bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment Procedure for Multiple Crack-Like Flaws in Fracture Assessment Diagram (FAD)
Authors: Konosu Shinji
Published: July 2009

Assessment of multiple discrete crack-like flaws is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, multiple crack-like flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between non-aligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction which indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete crack-like flaws in the Fracture Assessment Diagram (FAD) is proposed.
A New Approach to Simulate Transient Heat Transfer Within the Discrete Element Method
Authors: Rickelt S. , Wirtz S. , Scherer V.
Published: July 2009

The scope of this paper is to demonstrate the ability of a radial temperature model for spherical particles to allow for the calculation of the thermal behavior of granular assemblies with large particle numbers using Discrete Element simulations. The model efficiently accounts for inner particle heat transfer and is based on an analytical solution of the differential equation of heat conduction for a solid spherical particle with time and radius as independent parameters. It avoids the high computational costs of a numerical solution as well as the shortcoming of the assumption of uniform temperature profiles. To account for conduction due to multiple particle-particle or particle-wall contacts, each particle is divided into segments. Contact heat transfer on the particle scale is analyzed, comparisons with numerical solutions of Siu and Lee [1] for a contact of two spheres and a contact of a sphere with a wall were made for the adjustment and verification of the model. Results of a Discrete Element simulation using the radial temperature model for spheres stirred by moving walls are presented.
Assessment of the Real Fatigue Usage of the Volume Control System
Authors: Tulke Klaus-Dieter , Schoeckle Friedrich
Published: July 2009

As a major task of aging management, the quality status of every safety related system has to be assessed regularly. Thus the safety margin can be verified (and demonstrated) at every stage of operation and — if necessary — it can be reacted in time. One of the main aspects regarding the assessment of the quality status is the fatigue usage. Regarding the example of the volume control system of the nuclear power plant KKP 2 (PWR), the procedure to determine the actual fatigue usage is shown. There is a comprehensive monitoring of the global and the local loads of this system. The global monitoring is done using the plant instrumentation, the local monitoring is performed on the basis of individually installed transducers like thermocouples, displacement transducers, etc. Using the results of the monitoring the load cases are identified first and then their partial fatigue usage factors are summarized using the number of cycles determined by monitoring, usually. Thus it is demonstrated that all fatigue usage factors are below limits. However, if there are relevant new (i.e. not specified) transients these have to be analyzed and assessed. Regarding the volume control system the local monitoring showed “new” transients (thermal stratification) near a recuperative heat exchanger that were due to bypass operation. Consequently, the real actual fatigue usage was evaluated. In a first step, the relevant load cases (that were identified during the “local” monitoring history from 1991) were re-analyzed and correlated to the global signals. On this basis, the relevant transients and the number of cycles of the operation time without local monitoring (first startup of the plant in 1984) have been determined using the global signal records (digital and paper charts stored in archive). A conservative fatigue analysis showed that the maximum usage is related to the region of the inlet nozzles of the volume control system into the main coolant loops. With the proven history of transients the maximum fatigue usage D of this system was extrapolated to D = 0.27 (60 years of operation). The comprehensive global and local monitoring will be continued. On this basis the fatigue usage will be reviewed, regularly, and updated if necessary in future operation.
Prevention of Transformer Tank Explosion: Part 1 — Experimental Tests on Large Transformers
Authors: Muller Se´bastien , Brady Ryan , De Bressy Gae¨l , Magnier Philippe , Pe´rigaud Guillaume
Published: July 2009

Oil-filled transformer explosions are caused by low impedance faults that result in arcing in transformer tanks once the oil loses its dielectric properties. Within milliseconds, oil is then vaporized and the generated gas is pressurized because the liquid inertia prevents its expansion. The pressure difference between the gas bubbles and the surrounding liquid oil generates pressure waves, which propagate and interact with the tank. Then, the pressure peak reflections are building up the static pressure, which rises and leads to the tank explosion since tanks are not designed to withstand the resulting static pressure. This typical transformer incident is common. Indeed, conventional transformer protections are unable to react fast enough to prevent tank explosion that usually result in very expensive blackouts and fire damages for electricity facilities. This paper describes a transformer explosion prevention technology based on the direct mechanical response of a Depressurization Set to the tank inner dynamic pressure induced by electrical faults. Since transformers always rupture at their weakest point because of the static pressure increase, the Depressurization Set is designed to be this weakest point in term of inertia to break before the tank explodes. To evaluate its efficiency, experiments and computer simulations have been performed. Two experimental test campaigns were carried out, first by Electricite´ de France in 2002 and second, by CEPEL, Brazil, in 2004 on large scale transformers equipped with that prevention technology. These tests consisted in creating low impedance faults in oil filled transformer tanks. The 62 tests confirmed that the arc first creates a huge volume of gas that is quickly pressurized, generating one high pressure peak that propagates in the oil and activates the transformer protection within milliseconds before static pressure increases, thus preventing the tank explosion. Beside the experiments, a compressible two-phase flow numerical simulation tool was developed. The theoretical bases of this tool are presented in a parallel paper [1] and it is used here to study the pressure increase in an unprotected tank when subjected to an internal arcing which properties are similar to those used during the experiments. The fast tank depressurization induced by the transformer protection and its protective effects are thus highlighted.
Effect of Fiber-Reinforcement Material on the Leakage Failure in Polymer Composite Pressure Piping
Authors: Mertiny Pierre , Juss Kulvinder
Published: July 2009

Fiber-reinforced polymer composite piping has traditionally been produced using E-glass fiber materials. E-glass has been the preferred reinforcement phase due to its good corrosion resistance, low cost and wide availability. However, in recent years other materials have emerged on the market, or are becoming competitive in price. Mineral based basalt fibers and high-performance S-glass are examples of such materials. In the present study the performance of basalt and S-glass reinforcements was investigated in comparison to a commonly used advanced E-glass fiber material. Employing the same epoxy matrix phase, specimens from the various fiber materials were produced, and their leakage behavior was assessed using experimental means. It was observed that the type of fiber reinforcement had limited effect on leakage behavior of pressure-retaining pipe structures.
Numerical Analyses of Surge Line Piping to Assess Thermal Stratification Phenomenon
Authors: Woo Seung-Wan , Choi Shin-Beom , Chang Yoon-Suk , Choi Jae-Boong , Kim Young-Jin , Lee Jin Ho , Kim Jin-Su , Chung Hae-Dong
Published: July 2009

During the last two decades, thermal stratification has been issued as a critical problem in the nuclear power industry. Since the problem caused by this phenomenon also became important in Korea, it is necessary to quantify the thermal stratification effect to ensure the safety of the piping system. In this paper, detailed stress analyses of the surge line, considering the thermal stratification, are conducted. Parametric sensitivity analyses to find out an optimum model were carried out using pipe element models and full 3-D element models. For instance, in case of the pipe element model, the effect of starting location of thermal stratification and boundary condition were investigated. And, in case of the 3-D solid element model, the effect of boundary condition and thermal loading condition were assessed. The stress analysis results showed that the thermal stratification phenomenon significantly affected the integrity of the surge line piping. Also, establishment of insurge and outsurge conditions was derived as one of the further investigations.
On the Operating Tightness of B16.5 Flanged Joints
Authors: Payne James R. , Schneider Robert S.
Published: July 2009

The operating leak rate and tightness of a range of ASME B16.5 flanged joints [1] are calculated and compared for several gasket types, service categories and assembly methods. The methodology used includes proposed tightness based gasket constants and application of the basic principles of proposed new ASME rules for design bolt loads. It is straightforward and will be useful to those tasked with bolted joint tightness evaluations. The margin of bolt load available for joint relaxation is also examined. It is found that for modern graphite based gaskets, properly assembled joints have adequate tightness. PTFE based gaskets were not included in this study. This paper updates a similar but unpublished study presented several years ago.
A Comparison of 10 CFR 71 and the IAEA TS-R-1 Radioactive Material Transportation Regulations
Authors: Bajwa Christopher S. , Easton Earl P. , Osgood Nancy L. , Pope Ronald B.
Published: July 2009

The US regulations for certification of Type B packages are based in large part on those of the International Atomic Energy Agency (IAEA); however, the US has chosen to differ (or deviate) in some respects, from the IAEA regulations based on its national legislation, its technical experience, and efforts to minimize burden on shippers of radioactive materials in the US. This paper will provide a brief overview of some of the differences between 10 CFR Part 71 “Packaging and Transportation of Radioactive Material”, as implemented January 2008, and IAEA TS-R-1 “Regulations for the Safe Transport of Radioactive Material”, 2005 edition, discuss some of the differences between the two sets of regulations, and the reasons for those differences.
Prediction of Characteristic Length and Fracture Toughness in Ductile-Brittle Transition
Authors: Wang Z. X. , Li H. M. , Chao Y. J. , Lam P. S.
Published: July 2009

Finite element method was used to analyze the three-point bend experimental data of A533B-1 pressure vessel steel obtained by Sherry, Lidbury, and Beardsmore [1] from −160 to −45 °C within the ductile-brittle transition regime. As many researchers have shown, the failure stress (σf) of the material could be approximated as a constant. The characteristic length, or the critical distance (rc) from the crack tip, at which σf is reached, is shown to be temperature dependent based on the crack tip stress field calculated by the finite element method. With the J-A2 two-parameter constraint theory in fracture mechanics, the fracture toughness (JC or KJC) can be expressed as a function of the constraint level (A2) and the critical distance rc. This relationship is used to predict the fracture toughness of A533B-1 in the ductile-brittle transition regime with a constant σf and a set of temperature-dependent rc. It can be shown that the prediction agrees well with the test data for wide range of constraint levels from shallow cracks (a/W = 0.075) to deep cracks (a/W = 0.5), where a is the crack length and W is the specimen width.
Towards a Validation Database for Simulation of Fluidelastic Instability in Normal Triangular Heat Exchanger Tube Arrays
Authors: Mahon John , Meskell Craig
Published: July 2009

Models for fluidelastic instability are usually validated by comparing critical velocity predictions with experimental data. However, the scatter in this data make detailed validation problematic. As an initial step towards providing a validation database for fluidelastic instability, surface pressure measurements are presented for a cylinder in the third row of three normal triangular tube arrays (P/d = 1.32; 1.58; 1.97) with air cross flow. Surface pressure measurements were also made when the cylinder was statically displaced. Forces were calculated from the pressure measurements enabling an understanding of the force generation mechanism. The results show that the fluid force coefficients do not scale with the dynamic head but exhibit a dependency on Reynolds number and pitch ratio. However, no simple parametrisation was found for the lift force. Jet switching was found in P/d = 1.58 even when the tube was displaced. This phenomenon resulted in the large asymmetry observed in the pressure distribution around a static cylinder.
Application, Design and Operation Considerations for Brazed Aluminum Heat Exchangers in Liquefied Natural Gas Service
Authors: Miller D. Douglas , Belling Joe A. , Tettambel Jane C.
Published: July 2009

Brazed Aluminum Heat Exchangers (BAHX) are commonly used for heat transfer equipment in liquefied natural gas (LNG) services. Specific operational design parameters as well as mechanical design characteristics are critical to consider in the construction and ultimately for the operation of the unit in order to ensure a safe design and successful operation for the facility. The growth and demand for natural gas has been extensive in recent years as clean burning fuels have become more of a priority than coal plants. Due to limited natural gas supplies, many LNG facilities have been considered as a means to provide and meet the consumers’ needs for natural gas. These LNG facilities such as LNG import receiving terminals or LNG Liquefaction Plants have a need for handling cryogenic materials. In these LNG applications, BAHX are an ideal fit for this use and have many advantages as a result of being able to be designed for minimal approach temperatures as well as lower log mean temperature differences (LMTD) than other exchanger types. These parameters are key to the plant’s refrigeration and overall energy loads. Discussed and detailed in this paper will be various uses and applications for BAHX along with design considerations for their use. Details regarding materials of construction, maintenance, and other mechanical aspects will be presented that lead to a safe and reliable means for transferring heat.
Application of Equivalent CTOD Ratio to Fracture Assessment of Structural Components
Authors: Igi Satoshi , Ohata Mitsuru , Minami Fumiyoshi
Published: July 2009

Plastic constraint correction using the equivalent CTOD concept has been studied in the IST project. This project was carried out over a 3-year period with the foundation of METI in Japan, and the results were summarized in a draft standard, “Method of constraint loss correction of CTOD fracture toughness for fracture assessment of steel component.” Equivalent CTOD ratio β is proposed in terms of constraint loss correction between the fracture performance of steel structures and fracture toughness tests using the Weibull stress as the driving force of brittle fracture. This paper provides the application procedure of Equivalent CTOD ratio to the fracture assessment of structural components. Equivalent CTOD ratio was taken in the fracture assessment diagram, and discussed the applicability by comparison with large scale test result of structural component such as Edge Surface Crack Panel, Center Through-wall crack panel and so on.
Weld Overlay Size Sensitivity on Residual Stresses in a Welded Pipe
Authors: Chintapalli Aparna , Miessi G. Angah , Ku Francis H. , Yee Raymond K.
Published: July 2009

Weld overlay technique can be used on a welded pipe with a flaw in the butt weld to prevent it from cracking further. Due to the application of weld overlay on top of the weld, compressive stresses are developed in the pipe wall and the weld. These stresses counteract the effect of the residual stresses from the butt weld and tensile stresses produced in the pipe during normal operation. Existing guidelines in the nuclear industry specify minimum dimensions (length & thickness) of the weld overlay. However, there is no guideline regarding the optimum repair dimensions that should be used to obtain minimum residual stresses induced by the weld overlay technique. The optimum dimensions in this study refer to the minimum material that can be used for the weld overlay. This results in reduced cost, time and exposure to radiation. Hence a size sensitivity study is performed by varying three parameters, the width and thickness of the weld overlay, and the size of the pipe being repaired. The repaired pipe is assumed to be subjected to typical pressurizer water reactor (PWR) operating conditions. The weld overlay process is simulated using an axisymmetric finite element model. The axial and hoop stresses in the region of the butt weld after the weld overlay are compared. The results from this study will be analyzed to establish optimum dimensions of the weld overlay for various pipe sizes to mitigate axial and circumferential crack initiation at the butt weld.
Investigation of a Shell and Tube Exchanger in Process Gas Heating Service
Authors: Porter M. A. , Martens D. H.
Published: July 2009

The design requirements for a large shell and tube vertical heat exchanger (to be used in a sulfur recovery tail gas treatment unit) included startup, shutdown and upset conditions that would subject the exchanger to significant temperature changes. The exchanger was designed to the requirement of the ASME Boiler and Pressure Vessel Section VIII Division 1 [1]. A detailed analysis of the thermal profiles and related stresses was performed to confirm the use of a flexible tube sheet design. The heat exchanger uses high pressure superheated steam on the shell side to heat a low pressure process gas on the tube side. The heat exchanger was sized and thermally rated, using commercially available analysis software. The proposed design was analyzed by Finite Element methods that included both thermal and stress analysis. These evaluations confirmed that a flexible tube sheet design was satisfactory when using specific dimensions.
Optimization of Compression and Storage Requirements at Hydrogen Refueling Stations
Authors: Elgowainy Amgad , Mintz Marianne , Kelly Bruce , Hooks Matthew , Paster Mark
Published: July 2009

The transition to hydrogen-powered vehicles requires detailed technical and economic analyses of all aspects of hydrogen infrastructure, including refueling stations. The cost of such stations is a major contributor to the delivered cost of hydrogen. Hydrogen refueling stations require not only dispensers to transfer fuel onto a vehicle, but also an array of such ancillary equipment as a cascade charging system, storage vessels, compressors and/or pumps/evaporators. This paper provides detailed information on design requirements for gaseous and liquid hydrogen refueling stations and their associated capital and operating costs, which in turn impact hydrogen selling price at various levels of hydrogen demand. It summarizes an engineering economics approach which captures the effect of variations in station size, seasonal, daily and hourly demand, and alternative dispensing rates and pressures on station cost. Tradeoffs in the capacity of refueling station compressors, storage vessels, and the cascade charging system result in many possible configurations for the station. Total costs can be minimized by optimizing that configuration. Using a methodology to iterate among the costs of compression, storage and cascade charging, it was found that the optimum hourly capacity of the compressor is approximately twice the station’s average hourly demand, and the optimum capacity of the cascade charging system is approximately 15% of the station’s average daily demand. Further, for an hourly demand profile typical of today’s gasoline stations, onsite hydrogen storage equivalent to at least 1/3 of the station’s average daily demand is needed to accommodate peak demand.
Recent Applications of ASME Code Case N-513 for Evaluation of Nonplanar Leaking Flaws
Authors: McGill Robert O. , Den Herder Kari L. , Patten Daniel B. , Queen Steven P.
Published: July 2009

ASME Code Case N-513, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping, provides evaluation rules for the temporary acceptance of flaws, including through-wall flaws, in moderate energy Class 2 or 3 piping without performing repair/replacement activities. The Code Case has gone through three revisions with the latest approved by ASME Section XI being N-513-2. The Code Case allows for evaluation of both planar and nonplanar flaws. The planar flaw evaluation uses the rules in Appendix C of ASME Section XI. The nonplanar flaw evaluation uses the procedure provided in Code Case N-480. This Code Case has been used widely in the nuclear industry ever since it was published. Its use is expected to grow with plant aging and especially since Revision 2 was recently endorsed by the NRC in Regulatory Guide 1.147 without condition. The paper describes three specific applications of the Code Case to accept leaking flaws in piping components for continued operation till the end of the operating cycle when repairs could be performed. The use of this Code Case thus avoided costly and unnecessary shutdown of the plants in these cases. The evaluation procedures using this Code Case for these instances are described in the paper.
The Elastic Modulus Adjustment Procedure (EMAP) for Shakedown
Authors: Adibi-Asl R. , Reinhardt W.
Published: July 2009

A simple and systematic procedure is proposed for shakedown analysis using combination of linear and non-linear finite element analysis (FEA). The method can identify the boundary between the shakedown and ratcheting domains directly does not require a time history analysis (non-cyclic). The proposed method is based on elastic modulus adjustment procedure (EMAP) and non-cyclic elastic-plastic FEA. The aim of EMAP is to generate statically admissible stress distributions and kinematically admissible strain distributions. By modifying the local elastic moduli it is possible to obtain an inelastic-like stress redistribution. The method is first demonstrated with a two-bar structure model based on analytical routine. The analysis is then applied to some typical shakedown problems including the “classical Bree problem” and the “bi-material cylinder”.
R&D and Pre-Normative Needs for Generation IV Nuclear Reactors
Authors: Tonti Andrea , Renault Claude , Sperandio Morello , Baylac Guy , Delle Site Corrado , Carre´ Frank
Published: July 2009

The development of new generations of fission reactors requires the study of a new series of standards to cover the gap between actual codes and the needs generated by this kind of plants (Generation IV systems). Specific issues relate to high operating temperature of gas cooled reactors (above 700°C with a goal of 1000°C) and high fast neutron fluence on core structure in fast reactors. Material standards need to be updated to cover this temperature range and new materials need to be developed too. Also the resistance of materials submitted to irradiation is to be increased. This work draws the attention on what parts of Generation IV pressure equipments are not covered by existing codes and thus require specific normative measures.
Impact of Blending Ratio and Thermal Treatment on the Mechanical Behaviour of Polyethylene/Polypropylene Blends
Authors: Mourad Abdel-Hamid I.
Published: July 2009

In the recent years, blending of different polymers is receiving increasing attention from researchers for various reasons including the possibility of creating a material or product for new and more industrial applications to meet specific processing and performance requirements that cannot be satisfied by a single component. Polyethylene (PE) and polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications such as piping systems in pressure vessels and pipelines. The main objective of this work is to study the effect of the thermal treatment/aging and PE/PP blending ratio (composition range) on the mechanical behaviour (tensile and hardness) of PE, PP and PE/PP blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 weight percentage were prepared via injection molding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however thermal aging hasn’t affected the hardness showing a good correlation with the tensile properties.
Determining TNT Equivalency for Confined Detonations
Authors: King Kim W. , Vaught Chris R.
Published: July 2009

Explosive containment vessels are typically designed and rated to contain a specified amount of trinitrotoluene (TNT) explosive charge weight. However, in application, these units typically contain explosive materials other than TNT. Additionally, proof testing of explosive containment chambers with TNT explosive is rare due to the availability of TNT commercially. Therefore, it is desirable to determine the capacity of an explosive containment vessel using an equivalent charge weight with respect to the TNT capacity of the vessel. Traditional wisdom suggests detonation chambers with large charge to volume ratios respond primarily in an impulsive manner. This assumption suggests that the impulse factor only should be used to determine the equivalent charge weight. However, it is also recognized that TNT equivalence with respect to confined detonations is not well understood and using standard methods for establishing TNT equivalency factors may not be adequate for confined detonations. This paper will investigate this common problem of determining equivalent charge weights for a containment vessel. This is accomplished using hydrocode modeling, finite element analysis and experimental test results.
Selecting the Optimum Bolt Assembly Stress: Influence of Flange Type on Flange Load Limit
Authors: Brown Warren
Published: July 2009

In previous papers, practical limits on the maximum applied load for standard ASME B16.5 and B16.47 carbon steel, weld neck pipe flanges were examined. A new code equation for the tangential (hoop) stress at the small end of the hub for a weld neck flange was developed to facilitate calculation of the limits using elastic analysis. The results were verified against elastic-plastic Finite Element Analysis (FEA). In this paper, the work is extended to include other flange configurations, including loose ring flanges, slip-on flanges and flat plate flanges. This paper is a continuation of the papers presented during PVP 2006 and PVP 2007 (Brown [1, 2]) and it extends the scope of the proposed methodology for determining flange stress limits in determining the maximum allowable bolt load for any given flange size and configuration.
Selecting the Optimum Bolt Assembly Stress: Influence of Flange Material on Flange Load Limit
Authors: Brown Warren
Published: July 2009

In previous papers, practical limits on the maximum applied load for standard ASME B16.5 and B16.47 carbon steel, weld neck and slip-on pipe flanges were examined. A new code equation for the tangential (hoop) stress at the small end of the hub for a weld neck flange and new flange factors for a slip-on flanges were developed to facilitate calculation of the limits using elastic analysis. The results were verified against elastic-plastic Finite Element Analysis (FEA). In this paper, the work is extended to include other flange materials and verification is once again performed against elastic-plastic FEA. This paper is a continuation of the papers presented during PVP 2006, PVP 2007 and PVP 2008 (Brown [1–3]) and it extends the scope of the proposed methodology for determining flange stress limits in to any given flange material, size and configuration.
Experimental Investigation on Rubber-Expanded Tube-to-Tubesheet Joints of Zr Heat Exchangers
Authors: Yuan Biao , Wang Ying Zhi , Ma Xin , Tu Shan-Tung , Xi Yan-An , Tang Zhi Xiang
Published: July 2009

Mechanics of flexible expansion was expounded, and technology points of uniform rubber expanding in tube-to-tubesheet joints of Zirconium (Zr) heat exchangers were introduced. A series of pull-out strength and tightness experiments were performed for rubber-expanded tube-to-tubesheet joints. The experimental results show that the pull-out strength decreases linearly with increasing of operating temperature in the range of 20∼300°C, the pull-out strength of joints composed of Zr tubes attached to 16MnR and 316L tubesheets (abbreviated as Zr/16MnR and Zr/316L joints and heat exchangers include these joints are called Zr heat exchangers) drops much faster than that of joints composed of Titanium (Ti) tubes attached to 16MnR tubesheets (abbreviated as Ti/16MnR joints), and the joint strength can meet the requirements specified in Chinese code & standard at the experimental conditions. It is also found that the tightness of rubber expanded tube-to-tubesheet joints drops obviously with the increase of working temperature from 20 to 200°C, and the sealing performance of the joints enhances markedly when rubber-expanded tube-to-tubesheet joints are subsequently expanded with roller. Moreover, the influences of Enlargement Rate of Tubesheet Hole (ERTH) on the strength of rubber-expanded tube-to-tubesheet joints is discussed, it is observed that the pull-out strength of the connection joints with non-grooved tubesheet holes increases linearly with increasing of ERTH when the expanding pressure is not larger than 38 MPa, whereas this is not the case for the joint with grooved tubesheet holes.
New Formulation of Bolted Joint Stiffness
Authors: Nassar Sayed A. , Abboud Antoine
Published: July 2009

New formulation is proposed for a more accurate estimate of bolted joint stiffness. In this study, a novel approach is used to obtain an expression for an effective area to be used for determining the clamped parts stiffness. A more accurate estimate of the joint stiffness would naturally provide a more reliable prediction of the bolted assembly response to external loads. The effects of the grip length-to-diameter ratio, joint dimensions, and the contact radii ratio of the joint plates are investigated and analyzed. Experimental data and finite element (FEA) modeling are provided to evaluate the accuracy of the proposed formulation of joint stiffness.
Effect of Washers and Bolt Tension on the Behavior of Double-Lap S2-Glass Fabric Epoxy Composite Joints
Authors: Virupaksha Vinayshankar L. , Nassar Sayed A.
Published: July 2009

Experimental characterization of thick composite bolted joints is performed to study the effect of washer size and bolt preload on bearing properties. S2-glass fabric-epoxy composite coupons [0/90; +45/−45 @ 10 sets] of 12.5 mm thickness were tested under double shear tensile loading. Two different washer sizes and thicknesses were used in this investigation. A force washer is used to monitor the clamp load variation during the test. It has been found that the initial bolt tension (preload) and washer size have a significant effect on bearing stiffness and bearing strength of thick composite joints. For a low bolt preload, test data shows a significant clamp load increase with the joint displacement. However, the percentage increase in clamp load is reduced as the preload is increased to 50kN. The outward buckling and delamination of the laminate in the composite coupons were found to be the main cause for clamp load increase.
Design and Manufacture of Welded Plate Specimens for Residual Stress Experiments
Authors: Hurrell P. R. , Bridger K. , Bunney P. , Gill C. , Francis J. A. , Turski M. , Bate S. K.
Published: July 2009

A long-term UK research programme has been established in order to improve the understanding of thermo-mechanical behaviour and residual stresses generated in pressure vessel steel welds as well as developing finite element (FE) welding simulation methods. The production of representative test specimens is an important element of this research project, since quality measurement data are needed to validate FE models. This paper describes the design, development and manufacture of welded plate specimens used for residual stress (RS) experiments. To date, research has focused mainly on developing the understanding of SA508 pressure vessel steel welds. Specimen dimensions were selected to facilitate stress measurements using a range of techniques. The philosophy adopted was to start with relatively simple 1-pass weld specimens and gradually increase the complexity to multi-pass groove welds in plates. Simple 1-pass weld specimens were generally designed to investigate the effect of welding parameters on thermo-mechanical behaviour, such as heat-affected zone (HAZ) microstructures and phase transformations. Later specimens are more representative of multi-pass power plant welds. They are being used to study material thermal cyclic hardening/softening behaviour. Other issues of concern are also being investigated, such as the effect of restraint during welding on RS and the effectiveness of post weld heat treatment (PWHT). Specimens were also designed to study peak stresses arising at bead stop/start positions and whether such peak stresses are annealed in overlaying additional weld metal. These investigations were performed on multi-pass groove welds in both austenitic and ferritic steel plates. Practical issues encountered during welding trials are discussed, including plate distortion and magnetisation of the ferritic steel plates. Information is also provided about welding temperature measurements and metallurgical examinations.
Development of Testing Methodologies for Onsite Radioactive Material Storage Containers
Authors: Feldman Matthew R.
Published: July 2009

Based on a recommendation from the Defense Nuclear Facilities Safety Board, the Department of Energy (DOE) Office of Nuclear Safety Policy and Assistance (HS-21) has recently issued DOE Manual 441.1-1 entitled Nuclear Material Packaging Manual. This manual provides guidance regarding the use of non-engineered storage media for all special nuclear material throughout the DOE complex. As part of this development effort, HS-21 has funded the Oak Ridge National Laboratory (ORNL) Transportation Technologies Group (TTG) to develop and demonstrate testing protocols for such onsite containers. ORNL TTG to date has performed preliminary tests of representative onsite containers from Lawrence Livermore National Laboratory and Los Alamos National Laboratory. This paper will describe the testing processes that have been developed.
Comparison of Neutron Diffraction Residual Stress Measurements of Steel Welded Repairs With Current Fitness-for-Purpose Assessments
Authors: Paradowska Anna M. , Price John W. H. , Finlayson Trevor R. , Rogge Ronald B. , Donaberger Ronald L. , Ibrahim Raafat
Published: July 2009

In this research the neutron diffraction technique was used to investigate the residual stress distributions in carbon steel components with weld repairs. Two full penetration weld repairs were studied using a) the stringer bead and b) the temper bead weld techniques in 25 mm thick plate. The welds were not post weld heat treated. The focus of the measurements is on the values of the sub-surface and through-thickness strain/stress variation near the middle of the weld and the toe. The experimental results showed that both processes had high residual stresses particularly through the thickness. The measurements were compared with current fitness-for-purpose approaches, such as BS7910 and R6 showing that these approaches underestimated and overestimated the stresses in various regions.
Thoughts on the Deconvolution of Thermal- and Stress-States From Transient Histories
Authors: Segall A. E. , Engels D. , Hirsh A.
Published: July 2009

When thermal-shock is an issue, the underlying thermal- and stress-states are often difficult to determine because the boundary conditions must be known. For direct problems where the boundary conditions such as temperature or flux are known a priori, the procedure is usually mathematically tractable and can therefore be solved analytically. On the other hand, the inverse problem where the boundary conditions must be determined remotely is inherently ill-posed and therefore sensitive to errors. Moreover, there are only limited numbers of analytical solutions and they are usually restricted to timeframes before the thermal wave reaches the natural boundaries of the structure. Fortunately, generalized solutions based on either measured temperature- and/or strain-histories can be used to determine the underlying thermal excitation via a least-squares determination of coefficients that require the direct solution to enforce the data. Once the inverse problem is solved and the unknown boundary-condition determined, the resulting polynomial can then be used with the generalized Direct solution to determine the thermal- and stress-states as a function of time and position. For the two geometries explored (thick-walled cylinder under an internal transient with external convection and a slab with one adiabatic surface), excellent agreement was seen with various test cases for histories based on either temperature or strain. However, the strain-based solutions may be preferable since they do not suffer from time-lags associated with thermally thick structures. The derived solutions appear to be well suited for many thermal scenarios provided the analysis is restricted to the time interval used to determine the polynomial and the thermophysical properties are independent of temperature.
Manufacturing Methodology, Repair History, and Loadings for Westinghouse and Combustion Engineering Pressurizers, to Support Detailed Structural Integrity Evaluations of the Nozzle Safe End Configurations
Authors: Martin Cameron , Bamford Warren , Palm Nathan
Published: July 2009

As a result of the finding of several large in-service inspection (ISI) indications at the Wolf Creek Nuclear Plant in the Fall of 2006, a major calculational effort was undertaken to accurately define the structural integrity margins which exist for the dissimilar metal welds, specifically the safety, relief, spray, and surge nozzle-to-safe-end regions. The Alloy 82/182 weld region of each of these nozzles is susceptible to primary water stress corrosion cracking (PWSCC), and predicting the extent of cracking accurately requires a detailed treatment of the residual stress present due to both the welding process used for the manufacture, and the extent of repairs present. This paper will discuss the manufacturing process used and compare and contrast them. A review will be provided of the types of repairs typically made to these components, as well as the types of loadings which typically occur during service. Also discussed will be the process used to ensure the accuracy of these findings in application to the operating plants of interest.
Thermal Fatigue Cyclic-Down Shocks on 316L Model Pipe Components
Authors: Paffumi Elena , Nilsson Karl-Fredrik , Taylor Nigel
Published: July 2009

There is a continuing need for reliable thermal fatigue analysis tools to ensure that high safety levels are maintained in the main coolant lines of light water reactors. To advance the accuracy and reliability of thermal fatigue load determination, a combined experimental and numerical investigation has been conducted on cylindrical components of 316L stainless steel subjected to cyclic thermal shocks of varying intensity. Slightly different experimental conditions were applied in each test to explore the effect of ΔTmax values of increasing severity, the effect of a superimposed static axial load and a reduced test piece wall thickness. Particular attention is given in this work to the influence of a constant tensile axial load on the quenching down shock damage. A comparison between thermal down-shock tests with and without additional constant tensile load is analysed in details here below.
Dynamic Burst Pressure Simulation of Cylindrical Shells
Authors: Cheng Cunjiang , Widera G. E. Otto
Published: July 2009

The object of this study is to determine the short-term burst pressure of metal cylinders under short-term dynamic loading conditions. The finite element method via the use of the LS-DYNA code is used to carry out the study. The influence of the geometric parameters diameter (D) and wall thickness (T) as well as loading parameters such as the dynamic pressure vs. time function is examined. Additionally, an empirical formula based on experimental data and incorporating the ultimate dynamic strength of low carbon steel is developed. Based on the agreement between the results of the finite element analyses and those of the empirical formula, it can be concluded that a properly modeled FEA analysis can be employed with sufficient accuracy to study the short-term dynamic burst pressures of metal cylinders.
NULIFE Network of Excellence: Progress on Structural Integrity Issues Relating to Safety of Ageing Nuclear Power Plants
Authors: Taylor Nigel , Rintamaa Rauno , Aho-Mantila Irina , Lidbury David , Keim Elisabeth , Hultqvist Goran , van Dyck Steven , Chapuliot Stephane , Prunier Valery
Published: July 2009

The NULIFE (Nuclear Plant Life Prediction) network is a European network of excellence funded by the European Commission’s 6th Framework Programme [1] together with in-kind contributions of the participants. The network is made up of 11 work package leader organisations (contractors) and about 30 associate contributors and collaborators. NULIFE kicked-off in October 2006 and is working over a 5-year period to create a single organisation structure, capable of providing harmonised R&D at European level to the nuclear power industry and the related safety authorities in the area of lifetime evaluation methods for critical components.
Headspace Gas Evaluation of Welded Plutonium Storage Containers
Authors: Hardy Bruce J. , Harris Stephen P. , Arnold Matthew J. , Hensel Stephen J.
Published: July 2009

The Can Puncture Device (CPD) serves as a containment vessel during the puncture of nested 3013 containers as part of surveillance operations in K-Area. The purpose of the CPD sampling process is to determine the original pressure and composition of gasses within the inner 3013 container. The relation between the composition of the gas sample drawn from the CPD and that originally in the inner 3013 container depends on the degree of mixing that occurs over the interval of time from the puncture to drawing the sample. Gas mixing is bounded by the extremes of no mixing of gases in the inner container and that of complete mixing, in which case the entire CPD system is of uniform composition. Models relating the sample composition and pressure to the initial (pre-puncture) inner can composition and pressure for each of these extremes were developed. Predictions from both models were compared to data from characterization experiments. In the comparison, it was found that the model that assumed complete gas mixing after puncture, the Uniform Mixing Model, showed significantly better agreement with the data than the model that assumed no change in the composition of the inner container, referred to as the Non-Uniform Mixing Model. Both models were implemented as Microsoft® Excel spreadsheet calculations, which utilize macros, to include the effects of uncertainties and biases in the measurements of process parameters and in the models. Potential inleakage of gas from the glovebox is also addressed. The spreadsheet utilizing the Uniform Mixing Model, which was validated by data from the characterization tests, is used to evaluate the pre-puncture composition and pressure within the inner 3013 container. This spreadsheet model is called the Gas Evaluation Software Tool (GEST).
Repair Weldability at Overlay/Base Metal Interface of Petroleum Pressure Vessel
Authors: Kayano Rinzo , Mori Hiroaki , Nishimoto Kazutoshi
Published: July 2009

In order to extend the life of petroleum pressure vessels operated in long term, it is needed to establish the reliable repair welding technique. Weld cold cracking sometimes occurred in long-term operated petroleum pressure vessels due to hydrogen embrittlement by thermal stress and diffusible hydrogen after repair welding. The cracking was caused by the hydrogen concentration at the base meal of 2.25Cr-1Mo steel/overlaying metal of austenitic stainless steels interface during the service with high temperature and hydrogen partial pressure. The tendency was accelerated by carbide precipitation at the interface due to the post weld heat treatment (PWHT) and the operation with high temperature. That is, the crack susceptibility at the interface became markedly higher owing to the hydrogen embrittlement with metallurgical degradation by thermal embrittlement. To make clear the effect of weld thermal cycles during repair welding on the hydrogen content and weld cold cracking at the interface in the structural material of petroleum pressure vessels, the crack susceptibility was estimated by y-groove weld cracking test with varying overlay thickness and hydrogen exposure conditions. In addition, the hydrogen distribution in the material was calculated by the theoretical analysis using the diffusion equation based on activity. The crack susceptibility was raised with increase in the hydrogen content at the interface. It was concluded that the cracking could be prevented by controlling the repair welding process to reduce the hydrogen content at the interface.