bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Boundary Graphitization in P1 (C-1/2Mo) Alloy Pipe
Authors: McDonald Clark , Arnold John , Henry Jeff
Published: August 2013

Failure analysis performed on SA-335, Grade P1, Carbon-1/2Molybdenum (P1) steel pipe confirmed that failure in cold-formed bends was due to graphitization, but revealed that the graphite had developed in the affected material in a manner that has received little attention in the technical literature. In particular, the graphite developed in arrays of small micro-nodules preferentially concentrated within grain boundaries that were oriented normal to the hoop stress. The failure in question occurred after approximately 275,000 hours of operation at an average operating temperature of approximately 830F. Because of the preferential alignment of the graphitization, the material toughness in the tangential (hoop) direction was significantly degraded. While there is ample documentation of graphitization in P1 material after prolonged exposure to elevated temperatures, the observed morphology of volumetric grain boundary graphitization is very unusual. In response to this unique form of graphitization, cryo-cracking, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction were carried out to confirm that the small nodular “particles” within the grain boundaries were in fact graphite and not some other type of material contamination. Mechanical tests were also performed to assess the degree of material degradation, and the results have been compared to the damage levels observed in metallographic samples using a five-level damage ranking system developed for the purpose of surveying the multiple bends involved in the study. Many of the same factors that in previous studies have been identified as important influences on the formation of graphite in steel were observed in the samples examined as part of this failure analysis. These included the original steel making practice (i.e., high levels of aluminum), the original forming process (i.e., cold bending), and the service conditions (i.e., time and temperature).
New Seismic Isolation Systems for Floating Houses
Authors: Tsai C. S. , Su H. C. , Liao W. C. , Wang Yan-Ming
Published: August 2013

Inhabitable land has been decreasing due to the continual rise in sea levels caused by global warming. In response to this climate change, we need to consider looking for living spaces on water surfaces as well as building earthquake-resistant structures, particularly in flood and earthquake prone areas. This paper presents an experimental study on a new base isolation system in mitigating the response of a floating house that is located in a port. Experimental results show that the seismic response of the floating house was considerably reduced by the proposed isolation system with a proper displacement limit.
Determination of Actual Tensile and Fracture Characteristics of Critical Components of Industrial Plants Under Long Term Operation by SPT
Authors: Matocha Karel
Published: August 2013

The assessment of the residual lifetime of critical components of industrial plants requires the knowledge of mechanical properties prior to operation, respecting all technological operations realized throughout the manufacture of the component, and the knowledge of mechanical properties after actual time of operation (actual mechanical properties). Small Punch (SP) test technique enables measurement of the realistic material properties at the critical locations in the component both prior and after long-term operation. The paper shows the examples of the sampling of testing material from the critical components of the industrial plants and the procedures for determination of tensile and fracture characteristics by SP tests at ambient and low temperatures. The special attention is devoted to the test specimen orientation for determination of SP fracture energy ESP.
Creep Behaviour of P92 and P92 Welds at 675°C
Authors: Tanner David W. J. , Saber Mohammed , Sun Wei , Hyde Thomas H.
Published: August 2013

The results of an accelerated creep test programme on the leading new build high temperature power plant pipework ferritic steel P92 and two P92 welds are presented.

Tests were performed at 675°C, which is above the service operating temperature range recommended for P92, but allowed for more realistic operating stresses to be used. Comparison with similar tests of P92 at lower temperatures has shown that testing at 675°C produces the same general creep behavior, and can therefore be used for component life assessments in the service operating temperature range.

Axially loaded parent P92 material uniaxial round bar and notched bar specimens, given a heat treatment equivalent to that given post-welding, are compared with weld metal specimens and cross-weld specimens extracted from welds made using both a similar P92 consumable and a dissimilar IN625 nickel alloy consumable. Both welds exhibited typical premature ferritic steel weld failure at the heat-affected zone (HAZ) and parent material interface, known as Type IV.

The creep crack growth behavior of parent material, weld metal and the HAZ was studied using compact tension specimens. Impression testing was performed to determine the relative creep behavior of the HAZ. The HAZ was found to have the highest minimum creep strain rates and creep crack growth rates, indicating the relative weakness of this region.
Estimating Lower Bound Limit Loads: No Iterations/Modulus Adjustment
Authors: Simha C. Hari Manoj , Adibi-Asl Reza
Published: August 2013

We use the extended variational form of Mura and co-workers to estimate the lower bound limit loads for structures acted upon by a single load. Our scheme requires one elastic stress field either from a conventional finite element computation or analytical solution. No iterative stress field adjustments are required. We also adapt the scheme for structures with flaws by advancing a criterion that may be used to select sub-volumes of the structure that do not participate in the collapse. For structures with flaws, no ad hoc elastic modulus reduction at the stress concentration is required. Application of the proposed method is illustrated for some typical flawed and flaw-free structures and it is shown that the obtained multipliers are not overly conservative.
Submerged Pressure Vessel Testing Hazards
Authors: Montoya John , Ketchum Donald , Edel Matthew
Published: August 2013

It is common practice to proof test high pressure vessels prior to their use in the field. One technique for leak testing these vessels is submersion in water. A test failure at high pneumatic pressure and can pose several hazards to nearby personnel, such as projectile launch and blast loads. Submerged underwater testing can provide some level of protection from these hazards. However, it is largely unknown how much water cover is needed to prevent a projectile from escaping.

The purpose of this test program was to record the mitigating effects of water on hazards caused by a sudden pressure vessel failure. The test program entails submerging a pressure vessel underwater inside a tank. The vessel is then pressurized to failure, releasing a blast wave and launching a projectile. The event is recorded using high speed photography which is used to observe the effects of the gas release and the projectile motion. A discussion of the test events and associated physics is provided.
Practical Considerations When Conducting a Transient Analysis of a Heat Exchanger Tube Rupture
Authors: Thornton David R. , Sadowski Robert A. , Henry Philip A.
Published: August 2013

As part of operations, petrochemical and process plants sometimes require the exchange of heat between a high pressure fluid and a lower pressure fluid in shell-and-tube heat exchangers. In most cases, the high pressure fluid exists on the tubeside and the lower pressure is on the shellside. While rare, it is possible for a tube inside the exchanger shell to rupture suddenly, releasing the high pressure fluid into the shellside. If the pressure of the high pressure fluid exceeds the design pressure of the low pressure shell or its attached piping, it might be possible for the resulting pressure in the low pressure side to exceed permitted values. In such cases, API 521 provides guidance on assuring that sufficient pressure relief is available to limit the pressures on the heat exchanger(s)’ low pressure side. An overpressure analysis per API 521 can include both steady-state and transient analysis methods for determining that the pressures remain within acceptable levels. In situations where a large pressure differential exists between the high and low pressure sides of the exchanger, the transient, hydraulic analysis of the tube rupture event can be used as a tool to help mitigate over pressure. After briefly discussing the analysis methodology, this paper discusses some of the practical considerations and decisions that normally go into conducting the analysis.
Comparison of 2D and 3D Welding Simulations of a Simple Plate
Authors: Dewees David J.
Published: August 2013

Computer analysis of the welding process can now be reasonably carried out in 3D for many simple geometries. This allows direct comparison with more conventional 2D approximations for common heavier-walled joints. Multipass plate butt weld examples are presented, using a range of analysis techniques based on commercial finite element software and the results compared to one another. This project has application to a larger effort to understand the relationship between far-field displacement control boundary conditions and weld residual stress fields. Heat source, high temperature material property, constitutive and element birth and death modeling are also addressed.
Welding Residual Stress in a Large Diameter Nuclear Reactor Pressure Vessel Nozzle
Authors: Zhang Tao , Brust Frederick W. , Wilkowski Gery , Xu Heqin , Betervide Alfredo A. , Mazzantini Oscar
Published: August 2013

The Atucha II nuclear power plant is a pressurized heavy water reactor being constructed in Argentina. The original plant was designed by KWU in the 1970’s using the German methodology of break preclusion. The plant construction was halted for several decades, but a recent need for power was the driver for restarting the construction. Many times welding residual stresses in nuclear power plant can lead to cracking concerns. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe and nozzle joints with welds.

In this paper, a large diameter Reactor Pressure Vessel (RPV) hot-leg nozzle was analyzed. This is a nozzle from Atucha II nuclear power plant in Argentina. The main weld material is 20MnMoNi55 and ID welded cladding is made of 309L. The special materials and weld geometry will lead to interesting welding residual stress field. In addition, post-weld heat treatment (PWHT) region and boundary conditions could also play an important role in determining welding residual stress fields. Sensitivity analyses were conducted and the technical observation and comments will conclude the paper.
LBB Under Beyond Design Basis Seismic Loading
Authors: Zhang Tao , Brust Frederick W. , Wilkowski Gery , Xu Heqin , Betervide Alfredo A. , Mazzantini Oscar
Published: August 2013

The Atucha II nuclear power plant is a unique pressurized heavy water reactor (PHWR) being constructed in Argentina. The original plant design was by Kraftwerk Union (KWU) in the 1970’s using the German methodology of break preclusion. The plant construction was halted for several decades, but a recent need for power was the driver for restarting the construction. The US NRC developed leak-before-break (LBB) procedures in draft Standard Review Plan (SRP) 3.6.3 for the purpose of eliminating the need to design for dynamic effects that allowed the elimination of pipe whip restraints and jet impingement shields. This SRP was originally written in 1987 with a modest revision in 2005. The United States Nuclear Regulatory Commission (US NRC) is currently developing a draft Regulatory Guide on what is called the Transition Break Size (TBS). However, modeling crack pipe response in large complex primary piping systems under seismic loading is a difficult analysis challenge due to many factors. The initial published work on the seismic evaluations for the Atucha II plant showed that even with a seismic event with the amplitudes corresponding to the amplitudes for an event with a probability of 1e−6 per year, that a Double-Ended Guillotine Break (DEGB) was pragmatically impossible due to the incredibly high leakage rates and total loss of make-up water inventory. The critical circumferential through-wall flaw size in that case was 94-percent of the circumference.

This paper discusses further efforts to show how much higher the applied accelerations would have to be to cause a DEGB for an initial circumferential through-wall crack that was 33 percent around the circumference. This flaw length would also be easily detected by leakage and loss of make-up water inventory. These analyses showed that the applied seismic peak-ground accelerations had to exceed 25 g’s for the case of this through-wall-crack to become a DEGB during a single seismic loading event. This is a factor of 80 times higher than the 1e−6 seismic event accelerations, or 240 times higher than the safe shutdown earthquake (SSE) accelerations.
Fitness for Service of Degraded Grade 91 Pipe
Authors: Cohn Marvin J. , Paterson Steve R.
Published: August 2013

The use of creep strength enhanced ferritic alloys such as Grade 91 in fossil power plants has become popular for high temperature piping applications. Since Grade 91 has higher stress allowables than Grade 22, a designer can specify thinner component wall thicknesses, resulting in lower through-wall thermal stresses during transient events and lower material and piping support costs.

During the past two decades, Grade 91 has been used successfully in fossil power plants. However, this alloy has had some incidents of non-optimal weldment microstructure. In this case study, Brinell hardness tests of an ASME A182 Grade F91 (F91) wye block, including upstream and downstream F91 spools, revealed several readings of soft material, as low as 168HB. A study of creep rupture tests of degraded Grade 91 specimens revealed that the lower bound creep rupture curve of the degraded Grade 91 material is above the average creep rupture curve of Grade 22 material for the range of the specific piping operating stresses.

Based on the empirical evidence that the average Grade 22 material creep rupture curve is conservative for the creep rupture of degraded Grade 91 material, a life consumption evaluation was performed for the degraded Grade 91 weldments using Grade 22 creep rupture properties. A life fraction analysis was performed considering the redistributed maximum principal stresses, based on simulation of piping displacements obtained from the hot and cold walkdowns. This study also considered the recent history of the specific piping system operating pressures and temperatures.

This study also considered dissimilar metal welds, from ASME A182 Grade F91 (F91) to ASME A335 Grade P22 (P22) materials. It was determined that the Grades F91-to-F91 weldments had about 30% life consumption and the remaining lives were at least 7 years. The Grades F91-to-P22 weldments had less than 40% life consumption and the remaining lives were at least 15 years.
Pressure Distribution Inside Pipes due to DDT
Authors: Geng Jihui , Thomas J. Kelly
Published: August 2013

The ignition of a flammable gas mixture contained within a piping system can lead to damage or failure of the piping or system components. Flame propagation and acceleration within piping systems have been extensively studied. It has been well documented that, given sufficient flame propagation distance and/or the presence of turbulence generating features, flame acceleration within a pipe can lead to a deflagration-to-detonation transition (DDT). The high overpressures associated with a DDT can increase the potential for deformation or failure of the piping system relative to the loads associated with either a fast deflagration or steady-state detonation. This paper presents the results of numerical evaluations to predict the pressure distributions within a pipe run due to a DDT. The blast overpressure associated with a DDT was found to depend on a number of parameters, including: the rate of flame acceleration prior to the DDT, the length of piping occupied by the flammable mixture, the initial gas pressure and the flammable mixture concentration distribution along the pipe. This paper also provides a comparison of the blast loads associated with a steady-state detonation relative to those due to a DDT.
Comparison of ASME B31.1 Sustained Load Stresses to Corresponding Tresca Stresses
Authors: Cohn Marvin J.
Published: August 2013

Conventional United States designs of high energy piping (HEP) systems use the American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code. The analytical methodology in this code is based on linear elastic beam theory. The ASME B31.1-2010 Power Piping Code (Code) [1] recommends Equation 15 to calculate the piping stress due to sustained loads. Many practitioners believe that the sustained load stress (SL) results using Equation 15 are not significantly less than using a Tresca methodology for the same set of forces and moments. This paper provides a comparison of the ASME B31.1 SL stresses to the corresponding Tresca stresses in parent material, based on empirical HEP system stress analyses. The results of three piping system evaluations are considered, including examples of longitudinal stress lower than the circumferential stress and examples where the longitudinal stress is greater than the circumferential stress.

This study considers the elastic primary stresses on the outside surface of the pipe, prior to any creep redistribution. At locations where the longitudinal stress is greater than the circumferential stress, the SL stress is nearly the same as the elastic Tresca stress. At locations where the longitudinal stress is considerably less than the circumferential stress, the SL stress is considerably less than the elastic Tresca stress. This conclusion is due to the fact that the SL stress is primarily governed by longitudinal loading.

The paper also considers inelastic primary stresses, after complete creep redistribution. For piping materials operating in the creep regime, the axial and circumferential pressure stresses are eventually redistributed and are maximum at the outer surface of the pipe. After several years of operation, the Code SL stresses and elastic Tresca stresses are significantly less than the inelastic Tresca stresses. Consequently, the use of SL stresses and elastic Tresca stresses for estimating component inelastic primary stresses would be nonconservative.
Annealing Requirements for Flow-Formed Containment Vessels for Type B Radioactive Materials
Authors: Mok G. C. , Anderson B. L. , DeMicco M. F. , Hafner R. S. , Hagler L. B. , Russell E. W. , Syn C. K.
Published: August 2013

Flow forming, an advanced version of metal spinning, is becoming a popular technique for the fabrication of containers for the storage and transportation of radioactive materials. A previous article by the authors[1] gave a cursory review of the operation, benefits, and possible problems associated with this method. The same article also addressed the ASME Boiler & Pressure Vessel Code (ASME BPVC) requirements[2] of the method, and recommended desirable quality control measures. One of the recommendations was that the product be annealed after flow forming, even though the authors were not yet convinced that ASME BPVC always requires it. The current article reports new findings from a comprehensive review of material specifications, which ASME BPVC chose to adopt, or to ignore, for pressure application. The new findings suggest that ASME BPVC actually prefers annealing, so that the cold work has an insignificant effect on the product’s properties. Each ASME BPVC specification describes key property requirements and heat treatments to help meet the requirements.
Graded Approach to Small Modular Reactor Implementation
Authors: Culp William G. , Cintron-De Leon Brendaly
Published: August 2013

The regulatory process covers health and safety issues in the context of large power reactors; this paper addresses how requirements on designers and owners might be scaled for small modular reactors (SMR) in proportion to the risks for the type of technology.

Light water SMRs are designed to incorporate many of the fuel and passive safety features already described in the Design Control Documents and Final Safety Analysis Report (FSARs) for large power reactors. Regulations are written to principally address large and advanced power reactors. This paper proposes a several step process to simplify the process of getting design certification, a license to manufacture LWR type SMR, construct a SMR at multiple sites, and accelerate an applicant’s Early Site Review and Combined Operating License process.

This paper looks at issues identified by the NRC Commissioners in SECY 10, 0034, 3/28/10, Potential Policy, Licensing, and Key Technical Issues for Small Modular Reactor Designs, from the industry perspective. Since the SMR issues are less complex and involve less risk than the corresponding issues for large reactors, this paper describes theoretical means of reducing the scope, schedule, and cost of a SMR.
Application of a Remote Health Monitoring System for Pipeline Bolted Joints
Authors: Razi Pejman , Esmaeel Ramadan Ahmed , Taheri Farid
Published: August 2013

Early detection of bolt loosening is a major concern in the oil and gas industry. In this study, a vibration-based health monitoring strategy has been developed for detecting loosened bolts in pipeline. Both numerical and experimental studies are conducted to verify the integrity of the proposed method. Several damage scenarios for a bolted joint connecting two steel pipes (ASTM A53/A53M–07) are considered by simulating the loosening of the bolts through varying the applied torque on each bolt. An electric impact hammer is used to excite the pipe’s vibration in a consistent manner. The induced vibration signal is collected remotely via piezoceramic sensors bonded onto the pipe as well as the flange. The gathered vibration signals are transferred remotely to an in-house developed MATLAB code by a wireless data acquisition (DAQ) module. The data is processed with the embedded signal processing code, which incorporates normalization, filtering of data and the empirical mode decomposition (EMD) to establish an effective energy-based damage index. The assessment of the damage indices obtained for the damage scenarios verifies the integrity of the proposed methodology in identifying the damage and its progression in bolted joints.
Advantages of Bladder Surge Tanks in Pipelines
Authors: Young Winston B.
Published: August 2013

The paper advocates the use of bladder surge tanks to control pressure surges in pipelines created by transient operations. Transient pressures are created as a result of pumps starting and stopping as well as the opening and closing of valves. This paper describes why the utilization of bladder surge tanks is the best solution to transient operations. A bladder surge tank allows piping systems to meet pressure piping codes such as ASME B31.3 and B31.4. Controlling pressure transients reduces pressure stresses, thereby extending the pipeline’s operating life. This paper compares the use of a bladder surge tank to other methods to attenuate pressure transient in pipelines.

Generally, water and hydrocarbon pipelines operate safely throughout the world, but failure can occur as a result of pressure transients created by certain operating conditions. In addition, pipe materials are weakened as a result of years of operation and exposure to corrosion, pressure cycling fatigue and over-pressurization.

The usable life of piping materials can be significantly reduced by cyclic loading and surge pressure overstressing the material. Therefore, controlling pressure surges will increase pipeline life and reliability. This can be achieved by installing surge control equipment at the location of the transient event.
Influence of Austenitic Stainless Steel Base Metals on Hot Cracking Susceptibility of High Chromium Nickel-Base Filler Metals
Authors: McCracken Steven L. , Tatman Jonathon K.
Published: August 2013

Alloy 690 is a 30 wt% chromium base metal with excellent resistance to PWSCC. Alloy 52M (ERNiCr-7A) is weld filler metal that closely matches the composition of Alloy 690 and also exhibits excellent resistance to PWSCC [1]. Alloy 52M is currently used for new nuclear component fabrication and for repair and mitigation of PWSCC in operating nuclear power plants. Unfortunately, industry experience and laboratory testing has shown that Alloy 52M is susceptible to hot cracking when welding over some austenitic stainless steel base material compositions. Currently there is no clear understanding of the specific composition levels that increase the susceptibility to hot cracking. This paper summarizes preliminary results of an EPRI study on hot cracking susceptibility Alloy 52M when welded on a range of austenitic stainless steel samples [2]. The focus of the EPRI study was to identify high risk base metals with compositions that promote hot cracking and provide counter measures to mitigate or lessen the propensity for hot cracking.
Effectiveness of Excavate and Weld Repair on a Large Diameter Piping Dissimilar Metal Weld by Finite Element Analysis
Authors: Ku Francis H. , Riccardella Pete C. , Alleshwaram Aparna , Willis Eric
Published: August 2013

Finite element weld residual stress analyses are performed to investigate the effectiveness of a newly proposed repair option for primary water stress corrosion cracking (PWSCC) in dissimilar metal welds in PWRs: Excavate and Weld Repair (EWR). Analyses are performed on a 30″ (762mm) outside diameter (OD) and 3″ (76mm) thick stainless steel pipe connected to a low alloy steel nozzle with a dissimilar metal weld (DMW). Eight EWR cases are analyzed to evaluate the sensitivities in weld residual stresses due to variations in the width and depth of the EWR, including cases with and without a thin weld cap on top of the DMW. The results demonstrate that a wide EWR that extends beyond the original width of the DMW provides the maximum residual stress benefits to the DMW, in terms of reducing the as-welded residual stresses. It is also found that the presence of the weld cap yields only marginal residual stress benefits.
Improved Design of End Closure for Screw Locking Ring U Shaped Tube Heat Exchanger
Authors: Chen Ping , Luo Cong
Published: August 2013

This paper describes an improved design of end closure for screw locking ring U-shaped tube heat exchanger used in oil-refining process with use of the D-section shearing bolts as its load-carrying connectors between the tube channel cover and the top flange instead of the connection by acme screw locking ring and the strength calculating method for its main load-carrying components and an comparison with two others are presented. This new construction has the features of compacted design, saving material and easy assembling and disassembling etc.
Effect of Post-Weld Heat Treatment on the Plastic Buckling of Welded Cylindrical Shells
Authors: Wang Ji , Chen Zhiping , Yu Chulin
Published: August 2013

Storage tanks, silos and other welded cylindrical shell structures are usually constructed of rolled panels which are joined by patterned circumferential and longitudinal welds. Cold-formed residual stresses are produced during the cold bending process of steel panels, and obvious deformations and uneven distributed welding residual stresses are also produced because of the welding process. Studies have shown that residual stresses could weaken the critical buckling load of welded cylindrical shells under axial compression. Stress-relief post-weld heat treatment (PWHT) is a process that heats the workpiece gradually to 500∼650 °C, holding the temperature 0.5 hours then reducing the temperature slowly. Two cylindrical shell specimens are fabricated in this paper, and one is processed with stress-relief PWHT, while the other is not. The magnitude and distribution of residual stresses near the weld zone in each specimen are measured with an X-ray diffraction-based measurement system (named iXRD by the manufacturer), and initial imperfections and critical load of the specimens are obtained by the use of an axial buckling experiment platform. Thereafter, numerical simulations are conducted with measured geometric imperfections and residual stresses exerted into the finite element model. Finally, comparison of the critical loads of both cylindrical shell specimens is made, showing the effects of residual stresses on the plastic buckling of cylindrical shells under axial compression.
The MacArthur Maze Fire and Roadway Collapse: A “Worst Case Scenario” for Spent Nuclear Fuel Transportation?
Authors: Bajwa Christopher S. , Easton Earl P. , Adkins Harold , Cuta Judith , Klymyshyn Nicholas , Suffield Sarah
Published: August 2013

In 2007, a severe transportation accident occurred near Oakland, California, at the interchange known as the “MacArthur Maze.” The accident involved a double tanker truck of gasoline overturning and bursting into flames. The subsequent fire reduced the strength of the supporting steel structure of an overhead interstate roadway causing the collapse of portions of that overpass onto the lower roadway in less than 20 minutes. The US Nuclear Regulatory Commission has analyzed what might have happened had a spent nuclear fuel transportation package been involved in this accident, to determine if there are any potential regulatory implications of this accident to the safe transport of spent nuclear fuel in the United States. This paper provides a summary of this effort, presents preliminary results and conclusions, and discusses future work related to the NRC’s analysis of the consequences of this type of severe accident.
Safety Investigation of Buried Polyethylene Pipe Subject to Seismic Landslide
Authors: Ma Jinjin , Shi Jianfeng , Zheng Jinyang
Published: August 2013

As polyethylene (PE) pipes are widely used in the gas transportation system nowadays, increasing attention is attached to the safety of buried PE pipe under seismic load. In this paper, the related failure criterion is proposed and mechanical behavior of PE pipe subject to seismic landslide is investigated. Based on extensive tensile tests, an appropriate constitutive model of PE is selected and the parameters are estimated to simulate mechanical behavior of PE pipes using finite element method. The pipe is assumed to be loaded with a quartic polynomial bending deflection displacement along the axial direction and the soil acts linear elastic. From the numerical simulation results, it is concluded that cross-section deformation is the governing failure mode of buried PE pipe subject to seismic landslide and the critical pipe deflection is about 0.048. Failure criterion curves of seismic landslide are put forward with the combination of failure criterion and engineering practice. The proposed failure criterion curves serve as a foundation available not only for the safety design and assessment also for engineering acceptance criterion of the failure of PE pipe due to seismic landslide.
Spent Fuel Storage in the Post-Yucca Mountain Paradigm
Authors: Easton Earl , Bajwa Christopher , Li Zhian , Gordon Matthew
Published: August 2013

The current uncertainty surrounding the licensing and eventual opening of a long term geologic repository for the nation’s civilian and defense spent nuclear fuel (SNF) and high level radioactive waste (HLW) has shifted the window for the length of time spent fuel could be stored to periods of time significantly longer than the current licensing period of 40 years for dry storage. An alternative approach may be needed to the licensing of high-burnup fuel for storage and transportation based on the assumption that spent fuel cladding may not always remain intact. The approach would permit spent fuel to be retrieved on a canister basis and could lessen the need for repackaging of spent fuel. This approach is being presented as a possible engineering solution to address the uncertainties and lack of data availability for cladding properties for high burnup fuel and extended storage time frames. The proposed approach does not involve relaxing current safety standards for criticality safety, containment, or permissible external dose rates.
Probabilistic Parameter Sensitivity Study on Design Fatigue Curve for Carbon and Low-Alloy Steels
Authors: Takanashi Masahiro , Maeda Jyunki , Sakai Shinsuke
Published: August 2013

In a previous paper[1], we discussed the margins of the design fatigue curve in ASME Boiler and Pressure Vessel Codes Section III using a probabilistic approach. Limit state functions of the design fatigue curve for carbon and low-alloy steels were proposed in order to investigate the physical implication of the design margin. In the limit state functions, four parameters, namely, fatigue data scatter, size effect, surface roughness, and applied stress were taken into consideration as random variables. Based on the limit state functions, reliability index contours of the design fatigue curve were obtained together with the partial safety factors (PSFs).

Among these partial safety factors, the fatigue strength (or life) and the applied stress were predominant. The other parameters, the PSFs for the size effect and the surface roughness were small enough and almost constant. The parameter sensitivity, however, remains unknown and whether these parameters should be treated as constants or as random variables is also not clear.

In this study, a probabilistic parameter sensitivity study on the design fatigue curve was conducted to discuss how the design fatigue curve should be. Two sensitivities were computed. One is the rate sensitivity indicating the contribution of the mean value of the parameter in the probability of failure. The other is the probabilistic sensitivity to parameter dispersion. The parameters for the size effect and the surface roughness showed lower probabilistic sensitivities. This result suggests that the parameters can be considered as constants. In general, a higher number of parameters in a probabilistic model leads to more uncertainty and the design concept tends to be more conservative. We, therefore, proposed to deal with the parameters of the size effect and the surface roughness separately in the design fatigue curve to eliminate conservativeness.
Study on Vibration Attenuation Element Using Damping Polyurethane Gel Material
Authors: Furuya Osamu , Goda Kengo , Ishihana Kenta
Published: August 2013

The seismic safety should be constantly considered for mechanical, architectural and civil structures in Japan where is one of severe quake-prone countries in the world. The aseismic construction, seismically isolated structure and response control structure have been applied to the several structures for upgrading of seismic safety, and then the design technique for large scale structure in the current situation is close to standard range in recent years. However, the quake-proof technique for the smaller scale structure such as a detached house, server rack and art and craft has not yet been in the development stage until now, and especially there is a problem in the damping element in the practical use stage because the downsizing of damping element is often difficult to be adapted to design specification such as a performance, a cost, a mechanism and so on for comparatively small structure. In this study, the urethane material has been developed to use as a damping element in the response control device. The newly urethane gel material is compounded to become the characteristic that a spring element in the material to minimize the effect against the structural rigidity. This paper describes the efficiency of newly developed urethane gel material as a damping element is considered from several material characteristic evaluations and basic mechanical characteristic investigations.
Effects on Plasticity and Structural Integrity of Tube Expansion
Authors: Khan Rashid , Pervez Tasneem , Qamar Sayyad Zahid
Published: August 2013

This paper presents an investigation of the effects of cold expansion on plasticity and structural integrity of expandable tubulars. Down-hole tubular expansion has proven itself to be a vital technology in oil well applications. One of the challenges faced by researchers and field engineers in implementing and making down-hole tubular expansion technology cost effective is to conserve the structural integrity of tubular after the expansion process. Cold expansion affects the mechanical properties and induces residual stresses in the tubular, which could reduce its collapse, burst and fatigue ratings. Hence, a knowledge of variation of properties is required in correctly predicting the life span of tubular under given operational conditions. Cold expansion of tubulars under down-hole conditions is simulated at different strain rates using finite element method. The strain rates are varied by changing the velocity of mandrel used to expand the tubular. It is found that there are variations in contact pressure at tubular-mandrel interface, effective stress, equivalent plastic strain and thickness reduction during expansion process. These variations ultimately influence post-expansion properties of the tubular particularly the collapse and burst strengths, and hence its structural integrity. However, length shortening and surplus deformation have negligible effect on post-expansion properties of tubular.
Applicability of SE(T) and SE(B) Fracture Specimens in Crack Growth Measurements of Pipeline Girth Welds
Authors: Mathias Leonardo L. S. , Donato Gustavo H. B. , Ruggieri Claudio
Published: August 2013

This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-Δa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized side-grooved, clamped SE(T) specimens and 3P bend SE(B) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. The shallow-crack SE(B) specimen provides an R-curve which, albeit slightly more conservative, exhibits levels of J-values which are relatively comparable to the levels of J corresponding to the deeply-cracked SE(T) specimen at a fixed amount of crack growth, Δa. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE(T) and SE(B) specimens with weld centerline cracks.
Simulation of Notch Tip Stress/Strain Response of Zirconium Pressure Tube Material
Authors: Reinhardt Wolf , Doddihal Preeti , Ranganath Sampath
Published: August 2013

The Fitness-for-Service assessment of Zr 2.5Nb pressure tubes in CANDU reactors requires the evaluation of fatigue. As-designed, the pressure tubes do not contain notches, but in operation various degradation mechanisms, such as fretting and crevice corrosion, can generate flaws with small root radii. Since these flaws are exposed to the coolant, an assessment of environmental effects on fatigue life is needed, and fatigue tests are being conducted to obtain the fatigue curve.

The pressure tubes are located in areas of high neutron flux, and thus the material is subject to irradiation effects. Since tests of irradiated material in reactor coolant environment are very difficult to conduct, a mechanistic understanding of fatigue at notches in Zr 2.5Nb material is sought, to allow the best possible use of fatigue tests of irradiated material in air and unirradiated material in water.

As part of the effort to develop a mechanistic understanding, continuum-level simulations of the mechanical behaviour of unirradiated and irradiated Zr 2.5Nb material were performed using finite element analyses. Both monotonic and cyclic runs were conducted to investigate the difference between first-cycle and shakedown behaviour near the notch tip. To increase confidence in the result, finite element notch strain predictions were benchmarked with a Neuber notch strain model. The paper discusses observations and possible consequences of these simulations.
Dependence of Bonding Strength of Ceramic to Metal Joint on Interface Wedge Angle in Metal Side
Authors: Tateno Masayoshi , Yokoi Eiichiro
Published: August 2013

The focus of this study is to clarify a dependence of bonding strength of ceramic to metal joint on interface wedge angle in metal side. Each plate Si3N4-to-Cu or Ni joint with plane interface is produced by electric discharge machining. Geometrical shape at the edge of the interface is characterized by wedge angle defined as a configuration angle between free surface of each material and the interface. As the wedge angle of Si3N4 is right angle, the wedge angle of metal is set over from 30° to 180°. Each joint is bonded at high temperature by using thin braze metal under vacuum and slowly cooled. Tensile bonding strength of the joint is evaluated. Result shows that decrease of the wedge angle of metal side from right angle improves the bonding strength since it decreases the residual stress near edge of the interface on ceramic side. The highest bonding strength appears at the identical interface condition where fracture pattern changes. It appears that optimum edge angle for obtaining the highest bonding strength depends on bonding temperature and combination of bonded materials. This paper provides a useful geometrical interface shape to improve tensile bonding strength of ceramic to metal joint.
Evaluation of Fracture Toughness Behavior of SA508 Steel Considering Biaxial Loading Condition
Authors: Kim Jong-Min , Lee Ki-Hyoung , Lee Ho-Jin , Lee Bong-Sang
Published: August 2013

The crack-tip stress field and fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by the loading condition and crack geometry. Current guidance considers that the ductile-to-brittle transition is defined using uniaxially loaded specimens with a deep crack even when the reactor pressure vessel is under biaxial loading and the existence of deep crack is not probable through periodic in-service-inspection. Thus, such a constraint effect caused by differences between standard specimens and a real structure can overestimate the fracture toughness and affects the results of the structural integrity assessment.

The present paper investigates the constraint effect by evaluating the Mater Curve T0 reference temperature of PCVN (Pre-cracked Charpy V-Notch) and small scale cruciform specimens of SA508 Gr. 3 low alloy steel through the fracture toughness tests of theses specimens and 3-dimensional elastic-plastic finite element analyses. Based on the finite element results, the fracture toughness values of a small-scale cruciform specimen were estimated, and the geometry-dependent factors of the cruciform specimen considered in the present study were determined and then the transferability of the test results of these specimens were discussed.
Prediction of Creep Void Growth in Heat-Affected Zone of High Chromium Steel Weldments Considering Multiaxial Stress State
Authors: Murakami Eiji , Hashimoto Masamitsu , Kikuhara Seiji
Published: August 2013

This paper deals with a method for predicting creep void growth in heat-affected zone (HAZ) of high chromium steel weldments. The method has been proposed by authors based on the relationship between creep void density increasing rate and multiaxial stress state.

In this study, internal pressure creep tests of ASME grade 91 (9Cr-1Mo-Nb-V) tubes with longitudinal weldments subjected to several internal pressures have been conducted to reveal creep void growth behavior in HAZ. In addition, finite element creep analyses of the specimens at different creep strain rates in base metal, weld metal and HAZ have been carried out to investigate distribution of stresses and stress triaxiality factor in HAZ. A comparison between stress distributions and void distributions revealed that stress triaxiality factor predominantly affects growth behavior of creep voids. From the result, the relationship between creep void density increasing rate and the parameter as a function of principal stress and triaxiality factor was established. It was found that there is a proportional relationship between creep void density increasing rate and the parameter to represent stress multiaxiality on the logarithmic graph.

To verify proposed prediction method, the method was applied to the internal pressure creep test specimens at different experimental conditions. As a result, the predicted void distribution and void density increasing rates were in good agreement with experimental results.
The Residual Bolt Force and the Sealing Performance of Flanged Connections With Expanded PTFE Gaskets (Based on Test Results for One Year)
Authors: Kobayashi Takashi , Hagiri Taiki , Nishiura Kengou , Hiratsuka Masaaki , Itoi Katsutoyo
Published: August 2013

It is known that bolt forces reduce significantly after tightening bolted flanged connections in which expanded PTFE gaskets are used. Bolts are often post-tightened in practice after initial tightening to compensate for the reduction of bolt forces. The viscoelastic characteristic of expanded PTFE gaskets is thought to be the main cause for the phenomenon. Some gasket users are not confident whether the bolt forces remain above a minimum required gasket load until next maintenance. However, the long term characteristics of the residual bolt forces and the sealing performance of flanged connections have not been clarified yet.

In this study, using flanged connections with expanded PTFE gaskets, the reduction of bolt forces and the change in the sealing performance were measured at room temperature for one year. Based on the test results, the residual bolt force and the sealing performance were studied.

It was clarified that bolt forces converges to a certain level at early stage within almost 1000 hours. After that, the bolt forces were significantly affected by the ambient temperature change. This is because the thermal expansion of PTFE material is high and also the thermal characteristic of PTFE material has a temperature dependency. It was confirmed that although the bolt force reduced significantly at early stage, it is maintained in long-term. The sealing performance was improved due to the increased compression of gasket.