bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Fatigue Failures of Economizer Outlet Header Stub Tubes
Authors: Ellis Fred V.
Published: July 2008

Nondestructive and metallurgical examinations were performed following the failure of a stub tube for an economizer outlet header. The leak in the header stub tube was at circumferentially oriented cracks that initiated at the inside surface. The cracked regions were approximately 180° apart circumferentially and located on the sides of the tube inline with the header axis. This cracking pattern is consistent with an applied bending moment that is out of the plane of the tubing assemblies. The ultrasonic inspections used the failed tube as a calibration standard. The deepest cracks (reflectors as a percent of calibration standard) were found primarily at the ends of the header, the first sixteen rows from the north end and the last twenty-two from the south end. The cracking at the ends of the header is believed to be due to thermal loads and the restraint to expansion of the economizer tubing at the crown seals. Both cracked and failed tubes were metallurgically examined using visual inspection, fractography, and optical metallography. The fracture surface has beach marks and the crack shape is thumbnail or semi-elliptical, characteristic of fatigue cracking. There are multiple cracks and many of the shorter crack segments have joined or linked up to form the final crack length. The cracks are transgranular and oxide-filled. The failure mechanism is corrosion fatigue.
A Review of Aging Effects in Alloy 617 for Gen IV Nuclear Reactor Applications
Authors: Ren Weiju , Swindeman Robert
Published: July 2008

The literature was reviewed of aging and aging effects in Alloy 617 to determine the supplementary data needed to understand the response of the alloy to long-time exposure conditions being considered for structural components in Gen IV nuclear reactors. Most of the data were produced in connection with the international research effort supporting High Temperature Gas-Cooled Reactor (HTGR) projects in the 1970s and 1980s. Topics considered included microstructural changes, hardness, tensile properties, toughness, creep-rupture, fatigue, and crack growth. It became clear that, for the long-time, very high temperature conditions of the Gen IV reactors, a significant effort would be needed to fully understand and characterize property changes. Several topics for further research were recommended.
Hot Isostatic Pressing of Type 316L/304K and Monel 400 Powders for Pressure Boundary Components
Authors: Burdett W. Barry
Published: July 2008

Hot Isostatic Pressing (HIP) has been used for many years to consolidate porosity in cast metal shapes to improve mechanical properties. When applied to fine metal powders, it becomes possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties and reduced cost. NNS items from powder deliver cost savings by reducing initial material usage and subsequent machining costs. Powder production and HIP processing are automated methods, which also provide protection against forging route obsolescence. Setup costs are lower and batch sizes smaller. HIPped powder microstructures are isotropic and equiaxed, with uniformly fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Inclusion contents are lower and of more benign geometry, easing fracture assessment. Use of the technology has grown, particularly in the offshore oil industry where it is already established in high integrity applications, particularly in place of welded joints. Take-up in the more conservative nuclear industry has been slow. The quality of HIPped powder items can provide through life cost savings since there is greater assurance of structural integrity compared to welded or wrought components. In a broad programme of testing, it was established that HIPped powder 316L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance. Work has now been extended to Monel 400 nickel-based alloys and Type 304L. The manufacturing technology has been tailored to produce pressure-retaining components in these alloys for prototype testing.
Effect of Cr or Ta Coating Thickness on Near-Bore Temperatures and Coating Interface Stress for Cannon Firing Conditions
Authors: Underwood John H. , Troiano Edward , Mulligan Christopher P. , Vigilante Gregory N.
Published: July 2008

Finite difference calculations of one-dimensional, convection-conduction, non-reacting heat flow are described, focusing on near-cannon-bore temperatures using time-dependent combustion gas temperatures and convection coefficient data derived from cannon interior ballistic codes. Temperatures are obtained for a 0.1-to-1.0 mm thickness range of chromium or tantalum coating over pressure vessel steel substrate, using temperature-dependent conductivity and diffusivity data for pure chromium and tantalum and ASTM A723 steel. In-situ verification of calculated temperature profiles is done by comparing with metallographic observation of depths of the steel phase transformation at its well characterized temperature. The temperature profiles are used to estimate the thermal shear stress at the interface of a crack-generated coating segment, with segment length characteristic of that observed from cannon firing. Finite element thermo-mechanical analysis is used to verify that the temperature difference used to estimate interface shear stress and the resulting stress values are realistic. Results show that: [i] temperatures and interface stress are somewhat higher for Ta than Cr coatings due to the lower heat capacity of Ta; [ii] interface stress is higher for thinner coatings, as expected, but reaches a maximum at 0.1 to 0.2 mm thickness, because of the limited temperature range that can be present in a thinner coating; [iii] the characteristic length of coating segment relative to coating thickness has important control over interface shear stress, with the longer segment observed for tantalum coatings providing a significant reduction in average shear stress compared to the stress for the smaller segments observed with chromium coatings.
One Dimensional Moving Heat Source in Hollow FGM Cylinder
Authors: Jabbari Mohsen , Mohazzab Amir Hossein , Bahtui Ali
Published: July 2008

This paper presents the analytical solution of one-dimensional mechanical and thermal stresses for a hollow cylinder made of functionally graded material. The material properties vary continuously across the thickness, according to power functions of radial direction. Temperature distribution is symmetric, and transient. The thermal boundary conditions may include conduction, flux, and convection for inside or outside of hollow cylinder. Thermoelasticity equation is transient, including the moving heat source. The heat conduction and Navier equations are solved analytically, using the generalized Bessel function. A direct method of solution of Navier equation is presented.
Soil-Structure Interaction: Theoretical and Experimental Results
Authors: Broc Daniel
Published: July 2008

In the study of the seismic behaviour of structures, the Soil Structure Interaction (SSI) is concerned with the interaction between the soil, from which come the solicitation, and the structure (building, industrial installation, ...). The SSI can be considered as a kind of multi physic problem. The physical phenomena for the soil or the structure are described by the same equations. But, for the soil, the best point of view is to consider wave’s propagation in an infinite medium, whereas for the structure, the most suitable approach is, in many case, to use eigen modes on the modal basis. The currently used numerical methods for SSI consider two different domains, with interactions at the interface. Boundary Element Methods (BEM) and Finite Element Methods (FEM) can be used. An application is presented, with the interpretation of test performed in Japan, for a Structure Soil Structure Interaction (SSSI) problem, considering the interactions between two adjacent buildings during an earthquake. The tests were performed by JNES in Japan, and the interpretations presented here are performed by CEA, in France, using FEM methods. The field test experiments have been carried out by NUPEC (JNES) under different conditions with one building, two identical buildings or two different buildings in an excavation, for the “surface configuration”, and in the “embedded configuration”, when the excavation is filled. Forced vibration test and earthquake observations are being carried out in the field test. NUPEC proposed a theoretical model for the interpretation of the experimental results, including soil and buildings mechanical characteristics. The results obtained with this model are similar to the experimental ones. Sensibility analyses have been developed, based on the NUPEC theoretical model, for the forced vibration tests and the seismic motion. It is possible to reproduce, with numerical simulations, the fact that, for two buildings, the movement under a seismic solicitation is a little lower for two adjacent buildings than for one isolated building.
An Elastic-Plastic-Creep Finite Element Analysis for Small Punch Creep Test Specimens
Authors: Ling Xiang , Zheng Yangyan , Qian Zhengmai
Published: July 2008

An elastic-plastic-creep finite element model, incorporating a Von Mises plastic flow rule and a creep damage equation, was established based on the small punch creep test on Cr5Mo steel specimens at 550 °C and three different loads. Finite element analyses were performed to examine the variation of the central creep deflection and the creep strain with time and the evolution of creep damage. The sensitivity of the creep deflection and equivalent stress at the centre on the disc to mesh size is discussed. Numerical results presented in this paper confirm that the creep damage at the central part is high. The stress gradients are highest near the centre area of the specimen (from 0 to 1 mm). Therefore, accurate stress and strain can be obtained using refined meshes near the specimen center and coarse meshes in other places. The test results are in agreement with those of the numerical simulation and three different stages appearing in the curve of creep deflection, which are quite similar to those observed in conventional creep tests.
Cylindrically Anisotropic Tubes Containing a Line Dislocation
Authors: Wang Chung-Hao
Published: July 2008

An analytical solution of the problem of a cylindrically anisotropic tube which contains a line dislocation is presented in this study. The state space formulation in conjunction with the eigenstrain theory is proved to be a feasible and systematic methodology to analyze a tube with the existence of dislocations. The state space formulation which expediently groups the displacements and the cylindrical surface traction can construct a governing differential matrix equation. By using Fourier series expansion and the well developed theory of matrix algebra, the asymmetrical solutions are not only explicit but also compact in form. The dislocation considered in this study is a kind of mixed dislocation which is the combination of edge dislocations and a screw dislocation and the dislocation line is parallel to the longitudinal axis of the tube. The degeneracy of the eigen relation and the technique to determine the inverse of a singular matrix are thoroughly discussed, so that the general solutions can be applied to the case of isotropic tubes, which is one of the novel features of this research. The results of isotropic problems, which are belong to the general solutions, are compared with the well-established expressions in the literature. The satisfied correspondences of these comparisons indicate the validness of this study. A cylindrically orthotropic tube is also investigated as an example and the numerical results for the displacements and tangential stress on the outer surface are displayed. The effects on surface stresses due to the existence of a dislocation appear to have a characteristic of localized phenomenon.
Green’s Functions for a Point Force in a Three-Phase Cylinder Composite
Authors: Chao C. K.
Published: July 2008

This paper presents an alternative efficient procedure to analyze plane elasticity problems of a circularly cylindrical layered media subject to an arbitrary point force. Based on the method of analytical continuation in conjunction with the alternating technique, the elastic fields of the three-phase media are derived. A rapidly convergent series solution which is expressed in terms of an explicit general term of the complex potential of the corresponding homogeneous problem is obtained in an elegant form. As a numerical illustration, the interfacial stresses are presented for different material combinations and for different positions of the point force.
Experience in Operation and Reconditioning of High Pressure Cylinder Heads for Hypercompressors for LDPE
Authors: Giacomelli Enzo , Fani Riccardo , Battagli Paolo , Pieraccini Michele
Published: July 2008

For hyper-compressors safety, operation and maintenance are important characteristics to be accounted during the design for the various components as the process gas reaches pressures up to 350 MPa (50,000 psi). Special cylinder arrangements are used, practically compound pressure vessels, normally excluded by Pressure Vessels design codes, but needing very high attention. A great help is derived by the application of innovative methods of simulation and modelling. Hyper-compressor cylinder heads with axial valves are subjected to very high pressure because of the configuration. To maximize endurance of these components, special considerations regarding materials and technical procedures such as auto-frettage are usually adopted. During operation the pressure pulsations corresponding to discharge and suction influence the mode of operation. Sealing effects generate relative movement between the valve body and the cylinder head which result in the possibility of wear in the area of contact between the seals and the internal bore surface. In addition, assembly and disassembly of the valve requires careful attention to avoid damage to the inner surface.
Seismic Design of Floating Roof of Oil Storage Tanks Under Liquid Sloshing
Authors: Yamauchi Yoshihiko , Kamei Asamichi , Zama Sinsaku , Uchida Yoshinori
Published: July 2008

The 2003 Tokachi-oki earthquake caused the severe damage to oil storage tanks by liquid sloshing. Especially at Tomakomai in Hokkaido, the ground motions at the periods of 3 to 8 sec predominated, which were harmonized with the natural period of liquid sloshing of oil storage tanks, then seven single-deck-type floating roofs were damaged and sank. For the 30,000kl FRT(φ 42.7m), one of those tanks, with about 7 see of fundamental sloshing period, maximum sloshing wave height was estimated 3m and over. On the other hand, for the 100,000kl FRT(φ 78.2m) with about 12 sec of fundamental sloshing period, maximum sloshing wave height was estimated about 1.5m and the excitation of 2nd sloshing mode was considered to be strongly excited. Considering both of nonlinear behavior of a large amplitude wave of 1st sloshing mode and nonlinear effects of large deflection of a deck plate at 2nd sloshing mode, we established the simplified method of seismic design of single-deck-type floating roofs using modified velocity response spectrum. This spectrum was based on many studies, investigated by Zama [1] and others, of the prediction of long-period strong ground motion and of liquid sloshing of oil tanks in Japan.
A Structural Integrity Assessment of Underground Piping Associated With the Transfer of Radioactive Waste
Authors: Wiersma Bruce J. , Thaxton G. Donald , Plummer A. Scott
Published: July 2008

Radioactive wastes are confined in 49 underground storage tanks at the Savannah River Site. The waste is transported between tanks via underground transfer piping. An assessment of the structural integrity of the transfer piping was performed to ensure that the present condition of the piping was sound and to provide life expectancy estimates for the piping based on anticipated service. The assessment reviewed the original design of the piping, the potential and observed degradation mechanisms, the results from past inspections of the piping, and a Fitness-For-Service evaluation for a section of piping that experienced pitting in a locally thinned area. The assessment concluded that the piping was structurally sound. Assuming that service conditions remain the same, the piping will remain functional for its intended service life.
A Study on the Powder Consolidation of Metal Powder for Magnetic Material Using Underwater Shock Wave
Authors: Kawano Kazuhiro , Kim Young Kook , Hamashima Hideki , Itoh Shigeru
Published: July 2008

In order to consolidate metal powders, the present investigation uses a shock wave derived from the detonation of an explosive and it’s called a shock compaction method. In the present investigation, we employed an ultra-high pressure generation device in order to generate underwater shock wave. The underwater shock wave is derived from the detonation wave in a water container and after that underwater shock wave is converged in the central axis. Finally, the high pressure of underwater shock wave is uniformly impinged on the powders. In case of experimental data that is measured by manganin gauge, the peak pressure of underwater shock wave is 16.8GPa, the result of numerical analysis is 17.9GPa. Considering for the measurement error (1GPa), it seems to be good agreement between the result of numerical analysis and experiment. Nd-Fe-B magnetic material powders are tried to consolidate using the assembly under optional temperatures by heating system and the samples recovered under different conditions were examined in terms of magnetic properties.
Analysis of Shock Wave Propagating in PMMA
Authors: Hemuki Yosuke , Hamashima Hideki , Itoh Shigeru
Published: July 2008

There are a lot of studies related to the shock wave which generated by explosive, for example, explosive compaction, explosive cladding, and explosive forming. It is necessary and indispensable in these studies to know the material characteristics of container loaded with an explosive. Since the force of a shock wave changes with the material of containers. To investigate the material characteristics of a container, the shock wave propagating in the material has analyzed. In this research, Polymethylmethacrylate (PMMA) which usually used as loading container of explosive used as container material. For analysis, the pressure measurement experiment by the manganin gauge (Kyowa Electric Industrial Co., ltd.,), numerical analysis by LS-DYNA3D (commercial program based on the explicit finite element code) and optical observation by high-speed are used. A lot of data about the shock wave propagating in PMMA was obtained.
Evaluation of Creep Strength Reduction Factors for Welded Joints of Modified 9Cr-1Mo Steel (P91)
Authors: Tabuchi Masaaki , Takahashi Yukio
Published: July 2008

In order to review the allowable creep strength of high Cr ferritic steels, creep rupture data of base metal and welded joints have been collected and long-term creep strength have been analyzed in the SHC committee in Japan since 2004. In the present paper, the creep rupture data of 370 points for welded joint specimens of modified 9Cr-1Mo steel (ASME Grade 91) offered from seven Japanese companies and institutes were analyzed. These data clearly indicated that the creep strength of welded joints was lower than that of base metal due to Type IV fracture in HAZ at or above 600°C. From the activities of this committee, the master curve for life evaluation of welded joints of Gr.91 steel could be represented as follows: LMP==34154+3494(logσ)−2574(logσ)2,C=31.4 The reduction factor of 100,000 hours creep rupture strength of welded joint to base metal was concluded to be 0.75 at 600°C and 0.70 at 650°C for the Gr.91 steel.
Study on Explosive Forming of a Light Alloy Plate
Authors: Iyama Hirofumi , Itoh Shigeru
Published: July 2008

The explosive forming is one of the forming methods of metal plates has been performed since 1950. This method is different from usual static press forming. The metal plate is accelerated by underwater shock wave, which is generated by underwater explosion of an explosive. We have tried the experiment of aluminum alloy forming using this method. In this research, a forming limit for aluminum alloy has been clarified from the experimental results. Then, we have tried the numerical simulation for this method using finite difference method. In this research, two methods for forming aluminum plates using closed metal vessel and paper vessel are introduced and the results of numerical simulations corresponding to those experimental conditions are shown.
Numerical and Experimental Study of Destruction of Metal Pipes Through Use of High Explosive
Authors: Hamashima Hideki , Pericevic Ian Owens , Moatamedi Moji , Itoh Shigeru
Published: July 2008

Various liquids are commonly transported through metal pipes. For reasons of safety it is important to understand the behavior of pipes when subject to an explosive loading from within. This research paper is concerned with examining the expansion and destruction of metal pipes subjected to a high power explosion by high explosive. An experimental study was carried out for this research and visualized using high-speed camera images. Results were then compared to a computer simulation of the same problem. Numerical simulations are performed in three dimensions using the LS-DYNA code. Results obtained numerically compared well to those from experiment.
Efficient Modeling of the Relevant Effects for Water Hammer Calculation
Authors: Diesselhorst Tilman , Schnellhammer Werner
Published: July 2008

The essential features for an adequate simulation of water hammer effects are incorporated in the one-dimensional fluiddynamic code ROLAST. This code was developed for the calculation of transient load cases in piping networks, including active and passive components like pumps, valves, check valves, vessels, and allowing for various boundary and initial conditions. The essential models for water hammer treatment are described like condensation, air bubble behaviour and venting, and especially their adaptation to the 1D flow formulation. Examples of validation are given. The role of dissolved air is discussed. The effects of dynamic friction and coupling with the structural analysis on a realistic damping behavior are explained. The code allows the calculation of realistic water hammer loads on the system by considering the reaction of components like check valves at the some time.
The Capabilities and Limitations of Remote Visual Methods to Detect Service-Induced Cracks in Reactor Components
Authors: Cumblidge Stephen E. , Doctor Steven R. , Anderson Michael T.
Published: July 2008

Since 1977, the U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research has funded a multiyear program at the Pacific Northwest National Laboratory (PNNL) to evaluate the reliability and accuracy of nondestructive evaluation (NDE) techniques employed for inservice inspection (ISI). Recently, the U.S. nuclear industry proposed replacing current volumetric and/or surface examinations of certain components in commercial nuclear power plants, as required by the ASME Boiler and Pressure Vessel Code Section XI, with a simpler visual testing (VT) method. The advantages of VT are that these tests generally involve much less radiation exposure and examination times than do volumetric examinations such as ultrasonic testing (UT). However, for industry to justify supplanting volumetric methods with VT, an analysis of pertinent issues is needed to support the reliability of VT in determining the structural integrity of reactor components. As piping and pressure vessel components in a nuclear power station are generally underwater and in high radiation fields, they need to be examined by VT from a distance with radiation-hardened video systems. Remote visual testing has been used by nuclear utilities to find cracks in pressure vessel cladding in pressurized water reactors, core shrouds in boiling water reactors, and to investigate leaks in piping and reactor components. These visual tests are performed using a wide variety of procedures and equipment. The techniques for remote visual testing use submersible closed-circuit video cameras to examine reactor components and welds. PNNL has conducted a parametric study that examines the important variables that affect the effectiveness of a remote visual test. Tested variables include lighting techniques, camera resolution, camera movement, and magnification. PNNL has also conducted a laboratory test using a commercial visual testing camera system to experimentally determine the ability of the camera system to detect cracks of various widths under ideal conditions.
Water Hammer in Horizontal Water-Steam Counter-Current Flow
Authors: Gale Janez
Published: July 2008

A six-equation, one-dimensional, two-fluid model of the two-phase flow, incorporated into the recently developed computer code WAHA, was used to model water hammer transient initiated with liquid-vapor counter-current flow in the horizontal pipe. The applied flow regimes and closure relations of the WAHA code for the inter-phase exchange of mass, momentum and energy are described and discussed. Although the WAHA code flow regime maps turned out to be sufficient and accurate for simulations of the column separation type of the fast transients, the current analysis pointed out the need to introduce some limiting values for dispersed flow regime correlations in order to successfully simulate water hammer initiated by condensation-induced counter-current flow. The WAHA code with modified relaxation source terms was then successfully utilized for simulations of the experiments performed at the Hungarian PMK-2 test facility.
Substitution of High-Pressure Charge by Electrolysis Charge and Hydrogen Environment Embrittlement Susceptibilities for Inconel 625 and SUS 316L
Authors: Murakami Kota , Yabe Nobuaki , Suzuki Hiroshi , Takai Kenichi , Hagihara Yukito , Wada Yoru
Published: July 2008

Hydrogen-fuel-cell vehicles have been developed and the gaseous pressure in the current major storage tanks of the vehicles varies from 35 to 70 MPa because of the demand for the increase in running distance. Hydrogen refueling stations are required to be resistant to 100 MPa hydrogen gas and the alloys used for such stations are required to have an excellent resistance to hydrogen environment embrittlement (HEE). The purposes of the present study are to substitute the high-pressure gaseous charge of hydrogen by electrolysis charge and to evaluate hydrogen degradation susceptibilities for Inconel 625 and SUS 316L in the environments substituted by electrolysis charge. Electrolysis hydrogen was charged to Inconel 625 and SUS 316L at various electrolysis fugacities and gaseous hydrogen was charged from 0.3 to 45 MPa hydrogen gas at 90°C. Hydrogen states and contents were compared using thermal desorption analysis (TDA). Hydrogen degradation susceptibilities were evaluated using the slow strain rate technique (SSRT) at a constant extension rate of 8.6×10−6 /s at room temperature. The fundamental properties of thermal hydrogen desorption for Inconel 625 and SUS 316L were first analyzed to compare the hydrogen states after hydrogen charge by electrolysis and high pressure. The peak temperatures and profiles of hydrogen desorption do not change with charging temperature. When hydrogen is charged by electrolysis and high pressure until hydrogen saturation at 90°C, the peak temperatures and profiles are the same in both environments. This means that hydrogen diffusion during and hydrogen states after hydrogen absorption are independent of charging method in spite of the differences in adsorption and dissociation reaction on the specimen surfaces. Using Sieverts law, the fugacity of electrolysis can transform into gaseous pressure. This indicates that high-pressure hydrogen environments in pipes or other components at hydrogen refueling stations can be substituted by electrolysis charge. Fracture strain in Inconel 625 decreases as hydrogen content charged by electrolysis increases, whereas that in SUS 316L does not change regardless of the hydrogen content of 161.5 mass ppm. Grain boundary fracture is observed on the surface of Inconel 625 absorbing a hydrogen content of 27.5 mass ppm, which corresponds to 59.2 MPa hydrogen gas at R.T using Sieverts law. In contrast, the fracture surfaces of SUS 316L hydrogen-charged at extremely high fugacities remain ductile dimples. Thus, hydrogen degradation susceptibility is much lower for SUS 316L than for Inconel 625.
Negligible Creep Conditions for Mod 9Cr1Mo Steel
Authors: Riou Bernard , Escaravage Claude , Swindeman Robert W. , Ren Weiju , Cabrillat Marie-The´re`se , Allais Lucien
Published: July 2008

Mod 9Cr1Mo Steel (grade 91) is one of the materials envisaged for the Reactor Pressure Vessel of Very High Temperature Reactors. To avoid the implementation of a surveillance program covering the monitoring of the creep damage throughout the whole life of the reactor, it is recommended to operate the Reactor Pressure Vessel in the negligible creep regime. In this paper, the background of negligible creep criteria available in nuclear Codes is first recalled and their limitations analyzed. Then, guidance for deriving criteria more appropriate for mod 9Cr1Mo steel is provided. Finally, R&D actions in the U. S. and France to support the new approaches are discussed and recommended.
Techniques for Improved Reliability of Wall Thinning Estimation
Authors: Garud Yogendra S.
Published: July 2008

Wall thinning in pressure retaining components, especially due to the flow-accelerated corrosion, has been a significant factor affecting the safety and unplanned system downtimes. On the other hand, overestimating the impact of possible wall thinning often leads to unnecessary or expensive inspections and replacements. The simplified or quick (short-cut) methods of analysis and prediction often lack the requisite degree of accuracy and confidence. This paper presents a few techniques for better analysis of the wall thinning data to address these issues. These techniques make use of the statistical methods, pattern recognition, and optimization to perform a robust data filtering and thinning rate estimation that accounts for measurement uncertainty. The techniques are discussed with application to a large database and an inspection program. The impact of these analytical improvements is presented in comparison with results of the simplified method of analysis. The results include both the margin on remaining life and the projected wall thinning rates, with implications for inspections.
On Sterilization Using the Underwater Shock Wave Under Non-Heating Environment
Authors: Takemoto Ayumi , Oda Asuka , Iwahara Masayoshi , Itoh Shigeru
Published: July 2008

The establishment of the sterilization technology in non-heating environment is requested in the food industry and a lot of other fields. The existing sterilization technology using the high pressure is mainly liberating rapid pressure and a lot of loadings. In this research, the sterilization by a high pressure was tried by using the underwater shock wave caused by explosive. The detonating fuse was detonated with the percussion cap, and the shock wave was generated. Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Saccharomyces cerevisiae were used. The underwater shock wave barely causes heat. An excellent bactericidal effect of 100% was obtained in the maximum in the experiment that used S. cerevisiae.
Material Surveillance of CANDU Zirconium 2.5%Wt Niobium Pressure Tubes
Authors: Celovsky A. , Noye B. , Eager R.
Published: July 2008

There are 26 operating CANDU nuclear power plants, varying in size from 540 to 880 MW(e). The majority (18) of these plants are located in Canada, with others located in Argentina, Korea, China, and Romania. These plants entered commercial service at various times between 1971 and 2003. As such, some of the plants are more than 30 years old. In addition, there are new plants under construction and some older plants under refurbishment. Each plant contains between 380 and 480 fuel channels, for a total of almost 11,000 fuel channels currently in-service. A fuel channel is comprised a Zr-2.5%Nb pressure tube, stainless steel endfittings, a zircaloy-2 calandria tube, and a series of annulus spacers (Figure 1). The pressure tube serves to: i) Support and locate the nuclear fuel bundles, ii) Form part of the pressure boundary of the heavy water coolant system, and iii) Provide an additional boundary between the nuclear fuel and the external environment.
Effect of Shock Loading on Food Processing
Authors: Watanabe Toshiaki , Maehara Hironori , Oda Asuka , Itoh Shigeru
Published: July 2008

In the food industry, it is hoping high value-aided product and the increase in efficiency of food processing. On the other hand, we get an experimental result that the load of the shock wave improves an extraction of food, and soften food. But, the safe and high efficiency pressure vessel for the processing is necessary to apply these technologies to the food processing field actually. Therefore, we are planning the development of the pressure vessel for food processing. The fundamental data of the shock loading to food are necessary in order to make suitable vessel. As for these data, it is variety the specifications required by the kind of food and effect to expect. We report the result that shock wave loading was done to various food.
FEM-MD Coupling Simulation for Strength and Fracture Analyses Near Grain Boundary Zone of Structural Steels
Authors: Mochizuki Masahito , Higuchi Ryota , Katsuyama Jinya , Toyoda Masao
Published: July 2008

FEM-MD coupling method is proposed for the evaluation of the strength properties of structural steels. It is important to investigate the stress distribution by considering the microscopic heterogeneity and deformation near the grain boundary for clarification of the mechanism of fracture and the material design. FEM-MD coupling method is used to estimate the stress distribution. Especially, the influence of microstructure of steel on strength properties is investigated by estimating the difference of stress distributions caused by different distributions of the grain shape, such as grain diameter, aspect ratio and grain orientation.
Root Cause Analysis of SI Nozzle Thermal Sleeve Breakaway Failures Occurred at PWR Plants
Authors: Jo Jong Chull , Jhung Myung Jo , Yu Seon Oh , Kim Hho Jung , Yune Young Gill
Published: July 2008

Thermal sleeves in the shape of thin wall cylinder seated inside the nozzle part of each safety injection (SI) line at pressurized water reactors (PWRs) have such functions as prevention and relief of potential excessive transient thermal stress in the wall of SI line nozzle part which is initially heated up with hot water flowing in the primary coolant piping system when cold water is injected into the system through the SI nozzles during the SI operation. Recently, mechanical failures that the sleeves are separated from the SI branch pipe and fall into the connected cold leg main pipe occurred in sequence at some typical PWR plants in Korea. To find out the root cause of thermal sleeve breakaway failures, the flow situation in the in the junction of primary coolant main pipe and SI branch pipe and the vibration modal characteristics of the thermal sleeve are investigated in details by using both computational fluid dynamic (CFD) code and structure analysis finite element code. As the results, the transient response in fluid pressure exerting on the local part of thermal sleeve wall surface to the primary coolant flow through the pipe junction area during the normal reactor operation mode shows oscillatory characteristics with the frequencies ranging from 15 to 18, which coincide with the lower mode natural frequencies of thermal sleeve having a pinned support condition on the circumferential prominence on the outer surface of thermal sleeve which is put into the circumferential groove on the inner surface of SI nozzle at the mid-height of thermal sleeve. In addition, the variation of pressure on the thermal sleeve surface yield alternating forces and torques in the directions of two rectangular axes perpendicular to the longitudinal axis of cylindrical thermal sleeve, which causes both rolling and pitching motions of the thermal sleeve. Consequently, it is seen that this flow situation surrounding the thermal sleeve during the normal reactor operation can induce resonant vibrations accompanying the shaking motion of the thermal sleeve at the pinned support condition, which finally leads to the failures of thermal sleeve breakaway from the SI nozzle.
Integrity Assessment of Spherical Pressure Components With Local Corrosion and Hot Spots
Authors: Tantichattanont Pattaramon , Adluri Seshu , Seshadri Rangaswamy
Published: July 2008

Corrosion damage and hot spots are typical of damages that can occur in ageing pressure vessels and pipelines used in industrial processes. Internal and external corrosion could be the result of corrosive products stored inside or harsh environmental conditions on the outside. Hot spots are caused by damage due to loss of refractory lining on the inside wall of pressure components or due to maldistribution of flow containing catalyst and reactive fluids. The structural integrity of such ageing components needs to be evaluated periodically to establish the continued suitability of the vessels under operating conditions. The present paper develops a method for Level 2 (as categorized by API 579) structural integrity evaluations of spherical pressure vessels containing local corrosion damage or hot spot. The decay lengths for spherical shells subject to local damages have been studied based on stretching and bending effects using elastic shell theories so as to identify the reference volume participating in plastic action. A limit for “local” corroded spot or hot spot is defined by the size of damage that an onset of pure membrane action occurs inside the damaged area. The size of damage indicating the crossover from dominance of stretching effects on the damage behavior to that of bending effects is also presented. The lower bound recommended “remaining strength factors” for spherical pressure vessels containing corrosion or hot spot are formulated by application of Mura’s integral mean of yield criterion and the improved lower bound mα-multiplier. Three alternative recommendations are proposed. The effectiveness of the proposed methods is evaluated and demonstrated through illustrative examples and comparison with inelastic finite element analyses.
SPECTRA Thermal Fatigue Tests Under Frequency Controlled Fluid Temperature Variation: Transient Temperature Measurement Tests
Authors: Kawasaki Nobuchika , Kobayashi Sumio , Hasebe Shinichi , Kasahara Naoto
Published: July 2008

The coolant leakage by thermal striping phenomenon should be prevented at nuclear power plants and a lot of efforts are made to develop its evaluation methods. The frequency transfer function method can be used to obtain temperature and stress response to fluid temperature history using transfer function models; therefore it is considered as an excellent evaluation method. To measure temperature response of structures to fluid temperature variations and to confirm their frequency characteristics, transient temperature measurement tests were performed by JAEA. In the transient temperature measurement tests, three different frequencies of sinusoidal fluid temperature waves (0.05, 0.2, 0.5Hz) were controlled using frequency controlled thermal fatigue test equipment (SPECTRA) and temperature responses at inner and outer piping surfaces were measured along the test sections. Frequency effects on temperature attenuation during transfer process from fluid to structures were confirmed and the effective heat transfer function in frequency transfer function method was verified by transient temperature measurement test results.
New UK Research Programme on Fracture Mechanics
Authors: Yellowlees S. F. , Watson C. T.
Published: July 2008

A new long-term research programme has been launched in the UK. This involves Rolls-Royce plc and Serco Assurance, supported by UK industry and academia. A significant part of the programme is aimed at improving methodologies for assessing the significance of defects in structures, either by deriving new methodologies, further developing existing methodologies, and/or providing validation data. Current work packages include consideration of: • The treatment of secondary stresses; • Flaw characterisation; • Load history effects; • The interaction between ductile tearing and growth by other mechanisms; • Constraint. As these work packages mature, other topics may be considered such as: • Assessment methodologies for displacement/strain controlled loading; • The treatment of structures operating in or close to the brittle to ductile transition region; • The treatment of material interfaces; • Leak before break; • Crack arrest. The work is being undertaken by a combination of computational and experimental studies. The benefits of this work are intended to be the provision of more realistic assessment methodologies. In many instances this will be achieved by first validating the assumptions in current methodologies to provide a sound basis for the development of future methodologies. This paper presents an overview of the fracture mechanics research work being undertaken and provides examples of the outcome of some of the studies obtained to-date.
An Implementation of the Gurson-Tvergaard-Needleman Plasticity Model for ABAQUS Standard Using a Trust Region Method
Authors: Beardsmore D. W. , Wilkes M. A. , Shterenlikht A.
Published: July 2008

The Gurson-Tvergaard-Needleman (GTN) model is a material plasticity model in which the accumulation of ductile damage is represented by the nucleation, growth and coalescence of micro-voids. The model has been implemented in full for the ABAQUS finite element code. The model supports fully the nucleation, growth, and coalescence of voids, and differs from the porous plasticity model provided in ABAQUS/Standard. The GTN model is just one model from a particular class of pressure-dependent plasticity models in which the response is dependent on the development of the hydrostatic stress as well as the deviatoric stress tensor. A formal derivation of the constitutive equations is presented in this paper. It is shown that the model can be formally represented by a coupled system of four non-linear equations. A novel approach to solving the equations has been adopted based on a hybrid solution method and a trust region to ensure convergence. The solution of non-linear equations in more than one variable is usually attempted using iterative methods. For the calculation of a material’s response, the method adopted must be sufficiently robust to ensure that the correct result is obtained at each of the material points in the component or structure being modelled. Moreover, the solution method must be as efficient as possible for practical use. In this paper, we present an implementation of a trust region method that allows the solution of the GTN constitutive equations to be derived with confidence. The method utilises iterative corrections and a trust region surrounding the current estimated solution. In the early stages of the iteration, when the estimate may be far removed from the true solution, the steepest descent method is used to improve the solution, while at later stages Newton’s method, with its superior convergence, is used. A hybrid step (part steepest descent step, part Newton step) may also be taken using Powell’s dogleg method with the constraint that the corrections do not take the solution outside the current trust region. A measure of the quality of each step is used to shrink or expand the radius of the trust region during the iteration. The solution algorithm has been implemented in Fortran 90 as a user subroutine for ABAQUS/Standard. The method provides faster convergence than the porous plasticity model in ABAQUS and allows for the representation of void coalescence. Examples of application of the GTN model to study the response of axi-symmetric bars are provided and comparisons are made with the porous plasticity model where appropriate.
Qualification of Portable Phased Arrays to ASME Section V
Authors: Ginzel Robert K. , Ginzel Ed A. , Davis J. Mark , Labbe´ Simon , Moles Michael D. C.
Published: July 2008

This paper describes the processes required to approve new and advanced inspection techniques for ASME Section V, specifically for Olympus NDT’s OmniScan portable phased array unit. The rationale and processes required for Section V, both Article 4 and the new Article 14 for advanced techniques, is described. The various processes are applied to encoded electronic scanning (i.e. fixed angle raster scanning, or E-scans); the same processes can be applied to encoded Sectorial scans (S-scans) where the beam is swept through a range of angles, and manual S- and E-scans. A variety of techniques, procedures, methodology and reporting documents have been developed for phased arrays. In addition, an update is given on other code developments.
Development of Defect Interaction Criteria for Pipeline Girth Welds Subjected to Plastic Collapse Conditions
Authors: De Waele Wim , Denys Rudi , Lefevre Antoon
Published: July 2008

Multiple defects in welds, when detected, have to be assessed for interaction. Current defect interaction rules are largely based on linear elastic fracture mechanics principles (brittle material behaviour). Pipeline welding codes, however, specify toughness requirements to ensure ductile failure by plastic collapse. Therefore, the use of current (elastic) interaction rules for ductile girth welds can lead to unnecessary and possibly harmful weld repairs or cutouts. This paper reports on an assessment of the engineering significance of existing pipeline specific interaction criteria and on the development of new criteria. Rules for the interaction of coplanar surface breaking defects and ductile material behaviour have been developed on the basis of the performance requirement of remote yielding. The results of large-scale tensile tests illustrate that current interaction rules have a high degree of conservatism for plastic collapse conditions. The test data have been used to demonstrate that the developed procedure can be safely used for ductile girth welds.
Generating Well Defined Residual Stresses in Laboratory Specimens
Authors: Mahmoudi Amir-Hossein , Aird Christpher , Truman Christopher E. , Mirzaee-Sisan Ali , Smith David J.
Published: July 2008

Residual stresses play an important role in increasing and decreasing the possibility of failure. The magnitude and direction of the residual stresses is an important factor in the integrity of engineering structures, including those containing defects. Ideally, we would like to gain insight into the integrity of a structure through testing laboratory samples. The purpose of this paper is to review methods of introducing residual stresses into laboratory specimens that are either subsequently loaded to fracture or used to assess the influence of residual stress on material damage mechanisms. Three methods, mechanical, thermal and welding, are scrutinized and illustrative examples provided. The advantages and disadvantages are explored. We conclude that new methods that do not introduce microstructural changes during the generation of residual stress should be sought if an improved understanding of the effects residual stress on fracture is required.