bluuebunny/crossref_metadata_2025 huggingface dataset:
Creep-Fatigue Properties of the Candidate Materials of 700°C-USC Boiler
Authors: Kubushiro Keiji , Yoshizawa Hiroki , Itou Takuya , Nakagawa Hirokatsu
Published: August 2009

Creep-fatigue properties of candidate materials of 700°C-USC boiler are investigated. The candidate materials are Alloy 230, Alloy 263, Alloy 617 and HR6W. Creep-fatigue tests were conducted at 700°C and the effect of both strain range and hold time were studied. Experimental results showed that at 1.0% strain range, cycles to failure with 60 min strain holding is about 10% of that without strain holding, but at 0.7% strain range, cycles to failure with 60 min strain holding decreases down to about 1% of without strain holding. It appears that cycles to failure is decreased by increasing strain holding time at all tested strain ranges, and the effect of holding time is emphasized at small strain range. These phenomena depend on the kind of alloys.
Long Term Creep Rupture Strength of 9Cr1MoNbV Narrow Gap Welded Joints Improved by Normalizing and Tempering After Welding
Authors: Sato Takashi , Tamura Kohji , Mitsuhata Koichi , Ikura Ryuichi
Published: August 2009

With the increase of steam parameters of coal-fired thermal power plants, high strength 9%Cr steel containing niobium and vanadium became major material in high temperature boiler components. As the microstructure of these steels is tempered martensite, it is known that the softening occurs in HAZ of the weldment. In the creep rupture test of these welded joints the rupture strength is lower than that of the parent metal, and sometimes this reduction of strength is caused by Type IV cracking. To develop an effective method to improve the rupture strength of welded joints, a normalizing-tempering heat treatment after weld was proposed. 9Cr1MoNbV plates with a thickness of 40–50 mm were welded by 10 mm width automatic narrow gap MAG welding procedure using specially modified welding material. After normalizing at 1050C and tempering at 780C, material properties of the welded joints were examined. Microstructure of the HAZ was improved as before weld, and rupture strength of the welded joints was equal to that of the parent metal. The long term rupture strength of the welded joints as confirmed in the test exceeded 30,000 hours. This welding procedure has been applied to the seam weld of boiler hot reheat piping in USC plants successfully.
Numerical Analysis of the Effect of Diffusion and Creep Flow on Cavity Growth
Authors: Brust Frederick W. , Oh Joonyoung
Published: August 2009

In this paper, intergranular cavity growth in regimes, where both surface diffusion and deformation enhanced grain boundary diffusion are important, is studied. In order to continuously simulate the cavity shape evolution and cavity growth rate, a fully-coupled numerical method is proposed. Based on the fully-coupled numerical method, a gradual cavity shape change is predicted and this leads to an adverse effect on the cavity growth rates. As the portion of the cavity volume growth due to jacking and viscoplastic deformation in the total cavity volume growth increases, the initially spherical cavity evolves to V-shaped cavity. The numerical results are physically more realistic compared to results in the previous studies. The present numerical results suggest that the cavity shape evolution and cavity growth rate based on an assumed cavity shape, whether spherical or crack-like, cannot be used in this regime due to transitional coupled growth mechanisms.
Long-Term Creep Behaviour of E911 Heat Resistant 9% Cr Steel Weldments Fabricated With Filler Metals of Different Creep Strength
Authors: Mayr Peter , Cerjak Horst , Jochum Claus , Pasternak Jerzy
Published: August 2009

In this work an X11CrMoWVNb9-1-1 (E911) pipe with an outside diameter of 355 mm and a wall thickness of 43 mm was welded with three different filler metals by GTAW and SMAW process. The used filler metals differed in creep strength level, compared to E911 grade pipe base material creep strength. The long term objective of this work was to study the influence of weld metal creep strength on the overall creep behavior of the welded joints. Uni-axial creep tests at 600°C (873 K) and stresses ranging from 70 to 130 MPa were performed using cross-weld samples of all three welds. Fractured samples were investigated by optical microscopy, electron microscopy and hardness testing. The results showed that the use of undermatching weld metal of P91-type led to premature fracture in the weld metal at higher stress levels. At lower stresses the fracture location was shifted into the fine-grained heat affected zone (HAZ) and samples failed by characteristic Type IV failure mode. The use of matching (E911 type) and overmatching (P92 type) filler material increased the time to rupture only at high stress levels. The fracture mode for all samples at lower stress levels was identified as characteristic Type IV failure.
The Influence of Phase Transformations on Creep Resistance in Fe-Ni-Cr Alloys for Reformer Tube Applications
Authors: Laigo Johanne , Tancret Franck , Le Gall Rene´ , Christien Fre´de´ric , Furtado Jader
Published: August 2009

Heat resistant steels of the HP-series have widespread uses in the petrochemical industry in pyrolysis and reformer furnaces. The alloys are carbon-rich Fe-Ni-Cr alloys, with additions like Mn, Si, Nb, Ti, W... The typical microstructure of as-cast HP alloys is an austenite matrix with intergranular eutectic-like primary chromium carbides of the M7C3 type and niobium carbides of the MC type. Upon ageing, phase transformations occur. Intragranular secondary M23C6 carbides precipitate, which is thought to restrict dislocation motion, and intergranular M7C3 transforms into M23C6. Under certain thermal conditions, a partial transformation of the primary niobium carbides into a nickel-niobium silicide called G phase can occur. These phases may play a critical role during creep, but neither their role on mechanical properties nor the mechanisms of phase transformations are clearly identified. The aim of this study is to understand the role of each phase or phase transformation in the creep resistance of HP alloys. Consequently, a critical review of phase formation and transformations in such alloys is presented using a set of experimental and modelling techniques (electron microscopy, Castaing microprobe, creep tests at high temperature and neural networks modelling of mechanical properties...).
Effect of Vanadium and Niobium on Creep Strength in 10% Chromium Steel Analyzed by STEM-EDS
Authors: Mitsuhara Masatoshi , Yoshida Yu , Ikeda Ken-Ichi , Nakashima Hideharu , Wakai Takashi
Published: August 2009

The effect of vanadium and niobium on creep strengthening was studied in 10% chromium steels. Eleven kinds of samples which varied the additive amounts of vanadium and niobium were prepared. From the creep deformation behavior of them, the threshold stresses were estimated. The distribution maps of precipitates were obtained by STEM-EDS. In a steel with added 0.06% vanadium where no particles were observed in the lath, creep strength was slightly increased, indicating that it was not strengthened by a particle hardening effect in the lath. Lump-shaped precipitates and film-shaped precipitates including chromium and vanadium, which were observed on lath boundaries in the steel with added vanadium, are expected to inhibit the lath boundaries from migrating. This inhibition is the mechanism of the improvement in the steel with added vanadium. In the case of steels with added niobium, creep strength was found to be increased by dispersion hardening due to fine precipitates in the lath. The threshold stress was quantitatively estimated depending on the particle spacing. The estimated threshold stress corresponded to the one obtained by the creep deformation behavior. These results revealed that vanadium and niobium each have a role in improving creep strength. In steels with added both vanadium and niobium, the effect on creep strength was expressed by the sum of the effects due to each element, which were the retardation of the lath boundary migrations and the pinning of the dislocations in the lath.
Properties of 20Cr-25Ni-Mo-Nb-N Steel Tubes Exposed in Eddystone Unit No.1 Boiler for 75,000 Hours
Authors: Mimura Hiroyuki , Ishitsuka Tetsuo
Published: August 2009

A 20%Cr-25%Ni-1.5%Mo-Nb-N austenitic stainless steel tube, NF709, has been developed for boiler tube applications. The calculated maximum allowable stress values for NF709 is much higher than those for other austenitic stainless steel tubes. NF709 test tubes were exposed for 75,075 hours in Eddystone Unit No.1 boiler with a steam temperature of 615°C at the superheater outlet. The removed tubes were investigated metallurgically and mechanically. No severe corrosion was observed on the outer surface. No exfoliation of the outer layer of the steam oxidation scale was observed. One percent of Mo was in solid-solution state even after long-time exposure, which is useful for improving the creep strength. Cr23C6, Nb(C,N), NbCrN and TiN were the main precipitates and the σ(Sigma) phase was slightly detected only in the flame side. Charpy impact values at 20°C of NF709 tubes after exposure was over 40 J/cm2, acceptable for boiler tube use. The time to rupture for the exposed NF709 tubes became closer to that for unexposed ones at lower stresses. The above results indicate that NF709 is a promising material for superheaters and reheaters of power plants with advanced steam conditions.
Design Data Prediction for Grade 92 Steel
Authors: Wilshire Brian , Scharning Penelope J.
Published: August 2009

For Grade 92 steel (9Cr-0.5Mo-1.8W-V-Nb), multi-batch stress-rupture measurements are shown to be rationalized through relationships which involve only the activation energy for matrix diffusion (300 kJmol−1) and the ultimate tensile stress values at the creep temperatures. The resulting ‘master curve’ is at least as impressive as those obtained using traditional parametric methods, but with the empirical parameters replaced by physically-meaningful properties. These approaches lead to straightforward procedures for extended extrapolation of short-term data, with analyses of test results for creep lives less than 5000 hours predicting 100,000-hour rupture strengths. Indeed, noting that the allowable creep strengths for Gr. 92 steel have been reduced progressively as longer-term fracture data have become available, the present predictions coincide well with the lower limits of the most recent estimates determined for stress-temperature combinations producing failure in times up to 100,000 hours and more. Validation of the new methodologies can be achieved by independent analyses of standard property sets for other creep-resistant steels, introducing the prospect of a marked reduction in the scale and costs of the experimental programs currently undertaken to provide long-term engineering design data.
Analysis of the Creep Rupture Data of Alloy 617 for a High Temperature Gas Cooled Reactor
Authors: Kim Woo Gon , Yin Song Nan , Ryu Woo Seog , Jang Jong Hwa
Published: August 2009

Since very high temperature gas-cooled reactor (VHTR) components for a hydrogen production are designed for a lifetime of 30 to 60 years at a high-temperature of 950°C, a material selection is important, and also one of the most important properties in these metallic components is their longterm creep behavior. In this study, for selecting a suitable material for the intermediate heat exchanger (IHX), the hightemperature strengths of several candidate alloys approved for use by ASME VIII (boiler and pressure vessel code) were reviewed. From this review, alloy 617 was immediately selected as one of the best materials. In addition, to provide design data for a long duration for alloy 617, lots of creep data was collected through world-wide literature surveys of European Alloy-DB and available literature surveys. Using these data, a long-term creep life for alloy 617 was predicted for up to 106 hours based on the Larson-Miller (LM) parameter. Also, the creep rupture data was analyzed by a statistical treatment. Creep master curves for the creep-life prediction were presented for various standard deviations; 1σ, 1.65σ, 2σ and 3σ. A minimum design value for the creep-rupture time was found to be 10 times lower than the average value. Failure probability of the creep rupture data followed a lognormal distribution well.
The Design of Rectangular Metal Bellows
Authors: Broyles Robert K.
Published: August 2009

Rectangular metal expansion joints are commonly used in flue gas ductwork, turbine exhaust systems, and heat exchanger applications. The Standards of the Expansion Joint Manufacturers Association (EJMA) are widely referenced for the design of rectangular metal expansion joints. The 8th edition, 2005 addenda, contains equations for rectangular metal bellows pressure stresses, movement stresses, beam lateral deflection, fatigue life, and spring rate. This paper evaluates the accuracy of the EJMA equations based on failure reports and FEA studies. Both linear elastic and non-linear limit analyses are used for the evaluations. Improved methods are proposed for the determination of pressure capacity, beam deflection, moment of inertia, and corner rigidity. New lateral deflection limits and acceptance criteria are provided herein. This paper also includes design considerations for the pressure stops used to support bellows rails.
Catastrophic Failure of Flex Hose Bellows Due to Lateral Offset and Internal Pressure
Authors: Williams Dennis K.
Published: August 2009

This paper describes the analytical and empirical analyses conducted in the catastrophic failure of a flexible hose utilized in a petro-chemical environment. Specifically, the issues associated with the instability of the metal u-shaped bellows, from which the hose derives its overall flexibility and name, are reviewed and discussed in detail. In an effort to provide a comprehensive examination of the flexible hose’s use in the petro-chemical industry, a discussion of the applied mechanics associated with column buckling of the bellows (also known as “squirm”) is presented. In addition, the fabrication details that also proved detrimental to the structural adequacy of the subject flexible hose are highlighted. Results from an elastic-plastic finite element analysis of the u-shaped bellows are described and compared against previously published theoretical works on the instability of shells of revolution and most specifically, toroids. The applied loads in the finite element analyses include both internal pressure and transverse displacements (i.e., lateral offset). Furthermore, the guidance provided by the rules of the Expansion Joint Manufacturers Association Standards (EJMA) with regard to squirm are also reviewed and discussed. Finally, the results of the theoretical, empirical, and analytical investigations into the squirm phenomenon are utilized to identify some very practical solutions and recommendations to avoid the possibility of catastrophic failure of u-shaped bellows from column type instability.
Numerical Simulation of Vortex Shedding Past a Circular Cylinder in a Cross-Flow at Low Reynolds Number With Finite Volume Technique: Part 2 — Flow-Induced Vibration
Authors: Placzek Antoine , Sigrist Jean-Franc¸ois , Hamdouni Aziz
Published: August 2009

This paper is the sequel of the work exposed in a companion publication dealing with forced oscillations of a circular cylinder in a cross-flow. In the present study, oscillations of the cylinder are now directly induced by the vortex shedding process in the wake and therefore, the former model used for forced oscillations has been modified to take into account the effects of the flow in order to predict the displacement of the cylinder. The time integration of the cylinder motion is performed with an explicit staggered algorithm whose numerical damping is low. In the first part of the paper, the performances of the coupling procedure are evaluated in the case of a cylinder oscillating in a confined configuration for a viscous flow. Amplitude and frequency responses of the cylinder in a cross-flow are then investigated for different reduced velocities U* ranging from 3 to about 15. The results show a very good agreement at Re = 100 and the vortex shedding modes have also been related to the frequency response observed. Finally, some perspectives for further simulations in the turbulent regime (at Re = 1000) with structural damping are presented.
Corrosion Fatigue and Life Assessment of Tube Bends
Authors: Ellis Fred V.
Published: August 2009

Metallurgical examinations and life predictions were performed for six water-cooled tubing bends. All of the tubes had axially oriented cracks on the inside surface of the tube bends near the neutral axis position and one of the tubes had failed. The cracking was intermittent or semi-continuous indicating multiple crack initiation sites. The cracks were transgranular, oxide-filled, and branched. One sample was cold fractured and examination of the fracture surface in the SEM revealed beachmarks and thumbnail shaped cracks. The tube shape is nominally oval and the ovality varied from 5% to 8-1/2%. Increased hoop stresses are expected on the inside surface at the neutral axis of a bend due to ovality. The failure mechanism is corrosion fatigue. Life predictions were performed as an aid in inspections and fitness for service assessments. Because the cracking was near the neutral axis, the straight tube geometry was used for the crack growth calculations. A parametric approach was used with three initial crack depths and stress amplification values of 1, 1.2, and 1.5 to account for stress increases due to ovality. The failure criterion was the reference stress equal to the minimum flow stress of carbon steel. For a stress amplification of 1.5 times the pressure induced stress, the calculated lives were 2,420 cycles for an initial normalized crack depth of 10% and 130 cycles for an initial normalized crack depth of 30%.
Influence of Axial Force on the Deflection of Timoshenko Beam Structures Solved by DQEM
Authors: Chen Chang-New
Published: August 2009

The influence of axial force on the deflection of Timoshenko beam structures is analyzed by differential quadrature element method (DQEM). The DQEM uses the differential quadrature to discretize the governing differential equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.
Investigation of Numerical Methods for Modal Analysis of a Tube Bundle With Fluid-Structure Interaction
Authors: Sigrist Jean-Franc¸ois , Broc Daniel
Published: August 2009

Seismic analysis of tube bundle is of paramount importance in the safety assessment of nuclear installations. These analyses require in particular the calculation of frequency, mode shape and effective mass of the system eigenmodes. As fluid-structure interaction effects can significantly affect dynamic behaviour of immersed structures, the numerical modeling of the tube bundle has to take into account FSI. A complete modeling of heat exchangers (including pressure vessel, tubes and fluid) is not accessible to the engineer for industrial design studies. In the past decades, homogenization methods have been studies and developed in order to model tubes and fluid through an equivalent continuous media, thus avoiding the tedious task to mesh all structure and fluid sub-domains within the tube bundle. Few of these methods have nonetheless been implemented in industrial finite element codes. In previous papers (Sigrist & Broc, Pressure Vessel and Piping, Vancouver, July 2006), a homogenization method has been developed and applied to an industrial case for the modal analysis of a nuclear rector with internal structures and coupling effects modeling. The present paper aims at investigating the application of the proposed method for the dynamic analysis of tube bundle. The homogenization method is compared with direct and indirect fluid-structure coupled methods for the calculation of eigenmode frequencies, shapes and modal masses.
Simplified Inelastic Time Independent (SITI) Method for Predicting Creep
Authors: Abou-Hanna Jeries J. , Ali Osama , Tatikonda Venkata , McGreevy Timothy E.
Published: August 2009

In an effort to address inelastic creep behavior for very high temperature (VHT) applications, a unified state variable material model was used in a time dependent finite element analysis to generate isochronous curves. The resulting isochronous curves were then used in an efficient time-independent plastic analysis to predict the creep behavior of components. This simplified inelastic time-independent (SITI) method can significantly reduce the geometric and load uncertainties, and the over-conservatism in predicting inelastic strain levels. SITI is an effective and computationally efficient approach for predicting inelastic strains of components operating at high and very high temperatures such as the case in the Next Generation Nuclear Plant. This work compares the SITI inelastic strains to those obtained using fully inelastic time-dependent elastic-plastic-creep analysis, and illustrates the effectiveness of the approach in obtaining creep strain predictions without elaborate full inelastic time-dependent simulation.
Determination of Coupling Force Derivatives in Tube Bundles Using the Shape Sensitivity Equation Method
Authors: Watteaux R. , Mureithi N. , Pelletier D.
Published: August 2009

Flow induced vibration of tube bundles remains an important problem in the nuclear industry. A number of theories modeling fluidelastic instability have been developed. In those theories, understanding the influence of a tube on its neighbors is of primary importance. Since it is very difficult and time consuming to measure the complete set of cross-coupling effects, numerical simulations could provide a valuable alternative. The main purpose of this paper is to propose the Sensitivity Equation Method (SEM) as a new approach to finding the inter-cylinder coupling effects, which are usually quantified by the derivatives of lift and drag coefficients of all tubes with respect to the coordinates of the reference tube’s location.
Analysis of Hydrodynamic Penetration and Material Backflow
Authors: Lambert David
Published: August 2009

One-dimensional theory of hydrodynamic penetration for incompressible, inviscid conditions is re-visited to derive insightful relationships and provide a basis for discussing experimental observations. The 1-D Bernoulli equation produces simplified analytical relationships for such terms as the penetration depth, penetrator erosion rate, interface velocity, and other fundamental terms. Previous efforts [1,2] expanded this via a differential chain rule approach to establish relationships of energy and momentum flux and deposition rates of constant velocity and linear velocity gradient rod penetration events. A concise overview of the 1-D model is given followed by a selective grouping into relationships that might provide first-order criteria for making design considerations.
Fitness for Service Assessment of a Metal Loss Using Combination of Small-Scale Testing and DNV RP F101/API579 Procedures
Authors: Motarjemi A.
Published: August 2009

One of the major issues in the oil and gas industries is occurrence of corrosion on equipments in-service such as tanks, pressure vessels, piping, etc. Metal loss (general/localized) and pitting are amongst the typical corrosion damages. For assessing the significance of metal loss, information such as (a) geometry of the component, (b) a record of thickness measurements (point or profile readings) and (c) tensile properties such as Yield and Tensile strengths, preferably in the vicinity of the metal loss, are required. This information are usually fed into a Fitness for Service (FFS) assessment guideline/recommended practice such as DNV RP-F101 or API579, and a minimum required wall thickness (tmin), failure pressure or remaining life is derived. In the absence of actual tensile data (obtained from a conventional tensile test), specified minimum values (lower-bound), as suggested in the design codes, are currently the only other alternative. However, this paper is aimed at presenting two more alternative techniques; non-destructive test technique called Instrumented Indentation Testing (IIT) or Automated Ball Indenter (ABI) and a semi-destructive test technique, called Micro-Flat tensile (MFT). Both techniques are capable of determining the local tensile properties of the material in the vicinity of the metal loss. Values of the minimum required wall thickness (tmin), failure pressure and remaining life, using tensile data obtained from the IIT, MFT and specified minimum values are compared with the predictions based on the actual tensile data.
Development of Models Correlating Vibration Excitation Forces to Dynamic Characteristics of Two-Phase Flow in a Tube Bundle
Authors: Zhang C. , Pettigrew M. J. , Mureithi N. W.
Published: August 2009

Recent experiments reveal that somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions existed in a rotated triangular tube bundle subjected to two-phase cross flow. The quasi-periodic drag forces appear to be related to the momentum flux fluctuations in the main flow path between the cylinders. The quasi-periodic lift forces, on the other hand, are mostly correlated to the oscillation in the wake of the cylinders. The objective of this work is to develop semi-analytical models for correlating vibration excitation forces to dynamic characteristics of two-phase flow in a rotated triangular tube bundle and understanding the nature of vibration excitation forces. The relationships between the lift or drag forces and the dynamic characteristics of two-phase flow are established through fluid mechanics momentum equations. A model has been developed to correlate the void fraction fluctuation in the main flow path and the dynamic drag forces. A second model has been developed for correlating the oscillation in the wake of the cylinders and the dynamic lift forces. Although still preliminary, each model can predict the corresponding forces relatively well.
Evaluation of the Elliptical Flange Configurations for 24-Inch and 30-Inch Heater/Cooler Units
Authors: Alexander Chris , Armer Wade , Harbert Stuart
Published: August 2009

KOCH Heat Transfer Company contracted Stress Engineering Services, Inc. to perform a design/parameter study of a return bonnet used in hairpin heat exchangers that employs an elliptical flange design. The return bonnet is an important component of the heat exchanger as it can be removed to permit inspection of the heat exchanger tubes. The return bonnet is bolted to the hairpin leg flange. To maintain sealing integrity a gasket is placed between the return bonnet flange and the hairpin leg flange. The sealing efficiency of two return bonnet sizes (24-inch and 30-inch) was investigated in this study using finite element analysis. The sealing efficiency is an indication of how the contact pressure changes circumferentially around the gasket and is calculated by dividing the local contact pressure by the maximum contact pressure calculated in the gasket for each respective design. The study assessed the effects of geometric changes to the mating flanges. Using an iterative design process using finite element analysis, the elliptical flanges were optimized to maximize sealing efficiency. Upon completion of the study, the manufacturer successfully employed the modifications as evidenced with multiple successful hydrotests.
Tackling Erosion in Nuclear Piping Systems
Authors: Crockett Harold M. , Horowitz Jeffrey S.
Published: August 2009

Various mechanisms degrade power piping in nuclear power plants. The most important mechanism has been flow-accelerated corrosion (FAC). FAC has caused ruptures and leaks and has led to numerous piping replacements. U.S. utilities are using a combination of EPRI software and aggressive inspection programs to deal with FAC. However, current technology does not deal with erosive forms of attack including, cavitation erosion, flashing erosion, droplet impingement, and solid particle erosion. These forms of degradation have caused shutdowns and leaks have become a maintenance issue. To deal with these problems EPRI has begun a series of projects in this area. The first of these was a comprehensive report on erosion in piping systems. This work was followed with a computerized training module designed to educate utility engineers about erosive attack. Further steps are planned to deal with these forms of degradation. The first will be a meeting with knowledgeable EPRI and utility engineers to prioritize the damage mechanisms. From this meeting a research plan will be developed. This paper will present a description of erosive damage mechanisms and describe the planned R&D to deal with these mechanisms.
Preliminary Consideration of Alloys 617 and 230 for Generation IV Nuclear Reactor Applications
Authors: Ren Weiju , Swindeman Robert
Published: August 2009

Alloys 617 and 230 are currently identified as two leading candidate metallic materials in the down selection for applications at temperatures above 760°C in the Gen IV Nuclear Reactor Systems. Qualifying the materials requires significant information related to Codification, mechanical behavior modeling, metallurgical stability, environmental resistance, and many other aspects. In the present paper, material requirements for the Gen IV Nuclear Reactor Systems are discussed; certain available information regarding the two alloys under consideration for the intended applications are reviewed and analyzed. Suggestions are presented for further R&D activities for the materials selection.
A Simplified Approach to Finite Element Modeling of Anisotropic Screens
Authors: Krishnamurthy Sujay R. , Koves William J.
Published: August 2009

Structural pressure vessel internals such as flow inlet/outlet baskets, bed supports etc. often use anisotropic screens with wires (or beams) oriented in mutually orthogonal directions. Discrete modeling of the screen details result in excessive model size and prohibitive computing costs. It is preferable to model the structural response of these screens using an anisotropic plate. Commercial FEA codes offer linear elastic models with anisotropic inputs. Elastic coefficients for use in the commercial code ABAQUS™ were developed using anisotropic plate theory and were validated by comparing results from rigorous, discrete beam FEA models with isotropic material properties to anisotropic shell element models for static load, vibration and buckling analyses with various edge boundary conditions. Some of the limitations of the application of this particular method are discussed. Further, a procedure is outlined to extract discrete elastic screen stresses from the anisotropic results.
Short Term Relaxation of Stuffing Box Packings
Authors: Diany Mohammed , Bouzid Abdel-Hakim
Published: August 2009

The long term tightness performance of stuffing box packings, used in valves, is conditioned by the capacity of its material to maintain a contact pressure to a predetermined minimal threshold value. Due to creep, this contact pressure decrease with time depending on the creep properties and the stiffness of the housing. Assessing relaxation is a key parameter in determining the tightness performance of the stuffing box packing over time. Using Ansys software, an axisymmetric 2D finite element model is developed to assess the contact pressures between the packing material and the stem and the housing and its variation with time. The assessment of the packing relaxation is a major obstacle to the good leakage performance of the Stuffing Box Packing.
Tensile Stress-Strain Results for 304L and 316L Stainless Steel Plate at Temperature
Authors: Blandford R. K. , Morton D. K. , Snow S. D. , Rahl T. E.
Published: August 2009

The Idaho National Laboratory is conducting moderate strain rate (5 to 200 per second) research on stainless steel materials in support of the Department of Energy’s National Spent Nuclear Fuel Program. For this research, strain rate effects are characterized by comparison to quasi-static tensile test results. Considerable tensile testing has been conducted resulting in the generation of a large amount of basic material data expressed as engineering and true stress-strain curves. The purpose of this paper is to present the results of quasi-static tensile testing of 304L and 316L stainless steels in order to add to the existing data pool for these materials and make the data more readily available to other researchers, engineers, and interested parties. Standard tensile testing of round specimens in accordance with ASTM procedure A 370-03a was conducted on 304L and 316L stainless steel plate materials at temperatures ranging from −20°F to 600°F. Two plate thicknesses, eight material heats, and both base and weld metal were tested. Material yield strength, ultimate strength, ultimate strain, fracture strength, fracture strain and reduction in area were determined. Engineering and true stress-strain curves to failure were developed and comparisons to ASME Code minimums were made. The procedures used during testing and the typical results obtained are presented in this paper.
Serviceability Characterization of Composite Storage Tanks
Authors: Shkolnikov Vladimir M.
Published: August 2009

This paper outlines an analytical technique enabling serviceability characterization of a storage tank made of a Polymer Matrix Composite (PMC) with regards to a specified profile of long-term operation of the tank. The technique combines force-temperature exposure (conceivably changing over a tank’s service life) and fatigue properties of a composite utilized within the tank structure. Along with a serviceability assessment, the technique is capable of providing a well-grounded specification of design knock-downs and safety factors relevant to the conventional structural design procedure.
Final Proposal of Environmental Fatigue Life Correction Factor (Fen) for Structural Materials in LWR Water Environment
Authors: Higuchi Makoto , Sakaguchi Katsumi , Nomura Yuichiro , Hirano Akihiko
Published: August 2009

Low cycle fatigue life of structural materials diminishes remarkably as functions of various parameters in high temperature water simulating LWR coolant. Such reduction was estimated by the fatigue life reduction factor (Fen) and the equations to calculate Fen were developed and have undergone revision over the past ten years. The authors have endeavored to establish the method assessing fatigue damage at LWR power plants for the past 13 years in the Japanese EFT (Environmental Fatigue Tests) project under the financial support from the JNES (Japan Nuclear Safety Organization). The project terminated at the end of March in 2007. Final proposals of Fen equations were established for carbon, low-alloy, and austenitic stainless steels and nickel base alloys based on all the data obtained in the project. As the results, a small change in saturated strain rate for carbon and low-alloy steels in highly dissolved oxygen water and newly revised equations including slight change in saturated strain rate for stainless steels in BWR water as well as those for nickel base alloys were proposed. The difference between revised and previous model is essentially not large.
In-Flow Oscillation of Circular Cylinders in Cross-Flow
Authors: Nakamura Tomomichi , Haruguchi Hiroshi , Nakajima Hiroyuki , Sawada Toyohiro , Sugiyama Kozo
Published: August 2009

The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using totally nine cylinders in a water tunnel. Six cases, one single cylinder, two & three cylinders in parallel & in tandem, and a nine cylinder bundle, are examined. Every cylinder can move only in in-flow direction. The motion of cylinders is measured by the strain gages and by a high-speed digital video camera. The results are compared with the visualized vortex motion.
Properties of Fiberboard Overpack Material in the 9975 Shipping Package Following Thermal Aging
Authors: Daugherty W. L.
Published: August 2009

Many radioactive material shipping packages incorporate cane fiberboard overpacks for thermal insulation and impact resistance. Mechanical, thermal and physical properties have been measured on cane fiberboard following thermal aging in several temperature/humidity environments. Several of the measured properties change significantly over time in the more severe environments, while other properties are relatively constant. These properties continue to be tracked, with the goal of developing a model for predicting a service life under long-term storage conditions.
Numerical Simulation of the Weld Residual Stresses for a Man-Hole Drainage Nozzle in a Steam Generator: Design Comparison
Authors: Nicak Tomas , Hu¨mmer Matthias , Keim Elisabeth
Published: August 2009

The numerical welding simulation has developed very rapidly during the last few years. The problem complexity has increased from simple 2D axis-symmetric or cross-section models to full 3D models, which can describe the entire welding process more realistically — including start-stop effects. As recent research projects indicate, a quantitative assessment of the residual stresses magnitude by means of a 3D analysis is possible. Moreover, the structure integrity with respect to fatigue, fracture or Stress Corrosion Cracking (SCC) processes can be evaluated based on the welding simulation results superimposed with the operating load (or any arbitrary disturbance transient load). This makes a more accurate life time prediction of the welded components possible. Furthermore, in order to minimize the residual stresses in components, a parametric study can be performed considering important input data like heat input or bead sequencing. It would make the development of virtual welding procedures possible, which can essentially help to cut the design and operating costs. In this paper a full 3D numerical welding simulation for a man-hole drainage nozzle in a steam generator will be presented. Two design options are considered. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical FE analysis using the ABAQUS code. The paper will present a robust procedure allowing reasonable predictions of the residual stresses for complex structures in industrial practice.
Shaking Table Test of Passive Controlled Structure With New Friction Damper
Authors: Mikoshiba Tadashi , Minowa Chikahiro , Sato Takanori , Shao Li , Chiba Toshio
Published: August 2009

Under the effect of a large earthquake, the range of plastic comes into the column and the beam of the frame structure. By using energy dissipation devices, it is possible to reduce the response and the damage of the structure. A friction type damper which was a compact form and had high damping characteristics, was developed. It was made of steel plate, aluminum sliding plate, rubber washer and high tension bolt. To validate the performance of the new damper, the elemental tests and the shaking table test were conducted. In the shaking table test, frame structure composed of full scale member with friction damper was excited by actual seismic wave. As a result, it was found effective and had a high damping performance. This paper mainly reports the results of the shaking table test.
An Approximate Method for Determining the Limit Pressure of Piping Branch Junctions With d/D ≤ 0.5
Authors: Lee K. S. , Moreton D. N. , Moffat D. G.
Published: August 2009

A series of finite element computations have been conducted to establish the limit pressures for a range of piping branch junctions with d/D ≤ 0.5. The results have been compared with those obtained using existing assessment procedures. In general, the latter have been found to be conservative. An approximate method for calculating the limit pressure of a branch junction is proposed. This method supposes that the branch junction may be treated as a plain cylinder containing an axial through-wall crack. The crack length is dependent upon the type of branch junction. The limit pressure can be established using a modified form of a standard solution limit load solution for a cylinder containing an axial through-wall crack. This approximate method is shown to be valid for a wide range of junction geometries.
Modelling the Fabrication of a Pressure Vessel Toroidal Seal
Authors: Leggatt N. A. , Dennis R. , Hurrell P. R. , Gould S. E. , Kane R. R.
Published: August 2009

Welding remains the key process in fabricating, as well as repairing, pressure vessel systems. Unfortunately, many manufacturing and through life service problems occur in or near welded regions. The through life integrity of welded components, e.g. distortion, fatigue, fracture, metallurgy and corrosion control remains a key challenge for structural integrity. The work reported in this paper investigates the complex manufacture and assembly of a pressure vessel toroidal seal. The seal is first created by depositing a series of austenitic welds onto a ferritic pressure vessel to build up a plinth, thus forming a transition weld. The transition weld is then subject to a high temperature Post Weld Heat Treatment (PWHT) to stress relieve the welds and to temper the HAZ in the welds. An austenitic toroidal ring is positioned onto the plinths and welded in place thus forming the toroidal seal. The seal is manufactured from a 347 austenitic stainless steel comprising good ductility and corrosion resistance. The manufacture of the seal is simulated using 2D axisymmetric finite element analysis that are available to support both the design and integrity analysis of welded components. As well as the inherent residual stresses associated with welding, additional effects are important, for instance the austenitic to ferritic transition welds between the vessel body and plinths. This paper presents a novel approach to the simulation of weld metal deposition that is ideally suited to the modelling of transition welds and subsequent PWHT. The plinth welds undergo PWHT and so the creep behaviour of the welds is simulated. A series of intermittent as well as end of manufacture PWHT’s are investigated. Additionally the choice of material hardening law for the austenic weldment is studied. The full manufacturing history of the seal is taken into account within the analysis including welding, component machining and component geometry fit up.
An Acoustic Criterion for the Whistling of Orifices in Pipes
Authors: Moussou P. , Testud Ph. , Aure´gan Y. , Hirschberg A.
Published: August 2009

Whistling due to vortex shedding has been extensively studied in the case of cylinders in cross-flows, of flow separation above cavities and of shear layers with flow impingement feedback. Less attention has been given to pressure drop devices in piping systems, which are known to generate high noise levels due to single tones in gas systems, and even in water systems. Based on recent work of Auregan et Starobinski (1999), an experimental criterion is proposed to evaluate the whistling ability of a pressure drop device in the presence of plane waves acoustic feedback. The idea of the criterion can be summarized as follows: if for a given combination of incident pressure waves, the amount of acoustic power scattered is higher than the incident one, the pressure drop device behaves as an acoustic amplifier, so that whistling can occur if the adequate acoustic boundary conditions are met. The main advantage of this criterion is that it depends only on the acoustic scattering matrix of the device, rather than on the acoustics of the surrounding pipe. Results obtained in an air test rig with an inner diameter of 3 cm, a Mach number varying from 10−3 to 10−1 and a Reynolds number varying from 103 to 105 are reported for single hole orifices. Basing the Strouhal number on the thickness of the orifice and on the average velocity through the hole, thin single hole orifices with sharp angles appear to whistle at Strouhal numbers close to 0.2. Furthermore, it is shown that a thin orifice with a downstream bevel is prone to whistling, whereas the same orifice with the bevel upstream cannot whistle.
Enhanced Corrosion Resistance of Iron-Based Amorphous Alloys
Authors: Rebak Raul B. , Day S. Daniel , Lian Tiangan , Aprigliano Louis F. , Hailey Phillip D. , Farmer Joseph C.
Published: August 2009

Iron-based amorphous alloys possess enhanced hardness and are highly resistant to corrosion, which make them desirable for wear applications in corrosive environments. It was of interest to examine the behavior of amorphous alloys during anodic polarization in concentrated salt solutions and in the salt-fog testing. Results from the testing of one amorphous material (SAM2X5) both in ribbon form and as an applied coating are reported here. Cyclic polarization tests were performed on SAM2X5 ribbon as well as on other nuclear engineering materials. SAM2X5 showed the highest resistance to localized corrosion in 5 M CaCl2 solution at 105°C. Salt fog tests of 316L SS and Alloy 22 coupons coated with amorphous SAM2X5 powder showed resistance to rusting. Partial devitrification may be responsible for isolated pinpoint rust spots in some coatings.
An Approximate Damping Model for Two-Phase Cross-Flow in Horizontal Tube Bundles
Authors: Sim W. G.
Published: August 2009

An approximate analytical model, to predict the two-phase damping for upward cross-flow through horizontal bundles, has been developed. This model will allow researches to provide analytical estimates of the damping ratios. The existing semiempirical approach by Pettigrew and Taylor (2003) was approximated by taking the lower envelope of the damping data. To estimate the void fraction for the cross-flow, the void fraction model proposed by Feenstra etc (2000) is utilized. The development of the present damping model stemmed from the two-phase multiplier of pressure loss and the momentum flux of the two-phase flow. The important variables on the damping are identified. The results of the present model agree well with experimental damping ratios in air-mixtures for a sufficiently wide range of pitch mass ratio, quality and p/d ratios. It has also shown predictive capability for steam-water mixtures and Freon 11.
New Corrosion Mapping Technology at High Temperature Application
Authors: Saleem M. A. , Hulaibi A. A. , Carswell R. J.
Published: August 2009

Process industries such as oil, gas and petrochemical plants have critical process equipment operating at high temperatures. These equipment require periodic comprehensive integrity assessments for safe and reliable operation. Conventional NDE techniques such as manual ultrasonic are not only slow and subjective, but also often unsuccessful beyond 300°F (150°C). There have been tremendous efforts in the industry to invent suitable new technologies for high temperature application. Hence, comprehensive monitoring of large size equipment operating at higher temperatures remained as a challenging task for decades. In line with this requirement, and in an ongoing effort to deploy new technologies, Uthmaniyah Gas Plant (UGP) in Saudi Aramco, one of the largest gas processing plants in the world, partnered with the Inspection Department in a pilot test program to validate a new corrosion mapping technology at high temperature application up to 500°F. Implementation of this breakthrough technology for the first time in Saudi Aramco at UGP has been successful. This technology also has the capability to scan the process equipment at an operating temperature beyond 725°F (385°C). This paper provides an overview of the importance of a comprehensive assessment to critical process equipment operating at high temperature, ongoing developments to enrich the assessment capabilities and how this technology added value in enhancing the safety and reliability of the operating facility.