bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analytical Method for Estimating Welding-Induced Plastic Zone Size for Residual Stress Profile Development
Authors: Pei Xianjun , Song Shaopin , Dong Pingsha
Published: November 2015

As demonstrated in a recent comprehensive study on construction of full-field residual stress profiles for fitness-for-service assessment of pressure vessel and piping components, a reasonable estimate of welding-induced plastic zone size is necessary for introducing a shell theory based solution form (Song et al, 2015 [1–2]). This paper presents an analytical method for estimating plastic zone size by first solving an equivalent one dimensional heat transfer problem in which weld zone is represented by a line segment with initial temperature at melting. Thermoplasticity conditions are then imposed by assuming elastic perfectly plastic behaviors. Finally, an analytical expression is obtained to relate plastic zone boundary to maximum temperature field distribution experienced by material points within the whole domain over the entire heating and cooling history. The solution can be further expressed by a rather simple form with the identification of a characteristic length parameter that signifies inflection point of temperature distribution. So estimated plastic zone sizes for various welded joint types have been compared with finite element residual stress analysis results in which sequentially coupled welding heat transfer and thermo-mechanical analysis procedures are used. A good agreement has been achieved for all cases analyzed.

Compared with conventional finite element residual stress analysis procedures, this method offers significant simplicity and efficiency, while being reasonably accurate, particularly for applications in residual stress profile estimation and in evaluation of welding induced distortions in complex structures.
Effects of Seat Width on Development of Adhesions in Stainless Steel Trim Spring Operated Pressure Relief Valves
Authors: Bukowski Julia V. , Gross Robert E. , Goble William M. , Harris Stephen P.
Published: November 2015

Previous research has shown that stainless steel (SS) adhesions form in about half of new SS trim spring operated pressure relief valves (SOPRV). These adhesions require an additional force (beyond the spring force) to be applied by the process fluid to the disc in order for the valve to lift. This additional force may cause the SOPRV to fail its proof test (FPT) or even to fail to open (FTO) in the presence of excess process pressure. This paper expands on the previous findings to show how seat width relates statistically to whether or not these SS adhesions form and, if they do, whether or not they are of sufficient size to cause FPT or FTO.

The findings show it is statistically significant that SOPRV in the study population with seat widths greater than 0.030 inches (in.) formed adhesions more often than SOPRV with seat widths less than or equal to 0.030 in. Furthermore, for this population it is statistically significant that all FPT and FTO occurred on SOPRV with seat widths greater than or equal to 0.030 in. The ramifications of these findings to the safety performance of SS trim SOPRV are discussed.
Initial Investigation on the Effect of Bolt Loading Rate on the Need to Re-Torque PTFE Gaskets in Bolted Flanged Connections
Authors: Clarke Mandi M. , Grant Kenneth R. , Waterland A. Fitzgerald (Jerry)
Published: November 2015

Industry practice dictates that there is a minimum level of assembly stress to obtain gasketed joint tightness. In addition to the initial stress placed upon the gasket, it is maintained that a re-torque is often necessary with PTFE based gaskets to insure proper operating stress levels on the joint and gasket material system. This paper and research will explore the effect of bolt loading and flange assembly rate in bolted flanged connections utilizing PTFE gaskets.
Comparison of Methods for Evaluation of Crack Growth at Welds in Offshore Risers
Authors: Yin Fengjie , Cerkovnik Mark , Akhtar Wasy , Yang Tracy
Published: November 2015

In checking the fitness of fatigue critical welded structure, the stress concentration at the weld due to the weld geometry needs to be considered. Where fatigue is assessed using crack growth methodology, two approaches are commonly used. In the offshore industry in regions where BS 7910 [1] is followed, the effect of weld geometry is assessed using the Mk factor approach. The Mk factor directly magnifies the stress intensity. Mk factor solutions are available for T-butt weld joints from the British Standard BS7910.

Alternatively, API579 [2] offers stress intensity solutions that can account for the stress profile through the wall thickness of the pipe. In using this method, the engineer will use an FEA program to find the stress profile for use as an input for the stress intensity factor computation. Since the goal is the assessment of crack growth, the stress profile must represent the cyclic changes in stress. Further, a histogram of such profiles is required.

While the Mk factor approach of BS7910 offers the easier path by supplying factors for pre-solved geometries, the API approach offers an opportunity to refine the solution by conducting relatively simple linear FEA of the un-cracked component. This study compares the two approaches using an example taken from offshore riser fatigue analysis.
Simulation and Measurement of a Nonlinear Hydrodynamic Sloshing Force on a Rectangular Tank With Shallow Water Depth
Authors: Hara Kensuke , Watanabe Masahiro
Published: November 2015

This paper deals with a hydrodynamic sloshing force on a rectangular tank. In particular, we focus on a contribution of the nonlinear sloshing in shallow water depth to the hydrodynamic force. It is well known that the water wave in shallow water depth shows the characteristic behaviors such as the solitary wave by inherent nonlinearities. Therefore, the effect of nonlinearity is crucial for the estimation of the hydrodynamic sloshing force. Although these behaviors arises from the typical feature of the sloshing in shallow water depth, the theoretical analysis is essentially difficult because a lot of higher order nonlinear terms and eigenmodes have to be taken into account for accurate numerical predictions. Consequently, it yields complicated algebraic procedures. This study presents a formulation based on the Hamiltonian dynamics. In addition, the Dirichlet-Neumann operators (DNO) developed by Craig and Sulem was introduced to obtain an asymptotic description for the kinematic boundary condition of the liquid surface. The proposed approach facilitates the consideration of the nonlinearity for the formulation. Moreover, experiments were conducted to measure time histories of the wave height and the nonlinear fluid force due to the sloshing in a rectangular tank subjected to a horizontal excitation. As the results of frequency analyses for the time histories of the hydrodynamic force, many frequency spectra with the odd multiple of the dominant frequency were observed. These features were also obtained by the theoretical predictions by the proposed method.
High-Temperature Deformation Constitutive Law for Dissimilar Weld Residual Stress Modeling: Effect of Thermal Load on Strain Hardening
Authors: Yu Xinghua , Crooker Paul , Wang Yanli , Feng Zhili
Published: November 2015

Weld residual stress is one of the primary driving forces for primary water stress corrosion cracking in dissimilar metal welds (DMWs). To mitigate tensile residual stress in DMWs, it is critical to understand residual stress distribution by modeling techniques. Recent studies have shown that weld residual stress prediction using today’s DMW residual stress models strongly depends on the strain-hardening constitutive model chosen. The commonly used strain-hardening models (isotropic, kinematic, and mixed) are all time-independent and inadequate to account for the time-dependent (viscous) plastic deformation at the elevated temperatures experienced during welding. For materials with profound strain-hardening, such as stainless steels and nickel-based alloys that are widely used in nuclear reactor and piping systems, the equivalent plastic strain — the determinate factor of the flow stress — can be highly dependent on the recovery and recrystallization processes. These processes are in turn a strong function of temperature, time, and deformation rate. Recently, the authors proposed a new temperature- and time-dependent strain-hardening constitutive model: the dynamic strain-hardening constitutive model. The application of such a model has resulted in improved weld residual stress prediction compared to the residual stress measurement results from the contour and deep-hole drilling methods. In this study, the dynamic strain-hardening behavior of Type 304 stainless steel and Alloy 82 used in pressure vessel nozzle DMWs is experimentally determined. The kinetics of the recovery and recrystallization of flow stress are derived from experiments, resulting in a semi-empirical equation as a function of pre-strain, time, and temperature that can be used for weld residual stress modeling. The method used in this work also provides an approach to study the kinetics of recovery and recrystallization of other materials with significant strain-hardening.
Overview of Revisions to the ASME Boiler and Pressure Vessel Code Section VIII Division 3 for the 2015 Edition and Near Future
Authors: Peters Daniel , Maslowski Adam P.
Published: November 2015

This paper is to give an overview of the major revisions pending in the upcoming 2015 edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Section VIII Division 3, Alternative Rules for Construction of High Pressure Vessels, and potential changes being considered by the Subgroup on High Pressure Vessels (SG-HPV) for future editions. This will include an overview of significant actions which will be included in the upcoming edition. This includes action relative to test locations in large and complex forgings, in response to a report from the U.S. Chemical Safety and Hazard Investigation Board (CSB) report of a failed vessel in Illinois. This will also include discussion of a long term issue recently completed on certification of rupture disk devices. Also included will be a discussion of a slight shift in philosophy which has resulted in the linear-elastic stress analysis section being moved to a Non-Mandatory Appendix and discussion of potential future of linear-elastic stress analysis in high pressure vessel design.
Comparison of Different Thermal Aging Models to Assess Fully Aged Toughness in Cast Austenitic Stainless Steels
Authors: Uddin M. F. , Wilkowski G. M. , Kurth R. E. , Brust F. W. , Shim D.-J. , Rudland D.
Published: November 2015

Thermal embrittlement of cast austenitic stainless steels (CASS) occurs at reactor operating temperatures during the reactor design lifetime of 40 years leading to a reduction in their toughness and an increase in strength. Additionally most US nuclear plants have been given plant life extensions for 60-year operation, and consideration of further extension to 80 years is underway. As the fracture toughness reduces due to thermal embrittlement, some aged CASS materials have the potential to have exceedingly low toughness. CASS can also show high toughness variability due to the variability of its microstructure. Recently an ASME Section XI Code Case N-838 has been proposed to evaluate the flaw tolerance based on probabilistic fracture mechanics (PFM). An assessment of mechanical-property degradation is an input to perform the flaw evaluation procedure in CASS components. There are at least four different models for predicting the change in J-R curves in CASS due to thermal aging. One model is proprietary and the other three are the Argonne/NUREG-CR/4513R1, the French/EDF and a Japanese model.

In this work, two of the thermal aging models were reviewed, reproduced and validated against their example cases for each individual model. Both models were then utilized to assess the fully aged conditions for cases that covers a large spectrum of CASS J R curves with high COV (coefficient of variance). Finally, J-R curves distributions using both Argonne and French models were established by examining the actual chemical compositions of CASS materials found in some US PWR plants. The J-R curves distributions include 21 pipes/fittings in primary pipe loop as well as data from an EPRI report. The calculated toughness variability in a single LBB plant is compared using the Argonne and French models. Additionally the relationship of the “C” and “m” parameters used in the power-law J-R curve equations (J = C×Δam) was explored to determine the proper way to statistically vary the J-R curve in probabilistic analyses.
Bounding Residual Stress Intensity Factor Profiles for Fracture Assessment of Pipe Girth Welds
Authors: Bouchard P. John , Mathew Jino
Published: November 2015

The effect of residual stress on potential crack growth and fracture in welded structures is usually assessed through its contribution to the stress intensity factor (SIF) for the crack size and shape of interest. The idea of defining bounding residual SIF profiles for surface breaking circumferential cracks in pipe butt welds was presented at ASME PVP2013. The limiting profiles were based on through-thickness residual stress measurements for eight pipe girth welds. This paper presents new axial residual stress measurements made using the contour method for an Esshete 1250 stainless steel pipe girth weld. A wide variation in the through-wall distribution of axial residual stress around the circumference of the pipe is observed which has a significant effect on calculated values of SIF for postulated surface breaking circumferential cracks. Nonetheless, SIFs based on all of the new measurements (a total of 14 profiles) are comfortably bounded by the simple SIF prescriptions previously published.
Determination of High-Temperature Creep Property of High-Cr Steel Based Upon Indentation Test
Authors: Arai Masayuki , Ishikawa Takahiro , Takahashi Yukio , Kumagai Tomohisa
Published: November 2015

In this paper, the procedure which can estimate creep exponent and coefficient in Norton’s law from the impression size rather than the penetration depth is discussed based upon a high-temperature creep indentation test. Firstly, an analytical solution related to the change in impression size with dwelling time at an indentation load is formulated by solving problem of infinite creeping media embedding spherical cavity subjected to an inner pressure which characterizes an indentation load. The applicability of the formula to elastic-plastic-creeping model resembling an actual response is checked by conducting non-linear finite-element analysis combined with contact option. Finally, creep indentation tests are conducted for a high-Cr ferritic heat-resisting steel. It is shown that the creep parameters at a lower stress level can be estimated at temperature 873K.
Fatigue Crack Initiation and Growth Observation for 316 Stainless Steel Subjected to Equi-Biaxial Cyclic Loading
Authors: Iida Satoshi , Abe Shigeki , Nakamura Takao , Kamaya Masayuki
Published: November 2015

Fatigue accumulation is one of the ageing phenomena considered in the plant design and maintenance. The degree of fatigue damage is evaluated by cumulative usage factor using design fatigue curve, which is determined from results of uniaxial fatigue tests. The stress caused by thermal transients is generally equibiaxial, not uniaxial. Fluid temperature fluctuation due to changes in plant conditions, such as plant start-up and shutdown, is the primary cause of fatigue damage. For accurate fatigue damage evaluation, it is important to be conducted under equi-biaxial condition.

In this study, pressurized disc fatigue test was conducted in order to simulate the cyclic equi-biaxial stress. In order to clarify how the crack initiates and grows under the equi-biaxial stress condition. Cracking behavior was examined by replica observation method. The crack growth rates were identified by the change in the crack length. It was shown that the fatigue crack growth rate under equi-biaxial stress was faster than that under uniaxial stress for the same equivalent stress intensify factor. It was concluded that the reduction in the fatigue life under equi-biaxial stress was brought about by the accelerated crack growth.
European Design Rules for Tubesheets
Authors: Lidonnici Fernando , Site Corrado Delle
Published: November 2015

Tubesheets are usually designed according to different national or international design codes. The great majority of these standards is based on Gardner’s theory, elaborated more than 60 years ago. On the other hand these pressure components are critical in heat exchanger design, because they are subject to characteristic service damages which require a correct dimensioning and appropriate inspections during service.

This paper is aimed at comparing the different design methods, analyzing the theoretical background behind the rules.

Main focus is made to the alternative design method contained in Annex J of the European Standard EN13445-3.

With reference to the typical configuration of a fixed tubesheet exchanger with flanged connections, the results of the different design approaches are compared in order to find out the optimal configuration.

Benchmark examples are carried out using a commercial computer code with reference to heat exchangers with the tubesheets welded to the shell and bolted to the channel.

The results show the advantage of using Annex J which allows smaller thicknesses of the tubesheet in respect of the conventional approach used by TEMA, ASME Section VIII and EN 13445-3 clause 13.
Predicting the Creep Rupture Behavior of Austenitic Steel Using Finite Element Analysis
Authors: Hamelin Cory J. , Payten Warwick M.
Published: November 2015

The creep behavior of structural materials is often measured using uniaxial tension creep rupture tests. Unfortunately, the time required for austenitic steel samples to rupture under ideal (i.e. elastic stress) conditions is prohibitive. To accelerate creep rupture in these samples, a tensile stress in excess of the material yield strength is often applied and the post-load deformation is assumed to be largely creep-based. There is currently no method of measuring the creep deformation separately from the yield-induced plastic flow that may occur during such accelerated tests.

Using validated finite element models, the effects of creep and yield-induced plastic strain have been decoupled for a series of accelerated creep tests using 316H austenitic steel. The influence of continued yielding after the initial sample loading was predicted to be significant, which suggests the diffuse necking in the samples due to creep is responsible for stress intensification and further yield through the tests. These results suggest the initial plastic loading in accelerated creep tests may significantly influence the measured creep rupture time in these samples.
Shakedown and Ratcheting in ASME B&PV Code
Authors: Adibi-Asl R. , Reinhardt Wolf
Published: November 2015

Design by analysis rules for pressure vessels and piping such as those contained in the ASME B&PV Code, Section III NB or Section VIII Div. 2, provide requirements to avoid a ratcheting condition under cyclic loading. This paper reviews and compares various related provisions for elastic analysis in Section III NB or Section VIII Div. 2 of the ASME B&PV and compares with other standards, such as the RCC-MR Code. The paper provides recommendations on how the specified requirements should be considered and also discusses cases that need to be addressed in the code.
Assessment of the Temperature Dependence of Ferritic Steel Fracture Toughness on or Near the Lower Shelf
Authors: Kirk Mark , Erickson Marjorie
Published: November 2015

Within the American Society of Mechanical Engineers (ASME) the Section XI Working Group on Flaw Evaluation (WGFE) is currently working to develop a revision to Code Case N-830. This revision incorporates a complete and self-consistent suite of models that describe completely the temperature dependence, scatter, and interdependencies between all the fracture metrics (i.e., KJc, KIa, JIc, J0.1, and J-R) from the lower shelf through the upper shelf. A paper presented at the 2014 ASME Pressure Vessel and Piping Conference described most of these models; a companion paper at this conference describes the J-R model. This paper also supports the WGFE effort by performing an assessment of the appropriateness of Wallin’s Master Curve model to represent toughness data on the lower shelf, and by comparing the Master Curve with the current Code KIc curve on the lower shelf.

The work presented in this paper supports the following conclusions:

1. The Master Curve provides a reasonable representation of cleavage fracture toughness (KJc) data at lower shelf temperatures. A statistical evaluation of a large database demonstrates that the Master Curve works well to temperatures approximately 140 °C below To or, equivalently, approximately 160 °C below RTTo.

2. The percentile of cleavage fracture toughness data falling below a KIc curve indexed to RTTo varies considerably with temperature. At lower shelf temperatures as much as half of the data lie below the KIc curve, while at temperatures close to RTTo this percentage falls to approximately ≈ 1.5%. The current guidance of Nonmandatory Appendix A to Section XI to use structural factors of √10 or √2 is one means of addressing this inconsistency.

3. The inconsistent degree to which the KIc curve, with or without structural factors, bounds fracture toughness data cannot be fixed within the current Code framework for two reasons: the KIc curve does not reflect the actual temperature dependence shown by the fracture toughness of ferritic RPV steels, and the ratio of a mean or median toughness curve to a fixed percentile bound is not a constant value. It is for these reasons that in the next revision of Code Case N-830 the ASME WGFE is moving away from use of the KIc curve coupled with structural factors and, instead, is adopting models of fracture toughness that represent both the temperature trends and the scatter in the data with high accuracy.
Development of a New Type of Maintenance Management System Based on Reliability for Rotating Equipments in Typical Petrochemical Plant
Authors: Li Xiang , Jia Guodong , Wang Hui , Wang Weihua
Published: November 2015

Currently the reliability of rotating equipments in typical petrochemical plants, such as turbo machineries, centrifugal compressors, reciprocating compressors, fans, pumps, etc. plays an important role in a long-term operation of the plants. The important tasks for management technology research of rotating equipments are to build a new type of maintenance management platform and take an advantage of the reliability analysis technique for fault diagnosis and maintenance strategy optimization. In this paper, firstly, the development of maintenance management technology in China and overseas was introduced. The problems of traditional reliability analysis techniques were pointed out. Secondly, the key technologies of the new type of maintenance management system were introduced. Furthermore, the structure and work process of the new type of maintenance management system were proposed. Finally, the key contents and functions of this system were given.
Unit Dose Factors for Transportation of Radioactive Materials
Authors: Connolly Kevin J. , Kalinina Elena
Published: November 2015

It will be necessary in the future to transport spent nuclear fuel on a large-scale basis from nuclear power plant sites to interim storage and/or a repository. Shipments of radioactive material are required to comply with regulations limiting the dose rate to no more than 0.1 mSv (10 mrem) per hour at 2 meters from the sides of the vehicle transporting the package. Determining the resulting dose to the public will be necessary for a number of reasons (e.g., stakeholder concerns, environmental impact statements). In order to understand the dose consequence of such a transportation system, this paper describes a method for determining unit dose factors. These are defined as the dose to the public per unit distance traveled along a road, rail, or waterway from one shipment assuming unit values for the other route specific parameters. The actual dose to the public is calculated using unit dose factors, the dose rate due to the radiation field emanating from the package, and characteristics of the route itself. Route specific parameters include the speed of the conveyance, the population density, and characteristics of the environment surrounding the route; these are provided by a routing tool. Using these unit dose factors, in conjunction with a routing tool, it will be possible to quantify the collective dose to the public and understand the ramifications of choosing specific routes.
Failure Analysis of a Cracked Outlet Elbow in Coal Gasification Unit
Authors: Liu Wen , Shao Shanshan , Chen QiuPing , Shi Jin , Yang ZhiRong , Xu WenHui
Published: November 2015

A crack was observed on an outlet elbow of the pre-converter in coal gasification unit during operation. This paper details the investigation into the failure and highlights the most probable cause of failure based on available documents and experimental analysis. Visual examination, chemical components analysis, energy spectrum analysis, fracture analysis, metallurgical analysis, mechanical properties test and residual stress measurement were performed. The experimental results show that the primary crack initiated from inside and propagated to outer surface of the elbow. The content of titanium element was lower than the requirement in GB/T 14976-2002. Corrosion products were rich in O and S elements. Amounts of secondary cracks and strain induced martensite were observed. Furthermore, the residual stress on the inner surface near the crack tip was extremely high. According to the experiment results and the analysis of operating condition and history, the failure mechanism of the elbow is stress corrosion cracking. Sensitization of the stainless steel due to low Ti content and the faulty heat treatment contributed to the intergranular stress corrosion cracking.
3D Effects in Fluid Flow During 2D Vibrations: Experimental Analysis of FSI for an Enclosed Hexagonal Assembly
Authors: Sargentini Lucia , Cariteau Benjamin , Magnaud Jean-Paul , Monavon Arnault , Artini Gianluca
Published: November 2015

The purpose of this study is to improve the knowledge about the core behavior of a sodium fast breeder reactor (Na-FBR) through the fluid-structure interaction analysis during vibrations of short time scale (shutdown of Phénix reactor) as well as long time scale (earthquakes for ASTRID Project).

We designed a test-rig, PISE-1a, composed by one hexagonal assembly enclosed by an hexagonal containment with a narrow gap.

The experimental test-rig PISE-1a is used to determine the dynamic characteristics of the assembly, to calibrate instrumentation and for validating our numerical model.

Free vibration experiments in water allow to assess the added mass and added damping effect on the frequency. The fluid flow is affected by a 3D effect — named down-stroke flow — at the top and the base of the assembly. This effect produces a higher frequency than the 2D theoretical value. Investigation on this phenomena are provided by PIV methodology, which allows to show the displacement of the fluid as predicted by the theoretical analysis.
Fluidelastic Instability in Tube Arrays Subject to Two-Phase Cross Flow: A Porous Medium Approach
Authors: Tixier Eliott , Béguin Cédric , Étienne Stéphane , Pelletier Dominique , Hay Alexander , Ricciardi Guillaume
Published: November 2015

In nuclear power plants, heat exchangers undergo important flow induced vibrations, fluidelastic instability (FEI) being the most damaging one. Direct numerical simulations of such a phenomenon is currently an impossible task because of the considerable number of tubes and the two-phase nature of the flow.

The novelty of the present approach is to use a porous medium to model the tube bundle and the surrounding flow. The Navier-Stokes equations are averaged on a control volume and the tubes materialized by a porosity field and source terms that model the interactions between the fluid and the solid. New sets of fully coupled equations were developed and solved with a finite element solver using high order time integration schemes. The unsteady porous medium approach already developed for single-phase flow is extended to the Euler-Euler formulation to describe the two-phase mixture. Validation and calibration of the parameters are achieved by comparing the critical flow rate and the forces acting on the tubes with results from direct numerical simulations and experimental data for single-phase flows.
Influence of Plastic Prestrain on the Fatigue Crack Growth Resistance (da/dN vs. ΔK) of ASTM A36 Structural Steel
Authors: Donato Gustavo Henrique B. , Cavalcante Fábio Gonçalves
Published: November 2015

High responsibility components operating under cyclic loading can have their resistance against initiation and growth of fatigue cracks highly influenced by previous thermomechanical processing. Within the interest of the present work, different manufacturing processes and installation techniques incorporate cold plastic straining to engineering structures; two typical examples on the oil and gas fields are: i) the offshore pipelines installation method called reeling; ii) the fabrication of pipes using the UOE method and pressure vessels through calendering. Within this scenario, this work investigates the effects of plastic prestrain on the fatigue crack growth rates (da/dN vs. ΔK) of a hot-rolled ASTM A36 steel. Different from previous results from the literature, in which prestrains were applied directly to machined samples, in this work uniform prestraining was imposed to steel strips (1/2” thick) and specimens were then extracted to avoid (or minimize) residual stress effects. Prestrain levels were around 4, 8 and 14% and C(T) specimens were machined from original and prestrained materials according to ASTM E647 standard. Fatigue crack growth tests were carried out under load control in an MTS 810 (250 kN) equipment using R = 0.1. Results revealed that plastic prestraining considerably reduced crack growth rates for the studied material, which was expected based on the literature and hardening behavior of the studied material. However, results also revealed two interesting trends: i) the larger is the imposed prestrain, the greater is the growth rate reduction in a nonlinear asymptotic relationship; ii) the larger is imposed ΔK, the more pronounced is the effect of prestraining. Crack closure effects were also investigated, but revealed no influence on the obtained mechanical properties. Consequently, results could be critically discussed based on effective crack driving forces and elastic-plastic mechanical properties, in special those related to flow and hardening. The conclusions and success of the employed methods encourage further efforts to incorporate plastic prestrain effects on structural integrity assessments.
Development of Flaw Acceptance Criteria for Aging Management of Spent Nuclear Fuel Multiple-Purpose Canisters
Authors: Lam Poh-Sang , Sindelar Robert L.
Published: November 2015

A typical multipurpose canister (MPC) is made of austenitic stainless steel and is loaded with spent nuclear fuel assemblies. The canister may be subject to service-induced degradation when it is exposed to aggressive atmospheric environments during a possibly long-term storage period if the permanent repository is yet to be identified and readied. Because heat treatment for stress relief is not required for the construction of an MPC, stress corrosion cracking may be initiated on the canister surface in the welds or in the heat affected zone. An acceptance criteria methodology is being developed for flaw disposition should the crack-like defects be detected by periodic Inservice Inspection. The first-order instability flaw sizes has been determined with bounding flaw configurations, that is, through-wall axial or circumferential cracks, and part-through-wall long axial flaw or 360° circumferential crack. The procedure recommended by the American Petroleum Institute (API) 579 Fitness-for-Service code (Second Edition) is used to estimate the instability crack length or depth by implementing the failure assessment diagram (FAD) methodology. The welding residual stresses are mostly unknown and are therefore estimated with the API 579 procedure. It is demonstrated in this paper that the residual stress has significant impact on the instability length or depth of the crack. The findings will limit the applicability of the flaw tolerance obtained from limit load approach where residual stress is ignored and only ligament yielding is considered.
Closure Bolt Modeling for Seal Evaluation Under Extreme Thermal Loads
Authors: Klymyshyn Nicholas A. , Adkins Harold E. , Piotter Jason M.
Published: November 2015

The US Nuclear Regulatory Commission (NRC) recently completed an evaluation of a used nuclear fuel transportation package subjected to loads associated with the MacArthur Maze fire and overpass collapse of 2007. This historical event is used as the basis of an extreme accident scenario to investigate the performance of the package system under loads that are beyond regulatory limits and to assess the potential risk to the public. The accident scenario was modeled in a number of physics regimes, including fire dynamics models, thermal models, structural impact models, and structural thermal expansion models. In this case the thermal expansion behavior of the bolted closure was a key component of the leak rate calculations and offered a tough analytical challenge, which was ultimately resolved using a detailed nonlinear finite element model of the bolt threads with thread inserts discretely modeled. This paper describes the analytical steps that were taken, starting with classic bolt stress calculations and ending with sophisticated finite element analysis, while also putting the analysis into context of the larger analytical effort and the assessment of used nuclear fuel transportation package safety that is critical to the mission of the US NRC.
Experimental Testing of Pressure Pulse Propagation in Non-Newtonian Simulants With a Void Fraction of Non-Condensable Gas
Authors: Schmitt Kyle P. , Ligon Thomas C. , Minichiello John C.
Published: November 2015

This paper describes experimental work performed in support of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) to quantify the propagation and attenuation of pressure pulses as they move through piping systems filled with quiescent non-Newtonian simulants that support a void fraction of non-condensable gas. A subset of experimental results is presented in this paper and is shown to compare favorably to theoretical expectations. In general, the rate of attenuation of the propagating pulse increases with void fraction, pulse peak pressure, and the inverse of pulse duration, all a consequence of rarefaction wave accumulation at the shock front. The data developed from this experimental test program is supporting the development and validation of related analytical and numerical (CFD) models. These models are being developed with the practical objective of determining the length over which a pressure pulse propagating from an ignition event in a gas pocket remains structurally significant to piping at the WTP.

In addition to selected results and key conclusions, specific aspects of test preparation and conduct are discussed in this paper including the generation of pressure pulses with a mechanical impact at the liquid surface; the development of a well-dispersed gas phase (i.e., void fraction) using catalyzed decomposition of hydrogen peroxide in the simulant mixture; the retention of a void fraction by using mixtures with non-Newtonian (i.e., Bingham plastic) properties; and the in situ measurement of void fraction.
Cycle-Averaged Approximation of Heat Transfer Associated With Rayleigh-Plesset Gas Bubble Dynamics
Authors: Schmitt Kyle P. , Pellman Abby M. , Minichiello John C.
Published: November 2015

The presence of entrained gas bubbles in a bubbly media leads to both dispersive and dissipative effects on a pressure wave traveling through the system. The complete set of equations used to model this process involves the combination of macroscopic pressure propagation and Rayleigh-Plesset oscillations of individual gas bubbles. This results in disparate temporal and spatial scales that are difficult to solve numerically inside of a CFD framework.

This paper presents a simplification to the set of governing equations that specifically eliminates the need to model individual bubble oscillations by using a cycle-averaged approximation. Results generated with the simplified model are verified against equivalent results considering the full set of governing equations. The approximation is shown to capture the behavior of interest — e.g., the variation in gas phase volume that alters the bulk modulus of the bubbly media or the net transfer of mechanical energy to heat — without the additional effort required to model rapid dynamics that do not contribute substantially to the pressure wave decay.
Modelling of Ultrasonic Shot Peening
Authors: Robin Vincent , Gilles Philippe , Brosse Alexandre , Chaise Thibaut
Published: November 2015

Component manufacturing may induce cold work, residual stresses, microstructure changes and even surface defects. This initial condition is usually ignored in component integrity assessments, but can strongly affect its lifetime. For instance, it is well-known that a rough surface finish associated to the presence of tensile residual stresses may favor fatigue damage. In the same manner, cold work and tensile residual stress will assist initiation of Stress Corrosion Cracking (SCC) for susceptible materials. As the manufacturing process can affect the lifetime of the structure, mitigation treatments such as precompressive loadings, chemical treatments, film deposits or coatings may be applied to sensitive areas. The objectives of these complementary operations are to avoid or compensate negative effects of manufacturing consequences. In the industry surface mechanical treatments such as Ultrasonic Shot Peening (USP) are then used in order to improve surface integrity. Even if these mitigation treatments are well known to increase component lifetime regarding corrosion and fatigue damages, a good understanding of their consequences is required to assess their efficiency and perpetuity under operating conditions. Numerical modelling of USP is one solution to simulate the motion of beads in the peening chamber and to predict the level of stresses in the peened part as shown in this paper. This model which gives a better understanding of the effect on surfaces should help the manufacturers to select the best process parameters.
A Methodology for Optimizing Startup-Shutdown Transients for Pressure Vessel Integrity
Authors: Nimrouzi Hossein , Goldak John A. , Yetisir Metin
Published: November 2015

A robust methodology for the optimization of thermal start up and shut down cyclic loading of a Generation IV supercritical-water cooled reactor (SCWR) core is presented in the conceptual development stage. The goal is understand the design space and identify design issues that deserve additional analysis, not to finalize the design. Parameterization of the geometry of different parts of the plenum supported automatic mesh generation of the parts. This enabled the Design of Optimal Experiments to be automated for a prescribed design space to compute the sensitivity of the defined objective functions to each design parameter including mesh parameters. With this software framework, the optimized profile of temperature and pressure for start up and shut down cycles was investigated with respect to an objective function to minimize the effective plastic strain over a number of cycles. In particular, the optimized value of effective plastic strain at saturated pressure and temperature conditions was determined. The intent was to demonstrate a capability to do design by analysis for pressure vessels, i.e., design based on a 3D nonlinear coupled holistic macroscopic thermal/stress analyses.
HRSG Header Creep-Assessment Through a Procedure for the Italian Code Application and Comparison With the American Standard
Authors: Grisolia Ottaviano , Scano Lorenzo
Published: November 2015

Lower headers of bottom-supported heat-recovery steam generators (HRSG) may be critical because of their longitudinal dimensions, thermal expansions and external loading (the harp’s weight): Present work considers the creep analysis of the high-temperature-section (superheater /reheater) headers: they may be critical because of the long continued service (175000 hours or twenty years), larger dimensions and the external loads, including a negligible steam-drum weight fraction. The aim of the work is to compare life results from the Italian creep code with those predicted by the American standard API 579-1. This work also checks the compatibility of results coming from the two polynomial models in both Italian and API 579-1 procedures. Classical methods, applied using both ASME and Italian pressure formulae, show that, as for the evaporator-section header, the pressure contribution to longitudinal stress may be greater than bending alone; considering now the increased header’s weight, the stress ratio is also comparable to the evaporator’s. Consistency of results from numerical-model stress analysis (elastic) is good, confirming the pressure contribution is greatest. For the Level-1 assessment (B31.1 stresses), the Italian procedure and the API 579-1 return consistent creep life results, though the API 579-1 results appear more conservative than the Italian-procedure’s. Level-1 assessment, acted through an elastic finite element analysis (FEA), uses Larson-Miller parameter (LMP)-approach method with minimum stress-to-rupture data: the Italian procedure and API 579-1 return consistent creep life results when evaluated on the tubehole branch side, Italian-procedure’s appearing little more conservative than the API 579-1’s. For the Level-2 assessment (FEA stresses), again the Italian procedure and the API 579-1 return consistent creep life results with the Italian-procedure ones again a little more conservative than the API 579-1’s for both sides of the intersection. Level-3 assessment (incorporating creep, plasticity and relaxation) shows (short) creep lives similar to Italian-procedure’s.
The Effect of Tertiary Creep on Allowable Stress Values for Type 304 and 316 Stainless Steel for Elevated Temperature Nuclear Component Design
Authors: Sengupta Mainak , Nestell J. E.
Published: November 2015

The design and construction rules for nuclear components at elevated temperatures are currently in the ASME BPV Code, Section III, Division 1, Subsection NH, and will soon be incorporated in the new Section III, Division 5. The current allowable stresses are limited to 300,000 hours, which is equivalent to a 40-year design life. As a part of the Next Generation Nuclear Plant (NGNP) initiative, the allowable stress values are being revised to include higher temperatures and longer lifetimes. This is expected to support the design and construction of high temperature reactors for sixty-year (500,000-hour) design lifetimes. The technical bases for the revised temperature and time dependent stress allowable values for Type 304 and Type 316 stainless steels are presented in this paper. Since the allowable stresses at elevated temperatures are controlled by creep, the revised allowable stresses are based on Larson-Miller parametric analyses of creep data from Oak Ridge and NIMS, some of which was not available when the current allowable stresses were computed. The time-dependent stress intensity values (St) are based on ASME rules covering time to rupture, time to reach 1% strain and time to reach the onset of tertiary creep. The effect of the tertiary creep criterion on St at long times and high temperatures is significant. The tertiary creep criterion applied to the current Oak Ridge and NIMS data results in lower and more conservative high temperature and long time allowable stress values than those currently in Section III, NH. The potential reasons for the limiting tertiary creep effects are discussed, with the conclusion that the ASME graphical method specified to determine the onset of tertiary creep from the creep data is not appropriate for Type 316 stainless steel.
Effects of inclination angle during Al-doped ZnO film deposition and number of bending cycles on electrical, piezoelectric, optical, and mechanical properties and fatigue life
Authors: Li Tse-Chang , Kuan Ta-Hsuan , Lin Jen-Fin
Published: November 2015

A flat plate with an adjustable inclination angle between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate is designed for a deposition stage. Five inclination angles are used to prepare PET/aluminum-doped zinc oxide specimens in order to examine the effects of inclination angle and number of bending cycles on several parameters. The O2 peak intensity ratio (IRO2), obtained from x-ray photoelectron spectroscopy, is identified as one of the controlling factors of the electrical, optical, piezoelectric, and mechanical properties. The effect of inclination angle on IRO2 and the effects of IRO2 on the peak intensity ratios, IRZnO (002) and IRZnO (103), obtained from x-ray diffraction analyses, the composite grain size, and the residual stress in the thin film are investigated systematically. An increase in the inclination angle increases the peak intensity ratios of IRO2 and IRAl2O3, and reduces that of IRZnO. An increase in IRO2 decreases the volume fraction of IRZnO (002) but increases the residual stress of the thin film, and is favorable for the reduction of the composite grain size. The carrier mobility and electrical resistance decrease and carrier concentration increases when IRO2 and IRAl2O3 increase or IRZnO decreases. An increase in the residual stress reduces the fatigue life and piezoelectric coefficient of specimens. The application of a nonzero inclination angle increases the transmittance integration (TI) over the wavelengths of visible light and the intensities of the three peaks in the photoluminescence spectrum. A reduction in film thickness leads to increases in the energy gap and electrical resistance and a decrease in TI.
Viscous-to-viscoelastic transition in phononic crystal and metamaterial band structures
Authors: Frazier Michael J. , Hussein Mahmoud I.
Published: November 2015

The dispersive behavior of phononic crystals and locally resonant metamaterials is influenced by the type and degree of damping in the unit cell. Dissipation arising from viscoelastic damping is influenced by the past history of motion because the elastic component of the damping mechanism adds a storage capacity. Following a state-space framework, a Bloch eigenvalue problem incorporating general viscoelastic damping based on the Zener model is constructed. In this approach, the conventional Kelvin–Voigt viscous-damping model is recovered as a special case. In a continuous fashion, the influence of the elastic component of the damping mechanism on the band structure of both a phononic crystal and a metamaterial is examined. While viscous damping generally narrows a band gap, the hereditary nature of the viscoelastic conditions reverses this behavior. In the limit of vanishing heredity, the transition between the two regimes is analyzed. The presented theory also allows increases in modal dissipation enhancement (metadamping) to be quantified as the type of damping transitions from viscoelastic to viscous. In conclusion, it is shown that engineering the dissipation allows one to control the dispersion (large versus small band gaps) and, conversely, engineering the dispersion affects the degree of dissipation (high or low metadamping).