bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculations to Benchmark Probabilistic Fracture Mechanics Computer Codes
Authors: Simonen F. A. , Gosselin S. R. , Wilkowski G. M. , Rudland D. L. , Xu H.
Published: August 2009

This paper describes calculations to estimate component failure frequencies for components using the PRO-LOCA and PRAISE probabilistic fracture mechanics (PFM) computer codes. Other PFM codes are also described along with prior benchmarking efforts. The calculations of this paper focus on the failure mechanism of primary water stress corrosion cracking for operating conditions that were known to have failed field components. The objective was to benchmark the newly developed PRO-LOCA code against the older PRAISE code that had a much longer history of prior applications. It was established that advanced modeling capabilities in the PRO-LOCA code simulated parameters that were treated deterministically by the PRAISE code. Excellent agreement of numerical results from the two codes was established once the PRO-LOCA code was applied using selective deterministic treatments.
Risk-Based Inspection Applied to Main Steam and Hot Reheat Piping Systems
Authors: Cohn Marvin J.
Published: August 2009

Many utilities select critical welds in their main steam (MS) and hot reheat (HRH) piping systems by considering some combination of design-based stresses, terminal point locations, and fitting weldments. The conventional methodology results in frequent inspections of many low risk areas and the neglect of some high risk areas. This paper discusses the use of a risk-based inspection (RBI) strategy to select the most critical inspection locations, determine appropriate reexamination intervals, and recommend the most important corrective actions for the piping systems. The high energy piping life consumption (HEPLC) strategy applies cost effective RBI principles to enhance inspection programs for MS and HRH piping systems. Using a top-down methodology, this strategy is customized to each piping system, considering applicable effects, such as expected damage mechanisms, previous inspection history, operating history, measured weldment wall thicknesses, observed support anomalies, and actual piping thermal displacements. This information can be used to provide more realistic estimates of actual time-dependent multiaxial stresses. Finally, the life consumption estimates are based on realistic weldment performance factors. Risk is defined as the product of probability and consequence. The HEPLC strategy considers a more quantitative probability assessment methodology as compared to most RBI approaches. Piping stress and life consumption evaluations, considering existing field conditions and inspection results, are enhanced to reduce the uncertainty in the quantitative probability of failure value for each particular location and to determine a more accurate estimate for future inspection intervals. Based on the results of many HEPLC projects, the author has determined that most of the risk (regarding failure of the pressure boundary) in MS and HRH piping systems is associated with a few high priority areas that should be examined at appropriate intervals. The author has performed many studies using RBI principles for MS and HRH piping systems over the past 15 years. This life management strategy for MS and HRH critical welds is a rational approach to determine critical weldment locations for examinations and to determine appropriate reexamination intervals as a risk-based evaluation technique. Both consequence of failure (COF) and likelihood of failure (LOF) are considered in this methodology. This paper also provides a few examples of the application of this methodology to MS and HRH piping systems.
Evaluation for Environmental Fatigue of Notched Specimen of Ni-Base Alloy
Authors: Itatani Masao , Sakaguchi Katsumi , Saito Toshiyuki , Hayashi Takahiro
Published: August 2009

Fatigue tests were conducted on the notched specimens of Ni-base-alloy NCF600 in high temperature water. Notch root strain was analyzed by finite element method (FEM) to calculate the notch root strain rate and the environmental fatigue correction factor Fen. Relationship between notch root fictitious stress amplitude and corrected fatigue life in water FenNwater are compared with the fatigue data of smooth specimen in air (i.e. best-fit curve) and it was found that the corrected fatigue life data in water shows a little shorter but almost agree with best-fit curve in air for the specimen with Kt = 1.4A. For the specimen with Kt = 3, corrected fatigue life in water is longer than that in air and the difference between both lives becomes larger with decreasing stress amplitude. The longer fatigue life in sharp notched specimen than that in dull notched specimen at the same notch root stain amplitude is thought to be dominated by the difference in the crack propagation life since the stress distributions on the cross section are decisively different. It is concluded that the fatigue life of notched specimen in high temperature water is adequately predicted using the modified rate approach method when the notch root strain is appropriately estimated e.g. by FEM analysis even though it gives excessively conservative prediction for sharp notch at low stress amplitude. The aspect of environmental fatigue of notched specimens are summarized on carbon steel and stainless steels with Ni-base alloy studied in Japan Nuclear Energy Safety Organization (JNES) Environmental Fatigue Test (EFT) project.
Development of Test Equipment for Measuring Compression Characteristics of Sheet Gaskets at Elevated Temperature
Authors: Fukuoka Toshimichi , Nomura Masataka , Hata Yoshihiko , Nishikawa Takashi
Published: August 2009

Evaluation of the sealing performance of pipe flange connection is significantly important for the safety of pipe line structures. The compression characteristics of sheet gaskets primarily affect the mechanical behavior of flanged connections. It is known that the stiffness of sheet gaskets decreases with an increase in temperature. Therefore, the compression test must be conducted at various levels of elevated temperatures. From the experimental point of view, however, a great difficulty is involved in measuring the compression characteristics of gaskets at elevated temperature. For this reason, a definite testing procedure has not yet been established. In this paper, a prototype of compression test equipment has been developed for measuring the stress-strain curves of sheet gaskets at elevated temperature. The test equipment is compact and the experiments can be conducted with a fairly easy operation. It can control the gasket stress from zero to 30MPa while keeping the temperature of test specimen at different levels from room temperature to 300° C and higher. Aramid sheet gaskets are selected as test specimens. Experimental results show that the gasket stiffness drops with an increase in temperature. The shapes of the compression curves at different temperatures are similar, and those curves move in the direction of lower stiffness as the temperature is increased. It is concluded that the test equipment proposed here has a high promise to measure the stress-strain curves of sheet gaskets and estimate the sealing performance of pipe flange connections at elevated temperature.
The Effect of Friction on Load Distribution Around the Hole in Composite Pinned Connections
Authors: Yavari Vahid , Rajabi Iraj , Kadivar Mohammad Hassan
Published: August 2009

This paper presents analyses for computing and evaluating the behavior of the laminated composite plate at the contact area in single lap, mechanically fastened joints. The analyses involve three dimensional finite element models performed by ABAQUS 6.4-PR11 code to evaluate the stress distribution in contact surface, separation angle, the magnitude and location of maximum radial stress. Results are determined for quasi-isotropic model and attempts are made to validate the models with previous works. The variations of separation angles through the thickness are investigated and effects of friction and applied load level are discussed by using different friction coefficients at contact area. Non-symmetric separation about the bearing plane occurs and the separation angle is greater than 90° in some plies.
Determination and Qualification of Alternative Flange Assembly Procedures
Authors: Waterland Alfred F. , Frew James E. B. , Wyler Chris , Smith Stephanie
Published: August 2009

Alternative (non-traditional) flange assembly procedures offer the potential for reduced assembly time and physical effort in many industrial applications. While standards and procedures exist for the traditional, star pattern assembly procedure, there is currently only limited guidance for the selection and use of alternative assembly procedures. This paper summarizes the approach taken by the authors in determining potential assembly procedures, and the ultimate analysis and qualification undertaken to validate their use on a General Purpose Tank Car Hinged/Bolted Manway Connection. This case history study can serve as a guide to others in industry for selecting and qualifying alternative assembly procedures for their flanged equipment.
Research on Stress Corrosion Cracking of a Reboiler Cylinder in Desulfuration System
Authors: Lu Zhi-Ming , Sheng Song-En , Gao Zeng-Liang
Published: August 2009

The stress corrosion cracking causes of the reboiler served in desulfuration system of a refinery were analyzed. According to visual inspection, chemical composition and metallographic examination, microstructure and ingredients of the fracture analysis by scanning electron microscopy (SEM), it was found that there was no obvious plastic deformation near the fracture, the chemical composition of the base material and welds were within the range specified in standards, the metallographic examination showed normal microstructure of this type of steel, intergranular brittle fracture and secondary cracks were found on the microstructure fracture. It could be concluded that the crack of the reboiler cylinder was stress corrosion cracking accelerated by the aggressive environment rich of H2S and high welding residual stress. Based on the causes analysis results, the corresponding countermeasures and improvements were suggested.
Interactions Between Blast Loading and Dynamic Elastic Response of Containment Vessels
Authors: Dong Q. , Li Q. M. , Zheng J. Y.
Published: August 2009

The interactions between internal blast loading and dynamic elastic response of a containment vessel are studied in this paper. The blast loading history is proposed to be divided into three periods, i.e. the primary-shock period, the shock-reflection period and the pressure-oscillation period. It is shown that the initial response of the containment vessel is determined by the peak overpressure and duration of the primary-shock. However, during the shock-reflection period, the response of the containment vessel may be influenced by the shock reflection in the vessel, especially when the dominant frequency of the shock reflection is close to the dominant response frequency of the vessel, and the reflected shock pressure is coupled with the vessel response. During the pressure-oscillation period, the dynamic loading is mainly the oscillation of the internal pressure due to the oscillatory volume change of the vessel, which couples dissipatedly with the vibration of the vessel leading to reduced vibration amplitudes. These fundamental features in the elastic response of containment vessels are demonstrated through an elastic circular ring (or an infinite-length cylindrical shell), which are applicable to other containment vessels.
Sealing Performance Evaluation of Pipe Flange Connection Under Elevated Temperatures
Authors: Sawa Toshiyuki , Takagi Yoshio , Torii Hiroyasu
Published: August 2009

Since a lot of pipe flange connections are exposed to elevated temperature during operation, it is important to evaluate the sealing performance of the connections under operational temperature. In this study, the sealing performance of pipe flange connection was experimentally evaluated by measuring the amount of gas leakage at room temperature (RT), 100 °C and 200 °C in addition to internal pressure. Non-asbestos graphite gaskets were used in the experiment. The nominal size of the pipe flange used during the experimental study was 3 inch. The eight bolts and nuts were tightened according to ASME PCC-1 and the Japanese method (HPIS). During assembly, the axial bolt force was individually measured with strain gauges attached to each bolt. The scatter in the axial bolt force during the assembling process was examined and compared between the ASME and the HPIS. In addition, the gasket contact stress distribution of each assembly process was calculated by finite element method under elevated temperature and internal pressure. In the FE study, experimentally measured physical properties such as elastic modulus and thermal expansion were used. ηhe amount of leakage was estimated from the contact gasket stress distribution obtained by FE analysis. The estimated axial bolt forces were compared with those of experimental ones.
The Sealing Performance of a Large Diameter Bolted Joint Under Elevated Temperature
Authors: Sawa Toshiyuki , Kawasaki Naoki , Takagi Yoshio , Torii Hiroyasu
Published: August 2009

Flange rotation with internal pressure affects the sealing performance of pipe flange connections more with increasing the pipe nominal diameter. Therefore, it is hard to estimate the sealing performance of pipe flange connections with larger nominal diameter by using the test results of the sealing performance for pipe flange connections with small nominal diameter. In this study, the 20" diameter pipe flange connection was experimentally used as a large nominal diameter pipe flange connection and analyzed the stress in the connection. In the experiments, the sealing performance of the pipe flange connection was evaluated by measuring the amount of gas leakage at 50 °C and 100 °C under internal pressure. Non-asbestos graphite gaskets were used in the experiments. The bolts and nuts were tightened according to the Japanese method (HPIS Z103 TR). The gasket contact stress distributions of larger nominal diameter pipe flange connection were calculated by FEM under elevated temperature conditions as well as internal pressure application. The estimated results were compared with the experimental results. The results were also compared with the small nominal diameter test result and discussed.
Measurements and Evaluation of Sealing Behavior of Gaskets Based on the Test Method HPIS Z104 Proposed in Japan
Authors: Kobayashi Takashi
Published: August 2009

This paper discusses the gasket testing procedure HPIS Z104 established in Japan to obtain fundamental sealing behavior of gasket. The testing procedure consists of 11 combinations of gasket stresses and a constant internal pressure. It takes about 3 hours to complete one test, which is acceptable for gasket manufacturers. In order to demonstrate the validity of the testing procedure, measurements of leak rates of several types of sheet gaskets are carried out. Experimental formulas are proposed to approximate the sealing behaviors of gaskets. It is shown that the sealing behavior of gaskets can be well characterized using the proposed testing procedure and the experimental formulas.
A Computer Simulation Model for the Blow-Blow Forming Process of Glass Containers
Authors: Giannopapa C. G. , Groot J. A. W. M.
Published: August 2009

In glass container manufacturing (e.g. production of glass bottles and jars) an important process step is the blowing of the final product. This process is fast and is characterized by large deformations and the interaction of a hot glass fluid that gets into contact with a colder metal, the mould. The objective of this paper is to extend and further develop our finite element model [1] to be used for industrial purposes. To achieve this both steps of the forming of glass containers, namely blow-blow needs to be simulated and tested against real industrial problems. The model should be able to correctly represent the flow of glass, the energy exchange during the process and provide the final thickness of the final product. For tracking the geometry of the deforming inner and outer interface of glass, the level set technique is applied on a fixed mesh. At each time step the coupled problem of flow and energy exchange is solved by the model. Here the flow problem is only solved for the domain enclosed by the mould, whereas in the energy calculations, the mould domain is also taken into account. A non uniform temperature distribution is considered for the blowing of the preform. For all the calculations the material parameters (like viscosity) are based on the glass position, i.e. the position of the level sets. The velocity distribution, as found from this solution procedure, is then used to update the two level sets by means of solving a convection equation. A fast marching re-initialization algorithm is applied after each time step in order to let the level sets re-attain the property of being a signed distance function. The model is validated by several examples focusing on both the overall behavior (such as conservation of mass and energy) and the local behavior of the flow (such as glass-mould contact) and temperature distributions.
Plastic Collapse Load for Vessel With External Flaw Simultaneously Subjected to Internal Pressure and External Bending Moment: Experimental and FEA Results
Authors: Konosu Shinji , Kano Masato , Mukaimachi Norihiko , Komura Hiroyuki , Takada Hiroyuki
Published: August 2009

The newly-developed p-M diagram provides a means for readily evaluating the collapse load of pressure equipment with external flaws simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. In this paper, numerous experiments and FEAs for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are much the same as those calculated under the proposed p-M line based on the measured yield stress. The p-M line adopted in the Ibaraki FFS rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0–3.0, about 1.5–4.0 for the TES loads at LTA and 2.5–6.5 for the plastic instability (break) loads.
Refinery Valves: Assessment of Vulnerability and Potential Impact on Process Safety and Mechanical Integrity
Authors: Cheta Ayman
Published: August 2009

Valves play a key role as safeguards for process safety and mechanical integrity of petroleum refineries and chemical plants. Recent changes in the valve manufacturing industry have resulted in considerable variation in quality, which led to several serious industry incidents. This paper provides an assessment of vulnerability and potential impact on process safety and mechanical integrity.
SPECTRA Thermal Fatigue Tests Under Frequency Controlled Fluid Temperature Variation: Strength Tests
Authors: Kawasaki Nobuchika , Hasebe Shinichi , Kobayashi Sumio , Kasahara Naoto
Published: August 2009

Thermal fatigue strength tests subjected to sinusoidal fluid temperature waves were performed by the SPECTRA test facility, where frequencies were 0.05, 0.2, and 0.5Hz. Cracks were observed on the inner surface of cylindrical test pieces after testing. 0.05Hz’s wave caused a greater number of and deeper cracks than 0.5Hz’s wave under the same fluid temperature range and the same fatigue cycles. The crack initiation region of the 0.05Hz’s wave was larger than for the 0.5Hz’s wave. Estimated fatigue failure cycles based on the frequency transfer functions were compared with test results. Frequency-dependency in failure cycles was observed through these test results, and frequency transfer functions could estimate this dependency. The test results supported the fatigue damage evaluation method with frequency transfer functions.
A Multiphase Mixture Flow Model and Numerical Simulation for the Release of LPG Underground Storage Tank in Porous Environment
Authors: Zhang Ruihua , Chen Guohua , Huang Si
Published: August 2009

A physical process and mechanism of liquefied petroleum gas (LPG) flow dispersion in porous media for the releases at vapor and liquid region of Underground Storage Tank (UST) was analyzed. On the basis of the mixture model principle, a mathematical model was developed to simulate LPG flow dispersion in porous media. The gravity, capillary force, viscous force, interior resistance of porous media and gas-liquid interaction were incorporated into this model. And the non-Darcy coefficient of multiphase flow which is variable with Reynolds number was taken into account in the model, which was according with actual flow state. For LPG is insoluble in water, the formulation of LPG volumetric concentration was deduced, which simplifies computation process. The model was carried out to simulate a propane gas migration process in sand pond for UST release. From the simulation results, a detailed analysis was performed to investigate the effect of various influencing factors on infiltration flow: the direction of gas infiltration diffusion is influenced distinctly by gravity, release direction and the position of outlet in tank pond; the flow about release site and outlet is more active where the non-Darcy effect is obvious; the pressure drive is crucial for LPG infiltration; the gravity is a main factor to water infiltration; the saturation and viscous force of water can restrain the infiltration speed of propane. The model can lead to a good understanding of flow development and field effects of LPG in unsaturated porous media and can offer boundary conditions for modeling the subsequent fire explosion accidents.
Indicative Results and Progress on the Development of the Unified Single Solution Method for Fluid-Structure Interaction Problems
Authors: Giannopapa C. G.
Published: August 2009

This paper presents the progress on the development of a novel unified solution method for solving strongly coupled fluid-structure interaction problems. The method has been developed and fully tested for solids in [1]. The new approach is based on continuum mechanics formulation for fluids and structures where both continua can be solved using the momentum and continuity equation. The difference between the two continua lies in the constitutive equations. In this framework a single set of equations is used for the simultaneous solution of both fluid and solid. The common equations are written such that velocity and pressure are unknown variables for both continua. The discretisation method used for the solution of the problems is finite volumes. The physical interface between the two continua is treated as an internal part of the computational domain and no explicit exchange of information is needed. The test case used to demonstrate the idea is wave propagation in liquid filled flexible vessels. The solution is fully implicit and transient. Results regarding pressure, velocity and wall distention at different times and various locations along the tube are presented. The method is stable and robust and can be used for the next step of development and validation against classical analytical and numerical models.
Effects of Water Flow Rate on Fatigue Life of Structural Steels Under Simulated BWR Environment
Authors: Hirano Akihiko , Sakaguchi Katsumi , Shoji Tetsuo
Published: August 2009

Fatigue tests in simulated LWR environment of carbon and stainless steels were performed under high water flow rates between 7 to 10 m/s. For carbon steel, high flow rate of water clearly mitigated the environmental effect on the fatigue life at the high sulfur concentration of 0.016% which caused high environmental effect on a fatigue life. On the contrary, high flow rate of water slightly enhanced the environmental effect at the low sulfur concentration at or less than 0.008% which caused very low environmental effect. These results suggested that the environmental fatigue life under various flow rate conditions should be determined by the combination between the mitigating effect caused by flushing of the severe local environment and the enhancing effect caused by increase in corrosion potential. Low alloy steel showed the similar behavior as carbon steel. For stainless steel, flow rate had little effect on the fatigue life of type 316NG stainless steel. It suggested that there was no role of water flushing. For type 304 and 304L stainless steel, fatigue life has a tendency to decrease with increase in water flow rate. Fatigue lives of type 304 stainless steel under high flow rate of 7 to 10 m/s were shorter than those predicted by proposed fatigue life prediction equation by the Japanese EFT committee. This effect should be considered in an evaluation of environmental fatigue. No water flow effect was found in cast stainless steel.
Technical Issues on Seismic Design of Nuclear Piping Systems
Authors: Slagis Gerry C.
Published: August 2009

The design of nuclear piping systems has evolved significantly since the first Section III plants were constructed in the early 70s. Effective design to accommodate seismic loads is the dominant problem in the industry. The Section III code committee has been working since the late 80s to develop new seismic stress limits. Code revisions were incorporated in 1994, but to date, have not been accepted by NRC. Hence, appropriate piping seismic stress limits is one very significant technical issue. A second significant issue is revisions to seismic design requirements in 10CFR50 that NRC has made. It is now acceptable to design only for SSE loads, if the plant is shut down for inspection for a seismic event of equal to or greater than 1/3 the SSE. A third issue is whether the amplified response levels required for modern designs are reasonable and appropriate. The purpose of this paper is to explore these three issues. Recommendations are provided.
Technical Basis for Cases N-629 and N-631 as an Alternative for RTNDT Reference Temperature
Authors: Merkle J. G. , Yoon K. K. , VanDerSluys W. A. , Server W.
Published: August 2009

ASME Code Cases N-629/N-631, published in 1999, provided an important new approach to allow material specific, measured fracture toughness curves for ferritic steels in the code applications. This has enabled some of the nuclear power plants whose reactor pressure vessel materials reached a certain threshold level based on overly conservative rules to use an alternative RTNDT to justify continued operation of their plants. These code cases have been approved by the US Nuclear Regulatory Commission and these have been proposed to be codified in Appendix A and Appendix G of the ASME Boiler and Pressure Vessel Code. This paper summarizes the basis of this approach for the record.
Cracking of Alloy C-276 in an Acidic Environment
Authors: Pal Joydeep , Mukhopadhyay Chandan , Roy Ajit K.
Published: August 2009

Austenitic Alloy C-276 has been identified as a structural material for application in hydrogen generation using nuclear heat. Fracture-mechanics-based pre-cracked and wedge-loaded double-cantilever-beam (DCB) specimens have been tested in an acidic solution at ambient temperature for 15 and 30 days. Three levels of initial stress intensity factors (K1) were used to determine crack propagation following exposure of the DCB specimens to the test environment. The results indicate that the magnitude of K1 was substantially reduced after testing, the extent of reduction being more pronounced with specimens tested for a longer duration. Three different types of failures namely, striations, cleavage and ductile, respectively were noted in the tested specimens, as determined by scanning electron microscopy.
A Suggestion of Improvement Plan for ASME Sec. III Requirements Through the Construction Experience of Korea Standard Nuclear Power Plants: Hydrostatic Test Pressure and PWHT Temperature of P-No.4 Materials
Authors: Lee Sanghoon , Son Youngho , Lee Jaehoon , Kim Woosung , Yoon Seogchan
Published: August 2009

The minimum hydrostatic test pressure for class 2 and 3 components has been reduced from 1.5 to 1.25 times the Design Pressure in ASME B&PV Sec. III, Division 1 since 1999 addenda. If these requirements are applied to the system hydrostatic test as they are, the minimum hydrostatic test pressure of components and system becomes identical. Therefore it may happen that the test pressure imposed on components installed at low locations in the system exceeds the maximum permissible pressure due to the static head during the system hydrostatic test. PWHT temperature requirements for P-No.4 materials in various Construction Codes, such as ASME B31.1, Sec. I and Sec. VIII, except Sec. III have been unified and the minimum PWHT temperature became 649°C (120°F) since 2004 edition. When considering the mechanical properties of the weld, the minimum PWHT temperature of 593°C or that of P No. 4 materials in Sec. III is too low to reduce hardness and to increase toughness. When PWHT is performed on dissimilar material joints (e.g., between P-No.1 or P-No. 3 and P-No. 4) at 649°C (1200°F) in accordance with Sec. VIII etc., it is possible that the strength of the lower P-No. materials is decreased below the design strength because the PWHT temperature will exceed the tempering temperature of the lower P-No. materials. In this study, the cases of system hydrostatic test in UC-3, 4 units and Steam Generator Nozzle to feedwater pipe joint in Korea Standard Nuclear Power Plants (e.g., UC-3, 4 units, YK-3, 4 units and YK-5, 6 units) were reviewed and analyzed. And then problems of two cases were presented. It is suggested that the minimum system hydrostatic test pressure in Sec. III NC, ND should be decreased by the reduction rate of test pressure for components and the minimum PWHT temperature for P No. 4 materials in Sec. III should be 630°C (1166°F).
Development of Simplified Plastic Collapse Assessment Procedure for Vessel With Internal Surface Flaw
Authors: Konosu Shinji , Oyamada Kenji
Published: August 2009

A simplified assessment procedure using the p-M diagram, which can evaluate the plastic collapse load for pressure equipment such as vessels, piping and storage tanks with an internal surface flaw simultaneously subjected to internal pressure, p, and external bending moment, M, due to earthquake, etc., is derived by taking into account the influence of internal pressure acting on the flaw surface. For an internal surface flaw subjected to pressure, the already-proposed p-M diagram for an external flaw can be applied if the parameters for an internal surface flaw proposed in this paper are used. And the plastic collapse loads derived from the p-M diagram method are being verified by comparison with experimental results. It has been clarified that the parameters for internal surface flaws are also the same as those for external surface flaws where the ratio of thickness to outer radius of a vessel is significantly smaller than unity and internal pressure is small.
Ratcheting of Stainless Steel 304 Under Multiaxial Nonproportional Loading
Authors: Kim Kwang S. , Jiao Rong , Chen Xu , Sakane Masao
Published: August 2009

Ratcheting tests are conducted on stainless steel 304 under uniaxial, torsional, and combined axial-torsional loading. The ratcheting strain is predicted based on the constitutive theory that incorporates a modified Ohno-Wang kinematic hardening rule and Tanaka’s isotropic hardening model. The results show that the main features of the stress-strain response can be simulated with the constitutive model. The experimental and predicted ratcheting strains for nonproportional paths are found in decent correlation. Ratcheting strain depends highly on the loading path and load level, and less on cyclic hardening or softening of the material. The torsional ratcheting strain under mean shear stress with (or without) fully reversed axial strain cycling is found close to the axial ratcheting strain under equivalent mean stress with (or without) torsional strain cycling.
Evaluation of Failure Pressure of Locally Wall-Thinned Elbow by Real-Scale Pipe Tests
Authors: Kim Jin-Weon , Na Yeon-Soo , Lee Sung-Ho , Park Chi-Yong
Published: August 2009

This study performed a series of burst tests using real-scale pipe elbows containing simulated wall-thinning defect, to evaluate the effects of local wall-thinning on the failure pressure of pipe elbows. The tests were conducted under simple internal pressure at room temperature. In the tests, various wall-thinning geometries, such as thinning depth, length, and circumferential angle, and thinning locations, extrados and intrados, were considered. From the results of tests, the effects of thinning geometries and locations on the failure pressure of local wall-thinned elbows were investigated. The dependences of failure pressure on the thinning length and depth in the wall-thinned elbow were similar to those in the wall-thinned straight pipe. The failure pressure clearly decreased with increasing circumferential thinning angle, which was different from the results of wall-thinned straight pipe. Also, the failure pressures were compared with the results predicted by existing evaluation models. The existing models showed excessive conservatism. For intrados wall-thinning case, especially, the conservatism was significant and the variation in failure pressure with thinning geometries could not be properly predicted. For extrados wall-thinning case, the existing models appropriately estimated the dependence of failure pressure on the thinning length and depth. All specimens tested were failed by bulging followed by axial cracking. For extrados and intrados wall-thinned elbows, the crack always occurred at the minimum wall-thinned area. For entire circumferential wall-thinned elbow, however, the crack location depended on the axial thinning length.
Fluid Pressure on Rectangular Rigid Tanks Due to Uplift Motion
Authors: Taniguchi Tomoyo , Ando Yoshinori
Published: August 2009

This paper mathematically derives fluid pressure on a rectangular rigid tank with unit depth, which models a section of a center part of a flat-bottom cylindrical shell tank, accompanied with uplift motion. Employing boundary conditions consisting of fluid velocity imparted by motion of the side walls and bottom plate of the tank along with uplifting, the equation of continuity of fluid given by the Laplace equation is solved as the parabolic partial differential equation of Neumann problem. The fluid pressure is given by a function of the velocity potential. Comparison of mathematical results with numerical ones based on explicit FE analysis corroborates its accuracy and applicability on design procedure of flat-bottom cylindrical shell tanks.
Experimental Study of Evaluation Method of Vibrational Stress in Piping System Applying Multiple Laser Displacement Sensors
Authors: Shintani Masanori , Noda Michiyasu , Maekawa Akira , Sakashita Masakazu
Published: August 2009

In the pipe line installed in the nuclear power plant, there are many reports of damage caused by fatigue as a result of machine vibration of a pump etc. Vibrational stress evaluation by the method using the strain-gauge method or the accelerometer as one of the preventive measures of these oscillating troubles etc. is performed. However, since many special skill and working hours are required for these methods, the development of vibration measurement and stress evaluation technology which operates quickly and easily at the spot is desired. The purpose of this research is the development of a technique and equipment which measures vibrational stress immediately using a laser displacement sensor. In the measurement technique proposed, displacement by the bending vibration of piping which vibrates using three sets of laser displacement sensors is measured, and vibrational stress is obtained by calculating the strain produced from those displacement differences for piping. This measuring instrument is a non-contact system, and a miniaturization and short-time measurement of equipment are easy. This paper deals with the concept of the vibrational stress measurement technique, the theory of the measuring method, and the procedure, the authors propose, using three sets of the laser displacement sensors. Furthermore, using a cantilever model, vibration experiments are conducted, displacements and strain are measured. Next, comparison with the stress by using the displacement measured by the experiment based on this technique and the stress from the strain measured by the experiment is performed. The application possibility of the technique is described.
Computer Simulations to Address Pu-Fe Eutectic Issue in 3013 Storage Vessel
Authors: Gupta Narendra K. , Smith Allen C.
Published: August 2009

On November 22, 2005, the Manager of the Plutonium Finishing Plant (PFP) in Richland, WA issued an Occurrence Report involving a potential Pu-Fe eutectic failure mechanism for the stainless steel (SS) 3013 cans containing plutonium (Pu) metal. Four additional reports addressed nuclear safety concerns about the integrity of stainless steel containers holding plutonium during fire scenarios. The reports expressed a belief that the probability and consequences of container failure due to the formation of a plutonium-iron eutectic alloy had been overlooked. Simplified thermal models similar to the HAC thermal models used in the 9975 SARP were created and analyzed to address the Pu-Fe eutectic concerns. The model uses Rocky Flats configuration with 2 stacked Pu buttons inside a 3013 assembly. The assembly has an outer can, an inner can, and a convenience can, all stainless steel. The boundary conditions are similar to the regulatory 30 minutes HAC fire analyses. Computer simulations of the HAC fire transients lasting 4 hours of burn time show that the interface between the primary containment vessel and the Pu metal in the 9975 package will not reach Pu-Fe eutectic temperature of 400°C.
On Damping and Fluidelastic Instability in a Tube Bundle Subjected to Two-Phase Cross-Flow
Authors: Moran Joaquin E. , Weaver David S.
Published: August 2009

An experimental study was conducted to investigate damping and fluidelastic instability in tube arrays subjected to two-phase cross-flow. The purpose of this research was to improve our understanding of these phenomena and how they are affected by void fraction and flow regime. The working fluid used was Freon 11, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The damping measurements were obtained by “plucking” the monitored tube from outside the test section using electromagnets. An exponential function was fitted to the tube decay trace, producing consistent damping measurements and minimizing the effect of frequency shifting due to fluid added mass fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the Homogeneous Equilibrium Model (HEM) in terms of density and velocity predictions. It was found that the Capillary number, when combined with the two-phase damping ratio (interfacial damping), shows a well defined behaviour depending on the flow regime. This observation can be used to develop a better methodology to normalize damping results. The fluidelastic results agree with previously presented data when analyzed using the HEM and the half-power bandwidth method. The interfacial velocity is suggested for fluidelastic studies due to its capability for collapsing the fluidelastic data. The interfacial damping was introduced as a tool to include the effects of flow regime into the stability maps.
Effect of High Pressure Gaseous Hydrogen on the Tensile Properties of Four Types of Stainless Steels: Investigation of Materials Properties in High Pressure Gaseous Hydrogen—1
Authors: Nakagawa Hideki
Published: August 2009

Practical application of fuel cell vehicle has started in the world, and high-pressure hydrogen tanks are currently considered to be the mainstream hydrogen storage system for commercially implemented fuel cell vehicle. Application of metallic materials to the components of high-pressure hydrogen storage system: hydrogen tanks, valves, measuring instructions and so on, have been discussed. In this work, tensile properties of four types of stainless steels were evaluated in 45MPa (6527psig) and 75MPa (10878psig) high-pressure gaseous hydrogen at a slow strain rate of 3×10−6 s−1 at ambient temperature. Type 316L (UNS S31603) stainless steel hardly showed ductility loss in gaseous hydrogen, since it had stable austenitic structure. On the other hand, Type 304 (UNS S30400) metastable austenitic stainless steel showed remarkable ductility loss in gaseous hydrogen, which was caused by the hydrogen embrittlement of strain induced martensitic phase. Likewise, Type 205 (UNS S20500) nitrogen-strengthened austenitic stainless steel showed remarkable ductility loss in gaseous hydrogen, though it had stable austenitic structure in the same manner as Type 316L. The ductility loss of Type 205 was due to the hydrogen embrittlement of austenitic phase resulting from the formation of planar dislocation array. Furthermore, Type 329J4L (UNS S31260) duplex stainless steel showed extreme ductility loss in gaseous hydrogen, which was caused by the hydrogen embrittlement of ferritic phase.
Dynamic Buckling Test of Modified 1/10 Scale Model of Cylindrical Water Storage Tank
Authors: Maekawa Akira , Fujita Katsuhisa , Sasaki Toru
Published: August 2009

This study reports on the dynamic buckling experiment of a 1/10 reduced scale model of a large-scale cylindrical water storage tank by using a shaking table, and the buckling analysis by using both the simplified method and the finite element method. The dynamic buckling experiment is performed by using the reduced scale tank model whose initial imperfection has been measured. The tank model is filled with water up to 95% of the full level, and puts 200-weight on its top, overcoming the response reduction induced by the oval-type vibration. The sinusoidal waves are used as the input. As a result of the experiment, the bucking occurs on the tank and plastic deformation is observed on the side and bottom of the tank. Two methods of the buckling analysis are carried out. At first, the buckling load is estimated by using a simplified method adopted in the current Japanese guideline. The analytical result shows this method is conservative despite using the tank with initial imperfection. Secondly, the static buckling analysis with the finite element method is conducted. There is an issue how to treat the dynamic fluid pressure distribution of the contained water in the tank with regard to the static analysis, because the coupling between fluid and structure cannot be taken into consideration. In this study, the distribution of the dynamic fluid pressure is calculated in accordance with the Fischer’s method. The buckling load calculated by using the dynamic fluid pressure distribution agrees with that of the experiment approximately. Therefore, it is appropriate to apply this proposed static analytical method to seismic design.
Analysis of Causes for Cracking of Chinese Large High-Strength Steel Spheric Tank and Suggestion About Its Prevention
Authors: Chen Xuedong , Yuan Rong , Wang Bing , Yang Tiecheng , Li Pingjin , Cheng Chuanqing
Published: August 2009

In recent ten years, a number of cracking cases were reported on the in-service high-strength steel spheric tank made of 07MnCrMoVR and 07MnNiCrMoVDR steels (CF-62 steel for short) which were developed in China independently. Based on field survey, actual vessel inspection and failure analysis, it is pointed out that the quality of the steels, the problems existing in design and fabrication process and incompleteness of relevant standards are the major cause of cracking. Recommendations for cracking prevention of the high-strength steel spheric tank made of Chinese CF-62 steel are proposed.
Research and Development of Locally Installed Dampers Suitable for Industrial and Non-Industrial Structures by Using Displacement Amplification Mechanism
Authors: Watakabe Tomoyoshi , Fujita Satoshi
Published: August 2009

In Japan, many types of dampers are installed into various structures to reduce excessive responses during earthquakes. The demand for high performance, low cost dampers with wide range of applicability requires new developments in this area. This paper describes two new types of dampers using the displacement amplification mechanism. One of the dampers is designed to be installed in the connection of a column and a beam (“connecting-corner-damper”). The other is a damper of brace type, which enables to reduce the brace strength economically by adding the spring tension (“brace-damper”). Both dampers are designed to transmit displacements efficiently, and economically. This paper reports on the static loading test performed to investigate the fundamental characteristics of the viscoelastic material used as damping material in two dampers. Also, it describes the earthquake response analysis of an actual structure using dampers. The experimental results confirm that the viscoelastic material used in two dampers has displacement-, frequency- and temperature-dependent properties. The properties of the viscoelastic material are described by the non-linear-4-element model. Analytical results obtained by considering the characteristics of the viscoelastic material and the effect of the amplification mechanism principle confirm that each damper has good vibration control performance.
Study on Characteristics and Effects of Seismic Isolation System of Vertically Utilized Coiled Springs
Authors: Fukasawa Tsuyoshi , Kinoshita Akihiro , Fujita Satoshi
Published: August 2009

In recent years many structures employing seismic isolation systems have been constructed in Japan, the practical concern on the cost of seismic isolation systems has heightened. This paper describes the research and development of a new seismic isolation system using vertically utilized elastic and elasto-plastic coiled spring, and discusses analytical model for coiled spring. The basic concept of the earthquake isolation system that was constituted of bearing, restoration and damping elements is to realize cost effective design without any reduction in isolation performance. The restoration and damping elements of the isolation system were constituted by two types of coiled springs. The horizontal static tests were performed to evaluate the restoring characteristic and the mechanical model of elastic and elasto-plastic coiled spring. The restoration element of elastic coiled springs was made of using the two types of materials JIS SUP9 steel and JIS SUS 304 stainless steel. The elasto-plastic coiled springs of damping element also was made of using the two types of JIS SS 400 steel and JIS SWRM 17 steel. The characteristics of these coiled springs such as transverse stiffness and hysteretic damping and the validity of the analytical model were clarified through the static tests. Furthermore the response analyses based on the restoring force characteristics of experimental results were carried out to assess the isolation performance of this system.