bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Temperature Constitutive Behavior of Austenitic Stainless Steel for Weld Residual Stress Modeling
Authors: Qiao Dongxiao , Zhang Wei , Feng Zhili
Published: August 2013

Weld residual stress is a major driving force for initiation and growth of primary water stress corrosion cracking (PWSCC), which is a critical challenge for weld integrity of reactor pressure vessel nozzles in nuclear industry. Predicting weld residual stresses for the purpose of understanding and mitigating PWSCC requires the knowledge of material constitutive rule especially strain hardening behavior over a wide range of temperatures. Though it is adequate for describing deformation at low temperature, the conventional, rate-independent, elastic-plastic constitutive rule falls short in predicting the strong microstructure-mechanical interaction such as the softening due to recovery (dislocation annihilation and realignment) and recrystallization at elevated temperature in welding.

To quantify the extent of softening under temperature and strain conditions relevant to welding, a framework has been developed by combining advanced experimental techniques and finite element modeling. First, physical simulation in a Gleeble testing machine is used to simulate the temperature transients typical of dissimilar metal weld by subjecting round tensile bar shaped specimens to rapid heating and cooling. Second, the digital image correlation (DIC) technique is used to map the non-uniform strain field and extract local strain history needed for accurately determining the true stress vs. true strain curve of softened material. Third, the thermally-mechanically processed specimens are characterized metallographically to correlate the microstructure changes to the measured stress-strain behavior. Finally, a thermal-stress finite element model of three-bar frame is used to study the effect of softening on the predicted weld residual stresses. As a first step toward developing the much-needed, comprehensive material constitutive relation database for dissimilar metal weld, the framework has been applied to study AISI 304L austenitic stainless steel. The extent of softening due to different duration of high-temperature exposure is studied and its influence on final residual stresses is discussed.
Transient Heat Conduction in Functionally Graded Hollow Cylinders and Spheres
Authors: Akbarzadeh A. H. , Chen Z. T.
Published: August 2013

In the present work, transient heat conduction in functionally graded (FG) hollow cylinders and spheres is investigated based on the non-Fourier heat conduction theories. Since the heat transmission has been observed to propagate at a finite speed for applications with very low temperature, short-pulse thermal-heating, and micro temporal and spatial scales, dual phase lag (DPL) and hyperbolic heat conduction theories are considered in current study instead of the conventional Fourier heat conduction theory. Except the phase lags which are assumed to be constant, all the other material properties of the hollow cylinders and spheres are taken to change continuously along the radial direction according to a power-law formulation with different non-homogeneity indices. The heat conduction equations are written based on the dual phase lag theory which includes the hyperbolic heat conduction theory as well. These equations are applied for axisymmetric hollow cylinders of infinite lengths and spherically symmetric hollow spheres. Using the Laplace transform and Bessel functions, the analytical solutions for temperature and heat flux are obtained in the Laplace domain. The solutions are then converted into the time domain by employing the fast Laplace inversion technique. The exact expression is obtained for the speed of thermal wave in FG cylinders and spheres based on the DPL and hyperbolic heat conduction theories. Finally, the current results are verified with those reported in the literature based on the hyperbolic heat conduction theory.
Parallel Analysis of Incompressible Flow and Structure Interaction Using Partitioned Iterative Method
Authors: Kataoka Shunji , Kawai Hiroshi , Minami Satsuki , Yoshimura Shinobu
Published: August 2013

Dynamic response considering fluid structure interaction (FSI) is crucial in many engineering fields and the numerical methods to solve the FSI problems are keenly demanded in engineering field. Generally coupled phenomena can be simulated in either monolithic or partitioned methods, however the application of FSI analysis are limited because of its calculation costs. The partitioned method is now focused because it can re-use the existing flow and structural analysis solver without elaborated modification and it gives the same accuracy when iterative coupling approach is taken. When the partitioned method combined with the existing flow and structure solver which can solve large-scale analysis model, it is expected to solve realistic three dimensional complex FSI problems in acceptable durations. In this work, the partitioned FSI analysis system are developed using existing flow and structure solvers. The system is applied to several validation models and accuracy and efficiency of the solver are shown.
Empirical Estimation of the Abrasion Endurance Life of Epoxy Coatings for Applications on Transmission Pipelines
Authors: Mally Timothy S. , Walker Roger H. , French Jesse J.
Published: August 2013

Internal and external pipeline erosion due to suspended particulate matter, wax and sand content, and geoseismic motion can rapidly reduce pipeline wall thicknesses to critically low values. Due to low shrinkage rates on curing, epoxy polymer coatings are well suited for slowing the rate at which pipe wall thickness is lost. The abrasion resistance of an epoxy coating is a function of the hardness of the coating, the abrasive particle velocity, angle of impact, and particle size. This paper describes the authors’ attempts to estimate longevity of certain Bisphenol-A based epoxy coatings against particulate abrasion.

Details are presented for the abrasion resistance testing of four different commercial epoxy coatings. Experimental methodology is detailed consisting of two different methods of accelerated erosion testing: water-jet droplet erosion and fixed frequency mechanical abrasion. The methods are used to calculate abrasion endurance lifetime for a variety of pipeline installation environments.

Test samples are exposed to abrasive wear for a given period of time and material loss is measured. Loaded and unloaded abrasion testing is used to represent forces proportional to buried and non-buried piping. Erosion volume and time to the specified erosion depth are compared with control data on uncoated carbon steel substrates. This accelerated erosion data is transposed to reflect in-situ life expectancies.
Bolted Joint Assembler Qualification — Dream or Reality?
Authors: Brown Warren
Published: August 2013

This paper examines current industry efforts to introduce bolted joint assembler standardized training and qualification. Efforts on an international level are examined and the likelihood of success and the barriers to implementation are detailed. In addition, several models for establishing assembler qualifications are examined and comparatively discussed for both likelihood of implementation and, more importantly, likelihood of success in reducing bolted joint integrity issues via assembler qualification.
Shakedown Analysis of a Cylindrical Vessel-Nozzle Intersection Subjected to Steady Internal Pressures and Cyclic Out-of-Plane Bending Moments
Authors: Abdalla Hany F. , Younan Maher Y. A. , Megahed Mohammad M.
Published: August 2013

In the current research, the shakedown limit loads of a cylindrical vessel–nozzle intersection are determined via a simplified technique. The cylindrical vessel–nozzle intersection is subjected to a spectrum of steady internal pressure magnitudes and cyclic out–of–plane bending moments on the nozzle. The determined shakedown limit loads, forming the shakedown boundary, are utilized to generate the Bree diagram of the cylindrical vessel–nozzle intersection. In addition to the determined shakedown boundary, the Bree diagram includes the maximum moment carrying capacity (limit moments) and the elastic limit loads. The currently generated Bree diagram is compared with previously generated Bree diagram of the same structure, but subjected to in–plane bending. Noticeable differences regarding the magnitudes of the generated shakedown boundaries are observed. Moreover, only failure due to reversed plasticity response occurs upon exceeding the generated shakedown boundary unlike cyclic in–plane bending where the structure experienced both reversed plasticity and ratchetting failure responses. The simplified technique outcomes showed excellent correlation with the results of full elastic–plastic cyclic loading finite element simulations.
Influence of Prior Deformation on Creep Crack Growth Behaviour of 316H Austenitic Steels
Authors: Nezhad Hamed Yazdani , O’Dowd Noel P. , Davies Catrin M. , Mehmanparast Ali N. , Nikbin Kamran M.
Published: August 2013

The influence of pre-strain and pre-stress on creep crack growth behaviour of 316H austenitic steels is studied experimentally and numerically in this paper. Compact tension, C(T), specimens (25mm thickness) have been extracted from two steam headers, one as-received and one uniformly compressed to the strain value of 8%. The C(T) specimen extracted from the as-received header was compressed, introducing a non-uniform strain field. Creep crack growth (CCG) tests were performed at 550°C. Comparisons have been provided with the results from as-received C(T) specimens. Finite element (FE) analysis has been carried out to simulate the CCG behaviour of the C(T) specimens. By choosing the problem parameters appropriately, good agreement may be achieved between the FE predictions and the creep data.
Industrial Application of Small Punch Testing for In-Service Component Condition Assessment: An Overview
Authors: Dogan Bilal , Hyde Thomas
Published: August 2013

The Sampling and Small Punch testing (SPT) is a powerful technique based on tests using miniaturized specimens machined out small sampled material of components in service. At present, it is the only existing method capable of providing experimental characterization of service exposed materials of components and materials of new built plants. Small sampling is non-invasive and SPT provides direct measured material properties. It provides a significant technology capability that facilitates assessing power plant operating equipment for structural integrity and operational condition. The new method provides utility members an attractive option to interrogate equipment for making run/inspect/repair/replace decisions. The SPT technique supported by assessment software, NDE and Metallography, used to define guidelines for components life assessment cross the power generation and petro-chemical sectors, serving both utilities, and constructors. It addresses the industrial need for personalized material and welds data required for a) lifing of plant; consumed life and residual life of components, b) convenience of repairing, replacing, life of the new welds on old components, c) cost of component deterioration, cost of normal service, d) characterizations and qualifications of blade repairs, of coating materials-methods.

The first international SPT workshop was organized in June 27–28, 2011 in Nottingham, UK in order to discuss the state-of-the art SPT Creep and Fracture, and the draft CEN Cope of Practice (COP). The International SPT Experts Group serves as international forum for discussion and collaboration of industrial application of SPT methodology for in-service component life assessment. It is noted the draft CEN COP needs to be revised. Presently, European, Japanese and Indian national SPT project groups are running SPT tests and working on analysis programs.

The present paper reports on a) the use of SPT in materials and component characterization, and b) drafted technical program by the international experts group to harmonize international efforts on SPT testing and analysis for efficiency and cost effectiveness. The draft program to bring the SPT methodology to standardization and develop an engineering component condition assessment tool for industrial application.
Numerical Analysis of Intermittent Stick-Slip Behaviour of Tube-Support Interaction in Heat-Exchangers
Authors: Azizian Reza , Mureithi Njuki
Published: August 2013

Flow induced excitation forces in heat exchangers cause tube-support interactions. The long-term interaction is an important phenomenon which may cause fretting-wear of the tubes. Experimental tests of the interaction show the occurrence of stick-slip intermittent behavior in the tube response. Many factors are involved to precisely predict the interaction behavior including flow excitation forces, impact and friction forces. One of the explanations behind the intermittent stick-slip behavior may be interpreted by refinements in the conceptual choice of friction model and coefficient of friction. Therefore, among the factors above, the incorporated friction model plays an important role in the determination of the level of fretting-wear in the system. The friction model should satisfy two important criteria: the first important aspect is the strategy of the friction model to detect the cessation of sticking, the beginning of partial slipping and establishment of the sliding region. The second important aspect is defining a friction coefficient function for the entire system response to precisely represent the transient stick-slip regions. In the present work, the velocity limited friction model was compared with the LuGre model which is a rate dependent friction model. The effect of varying the break-away force and Stribeck effect on the stick-slip region was also investigated. Furthermore, the criteria to demarcate the stick-slip region in the LuGre model are discussed and a different method to incorporate the Stribeck effect and presliding damping in the Dahl friction model are proposed. Finally, a new hybrid spring-damper friction model inspired by the Cattaneo-Mindlin stress distribution in the contact region is proposed.
Common Misunderstandings About Gasket and Bolted Connection Interactions
Authors: Reeves David , Brown Warren
Published: August 2013

Unfortunately most people’s knowledge about bolted connections comes more from information that has been “passed down” from a variety of sources than a solid understanding of the physics and science that impacts pressure boundary bolted connection reliability. A correct understand of bolt and gasket interactions gives a person the skills to reliably solve a variety of sealing application problems. This paper looks at some of the more significant misunderstandings that inhibit people’s ability to effective resolve and prevent problems with bolted connections.
Evaluation of Fracture Behavior for Pressurized T-Pipe by Finite Element Analysis
Authors: Miura Naoki , Yamakami Katsuhiko , Iwahara Kotaro , Tsunokawa Kiyoharu , Miyao Kozo
Published: August 2013

T-pipe is one of the typical structural elements of LWR piping as well as T-joint. In the present situation, the evaluation of wall thinning for T-pipe is accomplished by assuring the sufficient strength around the opening area by using the design and construction code. This evaluation often assumes the replacement of a local wall thinning with a global wall thinning, which leads to excessively conservative prediction of burst pressures. In this study, three-dimensional finite element analysis was conducted to simulate the fracture behavior of a pressurized T-pipe test. The accuracy of the predicted burst pressures and appropriate modeling of the welded joint at the junction of the main and branch pipes were investigated. It was found that the burst pressure could be adequately predicted by applying a proper fracture criterion. Allocation of experimental tensile property of weld metal to the welded joint gave more accurate prediction; nevertheless, allocation of experimental tensile property of base metal to the welded joint enabled suitably conservative prediction.
Finite Element Analysis of Burst Pressure for Pipelines With Long Corrosion Defects
Authors: Zhu Xian-Kui , Leis Brian N.
Published: August 2013

Plastic collapse analysis and remaining burst strength determination are critical to a corroded pipeline in its fitness-for-service analysis and integrity assessment. For very long corrosion defects, the present authors proposed a theoretical solution for predicting the burst pressure of corroded pipe in terms of a newly developed average shear stress yield theory, and validated it using full-scale burst data for long real corrosion defects. This paper then presents a finite element analysis (FEA) procedure to determine the remaining burst pressure for a very long blunt defect. A burst failure criterion that is referred to as von Mises equivalent stress criterion is proposed first in reference to the von Mises theory. Detailed elastic-plastic FEA calculations are performed using ABAQUS for a series of corroded pipes with infinitely long defects in different widths. From the FEA results and using the proposed failure criterion, the numerical results of burst pressure are determined for the long defects. The results show that using the proposed failure criterion, the FEA simulation can accurately determine the burst pressure for corroded pipes with long defects that is consistent with the theoretical solution. The conventional assessment methods including ASME B31G, RSTRENG, PCORRC and LPC are also evaluated and discussed in comparison with the proposed theoretical solution of burst pressure for long corrosion defects.
Compaction Ring Analysis of Concrete Penetration
Authors: Loveless Justin T. , Conway Jennifer M. , Barkey Mark E. , Jones Stanley E.
Published: August 2013

The purpose of this paper is to report the results of laboratory scale penetration tests on aged fine particle concrete targets. Hardened 4340 steel (RC-50) projectiles were fabricated with ogive noses and flat ends for the purpose of the tests. The projectiles were 0.164 inches in diameter with varying lengths. The projectiles were launched from a 0.167 inch smooth bore powder gun, and the impacts were normal to the face of the target. The targets were small enough to permit two methods of measurement to find the penetration depth: direct measurement from the back of the projectile and x-rays of the target. The Compaction Ring Theory, presented earlier by Jones [1] and Nuckols[2], was then applied to the penetration depth data for the ogive-nose projectiles. Several of the equations to follow were first presented in those papers. However, two corrections were made to the theory previously presented involving the sign of the yield stress of the target in the radial stress equation and in deriving the penetration depth equation. These corrections will be described in more detail later. Since the Compaction Ring Theory in its generic form does not apply to flat-ended projectiles, it was modified to include this case. The results show reasonable correlation for target strengths that are consistent with the strain rates that are anticipated for the range of impact velocities that were used in the experiments.
Investigative Study of 2-D vs. 3-D Weld Residual Stress Analyses of the NRC Phase II Mockup
Authors: Ku Francis H. , Tang Shu (Stan) S.
Published: August 2013

Finite element weld residual stress analyses are performed to investigate the similarities and differences between two-dimensional (2-D) and three-dimensional (3-D) finite element analyses on weld residual stress predictions of the NRC Phase II Mockup. The Mockup resembles a typical pressurized water reactor (PWR) surge nozzle of 14″ in diameter which includes a dissimilar metal weld (DMW) connecting the safe end and a stainless steel weld (SSW) connecting the surge line piping. The 2-D analysis employs axisymmetric modeling approach, while the 3-D analysis utilizes moving heat source approximation techniques. The results demonstrate the variations in residual stresses among the weld bead start and stop locations. Comparing the 2-D and 3-D residual results against experiment measurements also reveal the limitations inherent to the 2-D analysis, while the 3-D analysis can produce results that are of closer match to experimental measurements.
Bending Fatigue Testing of Pipe and Piping Components Fabricated From High Density Polyethylene Materials
Authors: Adams Timothy M. , Munson Douglas , Hall Siegrid , Andrasik Jeffrey W.
Published: August 2013

Degradation of service water systems is a major issue facing nuclear power plant owners, and many plants will require repair or replacement of existing carbon steel piping components. High Density Polyethylene piping has been used in non-safety service water systems for over nine years and found to perform well, and is now permitted in the ASME Section III Boiler and Pressure Vessel Code, Division 1 for use in nuclear safety-related systems. To assist in this implementation of High Density Polyethylene piping in the ASME Boiler and Pressure Vessel Code, Section III, Division 1 for Safety Class 3 applications, Electric Power Research Institute initiated a testing program that includes tensile and fatigue testing of High Density Polyethylene piping and components and the development of data to evaluate slow crack growth that can emanate from surface scratches. Straight cantilever bending fatigue tests on PE 4710 pipe with a minimum cell classification of 445474C were previously conducted and the results presented at the 2008 PVP Conference in Chicago, Illinois. The tests were designed to comply with the requirements for fatigue testing given in Mandatory Appendix II of the ASME Boiler and Pressure Vessel Code, Section III, Division 1. Based on the straight pipe tests, Stress Intensification Factors can be calculated for other piping components. This paper reports on follow-on testing of PE 4710 cell classification 445574C piping components. The fatigue testing results showed one of the unique characteristics of High Density Polyethylene piping: a significant decrease in material stiffness from the first few test cycles to a lower value that remains almost constant until failure. Thus, Stress at Failure vs cycles at failure curves and Stress Intensification Factors were determined twice: first based on the initial cycle results and again at the midlife of the fatigue tests. This paper provides a description and overview of the test program, testing methods and materials tested. In addition, an overview and summary of the test program results are provided.
Dynamic Testing of High Density Polyethylene Vent and Drain Configurations
Authors: Munson Douglas , Adams Timothy M. , Nickholds Shawn
Published: August 2013

For corroded piping in low temperature systems, such as service water systems in nuclear power plants, replacement of carbon steel pipe with high density polyethylene (HDPE) pipe is a cost-effective solution. HDPE pipe can be installed at much lower labor costs than carbon steel pipe, and HDPE pipe has a much greater resistance to corrosion. This paper presents the results of the seismic testing of selected vent and drain configurations. This testing was conducted to provide proof of the conceptual design of HDPE vent and drain valve configurations. A total of eight representative models of HDPE vent and drain assemblies were designed. The models were subjected to seismic SQURTS spectral acceleration up to maximum shake table limits. The test configurations were then checked for leakage and operability of the valves. The results for these tests, along with the test configurations, are presented. Also presented are the acceleration data observed at various points on the test specimens.
Fire Testing of High Density Polyethylene Piping Systems
Authors: Munson Douglas , Decker Dana
Published: August 2013

Degradation of raw water piping systems is a major issue facing nuclear power plant owners. High density polyethylene (HDPE) is a cost-effective alternative to corrosion resistant alloys and has been found to perform well in power plant applications for over 10 years. When used above ground, fire resistance may be an issue. HDPE starts to melt at ∼235°F (115°C) and has an auto-ignition temperature of ∼662°F (350°C). Additionally, toxic gasses are released when it burns.

The paper summarizes the development of a method that can be used to protect HDPE piping from postulated fire events is situations where the system must remain operable or not contribute to the fire load. The method was demonstrated using a proof-of-concept fire test of four piping subassemblies that contained many of the fittings that are commonly found in HDPE piping systems. The assemblies were subject to a 3-hour fire test following the guidance of ASTM E119 followed by a hose stream test following the guidance of ASTM E2226. All four specimens survived the test, with each retaining its overall geometry, cross section, and structural and pressure boundary integrity.
Impact of Degradation of Polyethylene Films Under Simulated Climatic Conditions on Their Mechanical Behaviour and Thermal Stability and Lifetime
Authors: Dehbi Abdelkader , Djakhdane Khaled , Mourad Abdel-Hamid I.
Published: August 2013

Studying the impact of degradation of polyethylene tri-layer films under simulated climatic conditions, of North Africa, on their mechanical behaviour and thermal stability and lifetime is the main objective of this work. The films are produced by the co-extrusion technique which is used in several industrial applications such as the nuclear related applications. The climatic conditions such as temperature, solar radiation, wind, sand and humidity are crucial factors in the ageing process, degradation and lifetime of polymeric materials. At the molecular level, these conditions have severe structural modifications and oxidation in polymers which are the main mechanism of ageing. Polyethylene films have numerous industrial applications in which they are susceptible to such harsh environmental conditions. Samples in the form of polyethylene films of 180μm thickness are artificially aged at different conditions of temperature and humidity. Monitoring the degradation in physicochemical properties of polymer matrices used and their stabilizing additives is carried out by thermal analysis (DSC) and mechanical tests. The results revealed that the investigated climatic conditions have essential deteriorative effects on the performance of the film. The correlation between the modification in the material structure and the degradation in the film properties is discussed.
Detailed Finite Element Analysis of Darlington NGS Feeder Pipes With Locally Thinned Regions Below Pressure Minimum Thickness
Authors: Haq Irfan , Stojakovic Mike , Fabbri Sandy
Published: August 2013

Feeder Pipes in CANDU nuclear stations are experiencing wall thinning due to flow accelerated corrosion (FAC) resulting in locally thinned regions in addition to general thinning. In Darlington NGS these locally thinned regions can be below pressure based minimum thickness (tmin) in the straight pipe region (STR1) between Grayloc and Bend 1. The (tmin) is required as per ASME Code Section III NB-3600 Equation (1). A methodology is presented to qualify the locally thinned regions under NB-3200 (NB-3213 & NB-3221) using internal pressure loading only. Detailed finite element models are used for internal pressure analysis using ANSYS v11.0. All other loadings such as deadweight, thermal and seismic loadings are separately qualified under NB-3600 using a general purpose piping stress analysis software. The piping stress analysis is based on average thickness equal to tmin along with maximum values of ASME Code stress indices (Table NB-3681(a)-1). The requirement for the use of this methodology is that the average thickness of each cross-section with the locally thinned region shall be at least tmin. In contrast, the finite element analysis models are thinned to 0.75 tmin (in increments of 0.05 tmin) all-around the circumference in the straight section region allowing for flexible inspection requirements. In Darlington NGS there are 22 different types of feeder pipes which have been grouped into 6 types based on similarities in pipe size, straight section length, bend angle and orientation. Thickness versus the allowable axial extent curves were developed for 6 representative feeder types. The stress analysis results show that all Darlington NGS outlet feeder pipes are fit for service with locally thinned regions in STR1 with down to 75% of the pressure based minimum thickness.

This paper demonstrates the methodology and effectiveness of finite element analysis in extending the useful life of degraded piping components.
Status of French Road Map to Improve Environmental Fatigue Rules
Authors: Faidy Claude
Published: August 2013

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of RCC-M and ASME Codes [1, 2].

This paper will present the major technical improvements to obtain reasonable evaluation of potential fatigue damage through EDF road map. Recently new results [3] confirm possible un-conservative fatigue material data:

- High cycle fatigue in air for stainless steel,

- Environmental effects on fatigue S-N curve for all materials

- Fatigue Crack Growth law under PWR environment for stainless steel.

In front of these new results, EDF has developed a “Fatigue Road Map” to improve the different steps of Codified fatigue rules.

A periodic up-dating of proposed rules in the different French Codes: RCC-M, RCC-MRx and RSE-M with research of harmonization with other Code rules developed in USA, Japan and Germany in particular, will be done on a yearly basis. During the past 15 years, many results have been obtained through fatigue tests of stainless steel materials:

- mean and design fatigue curve in air,

- environmental effects on fatigue curves,

- plasticity effects,

- bi-axial load effects,

- mean stress effects,

- stress indices,

- transferability from small to large specimen,

- weld versus base metal.

In parallel, many new developments have been made in non-nuclear pressure equipment industry: like the reference stress of ASME Section VIII or the structural stress of EN 13445. These methods are mainly well adapted to fatigue pressure cycling.

In front of that situation, the French nuclear code organization needs to propose reliable rules for new design and for operating plants. Different proposals are under discussion and the status of the EDF proposals are presented in the paper.

The consequences could be important for the utilities because a large part of the in-service inspection program is connected to some fatigue usage factor level between 0.5 and 1.
Asset Management, Life Extension and Fitness for Service in the High Pressure Industry
Authors: Peters Daniel T. , Haley Kevin M.
Published: August 2013

Long term asset management is a key issue in the high pressure industry, but only limited and somewhat fragmented guidelines exist in the form of various “New-Construction” Design Codes and Standards. The high pressure industry is a niche industry and many applications are not covered completely by existing codes and standards. The paper will cover an overview of various ASME and API documents and provide an overall methodology for the implementation of an effective and logical asset management protocol including Fitness for Service guidelines which can be referenced in lieu of a comprehensive document being available.

ASME discontinued publication and distribution of the High Pressure Systems Standard (HPS-2003) [6] in September 2009. One of the most common uses for this document was the section on vessel requalification. The paper here will discuss the application of this requalification methodology, and its use in an overall high pressure asset management plan.

API 510 [5] and the National Board Inspection Code (NBIC) [13] cover the in-service inspection, repair, alteration, and rerating activities for pressure vessels-including vessels constructed and approved as jurisdictional special based upon jurisdiction acceptance of particular design, fabrication, inspection, testing, and installation. However those documents reference most of the technical requirements in the ASME construction codes for design, welding, NDE, and materials as being applicable for in-service pressure vessels. Also, API 510 and NBIC recognize FFS assessments for evaluating the structural integrity of in-service damage of pressure-containing components. This paper will discuss the use of those construction codes for use in a Fitness for Service assessment and the development of a comprehensive strategy for long term asset management using these guidance documents in conjunction with the ASME/API Inspection Planning guidelines.
Steam Line Integrity Analyses for LTO: Enhancing Credibility With Comprehensive Measurement
Authors: Rothenhöfer Horst , Manke Andreas
Published: August 2013

The safety relevant components of nuclear power plant Neckarwestheim 1 — in service since 1976 — have been reviewed and updated for long-term operation (LTO). The actions included hardware retrofits as well as updates of analysis according to the latest state of the scientific and technical knowledge. For large piping such as the steam lines, the established pipes have been retained while the supports have been optimized. All shock absorbers (snubbers) including corresponding inertia have been eliminated resulting in a defined guidance and statically defined displacements.

The integrity analyses for the optimized steam lines, including break preclusion, have been validated successfully with comprehensive measurements. The verification has delivered an extra high level of credibility, exceeding the “standard” requirements to achieve fitness for service in long-term operation.

Measurement and validation, which are the main focus of this paper, range from monitoring of service loads to the static and dynamic measurements of pressure, local temperatures and displacements during initial start-up after implementation of the design modifications. The proper function of supports has been proved and the quality of the simulation models has been confirmed.

Some expected and some unexpected dynamic events have been detected during blow-down tests. It was demonstrated that the amplitudes of all dynamic loads stay within limits.

The validation of analyses with comprehensive measurement has been an important proof of quality and delivered the redundancy required for the integrity of a nuclear power plant in service, enhancing the high level of safety even more.
Stress Analysis of the Bipartite Overlapping Expansion Joints of the Containment Penetration: Angra 2
Authors: Suanno Rodolfo L. M. , Maneschy José Eduardo de Almeida , Francioni Milton Kronenberg
Published: August 2013

During the 2010 outage of Angra 2 Power Plant the expansion joints of the containment penetration JMK05D0201 (LCQ50) which belongs to the blowndown system were found very distorted as shown in Fig. 1. The cause was an inadvertent over pressurization made during monthly tests to verify the set pressure. In order to leave the damaged expansion joint installed during one cycle, Eletronuclear conducted an elastic-plastic analysis which has demonstrated the joint could be in the position up to the next Angra 2 outage, in March 2012.

Considering that the option to replace the damaged expansion joint by another one is extremely complex, Eletronuclear decided to keep it in place and cover it by an expansion joint designed to resist all loads predicted in the original design specification. This new design is a two-sided (bipartite) bellows with longitudinal field welds.

This paper presents the fatigue and stress analysis of the bipartite overlapping expansion joints considering the loads defined in the design specification. Based on the results obtained, fatigue is not a concern and stress/strains are kept under acceptable values for all loading conditions. In addition, it also was demonstrated that the original design of the blowdown system was not impacted by the proposed design of the bipartite joint.
Cracking of Heavy Wall Steam Separators During Fabrication: An Investigation
Authors: Kumar Dilip , Ganhao Luis
Published: August 2013

On a recent project, four high pressure steam separator vessels were received from overseas after fabrication. There was suspicion on the quality of fabrication when non destructive examination (NDE) reports were reviewed. There were major concerns with the quality of radiographic films as they did not meet the ASMe Section VIII Div. 1 Code requirements as well as client specifications. Subsequent examination of welds using radiographic testing (RT) revealed crack-like features around nozzles in the region adjoining (but outside) the weld metal. Macro etching at the surface around nozzles showed that the weld area was extended beyond the apparent weld/base metal interface. Further examination of a cross section cut out from one vessel nozzle confirmed the initial doubts that weld repairs had been performed that were not reported. Metallography of the cross section indicated evidence of significant cracking associated with carbon contamination and very high hardness (up to 365 HV; in one particular case 609 HV) in affected areas. This was believed to be due to improper and incomplete cleaning by grinding after performing carbon arc or, flame gouging to remove a weld defect. Further detailed NDE was carried out using advanced ultrasonic testing (UT), i.e. phased array UT and time of flight diffraction (TOFD) and all defects (many new that were undetected by RT) were repaired per ASME Section VIII Div. 1 Code and client specification. This experience was a lesson for the design office and helped make a decision to be much more vigilant and to ask for greater quality surveillance on overseas fabrication of critical equipment for all future projects. The paper discusses the detailed investigation as well as findings.
A Collaborative Approach to Achieving a Gas-Tight Seal Using Expanded Polytetrafluorethylene (ePTFE) Gaskets in a Fiberglass-Reinforced Plastic (FRP) Lap-Joint Flanges
Authors: Czerwinski John , Garikipati Vijay K. , Jones Charlene N. , Pires Brad , Ludman John P. , McCauley Debra H. , Linnemann Brian
Published: August 2013

The work presented here is a collaborative approach to achieving a reliable gas tight seal in fiberglass reinforced plastic (FRP) flanged joints using expanded polytetrafluoroethylene (ePTFE) gaskets. There are many advantages to incorporating FRP flanged piping systems in today’s chemical process industry plant build. As regulations on reliability and fugitive emissions become stricter, it is more important than ever to eliminate possible damage and leak paths at the flanged connections in these systems. This paper details a case study on a collaboration between a chemical plant operator (end user), an ePTFE gasket manufacturer, and a FRP piping original equipment manufacturer. Over a twenty-four month period a FRP flanged system was designed and validated using a custom FRP stub and ring, also known as a lap joint, flange with an ePTFE gasket. The result was the development of a FRP bolted flange system that successfully achieved a reliable gas tight seal for aggressive chemicals. Beginning with a theoretical model and ending with experimental lab analyses, the conclusive results are included herein.
Structural Health Monitoring With Piezoelectric Wafer Active Sensors Exposed to Irradiation Effects
Authors: Lin Bin , Gresil Matthieu , Giurgiutiu Victor , Mendez-Torres Adrian E.
Published: August 2013

The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS) such as pressure vessels and piping (PVP) in a nuclear reactor. Technologies for the diagnosis and prognosis of PVP systems can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure. Recently investigated piezoelectric wafer active sensors (PWAS) open the possibilities to develop and deploy such system. Piezoelectric wafer active sensors are widely used in structural health monitoring (SHM) to determine the presence of cracks, delaminations, disbonds, and corrosion. Durability and survivability of PWAS under environmental exposures has been tested before. However the irradiation effects, pertinent to nuclear facilities for PWAS, have not been studied yet. This paper presents a study on PWAS that exposed to high energy gamma radiation. PWAS were irradiated using a Co-60 gamma source in an irradiator with different exposure times. The dose rate and total absorbed dose were calculated using Monte Carlo simulations (MCNPX). The PWAS material properties, electrical contact change were characterized through a series of tests. The electro-mechanical impedance spectrum (EMIS) of PWAS was measured before and after irradiation. This study not only provides the fundamental understanding of the PWAS irradiation survivability but also tests the potential of PWAS as irradiation sensors for nuclear applications.
Reheating Treatment of X100 Bend Pipe Steel
Authors: Zhang Xiao Li
Published: August 2013

Oil gas is the most clean fuel. Till 2020, the requirement of oil gas will increase 104%, but consumers are mainly live in developed cities, and oil and gas resources are located in ice field, hungriness, ocean and polar place. That is, the undeveloped resources are remote from the cities. It means, long distance transportation of gas is needed and higher grade pipeline steels must be developed. The second west-east gas project in china will use X80 grade steel in whole line, and as the exploitation of oil and gas resources have been diverted to outlying districts, and the need of high transport pressure for increasing gas delivery efficiency, the X100 pipe line steel will be mostly used before long. In this paper, the changes of micro structure and property after reheating treatment of X100 are discussed. This work will be helpful for future use of X100 bend pipes. The study has shown that for X100 steel which contains banite micro structure with dispersed residual austenite and Fe3C phase. The micro structure is the most homogenous when tempered at 550°C. When reheating regime is quenching from 950°C and tempering at 550°C, the microstruecture is B+PF+ P and the hardness of these steels matches with pipe. The fractotraph showed that these samples has adequate dimples in pars fibrosa, radiation area and shear zone, respectively, at −20°C. This indicates that when X100 pipe steels are reheattreated with this technique, it could gain right toughness.
Methods for the Experimental Evaluation of True Stress-Strain Curves After Necking of Conventional Tensile Specimens: Exploratory Investigation and Proposals
Authors: Ganharul Grace Kelly Q. , de Brangança Azevedo Nick , Donato Gustavo Henrique B.
Published: August 2013

Numerical elastic-plastic simulations have undergone significant expansion during the last decades (e.g. refined fracture mechanics finite element models including ductile tearing). However, one limitation to increase the accuracy of such models is the reliable experimental characterization of true stress-strain curves from conventional uniaxial tensile tests after necking (plastic instability), which complicates the direct assessment of the true stress-strain curves until failure. As a step in this direction, this work presents four key activities: i) first, existing correction methods are presented, including Bridgman, power law, weighted average and others; ii) second, selected metals are tested to experimentally characterize loads and the geometric evolution of necking. High-definition images are used to obtain real-time measurements following a proposed methodology; iii) third, refined non-linear FEM models are developed to reproduce necking and assess stresses as a function of normalized neck geometry; iv) finally, existing correction methods are critically compared to experimental results and FEM predictions in terms of potential and accuracy. The experimental results evaluated using high-definition images presented an excellent geometrical characterization of instability. FEM models were able to describe stress-strain-displacement fields after necking, supporting the exploratory validations and proposals of this work. Classical methodologies could be adapted based on experiments to provide accurate stress-strain curves up to failure with less need for real-time measurements, thus giving further support to the determination of true material properties considering severe plasticity.
Proposal of Revised Flaw Acceptance Criteria for Ultrasonic Examination of Welds in Section VIII Division 3: Part 2
Authors: Terada Susumu , Yoshida Toshio
Published: August 2013

The current flaw acceptance criteria for ultrasonic examination of welds in Table KE-301-1 and KE-301-2 of ASME Section VIII Division 3 (hereinafter Div.3) are almost similar to Code Case 2235 on ultrasonic examination of welds in lieu of radiography. This code case is based on general membrane stress and Charpy impact values of Section VIII Division 2 (hereinafter Div.2). The stress levels of Div.3 are higher due to lower design margin and larger stress gradient through the thickness due to large wall ratio than those of Div.2, and Charpy impact values requirements of Div.3 are also different from those of Div.2. Therefore, the flaw acceptance criteria on ultrasonic examination of welds for Div.3 should be reviewed. This paper is the second part of a two part paper. It describes the basic idea for review of flaw acceptance criteria in Div.3 and the proposed revised surface and subsurface flaw acceptance criteria for welds based on fracture mechanics evaluation.
Large effect of titanium precursor on surface reactivity and mechanical strength of electrospun nanofibers coated with TiO2 by atomic layer deposition
Authors: McClure Christina D. , Oldham Christopher J. , Walls Howard J. , Parsons Gregory N.
Published: August 2013

Encapsulating and functionalizing polymer nanofibers can improve the polymers chemical resistance and surface reactivity, enabling new applications including biosensing, flexible electronics, gas filtration, and chemical separations. Polymer fiber functionalization typically involves energy intensive wet chemical treatments and/or plasma exposure. Recent results show low temperature atomic layer deposition (ALD) to be a viable means to coat nanofibers with uniform and conformal inorganic and hybrid organic–inorganic layers. For this article, the authors describe how the mechanical properties of nylon-6 nanofibers are affected by ALD coatings of TiO2 and other metal oxides. They find that the stress–strain behavior of nylon-6 nanofibers depends strongly on the specific precursor chemistry used in the coating process. For ALD TiO2 coatings, titanium tetrachloride tended to embrittle the fibers, whereas titanium isopropoxide had a more subtle effect. Physical characterization shows that the TiCl4 diffused into the nylon-6 and reacted subsurface, whereas the titanium isopropoxide tended to react on the surface producing a more abrupt organic/inorganic interface. Results show that precursor choice is an important factor when designing thin film coating processes on polymeric substrates.