Straight Pipe Cyclic Analyses for Shakedown Verification Code Criteria

2003 ◽  
Author(s):  
Tehemton Bhagwagar ◽  
Robert Gurdal
Keyword(s):  
Cross Section ◽  
Plastic Material ◽  
Temperature Cycling ◽  
Stress Range ◽  
Secondary Stress ◽  
Straight Pipe ◽  
Linear Temperature ◽  
Pipe Cross Section ◽  
Primary Stress ◽  
Asme Code

The analyses performed in this paper are exclusively for a straight pipe subject to a constant primary stress and a cyclic secondary stress, as a result of a bending moment on the pipe cross-section. The constant primary stress is, in each analysis, from a CONSTANT dead-weight load and a CONSTANT internal pressure. The cyclic secondary stress is due to cyclic thermal expansion in the pipe, which is the result of a cyclic top-to-bottom linear temperature difference on the pipe cross-section. This temperature cycling produces a secondary stress range C2 ΔM Do / 2 I. This secondary stress range is either higher, or lower than the 3 * Sm stress limit from the ASME-Code. Twenty-four different cyclic elasto-plastic analyses have been performed for this paper. The same elastic perfectly-plastic material model is used for all twenty-four analyses. An attempt has been made to compare the results from the cyclic elasto-plastic analyses with the ASME-Code NB-3600 Rules and with the Efficiency Diagram developed in France for their Code. The main advantage of the Efficiency Diagram is that the decision whether shakedown occurs, or not, is not only a function of the secondary stress RANGE, but also of the CONSTANT primary stress that exists at that time. A relief to the current ASME-Code rules is suggested for the case of a low constant primary stress (less than Sy / 2).

Method for Selecting Stress States for Use in an NB-3200 Fatigue Analysis

2010 ◽  
Author(s):  
Thomas L. Meikle V ◽  
E. Lyles Cranford ◽  
Mark A. Gray
Keyword(s):  
Time History ◽  
Stress Range ◽  
Total Stress ◽  
Secondary Stress ◽  
Transient Stress ◽  
Automated Method ◽  
Relative Minimum ◽  
Asme Code ◽  
Time Histories ◽  
Stress States

In ASME Code Section III NB-3222.4 fatigue evaluations, selecting stress states to determine the stress cycles according to Section NB-3216.2, Varying Principal Stress Direction, can become a challenging and complex task if the transient stress conditions are the result of multiple independent time varying stressors. This paper will describe an automated method that identifies the relative minimum and maximum stress states in a component’s transient stress time history and fulfills the criteria of NB-3216.2 and NB-3222.4. Utilization of the method described ensures that all meaningful stress states are identified in each transient’s stress time history. The method is very effective in identifying the maximum total stress range that can occur between any real or postulated transient stress time histories. In addition, the method ensures that the maximum primary plus secondary stress range is also identified, even if it is out of phase with the total stress maxima and minima. The method includes a process to determine if a primary plus secondary stress relative minimum or maximum should be considered in addition to those stress states identified in the total stress time history. The method is suitable for use in design analysis applications as well as in on-line stress and fatigue monitoring.

Distinguishing Ratcheting and Shakedown Conditions in Pressure Vessels

2003 ◽  
Author(s):  
W. Reinhardt
Keyword(s):  
Thermal Stress ◽  
Kinematic Hardening ◽  
Pressure Vessels ◽  
Stress Range ◽  
Secondary Stress ◽  
Hardening Models ◽  
Asme Code ◽  
Elastic Shakedown

The nature of the boundary between stable cycling and ratcheting is discussed using several illustrative example scenarios. The examples are analyzed in the context of the elastic methods currently in the ASME Code to demonstrate the conservatism of the existing approach that exists in some cases, and the unconservative estimation that exists in others. It is shown that the limit on the linearized primary plus secondary stress range can be related to conditions for elastic shakedown in certain kinematic hardening models of plasticity, while the limits on thermal stress ratchet address only scenarios similar to the Bree problem.

Comparison Between the ASME Code NB-3600 Piping Design Branch Connection Stress Analyses and Finite Element Analyses

2015 ◽  
Author(s):  
Umar Faraz ◽  
Robert Gurdal
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Branch Pipe ◽  
Finite Element Analyses ◽  
Moment Stress ◽  
Design Rules ◽  
Pipe Cross Section ◽  
Class 1 ◽  
Asme Code ◽  
Stress Analyses

Stresses in Class 1 branch connections that consist of large bore run pipe with a reinforced branch nozzle should rarely be limited by the run–branch interface stresses. The end of the “branch nozzle – branch pipe” interface is the location on the branch nozzle one would expect to see the limiting stress. Therefore, it is important that reasonable Design Rules are maintained in the ASME Code Section III for the stress analyses of the Class 1 Piping branch connections to avoid over-predicting the “run pipe - branch nozzle” interface stresses. This will allow the analysts to concentrate on load reductions needed in a logical manner. In Class 1 Piping Design, the calculation of the branch total stress due to the moments is the result of the sum of the stresses from the run moment and of the stresses from the branch moment with these branch moment stresses being calculated using either the branch pipe cross-section or the branch nozzle cross-section. This in itself is already severe, when compared with other Piping Design Rules for branch connections. In addition, starting with the ASME Code year 2002, the branch-side moment stress is based exclusively on the branch pipe cross-section, which leads to a higher moment stress, and this higher moment stress is still absolutely added to the run-side moment stress. As indicated in that ASME Code year 2002 and beyond, this addition is independent of the length of the branch nozzle reinforcement. This leads to total moment stresses that are the sums of moment stresses that do not occur at all at the same location. The purpose of this technical paper is to compare a) the stresses calculated with the earlier more correct Class 1 Piping methodology from 2001 and before 2001; b) the stresses calculated with the more recent and more severe Class 1 Piping methodology; and c) the stresses from finite-element analyses. Conclusions are provided on what should be done for the future Class 1 Piping Design methodology of branch connections.

Stress Analysis and Structure Optimization for the Opening Flat Cover of Pressure Vessels

2012 ◽  
Vol 538-541 ◽  
pp. 3253-3258 ◽  
Author(s):  
Jun Jian Xiao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Analysis ◽  
Structure Optimization ◽  
Pressure Vessels ◽  
Secondary Stress ◽  
Element Analysis ◽  
Primary Stress ◽  
Flat Cover

According to the results of finite element analysis (FEA), when the diameter of opening of the flat cover is no more than 0.5D (d≤0.5D), there is obvious stress concentration at the edge of opening, but only existed within the region of 2d. Increasing the thickness of flat covers could not relieve the stress concentration at the edge of opening. It is recommended that reinforcing element being installed within the region of 2d should be used. When the diameter of openings is larger than 0.5D (d>0.5D), conical or round angle transitions could be employed at connecting location, with which the edge stress decreased remarkably. However, the primary stress plus the secondary stress would be valued by 3[σ].

Separation of Primary Stress in Finite Element Analysis of Pressure Vessel with the Principle of Superposition

2007 ◽  
Vol 353-358 ◽  
pp. 373-376 ◽  
Author(s):  
Bing Jun Gao ◽  
Xiao Ping Shi ◽  
Hong Yan Liu ◽  
Jin Hong Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Engineering Application ◽  
Total Stress ◽  
Principle Of Superposition ◽  
Element Analysis ◽  
Primary Stress ◽  
The Finite Element Analysis ◽  
Asme Code ◽  
Allowable Load

A key problem in engineering application of “design by analysis” approach is how to decompose a total stress field obtained by the finite element analysis into different stress categories defined in the ASME Code III and VIII-2. In this paper, we suggested an approach to separate primary stress with the principle of superposition, in which the structure does not need to be cut into primary structure but analyzed as a whole only with decomposed load. Taking pressurized cylindrical vessel with plate head as example, the approach is demonstrated and discussed in detail. The allowable load determined by the supposed method is a little conservative than that determined by limited load analysis.

Measuring Flow Pattern Asymmetry of Oil-Water Two Phase Flows Using Multi-channel Rotating Electric Field Conductance Signals

2018 ◽  
Vol 74 (1) ◽  
pp. 25-41 ◽  
Author(s):  
Yuansheng He ◽  
Yingyu Ren ◽  
Yunfeng Han ◽  
Ningde Jin
Keyword(s):  
Electric Field ◽  
Flow Pattern ◽  
Cross Section ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Time Asymmetry ◽  
Pipe Cross Section ◽  
Multi Scale ◽  
Oil Water

AbstractThe present study is a report on the asymmetry of dispersed oil phase in vertical upward oil-water two phase flow. The multi-channel signals of the rotating electric field conductance sensor with eight electrodes are collected in a 20-mm inner diameter pipe, and typical images of low pattern are captured using a high speed camera. With the multi-channel rotating electric field conductance signals collected at pipe cross section, multi-scale time asymmetry (MSA) and an algorithm of multi-scale first-order difference scatter plot are employed to uncover the fluid dynamics of oil-water two phase flow. The results indicate that MSA can characterise the non-linear behaviours of oil-water two phase flow. Besides, the MSA analysis also beneficial for understanding the underlying inhomogeneous distribution of the flow pattern in different directions at pipe cross section.

Non-Linear Stress Analysis of Complex Umbilical Cross-Sections

2002 ◽  
Author(s):  
Svein Sævik ◽  
Knut I. Ekeberg
Keyword(s):  
Cross Section ◽  
Axial Force ◽  
Plastic Material ◽  
Axial Strain ◽  
Development Program ◽  
Full Scale ◽  
Small Scale ◽  
Applied Theory ◽  
Element Formulation ◽  
Material Models

Nexans Norway is, together with Marintek, currently developing a software for detailed analysis of complex umbilical cross-section designs. The software development project combines numerical methods with small-scale testing of involved materials, as well as full-scale testing of a wide variety of umbilical designs, essential for calibration and verification purposes. Each umbilical design is modelled and comparisons are made with respect to global behaviour in terms of: • Axial strain versus axial force; • Axial strain versus torsion; • Torsion versus torsion moment for various axial force levels; • Moment versus curvature for different tension levels. The applied theory is based on curved beam and curved axisymmetric thin shell theories. The problem is formulated in terms of finite elements applying the Principle of Virtual Displacements. Each body of the cross-section interacts with the other bodies by contact elements which are formulated by a penalty formulation. The contact elements operate in the local surface coordinate system and include eccentricity, surface stiffness and friction effects. The software is designed to include the following functionality: • Arbitrary geometry modelling including helical elements wound into arbitrary order; • The helical elements may include both tubes and filled bodies; • Elastic, hyper-elastic, and elastic-plastic material models; • Initial strain; • Contact elements, including friction; • Tension, torsion, internal pressure, external pressure, bending and external contact loading (caterpillars, tensioners, etc.). The paper focuses on the motivation behind the development program including a description of the different activities. The theory is described in terms of kinematics, material models and finite element formulation. A test example is further presented comparing predicted behaviour with respect to full-scale test results.

Application of Thermal Sensors for Determination of Mass Flow Rate and Velocity of Flow in Pipes of Hermetic Systems

2019 ◽  
Vol 826 ◽  
pp. 117-124
Author(s):  
Yurii Baidak ◽  
Iryna Vereitina
Keyword(s):  
Temperature Distribution ◽  
Mass Flow Rate ◽  
Cross Section ◽  
Correction Factor ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Sensors ◽  
Pipe Surface ◽  
Pipe Cross Section

The paper relates to the field of measuring technologies and deals with the enhancement of thermoconvective method when it is applied for the experimental determination of such hydrodynamics indicators as mass flow rate and velocity of flow by their indirect parameters - capacity of the heater and the temperatures obtained from two thermal sensors, provided that they are located on the hermetic piping system surface. The issue of determination of correction factor on heterogeneity of liquid temperature distribution in the pipe cross section depending on pipe diameter and fluid movement velocity was clarified. According to the results of numerical calculations, the dependencies of temperature gradient on the pipe surface and the correction factor on the heterogeneity of the temperature distribution along the pipe cross-section under the heater in the function of the velocity of flow in pipes of different diameters are plotted. These dependencies specify the thermal method of studying the fluid flow in the pipes, simplify the experiment conduction, are useful in processing of the obtained results and can be applied in measuring engineering.

scholarly journals The role of the secondary stress in teaching the English rhythm

2018 ◽  
Vol 7 (3) ◽  
pp. 101-106
Author(s):  
Metin Yurtbasi
Keyword(s):  
Stress Function ◽  
Secondary Stress ◽  
Function Words ◽  
Intended Meaning ◽  
Primary Stress ◽  
Or Groups ◽  
Keywords Stress

In the phonological literature in English, which is a stress-timed language, the existence of at least three levels of stress is usually taken for granted. Words, phrases, utterances or sentences have a prominent element in one of their syllables, which usually correlates with a partner in the same unit, called the secondary stress. It so happens that in multi-syllable words or groups bearing more than two content words, there is also a tertiary stress. Function words neighbouring the content words are usually not stressed or they are reduced. In standard writing, the primary stress is indicated by an acute accent, the secondary stress by a grave accent while the lack of stress is not marked at all. This article proposes that the distinction between primary and secondary stress should have more prevalence in the pronunciation teaching curricula, as they expose the rhythm of English and convey the intended meaning clearly.   Keywords: Stress-timed language, primary stress, secondary stress, tertiary stress, rhythm.  

Experimental study of particle-driven secondary flow in turbulent pipe flows

2012 ◽  
Vol 709 ◽  
pp. 1-36 ◽  
Author(s):  
R. J. Belt ◽  
A. C. L. M. Daalmans ◽  
L. M. Portela
Keyword(s):  
Turbulent Flow ◽  
Secondary Flow ◽  
Stress Tensor ◽  
Reynolds Stress ◽  
Cross Section ◽  
Circular Pipe ◽  
Horizontal Pipe ◽  
Pipe Cross Section ◽  
Reynolds Stress Tensor ◽  
Pipe Flows

AbstractIn fully developed single-phase turbulent flow in straight pipes, it is known that mean motions can occur in the plane of the pipe cross-section, when the cross-section is non-circular, or when the wall roughness is non-uniform around the circumference of a circular pipe. This phenomenon is known as secondary flow of the second kind and is associated with the anisotropy in the Reynolds stress tensor in the pipe cross-section. In this work, we show, using careful laser Doppler anemometry experiments, that secondary flow of the second kind can also be promoted by a non-uniform non-axisymmetric particle-forcing, in a fully developed turbulent flow in a smooth circular pipe. In order to isolate the particle-forcing from other phenomena, and to prevent the occurrence of mean particle-forcing in the pipe cross-section, which could promote a different type of secondary flow (secondary flow of the first kind), we consider a simplified well-defined situation: a non-uniform distribution of particles, kept at fixed positions in the ‘bottom’ part of the pipe, mimicking, in a way, the particle or droplet distribution in horizontal pipe flows. Our results show that the particles modify the turbulence through ‘direct’ effects (associated with the wake of the particles) and ‘indirect’ effects (associated with the global balance of momentum and the turbulence dynamics). The resulting anisotropy in the Reynolds stress tensor is shown to promote four secondary flow cells in the pipe cross-section. We show that the secondary flow is determined by the projection of the Reynolds stress tensor onto the pipe cross-section. In particular, we show that the direction of the secondary flow is dictated by the gradients of the normal Reynolds stresses in the pipe cross-section, $\partial {\tau }_{rr} / \partial r$ and $\partial {\tau }_{\theta \theta } / \partial \theta $. Finally, a scaling law is proposed, showing that the particle-driven secondary flow scales with the root of the mean particle-forcing in the axial direction, allowing us to estimate the magnitude of the secondary flow.

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