bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and Testing of Freezing Phenomena in Piping Systems
Authors: Smith Kenneth M. , Van Bree Michael P. , Grzetic Joseph F.
Published: August 2009

From time to time installed piping systems, including wet sprinkler, potable water and cooling water systems, have failed due to freezing. The cost of such events is significant due to the need for system repair, the loss of service, and the secondary water damage that results. The presumption is often that the pipe was frozen at the point of failure. This paper describes the theory, calculations, and experiments that demonstrate that freezing of a pipe causes pressure in the system to rise between the frozen section of pipe and the blind end of the system. The piping system typically fails at a weak link in the system at a significantly elevated pressure. The location of the breech is almost always at a point in the system where the water is still liquid at the time of the breech. An additional consideration is that the high system pressure depresses the freezing temperature of the water, and a flash-freeze within the pipe occurs when the pressure suddenly drops after a piping system rupture. Armed with this knowledge, the site of the actual system freeze can often be found remote from the point of failure where remedy can be best effected to eliminate the root cause.
Synthesizing Magnetic Nanocomposite Fibers by Electrospinning Method
Authors: Asmatulu R. , Khan W. , Nguyen K. D. , Yildirim M. B.
Published: August 2009

Flexible magnetic nanocomposite fibers were produced by electrospinning method using a polymeric solution containing poly(acrylonitrile) and magnetite nanoparticles. Magnetic nanoparticles (∼10 nm) were prepared by a chemical co-precipitation of ferric and ferrous chloride salts in the presence of an ammonium hydroxide solution. The effect of magnetic particle concentrations (e.g., 0%, 1%, 5%, 10%, 20% and 30%) on nanocomposite fibers, distribution and morphology were studied using scanning electron microscopy (SEM). The experimental study indicated that the average diameters of the magnetic nanocomposite fibers were between 400 nm and 1.08 μm. The magnetic responds were also found to increase linearly with increasing percent loading of the magnetic nanoparticles. It is concluded that this study provides promising results for various applications, such as filtration and separation of micron and nanosize organic and inorganic particles, HF antenna fabrication and biomedical.
Development of a Carbon Nanotube-Based Electromechanical Resonator: Device Modeling
Authors: Ke Changhong
Published: August 2009

We present an electromechanical analysis of a novel double-sided driven carbon nanotube-based electromechanical resonator. The device comprises a cantilevered carbon nanotube actuated by two parallel-plate electrodes. Close-form analytical solutions capable of predicting the steady-state resonation of the device and its resonant pull-in conditions are derived using an energy-based method. Our close-form formulas clearly reveal the complex relationship among the device geometry, the driving voltages, and the device’s electromechanical dynamics. Our theoretical modeling shows that the stable steady-state spanning range of the resonating cantilever substantially exceeds the previously reported quasi-static pull-in limit for single-sided driven cantilevered nanotube-based NEMS, while the resonant pull-in voltage is only a small fraction of the quasi-static pull-in voltage. The unique behaviors of this novel device are expected to significantly enhance the applications of electromechanical resonators in the fields of signal processing, mass and force sensing, and chemical and molecule detection.
The Effect of Arterial Wall Deformability on Hemodynamics of CABG
Authors: Kouhi Esfandyar , Morsi Yos , Masood S. H.
Published: August 2009

In this study, hemodynamic forces in a three-dimensional (3D) computational model of Coronary Artery Bypass Grafting (CABG) with deformable and rigid walls were compared. A physiologic pulsatile non-Newtonian blood flow was considered in the arteries for both models. The artery walls in the distensible model were considered to be hyper-elastic with nonlinear strain dependent Young’s module and axial and radial degrees of freedom, while the deformability in all directions of the rigid model was restricted. The velocity distributions and magnitudes, vortex motions and the occurrence of recirculation zones were selected as the primary hemodynamic parameters in order to show the effect of deformability in the arterial wall and in calculating differences versus the rigid wall model. It was found that during systolic, the velocity magnitude at the host artery bed could vary by up to 80% depending on the longitudinal distance from the center of the anastomosis junction.
Rising Velocity of a Gas Plug in Vertical-Rectangular-Narrow Channels
Authors: Miyashita Tohru , Koizumi Yasuo
Published: August 2009

A bubble rising velocity in stagnant water in rectangular channels was examined. The width of the flow channels and the gap space between parallel walls were varied from 10 mm through 150 and from 1 mm through 10 mm, respectively. When the bubble had plug shape in the long side and also the short side, the bubble velocity took the same velocity as that in a circular pipe that had the same periphery. When the bubble lost the plug shape in the long side, the rising velocity became fast as the long side shape departed from the plug shape. When the long side was large enough for the bubble to have the shape of a bubble in open space, the bubble rising velocity was expressed well with the expression for the bubble rising velocity in open space. As the long side became narrow, the bubble rising velocity became slower than that for open space. When the gap spacing was quite narrow; 1 mm, and the long side was less than 20mm, the bubble stopped rising halfway in the flow channel.
Simulation, Design, and Implementation Based Undergraduate Research in Control Systems: Nonlinear Before Linear
Authors: McDonald Dale B. , Azouz Idir , Taylor Carrie-Anne
Published: August 2009

A typical undergraduate curriculum introduces linear control systems concepts only, often in a single elective course. This curriculum structure introduces challenges to student involvement in control systems research as nonlinear concepts are the focus of the majority of such efforts. With undergraduate participation in engineering research steadily increasing, nonlinear control concepts must be introduced prior to formal classroom study of linear systems. Given this reality, we propose an intense and relatively brief research program, consisting of three distinct phases. The program objective is to present a targeted educational experience in nonlinear control theory based upon the design and implementation of control laws developed for a particular nonlinear system class. Given significant interaction between the student and the faculty mentor, we believe that an excellent opportunity in undergraduate education and research will be realized, despite the student’s initial unfamiliarity with nonlinear control systems concepts. A research program consisting of three phases is proposed and initial technical results are presented to facilitate a candid discussion of the issues that may prevent undergraduate participation in research and to detail the manner in which many of these obstacles were overcome.
High Speed Micro Holographic PIV Measurements of Microorganisms
Authors: Zarzecki M. , Diez F. J.
Published: August 2009

Holographic particle image velocimetry (PIV) is a novel application of holography that allows for tracking of small particle sized objects in a small volume. Whereas regular PIV allows for the two in-plane components of the velocity field to be measured, and stereoscopic PIV allows for the three-components of the velocity field to be measured in a thin plane, holographic PIV allows for the three-components of the velocity to be measured for each individual particle present in the measuring volume, thus allowing to fully resolve fluid flows that are inherently 3D in nature. There are many examples of three dimensional flows in nature including turbulence flows, but another very interesting application very well suited for this technique involves tracking living microorganisms in order to study their motion and their means of propulsion. As part of this research a micro organism was tracked in three dimensions using a high speed microscopic holographic imaging method. The ability to track organisms in 3D allows better understanding and characterizing of their behavior including their propulsion methods, their feeding methods and their interaction with each other. The time resolved holograms were reconstructed in Matlab using Fast Fourier Transforms. A laser pointer was used as a source of coherent light, and a high speed PIV camera (Photron APX Ultima) was used to capture the images. A beam expander was used to increase the diameter of the laser beam allowing for a larger tracking area. Results with this system will show the trajectories in 3D of microorganisms as well as the three components of the velocity field showing the interaction of the organisms with their environment.
Development of Cryogenic Power Modules for Superconducting Hybrid Power Electronic System
Authors: Ye Hua , Haldar Pradeep
Published: August 2009

This paper presents the developments of high-performance integrated cryogenic power modules, where both driver components and power MOSFETs are integrated in a single package. These modules are designed to be used in liquid nitrogen environment with extreme thermal cycling for the cryogenic power inverters. Compact high-voltage, cryogenic integrated power modules with single power MOSFET that exhibited more than 14x improvement in on-resistance and continuous current-carrying capability exceeding 40A. A multi-power MOSFETs integrated cryogenic power module is then developed in order to further increase the power density and reduce the size and weight of the cryogenic power system. The multi-power MOSFETs module was demonstrated to be able to carry a current above 100A with only a small increase in footprint compared with the single power MOSFET module. At the current level of 100A, the multi-power MOSFETs module has an on-resistance of 5.5mU` at 77K, which is 6 times smaller than that of the single power MOSFET integrated module developed. Two different design approaches taken in the developments of these modules are discussed in this paper.
Energy Savings With Reversible Thyristor Controlled Rectifier
Authors: Gelman Vitaly
Published: August 2009

The paper deals with energy savings in Traction Systems available with Thyristor Controlled Rectifiers (TCR) and Reversible TCR (RTCR). TCR provides active voltage control, RTCR in addition has power recuperation into AC line. The energy balance of the TCR and diode rectifier systems are calculated, including losses in the rails, car’s power train and friction losses. The TCR advantages over diode rectifiers: better voltage regulation and fault current limiting allow us to reduce the number of substations and increase their service life. Major energy savings are through recuperation back to AC line using RTCR, with additional savings through increased DC bus voltage. The estimated energy savings depending on the system parameters, train speed profile, etc. can be as high as 50%.
Troubleshooting and Performing Diagnostics on Amtrak’s ACSES System Using PHW’s Inc. ACSESView Software
Authors: Ward Lamont B.
Published: August 2009

The Advanced Civil Speed Enforcement System (ACSES) is a positive train control system used on Amtrak’s North East Corridor (NEC) developed by PHW, Inc. To perform maintenance activities, the system can be downloaded from the On Board Computer (OBC) and the events can be displayed on a laptop using the ACSESView software. This paper will present how the software is used by maintenance personnel and engineers to troubleshoot and maintain the system.
Modeling Material Failure During Cab Car End Frame Impact
Authors: Stringfellow Richard , Paetsch Christopher
Published: August 2009

New standards have been proposed to increase the strength requirements for cab car end structures and impose further requirements on their ability to absorb energy during a grade-crossing collision [1, 2]. To aid in the development of these new standards, the Federal Railroad Administration (FRA) and the Volpe Center recently completed a set of full-scale tests aimed at assessing the quasi-static and dynamic crush behavior of these end structures. In support of this testing program, end frames designed to meet the new standards were fabricated and retrofitted onto the forward end of an existing cab car. A series of large-deformation quasi-static and explicit dynamic finite element analyses (FEAs) were performed to evaluate the performance of the design. Based on the results of a 2002 full-scale test in which a heavy steel coil impacted the corner post of an end frame built to these new standards, some fracture was expected in certain key end frame components during the tests. For this reason, a material failure model, based on the Bao-Wierzbicki fracture criterion [3], was implemented in the FEA model of the cab car end frame using ABAQUS/Explicit. The FEA model with material failure was used to assess the effect of fracture on the deformation behavior of cab car end structures during quasi-static loading and dynamic impact and, in particular, the ability of such structures to absorb energy. The failure model was implemented in ABAQUS/Explicit for use with shell elements. A series of preliminary calculations were first conducted to assess the effects of element type and mesh refinement on the deformation and fracture behavior of structures similar to those found on cab car end frames, and to demonstrate that the Bao-Wierzbicki failure model can be effectively applied using shell elements. Model parameters were validated through comparison to the results of the 2002 test. Material strength and failure parameters were derived from test data for A710 steel. The model was then used to simulate the three full-scale tests that were conducted during 2008 as part of the FRA program: a collision post impact, and quasi-static loading of both a collision post and a corner post. Analysis of the results of the two collision post tests revealed the need for revisions to both the design of some key end frame components and to key material failure parameters. Using the revised model, pre-test predictions for the outcome of the corner post test were found to be in very good agreement with test results.
Thermal Analysis of Railroad Bearings: Effect of Wheel Heating
Authors: Tarawneh Constantine M. , Fuentes Arturo A. , Wilson Brent M. , Cole Kevin D. , Navarro Lariza
Published: August 2009

Catastrophic bearing failure is a major concern for the railroad industry because it can lead to costly train stoppages and even derailments. Excessive heat buildup within the bearing is one of the main factors that can warn of impending failure. A question is often raised regarding the transfer of heat from a wheel during braking and whether this can lead to false setouts. Therefore, this work was motivated by the need to understand and quantify the heat transfer paths to the tapered roller bearing within the railroad wheel assembly when wheel heating occurs. A series of experiments and finite element (FE) analyses were conducted in order to identify the different heat transfer mechanisms, with emphasis on radiation. The experimental setup consisted of a train axle with two wheels and bearings pressed onto their respective journals. One of the wheels was heated using an electric tape placed around the outside of the rim. A total of 32 thermocouples scattered throughout the heated wheel, the axle, and the bearing circumference measured the temperature distribution within the assembly. In order to quantify the heat radiated to the bearing, a second set of experiments was developed; these included, in addition to the axle and the wheel pair, a parabolic reflector that blocked body-to-body radiation to the bearing. The appropriate boundary conditions including ambient temperature, emissivity, and convection coefficient estimates were measured or calculated from the aforementioned experiments. The FE thermal analysis of the wheel assembly was performed using the ALGOR™ software. Experimental temperature data along the radius of the heated wheel, the bearing circumference, and at selected locations on the axle were compared to the results of the FE model to verify its accuracy. The results indicate that the effect of thermal radiation from a hot wheel on the cup temperature of the adjacent bearing is minimal when the wheel tread temperature is at 135°C (275°F), and does not exceed 17°C (31°F) when the wheel tread is at 315°C (600°F).
Modern Energy-From-Waste Facilities: Leading the Way to a Sustainable Renewable Energy Future
Authors: Treshler Joseph R.
Published: August 2009

In recent years, Covanta Energy has successfully executed contracts with two Florida communities, Hillsborough and Lee County, to construct 50% processing capacity expansions to the existing 1200 TPD solid waste energy recovery facilities Covanta originally built and currently operates for each of these communities. Under new Service Agreements that commence following the completion of each expansion project, Covanta will continue to meet operating, maintenance and environmental performance standards established with Lee and Hillsborough Counties for these expanded facilities for another 10 and 20 years, respectively.
Lab-Scale Study on Fireside Superheaters Corrosion in MSWI Plants
Authors: Brossard Jean-Michel , Lebel Florimonde , Rapin Christophe , Mareˆche´ Jean-Franc¸ois , Chaucherie Xavier , Nicol Franc¸ois , Vilasi Michel
Published: August 2009

Combustion of the municipal waste generates highly corrosive gases (HCl, SO2, NaCl, KCl and heavy metals chlorides) and ashes containing alkaline chlorides and sulphates. Currently, corrosion phenomena are particularly observed on superheater’s tubes. Corrosion rates depend mainly on installation design, operating conditions i.e. gas and steam temperature and velocity of the flue gas containing ashes. This paper presents the results obtained using an innovative laboratory-scale corrosion pilot, which simulates MSWI boilers conditions characterized by a temperature gradient at metal tube on the presence of corrosive gases and ashes. The presented corrosion tests were realized on carbon steel at fixed metal temperature (400°C). The influence of the flue gas temperature, synthetic ashes composition and flue gas flow pattern were investigated. After corrosion test, cross section of tube samples were characterised to evaluate thickness loss and estimate corrosion rate while the elements present in corrosion layers were analysed. Corrosion tests were carried out twice in order to validate the accuracy and reproducibility of results. First results highlight the key role of molten phase related to the ash composition and flue gas temperature as well as the deposit morphology, related to the flue gas flow pattern, on the mechanisms and corrosion rates.
Alternative Financing for Enhanced Environmental Protection: The Intersection of Waste-to-Energy Technology and Solid Waste Flow Control Authority
Authors: DuBoff Scott M.
Published: August 2009

When local governments evaluate the environmental benefits and costs of alternatives for managing non-recyclable municipal solid waste, the relative costs of modern waste-to-energy (WTE) technology can be a significant stumbling block despite WTE technology’s environmental benefits. Although the preceding point is an important economic reality that has constrained WTE development in the United States, fortunately there is a highly effective means — the use of municipal solid waste “flow control” (or “facility designation”) authority — to overcome WTE’s perceived cost disadvantage. The relationship between flow control and WTE development, including significant encouragement for use of flow control as a result of the U.S. Supreme Court’s recent decision in United Haulers Association v. Oneida-Herkimer Solid Waste Management Authority, 127 S.Ct. 1786 (2007), is the focus of this paper, which will address the following topics: Policy Basis for Flow Control — Absent government intervention, management of municipal solid waste will seek the lowest cost (i.e., short-term cost) and frequently less environmentally protective alternatives. Flow control can counter the tendency to choose alternatives with lower short-term costs and at the same time facilitate implementation of the environmentally-preferable waste management alternatives a local government selects, such as WTE technology and other aspects of “integrated waste management.” Flow Control and the Courts — While the authority of a given local government to use flow control is grounded in state law, flow control also implicates matters that arise under federal law, such as Commerce Clause issues, given the possibility that solid waste regulation in one state can affect commercial interests in solid waste management in another state. Although concerns regarding claims of impact on interstate commerce prompted a negative Supreme Court response to flow control in C&A Carbone, Inc. v. Town of Clarkstown, 511 U.S. 383 (1994), the Court’s decision 13 years later in the Oneida-Herkimer case was in many ways just the opposite. WTE’s Correlation with Flow Control and Practical Guideposts — WTE development can be significantly advanced by the use of flow control. That conclusion is borne out by empirical data. The concluding portion of this paper addresses that topic as well as corollary issues, such as public-private collaboration for WTE development and other practical guideposts for implementing flow control ordinances.
Nonlinear Aeroelasticity Modeling Using a Reduced Order Model Based on Proper Orthogonal Decomposition
Authors: Feng Zhengkun , Soulaimani Azzeddine
Published: August 2009

Investigations of nonlinear aeroelasticity of flexible structures subjected to unsteady transonic flows were carried out by means of an aeroelasticity model coupled with a reduced order CFD model based on POD (proper orthogonal decomposition) method. The reduced order model is a three-dimensional with moving fluid boundaries. The CFD model order was reduced from more than 150000 of the full order model to 200 of the reduced order model and Limit Oscillation Cycle (LCO) was observed. The dynamic responses of the system were simulated with the coupled model. Qualitatively, the numerical simulations on AGARD 445.6 from the nonlinear aeroelasticity model coupled with the reduced order CFD model agree with those from the model coupled with the full order CFD model.
Prediction of Fully Plastic Failure Stresses for Pipes With Multiple Circumferential Flaws
Authors: Hasegawa Kunio , Saito Koichi , Iwamatsu Fuminori , Miyazaki Katsumasa
Published: August 2009

Fully plastic failure stress for a single circumferential flaw on a pipe is evaluated by the limit load criteria in accordance with Appendix E-8 in the JSME S NA-1-2004 and Appendix C in the ASME Code Section XI. However, multiple flaws such as stress corrosion cracking are frequently detected in the same circumferential cross section in a pipe. If the distance between adjacent flaws is short, the two flaws are combined as a single flaw in compliance with combination rules. If the two flaws separated by a large distance, it is not required to combine two flaws. However, there is no evaluation method for two flawed pipe in the JSME and ASME Codes. Failure stress for pipes with two circumferential flaws based on net-stress approach had been proposed by one of the authors. The present paper is concerned with the comparison of experimental data and the proposed theoretical method for pipes with circumferentially multiple flaws.
Quasi-Static Forces and Stability Analysis in a Triangular Tube Bundle Subjected to Two-Phase Cross-Flow
Authors: Shahriary Soroush , Mureithi Njuki W. , Pettigrew Michel J.
Published: August 2009

Although almost half of the process heat exchangers operate in two-phase flow, the complex nature of the flow makes the prediction of fluidelastic instability a challenging problem yet to be solved. In the work reported here, the quasi-static fluid force-field is measured in a rotated-triangle tube bundle for a series of void fractions and flow velocities. The forces are strongly dependent on void fraction, flow rates and relative tube positions. The fluid force field is employed along with quasi-steady models [1, 2], originally developed for single phase flows, to model the two-phase flow problem. Stability analysis is performed using the single flexible tube model [1] as well as constrained mode analysis [2]. The results are compared with dynamic stability tests [3] and show good agreement. The results of single flexible tube analysis and multiple flexible tubes tend to coincide at low structural damping as expected. The present work uncovers some of the complexities of the fluid force field in two-phase flows. The data are valuable since they are the necessary inputs to the class of quasi-static, quasi-steady and quasi-unsteady fluidelastic instability theoretical models. This database opens a new research avenue on the feasibility of applying quasi-steady models to two-phase flow.
Numerical Simulation of Vortex Shedding Past a Circular Cylinder in a Cross-Flow at Low Reynolds Number With Finite Volume-Technique: Part 1 — Forced Oscillations
Authors: Placzek Antoine , Sigrist Jean-Franc¸ois , Hamdouni Aziz
Published: August 2009

The numerical simulation of the flow past a circular cylinder forced to oscillate transversely to the incident stream is presented here for a fixed Reynolds number equal to 100. The 2D Navier-Stokes equations are solved with a classical Finite Volume Method with an industrial CFD code which has been coupled with a user subroutine to obtain an explicit staggered procedure providing the cylinder displacement. A preliminary work is conducted in order to check the computation of the wake characteristics for Reynolds numbers smaller than 150. The Strouhal frequency fS, the lift and drag coefficients CL and CD are thus controlled among other parameters. The simulations are then performed with forced oscillations f0 for different frequency rations F = f0/fS in [0.50–1.50] and an amplitude A varying between 0.25 and 1.25. The wake characteristics are analysed using the time series of the fluctuating aerodynamic coefficients and their FFT. The frequency content is then linked to the shape of the phase portrait and to the vortex shedding mode. By choosing interesting couples (A,F), different vortex shedding modes have been observed, which are similar to those of the Williamson-Roshko map.
Technical Basis and Application of New Rules on Fracture Control of High Pressure Hydrogen Vessel in ASME Section VIII, Division 3 Code
Authors: Rana Mahendra D. , Rawls George B. , Sims J. Robert , Upitis Elmar
Published: August 2009

As a part of an ongoing activity to develop ASME Code rules for the hydrogen infrastructure, the ASME Boiler and Pressure Vessel Code Committee approved new fracture control rules for Section VIII, Division 3 vessels in 2006. These rules have been incorporated into new Article KD-10 in Division 3. The new rules require determining fatigue crack growth rate and fracture resistance properties of materials in high pressure hydrogen gas. Test methods have been specified to measure these fracture properties, which are required to be used in establishing the vessel fatigue life. An example has been given to demonstrate the application of these new rules.
Evaluation of Two-Parameter Approaches to Describe Crack Tip Fields in Engineering Structures
Authors: Kamel Simon , O’Dowd Noel P. , Nikbin Kamran M.
Published: August 2009

The application of two parameter approaches to describe crack tip stress fields has generally focused on power law materials which limits the range of applicability of such approaches. In this work we consider the applicability of a J-Q or J-A2 approach (the latter is designated here as the J-A approach) to describe the stress fields for power law materials and for materials whose tensile behaviour cannot be described by a simple power law. The predictions of the two parameter approaches are compared with full field finite-element predictions. Results are presented for shallow-cracked and deep-cracked tension and bend geometries, as these are expected to provide the expected range of constraint conditions in practice.
Flow-Induced Vibrations of Bellows Structures Coupled With Vortex Street
Authors: Watanabe Masahiro
Published: August 2009

This paper deals with an experimental study on flow-induced vibrations of a two-dimensional flexible bellows structure subjected to fluid flow. Experiments are conducted to clarify the detailed characteristics of the flow-induced vibrations of periodic flexible convolutions coupled with vortexes generated in shear layer of the fluid flow. In the experiments, a test section consists of flexible convolutions supported by plate springs is set in a water channel and is subjected to water flow. The vibrations of the flexible convolution are measured with increasing flow velocity. The flow-induced responses are examined with changing the convolution pitch, number of the flexible convolutions and structural damping. Moreover, the dynamic behavior of the flow pattern coupled with the vibrating convolutions is visualized. As a result, it is found that flow-induced vibrations, with large amplitude and lock-in phenomenon, occur to the flexible convolutions. Two types of vibration modes with periodic large vortex street generated in the shear layer over the cavity between the convolutions are observed. It is clarified that the two types of periodic vortex streets are moving downstream synchronized with the flexible convolution vibrations. The vibration region (stability map) and the Strouhal number are clarified. Moreover, the excitation mechanism of the flow-induced vibration coupled with vortexes is discussed based on the flow patterns.
Acoustic Amplification of a Vertical Liquid Column Bouncing on a Gas Volume
Authors: Moody F. J.
Published: August 2009

There are reported cases where a pressure transducer was installed at the bottom end of a liquid-filled instrument tube for measuring pressure in a recirculation pipe. For example, in one case, a small diameter instrument tube extended a long distance downward from a power plant recirculation pipe to the transducer. A continuous pressure oscillation was observed, which was not consistent with any other measurements in the recirculation system. However, it was found from paper-and-pencil analyses that such an oscillation could be traced to a resonant frequency in the system if the vertical liquid column rested on a postulated trapped gas bubble, which could have remained after venting. The relative compressibility of the liquid column is also compared with the gas bubble compressibility to show when acoustics of the liquid column are important.
Influence of Axially Distributed Force on the Vibration of Euler-Bernoulli Beam Structures Solved by DQEM Using EDQ
Authors: Chen Chang-New
Published: August 2009

The influence of axially distributed force on the vibration of Euler-Bernoulli beam structures is analyzed by differential quadrature element method (DQEM) using extended differential quadrature (EDQ). The DQEM uses the differential quadrature to discretize the governing differential eigenvalue equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.
Residual Stress Effects on Cleavage Fracture
Authors: Sherry A. H. , Lee K. S. , Goldthorpe M. R. , Beardsmore D. W.
Published: August 2009

It is recognised that the driving force for the initiation and propagation of defects in materials may, under some circumstances, include contributions from both externally applied loads such as internal pressure in pressure vessels and piping and secondary stresses such as weld residual stresses. For non stress-relieved welds, residual stresses can provide a significant proportion of the crack driving force. This paper describes the results obtained from an experimental programme aimed at extending the understanding of residual stress effects on cleavage fracture. The paper describes the preparation and testing of standard and preloaded compact-tension specimens of an A533B pressure vessel steel at its Master Curve reference temperature. Standard tests on compact-tension specimens provide fracture toughness data which are broadly consistent with the conventional three-parameter Weibull model, with Kmin = 20 MPa√m and an exponent of about 4. The preloaded compact-tension specimens included a high level of tensile residual stress at the crack location. Fracture toughness data obtained using the test standards from these specimens fall significantly below the standard specimen data, since the contribution from residual stresses is ignored. However, when due account is taken of the residual stress on the crack driving force using a correct definition of the J-integral, the distributions of fracture toughness data from both specimen types are found to overlay each other. The definition of J used in this paper allows residual stress effects on fracture to be accounted for in a single fracture parameter.
Flaw Alignment Criteria Based on Limit Load Solutions for Non-Aligned Through-Wall Flaws
Authors: Bezensek B.
Published: August 2009

Multiple flaws are frequently replaced with simpler flaws according to the flaw alignment rules for the purpose of engineering assessment. Such rules typically compare the flaw separation distance with the characteristic dimension, such as flaw length or flaw depth. For configurations involving flaws on parallel offset planes, current ASME Boiler code, Section XI, Article IWA-3300 suggests a fixed distance of 12.4 mm between the offset flaw planes as a flaw alignment rule. Recent experimental work of Hasegawa et al [4] showed this criteria is not always conservative for ductile fracture. In this paper the analytical and computational methods are used to derive plastic collapse load for plates with twin non-aligned through-wall flaws. Results show that in a multiple flaw geometry the global plastic collapse load is independent of the flaw separation when horizontal and vertical separations between flaw tips are equal. Such geometries are of most interest, since experimental work shows that flaws in such geometries interact over distances several times larger than the characteristic distance (flaw length or thickness). A criteria for flaw alignment based on the ratio of a local to global limit load is derived. A local limit load is defined as the load to cause collapse of the ligament between the flaw tips. It is shown that the separation between parallel flaws should be more than three times the flaw length to maintain interaction below 15 per cent and ensure a conservative assessment.
Improving Thermal Performance of Radioactive Material Drum Type Packages by Using Heat Pipes
Authors: Gupta Narendra K.
Published: August 2009

This paper presents a feasibility study to improve thermal loading of existing radioactive material packages by using heat pipes. The concept could be used to channel heat in certain directions and dissipate to the environment. The concept is applied to a drum type package because the drum type packages are stored and transported in an upright position. This orientation is suitable for heat pipe operation that could facilitate the heat pipe implementation in the existing well proven package designs or in new designs where thermal loading is high. In this position, heat pipes utilize gravity very effectively to enhance heat flow in the upward direction Heat pipes have extremely high effective thermal conductivity that is several magnitudes higher than the most heat conducting metals. In addition, heat pipes are highly unidirectional so that the effective conductivity for heat transfer in the reverse direction is greatly reduced. The concept is applied to the 9977 package that is currently going through the DOE certification review. The paper presents computer simulations using typical of-the-shelf heat pipe available configurations and performance data for the 9977 package. A path forward is outlined for implementing the concepts for further study and prototype testing.
Comparison of Welding Residual Stress Solutions for Control Rod Drive Mechanism Nozzles
Authors: Rudland D. , Chen Y. , Zhang T. , Wilkowski G. , Broussard J. , White G.
Published: August 2009

In the last 7 years, the incidences of cracking in Alloy 600 control rod drive mechanism (CRDM) tubes and their associated welds have increased significantly. The cracking mechanism has been attributed to pressurized water stress corrosion cracking (PWSCC) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. During this time period, both the industry and the US Nuclear Regulatory Commission have been conducting detailed welding simulation analyses to predict the magnitude of these stresses in both the weld and tube material. To this point, a direct comparison of these analysis methodologies and results has not been made. In this paper, weld residual stress results from U.S. industry (conducted by Dominion Engineering) and the U.S. NRC (conducted by Engineering Mechanics Corporation of Columbus) for a steep angle (53 degrees) CRDM nozzle are compared. This comparison was performed for different yield strength tube materials, however only the low yield strength results are presented in this paper. The comparison illustrates the effect of weld analyses assumptions and suggests that simplifications in the analyses, i.e., lumping weld passes or material property assumptions, may lead to high predicted weld residual stresses.
Small Parameter Analysis of the Modified Tate Equations
Authors: Huguet Jesse A. , Reichwein Sarah , Jones Stanley E. , Walters William P.
Published: August 2009

The Tate Theory of penetration of armor targets by long rod penetrators [1,2] has been the benchmark one-dimensional model of this event for decades. The model is applied to metal-on-metal normal impact of cylindrical rod penetrators. The key physical parameters in the model are the penetrator and target strengths and densities (assumed constant), as well as the penetrator length. With these parameters and the impact speed, penetration depth for all combinations of the parameters can be evaluated. In a recent paper, Walters et al [3] showed that all of the important effects of the classic Tate Theory could be captured by a regular perturbation solution of the fundamental equations. The small parameter that they used was ε = Yp/ρpv02, where Yp is the penetrator yield strength, ρp is the penetrator density and v0 is the impact speed. In 1987, Jones et al [4] modified the equation of motion of the undeformed section to include mass loss and mushrooming at the interface with the target. The changes to the theory that result from these modifications bring the strengths of the target and penetrator into line with laboratory levels while achieving reasonable penetration depths. In this paper, we will show that the regular perturbation analysis used by Walters et al [3] can be extended to the modified system of equations from Jones et al [4] using the same small parameter mentioned in the previous paragraph. The perturbation process is carried out to terms of first order and an approximate analytical solution is found. This solution is then used to repeat the reduction of data given by Wilson et al [5] for Aluminum and Steel alloy penetrators normally impacting Aluminum and Steel targets. Another case involving heavy metal penetrators impacting Rolled Hard Armor (RHA) targets is also presented.
The Fatigue Properties of Laser Shock Processed Aluminum Alloy 7050
Authors: Zou Shikun , Cao Ziwen
Published: August 2009

In order to develop the application of laser shock processing (also named laser peening or LSP in short) as a strengthening technology for 7050 aluminum alloy fastener holes, the fatigue properties of laser shock-processed aluminum alloy specimens were investigated. At first, the dislocation density and surface residual stress induced in the shock affected zone was characterized and compared with that of the base material. Then, the fatigue specimens with stress-concentration hole (notch) were treated by LSP. The fatigue life of LSP-treated specimens were measured and compared with that of specimens made from base material without LSP. Fatigue tests were taken under special flight spectrum loading condition for mid-airframe. The results indicated that laser peening improved the fatigue life of all specimens tested. Specimens treated by LSP before hole-drilling had longer fatigue life than those specimens treated by LSP after hole-drilling. At last, the difference of both sequences was investigated by analyzing the plastic strain and residual stress induced by LSP. LSP induced both plastic strain and deformation at the surface layer. The plastic strain induced by LSP was shown to produce harmful orifices with sharp-angle near the edge of hole. The residual stress induced by LSP appears to remain compressive even after the hole-drilling process. In average, the fatigue life of specimens treated by LSP before hole-drilling was found to be 173% longer than that of untreated samples and approaching the life enhancement factor demonstrated by rod extrusion method (on specimens with large diameter holes).
Uniqueness of the Two Extremes Procedure for Quantifying Fracture Initiation at a Blunt Flaw
Authors: Smith E.
Published: August 2009

The author is involved in a wide-ranging research programme, whose objective is to extend the sharp crack fracture mechanics methodology to a blunt flaw, so as to take credit for the blunt flaw geometry. The basis of the approach is the process zone representation of the micro-mechanistic processes that are associated with fracture. In earlier work, a blunt flaw fracture initiation relation has been derived, subject to the restriction that the process zone size s is small compared with the flaw depth (length) or any other characteristic dimension, such as remaining ligament width, but not necessarily the flaw root radius ρ. The relation gives the critical elastic flaw-tip peak stress σpcr, and has been derived using a two extremes procedure, whereby the separate σpcr solutions for small and large s/ρ are blended together so as to give a single relation that is valid for the complete spectrum of s/ρ values. Equally well, one can develop a relation for σpcr, based on the separate solutions for vT, the relative displacement across the process zone at the flaw root. For the fracture initiation relation based on separate σpcr solutions to be meaningful, the relation should be close to that based on separate vT solutions. The objective of the work described in the present paper is to demonstrate that the two relations are indeed close to each other.
Estimation of SCC Crack Propagation Under Corrosion Environment by “SCAN”
Authors: Shiratori Masaki , Nakanishi Shin , Tanaka Yoshihiko , Iwamatsu Fuminori
Published: August 2009

In recent years, Japanese nuclear power plants meet the problems due to SCC (Stress Corrosion Cracking) that may seriously affect the integrity of the important components such as the pressure boundary or the reactor internals. Repair or replacement of the components with SCC has been taken in the past. However, establishment of a reliable evaluation method for the SCC crack propagation is expected, especially for surface cracks, under such complicated stress fields as residual stress. The authors have developed a software system called “SCAN” to evaluate the stress intensity factor, K, and to simulate fatigue crack propagation for surface cracks for arbitrarily distributed surface stress. In this paper we have extended its function to estimate SCC crack propagation based upon the propagation law described by the JSME (Japan Society of Mechanical Engineers) standard. And we call it “SCAN SCC Version”. In order to investigate the reliability of the developed system a simplified simulation model has been analyzed and the results are compared with those obtained by the algorithm of API and JSME standards. It has been found that it works well, that is, we can estimate reliable results easily by the proposed system. It is very useful because it can be applied to the problems of more complicated stress fields. Further, we have developed “SCAN circumferential crack version” which is effective to estimate the residual life of SCC crack propagation, for internal fully circumferentially cracked pipes. In order to take account of the effect of pipe compliance, we have proposed a simplified model to estimate K-values for the displacement controlled problem. An example problem shows how important it is to take account of the effect of pipe compliance when we think of the SCC crack propagation.
Reliability Assessment of PLR Piping Based on Domestic SCC Data
Authors: Machida Hideo
Published: August 2009

This paper describes effects of a probability of detection (POD) of a stress corrosion crack on the reliability of the piping in a nuclear power plant (NPP). Various POD curves were proposed using the results of Japanese study on the detection for the stress corrosion crack which is frequently observed in austenitic stainless steel piping of boiling water reactor (BWR). Based on the proposed POD curves, the reliability of a flawed pipe was analyzed using probabilistic fracture mechanics (PFM) code. The results suggest that the detectable crack depth and oversight probability (e.g. human error) is important on the reliability of piping with the stress corrosion crack. The reliability of piping depends on the detectable crack depth rather than the oversight probability when the detectable crack depth is larger than 3mm. Meanwhile, it depends on the oversight probability, when the detectable crack depth is 3mm or less.
A Critical Review of ASME BTH-1-2005 in the Design and Analysis of Vessel Lifting Lugs
Authors: Williams Dennis K.
Published: August 2009

This paper presents a critical review of the newly published ASME BTH-1-2005, which is intended to be a companion to ASME B30.20, Below the Hook Lifting Devices, a safety standard. The very limited structural design criteria contained in the latter standard was previously addressed in the literature by the current author and was compared against the various national and international regulations, codes, and standards in regard to the presumed factors of safety inherent in the designs of vessel lifting lugs. Based upon the criteria previously outlined and addressed, the current American National Standard ASME BTH-1-2005 is critically reviewed and the commentary that is now incorporated in such is analyzed in an effort to determine the adequacy of the updates in meeting and exceeding the current regulations in both the United States and Canada. The statutory and provincial regulations in both the United States and the province of Alberta, Canada are also reviewed and discussed with respect to the too often utilized phrase “factor of safety” (FOS). The implied implications derived from the chosen FOS are also outlined. Exemplar lugs on vessels are defined and the finite element analyses and closed form Hertzian contact problem solutions are presented and interpreted in accordance with the new ASME BTH-1-2005 structural design criteria. These results are again highlighted against the very limited design information contained within ASME B30.20. A review of the author’s prior recommendations made to revise the ASME B30.20 Below the Hook Lifting Devices safety standard are presented and discussed in light of the examples and technical justification presented in the following paragraphs. Contact stresses that are well known to exist between a lifting pin and clevis type geometry are also discussed in light of the new structural design criteria contained within ASME BTH-1-2005. Additional recommendations are provided for the design and analysis of vessel lifting lugs in consideration of current regulations.