ZHANG J Y, ZHANG X Z, ZHANG Y N, et al． Study on the stress state of multi-layer vessels considering random pre-tightening forces[J]. Journal of Henan Polytechnic University( Natural Science)， doi: 10.16186/j.cnki.1673-9787. 2026010046.

doi: 10.16186/j.cnki.1673-9787. 2026010046

Received： 2026-01-21

Revised： 2026-03-17

Online： 2026-04-23

Study on the stress state of multi-layer vessels considering random pre-tightening forces (Online)

ZHANG Juyin1, ZHANG Xuezong2, ZHANG Yongnan2, WANG Xueping1, XUE Ruiyuan2, LI Linbin2

1. Gansu Special Equipment Inspection and Testing Institute, Lanzhou 730050, Gansu, China;   2. School of Petrochemical Engineering，Lanzhou University of Technology，Lanzhou 730050, Gansu, China

Abstract: Objectives To ensure the long-term safe and stable operation of the multilayer wrapped vessel and to provide a theoretical basis for safety assessment throughout its life cycle, this study investigates the real stress distribution characteristics of multilayer vessels under loading. Methods A hydraulic pressure gradient test was conducted on a multilayer wrapped high-pressure reactor, during which discrete strain data on the outer surface of the cylinder were measured. Based on these measurements, a finite element model incorporating detailed geometric features of the layered plates was established. The discrepancies between theoretical solutions and experimental measurements after loading were compared to evaluate the influence of interlayer pre-tightening forces on stress distribution. Subsequently, a cylinder model considering randomly distributed interlayer pre-tightening forces was developed. By combining the stress variation characteristics at discrete measurement points during the hydraulic test with simulation results that account for pre-tightening effects, the closure behavior of interlayer gaps and the overall stress distribution pattern of the multilayer vessel were investigated. Results The results indicate that the factory hydrostatic test can effectively close the initial gaps between layers and promote cooperative load-bearing among the multilayer plates. However, under the combined effects of non-uniform pre-tightening forces and internal pressure, the stress distribution of the cylinder exhibits significant non-uniformity and random fluctuations in both radial and circumferential directions. This complex stress state not only increases the risk of localized plastic deformation or microcrack initiation but may also induce ratcheting effects, thereby significantly reducing the fatigue life of the vessel under cyclic loading. Conclusions The stress state of multilayer wrapped vessels is significantly influenced by the random pre-tightening forces introduced during manufacturing, resulting in load-bearing behavior fundamentally different from that of uniform single-layer cylinders. Therefore, manufacturing processes should be improved to enhance the uniformity of pre-tightening forces. To ensure safe operation during service, appropriate operating pressure regulations should be established to mitigate the accumulation of cyclic damage. In addition, regular inspections must be strengthened, with particular attention paid to regions exhibiting high stress oscillations to enable early damage detection and monitoring.

Key words: multi-layer wrapped vessel; hydrostatic test; stress state; pre-tightening force; fatigue life; non-uniformity