bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Hydrogen Permeation of Weldments for Two Low-Alloyed Steels With Different Microstructures
Authors: Tang Jian Qun , Gong Jian Ming
Published: May 2012

16MnR and SPV50Q low-alloyed steels, which have ferrite-pearlite and tempered martensite microstructures, respectively, are widely used to fabricate storage tanks for liquefied petroleum gas. However, during the process of operation, some cracks often occur on tanks made by these steels due to the presence of hydrogen, especially on weldments. The occurrence of this cracking is closely related to the diffusion and permeation of hydrogen in the steels. In order to explore the effect of different microstructures on hydrogen permeation and compare the hydrogen permeability of these two weldments, measurements were conducted on various metals (base metal-BM, heat-affected zone-HAZ, and welded metal-WM) cut from 16MnR and SPV50Q weldments by using electrochemical permeation tests. The results show that the microstructure has an important effect on hydrogen permeability. For 16MnR steel weldment, the diffusion coefficient of BM is the minimum due to the presence of the strong hydrogen traps in the interface between banded pearlite and matrix as well as the interface between inclusion and matrix. The microstructure of WM provides great grain boundary area as a hydrogen diffusion path and makes hydrogen easily diffuse, which results in the maximum permeation rate and diffusion coefficient. The fine-grained microstructure of normalized zone in HAZ acts as barriers for the hydrogen diffusion, which makes the permeation rate and diffusion coefficient of HAZ located between those of BM and WM. Similarly, for SPV50Q weldment, the permeation rate and diffusion coefficient increase in the order of BM, HAZ and WM. Those of BM are the minimum, which is correlated with the strong hydrogen trap due to the large quantities of dislocation within the lath martensite. Those of WM are the maximum for its strongly hydrogen diffusion path like WM of 16MnR weldment. As comparing the hydrogen permeability of 16MnR and SPV50Q weldment, the corresponding metals of the former always have greater permeation rate and diffusion coefficient than those of the latter, which is also due to its intrinsic microstructures.
Basic Study on Explosive Evaporation of Cryogenic Fluids by Contacting Normal Temperature Fluids in the Pressure Vessel
Authors: Watanabe Toshiaki , Iyama Hirofumi , Maehara Hironori , Itoh Shigeru
Published: May 2012

The mixture of the extreme low temperature fluid and the normal temperature fluid becomes the cause which causes pressure vessel and piping system crush due to explosive boiling and rapid freezing. In recent years in Japan, the demand of cryogenic fluids like a LH2, LNG is increasing because of the advance of fuel cell device technology, hydrogen of engine, and stream of consciousness for environmental agreement. On the other hand, as for fisheries as well, the use of a source of energy that environment load is small has been being a pressing need. Therefore, we carried out the experiments related to promotion of evaporating cryogenic fluids, in the contact directly of the water and liquid nitrogen.
Fatigue Design Margin Evaluation for Carbon and Low-Alloy Steels by Reliability-Based Load and Resistance Factor Method
Authors: Takanashi Masahiro , Higuchi Makoto , Maeda Junki , Sakai Shinsuke
Published: May 2012

This paper discusses the margins of the design fatigue curve in the ASME Boiler and Pressure Vessel Codes Section III from a reliability analysis point of view. It is reported that these margins were developed so as to cover uncertainties of fatigue data scatter, size effect, and surface condition[1], but the reasons for them remain unclear. In order to investigate the physical implications of the design margin, a probabilistic approach is taken for the collected fatigue data of carbon and low-alloy steels. In this approach, these three parameters are treated as random variables, and an applied stress is also taken into consideration as a random variable. For the analysis, to begin with, a limit state function for fatigue is proposed. Next, reliability index contours of the design fatigue curves for carbon and low-alloy steels are obtained based on the proposed limit state function. The contours indicate that the margins 2 on stress and 20 on life do not provide equal reliability. The margin 20 on life is more conservative and the margin became a minimum near intersections of the design curves with margins 2 on stress and 20 on life. For practical applications, the partial safety factors (PSF) for the target reliability are computed for all materials and several levels of coefficients of variation (COV) of the applied stress. A sensitivity analysis of the PSFs clarifies that only two parameters, the strength (or the life) and the applied stress, are predominant. Thus, the partial safety factors for these two parameters are proposed in a tabular form.
Design and Fabrication of the World’s First Filament–Wound Section X Class II Vessels
Authors: Du Juan , DiCarlo Paul , Richter Jess , Guess Clair
Published: May 2012

The world’s first filament-wound ASME Section X [1] Class II FRP(fiber reinforced plastic) vessels were built by Tankinetics Inc. in 2010. These vessels had semi-elliptical top and bottom, and were supported on skirts as shown in Fig.1. This paper is focused on the novelty of these vessels from design and fabrication standpoints. The design pressure is 50.76 psig. Ashland Derakane™ 470 resin is selected for the corrosion liner, and Derakane™ 510 N resin is used in the structural layer. The design is based on ASME Section X code [1] method A. For wind and seismic analysis, IBC 2006[3] and NBCC 2005[4] codes are followed. The domed top and bottom were made by hand lay-up method while the cylindrical shell section and skirt were made by filament winding technology. Filament winding is chosen for these pioneer vessels because it can produce stiffer, higher-strength laminates with much less fabrication time as compared to traditional hand lay-up process.
Accounting for Phase Transformations During Welding of Ferritic Steels
Authors: Hamelin Cory J. , Mura´nsky Ondrej , Luzin Vladimir , Bendeich Philip , Edwards Lyndon
Published: May 2012

The numerical application of solid-state phase transformation kinetics relating to conventional welding of ferritic steels is presented. The inclusion of such kinetics in weld models is shown to be necessary for capturing the post-weld residual stress field. To this end, a comparison of two approaches is outlined: a semi-empirical approach that uses thermodynamic transformation kinetics to predict phase morphology; and a fully empirical approach that directly links local material temperature to the present constituent phase(s). The semi-empirical analysis begins with prediction of TTT diagrams using thermodynamic principles for ferritic steels. The data is then converted to CCT diagrams using the Scheil-Avrami additive rule, including austenite grain growth kinetics. This information is used to predict the phases present under varying peak temperatures and cooling rates. In the fully empirical approach, dilatometric experiments of steel samples are performed during heating to simulate expected welding conditions. The constitutive response of the sample is then used as input for the subsequent numerical weld analyses. Input derived from each technique is transferred into weld models developed using the Abaqus finite element package. Model validation is carried out by direct comparison with neutron diffraction residual stress measurements on two beams of SA508 Gr.3 Cl.1 steel subjected to autogenous beam TIG welds under varying torch speeds, heat input and preheat conditions.
Dynamic Simulation of Piping System Around Safety Valve for Closed Discharge System
Authors: Sakamoto Yoshiaki , Izuchi Hisao , Suzuki Naoko
Published: May 2012

Reaction force of safety valves acting to the piping system is one of key factors for the piping system design around the safety valves. In case of open discharge system, it is well known that a large reaction force acts to the piping corresponding to the fluid momentum force at the atmospheric discharge. On the other hand, reaction forces for closed discharge system may be relatively small since the forces acting to the adjacent two points with flow direction change such as elbows and tees are balanced within very short period. However, large reaction forces may act as a result of unsteady flow just after the initial activation of the safety valve. API RP520 mentioned that a complex time history analysis of the piping system around the safety valves may be required to obtain the transient forces. This paper explains a method of a comprehensive dynamic simulation of piping system around safety valves taking interaction among the valve disc motion, the fluid transient for compressible flow and the piping structural dynamics into account. The simulation results have good agreement with the experimental data. The effectiveness of this method is confirmed throughout an application to actual piping system around safety valves.
Investigation of Bulging Behavior of Coke Drum: A Practical Analysis of Bulging Under Complex Quench Conditions
Authors: Yamamoto Toshiya , Arii Kazuaki , Huhetaoli  , Niimoto Shinta , Ohata Mitsuru , Tagawa Tetsuya , Minami Fumiyoshi
Published: May 2012

Coke drums undergo cyclic operations typically in the temperature range from room temperature to about 500°C (930°F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is uneven during quenching, and can vary in each cycle of the quenching operation. Such a complicated thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging and/or cracking. The authors have investigated the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis, considering the existence of the overmatch welds and uneven temperature field during quenching [1]. In this paper, a practical FE-analysis is developed to estimate the complex strain that leads to bulging under uneven temperature fields during quenching. The actual temperature and strain data during operation are collected by thermocouples and high temperature strain gauges. A thermal analysis model, including an evaluation of boiling heat transfer on the shell’s inner surface, is established to simulate the measured shell behavior of the coke drum. By utilizing this FE-analysis model, several parameters thought of as causal factors in bulging can be examined under the uneven temperature profile that is likely to occur during actual operation. This analytical approach can also provide effective technique for improvements in shell durability.
The Effect of the Stress and Strain in Stationary Small Crack Tips for the Different Crack Lengths
Authors: Fang Xiurong , Xue He , Tang Wei , Zhao Lingyan
Published: May 2012

The continued improvements in non-destructive testing (NDT) make it possible to detect smaller and smaller flaws in pressure vessel and piping. These small flaws are usually simplified as small cracks in structure integrity evaluation and remain life prediction in practice. Traditional fracture parameters can not be used to estimate the fatigue crack growth rate at the small crack tip, so there is not a normalized standard for structural durability and damage tolerance design. In this study the relationship between the stress and strain at the stationary crack tips and the ratio (a/W) of the different crack lengths (a) to the width of the specimen (W) is investigated by the elastic-plastic finite element method (EPFEM) with a central-crack plate model. The results indicate that if the ratio (a/W) is small enough, i.e. a/W⩽0.005, the plastic strain as damage variable should be performed using the small crack theory. Otherwise, damage-tolerant life calculations could be performed using the stress intensity factor.
Residual Stress by X-Ray Diffraction and Microstructure for Multi-Pass Girth Welded Pipe Joint in Austenitic Stainless Steel Type 316L
Authors: Hashimoto Tadafumi , Okano Shigetaka , Hirano Shinro , Mochizuki Masahito , Nishimoto Kazutoshi
Published: May 2012

Residual stress due to welding can result in brittle fracture, fatigue failure, and stress corrosion cracking in welded structures. Measuring residual stresses are of great importance, if crack propagation needs to be evaluated. However, it is especially known that the X-ray diffraction method makes remarkable different for austenitic stainless steel, because the microstructures in welds change from the original microstructures during welding thermal cycle. That is, there are the preferred orientation due to the unidirectional solidification and the grain growth in the heat-affected zone. In order to average the sin2Ψ plots to exclude them, Ψ oscillation of ±3 deg was performed and the incident beam size was broadened to 4 by 4 mm. Consequently, typical residual stress distributions due to welding were obtained to various conditions. The residual stress distribution measured by X-ray diffraction agrees very well with that the estimated by thermal-elastic-plastic analysis, if the spatial resolution is correlated. It is attributed that the δ-ferrite grows as the primary phase and the austenite precipitates or crystallizes as the secondary phase. When the secondary austenite nucleates with the Kurdjiumov-Sachs relationship which satisfy δ{110}//γ{111} and δ<111>//γ<110>, plate-like austenite grows randomly into the ferrite and austenite grains are braked up. That is, Specific systems in austenitic stainless steels should be classified, as a material that residual stress can be measured accurately by X-ray diffraction.
Examination of Factors in the Modified Rate Approach Method Under Various Conditions
Authors: Fukuta Yuichi , Asada Seiji , Nomura Yuichiro , Kanasaki Hiroshi
Published: May 2012

Fatigue life in elevated-temperature water is affected by water chemistry, temperature, and strain rate. To evaluate these effects, the environmental fatigue life correction factor was established. And to evaluate fatigue damage in actual plants where factors such as temperature and strain rate are not constant, the modified rate approach method was developed. In order to confirm the applicability of these methods, several tests were carried out under a condition in which strain rate changes in response to temperature and fatigue life could be evaluated with an accuracy of a factor of 3, but conservatism was observed. In this evaluation, conservatism of environmental fatigue prediction is studied. To minimize conservatism in environmental fatigue evaluation, four factors are examined. As a result of examination, we conclude that an improvement the environmental fatigue life correction factor and application of a strain range insensitive to the environment may reduce conservatism, and that investigation into the mechanism of reduction in fatigue life is necessary for further improvement.
Aeroacoustic Source of a Shallow Cavity in a Pipeline
Authors: Mohamed S. , Graf H. R. , Ziada S.
Published: May 2012

The flow-induced acoustic source of an axisymetric shallow cavity, coupled to longitudinal acoustic modes in a pipeline is characterized experimentally for circular pipes conveying fully developed turbulent flow. This aeroacoustic source is generated due to the interaction of the cavity shear layer oscillation with the resonant acoustic field in the pipe. The distributed aeroacoustic source is modeled by a lumped acoustic dipole source which is dependent on the Strouhal number and the acoustic particle velocity at the cavity. The amplitude and phase of this source are determined experimentally and presented in the form of a dimensionless complex source term.
Creep Damage Assessment Procedure for Weldment Parts of P91 Boiler Piping in USC Plants: Part I—Development of Stress Analysis Code for Boiler Piping Systems
Authors: Sakai Takayuki , Ogata Takashi
Published: May 2012

High-chromium steels have excellent high temperature strength properties and are therefore used for piping systems of ultra-super-critical (USC) power plants. Recently, type-IV damages occurred in heat affected zone (HAZ) and had often caused unexpected shutdown. The type-IV damages are due to dense concentration of creep voids on grain boundaries, and then quantitative prediction of void growth is an important subject to prevent a critical accident. To that end, it is necessary to obtain stress conditions under plant operation with high accuracy. The hoop or circumferential stress caused by steam or internal pressure can easily be estimated by a conventional FEM code. However estimation of system load caused by thermal expansion of pipe materials is difficult because of the complex structures of piping system. In this study, we developed a three-dimensional FEM code which can estimate both thermal expansion and creep deformation of complex piping system. Consequently, accurate stress analyses of weldments under plant operation become now enabled.
Manufacturing Status of JT-60SA Vacuum Vessel and the Related Technology of Welding
Authors: Shibama Yusuke K. , Masaki Kei , Sakurai Shinji , Shibanuma Kiyoshi , Sakasai Akira
Published: May 2012

JT-60SA is a fully superconducting coil tokamak upgraded from the JT-60U, and this paper focuses on the vacuum vessel (VV, 150 tons) design concept with the related technology of welding and its manufacturing status. The design concept is developed from the ASME Boiler and Pressure Vessel Code Section VIII Division 2, and the damage tolerant concept is adopted into the welding part hardly inspected. These weld joints are treated as a partial penetration and residual strength is evaluated in the design process. Consequently, accuracy of VV weld structure is enhanced due to reduction of the welding heat input and also less process of weld work is achieved. The vacuum vessel has been manufactured since Nov. 2009. Welding technology related to the VV is surveyed and developed in three stages; element test, 1-m size trail and 20-degree upper half mock-up manufacture. The welding methodologies are selected from element tests, and then the typical vessel segments as a 1-m size are tested. The welding conditions to control its quality and the distortion are evaluated, and the lower heat input condition is additionally researched. On the basis of these results, the manufacturing sequences are established through the large size trial of the mock-up manufacturing.
Effects of Nut Thinning due to Corrosion on the Strength Characteristics and the Sealing Performance of Bolted Flange Joints Under Internal Pressure
Authors: Kikuchi Tsutomu , Omiya Yuya , Sawa Toshiyuki
Published: May 2012

The effects of nut thinning due to corrosion on the strength characteristic and the sealing performance in 3B bolted flange joints under internal pressure are examined from both FEM calculations and experiments. The following results are obtained. When bolts and nuts in a bolted flange joint are tightened with 50% of yield stress, no yield region at the engaged screw thread occurs, however, when they arc tightened with 90% of the yield stress, a small scale yield region occurs at the roots of the engaged three screw threads from the bearing surface of the nut. While verifying this phenomenon using FEM, it was newly discovered that when the height of the nut was reduced to 1/3 (equivalent to approximately two threads) of the original dimensions according to the standards, the sealing performance could no longer be assured.
Numerical Simulation and Experiment of Interaction and Influence on Two Colinear and Offset Cracks by FRANC2D Software
Authors: Zhao Jianping , Wang Weiwei
Published: May 2012

By using the two-dimensional finite element software FRANC2D (Fracture Analysis Code 2D), the calculation of stress intensity factors at the crack tips has been implemented through simulating two collinear cracks and a pair of offset parallel cracks propagation. Interaction and influence between cracks of different geometry patterns with the cracks propagation were discussed. The influence of crack interaction on the direction of propagation was also represented. The results show that the interaction between cracks could produce either an enhancement or a shielding effect on the stress field depending on the geometry of cracks (including the positions of cracks, the lengths of cracks and so on). The stress field of two collinear cracks has always been enhanced and the maximum interaction would occur at the case where the two cracks have the same length. As for a pair of offset parallel cracks, the enhancement and the shielding effecting on the stress field form an inflection point at about the beginning of cracks overlap. The stress field has been affected by the ratio of lateral separation to crack length not the lateral separation 2h for a pair of offset parallel cracks. Once the two cracks overlap, the propagation directions of cracks would turn. The inflection point and turning would fade with the increase of the ratio of lateral separation to crack length. At the same time, some experimental tests were carried out to validate the analysis results.
Comparison of Pressure-Temperature Limit Curves Calculation
Authors: Lu F. , Qian H. Y. , Huang P. , Wang R. S.
Published: May 2012

Reactor Pressure Vessel (RPV) is one of the most important components in a nuclear power plant (NPP). The primary concern of aging mechanism for RPV is irradiation embrittlement. In order to prevent brittle fracture, during NPP heatup and cooldown processes, the pressure and temperature in RPV should be kept under the pressure-temperature (P-T) limit curve. The P-T limit curve method originated from a WRC bulletin in 1972 and was included in ASME Sec. XI App. G.. Since then, much effort for reducing the conservatism of the P-T limit curve calculation has been made in many countries. Technology developed over the last 30 years has provided a strong basis for revising the P-T limit curve methodology. Up to now, changes have been made in the latest version of the ASME and RCCM codes. In this paper, the P-T limit curve methodologies given by the ASME code, the RCCM code, and Chinese Nuclear Industry Standard EJ/T 918 are studied. The differences of the P-T curve methodologies in previous and current versions for the ASME and RCCM codes are discussed. Two P-T curve calculation methods based on the RCCM code Ver. 2007 are proposed, due to lack of specific description for the calculation method in the RCCM code. Comparison of the P-T curves obtained using methods from different codes is also performed. It shows that using static fracture toughness KIC instead of reference fracture toughness KIR to calculate P-T curves can increase acceptable operating region during NPP heatup and cooldown processes significantly. Comparing with the latest versions of the ASME and RCCM codes, the current Chinese Standard is more conservative.
Lagrangian Finite Element Formulation to Axisymmetric Liquid Sloshing
Authors: Yoshida Shoichi , Sekine Kazuyoshi , Tsuchida Tomohiko , Iwata Katsuki
Published: May 2012

The sloshing analysis of liquid storage tanks by the finite element method is basically categorized into two approaches, Lagrangian approach and Eulerian approach. In the Lagragian approach, the behavior of the fluid is expressed in terms of the displacements at nodal points. The advantage of the Lagragian method is that the computer code can be easily developed to modify an existing structural analysis code. The disadvantage is that some spurious modes are included in the vibration modes. The Lagrangian method is widely used in two- and three-dimensional problems. On the other hand, it has not been reported its applicability to the axisymmetric problem. This paper presents the applicability of the Lagragian method to the axisymmetric sloshing problem. The eigenvalue of an elemental stiffness matrix is analyzed in order to investigate the characteristics of the rotational stiffness to the compressibility of the fluid. As a result, this method is found to be difficult to apply to the axisymmetric problem if the equation of motion is directly solved using time integration. However, it gives the highly precise response solutions if the only sloshing modes are taken out and the modal analysis technique is used.
Main Steam Line Constant Spring Support Failures
Authors: Szasz Gyorgy , Wandell Christopher , Borrero Winston , Jaeger Mark
Published: May 2012

Several constant spring supports attached to the main steam lines (MSLs) at Palo Verde Nuclear Generating Station (PVNGS) failed over a period of several years. The continued failures presented a need to instrument the MSL piping and supports, such that data could be collected in support of a cause determination and problem resolution effort. Extensive monitoring and data acquisition was performed over an 18-month period in all three PVNGS operating units, encompassing several revisions to the instrumentation configuration. This document presents an account of the project, with a timeline of events, detailed information on the instrumentation and data analysis, and other engineering efforts. Ultimately, no single source of failure was identified, as several potential contributors were uncovered. Modifications were implemented to mitigate the hanger failures, and the instrumentation was used to verify their effectiveness. No further failures have occurred after implementation of the modifications.
Applying ASME PCC-1-2010 Appendix O to Joint Lifecycle Management
Authors: Brown Warren
Published: May 2012

Appendix O “Determining Joint Assembly Bolt Load’ was added in the 2010 version of ASME PCC-1 “Guidelines for Pressure Boundary Bolted Joint Assembly”. It outlines a method of calculating an appropriate assembly load for pressure vessel and piping bolted joints. However, the possible uses and scope of the appendix go well beyond only the selection of assembly bolt load. For example, the method can be applied to gasket selection or assembly method selection. The calculations in the appendix can easily be applied to quantify when certain technology can be employed and when it shouldn’t and can also be used as a tool to contribute to the overall gasket selection or assembly method selection process. In fact, once an understanding of the basic behavior of the joint is obtained, then the method can be applied to the full life-cycle of the joint, including use as a tool to determine the root cause of leakage. Basic procedures for performing these types of assessments and some pertinent examples are outlined in this paper.
Sensitivity Analysis of SCC Crack Extension Simulation
Authors: Ogawa Naoki , Hojo Kiminobu , Shim Do-Jun , Ogawa Kazuo
Published: May 2012

For the preliminary investigation of realistic SCC crack extension behavior, several crack extension simulation methods were applied to example problems. As for a mesh division procedure, two kinds of methods were employed. One is a conventional one which needs new mesh generation of finite element (FE) models following crack extension and the other one is X-FEM without new FE mesh generation. Also the effects of crack extension contained within the weld material and the crack growth rate dependence on the crack extension direction at the weld joint were considered. Under hypothetical liner stress distribution, the stress intensity factors from the FE analyses by the conventional mesh division procedure and X-FEM agreed well with those from the stress intensity factor K equations of a hand book in the case of semi-elliptical and semi circular cracks. As for the crack extension analysis, consideration of the direction dependent crack growth rate and limited crack extension within the hypothetical shaped weld groove boundary gave a large effect on the crack extension amount in the thickness direction.
Experimental Investigation on the Failure Estimation Method of Cracked Cylinders Subjected to Multi-Axial Loads
Authors: Li Yinsheng , Hasegawa Kunio , Miura Naoki , Hoshino Katsuaki
Published: May 2012

When a crack is detected in a stainless steel pipe during in-service inspections, the failure estimation method given in the codes such as ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the integrity of the cracked pipe. In the current codes, the failure estimation method considers the bending moment and axial force due to pressure. The torsion moment is assumed to be relatively small and is not considered in the method. Recently, an analytical investigation has been carried out by several of our authors on the limit load considering multi-axial loads including torsion, and a failure estimation method for combined bending moment, torsion moment and internal pressure is proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads, including the torsion, and to provide experimental support for the failure estimation method, experiments were carried out on small sized stainless steel cylinders containing a circumferential surface and a through-wall crack, taking into consideration the combined tensile and torsion loads. Based on the experimental results, the proposed failure estimation method is verified for cracked pipes subjected to multi-axial loads.
Axisymmetric Finite Element Analysis for Floating Roofs of Aboveground Storage Tanks Under Accumulated Rain Water Condition
Authors: Yoshida Shoichi
Published: May 2012

The floating roofs are used in large aboveground storage tanks to prevent evaporation of the content. The single-deck floating roof, which is considered herein, consists of a thin circular plate called a deck attached to a buoyant ring of box-shaped cross section called a pontoon. Under the accumulated rain water condition, the deck is deflected largely, and both its edge part and the pontoon are compressed circumferentially. Since the load condition due to the rain water depends on the deflected deck shape, it is difficult to find the unique equilibrium condition. This paper describes the deformation analysis for the single-deck floating roofs under the accumulated rain water condition using the geometrically nonlinear axisymmetric shell finite element method. The load incremental method, in which the equivalent nodal forces due to the rain water converges to coincide with the rain water load derived from both the current rain water volume and the deflected deck shape, is used.
Experimental Investigation of Coke Drum Material Behavior Under Complex Thermal-Mechanical Loading
Authors: Chen Jie , Xia Zihui
Published: May 2012

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries and oil sands plants. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. In order to better understand the damage mechanisms, an experimental investigation of coke drum material behavior under various thermal-mechanical loading conditions was performed. A thermal-mechanical material testing system is successfully designed and implemented. Six types of various thermal-mechanical cyclic tests were performed: 1. cyclic thermal loading under constant uniaxial stress; 2. in-phase thermal and mechanical stress cycling; 3. out-of-phase thermal and mechanical stress cycling; 4. fully-reversed uniaxial cyclic loading with in-phase thermal cycling; 5. in-phase thermal-axial stress cycling with constant circumferential stress; 6. in-phase thermal-axial stress cycling with mean stress. Some of theses tests are similar to the actual loading scenario experienced by the coke drums. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums such as bulging.
Research Progress on the Technique Application of Risk Based Management in Domestic Petrochemical Plants
Authors: Jia Guodong , Wang Hui , Li Xiang , Shi Jin , Wang Weihua
Published: May 2012

The advanced risk based management (RBM) technique is playing a more and more important role in raising the standard of business management, reducing the cost of production, ensuring the long period safe operation of plants. With the support of the High-technology Research and Development Program of China (863 project), National Key Technology R&D Program of China, Social Commonweal Research Project of The Ministry of Science and Technology of China, etc, many research achievements have been made by the units concerned. These achievements have been used widely in petrochemical plants now. In this paper, the application status of RBM technique of petrochemical plants in china was summed up in the aspects of the analysis flow, application status, problems and suggestions. Finally, the summary and outlook on the application of RBM technique in China were made.
Cyclic and SCC Behavior of Alloy 152 Weld in a PWR Environment
Authors: Alexandreanu Bogdan , Chen Yiren , Natesan Ken , Shack Bill
Published: May 2012

Alloys 600 and 182 are used as structural materials in pressurized water reactors (PWRs) and have been found to undergo stress corrosion cracking (SCC). Alloys 690 and 152 are the replacement materials of choice for Alloys 600 and 182, respectively. The objective of this work is to determine the crack growth rates (CGRs) in a simulated PWR water environment for Alloy 152. In order to meet the objective, specimens made from a laboratory-prepared Alloy 152 double-J weld in the as-welded condition were tested. For the SCC CGR measurements, the specimens were pre-cracked under cyclic loading in a primary water environment, and the cyclic CGRs were monitored to determine the transition from the fatigue transgranular fracture mode to the intergranular SCC fracture mode. The environmental enhancement of cyclic CGRs for Alloy 152 was minimal; nevertheless, the transition from transgranular to intergranular cracking was successful. Weld samples tested from the single heat of Alloy 152 exhibited SCC CGR rates of 10−11 m/s in the simulated PWR environment at 320°C, which is only about an order of magnitude lower than typical for Alloy 182.
Computation of Welding Distortions in T-Joints
Authors: Keina¨nen Heikki , Alhainen Jouni , Verho Martti
Published: May 2012

The main objective of the performed Control and Exploitation of Thermal Distortions (DISCO) project was to seek an overall concept for the control of thermal distortions. The scope of the project was limited to structural steels and to the processes most important to the participating industry. The possibility to apply the inherent strain method for modelling thermal deformations was examined by establishing an inherent strain database for the target arc welding and thermal cutting situations. The project was executed in cooperation with Lappeenranta University of Technology and four Finnish enterprises. Osaka University, Japan, was consulted concerning the inherent strain method. The work focused on structural steels representing two strength levels, and GMAW, FCAW, SAW and MAG welding processes. The computational practices were revealed for treating thermal distortions. Further actions included testing and modelling of welded T-joint with various plate thicknesses. The relationship between plastic strains and angular distortion (out-of-plane deformation with the weld as the axis of rotation) of fillet welded plate T-joints were studied using numerical analyses. A three dimensional thermo-elastic-plastic analysis incorporating the effects of a moving heat source and non-linear material properties was performed to obtain the plastic strain distributions and deformations. Procedures to define a simplified strain distribution (inherent strain) and to compute deformations were presented. The comparison of detailed thermo-elastic-plastic computation and measurements yielded a good correspondence. The simplified inherent strain type analysis underestimated somewhat the deformations. The technical basis for the creation of an inherent strain database was presented.
SCC Behavior of Alloy 52M/182 Weld Overlay in a PWR Environment
Authors: Alexandreanu Bogdan , Chen Yiren , Natesan Ken , Shack Bill
Published: May 2012

Weld overlays (WOL) of alloys believed to possess superior stress corrosion cracking (SCC) resistance are typically applied over welds made with SCC-susceptible alloys with the expectation that they will act as a barrier to SCC. The objective of this work is to investigate the behavior of a crack initiated in Alloy 182 as it approaches the Alloy 52M WOL interface. For this purpose, an Alloy 52M WOL was deposited on a double-J Alloy 182 weld. Compact tension specimens were fabricated with the notch in Alloy 182 and oriented towards the WOL, and tested in a simulated PWR environment. The first such test revealed that the SCC rates in Alloy 182 were found to decrease by an order of magnitude ahead of the interface, and that the crack advanced from Alloy 182 into Alloy 52M. The post test examination found that crack branching occurred at the interface between the two alloys. Growth in Alloy 52M along the interface appears severe, approx. 10−10 m/s. While for the most part (70%) the crack propagated along the interface, SCC cracking was also found to extend into Alloy 52M along the original direction. This cracking is substantial, yielding SCC rates of 10−11 m/s.
Numerical Simulations of Nonlinear Post-Critical Vibrations of an Airfoil After Flutter Instability
Authors: Hora´cˇek Jaromi´r , Feistauer Miloslav , Sva´cˇek Petr
Published: May 2012

The contribution deals with the numerical simulation of the flutter of an airfoil with three degrees of freedom (3-DOF) for rotation around an elastic axis, oscillation in the vertical direction and rotation of a flap. The finite element (FE) solution of two-dimensional (2-D) incompressible Navier-Stokes equations is coupled with a system of nonlinear ordinary differential equations describing the airfoil vibrations with large amplitudes taking into account the nonlinear mass matrix. The time-dependent computational domain and a moving grid are treated by the Arbitrary Lagrangian-Eulerian (ALE) method and a suitable stabilization of the FE discretization is applied. The developed method was successfully tested by the classical flutter computation of the critical flutter velocity using NASTRAN program considering the linear model of vibrations and the double-lattice aerodynamic theory. The method was applied to the numerical simulations of the post flutter regime in time domain showing Limit Cycle Oscillations (LCO) due to nonlinearities of the flow model and vibrations with large amplitudes. Numerical experiments were performed for the airfoil NACA 0012 respecting the effect of the air space between the flap and the main airfoil.
Finite Element Damage Simulations for Creep Crack Growth of SS316H With Different Geometries
Authors: Oh Chang-Sik , Kim Nak-Hyun , Lee Han-Sang , Kim Yun-Jae
Published: May 2012

In this paper, creep crack growth simulations were performed based on finite element (FE) damage simulations for several types of test specimens such as C(T), CS(T), SEN(T), M(T) and SEN(B). The Graham-Walles creep law was adopted to describe all three phases of creep. The Creep parameters were obtained from uni-axial creep test results of SS316H at 550°C. Damage model was also included based on creep ductility exhaustion concept, which is defined as the ratio of creep strain to the multi-axial creep ductility. Creep crack growth rates resulting from FE simulations were compared with the experimental data.
Computation of Low Reynolds Number Flow Around a Circular Cylinder Following a Horseshoe-Shaped Path
Authors: Baranyi La´szlo´
Published: May 2012

Two-degree-of-freedom vortex-induced vibration investigations of low-mass ratio circular cylinders show that the streamwise frequency of oscillations is about twice that of the transverse oscillation. These cylinders have been observed to trace Lissajous-type trajectories. Depending on the phase difference between in-line and transverse motions paths, different shapes can be obtained, such as trajectories resembling a figure 8 or a horseshoe. In this study low Reynolds number flow is investigated numerically for a cylinder placed in a uniform stream and forced to follow a horseshoe-like path. Investigations were carried out using a thoroughly tested finite difference code developed by the present author. The mechanical energy transfer between the fluid and the cylinder, time-mean and rms values of force coefficients are investigated. Computations are carried out for Reynolds numbers of Re=140, 200 and 250 in the lock-in domain against the frequency ratio while other parameters are kept constant. All investigations were carried out at two phase difference values, resulting in convex and concave arc paths called horseshoe-shaped paths. The mechanical energy transfer and the time-mean and rms values of force coefficients show that a sudden jump in values is often observed, affecting flow features. Positive energy transfer after the jump is common.
Very High Cycle Fatigue Behavior and Life Prediction of a Low Strength Weld Metal at Moderate Temperature
Authors: Zhu Ming-Liang , Xuan Fu-Zhen , Wang Zhengdong
Published: May 2012

The fatigue properties of a low strength weld metal in a dissimilar welding joint in high cycle and very high cycle regimes were investigated by fully reversed axial tests in air at room temperature and 370°C. A clear duplex S-N curve existed as a result of the transition of fatigue failure mode from surface-induced failure to internal-induced failure at 370°C, while the S-N curve was continuously decreased at room temperature. A new model was successfully proposed to predict fatigue life, and interpret the crack initiation modes transition from surface inclusion to interior inclusion. It was concluded that cracks were initiated by competition among non-metallic inclusions, welding pores and discontinuous microstructures in high cycle regime. While in the very high cycle regime, non-metallic inclusions were the dominant crack initiation mechanism which depended on stress level, inclusion size as well as inclusion depth.
Determination of Material Constants of Internal Time Theory of Plasticity and Creep for Fatigue Analysis and Creep-Fatigue Analysis
Authors: Watanabe Osamu
Published: May 2012

Recent computer hardware is greatly developed to make possible fatigue analysis and creep-fatigue analysis of structures, which takes much computational time in the past. The code and standard recommend the simplified method in the fatigue analysis and creep-fatigue analysis instead of the detailed inelastic finite element solutions. It is widely recognized that the employed constitutive model affects inelastic finite element solutions significantly. However, the inelastic finite element solutions can consider effects of geometry shape or boundary conditions easily compared to the simplified methods. The other advantage of the inelastic solutions can also assist the mechanism of inelastic deformations. Thus, the accurate inelastic finite element solution is still intense research subject in this area.. The present paper will study constitutive model and the determination method of the material constants for the fatigue analysis and creep-fatigue analysis in order to simulate inelastic behavior at saturated condition, which differs from those at the initial loading.
Crack Initiation/Propagation of Perforated Plate Under Displacement-Controlled Fatigue Test at Elevated Temperature
Authors: Watanabe Osamu , Akiyama Taisuke , Matsuda Akihiro
Published: May 2012

In structures having stress concentration under cyclic loading, a small crack initiates and it grows and propagates. The present paper shows the experimental results of the perforated plate having the different diameters and the prescribed different strain amplitude. In the specimens having a circular hole, a crack initiates at the hole side having the most severe stress concentration in the specimen, and then the other crack also starts to initiate at the opposite hole side. Growth of both cracks is observed from the photographs taken at each cycle to study the relation between crack growth and load decrease. The feature of crack growth initiating from multiple origins will be discussed for fatigue test. The crack initiation is evaluated by referring to the accumulation law using the simplified estimation scheme, and the crack growth is evaluated by referring the increment of J-Integral. The agreement for crack initiation and propagation with these test results will be discussed.
Proposal of Limit Moment Equation Applicable to Planar/Non-Planar Flaw in Wall Thinned Pipes Under Bending
Authors: Tsuji Masataka , Meshii Toshiyuki
Published: May 2012

In this paper, limit bending moment equation applicable to all types of planar and non-planar flaw in wall thinned straight pipes under bending was proposed. An idea to rationally classify planar/non-planar flaw in wall thinned pipes was proposed, based on the experimental observation focused on the fracture mode. The results point out the importance to distinguish axially and circumferentially long flaws in wall thinned pipes.
Effect of Creep Mismatch Factor on Steady State Creep Stresses in Welded Components With Heat Affected Zone
Authors: Han Jae-Jun , Lee Kuk-Hee , Kim Yun-Jae , Nikbin Kamran , Dean David
Published: May 2012

This paper describes steady-state stress on welded branch components using detailed three dimensional elastic creep finite element analyses. In our previous paper [1], it was found that the mismatch effect in creep on steady-state stresses within the weld metal for a various branch junction could be uniquely quantified by the mis-match factor, defined as a function of creep exponent and constant. In actual branch components, the branch junction contains the heat-affected zone (HAZ) when the branch pipe is welded. Thus, additional mismatch factor for HAZ should be presented. This paper deals with not only the mismatch effect for weld metal but also that for HAZ. The creep exponent and constant for the base and weld metal as well as HAZ were systematically varied to analyze under-matching, even-matching and over-matching conditions in creep. In order to investigate the effect of the loading mode, FEA was carried out under internal pressure and in-plane bending to the branch pipe. Two geometries such as large bore branch and medium bore branch were considered. It was found that steady-state creep stresses within HAZ can be quantified as mismatch factor with specific characteristics.
Hydrodynamic Interaction Between Whistling Axisymmetric Cavities in the Presence of a Coupling Longitudinal Standing Wave
Authors: Nakibog˘lu Gu¨nes¸ , Rudenko Oleksii , Golliard Joachim , Hirschberg Avraham
Published: May 2012

An axisymmetric cavity along a pipe is a commonly encountered construction in industrial applications, which can also be considered as a unit element of a corrugated pipe. At critical conditions such a configuration causes severe noise problems, called whistling. Whistling is a self-sustained oscillation, driven by a flow-acoustic interaction. In the current study, the hydrodynamic interaction between two such cavities is addressed in the presence of a coupling standing wave along the pipe. The phenomenon is investigated both experimentally and numerically. The hydrodynamic interaction has a strong effect both for the amplitude and for the Strouhal number of the whistling, which depends critically on the separation distance between two adjacent cavities.