bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a Viscoelastic Model for the Seismic Response of Base-Isolated Buildings
Authors: Uras R. A.
Published: February 2008

Due to recent developments in elastomer technology, seismic isolation using elastomer bearings is rapidly becoming an acceptable design tool to enhance structural seismic margins and to protect people and equipment from earthquake damage. With proper design of isolators, high-energy seismic input motions can be transformed into low-frequency, low-energy harmonic motions, and the accelerations acting on the isolated building may be significantly reduced. Several alternatives exist for the modeling of the isolators. This study is concerned with the use of a viscoelastic model to predict the seismic response of base-isolated buildings. The in-house finite element computer code, SISEC has been modified to incorporate a viscoelastic spring element, and several simulations are performed. Then, the computed results have been compared with the corresponding observed data recorded at the test facility.
Beam Motion With Unilateral Contact Constraints and Wear of Contact Sites
Authors: Johansson L.
Published: February 2008

In the present paper, a computational algorithm is proposed for the motion of a beam which is constrained by unilateral contact at prescribed contact sites. Special attention is focused on the numerical difficulties arising due to the iteration between the beam equation of motion and the contact algorithm, and a method to overcome these difficulties is suggested. The algorithm also includes wear, and the dynamical properties of the system are allowed to change gradually as the contact sites wear down.
Orthotropic Shallow Spherical Shell on a Kerr Foundation
Authors: Paliwal D. N. , Kanagasabapathy H. , Gupta K. M.
Published: February 2008

Parametric study involving foundation parameters and shell geometry is carried out for nonlinear static behavior of an orthotropic shallow spherical shell on a Kerr foundation. Study shows that the deflection reduces if the shell curvature or the foundation parameters of the shear layer and the lower spring layer are increased. Shells with immovable edges are found to be more prone and vulnerable to changes in various parameters than those with movable edges.
Crack Closure Effects on Fatigue Crack Growth Thresholds and Remaining Life in an HSLA Steel
Authors: Todd J. A. , Chen L. , Yankov E. Y. , Mostovoy S.
Published: February 2008

The effects of crack closure on the near-threshold corrosion fatigue crack growth behavior of Mil S-24645 HSLA steel and its weld metal have been investigated in air, ASTM seawater at the free corrosion potential, and ASTM seawater at −0.8V and −1.0V (SCE) using frequencies of 10, 2, and 0.2 Hz, and a stress ratio, R = 0.1. Remaining life, in the presence and absence of crack closure, has been estimatedas a function of applied stress range for a structure containing a 3-mm-deep surface semi-elliptical flaw.
Unstable Sloshing Vibration in a Thin Cylindrical Weir
Authors: Chiba M. , Kiuchi H. , Tani J.
Published: February 2008

Traveling unstable sloshing modes have been observed in experiments on the fluidstructure coupled system in a thin cylindrical weir. The unstable vibration was found to be classified into three types: i.e., traveling wave which travels along one circumference direction; traveling wave which travels in the clockwise and counterclockwise directions alternately; and stationary wave. Influences of the outer and the inner annular gap widths, the height of weir, the elastic rigidity of weir, and baffle plate on the characteristics of the unstable sloshing vibration were clarified.
Residual Stresses in Steel and Zirconium Weldments
Authors: Root J. H. , Coleman C. E. , Bowden J. W. , Hayashi M.
Published: February 2008

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.
A Study on the Large Ductile Deformations and Perforation of Mild Steel Plates Struck by a Mass—Part I: Experimental Results
Authors: Jones N. , Kim S.-B.
Published: February 2008

An experimental study is reported on the ductile deformation and perforation of plates struck at the center by solid cylindrical projectiles having the longitudinal axis normal to the plate surface. The plates, which are made from 4 to 8-mm-thick mild steel sheet, are fully clamped around a circular boundary and are struck by projectiles having blunt ends and traveling with impact velocities within the range 7.7–118.9 m/s. Comparisons are made in Part II with the static perforation behavior and with previously published experimental results and several empirical equations for the impact case. A new empirical equation, which retains the influence of the impact velocity on the perforation energy, is also proposed in Part II.
Fatigue Design Curves for 6061-T6 Aluminum
Authors: Yahr G. T.
Published: February 2008

A request has been made to the ASME Boiler and Pressure Vessel Committee that 6061-T6 aluminum be approved for use in the construction of Class 1 welded nuclear vessels so it can be used for the pressure vessel of the Advanced Neutron Source research reactor. Fatigue design curves with and without mean stress effects have been proposed. A knock-down factor of 2 is applied to the design curve for evaluation of welds. The basis of the curves is explained. The fatigue design curves are compared to fatigue data from base metal and weldments.
Fracture Analysis of Multiple Cracks in a Spinning Cylinder Experiment
Authors: Keeney J. A. , Bass B. R.
Published: February 2008

This paper presents finite-element analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The NESC was organized as an international forum to exchange information on procedures for structural integrity assessment, to collaborate on specific projects, and to promote the harmonization of international standards. The objective of the NESC-1 project is to focus on a complete procedure for assessing the structural integrity of aged reactor pressure vessels. Current plans for the testing program call for two large cracks to be installed in the NESC-1 cylinder separated by 90 deg. Three-dimensional finite-element analyses were carried out to determine: 1) the extent of interaction between multiple cracks in the cylinder; and 2) the predicted effects of using an initial cylinder temperature of 295°C and coolant temperature of 5°C in the experiment. The cylinder was modeled with innersurface through-clad cracks having a depth of 74 mm and aspect ratio of 2:1. The cylinder specimen was subjected to centrifugal loading followed by a thermal shock and analyzed with a thermo-elastic-plastic material model. The analytical results indicate that the stress-intensity factor changes less than 0.2 percent between a model with one crack and a model with four cracks evenly spaced around the circumference. Cleavage initiation is likely to be achieved for initial and coolant temperatures of 295 and 5°C, respectively.
A Simple Method of Calculating Lower-Bound Limit Loads for Axisymmetric Thin Shells
Authors: Boyle J. T. , Hamilton R. , Shi J. , Mackenzie D.
Published: February 2008

In this paper, a simple method for calculating lower-bound limit loads for shells is presented, based on Ilyushin’s and Ivanov’s generalized yield criterion, respectively, and using the elastic compensation procedure. Several examples, including torispherical and conical ends, radial nozzles, and a skirted vessel, are examined using this method. The results are compared with previously published results.
Notch-Stress Analysis by FE Submodeling
Authors: Weiß E. , Rudolph J. , Lietzmann A.
Published: February 2008

This paper presents experiences in detailed finite element analyses of pressure vessel components with respect to load-carrying capacity and fatigue strength. The application of the submodeling technique for shell-to-solid models is discussed.
The Effect of Crack Length Unevenness on Stress Intensity Factors Due to Autofrettage in Thick-Walled Cylinders
Authors: Perl M. , Alperowitz D.
Published: February 2008

The effect of crack length unevenness on the mode I stress intensity factors (SIFs) for large uniform arrays of radial cracks of unequal depth in fully or partially autofrettaged thick-walled cylinders is investigated. The analysis is based on the previously proposed “two-crack-length level model.” Values for KIA—the SIF due to the compressive residual stress field—for various crack arrays bearing n1 = n2 = 2−512 cracks, a wide range of nondimensional crack lengths l1/a=0.01−0.1, and numerous levels of autofrettage ε = 30−100 percent are evaluated by the finite element method for a cylinder of radii ratio of b/a = 2. The interaction range for different combinations of crack arrays and crack length is then determined. The obtained results show that the unevenness in the SIFs depends on all three parameters, i.e., the number of cracks in the array, the cracks’ lengths, and the level of autofrettage, while the interaction range between adjacent cracks is determined only by the relative length of the cracks and the density of the array.
Stress Analysis of Shell Intersections With Torus Transition Under Internal Pressure Loading
Authors: Skopinsky V. N.
Published: February 2008

Thin shell theory and finite element method were used to investigate shell intersections with torus transition. The developed special-purpose computer program SAIS is employed for elastic stress analysis of the shell intersections. Comparison of calculated results with experimental data are presented. The parametric study of models for the radial nozzle connections in shells under internal pressure loading was performed. The results are presented in graphical form. Nondimensional geometric parameters are considered to analyze the effects of changing these parameters on stress ratios in the shell intersections.
A Stress Analysis of a Taper Hub Flange With a Bolted Flat Cover
Authors: Sawa T. , Higurashi N. , Hirose T.
Published: February 2008

A bolted connection consisting of a cover on a pressure vessel flange with a metallic flat gasket on raised faces is analyzed as a four-body contact problem using axisymmetrical theory of elasticity. The contact stress distribution, the load factor (the relationship between an increment of bolt axial force and an internal pressure), and the gasket properties (the gasket seating width and the moment arm) are examined. In the analysis, the cover is replaced with a finite solid cylinder. The metallic flat gasket, the flange, and the hub are replaced with finite solid cylinders. The effects of the stiffness and the thickness of various size gaskets on the contact stress distribution are obtained by numerical calculations. Experiments were carried out to obtain the load factor, the maximum stress produced in bolts, and the stress produced on the hub. The analytical results obtained are shown to be consistent with the experimental results.
A Boundary Integral Approach to Attachment/Spherical Shell Interaction
Authors: Simos N. , Chassapis C.
Published: February 2008

In pressure vessel applications, the accurate evaluation of the state of stress in the vicinity of nozzles or rigid attachments is of vital importance to the structural integrity of the vessel. Consequently, a number of investigations have paid attention to the problem and, through analytical and numerical approaches, provided information concerning the effect of system parameters, such as shell curvature and attachment geometry, on stress concentration and effective shell stiffness. While analytical solutions have only been able to provide information to axisymmetric problems, finite element approaches have been widely used as an attractive alternative. In evaluating the latter, one can identify the high computational cost that accompanies analyses dealing with complex systems. In this study, the performance of a boundary integral scheme is assessed as a possible analytical and/or numerical tool in dealing with spherical shells interacting with attachments. Such method hopes to achieve a close to analytical solutions representation of the stress state in the vicinity of the attachment that is accompanied by significant reduction in the computational cost. To achieve this, a set of integral equations, which satisfy the edge constraints, are reduced to a system of algebraic equations. These integral equations utilize singular solutions obtained for deep (nonshallow) spherical shells, which in turn are more representative of the shell domain. Explicit comparisons, on the basis of representative shell-attachment interaction problems, between the finite element and boundary integral computational techniques are conducted in order to assess the performance and efficiency of the new method. Finally, shell stiffnesses in the form of insert translations and rotations are presented in dimensionless form.
Performance of Repair Welds on Service-Aged 2-1/4Cr-1Mo Girth Weldments
Authors: Viswanathan R. , Gandy D. , Findlan S.
Published: February 2008

This paper discusses the results of evaluations performed on service-aged piping using both conventional postweld heat treatments and temperbead repair techniques. The two repair weldments were accomplished on two 2-1/4Cr-1Mo pipe girth weldments which were removed from a utility hot reheat piping system in the fall of 1992 after 161,000 h of operation at 1000°F (538°C). Each repair was performed around one-half of the diameter of a pipe girth weldment, while the remaining half of the girth weldment was left in the service-aged condition. Post-repair metallurgical and mechanical test results indicated that both weld repairs produced improved remaining lives when compared to the service-aged girth weldments. Since the two ex-service weldments that were utilized in weld repairs exhibited different stress rupture strengths to start with, the performance of temper bead and postweld heat-treated (PWHT) repair could not be compared directly. It was clear, however, that life extension periods exceeding 30 yr could be achieved by temperbead repairs, with improved toughness and with no loss of stress rupture ductility, tensile strength, or yield strength. The temperbead repair improved the toughness of the service-aged weldment, while the postweld heat-treated repair lowered the HAZ toughness.
Amplification Factors for Equipment Design Subjected to Seismic Loading
Authors: Jategaonkar R. , Jaeger L. G.
Published: February 2008

A mathematical technique is developed to evaluate the seismic response of primary equipment supported directly by the main structure and also the response of secondary equipment supported by the primary equipment. The method can be used for structures ranging from the simple to the complex, and is amenable to calculations based on standard spreadsheet or numerical software or, if desired, can be programmed. The technique can be used to develop amplification factors for seismic motion between ground, structure, and equipment. Alternatively, the method can be utilized to develop the ground response (or structure motion) spectra for various structural damping ratios and also floor response (or equipment response) spectra directly from a ground motion spectrum given as datum. The results are compared with the results from other well-established methods. The proposed method has an advantage over the other methods in that it enables direct computation of the third level response, i.e., response of the secondary equipment supported by the primary equipment; also, the method can be readily applied to any shape of ground motion response spectrum given as datum.
Shakedown of Torispherical Heads Using Plastic Analysis
Authors: Kalnins A. , Updike D. P.
Published: February 2008

The condition of shakedown is examined for torispherical heads. The reason for using plastic analysis is to account for the strengthening that heads experience when subjected to internal pressure. Cyclic pressures are considered up to an allowable burst pressure that is based on the membrane stresses of the spherical part of the head. To simulate a proof test before service cycling, cases when the applied pressure is higher for the first cycle are also included. A definition of shakedown is used that places the limit of twice the yield strength on a fatigue stress parameter range that is defined in the paper. The equivalent stress and plastic strain ranges are calculated for ten head thickness-to-spherical radius ratios. From these data, shakedown pressures are obtained as fractions of the allowable burst pressure. By giving bounds for isotropic and kinematic strain-hardening models, the results are made independent from specific cyclic material behavior. It is also shown that if an elastic, geometrically linear algorithm is used, which is unable to account for the strengthening, the fatigue stress parameter range is overestimated for the thinner heads.
Status of Code Cases Related to Application of Risk-Informed Inservice Inspection in ASME Code Section XI
Authors: Hedden O. F.
Published: February 2008

ASME Code Section XI Cases N-577 and N-578, for application of risk-informed technology to examination of piping systems in nuclear power plants, are proceeding, with review and acceptance by ASME Board on Nuclear Codes and Standards and by the U.S. Nuclear Regulatory Commission remaining before implementation. Sources of support for a favorable reaction by NRC will be reviewed, starting with developmental research sponsored by NRC in the late 1980s. Extensive discussion in the engineering community as exemplified by forums presented by ASME PVP in 1994 and 1995 will be cited. Recent academic and NRC managerial support for risk-informed performance-based regulation will also be cited. The expressed need for risk neutrality will then be addressed.
A Case Study of Feedwater Heater Life Management
Authors: Becker B. R. , Pearce R. E. , Fricke B. A.
Published: February 2008

In the late nineteen eighties, electric utility companies, such as Kansas City Power and Light (KCPL), recognized the viability of extending the life of power plants by repairing or replacing major components instead of building entirely new facilities. As part of a strong life management program, a life evaluation can postpone the replacement of major components to future years. A physical condition assessment is the first step in a life evaluation. It requires the following information: 1) original design data; 2) component operating data; 3) knowledge of current industry practices; and 4) detailed component inspections. The second step in a life evaluation is an economic life assessment to ascertain the component’s current loss of performance. The cost associated with operating the component in its current degraded state is then compared to the cost of repairing or replacing the component. Based on this cost comparison, a course of action is determined to optimize the component’s life cycle cost. This paper describes the methodology of life management and its application to a feedwater heater at Kansas City Power and Light.
Economic Performance of the SCE Stirling Dish
Authors: Stone K. W. , Lopez C. W. , McAlister R. E.
Published: February 2008

In 1982 McDonnell Douglas Aerospace (MDA) and United Stirling AB (USAB) of Sweden formed a joint venture to develop and market a solar Stirling dish system. Eight modules were built and extensively tested from 1984 to 1988. Power production and daily energy-conversion efficiency as determined by field testing were characterized and modeled into a computer program. Included in this simulation are models of mirror soiling rate, wind spillage loss, mirror washing, and other maintenance outage time, operation and maintenance (O&M) costs, and equipment purchase cost. An economic model of a hybrid (combustion) receiver has been included in the simulation for illustrating the value of using solar energy when available and other fuels such as methane, natural gas, hydrogen, etc. when solar energy is not available or adequate. This paper describes the simulation and presents comparisons of the simulation to test data. The simulation also estimates both the O&M expenses and levelized energy costs for different production volumes.
Thermodynamics of Phase-Change Storage in Series With a Heat Engine
Authors: Charach C. , Conti M. , Bellecci C.
Published: February 2008

This paper addresses thermodynamics of phase-change storage elements in series with heat engines. It is assumed that the duration of the heat storage and the discharge are equal. It is also assumed that the same heat transfer fluid (HTF) with a constant flow rate is used for the whole cycle. The major constraint imposed on these systems is the stability of the temperature of the HTF supplied to the engine during the storage-discharge cycle. It is shown, for this setup, that the freezing point of the phase-change material (PCM) is defined by the First Law. Maximal stability corresponds to the freezing point equal to the arithmetic mean of the inlet temperatures of the hot and the cold streams. An analytic expression is developed for the Second Law efficiency of the heat storage-removal cycle for the phase-change element in series with an engine. It yields maximal entropy production in the absolute stability limit. Two analytically tractable models of a phase-change storage in series with a heat engine are studied in detail. One involves a PCM slab, and the second involves a PCM tube-and-shell heat exchanger.
A Direct-Heating Energy-Storage Receiver for Dish-Stirling Solar Energy Systems
Authors: Lund K. O.
Published: February 2008

Dish-Stirling solar receiver designs are investigated and evaluated for possible use with sensible energy storage in single-phase materials. The designs differ from previous receivers in utilizing axial conduction in the storage material for attenuation of the solar flux transients due to intermittent cloud cover, and in having convective heat removal at the base of the receiver. One-dimensional, time-dependent heat transfer equations are formulated for the storage material temperature field, including losses to the environment, and a general heat exchange effectiveness boundary condition at the base. The solar source flux is represented as the sum of steady and periodic cloud-transient components, with the steady component solved subject to specified receiver thermal efficiency. For the transient cloud-cover component the Fast Fourier Transform algorithm (FFT) is applied, and the complex transfer function of the receiver is obtained as a filter for the input flux spectrum. Inverse transformation results in the amplitudes and mode shapes of the transient temperature component. By adjustment of design parameters, the cloud-cover amplitude variations of the outlet gas temperature can be limited to acceptable magnitudes, thus simplifying control systems.
Estimation of Collector Performance Parameters From Daily System Tests
Authors: Wijeysundera N. E. , Hawlader M. N. A. , Foong K. Y.
Published: February 2008

A test procedure to estimate the daily mean values of the linear collector characteristics, FR,(τα) and FRUL, from the measured variation of the storage tank temperature was investigated. The Levenberg-Marquardt algorithm was used for parameter estimation. Two flat-plate collectors were tested over a period of 11 days each to study the feasibility of the test procedure. The tests were conducted under variable weather conditions and inlet water temperatures. The standard deviation for the daily mean values of FR(τα) and FRUL were about 2.8 percent and 4 percent, respectively. The differences between the daily mean values obtained by the proposed method and the steady-state test values for FR (τα) were about 4 percent to 7 percent, while for FRUL the differences were 9 percent to 13 percent.
A Gradient Maintenance Technique for Seawater Solar Ponds
Authors: Kleis S. J. , Li Haoming , Shi J.
Published: February 2008

Seawater solar ponds are being evaluated as a means of reducing heat losses from thermal refuge areas in outdoor mariculture ponds during cold weather. The thermal refuge areas are intended to provide a reliable means of protecting fish crops from lethal cold water temperatures in the winter months. A continuous filling technique is demonstrated for use in gradient zone maintenance of the seawater solar ponds. The technique allows indefinite operation of the refuge areas with a minimal amount of fresh water.
Vibration Control of Plates by Plate-Type Dynamic Vibration Absorbers
Authors: Aida T. , Kawazoe K. , Toda S.
Published: February 2008

In this paper, a new plate-type dynamic vibration absorber is presented for controlling the several predominant modes of vibration of plate (mainplate) under harmonic excitation, which consists of a plate (dynamic absorbing plate) under the same boundary condition as the main plate and with uniformly distributed connecting springs and dampers between the main and dynamic absorbing plates. Equations of motion of the system in the modal coordinates of the main plate become equal to those of the two-degrees-of-freedom system with two masses and three springs. Formulas for optimum design of the plate-type dynamic vibration absorber are presented using the optimum tuning method of a dynamic absorber in two-degrees-of-freedom system, obtained by the Den Hartog method. Moreover, for practical problems regarding large-scale plates, an approximate tuning method of the plate-type dynamic absorbers with several sets of concentrated connecting springs and dampers is also presented. The numerical calculations demonstrate the effectiveness of the plate-type dynamic absorbers.
Natural Vibration of a Cavity Backed Rectangular Plate Using A Receptor-Rejector System Model
Authors: Rajalingham C. , Bhat R. B. , Xistris G. D.
Published: February 2008

Forced vibration of a cavity backed rectangular plate is widely used to study the physics of noise transmission into an enclosure. In this context, the cavity backed plate is a dynamical system with coupled motion of the plate and the air cavity. The natural frequencies of the coupled system are the most important characteristics of the noise transmission into the cavity. This paper investigates the natural vibration of a cavity backed rectangular plate and presents numerical results for the particular case of a cavity backed simply supported plate. The natural vibration of the total system is viewed as the result of the interactions of various natural modes of vibration of its subsystems. The physics of the modal interactions is discussed using a receptor-rejector system model, and the dynamics of the cavity backed panel is investigated using the plate receptance and the cavity rejectance (inverse receptance) parameters. The modal interactions are further clarified using a cavity backed piston forming a single degree of freedom system. With the principle of superposition, the receptor-rejector system model can be used to analyze cavities with more than one flexible wall.
Fracture Analysis of the Heat-Affected Zone in the NESC-1 Spinning Cylinder Experiment
Authors: Keeney J. A.
Published: February 2008

This paper presents updated analyses of the cylinder specimen being used in the international Network for Evaluating Steel Components (NESC) large-scale spinning-cylinder project (NESC-1). The NESC was organized as an international forum to exchange information on procedures for structural integrity assessment, to collaborate on specific projects, and to promote the harmonization of international standards. The objective of the NESC-1 project is to focus on a complete procedure for assessing the structural integrity of aged reactor pressure vessels. A clad cylinder containing through-clad and subclad cracks will be tested under pressurized-thermal shock conditions at AEA Technology, Risley, U.K. Three-dimensional finite-element analyses were carried out to determine the effects of including the cladding heat-affected zone (HAZ) in the models. The cylinder was modeled with inner-surface through-clad cracks having a depth of 74 mm and aspect ratios of 2:1 and 6:1. The cylinder specimen was subjected to centrifugal loading followed by a thermal shock and analyzed with a thermoelastic-plastic material model. The peak KI values occurred at the clad/HAZ interface for the 6:1 crack and at the HAZ/base interface for the 2:1 crack. The analytical results indicate that cleavage initiation is likely to be achieved for the 6:1 crack, but questionable for the 2:1 crack.
Seismic Hazard and Damages—Avoiding Disaster Through Simulation, Experiment, and Experience
Authors: Shibata H.
Published: February 2008

This paper deals with the role of proving tests and a large shaking test facility for equipment and piping systems in conjunction with the development of aseismic design in the field of mechanical engineering, especially for nuclear power plants in Japan. To avoid seismic disaster and damage of equipment and piping systems as well as liquid storages, we had to differentiate the seismic design procedure in mechanical engineering from that for building and civil engineering structures. For this process, the dynamic analysis in this field is more significant than for other fields. The author has been trying to develop aseismic design since the design stage of the first nuclear power plant in 1958 based on his experience as a specialist of mechanical vibration. In the early 1970s, shaking tables were developed for this purpose in Japan. The largest one in Japan is a 1000-ton 2-D table. After the 1995 Kobe earthquake, we have been developing a new 1200-ton 3-D shaking table. In the paper, the author discusses the necessity of such a facility and presents a new concept of a numerical shaking table.
Further Evaluation of Creep-Fatigue Life Prediction Methods for Low-Carbon Nitrogen-Added 316 Stainless Steel
Authors: Takahashi Y.
Published: February 2008

Low-carbon, medium-nitrogen 316 stainless steel is a principal candidate for a main structural material of a demonstration fast breeder reactor plant in Japan. A number of long-term creep tests and creep-fatigue tests have been conducted for four products of this steel. Two representative creep-fatigue life prediction methods, i.e., time fraction rule and ductility exhaustion method were applied. Total stress relaxation behavior was simulated well by an addition of a viscous strain term to the conventional (primary plus secondary) creep strain, but only the letter was assumed to contribute to creep damage in the ductility exhaustion method. The present ductility exhaustion approach was found to have very good accuracy in creep-fatigue life prediction for all materials tested, while the time fraction rule tended to overpredict failure life as large as a factor of 30. Discussion was made on the reason for this notable difference.
A Robust Method for Inelastic Analysis of Components Made of Anisotropic Material
Authors: Babu S. , Iyer P. K.
Published: February 2008

A new robust method, called MARS (modulus adjustment and redistribution of stress), based on linear elastic finite element analyses has been proposed to evaluate inelastic strains in anisotropic bodies. The linearity of relaxation locus forms the basis of the method. A combination of modulus adjustment scheme and iterative strategy used in the MARS method satisfies the equilibrium and yield conditions, which in turn brings the static and kinematic distributions close to the actual distributions for a given load. Several notched bodies made of anisotropic material are analyzed using the MARS method and the inelastic strains evaluated are found to be in good agreement with those predicted using elastic-plastic finite element analysis.
The Effect of a Large Hole on the Stress Concentration Factor of a Satellite Hole in a Tension Field
Authors: Sloan C. S. , Cowell M. D. , Lehnhoff T. F.
Published: February 2008

Stress concentration factors have been determined for large hole to small hole diameter ratios (D/d) of 10 to 50 for two holes in an infinitely wide tension-loaded panel. Finite element analysis was used to model the system of two holes in a plate that approximates the infinitely wide and tall case. Both the D/d ratio and edge to edge hole spacing were examined for hole placement along an axis perpendicular to the direction of the tension field. It was found for large D/d ratios that the stress concentration factor was only dependent on the distance between the hole edges divided by the large hole diameter. For the configurations analyzed, the stress concentration factors varied from approximately 3 to 11.
The Impact of a Sphere on a Timoshenko Thin-Walled Beam of Open Section With due Account for Middle Surface Extension
Authors: Rossikhin Yu. A. , Shitikova M. V.
Published: February 2008

The problem on the normal impact of an elastic sphere upon an elastic Timoshenko arbitrary cross section thin-walled beam of open section is considered. The process of impact is accompanied by the dynamic flexure and torsion of the beam, resulting in the propagation of plane flexural-warping and torsional-shear waves of strong discontinuity along the beam axis. In addition, the process of impact is accompanied by large transverse deformations and large deflection of the beam in the place of impact, with the consequent generation of longitudinal shock waves and large membrane contractive (tensile) forces. Behind the wave fronts up to the boundaries of the contact region (the beam part with the contact spot), the solution is constructed in terms of one-term ray expansions. During the impact, the sphere moves under the action of the contact force which is determined due to the Hertz’s theory, but the contact region moves under the attraction of the contact force, as well as the twisting and bending-torsional moments and transverse and membrane forces, which are applied to the lateral surfaces of the contact region. Simultaneous consideration of the equations of sphere and the contact region motion leads to the Abel equation of the second kind, wherein the value characterizing the sphere and beam drawing together and the rate of change of this value are used as the independent variable and the function, respectively. The solution to the Abel equation written in the form of a series allows one to determine all characteristics of the shock interaction of the sphere and beam.
Residual Stresses in Weld-Deposited Clad Pressure Vessels and Nozzles
Authors: Jones D. P. , Mabe W. R. , Shadley J. R. , Rybicki E. F.
Published: February 2008

Results of through-thickness residual stress measurements are provided for a variety of samples of weld-deposited 308/309L stainless steel and Alloy 600 cladding on low-alloy pressure vessel ferritic steels. Clad thicknesses between 5 and 9 mm on samples that vary in thickness from 45 to 200 mm were studied. The samples were taken from flat plates, from a spherical head of a pressure vessel, from a ring-segment of a nozzle bore, and from the transition radius between a nozzle and a pressure vessel shell. A layer removal method was used to measure the residual stresses. The effects of uncertainties in elastic constants (Young’s modulus and Poisson’s ratio) as well as experimental error are assessed. All measurements were done at room temperature. The results of this work indicate that curvature plays a significant role in cladding residual stress and that tensile residual stresses as high as the yield stress can be measured in the cladding material. Since the vessel from which the spherical and nozzle corner samples were taken was hydrotested, and the flat plate specimens were taken from specimens used in mechanical fatigue testing, these results suggest that rather high tensile residual stresses can be retained in the cladding material, even after some mechanical loading associated with hydrotesting.
Techno-Economic Analysis of Solar Detoxification Systems
Authors: Goswami D. Y. , Sharma S. K. , Mathur G. D. , Jotshi C. K.
Published: February 2008

Solar detoxification technology has shown great promise for treatment of toxic compounds in the ground water and wastewater. However, detailed analysis of the impact of techno-economic parameters on the treatment cost for the detoxification process is lacking in the literature. In this paper, the impact of different process parameters on the treatment cost has been presented and various strategies for reducing the cost of treatment have been discussed. For the processes with the reaction rate constants less than 0.1 min−1, the system economics is very sensitive to the reaction rate constant and the unit reactor cost. However, for the reaction rate constant over 0.1 min−1 the general treatment costs can be reduced mainly by reducing the unit catalyst costs.
Heat Transfer and Flow Resistance of a Shell and Plate-Type Evaporator
Authors: Uehara H. , Stuhltra¨ger E. , Miyara A. , Murakami H. , Miyazaki K.
Published: February 2008

The performance test of a shell-and-plate-type evaporator designed for OTEC plants, geothermal power plants, and heat pump systems is reported. This evaporator contains 30 plates with a unit area of 0.813 m2, coated with aluminum powder on the working fluid side. Freon 22 is used as working fluid. Results show an overall heat transfer coefficient of about 5000 W/(m2K) when the heating water velocity is 1 m/s. The mean boiling heat transfer coefficient is compared with a previous correlation proposed by Nakaoka and Uehara (1988). The water-side pressure loss is also reported.
A Simple Method of Estimating Wind Turbine Blade Fatigue at Potential Wind Turbine Sites
Authors: Barnard J. C. , Wendell L. L.
Published: February 2008

This paper presents a technique of estimating blade fatigue damage at potential wind turbine sites. The cornerstone of this technique is a simple model for the blade’s root flap bending moment. The model requires as input a simple set of wind measurements that may be obtained as part of a routine site characterization study. By using the model to simulate a time series of the root flap bending moment, fatigue damage rates may be estimated at the potential wind energy sites. The model is evaluated by comparing these estimates with damage estimates derived from actual bending moment data; the agreement between the two is good. Data from two different turbine types were used for the evaluation. For each type the model was tested at only one site because data from other sites were not available. To more firmly establish the universality of the model, further evaluation is necessary using the model applied to the same turbine located at different sites.
Solar-Powered Photocatalytic Fiber-Optic Cable Reactor for Waste Stream Remediation
Authors: Peill N. J. , Hoffmann M. R.
Published: February 2008

The design and testing of a solar-powered fiber-optic cable reactor prototype for the photocatalytic destruction of organic pollutants is presented. A concentrating collector directs sunlight into a fiber-optic cable which transmits light to a TiO2 photocatalyst immobilized on the fibers and immersed in a reaction solution. The performance of the reactor using solar and artificial UV radiation are compared. The system is also compared to another fiber-optic cable reactor having a 50 percent higher photocatalytic surface area-to-reactor volume ratio to investigate mass transport limitations. Reaction rates for the oxidation of 4-chlorophenol of 25 and 12 μMmin−1 were measured for solar and artificial UV sources, respectively. The faster reaction rate using solar radiation is due to a higher UV light flux compared to the artificial source. Both fiber-optic reactor systems were determined not to be mass transport limited. Relative quantum efficiencies of φ = 0.014 and φ = 0.020 were determined for the solar and artificial irradiations, respectively. In agreement with previous findings, enhanced quantum efficiencies are attributed to a lower absorbed light intensity-to-photocatalytic surface area ratio. The solar reactor prototype was found to degrade effectively 4-chlorophenol and may prove useful for the in situ passive decontamination of subsurface and other remote environments.
An Integrated Approach to Wind Turbine Fatigue Analysis
Authors: Laino D. J. , Hansen A. C.
Published: February 2008

The wind turbine dynamics codes YawDyn and ADAMS have been interfaced with the LIFE2 code for fatigue life estimation via a new interface program, Dyn2LIFE. This work is sponsored by the National Renewable Energy Laboratory (NREL) with the intent of making it straightforward and practical for wind turbine designers to determine those aspects of their design and wind environment that will cause the most fatigue damage. Several parameters suspected of affecting turbine fatigue life are investigated through a model of the NREL Phase III Combined Experiment Rotor. This study proved the Dyn2LIFE code useful in creating LIFE2 input from YawDyn and ADAMS output, and also revealed some areas of possible expansion and improvement. Results from this study of a steel blade root suggest changes affecting the normal operation of the turbine alter fatigue life more than rare, high load events. Understanding how the material fatigue characteristics affect lifetime estimates is discussed in terms of the S-N curve utilized in this study. This paper presents the first results from an ongoing project. In the future, we plan to analyze a variety of turbine configurations to help identify those variables which may have the greatest influence on fatigue life.
Second Generation Sodium Heat Pipe Receiver for a USAB V-160 Stirling Engine: Evaluation of On-Sun Test Results Using the Proposed IEA Guidelines and Analysis of Heat Pipe Damage
Authors: Laing D. , Tra¨bing C.
Published: February 2008

At the DLR a second generation sodium heat pipe receiver for the Schlaich Bergermann und Partner (SBP) 9-kWe dish/Stirling system has been developed and constructed. Long-term operation occurred from Oct. 1992 until Aug. 1993 at the Plataforma Solar de Almeria (PSA) in Spain, accumulating 950 operating hours. The performance of the SBP 9-kWe system with a sodium heat pipe receiver is evaluated according to the guidelines for dish/Stirling performance evaluation by Stine and Powel, as proposed to the International Energy Agency (IEA). Tests were stopped due to a leak in the receiver absorber surface. The analysis of this damage are reported.
Reaction Kinetics of Paddy Husk Thermal Decomposition
Authors: Jain A. K. , Sharma S. K. , Singh D.
Published: February 2008

The physical characteristics, proximate analysis, elemental analysis and chemical analysis of paddy husk, an important renewable source of energy, are reported in this paper. The kinetic parameters for the thermal degradation of paddy husk at heating rates of 10 and 100°C min−1 and under atmospheres of air and oxygennitrogen mixture (5:95) have been evaluated from experimentally obtained TGA data. The limitations of the existing TGA models are discussed, and a modified model has been used for correlation of the data.
Extraction of Normal Modes from Contaminated Measurement With Noise for Highly Coupled Structures
Authors: Chen S. Y. , Ju M. S. , Tsuei Y. G.
Published: February 2008

A frequency-domain technique to extract the normal mode shapes from the contaminated FRF measurements for highly coupled structures is developed. The relation between the complex FRFs and the normal mode shapes is derived. It is found that the normal mode shape cannot be extracted exactly from the complex mode shape. However, an exact relation between the normal mode shape and the complex FRF does exist. In the present method, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. Hence, the effects of measurement noise can be reduced. A numerical example is employed to illustrate the applicability of the technique. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled structure.
Distributed Parameter Modal Filtering Using Smart Sensors
Authors: Tanaka N. , Snyder S. D. , Hansen C. H.
Published: February 2008

This paper considers the design of distributed parameter modal sensors called “smart sensors,” with a particular emphasis on filtering the combination of appropriately weighted vibration modes providing a specific performance index in control strategy. First, with a two-dimensional distributed parameter sensor using a PVDF film, the necessary and sufficient condition for sensing the transformed modes of a structure is derived. Then, by considering the practicability of the two-dimensional sensors, an alternative approach based upon one-dimensional smart sensors is presented. It is found that the latter approach holds the necessary condition for sensing the transformed mode. This problem is overcome by introducing multiple one-dimensional smart sensors. Moreover, the design procedure for the multiple one-dimensional smart sensors for measuring the transformed mode is established. Finally, an experiment is conducted, demonstrating the validity of the smart sensors.
Modelling of an Elastic Disk With Finite Hub Motions and Small Elastic Vibrations With Application to Rotordynamics
Authors: Flowers G. T.
Published: February 2008

In the modelling of flexible structures undergoing large overall motion and small elastic vibrations, it is necessary to include elastic displacement effects up to second order in the kinematical equations if the resulting differential equations are to be consistent. Elastic displacements are typically modelled using mode shapes and generalized coordinates, and second and higher order elastic effects (sometimes referred to as foreshortening) are often neglected in the development of kinematical relations. This study examines the implications of such effects in the modelling of an elastic disk with arbitrary base motions and small elastic vibrations. A general modelling procedure is described that is appropriate for the development of simulation models for such structures. An approximate technique is used to account for second order elastic terms in the kinematical relations. The modelling procedure is specialized to the case of an elastic disk undergoing a constant axial spin and infinitesimal displacements for all other degrees of freedom. Comparisons are made between the natural frequencies of a disk model with and without these elastic foreshortening effects and some conclusions are drawn as to the relative importance of such terms in rotor disk modelling.