bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Testing of Hybrid Magnetic Responsive Fluid for Vibration Damper
Authors: Sunakoda Katsuaki , Morishita Shin , Takahashi Seiichi , Hakata Toshiyuki
Published: July 2010

A new intelligent fluid is studied and developed. Rheological characteristics of the developed fluid change rapidly and can be controlled in the presence of an applied magnetic field. The developed fluid is a hybrid type fluid, and it consists consisting of carbonyl irons and super fine magnetite. Average diameters of carbonyl iron and super fine magnetite are a size in the order of a few microns and about 10 nano-meters respectively. Special treatment is made by coating the surface of carbonyl iron with super fine magnetite. Physical properties such as dispersion stability and thixotropical characteristics are examined. Shearing stress and pressure drops of the new fluid flow are examined and evaluated by changing the strength of magnetic fields. A small capacity damper is made, and damping tests are performed using the new fluids and also commercial MR fluid. Dynamic properties of the damper are evaluated. As a result of a series of studies, the developed hybrid magnetic responsive fluid is expected to be used as an intelligent fluid.
Study on Damage of Joint for Overhead Traveling Crane of Nuclear Power Plant Under Earthquake
Authors: Shintani Masanori , Nara Kentaro , Ogawa Yuji
Published: July 2010

This paper deals with research on the intensity analysis of universal joint of overhead traveling crane and the damage experiments of miniature universal joint. The Kashiwazaki Kariwa nuclear power plant suffered damage from the Niigata Chuetsu offing earthquake which occurred on July 16, 2007. The earthquake motion damaged a driving shaft coupling of an overhead traveling crane of the No. 6 nuclear reactor building. The damaged portion was the universal joint. The purpose of this research is to examine the cause of breakage and proposed measures of a universal joint. First, the cause of breakage is examined. Next, the breakage experiment of miniature universal joints (it hereafter calls a test piece) is conducted. Moreover, the analytical models of test piece are created, stress analysis is conducted, and the validity of analytical models is shown by comparing with the experimental result. Seismic response analysis of the building of nuclear power station is conducted, and the response acceleration of overhead traveling crane floor is calculated. The torque working to the universal joint of crane is calculated from the floor response acceleration. Furthermore, the analytical model of the universal joint of overhead traveling crane is created, stress is calculated by the torque and the cause of breakage is checked. One effective method which avoids breakage of the overhead traveling crane under earthquake is proposed.
Assessment of Inspection Performance Using Simulation Supported POD Curves
Authors: Jenson Fre´de´ric , Iakovleva Ekaterina , Reboud Christophe
Published: July 2010

A framework is proposed in this paper in order to estimate statistical criteria such as Probability Of Detection (POD) from numerical simulation data. The software dedicated to Non Destructive Evaluation (NDE) CIVA allows us to simulate an inspection for various techniques and setups. Uncertainty is taken into account using random number generators for various statistical distributions. Finally, the POD is estimated from the simulation results using a state-of-the-art approach which assumes a functional form for the statistical criteria. Application cases are shown for both Eddy Current (EC) and Ultrasonic Techniques (UT).
Construction of the Health Monitoring System of a Machine Structure
Authors: Shintani Masanori , Masaki Keita
Published: July 2010

When big power like an earthquake acts at the place that the machine is normally operating, abnormalities may occur to a machine. If the machine is operated without finding abnormally, danger may attain to mechanical fatal damage and a mechanical work pursuer. Therefore, detecting in the situation where mechanical abnormalities are operated is very important as a health monitoring system. In this research, the system that takes in the vibration wave on the rotation part of the machine currently rotated is constructed. A vibration wave is analyzed using time-frequency analysis (STFT, the Wigner distribution, wave let analysis) From the result, the system by which normal vibration and abnormal vibration are evaluated is constructed from random noise. As a result of comparing normal vibration with abnormal vibration, the peak may have occurred in the high frequency region. It turned out that the analysis result of an unsteady state has a peak 2000Hz–3000Hz of frequency domains, and 4000Hz–5000Hz also in STFT and Wigner distribution. I think that this becomes the important tool which distinguishes the stationary state and unsteady state in health monitoring.
Materials Databases and Knowledge Management for Advanced Nuclear Technologies
Authors: Hoffelner Wolfgang
Published: July 2010

International collaborations like the Generation IV initiative have the aim to create the technical basis for design and operation of advanced nuclear plants. Materials data shall be created in joint international materials projects. Data will be aggregated in databases like the “Generation IV materials handbook”. Mechanical data, but also microstructural information and information concerning materials production shall be included. This information will be used to create or amend code rules, to provide a basis for life-time analysis, damage assessments and for safety analyses. Such considerations need not only raw materials data but also tools for data analysis and evaluation. Multiscale modeling, establishing constitutive equations, development of advanced life-time prediction methods, quantitative correlation of mechanical properties with microstructure, quantification of environmental effects, tools for non destructive evaluation and condition based monitoring etc. are important analysis techniques needed for safe design and operation of advanced plants. These needs led the author to ask the question if current databases could not be enlarged by data evaluation and methods tools which could even end some day in the availability of web-based design codes and safety analyses. The database could also be used as a web-based discussion and development space. It could become then a powerful tool for knowledge management The paper will discuss this concept on basis of some examples.
Two-Phase Flow-Induced Forces on Bends in Small Scale Tubes
Authors: Cargnelutti Marcos F. , Belfroid Stefan P. C. , Schiferli Wouter
Published: July 2010

Two-phase flow occurs in many situations in industry. Under certain circumstances, this can be the source of flow-induced vibrations. The forces generated can be sufficiently large to affect the performance or efficiency of an industrial device. At worst, the mechanical forces that arise may endanger structural integrity. Thus, it is important to take these forces into account in designing industrial machinery to avoid problems during operation. Although the occurrence of such forces is well-known, not much is known about their magnitudes. Unfortunately, the amount of experimental data available in literature is rather limited. This paper describes an investigation into the forces in a two-phase flow in a 6mm pipe containing a bend. The results are analyzed based on flow regime and bend configuration. Finally, a simple model is proposed to predict the forces generated by slug flow.
Final Results of an Analytical Round Robin Exercise to Support Constraint Effects
Authors: Scibetta Marc , Altstadt Eberhard , Herna´ndez Callejas Rogelio , Lee Bong-Sang , Miura Naoki , Onizawa Kunio , Paffumi Elena , Serrano Marta , Tatar Levente , Yin Shengjun
Published: July 2010

There is strong interest from the nuclear industry to use the precracked Charpy single-edge notched bend, SE(B), specimen (PCVN) to enable determination of the reference temperature, T0, with reactor pressure vessel surveillance specimens. Unfortunately, for many different ferritic steels, tests with the PCVN specimen (10×10×55 mm) have resulted in T0 temperatures up to 25°C lower than T0 values obtained using data from compact, C(T), specimens. This difference in T0 reference temperature has often been designated a specimen bias effect, and the primary focus for explaining this effect is loss of constraint in the PCVN specimen. The International Atomic Energy Agency has developed a three-part coordinated research project (CRP) to evaluate various issues associated with the fracture toughness Master Curve for application to light-water reactor pressure vessels. One part of the CRP is focused on the issue of test specimen geometry effects, with emphasis on the PCVN bias. This topic area was organized in two parts, an experimental part and an analytical part with a view towards each part complementing the other. Within the analytical part, elastic plastic finite element methods are extensively used in order to access local stress and strain information that is the basic ingredient for most of the micromodels of cleavage fracture developed to date. In the framework of the international qualification and acceptance of such a tool for actual loss of constraint prediction, the validation of such tool is of prime importance. Therefore, a round robin exercise has been proposed and performed by ten laboratories from nine different countries. The round robin focuses on the modeling of realistic three-dimensional geometries containing shallow and deep crack. This round robin has been useful to qualify different finite element codes and to identify possible errors in the input file. The round robin demonstrates that errors in the input file can be easily introduced. Some remaining differences cannot be attributed to one particular finite element code or to actual errors. Those differences are attributed to the so called “user effect” which can only be reduced through in depth discussion and deep understanding of each finite element code. Independently of the used code and of relatively small user effect differences, it is found that shallow crack specimens are more sensitive to loss of constraint than deep crack specimens for a given specimen size. The difference in terms of reference temperature between the two geometries is evaluated to be about 40 °C. For a deep crack, loss of constraint is identified to appear at M values around 200. This value is larger than the one specified in current standard (M = 30). Increasing the M value to 200 will jeopardize the use of PCVN for the nuclear industry on the other hand bias introduced by M value of 30 is acceptable.
Statical Computation of the Main Building
Authors: Mo´ga Istva´n
Published: July 2010

This paper provides a preliminary systematic overview of the static computation and its preparation for the existing VVER-440/V213 type reactor building. The control static computation of building will be founded mainly on the current important American nuclear codes and regulations. In the preparation phase the selected standards for the application were determined. The harmonization with the Hungarian regulations is one of the main goals of the preparation. The report summarizes the main elements of this process.
Pessimisms Inherent in Current Treatments of Multiple Defects in Fracture Assessments
Authors: Smith Edwin , Beardsmore David W.
Published: July 2010

Fracture mechanics procedures such as R6 and BS7910 provide a number of rules for assessing multiple co-planar, interacting defects of regular or irregular shapes. These rules allow multiple defects to be replaced by a single, characterising defect that may be assessed conservatively using the procedures. Multiple elliptical or semi-elliptical defects in the wall of a pressure vessel or other pressurised component may be orientated such that their major axes are parallel to the wall, or else may be orientated arbitrarily. Where the orientation is arbitrary, care is needed to interpret appropriately the characterisation rules available in the procedures. The characterisation rules were originally intended to provide a basis for the assessment of cleavage fracture, although they have also been applied for the assessment of ductile fracture and fatigue. Recent experimental evidence and analytical studies have questioned the amount of conservatism inherent in the application of the characterisation rules, particularly with regard to cleavage fracture assessments. This paper describes an interpretation of the characterisation rules for multiple, arbitrarily orientated defects which has been accepted by the UK Technical Advisory Group on the Structural Integrity of Nuclear Plant (TAGSI). The paper examines the amount of pessimism in the procedure for the assessment of cleavage fracture at different temperatures in the ductile-brittle transition region. Although in general terms, the characterisation rules are likely to be conservative for temperatures in the upper transition, no definite safe minimum temperature can be set, and the conservatism of each application must be considered on a case-by-case basis with due consideration paid to the size of the crack tip plastic zone relative to the defect size.
Procedure to Guarantee Tightness of Bolted Flange Connections of Floating Type With Two Gaskets
Authors: Junek Lubomir , Bartonicek Jaroslav , Vrana Milan
Published: July 2010

To consider special demands, two gaskets floating between the flange faces are used for example in flanged connections of pressure vessels, valves, pumps etc. Tightness control can be one of the reasons to choose this design. The inner (primary) gasket has to tighten the internal pressure; the outer (secondary) gasket tightens possible leakage of the primary gasket. By the use of two identical gaskets in the same plane the procedure for the tightness proof is the same as in connections with one gasket. In many cases there are used two gaskets with different characteristics (deformation and tightness characteristics) in two tightening planes. The behaviour of this connection depends not only on the gasket characteristics but also on the tolerances of axial dimensions. The distribution of prestress on both gaskets is determined by the elastic-plastic deformations of both gaskets and tolerances of axial dimensions of the connection. The decrease of gasket stress in operation depends on the plastic deformations of both gaskets in operation, too. Depending on the demanded tightness class, the possible gasket stress during assembly and the gasket stress in operation determine the selection of suitable gaskets (with necessary gasket characteristics). It is necessary to take into account the internal pressure and possible pressure between primary and secondary gasket, too. In the paper the design of gaskets for this type of connection is discussed. Originally, it was used: - nickel ring as primary gasket, - asbestos packing as secondary gasket. Both gaskets have suitable deformation characteristics for the existing type of connection. The secondary gasket has low stiffness for the adjustment of an optimal stress on the primary gasket after prestressing. The primary gasket has a good relaxation behaviour. However, the nickel ring needs a very high local stress to achieve suitable tightness behaviour. This stress leads to plastic deformation of the flange surface during assembly, too, and this can induce leakage after the next assembly (with new rings) as operation experience showed. The use of asbestos packing is not allowed any more due to health reasons. This invoked a redesign of this gasket. The paper deals with gasket proofs and gasket characteristics for selection of suitable gaskets. Calculations of gasket stress distributions of both gaskets (elastic-plastic deformations) are presented. The analysis of the stress distribution allows reviewing the tightness class in operation incl. relaxation behaviour of the connection. Other recommendations are listed like the increase of connection safety by a reduction of bolt stiffness (better relaxation behaviour of the connection and higher bolt elongation), more accurately bolt elongation measurement, new assembly procedure, etc. Main target of the re-design is life time extension of connection, too.
Design Assessment of Austenitic Stainless Steel Components for Applications Covered by ASME III Class 1 Code Requirements
Authors: Willis J. R. , Lidbury D. P. G.
Published: July 2010

The UK Technical Advisory Group on the Structural Integrity of High Integrity Plant (TAGSI) has recently undertaken an assessment of a new method of classification of austenitic stainless steel components based on their safety function and the consequences of their failing to perform that function. The intent of the safety classification is to ensure that the probability of occurrence of any potential failure bears an inverse relation to the severity of its consequence, so that a low risk is incurred from failure of any type. Specifically, TAGSI was invited to: 1. consider circumstances under which Subsection NB of the ASME III Code for Class 1 components contributes adequate margins against gross failure of austenitic stainless steel components classified as High Integrity; and if necessary 2. define additional contributions that need to be met to provide assurance against gross failure of austenitic stainless steel components for the High Integrity severity level. In producing its response, TAGSI interpreted the Question as relating strictly to the austenitic stainless steel pipework and associated welds of the relevant class of PWR systems that have the safety classification of High Integrity. Dissimilar metal welds were excluded from consideration, and it was assumed that a robust EAC prevention strategy is in place. The generic response produced by TAGSI to the above Question is summarised within this framework.
Modal Techniques for Remote Identification of Nonlinear Reactions at Gap-Supported Tubes Under Turbulent Excitation
Authors: Delaune Xavier , Antunes Jose´ , Debut Vincent , Piteau Philippe , Borsoi Laurent
Published: July 2010

Predictive computation of the nonlinear dynamical responses of gap-supported tubes subjected to flow excitation has been the subject of very active research. Nevertheless, there is a need for robust techniques capable of extracting, from the actual vibratory response data, information which is relevant for asserting the components integrity. The dynamical contact/impact (vibro-impact) forces are of paramount significance, as are the tube/support gaps. Following our previous studies in this field using wave-propagation techniques [1–3], we apply modal methods in the present paper for extracting such information. The dynamical support forces, as well as the vibratory responses at the support locations, are identified from one or several vibratory response measurements at remote transducers, from which the support gaps can be inferred. As for most inverse problems, the identification results prove quite sensitive to noise and modeling error problems. Therefore, topics discussed in the paper include regularization techniques to mitigate the effects of non-measured noise perturbations. In particular, a method is proposed to improve the identification of contact forces at the supports when the system is excited by an unknown distributed turbulence force field. The important topic of dealing with the imperfect knowledge of the modal parameters used to build the inverted transfer functions is addressed elsewhere [4]. Here, the extensive identifications presented are based on the exact modal parameters and performed on realistic numerical simulations of gap-supported tubes subjected to flow excitation. We can thus confront the identified dynamical support contact forces and vibratory motions at the gap-support with the actual values stemming from the original nonlinear computations, with overall satisfying results.
Multiple Reflection and Transmission Theory for Wave Propagation in the Aorta
Authors: Giannopapa C. G. , Kroot J. M. B.
Published: July 2010

Wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flow. Theoretical and experimental investigations of traveling waves in flexible tubes have been performed by many researchers. The analytical one dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost involved in the modern time domain simulation models. Transition line theory allows including non uniformities of vessels by capturing them as several uniform segments. For assessing the validity of analytical and numerical models well defined in-vitro experiments are of great importance. The objective of this paper is to present a frequency domain transmission line analytical model based on one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogues. The analytical model is set up by multiple sections and a formulation is derived that incorporates the multiple reflections and transmissions of propagating waves through the interfaces of these sections. The aortic analogues include straight and tapered tubes. The pressure, flow and wall distention results obtained from the analytical model are compared with experimental data in two straight tubes and one tapered one with aortic relevance. The analytical models and the experimental measurements were found to be in good agreement for both the uniform and tapered tubes.
A Web-Based Uncertainty Plug-In (WUPI) for Fatigue Life Prediction Based on NDE Data and Fracture Mechanics Analysis
Authors: Fong Jeffrey T. , Marcal Pedro V. , Hedden Owen F. , Chao Yuh J. Bill , Lam Poh-Sang
Published: July 2010

Over the last thirty years, much research has been done on the development and application of failure event databases, NDE databases, and material property databases for pressure vessels and piping, as reported in two recent symposia: (1) ASME 2007 PVP Symposium (in honor of the late Dr. Spencer Bush), San Antonio, Texas, on “Engineering Safety, Applied Mechanics, and Nondestructive Evaluation (NDE).” (2) ASME 2008 PVP Symposium, Chicago, Illinois, on “Failure Prevention via Robust Design and Continuous NDE Monitoring.” The two symposia concluded that those three types of databases, if properly documented and maintained on a worldwide basis, could hold the key to the continued safe and reliable operation of numerous aging nuclear power or petrochemical processing plants. During the 2008 symposium, four uncertainty categories associated with causing uncertainty in fatigue life estimates were identified, namely, (1) Uncertainty-1 in failure event databases, (2) Uncertainty-2 in NDE databases, (3) Uncertainty-3 in material property databases, and (4) Uncertainty-M in crack-growth and damage modeling. In this paper, which is one of a series of four to address all those four uncertainty categories, we address Uncertainty-2 in NDE databases by developing a Web-based Uncertainty Plug-In (WUPI), which automates the uncertainty estimation algorithms of flaw sizing, fracture toughness, and crack growth vs. ΔK data such that NDE data from the field can be acted on by office engineers with a reduced feedback time for maintenance decision making.
Data Mining of General Corrosion of Most Commonly Used Alloys Using Kohonen Mapping
Authors: Kirsch Kathryn L. , Nahar Mst Kamru , Urquidi-Macdonald Mirna
Published: July 2010

This study was developed to provide an optimum method for designing metal alloys. Information on general corrosion of the most commonly used alloys, namely nickel-, iron-, aluminum-, stainless steel-, copper- and carbon-based alloys, was obtained from the National Institute of Standards and Technology (NIST). Parameters such as pH, temperature, conductivity, and composition of the electrolyte used in each experiment (alloy in contact with an environment), along with alloy composition (UNS) and corrosion rates, were collected. The parameters in the collected data were the electrolyte characteristics, the alloy composition, and the general corrosion rates. The data consisted of over 4000 samples. The next task was to cluster the data by similarities of the parameters. A web-based, publicly available Kohonen mapping software was used to perform the clustering analysis; the two dimensional Kohonen map was chosen. The map is composed of a number of cells on a plane of two dimensions and each cell stores a sample prototype representing that cell. Kohonen maps have the ability to preserve the topological properties of the data; i.e. samples with similar “high corrosion rates” will cluster together in a given cell of the map, while samples with “low corrosion rates” will cluster in a different cell, far apart from the cell storing the “high corrosion rates” samples. Once the Kohonen map is trained to cluster the samples by their corrosion rates, each one of the parameters of the samples (representing the electrolyte characteristics, the alloy composition and the general corrosion rates) is drawn as a function of the (X,Y) map position of the cell where the samples were stored. In this paper, we present the results obtained with nickel alloy data for which 1369 samples (or independent experiments) were collected.
Experiences With Controlled Deposition Welding and Fitness for Service in Coke Drums
Authors: Penso Jorge A. , Li M. Victor
Published: July 2010

Controlled deposition welding (CDW) is a joining technique to refine grains and to temper underlying heat affected zone (HAZ) in the base metal. Applications and technical justifications of CDW for coke drum repairs are presented in this article. CDW procedures have been developed and field implemented both offline and online. Computer modeling to predict weld microstructure and mechanical properties is used to pre-select welding variables and minimize laboratory testing. Several field cases are summarized. Coupons obtained from post weld heat treatment repairs and CDW repairs were collected and fatigue tested. Also shown are examples of fitness for service assessments to define repair strategy.
Shakedown/Ratcheting Boundary Determination Using Iterative Linear Elastic Schemes
Authors: Adibi-Asl R. , Reinhardt W.
Published: July 2010

This paper presents a robust non-cyclic method to identify the boundary between the shakedown and ratcheting domains (ratchet boundary) directly without the need for cyclic analysis. The solution can be obtained using only linear-elastic FEA. The method is based on lower bound formulation in shakedown theory, which is safe for design. It offers an attractive alternative to cyclic elastic-plastic analysis since it is simple, and requires considerably less computational effort and computer storage space. Another attractive feature is that the method provides a go/no go criterion for the ratchet boundary, whereas the results of a cyclic elastic-plastic analysis are often difficult to interpret near the ratchet boundary. The proposed method is applied to a number of configurations that include two-dimensional and three-dimensional effects.
Strength Assessment of Equipments and Piping of WWER Nuclear Power Plants
Authors: Vejvoda Stanislav
Published: July 2010

The Standard Technical Documentation (STD) of The Association of Mechanical Engineers (A.M.E.), Section III “Strength Assessment of Equipment and Piping of Nuclear Power Plant of VVER type” provides guides and requirements for elaboration of: - conclusive documentation for equipment, piping and their supports, manufactured and supplied or manufactured for replacement, for nuclear power plants of VVER type, 440 MW and 1000 MW; - conclusive documentation for repaired, replaced and innovated components of equipment, piping and their supports for nuclear power plants of VVER type, 440 MW and 1000 MW; - conclusive documentation on continuous lifetime usage of equipment, piping and their supports during the operation of nuclear power plants of VVER type, 440 MW and 1000 MW and determination of their residual lifetime; - documentation on degree of compatibility of equipment, piping and their supports for nuclear power plants of VVER type, 440 MW and 1000 MW with the ASME Code Section III, Division 1. The following principles of the Section III are discussed in the presentation: general structure of the Section III; design specifications and operational conditions; calculation of allowed stresses; stress categories groups (σ)1, (σ)2, (σ)R, and (σaF); limit criteria for stress categories groups; loading blocs; assessment on fatigue; assessment of two-frequency cyclic loading on fatigue; fatigue correction factors for multiaxial stress states and gradient of stresses, corrosion, welding and radiation; limits; determination of load at collapse; use of elastic and elastic-plastic analyses; elastic-plastic carrying capacity of components; stiffness of the nozzle opening.
Main Steam Piping Girth Weldment Stresses and Life Consumption Considering Malfunctioning Supports
Authors: Cohn Marvin J.
Published: July 2010

A high energy piping (HEP) program is important for the safety of plant personnel and reliability of the generating units. HEP weldment failures have resulted in serious injuries, fatalities, extensive damage of components, and significant lost generation. Since creep/fatigue is a typical failure mechanism, the probability of HEP failures increases with unit age. The main steam (MS) piping system is one of the most critical HEP systems. Weldment failures are typically due to a combination of high temperature creep and fatigue. Industry best practices include (1) the evaluation of historical operating conditions, (2) examinations of critical weldments to reveal NDE indications, microstructural material damage, and detailed geometry data, (3) hot and cold walkdowns to document the field piping system behavior and anomalies, (4) simulation of as-found piping displacements to estimate actual stresses, (5) ranking of critical weldments, (6) recommendations for support repairs and adjustments, (7) recommendations for future examinations, and (8) remaining life estimates at critical weldments. Appropriate examinations, condition assessments, and recommendations for corrective actions are provided as a cost-effective life management process to maintain the piping system integrity. This paper provides examples demonstrating that the girth welds ranked below the top five to six welds are subject to significantly less applied stress and have substantially more creep/fatigue life than the top ranked welds. Hanger adjustments, along with selective identification, NDE, and possible repairs of top ranked welds provide substantially greater life to MS piping systems. Some fitness-for-service and risk-based programs for MS piping system girth weldments recommend a stress evaluation using typical pressure vessel or boiler tube calculations, in which the hoop stress is the principal stress. In some cases, the effective weldment stresses can be more than 50 percent above the hoop stress, resulting in the estimated remaining lives less than 15 percent of the life estimates using the hoop stress methodology. Some HEP life management programs may vaguely discuss using the principal stress based on a finite element analysis of the piping system. These principal stress values may be based on a conventional as-designed piping stress analysis. In the majority of the as-found piping stress analyses performed by the author, the maximum as-found stresses are substantially greater than the maximum conventional as-designed piping stresses. Consequently, an as-designed piping stress analysis will typically underestimate the life of an HEP system and typically not predict the locations of maximum creep/fatigue damage.
Effect of Retained Austenite Parameters on Burring of Trip-Aided Sheet Steels
Authors: Nagasaka Akihiko , Sugimoto Koh-ichi , Murakami Toshio , Kawajiri Masahiro
Published: July 2010

Effect of retained austenite parameters on burring of (0.1–0.4)C-1.5Si-1.5Mn (mass%) ultra high-strength TRIP-aided sheet steels with porigonal ferrite matrix (TDP steels) having different retained austenite parameters was investigated for automotive applications. Thermal drilling is a process that uses friction to produce bushing in steel tubing and sheet. The combined rotational and downward force of the thermal drilling tool bit creates friction heat. The height of the bushing was roughly 3 to 4 times the original steel thickness. The bushing are ideal for thread applications, as the strength of threads was significantly increased. Hole notches of 5mm diameter were produced by mechanical punching for hole-expanding test. The stretch-flangeability was evaluated using hole-expanding ratio. The hole-expanding ratio of burring were completed in TDP steels. The higher tensile strength, the lower hole-expanding ratio of mechanical punching. In TDP steels, the burring resulted in much higher stretch-flangeability than the mechanical punching. We found that compared with mechanical punching, the burring contributed to the improvement of the tensile strength of 1100MPa class TDP steel with porigonal ferrilte matrix.
An Anisotropic Hardening Rule With Non-Associated Flow Rule for Pressure-Sensitive Materials
Authors: Choi K. S. , Pan J.
Published: July 2010

In this paper, cyclic plastic behaviors of pressure-sensitive materials based on an anisotropic hardening rule with two non-associated flow rules are examined. The Drucker-Prager pressure-sensitive yield function and the Mises plastic potential function are adopted to explore the cyclic plastic behaviors of pressure-sensitive materials or strength-differential materials. The constitutive relations are formulated for the initial loading and unloading/reloading processes based on the anisotropic hardening rule of Choi and Pan [1]. Non-associated flow rules are employed to derive closed-form stress-plastic strain relations under uniaxial cyclic loading conditions. The stress-plastic strain curves based on a conventional non-associated flow rule do not close, and show a significant ratcheting under uniaxial cyclic loading conditions. A new non-conventional non-associated flow rule is then formulated based on observed nearly closed hysteresis loops of pressure-sensitive materials. The stress-plastic strain curves based on the non-conventional non-associated flow rule show closed hysteresis loops under uniaxial cyclic loading conditions. The results indicate that the anisotropic hardening rule with the non-conventional non-associated flow rule describes well the strength-differential effect and the asymmetric closed hysteresis loops as observed in the uniaxial cyclic loading tests of pressure-sensitive materials.
Design of a PYTHON-Based Plug-In for Benchmarking Probabilistic Fracture Mechanics Computer Codes With Failure Event Data
Authors: Fong Jeffrey T. , deWit Roland , Marcal Pedro V. , Filliben James J. , Heckert N. Alan , Gosselin Stephen R.
Published: July 2010

In a 2007 paper entitled “Application of Failure Event Data to Benchmark Probabilistic Fracture Mechanics (PFM) Computer Codes” (Simonen, F. A., Gosselin, S. R., Lydell, B. O. Y., Rudland, D. L., & Wikowski, G. M. Proc. ASME PVP Conf., San Antonio, TX, Paper PVP2007-26373), it was reported that the two benchmarked PFM models, PRO-LOCA and PRAISE, predicted significantly higher failure probabilities of cracking than those derived from field data in three PWR and one BWR cases by a factor ranging from 30 to 10,000. To explain the reasons for having such a large discrepancy, the authors listed ten sources of uncertainties: (1) Welding Residual Stresses. (2) Crack Initiation Predictions. (3) Crack Growth Rates. (4) Circumferential Stress Variation. (5) Operating temperatures different from design temperatures. (6) Temperature factor in actual activation energy vs. assumed. (7) Under reporting of field data due to NDE limitations. (8) Uncertainty in modeling initiation, growth, and linking of multiple cracks around the circumference of a weld. (9) Correlation of crack initiation times and growth rates. (10) Insights from NUREG/CR-6674 (2000) fatigue crack growth models using conservative inputs for cyclic strain rates and environmental parameters such as oxygen content. In this paper we design a Python-based plug-in that allows a user to address those ten sources of uncertainties. This approach is based on the statistical theory of design of experiments with a 2-level factorial design, where a small number of runs is enough to estimate the uncertainties in the predictions of PFM models due to some combination of the source uncertainties listed by Simonen et al (PVP2007-26373).
Fatigue Crack Initiation and Growth in Stainless Steel Pipe Welds
Authors: Green D. , Smith R. D. , Taggart J. P. , Beardsmore D. , Robinson S.
Published: July 2010

Thermal fatigue cracks have been found in austenitic pipe work in many pressurised water reactors, caused by thermal cycling due to the passage of water at different temperatures along the pipe inner surface. The rates of crack initiation and growth for this situation are not well understood because of the stochastic nature of the temperature fluctuations. Therefore, large allowances must be made when assessing the integrity of this pipe work to this failure mechanism. Improved assessment of crack initiation and growth could enable increased plant availability, and better safety cases. A programme of work has been completed consisting of fatigue tests on thick 304L butt-welded pipe specimens, and accompanying predictions of crack initiation and growth. In each test, uniform thermal cycles were generated using a water jet on a small area of the pipe. The magnitude of the cycles differed between the tests. Crack initiation and growth were monitored using a dye penetrant technique, applied to the pipe inner and outer surfaces, together with destructive examination. Crack initiation predictions were made using fatigue data derived from mechanical fatigue tests on the same material as in the pipe specimens. Good predictions were made using a strain-life endurance curve at a temperature corresponding to the average temperature of the metal surface during the thermal cycle. Crack growth predictions were based on an inelastic finite-element model accounting for cyclic hardening, and an enhanced R5 procedure (1) with crack closure taken into account. A linear elastic fracture mechanics definition of a Paris law for crack growth was used, and plastic redistribution effects were included. Predictions were good for all of the experimental scenarios carried out. A further experimental and analytical programme is in hand using the same experimental arrangements, concerning variable amplitude thermal loading.
Assessment of State of Residual Stress of Hybrid Pressure Vessels
Authors: Schulz Michael , Gregor Christian
Published: July 2010

For fully carbon fibre wrapped pressure vessels with load sharing metallic liner (Type III), it was recognized that the state of residual stress given after the autofrettage process can change even if the vessel is stored without pressure. This change is influenced by temperature and time and has a direct effect on the residual lifetime of the vessel. To study the influence of the temperature on the state of residual stress an analytical model was applied which is based on the Classical Laminate Theory (CLT). According to the model, the critical conditions leading to a decrease in lifetime were identified. To confirm the results of the model temperature cycle tests were carried out. The results of the tests are compared with the analytical model and a finite element model. To investigate the influence of time on the state of residual stress, tests on vessels were performed. The tested vessels were aged without any pressure for a longer period of time after the autofrettage process. During these tests, the strain of the vessels was monitored.
Review of Pipe Wall Thinning and Seismic Evaluation in Japan
Authors: Miyano Hiroshi , Maeda Katsuji , Takizawa Masayuki , Sekimura Naoto
Published: July 2010

For nuclear power plants, the four major requirements are 1) high safety, 2) high reliability, 3) good economical acceptability, and 4) as few as possible environmental impact. However, it is still difficult to completely avoid problems for structural materials as structural stress corrosion cracking (SCC) and for piping systems as flow accelerated corrosion (FAC), liquid drop impulsion erosion (LDI). Especially FAC and LDI are uncertainty phenomenon as pipe wall thinning, so there is the piping rupture accident risk on all of piping systems under the specific conditions. In Japan, after in August 2004, the accident of the secondary pipe rupture in Mihama Power Plant Unit 3, The Kansai Electric Power Co., Inc. (KEPCO), R&D projects about pipe wall thinning phenomenon and mechanism had been promoted in many organizations. The other hand it is requested to evaluate the safety and reliability of piping systems of long term operating plant and with on special case of seismic condition. It was requested to be able to evaluate pipe wall thinning and its reliability with more accurate. This project had programmed under the government budget from 2006 planed until 2010 fiscal year [1]. At the mile stone of half span, the project had these fruits, 1) Computer program for FAC simulation, 2) Droplet phenomena for LDI simulation, 3) Simplified calculation model of pipe wall thinning for seismic evaluation.
BS 7910: History and Future Developments
Authors: Hadley Isabel
Published: July 2010

BS 7910, the UK procedure for the assessment of flaws in metallic structures, was first published almost 30 years ago in the form of a fracture/fatigue assessment procedure, PD6493. It provided the basis for analysing fabrication flaws and the need for repair in a rational fashion, rather than relying on long-established (and essentially arbitrary) workmanship rules. The UK offshore industry in particular embraced this new approach to flaw assessment, which is now widely recognised by safety authorities and specifically referred to in certain design codes, including codes for pressure equipment. Since its first publication in 1980, PD6493/BS 7910 has been regularly maintained and expanded, taking in elements of other publications such as the UK power industry’s fracture assessment procedure R6 (in particular the Failure Assessment Diagram approach), the creep assessment procedure PD6539 and the gas transmission industry’s approach to assessment of locally thinned areas in pipelines. The FITNET European thematic network, run between 2002 and 2006, has further advanced the state of the art, bringing in assessment methods from SINTAP (an earlier European research project), R6, R5 and elsewhere. In particular, the FITNET fracture assessment methods represent considerable advances over the current BS 7910 methods; for example, weld strength mismatch can be explicitly analysed by using FITNET Option 2, and crack tip constraint through Option 5. Corrosion assessment methods in FITNET are also more versatile than those of BS 7910, and now include methods for vessels and elbows as well as for pipelines. In view of these recent advances, the BS 7910 committee has decided to incorporate many elements of the FITNET procedure into the next edition of BS 7910, to be published c2012. This paper summarises the history of the development of BS 7910, its relationship with other flaw assessment procedures (in particular FITNET and R6) and its future.
Structural Vibration Control by Damping Parametric Excitation
Authors: Iba Daisuke , Masuda Arata , Sone Akira
Published: July 2010

This paper proposes a new method for utilization of variable damping in a vibration system. The coefficient of variable damping can be changed as that in the case of a sine wave, i.e. parametric excitation whose frequency can be arbitrarily selected. As a results of the parametric excitation, the vibration amplitude of the system increases because of the resonance at arbitrary frequency of the external input. We have confirmed the resonance of the damping parametric excitation by simulation and experiment and proposed a method of frequency response analysis of the vibration system with the parametric excitation of damping coefficient and the external harmonic excitation. In this paper, we consider about the SDOF vibration model with the external input that includes two frequency contents, and we propose a new vibration control method that the outputs interfere with each other by the parametric excitation. Finally, we confirm the effectiveness of the proposed control method by simulation.
Weld Distortion Control Methods and Applications of Weld Modeling
Authors: Brust F. W. , Wilkowski G. , Shim D. J. , Zhang T. , Kurth E.
Published: July 2010

Computational weld modeling is challenging because many of the processes of welding are highly nonlinear. Material melts and re-solidifies, very high transient thermal gradients are experienced, non-linear temperature dependent plastic straining and phase transformations can occur, among other sources of nonlinearity. Moreover, for weld modeling to have practical advantages in industrial production, computational solution times must be manageable since an optimum weld design of large, complex fabrications requires numerous separate analyses. Weld modeling technology is now advanced to where it can have an important impact on numerous fabricated structures. These include nuclear power plant components in commercial nuclear plants and nuclear ship structures, including Aircraft Carriers, Submarines, and Destroyers. The benefits of weld modeling include: • Significantly reduced Fabrication Costs. • Life cycle cost reduction from improved corrosion, and fatigue performance and damage reduction enhancement. • Elimination of non-valued added re-work fabrication costs. • Improve readiness by speeding the time from conception to service for new designs. • Outreach program to continue paradigm shift improvements in welded fabrications. Weld distortion control must be performed on three dimensional models. Here, extensive full-scale experiments have validated the accuracy and predictive power of models. It can be used to reduce fabrication cost and improve quality by minimizing and controlling distortions. Several application examples are presented to illustrate how to apply this tool in welded structure design and manufacture.