bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Yield Criteria on the Prediction of Shear Localization Considering the Inhomogeneous Distribution of Microstructure
Authors: Duan Xinjian , Metzger Don , Jian Mukesh
Published: August 2008

The occurrence of shear localization in structural materials is often associated with bifurcation in continuum solid mechanics. Many approaches such as J2 corner theory and the void model have been proposed to simulate this phenomenon by the use of FEM. In this paper, a new approach with a basis in microstructural inhomogeneity has been proposed and successfully applied to simulate large strain deformation in uniaxial tension of aluminium alloys. The method, in addition, takes advantage of a more suitable hardening law for Al alloys — namely the Voce equation. Further, the influence of various yield criteria (i.e. von Mises, Hill’s 1948 and Barlat’s 1991) on the prediction of shear localization is discussed in the present work. The predicted shear band angle is also compared with the measured value.
Analysis of a Thermal Fatigue Test of a Stepped Pipe
Authors: Jones D. P. , Holliday J. E. , Leax T. R. , Gordon J. L.
Published: August 2008

Results from thermal-structural finite element analysis (FEA) were used to predict cycles to crack initiation in thermal fatigue tests of stainless steel pipes. The pipes were fatigued by alternately pumping hot and cold low oxygen water every four minutes through 304 stainless steel pipes. The rapid change in water temperature imparted a thermal shock to the inner wall of the pipe. The pipes were stepped to four different thicknesses to give four different values of thermal shock stress depending on thickness. The pipes were pressurized to 17.2 MPa (2500 psi) and the temperature cycled between 38°C (100°F) and 343°C (650°F) in three seconds. This was followed by holding at 343°C for 237 seconds and then quenching to 38°C in three seconds followed by another 237 second hold period. Thermal cycling continued until significant cracking was detected on the inside surface of the pipes. Measurements of fatigue striation spacing on the fracture surfaces allowed determination of cycles to the initiation of defects 0.254 mm (0.01 inch) deep. Alternating stresses and strains were calculated using both elastic and elastic-plastic finite element analyses (FEA). The analysis results were used with a best-fit fatigue curve to predict cycles-to-crack initiation for comparison to the experimental data. Using elastic analysis corrected for stresses beyond yield in accordance with the ASME B&VP Code and the best-fit fatigue curve adjusted for low oxygen water environments resulted in under-estimates of the observed cycles to crack initiation from the tests. Improved predictions of cycles to crack initiation are possible by using an elastic-plastic FEA method with a kinematic hardening model along with the best-fit fatigue curve.
Elastic-Plastic Finite Element Analysis of Double-Edge Notched Fatigue Tests
Authors: Jones D. P. , Adams S. A.
Published: August 2008

The ASME Boiler and Pressure Vessel Code (B&PV) Committee, Subgroup on Design Analysis, established the Task Force on Elastic-Plastic Finite Element Analysis (TF-EP-FEA) to investigate how to use EP-FEA to assess ASME B&PV Code stress limits. The present paper presents results of an investigation by the TF-EP-FEA to apply EP-FEA to predict cyclic life of double-edge notched fatigue specimens. EP-FEA results are compared to fatigue test results for two notch root radii in 304 stainless steel double-edge notched flat bars loaded in cyclic tension-compression. An analytical exercise was defined such that several TF-EP-FEA members started from the same problem definition and used the ASME Code and an EP-FEA program to compute the cyclic life of the double-edge notched fatigue specimens. The results and techniques used by the investigators are compared and conclusions reached regarding which method correlated best for this problem. Commonalties in the approaches are listed that may be used to develop general guidelines for use of elastic-plastic FEA to show satisfaction of the fatigue design rules of the ASME B&PV Code.
Weight Functions for T-Stress for Edge Cracks in Thick-Walled Cylinders
Authors: Li J. , Tan C. L. , Wang X.
Published: August 2008

This paper presents T-stress solutions for an internal edge crack in thick-walled cylinders under complex stress distributions. First, the background of the weight function method for the calculation of T-stress is discussed. Then the T-stress results for edge-cracked cylinders obtained from extensive boundary element analyses are summarized. The crack geometries analyzed cover a wide range of radius ratios and relative crack lengths. The loading cases considered in the BEM analysis for the cracked cylinder are: i) crack face pressures with polynomial stress distributions acting on the crack face and ii) internal pressure or steady state thermal loading in the cylinder. Then, the T-stress results for uniform and linearly varying crack face pressure cases are used as the reference solutions to derive weight functions for T-stress. Boundary element results of T-stress for other nonlinear stress distributions are used to validate the derived T-stress weight functions. Excellent accuracy has been achieved. The weight functions derived are suitable for obtaining T-stress solutions for thick-walled cylinders with an internal edge crack under any complex stress fields.
Analytical Limit Loads for Tube Sections With Circumferential Degradation
Authors: Reinhardt W. , Wang X.
Published: August 2008

The fracture mechanics evaluation of tubes and pipes with circumferential degradation typically requires that the plastic limit load capacity be evaluated under a combination of axial force and bending moment loading. Most available analytical solutions are thin-wall approximations and may not work well for heavy-wall applications. The present paper derives an analytical limit load for a cylindrical pipe or tube with a partial circumferential, partial through-wall flaw and its bounding cases (through wall partial circumferential and uniform circumferential part-throughwall flaw). The solution is not in closed form, but can be easily solved with available mathematical software like MathCAD. The obtained limit loads for a steam generator tube are compared to those from simplified analytical solutions. The effect of tube supports on the limit load of a tube with non-axisymmetric flaw is discussed with a simplified model.
Study on Strain Concentration for Cylindrical Tubes Under Axial Compressive Loading
Authors: Ushijima Kuniharu , Haruyama Shigeyuki , Hanawa Hiroki , Chen Dai-Heng
Published: August 2008

In this paper, elastoplastic post-buckling behavior of cylindrical tubes under axial compression is studied by using finite element method. In our study, the effects of tube geometries and strain hardening characteristics on high strain concentrations in circumferential direction εθ which arise at the vertex of outward wrinkles are investigated. It is found that the maximum value of εθ depends on the thickness-to-radius ratio t/R and the nondimentional hardening coefficient Eh/E, and independent of the length-to-radius ratio L/R. In addition, in order to evaluate the maximum strain εθ,max, the effects of tube geometries and strain hardening characteristics on the deformed shapes of folding wrinkles are also discussed.
Plastic and Creep Analyses of the Superheater Header Tubeplate Using Linear Matching Method
Authors: Chen Haofeng , Ponter Alan R. S.
Published: August 2008

In 2003 ASME PVP conference, a series of numerical procedures for integrity assessment based upon recently developed Linear Matching Method were presented [1]. A typical example of holed plate was used to verify these procedures for the evaluation of plastic and creep behaviours of complex geometry components based on linear solutions, which can be easily implemented into the commercial FE code ABAQUS through user subroutines. In this paper, a more complex 3D tubeplate in a typical AGR superheater header is analysed for the shakedown limit, reverse plasticity, ratchet limit and creep relaxation based on application of the Linear Matching Method. Both the perfectly plastic model and the cyclic hardening model are adopted for the evaluation of the plastic strain range. For the evaluation of accumulated creep strains, flow stresses and elastic follow-up factors with differing dwell times at the steady cyclic state, a creep-reverse plasticity model is adopted. The total inelastic strain range over the cycle at the steady cyclic state is calculated. By comparing these results with ABAQUS step-by-step inelastic analyses, the applicability of the methods is verified.
Determination of the Three-Parameter Weibull Distribution and Confidence Bands From Experimental Fatigue Strength Data
Authors: Mahajerin Enayat , Burgess Gary
Published: August 2008

The S-N curve for the material used to make a pressure vessel is approximate because it is drawn from a limited number of test specimens. The resulting curve may be in error due to a variety of factors including surface condition, size, environment conditions, and stress concentrations. As a result, when the fatigue strength like the endurance limit is determined from the S-N curve by observing a definite break in the curve, it will be subject to error. Because of these uncertainties, it is necessary to use appropriate statistical methods to interpret the test results. In this paper, it is assumed that the percentage of failures for a given service life can be approximated by a three-parameter Weibull distribution. The Weibull distribution is flexible and has been shown to be suitable for structural reliability. The distribution is fitted to experimental data using a least square best fit approach applied to a discrete version of the cumulative probability distribution function, F(x). In practice a point-by-point estimate of the cumulative distribution function is used. As a result, it is necessary to establish confidence bands. The true curve of F(x) lies within these bands for a given probability.
Practical Criterion for Estimation of Notch Fatigue Strength
Authors: Matsuno Hiroshi , Mukai Yoshihiko
Published: August 2008

In the present study, a practical criterion for the estimation of the fatigue strength of notched specimens is discussed from a practical standpoint of design and maintenance of machines and structures. First of all, a hypothesis of “Fatigue Plastic Adaption” is proposed as one idea that is available to combine microscopic and macroscopic approaches to fatigue plasticity. The hypothesis expresses that, at a surface layer and at a notch root, elastic deformation arising at the cyclic maximum stress is transformed into local and inhomogeneous plastic deformation. Based on the hypothesis, mechanical models are constructed in order to simulate cyclic stress behavior at the surface layer and at the notch root. As a result, “Equivalent Stress Ratio” is formulated as a parameter for correspondence of cyclic stress conditions between notched and unnotched specimens. Moreover, on the basis of the hypothesis of the plastic adaptation, the equation of the equivalent stress ratio is also derived for the case of biaxial stress cycling in torsion, and it is finally expanded for the general case of proportional multiaxial stress cycling. The published fatigue data concerning tension-compression, bending, torsion and their combined loading are rearranged on the diagram where an abscissa indicates the equivalent stress ratio and an ordinate indicates the stress range at the notch root. As the result, it is recognized that the relation between the equivalent stress ratio and the notch-root-concentrated stress range is shown by a certain curve proper to material in spite of difference of stress concentration factors, loading types and mean stresses. Consequently, a criterion for notch fatigue strength is described on the basis of the equivalent stress ratio, i.e., the notch-root-concentrated stress range at the fatigue strength of the notched specimen for any nominal stress ratio is identical with the fatigue strength of the unnotched specimen for the equivalent stress ratio.
Onsite Packaging and Transport of Tritium Waste
Authors: Blanton Paul S. , Houghtaling T. Kurt
Published: August 2008

Radioactive material packagings designed for out-of-commerce shipments are not necessarily subject to the same regulatory requirements as packagings designed for in-commerce service. For example, DOE Order 460.1B permits application of the notion of Equivalent Safety to out-of-commerce shipping within DOE sites. Equivalent safety can be viewed as a reduction in 10 CFR 71 design conditions without a corresponding loss of public health and safety. This paper presents a packaging design identified as the Tritium Spent Melt Overpack (SMO) that successfully utilized equivalent safety at the Savannah River Site (SRS). Because the spent melt materials are highly radioactive, the container must be loaded and closed remotely. The SMO design is a based on twenty-foot long eighteen-inch diameter pipe, with one end closed by welded plate and the open end closed by a latching plug that incorporates bore seals. The SMO receives a single sixteen-inch diameter by 16-foot long crucible partly filled with the waste product from the tritium extraction process. The loaded overpack is moved from the SRS Tritium Extraction Facility inside a heavily shielded cask. Upon arrival at a waste silo designed to receive the overpack, it is removed from the shielding cask by remote means and placed in the long-term storage silo. This paper provides an overview of the SMO overpack design and its operation.
Radioactive Material Transportation Considerations With Respect to DOE 3013 Storage Containers
Authors: Hensel S. J. , Wu T. T. , Seward B. R.
Published: August 2008

This paper evaluates sealed hardware that meets the requirements of DOE-STD-3013, “Criteria for Preparing and packaging Plutonium Metals and Oxides for Long-Term Storage” [1] with respect to radioactive material (Type B quantity) transportation requirements. The Standard provides criteria for packaging of the plutonium materials for storage periods of at least 50 years. The standard requires the hardware to maintain integrity under both normal storage conditions and under anticipated handling conditions. To accomplish this, the standard requires that the plutonium be loaded in a minimum of two nested stainless steel sealed containers that are both tested for leak-tightness per ANSI N14.5. As such the 3013 hardware is robust. While the 3013 STD may provide appropriate storage criteria, it is not intended to provide criteria for transporting the material under the requirements of the Department of Transportation (DOT). In this evaluation, it is assumed that the activity of plutonium exceeds A1 and/or A2 curies as defined in DOT 49 CFR 173.431 and therefore must be shipped as a Type B package meeting the Nuclear Regulatory Commission (NRC) requirements of 10 CFR 71. The evaluation considers Type B shipment of plutonium in the 3013 hardware within a certified package for such contents.
Validation of Stress Corrosion Cracking Model for High Level Radioactive-Waste Packages
Authors: Lu S. C. , Gordon G. M. , Andresen P. L.
Published: August 2008

A stress corrosion cracking (SCC) model has been adapted for performance prediction of high level radioactive-waste packages to be emplaced in the proposed Yucca Mountain radioactive-waste repository. SCC is one form of environmentally assisted cracking resulting from the presence of three factors: metallurgical susceptibility, critical environment, and tensile stresses. For waste packages of the proposed Yucca Mountain repository, the outer barrier material is the highly corrosion-resistant Alloy UNS-N06022, the environment is represented by the water film present on the surface of the waste package from dripping or deliquescence of soluble salts present in any surface deposits, and the stress is principally the weld induced residual stress. SCC has historically been separated into “initiation” and “propagation” phases. Initiation of SCC will not occur on a smooth surface if the surface stress is below a threshold value defined as the threshold stress. Cracks can also initiate at and propagate from flaws (or defects) resulting from manufacturing processes (such as welding). To account for crack propagation, the slip dissolution/film rupture (SDFR) model is adopted to provide mathematical formulae for prediction of the crack growth rate. Once the crack growth rate at an initiated SCC is determined, it can be used by the performance assessment (not in the scope of this paper) to determine the time to through-wall penetration for the waste package. This paper presents the development and validation of the SDFR crack growth rate model based on technical information in the literature as well as experimentally determined crack growth rates developed specifically for Alloy UNS-N06022 in environments relevant to high level radioactive-waste packages of the proposed Yucca Mountain radioactive-waste repository.
Response of Ring Closures in Drop Tests of Typical-Weight 6M Packages
Authors: Smith Allen C. , Gelder Lawrence F. , Lutz Rex N.
Published: August 2008

Testing of 6M specification packages, performed in response to concerns over the integrity of the clamp-ring closure, showed that the clamp-ring was unable to retain the top in thirty foot drop tests of packages having the maximum allowed weight (290 kg or 640 lb). To determine if the clamp-ring closure was adequate for packages with lower contents weight, a series of tests were performed on packages weighing 147 kg (325 lb) at a range of impact angles. The results showed that the standard clamp-ring closure was unable to retain the top in tests of standard 6M packages weighing 147 kg (325 lb). A test employing a plywood disk enhanced closure with impact at 6.5° retained its top successfully.
General and Localized Corrosion of Austenitic and Borated Stainless Steels in Simulated Concentrated Ground Waters
Authors: Fix David V. , Estill John C. , Wong Lana L. , Rebak Rau´l B.
Published: August 2008

Boron containing stainless steels are used in the nuclear industry for applications such as spent fuel storage, control rods and shielding. It was of interest to compare the corrosion resistance of three borated stainless steels with standard austenitic alloy materials such as type 304 and 316 stainless steels. Tests were conducted in three simulated concentrated ground waters at 90°C. Results show that the borated stainless were less resistant to corrosion than the witness austenitic materials. An acidic concentrated ground water was more aggressive than an alkaline concentrated ground water.
Determination of the Crevice Repassivation Potential of Alloy 22 by a Potentiodynamic-Galvanostatic-Potentiostatic Method
Authors: Evans Kenneth J. , Wong Lana L. , Rebak Rau´l B.
Published: August 2008

Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In some aggressive conditions of high chloride concentration, temperature and applied potential, Alloy 22 may suffer crevice corrosion, a form of localized corrosion. There are several electrochemical methods that can be used to determine localized corrosion in metallic alloys. One of the most popular for rapid screening is the cyclic potentiodynamic polarization (CPP). This work compares the results obtained by measuring the localized corrosion resistance of Alloy 22 using both the CPP and the more cumbersome Tsujikawa-Hisamatsu Electrochemical (THE) method. The electrolytes used were 1 M NaCl and 5 M CaCl2, both at 90°C. Results show that similar repassivation potentials were obtained for Alloy 22 using both methods. That is, in cases where localized corrosion is observed using the faster CPP method, there is no need to use the THE method since it takes ten times longer to obtain comparable results in spite of the mode of corrosion attack is sometimes different in the tested specimens.
Computer Simulation of a Transportation Package Impacting Concrete and Soil Targets
Authors: Huang S. N. , Shiraga S. S. , Hay L. M.
Published: August 2008

This paper compares transportation mockup cask impact test results onto real surfaces with FEA numerical simulation results. The impact test results are from a series of cask impact tests that were conducted by Sandia National Laboratories (Gonzales 1987). The Sandia tests were conducted with a half-scale instrumented cask mockup impacting an essentially unyielding surface, in-situ soil, concrete runways, and concrete highways. The cask numerical simulations with these same surfaces are conducted with ABAQUS/Explicit, Version 5.8, The results are then compared and evaluated to access the viability of using numerical simulation to predict the impact behavior of transportation casks under hypothetical accident conditions.
Preliminary Elevated Strain Rate Material Testing to Support Accidental Drop Analyses of Radioactive Material Containers
Authors: Snow Spencer D. , Morton D. Keith , Rahl Tommy E. , Blandford Robert K. , Hill Thomas J.
Published: August 2008

The Idaho National Engineering and Environmental Laboratory (INEEL) developed an apparatus capable of supporting a wide variety of material studies and distinct component testing under impact loads. Material studies include material (metals, plastics, concrete, etc.) response due to bending, tension, shear, and compression loadings at elevated strain rates. Similar testing can also be performed on any distinct component fitting within the apparatus impact loading volume. This apparatus is referred to as the Impact Test Machine (ITM). The ITM is initially being used by the Department of Energy (DOE) to test 304L and 316L stainless steel tensile test specimens at various strain rates for comparison to static properties. The goal is to ultimately develop true stress-strain curves at various strain rates and temperatures for these steels. These curves can then be used in analytical simulations to more accurately predict the deformation and resulting material straining in spent nuclear fuel (SNF) containers, canisters, and casks under accidental drop events (Ref: Snow 1999, 2000). Test results can also help determine a basis for establishing allowable strain limits for these large deformation, inelastic events. This material investigation is currently in an early stage of development. This paper will discuss the results of tensile tests performed on test specimens employed in the formulation of the test process and initial checkout of the ITM.
Fernald Silos 1&2 Stabilized Waste Transport and Disposal Packages
Authors: Ahearn Mike J. , Pearson Samuel D. , Witt Charles R.
Published: August 2008

Approximately 7000 packages of stabilized waste from Silos 1&2 at the Fernald Closure Project in southern Ohio will be transported to a disposal facility. These packages have been designed to meet both transport regulations for an IP-2 package and waste acceptance criteria for the disposal facility. Key features of the package and transport conveyance designs are discussed, as well as the testing programs conducted during development of this equipment.
Health Monitoring of Piping Weld With Guided Waves
Authors: Cho Younho , Lee Chong Myoung , Rose Joseph L. , Park Ikkeun
Published: August 2008

In this study, a new technology based on the ultrasonic guided wave to inspect the weld part is presented. The characteristic of a guided wave to travel a long distance over a welded part provides an efficient inspection. This guided wave technique overcomes a tedious scanning procedure using a conventional bulk shear wave angle beam technique. A proper mode and frequency tuning process with knowledge of dispersion curves and wave structure profiles allows us to propose a promising alternative which makes it possible to alleviate such limitations encountered with the conventional technique. Some sample experimental data are also provided with a detailed guideline showing the utility of guided waves when using a proper mode selection for the weldment.
Defect Sizing in Pipeline Welds: What Can We Really Achieve?
Authors: Moles Michael
Published: August 2008

Pipelines are now using Fitness-For-Service (FFS) for accept/reject of weld defects. FFS requires accurate measurement of defect height for Fracture Mechanics assessments. The standard pipeline weld inspection technique of radiography is incapable of such measurements. However, the newer technique of ultrasonics can measure defect height, in principle. Initially ultrasonic amplitude methods were used for height measurement, but these proved unreliable. Now diffraction methods, especially Time-Of-Flight-Diffraction (TOFD), are being used in conjunction. This paper reviews previous work — mainly large nuclear studies like PISC II — and published pipeline sizing studies. The best nuclear sizing was within a few millimetres, using diffraction. In contrast to nuclear, pipeline AUT uses zone discrimination, focused transducers, much thinner material and simpler analysis techniques. Current accuracies are typically ± 1 mm (terminology undefined), which correlates with the beam spot size and typical weld pass. Requests for accuracies of ± 0.3 mm are probably unachievable, though future R&D should significantly improve pipeline sizing.
Elastic Guided Waves in Composite Pipes
Authors: Cho Younho , Rose Joseph L. , Lee Chong Myoung , Bogan Gregory N.
Published: August 2008

An efficient technique for the calculation of guided wave dispersion curves in composite pipes is presented. The technique uses a forward-calculating variational calculus approach rather than the guess and iterate process required when using the more traditional partial wave superposition technique. The formulation of each method is outlined and compared. The forward-calculating formulation is used to develop finite element software for dispersion curve calculation. Finally, the technique is used to calculate dispersion curves for several structures, including an isotropic bar, two multi-layer composite bars, and a composite pipe.
Ultrasonic Flexural Torsional Guided Wave Focusing in Pipe
Authors: Sun Zongqi , Rose Joseph L.
Published: August 2008

Ultrasonic flexural torsional guided wave properties, including the excitation and propagation have been studied recently. Natural focusing is one of the major characteristics exhibited by partial loading excitation. With the aid of phased array transducer we propose a wave focusing method to enhance the signal to noise ratio and defect resolution in pipe inspection. With time delays and amplitudes applied to different elements constructive wave interference at specific point can be achieved in order to focus wave energy. Focusing effect is examined by angular profile, which is the circumferential displacement distribution.
Nondestructive Evaluation of Concrete Structures by Laser Ultrasonic Method
Authors: Akamatsu Shigenori , Kamimura Tomosumi , Yokoi Katsunori , Shiba Haruya , Tanizawa Toshihiro , Uchida Shigeaki , Kotiaev Oleg G.
Published: August 2008

The nondestructive testing of concrete structures has been attempted using ultrasonic methods such as impact echo methods, though no automated remote testing method has been realized yet. The laser ultrasonic method is a non-contact nondestructive evaluation method that uses short laser pulses to generate and Continuous Wave (CW) laser radiation to detect ultrasonic waves. In the applications of ultrasonic to nondestructive testing, it is necessary to choice the characteristics of the ultrasonic field radiated by the ultrasonic transmitter. The characteristics of that exited by laser pulses determine the usefulness in detecting flaws. In this paper, we present experimental results of investigation of relation between the waveforms of the ultrasonic exited by Q-switched pulse laser and the wavelengths of the pulse laser in concrete. The experiment was carried out using the Q-switched pulse laser of several wavelengths. We clarify that it is possible to control the amplitude and the pulse width of P-wave by a choice of the pulse energy and the wavelength of the laser source respectively.
Ultrasonic In-Situ Monitoring of Aluminum Alloy During Solidification and Melting
Authors: Ihara Ikuo , Burhan Dikky , Seda Yoshihisa
Published: August 2008

In both research and production involving solidification of materials, it would be beneficial to have an in-situ, real-time characterization of the material properties during solidification process. In this work ultrasonic in-situ monitoring of aluminum alloy (Al-12.6%Si) during solidification and melting using a high temperature ultrasonic sensor is presented. The ultrasonic sensor used mainly consists of a conventional piezoelectric transducer, a titanium buffer rod as an acoustic waveguide and a cooling system. A steel reflector is assembled at the probing end of the sensor to make time-of-flight measurements. The sustainability of the sensor has been evaluated for long time immersion up to 16 hours in the molten aluminum alloy and the possible reaction at the outer wall of the titanium rod has been examined. It has been demonstrated that the titanium buffer rod has good wettability and sustainability to molten aluminum. Using the ultrasonic sensor, pulse echo measurements with the aluminum alloy have been performed in temperature range from 200 to 800 °C. The changes of the longitudinal velocity of the aluminum alloy during solidification and melting processes have been successfully monitored. In addition the change in the amplitude of reflected echoes during solidification is discussed.
An Investigation on Monitoring Methods of Creep Damage Using Ultrasonic Technique
Authors: Yokono Yoshikazu , Nagano Yoshihiro
Published: August 2008

The reliability of facilities under long-term operation, that is to prevent trouble or accident, is one of the most important matters in the field of petroleum and petrochemical plants. For this purpose, some kinds of non-destructive inspection methods are carried out periodically to detect damages or degradation of material. Moreover, to enrich the reliability of safety operation of the plants, continuous monitoring methods to detect material degradation without mistiming are required. Recently, ultrasonic method has been developed as a key technology to detect and evaluate the damage of materials. One of the advantages of ultrasonic technique is to obtain much information about microstructure change due to material degradation when ultrasounds travel through the material. Further, ultrasonic technique has also the potential ability to be applied for continuous monitoring methods. The objective of this study is to accomplish monitoring methods of creep damage using ultrasonic technique. A novel technique to acquire the ultrasonic data during uni-axial creep test is investigated as the first step of monitoring of creep damage. As a result, it is confirmed that the sound velocity in time domain decreases gradually in creep acceleration stage which starts at the creep life fraction of 0.6 and the gravity frequency in frequency domain begins to increase at the creep life fraction of 0.8. Therefore, the possibility to monitor the creep damage under continuous operation by ultrasonic technique is suggested.
Effect of Sputtering Gas Pressure and Bias Voltage on Mechanical Properties of TiN Coating Deposited by DC Magnetron Sputtering
Authors: Tanabe Hirotaka , Miyoshi Yoshio , Takamatsu Tohru , Awano Hitoshi , Yamano Takaaki
Published: August 2008

The mechanical properties of TiN films deposited on carbon steel JIS S45C by reactive dc magnetron sputtering under three sputtering gas pressures, 0.5Pa, 0.8Pa, and 1.76Pa were investigated. The residual stress once increased and then decreased with increasing bias voltage at 0.5Pa and 0.8Pa, but increased monotonously at 1.76Pa. These variations could be explained by the variations of the bombarding energy of a sputtered ion at each gas pressure. The variations of hardness and toughness correlated with the variation of residual stress. The variation of adhesive strength also could be explained by the variation of the bombarding energy with a model proposed in this study. A specific wear rate was also investigated, and it was found that to increase not only the hardness but also the adhesive strength is necessary to improve the wear resistance of TiN films.
Locomotive Wheel Inspection With EMAT Technology
Authors: Tittmann B. R. , Jayaraman S.
Published: August 2008

There is a need to analyze locomotive wheels for flank cracks in a non-destructive manner in order to prevent catastrophic failures. Flaw, shape, and size are desired parameters in establishing the quality of commercial tires. A variety of defects such as voids, inclusions, surface and internal cracks, or the like, must be discerned in order to prevent failure. This paper exhibits and compares the benefits of a number of different techniques used for flaw detection. Non-destructive evaluation (NDE) techniques used are magnetic particle inspection, dye penetrant, eddy current, electro-magnetic acoustic transducer (EMAT). The techniques vary in their ability to ascertain the flaw characteristics. Using a non-contact sensor such as the EMAT, to scan the wheels in an automated manner offers greater inspection speed at lower manpower. This paper reviews the basic concept of EMATs, introduces a recently developed technique for simulating EMAT performance by Finite Element calculation and features bench top results of waveform acquisition and signal-to-noise ratio dependence on lift-off. Next presented are calibration results for spark-eroded flaws in wheel sections for a variety of locations and sizes. Finally data are on flaw detection in a railroad service facility on several locomotives with wheels spinning at speeds up to 40 meters/minute. Results for both artificial and actual flaws are shown.
Degradation Estimation of 2.25CR-1Mo Steel by Barkhausen Noise Method
Authors: Cho Youn-Ho , Park Ik-Keun
Published: August 2008

In this study, various NDE parameters of the Barkhausen noise method, such as MPA (Maximum Peak Amplitude), RMS, IABNS (Internal Area of Barkhausen Noise on Signal) and average amplitude of frequency spectrum are investigated and correlated with thermal damage level of 2.25Cr-1.0Mo steel using wavelet analysis. Those parameters tend to increase while thermal degradation proceeds. It also turns out that the wavelet technique can help to reduce experimental false calls in data analysis.
A Priori Analysis of Explicit Algebraic Stress Models for a Turbulent Flow Through a Straight Square Duct
Authors: Naji H. , El Yahyaoui O. , Mompean G.
Published: August 2008

The ability of two explicit algebraic Reynolds stress models (EARSMs) to accurately predict the problem of fully turbulent flow in a straight square duct is studied. The first model is devised by Gatski and Rumsey (2001) and the second is the one derived by Wallin and Johansson (2000). These models are studied using a priori procedure based on data resulting from direct numerical simulation (DNS) of the Navier-Stokes equations, which is available for this problem. For this case, we show that the equilibrium assumption for the anisotropy tensor is found to be correct. The analysis leans on the maps of the second and third invariants of the Reynolds stress tensor. In order to handle wall-proximity effects in the near-wall region, damping functions are implemented in the two models. The predictions and DNS obtained for a Reynolds number of 4800 both agree well and show that these models are able to predict such flows.
The Influence of Inlet Geometry and Back Pressure on Cavitation and Noise Reduction in High Pressure Nozzles
Authors: Ni Weishun W. , Tucker Christopher L. , Able Steve D.
Published: August 2008

Cavitation is a phenomenon in fluid flow that can have devastating consequences on component life. The understanding of this occurrence and the compressibility effects in liquid flow are of utmost importance to the operation of fluid equipment. Reducing or eliminating cavitation is one of the most elusive and difficult tasks in ultra high-pressure technology, especially when nozzles are examined. There are several papers that have described cavitation, why and how it occurs, and a plethora of ideas or examples showing how it can be reduced. However, in waterjet applications (40–60 ksi), the application of backpressure (to reduce noise and cavitation), and the cavitation phenomenon itself, can reduce the cutting nozzle’s performance significantly. When studying cavitation, one must not only take into account the magnitude of the turbulence, but also the structure of the turbulence. Four different types of nozzle inlet geometry are investigated, as well as the influence of several levels of backpressure in “water only” waterjet applications. The experimental data will also be compared to a CFD simulation.
Micro Fluidics Modelling Using Computational Fluid Dynamics
Authors: Holdo̸ Arne Erik
Published: August 2008

Present day computing power has increased the capacity of numerical modelling. However, for complex situations such as those in micro-fluidic devices, the representation of forcs involved can be quite complex and cause a misrepresentation in modelling unless care is taken.
An Approximate Analytical Solution to Flame Length in a Ventilated Room
Authors: Awad Ahmad , Calay Rajnish K.
Published: August 2008

An analytical study to investigate small fire in a ventilated room is presented. Most existing studies are either numerical or experimental and correlations for predicting characteristics of flame propagation such as temperature difference, flame (plume) length and terminal velocity are based on empirical data. A simple mathematical -from the first principles- is developed to predict these characteristics. The predictions are compared with the published experimental data and good agreement has been obtained. Such a simple model would be very useful to practicing engineers for fire control programs, designing fire detection mechanisms.
Fluid Structure Interaction Modelling
Authors: Dale Jason J. , Holdo̸ A. E.
Published: August 2008

Numerical modeling of fluid/structure interaction (FSI) falls into the multi-physics domain and has significant importance in many engineering problems. It is an active research area in the field of computational mechanics and examples are found in diverse applications such as aeronautics, biomechanics and the offshore industries. As such, Computational Fluid Dynamics (CFD) and Finite Element (FE) analysis techniques have continuously evolved into this field. This paper presents one such technique and focuses on the further developments of a displacement based finite volume method previously presented by the author, in particular, its ability to now predict fixed displacement, normal, shear and thermal stresses and strains within a single CFD program. An advantage of this method is that a single solution procedure has the potential to be employed to predict both fluid, structural and fluid/structure interaction effects simultaneously.
A Stable Fluid Rigid Body Interaction Algorithm: Application to Industrial Problems
Authors: Abouri D. , Parry A. , Hamdouni A.
Published: August 2008

Fluid-mechanism interactions occur in a wide range of flow meter categories including turbine and positive displacement systems as well as many flow control devices. This paper outlines computational methods for calculating the dynamic interaction between moving parts and the flow in a flow meter system. Coupling of phenomena is allowed without need for access to the source codes and is thus suitable for use with commercially available codes. Two methods are presented one with an explicit integration of the equations of motion of the mechanism and the other with implicit integration. Both methods rely on a Navier-Stokes equation solver for the fluid flow. The more computationally expensive implicit method is recommended for mathematically stiff mechanisms such as piston movement. Example industrial applications shown are for positive displacement machines and axial turbines. The advances in mesh technology including deforming meshes with non-conformal sliding interfaces opens up this new field of application for Computational Fluid Dynamics and mechanical analysis in flow meter design.
Shell Vibration Modes in Thin Wall Pipes Transporting Liquids
Authors: Ibrahim Zakaria N.
Published: August 2008

Shell mode vibrations in pipes are characterized by their high frequencies relative to those of beam vibration modes. However, for thin walled large diameter pipes, these shell mode frequencies are slightly moderated. The shell mode frequencies are further moderated when the pipes are transporting liquids such as water or molten sodium. In this paper, the inertia of the transported liquid inside the pipe is included in the pipe shell mode frequency formulation. Admissible flow patterns, which satisfy the fluid continuity equation, and compatible with the motion of the pipe shell boundary, are postulated for the shell modes being investigated. Rayleigh’s energy method is used to compare the shell mode frequencies with and without the effects of the liquid inertia. Using water as liquid medium, the frequency of a typical large thin walled pipe is reduced by a factor ranging from 2 to 10. The pipe shell radial-circumferential bending modes are generally characterized by lower frequencies relative to the extension and/or longitudinal shell modes. The inclusion of water as a liquid medium results in further lowering these frequencies by additional 45% to 55%. The frequencies of the pipe shell radial-circumferential bending modes, including water as a liquid medium, could reach the same order of magnitude as those of the piping beam modes. Consequently, the latter are within the seismic cutoff frequency that can not be ignored.
Comparison of Code Coupling Scheme for Simulation of Fluid Structure Problems
Authors: Longatte E. , Bendjeddou Z. , Souli M.
Published: August 2008

Numerical simulation of industrial multi-physic problems is still a challenge to overcome as it generally requires large computational resources and may involve code coupling with appropriate numerical methods making data transfer possible, quick and accurate. Numerical simulation of fluid structure interactions and particularly of flow-induced vibrations is one of these issues; it is investigated in the present paper. In the present work one focuses his attention on methods for numerical simulation of flow-induced vibrations of tubes and tube bundles in presence of still water or laminar flows. Fluid structure code coupling process is described and first results of validation are presented. Fluid and structure codes are presented in the first section. Numerical scheme for code coupling process are investigated in the second part. Finally results of test cases are discussed in the last section.
ALE and Fluid/Structure Interaction in LS-DYNA
Authors: Souli M. , Sofiane Y. , Olovsson Lars
Published: August 2008

Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions and it can, through an Eulerian-Lagrangian coupling algorithm, be combined with a Lagrangian description of motion for parts of the model. The Eulerian formulation is not free from numerical problems. There are dissipation and dispersion problems associated with the flux of mass between elements. In addition, many elements might be needed for the Eulerian mesh to enclose the whole space where the material will be located during the simulated event. This is where the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation has its advantages. By translating, rotating and deforming the multi-material mesh in a controlled way, the mass flux between elements can be minimized and the mesh size can be kept smaller than in an Eulerian model. A new Fluid Structure coupling algorithms based on the penalty method is presented in this paper. The coupling algorithm and improved multi-material ALE-capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events, forging operations and penetration problems and airbag simulations. This paper contains five example problems that illustrate the current features of the code.
In-Plane Parametric Vibrations of Curved Bellows Subjected to Oscillating Internal Fluid Pressure Excitation
Authors: Watanabe Masahiro , Tachibana Eiji , Kobayashi Nobuyuki
Published: August 2008

This paper deals with the theoretical stability analysis of in-plane parametric vibrations of a curved bellows subjected to periodic internal fluid pressure excitation. The curved bellows studied in this paper are fixed at both ends rigidly, and are excited by the periodic internal fluid pressure. In the theoretical stability analysis, the governing equation of the curved bellows subjected to periodic internal fluid pressure excitation is derived as a Mathieu’s equation by using finite element method (FEM). Natural frequencies of the curved bellows are examined and stability maps are presented for in-plane parametric instability. It is found that the natural frequencies of the curved bellows decrease with increasing the static internal fluid pressure and buckling occurs due to high internal fluid pressure. It is also found that two types of parametric vibrations, longitudinal and transverse vibrations, occur to the curved bellows in-plane direction due to the periodic internal fluid pressure excitation. Moreover, effects of axis curvature on the parametric instability regions are examined theoretically.
Seismic Response Prediction of NUPEC’s Field Model Tests of NPP Structures With Adjacent Building Effect
Authors: Xu J. , Costantino C. , Hofmayer C. , Ali S.
Published: August 2008

As part of a verification test program for seismic analysis computer codes for Nuclear Power Plant (NPP) structures, the Nuclear Power Engineering Corporation (NUPEC) of Japan has conducted a series of field model tests to address the dynamic cross interaction (DCI) effect on the seismic response of NPP structures built in close proximity to each other. The program provided field data to study the methodologies commonly associated with seismic analyses considering the DCI effect. As part of a collaborative program between the United States and Japan on seismic issues related to NPP applications, the U.S. Nuclear Regulatory Commission sponsored a program at Brookhaven National Laboratory (BNL) to perform independent seismic analyses which applied common analysis procedures to predict the building response to recorded earthquake events for the test models with DCI effect. In this study, two large-scale DCI test model configurations were analyzed: 1) twin reactor buildings in close proximity and 2) adjacent reactor and turbine buildings. This paper describes the NUPEC DCI test models, the BNL analysis using the SASSI 2000 program, and comparisons between the BNL analysis results and recorded field responses. To account for large variability in the soil properties, the conventional approach of computing seismic responses with the mean, mean plus and minus one-standard deviation soil profiles is adopted in the BNL analysis and the three sets of analysis results were used in the comparisons with the test data. A discussion is also provided in the paper to address 1) the capability of the analysis methods to capture the DCI effect, and 2) the conservatism of the practice for considering soil variability in seismic response analysis for adjacent NPP structures.