bluuebunny/crossref_metadata_2025 huggingface dataset:
The Geometry of Steam Generator Tube and Its Relevance to the Occurrence of Stress Corrosion Cracking in Operating Nuclear Power Plants
Authors: Lee Deok Hyun , Hur Do Haeng , Choi Myung Sik , Kim Kyung Mo , Han Jung Ho , Song Myung Ho
Published: January 2011

Occurrences of a stress corrosion cracking in the steam generator tubes of operating nuclear power plants are closely related to the residual stress existing in the local region of a geometric change, that is, expansion transition, u-bend, ding, dent, bulge, etc. Therefore, information on the location, type and quantitative size of a geometric anomaly existing in a tube is a prerequisite to the activity of a non destructive inspection for an alert detection of an earlier crack and the prediction of a further crack evolution [1].
Effects of Residual Stresses on the High Cycle Fatigue Behavior of Ti-6Al-4V
Authors: Li Yu-Jia , Xuan Fu-Zhen , Wang Zheng-Dong , Tu Shan-Tung
Published: January 2011

Axial force-controlled fatigue tests are conducted at various stress ratios (R) on Ti-6Al-4V specimens prepared by two different manufacturing techniques (hard turning plus polishing with and without vacuum stress relieve anneal carried out after polishing). Residual stress is measured by using X-ray diffraction. Results indicate that the surface compressive residual stress lead to an increase of fatigue limit at a given life and stress ratio. This effect decreases with increasing stress ratio R. At R = 0.6, the effect of surface residual stress on fatigue limit fades away. In addition, the location of crack initiation shifts from surface to interior when the stress ratio changes from −1 to 0.6.
A Numerical Study of Uplift Motion of Flat-Bottom Cylindrical Shell Model Tank Subjected to Harmonic Excitation
Authors: Nakashima Teruhiro , Taniguchi Tomoyo
Published: January 2011

In analyzing the rocking motion of unanchored flat-bottom cylindrical shell tanks, the fluid-structure interaction and the impact between the tank bottom plate and tank foundation should be treated adequately. Employing harmonic excitation, this paper examines the applicability of the explicit FE-Analysis technique for analyzing the rocking motion of a flat-bottom cylindrical shell tank model. Since the tank model possesses a thick and elastic bottom plate, the model tank pivots upon from an edge of the bottom plate to another edge of that reciprocally. The rocking motion of the model tank to the harmonic excitation is numerically computed and the uplift displacement of the tank is compared with experimental result. Agreement between the numerical and experimental results implies that the explicit FE-Analysis is capable of analyzing the rocking motion of cylindrical shell tanks subjected to the earthquake excitation.
Compressed Non-Asbestos Gaskets Shelf Life Prediction
Authors: Veiga Jose´ C. , Junger Daniele F. , Sousa Ana Maria F.
Published: January 2011

The effectiveness of any gasket material to create and retain a static seal may be determined by many factors, such as resistance to the bolt load, flange finish, media, pressure, temperature, compressibility and environmental conditions. Moreover, it is important to consider the shelf life of the gasket. This is because gaskets often remain in storage for a long time before being installed. This paper presents a method to predict compressed non-asbestos gasket lifetime using an accelerated aging method, based on the compressibility property.
Required Properties of Seismic Isolation System for Nuclear Power Plants
Authors: Fujita Satoshi , Minagawa Keisuke , Kodaira Takeshi
Published: January 2011

In Japan, applications of seismic isolation systems to new generation nuclear power plants and fast breeder reactors have been expected in order to enhance seismic safety. However there are lots of restrictions for design of isolation systems, such as strong design seismic wave, deformation of piping between an isolated structure and a non-isolated structure, and so on. In addition combination of horizontal and vertical isolation has possibility to cause rocking motion if a three-dimensional isolation system is applied. Therefore isolation systems should be designed properly. Moreover the design of seismic isolation system has to consider influence on inner equipment and piping. This paper describes investigation regarding required properties and performance of seismic isolation system for nuclear power plants. The investigation is carried out by numerical analysis. In the analysis, various isolation devices such as friction pendulum bearings and so on are applied as well as natural rubber bearings.
Comparison Between Hysteresis Energy and Input Energy for Failure
Authors: Minagawa Keisuke , Fujita Satoshi , Kanaeda Shingo
Published: January 2011

Many methods for evaluation of seismic resistance have been proposed. Energy balance equation is one of the methods. The main feature of the energy balance equation is that it explains accumulated information of motion. Therefore energy balance is suitable to investigate the influence of cumulative load. We have already conducted some studies that applied the energy balance equation to mechanical structures. In the studies, we confirmed a relationship between input energy and fatigue failure. On the other hand, a relation between fatigue life and hysteresis energy (i.e. area of a hysteresis loop) is well known in the fatigue strength field, and a lot of knowledge has been reported. The input energy of the energy balance equation is essentially equivalent to the hysteresis energy. Therefore it is expected that input energy for failure is equivalent to hysteresis energy for failure. In this paper, two experiments are carried out. One is a fatigue fracture experiment and the other is a vibration experiment that causes fatigue failure to experimental models. Both experiments cause fatigue failure by same bending mode. Finally the input energy and hysteresis energy for failure are compared.
Dynamic Buckling Simulation of Cylindrical Liquid Storage Tanks Subjected to Seismic Motions
Authors: Maekawa Akira , Fujita Katsuhisa
Published: January 2011

A three-dimensional and elastic-plastic dynamic buckling analysis method that takes into consideration fluid-structure coupling and large deformation is proposed in order to accurately simulate the seismic response of cylindrical liquid storage tanks. The results of a dynamic buckling experiment of a tank using seismic motions closely match those of numerical simulation by the proposed method. The mesh size of the analytical model greatly influences the buckling analysis results. Optimization of the size is also discussed.
Application of Annular Damper Reaction Wall in Seismic Isolated LNG Tank
Authors: Zhang Rui-Fu , Weng Da-Gen , Ni Wei-Bo
Published: January 2011

Most of the large LNG tanks have a fundamental frequency between 2 and 10 Hz which involves range of resonance of most earthquake ground motions. It is a fact that tanks could be damaged easily in the earthquake, which had been proved in many cases in the past few decades. It is an effective way to reduce the response for an isolation system being used for large LNG storage tanks in the strong earthquake. However, the displacement of the isolation story for actual project is very large in soft site so that the design of connection components is relatively difficult. In order to solve this problem, isolation system which is composed of annular damper reaction wall, viscous dampers, and lead rubber bearings mounted on the top of the piles is presented in this paper. The annular damper reaction wall which is not connected with the piles is embedded into the ground independently. The multi-degree-of-freedom lumped mass model is used to solve the governing equations of motion in which convective, impulsive and rigid masses are included. Simplified model of an actual LNG tank which can contain 160000m3 gases is analyzed by using isolators and annular damper reaction wall. The efficiency of the isolation system is investigated by analyzing various parameters such as displacement of the isolation story, base shear and so on. The results show that isolation system is very effective to control the displacement of isolation story, and at the same time base shear and other parameters are also effectively controlled.
Elastic-Plastic Design by Analysis for Gross Plastic Collapse
Authors: Carmichael Rory , Mackenzie Donald
Published: January 2011

An investigation of the ASME VIII Div 2 elastic-plastic stress analysis method for protection against plastic collapse is presented. Four example configurations are considered and calculated design pressures are compared with values determined by alternative procedures based on limit analysis and bilinear hardening/the twice elastic slope criterion. It is found that the ASME VIII Div 2 procedure does not generally lead to evaluation of higher design pressures than the alternative approaches. In an example configuration demonstrating significant geometric strengthening, the allowable load is limited by the local strain criterion and in practice user-defined service criteria would be applied to limit permanent deformation under design conditions. In two example configurations that failed through membrane action, the evaluated design pressure was found to be less than that based on limit analysis. These initial results indicate that the more complex elastic-plastic stress analysis used in the ASME VIII Div 2 method does not necessarily lead to evaluation of higher design loads than alternative design routes. Further studies are required to determine the general circumstances in which the more complex analysis method is advantageous in design.
Maximum Shearing Stress of a Structure Subjected to Random Excitations
Authors: Choi Byounghoan , Yang Jianfeng
Published: January 2011

Section III of the ASME Boiler and Pressure Vessel Code provides stress limitations, which are developed based on the maximum shearing stress criteria (Tresca stress criteria). Structures in a nuclear plant are subjected to a variety of loadings (deterministic and random). Unlike the deterministic loadings, the structural responses subjected to random excitations (such as a load induced by a fluid turbulence) must be evaluated in probabilistic terms based on the random vibration theory. One way to evaluate the structural responses under this type of loading is the Monte Carlo simulation. However, in general, a Monte Carlo simulation requires a large sampling, which is not efficient for large structures. This paper implements the Advanced First-Order Reliability Method (AFORM) to evaluate the Tresca stresses at the predefined reliability level. The failure criterion to define the performance function is considered as the principal stress difference (Tresca stress). Numerical examples demonstrate that the proposed method is accurate and efficient.
Free Vibration Analysis of a Simply Supported Rectangular Tank Partially Filled With a Liquid
Authors: Jeong Kyeong-Hoon , Park Jin-Seok , Lee Won-Jae
Published: January 2011

This paper presents a theoretical analysis for the hydroelastic vibration of a rectangular tank partially filled with an ideal liquid. The wet dynamic displacement of the tank is approximated by combining the orthogonal polynomials satisfying the simply supported boundary conditions, since the rectangular tank is composed of four rectangular plates. As the facing rectangular plates are geometrically identical, the vibration modes of the facing plates can be divided into two categories: symmetric modes and asymmetric modes with respect to the vertical centerlines of the plates. The liquid displacement potential satisfying the boundary conditions is derived and the wet dynamic modal functions of the four plates are expanded by the finite Fourier transformation for a compatibility requirement along the contacting surface between the tank and the liquid. The natural frequencies of the rectangular tank in the wet condition are calculated by using the Rayleigh-Ritz method. The proposed analytical method is verified by observing an excellent agreement with three-dimensional finite element analysis results.
FEM Stress Analysis and Evaluation of the Sealing Performance in Box-Shape Flange Gasketed Connections Subjected to Internal Pressure
Authors: Tenma Kentaro , Kurosawa Ryou , Sawa Toshiyuki
Published: January 2011

Bolted connections inserting gaskets such as box-shape flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure. In designing the box-shape flange connections with gaskets under internal pressure, it is important to clarify the gasket stress distribution for evaluating the sealing performance of these connections. However, no research in which the sealing performance of these connections is examined under internal pressure has been carried out. Thus, the design for box-shape connection such as thickness of flange cover, number of bolts, gasket width and so on is not clarified. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM), taking into account a hysteresis in the stress-displacement curve of the gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test (JIS B2490), method for estimating an amount of leakage is examined. The leakage tests were also conducted to measure an amount of gas leakage using an actual box-shape flange connection with a gasket. The estimated results are in a fairly good agreement with the experimental results. In addition, the effect of gasket width, flange cover thickness and flange cover material is examined on the sealing performances of box-shape flange connections under internal pressure. The effects of the above factors are discussed on the sealing performance in designing box-shape flange connections.
Development of Fragility Curve Considering Aging of Oil Storage Tanks and Its Application to Risk Assessment of Industrial Complexes
Authors: Murakami Yoshihisa , Yamase Toshiro , Zama Shinsaku , Hirokawa Yoshihiro , Nishi Haruki , Yamada Minoru , Hirano Akiko , Kasai Naoya
Published: January 2011

The industrial oil complexes in Japan have been taking various countermeasures for prevention and reduction of disaster based on the regulations. Nevertheless, we cannot deny the possibility of breakout of severe disaster such as leakage of oil, fire, and explosion due to aging facilities, wrong operations, earthquakes and so on. Therefore, municipalities having industrial complexes are required to develop disaster prevention plans and to devise effective disaster prevention schemes. In order to effectively do that, Japan Fire and Disaster Management Agency has shown the guideline to appropriately implement risk assessment of industrial complexes for both in usual and during an earthquake based on the event tree analysis. Especially during an earthquake, the buckling of shell plate of an oil tank by strong ground motions brings the major disaster, because it is highly possible that the buckling breaks out in the vicinity of the bottom and a total quantity of oil outflows. Yamase (2006) proposed a fragility curve for the buckling of shell plate and applied it to the risk evaluation of oil tanks in Hokkaido District, northern part of Japan. However, the fragility curve was built based on only the design shell thickness data of the oil tanks in Kobe City, and the influence of aging deterioration was not considered. Then, we collected the data such as the shell plate thickness, height, diameter, and elapsed time from construction of several hundred oil tanks, and calculated the corrosion speed of the shell plates to consider the influence of aging deterioration of oil storage tanks, and newly developed a fragility curve from these data. As a result, the improved fragility curve leads to the several percent larger in the buckling outbreak probability for oil tanks built scores of years ago.
A Note on Hydraulic Leaks for Mobile Equipment
Authors: Awad Mahmoud I. , Alkelani Ali A.
Published: January 2011

Leaks in general and hydraulic leaks in specific are one of the major failure modes for mobile equipment. In-plant leak rates may range from 1 to 25%, while field leaks may range from 1 to 13% depending on the complexity of the system, assembly process, and parts quality. In this paper, the main potential leak causes are discussed and the performance of different types of fittings is compared; including JIC 37 Flare Fittings, O-Ring Boss Seal, and O-Ring Face Seal. Several potential improvement actions related to assembly process, torque specifications, and quality of manufactured fittings are recommended to reduce leaks. Among the many benefits leak reduction will result in are customer safety and satisfaction, assembly down time reduction, cost and warranty reduction, and environmental impact reduction.
Seismic Design Margin of the Piping and Support System: Part 1—Static Loading Test of the Support
Authors: Shirai Eiji , Yamada Takanori , Ikeda Kazutoyo , Yoshii Toshiaki , Kondo Masami , Okamoto Hiromu , Tai Koichi
Published: January 2011

On the evaluation of seismic design margin of the piping and support system in the nuclear power plant, the elasto-plastic behavior of support has played the important role in the seismic response analysis. It is desirable to establish the simple and effective non-linear modeling of the support in order to conduct the seismic response analysis considering each elasto-plastic characteristics of actual numerous supports in the piping system. On this point, this research project takes as its objectives to establish the simplified non-linear modeling of the support, in which the load-displacement characteristics are equivalent to the static loading test, in order to evaluate the seismic design margin. Static loading test of the support was designed to obtain the relationship between force and displacement characteristic at piping. The pipe support consists of a combination of a U-bolt, supporting elements such as a structural frame or a vibration actuator, a base plate and a concrete anchorage. Simulated seismic displacements were loaded into the piping to determine the failure mode and the limit load of support. The following were obtained as the static loading test. • The strength ratio of each test case is about 2.8 to 4.2, it turns out that limit load capacity of the support is much higher than the design allowable load. • The ductility ratio of the frame type support is higher than that of the oblique member type support. • Moreover, these test results are concurred well with the support failure modes of previous paper. Strength ratio = Tested failure capacity / Design allowable load. Ductility ratio = The displacement at the maximum load / The displacement at the start of yielding.
Overview of Code Case on Alternative Design Methodology by Using Elastic-Plastic Finite Element Analysis for Class 1 Vessels in the JSME Rules on Design and Construction
Authors: Asada Seiji , Hirano Takashi , Nagata Tetsuya , Kasahara Naoto
Published: January 2011

An alternative design methodology by using elastic-plastic finite element analysis has been developed and published as a code case of the JSME Rules on Design and Construction for Nuclear Power Plants (The First Part: Light Water Reactor Structural Design Standard). This code case applies elastic-plastic analysis to evaluation of such failure modes as plastic collapse, shakedown, thermal ratchet and fatigue. Advantages of this evaluation method are no use of stress linearization/classification, consistent use of Mises equivalent stress and applicability to complex 3-dimentional structures which are hard to be treated by the conventional stress classification method. The evaluation method for plastic collapse consists of the Lower Bound Approach Method, Twice-Elastic-Slope Method and Elastic Compensation Method. Cyclic Yield Area (CYA) criterion based on elastic analysis is applied to screening evaluation of shakedown limit instead of secondary stress evaluation, and elastic-plastic analysis is performed when the CYA screening criterion is not satisfied. Strain concentration factors can be directly calculated based on elastic-plastic analysis.
Research and Development of a Double Steel Bottom Structure of Oil Storage Tank
Authors: Chen Zhiping , Yan Liuchuan , Fang Zhou , Cao Guowei
Published: January 2011

Oil and gas leak accidents occur sometimes for the sever corrosion of existing large steel oil storage tanks with single bottom and the leak is not easily found. So a double steel bottom structure was proposed in this paper, which mainly consisted of a primary bottom, a secondary bottom, support components between the two bottoms and a leak monitoring device. The sealed containment space formed by the two bottoms could prevent leaking oil and gas from polluting the environment. And timely leak forecast would be available by detecting its internal gas compositions on line. 6 different support arrangements were given in this paper with a small test tank as an example. Finite element method was adopted to analyze the stress distribution on each bottom. And one of the 6 support arrangements with a suitable arrangement manner and angle steel amount was chosen as the final support arrangement of the test tank after a comprehensive consideration of stress level, deformation degree, angle steel weight and the ease of manufacture and so on.
Assessments of Residual Stress Due to Weld-Overlay Cladding and Structural Integrity of Reactor Pressure Vessel
Authors: Katsuyama Jinya , Nishikawa Hiroyuki , Udagawa Makoto , Nakamura Mitsuyuki , Onizawa Kunio
Published: January 2011

Austenitic stainless steel is cladded on the inner surface of ferritic low alloy steel of reactor pressure vessels (RPVs) for protecting the vessel walls against the corrosion. After the manufacturing process of the RPVs including weld-overlay cladding and post-weld heat treatments (PWHT), the residual stress still remain in such dissimilar welds. The residual stresses generated within the cladding and base material were measured as-welded and PWHT conditions using the sectioning and deep-hole-drilling (DHD) techniques. Thermal-elastic-plastic-creep analyses considering the phase transformation in heat affected zone using finite element method were also performed to evaluate the weld residual stress produced by weld overlay cladding and PWHT. By comparing analytical results with those measured ones, it was shown that there was a good agreement of residual stress distribution within the cladding and base material. Tensile residual stress in cladding is mostly due to the difference between the thermal expansions of cladding and base materials. It was also shown that taking the phase transformation during welding into account is important to improve the accuracy of weld residual stress analysis. Using the calculated residual stress distribution, fracture mechanics analysis for a postulated flaw during pressurized thermal shock (PTS) events have been performed. The effect of weld residual stress on the structural integrity of RPV was evaluated through some case studies. The result indicates that consideration of weld residual stress produced by weld-overlay cladding and PWHT is important for assessing the structural integrity of RPVs.
Research on Safety Assessment Method for Pressure Pipe With Incomplete Welding Defects Under Complicated Loadings
Authors: Jin Zhijiang , Wan Xianping , Jiang Chenghang
Published: January 2011

Since most pressure pipe materials have good toughness, the failure mode of pipe is usually the plastic failure controlled by limit load. The incomplete welding defect is very common in the pipe, and its existence will reduce the load-carrying capacity of pipes. The pipe with incomplete welding defects can be continued using only after passing the appropriate safety assessment, so the research on safety assessment procedure for pressure pipe with incomplete welding defects under combined bending, torsion and internal pressure loadings has a great theoretical and practical engineering value. By using theoretical analyzing method of plastic limit load, the plastic limit load of pressure pipe with different defect size or pipe diameter ratio are calculated in this paper, then safety assessment curved surface and its express equation are obtained by fitting calculation data. Finally a safety assessment procedure is developed for pressure pipes under combined bending, torsion and internal pressure loadings according to the curved surface.
Research on Producing the Electrode for Generating Underwater Shock Wave
Authors: Matsuo Nobuyuki , Tanaka Shigeru , Itoh Shigeru
Published: January 2011

Explosive welding is momentarily joint processing between a metal plate and other metal plate using impact energy generated by explosive detonating. Recently, from the specificity and economical efficiency of the joining method, it is used as one of the solid state joining technique. Explosive welding method has following advantages, no heat influence, instantaneous jointing process, and high joining strength. In this research, jointing between cupper pipe and threading stainless steel pipe was tried using explosive welding. Fabrication of a composite material with high intensity and sufficient conductivity is expected by joining copper pipe and stainless steel pipe. The junction section of the obtained sample was observed with the optical microscope, and good junction had been attained. Moreover, organization evaluation of the junction section was performed by EPMA analysis.
Development of Finite Element Model by Structure Assembly Method: Application to 3 Dimensional Modeling
Authors: Watanabe Osamu
Published: January 2011

Making a finite element model for pressure vessel and piping is laborious work and time-consuming. General purpose programs have a special mesh generation tool, which produces finite element model to be used in the analysis of structure, where automatic meshes are generated based on geometrical properties. Obtained mesh shape is generally irregular for complex structures. The present paper shows a development method of finite element model by assembling finite element models for structural component to the whole structure, as is seen in the procedure of actual structures. The finite element component models are prepared for cylindrical shell, spherical shell and nozzle etc., and finite elements for these components are connected to each other to build a whole structure. The present paper presents an application of 3D FE modeling by the proposed method, to show the features and mesh examples.
Thermal Aging Effect on Environmental Fatigue Life of CF8M Cast Stainless Steel at Strain Rate 0.04%/s Under PWR Operating Condition
Authors: Jeong Ill-Seok , Kim Wan-Jae , Jeon Hyun-Ik
Published: January 2011

In order to see the effect of thermal aging on environmental fatigue life of CF8M cast austenitic stainless steel (CASS), low-cycle environmental fatigue tests of thermally aged CF8M CASS at the condition of fatigue strain rate 0.04%/s were conducted at the operating condition, 15MPa, 315°C of pressurized water reactor (PWR) environment. Test results of low cycle fatigue life tests for thermally aged specimens simulating 60 operating years were compared with ones of un-aged CF8M CASS in room temperature air and PWR operating conditions to see the effect of the thermal aging on environmental fatigue life. This kind of experiment would be useful to verify the fatigue integrity of long-lived components and to predict plant safety of long term operation beyond design life because current approach of evaluating environmental fatigue is so conservative to apply it to the long-lived components in pressure boundary of nuclear power plants.
On-Line Monitoring System for Hydrogenation Equipment in Petrochemical Plants
Authors: Wang Zhengdong , Tu Shan-Tung , Xuan Fu-Zhen , Liu Changjun
Published: January 2011

A life monitoring and assessment system of pressure vessels and piping in petrochemical plants has been developed based on the structural integrity theory and web technology. Two industrial cases of the monitoring system are given in this paper for hydrogen processing reactor, hydrogen pipeline and furnace tube of hydrogen reformer. The monitoring system is established to predict hydrogen embrittlement for the wall materials of hydrogenation reactor and pipeline in petrochemical plants. A critical description of hydrogen induced cracking is introduced to set up a criterion for the embrittlement. The electrochemistry hydrogen sensor is designed for its feasibility of real-time monitoring and assessment of hydrogen embrittlement for the equipment. It is pursued by the research to make a more impersonal judgment of safety of the hydrogenation reactor with real time tracing of operation. A remote inspection system is created based on computer network technology to monitor the plant subjected to hydrogen attack. The on-line system is also founded to monitor the operation of the furnace tube of hydrogen reformer and predict its residual life. The system executes in the remote server to assess the life of the tube and issue the information through the internet. Therefore remote users can monitor and manage the tubes on real-time. A non-contacting temperature monitoring technique is introduced into the system using CCD camera. An assessment method is introduced in this paper to create a correspondent relationship between remaining life and damage accumulation. It is significant for the method to describe the tube damage or materials degradation under unstable operations including varied pressure, varied temperature, over-heat or thermal fatigue, etc. A life fraction model related to damage accumulation is adapted into a real time monitoring system to calculate the residual life for a selected tube and work out an optimum preventive maintenance project.
Development of In-Situ Monitoring Technique on a Crack of Steam Generator Tubing: The Effect of Thermal Treatment on the SCC of Alloy 600
Authors: Chang Hyun Young , Park Heung Bae , Kim Young Sik , Jang Yoon Young
Published: January 2011

TT (Thermal Treatment) for mill annealed Alloy 600 highly improves the resistance against IGSCC (Intergranular Stress Corrosion Cracking) in caustic solution, but its treatment changes the microstructure. The change of microstructure can affect the SCC resistance in various corrosion environments. This kind of corrosion can be monitored using an electrochemical noise measurement. Therefore, in this study, the effects of heat treatment on SCC resistance in Alloy 600 have been evaluated 0.1M Na2S4O6 at 25 °C from electrochemical noise measurement, and quantification has been tried for resistance against crack formation. While there was no generation of the stress corrosion crack of Alloy 600MA by reverse U-bend method in 0.1M Na2S4O6, the stress corrosion crack was generated in sensitized Alloy 600SE, SE+, and TT materials. The cracking could be detected using an electrochemical noise monitoring. Also, if the aging heat treatment is performed, the stress corrosion crack resistance is reduced. In the case of this behavior, it is analyzed that the stress corrosion crack resistance is closely related with the grain boundary corrosion rate based on the results of the micro-structural analysis for the chromium carbide distribution, the DL-EPR method, and the measuring of the grain boundary corrosion rate through the modified Huey test.
Effect of Material Factors on FAC Rate and Characteristics of Oxide Layer
Authors: Watanabe Yutaka , Abe Hiroshi , Miyazaki Takamichi
Published: January 2011

Combined effects of Cr content and pH on corrosion rate of carbon steels due to flow accelerated corrosion have been examined by experiments and their relation to oxide scale characteristics based on detailed oxide layer characterizations using transmission electron microscope with X-ray analyzer have been discussed. Effect of Cr content on FAC mitigation decrease continuously as pH is increased from neutral to 10.4 and effect of pH on that increase significantly from pH 9.1 to 9.4. Obvious Cr enrichment has been observed in the oxide layer of 1.01 wt% Cr content steel regardless pH condition. Cr concentration is highest at top surface of oxide layer, and that decrease from surface to oxide / metal interface gradually. It has been suggested that Cr enrichment stabilize oxide layer (decrease solubility and defect density of oxide layer), as a result, FAC suppressed.
Fracture Toughness Estimation of Miniature Specimens by Considering Geometry Effects
Authors: Choi Shin-Beom , Kim Young-Jin , Chang Yoon-Suk
Published: January 2011

Since small-sized specimens are widely used for fracture toughness tests to assure safety of a reactor pressure vessel in service, as a part of surveillance program, various geometry parameters affecting on the stress level near the crack-tip should be investigated for realistic assessment of cleavage fracture behavior. The aim of the present paper is to improve the current master curve method for typical miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimens. In this context, effects of thickness and side-grooves were quantified from comparing finite element (FE) analyses results in use of various PCVN specimens with and without side-grooves. Then, a scale factor to deal with geometry effects was suggested by employing the fracture toughness diagram, which was derived from FE analyses data of compact tension specimens and PCVN specimens. The scale factor was applied to calculate equivalent stress intensity factors influencing on the reference temperature embodied in the master curve method. The approach proposed in this paper will be useful to estimate fracture toughness of PCVN specimen made of SA508 carbon steel.
Stress and Deformation Analyses of Flanges Subjected to Bolt Loads and Internal Pressure
Authors: Kobayashi Takashi , Hamano Kota , Kikuchi Tsutomu , Sawa Toshiyuki , Nagata Satoshi
Published: January 2011

Deformation characteristics of pipe flanges are important in the leak rate based design of gasketed flanged connections. The deformation characteristics should be considered in the design of gasketed flanged connections as well as the equilibrium of force between the bolts and the clamped parts. Recently, finite element method (FEM) has widely been used in the analysis of flanged connections. However, analyses of pipe flanges based on the analytical method using classical theories such as the strength of materials are still important when parametric calculations of flanges are necessary. In this study, a method to analyze the stress and the deformation of welding neck type flanges is demonstrated and the validity of the analysis is checked. A software using Visual Basic for Applications (VBA) is developed based on the method. The advantages of the software are that stresses and the deformation of flanges are easily calculated by selecting a flange size and design conditions from a database. The validity of the results obtained by the software is also confirmed by comparing the calculated results with those obtained by FEA. A series of calculations have been done for Japanese Industrial Standard (JIS) flanges and the deformation characteristics are clarified when a flange is subjected to bolt loads and an internal pressure.
Expressions of Load and Structural Deformation Relationship for Cylindrical and Spherical Vessels Under Internal Pressure
Authors: Deng Yang-chun , Chen Gang
Published: January 2011

Large deformation analysis for pressure vessel is much more complex than small deformation analysis, therefore, right now, there is no common recognized direct solution for load bearing capacity of pressure vessel yet, and this restrict the application of large deformation analysis in pressure vessel design. This paper based on elastic-plastic theory and considered material strain hardening and structural deformation effects, expressions of load and structural deformation relationship were the first time being derived for cylindrical and spherical vessels under internal pressure. And its practical value is equivalent to principal stress equations of thin-walled cylindrical and spherical vessels with considering non-linear structural deformation effect. Based on the study above and by introducing true stress-strain relationship of materials, analytical solutions of plastic instability pressure for thin-walled cylindrical and spherical vessels were derived.
Regulatory Experience of Leak-Before-Break (LBB) Technology to the High Energy Piping Systems in Korea
Authors: Chung Yeon-Ki , Kim Jin-Su , Chung Hae-Dong , Choi Young-Hwan
Published: January 2011

The application of the leak-before-break (LBB) technology to the newly constructed pressurized water reactors (PWRs) has been approved for the several high energy piping systems inside containment in Korea. The main purpose of the LBB application for these systems at the design stage is the removal of the dynamic effects associated with the postulated double-ended guillotine break (DEGB) from design basis loads, as well as to the elimination of the pipe whip restraints and jet impingement barriers so as to increase the access the inspections. LBB technology is based on the low probability of pipe ruptures in the candidate piping systems using fracture mechanics and the insights from the state-of-the-art technology including operating experience. The procedures for LBB application is fundamentally based on the Unite States Nuclear Regulatory Commission (US NRC) requirements as detailed in the standard review plan (SRP) 3.6.3. However, a number of the additional requirements and issues are not specified in the review procedure during regulatory review were imposed and addressed during the review process. The regulatory review is focused on the confirmation on the methods for the elements in the screening criteria and several technical concerns on the determination of material properties, the validation of crack evaluation methods and leak rate estimation in the LBB evaluation considering the adequate margin. Although the application of the LBB has been approved by the safety authority for some high energy systems, the validation of LBB is continuously maintained in consideration of operating experience. In this paper, the regulatory positions for LBB application are described for the areas of screening criteria, leak rate estimation including the capability of leak detection system, material properties, load combination, crack stability methods, and margins in the crack stability evaluations. The issues encountered during the regulatory review such as the dynamic fracture test to consider the dynamic strain aging (DSA) of carbon and low alloy steel, thermal stratification and striping in the pressurizer surge line, water/steam hammer in main steam lines, and estimation of the crack opening area at the pipe-to-nozzle interface considering the asymmetry are also introduced. In addition, several regulatory actions to improve the reliability in the capability of leak detection systems and to clarify the screening criteria such as the corrosion resistance is provided.
Development of an Alternative Approach to the Acquisition of Fracture Toughness in Laboratory Specimens Containing Residual Stress
Authors: Hurlston R. G. , Sharples J. , Sherry A. H.
Published: January 2011

Welding is an essential process in many industries and is used for both the production and repair of nuclear plant, notably pressure vessels and piping. However, traditional welding processes can cause large amounts of residual stress to be generated within the structure. Current methodology for evaluating fracture toughness from specimens containing residual stresses, e.g. BS7448, relies heavily on engineering judgement. This can result in inaccurate, albeit generally conservative, values of fracture toughness being used in defect assessments. The aim of the work presented in this paper is to investigate the use of constraint based fracture mechanics to quantify ‘unique material fracture toughness’ from laboratory specimens containing residual stresses using the ‘apparent fracture toughness’ values derived from standard fracture toughness testing. This is achieved using an analytical knowledge of the effect of residual stress on crack-tip constraint and, if incorporated into fracture toughness methodology, remove the need for unreliable residual stress relaxation methods when using weld coupons for fracture toughness assessments. A novel mechanical method for generating residual stresses in single edge notch bend specimens has been assessed analytically. In this paper, computational analysis of low and high constraint bend specimens, each with and without residual stress, is used to demonstrate the principle and validity of the proposed method.
Presentation of the Afcen RCC-MRx Code for Sodium Reactors (SFR), Research Reactors (RR) and Fusion (ITER): General Overview
Authors: Lebarbe´ T. , Marie S. , Drubay B. , Gelineau O. , Bonne D. , De La Burgade Frantz
Published: January 2011

The next edition of the Afcen RCC-MR code, named RCC-MRx 2010, will be issued in French and English versions on November 2010 by AFCEN (Association Franc¸aise pour les re`gles de Conception et de Construction des Mate´riels des Chaudie`res Electro-nucle´aires). This Afcen RCC-MRx Code is the result of the merger of the RCC-MX 2008 developed in the context of the research reactor Jules Horowitz Reactor project, in the RCC-MR 2007 which set up rules applicable to the design of components operating at high temperature. This paper presents the code evolution from the 2007 edition of the RCC-MR code, such as: - Specific materials of research reactors and irradiation devices such as aluminium alloys or zirconium alloys are now added in the code. - Specific material properties and rules developed for such irradiated components.
Installation of Serrated Metal Core Without Full Disassembly of a Heat Exchanger
Authors: Currie Russ , Davis R.
Published: January 2011

The problem faced was to provide a sealing solution on a heat exchanger where certain restrictions were in place. Several years had passed since the bundle was last pulled, the concern over the service was that corrosion may be present on the flanges inspection had not been determined. The site had become congested since it was first installed which reduced the available movement of the bundle. Shutdown would be extended if floors had to be cut out, the exchanger dropped and rerouted to the edge of the platform. There were several unknowns; documentation on what had been done last time was sketchy, along with its location in the North Sea with climatic issues. The platform itself had replaced a facility which is remembered in history for major loss of life.
The Equivalency-Based Linear Regression Method for Statistical Analysis of Creep/Fatigue Data
Authors: Wei Zhigang , Rice Richard C. , Yatomi Masataka , Nikbin Kamran M.
Published: January 2011

Materials scientists and mechanical engineers working on structural integrity are making increasing use of statistical analysis in interpreting creep/fatigue data as they contain an inherent scatter which cannot be substantially reduced even under controlled testing conditions. In practice, in most cases the uniaxial failure or cracking data can be reasonably approximated by a straight line on log-log coordinates, indicating that there is a linear log relationship with the appropriate correlating parameter. Linear regression is the most used method in statistical data analysis and is being recommended in American Society for Testing and Materials (ASTM), British Standards (BS), Det Norske Veritas (DNV) and many other engineering standards. Recently, the current practice on linear regression as adopted by the engineering standards has been critically reviewed, and the shortcomings of these procedures have been clearly demonstrated. A new statistical method based on the equivalency between all variables involved has been proposed for S-N curve analysis. In this paper, a large amount of creep and fatigue data of engineering materials collected from several well known data bases generated in US, Europe, and Japan are systematically analyzed with conventional standard and the new equivalency method. The results are compared and discussed. Finally, a recommendation to improve the fitting parameters taking into account of the scatter in both axes is presented.
A Computer Simulation Model for the Stretch Blow Moulding Process of Polymer Containers
Authors: Groot J. A. W. M. , Giannopapa C. G. , Mattheij R. M. M.
Published: January 2011

Stretch blow moulding is a widely used technique e.g. for the production of PET bottles. In a stretch blow moulding process a hot preform of polymer is simultaneously stretched and blown into a mould shape. The process takes place at a fast rate and is characterised by large deformations and temperature gradients. In this paper the computer simulation model presented in is applied to the stretch blow process for the production of PET bottles. The model was previously developed by the authors for the simulation of 2D axial-symmetrical blow processes for the production of glass containers. The model is based on finite element methods and uses a level set method to track the interfaces between air and the material. The simulation model is modified in order to correctly describe the material behaviour of PET, take into account the stretch process and substitute the process parameters for stretch blow moulding. Furthermore, it is verified that the PET behaviour can be modelled as a non-newtonian, isothermal fluid flow, based on a viscoplastic material model. An application presented is the stretch blow moulding of a realistic PET water bottle.
Failure of a Seamless 2-1/4Cr – 1Mo Hot-Reheat Pipe Bend: Metallurgical Considerations
Authors: Thornley J. Cliff , Speelman John L. , Griffin Rob
Published: January 2011

Following the unexpected failure of a seamless hot-reheat pipe bend at Belledune Unit #2, New Brunswick, Canada, after 113,230 hot operating hours, an extensive metallurgical investigation was performed by RPC to assess the metallurgical condition of the bend, to identify the reasons for the premature failure and to evaluate the condition of the remaining pipe bends at the station. The metallurgical investigation included both on-site metallographic replication and examination of the bend material, as well as grain growth trials and mechanical tests, including short-term tensile, creep rupture and Charpy impact tests. The pipe bend was of P22 type steel of the correct composition but was extremely coarse grained. This extreme grain size resulted in low creep rupture ductility and promoted notch brittleness of the bend material in creep.
Effect of Bondline Thickness on Interfacial Fracture of Laminated Composite Materials
Authors: Ji Gefu , Ouyang Zhenyu , Li Guoqiang , Jerro H. Dwayne , Pang Su-Seng
Published: January 2011

The interfacial fracture of bonded structures is a critical issue for the extensive applications to a variety of modern industries. In the recent two decades, nonlinear fracture mechanics methods have been receiving intensive attentions for adhesively bonded joints. Extensive experimental efforts have been made to determine the toughness of adhesive joints. Several experimental studies have also been conducted to determine the interface cohesive law in bonded joints. However, very few studies investigated the effect of adhesive thickness on the interface cohesive laws. In the cohesive law, both fracture energy and the interfacial cohesive strength, as two critical parameters, have significant effect on the fracture behavior and joint’s structural capability. The present study presents the experimental investigation into how the adhesive’s thickness affect these two important parameters with the nonlinear fracture mechanics. The equivalent interface cohesive laws are experimentally determined for the bonded joints with various adhesive thicknesses. The experimental cohesive laws may provide valuable baseline data for simple analytical and numerical cohesive zone models. Based on the test results, the mechanism for the intrinsic fracture energy and plastic energy dissipation is discussed. Several other interesting conclusions are also obtained.