Abstract
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.
Highlights
Accepted: 9 December 2021Metal bellows are widely used in industry due to their bearing, vibration absorption, compensation, and sealing performance [1,2,3]
This paper aims to reveal the asymmetry of U-shaped metal bellows under single symmetrical tension and compression loading and its stability mechanism under symmetrical cyclic tension and compression (SCTC)
It was confirmed by the literature [4] that plastic deformation the wave crest and side wall areas, but not in the wave trough area
Summary
Accepted: 9 December 2021Metal bellows are widely used in industry due to their bearing, vibration absorption, compensation, and sealing performance [1,2,3]. The metal bellows expansion joint applied at the pipeline connection compensates for the axial displacement of the pipeline through its own elongation and shortening deformation [4,5]. Due to the influence of the wave structure and the work hardening of metal materials [6], the metal bellows exhibit loading asymmetry and cyclic loading instability during the tensile and compressive deformation processes. This characteristic of metal bellows is often ignored in engineering applications, resulting in large axial displacement and the elastic–plastic deformation of metal bellows. Research on the formability, compensation performance, deformation hardening performance, and fatigue life of metal bellows has been carried out by researchers [7,8,9]
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