bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Energy Approach to Assess Vibration and Fretting-Wear Damage in Process Equipment
Authors: Pettigrew Michel J. , Yetisir Metin , Fisher Nigel J. , Taylor Colette E. , Smith Bruce A. W.
Published: August 2009

Excessive flow-induced vibration causing fretting-wear damage can seriously affect the performance of process equipment such as heat exchangers, condensers, nuclear steam generators, nuclear fuels, reactor internals, and piping systems. Fretting-wear damage generally takes place between a vibrating structure and its supports. It can be predicted with a fretting-wear coefficient obtained experimentally and a parameter called work-rate that formulates the dynamic interaction between structure and support. The work-rate is essentially the rate of mechanical energy dissipated at the support. On the other hand, the total available mechanical vibration energy in a structure is related to its mass, vibration frequency, mode shape, damping, and vibration amplitude. This leads to the development of a simplified formulation based on energy considerations to relate the vibration response of a structure to fretting-wear damage at its supports. The basic energy equations and the formulation of a simplified energy relationship to predict fretting-wear damage are outlined in this paper. The relationship is verified against experimental data for a multi-span heat exchanger tube. The energy approach is also compared to time domain calculations performed with a non-linear finite element code. The results indicate that the simple energy approach may be very useful to estimate fretting-wear damage in practical situations. Finally, the application of the method is illustrated for a typical heat exchanger tube and for nuclear fuels.
A Novel Formulation of Elastic Interaction in Gasketed Bolted Joints
Authors: Alkelani Ali A. , Nassar Sayed A. , Housari Basil A.
Published: August 2009

A novel mathematical model is proposed for studying elastic interaction in gasketed bolted joints. The model predicts the tension changes in tightened bolts due to the subsequent tightening of other bolts in the joint. It also predicts the final clamp load distribution after the completion of joint tightening. The model is used to investigate the effect of various factors on the elastic interaction phenomenon; factors include the gasket thickness, bolt spacing, fastener preload level, and the tightening sequence of various bolts. Experimental verification is provided for the validation of the mathematical model. Experimental and analytical results are presented and discussed. The proposed model provides good prediction of the final clamp load in the joint. Moreover, the proposed model may be used to determine the level of initial bolt tension in each bolt that would be necessary to achieve the desired level of uniform clamp load in the joint at initial assembly.
Negative Creep Bolts and Gaskets
Authors: Efremov Anatoly
Published: August 2009

A basic concept of “negative” creep effect is examined with reference to bolted fasteners and gaskets. The “negative” creep results from shape recovery of initial shape of the bolt cores and gaskets manufactured from Shape Memory Alloys (SMAs) and shape-memorized to the compression (bolt cores) and “swelling” (gaskets) during the formation of stress-induced martensite. Constrained by adjacent rigid component parts of the assembly, the bolt cores and gaskets of SMAs display the “negative” creep effect under a variety of operational temperatures that are close to the temperatures of reverse martensitic phase transformation of the SMAs. Some examples of negative creep bolts and gaskets are considered.
Round-Robin Exercise on Instrumented Impact Testing of Precracked Charpy Specimens (IAEA Coordinated Research Program Phase 8)
Authors: Lucon Enrico , Viehrig Hans-Werner
Published: August 2009

Within topic area 2 (Loading Rate Effects) of the IAEA Coordinated Research Project Phase 8 (CRP-8), a round-robin exercise (RRE) was performed. This was aimed at measuring impact fracture toughness in the ductile-to-brittle transition region using precracked Charpy specimens of the JRQ steel tested on instrumented pendulum machines. The objective of the round-robin was twofold: 1) assessing the applicability of the Master Curve approach (ASTM E1921-05) to data obtained at impact loading rates of the order of 105 MPa√m/s; 2) validating a draft test procedure developed by sub-committee TC5 of the European Structural Integrity Society (ESIS), in the absence of an official testing standard (ISO or ASTM). A comprehensive analysis of the RRE results received to date will be presented in this paper, including an assessment of the overall data scatter and the lab-to-lab variability. In this context, an outlier data set has been identified and investigated in great detail. Based on the results presented, it is noted that the test procedure appears reliable and easy to follow for the various participants.
Prediction of Thermoacoustic Vibration of Burner/Furnace Systems in Utility Boilers
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: August 2009

Seven burner/furnace systems, three of which vibrated and four of which did not vibrate in operation are evaluated for thermoacoustic oscillations. The evaluation is based on the Rijke and Sondhauss models representing the combined burner/furnace (cold/hot) thermoacoustic systems. Frequency differences between the lowest vulnerable furnace acoustic frequencies in the burner axial direction and those of the systems’ Rijke and Sondhauss frequencies are evaluated to check for resonances. Most importantly, the stability of the Rijke and Sondhauss models is checked against the published design stability diagram of Eisinger [1] and Eisinger and Sullivan [2]. It is shown that thermoacoustic oscillation can be well predicted by the published design stability diagram with the vibrating cases falling into the unstable zone above the stability line and the non-vibrating cases congregating in the stable zone below the stability line. The evaluation suggests that the primary criterion for predicting thermoacoustic oscillations is the stability of the thermoacoustic system and that frequency differences or resonances appear to play only a secondary role. It is concluded, however, that in conjunction with stability, the primary criterion, sufficient frequency separation shall also be maintained in the design process to preclude resonances. The paper provides sufficient details to aid the designers.
Applications of Isochronous Data in Creep Analysis
Authors: Zhao Mingxin , Koves William
Published: August 2009

This paper evaluates the use of isochronous stress-strain material data for the creep analysis of metals in high temperature applications. Performing an inelastic analysis using isochronous stress-strain data is a simplified approach for computing time dependent behavior using an implicit time embedded method. This method has been widely used as an effective means to evaluate the creep behavior of complex components without performing a detailed time dependent creep analysis. In order to examine the effectiveness and limitations of this method, isochronous stress-strain material data was numerically constructed from a time dependent creep law at various temperatures, sustained stress levels, and time durations. Component stresses and strains are compared from results obtained by running both the isochronous time embedded inelastic and time dependent creep analyses for some example problems. The effectiveness and limitations of this method under different loading conditions, such as primary and secondary stresses, are demonstrated and explained. It is recognized that this method was not intended to apply to thermal stress problem, and the thermal problem was studied to understand constraint effects.
Effects of Strain Holding and Continuously Changing Strain Rate on Fatigue Life Reduction of Structural Materials in Simulated LWR Water
Authors: Higuchi Makoto , Sakaguchi Katsumi , Nomura Yuichiro
Published: August 2009

The fatigue life reduces remarkably with reduction in strain rate in simulated light water reactor (LWR) water but the effects of strain wave form on this reduction are still not clear. This paper provides fatigue life data obtained from stepwise strain rate change tests, sine wave tests and strain holding tests. The effects of varying strain rate on fatigue life reduction can be estimated very well by the modified rate approach (MRA) method in the case of the step wise strain rate changing as shown in authors’ previous papers [1, 2, 3, 4, 5]. In the case of sine wave, however, the fatigue life reduction is much less compared to that predicted by the MRA method. The mechanism of such difference is not clear and the quantitative assessment of the fatigue life reduction caused by irregular strain wave form in actual transient seems impossible. The current MRA method gives always conservative assessment for sine wave straining and thus it is judged that this method need not be revised any more. The fatigue life reduction caused by strain holding at the peak of straining cycle in simulated BWR water had been reported in the previous paper [6]. In actual thermal transients, however, strain is not usually held at the peak of straining cycle but at the point somewhat reduced from the peak after the stabilization of temperature. In considering this phenomenon, additional fatigue tests in which the strain was held at the point somewhat reduced from the peak were carried out. In such conditions, the fatigue life reduction caused by strain holding disappeared. The similar fatigue tests with peak strain holding were also carried out in simulated PWR water and no fatigue life reduction can be observed. Considering the effects of strain holding on fatigue, the model for evaluating fatigue life reduction in LWR water was revised.
Proposed Revision to Nuclear Piping Thermal Expansion Stress Limit
Authors: Slagis Gerry C.
Published: August 2009

Piping thermal expansion stress limits for ASME Section III Class 2/3 piping are directly based on the original thermal expansion stress rules given in B31.1-1955. Cyclic thermal expansion stresses are limited by Equation 10 to SA where SA is a function of the expected number of full temperature cycles. The Eq. 10 limit may be exceeded, if the pressure-plus-weight stresses are below their limit. This requirement is expressed as Eq. 11. The basis for Eqs. 10 and 11 is not well understood in the industry, and has caused confusion. One typical comment is — Why have an Eq. 10 limit if it can be exceeded? The history and development of the thermal expansion stress limits are presented. The thermal expansion stress limits from B31.1 are based on relaxation considerations and prevention of yield or creep strain even though the failure mode of concern is fatigue cycling. Hence, the thermal expansion stress limit is an implied and approximate limit on fatigue. Recommendations for changes to the Section III Class 2/3 rules are provided. A direct fatigue based stress limit is proposed.
Guided Wave C.U.I. Inspection
Authors: Sens Michael
Published: August 2009

Using guided wave, tens of meters of pipe can be quickly and completely screened from a single location. The ability of this system to send waves along the length of the pipe means that very difficult to inspect areas, such as road crossings, can be interrogated from a remote and easily accessible location. This paper discusses the practical application of a guided wave system to real world inspection and highlights the benefits and limitations.
An Improved Scaling Model of Buffeting Lift Forces in Air-Water Flows
Authors: Pascal-Ribot Sylviane , Blanchet Yves
Published: August 2009

This paper presents the results of a series of experiments to study the loading of a single rigid cylinder subjected to air-water cross-flow. Five rigid cylinders of same length and different diameters (12.15×10−3 m to 31.9×10−3 m) were tested over void fractions ranging from 10% to 80%. The fluctuating lift forces on the cylinder are measured and represented in the form of power spectral density. A scaling model of these forces previously developed from one series of experiments with one tube diameter (12.15×10−3 m) is tested on these new results by investigating the effect of tube diameter D. Unlike single phase results where the force spectra vary as D3, it is shown that for two-phase flows the force spectra vary as D2. The experimental data collapse remarkably well. Both local void fraction and flow regime appear to be sensitive parameters. It confirms the importance of a precise knowledge of the local characteristics of two-phase flows in the study of buffeting forces mechanisms.
Root Cause Analysis of Glovebox Glove Failure
Authors: Park Y. H. , Cournoyer Michael
Published: August 2009

The Nuclear Materials Technology (NMT) Division has the largest inventory of glovebox gloves at Los Alamos National Laboratory (LANL). Consequently, the minimization of unplanned breaches of the glove material, typically resulting in glove failures, is a significant safety concern in the daily operations in NMT Division facilities. To investigate processes and procedures that minimize unplanned breaches in the glovebox, information on glovebox glove failures has been compiled from formal records and analyzed using statistical methods. Based on these research results, the next step of the research is to identify root causes of glove failures and the actions adequate to prevent recurrence. In this paper, root cause analysis was conducted for a cleanup breach case study to demonstrate the computerized root cause analysis process. Based on analysis results, effective recommendations were generated.
Calculation of Material Properties Using Molecular Dynamics Simulation
Authors: Park Y. H. , Tang J.
Published: August 2009

This paper describes the calculation of material properties of copper (Cu) using the molecular dynamics method. Vacancy formation energy, bulk modulus, surface energy and melting point are calculated using different potentials such as the Morse potential and Embedded Atom Method (EAM). Results obtained from different potentials are discussed and compared with experimental results.
Flow-Induced Streamwise Oscillation of Two Square Cylinders in Tandem Arrangement
Authors: Okajima Atsushi , Kiwata Takahiro , Yasui Satoru , Mori Yoshiki , Kimura Shigeo
Published: August 2009

Flow-induced streamwise oscillation of two tandem square cylinders has been studied by means of free-oscillation testing in a wind tunnel. One cylinder was elastically supported so as to allow it to move in the streamwise direction; the other was fixed to the tunnel sidewalls. Small values of the reduced mass-damping parameter (Cn ≤ 1.63) have been considered. When the upstream cylinder is free to oscillate, there are two excitation regions: the first for reduced velocity, Vr, in the range 2.5 ≤ Vr ≤ 5 and cylinder gap distance to reference-length ratio, s, between 0.3 and 2, is due to movement-induced excitation accompanied by symmetrical vortex shedding, while the second, for 0.75 ≤ s ≤ 1.5 and 4.5 ≤ Vr ≤ 6.5, is due to vortex excitation by alternate Karman vortex shedding, accompanied with unstable limit-cycle oscillation. For wide gap distances over 2.5, an excitation region of the upstream cylinder occurs for 3.5 ≤ Vr ≤ 4.7, which is due to alternate Karman vortex shedding, and resembles the streamwise oscillation of a single cylinder. On the other hand, when the downstream cylinder is free to oscillate for narrow gap distances of 0.3 ≤ s ≤ 0.75, the response characteristics have an excitation region due to alternate Karman vortex shedding from the two cylinders, connected by dead water region between them, for 3.2 ≤ Vr ≤ 5.4. When s is greater than 1, the downstream cylinder experiences buffeting by wake fluctuation of the upstream cylinder.
Technical Basis of Proposed New Acceptance Standards for Class 1, 2 and 3 Piping
Authors: Miyazaki Katsumasa , Hasegawa Kunio , Miura Naoki , Kashima Koichi , Scarth Douglas A.
Published: August 2009

Acceptance Standards in Section XI of the ASME Boiler and Pressure Vessel Code have an important role as the first step in the flaw evaluation procedure. When a flaw size is within the allowable flaw size in the Acceptance Standard, the flaw is acceptable and analytical evaluation is not required. Although ASME Section XI has Acceptance Standards for Class 1 piping in IWB-3500, there are no Acceptance Standards for Class 2 and 3 piping. Furthermore, the development of the current Acceptance Standards for Class 1 piping was based on flaw detectability by ultrasonic inspection and consideration of fracture mechanics. In this paper, the development of proposed new Acceptance Standards for Class 2 and 3 piping, as well as for Class 1 piping, is described. The development methodology is based on a fracture mechanics approach. For Class 1 piping with high fracture toughness, the allowable flaw sizes were determined by limit load solution. For Class 1 piping, the intent was to maintain overall consistency with the current Acceptance Standards. Proposed Acceptance Standards for Class 2 and 3 austenitic piping were also developed by the methodology used to develop the proposed new Acceptance Standards for Class 1 piping. Allowable flaw sizes for both surface flaws and subsurface flaws for preservice and inservice examinations were developed.
Italian Life-Assessment Procedure for Creep-Operated Pressure Equipment
Authors: Tonti Andrea , Delle Site Corrado , Grisolia Ottaviano , Franchi Emanuela
Published: August 2009

Since 1989 ISPESL has emanated dispositions for pressure equipment designed to operate in the creep range according to time dependent mechanical properties. During the years, on the basis of the results of in-field examinations, a series of new provisions has been improved and sharpened the original procedure. During the last two years ISPESL has gone to revise and update the emanated regulations. Now a new entire legislation covers all the subjects and it is set as an advanced means of investigation for equipment working in the creep range: ISPESL technical procedure N. 48/2003. The elaborating of the legislation in matter has benefited from the previous experience, the indications of users and the European and international standards. The procedure is widely applied in Italian plants.
A Profile of Spencer H. Bush and His Five Decades of Scientific and Engineering Works
Authors: Hedden Owen F.
Published: August 2009

This paper will address three aspects of Dr. Bush’s career; the first will discuss his publications, the second his committee leadership involvement, and the third his recognition by industry. The first will attempt to address the scope of Dr. Bush’s technical interests in terms of the subjects discussed in his publications in the many phases of his career. The next will address his nuclear power industry leadership activities including committee chairmanships, with brief opinions of the importance of those assignments. Finally, the paper will discuss recognition he has earned, and given. References to his publications are provided.
Probabilistic Assessment Procedure for Crack-Like Flaws
Authors: McLaughlin James E. , Cater-Cyker Zachary D. , Budiman Benny S. , Guo Ruohua Z.
Published: August 2009

A statistical sampling technique was developed to perform a probabilistic assessment of crack-like flaws consistent with the procedures defined in API RP-579, Fitness-For-Service. Four random input variables were included in the assessment procedure. This included fracture toughness, flaw size, applied stress and residual welding stress. A statistical distribution was defined for each of these variables based on available data and previous studies on how best to define the variability of these input variables. A statistical sampling of these input variables was generated using computer code specifically developed for this purpose. The statistically defined sampling of input variables was evaluated using the VCE SAGE software modular for evaluating crack-like flaws. The output file from this evaluation consisted of a normalized brittle fracture term, Kr, and a normalized plastic collapse term, Lr. This output was statistically evaluated using specifically developed computer code to calculate a probability of fracture. This probability of failure is based on a limit state function defined by the fracture assessment diagram (FAD), which was statistically adjusted by wide-plate test results to more accurately reflect the actual probability of failure. This assessment procedure was developed to calculate a probability of failure in order to define the risk of fracture due to crack-like flaws consistent with the ExxonMobil risk matrix which is used to manage all risk-based decisions in the Corporation. Future work will be conducted to develop similar probabilistic assessment procedures for other forms of degradation, such as creep, high temperature hydrogen attack, thinning and local metal loss.
Application of the Hilbert-Huang Transform and Enhanced Noise Filtering to the Damage Detection of Structural Systems
Authors: Lin Jeng-Wen , Chen Hung-Jen , Tsai Chong-Shien
Published: August 2009

This paper proposes an enhanced noise filtering technique to the Hilbert-Huang transformation technology for the damage detection of structural systems using vibration measurements. The Hilbert-Huang transformation technology is a set of superior algorithms for analyzing non-linear and non-stationary signals and also for linear and stationary signals. However, the signals are filtered by reconstruction from “selected” intrinsic mode functions (IMFs), derived from the original signal through the empirical mode decomposition method. The proposed filtering technique offers the criterion for selecting the IMFs using the orthogonalization coefficient. Through the enhanced filtering, it is possible to increase the accuracy for the estimation of the time-varying system’s natural frequency, indicative of the degree of damage, which helps an effective design of a control system.
Efficacy of a Sliding Beam as a Nonlinear Vibration Isolator
Authors: Ibrahim R. A. , Somnay R. J.
Published: August 2009

The influence of friction due to beam sliding at its supports on its dynamic behavior and its efficacy as a nonlinear isolator is studied numerically under sinusoidal and random excitation excitations. Under sinusoidal excitation, the equation of motion of the system is solved numerically and the solution is utilized to estimate the system transmissibility. It is found that when the excitation frequency is increased beyond resonance, the friction at the sliding supports serves to improve the transmissibility. The dependence of the response on initial conditions establishes the basins of attraction for different values of friction coefficient and excitation frequency and amplitude. Under random excitation, the system response statistics are estimated from Monte Carlo simulation results for different values of friction coefficient and excitation power spectral density level. The friction is found to result in a significant reduction of the system response mean square.
Application of Draft Regulatory Guide DG-1144 Guidelines for Environmental Fatigue Evaluation to a BWR Feedwater Piping System
Authors: Mehta Hardayal S. , Hwang Henry H.
Published: August 2009

Recently published Draft Regulatory Guide DG-1144 by the NRC provides guidance for use in determining the acceptable fatigue life of ASME pressure boundary components, with consideration of the light water reactor (LWR) environment. The analytical expressions and further details are provided in NUREG/CR-6909. In this paper, the environmental fatigue rules are applied to a BWR feedwater line. The piping material is carbon steel (SA333, Gr. 6) and the feedwater nozzle material is low alloy steel (SA508 Class 2). The transients used in the evaluation are based on the thermal cycle diagram of the piping. The calculated fatigue usage factors including the environmental effects are compared with those obtained using the current ASME Code rules. In both cases the cumulative fatigue usage factors are shown to be less than 1.0.
Stress Intensity Factors of Various Surface Cracks Inside a Hollow Cylinder Under Steady State Thermal Striping
Authors: Meshii Toshiyuki , Shibata Kentaro
Published: August 2009

We consider a steady state thermal stress problem of a long hollow cylinder under thermal striping in this paper. The outer surface of the cylinder was adiabatically insulated, and the inner surface was heated axisymmetrically by a fluid with sinusoidal temperature fluctuations, whose temperature amplitude (ΔT) and angular velocity (ω) were constant. The heat transfer coefficient h was also assumed to be constant. The stress intensity factor (SIF) due to the thermal stress for a given cylinder configuration varies not only with these three parameters ΔT, ω and h, but also with time. It is in fact possible to calculate the transient SIF for a specific combination of cylinder configuration and the three parameters numerically. However, for a given cylinder configuration, we think it is of practical importance to know the maximum SIF for all possible combinations of ΔT, ω and h. This maximum SIF evaluation is time consuming. Thus in this paper, we present this maximum transient SIF for four type surface cracks inside a hollow cylinder for all possible combinations of ΔT, ω and h. Thin to thick-walled cylinders in the range of mean radius to wall thickness parameter rm/W = 10.5 ∼ 1 were considered. Crack configurations considered were 360 deg continuous circumferential, radial, semi-elliptical in circumferential and radial direction. Normalized crack depth for all cases was in the range of a/W = 0.1 ∼ 0.5. In case of semi-elliptical crack, the normalized crack length a/c was all in the range of 0.063 ∼ 1.
Comparison of Pump Impeller Orbit Curves Obtained by Measurement and FSI Simulation
Authors: Benra Friedrich-Karl , Dohmen Hans Josef
Published: August 2009

Raw sewage water typically contains large amounts of solids and fibers. The transport of water comprising such impurities with centrifugal pumps requires a special impeller geometry, in order to avoid operational disturbances by clogging. Non-clogging sewage water pumps are equipped with impellers featuring a small number of blades. Single-blade impellers comprise the smallest number of blades and provide therefore the biggest cross sections of the flow channel. But there are also disadvantages which occur during pump operation, because the time-variant flow in such pumps results in periodic unsteady flow forces which affect the impeller and which produce strong radial deflections of it. To determine the oscillations of the pump rotor induced by the exciting forces a coupled solution of the flow field in the pump and the structural mechanics of the pump rotor is required. In the present paper simulations which accomplish different coupling methods of the fluid dynamics and the structural dynamics have been carried out. In a first approach an explicit partitioned coupling method with simple interchange of boundary conditions has been applied. This approach disregards the feedback of the structural analysis to the flow and the results comply only roughly to the measurements. In a second attempt a fully coupling of the fluid dynamics and the structural dynamics has been carried out. The simulations are coupled by sending the computed flow forces at each time step as the load to the solver of the structural mechanics and the computed deflection of the impeller acts as a deformation of the computational grid of the fluid volume. The impeller orbit curves obtained by this method compare much better to the measurements.
Mechanical Buckling of Functionally Graded Cylindrical Shells Based on the First Order Shear Deformation Theory
Authors: Narimani Ramin , Karami Khorramabadi Mehdi , Khazaeinejad Payam
Published: August 2009

Buckling analysis of simply supported functionally graded cylindrical shells under mechanical loads is presented in this paper. The Young’s modulus of the shell is assumed to vary as a power form of the thickness coordinate variable. The shell is assumed to be under three types of mechanical loadings, namely, axial compression, uniform external lateral pressure, and hydrostatic pressure loading. The equilibrium and stability equations are derived based on the first order shear deformation theory. Resulting equations are employed to obtain the closed-form solution for the critical buckling load. The influences of dimension ratio, relative thickness and the functionally graded index on the critical buckling load are studied. The results are compared with the known data in the literature.
Anodic Polarization Behavior of Titanium Grade 7 in Dust Deliquescence Salt Environments
Authors: Evans Kenneth J. , Rebak Raul B.
Published: August 2009

It is planned to use the highly corrosion resistant titanium grade 7 (Ti Gr 7) and a high strength titanium alloy (Ti Gr 29) to fabricate the drip shield for the Yucca Mountain repository. Ti Gr 7 contains 0.15% Palladium (Pd) to increase its corrosion performance, mainly under reducing conditions. It was important to determine the corrosion behavior of Ti Gr 7 in concentrated brines at temperatures higher than 100°C, which may represent the behavior of dust deliquescence solutions. Tests were performed in concentrated NaCl + KCl solutions containing also nitrates and fluorides. Results show that Ti Gr 7 was highly resistant to general and localized corrosion. Some specimens were polarized to potentials higher than 4 volts. None of the tightly creviced specimens suffered crevice corrosion. The presence of fluoride promoted localized corrosion around the edges of the crevice former.
Long-Term Immersion Testing of Alloy 22 and Titanium Grade 7 Double U-Bend Specimens
Authors: Evans Kenneth J. , Stuart Marshall L. , Hailey Phillip D. , Rebak Raul B.
Published: August 2009

Double U-bend specimens of Alloy 22 (N06022) and Titanium Grade 7 (R52400) were exposed to a naturally aerated concentrated Basic Saturated Water (BSW) electrolyte at 105°C for over six years. Different type of discoloration of the Ti Gr 7 and Alloy 22 specimens was observed. General Corrosion was minimal and not distinguishable under a scanning electron microscope. None of the tested specimens suffered environmentally assisted cracking (EAC) or localized corrosion under the tested conditions. The specimens retained their residual stress after the long environmental exposure.
Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments
Authors: Lian Tiangan , Gdowski Gregory E. , Hailey Phillip D. , Rebak Raul B.
Published: August 2009

The nitrate ion (NO3−) is an inhibitor for crevice corrosion of Alloy 22 (N06022) in chloride (Cl−) aqueous solutions. Naturally formed electrolytes may contain both chloride and nitrate ions. The higher the ratio R = [NO3−]/[Cl−] in the solution the stronger the inhibition of crevice corrosion. Atmospheric desert dust contains both chloride and nitrate salts, generally based on sodium (Na+) and potassium (K+). Some of these salts may deliquescence at relatively low humidity at temperatures on the order of 150°C and higher. The resulting deliquescent brines are highly concentrated and especially rich in nitrate. Electrochemical tests have been performed to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 150°C at ambient atmospheres. Naturally formed brines at temperatures higher than 120°C do not induce crevice corrosion in Alloy 22 because they contain high levels of nitrate. The inhibitive effect of nitrate on crevice corrosion is still active for temperatures higher than 100°C.
Direct Damage Evaluation Method for Thermal Fatigue Based on Power Spectrum Density Functions
Authors: Sakai Shinsuke , Honda Kei , Okajima Satoshi , Izumi Satoshi , Kasahara Naoto
Published: August 2009

At an incomplete mixing area of high and low temperature fluids, fluid temperature fluctuation often occurs. It induces cyclic thermal stresses in the wall, which may result in fatigue crack initiation. Kasahara et. al. proposed the thermal fatigue evaluation method based on power spectrum density (PSD) in PVP05. This method generalizes the evaluation procedure by preparing PSD charts of fluid and frequency transfer functions of stress for various kinds of plant components. From design point of view, however, this method is too complicated due to the inverse Fourier transform and wave decomposition procedures named Rain Flow Cycle Counting (RFC). In this paper, simplified damage evaluation method for thermal fatigue is proposed by directly evaluating fatigue damage from PSD of stress. Since analytical treatment for evaluation of fatigue amplitude distribution based on PSD is difficult due to complicated procedure of RFC, direct evaluation method for RFC amplitude distribution from PSD is newly proposed. This method gives fatigue damage evaluation with safety margin. This paper shows the dependency of safety margin on geometry of PSD. Finally, application to design for thermal fatigue will be shown. Since PSD of stress in the wall near temperature fluctuation can be easily evaluated using Kasahara’s method, the proposed method will make thermal fatigue damage evaluation far easier.
Improvement of Proximity Rules for Subsurface Flaws in the Acceptance Standards of the JSME Code on Fitness-for-Service
Authors: Tamako Hiroaki , Miyazaki Katsumasa , Hasegawa Kunio
Published: August 2009

Allowable flaws for Class 1 vessels and piping are defined in the Acceptance Standards of JSME (The Japan Society of Mechanical Engineers) Code on Fitness-for-Service (FFS). When detected flaws are subsurface flaws located near component surface, the subsurface flaws are transformed into surface flaws. This is a proximity rule of subsurface flaws. This paper describes the inconsistencies of the subsurface flaws in the Acceptance Standards of vessels and piping. Authors have developed method to improve the inconsistencies and compared it with the proximity rules of the ASME Code Section XI.
Shakedown Limit Load Determination for a Kinematically Hardening 90-Degree Pipe Bend Subjected to Constant Internal Pressure and Cyclic Bending
Authors: Abdalla Hany F. , Megahed Mohammad M. , Younan Maher Y. A.
Published: August 2009

A simplified technique for determining the shakedown limit load of a structure employing an elastic-perfectly-plastic material behavior was previously developed and successfully applied to a long radius 90-degree pipe bend. The pipe bend is subjected to constant internal pressure and cyclic bending. The cyclic bending includes three different loading patterns namely; in-plane closing, in-plane opening, and out-of-plane bending moment loadings. The simplified technique utilizes the finite element method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full cyclic loading finite element simulations or conventional iterative elastic techniques. In the present paper, the simplified technique is further modified to handle structures employing elastic-plastic material behavior following the kinematic hardening rule. The shakedown limit load is determined through the calculation of residual stresses developed within the pipe bend structure accounting for the back stresses, determined from the kinematic hardening shift tensor, responsible for the translation of the yield surface. The outcomes of the simplified technique showed very good correlation with the results of full elastic-plastic cyclic loading finite element simulations. The shakedown limit moments output by the simplified technique are used to generate shakedown diagrams of the pipe bend for a spectrum of constant internal pressure magnitudes. The generated shakedown diagrams are compared with the ones previously generated employing an elastic-perfectly-plastic material behavior. These indicated conservative shakedown limit moments compared to the ones employing the kinematic hardening rule.
Pulse Wave Propagation and Reflection in Human Arteries by Pressure-Velocity Loop and Impedance Analysis
Authors: Chang Ye , Kaneko Shigehiko
Published: August 2009

To investigate the mechanism and the usage of the information of pulse wave propagation and reflection in human arteries are the objects of this study. In this study, an experimental apparatus simulating human circulatory system by using silicon tubes to examine the pulse wave propagation and reflection with and without branches has been developed. We examined the effect of eight parameters, such as flow rate, tube diameter, tube thickness etc., affecting waveform, PWV (Pulse Wave Velocity) and PV loop (Pressure-Velocity Loop). Numerical analyses were also carried out, and the relation between PV Loop and local impedance was discussed. Finally, the effect of eight parameters on the PWV and PV loop were clarified. It was also found that, the PV Loop includes much information on the tube characteristics, impedance, boundary condition, tube connection and reflection condition. Therefore, the PV loop method might be promising to be used in health diagnosis systems. In addition, we found that the effects of bifurcation angle on wave propagation and reflection were so little that they can be neglected in wave calculation models.
Impact Testing of Stainless Steel Material at Room and Elevated Temperatures
Authors: Morton Dana K. , Snow Spencer D. , Rahl Tom E. , Blandford Robert K.
Published: August 2009

Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern are not well documented. However, three previous papers [1, 2, 3] reported on impact testing and analysis results performed at the Idaho National Laboratory using 304/304L and 316/316L stainless steel base material specimens that began the investigation of these characteristics. The goal of the work presented herein is to add the results of additional tensile impact testing for dual-marked 304/304L and 316/316L stainless steel material specimens (hereafter referred to as 304L and 316L, respectively). Utilizing a drop-weight impact test machine and 1/4-inch to 1/2-inch thick dog-bone shaped test specimens, additional impact tests achieved target strain rates of 5, 10, and 22 per second at room temperature, 300, and 600 degrees Fahrenheit. Elevated true stress-strain curves for these materials at each designated strain rate and temperature are presented herein.
Understanding the Threshold Conditions for Stress Corrosion Cracking in Light Water Reactor Environments Based on the Deformation/Oxidation Mechanism
Authors: Shoji Tetsuo , Lu Zhanpeng , Takeda Yoichi
Published: August 2009

Stress corrosion cracking of structural materials is an important issue in light water reactors such as pressurized water reactors (PWR) and boiling water reactors (BWR). Proper disposition of the crack growth rate in terms of the engineering parameters is crucial for safe and economic long term operation. Threshold values of the stress intensity factor (K) have been used in some crack growth rate disposition guidelines such as JSME S NA1-2004 for austenitic stainless steels in BWR environments and flaw evaluation methodologies such as ASME XI Nonmandatory Appendix O-3230 for nickel-based Alloy 600 in PWR primary water environments. These threshold K values are based on the presently available experimental data that have been obtained mostly at relatively high K values. The threshold conditions for stress corrosion cracking in high temperature water are discussed more broadly for different cracking systems with various key-controlling parameters. The deformation/oxidation mechanism, which has been applied to quantification of the crack growth rate, is used here for analyzing the threshold conditions for stress corrosion cracking resulting from the interaction between the material and the environment under loading conditions.
3-D Modeling of Fluid-Structure Interaction With External Flow Using Coupled LBM and FEM
Authors: Kwon Y. W. , Jo J. C.
Published: August 2009

Three dimensional fluid-structure interaction was modeled using the coupled lattice Boltzmann and finite element methods. The latter technique was applied to model the structural behavior while the former was used to model the fluid field. For computationally efficient modeling of external flow over embedded pipes with their interaction, the pipes were modeled using 3-D beam elements rather than shell elements. This paper presents an algorithm for how to couple 3-D beam finite elements with the lattice Boltzmann grids so that the fluid-structure interaction can be properly modeled at the outer surfaces of pipes. Some numerical examples were analyzed using the developed technique, and the fluid-structure interaction characteristics were examined through the examples.
Fatigue Crack Growth Rate for Nickel-Based Alloys in PWR Environment
Authors: Nomura Yuichiro , Kanasaki Hiroshi
Published: August 2009

Reference fatigue crack growth rate (FCGR) curves for ferrite and austenitic stainless steels in light water reactors environments are prescribed in JSME S NA1-2004 in Japan. The reference FCGR curves in the environment in pressurized water reactors (PWR) are determined as functions of the stress intensity factor range, temperature, load rising time and stress ratio. However, similar reference FCGR curve for nickel-based alloys for PWR environment are not prescribed. In order to propose reference curve in PWR environment, fatigue tests of nickel-based alloys in a simulated PWR primary water environment were conducted. The results of the study show that FCGR in a PWR primary water environment increases with decreasing cyclic loading frequency f, increasing stress ratio R, and increasing temperature Tc.
Confirmation Method of Calibration by Visual Calibration Gauge on Surface Testing
Authors: Mori Masako , Kashiwa Toshibumi , Aoki Yoshimitsu
Published: August 2009

In 2002, Japanese Industrial standard JIS Z 2340 [1] has issued to provide the instruction of new methodology to calibrate the observing conditions of surface testing such as liquid penetrant and magnetic particle testing applying visual calibration gauges. The visual calibration gauges are the transparent plates, on which the line pairs printed to be used to confirm the resolution of visual testing observing view. The concept of line pair has been used to evaluate the resolutions of optical instruments, and the line pair value is a numerical value that shows how many line pairs can be distinguished as separate lines within 1 millimeter. In this paper, the background of the development and the general outlines of visual calibration gauges are introduced at first. And then applications of the gauges and detail process to calibrate the surface testing observing view conditions are also described.
New IQI for Digital Radiography
Authors: Mori Masako , Kashiwa Toshibumi , Aoki Yoshimitsu
Published: August 2009

Radiographic Test (RT) has been widely used in industries to detect inner defects of welded structures or any other significant components. Especially in the nuclear industry, film radiography is the dominant and standardized procedure in performing radiographic testing. Lately emphasis is on digital radiography. One of the most serious concerns for digitization is the lack of image resolution standardizing device like resolution gauge which would determine imaging parameters such as modular transfer function (MTF). This paper proposes line pair type image quality indicator (IQI) corresponding to the current IQIs for both hole and wire type. The advantage of this IQI is to enable easier calibration of testing conditions and quantification of digital RT image quality with required MTF that should be clearly defined in the examination procedures. Furthermore, to acquire “resolution-ensured” digital image of existing RT films, we developed line pair type standardization film. Prototypes of line pair type IQI and line pair type standardization film are currently in the validation study and trial implementing process. These results are also reported in this paper.
Revision of Proximity Rules for Subsurface Transforming to Surface Flaws for Class 1 Ferritic Vessels
Authors: Hasegawa Kunio , Miyazaki Katsumasa , Scarth Douglas A. , Merkle John G. , Cipolla Russell C.
Published: August 2009

There is a rule in Acceptance Standards of Class 1 ferritic vessel in the ASME B&PV Code Section XI describing that allowable subsurface flaws near a component surface are transformed to allowable surface flaws. This is the flaw-to-surface proximity rule for the subsurface flaws. If the subsurface flaw is located closer to the component surface, the subsurface flaw not allowed close to the component surface but may be acceptable after transforming it to a surface flaw. This is a discontinuity of a subsurface flaw in the current Acceptance Standard for Class 1 ferritic vessels. Authors had developed a solution for the discontinuity and proposed the proximity rule at the last ASME PVP 2006 conference. After the discussion at the ASME Code Working Group on Flaw Evaluation, the proposed proximity rule was revised. This paper describes the revision of new flaw-to-surface proximity rule to minimizing the changes to the current allowable subsurface flaws of the Acceptance Standards.
Piecewise Exact Solution for a Bridge With Sliding Type Isolators Under Earthquakes
Authors: Tsai C. S. , Chen Wen-Shin , Chiang T. C. , Chen B. J. , Chen Kuei-Chi
Published: August 2009

In recent years, the earthquake proof technology has been applied to seismic mitigation of structures including buildings, bridges, etc. The bridge system possesses large degree of freedoms, and nonlinear characteristics when structural control devices are involved. Therefore, the analysis for a bridge with nonlinear devices will be time consuming. In this study, a piecewise exact solution for a bridge isolated with sliding type isolators has been derived to simplify the analysis process. In this study, the system is modeled as two degrees of freedom to reasonably represent a large number of degrees of freedom of a bridge with sliding type isolators for obtaining a piecewise exact solution for the system response during earthquakes. In the meantime, the NSAT (Nonlinear Stress Analysis Techniques) computer program has also been used to analyze the response of the bridge with sliding type isolators. By comparing the results from the piecewise exact solution and the NSAT computer program, it can be found that the piecewise exact solution not only simplifies the calculation process, but also obtains the seismic responses of the isolated bridge with good accuracy under earthquakes.
Acoustic-Structural Coupling in Pipework
Authors: Goyder Hugh
Published: August 2009

If an acoustic resonance is set up in a pipework system then it may cause structural vibration which can lead to a catastrophic fatigue failure. An investigation is made into the coupling between acoustic waves and pipework stress with the objective of developing a simple method for determining if stresses are excessive. The analysis of the coupled acoustic and structural vibration results in a two-degree-of-freedom model with two natural frequencies and two damping ratios. This model is impractical as an assessment tool because the natural frequencies and damping ratios are either not known at all or are only known imperfectly. The model is therefore manipulated to give the stress corresponding to the most unfavourable conditions for the natural frequencies. This results in a useful assessment equation which may be used in practical circumstances. Comparisons are made with an alternative assessment method based on uncoupled behaviour.