bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of Beamforming Processing Techniques for Low Frequency Noise Source Identification in Mining Equipment
Authors: Camargo Hugo E. , Ravetta Patricio A. , Burdisso Ricardo A. , Smith Adam K.
Published: July 2010

In an effort to reduce Noise Induced Hearing Loss (NIHL) in the mining industry, the National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop noise controls for mining equipment whose operators exceed the Permissible Exposure Level (PEL). The process involves three steps: 1) Noise source identification (NSI), 2) development of noise controls, and 3) evaluation of the developed noise controls. For the first and third steps, microphone phased array measurements are typically conducted and data are processed using the conventional beamforming (CB) algorithm. However, due to the size and complexity of the machines, this task is not straight forward. Furthermore, because of the low frequency range of interest, i.e., 200 Hz to 1000 Hz, results obtained using CB may show poor resolution issues which result in inaccuracy in the noise source location. To overcome this resolution issue, two alternative approaches are explored in this paper, namely the CLEAN-SC algorithm and a variarion of an adaptive beamforming algorithm known as Robust Capon Beamformer (RCB). These algorithms were used along with the CB algorithm to process data collected from a horizontal Vibrating Screen (VS) machine used in coal preparation plants. Results with the array in the overhead position showed that despite the use of a large array, i.e., 3.5-meter diameter, the acoustic maps obtained using CB showed “hot spots” that covered various components, i.e., the screen deck, the side walls, the I-beam, the eccentric mechanisms, and the electric motor. Thus, it was not possible to identify which component was the dominant contributor to the sound radiated by the machine. The acoustic maps obtained using the RCB algorithm showed smaller “hot” spots that in general covered only one or two components. Nevertheless, the most dramatic reduction in “hot” spot size was obtained using the CLEAN-SC algorithm. This algorithm yielded acoustic maps with small and well localized “hot” spots that pinpointed dominant noise sources. However, because the CLEAN-SC algorithm yields small and localized “hot” spots, extra care needs to be used when aligning the acoustic maps with the actual pictures of the machine. In conclusion, use of the RCB and the CLEAN-SC algorithms in the low frequency range of interest helped pinpoint dominant noise sources which otherwise would be very hard to identify.
The Effect of Squeeze-Film Damping on Suppressing the Shock Response of MEMS
Authors: Yagubizade Hadi , Younis Mohammad I. , Rezazadeh Ghader
Published: July 2010

This paper presents an investigation into the response of a clamped-clamped microbeam to mechanical shock under the effect of squeeze-film damping (SQFD). In this work, we solve simultaneously the nonlinear Reynolds equation, to model squeeze-film damping, coupled with a nonlinear Euler-Bernoulli beam equation. A Galerkin-based reduced-order model and a finite-deference method (FDM) are utilized for the solid domain and for the fluid domain, respectively. Several results showing the effect of gas pressure on the response of the microbeams are shown. Comparison with the results of a multi-physics nonlinear finite-element model is presented. The results indicate that squeeze-film damping has more significant effect on the response of microstructures in the dynamic shock loads compared to the quasi-static shock loads.
Microfluidic Reactors for Bioluminescence Detection
Authors: Fan Z. Hugh , Mei Qian , Soper Steve
Published: July 2010

Bioluminescence detection is often achieved by using luciferase as an enzyme. When it is implemented in a microfluidic device, the enzyme must be properly mixed with luciferase assay reagents (LAR) to achieve enzymatic reactions. Two microfluidic reactors are investigated in this work for bioluminescence detection. The reactors were fabricated in poly(methylmethacrylate), PMMA, by hot embossing using a mold master with the reactor layouts made by high-precision micromilling. Reactor I device contains staggered herringbone mixers. Reactor II device has the same layout except that the mixers were replaced with smooth channels. We found that the mixing efficiency in Reactor I was 17.8 times higher than Reactor II. Theoretical analysis of the experimental results indicated that the required channel length of mixing was linearly proportional to the flow rate. A calibration curve for luciferase was obtained for both reactors. The limit of detection in Reactor I was determined to be 0.14 μg/mL of luciferase.
Optimization of First Mode Sensitivity of V-Shaped AFM Cantilever Using Genetic Algorithm Method
Authors: Moeini S. A. , Kahrobaiyan M. H. , Rahaeifard M. , Ahmadian M. T.
Published: July 2010

Atomic force microscopes (AFM) are widely used for feature detection and scanning surface topography of different materials. Contrast of topography images is significantly influenced by the sensitivity of AFM micro cantilever which means enhancement of sensitivity leads to increase of topography images resolution So, in the last years numerous scientists interested in studying the effects of different parameters such as geometric one on the sensitivity of AFM micro cantilevers. V-shape micro cantilever types of AFMs probe are widely used to scan various types of surfaces. In V-shape micro cantilevers, there are many geometric and design parameters which influence the flexural sensitivity of the micro beam, noticeably. In this paper evaluation of optimum geometric parameters and optimum cantilever slope is considered as a significant purpose in order to obtain maximum flexural sensitivity by using genetic algorithm optimization method. In the calculations, the normal and lateral interaction forces between AFM tip and sample surface is considered and modeled by linear springs which represent the contact stiffness of the sample surface. Also, a relation for flexural sensitivity of AFM cantilever as a function of geometric parameters and cantilever slope is derived which is used in optimization step by employing a genetic algorithm program. Using genetic algorithm method, the optimum geometric parameters and cantilever slope are calculated which maximize the flexural sensitivity of the first mode of a V-shape cantilever for various values of normal contact stiffness. These optimum parameters versus normal contact stiffness are presented in some result figures. The results show that for any contact stiffness, there are a cantilever slope and a set of geometrical parameters which provide the maximum sensitivity for AFM probe. Adopting these parameters for the design of V-shape micro cantilever according to the sample contact stiffness, maximum flexural sensitivity can be obtained, so that high contrast images are reachable.
A Simple Interfacial Design of Biomolecules to Nano/Micro-Devices for Highly Sensitive and Selective Protein Detection
Authors: Choi Seokheun , Chae Junseok
Published: July 2010

We present a novel immobilization technique via physical adsorption of biomolecules onto a sensing surface. The immobilization technique utilizes the competitive nature of protein adsorption onto the surface, offering the selectivity and sensitivity in detecting a target molecule. The SPR (Surface Plasmon Resonance) sensorgrams show that three human serum proteins, albumin, Immunoglobulin G (IgG) and fibrinogen, have different adsorption strengths to the surface and the competitive adsorption of individuals controls the exchange sequence. Using the competitive adsorption and exchange, we demonstrate that IgG is selectively and sensitively detected.
MEMS Thruster System for CubeSat Orbital Maneuver Applications
Authors: Huang Adam , Yang Eui-Hyeok
Published: July 2010

This paper reviews the previously developed attitude control micro-thruster propulsion unit (The Aerospace Corporation) and a high pressure piezoelectric microvalve (Jet Propulsion Laboratory), and follows up with a conceptual development effort that is currently underway to optimize the benefits of merging these two technologies. The goal is to provide orbital maneuver capabilities for future Air Force and NASA nano/pico-satellite missions, such as inspector satellites for post launch diagnostics, sparse array antennas, field measurements of space weather events, and the calibration of atmospheric drag in the thermosphere. The piezoelectric microvalve developed is capable of low power (3mW), high speed (>1kHz), and high pressure (70 bar absolute). The target warm gas Newton level propulsion system dry mass is 200 grams and with a volume of <100 cm3 and the intended first mission is to provide CubeSats the ability to operate at orbits of choice rather than opportunity.
Optimal Eigenvectors Design for Structural Noise Reduction Through Adaptive Sandwich Algorithm
Authors: Wu T. Y. , Chung Y. L.
Published: July 2010

The purpose of this research is to investigate the feasibility of utilizing the adaptive sandwich algorithm to find the optimal left and right eigenvectors for active structural noise reduction. As depicted in the previous studies, the structural acoustic radiation depends on the structural vibration behavior, which is strongly related to both the left eigenvectors (concept of disturbance rejection capability) and right eigenvectors (concept of mode shape distributions) of the system, respectively. In this research, a novel adaptive sandwich algorithm is developed for determining the optimal combination of left and right eigenvectors of the structural system. The sound suppression performance index (SSPI) is defined by combining the orthogonality index of left eigenvectors and the modal radiation index of right eigenvectors. Through the proposed adaptive sandwich algorithm, both the left and right eigenvectors are adjusted such that the SSPI decreases, and therefore one can find the optimal combination of left and right eigenvectors of the closed-loop system for structural noise reduction purpose. The optimal combination of left-right eigenvectors is then synthesized to determine the feedback gain matrix of the closed-loop system. The result of the active noise control shows that the proposed method can significantly suppress the sound pressure radiated from the vibrating structure.
Optimization of Component Reliability Allocation in a Complex Repairable System Using a System Total Reliability Risk Metric
Authors: Baun Ward O.
Published: July 2010

The task of allocating failure rates to components within a complex repairable system is executed early in a product development process in order to set reliability targets for those components. This allocation process is often accomplished versus more than one constraint, for instance to achieve an overall system-level failure rate, λsys, and to achieve an overall system life cycle unplanned maintenance cost (LCUMC) target. Presumably, there exists an optimum component allocation solution that would most effectively meet those goals, while minimizing risk to the ultimate product. In this context, risk is defined as the probability that some subset of the components will not achieve their allocation targets, and the impact, in the form of higher λsys, higher maintenance costs and lower customer satisfaction, of those higher component failure rates. However, with only λsys and LCUMC as constraints, finding such an optimum solution is difficult. Both λsys and LCUMC move together when evaluating different solutions—as a component’s failure rate allocation is reduced, it’s expected LCUMC is proportionally reduced. This affords no opportunity for trading one criterion versus the other. Additionally, this is a multi-dimensional, multi-criteria (MDMC) optimization problem for a complex system; each component’s failure rate is one variable that may be adjusted to find the best solution. To address the first difficulty, it is proposed that a third metric, the System Total Reliability Risk (STRR), be considered to facilitate such an optimization solution. The STRR is a measure of the aggregate product reliability risk inherent in the allocation solution chosen—the probability that the overall allocation solution might not be achievable and the potential impact of that miss. It is roughly a measure of the degree of difficulty to achieving the proposed component failure rate allocations, given that different types of components in a particular service generally have a limit to the best failure rate that can be achieved in practice. Employing a measure such as STRR offers the needed optimization countering force to allow for finding an allocation solution that meets the λsys and LCUMC targets, while reducing product reliability risks by selecting an allocation solution that may be easiest to achieve in practice. Addressing the second difficulty (finding an optimum solution to the MDMC problem) is accomplished through genetic algorithm-based techniques, where those algorithms search for an allocation solution with the highest degree of “fitness”. Fitness is measured as a function of the three constraints of the problem −λsys, system LCUMC, and STRR. The practical utility of such an approach is that it finds an allocation solution which minimizes the STRR, while still meeting the customer-driven reliability targets for λsys and LCUMC.
Vibration Analysis of Setar for Extracting the Frequency Response Function (FRF)
Authors: Mansour Hossein , Arzanpour Siamak , Alghassi Hedayat , Behzad Mehdi
Published: July 2010

Extraction of the frequency response of a musical instrument is the first step to analyze its vibration characteristic. This research introduces the results of several experiments implemented on Setar, a Persian long-necked lute. Setar has a wooden, reflective sound-box which is highly coupled with its surrounding air. High level of damping in addition to the composite properties in Setar, consequences dissimilar frequency domain vibration patterns. At lower frequencies, the response exhibits very distinct modal behavior, while in higher frequencies an overall effect of close modes is demonstrated. In this paper different approaches are utilized to handle both frequency regimes; and their advantages and limitations are compared to each other. The utilized methods are swept sine excitation, impact hammer, and the traditional Tap-Tone method. The characteristics of force excitation on body are first investigated, and then the frequency response function of Setar’s body is extracted between the excitation force as the input and resultant sound and acceleration as the outputs. This study not only leads us to modifications in design of Setar, but also serves as a platform for numerical modeling.
Experimental Assessment of Fatigue Reliability for High-Pressure Plunger Pumps
Authors: Panella Francesco W. , Reina Giulio
Published: July 2010

Current research at the University of Salento’s Department of Innovation Engineering aims to the development of the next generation of high-pressure pumps for Diesel common rail systems. In order to improve both performance and reliability, a better understanding of the mechanisms, underlying the fatigue behavior of high pressure reciprocating plunger pump, is necessary. Previous studies based on static and dynamic FEM simulations provided results to be confirmed by experimental tests. In this paper, we present an experimental approach to better assess the fatigue behavior of this critical component, toward an increase in both robustness, and speed and rail pressure. Based on the analysis of the worst contact conditions under service, the important parameters to be considered for the experimental set-up are isolated and selected; in particular the friction influence and the mutual position of the parts is crucial to establish the real stress state in the pump plunger.
A Three-Dimensional Wiener-Hopf Technique for General Bodies of Revolution: Part 1—Theory
Authors: Martinez Rudolph , Paul Brent S. , Eash Morgan , Ting Carina
Published: July 2010

This work, the first of two parts, presents the development of a new analytic solution of acoustic scattering and/or radiation by arbitrary bodies of revolution under heavy fluid loading. The approach followed is the construction of a three-dimensional Wiener-Hopf technique with Fourier transforms that operate on the finite object’s arclength variable (the object’s practical finiteness comes about, in a Wiener-Hopf sense, by formally bringing to zero the radius of its semi-infinite generator curve for points beyond a prescribed station). Unlike in the classical case of a planar semi-infinite geometry, the kernel of the integral equation is non-translational and therefore with independent wavenumber spectra for its receiver and source arclengths. The solution procedure begins by applying a symmetrizing spatial operator that reconciles the regions of (+) and (−) analyticity of the kernel’s two-wavenumber transform with those of the virtual sources. The spatially symmetrized integral equation is of the Fredholm 2nd kind and thus with a strong unit “diagonal” — a feature that makes possible the Wiener-Hopf factorization of its transcendental doubly-transformed kernel via secondary spectral manipulations. The companion paper [1] will present a numerical demonstration of the new analysis for canonical problems of fluid-structure interaction for finite bodies of revolution.
Empirical Mode Decomposition of AE Signal Processing Based on Hilbert-Huang Transformation
Authors: Li Wei , Dai Guang , Zhang Ying , Long Feifei , Wang Yanru
Published: July 2010

In this paper a new signal processing method of Hilbert-Huang transform is applied to analyze AE lead-breaking signals and loaded concrete AE signals. Empirical model of decomposition (EMD) and cubic interpolation were used in AE signals analysis which was based on the local characteristic time scale. After the decomposition inherent model function (IMF) can effectively preserve non-linear and non-stationary features of signals during the processing. Meanwhile, noises of signals were eliminated by using multi-dimension filter property of EMD. The above two signal’s IMF can be clearly shown on a time-frequency vs. energy distribution spectrum and marginal spectrum by Hilbert-Huang transformation. The results show that HHT can efficiently reflecting the intrinsic properties of signals. Besides, HHT method, which is more adaptive than other methods, had a bigger superiority in adaptability and frequency concentration, and it has batter localization property and visual result of the time-frequency domain.
Through Wall Cracking in High Temperature Rotary Cooler
Authors: Frith James , Frith Robert
Published: July 2010

After operating for a number of years, a high temperature rotary ore cooler suffered cracking. The cracks grew through the shell wall resulting in leakage of water from the water bath into the ore. Under the extreme temperature, the risk of water dissociation into hydrogen and subsequent explosion was of substantial concern and instigated the investigation in to the root cause of the cracking which was deduced to be driven by high thermally induced stresses. The root cause for the thermally induced stressing was found to be related to a design flaw that was not immediately obvious. The investigation outcome was a recommendation to change the design to eliminate the high localized stresses which were believed to be the driving force behind the corrosion fatigue crack propagation. This paper presents the investigation approach which included advanced thermal and stress analysis and reports on the general design principle that should be adopted to avoid thermal stress induced corrosion fatigue cracking under high temperature operation.
Study of the Effect of FRS and SAM on Pipe Seismic Stress Using Taguchi Method
Authors: Li Bing , Vijay D. K.
Published: July 2010

In this paper, the effect of floor response spectra (FRS) and seismic anchor movement (SAM) on the seismic stresses in the piping system is studied through a combination of finite element analysis (FEA) and the Taguchi Method. Class 3 piping systems according to ASME B&PV code Section III Subsection ND with different natural frequencies are analyzed in this study. Taguchi method is applied to create an orthogonal array to show the variability of FRS and SAM, which is taken as the ±20% variation over its nominal value. Based on the Taguchi orthogonal array, finite element simulations are carried out to obtain the seismic code stress in each piping system. From the Taguchi signal-to-noise (S/N) ratio analysis and the analysis of variance (ANOVA) of the seismic code stress results, the effect of FRS and SAM on the resultant seismic stress is given and expressed as a percentage. The study shows that the FRS is dominating the seismic stress for the piping system with low natural frequency (i.e., flexible system) while SAM is dominating the seismic stress for the piping system with high natural frequency (i.e., rigid system), for the piping system with a medium natural frequency, both FRS and SAM contribute to the seismic stress and the percentage of contribution of each parameter varies with the level of the system natural frequency. The results of this study also show that if the piping system is designed either too rigid or too flexible for the same layout, it will result in high resultant (primary plus secondary) seismic stress.
Empirical Expression of Tool Wear When Face Milling 416 SS
Authors: Mun˜oz de Escalona Patricia , Maropoulos Paul G.
Published: July 2010

During a machining process, cutting parameters must be taken into account, since depending on them the cutting edge starts to wear out to the point that tool can fail and needs to be change, which increases the cost and time of production. Since wear is a negative phenomenon on the cutting tool, due to the fact that tool life is reduced, it is important to optimize the cutting variables to be used during the machining process, in order to increase tool life. This research is focused on the influence of cutting parameters such as cutting speed, feed per tooth and axial depth of cut on tool wear during a face milling operation. The Taguchi method is applied in this study, since it uses a special design of orthogonal array to study the entire parameters space, with only few numbers of experiments. Also a relationship between tool wear and the cutting parameters is presented. For the studies, a martensitic 416 stainless steel was selected, due to the importance of this material in the machining of valve parts and pump shafts.
Fracture Mechanics of Tapered Cracks
Authors: Smith Edwin
Published: July 2010

The paper shows that for the Mode III loading of a tapered crack whose near tip profile is defined by the relation (y/c) = (x/c)m, the singularity order of the stress field is −1/2, as it is for a linear crack, irrespective of the m value. This result is a generalization of the result reached in an earlier paper by the author, for the particular case m = 3/2. The result’s implications to the quantification of fracture initiation at the root of a Mode I crack are discussed.
A New Test Method for Determining the Strength and Fracture Toughness of Cement Mortar and Concrete
Authors: Wang John Jy-An , Liu Ken C. , Naus Dan
Published: July 2010

The Spiral Notch Torsion Fracture Toughness Test (SNTT) was developed recently to determine the intrinsic fracture toughness (KIC) of structural materials. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45° pitch. KIC values are obtained with the aid of an in-house developed three-dimensional finite-element computer code, TOR3D-KIC. The SNTT method is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments. Application of the method to metallic, ceramic, and graphite materials has been demonstrated. One important characteristic of SNTT is that neither a fatigue precrack nor a deep notch are required for the evaluation of brittle materials, which significantly reduces the sample size requirement. In this paper we report results for a Portland cement-based mortar to demonstrate applicability of the SNTT method to cementitious materials. The estimated KIC of the tested mortar samples with compressive strength of 34.45 MPa was found to be 0.19 MPa √m.
Managing Change in a High Growth Environment: Reference to Bahrain/Arabian Gulf
Authors: Thomas Aby
Published: July 2010

The industrial and construction scenario with specific reference to the Oil & Gas Industry, in the Arabian Gulf Region is demanding on resources especially during ‘high growth times’ driven by high oil prices. This creates considerable shortages in man-power, materials and equipment in the region. The Bahrain Petroleum Company (BAPCO) a fully integrated Oil and Gas Company has embarked on a massive Strategic Investment Program with some major projects already on-stream. Alongside these major projects, Up-grade, debottlenecking and technology enhancement Projects form a sizable component of the Investment Program. The company has over the past years developed procedures and processes to manage work within the Oil and Gas Fields, Refinery, Tank Farms and its own Shipping Wharf Operations in keeping with the highest safety and quality requirements. Purpose of this paper/ presentation is to detail out the adaptation of these procedures, processes and contracting strategies to manage the changing environment for the installation of mechanical and piping systems, executed on applicable ASME/API codes. Presentation will include contracting strategies which along with prudent management through a combination of various types of work contracts ensured close quality and budgetary control.
Continuing Development of PRO-LOCA for the Prediction of Break Probabilities for Loss-of-Coolant Accidents
Authors: Rudland D. , Scott P. , Kurth R. , Cox A.
Published: July 2010

As part of a possible risk-informed revision of the design-basis break size requirements for operating commercial nuclear power plants as specified in the Code of Federal Regulations (CFR), the NRC began development of a probabilistic piping fracture mechanics code called PRO-LOCA. The initial development of this code and its background was published at a prior PVP conference. Since that time, the development of the PRO-LOCA code has continued through an international group program entitled Maximizing Enhancements in Risk Informed Technology (MERIT). The MERIT program includes participation from Canada, Korea, Sweden, UK, and the US (NRC and EPRI). The PRO-LOCA code, which aides in predicting piping break frequencies as a function of break size, incorporates many enhancements in technology since some of the earlier probabilistic codes (e.g., PRAISE) were developed. These enhancements include improved crack stability analyses, leak rate models, crack initiation and growth models, and material property data. In addition, degradation mechanisms such as primary water stress corrosion cracking (PWSCC) for dissimilar welds in pressurized water reactors (PWRs) are included in the PRO-LOCA code. This paper reviews the ongoing development of the PRO-LOCA code by giving a brief description of the recent updates made to the models embedded in the code. Some of these capabilities include improvements to crack initiation and growth models, welding residual stress distribution inputs, the addition of weld overlays, past and future inspections, the addition of importance sampling, and bootstrap methods for predicting confidence limits on output. The current version of the PRO-LOCA code was used for a sensitivity analyses in order to demonstrate the effects of welding residual stress uncertainty on the probability of leak and rupture. Plans for the continuing development of the PRO-LOCA code conclude this paper.
Comprehensive Integrity Assessment of Carbon Steel Feeder Pipes/Elbows Subject to Wall Thinning
Authors: Duan Xinjian , Kozluk Michael J. , Li Ming
Published: July 2010

This paper discusses the comprehensive integrity assessment of feeders fabricated from normalized pipe and elbow piping items subject to Flow Accelerated Corrosion (FAC) during in-service conditions. The arguments are based on the improved mechanistic understanding of FAC; review of international piping rupture events; examinations of removed feeders; burst-pressure tests of prototypical and ex-service feeder piping sections, the minimum acceptable wall thickness for feeder piping; and station feeder life cycle management plans. It is concluded that rupture of feeder pipe due to FAC is a very low probability event.
A Creep Crack Growth Study of a Low Alloy Butt Weld Subject to Internal Pressure and System Moments Using R5 Assessment Procedures
Authors: Shi Jinhua
Published: July 2010

Appropriate life predictions of components are essential to ensure safety operations of nuclear power plants, especially for welds operating at high temperatures where creep crack growth can be large and dominate their lives. In this paper, for a low alloy butt weld with a given set of loadings (temperature, internal pressure and system moments), a parametric creep crack growth study has been carried out using R5 assessment procedures as follows. • The plant has been operated for 209,200 hours and will be operating further for 47,300 hours; • Initial defect depths are 1, 2, 2.3, 3, 4 and 5 mm; • Crack aspect ratios (initial defect depth: defect half length) are 0.125, 0.2, 0.23, 0.3, 0.4 and 0.5. • Postulated defects are axial (internal and external) and circumferential (internal and external) semi-elliptical surface-breaking surface defects. The study results are presented by a series of graphs which show a minimum acceptable wall thickness for each initial defect depth and aspect ratio under the assessment conditions assumed. The graphs can be used for the plant life management to reduce the decision making time on these welds and to improve the plant power generation.
The Ultimate Strength of Cylindrical Liquid Storage Tanks Under Earthquakes: Elasto-Plastic Dynamic Analysis With FSI of Buckling Failure Modes
Authors: Mikami Akira , Sato Yuji , Otani Akihito , Iwamoto Kosuke , Iijima Toru
Published: July 2010

The objective of this study is to simulate the shaking test of a condensate storage tank (CST). In this test, the typical failure mode was an elephant-foot bulge (EFB) or a shear buckling. It is difficult to reproduce such buckling modes. However, at last, an analytical model which describes those modes with enough accuracy was achieved. The comparison between simulation results and experiments is explained. Acoustic theory and classical plasticity theory were used in the FEM simulation. The phase and magnitude of the response acceleration and hydraulic pressure obtained from the FEM simulation are well corresponded to those from the experiments. In addition, asymmetrical distribution of maximum and minimum hydraulic pressure is described.
Evaluation of Dynamic J-R Curve by Using Normalization Method for Long Crack Extension
Authors: Kim Kuk Cheol , Kwon Hee Kyung , Cho Hyun Chul , Kim Jeong Tae
Published: July 2010

The test method for the reliability of this research dynamic J-R curve for long crack extension based on normalization method was introduced on this research. For nuclear power plant piping material made of ferritic steel, dynamic J-R curve is one of the important material properties used to evaluate the integrity for piping with the critical leakage crack size under seismic loading such as earthquake loading on leak before brake design (LBB). The measurement of dynamic J-R curve by compliance method is very difficult due to the fast loading speed. Normalization method of ASTM E1820 code A15 is therefore often used because of the merit that J-R curve can be obtained by only using load–displacement curve without measuring the crack extension length during the test. However, there is a restriction that physical crack extension should not exceed the lesser length of 4mm or 15% of the initial uncracked ligament. For J-T analysis on LBB design, long crack extension data on J-R curve are needed to simulate the crack stability of long cracked piping corresponding to leakage rate of 10gpm. In this paper, to overcome this problem at applying for the normalization method, two specimens were used where one is for short crack extension and the other is for long crack extension. Utilizing the two test data, dynamic J-R curve over the crack extension length range designated to ASME code was estimated.
Confirmation of Validity of Hot Tapping Welding
Authors: Ogayu Yasushi
Published: July 2010

Branch connection to existing hydrocarbon pipelines are often attached by welding on the pipe while liquid or gas products are contained in or flowing in the pipe when it is not feasible, or impractical, to take the piping out of service. This procedure is called hot tapping. A problem, so-called “burn-through”, will occur when welding onto a pressurized pipe if the un-melted area beneath the weld pool has insufficient strength to contain the internal pressure of the pipe. It is reported by Battelle Institute that this burn-through problem will occur when inside surface temperature is in excess of 982 degree C regardless of internal pressure [1]. From the safety view points, this problem shall be avoided. In addition, the piping or equipment base metal thickness must provide support for the new connection and hot tapping machine. From these reasons, the minimum base metal thickness of approximately 5mm (to be precise 4.8mm) is recommended [2]. In this study, the validity of the minimum base metal thickness of 5mm was confirmed by means of “Thermal Analysis Computer Modeling for Hot-Tap Welding” developed by my company to confirm the effectiveness of the Thermal Analysis. This thermal Analysis can calculate the cooling rate and temperatures faithfully using heat elastoplastic finite element analysis. After the confirmation of that, we can determine the welding conditions and conduct the hot tapping operations safer. Prior to applying this thermal analysis tool to hot tapping models, reliability of this thermal analysis tool was confirmed by a preliminary experiment.
Updated Knowledge Implemented to the Revision of Environmental Fatigue Evaluation Method for Nuclear Power Plant in JSME Code
Authors: Higuchi Makoto , Nakamura Takao , Sugie Yasuaki
Published: July 2010

Many examinations concerning the fatigue life reduction for structural materials of nuclear power plants in water simulated LWR coolants had been carried out after the first paper had been recognized in Japan [1, 2]. Based on these results, the method to evaluate the fatigue damage for the materials exposed to the LWR coolant had been developed. After 1990s in Japan, the Environmental Fatigue Data Committee (EFD) of the Thermal and Nuclear Power Engineering Society (TENPES), the Project on Environmental Fatigue Testing (EFT) supported by the Japan Power Engineering and Inspection Corporation (JAPEIC) and the Japan Nuclear Energy Safety Organization (JNES) and some utility joint studies have investigated the environmental fatigue. In September 2000, the Nuclear Power Generation Safety Management Division of the Agency for Natural Resources and Energy, Ministry of International Trade and Industry issued “Guidelines for Evaluating Fatigue Initiation Life Reduction in the LWR Environment” (hereafter, called “the MITI Guidelines”) [3]. These guidelines include an equation to evaluate environmental fatigue and require electric utilities to consider the environmental effects in their Plant Life Management (PLM) activities. However, the MITI Guidelines do not provide specific and practical techniques for evaluating environmental fatigue under actual plant conditions. Accordingly, TENPES took on the task to produce one. In 2002 TENPES issued the “Guidelines on Environmental Fatigue Evaluation for LWR Component” [4, 5] (hereafter, called “the TENPES Guidelines”) based on the techniques developed by the EFD Committee. A set of Rules, called the Environmental Fatigue Evaluation Method (EFEM), was established in the Codes for Nuclear Power Generation Facilities - Environmental Fatigue Evaluation Method for Nuclear Power Plants (JSME S NF1-2006, EFEM-2006)[6], which was issued in March 2006 by reviewing the equations for the environmental fatigue life correction factor, Fen, specified in the MITI Guidelines, and the techniques for evaluating environmental fatigue specified in the TENPES Guidelines, and considering the new environmental fatigue data including JNES-SS report (August 2005) [7]. The EFEM revised version has been drafted by incorporating the updated knowledge described in JNES-SS report (April 2007) [8] and is scheduled to be issued by the end of 2009. This paper introduces the revision in it and their technical basis. Additionally, future issues are addressed to be considered in the improvement of the EFEM.
The Relationship of Radiation Embrittlement and Swelling for Austenitic Steels for WWER Internals
Authors: Margolin B. Z. , Kursevich I. P. , Sorokin A. A. , Neustroev V. S.
Published: July 2010

To investigate the effect of swelling upon mechanical properties of irradiated austenitic steel the investigations were conducted with steel 18Cr-10Ni-Ti and its weld irradiated up to same damage doses in two different temperature ranges: at the irradiation temperature of 330÷340°C when swelling is practically absent and at 400÷450°C when a considerable swelling level of 3÷13% is observed. Basing on the investigation results the temperature dependences of tensile properties of irradiated metal were constructed and analyzed. Fracture surfaces for ruptured specimens were examined by SEM. Comparative investigations of magnetization of irradiated metal at different irradiation temperatures were performed. It was concluded from the performed analysis of the results that in highly irradiated austenitic steel with considerable swelling a ductile to brittle transition is observed, which is caused of the Feγ→Feα phase transformation. The investigations of magnetization of metals with different swelling, as well as on the available literature data confirm a possibility of the Feγ→Feα phase transformation under considerable radiation swelling. The criterion is proposed allowing one to determine the radiation conditions under which the Feγ→Feα transformation make it possible a brittle fracture. The mechanism resulting in a sharp decrease of the ultimate tensile strength of highly irradiated metal is considered.
Dynamic Buckling Analysis of Cylindrical Water Storage Tanks: A New Simulation Method Considering Coupled Vibration Between Fluid and Structure
Authors: Maekawa Akira , Fujita Katsuhisa
Published: July 2010

This paper proposes a dynamic buckling analysis method which can accurately simulate the buckling behavior of cylindrical water storage tanks during an earthquake. The proposed method takes into account the behavior of oval-type vibration as well as beam-type vibration, which are coupled vibrations between the shell structure of the tank and the water stored in the tank. In the proposed method, both the tank and the stored water are three-dimensionally modeled by finite elements and time history analysis is conducted. Moreover, coupled analysis between the fluid and structure and large deformation analysis to the shell structure of the tank are also considered. The analytical results by the proposed method agreed well with those of experiments regarding occurrence of oval-type vibration, mode of buckling and buckling load. The method can accurately simulate the seismic response including the coupled vibrations and the process of damage such as buckling of the cylindrical water storage tank during an earthquake. In conclusion, the proposed dynamic buckling analysis method can quantitatively evaluate the seismic performance of water storage tanks such as seismic safety margin.
Crack Opening Area Solutions for Through-Wall Cracks in the Vicinity of Welded Attachments
Authors: Sharples J. K. , Charles R. , Madew C. J. , Budden P. J.
Published: July 2010

This paper presents the latest results of a finite element study undertaken to evaluate crack opening areas (COA) and stress intensity factors (KI) for through-wall cracks located in the region where an attachment is welded to a plate geometry. Both membrane and bend loads have been considered. In addition, COAs and stress intensity factors have been evaluated for the same crack sizes located in a simple plate geometry. These values have been determined by applying both membrane and bend stresses to the plain plate, the magnitudes of which correspond to those for the stress profile in the un-cracked complex geometry in the vicinity of where the cracks would be introduced. This has enabled information to be established on the conservatism or otherwise of using simple plate solutions to evaluate COAs and stress intensity factors for cracks in the complex geometry.
Fretting Corrosion Analysis on Packings of Hypercompressors
Authors: Shi Jun-Xia , Giacomelli Enzo
Published: July 2010

Secondary compressors for Low Density Poly-Ethylene are very critical machines. Safety aspects and reliability expectations determine a thorough evaluation of the service and the parameters involved. The solution used for the machine requires a long experience of positive results in these applications. Cylinder performance is strongly influenced by the design and also related to the combination of operation and maintenance activities. The capability to withstand the high fatigue stresses and the need to avoid any leakage of gas around the compressor area involves due considerations and design solutions to minimize such occurrences also during abnormal operations and emergencies. In addition to the cylinder valves, packings represent important components with great influence on the availability of machine and plant. The operating conditions of the packing, due to the high pressures involved, and the geometry of the components, create the condition for a relative movement of the cups mating surfaces. In general at disassembly, when maintenance and reconditioning activities are carried out wear, pitting, corrosion and local defects can be detected on the cups and sealing elements, as a function of the life of the cylinders. The condition of the cups may also evidence some damages, with evident deposit of polymers, oil and wear of the components. Fretting corrosion phenomena may be sometime the reason of failure of packing in hyper-compressors for LDPE production. In some cases the repeated occurrence of various abnormalities on the packing life and particular wear pattern on the cups bring to need to discover the reason of the problems and require an accurate investigation, by using advanced laboratory analyses. The results evidence that the origin of such phenomena can be found on the surfaces of the components and on the organic acids, as in such conditions they are able to originate and develop the corrosion reactions. There is a strong connection with process parameters and operating conditions. These situations and particular applications have to be evaluated to put in place adequate actions to improve or have more chances of a reliable and economic operation.
Presentation of RCC-MR Code 2007 for High Temperature Reactor and ITER Projects: Improvement of the Creep Fatigue Rules
Authors: Berton Marie-Noe¨l , Ancelet Olivier , Gelineau Odile , Sperandio Morello
Published: July 2010

The fourth edition of the RCC-MR code has been issued in French and English versions on October 2007 by AFCEN (Association Franc¸aise pour les re`gles de Conception et de Construction des Mate´riels des Chaudie`res Electro-nucle´aires). The RCC-MR creep-fatigue rules were developed and written in the framework of studies for the first SFR (Sodium Fast Reactors). These reactors were characterized by low primary loads and moderately high temperatures. These rules have been improved in the 2007 edition with the aim of decreasing the conservatisms in case of higher temperatures and/or higher pressures (for GEN IV Gas Cooled Reactors). Studies were realized to improve the rule on the following points: - the position of the temperature dwell time in the cycle: the current rule always considers that the dwell time is located at one of the extremes of the cycle, what can be very conservative in some cases, - the symmetrisation effect of the stabilized cycle, - the case where the primary loads vary during the cycle, - the primary and secondary stresses combination during the temperature dwell time for the evaluation of the stress relaxation. These works are based on viscoelastoplastic calculations of stabilized cycles and the new proposals are applied on different tests. The consequences on creep-fatigue damage evaluation can be very significant.
The Sensitivity of Risk-Informed Reactor Structural Integrity Analysis Results to Various Interpretations of Warm Pre-Stress
Authors: EricksonKirk Mark T. , Dickson Terry L.
Published: July 2010

Warm pre-stress, or WPS, is a phenomenon by which the apparent fracture toughness of ferritic steel can be elevated in the fracture mode transition if crack is first “pre-stressed” at an elevated temperature. Taking proper account of WPS is important to the accurate modeling of the postulated accident scenarios that, collectively, are referred to as pressurized thermal shock, and to the accurate modeling of routine cool-down transients. For both accident and routine cool-downs the transients begin at the reactor operating temperature (approximately 290°C for pressurized water reactors in the United States) and proceed to colder temperatures as time advances. The probabilistic fracture mechanics code FAVOR, which is being used by the NRC to provide the technical basis for risk-informed revisions of 10 CFR 50.61 and 10 CFR 50 Appendix G, adopts a model of WPS as part of its fracture driving force module. In this paper we assess the conservatism inherent to the FAVOR WPS model relative to a best-estimate WPS model constructed using data recently produced by the European Commission “SMILE” project and published by Moinereau and colleagues. Assessments of the conservatisms inherent to the so-called “conservative principle” WPS model, and also to a classic LEFM model that does not credit WPS are also made. The data presented herein demonstrate that, for an integrated analysis of PTS risk, the FAVOR and conservative principle WPS models both over-estimate the vessel failure risk by a factor of between 2 and 3× relative to the best estimate model. Our examination of the effect of WPS models on the predictions of individual transients reveals that for the severe transients that dominate risk there is little difference (usually less than 4×) between the conditional probabilities of crack initiation and of through wall cracking predicted by the different WPS models. There are considerable differences in the predictions of the various WPS and non-WPS models for low severity transients, however, the contribution of these transients to the total risk of vessel failure is small.
Assessment of Piping Field Failures and Burst Tests on Carbon Steel Pipes With Local Wall Thinning Using ASME Section XI Code Case N-597-2
Authors: Hasegawa Kunio , Meshii Toshiyuki , Scarth Douglas A.
Published: July 2010

One of the more common modes of degradation in power plant piping has been wall thinning due to erosion-corrosion or flow-accelerated corrosion. Extensive work has been performed to understand flow-accelerated corrosion mechanisms and develop fracture criteria of locally thinned pipes, since the tragic events at Surry Unit 2 and Mihama Unit 3. A large number of tests have been performed on carbon steel pipes, elbows and tees with local wall thinning. In addition, the American Society of Mechanical Engineers Boiler and Pressure Vessel Code provides procedures in Code Case N-597-2 for evaluation of wall thinning in pipes. This paper provides validation of the evaluation procedures in Code Case N-597-2 by comparing with the field rupture data and pipe burst test data. The allowable wall thinning from the Code Case N-597-2 procedures is shown to maintain adequate margins against rupture.