bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of Cold Worked Type 316L Stainless Steel in High Pressure Gaseous Hydrogen: Investigation of Materials Properties in High Pressure Gaseous Hydrogen—3
Authors: Ohmiya Shinichi , Fujii Hideki
Published: August 2009

Safety of on-board high-pressure hydrogen fuel tanks and piping systems in hydrogen refueling station is one of the most important subjects for upcoming hydrogen society featured by fuel cell vehicles. Type 316L austenitic stainless steel is known as a material in which the effect of hydrogen on mechanical properties is very small, so JIS SUS316L is recognized as the standard material for 35MPa type on-board fuel tank liner in the Japanese standard JARI-S001. However, solution treated 316L does not always have sufficient 0.2% proof stress, and materials having higher proof stress are strongly needed. One of the solutions is work-hardening of the material, which is conventionally used for piping systems for high pressure gas facilities. In this study, the effect of hydrogen on mechanical properties of 40% cold worked 316L in high-pressure gaseous hydrogen at 45MPa was investigated. Results are as follows: Any significant effect of hydrogen was not recognized in tensile tests using round bar type specimens at room temperature and 85°C. In axial fatigue life tests using sand glass type specimens (stress ratio R = −1) at room temperature, not so large difference was observed on S-N curves in air and in high pressure hydrogen. However, a little influence was observed in fatigue crack growth tests using half inch CT specimens at room temperature (R = 0.05). Microstructure observation reveals that any martensitic transformation did not occur. The degradation of fatigue crack growth rate in high pressure gaseous hydrogen is probably caused by the work hardened δ-ferrite which is generally contained in thick materials. However the effect of hydrogen is only limited and 40% cold worked type 316L stainless steel is considered to be used in high pressure hydrogen gas just like solution treated one.
Methodology of Fluid Flow Evaluation in the Lower Core and in Fuel Assembly Legs of a PWR With Code_Saturne
Authors: Le Maiˆtre-Vurpillot Christelle , Fournier Yvan
Published: August 2009

In order to better understand the stresses to which fuel rods are subjected, we need to improve our knowledge of the fluid flow inside the core and the fuel assembly, and we are particularly interested in the first spacer grid region, as fuel rod fretting has sometimes been observed. It has been seen experimentally in previous years that rotating mixing grids on EDF’s lock-up (a fuel assembly section subjected to fluid flow, with 2 spacer grid and 2 mixing grids) could let to different vibration levels with some fuel assembly types. This seems to confirm that the influence of fluid flow is of primary importance for fuel rod vibration (and thus fretting). A series of calculations are thus run with our incompressible Navier-Stockes solver, Code_Saturne with a classical RANS turbulence model. We limit to a scale of few assemblies for practical reasons. At this scale, most of the features of the fuel rods, nozzles, and guides tubes are represented, though the geometry of the spacer grids is still much simplified, and details such as debris-trapping grids are ignored. We have analysed the axial and transverse velocities for configuration with different fuel assembly types, and calculated an approximation of efforts on individual fuel rods. Local scale results are mainly qualitative, but they already enable us to obtain a better understanding of the effect of nozzle shape or heterogeneous fuel assemblies on the fluid flow. The nozzle geometry (and fuel rod cap positions) have a major influence on the levels of transverse velocity attained. We have run a good number of sensitivity verifications and built a solid methodology, when defining these calculations. To better validate local scale calculations, EDF R&D has built a small lower fuel rod assembly mock-up “BORA 3×7” (3×3 assemblies with 7×7 rods each). This mock-up is being used to obtain the velocity data. The calculations described in this paper are not refined enough to be able to directly correlate fluid flow and fuel cladding fretting in a quantitative manner, but are a step in this direction and may already improve our understanding of the local loads and spatial load variations a fuel assembly is subjected to.
Evaluation of Hydrogen Environment Embrittlement and Fatigue Properties of Stainless Steels in High Pressure Gaseous Hydrogen: Investigation of Materials Properties in High Pressure Gaseous Hydrogen—2
Authors: Omura Tomohiko , Miyahara Mitsuo , Semba Hiroyuki , Igarashi Masaaki , Hirata Hiroyuki
Published: August 2009

Hydrogen environment embrittlement (HEE) susceptibility in high pressure gaseous hydrogen was investigated on 300 series austenitic stainless steels and A6061-T6 aluminum alloy. Tensile properties of these materials were evaluated by Slow Strain Rate Testing (SSRT) in gaseous hydrogen pressurized up to 90MPa (13053 psig) in the temperature range from −40 to 85 degrees C (−40 to 185 degrees F). HEE susceptibilities of austenitic stainless steels strongly depended upon the chemical compositions and testing temperatures. A6061-T6 aluminum alloy showed no degradation by hydrogen. Fatigue properties in high pressure gaseous hydrogen were evaluated by the external cyclic pressurization test using tubular specimens. The tubular specimen was filled with high pressure hydrogen gas, and the outside of the specimen was cyclically pressurized with water. Type 304 showed a decrease in the fatigue life in hydrogen gas, while as for type 316L and A6061-T6 the difference of the fatigue life between hydrogen and argon environments was small. HEE susceptibility of investigated materials was discussed based on the stability of an austenitic structure.
Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: An Experimental Approach
Authors: Nakamura Izumi , Otani Akihito , Shiratori Masaki
Published: August 2009

In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned wall elbow, because the life of piping models with wall thinning subjected to out-of-plane bending may reduce significantly.
Numerical Simulation of Blast Loadings on a Thick-Walled Cylindrical Vessel
Authors: Deng Guide , Xu Ping , Zheng Jinyang , Chen Yongjun , Hu Yongle , Zhao Longmao , Ma Yuanyuan
Published: August 2009

Determining blast loadings on an explosion containment vessel (ECV) is the foundation to design the ECV. Explosion of TNT centrally located in a thick-walled cylindrical vessel and its impact on the cylinder was simulated using the explicit finite element code LS-DYNA. Blast loadings on the cylinder computed are in good agreement with the corresponding experimental results. Then wall thickness and yield stress of the cylinder were changed in the following simulation to investigate effect of shell deformation on blast loadings. It is revealed that shell deformation during the primary pulses of blast loadings is so slight that it has little influence on the blast loadings. Though the deformation may increase greatly after the primary pulses, the dynamic response of an ECV is mainly affected by the primary pulses. Therefore, decoupled analyses are appropriate, in which the shell of an ECV is treated as a rigid wall when determining blast loadings on it.
Tensile Deformation of Alloy 617 at Different Temperatures
Authors: Marthandam Vikram , Roy Ajit Kumar
Published: August 2009

Austenitic Alloy 617 has been identified as a candidate structural material in hydrogen generation using nuclear heat. A temperature of 950°C has been recommended to achieve the maximum efficiency in hydrogen generation involving numerous chemical reactions. The tensile properties of this alloy have been determined at temperatures ranging from ambient to 1000°C. Simultaneously, the fracture toughness of this alloy is being evaluated using fracture-mechanics-based compact tension specimen. This paper presents the results of tensile testing of this alloy as a function of temperature. The results of fractographic evaluations using scanning electron microscopy are also included.
Static and Dynamic J-R Tests for LBB Design Application of Ferritic Piping Materials
Authors: Kim Kuk Cheol , Suk Jin Ik , Sung Un Hak , Kim Byoung Koo , Kim Jeong Tae
Published: August 2009

Dynamic J-R tests for Leak-Before-Break (LBB) design, when rapid loading is applied, have traditionally been performed using Direct Current Potential Drop (DCPD) as the measuring method of crack extension length. However, for ferritic steel, it is difficult to determine the crack initiation point due to the pulse drop from the ferromagnetic phenomenon at the initial stage of the test. Recently, a normalization method using only load and load line displacement curves was proposed and used as a standard dynamic J-R test procedure in ASTM E1820. To compare dynamic J-R curves obtained by the two different test methods, tested results using DCPD was reanalyzed in accordance with the normalization method. In the normalization method, physical crack extension length is restricted to the lesser of 4mm or 15% of the initial uncracked ligament to minimize curve-fitting errors. However, in some of the DCPD data, the results for the specimen contained physical crack lengths that propagated beyond 4mm. Actually, without ductility information for the tested materials, the possibility of violating the physical crack extension restriction for normalization for a first test specimen is high. This paper evaluates the effect of physical crack extension length on the reliability of dynamic J-R properties for LBB design of reactor coolant piping materials for Korean Standard Nuclear Power Plants. The J-R properties between dynamic and static loading are also compared.
Prediction of the Local Areas of CANDU Feeder Pipes Highly Susceptible to Wall Thinning Due to Flow-Accelerated Corrosion
Authors: Kang Dong Gu , Jo Jong Chull
Published: August 2009

Flow fields inside feeder pipes have been simulated numerically using a CFD (computational fluid dynamics) code to calculate the shear stress distribution which is the most important factor to be considered in predicting the local regions of feeder pipes highly susceptible to FAC (flow-accelerated corrosion)-induced wall thinning. The CFD approach with schemes used in this study to simulate the flow situations inside the CANDU feeder pipes has been verified by showing a good agreement between the investigation results for the failed feedwater pipe at Surry Unit 2 plant in U.S. and the CFD calculation. Sensitivity studies of the three geometrical parameters such as angle of the 1st and 2nd bends, length of the 1st span between the grayloc hub and the 1st bend, and length of the 2nd span between the 1st and the 2nd bends have been performed. As the results of CFD analysis, it is seen that the local regions of feeder pipes of Wolsung Unit 1 in Korea, on which the wall thickness measurements have been performed so far, are not coincident with the worst regions predicted by the present CFD analysis where is the connection region of straight & bend pipe near the inlet part of the bend intrados. Finally, based on the results of the present CFD analysis a guide to the selection of the weakest local positions where the measurement of wall thickness should be performed with higher priority has been provided.
Effect of Weld Overlay Repair on Residual Stress and Crack Propagation in a Welding Pipe
Authors: Iwamatsu Fuminori , Yanagida Nobuyoshi , Miyazaki Katsumasa
Published: August 2009

Intergranular stress corrosion cracking (IGSCC) has been still one of concerns at the weld zone in boiling water reactors (BWRs). Therefore, Weld Overlay (WOL) process has been developed and applied to repair of BWR pipe joints. To understand residual stress and crack growth behavior is important to evaluate the reliability of pipe joints with WOL. In this paper, the residual stresses were calculated by using thermal elasto-plastic analysis by finite element method (FEM). The analytical model was assumed the primary loop recirculation (PLR) pipe joint with WOL followed by the Japanese guideline. The tensile hoop residual stress was changed to compressive stress on the inner surface of the pipe. On the other hand, tensile axial residual stress was occurred on the inner surface of the pipe by butt-welding and some WOL cases increased the tensile axial stress. In addition, the stress intensity factor for fully circumferential cracks was evaluated using calculated residual stress distributions. As a result, the effect of application of WOL on the crack growth behavior is insignificant in PLR pipe joint.
Fatigue Crack Growth Threshold of Austenitic Stainless Steels in Simulated PWR Primary Water
Authors: Tsutsumi Kazuya , Yamamoto Kenji , Nitta Yoshikazu
Published: August 2009

Fatigue crack propagation behaviors in PWR environment can be evaluated by using crack growth rate (CGR) curves which are given in JSME code on Fitness-for-Service for nuclear power plant. The CGR curves, however, are only defined in crack growth region and crack growth thresholds are not considered. Since there is a case that stresses in low ΔK region is applied to the components in case of fatigue, it is needed to investigate near-threshold fatigue CGR to establish fatigue assessment. In this study, CGR tests for stainless steels were carried out, and CGR in the region and ΔKth were obtained in simulated PWR primary water. It was found that CGR was accelerated in high temperature water compared to that in air and ΔKth existed even in water environment. ΔKth was influenced by temperature, stress ratio and frequency, independently of materials. Oxide-induced-crack-closure has an important role in high temperature water. ΔKth was formulated and ΔKth evaluation method, whose accuracy were ±25% between experimental data and evaluation value, was proposed.
Numerical Simulation of the Diffusion of Natural Gas Due to Pipeline Failure
Authors: Liu Yanlei , Zheng Jinyang
Published: August 2009

This paper introduces a numerical method to calculate the diffusion of natural gas due to pipeline failure, which provides an effective base for solving the problems of leakage of natural gas. A finite volumetric model and the corresponding numerical algorithm are established by using species transport and reaction module of FLUENT. In this method, several important parameters such as the mole fraction of components, pressure and temperature distributions within the calculating region are predicted to certain accuracy. Based on numerical results, the key factors affecting the natural gas diffusion such as the diameter of the hole and wind speed are also analyzed. The current study presents a clear view in dealing with the leakage of natural gas due to pipeline failure.
Design of Passive Vibration Control Device Based on GKYP Lemma
Authors: Zhang Song , Iba Daisuke , Sone Akira , Masuda Arata
Published: August 2009

This paper proposes a new method that is an optimization design of a passive vibration system based on linear control theory. A Force generated by spring and damper that are the design parameters of the passive vibration system have the same properties with a PD controller. So it is possible to apply a method that shapes an open-loop transfer function of the PD controller based on the GKYP lemma. By using the method, the gain and the phase of the transfer function can be designed with respect to each frequency band. As a result, it is not necessary to solve a difficult problem that is a bilinear matrix inequality problem obtained by an ordinary formulation.
Life Prediction of a Discrete Multi-Layered Explosion Containment Vessel
Authors: Chen Yongjun , Xu Ping , Zheng Jinyang , Deng Guide , Wu Xiaodan , Ma Yuanyuan , Sun Guoyou
Published: August 2009

A discrete multi-layered explosion containment vessel (DMECV) consists of a thin cylindrical inner shell and helically cross-winding flat steel ribbons, which has advantages of convenient in fabrication and low in cost. The DMECVs generally fall into one of two categories: vessels designed for one-time-use and those for multiple-use. For a multiple-use DMECV, it is important to predict its remaining life under explosive loading for safe application. A method based on the growth of fatigue cracks in the inner shell is presented to predict the total number of explosive tests that a DMECV can withstand. By integrating the Paris law, an expression was obtained to calculate the crack growth in a single explosive. Then the expression was used as a recursion relationship to determine the new crack size for the next test, when the critical crack size is reached, the maximum number of explosive tests was obtained. Results are presented and discussed for an initial axial side-crack in the inner shell of the DMECV.
Rupture Behavior of Multi-Pass Welded Joints of Heat Resistant Steel Subjected to Creep Loading
Authors: Yamazaki Masayoshi , Hongo Hiromichi , Watanabe Takashi
Published: August 2009

By Conducting long-term creep rupture tests for ferritic (2.25Cr-1Mo and 9Cr-1Mo-VNb) and austenitic (18Cr-8Ni and 16Cr-12Ni-2Mo-0.01C-0.07N) heat resistant steel multi-pass welded joints, creep rupture behavior and microstructures were examined. Constant-load creep rupture tests were conducted at 550 and 600 °C up to about 30,000h. Viewpoint in this study was centered on the influence of microstructure on the fracture location of welded joints in heat resistant steels. The results obtained are as follows; 1. The rupture location of the welded joint in austenitic heat resistant steel was found to shift from the base metal at the higher stress condition to the weld metal at lower stress condition at 550 and 600 °C. 2. In the welded joint of austenitic heat resistant steels, the last layer of weld metal showed considerably lager creep strain than the central layers of weld metal. 3. The rupture location of the welded joint in ferritic heat resistant steel was found to shift from the base metal or weld metal at the higher stress condition to the fine-grained HAZ adjacent to the base metal at lower stress condition at 550 and 600 °C. 4. Type IV creep crack initiation occurred in the fine grained HAZ region adjacent to the base metal for the weld metal pass overlap regions of multi-pass large welded joints specimen in 2.25Cr-1Mo steel. 5. Type IV creep crack of the 9Cr-1Mo-V-Nb welded joint nucleated in the curved part of the groove angle and propagated to the top part of the V-groove. It was found that the voids and cracks were initiated inside the plate thickness.
Cyclic and Fatigue Behavior of the P355NL1 Steel Under Block Loading
Authors: Pereira He´lder F. S. G. , De Jesus Abi´lio M. P. , Fernandes Anto´nio A. , Ribeiro Alfredo S.
Published: August 2009

Current fatigue analyses of metallic structures undergoing variable amplitude loading, including pressure vessels, are mostly based on linear cumulative damage concepts, as proposed by Palmgren and Miner. This type of analysis neglects any sequential effects of the loading history. Several studies have shown that linear cumulative damage theories can produce inconsistent fatigue life predictions. In this paper, both fatigue damage accumulation and cyclic elastoplastic behaviors of the P355NL1 steel are characterized, using block loading fatigue tests. The loading is composed by blocks of constant strain-controlled amplitudes, applied according to two and multiple alternate blocks sequences. Also, loading composed by blocks of variable strain-controlled amplitudes are investigated. The block loading illustrates that fatigue damage evolves nonlinearly with the number of load cycles, as a function of the block strain amplitudes. These observations suggest a nonlinear damage accumulation rule with load sequential effects for the P355NL1 steel. However, the damage accumulation nonlinearity and load sequential effects are more evident for the two block loading rather than for multiple alternate block sequences, which suggests that the linear Palmgren-Miner’s rule tend to produce better results for more irregular loading histories. Some phenomenological interpretations for the observed trends are discussed under a fracture mechanics framework.
Effects of Residual Stress by Weld Overlay Cladding and PWHT on the Structural Integrity of RPV During PTS
Authors: Udagawa Makoto , Katsuyama Jinya , Onizawa Kunio
Published: August 2009

In order to assess the structural integrity of a reactor pressure vessel (RPV), it is assumed that a surface crack resides through the cladding at the inner surface of the vessel. It is, therefore, important to precisely evaluate stress intensity factor (SIF) under the residual stress field due to weld overlay cladding and post-weld heat treatment (PWHT). In this work, numerical simulation based on thermal-elastic-plastic-creep analysis using finite element method was performed to evaluate residual stress distribution near the cladding layer produced by weld overlay cladding and PWHT. The tensile residual stress of about 400 MPa occurs in the cladding at room temperature after the PWHT. The residual stress distributions under the normal operating conditions (system pressure and temperature) of RPV were also evaluated. The effect of residual stress and evaluation methods on SIF behavior for various crack size were studied under typical pressurized thermal shock (PTS) conditions such as small break loss of coolant accident (SBLOCA), main steam line break (MSLB) and large break loss of coolant accident (LBLOCA). It is clarified from comparison of this weld simulation with the other simple methods that SIF is affected by residual stress by weld overlay cladding and PWHT.
Representation and Partitioning of Welding Residual Stress Distributions for Use in Structural Integrity Assessments
Authors: Toft Adam , Beardsmore David , James Peter , Sharples John , Martin Michael
Published: August 2009

In order to obtain good estimates of stress intensity factors in a structural integrity assessment, the accuracy with which a residual stress distribution is represented should be commensurate with the importance of localised peaks in residual stress, in particular where such peaks lie within the region under assessment. This paper describes work undertaken to investigate the importance of accurately representing residual stress distributions in structural integrity assessments. This has been carried out by comparing regular polynomial representations of residual stress distributions, combined with available weight function stress intensity factor solutions (as provided in the R6 procedures) with alternative polynomial representations of residual stress distributions, which provide a more accurate fit in the region of the crack. Such improvements in representation of residual stress profiles provide an indication as to how stress intensity factor solutions could, in future, be modified in order to result in improved accuracy of calculated stress intensity factors. Representation by partitioning residual stress profiles into membrane, bending and self-balancing components, in terms of providing a more straight-forward route for curve-fitting of residual stress profiles is considered. The investigation considers several transverse, through-thickness residual stress distributions. Stress intensity factors are calculated for a variety of crack sizes. Representation of the residual stress profiles in the stress intensity factor solutions are compared, as are the results of the stress intensity factor calculations. The conclusions arising provide guidance as to how current methods of curve fitting a residual stress distribution may be improved in cases where current methods may not be accurate. Advice is also provided as to the relative merits of representing residual stress distributions as a set of partitioned components or as a single distribution.
R5 Procedures for Assessing the High Temperature Response of Structures: Current Status and Future Developments
Authors: Dean David W. , Budden Peter J. , Ainsworth Robert A.
Published: August 2009

The R5 procedures have been developed within the UK power generation industry to assess the integrity of nuclear and conventional plant operating at high temperatures. Within R5, there are specific procedures for assessing creep-fatigue crack initiation in initially defect-free components (Volume 2/3) and for assessing components containing defects (Volume 4/5). This paper first describes in outline the current R5 Volume 2/3 and Volume 4/5 procedures. Attention is then focused on recent and proposed future developments in these procedures.
Crack Growth Analyses of SCC Under Various Residual Stress Distributions Near the Piping Butt-Welding
Authors: Katsuyama Jinya , Asano Wataru , Onizawa Kunio , Mochizuki Masahito , Toyoda Masao
Published: August 2009

Stress corrosion cracking (SCC) of core internals and/or recirculation pipes of austenite stainless steel (Type 316L) has been observed. When a SCC is detected at the reactor internals or pipes, it is necessary to calculate crack growth behavior of the crack for a certain operational period. The SCC initiates and grows near the welding zone because of high tensile residual stress by welding relative to the other contributing factors of material and environment. Therefore, the residual stress analysis due to welds of austenitic stainless piping is becoming important and has been already conducted by many researchers. In present work, the through-thickness residual stress distributions near multi-pass butt-welds of Type 316L pipes have been calculated by thermo-elastic-plastic analyses with the geometric and welding conditions changed and collected from literatures. Then crack growth simulations were performed using calculated and collected residual stress distributions. The effects of geometric and welding conditions on crack growth behavior were also discussed.
Project Prioritization via Optimization
Authors: Koc¸ Ali , Morton David , Popova Elmira , Kee Ernie , Richards Drew , Sun Alice , Hess Stephen
Published: August 2009

We consider a problem commonly faced in industry, involving annual selection of plant capital investments. A typical approach to such a problem uses a multi-knapsack formulation, which takes as input the available budget in each year, the stream of liabilities induced by selecting each project, and the profit, i.e., net present value, of each project. The goal is to select the portfolio of projects with the highest total net present value, while observing the budget constraint for each year, as well as any additional constraints. A portfolio selected in this manner can fail to hedge against uncertainties in the budget, the liability stream and the profit. So, we propose a model that forms an optimal priority list of projects, incorporating multiple scenarios for these input parameters. Our model is not a simplistic ranking scheme. Structural and stochastic dependencies among the projects are key to our approach. We apply our methods on a set of example projects from South Texas Project Nuclear Operating Company.
Simplified Primary Stress Evaluation Procedure for Thinned Class 1 Piping Elbow
Authors: Balakrishnan R. , Iyer San
Published: August 2009

Inelastic finite element analysis offers an alternate procedure to evaluate damaged piping components for their fitness-for-service purposes. Redistribution of stress resultants beyond yield taken into account in a typical inelastic analysis becomes significant as a damaged piping component may not satisfy code stress criteria based on elastic analysis. A complete inelastic analysis to estimate the limit load of the component may be a numerically intensive and cumbersome process. This paper involves a two step analytical process — unloading a component to satisfy code stress categories after a prior plastic distribution of stress resultants is setup in the component. Linearization of stresses in the thinned section has shown reduction in the general membrane and membrane plus bending stress intensities when analyzed using this simplified method. To illustrate the method, an analysis is performed on both thick and thin pipe with local thinning.
On the Correlation of Crack Resistance Curves on Upper Shelf Energy for German RPV Steels
Authors: Siegele Dieter , Hohe Jo¨rg , Nagel Gerhard
Published: August 2009

J-crack resistance (J-R) curves, numerically determined and based on correlation formulas with the upper shelf energy level (USE) of the Charpy transition curve have been compared with measured J-R curves for German RPV steels, determined from single specimen tests. The USE were determined as mean values of the results above 95% ductile fracture appearance, as available from usual application in irradiation surveillance programs and averaging the temperature effect. The J-R curves numerically determined by the Gurson material model give a good representation of the measured crack resistance curves and the application of the correlation with USE in U.S. NRC Regulatory Guide 1.161 results in enveloping approximations with conservativeness increasing with crack growth.
Non-Parameter System Identification of Isolated Bridge by Neural Networks Algorithm
Authors: Chiang W. L. , Pu J. P. , Liu T. Y.
Published: August 2009

The objective of this theme is to non-parameter identify and to compare the dynamic properties of the Lion-head river bridge located at Chia-I. The east bound of the bridge is designed and constructed as conventional, and the west bound as bridge isolated by lead-rubber bearings. Signals collected from the accelerometers installed on the bridge by the Central Weather Bureau will be processed. Back-propagation algorithm of Neural networks will be adopted and the nonlinear behavior of lead-rubber bearings will be simulated.
The Use of Digital Radiography in the Evaluation of Radioactive Materials Packaging Performance Testing
Authors: May Cecil G. , Gelder Lawrence F. , Howard Boyd D.
Published: August 2009

New designs of radioactive material shipping packages are required to be evaluated in accordance with 10 CFR Part 71, Packaging and Transportation of Radioactive Material. This paper will discuss the use of digital radiography to evaluate the effects of the tests required by 10 CFR 71.71, Normal Conditions of Transport (NCT), and 10 CFR 71.73, Hypothetical Accident Conditions (HAC). One acceptable means of evaluating packaging performance is to subject packagings to the series of NCT and HAC tests. The evaluation includes a determination of the effect on the packaging by the conditions and tests. Historically, that determination has required that packagings be cut and sectioned to learn the actual effects on internal components, either after each test to document the effects of that test, or after all testing is complete which determines the cumulative effect on the package. Digital radiography permits the examination of internal packaging components without sectioning a package. This allows a single package to be subjected to the entire series of tests. After each test, the package is digitally radiographed and the effects of particular tests evaluated. Radiography reduces the number of packages required for testing and also reduces labor and materials required to section and evaluate numerous packages. This paper will include a description of the digital radiography equipment used in the testing and evaluation of the 9977 package at SRNL. The equipment is capable of making a single radiograph of a full-sized package in one exposure. Radiographs will be compared to sectioned packages that show actual conditions compared to radiographic images.
Numerical Simulation of Tube Bundle Vibrations Under Cross Flow
Authors: Huvelin Fabien , de Morais Marcus Vinicius Girao , Baj Franck , Magnaud Jean-Paul , Longatte Elisabeth , Souli M’hamed
Published: August 2009

The present paper is dealing with the simulation of instability for a moving tube in a fixed tube bundle. The purpose is to improve the understanding of the instability threshold phenomenon by means of comparisons between numerical, experimental and analytical solutions. An improved serial staggered procedure is used for the coupling between the fluid and the structure solvers and an Arbitrary Lagrange-Euler (ALE) method is introduced to solve the flow in the presence of moving structures. Two flow solvers are compared, one with finite volume and one with finite element method. The moving tube is assumed rigid. First, the added mass and damping coefficients of the moving tube are computed in quiescent fluid and they are compared to an analytical solution. Second, the vibrations of the tube in a tube bundle under laminar cross flows are computed in 2D for different inlet flow velocities which can reproduce the stable and unstable dynamic regime of the structure. Finally, the comparison between numerical simulations and experiment is investigated.
Fatigue Comparison of Different High Pressure Materials and Design Consequences
Authors: Po¨lzl Manfred
Published: August 2009

Due to the continuous increase of production capacity in the last years for new low density polyethylene-high pressure plants, the licensors and plant owners take care to optimize the process efficiency and the complete manufacturing costs. Significant is the trend for big capacities of LDPE-plants in recent years. Especially in the area of development of high pressure materials a lot of work has been performed generally in order to optimize the plant investment cost and efficiency by using higher strength material. Due to a permanent improvement of material manufacturing, today we are able to use high strength and super clean materials with excellent toughness and fatigue properties. This allows a thinner wall thickness of the high pressure tubes and leads to technical and economic advantages — with lower material cost, lower equipment weight, a better heat transfer and an increase of plant efficiency.
The Effect of Fins on Fluidelastic Instability in In-Line and Rotated Square Arrays
Authors: Lumsden Robert H. , Weaver David S.
Published: August 2009

The study of fluidelastic instability in tube arrays has been ongoing for four decades. Although much research has been conducted, a full understanding of the mechanisms involved is still not available. Designers of cross-flow heat exchangers must depend on experience and empirical data from laboratory studies. As new designs are developed, which differ from these experimental facilities, there is an increased risk of failure due to fluidelastic instability. An experimental program was conducted to examine fluidelastic instability in in-line and rotated square finned tube arrays. Three arrays of each geometry type were studied; two with serrated, helically wound finned tubes of different fin densities, and the third, a bare tube which had the same base diameter as the finned tubes. The finned tubes under consideration were commercial finned tubes of a type typically used in the fossil and process industries. The addition of fins to tubes in heat exchangers enhances heat transfer due to the increased surface area and the turbulence produced by the flow moving over the fins. The resulting flow pattern/distribution due to the fins is therefore much more complicated than in bare tube arrays. Previous research has shown that an effective diameter of a finned tube is useful in the prediction of vortex shedding. This concept is used to compare the finned tube results with the existing bare tube array guidelines for fluidelastic instability. All of the tube arrays in the present study have the same tube pitch, and have been scaled to have the same mass ratio. Results for the rotated square arrays show that the use of an effective diameter is beneficial in the scaling of fluidelastic instability and the finned tube results are found to fit within the scatter of the existing data for fluidelastic instability. For in-line square arrays, the results indicate that fins significantly increase the stability threshold.
Effects of Weld Strength Mismatch on Estimation Procedures for J and CTOD Fracture Parameters Using SE(B) Specimens
Authors: Donato Gustavo H. B. , Ruggieri Claudio
Published: August 2009

This work presents an exploratory development of J and CTOD estimation procedures for welded fracture specimens under bending based upon plastic eta factors and plastic rotation factors. The techniques considered include: i) estimating J and CTOD from plastic work and ii) estimating CTOD from the plastic rotational factor. The primary objective is to gain additional understanding on the effect of weld strength mismatch on estimation techniques to determine J and CTOD fracture parameters for a wide range of a/W-ratios and mismatch levels. Very detailed non-linear finite element analyses for plane-strain models of SE(B) fracture specimens with center cracked, square groove welds provide the evolution of load with increased load-line displacement and crack mouth opening displacement which are required for the estimation procedure. The results show that levels of weld strength mismatch within the range ±20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials, particularly for deeply cracked fracture specimens. The present analyses, when taken together with previous studies, provide a fairly extensive body of results which serve to determine parameters J and CTOD for different materials using bend specimens with varying geometries and mismatch levels.
Hill Stress Calculations for Autofrettaged Tubes Compared With Neutron Diffraction Residual Stresses and Measured Yield Pressure and Fatigue Life
Authors: Underwood J. H. , deSwardt R. R. , Venter A. M. , Troiano E. , Hyland E. J. , Parker A. P.
Published: August 2009

Calculations of Bauschinger-modified residual stress in autofrettaged tubes using a simple elastic-plastic model based on the Hill method are compared with neutron diffraction measurements of hoop residual stresses in sections from a swage-autofrettage cannon tube. These residual stresses combined with pressurization stresses are used to describe tube yield pressure and fatigue lives, for comparison with laboratory measurements from cannon tubes from recent publications and new results. Gun steels in the yield strength range from 1000 to 1400 MPa are considered. Results from neutron diffraction measurements show a significantly shallower depth of overstrain in a swage autofrettaged tube compared with that predicted from earlier work with hydraulic pressure autofrettaged tubes, for the same amount of total bore hoop strain. This difference between depth of overstrain for swage and hydraulic autofrettage is incorporated into calculations of yield pressure corresponding to a small amount of permanent strain on the tube outer diameter. Comparison is made with measurements of yield pressure at the same amount of permanent strain. Comparison between calculated and measured yield pressure is good, suggesting a simple design method. Calculations of fatigue life using the classic Paris method compare well with measurements from cannon tests, once Bauschinger-modifications are made in near-bore hoop residual stresses and the difference in overstrain between swage and hydraulic autofrettage is incorporated in the model calculations.
Technical Basis for BWRVIP Stainless Steel Crack Growth Correlations in BWRs
Authors: Carter Robert , Pathania Raj
Published: August 2009

An intergranular stress corrosion cracking (IGSCC) growth model for unirradiated, thermally sensitized stainless steels and a methodology for assessment of through-wall crack growth in horizontal weld heat affected zones (HAZs) of boiling water reactor (BWR) core shrouds has been developed. This empirical model accounts for the variability of important IGSCC parameters such as coolant conductivity, stress intensity factor, K, temperature and electrochemical corrosion potential (ECP) in providing a conservative, yet realistic assessment of the crack growth rate. Data from various sources were used to derive the empirical crack growth correlation, including work from Electric Power Research Institute (EPRI)-sponsored research, work sponsored by the U. S. Nuclear Regulatory Commission (NRC) and in-plant crack arrest verification system (CAVS) data as well as laboratory data developed by the General Electric Nuclear Energy (GENE). The combined database from all the sources was evaluated to ensure that only relevant data was used in the model development. This refined database was used to derive the crack growth correlation using pattern recognition and multivariate modeling tools. For practical application to crack growth evaluation of stainless steel components, three approaches were developed for dispositions of flaws, i.e., a K-independent approach, a conservative 95th percentile K-dependent approach and a plant specific approach using actual BWR water chemistry data. An example problem representing actual BWR shroud conditions is presented that demonstrates how the current crack growth model, the weld residual stress and K can be used to perform a plant-specific evaluation of flawed shrouds. The results of this example demonstrated that significant operating periods are likely for most flawed conditions in BWR core shroud welds before ASME Code Section XI core shroud safety margins are challenged.
Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading
Authors: Pereira He´lder F. S. G. , De Jesus Abi´lio M. P. , Fernandes Anto´nio A. , Ribeiro Alfredo S.
Published: August 2009

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren-Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope S-N curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as non-conservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely R = 0, R = 0.15 and R = 0.3. Also constant amplitude fatigue data is generated for the investigated structural detail which is applied for indirect damage calculations. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels and stress ratios. In particular, a clear load sequence effect is verified for the two block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is non-linear. This suggests an important effect of the stress ratio on fatigue damage accumulation.
FEM Analysis and Evaluation of the Sealing Performance in Flexible Box-Shape Flanged Bolted Joints With Gaskets Subjected to Internal Pressure: Effect of the Bolt Pitch
Authors: Sawa Toshiyuki , Kurosawa Ryo , Tatsumi Yasuaki
Published: August 2009

Bolted joints with gaskets such as non-circular flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure as well as other loadings such as thermal, impact loadings and so on. In designing the non-circular flange connections with gaskets, it is important to evaluate the sealing performance of the non-circular flange connections with gaskets subjected to internal pressure. An important issue is how to evaluate the sealing performance in the box-shape bolted flange connections by using the contact gasket stress distributions at the interfaces, how to reduce a number of bolt and nuts, that is, how to enlarge the bolt pitch, and how to determine the initial clamping bolt force (preload) by using the new gasket constants. In this paper, the stresses of box-shape flange connection with gaskets subjected to an internal pressure are analyzed using the finite element method (FEM), taking account a hysteresis in the stress-strain curves of the gasket. The contact gasket stress distributions when the internal pressure is applied to the connection are analyzed. The leakage tests were conducted using an actual box-shape flange connection with a gasket Using the contact gasket stress distributions at the interfaces under an internal pressure (Helium gas was used) and the amount of the leakage measured in the experiment, the sealing performances are evaluated experimentally and theoretically by changing the bolt pitch in the connections. Discussion is made on the effect of the bolt pitch on the sealing performance in the above connections.
The Effect of Bolt Size on the Assembly Nut Factor
Authors: Brown Warren , Marchand Luc , E´vrard Arnaud , Reeves David
Published: August 2009

This paper details recent testing that was performed as an extension of earlier work on nut factor and high temperature breakout performance of selected anti-seize products. Comparison is made between results obtained using bolt diameters from 3/4 inch to 2 inch, two different anti-seize products (Molybdenum and Nickel) and two different bolt materials (ASTM A193-B7 & ASTM A193-B8M). In addition, common equations used for the determination of achieved bolt load from a given torque are examined and compared from a practical perspective in light of the nut factor test results. The test methods that were used are designed to closely mimic actual bolt assembly in a process plant environment. The paper, therefore, presents useful information that will enable more accurate assembly of bolted flanged joints on pressure vessels and piping in any process plant environment.