bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-Term Leak Tightness of O-Ring Seals in the 9975 Shipping Package
Authors: Hoffman Elizabeth N. , Skidmore T. Eric , Daugherty William L.
Published: January 2011

O-ring seals in the 9975 shipping package containment vessels are fabricated from a Viton® GLT or GLT-S compound. Long-term testing of these O-rings has been performed to support service life predictions for packages used for long-term storage. Since the only criterion for O-ring performance is to maintain a leak-tight seal, leak testing is the primary indicator of service life. Fixtures have been aging at elevated temperatures to provide data for service life predictions. Limited leak test failures have been observed at the higher temperatures. This provides the opportunity for comparison to trends based on other O-ring properties, such as compression stress relaxation (CSR). Initial data suggest that the CSR data have some predictive value for a leak-tight service life, but other factors can complicate efforts to draw definitive conclusions.
The Design of a Self-Monitoring Thermoplastic Composite Pipe for High Pressure Gas/Liquid Transport
Authors: Kanninen Melvin F. , Stonesifer Randall B. , Bethel Kyle
Published: January 2011

Pipes made of high density polyethylene (HDPE) and other thermoplastic materials do not corrode. However, this considerable advantage, because HDPE is limited to a line pressure of 125 psig, cannot be utilized for the replacement or rehabilitation of trunk lines in gas/liquid distribution systems and transmission lines where pressures range from 150 psig up to 1500 psig or more, without some form of reinforcement. This paper describes an advanced technology for accomplishing this by use of a composite of thermoplastic materials. This technology can be used for high pressure applications in either a stand-alone mode, or as a pipe within a pipe, by its insertion into an existing damaged/degraded high-pressure steel pipeline. In either mode, arbitrarily high pressures can be achieved, health can be monitored with a built-in fiber optic sensor system, and wall loss due to corrosion precluded. The focus of the paper is on addressing some of the ancillary issues that arise in the utilization of the technology that are not usually of concern in steel pipelines: nonlinear stress analysis of heterogeneous materials, time/temperature dependent mechanical properties, greenhouse gas permeation, and the diminution of flow area associated with internal reinforcement.
Aging Model for Cane Fiberboard Overpack in the 9975 Shipping Package
Authors: Daugherty W. L. , Harris S. P.
Published: January 2011

Many radioactive material shipping packages incorporate a cane fiberboard overpack for thermal insulation and impact resistance. Mechanical, thermal, and physical properties have been measured on cane fiberboard following thermal aging in various temperature/humidity environments. Several of the measured properties change significantly over time in the more severe environments, while other properties are relatively constant. Changes in each of the properties have been fit to a model to allow predictions of degradation under various storage scenarios. Additional data are being collected to provide for future refinements to the models.
Failure Criterion for Varying Strain Rates
Authors: Tan Kian Sing , Kwon Young W.
Published: January 2011

Strain rate affects the behaviors of engineering structural materials, such as metals and composites, in terms of their stiffness and strength. In particular, yield and failure strengths and strains depend on the strain rate applied to the materials. When a structural material is subjected to a typical dynamic loading, the material usually undergoes various strain rate loading conditions. Then, the main question is whether the material is going to fail or not. To the authors’ best knowledge, there has been no failure criterion proposed for a varying strain rate loading condition. This paper presents a failure criterion under non-uniform strain rate conditions. Experiments were also conducted to support the proposed failure criterion using aluminum alloy AA3003-H14. This study also investigated the failure envelopes in terms of strain rates and the normalized failure strengths. Furthermore, evaluations of various stressstrain relations under different strain rate loading conditions were also undertaken.
Development of Base-Isolation House Using Sliding Device
Authors: Mikoshiba Tadashi , Minowa Chikahiro , Terai Masakazu , Sato Takanori , Maruyama Yoshihiro , Chiba Toshio
Published: January 2011

By setting the isolation system between the foundation of the house and the foundation ground, it makes it possible to scale back the influence of the earthquake. A sliding isolator, which is compact and has stable isolation characteristics, had been developed. It was made of a plate with multi convex cell and a sliding plate. This system is a sliding isolator with multipoint contact. The static tests, the shaking table tests and analysis were conducted to confirm the damping capacity of the sliding device. In the element tests, the coefficient of static and dynamic friction and the change in the friction of the total system resulting from construction error were investigated. Movement of the base-isolated house and twisting of the base-isolated house with eccentric load under the actual earthquake loading were surveyed in the shaking table tests. As a result, it was effective and had a stable performance.
Crack Growth Analysis in Weld-Heat Affected Zone Using S-Version FEM
Authors: Kikuchi Masanori , Wada Yoshitaka , Shimizu Yuto , Li Yulong
Published: January 2011

Fracture in the heat affected zone (HAZ) in welding has been a serious problem for the integrity of machines. Prediction of fracture behavior due to the residual stress field in HAZ is important. In this paper, the S-Version FEM(S-FEM) is applied to simulate the crack growth under thermal and residual stress fields. For evaluation of the stress intensity factor, the virtual crack closure integral method (VCCM) is employed. In order to confirm the validity of this analysis, numerical results are compared with previously reported analytical and experimental results. Then, a crack growth analysis in a piping structure with a welding joint was conducted. The residual stress data was provided by JAEA, Japan Atomic Energy Agency, based on their numerical simulation. Using S-FEM, two- and three-dimensional analyses are conducted, and crack growth behavior under thermal stress field is studied and discussed.
Overview of Implementation of Probabilistic-Risk-Assessment-Based Seismic Margin Analyses in Design Certification and Combined License Applications
Authors: Xu Jim
Published: January 2011

The licensing process for new reactors in the United States was established in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” which provides requirements for early site permit (ESP), standard design certification (DC), and combined license (COL) applications. In this process, an application for a COL may incorporate by reference a DC, an ESP, both, or neither. This approach allows for the early resolution of safety and environmental issues. The safety issues resolved by the DC and ESP processes are not reconsidered during a COL review. However, a COL application that incorporates a DC by reference must demonstrate that pertinent site-specific characteristics are confined within the envelopes established by the DC’s site parameters. This paper provides an overview of the implementation of probabilistic risk assessment (PRA) based seismic margin analyses in DC and COL applications. In addressing the severe accident preventions and mitigations for new reactors, 10 CFR 52.47(a)(27) requires that the final safety analysis report for a DC application describe the design-specific PRA and its results. Regulatory Guide 1.206, “Combined License Applications for Nuclear Power Plants (LWR Edition),” issued June 2007, further states that the scope of this assessment should be a Level 1 and Level 2 PRA that includes internal and external hazards and addresses all plant operating modes. However, the staff recognized that it is not practical for a DC applicant to perform a seismic PRA because a DC application would not contain site-specific seismic hazard information. As an alternative approach to a seismic PRA, the staff proposed a PRA-based seismic margin analysis in SECY-93-087, “Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs,” dated April 2, 1993, and the Commission approved it in the corresponding staff requirements memorandum, dated July 21, 1993. This analysis preserves key elements of a seismic PRA to the maximum extent possible and estimates the design-specific plant seismic capacity in terms of sequence-level high confidence of low probability of failure capacities and fragility for all sequences leading to core damage or containment failures up to approximately 1.67 times the ground motion acceleration of the design-basis safe-shutdown earthquake. Using this approach, the analysis can demonstrate acceptably low seismic risk for a DC. This paper discusses the implementation aspects of PRA-based seismic margin analyses in support of a DC application and post-DC updating activities, including COL updates to incorporate site- and plant-specific features and post-COL verifications.
Effect of Side Grooves on Compliance, J-Integral and Constraint of a Clamped SE(T) Specimen
Authors: Shen Guowu , Tyson William R. , Gianetto James A. , Park Dong-Yeob
Published: January 2011

The effect of side grooves on crack mouth opening displacement (CMOD) compliance, distribution of J-integral and crack-tip constraint parameters Q and A2 along the thickness of a clamped single-edge-notched tension (SE(T)) specimen were studied by finite element analysis (FEA). Focus was on the effect of depth of side grooves on J-integral and constraint parameters Q and A2 for shallow and deep cracks. The 3-D results were compared with those of SE(T) specimens in plane strain. The results show that the effective thickness equation used in ASTM E 1820 to evaluate compliance of side-grooved SE(B) and C(T) specimens can be used for clamped SE(T) specimens with reasonable accuracy. The results also suggest that the depth of the side grooves affects the distribution of the J-integral: the highest J-integral is at the center of the thickness for a SE(T) specimen with side grooves equal to or less than 10% of total thickness, and near the root of the side grooves for side grooves greater than 10% for a deeply-cracked specimen when the applied load P≥PY. The FEA results also show that the depth of side grooves affects the distribution of the constraint parameters: the crack-tip constraint is highest at the center of the thickness for a specimen with 0% side grooves (plain-sided), and near the root of the side grooves for side grooves equal to or greater than 10%. It was also found from FEA that the crack-tip constraint of a SE(T) specimen with 20% side grooves with shallow (a/W = 0.2) or deep (a/W = 0.5) crack is higher than that of a SE(T) specimen with the same crack depth in plane strain. As a result, the J-resistance of a SE(T) specimen with 20% side grooves may be lower than that of the same specimen in plane strain.
Influence of Strength Mismatch and Weld Residual Stress on Fatigue Crack Growth Behavior for Pipeline Steel Including Closure Effects
Authors: Sarzosa Burgos Diego Felipe , Ruggieri Claudio
Published: January 2011

The integrity of mechanical components, particularly when they undergo significant fatigue damage for the duration of operating life, can be strongly influenced by the presence of residual stress fields and mechanical heterogeneity. Premature closure of crack flanks greatly influences fatigue crack growth rate. To estimate the crack closure in any welded structure, the residual stresses and strength mismatch in the vicinity of the crack tip should be considered. Extensive elastic-plastic finite element analyses have been carried out to investigate detailed crack closure behavior in heterogeneous compact tension (CT) specimens with three levels of weld strength mismatch and imposed uniform tensile residual stress field. The restriction on uncraked ligament imposed by E-647 is rather unconservative because it does not ensure linear elastic behavior at the crack tip. A relationship between the crack opening loads, the mismatch level and maximum applied stress intensity factor was obtained for small scale yielding (SSY) condition. This equation shall be used for fast estimations of closure effects for welding joints. A homogeneous, soft material has the largest crack opening loads, while a heterogeneous material with 50% overmatch conditions has the smallest opening load under SSY condition. Residual tensile stresses have detrimental effects on the fatigue resistance of the material. On average, residual tensile stresses, with magnitude equal to 0.5σy of the base metal, increase the Fatigue Crack Growth Rate (FCGR) by 40% when compared to the case without residual stress under SSY condition. Moreover, overmatch conditions in welded joints have detrimental effects on fatigue crack propagation rate. The fatigue life can be reduced by more than 70% for a condition of 50% overmatch when compared with the evenmatch condition.
Effect of Hot Feed Injection Time on Thermal Fatigue Life of Shell-to-Skirt Junction Area of Coke Drums
Authors: Oka Masaaki , Ambarita Himsar , Kawashima Kenichi , Daimaruya Masashi
Published: January 2011

Coke drums are subjected to cyclic thermal and mechanical loads. Thus, their operational life is much shorter than other equipments in the refinery. The major typical location of failure due to thermal fatigue in coke drums is the shell-to-skirt junction. There are two times observed peak strains in every cycle. First time is when the hot feed is injected and second time is when the cold water is injected. The second time is unpredictable due to complex solid coke formation inside the drum, but the first one is controllable due to hot feed injection time. The main objective here is to explore effect of the hot feed injection time on thermal fatigue life of the junction. Four identical coke drums for dimensions and operating cycle time, named as A, B, C, and D, with cyclic period of 48 hours were taken into analyses. Temperatures operations and strains histories have been measured in every minute for a total of 145 cycles. FEM analyses were firstly performed to find the most severe location in the area of junction. The strains history and FEM results are used to calculate thermal fatigue life. The thermal fatigue life is calculated base on low cycle fatigue properties using engineering steels for high temperature components issued by National Institute for Materials Sciences (NIMS) in Japan. Number of cycle to fracture versus injection time for each coke drum is plotted. Best fitting is then used to develop equation of number of cycle to fracture as a function of the injection time. The results show that the injection time strongly affects the number of cycle to fracture. Although all coke drums are identical, every coke drum shows different operational characteristics. The averaged injection time for coke drum-A, B, C, and D are 449.1 minute, 430.6 minute, 526.9 minute, and 529.4 minute, respectively. If they are operated at their averaged injection time, the developed equations show that their operational life are 3155 cycles, 3086 cycles, 7979 cycles, and 5066 cycles, respectively. In the case of coke drum-A, for instance, by extension of the injection time of 1 minute, the expected additional number of cycles to fracture is estimated in order of 8.87 cycles.
Behavior of Plastic Collapse Moments for Pipes With Two Non-Aligned Flaws
Authors: Hasegawa Kunio , Miyazaki Katumasa , Saito Koichi
Published: January 2011

Alignment rules for multiple flaws vary between fitness-for-service procedures in different countries. In order to understand the behavior of alignment rules, quasi static failure bending tests have been performed on 2- and 4-inch diameter full-scale pipes with two similar flaws at ambient temperature. The pipe materials employed in the experiments were both ferritic and stainless steels. The two flaws are circumferential surface flaws situated inside the pipes. The non-aligned flaws are located in the circumferential distance S and axial distance H. The experiments showed that when the flaw shapes were short and deep, maximum loads occurred after the flaws had penetrated to the outer wall of the pipes. When the flaws were long and shallow, maximum loads occurred at the point when the flaws penetrated the outer wall of the pipe. With respect to the maximum loads under the condition of the same circumferential distance S, the maximum loads were found to increase with increasing axial distance H for short and deep flaws. However, the maximum loads were found to be unaffected by H for long and shallow flaws.
Shaping a Middle Surface of Dished Head of a Circular Cylindrical Pressure Vessel
Authors: Lewinski J. , Magnucki K.
Published: January 2011

The paper is devoted to a dished head of a pressure vessel subject to internal uniform pressure. A short survey of optimal design of a pressure vessel and its head is presented. The problem of shaping of middle surface of a dished head with the use of trigonometric series is depicted. As a criterion of the shaping process the continuity of curvatures of the surfaces in the joint of the circular cylindrical shell and the dished head is assumed. Results of the numerical calculation for optimal shapes of head are presented in figures.
Stability of Elastic Orthotropic Circular Cylindrical Vessels
Authors: Magnucki Krzysztof , Wittenbeck Leszek
Published: January 2011

This paper is devoted to stability investigation of orthotropic circular cylindrical vessels subjected to external pressure. An untypical orthotropic structure that consist of two layers: smooth-external and corrugated-internal is proposed. The investigation is divided into two steps. In first one analytical formulas describing buckling behaviour are derived. In second step numerical analysis is performed by using FEM to obtain the correlation between analytical and numerical results. Authors also considered linear and nonlinear buckling analysis. During the linear analysis the influence of vessel geometry on critical pressure is determined. Nonlinear analysis is carried out to create equilibrium paths which show the behaviour of vessels in post-buckling state. The results of the analysis are presented in figures.
An Economics-Based Intelligence (EI) Tool for Pressure Vessel and Piping (PVP) Failure Consequence Estimation
Authors: Chapman Robert E. , Fong Jeffrey T. , Butry David T. , Thomas Douglas S. , Filliben James J. , Heckert N. Alan
Published: January 2011

This paper is built around ASTM E 2506, Standard Guide for Developing a Cost-Effective Risk Mitigation Plan for New and Existing Constructed Facilities. E 2506 establishes a three-step protocol—perform risk assessment, specify combinations of risk mitigation strategies for evaluation, and perform economic evaluation—to insure that the decision maker is provided the requisite information to choose the most cost effective combination of risk mitigation strategies. Because decisions associated with low-probability, high-consequence events involve uncertainty both in terms of appropriate evaluation procedures and event-related measures of likelihood and consequence, NIST developed a Risk Mitigation Toolkit. This paper uses (a) a data center undergoing renovation for improved security, and (b) a PVP-related failure event to illustrate how to perform the E 2506 three-step protocol with particular emphasis on the third step—perform economic evaluation. The third step is built around the Cost-Effectiveness Tool for Capital Asset Protection (CET), which was developed by NIST. Version 4.0 of CET is used to analyze the security- or failure-related event with a focus on consequence estimation and consequence assessment via Monte Carlo techniques. CET 4.0 includes detailed analysis and reporting features designed to identify key cost drivers, measure their impacts, and deliver estimated consequence parameters with uncertainty bounds. Significance of this economics-based intelligence (EI) tool is presented and discussed for security- or failure-consequence estimation to risk assessment of failure of critical structures or components.
Investigation Into the Effect of Thread Root Condition on the High Cycle Fatigue Performance of a Metric Threaded Fastener
Authors: Munn Brian S. , Li Keyu
Published: January 2011

This paper presents an experimental investigation into the effect of thread root condition on the high cycle fatigue behavior of a tightened M12 metric fastener under a fully reversed, cyclic load. Two conditions were mechanically created at the fastener thread root. The first had an elastic condition with no localized plastic straining, and the second had localized plastic straining at the thread root. The elastic or plastic condition at the thread root was created by tightening the metric fastener into a fabricated steel joint at several different input or tightening torque levels prior to the application of a fully, reversed cyclic load. The fully reversed cyclic load was applied and a staircase methodology used in accordance to International Standard (ISO) 3800:1993(E). Fatigue results were also evaluated in conformance with (ISO) 3800:1993(E) to determine fatigue strengths at five million cycles. All fatigue tests were run at a rate of 50 Hz under a simple, sinusoidal wave form until either failure (rupture) or five-million cycles was attained and the test suspended. The fatigue strength values were then plotted on a graph of applied stress amplitude versus nominal mean stress level commonly referred to as a Modified Goodman diagram for bolted joints. The plotted fatigue strength data was not linear but displayed a knee or a bend. This knee or bend represents a transition point in the fatigue behavior of the threaded fastener. To describe the fatigue behavior, a bi-linear model has been applied. This bi-linear model is based on the local condition at the thread root. The knee represents a transition in condition from elastic to plastic behavior at the thread root. The result of this study shows that fastener fatigue behavior was influenced by the condition at the thread root.
Method for Generating Design Earthquake Time Histories With an Emphasis on Maintaining Phasing
Authors: Spears R. E.
Published: January 2011

A method has been developed which takes a seed earthquake time history and modifies it to produce a time-history with a given design response spectrum. It is a multistep process with an emphasis on maintaining phasing during the strong motion duration. Initially, the seed earthquake time history is broken into a series of separate time histories which added together produce the original time history. Each separate time history is drift corrected using modifications only outside the strong motion duration of the seed earthquake time history. This allows the separate time histories to be individually scaled to improve the response spectrum match while the phase of the motion during the strong motion duration remains unchanged. To further improve the design response spectrum match, low cycle, low energy waves are added. This is primarily to control the response at higher frequency. These waves are tuned to improve the response at existing peaks.
Failure Frequency Estimates for Boiling Water Reactor Pressure Vessels
Authors: Simonen F. A. , Gosselin S. R. , Rhoads J. E. , Chiang A. T.
Published: January 2011

This paper reviews estimates of rupture frequencies for reactor pressure vessels (RPV) at boiling water reactor (BWR) nuclear power plants as reported in the literature. Results permit improved probabilistic risk assessments (PRA) for severe accidents that could cause core damage and/or challenge the capabilities of BWR reactor containment systems. Current and historical estimates of failure frequencies are considered for light water reactors in general and more specifically for BWR plants. The focus is on large ruptures that could give flow rates exceeding the rates associated with double ended breaks of large diameter recirculation piping. Rupture frequencies for BWR vessels as used for PRA evaluations have historically been assigned low values (e.g. 10−7 to 10−6 per vessel per year). The objective of the present work was to establish possible technical bases for more realistic values of rupture frequency (i.e. 10−8). Historical estimates from the early WASH-1400 reactor safety study were first reviewed and used as a point-of-reference. More recent estimates came from various sources such as a U.S. Nuclear Regulatory Commission expert elicitation process that estimated Loss-of-Coolant Accident (LOCA) frequencies. Other studies both by industry and by the USNRC have addressed rupture frequencies for BWR vessels subject to low-temperature-over-pressure (LTOP) events. On the other hand, recent comprehensive evaluations have focused mostly on RPV failure frequencies for pressurized water reactors (PWRs) caused by pressurized thermal shock events. An important consideration was that rupture frequencies for BWR vessels are believed to be lower than those for PWR vessels, because BWR vessels are less embrittled than PWR vessels and are subject to less severe thermal transients. The review concludes that prior studies support an estimate of 10−8 or less for BWR vessel rupture frequencies. Probabilistic fracture mechanics calculations for individual vessels accounting for plant specific conditions are recommended to support even lower estimated frequencies. Use of more realistic vessel rupture frequencies in a plant’s PRA provides an improvement in not only the perceived plants risk of core damage, but also provides better decision making for plant operation and maintenance activities in that a conservative initiating event treatment within a PRA can mask other initiating events of higher importance.
A New Approach to Elastodynamic Response of Cylindrical Shell Based on Generalized Solution Structure Theorem for Wave Equation
Authors: Xu Shugen , Wang Weiqiang , Liu Yan
Published: January 2011

In this paper, a generalized solution structure theorem has been provided. It can be use to solve the wave equation about the structural response of cylinder under the dynamic pressure. This new approach also can be used to solve a batch of partial differential equations with the similar form. A detailed derivation process has been given to show how the solution is obtained. Finally, a practical example is presented, and all the elastodynamic response data at any point during dynamic pressure can be acquired conveniently.
Numerical Simulation of Fatigue Crack Propagation in Round Bar Using S-FEM and Experimental Verification
Authors: Maitireyimu Maigefeireti , Kikuchi Masanori , Geni Mamtimin
Published: January 2011

In this paper, a methodology for a three-dimensional simulation of fatigue crack growth behavior in a round bar is presented. This method is based on linear elastic fracture mechanics and S-version FEM (S-FEM) is employed for numerical analysis. Plasticity induced crack closure effect is considered by integrating a crack opening model into simulation method. This crack opening model is obtained from a result of a cyclic elastic-plastic finite element analysis. The accuracy of the solution for stress intensity factor (SIF) is checked by comparing with the available solutions in literature. For verification, experiments are conducted on round bars with single cracks and two cracks. A simulation of single crack propagation is conducted and the crack shape change prediction is compared with the experimental result. Two cracks problem is qualitatively investigated by experiments. In simulation, the shape change and SIF are shown. Results give acceptable predictions comparing to Experimental results. It is notable that the behavior of two cracks on the different plane can be easily simulated. The interaction of two cracks is discussed.
Development of LBB Assessment Method for Japanese Sodium Cooled Fast Reactor (JSFR) Pipes: 2—Crack Opening Displacement Assessment of Thin Wall Pipes Made of Modified 9Cr-1Mo Steel
Authors: Wakai Takashi , Machida Hideo , Arakawa Manabu , Enuma Yasuhiro , Asayama Tai
Published: January 2011

This paper presents crack opening displacement (COD) evaluation methods used in leak before break (LBB) assessment of sodium piping system in the Japanese sodium cooled fast reactor (JSFR). Thin wall and low work hardening material are features of piping of JSFR. Detectability of coolant sodium is very high, the target leak detection performance of leak detector of JSFR is 100g/hr. Internal pressure of JSFR piping is very low, and large through wall crack is allowable to satisfy LBB condition. The existing COD evaluation method cannot be applied to the piping of JSFR which has above-mentioned features. Finite element analysis (FEA) were performed to evaluate COD for thin wall and low work hardening material piping with a circumferential through wall crack. These analytical results were arranged into engineering evaluation formulae. Proposed method gives high accuracy COD estimation, and is applicable to LBB assessment of JSFR piping.
Improvement of Flange Tightening Method for Small Bore Low Rating Bolted Flanges
Authors: Mori Masako , Nebu Akira , Kanno Takashi
Published: January 2011

An appropriate flange tightening methods for small bore and low rating piping flange joints are discussed to improve the sealing performance of the bolted flange joints and the workability of flange tightening work. The lubricant on the thread of the bolts and the nut-seating surface can minimize the variability of axial force acting on flange bolts, however this process might make it harder to tight the bolts uniformly especially for small bore low rating flanges. In this paper the appropriate condition to apply lubricant is clarified by a series of bolt tightening tests and sealing tests results. On the other hand, for the bolted flanges using spiral wound gaskets, measuring the gasket compressed dimensions help us to prevent uneven tightening balance and to perform the appropriate tightening work. Appropriate gasket compressed dimensions are also clarified to ensure the sealing performance for the flanges based on the sealing tests results. Based on these test results, recommended flange-tightening methods have been summarized as an instruction in tightening work procedure to improve the sealing performance of the bolted flanges and the workability of flange tightening work.
Stress Analysis of Miter Joint in Pipeline Under Internal Pressure or In-Plane Bending Loading
Authors: Zhu Xian-Kui , Leis Brian N. , Feier Ioan I.
Published: January 2011

This paper presents an elastic stress analysis for miter joints in a pipeline under internal pressure or in-plane bending. Using the three-dimensional theory of elasticity, Green and Emmerson [1] obtained two general expressions of hoop and axial stresses for a mitered pipe, and two specific solutions at the plane of joint for the loading cases of internal pressure and in-plane bending. However, their solution of axial stress for bending case is incorrect, and the stress variations with the pipe axis are not provided. Based on their general expressions, the closed-form solutions of hoop and axial stresses are obtained as functions of the radial location r, the circumferential angle θ, and the half miter angle α, in addition to the applied loading, geometry and material parameters. From these results, the solutions of hoop and normal stresses are obtained at the plane of joint for the two loading scenarios. The proposed theoretical solutions are then validated by three-dimensional finite element results, respectively for elastic loading cases of internal pressure and in-plane bending. The comparison shows that all proposed theoretical solutions of hoop and axial stresses at the plane of joint and in the pipe are in good agreement with the finite element results for both loading cases. The stress analysis shows that the maximum tensile stresses occur on the outside surface at the intrados for the two loading cases, the maximum stresses increase with increasing miter angle, and the axial effect of miter joint stresses on a pipe is limited to length scales in a fraction of the pipe diameter.
Incorporation of Strain Hardening Effect Into Limit Load Analysis
Authors: Gudimetla P. S. Reddy , Adibi-Asl R. , Seshadri R.
Published: January 2011

In this paper a novel method for finding out limit loads in the components or structures by incorporating strain hardening effects is presented. This has been done by including certain amount of the strain hardening into limit load analysis, which normally idealizes the material to be perfectly plastic. The typical strain hardening curves including bilinear hardening and Ramberg-Osgood material models are investigated. The paper also concentrates on plastic reference volume correction concept to find the active volume participating in plastic collapse. The reference volume concept in combination with mα-Tangent method is used to estimate the lower bound limit load of different components.
Effects of Torsion on Equivalent Bending Moment for Limit Load and EPFM Circumferential Pipe Flaw Evaluations
Authors: Hoang Phuong H. , Hasegawa Kunio , Bezensek Bostjan , Li Yinsheng
Published: January 2011

The circumferential flaw evaluation procedures in ASME Boiler and Pressure Vessel Code, Section XI non-mandatory Appendix C are currently limited to straight pipes under pressure and bending loads without consideration of torsion loading. The Working Group on Pipe Flaw Evaluation of the ASME Boiler and Pressure Vessel Code is developing guidance for considering the effects of torsion by a mean of an equivalent bending moment, which is a square root of sum square (SRSS) combination of bending moment and torsion load with a weighted factor for torsion moment. A torsion weighted factor for, Ce is established in this paper using large strain finite element limit load analysis with elastic-perfectly plastic materials. Planar flaws and non-planar flaws in a 10.75 inch OD pipe are investigated. Additionally, a finite element J-integral calculation is performed for a planar through wall circumferential flaw with elastic plastic materials subjected to bending and torsion load combinations. The proposed Ce factor for planar flaws is intended for use with the ASME B&PV Section XI, Appendix C for limit load and EPFM circumferential planar flaw evaluations.
A Comparative Study on Elastic Behavior of Trefoil Patterned Perforated Plate
Authors: Cho Min-Ki , Ha Chang-Hoon , Kim Moo-Yong , Lee Sang-Cheol , Koo Jea-Mean , Seok Chang-Sung
Published: January 2011

A tube support plate is one of the significant parts of a steam generator, which confines the rotational and translational motion of tubes caused by the hydraulic and seismic load. It also provides a flow path along the tubes. There are various types of tube support plates according to the component designer’s preference. In this investigation, ten types of trefoil Broached Tube Support Plate (BTSP) specimens made from ASME stainless steel were analyzed and tested to determine the appropriate shape of trefoil BTSP in the view of the elastic properties including elastic modulus and Poisson’s ratio. The types of trefoil BTSP specimens were designated as SI through S5 and L1 through L5 for S and L types, respectively. These specimens are categorized by the shape and dimension of broached hole. Ten specimens were investigated through finite element analysis, and compression and bending tests. The dimensions of the test specimens were decided through a previous research study done to examine appropriate shape for the compression and bending tests. The equivalent elastic properties of BTSP were obtained by the finite element analysis as per different loading orientation as well as the various specimen types. Autodesk® Inventor™ software was used to make the analytical model and ABAQUS® software was used for the analysis and post-processing. The equivalent elastic properties of BTSP specimens were also acquired by the compression and bending tests. From the results of the finite element analysis, and the compression and bending tests, the appropriate shapes of trefoil BTSP with regard to the equivalent elastic modulus, and Poisson’s ratio are suggested as L4, S3, and S4.
A Bolt-Nut Loosening Mechanism in Bolted Connections Under Repeated Transverse Loadings (Effect of Inclined Bearing Surfaces on the Loosening)
Authors: Sawa Toshiyuki , Ishimura Mitsutoshi , Karami Atsushi
Published: January 2011

Loosening accidents sometimes occur under several types of loadings such as winds, vibrations, earthquakes, impact loads and thermal changes. Recently, some studies have been conducted on the screw thread loosening in bolted joints under repeated transverse loadings. It is well known that bolted joints are easily loosened when repeated transverse loadings are applied. While, in assembling bolted joints, the contact surfaces between a bolt head/nut and a clamped part are inclined geometrically. However, a lot of researches have dealt with the bolted joints in which the bearing surfaces are perfectly contacted without the inclined surfaces. Thus, it is necessary to examine the incline of the bearing surfaces on the loosening in bolted joint. A lot of parts for preventing the loosening have been proposed and sold at market. Among these parts, the authors have demonstrated that eccentric nuts are especially expected to be the solution for preventing the loosening of the joints under repeated transverse loadings. However, a few studies have been carried out on the loosening and loosening mechanism in bolted joints with inclined bearing surface and the effective solution for preventing loosening of bolted joint with the inclined bearing surfaces under the repeated transverse loadings. Thus, it is necessary to examine the effect of the incline at the bearing surfaces on the loosening and to evaluate the solutions for preventing loosening of the bolted joints with the inclined bearing surfaces. In this study, the effect of the incline at the bearing surfaces on the loosening is examined using FEM calculations. In the FEM calculations, the incline angle at the bearing surfaces is changed as 0, 2 and 3 degree, respectively. The experiments to measure the loosening in bolted joints were carried out using Junker’s testing machine to validities of the FEM calculations for revealing the effect of the loosening in the joints with the inclined bearing surfaces. In addition, nut parts for preventing the loosening in bolted connections with the inclined bearing surface under repeated transverse loadings are examined using the FEM calculations. As the result, it is seen that the loosening increases as the angle of incline increases. In addition, it is observed that bolted joints in which almost nut parts for preventing loosening are applied are loosened easily while the eccentric nut does not loosened. Discussion is made on the loosening mechanism in bolted joints under repeated transverse loadings.
Computational Comparisons of Homogeneous and Statistical Descriptions of Steel Subjected to Explosive Loading
Authors: Hopson Michael V. , Lambert David E. , Weiderhold Joseph
Published: January 2011

Experiments were conducted by the Munitions Directorate at the Air Force Research Laboratory to investigate the fracture and fragmentation of two different metals due to explosive loading. The first metal, Eglin Steel 1 (ES-1), was a high strength steel alloy configured as a thin shell surrounding the explosive core. The second metal, Aero 224, was a tungsten alloy configured as a stack of rings around the explosive core. The two different configurations generated two different stress states, plane-strain and uniaxial stress. The radial expansion velocity of the ES-1 shell was recorded via a photonic Doppler velocimeter (PDV). Also, the fragments from the ES-1 shell test and Aero 224 ring test were soft captured in a water tank. Complimentary computational analysis was conducted at the Naval Surface Warfare Center Dahlgren Division. The Eulerian wave propagation code, CTH, was used to analyze the stress states of the different configurations and also investigate the use of statistical compensation on explosive fragmentation. The stress states were examined in the context of stress triaxiality where triaxiality is defined as the ratio of pressure to the Von Mises stress. From the computational analysis both the ES-1 shell test and Aero 224 ring test approached, but did not reach the ideal triaxial values for plane-strain and uniaxial stress. Lastly, parametric calculations were conducted in order to determine the effectiveness of using a statistically compensated Johnson Cook fracture model to simulate the non-homogeneous nature of the ES-1 and Aero 224. While using the model did result in different fragment distributions, all the resulting distributions were less accurate than the baseline homogeneous calculation. Scrutiny of the early time fragment formation in the statistically compensated calculations revealed a mesh bias which caused material failure on surfaces parallel to the Cartesian axes. This preferential fracture produced rarefaction waves which prohibited further fragmentation thus generating fragment distributions larger than those observed in the Aero 224 ring test. Potential solutions for this issue will be explored in the future.
Analysis of JNES Seismic Tests on Degraded Piping
Authors: Zhang Tao , Brust Frederic W. , Wilkowski Gery , Shim Do-Jun , Nie Jinsuo , Hofmayer Charles H. , Ali Syed A.
Published: January 2011

Nuclear power plant safety under seismic conditions is an important consideration. The piping systems may have some defects caused by fatigue, stress corrosion cracking, etc., in aged plants. These cracks may not only affect the seismic response, but may also grow and break through causing loss of coolant. Therefore, an evaluation method needs to be developed to predict crack growth behavior under seismic excitation. This paper describes efforts conducted to analyze and better understand a series of degraded pipe tests under seismic loading that was conducted by Japan Nuclear Energy Safety Organization (JNES). A special “cracked-pipe element” (CPE) concept, where the element represented the global moment-rotation response due to the crack, was developed. This approach was developed to simplify the dynamic finite element analysis. In this paper, model validation was conducted by comparisons with a series of pipe tests with circumferential through-wall and surface cracks under different excitation conditions. These analyses showed that reasonably accurate predictions could be made using the ABAQUS connector element to model the complete transition of a circumferential surface crack to a through-wall crack under cyclic dynamic loading. The JNES combined-component test was analyzed in detail. The combined-component test had three crack locations and multiple applied simulated-seismic block loadings. Comparisons were also made between the ABAQUS FE analyses results to the measured displacements in the experiment. Good agreement was obtained and it was confirmed that the simplified modeling is applicable to a seismic analysis for a cracked pipe on the basis of fracture mechanics. Pipe system leakage did occur in the JNES tests. The analytical predictions using the CPE approach did not predict leakage, suggesting that cyclic ductile tearing with large-scale plasticity was not the crack growth mode for the acceleration excitations considered here. Hence, the leakage was caused by low-cycle fatigue with small-scale yielding. The procedure used to make predictions of low-cycle fatigue crack growth with small-scale yielding was based on the Dowling ΔJ procedure, which is an extension of linear-elastic fatigue crack growth methodology into the nonlinear plasticity regime. The predicted moments from the CPE approach were used using a cycle-by-cycle crack growth procedure. The predictions compare quite well with the experimental measurements.
Fatigue Modelling of a Notched Geometry Under Variable Amplitude Loading Supported on Elastoplastic FEM Analyses
Authors: Pereira He´lder F. S. G. , De Jesus Abi´lio M. P. , Ribeiro Alfredo S. , Fernandes Anto´nio A.
Published: January 2011

Despite intensive research has been carried out to understand the fatigue behavior of steel notched geometries, under variable amplitude loading, no definite and general robust models have been derived so far. Therefore, any effort to increment the knowledge in the topic is welcome. Within this premise, it is proposed an assessment of existing variable amplitude data, which has been derived by authors for a notched geometry, made from a low carbon pressure vessel steel (P355NL1), within the local approaches and linear damage summation framework, and supported by elastoplastic finite element analyses. Several variable amplitude loading are selected and analyzed using alternative configurations of kinematic hardening plasticity models (e.g. Chaboche’s model with distinct constants superposition). The predictions are assessed using available experimental data as well as with predictions made with simplified empiric elastoplastic tools. This paper highlights the difficulties on performing such elastoplastic analysis and compares the obtained results with those obtained using more classical tools for elastoplastic analysis. Fatigue predictions based on elastoplastic analysis made using the Chaboche’s model, with a finite element model, were significantly more accurate than predictions based on simplified elastoplastic analysis. The proposed information has important practical relevance.
Probabilistic Seismic Soil Structure Interaction Analysis of the Mu¨hleberg Nuclear Power Plant Reactor and SUSAN Buildings
Authors: Nakaki David K. , Hashimoto Philip S. , Johnson James J. , Bayraktarli Yahya , Zuchuat Olivier
Published: January 2011

Probabilistic seismic soil-structure interaction (SSI) analysis was performed for the Mu¨hleberg Nuclear Power Plant Reactor and SUSAN Buildings in support of the seismic probabilistic saftety assessment of the plant. An efficient hybrid method, employing computer programs SASSI2000 and CLASSI presented in a companion paper, was used in this analysis. The method takes advantage of the capability of SASSI2000 to analyze embedded structures with irregular geometry and the computational efficiency of CLASSI to rapidly perform the SSI response analysis of large structure models. Fixed base finite element models of the buildings were first developed from which the structure geometry, nodal masses, natural frequencies, and mode shapes were extracted. The structure embedments were modeled using SASSI2000. Impedance functions and scattering vectors were calculated by imposing rigid body constraints to the embedded foundation. The fixed base structure dynamic properties and the foundation impedances and scattering functions were input to CLASSI to perform the response analysis. The probabilistic analysis was performed following the Latin Hypercube Simulation (LHS) approach documented in NUREG/CR-2015. Variables defined by probability distributions were sampled according to a stratified sampling approach. The combination of the parameters for each simulation was determined by Latin Hypercube experimental design. Variables in the LHS included the earthquake ground acceleration time histories, structure stiffness and damping, and soil stiffness and damping. Thirty response simulations were performed using CLASSI in which the variable values were randomly selected. The use of CLASSI has the advantage that the response analysis simulations can be executed in a fraction of the time that would be required with SASSI2000 alone. For each simulation, in-structure response spectra (ISRS) were calculated at selected locations in the buildings. Probabilistic distributions, described by the median and 84th percentile response spectra, were calculated from the thirty simulations. The probabilistic ISRS are subsequently used in the seismic fragility evaluations of selected essential equipment.