bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation on Constraint Effect of Reactor Pressure Vessel Under Pressurized Thermal Shock
Authors: Ogawa Naoki , Yoshimoto Kentaro , Hirota Takatoshi , Sakaguchi Shohei , Oumaya Toru
Published: January 2014

In recent years, the integrity of reactor pressure vessel (RPV) under pressurized thermal shock (PTS) accident has become controversial issue since the larger shift of RTNDT in some higher fluence surveillance data raised a concern on RPV integrity. Under PTS condition, the combination of thermal stress due to a temperature gradient and mechanical stress due to internal pressure causes considerable tensile stress inside the wall of RPV. Currently, RPV integrity is assessed by comparing stress intensity factor on a crack tip under PTS condition and a reference toughness curve based on the fracture toughness data of irradiated compact specimens. Since PTS loading is large enough to cause plastic deformation, a crack tip behavior on the inner surface of RPV can be explained by elastic-plastic fracture mechanics using the J-integral.

In this study, 3D elastic plastic finite element analyses were performed to assess the crack tip behavior on surface of a RPV under Loss of coolant Accident, which causes one of the most severe PTS condition. In order to quantify the constraint effect on a surface crack, J-Q approach was applied. The constraint effect of a surface crack was compared with a compact specimen and its influence on the fracture toughness was assessed.

As a result, the difference of constraint effect was clearly obtained. And it is recommended to consider constraint effects in the evaluation of structural integrity of RPV under PTS.
The Effects of Gravity on Structural Vibration
Authors: Jones J. William , Nickell Robert E. , Bulat William
Published: January 2014

A simplified method for incorporating gravitational effects into the analysis of structural vibrations, and for determining the relative importance of those effects, has been developed. The nonlinear effect has been simplified by incorporating only the first-order gravitational effects into the structural stiffness formulation, and demonstrating through both analysis and experiment that the first-order stiffness additions are sufficient to accurately characterize the gravitational effects in most cases. The simplified formulation also provides a convenient method for determining the conditions under which the effects of gravity should be considered.
Evaluating Fitness-for-Service Assessment Procedures for Pressurized Components Subject to Local Thin Areas Near Structural Discontinuities
Authors: Prueter Phillip E. , Dewees David J. , Brown Robert G.
Published: January 2014

Current minimum spacing requirements for local thin areas near structural discontinuities in pressurized components are outlined in Part 5 of API 579-1/ASME FFS-1, Fitness-For-Service. For Level 1 and Level 2 assessments, it is recognized that the current spacing criteria can be overly conservative. This paper examines preliminary results from a Materials Properties Council Fitness-For-Service Joint Industry Project that is intended to evaluate the current spacing criteria and develop a potential methodology for new assessment procedures based on computational results. Finite element models are employed to examine the interaction of stresses between local thin areas and stiffening rings and to investigate the relationship between local thin area spacing and pressure capacity. Performance is compared for models with and without areas of local metal loss near stiffening rings to form a potential basis for an improved assessment procedure. Furthermore, a criterion for classifying stiffening rings as major axisymmetric structural discontinuities is proposed.
Assessing Flanged Joint Leakage and Tube-to-Tubesheet Joint Failure due to Fluid Temperature Differentials in a Floating Head Heat Exchanger Using Finite Element Analysis
Authors: Prueter Phillip E. , Macejko Brian , Dewees David J. , Brown Robert G.
Published: January 2014

This paper uses three dimensional (3D) finite element analysis (FEA) to investigate the likelihood of leakage at the head-to-tubesheet joint and the possibility of failure at the tube-to-tubesheet joints due to temperature differentials between the shell-side and tube-side process fluid in a four-pass, floating head heat exchanger. The gasket at the floating head-to-tubesheet joint is explicitly modeled and the flange bolts are included with the appropriate amount of preload. Steady-state heat transfer analysis is performed on the 3D model to obtain realistic temperature gradients that are used to evaluate the system behavior in the ensuing structural analyses. Furthermore, different methods of approximating the stiffness of the tube bundle and the corresponding gasket stresses and tubesheet deflections are investigated in detail and compared. These comparisons indicate that simplified methods of modeling the tube bundle permit efficient thermal-mechanical evaluation of complex, multi-pass heat exchangers while achieving reasonable tubesheet and flanged joint behavior.
Ductile Fracture Simulation of a Pipe of Steam Generator in PWR
Authors: Miyajima Yuuki , Kikuchi Masanori , Takahashi Akiyuki
Published: January 2014

Ductile fracture of steam generator pipes may occur due to inner pressure. The final fracture process by inner pressure occurs as a burst of a pipe, and ductile high speed crack growth occurs with large deformation of the structure. For the simulation of such fracture process, Gurson’s yield function is used as a constitutive equation, and large deformation theory is employed. As the simulation is conducted by load control condition, it is difficult to simulate burst phenomenon. Final fracture condition is discussed and finally crack opening displacement is chosen as burst fracture criterion. Fracture simulations of a pipe with multiple through cracks are conducted by changing distances between two crack tips. Burst loads are evaluated, and they are compared with estimated values by Maintenance rules. Surface crack problems are also simulated. Burst loads are also compared with results by limit load analysis method. Conservativeness of conventional evaluation methods are studied and discussed.
Development of Pipe Wall Thinning Evaluation Method and Prediction Tool
Authors: Yoneda Kimitoshi , Morita Ryo , Fujiwara Kazutoshi , Inada Fumio
Published: January 2014

Flow accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI) are the main pipe wall thinning phenomena in piping system of power plants in Japan. Authors have promoted the development of prediction method to evaluate local thinning trend by FAC/LDI. To apply the method to pipe wall thinning management in power plants, it is required to be transformed into practical tools for easy usage. In Japan, discussion is being made to considerate the introduction of prediction tools into wall thinning management based on wall thickness measurement at present.

Authors have simplified their FAC/LDI models to predict wall thinning trend one-dimensionally along piping layout, and applied to actual thinning data of power plants. With PWR’s FAC data and BWR’s LDI data, maximum thinning rate for each pipe elements were roughly predictable with considerable accuracy. Especially for high thinning rate data, which is important in plant management, the model was able to evaluate within the factor of 2. By installing this model, prediction software “FALSET” was developed, equipped with practical functions for the management. With the further verification and improvement of each function, there are prospects for this software to be utilized as a management tool in power plants.
Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (3) Development of the Material Strength Standard of Modified 9Cr-1Mo Steel
Authors: Onizawa Takashi , Nagae Yuji , Takaya Shigeru , Asayama Tai
Published: January 2014

This paper describes the material strength standard of Modified 9Cr-1Mo (ASME Gr.91) steel in the design code for fast reactors of 2012 edition published by the Japan Society of Mechanical Engineers. Modified 9Cr-1Mo is to be used for primary and secondary coolant circuits, including intermediate heat exchangers and steam generators for the Japan Sodium Cooled Fast Reactor (JSFR). Modified 9Cr-1Mo steel was developed in Oak Ridge National Laboratory in the United States. Application of Modified 9Cr-1Mo to JSFR needs the material strength standard. Therefore, the authors developed the material strength standard. The material strength standard involved allowable limits such as S0, Sm, Su, Sy, SR and St and so on, environment effects such as sodium effects. In addition, material characteristic equations (Creep rupture equation, creep strain equation and equation of best fit curve for low-cycle fatigue life and so on) necessary for the allowable limits were involved. This paper describes the contents of the material strength standard.
Deformation of a Pipe Bend as an Element of a Piping System Under Harmonic Loading
Authors: Batura Anatolii , Orynyak Igor , Radchenko Sergii , Borodii Mykhaylo
Published: January 2014

Analysis of the vibration behavior of a pipe bend was conducted by the methods of the shell theory. To take into account with a high accuracy the ovalization of this piping element under harmonic vibrations authors proposed to use an analytical expression for the dynamic coefficient of the bend flexibility, which is the analog of well-known static Karman’s coefficient. This original approach allows to use beam models instead of the complex shell models for rigorous pipeline modeling.
Structure Dynamics Analysis in Inhomogeneous Density Flows
Authors: Rajaomazava Tolotra Emerry , Benaouicha Mustapha , Astolfi Jacques-André
Published: January 2014

The dynamics of a 2d-hydrofoil section immersed in inhomogeneous density flows is studied. A model based on a decomposition of the fluid variables (velocity and pressure) into two components is used. The first components describe the flow of the fluid around the hydrofoil while the second ones are related to the flow generated by the vibration. The linearized equations governing the flow induced by the vibration of the structure are then obtained. The effect on the structure dynamics of the fluid mass density variation at the fluid-structure interface is studied. The results are compared to the homogeneous flow case and analyzed.
Impact of Thermal Hazards on Process Buildings Using CFD Techniques
Authors: Raibagkar Anay , Edel Matthew
Published: January 2014

The impact of thermal hazards on process buildings is an important component of site hazard evaluations. API RP-752 recommends that process facilities analyze thermal hazards and assess their impact to onsite buildings and their occupants. Thermal loads resulting from fires in process units and equipment can have a significant impact on buildings, especially if the building is close to the fire source. Some buildings may be designed for blast and toxic protection, which allows the buildings to be located near process units and equipment, but possibly exposed to thermal hazards from a potential fire.

Screening-level thermal models typically used in process safety applications cannot account for detailed building geometries and how they may affect thermal impact from fire on building occupants. A more robust approach using the Fire Dynamics Simulator Computational Fluid Dynamics (CFD) code has been used in this study to assess the impact of thermal hazards on a target building located downstream of a jet fire. Temperature and radiation increases inside the building due to the thermal loads at the building exterior surface were calculated. The results indicate that buildings can provide protection to occupants depending on exposure time and building/insulation design. The results clearly show that a detailed CFD model can be effectively used to assess the thermal impact of incident radiation on buildings and to assist designers with determining requirements for the building envelope to provide protection to building occupants.
Main Issues on the Seismic Design of Industrial Piping Systems and Components
Authors: Paolacci Fabrizio , Reza Md. Shahin , Bursi Oreste S. , Gresnigt Arnold M. , Kumar Anil
Published: January 2014

A significant number of damages in piping systems and components during recent seismic events have been reported in literature which calls for a proper seismic design of these structures. Nevertheless, there exists an inadequacy of proper seismic analysis and design rules for a piping system and its components. Current seismic design Codes are found to be over conservative and some components, e.g., bolted flange joints, do not have guidelines for their seismic design. Along this line, this paper discusses about the main issues on the seismic analysis and design of industrial piping systems and components. Initially, seismic analysis and component design of refinery piping systems are described. A review of current design approaches suggested by European (EN13480:3) and American (ASME B31.3) Codes is performed through a Case Study on a piping system. Some limits of available Codes are identified and a number of critical aspects of the problem e.g., dynamic interaction between pipes and rack, correct definition of the response factor and strain versus stress approach, are illustrated. Finally, seismic performance of bolted flange joints based on the results of experimental investigations carried out by the University of Trento, Italy, will be discussed.
Frequently Overlooked Heat Exchanger Design Conditions
Authors: Gutkovsky Andrey , Taagepera Jaan
Published: January 2014

This paper explores the current design methodology for heat exchanger channel pass partition plates using ASME and TEMA design rules. Unanticipated elevated stress levels above allowable stress may exist at the channel pressure boundary due to differential pressure. In performing finite element analysis on two-pass heat exchanger channel geometry, elevated bending stress magnitudes were identified on the channel pressure boundary in the vicinity of the pass partition plate. These elevated stresses are induced by the pressure drop across channel passes, which load the pass partition plate and subject the channel pressure boundary to a bending stress which is frequently not evaluated. The combined membrane and bending stress may exceed allowable limits. This paper is intended to highlight this potentially overlooked loading condition in the design of heat exchanger channels.
The Application of Combined Buckling Mode Imperfections on Shell Structures
Authors: Laird Sean , Frith Robert
Published: January 2014

This paper presents the results of a numerical investigation for applying a combination of buckling mode shapes as an initial imperfection to shell geometries under external pressure. The effect that imposed imperfections had on the critical buckling pressure was found to be dependent upon both the shell geometry and the characteristics of the imposed imperfection. Imperfections were generated via linear combinations of the linear elastic buckling mode shapes, with the fundamental mode having the greatest influence. For a number of tests, inclusion of higher order modes into the initial imperfection caused an increase in the critical buckling pressure. This behaviour was observed for both elastic and plastic material models.

For the purpose of limiting the extent of the analysis, the magnitudes of imposed imperfections were maintained within the industry required fabrication tolerances and in particular, acceptable out-of-roundness. The purpose of this paper is to present the methodology and results from this imperfection investigation. Additional testing and discussion may allow a design methodology to be developed that addresses the application of initial imperfections in shells under external pressure.
Application of Gurson Model to Ni-Based Alloy Weld Joint Pipe With an Axial or a Circumferential Surface Flaw: Phase II
Authors: Hojo Kiminobu , Watanabe Daigo
Published: January 2014

The previous paper ASME PVP2012[1] reported application of Gurson model to the fracture test results using pipe models with part-through wall cracks on the dissimilar metal (DM) welds. The predicted maximum loads and the crack behaviors after penetration did not agree well. These results may originate from improper parameter values of Gurson model. This paper revised these parameters and improved the estimated fracture behaviors of the pipe models. A suitable fitting process of Gurson parameters was also proposed.
Stress Intensity Factors for Cracks With Large Aspect Ratio in Cylinder
Authors: Li Yinsheng , Doi Hiroaki , Hasegawa Kunio , Osakabe Kazuya , Okada Hiroshi
Published: January 2014

A number of surface cracks with large aspect ratio have been detected in components of nuclear power plants in recent years. The depths of these cracks are even larger than the half-lengths. The solution of the stress intensity factor is very important for the structural integrity assessment of such cracked components. However, in the current codes, such as ASME Boiler and Pressure Vessel Code Section XI and the JSME Rules on Fitness-for-Service for Nuclear Power Plants, solutions of the stress intensity factors are provided for semi-elliptical surface cracks with a limitation of a/l ≤ 0.5, where a is the crack depth and l is the crack length. In order to assess structural integrity in a more rational way, the authors previously developed solutions of the stress intensity factor for semi-elliptical surface cracks in flat plates with a/l = 0.5 to 4 and a/t = 0.0 to 0.8, where t is the wall thickness. In this study, the solutions of the stress intensity factors were calculated for circumferential and axial surface semi-elliptical cracks with large aspect ratios in cylinders. The geometrical dimensions focused on were in the ranges of a/l = 0.5 to 4, a/t = 0.0 to 0.8 and t/Ri = 0 to 1/2, where t is the wall thickness and Ri is the inner radius of the cylinder. Some solutions were compared with the available existing solutions in order to confirm their applicability.
A Direct Evaluation of Plastic Shakedown Limit of a Piping Nozzle Structure Under Superposed Multiple Loadings
Authors: Chen Geng , Simon Jaan-Willem , Weichert Dieter
Published: January 2014

In this paper, the plastic shakedown limit of a piping nozzle structure in the critical knuckle region is evaluated by a direct method based on Melan’s theorem. We assume the structure is loaded simultaneously by inner pressure, axial loading and in-plane moment that are varying independently from each other. In this sense, the shakedown limit calculation is performed in a three dimensional load space and considers several possible loading combinations. A three dimensional feasible load domain is eventually retrieved by constructing the problem as a large-scale optimization problem and solving it by an interior-point algorithm.
Fully Automated SCC and Fatigue Crack Propagation Analyses on Deep Semi-Elliptical Flaws
Authors: Sugawara Kota , Koya Hirohito , Okada Hiroshi , Li Yinsheng , Osakabe Kazuya , Kawai Hiroshi
Published: January 2014

In this paper, some results of crack propagation analyses of deep initially semi-elliptical flaws under assumed residual stress fields are presented. The crack propagation analyses were performed by using a software system that has been developed by Okada and his colleagues. It is based on a conventional finite element program but uses the quadratic tetrahedral finite elements to model the structure with the crack. The finite element model with the crack can be generated in an automated manner. The stress-intensity factor computations are performed by using the virtual crack closure-integral method (VCCM) for the quadratic tetrahedral finite element which was also proposed by Okada and his colleagues. The automatic meshing scheme for the crack propagation analyses has also been developed by the authors.

By the authors’ previous publication, it was shown that the stress intensity factor of deep semi-elliptical surface flaw under assumed residual stress field reached its maximum value at the mid-depth of the crack. Hence, in present study, in order to investigate the feature of the crack propagation of deep surface cracks, we are conducting crack propagation analyses that can predict the crack extension from each point along the crack front for an arbitrary shaped surface flaw. It can also account for material anisotropy in the crack propagation behavior. Then, the SCC crack propagation analyses for a deep semi-elliptical surface flaw in a plate under assumed residual stress fields are being conducted.

The results of the crack propagation analyses suggest that the shapes of the crack after the SCC crack propagation may not be exact semi-elliptic in its shape. In this paper, the analytical procedures and some results are presented. The same analytical procedures can be adopted to perform fatigue crack propagation analyses.
Synchronization Characteristics of Vortex Shedding From Tube Banks on Acoustic Resonance
Authors: Hamakawa Hiromitsu , Nishida Eiichi , Asakura Kenta
Published: January 2014

In the present paper the attention is focused on vortex shedding synchronization on acoustic resonance in in-line tube banks which occurred in the two-dimensional model of boiler. And we have examined the verification of proposed modeling method. We measured the characteristics of acoustic resonance, acoustic damping, the pressure fluctuation on the surface of tubes at the nodes of acoustic pressure and the acoustic pressure fluctuation on the side wall of the duct. As the acoustic mode number increased, the acoustic damping ratio decreased. As the tube pitch ratio in the flow direction decreased, the acoustic damping increased for all acoustic modes and the vortex shedding frequency became broad-band. The multiple resonance modes of lower acoustic damping were generated within the broad-band vortex shedding frequency. If the acoustic resonance occurred, the peak level of spectrum of surface pressure fluctuation and the coherence between vortex shedding and wall acoustic pressure in the tube banks also increased. The features of experimental results agree well with those obtained by using the proposed modeling method. We have discussed the characteristics of vortex shedding synchronization by using proposed the modeling method.
Integrity Evaluation of Korean Nuclear Reactor Pressure Vessel Under Pressurized Thermal Shock Conditions According to JEAC
Authors: Kim Se-Chang , Choi Jae-Boong , Cho Doo-Ho , Lee Sang-Min , Kim Yong-Beum , Chung Hae-Dong
Published: January 2014

In nuclear power plant, reactor pressure vessel (RPV) is the primary equipment that contains reactor cores and coolant. The RPV integrity should be evaluated in consideration with transient operation conditions and material deterioration. Especially, the pressurized thermal shock (PTS) has been considered as one of the most important issues regarding the RPV integrity since Rancho Seco nuclear power plant accident in1978.

In this paper, integrity evaluation of Korean RPV was performed by using finite element analysis. PTS conditions like small break loss of coolant accident (SBLOCA) and Turkey Point steam line break (TP-SLB) were applied as loading conditions. Neutron fluence data of actual RPV operated over 30 years was used to determine fracture toughness of RPV material.

The 3-dimensional finite element model including circumferential surface crack was generated for fracture mechanics analysis. The RPV integrity was evaluated according to Japan Electric Association Code (JEAC).
Calculation Approach of Optimum Cutting Surfaces of Extra Length of Pipe Spools
Authors: Kitahara Takashi , Yamamoto Yuichi , Tagawa Yasutaka
Published: January 2014

To connect a pipe spool between existing pipes with high accuracy for power plant constructions, a calculation approach which figures out appropriate cutting positions and angles of extra length areas of the spool has been developed. In this approach, center positions and axes of end surfaces are modeled numerically based on three-dimensional measurement of each pipe, and the appropriate cutting surfaces are calculated by geometric analysis of the models with considering for ease of cutting work at the construction site.

This paper described a modeling method of pipes, a calculation algorithm of the proper cutting surfaces of the spool, and a verification result of the calculation.
Acoustic Resonance of a Steam Line Gate Valve
Authors: Lafon Philippe , Lacombe Romain , Crouzet Fabien , Daude Frédéric , Ziada Samir , Bailly Christophe
Published: January 2014

A pure tone phenomenon has been observed at 460 Hz on a piping steam line of a power plant. The source has been identified to be generated in a gate valve and to be of cavity noise type. This paper presents the investigations carried out on experimental models in order to analyze the problem. 2D and 3D axisymmetric models are used and lock-in situations between shear layer modes and acoustic duct modes are proven to give rise to powerful tones. Some counter measures are also tested with the objective of lowering the amplitude of pressure oscillations.
Consideration of Creep in Design Rules of AFCEN RCC-MRx 2012 Code
Authors: Lebarbé T. , Petesch C. , Lejeail Y. , Lamagnère P. , Dubiez-Le Goff S.
Published: January 2014

The 2012 edition of the RCC-MRx Code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires). This 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 and to the Vacuum Vessel of ITER.

This new edition is the opportunity to publish also the background of the rules. This paper is one illustration of what may be such a document, on a dedicated example, the creep rules. It contains an overview of the design rules associated to the creep damage and explains the purpose and the origins of these rules. This type of exercise is going to be generalized to all the parts of the code in AFCEN technical publications, the criteria.
Comparison of P92 Steel Fatigue Test Results in Relation to Specimen Size and Manufacturing
Authors: Volak Josef , Bunda Zbynek , Mentl Vaclav
Published: January 2014

This paper describes fatigue properties of steel P92. This material is used as a standard in the energy industry, especially for production of pipes and flange branches and distance pieces of supercritical steam turbines. This material contains (unlike material P91) up to 2% of tungsten which has positive influence on creep strength increase. Compared to the P91 material, it is possible to reduce wall thickness of the P92 pipe up to 20%. Fatigue tests were carried out on standard samples and compared with SFT samples (Small Fatigue Test). SFT samples can be gently withdrawn from energy component by SSam 2 device made by company Rolls Royce. There is no necessity for shutdown of power plant. Thanks to the existing correlations between SFT and Fatigue tests, it is possible to determine mechanical properties of material from a small amount of withdrawn material. At the same time a comparison between a traditional way of sample production and a sample production by means of waterjet cutting was carried out.
Creep-Fatigue Tests and Life Prediction Models for Structural Integrity Assessment of 9Cr-1Mo (Grade 91) Steels
Authors: Filippini Mauro , Catelli Riccardo , Cristea Mihaela E.
Published: January 2014

High temperature strain controlled fatigue and creep-fatigue tests have been carried out on Grade 91 martensitic steel, according to the procedure of the newly developed ASTM E2714 standard. In this paper, the results of these tests are discussed and evaluated according to different damage calculation procedures (e.g. time fraction rule, ductility exhaustion method) for the purpose of validating life prediction models that could be used for the assessment of structural integrity of components in Grade 91 steels operating at high temperatures.
User’s Design Specification Preparation for 2¼Cr-1Mo-¼V Reactors in Accordance With ASME Section VIII, Division 2 Code and Code Case 2605
Authors: Stefanovic Radoslav , Avery Alicia , Bardia Kanhaiya , Kabganian Reza , Oprea Vasile , Seipp Trevor
Published: January 2014

Today’s hydroprocessing reactor manufacturers use 2¼Cr–1Mo–¼V steel to build lighter reactors than conventional Cr-Mo reactors. Manufacturing even lighter hydroprocessing reactors has been enabled with the introduction of the new ASME Section VIII Division 2 Code, initially released in 2007. The higher allowable stresses in the new Division 2 for these Vanadium-modified steels permits even lighter reactors to be built while maintaining suitable design margins. The new Division 2 Code requires additional engineering to ensure safe design. One of the challenges the engineer is faced with, is preparation of the User’s Design Specification (UDS) including new and more stringent requirements for fatigue evaluation. As the operating temperature of the rector is higher than 371°C, engineers have to evaluate the fatigue life of the reactor in accordance with Code Case 2605 (CC2605). CC2605 requires inelastic analysis and evaluation effects of creep. Vanadium-modified reactors require additional care during fabrication to prevent higher hardness around weld areas, reheat cracking, and reduced toughness at lower temperatures in the “as welded” condition.

This paper provide guidance for the preparation of an ASME Section VIII Division 2 User’s Design Specification including process descriptions of all the cycles expected for the life of the rector and analysis requested by CC2605. An example of such an analysis, including finite element analysis results, is provided in this paper. Requirements to provide the material specification is also discussed with an emphasis on prevention of reheat cracking, hardenability, and temper and hydrogen embitterment.
Boiling Water Reactor Recirculation Line Break Acoustic Loads: A Bounding Approach
Authors: Sommerville Daniel
Published: January 2014

Recent industry communications have identified issues pertaining to incorrectly calculated recirculation line break acoustic loads or structural evaluations that need to include, but have previously excluded, the recirculation line break acoustic loads. Various organizations have studied the recirculation line break event and have developed methodologies to calculate the decompression loads caused by this event on various boiling water reactor internal components. In general, loads are calculated in a plant specific and operating condition specific manner. Once these loads are available then the necessary structural evaluations can be performed. With the various flexibility options that an operating boiling water reactor can be licensed for it can become difficult to know when the recirculation line break acoustic loads must be updated and subsequently, which structural evaluations must be updated as well. In this paper a simple extension of an existing, benchmarked, acoustic loads methodology is suggested in which a bounding set of input parameters is evaluated in order to predict acoustic loads that will bound all flexibility options that are currently implemented at operating plants. The objective of this approach is to save the utilities time and money by enabling a single iteration of loads calculation and structural analysis. This approach is shown to produce loads that are approximately a factor of 1.5 larger than those predicted using typical operating parameters.
Stress Intensity Factor Solutions for Welds Between Two Sheets of Different Materials and Thicknesses Under Plane Strain Conditions
Authors: Lai Wei-Jen , Pan Jwo , Tran Van-Xuan
Published: January 2014

In this paper, analytical stress intensity factor solutions for welds in lap-shear specimens of different materials and thicknesses under plane strain conditions are presented in the normalized forms. The stress intensity factor solutions for welds are expressed in terms of the structural stresses based on a strip model. The analytical stress intensity factor solutions are selectively verified by the results of the two-dimensional finite element analyses. The interface crack parameters for the stress intensity factor solutions for welds in lap-shear specimens of dissimilar steel, aluminum, magnesium, and copper sheets are listed for different thickness ratios. The analytical stress intensity factor solutions are obtained and selectively presented in the normalized forms as functions of the specimen thickness ratio for the combination of aluminum and steel sheets for fracture and fatigue analyses.
Effects of Strain Rate on the Very High Cycle Fatigue Properties of Low Alloy Steel SFVQ1A
Authors: Nakamura Takashi , Oguma Hiroyuki , Nukaya Shingo
Published: January 2014

Uni-axial fatigue tests up to 109 cycles were conducted at two cyclic frequencies (10 and 250 Hz) under several stress ratios (R = −1, 0.1, and 0.5) to investigate the effects of strain rate on the very high cycle fatigue properties of SFVQ1A, which is equivalent to ASTM A508 Cl.3. Longer fatigue lives and 5% higher fatigue limit were measured at 250 Hz than those at 10 Hz for R = −1. Under R = 0.1 and R = 0.5, however, the fatigue properties did not differ between 10 and 250 Hz. Observations of fracture surfaces clarified that all fractures under R = −1 and R = 0.1 were caused by a general crack growth process from non-metallic inclusion(s) at the specimen surfaces. In contrast, the entire fracture surface under R = 0.5 was covered with a dimpled pattern. The fatigue mechanism was considered to be due to ductility exhaustion through ratcheting behavior under high mean stress. The longer fatigue lives and larger fatigue limit at 250 Hz under R = −1 was explained by the increase in crack growth resistance at a high strain rate based on crack growth behaviors and the da/dN-ΔK relation. No differences in fatigue properties between different frequencies under R = 0.1 and 0.5 were likely caused by the negligible effect of strain rate compared with the increase in material strength during fatigue loading, which resulted from strain hardening induced by maximum cyclic stress that was larger than yield stress.
Optimization Analysis on the Structure Parameters of a 20×104 m3 Ultra-Large Tank for Crude Oil Storage
Authors: Feng Wenzhuo , Chen Zhiping , Shen Xinliang , Zhou Fan , Fan Haigui
Published: January 2014

With the advantages of low investment, small footprint, ease of operation management etc., large-scale vertical tanks for crude oil storage have become an obvious trend. However, stress intensity of the tank wall increases with constant enlargement of oil tank’s parameters, and the yield strength of the steel used as tank wall material can not be more than 490 MPa. Besides, the maximum thickness of shell plate generally should be not over 45 mm subjected to the restriction of manufacturing process. So, it is important to design the structure of tank reasonably and reduce the stress as much as possible. This paper combines theoretical analysis and numerical simulation together, analyzing and calculating the stress of shell plate and bottom plate of an ultra-large tank for crude oil storage which is 200000 cubic meters, and comparing the stress level of three design schemes about shell plate and bottom annular plate, then giving a scheme whose stress distribution is more reasonable. The study shows that combined cylindrical shell method is applicable to the theoretical stress calculation of shell plates of ultra-large crude oil storage tanks, finite element method using contact element could simulate the stress distribution of bottom plate well, and give the optimal structure parameter scheme by controlling the hoop stress of tank wall and radial stress of bottom plate. The result of this paper has a certain practical guiding significance to the optimization design of ultra-large tanks for crude oil storage.
Plan and Status of Development of Design Fatigue Curves: Phase 1
Authors: Asada Seiji , Hirano Akihiko , Itatani Masao , Yasuda Munehiro , Sera Takehiko , Kobayashi Hideo
Published: January 2014

In order to develop and propose new design fatigue curves for austenitic stainless steels, carbon steels and low alloy steels that are rational and have clear design basis, Design Fatigue Curve (DFC) subcommittee has been established in the Atomic Energy Research Committee in the Japan Welding Engineering Society and the study on design fatigue curves are going on. This paper introduces the plan and status of the activities of the DFC subcommittee.
A Method for Prediction of Forming Strain for Cold Stamping Formed Head Made of S30408 Austenitic Stainless Steel
Authors: Zhu Xiaobo , Miao Cunjian , Ma Li
Published: January 2014

Large deformation takes place in the forming process of cold stamping formed head. Such large forming strain induces large content of martensite transformation and then decreases the plasticity and ductility in transformation regions, which will affect the safety of head used under low temperature. Therefore, having an accurate prediction of forming strain can provide the basis for safe use of cold stamping formed heads. In this paper, a method for predicting forming strain is put forward. A prediction model is established through cold stamping forming test and FEA. Meanwhile, a forming strain prediction interval based on statistic analysis is also established, which is then proved to have a good prediction of foming strain for cold stamping formed head made of S30408 metastable ASS through test verification.
Development of an Expert System to Characterize Weld Defects Identified by Ultrasonic Testing
Authors: Shahriari D. , Zolfaghari A. , Jahazi M. , Bocher P.
Published: January 2014

Welded structures are examined nondestructively, particularly for critical applications where weld failure can be catastrophic, such as in pressure vessels, load-bearing structural members, and power plants. Ultrasonic Testing (UT) is used in the examination of welds in thinner and thicker gauge materials where the size and location of the flaws are important to detect and interpret. Despite the advantages of the ultrasonic technique, the classification of defects based on ultrasonic signals is still frequently questioned, since the analysis and the identification of defect types depend exclusively on the experience and knowledge of the operator. The problem becomes more acute when high inspection rates, high probability of detection, and low number of false results are required. Thus, the correct classification of the type of flaw present in the material reduces measurement errors, increasing the confidence in the test and consequently the safety of the welded structure during service. In the present study, a new algorithm that allows for the detection and measurement of the length and type of weld defects is proposed. The system is based on a coupled dynamic and static patterns in an A-Scan and uses the defects cited in DIN EN 1713 standard as reference for evaluation. The proposed expert system has been evaluated and validated by examining several specimens containing various types of natural (non-artificial) defects identified in the mentioned standard. The results indicate that, the proposed algorithm has a clear potential in automatic defect detection and presents many advantages to the manual method for defect detection and characterization.
Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (6) Design Margin Assessment for the New Materials to the Rules
Authors: Ando Masanori , Watanabe Sota , Kikuchi Koichi , Otani Tomomi , Satoh Kenichiro , Tsukimori Kazuyuki , Asayama Tai
Published: January 2014

New 2012 edition of JSME code for design and construction of fast reactors (FRs code) was published by Japan society of mechanical engineers (JSME). Main topic of the current JSME FRs code 2012 edition is registration of the two new materials, 316FR and Mod.9Cr-1Mo steel. Besides the allowable strength values and material properties were standardized for the registration, the design margins for the new materials to the rules for the components and piping serviced at elevated temperature described in the JSME FRs code were assessed. To confirm the design margins, a series of the assessment program for the new materials to the conventional design rules was performed using the evaluation of the experimental data and finite element analysis. Namely, the design margin including the evaluation procedure of creep-fatigue damage, strain range and the others were assessed based on the background concept of the conventional JSME FRs code. Since a number of the evaluation procedures described in the JSME FRs code were investigated, a several topical assessments of these are reported in this paper. Besides the assessed results of the evaluation of the accumulated creep-fatigue damage and enhanced creep strain are reported, the assessments results of the design margin including the concept of the elastic follow-up originally applied in the JSME FRs code were covered in this paper. Through these assessments, the enough design margins for new materials to the rules were confirmed.
Application of the Bayesian Updating to the Load and Resistance Factor Design (LRFD) Method
Authors: Nakasone Yuji
Published: January 2014

The present study has attempted to apply the Bayesian updating to the LRFD, or Load and Resistance Factor Design method. The LRFD method takes into account the statistical distribution of the material resistance and those of the applied loads. The LRFD method can reflect the degrees of different uncertainties of the resistances of the materials and the loads. Thus, the LRFD method can attain the optimal design which can keep up an adequate reliability level of the components designed, whereas the conventional allowable stress design (ASD) method cannot. The LFRD method, however, requires vast amount of statistical data for the material resistances and the applied loadings of different kinds. The present study proposes the Bayesian updating scheme which requires only a small amount of statistical data for the material resistance and the various load item distributions to calculate the values of the partial design factors used in the LRFD method. It is revealed that the median of the updated distributions of the estimated standard deviations can give adequate reliability index values higher than the target reliability index value corresponding to a fracture probability of 0.01% even for a small number of the statistical data, say, less than 20. This paper also compares and discusses the LRFD method with the updating scheme and the conventional ASD method, showing that the updated LRFD method can maintain the reliability index value higher than the target index value whereas the ASD method cannot.
Numerical Analysis of Hydrogen Distribution in Welds of Stainless Clad Steels for Hydrogen Storage Pressure Vessels
Authors: Mori Hiroaki , Kayano Rinzo , Ogiwara Hiroyuki , Saida Kazuyoshi , Nishimoto Kazutoshi
Published: January 2014

Numerical analysis of hydrogen distributions in the welds of stainless clad steels, which are the structural material of hydrogen storage pressure vessels, was conducted to predict the hydrogen embrittlement in the pressure vessels. The theoretical model for the calculation was based on the activity of hydrogen considering residual stresses induced by welding and hydrogen accumulating sites such as precipitates and dislocations.

From the calculations, hydrogen concentrates at the center of weld metals in both of longitudinal and circumferential directions in welded joints of stainless clad steels. However, the hydrogen contents were much lower than those in the carbide layers, in which are observed in steels with weld overlay of stainless steels, as the calculation of hydrogen distribution in the materials using the higher evaluated diffusion coefficient of hydrogen with considering margin of safety.

Therefore, it seemed that the risk of cold cracking due to hydrogen embrittlement was sufficiently lower in the welds of stainless clad steels during many cycles of shutdown and restart of the pressure vessels in long-term operation.
FEM Stress Analysis and the Sealing Performance Evaluation of Bolted Flanged Connections With Metal Flat Gaskets
Authors: Kondo Koji , Tsubaki Shota , Sawa Toshiyuki , Omiya Yuya , Sato Koji
Published: January 2014

Metal gaskets have been used in bolted flanged connections under higher pressure and higher temperature conditions. However, it is difficult to estimate the sealing performance of the metal contact interfaces in the connections. Thus, it is necessary to study on the sealing characteristics of the metal to metal contact gasket in the connections under higher internal pressure and higher temperature. In this study, firstly, the sealing behavior test taking into account load history is carried out in detail using metal flat gaskets according to JIS B2490. Secondly, to examine the effect of the gasket contact area and surface roughness of metal gasket on the sealing behavior of metal-metal contact, the sealing behavior test is carried out using metal flat gaskets which has several types of gasket width and surface roughness. Thirdly, the amount of leakage is measured for bolted flanged connections with metal flat gaskets. The relationship between the gasket contact stress and the leak rate is obtained. Furthermore, the contact gasket stress distributions in the connection are analyzed using FEM stress analysis. Using the obtained gasket stress distribution, the sealing performance is estimated taking into account the gasket contact area and surface roughness of the metal flat gasket. The estimated result is compared with the measured results. In the results, the effect of the yield stress and the plastic deformation of the gasket surface are found to be important on the sealing mechanism.
Production and Evaluation of Pressure Vessel for Highly Effective Rice Powder Manufacturing Using Underwater Shock Wave
Authors: Shimojima Ken , Higa Yoshikazu , Higa Osamu , Higa Katsuya , Takemoto Ayumi , Itoh Shigeru
Published: January 2014

The rice-powder paid to attention in Japan, because rice-powder is able to process the various foods. But, conventional method of manufacturing rice-powder generates heat when crushing of rice. The pressure vessel for rice-powder using underwater shock wave at Okinawa National College of Technology has been developed. Merit of this crushing processing is dryness and non heating. The decrease of the manufacturing cost can be expected. The power supply to generate the pressure vessel and the shock wave for crushing and the transportation device of rice was developed. The amount of the milling flour of the first prototype device was 450[g/h]. Then, the pressure vessel is improved, the shock wave generation energy is improved, and the amount of the milling flour has been improved with 2kg per hour. In this report, the outline of the improved device is described. And, the factor that influences the milling flour is shown, and the evaluation method is described.
A Benchmark Study of Bending Limit Load Finite Element Analysis for Locally Wall Thinned Pipes
Authors: Hoang Phuong H. , Bezensek Bostjan , Rathbun Howard J.
Published: January 2014

Finite element analyses (FEA) have been used to study the effects of multi-axial loadings on bending limit load of local wall thinned pipes. It has been shown by investigators that torsion can be combined with bending moments using SRSS (Square Root of the Sum of the Squares) method for planar flaws with a limited axial extent. The treatment of torsion for non-planar flaws, which exceed the axial extent limit, will be a subject for future investigations. Since the reported FEA results are for various pipe sizes, flaw shapes with different mesh sizes, element types and computer codes, a set of benchmark problems was proposed and analyzed by participating investigators. The benchmark analysis results are presented in this paper.