by means of experiments and finite element simulation. It was shown that the results obtained from finite element (FE) analysis in this research presented a relatively accurate critical torque value and a consistent buckling instability mode, compared with the experimental results. On this basis, the effects of common defects such as thickness thinning on the torsional stability of bellows were investigated. Considering the geometric defect of thickness thinning, the error of FE analysis was reduced further, and it was found that the defect could significantly decrease the stability of the bellows. The above analysis results could provide a reference for structural design and post-buckling analysis of bellows. Full article

The U-shaped metal bellows expansion joint compensates for the pipeline displacement by its own deformation. The compensation performance of the metal bellows in the initial stage of tension and compression deformation is unstable. In this paper, the symmetrical cyclic tension and compression (SCTC) process of metal bellows was simulated by ABAQUS software. Then, the SCTC process experiment of metal bellows was completed on the universal material testing machine. The distribution law of axial load with displacement and that of axial stiffness and yield load with cycles of metal bellows were obtained. Finally, the X-ray diffraction peak confirmed the deformation-induced martensite in the wave trough and proved that the plastic strain and hardness values of metal bellows increased with the displacement amplitude. The microstructure in the wave trough area was observed by a Zeiss microscope, and the stability characteristics mechanism of the metal bellows was revealed. The martensite in the wave trough increases the grain boundary area under SCTC loading. The forward movement of the slip band in the grain caused by large deformation reached an equilibrium state with the resistance at the grain boundary, which promotes the macroscopic mechanical properties of the metal bellows to be stable characteristics under SCTC loading. Full article

Having higher capacity to undertake pressures and larger compensation ability compared with the U-shape bellows, toroidal or Ω-shape bellows are being more and more widely used in engineering. The wave-shape and wall thickness reduction of bellows are the most important parameters for measuring the hydroforming quality of the bellows. In order to provide references for actual manufacturing, it is valuable to study the factors influencing the hydroforming process and quality of the bellows. In this paper, finite element simulations of the hydroforming process of a monolayer and single-wave toroidal bellows and a two-layer and four-wave toroidal bellows were carried out. Stress and strain distributions before and after unloading were analyzed and the wave height and wall thickness reduction were examined. The numerical results were verified by the actual hydroforming measurements. In addition, ranges of the significant structural or operating factors for producing better bellows were studied and a formula to compute the wall thickness reduction was fitted based on the sufficient numerical results of the hydroforming simulations. Full article

An expansion joint is mainly composed of bellows and other components; it is attached on a container shell or pipe to compensate for the additional stress caused by temperature differences and mechanical vibrations. In China, the expansion joint fatigue tests are often used to assess the quality of products. After fatigue tests, convolution pitch will be changed. The amount of change is an important index that can be used to evaluate bellows expansion joints. However, the convolution pitch detection is mainly done manually and randomly by inspection agencies before shipping to the end users. This common practice is not efficient and is often subjective. This paper introduced a novel method for automatically detecting the change of the convolution pitch based on a laser line scanner and data processing technology. The laser line scanner is combined with a precision motorized stage to obtain the point cloud data of the bellows. After denoising and fitting, a peak-finding algorithm is applied to search for the crest of a convolution. The method to find the convolution pitch and the decision that needs to be made to ensure product eligibility are described in detail. A DN500 expansion joint is used as a sample to illustrate the efficiency of the system. The application of the technique intuitively allows a higher precision and relative efficiency in quality inspection of bellows expansion joints. It has also been implemented in the Special Equipment Safety Supervision and Inspection Institute of Jiangsu province with great success. Full article