Effects of Diameter to Thickness Ratio and External Pressure on the Velocity of Dynamic Buckle Propagation in Offshore Pipelines

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Z. Omrani ◽  
K. Abedi ◽  
A. R. Mostafa Gharabaghi
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Element Model ◽  
External Pressure ◽  
Thickness Ratio ◽  
Small Scale ◽  
Element Analysis ◽  
Models Comparison ◽  
Buckle Propagation ◽  
Exerted Pressure

In this paper, a numerical study of the dynamic buckle propagation, initiated in long pipes under external pressure, is presented. For a long pipe, due to the high exerted pressure, local instability is likely to occur; therefore, the prevention of its occurrence and propagation are very important subjects in the design of pipelines. The 3D finite element modeling of the buckle propagation is presented by considering the inertia of the pipeline and the nonlinearity introduced by the contact between its collapsing walls. The buckling and collapse are assumed to take place in the vacuum. The numerical results of the nonlinear finite element analysis are compared with the experimental results obtained by Kyriakides and Netto (2000, “On the Dynamics of Propagating Buckle in Pipelines,” Int. J. Solids Struct., 37, pp. 6843–6878) from a study on the small-scale models. Comparison shows that the finite element results have very close agreement with those of the experimental study. Therefore, it is concluded that the finite element model is reliable enough to be used for nonlinear collapse analysis of the dynamic buckle propagation in the pipelines. In this study, the effects of external pressure on the velocity of dynamic buckle propagation for different diameter to thickness ratios are investigated. In addition, the mathematical relations, based on the initiation pressure, are derived for the velocity of buckle propagation considering the diameter to thickness ratio of the pipeline. Finally, a relation for the buckle velocity as a function of the pressure and diameter to thickness ratio is presented.

An experimental and numerical study of the mechanical properties of a cross-linked polyethylene subject to low-velocity impacts

2018 ◽  
Vol 233 (8) ◽  
pp. 1604-1618
Author(s):  
Andrew Cummings
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Numerical Study ◽  
Element Model ◽  
Dynamic Mechanical Properties ◽  
Small Scale ◽  
Analysis Model ◽  
Low Velocity ◽  
Element Analysis ◽  
Rate Dependent

The response of a thermosetting cross-linked polyethylene, commercially referred to as Vitrite, has been studied experimentally and numerically. Two different testing programmes have been carried out; the first to characterise the mechanical properties of the material, and the second to provide information to validate a finite element model. Strain-rate dependent stress–strain curves have been obtained to determine the static and dynamic mechanical properties of Vitrite in tension and compression. Guided drop testing of a mass onto small scale samples has been used to study their deformation and rebound response. This has been compared to the deformation results of a finite element analysis model of the drop tests using the data obtained from the material characterisation tests as input to the model.

scholarly journals STUDY ON NONLINEAR PAVEMENT RESPONSES OF LOW VOLUME ROADWAYS SUBJECT TO MULTIPLE WHEEL LOADS / NETIESINĖS KELIO DANGOS PRIKLAUSOMYBĖS NUO MAŽO INTENSYVUMO KELIŲ, VEIKIAMŲ DAUGKARTINĖMIS RATŲ APKROVOMIS, TYRIMAS

2011 ◽  
Vol 17 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Minkwan Kim ◽  
Joo Hyoung Lee
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Asphalt Pavement ◽  
Three Dimensional ◽  
Nonlinear Behavior ◽  
Element Model ◽  
Element Analysis ◽  
Nonlinear Stress ◽  
Low Volume ◽  
Stress Dependent

This paper describes numerical analyses on low volume roads (LVRs) using a nonlinear three-dimensional (3D) finite element model (FEM). Various pavement scenarios are analyzed to investigate the effects of pavement layer thicknesses, traffic loads, and material properties on pavement responses, such as surface deflection and subgrade strain. Each scenario incorporates a different combination of wheel/axle configurations and pavement geomaterial properties to analyze the nonlinear behavior of thinly surfaced asphalt pavement. In this numerical study, nonlinear stress-dependent models are employed in the base and subgrade layers to properly characterize pavement geomaterial behavior. Finite element analysis results are then described in terms of the effects of the asphalt pavement thickness, wheel/axle configurations, and geomaterial properties on critical pavement responses. Conclusions are drawn by the comparison of the nonlinear pavement responses in the base and subgrade in association with the effects of multiple wheel/axle load interactions. Santrauka Straipsnyje aprašoma skaitinė mažo intensyvumo kelių analizė, taikant netiesinį—erdvinį baigtinių elementų modelį. Skirtingi dangų paviršiaus variantai analizuojami siekiant ištirti, kokiąįtaką kelio dangos elgsenai, t. y. poslinkiams ir kelio pagrindo deformacijoms, turi dangų sluoksnių storiai, eismo apkrovos ir medžiagų savybės. Kiekvienas kelio dangos variantas turi skirtingas ratų arba ašies ir geometrinių savybių formas, kad būtų galima išanalizuoti netiesinę plonos asfalto dangos paviršiaus elgseną. Šioje skaitinėje analizėje nagrinėjami netiesiniai įtempių modeliai, kurie buvo taikomi pagrindo sluoksniams, siekiant tinkamai apibūdinti geometrinę kelio dangos elgseną. Baigtinių elementų analizės rezultatai toliau nagrinėjami atsižvelgiant į asfalto dangos storį ar ašies formą ir geometrines savybes, priklausomai nuo kritinės kelio dangos būklės. Išvados buvo gautos lyginant netiesines kelių dangos priklausomybes pagrindo sluoksnyje, atsižvelgiant į jų sąveiką su daugkartine ratų apkrova.

Periodic and Fixed Boundary Conditions for Multi-Scale Finite Element Analysis of Flexible Risers

2016 ◽  
Author(s):  
M. T. Rahmati ◽  
G. Alfano ◽  
H. Bahai
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Element Model ◽  
Small Scale ◽  
Flexible Pipe ◽  
Element Analysis ◽  
Time Saving ◽  
Flexible Risers

In this paper the implementation of two types of boundaries, periodic and fixed in-plane boundaries, for a detailed finite-element model of flexible risers is discussed. By using three-dimensional elements, all layer components are individually modelled and a surface-to-surface frictional contact model is used to simulate their interaction. The approach is applied on several riser models with various lengths and layers. It is shown that the model with periodic boundaries can be effectively employed in a fully-nested (FE2) multiscale analysis based on computational homogenization. In fact, in this model only a small fraction of a flexible pipe is needed for a detailed nonlinear finite-element analysis at the small scale. The advantage of applying periodic boundary conditions in capturing the detailed nonlinear effects and the efficiencies in terms of significant CPU time saving are demonstrated.

Cost-Effective Method of Optimization of Stacking Sequences in the Cylindrical Composite Shells Using Genetic Algorithm

2020 ◽  
Author(s):  
Ehsan Daneshkhah ◽  
Reza Jafari Nedoushan ◽  
Davoud Shahgholian ◽  
Nima Sina
Keyword(s):  
Genetic Algorithm ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Experimental Tests ◽  
Cost Effective ◽  
Element Model ◽  
External Pressure ◽  
Element Analysis ◽  
Cost Effective Method ◽  
Critical Buckling Pressure

Buckling is one of the common destructive phenomena, which occurs in composite cylinders subjected to external pressure. In this paper, different methods to optimize stacking sequence of these cylinders are investigated. A finite element model is proposed in order to predict critical buckling pressure and the results are validated with previous experimental data. Theoretical analysis based on NASA SP‐8007 solution and the simplified equation for cylinder buckling of ASME RD-1172 are presented and discussed. The results of theoretical and finite element analysis and experimental tests are compared for both glass and carbon epoxy cylinders. Using NASA and ASME formulations, optimal laminations of cylinders in order to maximize buckling pressure, are obtained by genetic algorithm method. Suggested laminations and the values of corresponding critical buckling pressure calculated by finite element analysis, are presented and compared in various states. Obtained results show that while predicted buckling loads of finite element analysis are reliable, NASA formulation can be used in a very cost-effective method to optimize the buckling problems.

Finite Element Analysis of Steel Frame Beam-Column Irregular Joints with a Strengthened External Diaphragm

2014 ◽  
Vol 578-579 ◽  
pp. 274-277
Author(s):  
Wei Ning Sui ◽  
Qing Ze Shi ◽  
Zhan Fei Wang ◽  
Xue Bai
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Model ◽  
Thickness Ratio ◽  
Element Analysis ◽  
Panel Zone ◽  
Flange Thickness ◽  
Load Displacement ◽  
Joint Load ◽  
Analysis Models

Finite element analysis methods were conducted to investigate the seismic performance of panel zone at the connection of square steel column and two H-shaped beams with different heigth level by using ABAQUS. Compared with the previous test ,which verifies the correctness of finite element model. The paper sets up a total of 11 finite element analysis models, The changes of the web thickness, thickness of beam flange, diameter-thickness ratio in the finite element analysis models are studied, Which affect the beam end joint load - displacement curves and stress distribution.Studies have showed that: the beam flange thickness ratio and the beam offset ratio has insignificant influence on the load-displacement curves. The diameter to thickness ratio have sharp influence on the load-displacement curves.

A Combined Experimental and Numerical Study of the Effect of Surface Roughness on Nanoindentation

2019 ◽  
Vol 11 (07) ◽  
pp. 1950070
Author(s):  
M. Nazemian ◽  
M. Chamani ◽  
M. Baghani
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Finite Element ◽  
Rough Surface ◽  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Element Analysis ◽  
Three Dimensional Finite Element ◽  
Effect Of Surface

Gold and copper thin films are widely used in microelectromechanical system (MEMS) and nanoelectromechanical system (NEMS) devices. Nanoindentation has been developed in mechanical characterization of thin films in recent years. Several researchers have examined the effect of surface roughness on nanoindentation results. It is proved that the surface roughness has great importance in nanoindentation of thin films. In this paper, the surface topography of thin films is simulated using the extracted data from the atomic force microscopy (AFM) images. Nanoindentation on a rough surface is simulated using a three-dimensional finite-element model. The results are compared with the results of finite-element analysis on a smooth surface and the experimental results. The results revealed that the surface roughness plays a key role in nanoindentation of thin films, especially at low indentation depths. There was good compatibility between the results of finite-element simulation on the rough surface and those of experiments. It is observed that on rough films, at low indentation depths, the geometry of the location where the nanoindentation is performed is of major importance.

Buckle Propagation in Pipelines Under Non-Uniform Pressure

2006 ◽  
Author(s):  
R. Talebpour ◽  
K. Abedi ◽  
A. R. M. Gharebaghi
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Local Buckling ◽  
Internal Flow ◽  
External Pressure ◽  
Numerical Results ◽  
Uniform Pressure ◽  
Element Analysis ◽  
Element Modeling ◽  
Buckle Propagation

Preventing the occurrence of local buckling due to external pressure is one of the main concerns in design of offshore pipelines. However, when a pipeline is designed for deepwater, prevention of the propagation of local buckling along the pipeline has more importance. Therefore, the study of buckle propagation phenomenon and its prevention is a subject of many researches in the past 25 years. Great amount of these researches have focused on appropriate estimation of buckle propagation pressure. In this paper, details of 3-D finite element modeling for buckle propagation simulation are outlined. In order to verify the accuracy and validity of the finite element modeling, the numerical results, obtained from nonlinear finite element analysis have been compared with the results of the experimental study on full-scale models, undertaken by C-FER Technologies, Canada, which have been published by Toscano et al. (2002). Comparison shows that the finite element results have very close agreement with the experimental behaviour. Also, in the present paper, numerical results of Toscano et al. are discussed; and the study shows that the proposed method, outlined in this paper, gives more appropriate results than the proposed method by Toscano et al. In addition, the buckle propagation of pipeline under the uniform external pressure as well as non-uniform pressure, due to the presence of the internal flow (when the pipe is not full of fluid) is studied. The change of buckle propagation pressure is determined by the proposed method.

Finite Element Analysis of Clamp-On Buckle Arrestor for Pipe-in-Pipe Flowlines by Reel-Lay Installation

2008 ◽  
Author(s):  
Jason Sun ◽  
Paul Jukes
Keyword(s):  
Finite Element ◽  
Deep Water ◽  
Pipe Wall ◽  
Mechanical Design ◽  
Local Buckling ◽  
External Pressure ◽  
Design Parameters ◽  
Element Analysis ◽  
Buckle Propagation ◽  
Buckle Arrestors

Development of deep water oil reservoirs are undertaken in the Gulf of Mexico (GoM) where the flowlines are installed in the water depths in excess of 3,050m (10,000ft). Deepwater external pressure becomes so significant that it makes local buckling or accidental collapse propagate along the pipeline. Such propagation will not stop until it reaches a region where the external pressure falls below the propagating pressure or where the pipe wall is strengthened. Field data indicates that once a buckle happens, the flowline could collapse many kilometers instantly. It concludes that buckle propagation could cause substantial economical impact if left uncontrolled. For pipe-in-pipe (PIP) flowline, due to lack of pressure differential, the outer pipe becomes a fragile component in terms of buckle propagation. One way to prevent the propagation of local buckling or collapse is to utilize the buckle arrestors of various types. Clamp-on buckle arrestor is so far the best choice for the flowlines to be installed by the Reel-Lay method. The objective of this paper is to present the results of a finite element (FE) study, to reveal the phenomena of collapsing/propagating of the pipe-in-pipe flowline, and to investigate the effectiveness of Clamp-on buckle arrestor for deep water flowlines. Sensitivities of key design parameters are explored with the purpose of guiding detail mechanical design of the clamp-on buckle arrestor.

The Computation of Accurate Buckling Pressures of Imperfect Thin-Walled Cylinders

2010 ◽  
Author(s):  
Caitri´ona de Paor ◽  
Denis Kelliher ◽  
Kevin Cronin ◽  
William M. D. Wright
Keyword(s):  
Finite Element ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Small Scale ◽  
Thickness Variation ◽  
Geometrically Nonlinear ◽  
Element Analysis ◽  
Highly Sensitive ◽  
Wall Thickness Variation ◽  
Nonlinear Static

The buckling capacity of thin cylindrical shells subject to uniform external pressure is investigated in this paper. Thin cylindrical shells are known to be highly sensitive to geometric and material imperfections such as wall thickness variation, non-circularity and random geometric imperfections. The effect of imperfection on the buckling load is studied using finite element (FE) models and laboratory experiments. Imperfection measurements are taken on small scale steel cans and these measurements are modelled and analysed using a geometrically nonlinear static finite element analysis. The cans are then tested in the laboratory and the results compared with those predicted by the FE models and theory.

scholarly journals Numerical Study of the Active Tendon Control of a Cable-Stayed Bridge in a Construction Phase

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
M. H. El Ouni ◽  
N. Ben Kahla
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Force Feedback ◽  
Numerical Study ◽  
Element Model ◽  
Small Scale ◽  
Cable Stayed Bridge ◽  
Displacement Sensors ◽  
Out Of Plane ◽  
Cable Vibrations

This paper investigates numerically the active tendon control of a cable-stayed bridge in a construction phase. A linear Finite Element model of small scale mock-up of the bridge is first presented. Active damping is added to the structure by using pairs of collocated force actuator-displacement sensors located on each active cable and decentralized first order positive position feedback (PPF) or direct velocity feedback (DVF). A comparison between these two compensators showed that each one has good performance for some modes and performs inadequately with the other modes. A decentralized parallel PPF-DVF is proposed to get the better of the two compensators. The proposed strategy is then compared to the one using decentralized integral force feedback (IFF) and showed better performance. The Finite Element model of the bridge is coupled with a nonlinear cable taking into account sag effect, general support movements, and quadratic and cubic nonlinear couplings between in-plane and out-of-plane motions. Finally, the proposed strategy is used to control both deck and cable vibrations induced by parametric excitation. Both cable and deck vibrations are attractively damped.

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