bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical and Finite Element Multi-Shell Modelling of an Intervertebral Disc
Authors: Demers Sébastien , Bouzid Abdel-Hakim , Nadeau Sylvie
Published: August 2013

The objective of this study is to develop an analytical model of an intervertebral disc capable of predicting stresses and deformations in the anulus fibrosus. The anulus fibrosus is treated as a multi-shell structure for which membrane theory applies and the junction with the end plates assumed rigid is treated with beam on elastic foundation theory. The displacements and stresses of the anulus fibrosus, when the disc is subjected to a compressive force are investigated. The discontinuity stresses are superimposed to those of the membrane stresses to estimate the stress state of the anulus fibrosus. The analytical results are compared to those of a finite element model for validation. The analytical and the finite element models show the same general trend, but their relative difference in estimating the stresses is rather high. However, both models show that the highest circumferential stress is located on the innermost lamella at the transverse plane. Furthermore, the stresses decrease through the disc thickness and at the vicinity of the endplates. These results allow to indicate, analytically, the location for maximal principal stresses in the anulus fibrosus.
Fatigue Test for Two-Holes Diagonally-Placed Plate at Elevated Temperature
Authors: Kinoshita Keisuke , Watanabe Osamu
Published: August 2013

The objective of the present study is to evaluate fatigue strength of a perforated plate at an elevated temperature of 550°C under displacement-controlled loading. Specimens having two circular holes have stress concentrations near the hole sides. The two holes in the specimen made of SUS304 stainless steel are placed at an angle of 30°, 60° and 90° measured from the loading direction. Stress concentration factors of these specimens, having the complicated stress pattern distribution, were estimated by the finite element method (FEM). Based on the stress concentration factor, the inelastic strain was estimated by the simplified equation of the Stress Redistribution Locus (SRL) method, and the estimated strain was compared to the experimental Best Fit Fatigue (BFF) curve. Crack initiation cycles were determined from graph showing the crack propagation process, which were measured by a CCD camera at a regular interval cycle. Crack initiation cycles were smaller than failure cycles of 75% load decreasing point. By using these inelastic local strain and crack initiation cycles, the experimented results were predicted well by the present complicated structures.
Improvement of Fatigue Limit by Shot Peening for High-Strength Steel Containing a Crack-Like Surface Defect: Influence of Stress Ratio
Authors: Yasuda Jun , Takahashi Koji
Published: August 2013

It is well known that shot peening (SP) prevents the initiation and propagation of fatigue cracks and improves the fatigue limit of metals. It was recently reported that a surface crack can be rendered harmless by SP. Actual pressure vessels are generally operated under a positive stress ratio (R > 0). However, the effects of SP on the improvement of fatigue limits under R > 0 remain unclear. If these effects were clarified, the structural integrity of pressure vessels could be advanced. Thus, in this study, we investigated the influence of SP on fatigue limits and on the crack size that could be rendered harmless by SP under R > 0.

High-strength steel specimens containing a semi-circular slit were subjected to SP. Bending fatigue tests were carried out under R = 0.4. The fatigue limits of the SP specimens increased 50∼100% compared with Non-SP specimens. Slits under 0.2 mm in depth were successfully rendered harmless by SP. The increasing ratios of the fatigue limit under R = 0.4 were lower than those under R = 0. However, the size of semi-circular slit that can be rendered harmless by SP remained the same. The size of the slit that can be rendered harmless can be predicted by calculating stress intensity factors.
Assessment of Ductile Cast Iron Fracture Mechanics Analysis Within Licensing of German Transport Packages
Authors: Komann Steffen , Kiyak Yusuf , Wille Frank , Zerbst Uwe , Weber Mike , Klingbeil Dietmar
Published: August 2013

In recent years BAM was involved in several licensing procedures of new package designs for the transport of radioactive material, where the cask body was made of Ductile Cast Iron (DCI). According to IAEA regulations type B(U) packages must withstand the defined accident conditions of transport. For the cask material DCI, it is necessary to determine the brittle fracture behaviour. Due to the complex structure of the cask body and the dynamic loading a fracture mechanical assessment in an analytical way is not always possible. Numerical calculations are necessary to determine the fracture mechanical load in the component. At the first step a numerical analysis has to be done to identify the loading state at the cask body. Secondly an analysis of a detail of the cask body is made considering the boundary conditions of the global model. An artificial flaw is considered in this detailed model to calculate the fracture mechanical loading state. The size of the artificial flaw is characterized by the ultrasonic inspection used for the quality assurance of the package. The applicant developed additional analysis tools for calculation of stress intensity factor and/or J-Integral.

The paper describes the authority assessment approach for the DCI fracture mechanics analysis.
Derivation of Input Distributions for Probabilistic Evaluation Using In-Reactor Measurements
Authors: Nadeau Eric
Published: August 2013

Candu Energy Inc. (former commercial operation of AECL) has developed probabilistic tools to support nuclear plant operators with a risk-based fuel channel management strategy. One such tool is used to evaluate the probability of pressure tube rupture resulting from pressure tube to calandria tube contact and hydride blisters. This tool assumes that PT rupture occurs when delayed hydride cracking (DHC) initiates in a blister. The objectives of the probabilistic assessments are to:

• Determine the overall risk of PT rupture in the reactor core for comparison with the acceptance criteria.

• Determine the risk of PT rupture for specific fuel channels to assist in the development of an inspection/maintenance strategy.

• Evaluate the risk reduction that would result from different fuel channels inspection/maintenance scenarios.

• Optimize inspection/maintenance programs.

The distributions of the most critical input distributions can be derived by benchmarking against in-reactor measurements. Two benchmark methods were developed to take advantage of the recent advancements in the accuracy of the inspection tool that measures the gap profile between the PT and the CT.
Thermomechanical Analysis of Pressure Vessels
Authors: Benson Michael , Rudland David , Kirk Mark
Published: August 2013

Regulatory Guide (RG) 1.161 and American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section XI, Nonmandatory Appendix K contain stress intensity factor (SIF) equations for both the internal pressure and thermal gradient loading cases. However, the technical basis behind these equations was developed only for Ri/t = 10, were Ri is the inner vessel radius and t is the vessel thickness. While this geometry is appropriate for most pressurized water reactors (PWR), most boiling water reactor (BWR) vessels have Ri/t = 20. This paper explores the validity of applying these SIF equations to BWRs. This confirmatory work includes calculating SIF by independent methods. The one-dimensional heat equation is solved to provide a physical basis for the thermal stresses.
Equilibrium Based Curve Fitting Method for Test Data With Nonuniform Variance
Authors: Wei Zhigang , Yang Fulun , Maleki Shervin , Nikbin Kamran
Published: August 2013

A recently developed equilibrium based curve/surface fitting method is extended to linear function with heteroscedastic data (variable variance). The concept of equilibrium weighted ‘force’ and ‘moment’ is proposed to derive curve fitting formulae, which are exactly the same as that obtained with the traditional weighted least squares (LS) method for a linear function. Furthermore, a system of four equations, i.e., a “force” equilibrium equation, a “moment” equilibrium equation, a “equivalency” equation, and a “moment balance” equation have been established to solve both mean curve and the standard deviation simultaneously. Finally, the application of these methods to data of fatigue and creep lives is presented.
Properties of Bimetallic Core-Shell Nanoclusters
Authors: Park Y. H. , Hijazi I.
Published: August 2013

Gold (Au) and copper (Cu) materials and their combination exhibit the most of the main wanted properties in nanostructures. Nobel metals such as Au and Cu have important magnetic, electronic, optical, catalytic and thermal properties. Compared to monometallic clusters, bimetallic nanoclusters have more degrees of freedom and distinct properties due to the presence of two different metals. It is also well known that the shape, surface topography, segregation, mixing, ordering, energetic stability, and electronic structures of bimetallic nanoclusters may depend significantly on their composition. This affords greater opportunity to control their properties by modifying composition as well as size. In this work, we investigated magnetic and electronic properties for AuCu bimetallic core-shell structures and showed that the CuAu coreshell can have a half-metal property through chemical composition modification. Half-metallic ferromagnets attract increasing research interest as potential materials for spintronic device applications.
Failure Probability Assessment for a Boiling Water Reactor Pressure Vessel Under Low Temperature Over-Pressure Event
Authors: Chou Hsoung-Wei , Huang Chin-Cheng , Chen Bo-Yi , Lin Hsien-Chou , Liu Ru-Feng
Published: August 2013

The fracture probability of a boiling water reactor pressure vessel for a domestic nuclear power plant in Taiwan has been numerically analyzed using an advanced version of ORNL’s FAVOR code. First, a model of the vessel beltline region, which includes all shell welds and plates, is built for the FAVOR code based on the plant specific parameters of the reactor pressure vessel. Then, a novel flaw model which describes the flaw types of surface breaking flaws, embedded weld flaws and embedded plate flaws are simulated along both inner and outer vessel walls. When conducting the fracture probability analyses, a transient low temperature over-pressure event, which has previously been shown to be the most severe challenge to the integrity of boiling water reactor pressure vessels, is considered as the loading condition. It is found that the fracture occurs in the fusion-line area of axial welds, but with only an insignificant failure probability. The low through-wall cracking frequency indicates that the analyzed reactor pressure vessel maintains sufficient stability until either the end-of-license or for doubling of the present license of operation.
Remote Field Eddy Current Testing Technology for Ferromagnetic Heat Exchanger Tubes
Authors: Chen Yubao , Zheng Jiong , Luo Weijian
Published: August 2013

As a conventional NDT method, eddy Current testing (ET) has been greatly developed both in instrumentation and technique in recent years. Remote Field Eddy Current Testing (RFET) is a representation of this advancement. The principle of RFET and the composition of the testing system are detailedly discussed in this paper. And then, its application in the ferromagnetic heat exchanger tubes is described simply.
Pressure Build-Up Inside Packages Containing Wet Intermediate Level Radioactive Waste due to Thermal Loads
Authors: Nehrig Marko , Bletzer Claus , Wille Frank
Published: August 2013

Over the last years several transport approval procedures were finished for ductile cast iron containers containing wet intermediate level waste. BAM was involved in the assessment of mechanical and thermal aspects, activity release and material and component behavior regarding fulfillment of the regulatory requirements.

The radioactive contents of these package designs which were not dried, only drained, consist of saturated ion exchange resin and a small amount of free water. Regarding wet contents, the most interesting point, however, is the pressure build-up inside the package due to vaporization. This could be caused by radiolysis of the liquid and must be taken into account for the storage period.

The paper deals primarily with the pressure build-up inside the package caused by the regulatory thermal test (30 min at 800°C) as part of the cumulative test scenario under accident conditions of transport. The pressure build-up is estimated by calculation in a very conservative way regarding conduction and heat radiation. To get trustworthy results without an exact specification of the content, physical fire tests should be conducted. This paper will result in the strong advice, that contents should be dried to ensure a positive outcome of the safety assessment.
Investigation on Detection of COV Based on Infrared Camera
Authors: Thomas Benjamin , Sauger Emmanuel , Fily Sébastien , Lejeune Hubert
Published: August 2013

In order to reduce emission of pollutants, regulations such as Clean Air Act in the United States of America or the Integrated Pollution Prevention and Control (IPPC) and the Industrial Emission Directive (IED) in Europe have been voted. On sites like refineries, the end users have implemented systematic control of Volatile Organic Compounds (COV) in the atmosphere, on their equipments (valves, flanges, pump, compressor…).

These controls involve methods of detection such as sniffing with a Flame Ionization Detector (FID) managed by an operator according to EPA21 method. This method is time-consuming and exposes operators to hazardous situations when statistical counting shows that the global emission are often connected with few equipments in refineries. Thus, the use of specific IR imaging with a camera as a remote control method sensible to selected organic gases seems a very attractive alternative, even if this method does not able to quantify very accurate leakage rates.

This study presented here investigates the influence of several parameters on the detection of COV with IR camera, under controlled laboratory conditions. External parameters such as distance of view, type of gas, wind, and camera configuration parameters are investigated.

The measurement enables definition of the limits of the IR imaging method. If the study shows that the camera must be operated by skilled and trained personal to camera tuning and image analyzing, it remains a very interesting alternative method to sniffing in many cases. The next step of the study will involve the use of the camera on various kind of sites using organic gases.
Fatigue Evaluation for Thermally Stratified DVI Piping
Authors: Lee Hwan Ho , Lee Joon Ho , Lee Dong Jae , Hur Seok Hwan , Nam Il Kwun , Bae Jae Hwan
Published: August 2013

A numerical analysis has been performed to estimate the effect of thermal stratification in the safety injection piping system. The Direct Vessel Injection (DVI) system is used to perform the functions of Emergency Core Cooling and Residual Heat Removal for an APR1400 nuclear power plant (Korea’s Advanced Power Reactor 1400 MW-Class). The thermal stratification is anticipated in the horizontally routed piping between the DVI nozzle of the reactor vessel and the first isolation valve. Non-axisymmetric temperature distribution across the pipe diameter induced by the thermal stratification leads to differential thermal growth of the piping causing the global bending stress and local stress. Thermal hydraulic analysis has been performed to determine the temperature distribution in the DVI piping due to the thermal stratification. Piping stress analysis has also been carried out to evaluate the integrity of the DVI piping using the thermal hydraulic analysis results. This paper provides a methodology for calculating the global bending stresses and local stresses induced by the thermal stratification in the DVI piping and for performing fatigue evaluation based on Subsection NB-3600 of ASME Section III.
STYLE: Comparison of Leak-Before-Break Methodologies Applied in Europe
Authors: Sharples John
Published: August 2013

The paper presents results of a sub-task of the STYLE project currently running within the 7th Framework EU programme by way of an overview of leak-before-break (LBB) methodologies used in the nuclear industry of several European countries (Germany, France, UK, Netherlands, Czech Republic, Spain and Hungary).

In relation to the various participating countries, the overview specifically focuses on: practices and procedures; regulatory position; evolution; application; past, present and planned future LBB research activities; and, future plans.

A qualitative comparison of the different methods employed in the various countries is included with the commonalities and differences among the approaches being highlighted.
A Numerical and Experimental Study of the Factors Influencing the Differences in Cleavage Fracture Behaviour Between CVN and SENB Specimens
Authors: Smith Robin J. , Horn Anthony J. , Sherry Andrew H.
Published: August 2013

The cleavage fracture behaviour of Charpy V-notch (CVN) and Single Edge Notch Bend (SENB) specimens differ due to the effects of notch root radius, notch depth, notch flank angle and loading rate. This paper presents an experimental and numerical study of the cleavage fracture behaviour of CVN, SENB and a range of non-standard intermediate specimen geometries. The intermediate geometries were selected to provide a basis for quantifying the differences in cleavage fracture behaviour between the CVN and SENB specimens by isolating the individual effects of notch-root radius, notch flank angle and notch depth. Finite element analyses were used to quantify crack and notch-tip stress fields. The study also includes a comprehensive experimental programme covering the range of notch geometries modelled using finite element analysis. The overall aim of the project is to establish links between Wallin’s Master Curve for fracture toughness and the common temperature dependence of Charpy energy observed by EricksonKirk et al.
Limit and Shakedown Loads Determination for Locally Thinned Wall Pipe Branch Connection Subjected to Pressure and Bending Moments
Authors: Hafiz Youssef A. F. , Younan Maher Y. A. , Abdalla Hany F.
Published: August 2013

In this paper the shakedown limit load for unreinforced locally thinned wall pipe branch connection is determined using the Simplified Technique. Loadings were considered to be internal pressure, as a steady load, with in-plane bending or with out-of-plane bending applied on the branch, as alternating loads. Two locations of local wall thinning were taken; one was on the run pipe opposite to the branch and other on the branch at the maximum tension stress side of the bending moment applied whether in in-plane or out-of-plane situation. Two Finite Element (FE) limit load models were used to verify the modeling of the pipe branch connection with its local wall thinning. First model results were compared with experimental data taken from the literature, and the second results were compared with numerical models taken also from the literature and also compared with API 579 “Fitness For Service” (FFS), part-five, level-two assessment procedure. First and second comparisons lead to good agreement but for API 579 comparison it was found that it is slightly changing with the depth of the local wall thinning but does not reflect the expected behavior of the limit load as the FEA models showed. For the results of the shakedown limit load analysis, Bree diagrams were constructed to show elastic, shakedown and plastic collapse regions. Then, comparison was made to show the effect of the local wall thinning depth and location on previous limits. Finally, the shakedown results were verified using the elastic-plastic ratcheting analysis of API 579, level three assessment and it showed successfully the shakedown, ratcheting and reversed plasticity regions. This verifications and results can prove that the Simplified Technique can be used as a level-three ratcheting assessment in API 579.
Isothermal Fatigue Responses and Constitutive Modeling of Haynes 230
Authors: Barrett Paul Ryan , Menon Mamballykalathil , Hassan Tasnim
Published: August 2013

Constitutive models are an integral part of a lifing system because it allows for accurate estimation of stresses and strains at failure locations of interest. Constitutive models can be properly defined in a material subroutine of a finite element code. The computational capabilities of today are far higher, allowing for more comprehensive models that can provide more accurate results. Macroscopic models that are physically based, phenomenological models characterize the material behavior on a larger scale that provides invaluable insights even at such length scales which are compatible for industrial application. A unified viscoplastic model based on nonlinear kinematic hardening (Chaboche type) with several added features such as nonproportionality, multiaxiality, strain range dependence, and thermal recovery is being implemented in ANSYS through the User Programmable Features. The simulation capability of the model will be experimentally validated on a nickel based superalloy, HA230. The experimental database encompasses a broad set of low cycle fatigue, symmetric, uniaxial strain-controlled loading histories which include isothermal with and without hold times, with and without a mean strain, at temperatures ranging from 75°F to 1800°F. Simulations from the modified model compared to the experimental responses will be presented to demonstrate the strengths and weaknesses.
Lifetime Estimation of Aluminum Plate Fin Heat Exchangers
Authors: Hölzl Reinhold
Published: August 2013

Aluminum Plate Fin Heat Exchangers (Al-PFHE) are often used in low temperature applications of chemical plants when huge heat transfer capacities are required. Typically the equipment is insulated or installed in insulated containments — so called “Cold Boxes”. Al-PFHE may either fail by corrosion or by mechanical overload due to trip scenarios or blockage / fouling. No failures due to mechanical overload should occur under the conditions of the ALPEMA [9] guideline (ALPEMA = Aluminum Plate-fin Heat Exchanger Manufacturer’s Association). However, ALPEMA doesn’t describe all operational situations in the exchanger block itself and the ALPEMA load conditions are not followed in all cases. The specific design of Al-PFHE does not allow standard inspection and maintenance procedures, which makes it difficult to evaluate the equipment condition and the expected remaining service life. Corrosion, blockage, fouling, and mechanical/thermal overload are the key degradation mechanisms that operators need to control to avoid premature failure of their aluminum plate fin heat exchangers. This paper describes how to incorporate finite element analysis and dynamic process simulation in the design and operation to evaluate the lifetime of Al-PFHE.
Tüv Nord Group Strategy Concept Coop: An Answer for the New Requirements of the Power Plant Flexibilisation
Authors: Trieglaff Ralf , Rieck Detlef , Schulze Astrid , Schulz Axel
Published: August 2013

The ambitious German energy program predicts a rapid expansion of regenerative power generation. Caused by the fluctuating nature of regenerative forms of energy, the need for backup capacities in the form of similar-sized thermal power plants is clear. Consequently, components of gas and coal-fired power plants are exposed to sharp transients and a high number of cycles.

If German design regulations are observed, these operating requirements will lead to high levels of depletion of the integrated components. As a result, inspection and maintenance efforts will also increase. A reduction in the components’ life cycle can lead to a significant increase in costs.

To effectively deal with significantly higher requirements, the TÜV NORD Group has designed a strategy, COOP (Cycle Optimized Operation), that allows, on the one hand, a reduction of conservative assessments and, on the other hand, the development of new safety standards in the evaluation of the service life.
Sensitivity Analysis of Fitness-For-Service Assessment Based on Reliability for Cylindrical Pressure Vessels With Local Metal Loss
Authors: Kaida Takuyo , Izumi Satoshi , Sakai Shinsuke
Published: August 2013

The concern with Fitness-For-Service (FFS) assessment using stochastic analysis for aged pressure equipments with local metal loss has been growing for the last several years. The structural integrity assessment based on reliability helps to make a decision as to whether to run or repair the equipments with local metal loss. As for analysis of failure probability, it is important to clear which variables affect highly the structural integrity. The stochastic property of the influential parameter needs to be clarified. There has, however, been little study to analyze quantitatively the sensitivity of the parameters for the FFS assessment of the components with local metal loss. In this study, the effects of parameters on plastic collapse of the damaged component were evaluated utilizing parameter sensitivity study. Additionally, sensitivity indices for the component with several shapes of local metal loss were analyzed. It was found from the results that the corrosion rate has much influence on probability of failure. Finally, practical stochastic analysis procedure for the component with local metal loss was proposed. In the proposed procedure, the parameter which has consistently low sensitivity to limit state was used as constant value.
Property Data, Materials Test Results and Materials Design Data: Systems for Their Efficient Management
Authors: Marsden William M. , Cope Elizabeth R.
Published: August 2013

The design, construction, and longevity of nuclear facilities rely on high quality information being collected, managed, and made available to the designers and engineers who need it. They require quick and easy access to a wide variety of material information: micrographs, stress-strain curves, fatigue and creep curves, corrosion measurements and images, reports, and test data files. Moreover, inter-relationships (e.g., between design data, test data, processing history, and service history) must be carefully captured to ensure traceability. Information alone is not enough: tools are needed to manage, search, and apply this information—for example finding corrosion data from similar pipe joints across multiple applications, and using this experience to make the right choice in subsequent projects. Data needs to be stored in a consistent format to enable comparison of tests over long time-periods, and it must be possible to accurately export it in a wide variety of formats. Looking forward, automatic data capture from test machines and field engineers can ensure accuracy, traceability, and consistency, as well as improving feedback to design engineers from service history and in-the-field test data and experience. This paper shows how meeting these information management needs can help promote innovative, safe, and cost-efficient design.
Small Bore Piping System Fatigue — Determination of Favored Crack Location and Related Admissible Vibration Criterion
Authors: Berger Julien , Guillou Jacques , Poirier Emilie
Published: August 2013

Each year, a few cracking of small bore piping systems occurs in French Nuclear Power Plant (NPP) due to vibratory fatigue. The particular design of such small bore piping system (basically composed of a socket, a small pipe and a valve with or without tubing) allows the crack initiation at two different locations of the socket weld toes: on the main pipe or on the small bore piping. The favored location depends on specific features, from geometrical and material characteristics to the weld quality.

The knowledge of the favored location with its related vibratory limit is an important issue in terms of inspection plans, plant availability and integrity of safeguard systems.

The main purpose of the present work is to provide analytical expressions for estimating the location of a potential failure by cracking fatigue and its initiation. This threshold is given by a vibratory limit expressed in terms of root mean square velocity. Inherent uncertainties (e.g. preload, weld quality…) impose to consider the proposed expressions as guidelines for the prediction of the crack location and initiation.
Determination of Minimum Vessel Wall Thickness Under Design Condition Loadings
Authors: Ratcliffe Simon E.
Published: August 2013

During the concept design phase of a series of pressure vessels for nuclear application, an approach was developed to provide minimum vessel sizing under dynamic loading conditions. Calculations had been undertaken to determine an initial tentative vessel wall thickness using ASME III Subsection NB, however only a limited assessment of mechanical loading was undertaken.

This paper outlines a static analysis approach for extending the structural analysis of a pressure vessel shell to include design condition loadings. These include dynamic loading, support reactions and external piping reactions which can have a significant influence on the required minimum wall thickness.

This paper is limited to outlining generic rules and assumptions that can be applied to the preliminary concept design of pressure vessels. The method was originally captured to aid knowledge sharing within the design team. It does not prescribe an exact methodology but rather an interpretation and application of the design code. The aim is to provide a better defined vessel geometry upon which to base the detailed finite element stress analyses for both design and service conditions. The perceived benefit of this approach is that there will be a lower likelihood of major design changes being during the detail phase.
Modelling the Graphite Fracture Mechanisms
Authors: Jacquemoud C. , Marie S. , Nédélec M.
Published: August 2013

In order to define a design criterion for graphite components, it is important to identify the physical phenomena responsible for the graphite fracture, to include them in a more effective modelling.

In a first step, a large panel of experiments have been realised in order to build up an important database; results of tensile tests, 3 and 4 point bending tests on smooth and notched specimens have been analysed and have demonstrated an important geometry related effects on the behavior up to fracture.

Then, first simulations with an elastic or an elastoplastic bilinear constitutive law have not made it possible to simulate the experimental fracture stress variations with the specimen geometry, the fracture mechanisms of the graphite being at the microstructural scale. That is the reason why a specific F.E. model of the graphite structure has been developed in which every graphite grain has been meshed independently, the crack initiation along the basal plane of the particles as well as the crack propagation and coalescence have been modelled too. This specific model has been used to test two different approaches for fracture initiation: a critical stress criterion and two criteria of fracture mechanic type. They are all based on crystallographic considerations as a global critical stress criterion gave unsatisfactory results. The criteria of fracture mechanic type being extremely unstable and unable to represent the graphite global behaviour up to the final collapse, the critical stress criterion has been preferred to predict the results of the large range of available experiments, on both smooth and notched specimens. In so doing, the experimental observations have been correctly simulated: the geometry related effects on the experimental fracture stress dispersion, the specimen volume effects on the macroscopic fracture stress and the crack propagation at a constant stress intensity factor. In addition, the parameters of the criterion have been related to experimental observations: the local crack initiation stress of 8MPa corresponds to the non-linearity apparition on the global behavior observed experimentally and the the maximal critical stress defined for the particle of 30MPa is equivalent to the fracture stress of notched specimens.

This innovative combination of crack modelling and a local crystallographic critical stress criterion made it possible to understand that cleavage initiation and propagation in the graphite microstructure was driven by a mean critical stress criterion.
Application of a Large-Scale Database System for the Analysis and Design of the US EPR™ Standard Nuclear Power Plant
Authors: Jung Se-Kwon , Harrold Joseph , Alchaar Nawar
Published: August 2013

Due to the increased size and complexity of large-scale commercial and industrial structures, it is increasingly challenging to manage key engineering data including analysis and design results of these structures. This paper presents a novel approach of using large-scale database systems as a means to gather, organize and manage key analysis and design results of a large-scale structure. Specifically, this paper describes in detail the development process of the backend database management system (DBMS) for the U.S. EPR™ Standard Nuclear Power Plant (NPP) Nuclear Island (NI) structures. The database system consists of three parent database tables to represent three representative groups of load combinations applicable to the U.S. EPR™ Standard NPP. Inheriting all characteristics of an applicable parent table, a primary child table in the database system represents a particular U.S. EPR™ NI Safety-Related structure in its entirety while a secondary child table a group of slabs or walls of the structure. Each secondary table is comprised of database fields that are representative of various structural demands, section capacities, reinforcing ratios, and demand-to-capacity ratios for three reinforced concrete design conditions (i.e., combined axial force and bending design, in-plane shear design, and out-of-plane shear design). The complete database system with fully populated tables is a central repository where all analysis and design results for the U.S. EPR™ NI Common Basemat structures are stored and sorted. To facilitate data queries from the developed backend database system, this paper introduces a user-friendly frontend interface program developed using Visual Basic Application (VBA) with Excel. Potential benefits of the developed database system are demonstrated with simple application examples involving simple data queries only followed by complex engineering tasks that require a more advanced form of data queries.
Buckling of Truncated Cones With Localized Imperfections
Authors: Błachut J.
Published: August 2013

The paper shows that both the inward and outward bulge-type axisymmetric shape imperfections can significantly lower the buckling strength of steel conical shells. The FE results are provided for: (i) axial compression, (ii) external pressure, and (iii) combined action of both loads. Sensitivity of buckling loads to outward bulges has not been generally known or expected. It is shown that the sensitivity of buckling load depends not only on the shape, amplitude but also on the position of the imperfection along the slant.

Geometry of recently tested cones was also used in order to assess the influence of measured shape deviations on the buckling strength. The amplitudes of imperfections in these machined models were small (up to 5 % of wall thickness). As a result their influence on the buckling strength was found to be negligible.
Closed-Form Solutions for Code Case 2286 Allowable Compressive Stresses Analogous to Vacuum Chart Method
Authors: Baid Harsh Kumar , LaBounty Donald , Chatterjee Amiya
Published: August 2013

The allowable compressive stresses in pressure vessels can be calculated either from ASME Section VIII Division 1, Paragraph UG-28 vacuum chart method [2] or Code Case 2286 [1]. Code Case 2286 has been incorporated into ASME Section VIII Division 2, Part 5. For Division 1 vessels, the vacuum chart method is a user-friendly tool for determining allowable compressive stress. In this paper, the authors present the development of allowable compressive stress data based on closed-form solutions of Code Case 2286. These closed-form solutions yield exact allowable compressive stress values which are not influenced by any kind of sensitivity. The development presented in the paper is also user-friendly, similar to the vacuum chart, for the determination of allowable compressive stresses. These designs, based on Code Case 2286, are economical without any compromise in the safety of the pressure vessel. Examples are included to demonstrate the results.
Visco-Elastic FEM Stress Analysis of Bolted Flange Connections With PTFE-Blended Gaskets Under Elevated Temperature
Authors: Sato Koji , Kurokawa Shinya , Sawa Toshiyuki
Published: August 2013

Bolted flange connections with gaskets have been used under high temperature and long-term conditions. Sometimes leakage accidents occur from the gasket interfaces due to the creep and relaxation phenomena. In the present paper, the changes of the gasket stress in bolted flange connections under high temperature conditions for a long-term are analyzed using FEM calculations taking into account the gasket temperature dependency. The gaskets used are PTFE-blended (V#GF300). It’s shown that the effect of the temperature on the stress-strain relationship of the gasket is substantial. The changes in the gasket stress of the connections for 12 months are analyzed using the FEM. The effects of nominal diameter of flanges, retightening and the fluid temperature (20 to 300 °C) on the change of gasket stress in the connections under elevated temperature are examined using the FEM calculations. It is found that the reduction in the gasket stress is over 40%. In addition, experiments to measure the axial bolt force were carried out. The calculated results are in a fairly good agreement with the experimental results. The results reveal that the long-term behavior of the bolted flange connections can be estimated in our study. Discussion is made on the effects of the bolt preload and retightening on the reduction of the gasket stress and the sealing performance.
A Study on Fatigue and Creep-Fatigue Life Assessment Using Cyclic Thermal Tests With Mod.9Cr-1Mo Steel Structures
Authors: Ando Masanori , Kanasaki Hiroshi , Date Shingo , Kikuchi Koichi , Satoh Kenichiro , Takasho Hideki , Tsukimori Kazuyuki
Published: August 2013

In a component design at elevated temperature, fatigue and creep-fatigue is one of the most important failure modes, and fatigue and creep-fatigue life assessment in structural discontinuities is important issue to evaluate structural integrity of the components. Therefore, to assess the failure estimation methods, cyclic thermal loading tests with two kinds of cylindrical models with thick part were performed by using an induction heating coil and pressurized cooling air. In the tests, crack initiation and propagation processes at stress concentration area were observed by replica method. Besides those, finite element analysis (FEA) was carried out to estimate the number of cycles to failure. In the first test, a shorter life than predicted based on axisymmetric analysis. Through the 3 dimensional FEA, Vickers hardness test and deformation measurements after the test, it was suggested that inhomogeneous temperature distribution in hoop direction resulted in such precocious failure. Then, the second test was performed after improvement of temperature distribution. As a result, the crack initiation life was in a good agreement with the FEA result by considering the short term compressive holding. Through these test and FEA results, fatigue and creep-fatigue life assessment methods of Mod.9Cr-1Mo steel including evaluation of cyclic thermal loading, short term compressive holding and failure criterion, were discussed. In addition it was pointed out that the temperature condition should be carefully controlled and measured in the structural test with Mod.9Cr-1Mo steel structure.
Quantifying the Constraint of Three-Dimensional Biaxially Loaded Specimens Containing Semi-Elliptical Cracks Using the J-A2 Method
Authors: Sharpe L. W. , Chao Y. J.
Published: August 2013

Fracture toughness is an important material property used to assess the structural integrity of mechanical components containing cracks. Often, the fracture toughness depends upon the geometry of the component as well as the applied loading. This dependence is referred to as the constraint effect in fracture. The two parameter J-A2 method can be used to quantify the constraint effect. The J-A2 method is a more accurate representation of the stress fields near the crack compared to the classical HRR solution, as additional terms from the series solution are used. The subject of the current study is to apply the J-A2 method to published fracture toughness data of three-dimensional, flat plates containing semi-elliptical cracks and subjected to both uniaxial and biaxial loading to determine the constraint effect and also to determine if the method can be used to predict fracture. The J-A2 results of the flat plates are compared to those of 3PB specimens to determine if loss of constraint exists. Finite element analysis models were developed for each specimen to determine the constraint parameter A2 for each applied loading. The results of the current study reveal that both the uniaxial and biaxial loaded plates exhibit loss of constraint relative to the 3PB specimen and biaxial load increases the constraint of the uniaxially loaded specimen. Further, the J-A2 method shows potential as a tool to predict failure with different constraint level.
The Impact of Axi-Symmetric Boundary Conditions on Predicted Residual Stress and Shrinkage in a PWR Nozzle Dissimilar Metal Weld
Authors: Bendeich Philip J. , Muránsky Ondrej , Hamelin Cory J. , Smith Mike C. , Edwards Lyndon
Published: August 2013

Simulation of a dissimilar metal weld (DMW) in a pressurised water reactor (PWR) nozzle was performed to predict both axial distortion and hoop residual stresses in the weld. For this work a computationally efficient axi-symmetric finite element (FE) simulation was carried out rather than a full 3D analysis. Due to the 2-dimensional nature of the analysis it was necessary to examine the effect of structural restraint during welding of the main dissimilar metal weld (DMW). Traditionally this type of analysis is set up to allow one end of the structure, in this case the safe-end forging, to be unrestrained in the axial direction during welding. In reality axial expansion and subsequent contraction of deposited weld metal at the current torch position is restrained by solidified material both ahead and behind the torch. Thus the conventional axi-symmetric analysis is under-restrained in the axial direction at least during the early weld passes. The significance of this was examined by repeating the current simulation with the safe-end forging fixed to limit expansion during the heat up cycle. Contraction was however, allowed during cooling cycle. This modified boundary control method provided a significantly improved prediction of the axial distortion across the weld as well as improved prediction of through wall axial and hoop residual stresses.
Study on the Cause and Nondestructive Test of Backside Cracks in Stainless Steel Linings
Authors: Cao Huai-xiang , Wang Chun-mao , Qiu Xing-qi
Published: August 2013

In this paper, the cause and nondestructive test technology of backside cracks were studied. On the one hand, failure analysis revealed that, the backside cracks, which were found universally in the stainless steel inner linings of urea reactors in recent years, were caused by the interaction of wet hydrogen sulfide (H2S) and chloride ions (Cl−) stress corrosion cracking (SCC), and the source of the H2S and Cl− was the leak detection steam. On the other hand, the use of Lamb wave inspection was studied because of the inapplicability of other inspection methods. The dispersion curves of phase and group velocities of 316LMod stainless steel linings were derived out according to the Rayleigh-Lamb equation. The main Lamb wave mode of the backside defects was drawn out by 2D FFT to echo signals of the test plate including artificial defects. Then, the Lamb wave testing parameters of 8mm 316LMod stainless steel were defined. The defect equivalent evaluation diagram was given through the defect recognition of the test plate including artificial defects. And the quantitative evaluation of Lamb wave inspection to the backside defects was realized. After all the analysis done, the measures to avoid backside cracks were put forward, and the inspection technology was verified by applications on urea reactors.
Effects of Scattered Bolt Preload on the Sealing Performance of Pipe Flange Connection With Gaskets Under External Bending Moment and Internal Pressure
Authors: Sawa Toshiyuki , Takagi Yoshio , Sato Koji , Omiya Yuya , Doi Hayato
Published: August 2013

Bolted pipe flange connections have been widely used in mechanical structures such as oil, chemical plants and so on. Sometimes leakage accidents occur from the connections. In assembling the pipe flange connections, the bolt preloads are scattered and then the connections are subjected to external bending moment due to earthquake as well as internal pressure. In the present paper, the changes in the axial bolt forces are measured in assembling. The bolts are tightened with torque wrench. Using the history of the bolt force changes, the gasket stress distributions on the connection with gaskets are analyzed using FEM. Then the gasket stress distributions on the connections under external bending moment and internal pressure are analyzed. Using the gasket stress distributions, the amount of leakage of the connections is estimated while the basic gasket characteristics have been measured according to JIS B 2251. The amount of leakage of the connection was measured for the various gasket stresses. The estimated results are in a fairly good agreement with the measured results. It is found that the effect of the scatter of bolt preload is substantial on the sealing performance of the connections. Discussion is made on the sealing characteristics of the connections. The change of axial bolt force obtained from experimental result and FEM result are fairly good agreement.
Improvement of Extracted Volume of Sugarcane Using Underwater Shock Wave
Authors: Shimojima K. , Naha K. , Miyafuji Y. , Kuraya E. , Watanabe K. , Itoh S. , Takemoto A.
Published: August 2013

The productivity improvement of food is necessary because the rate of food self-sufficiency of Japan is low. And then, the high efficient food processing is developed in Japan. On the other hand, the ratio of the production of sugarcane is high in the primary industry in Okinawa Prefecture. The rate of profit in the sugar manufacturing by sugarcane is lower than other primary industry goods, because the production cost is high. In this research, the sugar manufacturing method by sugarcane in high efficiency was developed using underwater shockwave. In this paper, to crush hard food like sugarcane, the pressure vessels of three dimensional oval structure is proposed. It is clear that the effect of the improvement of the juice extraction rate using the pressure vessel.