bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Analysis of a PWR Core Internal Baffle Structure
Authors: Pe´niguel Christophe , Rupp Isabelle , Ligneau Nathalie , Tommy-Martin Michel , Beloeil Laurent , Lemaire Emmanuel
Published: July 2008

The internal core baffle structure of a PWR consists in baffles and formers attached to the barrel. Each baffle being independent, the connection between the core baffle sheets, the formers and the core barrel is done thanks to a large number of bolts (about 1500). After inspection, some baffle bolts have been found cracked. This behaviour is attributed to Irradiation Assisted Stress Corrosion Cracking (IASCC). In order to compute accurately the temperature distribution affecting these bolts, EDF has set up a research program. Due to symmetry reasons, only a 45° sector has been accounted for. The three-dimensionnal neutron flux and the gamma induced internal heating are calculated with a Monte-Carlo particle transport code named Tripoli-4. The by-pass flow inside the cavities is computed with the CFD code Code_Saturne with a finite volume technique. Finally, the temperature distribution inside the structure (including all bolts which leads to a considerable solid mesh size — about 236 millions tetraedra) is computed by the thermal code Syrthes using a finite element approach, taking into account both the heating due to the gamma heating deposit and the cooling by the by-pass flow. Calculations show that the solid thermal field obtained exhibit strong temperature gradients and high temperature levels but in very limited zones located inside the material. As expected mainly very limited regions located inside the material and near the corner close to the reactor center are exposed to high temperature levels. On the other hand, calculations clearly confirm that external bolts thightening the core barrel and the formers see temperature much lower than those thightening the baffles.
Issues Regarding Use of Master Curve Data in Resetting Initial RTNDT
Authors: Yoon K. K. , Hall J. B.
Published: July 2008

The B&W Owners Group submitted justification for resetting the initial RTNDT for the Linde 80 weld materials using ASME Code Case N-629/N-631 to the US Nuclear Regulatory Commission and received the NRC Safety Evaluation Report with some adjustments. Two major issues were encountered during the review and approval process: 1) The pressurized thermal shock experiment data from Oak Ridge National Laboratory with full-length axial (very long) cracks fall below the Code Case curve. This observation led to the question whether there are implicit crack size limitations in the code case, and 2) For the large populations of data examined, a larger portion of data falls below the Code Case N-629/N-631 curve than the ASME KIC curve, prompting a question whether the code case is functionally equivalent to the ASME KIC curve. This paper describes these major issues and how they were addressed.
Shakedown of a Thick Cylinder With a Radial Crosshole
Authors: Camilleri Duncan , Mackenzie Donald , Hamilton Robert
Published: July 2008

The shakedown behaviour of a thin cylinder subject to constant pressure and cyclic thermal loading is described by the well known Bree diagram. In this paper, the shakedown and ratchetting behaviour of a thin cylinder, a thick cylinder and a thick cylinder with a radial crosshole is investigated by inelastic finite element analysis. Load interaction diagrams identifying regions of elastic shakedown, plastic shakedown and ratchetting are presented. The interaction diagrams for the plain cylinders are shown to be similar to the Bree Diagram. Incorporating the radial crossbore in the thick cylinder significantly reduces the plastic shakedown boundary on the interaction diagram but does not significantly affect the ratchet boundary. The radial crosshole can therefore be regarded as a local structural discontinuity and neglected when determining the maximum shakedown or (primary plus secondary stress) load in Design by Analysis.
Effects of Shear Thinning on Taylor-Couette Flow: A Model for Synovial Fluid Flow
Authors: Ashrafi Nariman
Published: July 2008

The effect of shear thinning on the stability of the Taylor-Couette flow (TCF) is explored for a Carreau-Bird fluid in the narrow-gap limit to simulate journal bearings in general. Also considered is the changing eccentricity to cover a wide range of applied situations such as bearings and even articulation of human joints. Here, a low-order dynamical system is obtained from the conservation of mass and momentum equations. In comparison with the Newtonian system, the present equations include additional nonlinear coupling in the velocity components through the viscosity. It is found that the critical Taylor number, corresponding to the loss of stability of the base (Couette) flow becomes lower s the shear-thinning effect increases. Similar to Newtonian fluids, there is an exchange of stability between the Couette and Taylor vortex flows. However, unlike the Newtonian model, the Taylor vortex cellular structure loses its stability in turn as the Taylor number reaches a critical value. At this point, A Hopf bifurcation emerges, which exists only for shear-thinning fluids. Variation of stresses in the narrow gap has been evaluated with significant applications in the non-Newtonian lubricant.
A Qualified Method for Fluid-Structure Interaction in Piping Design
Authors: Hartmann Miks
Published: July 2008

In piping design hydraulic load cases and the resulting dynamic structural loads are induced and generated by strongly time dependent pressure surges and subsequent oscillations. Therefore, with liquid filled piping, the implementation of fluid-structure interaction by coupling the fluiddynamic and the structural dynamic codes gives a substantial contribution to more realistic loading results. Considering this effect, usually a load reduction due to energy losses and the phase and frequency shift from fluid to structure and vice versa is achieved. In cases of fluid structure resonance the results are more reliable and can help to develop an optimized support concept. To realize the coupled calculation of both codes they are bundled by a special user environment, where the coupling points are specified and marked. We describe the input of fluid forces at those points and the treatment of the liquid masses inside the piping, as well as the method of back-coupling the resulting structural displacements into the fluid calculation. The method was validated against measurements of load cases in power plant piping systems and experimental results for various boundary conditions. The most realistic results were obtained by combining the coupling with the application of dynamic friction in the fluid code.
Design of Mobile HDPE Water Tanks: A Practical Design Exercise for Senior Students in Mechanical Engineering
Authors: Seibi A. C. , Pervez T.
Published: July 2008

Engineering design is becoming an integral part of any engineering program seeking international recognition and accreditation. Design practices are becoming a necessary experience to senior students nowadays in all engineering programs. The final year design project offered at Sultan Qaboos University in Oman gives senior students the chance to integrate their knowledge accumulated through already taken courses in the Mechanical Engineering Department to design particular products, experiments, and/or mechanical systems. In addition to gaining hands on experience of the design process, students were able to develop their communication skills and team work spirit. Throughout the whole year, students knowledge and expertise are enhanced through direct contact with their project advisor(s), project related memos, oral presentations, memos, posters, and written progress and final reports. The present paper describes the design process followed by a group of three senior students starting from understanding the problem and developing conceptual designs to the end product. CAD tools such as AutoCAD and ABAQUS were used to complete the design, build a prototype, and test it.
Numerical Simulation for Development of Pressure Vessel for Food Processing by Shock Loading
Authors: Otsuka Masahiko , Watanabe Toshiaki , Itoh Shigeru
Published: July 2008

In this study, it has aimed at the design of the pressure vessel where an underwater shock wave is applied to food efficiently. This study aims at the desigh of a pressure vessel in which the underwater shock wave generated by the underwater explosion of detonating fuse was experimentally investigated by the optical observation and the pressure measurement. Therefore the pressure vessel is designed so that suitable pressure may apply on food. This designed vessel is evaluated by the numerical analysis that used LS-DYNA3D. The interaction of the underwater shock wave, the incident wave and the reflected wave are investigated by the numerical analysis. The agreement between the experimental results and the numerical analysis was found to be good.
Failure Behavior of Carbon Steel Pipe Having Local Wall Thinning Near Tee Joint
Authors: Ando Kotoji , Takahashi Koji , Hisatsune Masakazu , Hasegawa Kunio
Published: July 2008

Monotonic four-point bending tests were conducted using tee pipe specimens having local wall thinning. The effects of local wall thinning on the failure behaviors of tee pipes were investigated. Local wall thinning was machined on the inside of pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area were l = 100 mm in eroded axial length, d/t = 0.5 and 0.8 in eroded ratio, and 2θ = 90° and 180° in eroded angle. The area undergoing local wall thinning was subjected to tensile stress. It was found that fracture type could be classified into ovalization or crack initiation, depending on eroded ratio. Three-dimensional elasto-plastic analyses were also carried out using finite element method to discuss the effects of position and geometries of wall thinning in both tee pipes and straight pipes.
Effect of Geometric and Welding Conditions on Through-Thickness Residual Stress
Authors: Mochizuki Masahito , Katsuyama Jinya , Toyoda Masao
Published: July 2008

Recently, stress corrosion cracking (SCC) of core internals and/or recirculation pipes of austenite stainless steel (SUS316L) has been observed. SCC is considered to occur and progress at near the inner surface of the welding zone in butt-welded pipes, because of the tensile residual stress introduced by welding. In present work, three-dimensional and axisymmetric thermo-elastic-plastic finite element analysis have been carried out, in order to clarify the effect of geometric and welding conditions in circumferential welding zone on the residual stress. In particular, butt-welding joints of SUS316L-pipes have been examined. The residual stress was simulated by three-dimensional and axially symmetric models and the results were compared and discussed in detail.
Variational Analysis of Sloshing in Spherical Industrial Vessels Under Earthquake Loading
Authors: Patkas L. A. , Karamanos S. A.
Published: July 2008

A variational formulation is developed for calculating liquid sloshing effects on the dynamic response of spherical containers under external dynamic excitation. The velocity potential is expressed in a series form, where each term is the product of a time function and the associated spatial function. Because of the configuration of the containers, the associated spatial functions are non-orthogonal, and the problem is not separable and results in a system of coupled non-homogeneous ordinary linear differential equations, which is solved numerically. The solution can be obtained through either direct integration or modal analysis. Sloshing frequencies and masses are calculated rigorously for arbitrary liquid height, and convergence of the solution is thoroughly examined. Particular emphasis is given on the cases of half-full spheres, where explicit expressions for the coefficients of the governing equations are derived. Furthermore, the behavior of nearly-full and nearly-empty vessels is briefly discussed.
New UK Research Programme on Residual Stresses
Authors: Bate Steve K. , Watson Chris
Published: July 2008

A new long-term research programme has been launched in the UK. This involves Rolls-Royce plc and Serco Assurance, supported by UK industry and academia. A significant part of this programme is aimed at progressing the understanding of weld residual stresses and the implementation of finite element simulation and residual stress measurement for assessing the structural integrity of engineering structures and components. The work includes: (1) Finite element modelling to investigate heat source representation, material behaviour and 3D v 2D effects. (2) Design and manufacture of mock-ups for supporting validation. (3) Residual stress measurement. (4) Weld design. (5) Residual stress profiles. (6) Material testing. (7) Development of a procedure for residual stress modelling. The work is being undertaken by a combination of finite element analyses and residual stress measurement using a variety of techniques. This paper presents an overview of the research work being undertaken and provides examples of the outcome of some of the studies obtained to-date.
An Alternative Method to That of the R6 Procedure for the Treatment of Combined Primary and Secondary Loading
Authors: Hooton D. G. , Sharples J. K. , Yellowlees S. F. , Watson C. T.
Published: July 2008

An alternative definition for the assessment point parameter Kr of the R6 defect assessment procedure is proposed, for combined primary and secondary loading. This alternative definition removes the requirement to calculate a plasticity correction factor for secondary stresses, ρ (or V), used in the conventional R6 definition of Kr. To compare these definitions, both the R6 procedure and the alternative method are presented as Crack Driving Force (CDF) estimation schemes. The required inputs to these estimation schemes have been determined from finite element analyses, for the particular case, of a thick-walled cylinder with a fully circumferential internal defect and subjected to internal pressure and a radial through-wall temperature gradient. Comparisons of CDF estimates with those determined from full inelastic finite element analyses have shown, for the cases studied, that both the R6 and alternative approaches provide conservative estimates of CDF compared to those obtained from finite element analyses, with the degree of conservatism far greater for the conventional R6 approach. Further finite element validation with different geometries, loadings and material properties is required before the alternative procedure could be considered for inclusion in the R6 defect assessment procedure as an alternative to the procedure of the main section of the document.
High Temperature Diffusion of Oxygen in Chromite
Authors: O’Toole Stephen , Stevens Nicholas
Published: July 2008

Molecular dynamics was used to calculate the diffusion coefficient of oxygen over a temperature range of 900–1700K. The chromite (FeCr2O4) system used consisted of 448 ions in a spinel structure. The spinel consisted of Fe2+ in tetrahedral sites and Cr3+ ions in octahedral sites surrounded by O2− ions. Schottky defects were made in the system by removing 10 oxygen ions, 4 iron ions and 4 chromium ions. The trajectory files from the simulations were examined for oxygen movement via a vacancy hopping mechanism and the mean-squared displacement of oxygen was plotted against time. A linear fit was performed to the plots and Einstein’s relationship was used to derive the diffusion coefficient from the gradient. The diffusion coefficients were then plotted against temperature and an Arrhenius expression was fitted to the trend and compared with the experimental trend calculated by Takada & Adachi.
Load Distribution Between the Shell and a Stiffening Ring Adjacent to the Saddle Support
Authors: Bardia Kanhaiya L. , LaBounty Donald G. , Basic Michael M.
Published: July 2008

In a Zick analysis of a horizontal pressure vessel on two saddle supports with stiffening rings, there is no direct method of determining the distribution of the load between one stiffening ring adjacent to the saddle support and the shell. In this paper, the authors discuss a method of calculating the load distribution between the stiffening ring and the shell. After establishing the load distribution, the stresses in the ring and shell are calculated and compared against the allowable stresses in the ASME Code.
Life Management of Main Steam and Hot Reheat Piping Systems: Part 1
Authors: Cohn Marvin J.
Published: July 2008

Many utilities choose critical girth welds in their main steam (MS) and hot reheat (HRH) steam piping by consideration of some combination of the ASME B31.1 Code [1] (Code) highest sustained load and thermal expansion stresses, terminal point locations, and fitting weldments subject to stress intensification. As an alternative, a life management methodology is used to prioritize material damage locations based on realistic stresses and applicable damage mechanisms. This methodology is customized to each piping system, considering applicable affects, such as operating history, measured weldment wall thicknesses, observed support anomalies, actual piping thermal displacements, and more realistic time-dependent multiaxial stresses. The life management methodology for MS and HRH critical girth welds may be considered as a rational approach to determine critical weldment locations for examinations and to determine appropriate reexamination intervals as a risk-based evaluation technique. This methodology has been implemented over the past 15 years to provide more realistic estimates of actual displacements, strains, stresses, and material damage based on the evaluation of field conditions. This high energy piping life consumption (HEPLC) methodology can be described as having three basic phases: data collection, evaluation, and recommendations. The data collection phase includes obtaining design and post construction piping and supports information. The effects of current anomalies are evaluated to prioritize critical examination locations. Results of the examinations at the most critical locations are used to determine the degree of material damage at lead-the-fleet locations. The author has performed many HEPLC studies of MS and HRH piping systems. This paper will provide examples of data collection results and documentation of observed piping system anomalies.
Analysis of Pressure Vessel Sloshing
Authors: McGuffie S. M. , Porter M. A.
Published: July 2008

ASME BPVC Section VIII Division 1 Paragraph UG-22 (f) requires consideration of the loadings from seismic conditions. For a vessel containing a fluid, the loading due to sloshing must be considered. ASCE Standard 7-02 (Section 9.14.7.3) states that a damping value of 0.5% can be used to account for the fluid sloshing. This can lead to an overly conservative design by over-estimating the loads on the tank structure. A time-history analysis was performed on a horizontally mounted pressure vessel experiencing 3-axis time history loads in order to determine if this method is more accurate in determining the loads. The analysis employed a 3-dimensional computational fluid dynamics (CFD) model, using transient time-history techniques. The reactions at the mounting locations were compared to the reactions computed using closed form solutions, demonstrating good correlation. The results show that CFD is an excellent tool for investigating seismic sloshing loads in vessels.
A Microstructure-Based Probabilistic Model for Cleavage in RPV Steels
Authors: Ortner Susan R.
Published: July 2008

In both simple ferrite-carbide materials, and more complex ferritic steels, cleavage is mediated by the fracture of the particles they contain. If particle cracking is easy, then extension of the resulting particle-sized microcracks into the ferrite matrix, can become the critical step in inducing fracture. Under these circumstances, brittle fracture is essentially stress-controlled, and several models use this as a basis for failure prediction. Fracture toughness data from a series of MnMoNi steels are presented, together with observations of fracture initiation sites, and calculations of the stresses and strains pertaining to these locations at failure, to show that there are circumstances under which particle cracking is not easy. A strain criterion is found to describe the probability of particle cracking effectively. A previously-published, stress-based model is generalised to include the strain criterion. The more general model correlates initiation site properties with K, and predicts a marked temperature-dependence of K (i.e. a ductile-to-brittle transition), even though the only temperature-dependent input parameters are the flow properties. Other input parameters for the model are linked explicitly to the microstructure. The relative dominance of particle cracking and microcrack extension in cleavage depends most strongly on initiating particle type, and final quench severity.
Nonlinear Finite Element Analysis of Moving Coil Loudspeaker Suspension
Authors: Viswanatha Naveen , Avis Mark , Moatamedi Moji
Published: July 2008

The surround and the spider of the loudspeaker suspension are modelled in ANSYS to carry out finite element analysis. The displacement dependent nonlinearities arising from the suspension are studied and the material and geometric effects leading to the nonlinearities are parameterised. The ANSYS models are simulated to be excited by a sinusoidal load and the results are evaluated by comparison with the results obtained by a physical model. The paper illustrates how practical models can be analysed using cost effective finite element models and also the extension of the models to experiment on various parameters, like changing the geometry for optimisation, by computer simulation.
Plastic Instabilities in Spherical Shells Under Load, Displacement, and Impulsive Loading
Authors: Duffey Thomas A. , Doyle Derek
Published: July 2008

Plastic instabilities that could potentially develop in spherical shells under a variety of symmetric loading conditions are examined. First, a literature survey of both static and dynamic instabilities associated with spherical shells is presented, with emphasis on plastic tensile instability. Then, building upon work done elsewhere for cylindrical shells, a plastic instability condition for spherical shells subjected to displacement controlled and impulsive loading is developed and compared with earlier results reported in the literature. It is found that the instability point for displacement controlled loading and impulsive loading of a spherical shell is the same as for a uniaxial tension specimen and for an impulsively loaded plane-strain ring/cylinder. In addition, a simple, one-dimensional strain-softening model is developed that investigates the relationship between instabilities associated with displacement-controlled loading and impulsive loading. Conclusions of this work are that there are two fundamental types of instabilities associated with failure of spherical shells: local and global. Moreover, the local instability, associated with failure under displacement control and impulsive loading, is found to require an imperfection to develop, whereas the global instability does not require an imperfection. The need for experiments to verify these results is discussed.
High Temperature Ultrasonic Inspection of Pressure Vessels and Piping Systems
Authors: Carswell R. J.
Published: July 2008

Corrosion is one of the petrochemical industry’s leading causes of equipment failure, repair, and replacement. Pressure vessels and piping systems and are subject to various attack mechanisms at elevated temperature, which if undetected can reduce their reliability. This can result in various safety issues, unscheduled shutdowns and catastrophic failures. Detecting corrosion and identifying corrosion rates while equipment is on-stream can assist Engineers and operational personnel in managing Plant shutdowns by forecasting equipment life and scheduling repairs and replacement. This paper describes the equipment and procedure to inspect pressure vessels and piping systems at elevated temperatures up to 385°C.
Instrumented-Indentation-Technique-Based Residual Stress Characterization for Weldment of Structural Components
Authors: Kwon Dongil , Lee Jung-Suk , Kim Kwang-Ho , Motarjemi Afshin , Speck Julian
Published: July 2008

The weld joints in structural components have long been considered important sites for safety and reliability assessment. In particular, the residual stress in piping weldments induced by the welding process must be evaluated accurately before and during service. This study reports an indentation technique for evaluating welding residual stress nondestructively. Indentation load-depth curves were found to shift with the magnitude and direction of the residual stress. Nevertheless, contact depths in the stress-free and stressed states were constant at a specific indentation load. This means that residual stress induces additional load to keep contact depth constant at the same load. By taking these phenomena into account, welding residual stress was obtained directly from the indentation load-depth curve. In addition, the results were compared with values from the conventional hole-drilling and saw-cutting method.
Recent Experience With Weld Overlay Repair of Indications in Alloy 182 Butt Welds in Two Operating PWRs
Authors: Bamford Warren , Newton Bruce , Seeger Don
Published: July 2008

Recent service experience with Alloy 182/82 butt welds in PWR primary piping and its joints with major components has revealed stress corrosion cracking. This mechanism of environmental cracking is known to have long incubation times, so these incidences of cracking have not been numerous to date, but it is becoming increasingly evident that this may not be the case in the future. This paper provides a summary of two recent repairs which were performed as a result of the finding of indications during in-service inspections. The weld overlay repairs followed the guidelines of code case N504, but a number of supplementary requirements were added. In each case, the repair had to be initiated with no warning other than the knowledge that the inspection was underway. The design of the weld overlay repair was done while the repair equipment was being mobilized, and the repair went as planned, with the final inspections showing that the weld overlay was flawless. In each case excellent cooperation between the plant personnel, the engineering designers, the inspectors, and the welders made for an excellent end product. In addition to a review of the processes used for each of the key steps in the repair, a review of lessons learned will be provided, so that operating plants which may face similar issues in the future can benefit from this experience.
Stochastic Finite Element Method (FEM) and Design of Experiments for Pressure Vessel and Piping (PVP) Decision Making
Authors: Fong Jeffrey T. , Filliben James J. , deWit Roland , Bernstein Barry
Published: July 2008

Using an example from a recent study of the finite element method (FEM) solutions of the natural frequencies of single-crystal silicon cantilevers in atomic force microscopy (AFM), we present the results of an analysis using two powerful tools of engineering statistics, namely, (a) stochastic FEM, and (b) design of experiments. The analysis of the FEM results using ABAQUS, ANSYS, and LS-DYNA anisotropic elastic element types yields conclusions that engineers can use to justify decisions with quantitative measure of uncertainties. For PVP engineers, we show with an example that this methodology is equally applicable to their decision making process and the appropriate risk assessment.
Finite Element Limit Loads for Circumferential Through-Wall Cracked Pipe Bends Under In-Plane Bending
Authors: Kim Yun-Jae , Oh Chang-Sik , Kim Young-Il , Park Chi-Yong
Published: July 2008

This paper proposes plastic limit and collapse loads for circumferential through-wall cracked pipe bends under in-plane bending, based on three-dimensional finite element limit analyses. The material is assumed to be elastic-perfectly-plastic, but both the geometrically linear (small strain) and the geometrically nonlinear (large geometry change) options are employed. Regarding crack location, both extrados and intrados cracks are considered. Moreover, for practical application, closed-form approximations of plastic limit and collapse loads are proposed based on the FE results, and compared with corresponding solutions for straight pipes.
Design by Analysis: Direct Route for Cases With Pressure and Thermal Action
Authors: Rauscher Franz
Published: July 2008

This paper focuses on the usage of Direct Route for Design by analysis (DBA), which is included in the new European standard for unfired pressure vessels (EN 13445-3 [1]). The Direct Route addresses failure modes directly, having, therefore, advantages in comparison to the traditional method, which is stress categorization. Special attention is given to the Progressive Plastic Deformation design check (PD-DC) with space and time-dependent temperature distribution and the Fatigue design check (F-DC) with stress components which do not vary simultaneously. As a simple demonstration example, a nozzle with cold media injection is used to show how the Direct Route can be applied in such cases. This example is analyzed with abruptly changing injection temperature, which makes a transient thermal analysis necessary. In the case of the Progressive Plastic Deformation design check (PD-DC), Melan’s shakedown theorem and cycling of a Finite Element (FE) model with a linear-elastic ideal-plastic material model are used. In the case of the Fatigue design check (F-DC) some problems are discussed: One of them is cycle counting in the case of non-proportional loading, another one is the use of structural stresses and stress concentration factors.
Comparison of Design by Analysis Methods
Authors: Schindler Sebastian
Published: July 2008

The paper discusses the advantages and disadvantages of the two well known Design by Analysis methods for unfired pressure vessels: the stress categorisation method (as given e.g. in the 2004 ASME B&BV Code Section VIII Division 2 [1], and EN 13445-3 Annex C [2]) and the new Direct Route (using elastic-plastic finite-element analysis) as given in EN 13445-3 Annex B [2]. A comparison of results is given for examples of various degree of difficulty to show the principal ideas and the applicability of the two approaches: a dished end with a nozzle in the knuckle region, a cylindrical shell to flat end connection and a rather complex header of an air cooler with rectangular cross section. As shown by the considered examples, the Direct Route method gives unique solutions (which is not always the case for stress categorisation) and can be advantageous in some cases, but requires a more time consuming analysis. The questionable design limits given by the 3f-criterion of the stress categorisation method can be avoided by usage of the progressive plastic deformation design check of the Direct Route if the required number of action cycles is low.
Analysis of Threshold Stress Intensity Factors KIH to Fracture Hydrides in Zr-2.5Nb Pressure Tubes
Authors: Kim Kang S. , Kim Young S. , Cheong Yong M. , Im Kyung S. , Ahn Sang B.
Published: July 2008

Delayed Hydride Cracking (DHC) tests are conducted by using CT specimens of Zr-2.5Nb at 250 °C. The test data is inputed for the FEM model. The stresses of the hydride and Zr-2.5Nb elements near the crack tip of the FEM model are examined. Also, the plastic zone size and average stresses near the crack tip are calculated for checking the effects of the plastic constraint. The material behavior of the elements near a crack tip, the hydride expansion stress, the hydride fracture strength and the size of the plastic zone according to each K are found. Also, Stage I and Stage II of the unique DHC phenomenon can be explained through an analysis of the plastic constraint force in the plastic zone.
Cyclic Loading of Thick Pressure Vessels
Authors: Mahbadi H. , Eslami M. R.
Published: July 2008

In this article cyclic loading of thick cylindrical and spherical vessels under thermal and mechanical loads are investigated. A new and efficient numerical iterative method is proposed and used to analyze the structural behavior under cyclic loading conditions. The results are verified with the known data given in the literature.
Assessment by Time-Kill Methodology of the Synergistic Effects of Oritavancin in Combination with Other Antimicrobial Agents against
Staphylococcus aureus
Authors: Belley Adam , Neesham-Grenon Eve , Arhin Francis F. , McKay Geoffrey A. , Parr Thomas R. , Moeck Gregory
Published: July 2008

Oritavancin is a semisynthetic lipoglycopeptide in clinical development for serious gram-positive infections. This study describes the synergistic activity of oritavancin in combination with gentamicin, linezolid, moxifloxacin, or rifampin in time-kill studies against methicillin-susceptible, vancomycin-intermediate, and vancomycin-resistant
Staphylococcus aureus
.
The Sialylated Lipooligosaccharide Outer Core in
Campylobacter jejuni
Is an Important Determinant for Epithelial Cell Invasion
Authors: Louwen Rogier , Heikema Astrid , van Belkum Alex , Ott Alewijn , Gilbert Michel , Ang Wim , Endtz Hubert P. , Bergman Mathijs P. , Nieuwenhuis Edward E.
Published: July 2008

Campylobacter jejuni
is a frequent cause of bacterial gastroenteritis worldwide. Lipooligosaccharide (LOS) has been identified as an important virulence factor that may play a role in microbial adhesion and invasion. Here we specifically address the question of whether LOS sialylation affects the interaction of
C. jejuni
with human epithelial cells. For this purpose, 14 strains associated with Guillain-Barré syndrome (GBS), 34 enteritis-associated strains, the 81-176 reference strain, and 6 Penner serotype strains were tested for invasion of two epithelial cell lines.
C. jejuni
strains expressing sialylated LOS (classes A, B, and C) invaded cells significantly more frequently than strains expressing nonsialylated LOS (classes D and E) (
P
< 0.0001). To further explore this observation, we inactivated the LOS sialyltransferase (Cst-II) via knockout mutagenesis in three GBS-associated
C. jejuni
strains expressing sialylated LOS (GB2, GB11, and GB19). All knockout strains displayed significantly lower levels of invasion than the respective wild types. Complementation of a Δ
cst-II
mutant strain restored LOS sialylation and reset the invasiveness to wild-type levels. Finally, formalin-fixed wild-type strains GB2, GB11 and GB19, but not the isogenic Δ
cst-II
mutants that lack sialic acid, were able to inhibit epithelial invasion by viable GB2, GB11, and GB19 strains. We conclude that sialylation of the LOS outer core contributes significantly to epithelial invasion by
C. jejuni
and may thus play a role in subsequent postinfectious pathologies.
Prophylactic and Therapeutic Efficacy of a Fully Human Immunoglobulin G1 Monoclonal Antibody to
Pseudomonas aeruginosa
Alginate in Murine Keratitis Infection
Authors: Zaidi Tanweer , Pier Gerald B.
Published: July 2008

Treatment of ulcerative keratitis due to
Pseudomonas aeruginosa
is difficult, time-consuming, and uncomfortable owing to the need for the frequent application of antibiotic drops to the infected corneal surface. We examined here whether a fully human immunoglobulin G1 monoclonal antibody (MAb) specific to the conserved alginate surface polysaccharide of
P. aeruginosa
could mediate protective immunity against typically nonmucoid strains isolated from human cases of keratitis. MAb F429 effectively opsonized alginate-positive, but not alginate-negative, nonmucoid strains in conjunction with phagocytes and complement. Prophylactic administration of MAb F429 18 h prior to infection with two clinical isolates significantly reduced bacterial levels in the eye and the associated corneal pathology. Along similar lines, systemic intraperitoneal injection, as well as topical application of the MAb onto the infected eye, starting 8 h postinfection in both experimental protocols resulted in significant reductions in bacteria in the eye, as well as minimizing pathological damage to the cornea. These findings indicate that MAb F429 could be useful as an additional therapeutic component for the treatment of
P. aeruginosa
keratitis.
Campylobacter-Induced Interleukin-8 Secretion in Polarized Human Intestinal Epithelial Cells RequiresCampylobacter-Secreted Cytolethal Distending Toxin- and Toll-Like Receptor-Mediated Activation of NF-κB
Authors: Zheng Jie , Meng Jianghong , Zhao Shaohua , Singh Ruby , Song Wenxia
Published: July 2008

Campylobacter jejuniandCampylobacter colicolonize and infect the intestinal epithelium and cause acute inflammatory diarrhea. The intestinal epithelium serves as a physical barrier to, and a sensor of, bacterial infection by secreting proinflammatory cytokines. This study examined the mechanisms forCampylobacter-induced secretion of the proinflammatory chemokine interleukin-8 (IL-8) by using polarized T84 human colonic epithelial cells as a model.C. jejuniincreased the secretion of both IL-8 and tumor necrosis factor alpha (TNF-α) in polarized epithelial cells. However, the increase in IL-8 secretion was independent ofCampylobacter-stimulated TNF-α secretion. Polarized T84 cells secreted IL-8 predominantly to the basolateral medium independently of the inoculation direction. While there was a significant correlation between the levels of IL-8 secretion andCampylobacterinvasion, all 11 strains tested increased IL-8 secretion by polarized T84 cells despite their differences in adherence, invasion, and transcytosis efficiencies. Cell-free supernatants ofCampylobacter-T84-cell culture increased IL-8 secretion to levels similar to those induced by live bacterial inoculation. The ability of the supernatant to induce IL-8 secretion was reduced by flagellum and cytolethal distending toxin (CDT) gene mutants, treatment of the supernatant with protease K or heat, or treatment of T84 cells with the Toll-like receptor (TLR) inhibitor MyD88 inhibitory peptide or chloroquine. NF-κB inhibitors orcdtBmutation plus MyD88 inhibitor, but notflaA cdtBdouble mutations, abolished the ability of the supernatant to induce IL-8 secretion. Taken together, our results demonstrate thatCampylobacter-induced IL-8 secretion requires functional flagella and CDT and depends on the activation of NF-κB through TLR signaling and CDT in human intestinal epithelial cells.
Soil–Ice Behavior in a Model Retaining Structure
Authors: Warder David L. , Andersland O. B.
Published: July 2008

Experimental creep data on model cylindrical retaining structures formed from two frozen soils, saturated Ottawa sand and Ontonagon (Sault Ste. Marie) clay, are presented. The sand–ice behavior in the model barrier is analyzed using a constitutive relationship which includes the state of stress, state of strain, time, and temperature. Displacement rates at the inner wall surface calculated according to the creep relationship agree with measured rates for properly chosen values of a parameter which modifies the contribution of the deviatoric stress component to the creep rate.The axial force observed at the sample ends provided information as to the soil–ice behavior during primary and secondary creep. For the sand–ice material this axial force did not reach its final value until steady-state creep was approximated. This indicates that Poisson's ratio may change depending on the stage or development of the creep deformations. This behavior was not observed for the frozen clay. The stress – strain – time behavior for the two soils differed considerably due to the greater amounts of unfrozen water in the frozen clay (about 50 %) as compared with the saturated Ottawa sand (little or none).
The Slurry Trench Cut-off for the Duncan Dam
Authors: Duguid D. R. , Forbes D. J. , Gordon J. L. , Simmons O. K.
Published: July 2008

A slurry trench cut-off was constructed for the Duncan Dam. Two failures of the trench wall occurred during construction, one of which required relocation of a portion of the cut-off to avoid delaying construction of the dam. The relocated cut-off was successfully constructed from a higher ground elevation, using a denser slurry, produced by mixing in more silt. To analyze the failures a nomograph was developed which can be used to determine the required slurry density for trench wall stability. The stability analysis, first developed by Morgenstern and Amir-Tahmasseb was confirmed. The hydrostatic head drop across the cut-off varies from 85 to 90 % of the gross head on the dam. Differential settlement of almost 10 ft (3 m) has occurred along the cut-off after completion without detrimental effects. Readings over the last 3 years indicate no reduction in the efficiency of the cut-off.
Geological Data Handling in Urban Areas
Authors: Grice R. H.
Published: July 2008

A data handling system is being developed to facilitate the handling of engineering geology data collected by a number of independent observers in an urban area. The aim is to provide an economical mechanism for the preservation of a maximum amount of data which may be acquired by individual investigations, and for selective retrieval and presentation of such data.
Settlements of Two Multistory Buildings in Edmonton
Authors: DeJong J. , Harris M. C.
Published: July 2008

Settlement observations have been taken over a period of about 6 years for two multistory buildings on a clay till. The CN Tower is founded on spread footings and the Avord Armson on Franki expanded base concrete piles; both buildings have settled a maximum of about 3 cm ([Formula: see text]). The settlement measurements showed a rapid response to loading during the construction period. Analysis of the foundations by elastic theory is shown to account satisfactorily for the overall settlement pattern during the construction period. The modulus of elasticity derived from the observations is stress dependent, decreasing with increasing load intensity. A small amount of long-term settlement has occurred at the end of construction; after 6 years it is less than about 20% of the total. Predictions of settlement using parameters obtained from soil samples taken at the sites are unrealistically high when compared with measured settlements.
Effect of Freeze–Thaw Cycling on Stress–Strain Characteristics and Volume Change of a Till Subjected to Repetitive Loading
Authors: Culley R. W.
Published: July 2008

To assess benefits to be gained from increasing compaction specifications for subgrades, a laboratory program was performed to determine the effect of closed-system freeze–thaw cycling on resilient and residual strains, resilient moduli, and volume changes of till specimens that had been compacted to various densities and water contents and subjected to repetitive loading in a constant triaxial stress system.The study showed that if compaction of this soil was increased to a higher density at a lower water content, strains, modulus, and freeze–thaw effects would be improved to such an extent that a significant reduction in pavement structure would be possible. It also showed that the extent to which a reduction could be made was dependent on the ability of the subgrade to maintain the compaction density and water content throughout its design life.
Uplift Resistance of Augered Footings in Fissured Clay
Authors: Adams J. I. , Radhakrishna H. S.
Published: July 2008

The ultimate uplift capacity of augered footings in relatively insensitive and intact clays is computed on the basis of the undrained shear strength of clay. Fissured clays, which may be the result of surface desiccation or preconsolidation, give different values of strength according to the type of test and size of specimen used. The actual strength mobilized in this type of clay under uplift loads was determined by a number of full-scale tests performed on both belled and straight-sided footings. These tests showed that the uplift strength mobilized in fissured clay was only one-third of its intact strength and very nearly equal to its undrained residual or fissured strength. Soil strains adjacent to the belled footings indicated a complex failure mechanism which varied with depth of the foundation. The uplift resistance of straight-sided footings was found to be largely the result of adhesion between the soil and the footing.
Temperature-dependent Specific Heats of Dry Soil Materials
Authors: Kay B. D. , Goit J. B.
Published: July 2008

Specific heat measurements have been made on several soil materials at different temperatures in order to obtain a generalized functional relation between specific heat and temperature. Specific heats were found to vary linearly with temperature from 200 to 300 °K (−73 °C to + 27 °C) and extrapolated close to zero at 0 °K. Consequently, the functional relation between specific heat and temperature for soil materials may be approximated as Cp = mT where Cp is the specific heat, T is the absolute temperature (°K), and m is a proportionality constant. Such a relation permits the prediction of the specific heats at any temperature normally encountered in the field once reliable specific heats have been determined at a single temperature.
Vertical Stress Components Produced by Axially Symmetrical Subsurface Loadings
Authors: Geddes James D.
Published: July 2008

From a consideration of the Mindlin solution relating to the stresses produced by a subsurface point load in a semi-infinite, homogeneous, isotropic, linearly elastic medium, equations are developed for the intensity of vertical stress on the axis of loading caused by a number of axially symmetrical distributions of subsurface load. The results are also presented in the form of tables of stress coefficients which permit the rapid evaluation of stresses. In the case of a uniform distribution of pressure, the errors associated with the neglect of the depth, below the surface of the medium, at which loading is applied are evaluated. Sufficient data is given to permit the production of influence charts of the Newmark type to cover other distributions of subsurface loadings.
An evaluation of the liquefaction potential of the Fraser Delta
Authors: Byrne Peter M.
Published: July 2008

Empirical and analytical methods for predicting the occurrence of liquefaction of foundation soils during an earthquake are examined and applied to the Fraser Delta area of British Columbia. The area is diked and at present has a population of about 150 000 people who reside mainly in low-rise buildings. Liquefaction of the foundation soils would cause severe damage to buildings, services, highway and railway links, and the dikes.Application of empirical methods based on blow count values indicates that liquefaction of the foundation soils could occur. Application of analytical methods indicates that liquefaction could occur in the event of an earthquake having a maximum ground surface acceleration of 0.12g (the 100 year value).The effects of various remedial measures are examined and it is shown that densification, drainage, and fill loading serve to reduce the tendency for liquefaction to occur. The presence of a low permeability layer close to the surface may cause liquefaction to occur by impeding the drainage.Construction that involves placing large sand fills with adequate drainage through the surficial low permeability layer to support low rise buildings would seem to be the least hazardous for this region.