bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Seismic Response of High-Speed Rotational Disk-Shaft System
Authors: Ito Tomohiro , Hatta Masayoshi , Shintani Atsuhiko , Nakagawa Chihiro
Published: August 2013

Recently, huge earthquakes occurred in the world, such as Great East Japan Earthquake in Japan or huge earthquake in New Zealand in 2011. In Niigata-ken Chuetsuoki earthquake in 2007, turbine blade collisions with the casing were found. Therefore, it is very important to clarify the seismic response behaviors of the high-speed rotational shaft like turbine shafts, because high-speed rotation will cause characteristic dynamic effects, such as gyro moment.

In this study, seismic responses of a disk-shaft system are evaluated analytically. The disk-shaft system is treated as an elastic shaft with a rigid disk. In this analysis, gyroscopic effects of a rotating disk are also considered. Equations of motion are derived for the translational and rotational motions when the system is subjected to both horizontal and vertical seismic excitations. Response behaviors of a rotating disk-shaft system are evaluated for sinusoidal excitations and seismic wave excitations. In the sinusoidal excitations, excitation frequencies and rotational speed are varied, and in the seismic wave excitations, seismic responses are evaluated for the waves with various predominant frequencies.
Bolt Preload Reduction of Pipe Flange Connections After Plant Shutdown
Authors: Fukuoka Toshimichi , Nomura Masataka , Uemori Yuutaro , Sato Koji
Published: August 2013

When pipe flange connections clamped with sheet gaskets are subjected to thermal load, the bolt preloads that tighten a pair of pipe flanges tend to decrease. It has been studied in the previous paper why and how the bolt preloads decrease, in which the loading and unloading curves of sheet gaskets at elevated temperature are expressed by means of simple equations. Meanwhile, it is also known that the bolt preloads are likely to decrease when the plant is shut down. In this paper, a numerical procedure, which can predict the amounts of bolt preload reduction occurred in the shutdown process, is proposed using axi-symmetric finite element method (FEM). The analytical objects are pipe flange connections tightened with aramid sheet gaskets. In the finite element formulation, stress-strain curves of the gaskets after plant shutdown are approximated by simple curves, considering that the hysteresis appeared in the curves is considerably small, comparing to that between the loading and unloading curves in the running condition. It is shown that the bolt preloads are decreased by as much as from 40% to 50% of those in the running condition. The validity of the proposed numerical method is confirmed by comparing the numerical results of the bolt preload reduction to experimental ones.
A Study of the Effect of Hardening Model in the Prediction of Welding Residual Stress
Authors: Joosten Martina M. , Gallegillo Martin S.
Published: August 2013

The presence of residual stresses can significantly affect the performance of manufactured products. The welding process is one of the most common causes of large tensile residual stresses, which may contribute to failure by brittle fracture or cause other forms of failure such as damage by corrosion and creep. Welding is a widely used method of fabrication and it can generate high levels of residual stress over significant proportions of the thickness of a component. In order to study the effect of material characterisation on computer based predictions of welding residual stresses, the presented work was carried out as part of the European Network on Neutron Techniques Standardisation for Structural Integrity (NeT). Within the NeT, a task group is investigating a three-pass Tungsten Inert Gas (TIG) weld benchmark. The three-pass specimen offers the possibility of examining the cyclic hardening and annealing behaviour of the weld metal and heat affected zone. A 3D model of the benchmark NeT problem was set up using ABAQUS v6.9.1 and validated against measurements. This paper presents the finite element work. Future papers from the NeT shall present experimental measurements. Different hardening models were considered in order to study their effect on the residual stresses. The different hardening models were isotropic hardening, linear and nonlinear kinematic hardening and combinations of these. Also the effect of annealing on the hardening behaviour is studied. Finally, the results of the simulations are compared to residual stress distributions as given in several standards.
Effect of Rotational Stiffness Evolution at Crack Part on Critical Crack Size in SFR
Authors: Wakai Takashi , Machida Hideo , Yoshida Shinji
Published: August 2013

This paper describes the efficiency of the deployment of rotational stiffness evolution model in the critical crack size evaluation for Leak Before Break (LBB) assessment of Sodium cooled Fast Reactor (SFR) pipes. The authors have developed a critical crack size evaluation method for the thin-walled large diameter pipe made of modified 9Cr-1Mo steel. In this method, since the SFR pipe is mainly subjected to displacement controlled load caused by thermal expansion, the stress at the crack part is estimated taking stiffness evolution due to crack into account. The stiffness evolution is evaluated by using the rotational spring model. In this study, critical crack sizes for several pipes having some elbows were evaluated and discuss about the effect of the deployment of the stiffness evolution model at the crack part on critical crack size. If there were few elbows in pipe, thermal stress at the crack part was remarkably reduced by considering the stiffness evolution. In contrast, in the case where the compliance of the piping system was small, the critical crack size could be estimated under displacement controlled condition. As a result, the critical crack size increases by employing the model and LBB range may be expected to be enlarged.
Effectiveness of AE On-Line Testing Results of Atmospheric Vertical Storage Tank Floors
Authors: Xu Yanting , Wang Xiaowei , Wang Xianggang , Wang Yadong
Published: August 2013

By comparing acoustic emission (AE) online inspection results of vertical tank floors with validation testing results by other methods including magnetic flux leakage (MFL), visual examination (VT), Magnetic Particle Testing (MT) or Penetrant Testing (PT), vacuum leak detection or destructive cutting, the dependability and precision of AE inspection results are analyzed, and the successful experience of AE online testing of atmospheric tank floors is summarized.
Numerical Simulation of Mecano-Welding Process for Cylinder Manufacturing
Authors: Feng Zhengkun , Champliaud Henri
Published: August 2013

Pyramidal three-roll bending has the advantage of simple configuration and is widely used in manufacture. However, the bent shape has two planar zones near the front and rear ends. This paper proposes the modeling of the mecano-welding process which provides improved circularity of the bent shape. This process includes three sub-processes: the first sub-process is the roll bending from a plate with cylindrical rolls, the second sub-process which is the gas metal arc-welding process used to join the gap of the bent tubular section, and the third sub-process is the rerun roll bending of the welded shape. Results of the simulation of the first two sub-processes under the well-known ANSYS and ANSYS/LS-DYNA environment are reported. The bent shape after the first roll bending, the distributions of the temperature and residual stress after the welding are illustrated.
Large Vessel Nozzle Penetration Geometric Optimisation Study in 3D Incorporating Design of Experiments Techniques
Authors: Towse Adam , Martin Michael , Allen Adrian , Andrews Chris
Published: August 2013

This paper describes the results of an optimisation study into the effects of changing geometrical variables local to the nozzle entry on a large pressure vessel. The purpose of the study was to quantify the effects of altering the geometry, and thereby provide trade-offs between key responses such as primary strength and shakedown performance.

A 3D Finite Element model was built of a 90 degree sector of the pressure vessel which was sufficiently detailed to allow the thermal and structural effects of the vessel remote from the nozzle to be included. Specifically, this included the thermal and structural influence of the closure head and bolting assembly. The model was then parameterised for 5 independent variables, including the extent of the nozzle reinforcement, crotch corner fillet radius and nozzle thickness. The parameterised model was then subjected to a number of thermal and structural transient analyses during Level A operation, as well as a representative strength loadcase.

A full factorial design study was undertaken, comprising of separate 243 analysis runs covering the 5 independent variables at 3 levels. A number of output metrics were monitored, and the effects on the output metrics resulting from changes to the inputs were quantified. Due to the full factorial nature of the experimental design, interactions between variables could also be investigated.

The response for each output metric was then fitted to a response surface, which allows a polynomial (meta-model) of each metric to be calculated. These responses were input to a simple Excel chart which allows the designers to perform rapid what-if design scenarios, and see the resulting effects of their changes on the responses. This allows the trade-offs between responses, for example shakedown and strength trade-off for shell thickness, to be easily seen and quantified.
Fitness-for-Service Assessment of a Steam Pipeline Operating in the Creep Range After 230000 Hours of Service
Authors: Scano Lorenzo
Published: August 2013

High energy pipes, carrying steam at high pressure and temperature, are very common in the industry. In this paper, a Fitness-For-Service assessment was performed for a pipeline connecting the boiler of a paper mill to the cogeneration turbine and the process headers. A pressure of 6.4 MPa and a temperature of 475 °C were the operating conditions for 230000 hours of continued service, thus arising concern about metal loss due to erosion/corrosion and high temperature creep damage. Original pipeline design information was unknown, hence, an extensive NDE program was carried out to obtain the required data for the FFS analysis. Because of the elevated number of in-service hours, an API 579-1 Level 3 assessment was required and a FE shell model of the line was set up to evaluate plastic strain accumulation due to creep through a time-dependant inelastic analysis. The predicted critical components were then investigated experimentally taking metallographic replicas in situ and the actual damage was finally, qualitatively, compared with that calculated with the API 579-1 procedures, with good agreement. The results of the assessment led to an estimate of 70000 hours of residual life for the pipeline and could drive the planning for future NDE according to a RBI approach.
Acoustic Resonance in a Reservoir-Double Pipe-Orifice System
Authors: Tijsseling Arris S. , Hou Qingzhi , Svingen Bjørnar , Bergant Anton
Published: August 2013

Acoustic resonance in a two-pipe system is simulated with four different models for the periodic excitation. Analytical solutions are provided in full for the three linear excitations. Exact numerical results are presented for the nonlinear excitation. The influence of a large-diameter supply pipe (instead of a constant-head reservoir) on the system’s fundamental frequencies and mode shapes is studied. The peculiar behaviour of wave reflection at an orifice is fully explained.
Residual Stress Predictions on a 29″ Narrow Gap Dissimilar Metal Weld and Comparison With a 14″ Configuration
Authors: Courtin Stéphan , Ficquet Xavier , Lê Thi Thuy Trang , Gilles Philippe , Yescas Miguel
Published: August 2013

AREVA has developed narrow gap weld techniques to perform junctions between low alloy steel heavy section components and austenitic stainless steel piping systems. In parallel, for a good understanding of welding and post weld heat treatment consequences, numerical welding simulation has already demonstrated its relevance to predict residual stress fields in welded components [1].

This paper presents Finite Element (FE) simulations of a 29″ multipass narrow gap Dissimilar Metal Weld (DMW) configuration, the welding simulation including non linear kinematic hardening models, phase transformations and visco-plastic calculations for reproducing the post weld heat treatment.

The numerical results are compared to measurements obtained by the deep hole drilling technique [2]. This work gives another evidence of the relevance of the numerical welding simulation. Particularly, the comparison with a 14″ configuration [3] gives some elements to assess on the validity of both numerical and experimental techniques and on the weld thickness effect.
Prediction of Lower Bound Fracture Toughness in the Transition Temperature Region by T33-Stress
Authors: Lu Kai , Meshii Toshiyuki
Published: August 2013

It is well known that the fracture toughness Jc in the ductile-to-brittle transition temperature region depends highly on the specimen thickness (hereafter, TST). The TST effect on Jc, which Wallin [1] described as Jc (∝ KJc2) ∝ B(-1/2) (Jc was calculated from the equations outlined in ASTM E1820 [2], KJc was derived from Jc as KJc = (Jc·E′)1/2; E′ = E/(1−ν2), B: TST), has been reproduced by Anderson et al. [3] based on the weakest link model. However, as Anderson et al. [3] themselves admit, Jc does not decrease indefinitely with B. On the other hand, Meshii et al. [4–6] tried to explain this TST effect on Jc as a mechanical issue. They obtained the same relationship, Jc ∝ B(-1/2) from the fracture toughness test for a non-standard CT and 3PB specimen (non-standard on the point that planar configuration was identical and thickness to width ratio B/W was varied from 0.25 to 0.5) and the stress intensity factor (SIF) corresponding to fracture load Pc denoted as Kc (Kc was calculated from the equations outlined in ASTM E399 [7]), was almost constant for TST. They also reproduced the experimental tendency by large strain FEA under the assumption based on their experimental observation that Kc was independent of TST. In addition, they expressed the TST effect on Jc by correlating Jc with the out-of-plane elastic T-stress T33.

We thought that if TST effect on Jc is a mechanical issue, the lower bound Jc for TST could be predicted by FEA under some assumption such as Kc = constant for TST, and the TST corresponding to the lower bound Jc could be predicted by T33. However, before proceeding to this prediction, we thought we have to understand the candidate assumption for prediction more deeply, i.e, understand why Kc was constant for TST.

Thus in this work, we attempted to explain the reason why Kc was constant for TST. Our idea was to apply the well-known “planar” failure criterion to our out-of-plane TST issue. After demonstrating our idea was valid, the lower bound Jc of carbon S55C for non-standard 3PB specimen was predicted based on this planar failure criterion and the large strain elastic-plastic FEA. The results showed that Jc showed a lower bound for specimen of B/W ≥ 1.5. In addition, it was shown that this threshold B/W could be estimated by the elastic out-of-plane T33.
Creep Life Prediction of Gr.91 Using Creep Parameters in Transient Region
Authors: Abe Fujio
Published: August 2013

The creep deformation behavior and its effect on creep life have been investigated for Gr.91 by analyzing creep strain data in the NIMS Creep Data Sheet. The creep life tr is mainly determined by the minimum creep rate ε̇min, indicating tr ∝ (ε̇min)−1. The ε̇min is mainly determined by the time to minimum creep rate tm, indicating ε̇min ∝ (tm)−1. Then the creep life is correlated with the tm as tr=3.7tm, where the constant 3.7 is as an average value for a wide range of temperature (450–725 °C), stress (40–450 MPa) and test duration (11–68,755 h). Using this equation, we can predict the creep life by carrying out a short-term creep test for up to the end of transient region, corresponding to about 30% of creep life. The (tm/tr), the ratio of duration of transient region to the creep life, slightly decreases with decreasing stress and is evaluated to be 0.22 at 100 MPa and above 550 °C, which gives us tr= 4.5 tm at 100 MPa. Taking the stress dependence of the (tm/tr) into account, the accuracy of creep life prediction is further improved.
Progress on Mechanisms of the Strain Growth Phenomenon in Containment Vessels
Authors: Dong Q. , Gu Y. , Hu B. Y.
Published: August 2013

Strain growth is a phenomenon observed in the elastic response of containment vessels subjected to internal blast loading. The local response of the vessel may become larger in a later stage than its breathing mode response during the initial stage. The strain growth phenomenon has attracted great attention since it was first observed in 1976, and numerous researches have been conducted to investigate the mechanisms of the strain growth phenomenon in containment vessels. In this paper, some typical results on studying the mechanisms of strain growth in cylindrical and spherical containment vessels will be given, and the discovery of the mechanism of nonlinear modal coupling is especially highlighted. The present review may provide a good understanding on the dynamic response characteristics of cylindrical and spherical containment vessels subjected to internal blast loading.
Counter-Intuitive Behavior in Elastic-Plastic Spherical Shells and the Application to the Design of Containment Vessels
Authors: Gu Y. , Hu B. Y. , Dong Q.
Published: August 2013

Counter-intuitive phenomenon has been reported in beams, plates and rings. In this paper, we present thorough investigation on the counter-intuitive breathing mode response of elastic-plastic spherical shells subjected to impulsive loading, which is due to the combined effects of the plastic energy dissipation and the kinematic hardening of the shell material. It is proposed that the application of the present discovery may achieve a proper design of explosion containment vessels. The present study may also help improve the understanding on the dynamic response of elastic-plastic spherical shells subjected to impulsive loading.
Consideration of Environmentally Assisted Fatigue in Austenitic Stainless Steel: Calculation and Practical Application
Authors: Reese Sven H. , Seichter Johannes , Klucke Dietmar
Published: August 2013

The influence of LWR coolant environment to the lifetime of materials has been discussed recent years. Nowadays the consideration of environmentally assisted fatigue is under consideration in Codes and Standards like ASME and the German KTA Rules (e.g. Standard No. 3201.2 and Standard No. 3201.4) by means of so called attention thresholds. Basic calculation procedures in terms of quantifying the influence of LWR coolant environment by the Fen correction factor were proposed by Higuchi and others and are given in NUREG/CR-6909.

This paper deals with the application of the proposed assessment procedures of ANL and the application to plant conditions. Therefore conservative assessment procedures are introduced without assuming the knowledge of detailed stress and strain calculations or temperature transients. Additionally, detailed assessment procedures based on Finite-Element calculations, respecting in-service temperature measurements including thermal reference transients and complex operational loading conditions are carried out. Fatigue evaluation of a PWR primary circuit component is used in order to evaluate the influence of plant like conditions numerically.

Conclusions regarding the practical application are drawn by means of comparing the ANL approach considering laboratory conditions, conservative assessment procedures for the determination of cumulative fatigue usage factors of plant components and detailed assessment procedures. Plant like loading conditions, complex component geometries, loading scenarios and reference temperature transients shall be taken into account. Practical issues like the determination of the mean temperature or the strain rate have to be considered adequately.
Evaluation of Cumulative Damage From Drop to Puncture Conditions
Authors: Choi Woo-Seok , Lee Sanghoon , Bang Kyoung-Sik , Lee Ju-Chan , Seo Ki-Seog
Published: August 2013

During safety assessments of transport packages, cumulative damages are naturally accumulated for assessments performed using physical tests specimens. However, the cumulative damages are not as easily accounted when assessments are by numerical simulations. While analysts are comfortable with simulating packages for single events, it is not yet common practice to incorporate the effect handed over from a former event to the next, in a series of sequential load events. Thus, many numerical simulations in SAR (Safety Analysis Report) represent just a single event in the series of sequential event comprising the required accident condition. These single event numerical simulations are then based on initial conditions different from the analogous physical test specimen, which could contribute to a growing disparity in results between assessments by physically testing compared to numerical simulation. The reason why analyses do not consider the cumulative damage is difficulties in delivering the final result of the previous analysis to the current analysis.

The hypothetical accident conditions described in the IAEA regulations include drop, puncture, fire, and water immersion conditions, which should be sequentially simulated. There can be cumulative damage between two accident conditions, such as drop and puncture, puncture and fire, and so forth. In this study, as the first step to consider cumulative damage, an analysis technology to perform a puncture analysis incorporating the final response field from a prior drop analysis is proposed. The necessity and validity of the proposed analysis technology are evaluated by a comparison with the results obtained by performing each analysis independently.
The Effect of Ovality and Thickness Variations on Stress Analysis of Tube Bends Under Internal Pressure
Authors: Chen Yu , Parker Jonathan
Published: August 2013

Corrosion fatigue damage has resulted in the catastrophic failure of several riser and supply tubes in fossil boilers operating under sub-critical conditions. Most of the damage has been found on the neutral axis of tube bends and the damage mechanism was identified as corrosion fatigue. Significant stress concentrations will always be found associated with high tube ovality and significant thickness variations.

The purpose of this study is to demonstrate the effect tube bend geometry on the stress distributions developed due to the internal pressure. The work was performed to consider how the stresses present in tube bends vary with ovality and thickness variations (thinning/thickening). Ovality and thickness variations in tube bends, which are generally introduced during the bending process, were modeled into the three-dimensional finite element models (FEM). The finite element models considered five different degrees of ovalization of the cross-section at the center of the bend. For each model the maximum principal stress values and distribution of stresses within tube bends were evaluated. The finite element analysis (FEA) predictions were compared with the actual locations of corrosion damage on the tube bend and reasonably predicted where cracks should be expected to initiate and propagate, and where cracks should not be anticipated.
Hot Isostatically Pressed (HIPed) Large Bore Valves for a Pressurised Water Reactor (PWR) Application
Authors: Sulley John , Bohan Michael
Published: August 2013

This paper presents an overview of the work undertaken by Rolls-Royce to introduce Hot Isostatically Pressed (HIP) large bore valve, 304 stainless steel, pressure boundaries into Pressurised Water Reactor (PWR) plant. It presents the work from a design justification/manufacturing quality assurance perspective, rather than from a pure metallurgical perspective.

Although the HIP process is not new, it was new in its application to Rolls-Royce designed nuclear reactor plant. As a consequence, Rolls-Royce has implemented an evolving, staged approach, starting with HIP bonding of solid valve seats into small bore valve pressure boundaries. This was followed by powder HIP consolidation of leak-limited, thin-walled toroids, and has culminated in the powder HIP consolidation of thick-walled components, such as large bore valves. The paper provides an overview of each of these stages, the method of manufacture for the valve pressure boundary components, and the approach taken with respect to justification.

Mechanical testing results of prolongations taken from a valve body and valve operating cylinder are presented. A range of test results is provided covering, as examples: tensile, charpy, and cantilever fatigue endurance tests.

The paper describes the benefits that Rolls-Royce has realised so far through the introduction of HIPed components. Structural integrity benefits are described, such as improved grain structure, mechanical properties, and ultrasonic inspection. Project-based benefits are also described, such as provision of an alternative strategic sourcing route, cost and lead-time reductions.

The paper details the quality assurance steps Rolls-Royce specify in order to provide HIPed products that meet the necessary quality requirements for application in a PWR environment.
On the Development of a New Bolt Spacing Formula
Authors: Do Tan Dan , Bouzid Abdel-Hakim , Dao Thien-My
Published: August 2013

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a non-uniform distribution of gasket contact stresses in the radial and circumferential direction. Many factors contribute to such a failure; the flange and gasket stiffness and bolt spacing design combinations being a couple of them.

In our recent papers the effects of bolt spacing was investigated based on the theory of circular beams resting on a linear elastic foundation and based on the theory of ring on non-linear elastic foundation. The variations of the contact stress between bolts were of a concern. This paper is an extension of the work in which an analytical solution based on the theory of circular beams resting on a linear elastic foundation has been developed to determine flange bolt spacing. The relationship between bolt spacing, gasket compression modulus and flange thickness is deduced from an analysis that considers a maximum tolerated gasket contact stress difference between any two bolts.
Supplemental Stress and Fracture Mechanics Analyses of Pressurized Water Reactor Pressure Vessel Nozzles
Authors: Walter Matthew , Yin Shengjun , Stevens Gary L. , Sommerville Daniel , Palm Nathan , Heinecke Carol
Published: August 2013

In past years, the authors have undertaken various studies of nozzles in both boiling water reactors (BWRs) and pressurized water reactors (PWRs) located in the reactor pressure vessel (RPV) adjacent to the core beltline region. Those studies described stress and fracture mechanics analyses performed to assess various RPV nozzle geometries, which were selected based on their proximity to the core beltline region, i.e., those nozzle configurations that are located close enough to the core region such that they may receive sufficient fluence prior to end-of-life (EOL) to require evaluation of embrittlement as part of the RPV analyses associated with pressure-temperature (P-T) limits. In this paper, additional stress and fracture analyses are summarized that were performed for additional PWR nozzles with the following objectives:

• To expand the population of PWR nozzle configurations evaluated, which was limited in the previous work to just two nozzles (one inlet and one outlet nozzle).

• To model and understand differences in stress results obtained for an internal pressure load case using a two-dimensional (2-D) axi-symmetric finite element model (FEM) vs. a three-dimensional (3-D) FEM for these PWR nozzles. In particular, the ovalization (stress concentration) effect of two intersecting cylinders, which is typical of RPV nozzle configurations, was investigated.

• To investigate the applicability of previously recommended linear elastic fracture mechanics (LEFM) hand solutions for calculating the Mode I stress intensity factor for a postulated nozzle corner crack for pressure loading for these PWR nozzles.

These analyses were performed to further expand earlier work completed to support potential revision and refinement of Title 10 to the U.S. Code of Federal Regulations (CFR), Part 50, Appendix G, “Fracture Toughness Requirements,” and are intended to supplement similar evaluation of nozzles presented at the 2008, 2009, and 2011 Pressure Vessels and Piping (PVP) Conferences. This work is also relevant to the ongoing efforts of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code, Section XI, Working Group on Operating Plant Criteria (WGOPC) efforts to incorporate nozzle fracture mechanics solutions into a revision to ASME B&PV Code, Section XI, Nonmandatory Appendix G.
Spectral Difference Solution of Incompressible Flow Over an Inline Tube Bundle With Oscillating Cylinder
Authors: Cox Christopher , Liang Chunlei , Plesniak Michael
Published: August 2013

A high-order spectral difference (SD) method for solving the Navier-Stokes equations on moving, deformable unstructured grids has been developed [1]. In this paper, the SD method and the artificial compressibility method (ACM) are integrated with a dual time-stepping scheme to model unsteady incompressible viscous flow past an inline tube bundle of cylinders equally sized (diameter = d) and spaced (spacing = 2.1*d) over an unstructured grid. Flow simulation results are obtained using a fourth-order space accurate SD method. Two forced oscillation cases are considered; (1) 1st cylinder oscillation and (2) 2nd cylinder oscillation. The Reynolds number used for both cases is 100 and the flow is laminar. Forced oscillation is performed in the tranverse direction, and the subsequent altering of the flow physics of the system is studied. The frequency of vortex shedding behind each cylinder is the same. Root mean square results show that the lift coefficient is greatest for the 4th inline cylinder in both cases. Furthermore, a reduction in both lift and drag coefficients is seen from case (1) to case (2).
Creep Failure Simulations for 316H at 550°C
Authors: Kim Nak Hyun , Kim Yun Jae , Davies Catrin M. , Nikbin Kamran M. , Dean David W.
Published: August 2013

In this work a method to simulate failure due to creep is proposed using finite element damage analysis. The creep damage model is based on the creep ductility exhaustion concept. Incremental damage is defined by the ratio of incremental inelastic (plastic & creep) strain and multi-axial ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to almost zero to simulate progressive crack growth. The model is validated through comparison with experimental data on various sized compact tension, C(T), specimens of 316H stainless steel at 550 °C. The influence of the inelastic strain rate on the uniaxial ductility is considered. Good agreement is found between the simulated results and the experimental data.
Multilayer Urea Reactor Safety Evaluation Based on Acoustic Emission Examination
Authors: Song Mingda , Wang Weiqiang , Cao Huaixiang , Wang Lixin , Zhang Bo
Published: August 2013

Safety evaluation of urea reactors containing defects was studied based on acoustic emission examination and subsequent dissection. First, acoustic emission examination was conducted in the process of pressure testing during the hydro test and the existed defects of the urea reactor were detected and comprehensively evaluated. Second, the dissection results of the multilayer urea reactor confirmed that the acoustic emission source locations were heavy weld radial expansion cracks. Third, crack stress intensity factors were calculated in accordance with the finite element analysis results and actual crack sizes which were acquired during urea reactor dissection. Based on the crack stress intensity factors, the remaining life of the multilayer urea reactors can be estimated during the acoustic emission testing process in accordance with the acoustic emission source location appearance pressures.
Mechanical Characterization for a Large Test Design of a Dissimilar Metals Welding With a Narrow Gap Nickel Alloy Weld: Experimental and Numerical Analysis on Specimens
Authors: Bourgeois Myriam , Ancelet Olivier , Marie Stéphane , Chapuliot Stephane
Published: August 2013

Dissimilar metal welds are a common feature of light water reactors in connections between ferritic components and austenitic stainless steel piping systems. Inspection difficulties, variability of material properties and residual stresses all combine to create problems for structural integrity assessment.

Within the framework of European project STYLE, a fracture test on a pipe containing a through wall crack in a narrow gap Nickel alloy Dissimilar Metals (DMWinc) is under preparation. The work is focusing on the nickel alloy - ferrite steel interface which is the weakest area of such welded pipes in front of ductile tearing. The study temperature is 300°C, which covers typical temperatures in components like hot pipes in the primary coolant system of pressurized water reactors.

This paper gives an overview of the program and the first results of works which is been carried out by the French Atomic Energy Commission and Alternative Energies (CEA) in order to study the mechanical properties and integrity of component of the DMWinc pipes provided and designed by AREVA France.
Prediction of Leak Rates Through Porous Gaskets at High Temperature
Authors: Grine Lotfi , Bouzid Abdel-Hakim
Published: August 2013

The ability of a gasket to maintain tightness under different operating conditions has been studied extensively in recent years. However most of the research studies conducted on leakage predictions was performed at room temperature. The aim of this work is to predict leakage through gaskets take into account the effect of the temperature on the fluid properties changes and gasket internal structural characteristics. The analytical model of slip flow regime to evaluate the mass leak rates through a porous gasket developed in [1] was used in this study. The results from the model were validated and compared with experimental data obtained from tests conducted on the Universal Gasket Rig with two different gases (Helium, Nitrogen). The leak rates measured are in the range of 1 to 10−4 mg/s, which is measurable using a pressure rise technique.

As a second objective the influence of the gasket displacements caused by stress and temperature on the flow leakage was studied. A relationship between displacement or void thickness and leakage is clearly demonstrated. The slip flow regime model is capable of predicting leakage at temperature with reasonable accuracy.
Vortex-Shedding From Various Yawed Tandem Circular Cylinder Arrangements
Authors: Wilkins Stephen J. , Hall Joseph W.
Published: August 2013

The struts of a landing gear can be modeled as a tandem cylinder system where one cylinder is yawed to the mean flow direction. The current experimental investigation will examine the effect that yawing either the front or rear cylinder will have on the pressure fluctuations and associated unsteady flow field. This will be accomplished using 24 simultaneous unsteady wall pressure measurements on the cylinder wall. Two yaw angles will be examined here, α = 80° and α = 60°, for both the yawed upstream and yawed downstream cases.
An Overview of Risk Management Planning for Hot-Isostatic Pressure Treatment of High-Level Waste Calcine for the Idaho Cleanup Project
Authors: Preussner Brian D. , Nenni Joseph A. , Balls Vondell J.
Published: August 2013

The Calcine Disposition Project (CDP) of the Idaho Cleanup Project (ICP) has the responsibility to retrieve, treat, and dispose of the calcine stored at the Idaho Nuclear Technology and Engineering Center (INTEC) located at the Idaho National Laboratory. Calcine is the granular product of thermally treating, or calcining liquid high-level waste (HLW) that was produced at INTEC during the reprocessing of spent nuclear fuel (SNF) to recover uranium. The CDP is currently designing the Hot Isostatic Pressure (HIP) treatment for the calcine to provide monolithic, glass-ceramic waste form suitable for transport and disposition outside of Idaho by 2035 in compliance with the Idaho Settlement Agreement.

The HIP process has been used by industry since its invention, by Battelle Institute, in 1955. Hot isostatic pressing can be used for upgrading castings, densifying pre-sintered components, and consolidate powders. It involves the simultaneous application of a high pressure and temperature in a specially constructed vessel. The pressure is applied on all sides with a gas (usually inert) and, so, is isostatic. The CDP will use this treatment process (10,000 psi at 1,150 C) to combine physically and chemically a mixture of calcine and granular additives into a non leachable waste-form.

The HIP process for calcine involves filling a metal can with calcine and additives, heating and evacuating the can to remove volatiles, sealing the can under vacuum, and placing the can within the HIP machine for treatment. Although the HIP process has been in use for over 50 years it has not been applied in large scale radioactive service. Challenges with retrofitting such a system for Calcine treatment include 1) filling and sealing the HIP can cleanly and remotely, 2) remotely loading and unloading the HIP machine, and 3) performing maintenance and repair on a 300 ton, hydraulically actuated machine in a highly radioactive hot cell environment.

In this article, a systems engineering approach, including use of industry-proven design-for-quality tools and quantitative assessment techniques is summarized. Discussions on how these techniques were used to improve high-consequence risk management and more effectively apply failure mode, RAMI, and time and motion analyses at the earliest possible stages of design are provided.
Prediction of Creep Crack Growth for Modified 9Cr-1Mo at 600°C
Authors: Kim Nak Hyun , Kim Yun Jae , Kim Woo Gon , Lee Hyeong Yeon
Published: August 2013

This paper introduce theoretical creep crack growth prediction model and provides experimental validation of the approach for simulating creep crack growth using finite element analysis method, recently proposed by the authors. The FE creep damage model is based on the creep ductility exhaustion concept, and incremental damage is defined by the ratio of incremental creep strain and multi-axial creep ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to zero to simulate progressive crack growth.

For validation, simulated results are compared with experimental data for a compact tension specimen of modified 9Cr-1Mo at 600°C under various loading levels. The simulated results agree well with experimental C*-da/dt data. The test data are also compared with theoretical CCG prediction model.
Numerical Study of the Short Crack Initiation in Polycrystalline Aggregates
Authors: Guilhem Yoann , Stéphan Jean-Michel , Curtit François , Cailletaud Georges , Basseville Stéphanie
Published: August 2013

Fatigue life of polycrystalline materials is mainly governed by the early stages of surface short cracks. Initiation and micro-propagation phases, which represent from 50% to 80% of total component life, are experimentally proven to depend on material microstructure. The aim of this numerical study is to highlight the influence of local parameters (e.g. crystallographic orientation) on the short crack initiation. Finite element computations are performed with a crystal plasticity model. The investigations are carried out on 316L Stainless Steel with different fatigue loadings and various surface roughnesses. A qualitative study of volumetric strain localization is carried out to distinguish uniaxial and biaxial results. The slip plane activity in surface grains is characterized. Many configurations are tested to provide a statistical point of view. Results revealed the strong vulnerability of surface grains with a high Schmid factor on systems that produce extrusions. It is also demonstrated that taking account of geometrical singularities can strongly change the plastic strain localization due to crystal orientation.
Metallic Ring Type Joints (RTJ): Overview and Recent Developments
Authors: Currie Russ
Published: August 2013

The paper discusses the variety of metallic gaskets used in ASME B16.5 Ring Type Joint (RTJ) flanges.

Highlights the differences between ASME and API topside and subsea engineering standards with regard to geometry and types.

Discusses various testing carried out and its relevance to the development of alternative sealing products to be used in RTJ assemblies.

Gives a brief overview and findings of the application of finite elemental analysis to two commonly used gasket profiles namely; Oval and Octagonal.

Presents and discusses bolt relaxation test data on assembled RTJ connections using a flange demonstration unit (FADU). Comparing standard gaskets with serrated and faced products.

Introduces the next step in soft facing materials.
Effect of Weld Residual Stress Fitting on Stress Intensity Factor for Circumferential Surface Cracks in Pipe
Authors: Shim Do-Jun , Kerr Matthew , Xu Steven
Published: August 2013

Recent studies have shown that the crack growth of PWSCC is mainly driven by the weld residual stress (WRS) within the dissimilar metal weld. The existing stress intensity factor (K) solutions for surface cracks in pipe typically require a 4th order polynomial stress distribution through the pipe wall thickness. However, it is not always possible to accurately represent the through thickness WRS with a 4th order polynomial fit and it is necessary to investigate the effect of the WRS fitting on the calculated stress intensity factors.

In this paper, two different methods were used to calculate the stress intensity factor for a semi-elliptical circumferential surface crack in a pipe under a given set of simulated WRS. The first method is the Universal Weight Function Method (UWFM) where the through thickness WRS distribution can be represented as a piece-wise cubic fit. In the second method, the through thickness WRS profiles are represented as a 4th order polynomial curve fit (both using the entire wall thickness data and only using data up to the crack-tip). In addition, three-dimensional finite element (FE) analyses (using the simulated weld residual stress) were conducted to serve as a reference solution.

The results of this study demonstrate the potential sensitivity of stress intensity factors to 4th order polynomial fitting artifacts. The piece-wise WRS representations used in the UWFM was not sensitive to these fitting artifacts and the UWFM solutions were in good agreement with the FE results.
Initial Development of the Extremely Low Probability of Rupture (xLPR) Version 2.0 Code
Authors: Rudland D. , Harrington C.
Published: August 2013

NRC Standard Review Plan (SRP) 3.6.3 describes Leak-Before-Break (LBB) assessment procedures that can be used to assess compliance with the 10CFR50 Appendix A, GDC-4 requirement that primary system pressure piping exhibit an extremely low probability of rupture. SRP 3.6.3 does not allow for assessment of piping systems with active degradation mechanisms, such as Primary Water Stress Corrosion Cracking (PWSCC) which is currently occurring in systems that have been granted LBB approvals.

Along with a series of existing qualitative steps to assure safety in LBB-approved lines experiencing PWSCC, NRC staff, working cooperatively with the Electric Power Research Institute through a memorandum of understanding, is developing a new, modular based, comprehensive piping system assessment methodology to directly assess compliance with the regulations. This project, called eXtremely Low Probability of Rupture (xLPR), will model the effects and uncertainties of relevant active degradation mechanisms and the associated mitigation activities. The resulting analytical tool will be comprehensive with respect to known and significant materials challenges (PWSCC, etc.), vetted with respect to the technical bases of models and inputs, flexible enough to permit analysis of a variety of in-service situations and adaptable such as to accommodate evolving and improving knowledge.

A multi-year project has begun that has been focused on the development of a viable method and approach to address the effects of PWSCC as well as define the requirements necessary for such a modular-based assessment tool. As reported in a previous paper, the first version of this code was developed as part of a pilot study, which leveraged existing fracture mechanics based models and software coupled to both a commercial and open source code framework to determine the framework and architecture requirements appropriate for building a modular-based code with this complexity. The pilot study focused on PWSCC in pressurizer surge nozzles, and was meant to demonstrate the feasibility of this code and approach and not to determine the absolute values of the probability of rupture.

This paper examines the plans for the xLPR Version 2.0 model which will broaden the scope of xLPR to all LBB-approved primary piping in pressurized water reactors (PWR), using an incremental approach that incorporates the design requirements and lessons learned from previous iterations. After a review of the Version 1.0 final results, this paper will document the plans for Version 2.0 including the revised management structure, the technical scope, and the progress in the code development effort to date.
A Novel Fracture Specimen for Assessment of Circumferential Complex-Cracks in Pipes
Authors: Shim Do-Jun , Wilkowski Gery , Kalyanam Sureshkumar , Brust Frederick
Published: August 2013

The existence of a complex-crack in the US nuclear plant fleet was first discovered at the Duane Arnold BWR plant where large circumferential IGSCC cracks were found in several safe ends. In order to characterize the fracture behavior of these complex-cracks, several research projects were conducted which included full-scale pipe tests. Since then, little work has been conducted on this topic until recently. The occurrence of PWSCC in PWR plants raised the concern that a complex-crack could develop in dissimilar metal welds under certain conditions. This was demonstrated by using a detailed 3D finite element analyses that allowed a natural PWSCC crack growth. Thus, there is a need to further investigate the fracture behavior of a complex-crack in a pipe.

In this paper, lessons learned from the past complex-cracked pipe tests are summarized first. Then, based on the findings from the past work, a novel complex-cracked fracture specimen was proposed to characterize a complex-crack in a pipe. The typical C(T) and SEN(T) specimens were modified by inserting an additional notch only on one side of the specimen. These specimens were used to analyze the past complex-cracked pipe tests. The experimental results obtained from the modified SEN(T) specimen, namely complex-cracked tension [CC(T)-2] specimen, were able to reproduce the complex-crack fracture behavior observed in past pipe tests.