Buckling of Corroded Torispherical Shells Under External Pressure

2018 ◽  
Author(s):  
J. Błachut
Keyword(s):  
Carrying Capacity ◽  
External Pressure ◽  
Collapse Mechanism ◽  
Load Carrying Capacity ◽  
Collapse Pressure ◽  
Buckling Strength ◽  
Wall Thinning ◽  
Strength Based ◽  
Load Carrying ◽  
Bifurcation Buckling

The current paper examines the effects of corrosion induced wall thinning on buckling of domed closures onto cylindrical vessels. It is assumed that corrosion is axisymmetric and that the wall is corroded on inside, only. The ratio of corroded wall thickness, tc, to the non-corroded thickness, t, is varied between 0.10 ≤ tc/t ≤ 1.0. Both depth of corrosion and its meridional extend are varied during numerical calculations. Three modelling scenarios for placement of corrosion are considered: (i) corrosion confined to the knuckle, (ii) corrosion spanning evenly the knuckle and spherical parts, and (iii) patchtype area positioned at the apex. Numerical results indicate that the following factors influence buckling performance of the dome: (i) meridional position of corroded area, (ii) depth of corrosion itself, and (iii) meridional span of corroded wall. For example, wall thinning of 10 % over 10 % of meridional length causes almost 20 % drop in buckling strength. The largest drop of load carrying capacity is found when the corroded wall is at the knuckle/crown junction. Here it is shown that assessment of strength based on the collapse mechanism is not only wrong but dangerous. For the case of the corroded dome, the collapse pressure overestimates the load carrying capacity associated with asymmetric bifurcation buckling by 40 %.

Lifting Pipeline Buckling under External Pressure Base on Imperfect Reason

2011 ◽  
Vol 337 ◽  
pp. 789-794
Author(s):  
Zhi Jin Zhou ◽  
Zhao Wang ◽  
Yi Min Xia
Keyword(s):  
Carrying Capacity ◽  
Deep Sea ◽  
External Pressure ◽  
Future Application ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Important Conclusion ◽  
Collapse Pressure ◽  
Load Carrying ◽  
Pressure Maximum

The deep-sea pipe is an important part of mining lifting projects in the ocean floor. The uniqueness of environment conditions and design needs to determine the unforeseeable risks and challenges during the laying of pipeline. Based on extensive studies of loads acted on the pipeline and corresponding possible limit states for each installation method, a series of investigations on load-carrying capacity and buckling response of pipes under different loading combinations and various types defects (such as uniform ovalities)were carried out. In these calculations, the collapse pressure has been associated with the pressure maximum of a uniformly deforming long pipe. In experiments in a stiff pressure lifting pipelines, collapse is always localized as shown in Figures 3 and 4.However,because pipe’s localization takes place after the pressure maximum, the collapse pressure yielded by the 2-D analysis suffices for most cases. Exceptions are pipes with local imperfections, in the form of dents. The adequacy of this important conclusion will be demonstrated in the future application, where such predictions are compared to experiments.

Investigation of Burst Pressure in T-Joints With Wall-Thinning by Using FEA

2017 ◽  
Author(s):  
Atsushi Yamaguchi
Keyword(s):  
Carrying Capacity ◽  
Safety Margin ◽  
Pressure Vessels ◽  
Burst Pressure ◽  
Load Carrying Capacity ◽  
Working Pressure ◽  
Element Analysis ◽  
T Joints ◽  
Wall Thinning ◽  
Load Carrying

Boilers and pressure vessels are heavily used in numerous industrial plants, and damaged equipment in the plants is often detected by visual inspection or non-destructive inspection techniques. The most common type of damage is wall thinning due to corrosion under insulation (CUI) or flow-accelerated corrosion (FAC), or both. Any damaged equipment must be repaired or replaced as necessary as soon as possible after damage has been detected. Moreover, optimization of the time required to replace damaged equipment by evaluating the load carrying capacity of boilers and pressure vessels with wall thinning is expected by engineers in the chemical industrial field. In the present study, finite element analysis (FEA) is used to evaluate the load carrying capacity in T-joints with wall thinning. Burst pressure is a measure of the load carrying capacity in T-joints with wall thinning. The T-joints subjected to burst testing are carbon steel tubes for pressure service STPG370 (JIS G3454). The burst pressure is investigated by comparing the results of burst testing with the results of FEA. Moreover, the maximum allowable working pressure (MAWP) of T-joints with wall thinning is calculated, and the safety margin for the burst pressure is investigated. The burst pressure in T-joints with wall thinning can be estimated the safety side using FEA regardless of whether the model is a shell model or a solid model. The MAWP is 2.6 MPa and has a safety margin 7.5 for burst pressure. Moreover, the MAWP is assessed the as a safety side, although the evaluation is too conservative for the burst pressure.

A study into the ability of SPD to restore the buckling strength and modes of rib stiffened panels with simulated stress corrosion cracks

2017 ◽  
Vol 8 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Rhys Jones ◽  
Neil Matthews ◽  
Daren Peng ◽  
Nicholas Orchowski
Keyword(s):  
Experimental Study ◽  
Stress Corrosion ◽  
Carrying Capacity ◽  
Particle Deposition ◽  
Load Carrying Capacity ◽  
Load Path ◽  
Premature Failure ◽  
Content Type ◽  
Buckling Strength ◽  
Load Carrying

Purpose The purpose of this paper is to describe the results of a combined numerical and experimental study into the ability of supersonic particle deposition (SPD) to restore the load carrying capacity of rib stiffened wing planks with simulated stress corrosion cracking (SCC). Design/methodology/approach In this context the experimental results reveal that SCC can result in a dramatic reduction in the load carrying capacity of the structure and catastrophic failure via cracking that tears the length of the structure through buckling. A combined numerical and experimental study then reveals how this reduction, in the load carrying capacity can be overcome by using SPD. Findings This paper is the first to show that SPD can be used to restore the load carrying capacity of rib stiffened structures with SCC. It also shows that SPD repairs can be designed to have only a minimal effect on the local stiffness and hence on the load path. However, care should be taken to ensure that the design is such that premature failure of the SPD does not occur. Originality/value This is the first paper to show that a thin layer of SPD deposited 7,075 aluminium alloy powder on either side of the SCC-simulated stiffener has the potential to restore the load carrying capability of a rib stiffened structure. As such it represents an important first step into establishing the potential for SPD to restore the buckling strength of rib stiffened wing panels containing SCC.

An Experimental Study on the Evaluation of Failure Behavior of Pipe With Local Wall Thinning

2002 ◽  
Author(s):  
Jin Weon Kim ◽  
Chi Yong Park
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
Carrying Capacity ◽  
Axial Length ◽  
Failure Behavior ◽  
Load Carrying Capacity ◽  
Wall Thinning ◽  
Load Carrying ◽  
Deformation Ability ◽  
Local Wall Thinning

The pipe failure tests were performed using 102mm-Sch.80 carbon steel pipe with various simulated local wall thinning defects, in the present study, to investigate the failure behavior of pipe thinned by flow accelerated corrosion (FAC). The failure mode, load carrying capacity, and deformation ability were analyzed from the results of experiments conducted under loading conditions of 4-point bending and internal pressure. A failure mode of pipe with a defect depended on the magnitude of internal pressure and axial thinning length as well as stress type and thinning depth and circumferential angle. Also, the results indicated that the load carrying capacity and deformation ability were depended on stress state in the thinning region and dimensions of thinning defect. With increase in axial length of thinning area, for applying tensile stress to the thinning region, the dependence of load carrying capacity was determined by circumferential thinning angle, and the deformation ability was proportionally increased regardless of the circumferential angle. For applying compressive stress to thinning region, however, the load carrying capacity was decreased with increase in axial length of the thinned area. Also, the effect of internal pressure on failure behavior was characterized by failure mode of thinned pipe, and it promoted crack occurrence and mitigated a local buckling of the thinned area.

On the Choice of Initial Geometric Imperfections in Externally Pressurized Shells

1999 ◽  
Vol 121 (1) ◽  
pp. 71-76 ◽  
Author(s):  
J. Błachut ◽  
O. R. Jaiswal
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Carrying Capacity ◽  
Circular Cross Section ◽  
Load Carrying Capacity ◽  
Geometric Imperfections ◽  
Elliptical Cross ◽  
Buckling Strength ◽  
Load Carrying ◽  
Initial Geometric Imperfections

Localized and global, of eigenmode type, initial geometric imperfections were superimposed on perfect torispherical, ellipsoidal, and toroidal shells of circular and elliptical cross section. Reduction of the load-carrying capacity was then calculated numerically for various geometries and the yield point of material which was assumed to be mild steel. Results show that the buckling strength of torispheres and ellipsoids could be strongly affected by imperfections, but reduction of its magnitude was dependent on the choice of imperfection shape and, more importantly, on the imperfection’s location. Calculations carried out for closed toroids of circular cross section show that these shells are not sensitive to eigenmode-type imperfections, while toroids with elliptical cross sections are sensitive to eigen-imperfections.

Buckling of Barreled Shells Subjected to External Hydrostatic Pressure

2000 ◽  
Vol 123 (2) ◽  
pp. 232-239 ◽  
Author(s):  
J. Błachut ◽  
P. Wang
Keyword(s):  
Carrying Capacity ◽  
Ultimate Load ◽  
Load Capacity ◽  
External Pressure ◽  
Load Carrying Capacity ◽  
External Hydrostatic Pressure ◽  
Buckling Loads ◽  
Load Carrying ◽  
Initial Geometric Imperfections ◽  
Steel Cylindrical Shell

The paper considers barreling of a mild steel cylindrical shell as a way of improving its load carrying capacity when subjected to static external pressure. Numerical results show that the load carrying capacity can be increased from 1.4 to 40 times above the load capacity of mass equivalent cylinders. The effect of end boundary conditions on the ultimate load is examined together with sensitivity of buckling loads to initial geometric imperfections.

Investigation of Burst Pressure in Pipes With Square Wall Thinning by Using FEA and API579 FFS-1

2013 ◽  
Author(s):  
Atsushi Yamaguchi
Keyword(s):  
Carrying Capacity ◽  
Safety Margin ◽  
Pressure Vessels ◽  
Fe Analysis ◽  
Burst Pressure ◽  
Load Carrying Capacity ◽  
Working Pressure ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Load Carrying

Boilers and pressure vessels are heavily used in chemical industrial plants and equipment is inspected periodically for damage. The most common type of damage is wall thinning due to Flow-Accelerated Corrosion (FAC) or corrosion under insulation (CUI). Any damage must be repaired or replaced as necessary. On the other hand, optimization of the time required in order to replace damaged equipment by evaluating the load carrying capacity of pipes with wall thinning is expected in chemical industrial field. In the present study, FE analysis is used in order to evaluate the load carrying capacity in pipes with wall thinning. Burst pressure is a measure of the load carrying capacity in pipes with wall thinning. The pipes subjected to burst testing are carbon steel tubes for pressure service STPG370 (JIS G3454). The examined wall thinning is rectangular, and the eroded depth is half the pipe wall thickness. The burst pressure is investigated by comparing the results of burst testing with the results of FE analysis. Moreover, the reduced maximum allowable working pressure (MAWPr), which is calculated by fitness-for-service (FFS) assessment, and the safety margin for burst pressure are investigated. The burst pressure calculated by FEA agrees well with the test results, except for square wall thinning for circumferential angles of less than 15°. Also, the safety margin of MAWPr based on FFS-1 Part 4 is over 4.0 times for burst pressure.

An Assessment on the Plastic Capacity of Pipe-in-Pipe Systems Under Damage Progression Effect

2021 ◽  
Vol 88 (4) ◽  
Author(s):  
Farhad Davaripour ◽  
Bruce W.T. Quinton ◽  
Kenton Pike
Keyword(s):  
Carrying Capacity ◽  
Phase 1 ◽  
Lateral Load ◽  
External Pressure ◽  
Combined Loading ◽  
Load Carrying Capacity ◽  
Plastic Damage ◽  
Damage Progression ◽  
Structural Resistance ◽  
Load Carrying

Abstract In recent years, pipe-in-pipe (PiP) systems have been employed in an increasing number of subsea projects. According to the previous studies, the external pressure required to develop the initial local buckle on the PiP system is significantly higher than the pressure required to propagate the buckle along the system. In this respect, it is reasonable to investigate a novel topic where the propagation of buckle is induced by a lateral interference load instead of external pressure (e.g., diagonal fishing gear impact). On this subject, the recent studies showed the progression of plastic damage along a single-walled pipe, which is induced by a lateral load, could significantly lower the load-carrying capacity of the pipe. The present study investigates this finding for a PiP solution under a two-phase loading condition: in phase 1, the PiP solution is subject to 75 mm perpendicular indentation, and in phase 2, the resulting plastic damage in phase 1 is translated and induced longitudinally along with the PiP system. Furthermore, using finite element analyses, the effect of combined loading (axial and lateral load) on the load-carrying capacity of the PiP specimen is investigated. The test results show that upon the initiation of damage progression, the load-carrying capacity of the PiP specimen (against the lateral indentation) declines by 10%. Also, the numerical results show that the structural resistance of a PiP specimen against a lateral indentation drops significantly when the inner pipe is subject to axial compression.

A model approach for considering nonmetallic inclusions in the calculation of the local tooth root load-carrying capacity of high-strength gears made of high-quality steels

2019 ◽  
Vol 233 (21-22) ◽  
pp. 7309-7317 ◽  
Author(s):  
D Fuchs ◽  
S Schurer ◽  
T Tobie ◽  
K Stahl
Keyword(s):  
Carrying Capacity ◽  
Nonmetallic Inclusions ◽  
High Strength ◽  
Steel Matrix ◽  
Tooth Root ◽  
Load Carrying Capacity ◽  
Strength Based ◽  
Load Carrying ◽  
Root Strength ◽  
Gear Steels

Demands for higher performance have caused a need for improved component characteristics, e.g. through surface strengthening of gears and increased cleanliness of gear steels. Unfortunately, a resultant drawback is that cracks in such high-strength gears are more often initiated in the material matrix at nonmetallic inclusions and not at the surface. In standardized calculation methods, the degree of cleanliness of steels is not yet directly correlated to the tooth root load-carrying capacity. This paper considers the effects of nonmetallic inclusions in the steel matrix on the tooth root strength based on the theoretical approach of Murakami.

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