bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of radiological assessment of ulnar trochlear notch sclerosis in dysplastic canine elbows
Authors: Burton N. J. , Toscano M. J. , Barr F. J. , Owen M. R.
Published: August 2008

Objectives: The objectives of this study were to quantify the sensitivity and specificity of visual assessment of radiographs of the canine elbow in detecting ulnar trochlear notch sclerosis, to establish interobserver and intra‐observer variation for the presence and grade of sclerosis and to quantify the effect of radiographic exposure on observer grading.

Methods: Mediolateral elbow radiographs were obtained from Labrador retrievers (n=34) aged between six and 18 months. Radiographs from dogs with an arthroscopic diagnosis of fragmented medial coronoid process (n=17) and those from a control population (n=17) were subjected to observer grading for the presence or absence of and the grade of ulnar trochlear notch sclerosis. Interobserver and intra‐observer variation and observer sensitivity and specificity were calculated. Digital data from the ulnar trochlear notch were correlated with mean observer grade to quantify the effect of radiographic exposure on observer grade.

Results: Interobserver agreement was “fair” (kappa=0·251 to 0·369) and intra‐observer agreement was “moderate” to “substantial” (kappa=0·462 to 0·667). The sensitivity of observer assessment was 72 per cent with a specificity of 22 per cent. Mean observer grade was not significantly correlated with the degree of radiographic exposure (P=0·70).

Clinical Significance: Ulnar trochlear notch sclerosis is a phenomenon associated with fragmented medial coronoid process. However, interobserver agreement in grading this feature is only fair, being identified by observers with moderate sensitivity but with relatively poor specificity. This low specificity may predispose to overdiagnosis in clinical cases. Intra‐observer agreement is moderate to substantial, suggesting that individuals can reliably quantify this radiological feature on multiple occasions. The ability of observers to assess the degree of sclerotic change is not significantly affected by radiographic exposure.
Early hip laxity examination in predicting moderate and severe hip dysplasia in Estrela Mountain Dog
Authors: Ginja M. M. D. , Gonzalo‐Orden J. M. , Melo‐Pinto P. , Bulas‐Cruz J. , Orden M. A. , San Roman F. , Llorens‐Pena M. P. , Ferreira A. J. A.
Published: August 2008

Objectives:To determine the reliability of early passive hip laxity examination in predicting moderate and severe hip dysplasia.

Methods:The passive hip laxity of 104 Estrela Mountain dogs was evaluated using the Ortolani method, conventional hip‐extended radiography and the PennHIP method, when the animals were between four and 12 months of age. After the age of one, dogs were re‐examined for hip dysplasia using the Fédération Cynologique Internationale scoring system. The passive hip laxity results were subsequently compared with the Fédération Cynologique Internationale scores for sensitivity, specificity, positive predictive value, negative predictive value and accuracy.

Results:The PennHIP method achieved the best results in specificity (93 per cent), positive predictive value (91 per cent) and accuracy (88 per cent), and the Ortolani method was the best in sensitivity (92 per cent) and negative predictive value (92 per cent).

ClinicalSignificance:The Fédération Cynologique Internationale grades D and E can be predicted with confidence even before animals are one year old.
Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor—Part I: Flow Field at Midspan
Authors: Mailach Ronald , Lehmann Ingolf , Vogeler Konrad
Published: August 2008

In this two-part paper, results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In Part I of the paper, the flow field at midspan of the rotor blade row will be discussed. Different aspects of the blade row interaction process are considered for the design point and an operating point near the stability limit. The periodical unsteady blade-to-blade velocity field is dominated by the incoming stator wakes, while the potential effect of the stator blades is of minor influence. The inherent vortex structures and the negative jet effect, which is coupled to the wake appearance, are clearly resolved. Furthermore the time-resolved profile pressure distribution of the rotor blades is discussed. Although the negative jet effect within the rotor blade passage is very pronounced, the rotor blade pressure distribution is nearly independent of the convectively propagating chopped stator wakes.
The Influence of Sweep on Axial Flow Turbine Aerodynamics in the Endwall Region
Authors: Pullan Graham , Harvey Neil W.
Published: August 2008

Sweep, when the stacking axis of the blade is not perpendicular to the axisymmetric stream surface in the meridional view, is often an unavoidable feature of turbine design. In a previously reported study, the authors demonstrated that sweep leads to an inevitable increase in midspan profile loss. In this paper, the influence on the flowfield close to the endwalls is investigated. Experimental data from two linear cascades, one unswept, and the other swept at 45 deg but having the same overall turning and midspan pressure distribution, are presented. It is shown that sweep causes the blade to become more rear loaded at the hub and fore loaded at the casing. This is further shown to reduce the penetration of the secondary flow at the hub, and to produce a highly unusual secondary flow structure, with low endwall overturning, at the casing. A computational study is then presented in which the development of the secondary flows of both blades is studied. The differences in the endwall flowfields are found to be caused by a combination of the effect of sweep on both the endwall blade loading distribution and on the bulk movements of the primary irrotational flow.
Large Eddy Simulation of Leading Edge Film Cooling—Part II: Heat Transfer and Effect of Blowing Ratio
Authors: Rozati Ali , Tafti Danesh K.
Published: August 2008

Detailed investigation of film cooling for a cylindrical leading edge is carried out using large eddy simulation (LES). The paper focuses on the effects of coolant to mainstream blowing ratio on flow features and, consequently, on the adiabatic effectiveness and heat transfer coefficient. With the advantage of obtaining unique, accurate, and dynamic results from LES, the influential coherent structures in the flow are identified. Describing the mechanism of jet-mainstream interaction, it is shown that as the blowing ratio increases, a more turbulent shear layer and stronger mainstream entrainment occur. The combined effects lead to a lower adiabatic effectiveness and higher heat transfer coefficient. Surface distribution and span-averaged profiles are shown for both adiabatic effectiveness and heat transfer (presented by Frossling number). Results are in good agreement with the experimental data of Ekkad et al. [1998, “Detailed Film Cooling Measurement on a Cylindrical Leading Edge Model: Effect of Free-Steam Turbulence and Coolant Density,” ASME J. Turbomach., 120, pp. 799–807].
Prestall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation
Authors: Chen Jen-Ping , Hathaway Michael D. , Herrick Gregory P.
Published: August 2008

Computational fluid dynamics calculations using high-performance parallel computing were conducted to simulate the prestall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial fast Fourier transform analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.
Real-Time Force and Moment Estimation for Mechanical Gas Face Seal Systems Using Reduced-Order Kalman Filters
Authors: Zhang Haojiong , Landers Robert G. , Miller Brad A.
Published: August 2008

A method using reduced-order Kalman filters is developed to estimate the thin gas film axial force and moments in real time for mechanical gas face seal systems in a flexibly mounted stator configuration. First-order Gauss–Markov stochastic models, combined with the stator motion equations, form the basis for the reduced-order Kalman filter estimators. Two schemes are presented to estimate axial force and moments based on stator motion measurements. In one scheme, the force and moments are directly estimated and, in another scheme, a set of proper orthogonal decomposition weighting functions is estimated, from which the gas film force and moments are computed. Both estimators are shown to approximate the gas film axial force and moments successfully for different forcing functions over a wide range of compressibility numbers.
Feedback Linearization Tracking Control of Vehicle Longitudinal Acceleration Under Low-Speed Conditions
Authors: Yang Bin , Keqiang Li , Nenglian Feng
Published: August 2008

This research addresses the modeling, design, and implementation of a longitudinal acceleration tracking control (LATC) system for a test vehicle at low speeds. An electronic throttle actuator for LATC system application is introduced first, which can be used to perform the switching of three functions arbitrarily: automatic LATC, manual drive-by-wire, and pure manual operation. Then, a nonlinear dynamics model for the test vehicle is proposed by using a state-space equation, and several major nonlinear components including the engine, torque converter, transmission, and electronic throttle actuator are considered simultaneously in this model. Furthermore, focusing on the electronic throttle actuator, the strong nonlinear factors induced by the Coulomb friction and torsion of the return spring are analyzed. In view of the nonlinearity of the proposed model, the concept of feedback linearization is employed to convert the nonlinear system into a linear canonical form, and the analysis of the stability caused by the model’s uncertainty is also discussed. Finally, an acceleration feedback linearization controller and a Kalman filter are introduced. They adopt the linear canonical form, which represents a simpler structure. The performance in tracking desired acceleration at low speeds is confirmed by both computer simulations and experiments.
Seismic Proving Test of Ultimate Piping Strength: Safety Margin of Seismic Design Code for Piping
Authors: Suzuki Kenichi , Abe Hiroshi
Published: August 2008

The proving test of a large-scale piping system and elasto-plastic analyses were conducted to assure safety margins of current and newly proposed seismic design codes for piping in Japanese nuclear power plants. Two test models were used, one for the design method confirmation test and one for the ultimate strength test. The allowable acceleration safety margin (MA) was defined as the ratio of Af/AS2, where Af is the maximum input acceleration corresponding to piping failure in a single seismic input, and AS2 is the maximum allowable input acceleration for the S2 seismic wave according to Japanese seismic design codes for Class 1 piping components. When the current code was applied to the design method confirmation test model, associated with the 10% broadened response spectrum of the S2 seismic wave for a PWR building, MA was revealed to be 9.6 for a frequency ratio (RW) of 0.7. Without the response spectrum broadening, MA decreases to 4.9. Redefined as the ratio in terms of the displacement and cyclic peak stress of the highest stressed component, the safety margins (MD, MFC) tend to change to 7.7 and 3.7, respectively. The newly proposed code includes the following modifications from the current code rules: 1) only the allowable stress limits to prevent fatigue failure is ruled for the “S2” seismic wave, 2) a new diagram of the Ke factor in the fatigue design analysis is implemented. The safety margin MA of the proposed code with the broadened spectrum was revealed to be still as high as 6.6 for RW = 0.7. Analytical evaluation was conducted to discuss the tendency of the safety margins for seismic input conditions that differ from RW = 0.7, and the degree of conservatism or margin included in design analysis methods, whose degree is related to the safety margins.
Numerical Study of Metal Forming Simulation Using Elasto-Plastic and Rigid-Plastic Meshfree Analysis
Authors: Park Young H.
Published: August 2008

In this paper, material processing simulation is carried out using a meshfree method. The domain of the workpiece is discretized using the Lagrangian Reproducing Kernel Particle Method (RKPM) where no external meshes are used. The meshfree method is formulated for elasto-plastic material model as well as rigid-plastic model. For elasto-plastic model, a finite plasticity theory is formulated based on the multiplicative decomposition to handle large deformation problems. A rigid-plastic material model is also employed using flow formulation based on the assumption that elastic effects are insignificant in the metal forming operation. A comparative study between elasto-plastic and rigid-plastic RKPM methods was conducted to demonstrate consistency of the results from elasto-plastic and rigid-plastic simulations for a metal forming application.
Safety Relief Valve Vent Sizing Using Steam Flow Properties
Authors: Ibrahim Zakaria N.
Published: August 2008

Safety relief valve vents in power plants are typically sized by treating steam flow as a perfect gas flow. ANSI B31.1 [1] and an ASME paper by G. S. Liao [2] provided the power industry with the guidance for using this approximation. The perfect gas approximation of the steam flow furnished the engineers with the simple formulations currently available in References 1 and 2. Modern computational techniques allow the accuracy of vent sizing calculations to be improved by eliminating the perfect gas assumption. The following methodology uses ASME steam property tables [3] assuming adiabatic flow through one or more constant area pipe sections connected by reducers. Compressible flow Fanno-Line differential equations for continuity, momentum, energy, and state [4] are generalized to handle the steam thermodynamic properties. These equations are simultaneously solved numerically to determine the flow thermodynamic state at any location along the vent. The differential equations are integrated utilizing steam thermodynamic functions [3], in conjunction with the Math-Cad’s Runga-Kutta method [5]. Both choking and non-choking conditions are considered at the vent exit. Closed discharge backpressures and open discharge blowback are addressed. Amendment to the ASME ANSI B31.1 Power Piping Code [1], to include the differential equations formulation for the constant area adiabatic steam flow is also proposed.
Analysis for Vehicle Interior Noise Using Helmholtz Resonator
Authors: Kozukue Wakae , Hagiwara Ichiro , Mohri Yasuhiro
Published: August 2008

In this paper the reduction analysis of the so-called ‘booming noise’, which occurs due to the resonance of a vehicle cabin, is tried to carry out by using the finite element method. For the reduction method a Helmholtz resonator, which is well known in the field of acoustics, is attached to a vehicle cabin. The resonance frequency of a Helmholtz resonator can be varied by adjusting the length of its throat. The simply shaped Helmholtz resonator is set up to the back of the cabin according to the resonance frequency of the cabin and the frequency response of the sound pressure at a driver’s ear position is calculated by using the finite element method. It is confirmed that the acoustical characteristics of the cabin is changed largely by attaching the resonator and the sound quality is quite varied. The resonance frequency of the resonator can be considered to follow the acoustical characteristics of the cabin by using an Origami structure as a throat. So, in the future the analysis by using an Origami structure Helmholtz resonator should be performed.
Cavity Growth Simulation of 2.25Cr-1Mo Steel Under Creep-Fatigue Loading
Authors: Ogata Takashi
Published: August 2008

High temperature components in thermal power plants are subjected to creep-fatigue loading where creep cavities initiate and grow on grain boundaries. Development of a quantitative evaluation method of cavity growth is important for reliable maintenance of these components. In this study, a creep-fatigue test was carried out at 600°C on 2.25Cr-1Mo steel in a scanning electron microscope, and continuous observation of cavity growth behavior on the surface during the test was made. Based on the cavity growth observation, existing cavity growth models were modified and a simulation result by the modified model was discussed by comparing with observed cavity growth behavior. From the observation, spherical shape cavities initiate and grow up to their length of 2μm on the grain boundaries at initial stage of damage, and then these cavities change their shape to crack-like to grow until their length reaches around 10μm. Finally, crack-like cavities coalesce each other to form one micro crack along a grain boundary. It can be concluded that cavity growth rates of these cavities are controlled by diffusion and power law creep under constrained condition based on theoretical consideration of cavity growth mechanism. Through these discussions, a new cavity growth model was proposed by modifying conventional models. Both spherical and crack-like cavity growth rate equations were derived from the modified cavity growth model. It was indicated that measured cavity growth rate was well predicted by the growth rate equations derived from the modified model, and a cavity growth simulation result corresponds to the change in the maximum cavity size with cycles under the creep-fatigue loading.
Methods of Determining a Damping Ratio From a Simple Impact Test
Authors: Chandler Cordelia K.
Published: August 2008

Numerous tests have been performed in the nuclear industry to determine damping ratios for the analysis of steam generator tube bundles. Several methods have been used to analyze the response data, including the logarithmic decrement method, the half-power point method, and curve-fitting methods. Theoretically, the methods give the same damping results; however, in practice, the results may be appreciably different. Each of these methods presents certain difficulties in determining a damping ratio. For the half-power point method, the difficulties include selecting a sampling rate, setting a time span, and the use of a window to truncate the data. The difficulties associated with the logarithmic decrement method include selecting the initial and final peaks and selecting an appropriate frequency. In both cases, most of the difficulties arise from the need for subjective decisions by the engineer or technician. Blind curve-fitting methods have been shown to underestimate the actual damping. A practical comparison of these three methods was performed on damping data from a simple impact test. While the half-power point method and curve-fitting methods are useful tools to validate damping results, a logarithmic decrement method that averages the damping over a number of cycles appears to provide the most consistent and realistic damping results for SG tubes.
Corrosion Fatigue Results for Alloy 690 Tubing in a PWR Secondary Environment
Authors: Young Bruce A. , King Peter J.
Published: August 2008

Previous corrosion fatigue results [1,2,3] have shown no enhancement to the crack growth rate of Alloy 690 in a Pressurized Water Reactor (PWR) or a low dissolved oxygen (DO) concentration (less than 10 ppb) environment under open-circuit potential conditions. This research compared corrosion fatigue literature data for Alloy 690 plate, which used conventional compact tension, C(t), specimens; to Alloy 690 tests conducted using steam generator tubing (S-193). There was some concern that the results on plate material may not be representative of the behavior of steam generator tubing due to grain size, section thickness or other processing variables. The overall objective of this research was to determine if steam generator tubing response in a PWR secondary side environment could be modeled using the literature data from plate material. Fatigue crack growth rate data for Alloy 690, on an actual service heat of steam generator tubing in a low dissolved oxygen PWR secondary side environment, was generated using a circumferentially throughwall cracked tube specimen. The new data generated, along with the literature data, were compared to a modified corrosion fatigue model. The results showed the tube material behaved similarly to the plate material and thus standard specimen geometries, for example, compact tension specimens, tested on thick section materials could be used to characterize tube material response under these environmental conditions.
Comparing the Benefits of Monitoring Versus Preemptive Replacement or Repair
Authors: Woodcock Joel , Houssay Laurent P.
Published: August 2008

Today, utilities are faced with many equipment maintenance decisions, including whether to implement periodic replacement or to begin an inspection or condition monitoring program. Determination of an optimum maintenance strategy can be difficult because of the financial implications and the probabilistic aspect of the aging process. The Proactive Aging Management (PAM) Tool is a program that can be implemented by utilities to achieve maintenance optimization. PAM supports the decision making process by providing a financial analysis that assesses the impact of outage, inspection, repair and replacement costs together with the effects of aging on the failure rates of a particular component. PAM evaluates the present value of each maintenance strategy and optimizes maintenance parameters such as replacement date or inspection frequency. Component level models in PAM allow the system engineer to determine the best maintenance strategy for a given component. This paper describes an application of PAM that compares the options of inspection or proactive replacement to a base case run-to-failure strategy. The net present value (NPV) over the life of the plant is the metric by which strategies are compared. The NPV is generated for several combinations of inspection and proactive replacement costs. The results provide insight on the optimum choice based on the respective relative costs of each strategy.
Comparison of Models Predicting the Fatigue Behavior of Austenitic Stainless Steels
Authors: Solomon H. D. , Amzallag C.
Published: August 2008

This paper compares the various models used to describe the fatigue behavior of Austenitic Stainless Steels. This was done for newly produced GE/EDF fatigue results and for hundreds of other data points gleaned from the literature. This comparison was made for several subsets of the data, comprising: 304 and/or 316SS, below and/or above 100°C, loading by tensile and/or bending, and for tests run in air and/or various reactor water environments. Most approaches gave reasonable correlations in the low cycle regime, but some were better than others, depending upon the subset considered. Of most critical concern was the predicted endurance limit. The Langer model used a non-conservative (too high) endurance limit. Better agreement was found for the models produced by ANL, Jaske and O’Donnell, Tsutsumi, Higuchi and Leax. These models are statistically compared by subset.
Heat Transfer Analysis of Storage Structures for PALTEM Maintenance Sheets
Authors: Jou Rong-Yuan , Lee Kuang-Chyi , Yu Hsin-Her , Lee I-Ju , Lin Chien-Chang
Published: August 2008

Steady convection of air inside a storage enclosure for PALTEM maintenance sheets is investigated to evaluate the interior temperature distribution. Stream function-vorticity formulation is used to model the momentum and the energy transports in this 2D enclosure. Geometries of length-to-height aspect ratios of 2.5 and 5 are investigated. Temperature distributions for Rayleigh numbers in the laminar regime of 101 to 105 are explored for two different types of boundary conditions (type I and type II). These two types of boundary conditions have a practical importance especially in simulating the environment heating upon the storage structure. From the design viewpoint, type II conditions seem to be more proper to storage the maintenance sheets.
Study on Improvement of the Suction Valve Using PIV Technique
Authors: Koyabu Eitaro , Tsukiji Tetsuhiro , Matsumura Yoshito , Sato Taizo
Published: August 2008

The simplified test model of the commercial reciprocating compressor for an automotive air-conditioner is used to measure the displacement of the suction valves using a strain gauge and to investigate the velocity distributions of the discharge flow from the valves using the particle image velocimetry system. This paper is focused on the effects of shape of the suction valve on the vibration-reduction. The size of the suction valve hole and the width of the tip of the suction valve are changed as main parameters of the valve shape. First, the size of the conventional valve hole and the width of the tip of the conventional valve are changed and seven new valves are manufactured to reduce the vibration of the valve. Consequently, it is found that one shape of the new valves is the most effective for the vibration-reduction. Next, the influence of the natural frequency on the vibration-reduction is investigated using one shape of the new valves by changing the material and the thickness of the valve. In addition, the relation between the conventional valve and the new valves are also estimated by the pressure loss. Finally, the reason of the vibration-reduction for one shape of the new valves is discussed from the results of the flow analysis around the valve. The vibration-reduction for one shape of the new valves is confirmed by measurement of the displacement of the valve in the reciprocating compressor for the automotive air-conditioner.
The Influence of the Bauschinger Effect on the Stress Intensity Factors for a Radially Cracked Autofrettaged Thick-Walled Cylinder
Authors: Perl M. , Levy C. , Rallabhandy V.
Published: August 2008

The influence of the Bauschinger Effect (BE) on the three dimensional, Mode I, Stress Intensity Factor (SIF) distributions for arrays of radial, internal, surface cracks emanating from the bore of a fully or partially autofrettaged thick-walled cylinder is investigated. A thorough comparison between the prevailing SIFs for a “realistic” - Bauschinger Effect Dependent Autofrettage (BEDA) and those for an “ideal” - Bauschinger Effect Independent Autofrettage (BEIA) is done. The 3-D analysis is performed via the finite element (FE) method and the submodeling technique, employing singular elements along the crack front. Both autofrettage residual stress fields, BEDA and BEIA, are simulated using an equivalent temperature field. More than 300 different crack configurations are analyzed. SIFs for numerous crack arrays (n = 1–64 cracks), a wide range of crack depth to wall thickness ratios (a/t = 0.01–0.2), various ellipticities (a/c = 0.5–1.5), and different levels of autofrettage (ε = 30%–100%) are evaluated. The Bauschinger Effect (BE) is found to considerably lower the beneficial stress intensity factor due to autofrettage, KIA, by up to 56%, as compared to the case of “ideal” autofrettage. The reduction in KIA varies along the crack front with a maximum at the point of intersection between the crack plane and the inner surface of the cylinder, decreasing monotonically towards the deepest point of the crack. The detrimental influence of the BE increases as the number of cracks in the array increases and as crack depth decreases. For a partially autofrettaged cylinder, as the level of overstrain becomes smaller the influence of the BE is considerably reduced. As a result, the SIFs due to 100% BEDA differ by less than 10% as compared to 60% BEDA, and on the average the difference is only about 2–4%.
The Influence of Pipe Motion on the Integrity of Liquid-Filled Pipes Subjected to Pressure Transients
Authors: de Freitas Rachid Felipe Bastos
Published: August 2008

This work presents a structural itegrity model for piping systems conveying liquids which takes the axial fluid-structure interaction into account. The model is used to numerically investigate the influence of pipe motion on the degradation of the piping when fast transients are generated by valve slam. The resulting mathematical problem is formed by a system of non-linear partial differential equations which is solved by means of an operator splitting technique, combined with a Glimm’s method. Numerical results obtained indicate that high piping flexibility may introduce a substantial increase in damage growth along the pipes.
Earthquake Proof Efficiency of Sliding Base Isolator With Dog-Bone Type Damping
Authors: Tsai C. S. , Chiang Tsu-Cheng , Chen Bo-Jen
Published: August 2008

In recent years, there have been more and more seismic retrofit applications of using base isolators in seismic prone regions. In the past, the focuses of researches on the efficiency of various base isolators have been aimed at their behavior under earthquakes without long predominant periods. The doubts of efficiency of the base isolator nearby active faults or located at a soft deposit soil have been raised by researchers. It is revealed from previous studies that the seismic responses of the base isolated structure are significant due to the influence of resonance. In order to minimize the inherent shortcomings of base isolators, various base isolators with dog bone type of friction behavior have been proposed in this study. In the meanwhile, the exact solutions used to describe the behavior of the proposed isolators have also been derived in this study. The numerical studies show that the displacement responses of proposed isolators under near fault earthquakes and ground motions with long predominant periods are much lower than those of the traditional FPS and VCFPS devices. Hence, the required dimensions of proposed isolators can be smaller than those for the FPS and VCFPS isolators.
Drop Testing of DOE Spent Nuclear Fuel Canisters
Authors: Snow Spencer D. , Morton D. Keith , Rahl Tommy E. , Blandford Robert K. , Hill Thomas J.
Published: August 2008

The National Spent Nuclear Fuel Program (NSNFP) at the Idaho National Engineering and Environmental Laboratory (INEEL) prepared four representative Department of Energy (DOE) spent nuclear fuel (SNF) canisters for the purpose of drop testing. The first two canisters represented a modified 24-inch diameter standardized DOE SNF canister and the second two canisters represented the Hanford Multi-Canister Overpack (MCO). The modified canisters and internals were constructed and assembled at the INEEL. The MCO internal weights were fabricated at the INEEL and assembled into two MCOs at Hanford and later shipped to the INEEL for drop test preparation. Drop testing of these four canisters was completed in August 2004 at Sandia National Laboratories. The modified canisters were dropped from 30 feet onto a flat, essentially unyielding surface, with the canisters oriented at 45 degrees and 70 degrees off-vertical at impact. One representative MCO was dropped from 23 feet onto the same flat surface, oriented vertically at impact. The second representative MCO was dropped onto the flat surface from 2 feet oriented at 60 degrees off-vertical. These drop heights and orientations were chosen to meet or exceed the Yucca Mountain repository drop criteria. This paper discusses the comparison of deformations between the actual dropped canisters and those predicted by pre-drop and limited post-drop finite element evaluations performed using ABAQUS/Explicit. Post-drop containment of all four canisters, demonstrated by way of helium leak testing, is also discussed.
Numerical Correlation of Fracture Behavior in Axially Cracked Pipelines Using Constraint Designed Fracture Specimens
Authors: Cravero Sebastian , Ruggieri Claudio
Published: August 2008

This work explores applications of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The primary objective is to gain some understanding of the potential applicability of SE(T) specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading, each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. A key outcome of this investigation is that toughness data measured using SE(T) specimens appear more applicable for cleavage fracture predictions of pressurized pipelines and cylindrical vessels than standard, deep notch fracture specimens under bend loading. The results encourage further development of constraint-designed SE(T) specimens for fracture assessments of pressurized pipes and cylindrical vessels.
Response of Soil and a Submerged Tunnel During a Thrust Fault Offset Based on Model Experiment and Numerical Analysis
Authors: Lin M. L. , Jeng F. S. , Wang H. J. , Wang C. P. , Chung C. F. , Yao Daniel C. T. , Chan S. J.
Published: August 2008

Observed from the earthquake disasters occurred over the decades in Taiwan, the deformation of near surface soil was the major cause lead to damages of underground structures or pipe lines; for instance, the damage of diversion tunnel of Shih-Kang Dam in Chichi earthquake is a typical case. To study the process of fault propagation as well as the associated soil and structure deformation during a fault offset event, model experiments of simulating thrust fault offset were set up, in which non-cohesive sands was adopted simulating near surface soil. The results, obtained from experiment studies and numerical analyses based on finite element method were then compared to further explore the behavior of soil, structure during faulting process. The soil deformation obtained from numerical analysis complies with the outcome from model experiments. In the near future, when conducting a risk evaluation for earthquake-induced damage on underground structure, a numerical stimulation can provides helpful quantity analysis and can serve as a handy tool for the earthquake resistance design.
Seismic Analysis of a Nuclear Reactor With Fluid-Structure Interaction
Authors: Sigrist Jean-Franc¸ois , Broc Daniel , Laine Christian
Published: August 2008

The present paper is related to a seismic analysis of a naval propulsion ground prototype nuclear reactor with fluid-structure interaction modeling. Many numerical methods have been proposed over the past years to take fluid/structure phenomenon into account [14] in various engineering domains, among which nuclear engineering in seismic analysis [15]. The purpose of the present study is to apply general methods on a global approach of the nuclear reactor. A simplified design of the pressure vessel and the internal structure is presented; fluid-structure interaction is characterized by the following effects: • added mass effects are highlighted with the calculation of an added mass operator, obtained from a finite element discretisation of the coupled problem. The numerical model is developed within the CASTEM code using an axi-symmetric model of the industrial structure; • coupling effects between the external and internal structure via the confined inner fluid are also illustrated and numerically described with the added mass operator; • added stiffness effects are taken into account with an added stiffness matrix describing pre-stress effects due to a static pressure loading simulating the actual operating conditions of the reactor. The expected fluid-structure interaction effects on the nuclear pressure vessel and their numerical modeling leads to the definition of a global coupled model which can be used to perform a seismic analysis. A modal analysis is first performed and classical linear methods (static, spectral and temporal) are then applied on the studied structure with taking fluid-structure into account.
Impact of PWSCC and Current Leak Detection on Leak-Before-Break Acceptance
Authors: Wilkowski Gery , Wolterman Rick , Rudland Dave
Published: August 2008

This paper assesses the effect of using primary water stress corrosion cracking (PWSCC) crack morphology parameters (roughness, number of turns, and actual flow path/pipe thickness) in determining the difference in the leakage crack length, and how the difference in the leaking crack lengths changes typical margins from past LBB submittals and published reports. Several past LBB submittal cases were selected; in addition, cases from generic LBB reports published by EPRI were also selected. The results of the analyses showed that the past submittals by nuclear steam system supply (NSSS) companies frequently used the surface roughness comparable to an air-fatigue crack with no turns and the actual flow path equal to the thickness of the pipe. This condition would give the shortest possible leakage flaw length. The roughness, number of turns, and actual flow path to thickness ratio for PWSCC cracks were determined from photomicrographs of service-removed cracks. When using the PWSCC crack morphology parameters that corresponded to the crack growing parallel to the long direction of the dendritic grains (V.C. Summer and Ringhals cases), then the leakage flaw length increased 69 percent over the air-fatigue crack length at the same leak rate. Using the same critical crack length as was used in the initial LBB submittals and the published documents, the margins on the crack length changed from 1.77 to 6.0 for the initial submittals (which we also reproduced) to 0.88 to 2.74 from our calculations for a PWSCC crack. If the crack grew in the buttered region of the bimetallic weld, then based on metallographic sections from service-removed flaws, there would be a more tortuous flow path. For this crack condition, in all but one case, the margins on the normal operating versus N+SSE crack lengths were below the safety factor of two required for LBB approval. The average margin decreased from 3.39 for the air-fatigue crack to 1.55 for the PWSCC crack growing transverse to the long direction of the dendritic grains. This was about an additional 20 percent decrease in the margin from the case of having the PWSCC grow parallel to the long direction of the dendritic grains. These results show that LBB is difficult to satisfy for PWSCC susceptible pipe using the current SRP 3.6.3 LBB approach. This LBB assessment did not consider the possible development of a long circumferential surface crack, which would be more detrimental to LBB behavior. Such cracking behavior would violate the LBB screening criterion.
Application of Constraint Corrected J-R Curves to Fracture Analysis of Pipelines
Authors: Zhu Xian-Kui , Leis Brian N.
Published: August 2008

Fracture properties of API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimental J-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for X80. It is shown that the predicted J-R curves developed in this paper match well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.
Analytic Prediction of Plastic Collapse Failure Pressure of Line Pipes
Authors: Zhu Xian-Kui , Leis Brian N.
Published: August 2008

Accurate prediction of burst pressure of line pipes is essential for the safety design and integrity assessment of transmission pipelines. Different analytical and empirical formulae for determining the limit load of defect-free pipes have been proposed, but none is widely accepted and broadly validated. The commonly used method to determine the burst pressure by code in pipeline industry is based on the hoop stress of a pipe when it reaches a critical stress, such as flow stress or ultimate tensile stress of the pipeline steel. Recent experiments have shown that the criterion by code may be too conservative for modern high strength pipeline steels. Based on the plastic instability theory and the von Mises or Tresca yield criterion, theoretical solutions to predict the burst pressure of defect-free pipes have been proposed for years. However, it can be shown that experimental data for various pipeline steels lie between the two theoretical solutions of burst pressure of pressurized defect-free pipes, and fit the average result of the two solutions. In general, the von Mises prediction is the upper bound, and the Tresca prediction is the lower bound of burst pressure. Because traditional criteria like Mises and Tresca tend to bounded experimental data, a new failure criterion referred to as Average Shear Stress criterion is proposed. A plastic collapse analysis solution is developed as the corresponding theoretical solution of pipe limit pressure at plastic collapse. The new solution is formulated as a function of pipe geometry, strain hardening exponent and ultimate tensile stress of materials. Finite element results and experimental data are then introduced to validate the proposed solution. Comparisons indicate that the present solution matches the numerical results and the average experimental data of burst pressure of defect-free pipes for various pipeline steel grades.
Experimental Investigation of Steam Condensation Phenomenon in a Multi-Hole Sparger
Authors: Park C. K. , Song C. H. , Jun H. G. , Yoon Y. J.
Published: August 2008

A series of steam condensation tests using a simplified version of the prototypic unit cell sparger that will be used in an APR1400 has been performed. The range of the steam mass fluxes for the condensation tests was selected to define the transition from a condensation oscillation regime to a stable condensation regime. The test results show that the dynamic load at the quench tank increases as the water temperature increases up to 80 °C and that it decreases rapidly at higher temperatures. In addition, the dominant frequency of the condensation induced pressure wave increases up to 60 °C and then it decreases very steeply. The results also show the average local-to-bulk temperature difference reaches up to 8.4 °C and the hole pattern used in the unit cell sparger can be used up to the local saturation temperature without inducing an unstable condensation phenomenon.
Numerical Analysis of Flutter in a Transonic Low Pressure Steam Turbine
Authors: Crouzet Fabien , Lafon Philippe
Published: August 2008

High levels of vibrations have been observed on the last row blades of a low pressure steam turbine for nominal operating conditions. A self-excited phenomenon known as flutter is suspected to be the cause of the vibrations for non-stall transonic conditions. The non-homogeneous distribution of vibratory levels on the row is attributed to mistuning effects. They are beyond the scope of our study. A time-dependent ALE formulation of Euler equations is derived on a quasi-3D domain and coupled with a one-degree-of-freedom structural model. The work-by-cycle (WBC) method is performed in order to analyse the stability of the vibrating blades in the surrounding flowfield, for a perfectly tuned assembly. On the top part of the blades, the flow is transonic and fully attached. It is shown that, for these operating conditions, the cascade aeroelastic behaviour is linear. By using the influence coefficient method, an instability region is exhibited. The effects of the flowfield on the vibrating blades are discussed. They are expressed in terms of added damping and stiffness in order to be used as the input data of a structural mistuning analysis.
Cavitating Orifice: Flow Regime Transitions and Low Frequency Sound Production
Authors: Testud Philippe , Hirschberg Avraham , Moussou Pierre , Aure´gan Yves
Published: August 2008

Detailed data are provided for the broadband noise in a cavitating pipe flow through a circular orifice in water. Experiments are performed under industrial conditions, i.e., with a pressure drop varying from 3 to 30 bars and a cavitation number in the range 0.10 ≤ σ ≤ 0.77. The speed of sound downstream of the orifice happens to vary spontaneously for a given set of hydraulic conditions. In the intermediate ‘developed cavitation’ regime, whistling associated with periodic vortex shedding is observed. In the ‘super cavitation’ regime, a vapor cloud develops itself and the whistling disappears. The broadband noise in each regime is presented and its dimensionless representation is discussed.
Experimental Investigation and Finite Element Analysis of the Free Vibration Problem of Bolted Joint
Authors: Fukuoka Toshimichi
Published: August 2008

Evaluation of the natural frequency and the natural mode of vibration of bolted joints is particularly important to avoid the failure of the structure due to resonance. In this paper, natural frequencies of the bending vibration of a bolted joint with simple configuration are measured with strain gages mounted on the surface of test specimen, and the effects of surface roughness, axial bolt force and bolt position are systematically investigated. Then, a numerical approach is proposed to analyze the free vibration problem of bolted joint, where selective reduced integration (SRI) scheme is introduced into the finite element formulation to improve the computation efficiency in solving the concerned eigen value problems. The effectiveness of the numerical procedure proposed here is validated by experimental measurements of the natural frequencies of the first mode.