bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Environments on the Fatigue Life of Pressure Vessel Steel in High-Temperature Water
Authors: Cho Hyunchul , Kim In-Sup
Published: August 2008

Low cycle fatigue (LCF) tests in room temperature air and in high-temperature oxygenated water were performed to clarify environmental effects on the fatigue life of SA508 Cl.3 reactor pressure vessel steel. In room temperature air, the cyclic stress responses showed an initial hardening and a moderate cyclic softening during deformation. On the other hand, for tests performed in high-temperature water, the cyclic stress responses were observed to induce an enhanced hardening, that is a secondary hardening due to dynamic strain aging (DSA). Fatigue life in high-temperature oxygenated water was shorter than that in room temperature air. The main reason of the life decrease may be a synergistic effect between environmental parameters and loading parameters. It may be considered that the reduction of the fatigue life was related to slip oxidation/dissolution and hydrogen embrittlement.
High-Cycle Fatigue Strength and Residual Stress in Welded Joints of Structural Steels
Authors: Mochizuki Masahito , Toyoda Masao
Published: August 2008

Improvement of high-cycle fatigue strength by reducing residual stress in welded joints is studied in this paper. 10% Nickel and 10% Chromium are involved in the developed welding material for producing the property of thermal shrinkage by martensitic phase transformation at a low temperature and for generating compressive residual stress during cooling process. A cruciform fillet-welded joint is used for the numerical simulation of the thermal elastic-plastic finite-element analysis with coupling phase transformation effect. Distribution of the computed residual stress agrees with the measuring values by strain gauge. Compressive residual stress mostly distributes in the weld metal for both longitudinal and transverse directions with weld line. Fatigue test is also performed in order to clarify the effect of the developed weld material on fatigue strength. Developed weld metal has much higher characteristics for high-cycle fatigue strength than a conventional one. Increase effect of fatigue strength is shown by the modified Goodman diagram when residual stress is treated as mean stress. Weld metal with the property of low-temperature phase transformation is effective to reduce residual stress and to improve fatigue strength.
Frequency Effects on Gigacycle Fatigue Properties of High-Strength Steels
Authors: Furuya Yoshiyuki , Matsuoka Saburo , Abe Takayuki
Published: August 2008

This report will reveal a series of fatigue test results for high-strength steels at 100 Hz and 20 kHz and discuss frequency effects on gigacycle fatigue properties. The 20 kHz fatigue testing machine is an effective tool to conduct gigacycle fatigue tests in a reasonable term, while frequency effects have to be carefully investigated before applying the machine. The fatigue tests were conducted for two kinds of high-strength steels, that were a low-alloy steel and a spring steel. These fatigue test results showed that the frequency effects were negligible even at 20 kHz in case of fish-eye fracture. The fatigue properties in the fish-eye fracture region showed a good agreement between the 100 Hz and 20 kHz tests. Besides, ODAs (Optically Dark Areas) were also observed on the fracture surface even in 20 kHz tests and no difference was found in the ODA sizes between the 100 Hz and 20 kHz tests. These results meant that the 20 kHz tests could provide us appropriate results at least in the fish-eye fracture region. Therefore, the 20 kHz tests were applicable on the evaluation of gigacycle fatigue properties in high-strength steels.
Low Cycle Fatigue Analysis of Storage Canisters Due to Expansion of Contents
Authors: Flanders Harry E.
Published: August 2008

Qualification of storage canisters due to the expansion behavior of plutonium metal during phase transitions requires a combined experimental and analytical modeling effort. Tests were conducted at Los Alamos National Laboratory to define the expansion behavior of plutonium metal during the alpha-beta-gamma phase transitions. Test results showed that the expansion is anisotropic due to the container wall constraint. The plutonium expansion parameters were calculated from test data, and combined with a finite element analysis (FEA) to determine the stress state of the storage canisters. Strain values were computed and compared with the ASME Code secondary and peak stress limits. Since the applied expansion strain exceeds the strain of 10 cycles in the ASME Code design fatigue curve, the ASME Code design fatigue curve was extended to values below 10 cycles.
High Cycle Thermal Fatigue on a Mixing Zone of Auxiliary Cooling System
Authors: Taheri Said
Published: August 2008

An over-loading due to welding or surface finishing may be decomposed into a static stress (mean stress) and a pre-hardening (plastic strain). We show that for a stainless steel a pre-hardening enhances the fatigue life in stress control in contrast with strain control. Under high cycle thermal fatigue the presence of stripping more frequent near the weld is then related to combination of detrimental effects of pre-hardening in strain control and positive mean stress. Moreover we show that for a thin structure it is very difficult to evaluate the residual welding stress near a weld tip because of the dependence of the stress on spatial second derivative of the temperature of welding. Concerning surface finishing in the case of shot pinning we conclude that beneficial effect of a negative mean stress on fatigue life may be cancelled by the detrimental effect of pre-hardening in the case of strain control.
Prediction of Fatigue Crack Propagation of Sub-Surface Cracks by “SCAN”
Authors: Shiratori Masaki , Yoshikawa Naoki , Iwamatsu Fuminori , Matsushita Hisao , Omata Shigeo , Matsuda Hiroyuki , Miyoshi Toshiro
Published: August 2008

The authors have proposed an influence function method by which stress intensity factor, K, of surface cracks can be calculated easily for arbitrarily distributed surface stresses. They have developed the database of influence coefficients, Kij, for various types of surface cracks through a series of finite element analyses [1]. And they also have developed a software system “SCAN”, based upon the above developed database, by which K-values of surface cracks can be evaluated promptly, and further, fatigue crack propagation can be simulated easily by a personal computer. In this paper the authors have studied how they can apply the SCAN system to the problem of the sub-surface cracks. They have developed “SCAN Sub-Surface Crack Version”, where SCAN is improved by newly analyzed influence coefficients for a series of sub-surface cracks, and by following the scenario described in ASME CODE, SECTION XI [2]. They have found that the database of a surface crack in a flat plate already installed in the SCAN system, with the above described Kij database for sub-surface cracks, can be applied to this problem with satisfactory accuracy, which means the K-values of this problem can be evaluated promptly by the SCAN system, and the propagation of small sub-surface cracks can be simulated easily.
Case Study of the Use of API 581 on HK and HP Material Furnace Tubes
Authors: Noori Soudabeh A. , Price John
Published: August 2008

Risk-based inspection guidelines have been created by several technical societies, most notably the ASME and API. This study intends to show how one of these techniques, American Petroleum Institute, API 581 assesses risk and determines inspection intervals of furnaces tubes. The paper also explains the difficulties of applying API 581 and discusses the meaning of the results and the inspection program proposed in API 581.
An Integrated Approach for the Structural Reliability Evaluation of Fast Breeder Reactor Components
Authors: Asayama Tai , Kawasaki Nobuchika , Morishita Masaki
Published: August 2008

For the improvement of structural design of fast breeder reactors, a new method for the optimization of structural reliability is proposed. This method approximates failure probability of a component by a linear formulation of various design variables. The formulation is obtained by a theoretical calculation extended by numerical considerations based on Monte Carlo simulation. This method allows a designer to optimize reliability without trial-and-error type calculations.
Field Vibration Tests and Dynamic Stability Analysis of a Full-Scaled Tainter-Gate
Authors: Anami Keiko , Ishii Noriaki , Knisely Charles W.
Published: August 2008

This study presents results from in-air and in-water field vibration tests of a 29-ton full-scaled Tainter-gate installed on a river in Japan. These tests were conducted to confirm the validity of our theoretical analyses especially for a large value of Froude number. First, with the gate raised, an in-air experimental modal analyses, using an impact hammer and accelerometers, was conducted to determine the natural frequencies and the damping ratios for two modes of gate vibration. These two modes corresponded to the rigid body vibration of the whole gate around the trunnion pin and the streamwise rotational vibration of the skinplate. Subsequently, with the gate again lowered and exposed to flowing water, the gate vibration characteristics were carefully measured. Only weak, unsynchronized vibrations were recorded and the gate was found to be dynamically stable. A theoretical analysis developed to predict the hydrodynamic pressure, the vibration frequency ratios and the dynamic stability were applied to the full-scaled gate. The theoretical analysis correctly predicted both the measured frequency ratios and the gate’s dynamic stability.
On the Governing Contingency for Pressure-Relief Device Sizing
Authors: Short W. E.
Published: August 2008

Equipment and piping systems that operate under pressure need to be protected from excessive overpressure. This is accomplished with the installation of pressure-relief devices, which must be properly sized and specified for the intended service conditions. To adequately size a pressure-relief device to provide overpressure protection for equipment and piping, several relief event scenarios always should be considered. Ultimately, overpressure protection is provided with the installation of pressure-relief devices that are specifically sized, specified and installed for the postulated governing overpressure contingency. Too often, pressure-relief devices are sized based on the possibly erroneous presumption that fire exposure will be the most likely governing contingency. Historically, the fire exposure contingency has been emphasized to such an extent that pressure-relief devices often are assessed solely on the basis of fire exposure. Substantiation of this presumption, however, is not obvious in the literature. In fact, one can argue that there are many relief contingencies other than fire exposure which may govern the relief device size. Furthermore, neglecting consideration of other relief contingencies can present a potentially dangerous situation. This paper presents results from a study intended to examine which overpressure relief contingency, if any, most often governs the size of relief devices that are used to protect equipment and piping systems. From previous related work, seven relief contingencies are described and emphasized by the author. For this study, relief device sizing data was compiled from a number of chemical and petrochemical project applications to provide a reasonable sample of contingencies that governed the sizes of existing and new safety-relief valves and rupture discs [1,2,3].
Two-Phase Flow Through a Relief Valve Discharging Into a Water Filled Pipe
Authors: Ezekoye L. I. , Matty T. J. , Swantner S. R.
Published: August 2008

Relief valves provide overpressure protection of components and systems. To properly size them, one needs to know the fluid conditions upstream and downstream, the physical and thermal properties of the fluids at the postulated relieving conditions, a model that can be used to predict the capacity and the geometry of the inlet and outlet conditions. However, in many applications, it is not uncommon that some of the information needed to properly size relief valves may be missing. For example, there may not be information on the inlet and outlet pipe configuration, which may influence the flow conditions. For single-phase flows, neglecting inlet and outlet piping configurations may have minimal effect on the capacity. However, for fluids that are slightly subcooled with a potential for flashing, the effect may be significant. The problem is magnified by the fact that, unlike single phase flows where the ASME standard provides a method for sizing single phase relief valve capacity, there is no standard model for sizing two-phase flow relief capacity. In this paper, we present the sizing of a relief valve for a slightly subcooled water application with attached piping using the ASME and the OMEGA methods to illustrate the differences in their estimates.
A Forced Vibration Response-Based Damage Identification Method for Cylindrical Shells
Authors: Lee Usik , Kim Sunghwan , Cho Jooyong
Published: August 2008

This paper presents a feasibility study on a structural damage identification method (SDIM) developed herein for cylindrical shells. The SDIM is derived directly from the governing differential equations of motion of damaged cylindrical shells. A damage distribution function is used to represent the distribution and magnitudes of local damages within a cylindrical shell. In contrast with most of existing modal parameters-based SDIMs, which requires only model parameters measured in both intact and damaged states, the present SDIM utilizes the FRF-data in the damaged state instead of the modal parameters in the damaged state. By virtue of utilizing FRF-data, a sufficient number of equations can be derived by choosing as many sets of excitation frequency and FRF measurement point as needed. The feasibility of the present SDIM is numerically tested through some illustrative examples, taking into account the random noises in FRF-data.
On the PD Control of Rotating Flexible Arms Driven by Stepper Motor
Authors: Ismail S. Zahi , Al-Qaisia A. A. , Al-Bedoor B. O.
Published: August 2008

In this work, a dynamic model of a flexible-arm attached to a hub with flexible-joint and flexible torsional support is presented. The Lagrangian approach in conjunction with the finile element method is employed in deriving the equations of motion, within the assumption of small deformation theory. The control strategy adopts the approach of applying encounter torque supplied by a small DC motor fixed to a bed, which is recessed to the hub by the torsional spring. The control torque will be applied to the arm root to control the dynamics of the flexible arm and produce minimum tip deflection with precise positioning. Comparisons between rigid arm control and flexible arm are conducted. The control torque of the equivalent linear system is applied on the nonlinear model. Simulation results of the nonlinear and the linearized controlled models are compared and the results are discussed to show the efficiency of the proposed control strategy.
Pressure Vessel Management: A Plant Perspective
Authors: Almon Walter S.
Published: August 2008

This paper addresses a methodology to maintain pressure vessels per ASME Section VIII, Division 1 Code and jurisdictional requirements, for new and existing pressure vessels. The pressure vessels discussed are drums, towers, shell & tube heat exchangers, and air-cooled exchangers, all designed and built per ASME Section VIII, Division 1. The methodology applies to vessels in refineries, gas plants, oilfield facilities, and chemical plants. Vessel adequacy is maintained via Codes, non-destructive testing, materials, inspection, company standards, welding procedures, inspection/maintenance standards, and jurisdictional requirements. Unique maintenance software, “PVCalc”, can aid in vessel calculations, to calculate the pressure rating, and remaining life, per the original edition of the Code under which the vessel was built. New vessel designs should be thoroughly reviewed, as the author’s experience over the last eight years is that approximately 65 to 80 percent of all vessel designs contain design errors (mostly minor) per ASME Code.
Risk-Based Inspection as a Reliability-Engineering Tool for Fixed Equipment Decisions
Authors: Poulassichidis Tony
Published: August 2008

Risk Based Inspection (RBI) results in calculating a risk value for each piece of plant fixed-equipment. Usually RBI implementation results in fixed-equipment inspection program modification. Inspection is specified for equipment items that exceed Owner acceptable risk criteria while it is waived for equipment that is below acceptable risk levels. In RBI analysis, equipment risk value consists of a Likelihood-of-Failure (LOF) and a Consequence-of-Failure (COF) element. Furthermore LOF value is the sum of different equipment damage mechanisms (internal corrosion, external corrosion and cracking mechanisms). This paper describes on Olefins plant gains from applying RBI as a reliability-engineering tool instead of an inspection optimization tool. Based on RBI calculated risk values, fixed-equipment relative risk ranking is established to: • set priorities and focus our attention on the critical areas; • justify capital investment for Lifetime Extension projects; • proactively address Loss of Primary Containment and Process safety issues.
The Assignment of SIL Targets to Overpressure Protection in Reactive Systems
Authors: Dejmek Kimberly A. , Wehrman Ken A.
Published: August 2008

The assignment of performance targets, or target Safety Integrity Levels (SILs), is a critical step in the application of the Safety Instrumented System (SIS) standards, i.e., ANSI/ISA S84.0.01-1996, IEC 61508 and IEC61511. Although the SIL is a key concept in the implementation of the standards, the development and application of a method for determining the target SIL has been left to the owner/operator. The standards do, however, provide guidance on this topic and present a number of techniques that can be considered, including risk matrix, risk graph, and Layers of Protection Analysis (LOPA). Generally, the methods for SIL assignment are qualitative or semi-quantitative risk assessment methods that are based upon the judgments of an assignment team. In most cases the methods based on expert opinion and limited historical data are adequate. However, in the case of overpressure protection for reactive systems, the number and complexity of the scenarios often overwhelms these simplified approaches. There are warning signs that can aid in the identification of cases where the simplified methods may break down and provide non-conservative results. In cases such as this, a quantitative assessment should be conducted to evaluate the likelihood of SIF demands, the risk reduction supplied by the other protection layers, with the aim of determining the risk reduction required from the instrumented overpressure protection system.
Root Cause Evaluation on Suction Piping Vibration of Auxiliary Feedwater Pump
Authors: Jeon Chang-Bin , Choi Byoung-Hwa , Park Mun-Baek
Published: August 2008

Abnormal vibration was observed in the suction piping of Auxiliary Feedwater (AF) pump during a pre-operational test at an operating nuclear power plant in Korea. The vibration and noise were initiated when a recirculation valve located downstream of the pump was gradually closed to about 80%. The vibration reached its peak when the recirculation valve was in a fully closed position. After the test, it was found that the bearing of AF pump was damaged. The vibration of suction line was measured during a retest and the cause of vibration was evaluated. This paper presents a root cause of the vibration problem experienced in the pump suction piping. It also reviews the relationship between the vibration of suction piping and minimum flow operations. In conclusion, the pulsation frequency generated from the pump internal during a low flow operation of the pump caused the suction piping vibration.
Flow in the Converging Mini-Channels
Authors: Karng Sarng Woo , Lee Yoon Pyo , Kim Jin-Ho S.
Published: August 2008

Recently mini-channels or micro-channels are widely used for cooling the high density power electronic devices. Especially, the channels are used in small and high efficient equipments such as heat pipes and heat exchangers. Interfacial velocities between liquid and gas phases are very important in mini or micro-channels. In this paper, an experiment and a numerical analysis on the interfacial velocities were performed. In the experiment, the interfacial velocities which were measured by the high-speed CCD camera were about 26∼33 cm/s and the velocities increased as the inclination angle did. In the numerical experiment, CFD-ACE+, a commercial program, was used, the velocities had similar values with experimental results. As the inclination angle and the contact angle increased, the interfacial velocities did because of the surface tension which causes to move the interface. The effect of inclination angle was larger in the converging channels than in straight channels.
A Simple Predictive Method of Steam Pipe Forces From Stop Valve Closure
Authors: Norton Kellie , Moody F. J.
Published: August 2008

Piping systems that are subject to a fast closing valve are susceptible to large steamhammer forces. The steamhammer force is a result of high-speed pressure waves propagating through the pipe that create sizeable pressure gradients in the pipe. This paper introduces a simple predictive method of the pipe forces induced by the pressure gradients in a steam pipe resulting from stop valve closure. The case of instant valve closure is also examined for comparison. The assumptions in this analysis are that the stop valve closure is linear, the pressure losses from any bends in the pipe can be ignored, the downstream pressure is constant, the steam flow is at a constant pressure, and finally the pipe walls are rigid at a constant radius. The method introduces functions that are constant along diagonal lines on the time-space graph. The pressure and velocity along these lines can be computed from the initial conditions and boundary conditions. Finally, the pipe forces are calculated using the pressures in the targeted regions of the pipe.
Blowdown/Jet Impingement Force-Time History
Authors: Katze Donald
Published: August 2008

The approximate blowdown/jet impingement force resulting from the rupture of a pipe into a low back pressure receiver is presented. The pipe fluid is an ideal gas flowing under isentropic conditions. Initial flow with Mach numbers up to 0.25 is considered. Solution of the governing thermal hydraulic equations is by the method of characteristics and application is by a wave diagram.
Strength Estimates for High Velocity Penetration of Geological Targets by the Compaction Ring Theory
Authors: Nuckols D. Zach , Jones S. E.
Published: August 2008

Existing theories for rigid body penetration model the target response to a penetration process as a cavity-expansion. A new analysis, however, offers an innovative approach to rigid body penetration of porous geological targets. The theory analyzes the formation of a compacted ring of target material observed around the boreholes in recovered targets. Applying fundamental laws of motion to an element during the formation of the ring leads to estimates for the three stresses that control the penetration event. A retarding force on the projectile nose is derived and then used to arrive at an estimate for penetration depth. The penetration depth equation, resulting from this model, is dependent upon known projectile properties, target material properties, and the impact velocity. Neglected are the effects of friction and shear. The solving procedure returns an estimate for the target yield strength. The model can then be used to predict the penetration of any penetrator into the target material. The results are promising and in agreement with the experimental observations.
Dynamic Buckling and Instability in Soil and Sand Penetration
Authors: Jones S. E. , Hughes M. L. , McCann T. G. , Haydel K. M.
Published: August 2008

In this paper, an initial attempt has been made to analytically model what has been experimentally observed when ogival-nose penetrators were fired at high velocities (up to 1500 m/sec) into soil-type (particulate) materials. Although very little experimental data of this type is available, in several instances, penetrators recovered after tests of this type were conducted were severely deformed, exhibiting excessive bending in their shank regions. The result of this initial effort is an estimate for the velocity limit that avoids the growth of lateral disturbances that will ultimately fail the penetrator. In spite of the many approximations and assumptions that were made in the development of the theory, the results are very promising and offer a path to more sophisticated results.
Finite Element Modeling of Brinell and Rockwell Hardness Testing of Metals
Authors: Rule William Keith
Published: August 2008

Hardness test results provide a convenient and economical means of specifying material performance characteristics and are useful in quality control. Quantifiable hardness testing is at least 150 years old but, due to the complex deformation processes that occur during indentation, in many ways physical insights on the test are still lacking. Finite element codes can now accurately simulate complex, time-varying stress and strain states. Such codes can be used as a tool to study the hardness test and with the knowledge gained perhaps make such testing more useful for validating the material models used for impact simulations. In this paper the EPIC finite element code with the Johnson-Cook strength model was used to numerically simulate. Brinell, and Rockwell B, C, and F hardness tests (as appropriate) for 24 different metals.
Bullet Impact on Steel and Kevlar®/Steel Armor: Computer Modeling and Experimental Data
Authors: Preece Dale S. , Berg Vanessa S.
Published: August 2008

Computer hydrocode analyses and ballistic testing have been used to investigate the effectiveness of steel plate armor against lead/copper bullets commonly available in the U.S. and across the world. Hydrocode simulations accurately predict the steel plate thickness that will prevent full penetration as well as the impact crater geometry (depth and diameter) in that thickness of steel armor for a 338 caliber bullet. Using the hydrocode model developed for steel armor, studies were also done for an armor consisting of a combination of Kevlar® and steel. These analyses were used to design the experiments carried out in the ballistics lab at Sandia National Laboratories. Ballistics lab testing resulted in a very good comparison between the hydrocode computer predictions for bullet impact craters in the steel plate armor and those measured during testing. During the experiments with the combination armor (Kevlar®/steel), the steel became a witness plate for bullet impact craters following penetration of the Kevlar®. Using the bullet impact craters in the steel witness plate it was determined that hydrocode predictions for Kevlar® armor are less accurate than for metals. This discrepancy results from the inability of the hydrocode (Eulerian) material model to accurately represent the behavior of the fibrous Kevlar®. Thus, this paper will present the hydrocode predictions and ballistics lab data for the interaction between a lead/copper bullet and several armoring schemes: 1) steel, 2) Kevlar®, and 3) a Kevlar®/steel combination.
Assessment of U.S. Embrittlement Trend Equations Considering the Latest Available Surveillance Data
Authors: Server William L. , Lott Randy G. , Rosinski Stan T.
Published: August 2008

The mechanistically-guided embrittlement correlation model adopted in ASTM E 900-02 was based on a database of U.S. surveillance results current through calendar year 1998. There exists now an extensive amount of new surveillance data that includes a large amount of boiling water reactor (BWR) results from an integrated, supplemental surveillance program designed to augment the plant-specific BWR surveillance programs. These recent data allow a statistical test of the ASTM E 900-02 embrittlement correlation, as well as the NRC correlation model currently being used in the pressurized thermal shock (PTS) re-evaluation effort and the older Regulatory Guide 1.99, Revision 2 correlation. Even though the ASTM E 900-02 embrittlement correlation is a simplified version of the NRC model, a comparison of the two embrittlement correlation models utilizing the new database has proven to be revealing. Based on the new BWR data, both models are inadequate in their ability to predict BWR results; this inadequacy has even more significance for extrapolation outside of the database for BWR heat-up and cool-down curves, as well as some pressurized water reactor (PWR) heat-up curves. Other aspects of the two models, as revealed from this preliminary look at the new data, are presented.
Experimental Program to Monitor the Irradiation Induced Embrittlement of the French Reactor Pressure Vessel Steels
Authors: Chas Guillaume , Rupa Nathalie , Bourgoin Josseline , Hotellier Astrid , Saillet Se´bastien
Published: August 2008

By monitoring the irradiation-induced embrittlement of materials, the Pressure Vessel Surveillance Program (PVSP) contributes to the RPV integrity and lifetime assessments. This program is implemented on each PWR Unit in France; it is mainly based on Charpy tests, which are widely used in the nuclear industry to characterize the mechanical properties of the materials. Moreover, toughness tests are also carried out to check the conservatism of the PVSP methodology. This paper first describes the procedure followed for the Pressure Vessel Surveillance Program. It presents the irradiation capsules: the samples materials (low alloy Mn, Ni, Mo vessel steel including base metals, heat affected zones, welds and a reference material) and the mechanical tests performed. Then it draws up a synthesis of the analysis of about 180 capsules removed from the reactors at fluence levels up to 7.1019 n/cm2 (E > 1 MeV). This database gathers the results of more than 10,000 Charpy tests and 250 toughness tests. The experimental results confirm the conservatism of the Code-based methodology applied to the toughness assessment.
Manufacturing and Properties of Closure Head Forging Integrated With Flange for PWR Reactor Pressure Vessel
Authors: Suzuki Komei , Murai Etsuo , Tanaka Yasuhiko , Kurihara Iku , Sasaki Tomoharu , Koyama Yoichi
Published: August 2008

Closure head forging (SA508, Gr.3 Cl.1) integrated with flange for PWR reactor pressure vessel has been developed. This is intended to enhance structural integrity of closure head resulted in elimination of ISI, by eliminating weld joint between closure head and flange in the conventional design. Manufacturing procedures have been established so that homogeneity and isotropy of the material properties can be assured in the closure head forging integrated with flange. Acceptance tensile and impact test specimens are taken and tested regarding the closure head forging integrated with flange as very thick and complex forgings. This paper describes the manufacturing technologies and material properties of the closure head forging integrated with flange.
Microstructural Banding and Biaxial Fracture Toughness Tests in a Specially Heat-Treated Reactor Pressure Vessel Steel
Authors: Nanstad Randy K. , Sokolov Mikhail A. , Maziasz Philip J.
Published: August 2008

The Heavy-Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) includes a task to investigate the effects of constraint on the cleavage initiation fracture toughness of reactor pressure vessel (RPV) steels in the lower transition temperature region using relatively large cruciform fracture toughness specimens under varying degrees of biaxial loading. One of the materials used for the project was a plate of A533 grade B steel (HSST Plate 14A) which was specially heat treated to result in a yield strength comparable to that of a radiation-sensitive RPV steel near the end of design life. During the testing phase to characterize the fracture toughness behavior of the plate with uniaxial three-point bend specimens, some relatively low fracture toughness values were observed. Subsequent metallography revealed the presence of varying degrees of dark bands in the microstructure. These observations prompted an investigation of the relationship between the experimentally determined fracture toughness results and the microstructure of the plate steel used for the biaxial-loading effects project, especially with regard to the results obtained from the biaxial test specimens. The primary issue in the investigation is whether the fracture toughness results obtained from the biaxially loaded specimens were influenced by the steel microstructure in a biased manner, i.e., were the observation regarding effects of biaxial loading on fracture toughness significantly affected by the microstructural segregation in heat treated HSST Plate 14A. A secondary issue is whether segregated microstructures are common in steels used for RPV construction and if the current procedures for evaluating fracture toughness of RPV steels adequately account for such microstructures. Various metallurgical tools, including metallography, microhardness testing, scanning electron fractography, electron microprobe analysis, and analytical electron microscopy were used to characterize the nature of the bands and evaluate the potential effects on the fracture toughness results.
The Practical Application of 36% Ni Steel Piping in LNG Plants
Authors: Yamamoto Eiichi , Sakata Kentaro , Seo Nobutaka , Enuma Kazushi , Uchino Seiichi , Murakami Yoshiaki , Kojima Toshifumi
Published: August 2008

Conventionally, 18-8 stainless steel has been used for the facility of cryogenic service in LNG plant because of the excellent toughness. Although 18-8 stainless steel piping requires pipe looping to relax thermal expansion in the cryogenic piping of LNG plant, 36% Ni steel (generally called as Invar) piping does not require pipe looping due to its low coefficient of linear expansion of about one-tenth of that of 18-8 stainless steel. Elimination of pipe looping makes significant reduction of the piping cost by reducing the number of elbows, welding points and adoption of small diameter of piping. Furthermore, it is possible to reduce the tunnel diameter, when the piping is installed in a tunnel. However, conventionally, it has been known that there is a difficulty in adopting the material from the viewpoint of weldability, which is reheat cracking at the weld metal in multi-layer welding. So, we have developed an excellent welding technology for 36% Ni steel with a new welding consumable. In order to adopt 36% Ni steel to the cryogenic piping in LNG plant, comprehensive experiments to find out the properties such as mechanical properties, corrosion resistance, weldability, nondestructive inspection and thermal stress analysis were conducted. By using the results the appropriate welding procedures were established and 36% Ni steel was used for the Ohgishima LNG receiving terminal of Tokyo Gas Company.
A Study on the Stress Interaction Between Annular Plate and Foundation of the Oil Storage Tank
Authors: Kawama Itsuo
Published: August 2008

The annular area of the cylindrical oil storage tank is the part which is received the structural damage from the earthquake force. The design method of the foundation in this area is only to check the bearing pressure from the tank structure to the foundation. However, the deformation of annular plate and foundation are important value at the large earthquake. The safety of this area must be decided by the interaction of foundation and tank structure. This study examined the effect of foundation structure and material on the annular area of the tank by the finite element method. The result from this examination is showing that the crushed stone under the annular area of the tank is important to resist the earthquake force from tank structure.
Development of Diagnostics Evaluation Method for Shell-to-Annular Joint of the Oil Tank Under Ultra Low Cycle Fatigue
Authors: Igi Satoshi , Kawahara Masanori , Kawano Kazuma , Sekine Kazuyoshi , Kaita Shinichi
Published: August 2008

Since the past decade, diagnostics evaluation method for the oil tank under ultra low cycle fatigue was continuously discussed through several committees in Japan High Pressure Institute (JHPI). It has been supposed that the shell-to-annular joints of the oil tank would suffer from large cyclic plastic strains of several percentages by the effect of bending moments caused by large earthquake. Few studies have been reported about fatigue crack growth estimation for such large plastic strain region. In order to assess the structural integrity of the oil tank, extensive efforts are required to establish the estimation technique of the fracture behaviors and the criterion of maintenance under cyclic plastic strains to prevent or minimize fatal accidents. The JHPI committee aims to establish the Fitness-for-Service procedure for national large oil tank. This paper reports the summary of the activity of the committees toward the establishment of the method to estimate crack growth life under repeated large plastic loading. Crack growth behaviors under large cyclic plastic strains were examined experimentally under both axial loadings and bending loadings of a plate with a surface flaw. A series of three-dimensional FEM analyses was also carried out to obtain J-integral value for shell-to-annular joint with various crack sizes. A diagnostics evaluation method for shell-to-annular joint of the oil tank under supposed large earthquakes were developed by using these results with taking into account of the accompanied various extra phenomena such as new micro-cracks initiation, irregular crack growth due to crack coalescence, crack initiation and growth at the back surface of the specimen, etc.
Liquid Sloshing of Oil Storage Tanks and Long-Period Strong Ground Motions in the 2003 Tokachi-Oki Earthquake
Authors: Zama Shinsaku
Published: August 2008

The 2003 Tokachi-oki earthquake caused the severe damage to oil storage tanks by liquid sloshing. Especially at Tomakomai, two tank fires broke out and six floating roofs sank. Seismograms showed that long-period motions were predominant and duration became longer when the seismic waves propagated into the Yufutsu Plain, where Tomakomai is located. Sloshing wave heights (Wh) of all tanks were calculated by two-dimensional response analysis. It was found that estimated Wh exceeded 3 m at periods 5 and 7.5 sec, and exceeded 2m from 3.5 to 9 sec of sloshing period and that severe damaged tanks had the highest Wh at each period in general.
1D and 3D CFD Simulation of Exhaust-Gas Aftertreatment Devices: Parameter Optimization via Genetic Algorithm
Authors: Wanker R. , Wurzenberger J. C. , Higbie D.
Published: August 2008

Future limits on emissions for both gasoline and Diesel engines require adequate and advanced systems for the aftertreatment of the exhaust gas. Computer models as a complementary tool to experimental investigations are indispensable to design reliable after-treatment devices such as catalytic converters and Diesel particulate filters. Therefore, the objective of this contribution is to present an integrated 1D to 3D simulation workflow of catalytic converters (Three-Way-Catalyst, Diesel Oxidation Catalyst, Selective Catalytic Reduction Catalyst, ...) and Diesel particulate filters. The parameters or sets of parameters are obtained by a fast and efficient 1D-approach of BOOST. They are readily transferable to the 3D simulation code FIRE to investigate detailed aspects such as spatial distribution of temperatures or heat losses. Thus, identical models predicting flow, energy and conversion of species of the exhaust gas were employed to both the 1D gas exchange/cycle and the 3D CFD simulation code. This approach allows to carry out a basic analysis and to define first layouts for the exhaust system. Characteristic parameters of this first design stage are used for the multi-dimensional simulation to evaluate the overall performance including fine tuning of aftertreatment systems.
Optimum Size Determination for Air Cooled Heat Exchanger (ACHE) via Genetic Algorithm
Authors: O¨zkol Ibrahim , Celik Serhat
Published: August 2008

Sizing an air-cooled heat exchanger requires tedious, time-consuming calculations to balance air and liquid heat-transfer properties according to the temperature requirements. There are some constraints to make the design better. The airside pressure drop (ΔPa) and the number of heat transfer units (NTU) are two of them. The minimum ΔPa requires the minimum fan power. As a result of this the operational cost can be minimized. In some environmental conditions the noise can be minimized too. NTU includes the size of the heat exchanger and fluid heat transfer capacities. It is very important for producer to drop the cost of production and logistic. Imagining the transport of hundreds goods make us understand the importance of this parameter easily. There are a lot of work in literature to make the design of air-cooled heat exchanger easy. But most of them have irreversible calculations and all the calculations should be carried out many times till getting the acceptable results. These trial and error calculation require much time. To overcome such difficulties, today, in many engineering problems there is a mass application of heuristic algorithms. The most common of these is genetic algorithms. The design of an optimum heat exchanger is a formidable challenge for designers. First, such a design involves a large number of parameters to be optimized. It is almost impossible to find an optimum design by the traditional “trial and error” method. Second, design is usually a multi objective and multi-point problem that simultaneously has to content with a variety of design criteria. In this study, we obtained accurate and robust answers in a few minutes by developping a computer code using genetic algorithm. It is also possible to find the optimum size of any heat exchanger by making required changes in the code according to the type of heat exchangers.
Computational Modeling of Laser Induced Heating
Authors: Reich Alton J. , Tham Choon , Smith Stan
Published: August 2008

Lasers are increasingly being used as a heat source in industrial applications due to their ability to deliver energy at a distance. In order to properly design systems that involve laser heating, accurate information about heat up rates is required. In complex systems, the rate of heating is a function of the laser parameters; such as spot size, beam intensity and beam profile; surface treatments and their characteristic coupling coefficient; and fluid convection adjacent to the surface being heated. This paper will describe recent efforts to simulate the heating of an enclosed container using a laser. The model complexity required to achieve good results, relative to test data, will be discussed.
Numerical Analysis of Natural Convection and Phase Change Problem With Finite Volume Method
Authors: Jeong Gi Ho , Jeong Soo In , Kim Kui Soon , Ha Man Young
Published: August 2008

A numerical analysis is performed in this study to observe the phase change and natural convection problem occurring in the confined geometry. The unsteady, incompressible 3-D Navier-Stokes equation and energy equation have been considered as governing equation in this study. In addition, numerical tools based on finite volume method were developed and those were found to be tools to analyze phase change and natural convection problem with qualitative accuracy. For verification, phase interfacial lines and flow patterns were compared to previous studies and showed good agreements for the case of square cavity and extended cubic. For application, phase change and natural convection problem inside circular pipe were considered. With and without axial flow cases were compared with each other to observe the effect of axial flow on the flow pattern and phase change characteristics. It was found that the forced convective flow tends to disturb the formation of ice-plug and natural convective flow tends to promote the energy exchanges and expedite the formation of ice-plug.
reCAPTCHA: Human-Based Character Recognition via Web Security Measures
Authors: von Ahn Luis , Maurer Benjamin , McMillen Colin , Abraham David , Blum Manuel
Published: August 2008

CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) are widespread security measures on the World Wide Web that prevent automated programs from abusing online services. They do so by asking humans to perform a task that computers cannot yet perform, such as deciphering distorted characters. Our research explored whether such human effort can be channeled into a useful purpose: helping to digitize old printed material by asking users to decipher scanned words from books that computerized optical character recognition failed to recognize. We showed that this method can transcribe text with a word accuracy exceeding 99%, matching the guarantee of professional human transcribers. Our apparatus is deployed in more than 40,000 Web sites and has transcribed over 440 million words.
Transient Electronic Structure and Melting of a Charge Density Wave in TbTe
3
Authors: Schmitt F. , Kirchmann P. S. , Bovensiepen U. , Moore R. G. , Rettig L. , Krenz M. , Chu J.-H. , Ru N. , Perfetti L. , Lu D. H. , Wolf M. , Fisher I. R. , Shen Z.-X.
Published: August 2008

Obtaining insight into microscopic cooperative effects is a fascinating topic in condensed matter research because, through self-coordination and collectivity, they can lead to instabilities with macroscopic impacts like phase transitions. We used femtosecond time- and angle-resolved photoelectron spectroscopy (trARPES) to optically pump and probe TbTe
3
, an excellent model system with which to study these effects. We drove a transient charge density wave melting, excited collective vibrations in TbTe
3
, and observed them through their time-, frequency-, and momentum-dependent influence on the electronic structure. We were able to identify the role of the observed collective vibration in the transition and to document the transition in real time. The information that we demonstrate as being accessible with trARPES will greatly enhance the understanding of all materials exhibiting collective phenomena.