On the flip-flop mode of dynamic buckle propagation in tubes under external pressure

Published on Oct 1, 2021in Extreme Mechanics Letters4.806
· DOI :10.1016/J.EML.2021.101378
L. H. Lee9
Estimated H-index: 9
(University of Texas at Austin),
Stelios Kyriakides70
Estimated H-index: 70
(University of Texas at Austin),
Theodoro A. Netto16
Estimated H-index: 16
(UFRJ: Federal University of Rio de Janeiro)
Sources
Abstract
Abstract null null Buckle propagation in offshore pipelines is a catastrophic mode of failure critical to the design and operation of such structures. The collapse of a locally weakened section in the pipeline can initiate a buckle that travels at high velocity, flattening long sections of the structure. The propagating buckle velocity increases with the ambient pressure and, as the collapse pressure of the pipe is approached, propagation switches to the flip-flop mode — first reported in Kyriakides and Babcock [1979]. In this letter, the problem is revisited; new experiments that capture the dynamic buckle propagation and the formation of a flip-flop are first presented, followed by numerical simulations. The combined results further elucidate the dynamics of buckle propagation and the unique flip-flop mode.
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#1Stelios Kyriakides (University of Texas at Austin)H-Index: 70
#2T. A. Netto (University of Texas at Austin)H-Index: 6
Abstract A combined experimental and analytical study of the dynamic propagation of buckles initiated in long pipes under external pressure is presented. The experiments involve measurement of the steady-state velocity of buckles initiated in stainless steel tubes with D / t =27.9. Results from tubes pressurized by air or water are presented for pressure levels ranging from the propagation pressure to the collapse pressure of the tube. The buckle velocity in air was found to be significantly hig...
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#1T. A. Netto (University of Texas at Austin)H-Index: 6
#2Stelios Kyriakides (University of Texas at Austin)H-Index: 70
Abstract A design methodology for integral buckle arrestors for deepwater pipelines was presented in a previous study (Park TD, and Kyriakides S., International Journal of Mechanical Sciences 1997;39:643–69). It was based on experiments and analyses in which buckles engaged the arrestors quasi-statically. In this two-part paper series, the performance of the same arrestors is reevaluated under the more realistic dynamic buckle propagation conditions encountered in the sea. The experimental progr...
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#1T. A. Netto (University of Texas at Austin)H-Index: 6
#2Stelios Kyriakides (University of Texas at Austin)H-Index: 70
Abstract In the second part of this study we present models for simulating the quasi-static and dynamic propagation and arrest of buckles in pipelines. The models are developed within the framework of the nonlinear finite element ABAQUS and are used to simulate the quasi-static and dynamic arrest experiments in Part I. They are based on finite deformation kinematics and properly treat the contact that develops in the collapsed tube behind the propagating buckle. In the quasi-static model, the tu...
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#1T.-D. Park (University of Texas at Austin)H-Index: 3
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#1J. Y. Dyau (University of Texas at Austin)H-Index: 3
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Abstract Local imperfections induced in long tubes subjected to high external pressures can lead to local collapse, from which a propagating buckle can be initiated. This can result in catastrophic collapse of large sections of the structure. The propagation pressure is the lowest pressure at which such a buckle will propagate. For common structural metal tubes with diameter-to-thickness ratios of less than 100, the propagation pressure is typically half an order of magnitude lower than the coll...
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#1J. Y. Dyau (University of Texas at Austin)H-Index: 3
#2Stelios Kyriakides (University of Texas at Austin)H-Index: 70
Abstract It is well known that long cylindrical shells used in many practical applications involving external pressure loading collapse catastrophically due to a limit load instability. The limit load is due to interaction between geometric nonlinearities and material nonlinearities due to plasticity. This paper addresses the mechanism of collapse triggered by the limit load instability. It is found that following the limit load the collapse quickly localizes to a section of the shell a few diam...
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#1Stelios KyriakidesH-Index: 70
If an offshore pipeline locally buckles in the presence of sufficiently large external pressure, a propagating buckle is initiated. The buckle propagates along the pipeline until it encounters a region of adverse conditions -- low pressure or an arresting device. The lowest pressure at which a buckle propagates is defined as the Propagation Pressure. An experimental study of this quantity is presented and a semiempirical expression derived by examining various models of the phenomenon. The dynam...
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#1Stelios KyriakidesH-Index: 70
#2C. D. Babcock (California Institute of Technology)H-Index: 16
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#1Ruoxuan Li (IST: Instituto Superior Técnico)
#2C. Guedes Soares (IST: Instituto Superior Técnico)H-Index: 87
Abstract null null A numerical simulation study explores the effects of initial defects on the collapse strength of pipelines under external pressure, with a focus on the coupling effect of multiple initial defects. The collapse strength of pipelines with only one initial defect is studied and the effects of the length and amplitude of the defect are determined. Then, pipelines with multiple initial defects are analysed and the effect of the distance between two initial defects is investigated. ...
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