bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reconsidering the Effect of Stress Biaxiality on Pipe Burst (Effect of Axial Loading on the Onset of Plastic Instability)
Authors: Yoshii Kan , Meshii Toshiyuki 
Published: November 2014

Pipe failure under internal pressure loading is understood as due to the onset of plastic instability. Law et al. [1] extended the Considere’s construction [2], which predicts the onset of plastic instability for tensile test specimen, so that it can predict the onset of plastic instability, and thus burst of pipes under internal pressure. They noted that “It is important to note that the reduced stress and strain where instability occurs is not a result of the biaxial stress state, but of the vessel geometry where increased stress comes from both increased inner diameter and reduced wall thickness” [1]. However, they intrinsically assumed that the cylinder plane that experiences instability is in plane strain state. Considering the fact that power plant pipes are often subjected to axial force from sources such as thermal expansion/contraction or fixing, the effect of deviation from the plane strain conditions should be considered.
For this purpose, the onset of plastic instability of the elastic-plastic internally pressurized 1) 2D plane strain pipe, 2) 3D pipe and 3) 3D pipe additionally subjected to axial force, were compared. The results showed that the onset of plastic instability could be monitored at the pressure when pRm−σθt > 0 for all the cases. Here, Rm, σθ, and t are the current mean radius, circumferential stress at mean radius and thickness at pressure p. However, the strain at this instability pressure showed non-negligible change due to presence of axial loading. On this meaning, the biaxiality affected the onset of plastic instability.
Probabilistic Fracture Analysis of Circumferentially Cracked Pipes
Authors: Bhimanadam V. R. , Blom F. J. 
Published: November 2014

In the framework of the R6 development programme on leak before break NRG developped a probabilistic fracture-mechanics model for analyzing circumferential through-walled cracked pipe made of Type 304 stainless steel, subjected to bending loads. An elastic-plastic analysis has been carried out using ANSYS for estimating J-integral as a function of moment load. The validity of the J-integral based on the ANSYS calculations was evaluated by comparison with LBB.ENG2 method and Rahman’s calculations.
Probabilistic fracture analysis has been carried out using ANSYS Probabilistic Design System (PDS) module to find out the failure probability of a pipe as a function of applied moment. These results have been compared with LBB.ENG2 probabilistic calculations, which has been developed using MATLAB.
To achieve high efficiency, accuracy and robustness to design structural component with a low probability of failure, Advanced sampling methods (ADIS) have been used for probabilistic calculations. These ADIS results have been compared with Monte Carlo probabilistic results.
The probabilistic method is subsequently extended to a Leak Before Break case (LBB). It is demonstrated that the probability of failure reduces when more probabilistic data for input parameters is added instead of using deterministic safety factors.
Breech Lock Exchangers, Obtaining Leak Free Performance
Authors: Reeves David , Clover David 
Published: November 2014

High pressure screw plug (also called breech lock) exchangers are arguably the most complicated bolted connection in a refinery. After traveling around the world helping facilities turn these exchangers from chronic leakers (from internal tubesheet and external diaphragm and B style shell leaks) to one of the most reliable heat exchangers in the plant, it is very clear to me that manufacturers, engineers and mechanics struggle to correctly understand the interactions between gaskets, internal pressure, the two circles of external push bolts that are part of A style exchangers and all the internal parts.
Some manufactuers have given up on trying to make these connections operate leak free, and prefer to weld in the tubesheets and diaphragms. This significantly adds to the cost and time needed to open and close these exchangers, as special equipment is needed to machine out the parts and weld them back together again.
There are a handful of equipment manufacturers that build these exchangers, and while there are differences from one manufacturer to the next, once the basic design is understood, the reader should be able understand that they are all basically the same when it comes to the few critical steps that must be followed when opening and closing these exchangers.
In order to obtain reliable leak free performance, all the basic sealing tools must be employed, including:
1. A spreadsheet that will easily analyze the critical variables;
2. Correct gasket selection;
3. Correct assembly procedures that focus on important steps including proper spacing of internal parts and obtaining consistent thread friction;
4. And finally hot torqueing the exchangers after startup.
The goal of this paper to provide the end-user with a good understanding for how parts interact and how the bolted connections function, so that they might also achieve reliable, leak free performance. This paper will explain:
1. How the connections work;
2. Common misunderstanding about screw plug exchangers;
3. Pressure Testing Screw Plug Exchangers;
4. Analyzing the design and calculating the important variables;
5. The key assembly steps that must be included in all assembly procedures;
6. Important design considerations when building new exchangers.
MAI Benchmark Campaign of International Software for Reactor Pressure Vessel Integrity Assessment
Authors: Dautreme Emilie , Remy Emmanuel , Sueur Roman , Fontes Jean-Philippe , Aubert Karine , Soneda Naoki , Yamamoto Masato , Hardin Tim , Gamble Ron 
Published: November 2014

Nuclear Reactor Pressure Vessel (RPV) integrity is a major issue concerning plant safety and this component is one of the few within a Pressurized Water Reactor (PWR) whose replacement is not considered as feasible. To ensure that adequate margins against failure are maintained throughout the vessel service life, research engineers have developed and applied computational tools to study and assess the probability of pressure vessel failure during operating and postulated loads. The Materials Ageing Institute (MAI) sponsored a benchmark study to compare the results from software developed in France, Japan and the United States to compute the probability of flaw initiation in reactor pressure vessels. This benchmark study was performed to assess the similarities and differences in the software and to identify the sources of any differences that were found. Participants in this work included researchers from EDF in France, CRIEPI in Japan and EPRI in the United States, with each organization using the probabilistic software tool that had been developed in their country.
An incremental approach, beginning with deterministic comparisons and ending by assessing Conditional Probability of crack Initiation (CPI), provided confirmation of the good agreement between the results obtained from the software used in this benchmark study. This conclusion strengthens the confidence in these probabilistic fracture mechanics tools and improves understanding of the fundamental computational procedures and algorithms.
An Analysis of In-Flow Fluidelastic Instability Based on a Physical Insight
Authors: Nakamura Tomomichi 
Published: November 2014

Fluidelastic vibration of tube arrays caused by cross-flow has recently been highlighted by a practical event. There have been many studies on fluidelastic instability, but almost all works have been devoted to the tube-vibration in the transverse direction to the flow. For this reason, there are few data on the fluidelastic forces for the in-flow movement of the tubes, although the measured data on the stability boundary has gradually increased.
The most popular method to estimate the fluidelastic force is to measure the force acting on tubes due to the flow, combined with the movement of the tubes. However, this method does not give the physical explanation of the root-cause of fluidelastic instability.
In the work reported here, the in-flow instability is assumed to be a nonlinear phenomenon with a retarded or delayed action between adjacent tubes. The fluid force acting on tubes are estimated, based on the measured data in another paper for the fixed cylinders with distributed pressure sensors on the surface of the cylinders. The fluid force acting on the downstream-cylinder is assumed in this paper to have a delayed time basically based on the distance between the separation point of the upstream-cylinder to the re-attachment point, where the fluid flows with a certain flow velocity.
Two models are considered: a two-cylinder and three–cylinder models, based on the same dimensions as our experimental data to check the critical flow velocity. Both models show the same order of the critical flow velocity and a similar trend for the effect of the pitch-to-diameter ratio of the tube arrays, which indicates this analysis has a potential to explain the in-flow instability if an adequate fluid force is used.
Burst Cause Analysis of the High Temperature Steam Pipe in Heavy Oil Well
Authors: Liu Qiang , Song Sheng-yin , Feng Yao-rong , Duan Bo 
Published: November 2014

The high temperature steam pipe used in one heavy oil well in China burst. This failure pipe was investigated and analyzed by macroscopic analysis, material tests (including chemical composition, metallurgical analysis & mechanical property) and fracture surface scanning electronic microscopy (SEM) analysis. Then it can be concluded that the mechanical properties of the burst pipe accord with related standards, and that the fracture surface is a typical brittle fracture. The herringbone stripes were found on the fracture surfaces and pointed to a fracture source where there were over 1.6mm deep mechanical damages on the pipe surface. After micro hardness testing near mechanical damage area and the nearby substrate, it was found that the toughness of mechanical damage area was low. The expanding diameter of the burst pipe was also investigated. Because the residual water in the pipe was pushed by high temperature steam when the steam was turned on, the speed of water was very fast, and the stress caused by water hammer were higher than yield pressure of the pipe, which is the internal pressure in the pipe and which could produces a maximum hoop stress in the pipe equal to the yield strength of the pipe material, the pipe would be expanded.
The fracture surface is a typical brittle fracture. There are two mechanical damages on the fracture source, and the pipe burst because of the mechanical damages and huge impact of water hammer.
Project STYLE: Post-Test Analysis of Mock-Up3
Authors: Nicak Tomas , Schendzielorz Herbert , Keim Elisabeth , Meier Gottfried , Moinereau Dominique , Le Delliou Patrick 
Published: November 2014

The safety and reliability of all systems has to be maintained throughout the lifetime of a nuclear power plant. Continuous R&D work is needed in targeted areas to meet the challenges of long term operation of existing and new plants designs. The European project STYLE aims to develop and validate advanced methods of structural integrity assessment applicable in the ageing and lifetime management of primary circuit components.
There are three large scale mock-up tests in STYLE each of them dedicated to investigate specific effects. This paper presents the work related to Mock-up3, which is dedicated to investigate influence of cladding on the crack initiation and propagation as well as the transferability of material properties from small scale specimens to a large scale component.
The performed post-test analyses focus on both the further understanding and interpretation of the Mock-up3 test and on the effect of cladding on structural integrity and LBB behavior of reactor coolant pressure boundary components.
Application of Seismic Isolation Systems to High-Raised Houses in Lowland Regions
Authors: Su H.-C. , Tsai C. S. 
Published: November 2014

According to the statistics of the World Bank between years 1970–2010, most economy losses caused by disasters in rich countries were due to floods and earthquakes. The East Asia was the most disastrous area in terms of the death toll caused by earthquakes, which proved that the earthquake is unpredictable. To cope with the crisis of the rise of the sea level, the concept of Marine Cities has been proposed. The most famous one among these concepts is the Dutch amphibious house. People living in earthquake and flood prone areas should be aware of the threat from oceans. Therefore, Ministry of Interior in Taiwan passed the rule 4 No. 2 in the chapter of the design and construction regulations to allow the use of high-raised buildings for reducing life and property loss. Furthermore, the most threatening natural hazards we are facing over a long period of time are floods and earthquakes. When are focusing on the flood resistant buildings in flood-prone areas, we should also aim at the prevention of earthquake disasters.
The purpose of this study is to simulate the seismic behavior of the high-raised structures with different water levels, which are capable of flood resistance. We also propose a new seismic isolation system for these structures and study its efficiency in protecting these types of structures from earthquake damage. It appears from experimental results that the seismic responses of high-raised houses have been significantly reduced by the proposed device. Experimental results also disclosed that the proposed concept in this study is feasible for protecting structures in lowlands from damage resulting from floods as well as earthquakes.
Technical Basis for Proposed Fourth Revision to ASME Code Case N-513
Authors: McGill Robert O. , DeBoo Guy , Cipolla Russell C. , Houston Eric J. 
Published: November 2014

Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to moderate energy, Class 2 and 3 systems, so that safety issues regarding short-term, degraded system operation are minimized. The first version of the Code Case was published in 1997. Since then, there have been three revisions to augment and clarify the evaluation requirements and acceptance criteria of the Code Case that have been published by ASME. The technical bases for the original version of the Code Case and the three revisions have been previously published.
There is currently work underway to incorporate additional changes to the Code Case and this paper provides the technical basis for the changes proposed in a fourth revision. These changes include addressing the current condition on the Code Case acceptance by the US Nuclear Regulatory Commission (NRC), clarification of the Code Case applicability limits and expansion of Code Case scope to additional piping components. New flaw evaluation procedures are given for through-wall flaws in elbows, bent pipe, reducers, expanders and branch tees. These procedures evaluate flaws in the piping components as if in straight pipe by adjusting hoop and axial stresses to account for the geometry differences. These changes and their technical bases are described in this paper.
Large-Eddy Simulations of Turbulence-Induced Vibrations in Annular Pipe Flow
Authors: De Ridder Jeroen , Degroote Joris , Vierendeels Jan , Van Tichelen Katrien , Schuurmans Paul 
Published: November 2014

This paper investigates the turbulence-induced vibration of a circular beam in annular pipe flow. Vibrations induced by turbulence are one of the causes of fatigue and fretting wear in process environments. Although the small-scale vibrations are normally not leading to immediate failure of structural components, they typically result in long term damage.
To predict the amplitude of these subcritical vibrations, current methods require an accurate description of the incident pressure field. However, measurements of cross-spectral pressure fields in annular geometries are rare. Models to describe the pressure field have a tendency to provide only descriptive information, after a series of experiments have been performed. Therefore this paper aims to predict the pressure field numerically, by means of wall-resolved large-eddy simulations.
In order to validate this approach the flow field of an experiment available in literature is computed. In the conditions simulated, water is flowing at 10 m/s in an annulus with a hydraulic diameter of 1.27cm. Pressure correlations obtained from the computations are compared to descriptive models such as the Corcos and Chase models. The numerical power spectra are also compared to experimental spectra.
A Novel High Cycle Fatigue Assessment of Small-Bore Side Branches: Tailor-Made Acceptable Vibration Levels Based on the Remaining Life of Existing Structures
Authors: van Beek Pieter , Pijpers Richard , Macdonald Kenneth , Maljaars Johan , Lunde Knud , Korst Harry , Hansen Frode 
Published: November 2014

In the process systems of offshore installations, welded small-bore side branches can prove vulnerable to high-cycle fatigue failure due to vibrations. This is especially the case for welded connections at tie-in points to the main pipe which are often critical details. International standards and guidelines therefore provide maximum acceptable vibration levels to ensure long term safe operation. In some guidelines, however, these acceptable vibration levels are phrased in terms of screening levels and in practice can be unduly conservative. Process pipework might then unjustly be regarded as unsafe based on measured vibrations in the field. This is especially true for offshore systems, which are characterized by low mechanical damping in the structure. This may result in overdesigned piping or over-conservative operational limits in order to keep vibration levels within the acceptable range. Furthermore, the screening methods and any detailed fatigue assessments typically use established stress-life (S-N) based fatigue design methods where uncertainty exists in the very high-cycle regime.
This paper describes a novel and advanced tailor-made fatigue assessment method whereby acceptable vibration levels are based on maximum acceptable stress ranges for individual side branches. The acceptable stress ranges for each critical welded connection are based on a fracture mechanics analysis of fatigue crack growth. This method also minimizes the cantilevered (overhung) mass of small-bore side branches, whilst remaining safe for long-term operation.
To illustrate the strength of the assessment methodology in practice, this paper describes the application of the procedure to a 2″ side branch connected to a main piping system. A fracture mechanics model and a detailed 3D finite element model are made. By comparing the stress ranges from the fracture mechanics model with the normalized stress ranges obtained from the dynamic FE analysis, maximum acceptable vibration levels for this particular side branch have been derived. The method is validated with experimental modal analysis and strain gauge measurements.
Numerical Modeling of Turbulent Cavitation Flows in Safety Relief Valves
Authors: Couzinet Anthony , Gros Laurent , Pinho Jorge , Chabane Said , Pierrat Daniel 
Published: November 2014

Safety relief valve (SRV) is still the ultimate security component of pressure vessels or piping equipment. It does not take the place of a regulating or control valve but it aims to protect devices and people by preventing damage due to overpressure in the system. This is ensured by discharging an amount of fluid when excessive rising pressure occurs. For the incompressible flows, the discharge coefficient of the relief valve can be modified by cavitation development under specific operating conditions. Then, the sizing of the valve doesn’t correspond to the flow discharged resulting in severe damage.
This study aims to demonstrate the capability of numerical modeling to predict the evolution of discharge coefficient under cavitation conditions. URANS simulations have been performed with ANSYS CFX 13.0 using Shear Stress Transport modeling. A Rayleigh-Plessey model is used to predict the development of cavitation in the relief valve. A modification of the saturation vapor pressure is proposed in the cavitation model to take into account the turbulent effects on the cavitation development.
Additionally a Plexiglas mock-up has been built for flow visualization and two valve discs are used to measure the discharge coefficient or the flow force acting on the valve. Numerical and experimental approaches are compared first by analyzing qualitative results through flow visualization and also by evaluating hydraulic characteristics of the SRV.
Additional Data Concerning French PWR RPV Steel to Evaluate the Relevance of a Size Effect Correction on Toughness in the Ductile-to-Brittle Transition
Authors: Jacquemoud C. , Delvallée-Nunio I. , Nédélec M. , Balestreri F. 
Published: November 2014

In the ductile-to-brittle transition range of ferritic steels, fracture toughness exhibits a size effect. Up to now, in the safety demonstration of the French Reactor Pressure Vessel (RPV) integrity, a size effect correction has been considered by the operator to take into account fracture toughness variation of ferritic steels with crack length. The correction consists in increasing the toughness estimated on the RCC-M curve by a factor which depends on a reference length and on the crack length considered.
IRSN has already examined the relevance of this correction through statistical analysis of toughness results coming from two ferritic steel databases. To complete its evaluation on French RPV steel, IRSN has supported a large experimental campaign on 16MND5 steel at different temperatures in the ductile-to-brittle transition (from −150°C to −50°C), including tests on various Compact Tension (CT) specimen geometries. Specimens with semi-elliptical crack have been also considered.
The results confirm the observations made in its previous study: a size effect exists on mean or median toughness, for the latter more or less in accordance with Beremin theory. Nevertheless, the minimum toughness appears to be independent of the specimen geometry. This indicates that the use of a size effect correction on minimum toughness is not relevant.
Benchmark Evaluations to Compare R6 Calculations to European Engineering Assessment and Leak-Before-Break Methods Based on STYLE Mock-Up Experiments
Authors: Madew Colin , Sharples John , Budden Peter , Lauerova Dana 
Published: November 2014

As part of the recent STYLE European project, three large scale mock-up experiments (Mock-up 1, Mock-up 2 and Mock-up 3) were performed. The Mock-ups were representative of nuclear power plant locations containing welds or cladding and contained an initial defect, either through-wall or surface breaking, and were loaded under four point bending conditions.
Benchmarks based on each of these experiments were launched to investigate current Engineering Assessment Methods (EAMs) and Leak-before-Break (LbB) procedures used throughout Europe and how the application of these methods compare to each other and to the experimental data. Parameters that were specified for the benchmark participants to evaluate included crack opening displacement (COD), critical crack size, limit load, and load vs various amounts of ductile tearing.
This paper presents and compares the results of the calculations performed by the participants in the benchmark. It focuses on the AMEC calculations using R6 and draws conclusions regarding its relative conservatism compared with each of the other methods and through comparison with the results of the Mock-up experiments.