bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Different Braided Packing Materials and Number of Rings on Stem Torque and Sealability
Authors: Veiga Jose´ , Gira˜o Carlos D. , Cipolatti Carlos F.
Published: July 2010

This paper introduces a test device and a protocol that simulates packing performance in different size valve stuffing boxes and stems. This test device enables measurement of braided packing compression, relaxation, axial force at the bottom of the stuffing box, the torque generated upon stem turning and the influence of the number of packing rings on stem torque. It also enables comparisons between different braiding yarns materials, impregnations and correlations with seating stress, stem torque and sealability. Test results showing these comparisons and correlations are reported.
An Elementary Study of SPH-Based Simulations for Free Surface Flows With Gravity and Compressibility Effects in Cylindrical Confinement
Authors: Oger Guillaume , Jacquin Erwan , Le Touze David , Alessandrini Bertrand , Sigrist Jean-Franc¸ois
Published: July 2010

The design of nuclear pressure vessel requires the description of various dynamic effects, among which fluid-structure interaction. In some configurations, gravity effects (in the low frequency range) and compressibility effects (in the high frequency range) are of paramount importance and have therefore to be accounted for. The present paper is concerned with the description of free surface flows with gravity and compressibility effects, using a SPH (Smoothed Particle Hydrodynamics) method in circular confinement, with expected applications to the dynamic analysis of auxiliary nuclear component for naval propulsion. For the system under concern, the range of dynamic solicitation extends from low frequency (for seismic analysis of grounded prototype) to high frequency (for shock analysis of embarked reactors); it is therefore of particle interest to employ a numerical techniques which allows the description of linear and non-linear free surface effects, which can be expected in both cases. SPH method gives promising perspective for simulation of sloshing flows in various configurations; the present paper investigates the use of such a technique in the context of three-dimensional problems with cylindrical confinement.
Investigation of the Performance of the Contour Residual Stress Measurement Method When Applied to Welded Pipe Structures
Authors: Dennis R. J. , Leggatt N. A. , Kutarski E. A.
Published: July 2010

The ‘Contour Method’ is a relatively new relaxation method for residual stress measurement and may be seen as an evolution of established methods such as hole drilling. The general procedure when applying the Contour Method is cutting, measurement and calculation of residual stress normal to the cut plane using Bueckner’s principle of elastic superposition. That is the residual stresses are determined from the measured profile of a cut surface. While the Contour Method is simple in concept there are certain underlying issues relating to the cutting process that may lead to uncertainties in the measured results. Principally the issues are that of constraint and plasticity during the cutting process and the influence that they have on the measured residual stresses. Both of these aspects have been investigated in previous work by simulating the entire contour measurement method process using finite element techniques for ‘simple’ flat plate welded specimens. Here that work is further investigated and extended by application to a 316 Stainless Steel welded pipe structure containing a part-circumferential repair. This more complex structure and residual stress field is of significantly greater engineering interest. The key objective of this work is to ascertain the feasibility of and further our understanding of the performance of the Contour Method. Furthermore this work has the potential to provide a method to support the optimisation of the contour measurement process when applied to more complex engineering components.
Review of the Current Conservatisms in the Assessment of Thin-Walled Structures
Authors: Kulka R. S. , Price A. J.
Published: July 2010

Current methods for performing fracture mechanics assessments of thin-walled structures possess significant levels of conservatism, since they are often for general use with both thin-walled and thick-walled structures. In many industries, there are significant commercial drivers for reducing the amount of conservatism in these assessments. An enhanced understanding of the fracture behaviour of thin-walled structures in different situations may lead to the development of more appropriate structural integrity assessments. A review of the information pertaining to fracture mechanics analysis of thin-walled structures has been conducted. There are indications that improvements to the best practice methodology may be made, through improved tensile and toughness properties, consideration of limit loads, and the effect of residual stress distributions.
Sealing Performance Evaluation of Pipe Flange Connection With Spiral Wound Gasket Under Cyclic Thermal Condition
Authors: Takagi Yoshio , Torii Hiroyasu , Sawa Toshiyuki , Omiya Yuya
Published: July 2010

Although a lot of pipe flange connections are exposed to elevated temperature during long-term plant operation, a sealing performance of the pipe flange connections at elevated temperature is not well understood because of the experimental difficulty and the analytical problems which result from the lack of the materials properties of gaskets at elevated temperature. The authors have been evaluating the effects of the material properties of spiral wound gaskets (SWG) and the sealing performance of the pipe flange connections at elevated temperature with numerical and experimental analysis. The gasket stress induced by the mismatch of the thermal expansion between the gasket and flange/bolt increased as increasing the temperature in the case that the thermal expansion coefficient of the gasket was larger than that of bolt/flange material and the sealing performance of the pipe flange connection was improved. However, the thermal expansion coefficient declines at temperatures higher than 210 °C. In addition, the binder compositions of SWG vaporize and the mechanical properties slightly change at high temperature such as higher than 200°C. Therefore, the sealing performance of pipe flange connection with SWG might decline more than 200°C. The sealing performance and long-term durability of pipe flange connection with SWG at elevated temperature were evaluated in this study. The long term leakage test with heat cycle revealed that the sealing performance of pipe flange connection didn’t show any degradation for 21 days. The compression tests for the new, the thermal aged and the used gaskets were done to investigate the effect of material characteristics on the long term sealing performance. In addition to the leakage test and the compression tests, the thermal characteristics of SWG were evaluated by the Thermogravimetry/Differential Thermal Analyzer (TG/DTA) measurement. The measurement showed the weight loss of SWG more than 130°C. According to those experimental results and FE analysis, the effect of temperature on the sealing performance was discussed.
Effects of Scatter in Axial Bolt Force on the Sealing Performance of Pipe Flange Connections at Elevated Temperature
Authors: Sawa Toshiyuki , Omiya Yuya , Takagi Yoshio , Torii Hiroyasu
Published: July 2010

Since scatter in axial bolt force exists in assembling pipe flange connections, it is important to evaluate the effect of scatter in axial bolt force on the sealing performance of pipe flange connection. The FE and experimental analyses were done to evaluate the effect of scatter in axial bolt force on the sealing performance of pipe flange connections with 3″ (NPS 3″) and 20″ (NPS 20″) nominal diameters. The axial bolt force was measured with strain gauges mounted on the shank of each bolt. The two kinds of torque controlled assembly procedures, ASME PCC-1 procedure and JIS 2251 procedure, were evaluated as an assembling procedure and compared the scatter in axial bolt force with that of the uniform axial bolt force condition. The results revealed that the significant difference was not observed between ASME PCC-1 and JIS 2251 procedures. The scatter in axial bolt force were not changed at elevated temperature, however, the axial bolt force increased when increasing the temperature. Therefore, the tightness of the flanged connection is improved with increasing the temperature up to 200 °C. The assembly efficiency was evaluated with the experimental results of 20″ nominal diameter leakage tests and FE analyses. In addition to the scatter in the assembly axial bolt force, the flange rotation affected the axial bolt force when internally pressurized. As a result, the tightness parameter, Tp, was slightly lower than that evaluated with the assembly efficiency, η = 0.85, defined in ASME PCC-1 procedure. The results are discussed and a modified assembly efficiency is proposed.
Improved Construction of End Closure Seal Using D-Shaped Shearing Bolted Connection for Pressure Vessels
Authors: Chen Ping , Liu Haobo , Duan Chenghong , Luo Fan
Published: July 2010

This paper describes a new improved structural type of end closure with use of D-shaped shearing bolts by which the head can be opened and closed easily & quickly, and use of metallic self-energized C-ring or O-ring as its sealing gaskets for pressure vessels. Strength analysis and calculation methods for its key components are recommended. This new structure has reliable safety, compact, easy assembly and cost effective in materials etc. Its size and operating pressure should be unlimited, so it can be widely used in industries.
Validation and Optimization of ARCMAC and Strain Mapping Systems for Creep Measurement
Authors: Maharaj Chris , Palmer Iain , Dear John
Published: July 2010

Research is ongoing to validate and optimize the E.ON UK auto-reference creep management and control (ARCMAC) system for high temperature piping creep measurement. In conjunction with the ARCMAC system, research is also being undertaken to incorporate digital image correlation (DIC) into creep strain evaluation, via a rugged high temperature pattern. The aim is to have comprehensive monitoring of creep strain in high temperature steam pipes including bends, joints, welds and other pipe structural features. This paper firstly presents work done into the determination of the best method to capture and process ARCMAC images. It was found that a bi-cubic interpolation resizing function with a combined high light intensity image gives the best results with respect to accuracy and repeatability of image acquisition. Also presented was the testing of a modified (prototype) ARCMAC camera with modified (prototype) ARCMAC gauges. The prototype ARCMAC camera, based on a DSLR camera, is approaching the accuracy of the conventional ARCMAC but an improved lens system would be desirable. For the prototype gauge, it was found that the edge-finding technique using the knife-edge was just as accurate as using the target ball reflection for strain analysis. Both techniques can be used independently to evaluate creep strain. Finally, preliminary high temperature testing results for both the ARMCAC and DIC technique are presented. For the ARCMAC gauge and the DIC high temperature pattern, small changes in strains were observed over time that were not due to sample deformation. Reasons for these small changes in strain were identified and solutions arrived at. All results are very promising and it is foreseen that a combined ARCMAC/DIC tested technique will be applied to plant piping components soon.
An Investigation of the Stress Intensity Factor Along a Corner Crack in Pressurizer Vent Nozzle Penetration Weld
Authors: Lee Sang-Min , Park Jeong-Soon , Kim Jin-Su , Choi Young-Hwan , Chung Hae-Dong
Published: July 2010

Elastic-plastic fracture mechanics as well as linear-elastic fracture mechanics may be applied to evaluate a flaw in ferritic low alloy steel components for operating conditions when the material fracture resistance is controlled by upper shelf toughness behavior. In this paper, the distribution of the stress intensity factor along a corner crack using elastic-plastic fracture mechanics technique is investigated to assess the effect of a structural factor on mechanical loads in pressurizer vent nozzle penetration weld. For this purpose, the stress intensity factor and plastic zone correction of a corner crack are calculated under internal pressure, thermal stress and residual stress in accordance with Electric Power Research Institute (EPRI) equation and Irwin’s approach, respectively. The resulting stress intensity factor and plastic zone correction were compared with those obtained from Structural Integrity Associates (SIA) and Kinectrics, and were observed to be good agreement with Kinectrics results.
Analysis of Surface Strains and Leakage Behavior in Composite Pipes and Vessels Using Digital Image Correlation Technique
Authors: Scheuer Renke , Mertiny Pierre , Bormann Dirk
Published: July 2010

Pipe and vessel structures made from fiber-reinforced polymer composites are know to commonly outperform metallic structures in terms of corrosion resistance and strength-to-weight ratio. However, composite pressure piping and vessels without internal lining are prone to leakage failure caused by matrix cracking. Microscopic fractures in the often brittle matrix phase grow and coalesce under loading, forming a network of matrix cracks that facilitates fluid to permeate the pipe or vessel wall. Hence, liners are often incorporated into composite pressure containment structures. Leakage failures usually occur considerably below pressures causing rupture of composite pipes and vessels. Hence, more efficient designs may be obtained if liners could be avoided altogether. To achieve this goal a thorough understanding of the damage mechanisms leading to leakage failure is required. Composite pressure piping and vessels are generally manufactured using filament winding or similar techniques. Resulting interwoven fiber architectures are generally considered to influence strain patterns and leakage behavior. Classical experimental methods are usually unable to verify this hypothesis, and therefore modeling techniques have largely been employed. In the present study, the effect of fiber architecture on surface strain patterns and the initiation of leakage were investigated experimentally using digital image correlation technique. Surface strain maps were produced for tubular filament-wound composite specimens subjected to combined internal pressure and axial traction. The findings of this study indicate that no distinct correlation exists between surface strain patterns and leakage initiation points.
Analysis of Constant and Variable Amplitude Strain-Life Data Using a Novel Probabilistic Weibull Regression Model
Authors: Pinto Herna´n , De Jesus Abi´lio M. P. , Ferna´ndez Canteli Alfonso
Published: July 2010

The relation between the total strain amplitude and the fatigue life measured in cycles is usually given as strain-life curves based on the former proposals of Basquin for the elastic strain-life and Coffin-Manson for the plastic strain-life. In this paper, a novel Weibull regression model, based on an existing well established Weibull model for the statistical assessment of stress-life fatigue data, is proposed for the probabilistic definition of the strain-life field. This approach arises from sound statistical and physical assumptions and not from an empirical proposal insufficiently supported, provides an analytical probabilistic definition of the whole strain-life field as quantile curves both in the low-cycle and high-cycle fatigue regions, deals directly with the total strain without the need of separating its elastic and plastic strain components, permit dealing with run-outs, and can be applied for probabilistic lifetime prediction using damage accumulation. The parameters of the model can be estimated using different well established methods proposed in the fatigue literature, in particular, the maximum likelihood and the two-stage methods. In this work, the proposed model is applied to analyze fatigue data, available for a pressure vessel material — the P355NL1 steel, consisting of constant amplitude, block and spectrum loading, applied to smooth specimens, previously obtained and published by authors. A new scheme to deal with variable amplitude loading in the background of the proposed regression strain-life Weibull model is described. The possibility to indentify the model constants using both constant amplitude and two-block loading data is discussed. It is demonstrated that the proposed probabilistic model is able to correlate the constant amplitude strain-life data. Furthermore, it can be used to correlate the variable amplitude fatigue data if the model constants are derived from two block loading data. The proposed probabilistic regression model is suitable for reliability analysis of notched details in the framework of the local approaches.
Buckling Analysis of Plastic Pipe Reinforced by Cross-Winding Steel Wire Under Bending
Authors: Li Xiang , Zheng Jinyang , Shi Fengjian , Qin Yongquan , Xu Ping
Published: July 2010

A plastic pipe reinforced by cross helically wound steel wires (PSP) has been developed rapidly in China as a new type of metal-plastics composite pipes. To deeply understand the mechanical properties of PSPs under pure bending, a four-layer analytical model is proposed based on Donnel theory. Additionally, a 3D finite element model (FEM) of PSPs under bending using an eigenvalue method is present. Good agreement between the theoretical results and finite element results is obtained, which shows that the proposed FEM can predict the buckling moments of PSPs. Further, A FEM of the PSP under bending is preformed by using the geometrically nonlinear finite element analysis (FEA). The buckling load is found by searching a bifurcation point on the geometrically nonlinear deformation path and the corresponding buckling mode is obtained from the eigenvalue analysis. Finally, the influence of the pipe lengths, design parameters and initial flaws on the buckling moment is analyzed using nonlinear FEA.
Advanced Fe-Cr Alloys Studied by Pulsed Low Energy Positron System Before and After Helium Ions Implantation
Authors: Sojak Stanislav , Krsˇjak Vladimi´r , Egger Werner
Published: July 2010

Positron annihilation spectroscopy (PAS) is a non-destructive technique which provides information about microstructural damage of structural materials. In this paper, the Pulsed Low Energy Positron System (PLEPS) at the research reactor FRM-II at TU Munich was used to study depth profiling of binary Fe-Cr alloys. Fe-Cr model alloys with different chromium content were investigated in the as-received state as well as after helium ion implantation (dose up to 6.24×1017 ions/cm−2). Measured results show changes in the size of defects after implantation and also in non-implanted specimens depending on the Cr content.
Material Selection Methodology Used in Czech NPP
Authors: Matocha Karel
Published: July 2010

The paper describes the structure of the Standard Technical Documentation A.M.E Section II “Material Properties for Equipments and Pipings of WWER Nuclear Power Plants”. It provides instructions for selection and qualification of parent materials used for manufacture, repair, reconstruction or replacement of selected equipments of WWER NPP and specifies requirements for mechanical characteristics and physical properties.
Effects of Water Jet Peening and Hardening Treatment on Fatigue Properties of SCr420
Authors: Shimamoto Akira , Kubota Ryo , Yang Sung-mo , Choi Dae-kue , Jia Weiping
Published: July 2010

An experimental study of high pressure water jet peening treatment on chromium steal SCr420 H3V2L2 is conducted to study the effects of cavitation impacts of high-speed water on fatigue crack initiation and propagation of notched specimens. There are six different kinds of specimens. First three kinds are treated with; only annealing, only water quenching, and only oil quenching. Other three kinds are treated with above heat treatment and water jet peening, respectively. An axial tensile fatigue tests’ condition is 260MPa maximum stress amplitude, 0 stress ratio and 10Hz frequency, while in-situ observation by SEM is employed. Although fatigue life of the specimens with annealing and water jet peening is shorter than that of only annealing, fatigue life of water and oil quenching with water jet peening specimens is obviously longer than those without water jet peening treatment. Water jet peening has increased residual stress inside the specimens on the latter case and raised their fatigue strength. In-situ observation on the crack tips approves above analysis.
Cracking in Welds of Heavy-Wall Stainless Steel and Nickel Alloy Piping During Fabrication
Authors: Kiso Tomoaki , Ishii Kunio , Seshimo Ichiro
Published: July 2010

Heavy-wall austenitic stainless steel and nickel alloy piping components can sometimes suffer cracking during fabrication. Cracking occurs in the materials during fabrication as a result of solidification cracking during welding and reheat cracking (also referred to as stress relaxation cracking or stress relief cracking) during postweld heat treatment (PWHT) such as solution heat treatment or stabilizing heat treatment. This paper describes several case studies of recent cracking in welds of heavy-wall piping components fabricated from Type 321 stainless steel and Alloy 800HT that have occurred during fabrication. The severe cracking occurred in weld metal in each of the heavy-wall components. As a result of investigations, it was concluded that most likely cause for the cracking was a result of reheat cracking occurring during PWHT.
Use of Local Approach Methods With Non-Proportional Load Histories
Authors: Lewis S. J. , Truman C. E. , Smith D. J.
Published: July 2010

So-called ‘local approach’ methods for fracture analyses, such as the commonly used Beremin model, are attractive as a means to predict component failure due to their flexibility and applicability to a wide range of geometries. However, in cases where cyclic loading occurs, resulting in the accumulation of plastic strain and accompanying residual stress, the validity of the Beremin approach is questionable. This work investigates the applicability of a range of alternative local approach methods to model material failure behaviour in such cases, as well as commenting on the calibration and physical basis of such methods.
Evaluation Method of U-Bolt Energy Absorption
Authors: Shirai Eiji , Zaitsu Tetsuya , Ikeda Kazutoyo , Yoshii Toshiaki , Kondo Masami , Fujiwara Yoshihisa , Shinma Satoshi
Published: July 2010

At domestic PWR plants in Japan, one of the major key issues is earthquake-proof safety [1–3]. Recently, a design procedure using energy absorption, not conventional rigid design, was authorized according to revised review guidelines for aseismic design (JEAC4601). Therefore, we focused on the design technique that utilizes energy absorption effects to reduce the seismic responses of the piping system with U-Bolt, by the static and dynamic tests of simplified piping model supported by U-Bolt. The force-displacement characteristics and a fatigue diagram were obtained by the tests.
Effective Mass of Fluid for Rocking Motion of Flat-Bottom Cylindrical Tanks
Authors: Taniguchi Tomoyo , Segawa Toru
Published: July 2010

In analyzing the rocking motion of the flat-bottom cylindrical tanks subjected to severe earthquakes, the effective mass of fluid for the rocking motion and its moment inertia around the pivoting bottom edge of the tank would be indispensable dynamical properties, because they couples the fluid-shell interaction motion, the so-called bulging motion, with the rocking motion. This paper quantifies them based on the equilibrium of the fluid pressure and inertia force accompanying the angular acceleration acting on the pivoting bottom edge of the tank. Employing a general mathematical solution for the fluid pressure that can calculate either fully or partially uplifted tank bottom, this paper presents mathematical formulae of the effective mass of fluid for the rocking motion and its moment inertia. These quantities are given by an explicit function of dimensional variables of the tank but with Fourier series. For designer’s convenience, the effective moment inertia and effective mass of fluid for the rocking motion and its center of gravity from the pivoting bottom edge are normalized accordingly and are depicted on diagrams.
Sensitivity of Predicted Weld Residual Stresses in the NeT Task Group 1 Single Bead on Plate Benchmark Problem to Finite Element Mesh Design and Heat Source Characteristics
Authors: Bendeich Philip J. , Smith Mike C. , Carr David G. , Edwards Lyndon
Published: July 2010

A single weld bead deposited on a flat plate is a deceptively simple problem that is, in practice, a significant challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in an extensive programme of measurement and simulation extending from 2002 to 2008. Thus, the NeT bead on plate forms an ideal benchmark problem for the development of weld residual stress simulation techniques. It is often difficult to separate the influence of different analysis variables in a large collaborative study such as NeT Task Group 1. This paper examines sensitivity to mesh design, element type, and heat source characteristics in a closely controlled study using several different mesh designs, element types (both tetrahedral and hexahedral), and heat sources, but the same material constitutive model and finite element analysis code. It complements a companion paper that varies material constitutive models. A dedicated heat source modelling tool with a semi-automatic interface to the ABAQUS finite element code has been used to vary the heat source characteristics, thus facilitating rapid and controlled sensitivity studies without the need for bespoke heat source coding within ABAQUS.
Overview of the Revised JEAC4201-2007, Japanese Code of Surveillance Tests for Reactor Vessel Materials
Authors: Hirano Takashi , Asada Seiji , Yamashita Norimichi , Iwasaki Masanobu , Tomimatsu Minoru
Published: July 2010

The Japan Electric Association Code, JEAC 4201, “Method of Surveillance Tests for Structural Materials of Nuclear Reactors” was revised in 2007. Major revised points of JEAC4201-2007 are: 1) A new irradiation embrittlement correlation method, 2) Reconstitution of surveillance specimen, 3) Long-term surveillance program. An overview of the revised JEAC 4201-2007 is presented in this paper.
Reliability Estimation of a Natural Gas Pipeline With Surface Crack
Authors: Lee O. S. , Kim H. M. , Kim D. H. , Choi H. B.
Published: July 2010

The reliability estimation of API 5L X65 natural gas pipeline with a semi-elliptical crack along a pipeline surface is performed by utilizing the probabilistic methods, such as the First Order Reliability Method (FORM) and the Second Order Reliability Method (SORM). The probabilistic method accounts for the uncertainties in the load and the resistance parameters on the Limit State Function (LSF). The LSF is formulated with the help of fracture control concept including the Stress Intensity Factor (SIF) for a natural gas pipeline with cracks or crack like defects. The hoop stress due to the internal pressure is considered to be a major load. The effects of probabilistic distribution characteristics of random variables, on the failure probability are systematically investigated. The probabilistic distribution characteristics of random variables include the normal, the log-normal and the Weibull distributions. The results obtained by using the FORM and the SORM are compared with those determined by the Monte Carlo Simulation (MCS).
A Comparison of Fracture Assessment Methods in Several Structural Integrity Assessment Procedures
Authors: Yang Tiecheng , Chen Xuedong , Fan Zhichao
Published: July 2010

For the fracture assessment method internationally used in different structural integrity assessment procedures, such as R6, BS 7910, FITNET API 579 and GB/T 19624, this paper gives the results of analytical comparisons in combination with specific calculation examples by comparing different assessment options or levels, the partial safety factors (PSFs), limit load solutions, stress intensity factor solutions, residual stress distribution and treatment methods, secondary stresses and ρ factor solutions etc., which provide a basis for improvement of fracture assessment methods.
A Residual Stress Analysis of a Corner Crack in Pressurizer Vent Nozzle Penetration Weld
Authors: Lee Sang-Min , Park Jeong-Soon , Choi Young-Hwan , Chung Hae-Dong , Cho Doo-Ho , Chang Yoon-Suk , Kim Young-Jin
Published: July 2010

There are some ferritic low alloy steel components including dissimilar metal welding parts in a nuclear power plant. Residual stress induced by welding process is one of the factors that may lead a sound component to have a defect. Therefore it is necessary that the distribution of residual stress is obtained to predict the behavior of a dissimilar metal welding part. In this paper, the distribution of residual stress obtained by finite element analysis is investigated to assess the stress intensity factor of a corner crack in pressurizer vent nozzle penetration weld. Then the stress intensity factor and plastic zone correction of a corner crack are calculated under internal pressure, thermal stress and residual stress in accordance with Electric Power Research Institute equation [1]. The resulting stress intensity factor and plastic-zone correction were compared with those obtained from Structural Integrity Associates.
Numerical Simulation on the Sound Field of Gas Valve Due to Inner Leakage
Authors: Wang Bing , Wang Yadong , Liang Wenjun , Sheng Shuiping , Guo Jianping , Zhang Liang
Published: July 2010

Recently, acoustic testing method has been widely used for valve leakage inspection. Traditional method has difficulty carrying out research on the acoustic testing of valve leakage due to the complex geometry of the valve and the effect of flow on sound field. Thus, a numerical method was put forward based on Reynolds average N-S equation and k – ε equation in order to investigate the flow of the inner leakage of ball valve, needle valve and gate valve. Furthermore, difference time domain method was adopted to simulate the noise field of the flow based on Lighthill acoustic equation. And the characteristics of acoustic distribution were obtained. The results showed that turbulent flow was the main cause of jet noise inner the valve due to gas leakage. And the acoustic distribution had directivity. There were about 10 ∼ 25dB difference between the upstream and downstream of the leaking valve. The position with the highest sound pressure was also found out.
Research and Development of Damping Device for Light Weight Mechanical Structure Using Damping Effect Caused by Eddy Current
Authors: Furuya Osamu , Ogata Keiji , Tanaka Toyohiko , Kurabayashi Hiroshi
Published: July 2010

A base-isolation and vibration control technique has been applied positively to architectural and civil structures after Kobe earthquake, and now the techniques are adopted as general vibration reduction technique for many structures. In such situation, an application of the vibration attenuation device to the small-scale structure has been carried out actively in recent years. Especially, in the important institution of the cities such as a refuge place, a hospital, a school, an information and a communication institution where function maintenance is needed, it is important to maintain its performance of the machinery and equipment in the facility with an upgrade of structural seismic safety. Moreover, in the future, upgrading of seismic safety of the particular equipments is urgent business. This study has been examined a low cost and compact damping device for base-isolation system of light weight mechanical structures like a computer server rack. In this paper, the experimental and analytical results on the basic performances of the damping device using damping effect by Eddy-Current.
Semi-Active Control of Civil Structures With a One-Step-Ahead Prediction of the Seismic Response
Authors: Hiramoto Kazuhiko , Matsuoka Taichi , Sunakoda Katsuaki , Fukukita Akira , Yamazaki Issei
Published: July 2010

We propose a semi-active control of civil structures based on a one-step-ahead prediction of the seismic response. The vibration control device (VCD), which has been developed by authors, generates two types of resistance forces, i.e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that the Euclidean norm of the one-step-ahead predicted seismic response is minimized. As an example a semi-active control of a fifteen-story building with three VCDs is considered. The simulation results show that the proposed semi-active control achieves superior performance on vibration suppression compared with a passive control case where the damping coefficient of each VCD is fixed at its maximum value.
Effect of Additional Irradiation at Different Fluxes on RPV Embrittlement
Authors: Dohi Kenji , Nishida Kenji , Nomoto Akiyoshi , Soneda Naoki , Matsuzawa Hiroshi , Tomimatsu Minoru
Published: July 2010

The effect of the neutron flux at high fluence on the microstructural and hardness changes of a reactor pressure vessel (RPV) steel was investigated. An accelerated test reactor irradiation of a RPV material, previously irradiated in commercial reactors, was carried out at the lowest possible neutron fluxes in order to obtain neutron fluences up to approximately 1×1020 n/cm2 (E>1MeV). State-of-the-art experimental techniques such as three-dimensional atom probe were applied to carry out advanced quantitative characterization of defect features in the materials. Results for the same material irradiated in both high and low flux conditions are compared. For neutron fluences above 6×1019 n/cm2 (E>1MeV) the difference in the neutron fluence dependence of the increase in hardness is not seen for any neutron flux condition. The volume fraction of solute atom clusters increases linearly with neutron fluence, and the influence of neutron flux is not significant. The component elements and the chemical composition of the solute atom clusters formed by the irradiation do not change regardless of the neutron fluence and flux. The square root of the volume fraction of the solute atom clusters is a good correlation with the increase in hardness.
Risk-Based Applications in Industry
Authors: Fo´tos Re´ka , To´th La´szlo´
Published: July 2010

The concept of risk evaluation exists for centuries. It is present everywhere, in the economy, in the industry and in our everyday life. In the decades past, the role of risk concept is increasing continuously, which is due to a lot of reasonable reasons. The paper shows, why the risk-based applications are extended in more and more branches of industry. This likes to be a “communication interface” between the “economists” and “engineers”. This new improvement in inpection planning involves numerous benefits, but raises some questions, e.g. from the regulatory point of view. What are needed to implement the risk-based strategy and for what can we expected as the result of it? The paper shows a solution of the implementation of the risk-based methodologies, which main principles can be applied in the most fields of industry. The main aim is to focus the maintenance and inspection efforts on the highest risk elements, but how can we establish an adequate order between them, on the basis of risk? Are there any standards or guidelines for risk-based strategies in the different industries? The paper tries to summarize the current state of risk-based approaches, considering the benefits and difficulties of it. The paper concentrates on the nuclear industry, which is one of the most controversial industries, since the whole society is divided on this issue. The concept of risk is unthinkable in this field for a lot of people, including some regulatory bodies. As opposed to it, in some countries there are an acceptable process is the risk-based managing of nuclear power plants. What is the cause of this sharp difference? The purpose of this article is to demonstrate the state of the art in this field and to show the trends in the development of risk-based approaches.
Active Sloshing Control by Using Movable Plates Device Based on Flow Control Method
Authors: Hara Kensuke , Watanabe Masahiro , Hirai Kazuki
Published: July 2010

This paper deals with an experimental study of an active control technique for the suppression of sloshing based on flow control in the tank. In this paper, we proposed the active feedback control method by using movable plates which are set in liquid. In the experiment, the present method is applied to the 2-dimensional problem of sloshing which occurs in the rectangular tank due to a horizontal excitation. The sloshing are suppressed by the active feedback to the rotation of the movable plate installed in liquid. The suppression performances are examined by changing the phase difference between the control signal of rotation angles of the movable plate and the liquid surface displacement (phase-shift). The performance of proposed method is evaluated by the time history, the root mean square value and frequency-response of the surface wave displacement under the active feedback control. Moreover, the effects of movable plate number and installation position on the suppression performance are clarified. On the other hand, the visualization experiment is conducted to obtain the flow pattern in the tank when the sloshing is controlled by the present method. The decreasing mechanism of the surface wave is discussed by the result of the visualization experiment. As a result, it is shown that the proposed control devics and active control method suppress the sloshing effectively. Furthermore, it is found that the changes of flow pattern by the drive of movable plate cause the suppression of sloshing in the visualization experiment.
Measurement of Fatigue Crack Growth Rates for Steels in Hydrogen Storage
Authors: Wada Yoru , Takasawa Kouichi , Ishigaki Ryoji , Tanaka Yasuhiko , Iwadate Tadao
Published: July 2010

Fatigue crack growth rates (da/dN) in up to 90MPa high-pressure gaseous hydrogen environments of quenched and tempered low alloy Cr-Mo steel: JIS-SCM435 with ultimate tensile strength level of 950MPa were measured utilizing a cycle, ranging from 0.3sec from 1000sec long with a road ratio R = 0.1. The longer cycle time tests (15sec to 1000sec per cycle) were conducted utilizing internal pressure test apparatus by utilizing cylinder (= CY) specimens, while shorter cycle (0.3sec to 25sec per cycle) tests were performed utilizing fatigue test machine using compact tension (= C(T)) specimens. Crack depth of CY specimens were measured by Time Of Flight Diffraction (TOFD) technique and the crack length of C(T) specimens were measured by compliance technique. Both C(T) and CY specimen showed accelerated sub-critical crack growth in gaseous hydrogen compared that in air or inert gas atmosphere. The effect of load ratio was also evaluated.
IAEA Coordinated Research Project on Master Curve Approach to Monitor Fracture Toughness of RPV Steels: Effect of Loading Rate
Authors: Viehrig Hans-Werner , Lucon Enrico , Server William L.
Published: July 2010

The Master Curve (MC) approach procedure standardized in ASTM E1921 is defined for quasi-static loading conditions. However, the extension of the MC method to dynamic testing is still under discussion. The effect of loading rate can be broken down into two distinct aspects: 1) the effect of loading rate on Master Curve To values for loading rates within the loading rate range specified in ASTM E1921 for quasi-static loading, and 2) the effect of loading rate on Master Curve To values for higher loading rates. The IAEA CRP8 includes both aspects, but primarily focuses on the second element of loading rate effects, i.e. loading rate ranges above the upper limit of the E1921 standard and it comprises: - results of a round-robin exercise to validate the application of the Master Curve approach to precracked Charpy (PCC) specimens tested in the ductile-to-brittle transition region using an instrumented pendulum, - Master Curve data obtained at different loading rates on various RPV steels, in order to assess the loading rate dependence of To and compare it with an empirical model proposed by Wallin, and - the comparison of results from unloading compliance and monotonic loading in the quasi-static range.
Assessment of Overlapped Internal and External Volumetric Flaws in p-M Method
Authors: Konosu Shinji , Miyata Hikaru
Published: July 2010

Assessment of overlapped internal and external volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, the procedures have not yet defined how to assess these flaws. In this paper, a new procedure for these volumetric flaws is proposed for assessing the flaws by the p-M (pressure-moment) diagram method, which is a simple assessment procedure. Numerous FEAs for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.
Modelling of Prestrain Effects on Fracture Using Local Approach Methods
Authors: Lewis S. J. , Truman C. E. , Smith D. J.
Published: July 2010

The effects of load history on component fracture behaviour have been studied at length in terms of the generation and resulting influence of residual stresses. Despite this, the effect of plastic strain history, separate from the generation of residual stresses, is still not clearly defined. This work presents an investigation into the effect of accumulated strain on subsequent fracture behaviour. The effects of load history on low temperature cleavage fracture are modelled by means of a number of local approach methods, accounting for variations in stress and strain throughout the component’s load history. Prior strain was found to reduce the mean fracture load of 20mm thick CT specimens, irrespective of the level of room temperature strain applied. Local approach methods, calibrated to low and high constraint fracture data, were able to correctly predict a reduction in fracture load, although the exact magnitude of the reduced loads were not always correctly resolved. Further experimental data and further work on model formulation is needed to confirm the conclusions drawn here.
Dynamic Response of a Turbulent Cylinder Wake to Forced Excitation
Authors: Konstantinidis Efstathios , Liang Chunlei
Published: July 2010

Three-dimensional large-eddy simulations were carried out to determine the dynamic response of a turbulent cylinder wake to forced excitation at a subcritical Reynolds number of 2580. The excitation frequency was varied across the primary lock-on range while the amplitude of sinusoidal velocity perturbation and the mean velocity imposed at the inflow boundary were kept constant. The velocity fluctuations in the wake and the fluctuating forces on the cylinder are analyzed employing spectral, time-domain and phase-portrait methods. The results show that the dynamic response of the inline force is different than that of the transverse one on the border of the lock-on range; while the inline force exhibits a phase-locked response, the transverse force indicates an intermittent response. This behavior is linked to the wake dynamics which is similar to that of the transverse force. This result is explained on the basis of the Morison equation which shows that the inline force is biased by the inertial components associated with the added mass and pressure waves in unsteady flows. It is further shown that the existence of a mean velocity component alters radically the dynamics of the inline force and appropriate ranges of a dimensionless parameter are proposed to describe the response.
Influence of Multiaxial Stresses on Creep Properties of Phosphorus Alloyed Oxygen Free Copper
Authors: Wu Rui , Jin Lai-Zhe , Sandstro¨m Rolf
Published: July 2010

Phosphorus alloyed oxygen free copper (Cu-OFP) canisters are planned to be used for spent nuclear fuel in Sweden. The copper canisters will be subjected to creep under multiaxial stress states in the repository. Creep tests have therefore been carried out using double notch specimens having a notch acuity of 0.5 in Cu-OFP at 75°C. The creep results from the notched specimens are compared with those from the smooth ones. It shows that the creep lifetime for notched specimens can be estimated to be two orders of magnitude or more longer than that for the smooth ones, indicating notch strengthening for the investigated Cu-OFP material. Metallographic examinations after failure show that pores and creep cavities to a limited extent are observed only adjacent to fracture. To interpret the tests for the notched creep specimens, finite element computations have been performed with a new basic model for primary creep without fitting parameters. The creep strain versus time could be simulated successfully. Initially the stresses at the notches are almost twice as high as in the centre of the specimens. The highest stresses are relaxed rapidly. At the studied temperature 75°C, the creep exponent of Cu-OFP is about 85, thus, deep down in the power-law breakdown regime. This contributes strongly to the homogenous stress distribution across the centre section. Since the redistribution of stresses has taken place before large creep deformation has occurred, the specimens are not notch sensitive in agreement with observations.
Simulation of Temperature Field of TIG Welding Using FDM
Authors: Tailor D. H. , Srinivasan K. N. , Channiwala S. A. , Panwala M. Sohel M.
Published: July 2010

Welding is one of the most important material-joining processes widely used in industry. Low carbon steel and stainless steel with thin plates are widely used in the fabrication of pressure vessels and other components. Thin plates are joints together by the Tungsten inert gas welding (GTAW) methods. Temperature distribution that occurs during welding affects the microstructure, mechanical properties and the residual stresses that will be present in the welded material. This paper discusses the development of a model for the temperature distribution during butt welding at different heat inputs using Finite difference method (FDM). The model is created from first principles of heat transfer and utilizes contact conduction that is a function of temperature, Gaussian heat distribution, and many material properties that vary with temperature. The temperature distribution curves obtained with this model are presented. This transient temperature field has been validated with experimentation of measuring temperature during welding of butt welded of low carbon steel using GTAW process. Using this FDM code, the range of error between the model and experimental results is −11.21 to 2.63%, demonstrating the accuracy of the model.