bluuebunny/crossref_metadata_2025 huggingface dataset:
Full Scale VIV Response Measurements of a Drill Pipe in Gulf of Mexico Loop Currents
Authors: Beynet Pierre , Shilling Roy , Campbell Mike , Tellier Elizabeth , Howells Hugh
Published: July 2009

In September 2004 BP retrieved a Gulf of Mexico drilling riser due to excessive loop currents. Whilst waiting for the currents to diminish an impromptu full scale riser Vortex Induced Vibrations (VIV) test was carried out using the drilling riser standalone monitoring system. A 6-5/8 inch drill pipe was instrumented and deployed under the drilling vessel to a depth of 1,000ft. The drilling vessel drift was varied relative to the loop current to produce a range of current profiles and surface current speeds. Current loading along the length of the drill pipe was measured using the on-board acoustic doppler current profiler (ADCP). The paper describes the test set-up and measured VIV response. It includes observations of cross flow VIV, in-line VIV and additional response at higher frequencies not currently predicted with industry VIV analysis tools.
Concept of an Offshore Aquaculture System With an Automated Feeding Platform
Authors: Tsunoda Tomoyuki , Kitazawa Daisuke , Kinoshita Takeshi , Ito Sho , Bao Weiguang , Itakura Hiroshi , Fujino Masatoshi
Published: July 2009

With the increasing world demand for seafood and environmental problems in coastal aquaculture, offshore area has been increasingly expected to be utilized for aquaculture. The present study proposed the concept of an offshore aquaculture system with an automated feeding platform. The offshore aquaculture system has fewer effects on the surrounding marine environment through the rapid diffusion of organic wastes than the coastal one. The offshore area then provides clean waters for cultured fish. On the other hand, the offshore aquaculture system is subject to the severe natural condition such as typhoon attack. Actually, in the current aquaculture system, the cultured fish is starved during a few days before and after typhoon attack since the feeding ship is not able to approach the offshore sea cages, which is submerged every time around 10m below the sea surface to escape from high waves and strong currents. The automated feeding system should be therefore developed to enable the cultured fish to grow faster under the severe natural condition. The proposed system consists of several submerged fish cages and a feeding platform, which includes fuel tanks, feed storage silos, and an automated feeding machine. The feeding platform was designed by numerical analysis and tank model test in order to suppress its motion as small as possible. The motion of the feeding platform was first predicted by numerical analysis. The unmoved point was formed at each period of the incident wave. It moves upward as the period of the incident wave increases. Consequently, the point at 8m below the sea surface (3m above the bottom of the feeding platform) is the best one to attach the feeding hose. As a result of tank model test, pitch and heave motions of the feeding platform were dominant in the waves with short (1.5 seconds) and long (3.1 seconds) periods, respectively. An unmoved point was observed on the surface of the feeding platform as predicted by the numerical model, while the top of the feeding platform moved more largely. The unmoved point for the feeding hose was specified at above the bottom of the feeding platform.
Using Remote Sensed Data for Wave Energy Resource Assessment
Authors: Pontes M. T. , Bruck M.
Published: July 2009

The conversion of the energy contained in ocean waves into an useful form of energy namely electrical energy requires the knowledge at least of wave height and period parameters. Since 1992 at least one altimeter has been accurately measuring significant wave height Hs. To derive wave period parameters namely zero-crossing period Tz from the altimeter backscatter coefficient various models have been proposed. Another space-borne sensor that measures ocean waves is SAR (or the advanced ASAR) from which directional spectra are obtained. In this paper various models proposed to compute Tz from altimeter data are presented and verified against a collocated set of Jason altimeter and NDBC buoy data. A good fitting of altimeter estimates to buoy data was found. Directional spectra obtained from ENVISAT ASAR measurements were compared against NDBC buoy data. It was concluded that for the buoys that are more sensitive to long low-frequency wave components the fitting of wave parameters and spectral form is good for short spatial distances. However, since the cut-off ASAR frequency is low (reliable information is provided only for long waves) their use for wave energy resource assessment in areas where wind-waves are important is limited.
The Galicia HF Experience: Analysis of the Results of the SeaSonde HF Radar Experience in Galicia
Authors: Agostinho Pedro , Garcia Javier , Whelan Chad , Alonso-Martirena Andre´s
Published: July 2009

Two long-range CODAROS SeaSonde HF radar stations were installed and operated for three months (Nov 2005 to Feb 2006) in the Galician coast, the main area affected by the Prestige disaster. During this period, all the produced data were freely distributed in real time via Internet. The dissemination system was fully integrated with the Puertos del Estado web products, which are providing real time data of several oceanographic and atmospheric parameters, such as sea level and waves. One of the buoys of the Puertos del Estado deep-water network, equipped with a current meter, is moored in the area covered by the Radar system. Analysis of the three months of data shows good correlation between both sources of information (RMS of 5.11 cm/s for u component and 6.67 cm/s for ν) [1]. Additionally, a lagrangian buoy was released in the area, in order to analyze the benefit of employing HF radar currents for the tracking of drifting objects. The validation exercise with the drifting buoy was carried out inside the ESEOO project; the analysis was lead by University of Cantabria and Imedea balear, as part of their modeling tasks inside ESEOO, and the drifting buoy was released by SASEMAR, the Spanish Coastguard, as part of an ESEOO exercise [2]. A particle model was employed with and without the use of HF radar currents. Results of the experiment clearly show a positive impact of the use of measured current. When using HF data, the search and rescue areas are reduced, in average, in 49%. In this work, results from this experience will be analyzed in detail, making special focus in the scientific aspects of the comparison with the moored and drifting buoys.
Sloshing in LNG Tanks: Assessment of High and Low Pressures
Authors: Schreier Sebastian , Paschen Mathias
Published: July 2009

In the assessment of 2D numerical simulations of liquid sloshing in partially filled membrane-type cargo tanks of LNG Carriers high pressure impacts and also particularly low pressures have been identified. One high pressure impact at low filling levels and one sloshing impact leading to particularly low pressures at high filling levels are studied in greater detail. The results of these investigations are presented and conclusions are drawn with respect to the underlying physics of the two phenomena.
Oil Spill Modeling at Shwueihat Power and Desalination Plant
Authors: Mohamed Khaled A.
Published: July 2009

Oil spill modeling is a powerful tool that can be used for predicting the trajectory and concentration of an oil spill in contingency event. The National Energy and Water Research Center (NEWRC) of Abu Dhabi Water and Electricity Authority is developing early oil spill warning system for all Abu Dhabi power and desalination plants. The oil spill warning system enables the NEWRC to give early warning signal to plant, which may be threatened by an oil contamination. The Particle Tracking Module (PART) of Delft3D software package of Delft Hydraulics, The Netherlands is used in the setup of the oil spill warning system. This study shows the procedures that were followed to setup the oil spill warning system for one of the largest power and desalination plant in Abu Dhabi Emirate, which is Shwueihat Plant. The oil spill modeling can be used to determine the potential risk of oil contamination at the seawater intake of the plant due to the oil released from any possible oil sources. Case study is presented in the paper to demonstrate the use of the oil spill modeling to predict the trajectory and concentration of the oil slick released from oil source near the Shwueihat Power and Desalination Plant.
Extreme Wave Loads
Authors: Caires Sofia , van Gent Marcel R. A.
Published: July 2009

This paper compares three main methods for estimating extreme wave loads with a view towards determining the sensitivity of estimates to the particular approach chosen. The approaches considered include: a) The generally used ad-hoc procedure of performing an extreme value analysis of the Hs data, trying to find a relationship between wave height and period at the storm peaks and then, once the return values of extreme wave heights are estimated, estimating the associated return value of the wave period by means of the relationship found. b) The ‘structure variable method’ in which the pairs wave height and period observations are converted into univariate loads to which univariate extreme value theory is applied to estimate the return value of the structural load. c) The multivariate extreme value approach suggested by [1] in which a ‘multivariate return value’, namely the most probable value of the wave period conditional on a return value of the wave height, is estimated. Our study is based on a 44-yr long timeseries of wave conditions created using the shallow water wave model SWAN and calibrated ERA-40 data. The results suggest that the three approaches yield similar estimates. However, the ad-hoc procedure a gives the least conservative estimates. Approach c provides results that apply to any choice of load function and which to a certain extent are independent of the location in which the estimates are obtained, for which reason it may generally be the preferred one.
Localized Finite Element Method on Hydroelastic Responses of OWC-Embedded VLFS
Authors: Kyoung Jo Hyun , Hong Sa Young
Published: July 2009

Localized Finite Element Method is applied to analyze the hydroelastic response of VLFS with OWC (Oscillating-Water-Column) chamber. To reduce the hydroelastic response and the drift force, the OWC-embedded VLFS is proposed. The OWC chamber effects on the hydroelastic response and drift force are investigated by changing the location and the draft of OWC chamber. The hydroelastic motion of VLFS is analyzed by the mode superposition method. The drift force is obtained by far-field method. As a numerical validation, the hydroelastic response of the proposed model is compared with the model experiment.
Influence of the Third Order Nonlinearity on the Distribution of Wave Height Maxima in an Offshore Basin
Authors: Petrova Petya G. , Guedes Soares C. , Cherneva Zhivelina I.
Published: July 2009

The effect of the coefficient of kurtosis, λ40, on the distribution of wave height maxima has been investigated. The data set used consists of water surface displacements in irregular deep water unidirectional wave fields generated in an offshore basin and defined by the JONSWAP spectrum. The full-scale records are of almost 3h17min duration. The measurements have been performed at ten equidistant gauges along the basin, which permits to follow the changes in wave statistics away from the wave-generator. Subsequently, the records have been split into series of different length, corresponding to N = 100, 200 and 300 waves, and the probability density functions and the exceedance probabilities of the maximum wave heights have been constructed conditional on λ40. They have been compared with the modified Edgeworth-Rayleigh model of Mori and Janssen [1] applied to the maximum wave heights. The theoretical expressions are formulated as a simple function of the coefficient of kurtosis and the number of waves in the sample. The coefficient of kurtosis, reflecting the third order nonlinearity, is found to increase with the distance from the wave-maker. The considered theoretical density curves describe only qualitatively the shift of the empirical mode towards higher values. The tendency of the peak of the distribution to diminish with increase of λ40 has been observed. However, the most probable wave height remains underestimated by the theory for all classes of λ40, regardless of the length of the time series. Finally, the probability that a certain normalized height level Hmax/Hs will be exceeded increases with the increase of λ40, as being theoretically predicted, although it is overestimated by the theory in the lower range of values of λ40 and underestimated over the higher range of values of λ40.
Dynamic Analysis of a Steam Generator Tube Bundle With Fluid-Structure Interaction
Authors: Sigrist Jean-Franc¸ois , Broc Daniel
Published: July 2009

The present paper deals with the dynamic analysis of a steam generator tube bundle with fluid-structure interaction modelling. As the coupled fluid-structure problem involves a huge number of degrees of freedom to account for the tube displacements and the fluid pressure evolutions, classical coupled methods can not be applied for industrial studies. In the present case, the three-dimensional fluid-structure problem is solved with an homogenisation method, which has been previously exposed and successfully validated on a two-dimensional elementary tube bundle (J.F. Sigrist, D. Broc; Investigation of Numerical Methods for Modal Analysis of Tube Bundle with Fluid-Structure Interaction; Pressure Vessel and Piping, San Antonio, 22–26 July 2007). Formulation of the homogenisation method for general three-dimensional cases is exposed in the paper. Application to a simplified (however representative of an actual industrial nuclear component) steam generator is proposed. The problem modelling, which includes tube bundle, primary and secondary fluids and pressure vessel, is performed with an engineering finite element code in which the homogenisation technique has been implemented. From the practical point of view, the analysis highlights the major fluid-structure interaction effects on the dynamic behaviour of the steam generator; from the theoretical point of view, the study demonstrates the efficiency of the homogenisation method for periodic fluid-structure problems modelling.
Equipment Reliability: When Utility Meets Manufacturing
Authors: Eglin John , Woodcock Joel
Published: July 2009

In a world striving for continuous improvement, the utility and manufacturing industries appear to have taken different paths to success. But are they the same and can we learn from them to take a revolutionary step towards manufacturing excellence for Westinghouse Nuclear Fuel? The safety critical environment that is the hallmark of the nuclear industry has led the Institute of Nuclear Power Operations (INPO) to develop a rigorous and disciplined approach to equipment reliability that is repeated across the nuclear generation industry. This is manifested in well documented processes and procedures in response to the heavily audited power generation segment. INPO’s Equipment Reliability guideline, AP-913, is a top down methodology that captures equipment history and best practices to tie together activities throughout a station to improve reliability. Manufacturing however is breeding a culture of continuous improvement, or “kaizens”, where “Lean” and “Total Productive Maintenance” (TPM) tools and techniques drive a multiplicity of incremental improvements. The manufacturing concepts and approaches of Lean and TPM were developed originally in Japan by such companies as Toyota and Motorola and formalized by the Japan Institute of Plant Management as an equipment management strategy, which was designed to support the Total Quality Management strategy. Lean and TPM are fostered by professional societies and are well described in a body of literature with decades of experience. Since this paper provides a cross-discipline comparison in a primarily nuclear applications conference, introductory material for the TPM methodology is referenced, while only overview concepts are described herein. It is hoped that this will spur the reader to develop a more complete understanding of TPM, to further integrate these applications in both industries. This paper provides an initial overview of how Westinghouse Fuel Manufacturing is developing an equipment reliability programme that is exploiting the best practices of the AP-913 integrated processes with the strong continuous improvement tool set of manufacturing. We have just begun to roll-out the new processes and guidelines. In future papers, more detailed comparisons and lessons learned from implementation will be described.
Mechanism Based Unified Creep Model Incorporating Damage
Authors: Bonora Nicola , Esposito Luca
Published: July 2009

Although it is often said that diffusional flow creep is out of the practical engineering applications, the need for a unified model capable to account for the resulting action of both diffusional and dislocation type creep is justified by the increasing demands of reliable creep design for very long lives (exceeding 100.000h), high stress-low temperatures and high temperature-low stress regimes. In this paper, a unified creep model formulation, in which the change of the creep mechanism has been accounted for through an explicit dependence of the exponent n on stress and temperature, has been proposed. The model has been also extended incorporating damage processes, characteristics of creep stage IV, adopting a time independent damage formulation proposed by the authors. An application example of the proposed approach to high purity aluminum is given.
Vibro-Impact Interaction of Ships With Ice
Authors: Grace I. F. , Ibrahim R. A.
Published: July 2009

Impact dynamic interaction of ships with solid ice or stationary rigid structures is a serious problem that affects the safe operation and navigation in arctic regions. The purpose of this study is to present two analytical models of impact interaction between ship roll dynamics and one-side rigid barrier. These models are the phenomenological modeling represented by a power law in stiffness and damping forces, and Zhuravlev non-smooth coordinate transformation. Extensive numerical simulations are carried out for all initial conditions covered by the ship grazing orbit for different values of excitation amplitude and frequencies of external wave roll moment. The basins of attraction of safe operation are obtained and reveal the coexistence of different response regimes such non-impact periodic oscillations, modulation impact motion, period added impact oscillations, chaotic impact motion and unbounded rotational motion. The results are summarized in the bifurcation diagram in terms of response amplitude-excitation amplitude plane.
Comments on the Process Zone Methodology When Applied to Delayed Hydride Cracking in CANDU Zr-Nb Pressure Tube Material
Authors: Smith E.
Published: July 2009

The paper discusses the application of the process zone model to the problem of hydrided region formation and Delayed Hydride Cracking (DHC) in CANDU Zr-Nb pressure tube material. The special characteristics of the process zone approach, as used for the DHC problem, are highlighted, while making comparisons with the way in which it is more generally applied in other engineering situations.
Effects of Neutron Irradiation on the Fracture Toughness of RPV Materials: Prediction of Material Property Changes for Irradiated Euro Reference Material ‘A’ and Other RPV Materials
Authors: Lidbury David , Beardsmore David
Published: July 2009

A micromechanistic model is used to estimate the irradiation-induced change in the Master Curve reference temperature for cleavage fracture as a function of the associated change in material yield stress relative to the yield stress in the unirradiated condition. The model is shown to predict well the behaviour of Euro Reference Material A (quenched and tempered 22NiMoCr37 ring forging) irradiated at temperatures of T = 285°C and T = 150°C with neutron fluences of 4.3E+19 n/cm2 (En > 1MeV) and 3.1E+19 n/cm2 (En > 1MeV) respectively. Further validation of the model is provided with reference to published data for a range of irradiated RPV plate, forging and weld materials, where measured and predicted values of the change in the Master Curve reference temperature are successfully compared. For the LWR materials and irradiation conditions considered, the fitted parameters of the model are consistent with the view that the primary effect of neutron irradiation is to increase the friction stress for plastic flow of crack-tip material, whereby the irradiation-induced change in yield stress may be associated with a change in a non-hardening, athermal term e.g. as described in the Zerelli-Armstrong constitutive equation. The model predictions compare well with trend curves due to Sokolov and Nanstad, and Wallin and Laukkanen. A particular advantage of the model, compared with these more general formulations, is that it is potentially better suited to a more detailed analysis and interpolation of RPV material datasets covering a range of irradiation conditions where flow properties are reasonably well characterised.
Application of Electromagnet Using Magnetization or Demagnetization for Magnetic Damper
Authors: Matsuoka Taichi , Sunakoda Katsuaki
Published: July 2009

In this paper the authors develop a new type of a hybrid magnetic damper which has a variable damping force generated by hybrid electromagnets. The hybrid electromagnet is composed of a ferrite core combined with a rare-earth magnet. The damper can make the damping coefficient increasing from neutral value with magnetized field, or otherwise decreasing it with demagnetized field. It has also a fail-safe mechanism under an electrically malfunction. In order to determine the magnetic damping coefficients created by eddy current depend on a shape of a magnet and a conductive disk, it is accurately calculated by using an arc shape. For investigating about dynamic properties, resisting force characteristics are measured by using a vibration actuator. In experimental results, the damper has a damping coefficient which is proportional to current squared increasing and decreasing from neutral value. Seismic response simulations of one-degree-of-freedom system with the hybrid damper are calculated using LQR control. The effects of vibration suppression are confirmed numerically.
On-Board Dynamic Strain System for Turbine Engine Ground Testing
Authors: Reich Alton , Doherty Steve , Shaw James , Nelius Andrew E. , Williams Keith
Published: July 2009

The Arnold Engineering Development Center (AEDC) testing complex includes more than 50 wind tunnels, test cells, arc heaters, and other specialized test facilities. Of these, 27 units have capabilities that are unmatched in the United States, and 14 are unmatched in the world. These unique facilities pose equally unique testing challenges, including several related to test preparation. A dynamic strain measurement system feasibility demonstrator for turbine engine ground testing applications was developed as the product of a Small Business Innovative Research (SBIR) phase 1 contract. System specifications include 40 kHz minimum bandwidth, 0–65°C operating temperature, IEEE-1451 (“smart sensor plug and play”) compliance, and synchronized sampling per IEEE-1588. The transducer interface for each channel features hardware-configurable bridge completion, an instrumentation amplifier, a remotely configurable antialiasing filter, and a combined A-D/microcontroller on a 5 square inch circuit board. The A-D/microcontroller stores essential transducer information locally and converts the amplified analog signal into digital data. The network interface from 12 transducer channels to the host computer comprises an FPGA and a microprocessor with integral IEEE-1588. Data systems of this type will reduce engine test cell wiring to control room, improve noise immunity, reduce engine installation time, enable faster calibration, and reduce per channel instrumentation cost.
FEM Stress Analysis of Tee Intersections With LTA
Authors: Ahmad T. , Qadir M. , Redekop D.
Published: July 2009

In this work a three-dimensional finite element study is carried out of pressurized piping tee (tee) intersections, with local area wall thinning (LTA). Two types of stress analysis are carried out, dealing respectively with the determination of the stress concentration factor (SCF), and of the plastic collapse load. Stress values determined for vessels with uniform thickness are compared with previously published work. An evaluation is then made of the effect on the SCF values of varying the size and shape of the LTA around the intersection. This is followed by a parametric study in which the SCF and the collapse load are computed for intersections with different depths of wall thinning. Finally, comments are made on the fatigue of tees with LTA having cyclical loading superimposed on the constant pressure loading.
In-Situ Observations of Intergranular Stress Corrosion Cracking
Authors: Duff Jonathan A. , Marrow Thomas J.
Published: July 2009

The development and validation of predictive models for intergranular stress corrosion cracking requires knowledge of short crack growth kinetics in response to mechanical driving forces. A new experimental method for in-situ observation of the early stages of crack growth during stress corrosion cracking, via full field Digital Image Correlation, is described and data for crack growth development are presented. Intergranular stress corrosion cracks were nucleated in sensitised 304 stainless steel under static uniaxial flexural deflection, within a potassium tetrathionate environment. High resolution optical images of a 2mm by 2mm area are recorded through the test solution during the experiment. The raw images show no observable cracking. However, the high sensitivity of digital image correlation allows small crack opening displacements to be detected. The derived strain map of the sample surface thereby enables imaging of the cracks. Surface cracks with lengths exceeding approximately 30μm can be observed. Post processing of the strain maps is then used to track the development of the cracks.
Analytical Method for the Calculation of J Parameter for Surface Cracks in Piping Welds
Authors: Marie S. , Kayser Y. , Drubay B. , Le Delliou P. , Gilles P. , Barthelet Bruno , Schwab J.
Published: July 2009

RSE-M and RCC-MR codes provide flaw assessment methodologies and related tools for Nuclear Power Plant. AREVA, CEA and EDF developed in particular a large set of compendia for the calculation of the parameter J for various components (plates, pipes, elbows, ...) and various defect geometries. The last step of these developments deals with the weld joints : since 2004, the partners are developing a methodology to calculate the J parameter for a defect located in a weld, less conservative than usual methods. This methodology is based on the definition of an equivalent material that leads to the same J value (with same loading conditions and defect geometry) than the bi-material component. The stress-strain curve of this equivalent material is deduced from a combination of the tensile curves of the base metal and of the weld metal. The weigth coefficients applied are specifically defined for the J calculation and generalized to deal with any weld joint geometry.
Weld Residual Stress and Distortion Analysis of the ARES I-X Upper Stage Simulator (USS)
Authors: Brust Frederick W. , Raju Ivatury , Cheston Derrick , Dawicke David , Phillips Dawn
Published: July 2009

An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). The Ares system of space launch vehicles is the US National Aeronautics and Space Administration’s plan for replacement of the aging space shuttle. The new Ares space launch system is somewhat of a combination of the space shuttle system and the Saturn launch vehicles used prior to the shuttle. Here, a series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on fatigue and fracture life. While the main focus of this paper is a discussion of the weld modeling procedures and results for the USS, a short summary of the CIFS assessment is provided.
Numerical Approach to Improve Flushing Efficiency by a Dynamic Morphological Model
Authors: Ghoreishi S. H. , Naji H. , Tabatabai M. R. M. , Mompean G.
Published: July 2009

The process of sediment flushing is simulated by a 3D numerical model in which sediment and flow interaction are reflected in the reservoirs. RANS equations are solved numerically by finite volume with a k-ε turbulence model. The convection-diffusion equation for the sediment concentration is solved. The Van-Rijn’s reference level concentration equation is adopted as a boundary condition. Bed changes are obtained by application of sediment continuity equation. The numerical results show that the flushing efficiency is related to the outflow discharge, initial conditions of water level and number and location of the bottom outlets.
Acceptance Criteria for Repair Method Using Fillet Welded Patches
Authors: Ogayu Yasushi
Published: July 2009

When local wall thinning damage (including through-wall) caused by erosion, corrosion and other local deterioration mechanisms is detected in pressure vessels, repair method called “Fillet Welded Patches” is often applied to them for recovering their reliability. However, it does not appear that the acceptance criteria, such as “dimension of fillet weld throat”, “wall thickness of patch plate” and “overlap length between patch and base metal”, on this weld repair method are clearly confirmed. So, this sort of repair method has not been authorized in Japan. Therefore, finite element method (FEM) analysis was used to calculate and evaluate stress and stress distribution around fillet welded patch to confirm the acceptance criteria for these important factors. In addition, accuracy of the FEM was also verified by comparing stresses and its distribution calculated by means of the FEM analysis and those obtained from pressure test.
Wave Propagation in Thin-Walled Aortic Analogues
Authors: Giannopapa C. G. , Kroot J. M. B.
Published: July 2009

Research wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flow. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models well defined in-vitro experiments are of great importance. The objective of this paper is to present a frequency domain transmission line analytical model based on one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogues. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, flow and wall distention results obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical models and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account.
Blow-Out Safety of Gaskets for Bolted Flange Connections
Authors: Roos Eberhard , Bartonicek Jaroslav , Kockelmann Hans , Hahn Rolf
Published: July 2009

Safety-relevant bolted flange connections used in industrial plants require in addition to the strength and tightness proof a proof of blow-out safety of the gaskets within the scope of design. In order to assess the behaviour of a gasket concerning its blow-out safety it is essential to know the gasket characteristics which describe the sealing and creep-relaxation behaviour. To prove the blow-out safety of bolted flange connections a reproducible experimental test method was developed. This method can be used to complement the design of bolted flange connections with the aspect blow-out safety. The investigated soft gaskets show four different types of behaviour with regard to the blow-out safety. They characterize the hazardous potential in form of blow-out and cause the classification of different gasket types and materials.
Effects of a Single Overload Event on the Fatigue Crack Growth Rate of a Low Alloyed Rotor Steel
Authors: Le Roux J. C. , Hasnaoui F.
Published: July 2009

The aim of this work is to study the effect of the overload on the fatigue crack growth rate properties of a low alloyed steel used for rotor disk. On one hand, experimental fatigue tests during which a single overload event is applied are performed on CT specimens. Different loading conditions are imposed in order to study the effects of these parameters on the retardation of the fatigue crack due to the overload. On the other hand, two dimensions elastic plastic Finite Element calculations of crack propagation using nodes release method were used to estimate the effects of a single overload event on the fatigue crack growth rate. Different loading conditions, as for the experimental tests, are used in order to study numerically the effects of these parameters on the retardation of the fatigue crack due to the overload. The experimental and numerical results show the decrease of the crack growth rate due to the overload. This decrease depends on different parameters as overload ratio, stress ratio used for the constant amplitude cyclic loading and ΔK at which the overload is applied. From experimental test results, it can be observed that the decrease is as significant as the overload ratio is high, and as the ΔK at which overload is applied and stress ratio are low. Numerical results show similarities with experimental results, for instance the decrease of the fatigue crack growth is linked to the increase of the overload ratio or to the decrease to the ΔK at which overload is applied. Differences are also observed i.e. the increase of the stress ratio seems to increase the effect of the overload in the numerical calculations in contrary of the experimental results. By comparing to the numerical results, the quality of the results obtained from simplified models has been assessed in regard of the overload effect. A modified Kim and al. model seems to be representative of the different effects of the overload on the fatigue crack growth rate. The future work to be done consists to improve the comparison between experimental and numerical studies.
Crack Initiation Process for Semi-Circular Notched Plate in Fatigue Test at Elevated Temperature
Authors: Bubphachot Bopit , Watanabe Osamu , Kawasaki Nobuchika , Kasahara Naoto
Published: July 2009

Crack initiation and propagation process of fatigue test in semi-circular notched plates at elevated temperature were observed by the CCD video camera. Test specimens are made of SUS304 stainless steel, and temperature is kept to be 550°C, and geometry of semi-circular notched plate specimens are changed by diameter size of the circular hole. Photographs in all cycles were recorded to investigate crack initiation process in structural components having stress concentration and obtain number of cycle of crack initiation (Nc). The test results were compared with predictions by Stress Redistribution Locus (SRL) method and Neuber’s rule’s method.
Reliability-Based Derivation of Partial Safety Factor for Structural Integrity Assessment
Authors: Pan Shuo , Zhao Jianping
Published: July 2009

When there are uncertainties in the input random variables, or scatter in the material properties, probabilistic assessment is a useful tool for decision making in the field of safety analysis. The partial safety factor (PSF) method was aimed on ensuring that the failure probability did not exceed a target value. In order to be conservative the input value for each random variable during the assessment procedure should be multiplied by the partial safety factors. So it is essentially a deterministic assessment using conservative values of the input random variables and a relatively simple and independent method of assessing failure probabilities using R6 failure assessment diagram. The application of partial safety factors is an important breakthrough of assessment in structures containing defects. In recent years, sets of PSFs for load, defect size, fracture toughness and yield stress had been given in two standards, BS7910 and API579. However, the recommended PSFs in both standards were larger than the original PSFs in PD6493 which was replaced by BS7910. It is therefore a new method of calculating PSFs should be found to prove which is more appropriate and convenient for engineering application. In the case of the partial safety factor method target reliabilities in the range from 0.001 to 0.00001 were considered and new series of PSFs were derived from the results of reliability analysis for the linear elastic fracture mode and elastic-plastic fracture mode. After comparing with the PSFs in BS7910 and API 579, it is concluded that the partial safety factors were generally conservative compared to our research work.
Intensity Analysis and Damage Experiment of a Universal Joint
Authors: Shintani Masanori , Nara Kentaro
Published: July 2009

This paper discusses research on the intensity analysis and damage experiments of a universal joint. The Kashiwazaki Kariwa nuclear power plant suffered damage from the Niigata Chuetsu offing earthquake which occurred on July 16, 2007. The earthquake motion damaged a driving shaft coupling of an overhead traveling crane of the No. 6 nuclear reactor building. The damaged portion consisted of the universal joint. The target of this research focuses on the universal joint and the cause of its damage from the earthquake, as well as the design of proposed measures. As a cause of the damage it is thought that the universal joint was loaded from the torque of the earthquake motion. The torque that loaded to the universal joint is calculated from the earthquake motion. The stress that loaded to the universal joint is calculated by an analysis by 3DCAD (Three Dimensional Computer Aided Design) and CAE (Computer Aided Engineering). In the experiment, a miniature model of the universal joint is loaded with the torque and damaged. Similarly, in the analysis by 3DCAD and CAE, the miniature model is loaded with the torque and damaged. The experimental result is compared with the analysis result and the validity of the analysis is examined. The proposed measures to improve the design of the universal joint to form earthquake loads are examined by 3DCAD and CAE.
Theoretical Analysis and Numerical Simulation on the Hydraulic Expansion of Double-Layered Tubes
Authors: Liu Fujun , Zheng Jinyang , Ding Shoubao , Guo Xiaolian
Published: July 2009

The quality of hydro-expanded double-layered tubes depends on the hydro-expanding pressure. Therefore, it is very important to determine the range of the hydro-expanding pressure accurately during the fabrication of double-layer tubes. According to theories of elasticity and plasticity, the responses of double-layered tubes subjected to five kinds of cases were analyzed during the hydro-expanding process. And the stress and strain for inner and outer tubes of double-layered tubes were discussed. By using the relation of deformed compatibility of hoop strain, suitable condition of hydraulic expansion and variable range of hydro-expanding pressure were obtained, and the calculating formulas between the hydro-expanding pressure and residual contact pressure was derived. Use the non-linear FEA MSC.patran/marc code to simulate the deformation and stress distribution, the whole process of hydraulic expansion was numerically investigated, in which the nonlinearities of the material, geometry and contact were all taken into account. The results show that the range of the hydro-expanding pressure from the numerical simulation is in good agreement with those from theoretical calculation with a maximum relative error of 6.52%. The investigation on the hydraulic expansion of double-layered tubes may guide the engineering design and provide references for further research.
Foam Density Sensitivity Study for the 9977 Package
Authors: Gorczyca Jennifer L. , Wu Tsu-Te
Published: July 2009

Two layers of insulation fill the volume of the 9977 package between the drum liner and the shell. One of these layers is composed of General Plastics FR-3716 polyurethane foam (also known as Last-A-Foam®), poured through fill holes in the drum bottom and foamed in place. There was concern that the density of the foam insulating layer may vary due to the manufacturing process and that variations in foam density would compromise the safety basis of the package. Thus, a structural finite element analysis was performed to investigate this concern. The investigation examined the effect of replacing the material properties for the FR-3716 polyurethane foam, which has a density equal to 16 lbm/ft3, with material properties of similar foam with varying densities through finite element analysis of hypothetical accident conditions (HAC) pertaining to impact conditions. The results showed that the functional performance of the containment vessel (CV) was not compromised under the conditions investigated.
Nuclear PWR Plants: Managing the Expertises of Cast Components Removed From Reactor Coolant Circuit
Authors: Bezdikian Georges
Published: July 2009

The French utility has organized the aging degradation assessment for nuclear plants in operation in maximum safety rules. Also the utility decided to engaged large program of expertises, for each degradations identified, based on research and development activities and prediction criteria program of Nuclear Plants in function of several actions: expertises, data bases on characteristics, etc. This paper shows the expertise results and thermal aging for cast duplex stainless steel studies on reactor coolant circuit components engaged to evaluate and to monitor the toughness evaluation and increasing factor. Also this paper presents the strategy associated. This paper shows the applications were evolved for 3-loop PWR plants. The monitoring was mainly oriented on evaluation of the ratio computation and measurement. This integrity assessment and expertises results values available periodically were performed considering: • the life evaluation of the plants and alternative maintenance actions, • the large database from cast reactor coolant component assessed after removed from nuclear power plants, • the identification of degradation for different components and prediction criteria proposed. The results obtained are updated in the periodic maintenance program and in volume of expertise database for life management.
Grain-Scale Heterogeneity Effect on Mechanistic Modelling of Cleavage Fracture of a Ferritic RPV Steel Forging Material
Authors: Zhao Xinglong , Quinta da Fonseca Joa˜o , Sherry Andrew , Lidbury David
Published: July 2009

Improving brittle fracture prediction is crucial for structural integrity assessment. In current safety assessments, fracture mechanics treats polycrystalline steels as homogeneous continua. In reality, deformation of structural steels is heterogeneous. Part of this heterogeneity is due to the elastic and plastic anisotropy of their constituent (often randomly orientated) grains. This paper will compare the predicted failure stresses from tensile tests performed on a ferritic pressure vessel steel using the crystal plasticity finite element approach alongside measured carbide distribution and classical Beremin cleavage model. Available tensile data of 22NiMoCr37 steel at low temperature (−91°C and −154°C) were analysed using Bridgman solutions to account for the necking effect on the stress state at the centre of necking where brittle cracking initiates. This stress state imposed on representative volume element (RVE) made up of 10×10×10 randomly orientated grains, whose deformation is simulated using crystal plasticity finite element modelling (CPFEM). Randomly distributed carbides were produced based on the measured carbide size distribution and density for this steel. By assuming carbides as Griffith microcracks, the cleavage fracture stress in each grain can be assessed based the maximum principal stress on the cleavage crystal plane and an assumed surface energy. By repeating the random carbide distribution 1,000 times, brittle fracture probability can be calculated. Detailed examination shows that the above approach is actually a verification of the BEREMIN local approach model for cleavage fracture. The modelling results were compared with the available ductility data at −91°C and the interpolated ductility data at −154°C at the centre of necking. It is foreseen that this approach will lead to improvements in brittle fracture modelling in heterogeneous ferritic steels by introducing realistic surface energies and real defect distributions in specific materials, when used alongside the CPFEM submodelling approach.
Toward a Global Model for FSI in Tube Bundles
Authors: Broc Daniel , Duclercq Marion
Published: July 2009

It is well known that a fluid may strongly influence the dynamic behaviour of a structure. Many different physical phenomena may take place, depending on the conditions: fluid at rest, fluid flow, little or high displacements of the structure. Inertial effects can take place, with lower vibration frequencies, dissipative effects also, with damping, instabilities due to the fluid flow (Fluid Induced Vibration). In this last case the structure is excited by the fluid. The paper deals with the vibration of tube bundles in a fluid, under a seismic excitation or an impact. In this case the structure moves under an external excitation, and the movement is influenced by the fluid. The main point in such system is that the geometry is complex, and could lead to very huge sizes for a numerical analysis. Many works has been made in the last years to develop homogenization methods for the dynamic behaviour of tube bundles (/2/ and /3/). The size of the problem is reduced, and it is possible to make numerical simulations on wide tubes bundles with reasonable computer times. These homogenization methods are valid for “little displacements” of the structure (the tubes), in a fluid at rest. The fluid movement is governed by the Euler equations. In this case, only “inertial effects” will take place, with globally lower frequencies. It is well known that dissipative effects due to the fluid may take place, even if the displacements of the tube are no so high, or if the fluid is not still (/4/, /5/, /6/ and /8/). Such effects may be described in the homogenized models by using a Rayleigh damping, but the basic assumption of the model remains the “perfect fluid” hypothesis. It seem necessary, in order to get a best description of the physical phenomena, to build a more general model, based on the general Navier Stokes equation for the fluid. The homogenization of such system will be much more complex than for the Euler equations. The paper doesn’t pretend to give a general solution of the problem, but only points out the most important key points to build such homogenized model for the dynamic behaviour of tubes bundles in a fluid.