Fatigue life and reliability analysis of AISI 316L bellows under operating loads

Abstract

Metal bellows are core components for displacement compensation and sealing in pipeline systems, yet are prone to fatigue failure under long-term alternating loads, which impairs pipeline operational safety and service life. To accurately evaluate the fatigue reliability of expansion joint bellows, this paper focuses on hydraulically formed AISI 316L U-shaped seamless bellows and systematically conducts material low-cycle fatigue tests, standard theoretical calculations, finite element simulations, and full-scale fatigue verification tests. Key fatigue parameters of AISI 316L stainless steel were obtained via strain-life tests. Theoretical fatigue life was calculated per GB/T 12777—2019, while a refined FE model was established to simulate fatigue damage responses under multiaxial load coupling. Reliability modeling and statistical analysis of 24 sets of full-scale test data were performed based on the three-parameter Weibull distribution. Results show that the theoretical life is 3650 cycles, the FE-predicted life is 5803 cycles, and the full-scale test median life is 11984 cycles. The fatigue life reaches 8788 cycles at 0.99 reliability. This study constructs a material-simulation-test integrated evaluation system for hydraulically formed bellows, providing theoretical and data support for their structural optimization, material selection, and safe engineering service.