bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of High Energy Absorbing Seismic Tie With I-Sectional Shape for Thermal Power Boiler Structure
Authors: Aida Kiyoshi , Kawamura Kotaro
Published: January 2014

This paper deals with new types of steel seismic ties, which are energy absorbing devices installed between boiler and its support structure. To enhance the aseismic reliability of the boiler and its support structure, energy absorbing capacities of the seismic ties must be increased. To increase the capacities, sectional shapes of the seismic ties have been optimally designed. Concretely, I-section seismic ties as new types have been gained by optimizing the design parameters, material (conventional carbon steel and low yield strength steel), sectional height, web thickness, flange thickness under conditions to maximize absorbing energy and to restrict the reaction force equal to or smaller than that of round-section current seismic tie. As a result of cyclic load testing using 1/3 scale model, it was verified that energy absorption of the new types of seismic ties were 16–23 % larger than that of the current seismic tie.
Numerical Prediction of Pressure Gradient of Slurry Flows in Horizontal Pipes
Authors: Messa Gianandrea Vittorio , Malin Michael , Malavasi Stefano
Published: January 2014

Pipe flows of solid-liquid mixtures in the form of slurries are frequently encountered in many engineering applications. The pressure gradient is perhaps the most serious concern of designers, as it dictates the selection of pump capacity. Due to their versatility, in the sense of applicability to large scale systems and more complex flows, CFD models have been an attractive tool in recent years. The fully-suspended flow of solid-liquid slurries in horizontal pipes is simulated by means of a two-fluid model. In particular, the effect of the wall boundary condition for the solid phase on the pressure gradient is discussed, considering different alternatives. The numerical predictions were compared to experimental measurements from open literature over a wide range of operating conditions, in terms of pipe diameter (53.2 to 103 mm), grain material (glass beads and sand), particle size (90 to 370 μm), slurry velocity (1.5 to 8 m/s), and mean solids concentration (up to 40%). The equilibrium wall function of Launder and Spalding for smooth walls proved adequate for fully-suspended flows, but overestimates the losses if the particles are large compared to the boundary layer thickness. Guidelines are provided for defining the numerical set-up and evaluating the uncertainty of the numerical results.
Comparison of Metal Temperatures Obtained From Conjugate Heat Transfer CFD Analysis and Thermal Finite Element Analysis of a Valve
Authors: Bowie Gareth , Fletcher Andrew , Reed Gary , Davenport Lewis , Hugill Peter
Published: January 2014

This paper describes the results of a three dimensional Computational Fluid Dynamics (CFD) simulation of a rapid temperature increase in liquid water flowing through a relief valve, using Conjugate Heat Transfer (CHT) to predict the solid domain temperatures.

Surface Heat Transfer Coefficient (HTC) and bulk fluid temperature histories extracted from this simulation have been applied to a thermal structural Finite Element (FE) analysis of the valve body, providing an additional set of solid domain temperatures for comparison.

The aim of this paper is to compare the precision of the solid domain temperatures predicted by the CHT and HTC/FE simulations.
Long Term Performance of PE4710 Materials in Disinfectant Treated Nuclear Raw Water Systems
Authors: Summe Alexander M. , Munson Douglas P. , Oliphant Kenneth , Chung Sarah
Published: January 2014

Degradation of service water systems is a major issue facing nuclear power plants and many plants will require repair or replacement of existing carbon steel piping components. High-density polyethylene (HDPE) has been used in non-safety service water systems for over ten years and has demonstrated superior performance. However, there still exist knowledge gaps around material properties, inspectability, and long-term performance. Specifically, there is a lack of insight on the aging of HDPE piping in disinfectant treated service water systems. This paper summarizes the methodology and results of predicting the expected life time of HDPE piping exposed to oxidizing biocides in numerous end-use scenarios. The aging mechanism of concern is Stage III Chemical-Mechanical degradation, where the polymer is oxidized by biocides and then experiences slow crack growth (SCG). An Aging Model is used to provide general predictions of pipe service life. The results were analyzed for trends and limiting or sensitive operating parameters were identified. For most applications, the specific resin used in the model demonstrated good performance for lifetimes of well over 40 years.
Three-Dimensional Finite Element Analysis of Rigid Flanged Shaft Coupling Subjected to Twisting Moment
Authors: Okayama Koichi , Fukuoka Toshimichi
Published: January 2014

A reamer bolt is commonly used when clamping a rigid shaft coupling subjected to large shear force. Although some joint design procedures assume that the applied shear force transmits only through the reamer surface, it is also supported by the friction force on the contact surfaces. Accordingly, to design the coupling clamped by reamer bolts, it is important to evaluate the ratio of the shear forces supported by the reamer surface and the friction force, which is defined as shear force transfer ratio (SFTR) here.

In this study, distributions of SFTR and the bending stresses along the reamer surface are analyzed by three-dimensional FEM, focusing on the effects of the fit between the reamer bolt and bolt hole, the scatter of initial bolt stress and the misalignment of the connecting shafts. Numerical results quantitatively clarify how the amounts of the SFTR and the bending stresses as the friction coefficients, the fit and the magnitude of misalignment are changed. As for an offset misalignment, it is found that its effect on the bending moment generated in the shaft body is negligibly small, if the offset between two shafts in radial direction is less than 10mm which is 1% of the total shaft length.
Behavior of Flange Joints Under Combined Internal Pressure and Thermal Loading: The Case of Using Metal-to-Metal Contact Type Gaskets
Authors: Ma Kai , Zhang Yi , Zhang Lanzhu , Guan Kaishu
Published: January 2014

In a bolted flange joint, metal-to-metal contact type gasket takes over only part of the bolt load to achieve seating stress, and the additional bolt load is transmitted to the metal-to-metal contact to compensate for the unloading effects due to internal and external loadings. Due to this advantage, flange joints with metal-to-metal contact type gaskets are gradually used in chemical industry, nuclear power industry, etc. A three-dimensional nonlinear finite element model is developed to highlight the complex behavior of the flange joint with metal-to-metal contact type gasket under combined internal pressure and thermal loading. Despite of the common perception that the gasket stress in the metal-to-metal contact type gasket stays constant, reduced gasket stress is concluded due to flange rotation and joint thermal expansion.
Study on Seismic Assessment of Mechanical Members Focused on Energy
Authors: Seki Hajime , Fujita Satoshi , Minagawa Keisuke
Published: January 2014

Generally, mechanical members are required to be highly safe to withstand a lot of earthquakes. Specially, seismic evaluation and design techniques for mechanical members have been required in earthquake-prone countries. According to studies on failure of pipes, the critical load due to earthquake is a cyclic loading. Therefore, the design techniques that are able to evaluate cumulative damages is needed. Recently, relationship between failure and energy has been examined by paying attention to the Energy Balance equation which is said to be effective as an earthquake response analysis technique. This study carries out failure experiments using simple mass point models having various cross section based on Energy Balance Method. Although the target model in our earlier study was a simple single degree of freedom model of hundreds of gram order, in order to perform detailed earthquake-proof evaluation for actual mechanical members, examination by large mass type models is needed. The consideration of the influence of the section modulus or the moment of inertia area on the energy required to failure is examined by using the model on the order of tens of kg, by focusing on the local response for the strain at the point of failure.
Definition of a Cut-Off Natural Frequency for Small Bore Pipework Connections
Authors: McGhee James S. G. , MacDonald Stanislav , Hamilton John P. , Wally Gernot
Published: January 2014

Vibration induced fatigue failures (VIFF) of pipework small bore connections (SBCs) due to turbulent flow excitation continue to occur in process piping systems, resulting in elevated safety risks and costly interruptions to normal operations. One of the primary causes of these failures is poor design.

When the valve and pipe components in an SBC assembly combine to produce a fundamental natural frequency that is low, the SBC can readily be excited into a high vibration condition. In this high vibration condition, the threat of VIFF increases significantly. One of the primary design goals for SBCs should therefore be to achieve a high natural frequency, however, this is very rarely considered in the existing design process. Reasons for this include the lack of understanding of the importance of natural frequency to the vulnerability of the design and a lack of information on how high this target natural frequency must be when it is considered.

In this paper, the concept of a cut-off natural frequency is defined, above which the probability of VIFF of SBCs is negligible. If this concept is incorporated into the design process for SBCs a decrease in the number of failures of SBCs due to vibration should be realised.
Prediction of Pipe Girth Weld Residual Stress Profiles Using Artificial Neural Networks
Authors: Mathew Jino , Moat Richard J. , Bouchard P. John
Published: January 2014

Defect assessment procedures such as BS7910, R6 and API 579-1 provide bounding profiles that can be used to characterise the residual stresses present in a weld. The bounding profiles in BS7910 and the R6 procedure have been based on examination of residual stress measurements and expert judgment. This approach suffers from the drawback that the upper bound curve can increase as more measurements and data scatter are obtained. The consequence of this is that structural integrity assessments of defective plant can be over-conservative by a large margin, and may lead to unnecessary and costly repair or inspection. This paper presents work exploring the use of artificial neural networks to predict more realistic residual stress profiles in austenitic stainless steel pipe girth welds. The network is trained using a set of baseline experimental stress data and then tested using previously unseen data. The committee of networks has been implemented and optimised using a maximum likelihood based algorithm. The neural network is validated by comparing predictions with neutron diffraction residual stress measurements of two girth welds 25 mm thick produced using different welding parameters. The capability of the neural network approach is discussed by comparing predictions with stress profiles recommended in the R6 procedure and its potential for development evaluated.
The Qualification of BWR Steam Dryer Weldments Exposed to Cyclic Loading Using Finite Element Methods
Authors: Breach Michael R.
Published: January 2014

The qualification of welds other than full penetration groove welds exposed to cyclic loading using finite element methods requires an understanding of the basis behind classical methodologies. These methodologies usually address nominal stresses.

The nominal stress (S-N) method was the first approach developed to try to understand this failure process and is still widely used in applications where the applied stress is nominally within the elastic range of the material and the number of cycles to failure is large. From this point of view, the nominal stress approach is best suited to that area of the fatigue process known as high cycle fatigue. Cracks and discontinuities will cause stress redistribution and concentrations leading to secondary and peak stresses additive to the nominal stress when referencing the S-N curves.

Therefore, fundamental to the qualification of weldments of components and structures is the determination of the nominal stress field; however, this can be problematic for several reasons:

• Secondary, Peak stress arising from structural discontinuities can mask the actual nominal stress field.

• There may be an insufficient number of elements and/or integration points through the thickness to rely on linearization techniques, to separate the nominal stresses from the secondary and peak stresses due to the high cost of using bricks or tetrahedrons.

• In complex shell structures, the nominal stress field in weldments that satisfies equilibrium against externally applied loads is not readily distinguished; this is due to the shear preponderance of mesh sensitive discontinuities.

Herein, is a summary of methods to address the aforementioned problem and guidance in determining the true peak stresses and their qualification. Methods documented in ASME BPV Code Section VIII Div. 2, and various papers are compared. These methods will be used to assess existing methods that may be used in the industry. ASME BPV Code Section III Subsections NG and NB will be used as a basis to classify and qualify the weldment stresses.
Simulating Explosive Detonations Within Multiroom Buildings
Authors: Vaughan David , Mould John , Levine Howard , Tennant Darren
Published: January 2014

The detonation of an explosive charge within a building produces complex propagating blast pressures that are strongly influenced by the building’s room layout and construction of interior walls. This paper looks at the effects of internal blast on common, non-structural steel stud or wood stud walls and unreinforced CMU walls in various multi-room configurations. Their blast response is investigated through experimental and numerical models with the goal of quantifying the blast pressure propagation into rooms adjacent to the blast. Risk assessments to power generation facilities should consider the potential for an explosive event within control buildings or other support facilities. These events could be an accidental explosion or the result of a terrorist action. A better understanding of the failure mechanisms and pressure transmission characteristics of typical power generation facility structures will lead to improved vulnerability assessments of these types of structures and the critically important control equipment located within them.
Ductile Tearing Prediction in Welds Considering Hydrogen Embrittlement
Authors: Robin Vincent , Gilles Philippe , Mourgue Philippe , Tchoukien David
Published: January 2014

Some flaws may appear in metal components, in the weld region, and more especially in the case of electron beam girth weld in the slope area of the process (start and stop of the welding operation). These initial flaws can growth with delay even without any external loads. Indeed close to the junction, the material undergoes the combination of high tensile residual stresses due to welding operation and the presence of hydrogen brought by manufacturing process. Hydrogen assisted cracking is then suspected to explain the origin of crack growth through hydrogen embrittlement of the base metal.

To understand by numerical modeling, at least qualitatively, the scenario of appearance of such cracks and their evolution, without any external load or under pressure load, the proposed approach consists first in simulating the welding process and its consequences on residual stress distribution and hydrogen concentrations [1]. The hydrogen diffusion computation is pursued after the welding operation simulation in order to highlight the most critical moment at which macroscopic defects may appear. Then, a macroscopic defect is created in the so determined critical zone, the stability of which is studied by estimating the energy release rate at the crack front and by comparing these values with experimental data such as the critical energy release rate at initiation and the tearing resistance curves which may depend on the hydrogen content. So, it is numerically possible to propagate the defect in the time, considering hydrogen diffusion and residual stress rebalancing, by successive crack front definition performed as the crack tip region exceeds the critical energy release rate [14]. Finally, the evolution of the defect is estimated in the same way under pressure test loading conditions. Results and discussions are presented to propose an engineering approach for the design assessment of such specific weld junctions with a low and hydrogen dependant toughness.
Investigations on Crack Propagation Under Cyclical Isothermal and Thermo-Mechanical Loadings for a Type 304-L Stainless Steel Used for Pressurized Water Reactor
Authors: Gourdin C. , Rossillon F. , Le Delliou P. , Perez G. , Fissolo A.
Published: January 2014

The integrity of structures exhibiting flaws in Pressurized Water Reactor (PWR) has to be assessed to meet safety criteria. This paper deals with crack-propagation under cyclic thermo-mechanical loadings, as encountered in class I austenitic pipes of PWR’s. To have a conservative and reliable assessment of the crack propagation due to the in-service loading, various codes and standards use simplified method. For example, RSE-M introduces a plastic correction depending on the proportion of the mechanical loading. An improvement of the current method requires additional investigations. Moreover, components loaded with transient or thermal fluctuations are not really in strength-controlled conditions.

To this end, a new device called “PROFATH” was designed. The specimen is a pre-cracked thick-walled tube undergoing a set of thermal cycles and loaded with a static mechanical force. During the first part of the cycle, a high frequency induction coil heats the external wall. Then, the heating system stops and the specimen is cooled down by running water inside the tube. Finite element calculations show that only a region half-way along the tube should be heated to ensure adequate structural effect. In the heated zone, the machining of a sharp circumferential groove ensures the propagation of a unique crack. An electro-mechanical jack controls the level of the mechanical static load.

To obtain a very precise thermal mapping, a specific specimen with dedicated instrumentation is used: 20 thermocouples are appropriately located on the outer surface and along the wall thickness. During the test, the crack-propagation is estimated through crack-opening measurements (compliance method). To improve actual measurements, installation of a laser extensometer sensor is now in progress.
Validation of Plastic Collapse Assessments Using BS 7910:2013 and R6 Procedures
Authors: Eren Şefika Elvin , London Tyler , Yang Yang , Hadley Isabel
Published: January 2014

The British Standard, BS 7910 Guide to Methods for Assessing the Acceptability of Flaws in Metallic Structures is currently under revision [1]. Major changes have been undertaken, especially in the fracture assessment routes, and this paper specifically addresses the assessment of proximity to plastic collapse, usually expressed as the parameter Lr via either a reference stress or limit load approach.

In the new edition of BS 7910, the reference stress approach has been retained for the assessment of many geometries, mainly for reasons of continuity. However, new limit load solutions (originating in the R6 procedure) are given for use in the assessments of strength mismatched structures or clad plates.

In general, a reference stress solution and a limit load solution for the same geometry should deliver the same value of Lr. However, recent comparative studies have shown differences in the assessment of plastic collapse depending on whether the reference stress solutions in BS 7910:2013 or the limit load solutions in R6 are used for the calculation of Lr.

In this paper, the extent of the difference in the assessment results with respect to the choice of solutions and boundary conditions are discussed. The results of the assessments in accordance with BS 7910 and R6 are compared with the results of numerical assessments obtained via Finite Element Analysis (FEA).

The collapse loads observed in various wide plate tests conducted in the last 20 years are also compared with the collapse loads predicted by BS 910:2013, R6 and FEA.

Finally, observations regarding the accuracy of different Codes and FEA are discussed.
Microstructural Modelling of P91 Martensitic Steel Under Uniaxial Loading Conditions
Authors: Golden Brian , Li Dongfeng , O’Dowd Noel
Published: January 2014

The changing face of power generation requires an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through microstructurally motivated modelling studies. This paper deals with the comparisons of predictions of the mechanical response of a power plant steel (P91), obtained from a model with a measured microstructure with those obtained from a numerically simulated microstructure. Electron backscatter diffraction (EBSD) is employed to obtain the orientation of the martensitic grain structure of the steel. This information is incorporated within a representative volume element (RVE) to represent the material microstructure. A non-linear, rate dependent, finite strain crystal plasticity model is used to represent the deformation of the material, with the orientation of each finite-element integration point determined from the EBSD analysis. The deformation under uniaxial tension is analysed. Due to the inhomogeneous microstructure strong strain gradients are generated within the RVE even under remote homogenous strain states. It is seen that peak stress/strain states are associated with particular features of the microstructure. The results taken from the model are compared with those obtained with an equiaxed microstructure generated using the Voronoi tessellation method.
The Influence of Geometry on Residual Stress Around Repair Welds
Authors: Walsh Joanna N. , Mark Alison F. , Abdolvand Hamid , Francis John A. , Pellereau Ben , Bate Steve , Hofmann M. , Withers P. J.
Published: January 2014

Residual stress mitigation is a key strategy in the design and manufacture of nuclear power plant components for the prevention of component failure and the extension of power plant lifetimes. Repair welds comprise significant non-steady-state features that contribute to complex residual stress profiles that must be understood, modeled and minimized to ensure the efficiency of the repair. This is of particular importance given that in-situ measurement, and post weld heat treatment of residual stress profiles in repair welds is often impractical. Previous work indicates that the highest stresses accumulate at the ends of the repair where the weld pass stops overlap. Here we present a series of neutron diffraction measurements on two three-pass slot welds with different end slope angles to determine the effect of staggering the weld pass stop locations. It is shown that significant reductions in peak stresses can be made by decreasing the steepness of the end of the slot to stagger the weld stop locations for different beads. Additionally, these are the first reported measurements of residual stress in the new SA508 grade 4N steel which has been designed for deployment in future advanced PWR systems.
Closed-Form Calculation of Stress Intensity Factor for an Axial ID Surface Flaw in Cylinder Subjected to Weld Residual Stresses
Authors: Scarth Douglas A. , Xu Steven X.
Published: January 2014

A method for calculating the stress intensity factor for linear elastic fracture mechanics based flaw evaluation is provided in Appendix A-3000 of ASME Section XI. In the 2010 Edition of ASME Section XI, the calculation of stress intensity factor for a surface crack is based on characterization of stress field with a cubic equation and use of influence coefficients. The influence coefficients are currently only provided for flat plate geometry in tabular format. The ASME Section XI Working Group on Flaw Evaluation is in the process of rewriting Appendix A-3000. Proposed major updates include the implementation of explicit use of Universal Weight Function Method for calculation of the stress intensity factor for a surface flaw and the inclusion of closed-form influence coefficients for cylinder geometry. The explicit use of weight function method eliminates the need for fitting polynomial equations to the actual through-thickness stress distributions at crack location. In this paper, the proposed Appendix A procedure is applied to calculate the stress intensity factors in closed-form for an axial ID surface flaw in a cylinder subjected to a set of nonlinear hoop weld residual stress profiles. The calculated stress intensity factor results are compared with the results calculated based on the current method in Appendix A using cubic equations to represent the stress distribution. Three-dimensional finite element analyses were performed to verify the accuracy of the stress intensity factor results calculated based on the current and proposed Appendix A procedures. The results in this paper support the implementation of the proposed stress intensity factor calculation procedure into ASME Code.
Recent PWAS-SHM Developments in the Laboratory for Active Materials and Smart Structures
Authors: Giurgiutiu Victor
Published: January 2014

This paper will present recent results obtained in the Laboratory for Active Materials and Smart Structures in the development of piezoelectric wafer active sensors (PWAS) technologies for structural health monitoring (SHM) applications. One development consists in a carefully conducted study of the convergence of commercially available finite element method (FEM) codes used in the simulation of guided waves traveling in thin-wall structures. Furthermore, the interaction of these waves with various types of damage was studied with the FEM method and compared with experimental results. Another development consists in an analytical model for the prediction of the interaction between PWAS-generated guided waves and structural damage. This topic has been developed and coded in a MATLAB GUI under the name of Wave Form Revealer (WFR). The WFR software allows for the linear and nonlinear analysis of multimodal guided waves in interaction with various damage types characterized by damage interaction parameters. The study of energy transduction between the PWAS and thin-wall structure subjected to guided wave SHM was undertaken in the context of multiple guided wave modes and very interesting energy tuning principles for optimal power consumption have been developed. The paper ends with conclusions and suggestions for further work.
Aging Management of French PWR Nuclear Steam Generators Using Statistical Modeling
Authors: Chaudhary Amit , Mathon Cédric , Gay Nadine
Published: January 2014

Electricité de France (EDF) has recently announced its intentions to extend the lifetime of some of its plants to 60 years which has lead to a large advance order of steam generators (SG) and therefore an intensive period of replacement. The detailed planning required during a shutdown and the industrial constraints for design and manufacturing necessitate the decision for a replacement to be taken a few years in advance. Predicting the end of life of a SG is principally governed by the level of degradation of the tube bundle which is largely dependent on the tube material and time in service. EDF carries out a risk assessment on the life of each SG based on the percentage of tubes plugged determined using statistical modeling that take into account factors such as the evolution and type of degradation. In addition, SG tube plugging rates have to be anticipated in advance to ensure the heat exchange capacity is within safety guidelines. This paper provides an overview of the status of active degradation growth rates and different calculation methods used at units with A600TT and A690TT tubing. Furthermore, their application on predicting the number of tubes to be plugged is illustrated. Finally, statistical models used to predict the evolution of different degradation types are also detailed.
PLiM Lessons After Fukushima
Authors: Rothenhöfer Horst
Published: January 2014

After each severe nuclear incident new safety requirements arise. So the desirable action list gets longer and more specific every time. On the other hand way too many plants have not yet implemented lessons learned from past incidents. The challenge is to prioritize required and desirable measures and implement them incrementally in the sense of continuous improvements.

In parallel, there is the plant life management process (PLiM) that gives the framework for single measures. Each remarkable event has to be assessed with PLiM criteria. Could the event have been prevented by implementing the state of the scientific and technical knowledge or has something happened that requires an update of this knowledge?

Some details of the Fukushima event are discussed in the paper. These examples demonstrate that safety can be improved just by the application of proven practices which some operators have applied many years before the Fukushima incident. More examples, not only from the Fukushima incident are given in the paper.

The conclusion of all these details is that it is necessary to share and implement best practices in a continuous PLiM process rather than defining new safety requirements after single severe incidents. Nuclear safety primarily does not require new knowledge but to take responsibility and implement measures according to available knowledge. This insight links PLiM to the need for an appropriate safety culture, both of which are prerequisite for nuclear safety.

The motivation for operators to implement these practices is not only to improve safety but to maximize uptime of a plant and deciding for relevant measures which pays back the money invested in the long run.
Nondestructive Testing Method and Testing Time Choice of Pressure Equipment
Authors: Guan Weihe , Chen Xuedong , Yan Changzhou , Fan Yu , Tao Yuanhong
Published: January 2014

The engineering risk of pressure equipment is closely related on the structure and material of equipment as well as the parameters such as pressure, temperature, medium environment, etc., which it withstands. In order to reduce and control the engineering risk of the pressure equipment, appropriate nondestructive testing method and testing chance must be adopted at the stages of design, manufacture and installation to control the product quality and assess its safety status at the operation stage of pressure equipment. In this paper the importance of nondestructive testing method and chance selection for pressure equipment is discussed based on engineering cases. This paper shows that nondestructive testing technique is an important means for product quality control of pressure equipment and is also important guarantee for its safe operation. Under the condition that appropriate nondestructive testing method and testing chance are selected, the engineering risk of pressure equipment can be minimized.
Failure Prediction of Curved Wide Plates Using the Strain-Based Failure Assessment Diagram With Correction for Constraint and Notch Radius
Authors: Horn Anthony J. , Trull Mikhail , Hertelé Stijn
Published: January 2014

The strain-based failure assessment diagram (SB-FAD) has been developed for predicting failure from flaws in components subjected to high plastic strains. In this paper, a combined numerical and experimental approach is used to apply the SB-FAD to predict failure from a series of API 5L grades X80 and X100 curved wide plate (CWP) specimens with shallow notches machined into the pipe girth weld. For the CWP specimens tested in this work, the SB-FAD in its unmodified form resulted in over-conservative predictions of failure. This is attributed to the SB-FAD assuming high constraint conditions and the presence of a sharp fatigue crack, whereas the CWP specimens tested in this work were low constraint and contained a shallow machined notch without fatigue cracks. A modification of the SB-FAD is then proposed to account for non-sharp defects loaded to high plastic strains under conditions of low constraint. The resulting predictions of the modified SB-FAD show significantly reduced conservatism compared to the unmodified SB-FAD.
Investigating the Influence of Fluid-Structure Interaction on Leak-Before-Break Analyses With a New Finite Element Method
Authors: Gill Peter J. , Sharples John , Davey Keith
Published: January 2014

This paper describes a new finite element method to analyse Leak-before-Break using the extended finite element method (XFEM). Traditionally, a Leak-before-Break analysis is performed using a methodology outlined in a Structural Integrity Assessment Procedure such as R6. This may achieve sufficient accuracy for the application of interest. However, there may be times when finite element (FE) analysis is required. With this in mind, a finite element model has been developed in which all the physics of the crack and leak rate is bundled into a special element, with only the crack size and position, external loads and fluid properties required as an input. All the meshing and leak rate calculation is dealt with by the code. This means that Leak-before-Break procedures can be performed more efficiently, even if FE modelling is required. The element was implemented in MATLAB and then used to investigate thermo-mechanical behaviour of a leaking thermo-fluid in a plate. For bulk fluid temperatures 20°C hotter than the structure, it was found that the leak rate was reduced by 40% due to crack closure.
Wave Propagation in Tapered Vessels: New Analytic Solutions That Account for Vessel Distensibility and Fluid Compressibility
Authors: Papadakis George
Published: January 2014

The central aim of this paper is to contribute to the understanding of the effect of vessel tapering on the propagation of pressure and velocity wave forms. It presents new analytic solutions for the temporal and spatial variation of these two variables that account for weak fluid compressibility. It extends previous work of the author in which only the effect of wall deformation (i.e. vessel distensibility) was taken into account. The solutions are derived in the frequency domain and can account for the steady solution component (d.c. component) obtained by taking the asymptotic value for very low frequencies. It is shown that the effect of compressibility makes the equations more complex but it is still possible to derive closed form analytic solutions in terms of Bessel functions of orders 1/3 and 4/3. The analytical solutions are compared with 3D FSI simulations for the case of propagation of a step pressure variation at the inlet of a tapered vessel. Good agreement is observed between the 1D analytical and 3D numerical solutions.
IAEA Activities on Concrete Ageing in Containment and Other Structures in Nuclear Power Plants
Authors: Kang Ki-Sig , Moore John H.
Published: January 2014

Significant industry developments over the past decade have placed concrete ageing at the forefront of life extension decisions related to nuclear power plants. Recent issues encountered include alkali–silica reactivity in concrete, delamination events, larger than anticipated loss of pre-stressing force, spent fuel pool leakage, corrosion of steel reinforcement in water intakes, and others.

Concrete structures at nuclear power plants are being asked to perform for longer periods than originally design life. Utilities around the world are investigating plant service life extensions (with 60 years or more total being a quoted target), and for some projects delayed construction schedules, and/or decommissioning strategies that involve the use of containment as a “safe store” for periods of up to 100 years, mean that containment buildings and other concrete structures often have to perform their functions for a time period significantly greater than their initial design life. Newer plants are designed with design lives of 60 years or more.

Concrete is a durable material and its performance as part of the containment function in NPPs has been good. However, experience shows that ageing degradation of concrete structures, often caused or accelerated by factors such as faulty design, use of unsuitable or poor quality materials, improper construction, exposure to aggressive environments, excessive structural loads, and accident conditions, can impair its safety functions and increase risks to public health and safety. Effective ageing management of concrete containment buildings and other concrete structures is therefore required to ensure their fitness-for-service throughout the plant service life and during decommissioning.

The paper presented will present current International Atomic Energy Agency activities in the area of concrete structures and ageing management, and point to where guidelines and best practises related to concrete structure ageing management, relevant operating experience, and applicable codes and standards may be located.
Life-Cycle Cost Assessment of Seismically Base-Isolated Large Tanks in LNG Plants
Authors: Wang Hao , Weng Dagen
Published: January 2014

A new methodology is being introduced to address the life-cycle cost (LCC) of base-isolated large liquefied natural gas (LNG) tanks. The relationship between LCC and seismic fortification intensity is established to evaluate how much reduction of earthquake force can minimize the LCC. Each composition of LCC is analyzed including the initial cost, the isolators cost and the excepted damage cost. The isolators cost consists of the cost of lead rubber bearings and dampers. The cost of lead rubber bearings is proposed proportional to its volume and the cost of dampers is not only related to its maximum displacement but also to its tonnage. The concept of seismic intensity is being used to estimate the expected damage cost, greatly simplifying the calculation. Moreover, a tank in a LNG receiving terminal in China is employed as an example to assess its LCC in isolated and non-isolated situation respectively. The results show that the proposed method is efficient and the expected damage cost is enormously reduced because of the application of isolators, which leads to the reduction of the LCC of the tank.
Residual Stress Analysis of In-Service Welded Gas Pipelines
Authors: Koch Felix , Kuna Meinhard , Hübner Peter , Enderlein Marco
Published: January 2014

Maintenance work and extension of gas pipelines have to be done mostly with the pipeline being in operation to ensure continuous network coverage. Therefore, in-service welding operations are inevitable for both situations. The present paper focuses on a circumferential fillet weld connecting a high-pressure gas pipeline with a T-fitting, which is suitable for stoppling and the construction of connection branches. Against the background of safety assessment and process optimization the welding procedure is investigated by means of experiment and simulation. The simulation is based on the finite element method and predicts the temperature field as well as the evolution of the microstructure and the residual stresses during welding and cooling. The heat input during welding is modeled using the double ellipsoid heat source by Goldak, which is adapted to multi-pass welding and implemented in the commercial software ABAQUS. The microstructure evolution is analyzed by a phase transformation model based on the Avrami equation. A subsequent stress analysis provides results regarding the residual stresses. The simulation is validated by welding experiments dealing with a three-pass fillet weld. The experimental and numerical results are presented and compared by means of macrosections and thermocouple measurements.
Application of Common Basis Stress Evaluation Methodology for Environmentally Assisted Fatigue for a Pressurized Water Reactor
Authors: Weitze William F. , Gilman Timothy D. , Drenth Lora
Published: January 2014

United States (US) Nuclear Regulatory Commission (NRC) report NUREG-1801, the Generic Aging Lessons Learned (GALL) Report [1], identifies acceptable aging management programs, including programs for fatigue and cyclic operation, and is used by the NRC to evaluate license renewal applications. This includes fatigue usage analyses that account for reduced fatigue life for components in a reactor water environment. Originally, it was considered acceptable for the purpose of license renewal to evaluate only the sample locations identified in NUREG/CR-6260. Recently, however, the NRC staff has been requesting license renewal applicants to demonstrate that the locations identified in NUREG/CR-6260 are the limiting locations for environmentally assisted fatigue (EAF), such that EAF evaluations are limited to the NUREG/CR-6260 locations. Any locations not bounded by the NUREG/CR-6260 locations would then be specifically addressed. A methodology has been developed for EPRI, called common basis stress evaluation (CBSE), to perform simplified stress and fatigue usage analyses in a consistent manner such that many locations can be compared for fatigue usage with and without the use of EAF, even if prior analyses of these locations were not consistent in level of detail, and even if some locations have never been evaluated for fatigue usage. This paper presents the first application of this methodology.
A New Experimental Approach for Measuring Friction Coefficients of Threaded Fasteners Focusing on the Repetition of Tightening Operation and Surface Roughness
Authors: Fukuoka Toshimichi , Nomura Masataka , Kawabayashi Hiromu
Published: January 2014

Torque method is widely used when tightening threaded fasteners. Although it has a great advantage of easy operation, the scatter of bolt preloads inevitably occurs due to the scatter of friction coefficients. Friction coefficients on the contact surfaces are affected by various factors such as joint materials, surface roughness, tightening speed, etc. To evaluate the effects of those factors with high accuracy, experimental errors must be suppressed as low as possible.

In this study, a new simple test equipment for measuring the friction coefficients is designed, in which the strain gages are attached to the equipment to eliminate the experimental errors caused by the gages being attached to each test specimen. Using the equipment, friction coefficients on the thread surface and nut loaded surface are measured separately. Experimental results show that the surface roughness has a smaller effect when using threaded fasteners made of stainless steel than the case of carbon steel fasteners. As for the repetition of tightening operations, it is found that the removal of metal power, which is generated by the galling between the mating surfaces, is effective for reducing the scatter of friction coefficients.
Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (2) Development of the Material Strength Standard of 316FR Stainless Steel
Authors: Onizawa Takashi , Nagae Yuji , Takaya Shigeru , Asayama Tai
Published: January 2014

This paper describes the material strength standard of 316FR stainless steel in the design code for fast reactors of 2012 edition published by the Japan Society of Mechanical Engineers. 316FR stainless steel is to be used for a reactor vessel and internals for the Japan Sodium Cooled Fast Reactor (JSFR). 316FR was developed in Japan by optimizing chemical composition within the specifications of SUS316 in the Japanese Industrial Standard which is equivalent to Type 316 stainless steel. The optimization was performed from the viewpoint of maximizing the creep resistance under fast breeder conditions. Application of 316FR stainless steel to JSFR needs the material strength standard. Therefore, the authors developed the material strength standard. The material strength standard involved allowable limits such as S0, Sm, Su, Sy, SR and St and so on, environment effects such as irradiation effects and sodium effects. In addition, material characteristic equations (Creep rupture equation, creep strain equation and equation of best fit curve for low-cycle fatigue life and so on) necessary for the allowable limits were involved. This paper describes the contents of the material strength standard.
Capacity Analysis of PE Pipeline With Non-Planar Defect
Authors: Jiang Weijie , Zhao Jianping , Chen Dingyue
Published: January 2014

A tensile test of buried PE pipe is designed to test the mechanical performance. Then the constitutive model for the PE pipe can be established. The limit load of the PE pipe with local thinning defect can be studied with the method of combining the orthogonal design of experiment and finite element analysis. Then the factors of local thinning defect pipe limit load factors can be analyzed. The results show that the depth of the defect has a great effect on the limit load (internal pressure and bending moment) of PE pipe. The effects that the axial length of the defect and the circumferential length of the defect have on the limit load are not significant.
Measurement of Elastic Follow-Up for Combined Applied and Residual Stresses
Authors: Horne Graeme , Peel Matthew J. , Smith David J.
Published: January 2014

Tensile residual stress can reduce the load carrying capability of a structure. However, residual stresses may be redistributed during the life of a component by, for example, permanent deformation. This paper explains an experiment carried out to understand how applied and residual stresses interact and to seek a method of measuring elastic follow-up during the interaction. A friction stir welded aluminium alloy plate was subjected to a series of incrementally increasing load and unload cycles, whilst simultaneously measuring residual stresses and deformation. In-situ loading of the specimen during the residual stress measurements allowed the relaxation of the residual stress to be quantified. The elastic follow-up has been estimated and measured by considering both the structural stiffnesses of the specimen and the relaxation of the residual stress. It was found that global yielding, which can result in no net change of incompatibility, has to be considered when calculating elastic follow-up. An estimation of the elastic follow-up factor based on the structural stiffnesses of the specimen was found to be non-conservative and an elastic follow-up factor of 2.9 was measured. That is three times as much plastic strain is required to relax the residual stress when compared to the fixed-displacement case.