scholarly journals CREEP OF A THICKWALLED QUASILINEAR VISCOELASTIC TUBE UNDER A CONSTANT EXTERNAL AND INTERNAL PRESSURE

2021 ◽  
Vol 83 (2) ◽  
pp. 170-187
Author(s):  
L.A. Kabanova ◽  
A.V. Khokhlov
Keyword(s):  
Stress Field ◽  
Internal Pressure ◽  
Creep Curve ◽  
Viscoelastic Model ◽  
Sufficient Conditions ◽  
External Pressure ◽  
Creep Function ◽  
Initial Moment ◽  
Exponential Nonlinearity ◽  
Prolonged Observation

We consider the creep problem for a quasilinear viscoelastic model of a thickwalled tube, loaded with constant internal and external pressure; the material is supposed to be incompressible. An exact solution to this problem was received by one of the authors in previous papers, assuming the state of a tube to be plain deformation; hereby we study properties of this solution for arbitrary material functions of quasilinear viscoelasticity constitutive relation. A criterion of stress stationarity is derived; the stress field of a thickwalled tube under a constant pressure evolves in time in the case of unbounded creep function and arbitrary nonlinearity function, except some particular types. The monotonicity of stress field components is studied: the radial stress monotonicity depends only on internal and external pressure values (for internal pressure, greater than an external one, it is negative and increases in radii). For other stress components, there are derived sufficient conditions of monotonicity. For an exponential nonlinearity function and unbounded creep function, a creep curve is determined to be concave up at the initial moment, and concave down during prolonged observation; the creep curve of a bipower nonlinearity function model may change its convexity. The stressstrain state of a model with a bounded creep function is proved to be bounded.

Fitness for Service Assessments of Bulging and Out-of-Round Structures

2004 ◽  
Author(s):  
Peter Carter ◽  
D. L. Marriott ◽  
M. J. Swindeman
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Model ◽  
External Pressure ◽  
Element Analysis ◽  
Structural Imperfection ◽  
Level 2

This paper examines techniques for the evaluation of two kinds of structural imperfection, namely bulging subject to internal pressure, and out-of-round imperfections subject to external pressure, with and without creep. Comparisons between comprehensive finite element analysis and API 579 Level 2 techniques are made. It is recommended that structural, as opposed to material, failures such as these should be assessed with a structural model that explicitly represents the defect.

A Theoretical and Experimental Analysis of the Bending Behavior of Unbonded Flexible Pipes

2014 ◽  
Author(s):  
Tatiana Vargas-Londoño ◽  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Structural Response ◽  
Experimental Tests ◽  
Theoretical Models ◽  
External Pressure ◽  
Local Behavior ◽  
Flexible Pipes ◽  
Floating System ◽  
Bending Loads

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of the pipe that have to be properly evaluated in order to ensure integrity of the line. Research has been done on the local behavior of flexible pipes under combined axisymmetric loads as well as under bending loads. However, there is a lack of research combining both axisymmetric and bending loads, as also in the study of the strains in the tensile amour layers of the pipes, aspects which are important for the calibration of theoretical models to predict such behavior. Based on that, this study aims to evaluate the local behavior of flexible pipes under combinations of axisymmetric (tension, and internal pressure) and bending loads via a series of experimental tests in a 9.13″ I.D pipe. In the experimental tests, the behavior of the pipe was studied for three load combinations: i) bending combined with tension; ii) bending combined with internal pressure; and iii) bending combined with tension and internal pressure. Based on these tests, the authors obtained the strains in the tensile armor layer, axial elongation due to tension, axial reaction forces due to internal pressure, and deflection due to bending. These measurements were used to calibrate a theoretical model devoted to simulate the pipe’s response, getting accurate results for stiffness and stresses of the pipe in each scenario.

A Conceptual Model of Green HRM Adoption Towards Sustainability in Hospitality Industry

2019 ◽  
pp. 400-421 ◽  
Author(s):  
Yusmani Mohd Yusoff ◽  
Mehran Nejati
Keyword(s):  
Human Resource Management ◽  
Internal Pressure ◽  
Financial Performance ◽  
Human Resource ◽  
Hospitality Industry ◽  
External Pressure ◽  
Resource Based View ◽  
Proposed Model ◽  
Level Of Understanding ◽  
Green Human Resource Management

This chapter seeks to provide a better understanding on the predictors of green human resource management which can result in improved environmental and financial performance across hospitality industry. The proposed model has been constructed from the perspective of external pressure (i.e., normative) and internal pressure (manager's environmental concerns) by using the Institutional Theory and Resource Based View Theory. The chapter examines the antecedents of sustainability in hospitality industry in terms of improved financial and environmental performance. It therefore expands the level of understanding on mechanisms which leads to corporation sustainability. While the chapter is written with a focus on hospitality industry, the proposed model is applicable to corporations across other sectors.

On the response and prediction of multi-layered flexible riser under combined load conditions

2019 ◽  
Vol 36 (8) ◽  
pp. 2507-2529 ◽  
Author(s):  
Mengsha Liu ◽  
J.Y. Li ◽  
Lixin Chen ◽  
J.S. Ju
Keyword(s):  
Numerical Simulation ◽  
Internal Pressure ◽  
Internal Force ◽  
External Pressure ◽  
Prediction Methods ◽  
Flexible Riser ◽  
Content Type ◽  
Combined Load ◽  
Simulation Results ◽  
Load Conditions

Purpose The internal force is more complicated in a combined load case than in a single load case, and the influence of the combined load on the stress cannot be neglected. The purpose of this paper is to study the mechanical behavior of the flexible riser under combined load conditions of tension and internal pressure or external pressure. Design/methodology/approach The mechanical behavior of the flexible riser under combined load conditions is studied by numerical simulation with a nine-layer detailed finite element model. The layers of flexible riser are modeled separately, and the interactions between layers have been taken into consideration in numerical simulation. Findings Under tension and internal pressure or external pressure, the pressure armor will bear extra external pressure because of the squeezing actions between layers caused by tension, and the extra external pressure will increase proportionately with the increase of the tension. Under internal pressure and tension, the internal stress for tension armor was nearly unchanged compared to that under unique tension load, whereas under external pressure and tension, the change of internal stress for tension armor was significant. Prediction methods of internal force for pressure armor and tension armor under pressure and tension are given, and the result from the formula agrees well with the simulation results. Originality/value The prediction methods on the internal force of flexible riser proposed in this study are proven accurate, with numerical simulation results, and the prediction methods are convenient for engineering applications.

Ethical problems related to intravenous fluids in nursing homes

2014 ◽  
Vol 21 (8) ◽  
pp. 890-901 ◽  
Author(s):  
May-Elin T Horntvedt ◽  
Maria Romøren ◽  
Betty-Ann Solvoll
Keyword(s):  
Decision Making ◽  
Nursing Homes ◽  
Internal Pressure ◽  
Collaborative Research ◽  
Ethical Problem ◽  
Organizational Factors ◽  
External Pressure ◽  
Intravenous Fluids ◽  
Research Project ◽  
Ethical Problems

Background: Intravenous fluids and/or antibiotics are applied to only a limited extent in Norwegian nursing homes, and the patients are often sent to hospital in these situations. A transfer and a stay in hospital may be unnecessary strains for frail older patients. Given this background, a collaborative research project was initiated in a Norwegian county in 2009. A teaching programme was developed, which aimed to strengthen the awareness of ethics, assessments and practical procedures related to intravenous fluid and/or antibiotics among healthcare professionals. Objectives: This qualitative study aimed to increase our knowledge of the ethical problems experienced by nursing home nurses in situations related to the administration of intravenous fluids and/or antibiotics. Research design: An exploratory design was used, and five focus group interviews were conducted with 26 registered nurses. A hermeneutic analytic approach was applied. Ethical considerations: This study was reported to the Norwegian Social Science Data Services in May 2010. The Regional Committee for Medical and Health Research Ethics approved the collaborative research project. Findings: The analysis showed that the nurses experienced difficult decision-making situations, which were interpreted as external pressure and internal pressure. External pressure emerged in interactions with patients and relatives. Organizational factors were also interpreted as external pressure. Internal pressure was interpreted as the nurses’ experience of feeling inadequate in situations where it was difficult to protect the dignity of patients. Discussion: These findings correspond with international studies, which show that ethical problems often arise during decision-making situations. Conclusion: In agreement with the definition of an ethical problem, we found that the nurses experienced uncertainty and disagreements about how situations should be managed. External and internal pressures related to intravenous fluids and/or antibiotics in nursing homes have not been reported in previous studies. Thus, these findings merit further exploration.

The Reasons Why Suspects Confess during Custodial Interrogation: Data for Northern Ireland

1992 ◽  
Vol 32 (3) ◽  
pp. 204-212 ◽  
Author(s):  
G H Gudjonsson ◽  
I Bownes
Keyword(s):  
Northern Ireland ◽  
Internal Pressure ◽  
External Pressure ◽  
Police Interrogation ◽  
Factors Associated ◽  
Property Offences

This study looks at the reasons offenders give for having confessed during police interrogation. A number of hypotheses were tested, following the work of Gudjonsson and Petursson (1991) on an Icelandic prison sample. The subjects were 80 offenders who were serving prison sentences in Northern Ireland for violence, sex or property offences. The subjects completed the Gudjonsson Confession Questionnaire. All of the hypotheses tested were supported, indicating that there are three primary factors associated with the reasons why criminals make confessions during interrogation. These factors are referred to as Internal Pressure, External Pressure and Proof. The factors were found to be associated with the type of offence committed and the attitude of the offender towards his confession.

A Study of the Conservatism in ASME BPVC Section VIII Division 2 Opening Design for External Pressure

2019 ◽  
Author(s):  
Barry Millet ◽  
Kaveh Ebrahimi ◽  
James Lu ◽  
Kenneth Kirkpatrick ◽  
Bryan Mosher
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
External Pressure ◽  
The Other ◽  
Finite Element Analyses ◽  
Division 1 ◽  
Section Viii ◽  
Allowable Compressive Stress ◽  
Division 2

Abstract In the ASME Boiler and Pressure Vessel Code, nozzle reinforcement rules for nozzles attached to shells under external pressure differ from the rules for internal pressure. ASME BPVC Section I, Section VIII Division 1 and Section VIII Division 2 (Pre-2007 Edition) reinforcement rules for external pressure are less stringent than those for internal pressure. The reinforcement rules for external pressure published since the 2007 Edition of ASME BPVC Section VIII Division 2 are more stringent than those for internal pressure. The previous rule only required reinforcement for external pressure to be one-half of the reinforcement required for internal pressure. In the current BPVC Code the required reinforcement is inversely proportional to the allowable compressive stress for the shell under external pressure. Therefore as the allowable drops, the required reinforcement increases. Understandably, the rules for external pressure differ in these two Divisions, but the amount of required reinforcement can be significantly larger. This paper will examine the possible conservatism in the current Division 2 rules as compared to the other Divisions of the BPVC Code and the EN 13445-3. The paper will review the background of each method and provide finite element analyses of several selected nozzles and geometries.

Finite Axisymmetric Deformations of Initially Cylindrical Reinforced Membranes

1972 ◽  
Vol 45 (6) ◽  
pp. 1677-1683 ◽  
Author(s):  
A. D. Kydoniefs
Keyword(s):  
Stress Field ◽  
Internal Pressure ◽  
Energy Function ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Incompressible Material ◽  
Parameter System ◽  
Axial Section ◽  
Variable Pitch ◽  
Two Parameter

Abstract We consider the axisymmetrie deformations of an initially cylindrical membrane composed of an elastic, homogeneous, isotropic and incompressible material reinforced with a two-parameter system of perfectly flexible and inextensible helicoidal cords of variable pitch. The undeformed configuration is determined so that the deformed membrane has a given axial section under specified internal pressure. The corresponding stress field and cord tensions are obtained. The solution given is exact and valid for the general form of the strain—energy function.

Research on Residual Strength of Corroded Tubing of Gas Well With Sustained Casing Pressure

2015 ◽  
Author(s):  
Li Sun ◽  
Jianchun Fan ◽  
Xing Meng ◽  
Ximing Zhang ◽  
Yuting Sun ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Residual Strength ◽  
Equivalent Stress ◽  
External Pressure ◽  
Defect Depth ◽  
Gas Well ◽  
Sustained Casing Pressure ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Casing Pressure

Corrosion and sustained casing pressure have serious threats to the integrity of tubing of gas well. Researching the residual strength of corroded tubing has great significance to ensure the safety of gas well. The finite element method was used to study the relationships between residual strength and corrosion defects size, internal pressure, external pressure, axial load. The results show that, for tubing with uniform corrosion, the defect depth, internal pressure and external pressure have greater impacts on the von Mises equivalent stress of tubing, and the defect width and defect length have little effects on it. For tubing with pitting corrosion, the defect depth, internal pressure and external pressure have greater impacts on the von Mises equivalent stress of tubing, while the defect radius has little effect on it. These simulation data were fitted into the functions of residual strength of corroded tubing according to different corrosion morphology types. Both of the verifications of the fitting results show that most of the error between the original calculation data and the fitting calculation data is less than 4%. The fitting formulas can be used conveniently to evaluate the safety of the tubing of gas well with sustained casing pressure.

Long-Term Stress Analysis of Plastic Pipe Reinforced by Cross-Winding Steel Wire

2008 ◽  
Author(s):  
Xiang Li ◽  
Jinyang Zheng ◽  
Yaxian Li ◽  
Ping Xu ◽  
Chunying Zheng ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Volume Fraction ◽  
Axial Strain ◽  
Steel Wire ◽  
Creep Behaviour ◽  
Viscoelastic Model ◽  
Time Dependent ◽  
Hoop Strain ◽  
Steel Wires ◽  
Plastic Pipe

Plastic pipe reinforced by cross helically wound steel wires (PSP) is a new type of metal-plastics composite pipe developed in China. Time-dependent properties of PSP are investigated theoretically and experimentally in this paper. Although the steel wire can carry most of the loading in a liner elastic way, the time dependent behavior shown in the PSP should be further analyzed and described. Based on the structural features of PSP and the viscoelastic behaviors of HDPE in matrix, a three layer viscoelastic model is proposed to calculate time-dependent elastic stresses and strains in the PSP subjected to internal pressure. The experimental results show that the hoop strain decreases slowly, while the axial strain increases by 0.16% in 14000 minutes at constant internal pressure. Good agreement between theoretical results and experimental data shows that the three layer viscoelastic model is able to predict the time-dependent relationship of stress and strain in PSP. The effects of volume fraction and winding angle of the steel wires on the creep behaviour of the PSP subjected to an internal pressure are discussed in the end.

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