bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Optimization Methodology on Vehicular Crash Reconstruction
Authors: Guan Fengjiao , Belwadi Aditya , Han Xu , Yang King H.
Published: July 2010

In vehicular crash reconstruction, software packages such as PC-Crash, SMAC (Simulation Model of Automobile Collisions), WinSmash and HVE (Human Vehicle Environment) use physical evidences such as tire marks along with measurements of the deformed vehicles and photographs of the accident scene to determine the crash energy, impact velocity, and Principal Direction Of Force (PDOF). However, accurate determination of these parameters requires more sophisticated numerical methods, such as Finite Element (FE) modeling. At present, multiple runs of FE models need to be performed on a trial-and-error basis before the model predicted results are consistent with the actual ones. An optimization method to quickly and accurately determine key sensitive parameters in vehicular accident reconstruction is desired. We propose the use of Kriging model and sequential quadratic programming in conjunction with Latin Hypercube Sampling (LHS) to minimize the time needed for reconstruction and minimize the disparity between the actual and FE model predicted vehicular deformations. A selected number of modeling parameters, namely the velocity of impact, PDOF and initial impact position, are varied using this optimization approach until the deformation of six points measured on the impacted vehicle closely matches those measured in real world case. The optimization is performed in two stages. In the first stage, an approximated model was created by simplifying detailed FE models of the vehicles involved to reduce the simulation time without sacrificing accuracy. In the second stage, an assessment index ‘E’, the objective function, is maximized. To improve computational efficiency, the Kriging model is employed. The sampling points are distributed uniformly over the entire design space using the LHS. For evaluating the approximated model’s performance, the regression parameter is used as the error indicator. The objective functions based on approximated models are optimized using a sequential quadratic programming which has a higher efficiency and better convergence. Results show that through the application of this method, the deformations of the key points are in accord to the measured deformation within a small window of variability. The average difference between the deformation measured from the actual crash and that calculated from FE simulation using the optimum parameters as inputs is around 31 mm. The difference in the assessment index calculated from FE simulation with optimal assessment parameters and that from the Kriging model is only 1%. The proposed optimization methodology is a good tool to promptly reveal key parameters in a crash while simultaneously providing scientific basis for crash reconstruction.
Characterization of Hybrid-Nano Polymer Solar Cell
Authors: Domakonda S. , Gouti L. , Earles S. , Baum C. , Ramesh S. , Mitra K.
Published: July 2010

The efficiency of hybrid solar cell depends mainly on the exciton dissociation efficiency and charge mobility. The exciton dissociation efficiency can be improved by increasing the interfacial area between the nanoparticles and polymer. Charge mobility can be improved by proper distribution of nanoparticles in polymer to form better permitting path of each material. Both these parameters are strongly dependant on better distribution of nanoparticles in the polymer. The approach used in this research is the application of star dispersant to the photo active layer, specifically designed for conducting polymers. This dispersant will modify the arms of conducting polymer to have a high compatibility with nanoparticles and provide better distribution. The patterning of these polymers is achieved by wet etching process. Finally, Indium is used as a contact between P3HT and ITO to measure voltage and current characteristics. A number of specimens are prepared with and without the introduction of star dispersant. Absorption spectrum analysis and Photoluminescence (PL) measurements are performed to characterize the optical properties of active layer. Parametric study involving influence of the nano-composite film morphology with and without star dispersant for Photoluminescence measurement and I-V characteristics of hybrid nano-polymer solar cells have been studied. Structural characterization revealed that with the application of the dispersant, better mixing of the nanoparticles and the polymer can be achieved. This will in turn increase the interface area and improve exciton dissociation.
Oxygen Enhanced Exhaust Gas Recirculation for Compression Ignition Engines
Authors: Salt Tom , Tree Dale R. , Kim Chiwon
Published: July 2010

The benefits of oxygen enhancement in conjunction with EGR on emissions were investigated in a single-cylinder direct injection diesel engine. Cylinder pressure, NOx, and particulate were measured for EGR sweeps with and without oxygen enhancement. In all cases, the total flow of oxygen to the cylinder was maintained constant. This was achieved by increasing cylinder pressure for typical EGR (N-EGR) and by adding oxygen to the intake stream for oxygen-enhanced EGR (O-EGR). The results show that O-EGR produced a substantially better combination of NOx and particulate than N-EGR. In the N-EGR cases, the EGR dilutes the oxidizer causing lower NOx and higher particulate. In O-EGR, flame temperature reduction leading to lower NOx is achieved by a combination of higher molar specific heats of CO2 and H2O and dilution. Particulate emissions decreased or remain constant with increasing O-EGR. In addition to the obvious challenge of providing a source oxygen to an engine, two operational challenges were encountered. First, as EGR was increased, the ratio of specific heats (Cp/Cv) of the cylinder intake charge decreased and decreased the compression temperature, causing significant changes in ignition delay. These changes were compensated for in the experiments by increasing intake temperature but would be challenging to manage in transient engine operation. Second, the increased water concentration in the exhaust created difficulties in the exhaust system and was suspected to have produced a water emulsion in the oil.
Non-Premixed CH4 Combustion in a Porous Medium
Authors: Tarokh A. , Mohamad A. A. , Jiang L.
Published: July 2010

Combustion process is the major contributor to the air pollution, such as CO, unburned hydrocarbon, soot and NOx, etc. Porous media can be a good candidate for improving the combustion efficiency and reducing pollution formation. Premixed combustion has been extensively investigated in the literature, experimentally and computationally. However, investigation of non-premixed combustion in porous media is limited in the open literature, which is the topic of this paper. The present work deals with the numerical modeling of methane/air non-premixed combustion in porous media. Physical problem that is considered here is fuel jet which is injected to the air in free flame case and injected into a porous medium, in the porous medium combustion case. The flow is assumed turbulent and standard k-ε model with standard wall functions is used in the simulation. The solid porous structure is assumed to be composed of alumina fiber material with temperature dependent heat conductivity. Discrete Ordinate method is used to solve radiative transport equations. The governing equations are solved using finite volume method. The results show that the combustion in porous media has superior combustion efficiency and significantly lower NOx and CO emissions compare to the free flame. This is due to the lower maximum temperature in porous media combustion. In comparison with the free flame case where the combustion zone is narrow and long, the results shows the combustion zone in porous media is shorter in axial and wider in radial direction.
Reduced Order Modeling of Entrained Flow Solid Fuel Gasification
Authors: Monaghan Rory F. D. , Kumar Mayank , Singer Simcha L. , Zhang Cheng , Ghoniem Ahmed F.
Published: July 2010

Reduced order models that accurately predict the operation of entrained flow gasifiers as components within integrated gasification combined cycle (IGCC) or polygeneration plants are essential for greater commercialization of gasification-based energy systems. A reduced order model, implemented in Aspen Custom Modeler, for entrained flow gasifiers that incorporates mixing and recirculation, rigorously calculated char properties, drying and devolatilization, chemical kinetics, simplified fluid dynamics, heat transfer, slag behavior and syngas cooling is presented. The model structure and submodels are described. Results are presented for the steady-state simulation of a two-metric-tonne-per-day (2 tpd) laboratory-scale Mitsubishi Heavy Industries (MHI) gasifier, fed by two different types of coal. Improvements over the state-of-the-art for reduced order modeling include the ability to incorporate realistic flow conditions and hence predict the gasifier internal and external temperature profiles, the ability to easily interface the model with plant-wide flowsheet models, and the flexibility to apply the same model to a variety of entrained flow gasifier designs. Model validation shows satisfactory agreement with measured values and computational fluid dynamics (CFD) results for syngas temperature profiles, syngas composition, carbon conversion, char flow rate, syngas heating value and cold gas efficiency. Analysis of the results shows the accuracy of the reduced order model to be similar to that of more detailed models that incorporate CFD. Next steps include the activation of pollutant chemistry and slag submodels, application of the reduced order model to other gasifier designs, parameter studies and uncertainty analysis of unknown and/or assumed physical and modeling parameters, and activation of dynamic simulation capability.
Analysis of Wheel/Rail Contact Geometry in Turnout Section
Authors: Sugiyama Hiroyuki , Tanii Yoshimitsu , Suda Yoshihiro
Published: July 2010

In this investigation, a numerical procedure that can be used for the analysis of wheel/rail two-point contact geometries in turnout sections is developed. In turnout section, the tongue rail changes its shape along the track. Cross-sectional shapes of the tongue rail, therefore, need to be generated by interpolations along the rail and these profiles are used to determine the location of contact points for given location of wheelset along the track trajectory. Numerical examples of wheel/rail contact in point section are presented in order to demonstrate the use of the procedure developed in this investigation and the effect of wheel profiles on the contact configuration in turnout section is discussed.
Investigation on the Effect of Storage Time on Bond Strength Between Plasma Activated Silicon Wafers
Authors: Soman Joel , O’Neal Chad B.
Published: July 2010

This paper investigates the effect of storage time on the bond strength of plasma-activated silicon (Si) wafers. Plasma activation was carried out in a reactive ion etch chamber using O2 gas. The activated wafers were stored in a clean room environment for specific time intervals before pre-bonding them (in a high vacuum environment) using a substrate bonder. Steps involved in wet chemical activation and pre-bonding of the wafers were discussed in detail. The pre-bonded wafers were thermally annealed. The bond quality, in addition to the bond strength, of in-situ and ex-situ thermal annealed wafer pairs were evaluated. The bond quality was determined using near-infrared imagery, and tensile tests were conducted on dies diced out from the bonded pair. The chemistry involved during activation, storage, pre-bonding, and thermal annealing was investigated thoroughly. The bond quality and bond strengths of wafers for corresponding storage times were compared using the near-infrared imagery and tensile tests respectively. Finally interesting phenomenon, like the increase in bond strength after a particular storage time, was studied and explained.
A CAD-Based Methodology for Motion and Constraint Analysis According to Screw Theory
Authors: Franciosa P. , Gerbino S.
Published: July 2010

The need for a designer to have a tool able to do motion and constraint analysis, to check for the under-constrained and/or over-constrained status of an assembly, is strategic in a design contest where several changes are made during the design process by using CAD. Traditional kinematic tools provide little information on over-constraints at 3D level. Screw theory has been already used in mechanical assemblies, in a top-down design, to do motion and constraint analysis. This theory is here used to analyze mechanical assemblies in the contest of a feature-based CAD system. The structure of the CAD assembly is captured and described as assembly graph, similar to Datum Flow Chain, through which the motion or constraint status of any part (in terms of twist and wrench matrices), can be obtained. The underlying algorithm is based on the Kirchoff’s rules successfully applied by Davies to mechanisms. How to automatically create the assembly graph, detect the useful loops and then write the loop kinematic equations is described. Three case studies are presented related to CAD assemblies of mechanisms built up in SolidWorks® CAD system by Dassault Systemes from which assembly constraints have been acquired.
Effect of Different Welding Speeds on Mechanical Characterictics, Micro and Macrostructure in Dissimilar Friction Stir Butt Welding of AA6061-T6 and AA7075-T6
Authors: Bahemmat Pouya , Haghpanahi Mohammad , Besharati Mohammad Kazem , Rahbari Alireza
Published: July 2010

In this article, the effect of FSW process parameters on weldability and properties of two dissimilar aluminums joint, AA6061-T6 and AA7075-T6, is investigated. The experiments are conducted to study the role of different welding speeds. Weldability in each fabricated weld is evaluated using macrostructure for sound and defective welds. The mechanical characteristics are determined by comparing the ultimate strength, percentage of elongation for different welding speeds. Besides, microstructural analysis is performed for studying the influence of welding speed on microstructural properties in the weld zone. The results show that the welds were produced with 80 and 100 mm/min are free defects and the rest welds have some defects at SZ, however the weld strength made with 120 mm/min has superiority on the weld. Consequently, the optimum welding speed for fabricating the high quality welds is obtained in this research.
Application of Digital Volume Correlation Algorithm to Cell Mechanics
Authors: Kwon Hyock J. , Zhao Boxin , Rao Praveen N. P.
Published: July 2010

This study developed a digital volume correlation (DVC) algorithm based on fast normalized cross-correlation to measure the 3-dimensional deformation of soft gels, which was further utilized as a force sensor for cell mechanics studies. The developed algorithm was applied to the 3-D volume images of a gel acquired by confocal microscope to measure the deformation of the gel. The gel contained uniformly-dispersed florescence-labeled microbeads so as to generate a necessary speckle pattern for cross-correlation. The developed algorithm has been validated both analytically and experimentally, and applied to investigate cell mechanics by measuring the displacement field induced by the cell motion. Then, surface traction force generated by cells can be quantified through the conventional linear elasticity theory without any further assumption.
Transient Flow Analysis of Spring Loaded Pressure Safety Valve
Authors: Song Xue Guan , Kim Seong Gul , Wang Lin , Park Young Chul
Published: July 2010

Transient flow analysis with moving mesh in computational fluid dynamics (CFD) has become useful and popular. However, in many practical applications, the uses of moving mesh are restricted by the geometric complexity. This paper carried out transient flow analysis of incompressible fluid through safety valve of complicated geometry in three dimensions by using moving mesh. To deal with the complex geometry of safety valve, some novel techniques of mesh generation and modeling are used to ensure the model of safety valve’s disc can move upward and downward successfully without negative volume. Then several constant inlet pressures are given to simulate the safety valve under different overpressure conditions. Herein, the response parameters including the displacement of disc, fluid flux through the valve, fluid force applied on the disc are calculated and monitored. Through analysis of these data, this work demonstrates clearly behavior of safety valve, and will help the researcher improve the design of safety valve in the future.
Evaluation of Nanocrystalline Coatings for Coal-Fired Ultra-Supercritical Boiler Tubes
Authors: Cheruvu N. Sastry , Wei Ronghua , Govindaraju Madhavrao , Gandy David W.
Published: July 2010

Cyclic oxidation behavior and microstructural degradation of nanocrystalline Ni-20Cr-xAl (where x = 4, 7, and 10 wt.%) coatings have been investigated. The coatings were deposited on Haynes 230 samples using a magnetron sputtering technique. Cyclic oxidation tests were conducted on the coated and uncoated samples at peak temperatures of 750°C and 1010°C for up to 2070 thermal cycles between the peak and room temperatures. The results showed that a dense Al2O3 scale was formed on the external surface of all coatings after exposure at both temperatures. All three coatings showed no evidence of internal oxidation after exposure at 750°C. Among the three coatings, the coating containing 4 wt.% Al only showed evidence of internal oxidation along the columnar grain boundaries after exposure at 1010°C. The Al2O3 scale exhibited good spallation resistance during cyclic oxidation tests at both temperatures. As the Al content in the coating increased from 4 to 7 or 10 wt.%, thermal exposure led to precipitation of coarse Al-rich particles at the coating/substrate interface. In addition, thermal exposure at both temperatures led to rapid depletion of Al in the coating and grain coarsening of the coatings. The improvement in oxide scale spallation resistance and accelerated depletion of aluminum are attributed to the ultrafine grain structure of the coating and oxide scale.
The Engineering Approach to Estimation of Ductile Crack Growth Under Nonisothermal Loading
Authors: Minkin A. J. , Margolin B. Z. , Kostylev V. I. , Piminov V. A.
Published: July 2010

The approaches to estimation of ductile crack growth under nonisothermal thermal-stress loading are considered in the paper. It is shown that in a number of cases when using isothermal JR-curves an estimation of ductile crack growth can be nonconservative. The engineering approach is proposed to estimate the value of ductile crack growth with regard to an actual history of nonisothermal thermal-stress loading. The paper cites an example of construction of nonisothermal JR-curves for the material of anticorrosive cladding of reactor pressure vessel (PVR) of WWER. Prediction of nonisothermal JR-curves by the use of finite element method (FEM) is made. It is shown that the nonisothermal JR-curves obtained by FEM and the proposed engineering approach are of a similar nature.
Modification of Pre-Cracked Charpy Specimens for Surveillance Specimen Programs
Authors: Margolin Boris , Nikolaev Vladimir , Fomenko Valentin , Ryadkov Lev
Published: July 2010

Application of pre-cracked Charpy specimens with various depth of side-grooves is considered for fracture toughness prediction. Recommendations for prediction of temperature dependence of fracture toughness are given when using small-sized specimens with deep side-grooves. Test results of about 500 specimens, cut from materials with various degrees of embrittlement are presented. On the basis of 3D calculations by finite element method the procedure used in standard ASTM E 1921 for calculation of Ke and J, is developed for bending specimens with deep side-grooves. An attempt is undertaken to explain the obtained experimental data from the standpoints of the available criteria of brittle fracture based on calculation analysis of stress and strain fields (SSF) of SE(B)-10 specimens with various depths of side-grooves.
Further Evidence for Acoustic Resonance in Full Size Steam Generator and Tubular Heat Exchanger Tube Banks
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: July 2010

In the previous publications by Eisinger, F.L., Francis, J.T., and Sullivan, R.E., 1996, “Prediction of Acoustic Vibration in Steam Generator and Heat Exchanger Tube Banks”, ASME Journal of Pressure Vessel Technology, Vol. 118, pp. 221–236 and Eisinger, F.L. and Sullivan, R.E., 1996, “Experience with Unusual Acoustic Vibration in Heat Exchanger and Steam Generator Tube Banks”, Journal of Fluids and Structures, Vol. 10, pp. 99–107, prediction criteria for acoustic vibration or acoustic resonance were formulated utilizing flow and acoustic parameters derived from operating steam generator tube banks. Various parameters were used in those formulations, including the dominant parameter MΔp where M is the Mach number of the crossflow through the tube bank and Δp is the pressure drop through the tube bank. Here we present further evidence derived from operating experience of full size steam generator and tubular heat exchanger tube banks of which 19 experienced acoustic vibration or acoustic resonance and 27 experienced no vibration or no acoustic resonance within the operating flow range. The present data show that the decisive parameter predicting the acoustic vibration or acoustic resonance of a tube bank is the acoustic particle velocity. The acoustic particle velocity separates the acoustically vibrating banks from those non-vibrating very clearly. The behavior is demonstrated graphically showing the dimensionless acoustic particle velocity as a function of input energy parameter MΔp, Mach number M, Reynolds number Re and also Helmholtz number He = MS where S is the Strouhal number. This finding indicates that the acoustic particle velocity criterion shall be used in conjunction with the previously used criteria as the basis for the prediction of acoustic resonance in full size steam generator and tubular heat exchanger tube banks.
Progress in the Analysis of Duplex CT Specimen Test Results Using FE Analysis to Assess the Crack Behaviour in Heterogeneous Materials
Authors: Daniels B. D. , Wilkes M. A. , Birkett R. P.
Published: July 2010

Currently, structural integrity safety cases are based on avoidance of fracture initiation, providing a pessimistic estimate of structure life. However, crack behaviour at heterogeneous junctions is an area where understanding is particularly limited. Improved data regarding the behaviour of defects at such junctions after initiation may lead to improved assessment of real structures containing welded joints. Furthermore, justification of stable tearing at a material interface would result in increased demonstrable safety and higher plant availability. An experimental study has been carried out to investigate the ductile fracture behaviour of a crack approaching material interfaces. The aim has been to examine and refine current guidelines in the R6 defect assessment procedure. The experiments have been supported by 3D finite element modelling of the specimens and by R6 calculations. A further assessment of the standard (25mm) CT specimen results indicated that the R6 guidance on usage of the toughness in the crack tip medium may not always be conservative. However, the assessment points are conservative when the lowest yield strength or the weighted average yield strength values are used in the R6 fracture assessment.
Study on Generation Mechanism of Abnormal Vibration of Flow Dynamic Conveyer
Authors: Ishihara Kunihiko
Published: July 2010

The FDC (Flow Dynamics Conveyer) has often been used in power plants and iron works because of superiority in low noise compared with a roller type conveyer and it is excellent in low noise and low power. The FDC consists of a trough and a belt, and the air is supplied from a series of holes provided on the trough. However, large vibrations occur when the flow rate reaches a certain value. This abnormal vibration is defined to be self-excited vibration caused by leakage flow induced vibration here. In this study, as the first step, the theoretical model of a non tapered clearance flow passage is assumed and the natural frequency is calculated. On that basis, experiments are conducted and the validity of the theory is examined. As the second step, in the case of a tapered clearance flow passage, the concentrated load is added to the belt. The effects of the belt deformation, the flow rate and the added loads on the clearance flow are examined and the generation mechanism of the abnormal vibration is considered. As a result, it was clarified that the generation mechanism of the self-excited vibration was due to the phase shift by the change of the parameters.
Effects of Post Weld Heat Treatment Residual Stress on the Creep of Elbow Welded Joint
Authors: Zhou Changyu , Zhang Guodong
Published: July 2010

It is well known that type IV crack emerges in the high temperature welded components. Although the welding residual stress will drop after post weld heat treatment (PWHT), the PWHT residual stress still remains in the welded joint. When the joint is in service at high temperature and under high pressure, the PWHT stress and pressure will induce the creep strain in the welded joint of the elbow of T91 boiler tubes. Usually, it is considered that the PWHT stress will relax at high temperature environment and is ignored by many researchers. In this paper, by the finite element analysis codes ABAQUS and the function of RESTART, a sequential coupling calculating program for creep based on welding residual stress has been developed by establishing the model of temperature field, residual stress and creep analysis. The welding residual stress and creep of elbow welded joint for T91 boiler tubes was simulated by the program. According to the finite element calculation results, the PWHT stress has a great influence on the T91tube creep. This method established the basis of calculating the effects of welding residual stress on the creep of welded joint. Firstly, the welding residual stress and the PWHT stress was simulated by ABAQUS. Based on the work, the stress distribution of the T91 tube elbow can be obtained under internal pressure and the PWHT stress. Secondly, for the elbow welded joint the creep under the internal pressure only and the creep under internal pressure and PHWT stress can be simulated by the ABAQUS codes. Then comparison of creep strain in the elbow welded joint with PWHT stress and with internal pressure is made in the paper. Although the stress induced by the PWHT and internal pressure would relax in a short time, the creep strain of the elbow welded joint is still influenced by initial stress state. The results shown that the PWHT stress can not be ignored for the creep analysis of the elbow welded joint. So it can be considered that the PWHT residual stress is one of possible failure factors for the elbow welded joint. The design of high temperature elbow welded joint need to consider the influence of the PWHT residual stress. This paper will provide a more comprehensive means for life assessment of the welded joint in service.
Metal Dusting Corrosion of Alloy Cr5Mo in H2-CO Gas Mixtures
Authors: Hu Guiming , Zhou Changyu , Chen Cheng , Lei Na
Published: July 2010

Metal dusting is a catastrophic phenomena of high temperature corrosion, which occurs in severe carburizing environments (carbon activity aC>1.0) at temperatures 400–900 °C. It causes not only phase changes but also removal of materials (pitting or thinning) and serious material deterioration. The present study focuses on the fundamental understanding of the corrosion of low alloy steels Cr5Mo in carbon-supersaturated environments (50CO-50H2) at 600 °C over different holding times. Scanning-electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), nano-indentation, and nano-scratch tester are used to investigate the microstructure and its mechanical properties. An interesting continuous thick layer composed of Ha¨gg carbide (Fe5C2) and less cementite (Fe3C) was present on top of the samples, which was ever observed in pure iron but not in alloy steels. This layer grew thicker with increasing holding times and showed very different mechanical properties with the carburized layer which was below the Ha¨gg carbide layer. And the carburized layer could not form a continuous and homogeneous layer of Fe3C even in longer holding times. The cementite only formed at grain boundaries. The results show that also as for low alloy steels at very high carbon activities a second iron carbide, Ha¨gg carbide (Fe5C2), forms on the surface instead of the decomposing process of the metastable carbide, cementite (Fe3C).
Constraint-Correction of Cleavage Fracture Data From Miniature Specimens and Improved Estimates of Lower Bound Fracture Toughness
Authors: Madew Colin J. , Beardsmore David W. , Howells Richard O.
Published: July 2010

Current assessments of pressurised components use fracture data collected on conventional size, 25 mm and 10 mm thick fracture specimens. It would be advantageous to be able to measure fracture toughness on what has commonly been termed miniature specimens (i.e. smaller than 10mm) as this would allow a more economical use of available plant material. However, tests on miniature specimens generally produce values of fracture toughness which over-estimate the fracture toughness of the material (as evaluated from the 25 mm or 10 mm specimens). In particular, the measured scatter in the data exhibits lower-bound values that are higher than the values obtained with conventional size specimens. A study has thus been undertaken in order to examine a methodology to derive fracture toughness from miniature specimens and allow a better determination of the lower-bound values. When cleavage fracture toughness tests are carried out using miniature specimens, the values of critical J obtained do not directly determine the cleavage fracture toughness of the material. This is because a loss of crack-tip constraint will generally occur before fracture. In such cases, it is necessary to apply an appropriate constraint correction to map the measured values to their equivalent small-scale yielding values. This paper uses a method for carrying out constraint corrections in order to assess data obtained from a recent UK miniature fracture toughness specimen testing programme. The method is based on the notion of matching areas enclosed by a same-stress contour of maximum principal stress around the crack tip in the specimen and small-scale yielding geometries. In applying the method, two-dimensional, plane strain finite element models of the specimen geometries have been developed together with a boundary layer model of the reference small-scale yielding condition to determine the appropriate areas.
Exact Computation of the Axial Vibration of Two Coupled Liquid-Filled Pipes
Authors: Tijsseling Arris S.
Published: July 2010

A simple recursion is presented that finds exact solutions to the problem of two coupled axially-vibrating liquid-filled pipes. Fluid-structure interaction at pipe ends and junction, and along the pipe because of axial-radial Poisson contraction, is taken into account. The solutions obtained for a waterhammer problem show unprecedented details that resemble noise.
The Sealing Performance Evaluation of Bolted Flexible Box-Shaped Flange Joints Under Thermal Conduction Conditions
Authors: Kurosawa Ryou , Sawa Toshiyuki , Omiya Yuya , Tenma Kentaro
Published: July 2010

Bolted joints with gaskets such as flexible box-shaped flange joints have been used in mechanical structures. The joints are usually used under internal pressure as well as other loadings such as thermal, impact loadings and so on. In designing the bolted flexible box-shaped flange joint with gaskets, it is important to evaluate the sealing performance of the joints under internal pressure and thermal conduction conditions. In this paper, the contact gasket stress distributions and changes in bolt load in the bolted flexible box-shaped flange joint with joint sheet gaskets subjected to internal pressure and thermal conduction condition are analyzed using the finite element method (FEM). The leakage tests were conducted using an actual box-shaped flange connection with a joint sheet gasket. Using the contact gasket stress distributions under internal pressure at an elevated temperature (Helium gas) obtained from the FEM calculations and the amount of the gas leakage measured in the experiment, the sealing performances are evaluated experimentally and numerically. In addition, the effect of the thermal conduction condition on the sealing performance is examined. Furthermore, a method how to determine the bolt preload of the flexible box-shaped flange joint at an elevated temperature for a given tightness parameter is demonstrated. Discussion is made on the sealing performance.
On the Modelling of Noise Generation in Corrugated Pipes
Authors: Goyder Hugh
Published: July 2010

The offshore oil and gas industry uses pipes which are made flexible by means of a corrugated construction. Those pipes that run from a platform to the seabed are known as risers while those that connect two pipes on the seabed are known as jumpers. Gas flowing within the pipe interacts with the corrugations and generates noise. This noise is of concern because it is of sufficient amplitude to cause pipework vibration with the threat of fatigue and pipe breakages. This paper examines the conditions that give rise to the large noise levels. The conditions for the onset of noise are investigated using an eigenvalue approach which involves the effect of damping due to losses from the pipe boundaries and pipe friction. The investigation which is conducted in terms of reflection conditions shows why only few of the very many possible natural frequencies are selected. The conditions for maximum noise response are also investigated using a non-linear model of vortex shedding. Here an approach is developed in which the net power generated along a single wavelength is calculated.
Methodology for the Determination of a Set of Safety Factors That are Consistent for Design Code and Fitness-for-Service Code: Framework
Authors: Asayama Tai
Published: July 2010

This paper introduces a methodology for the determination of a complete set of safety factors that maintains consistency between design code and fitness-for-service code of nuclear components. The purpose of the work is to materialize the System Based Code concept, which is indispensable for the development of next generation nuclear reactors. The methodology consists of three principles proposed by the author which should be the basis of code development for new next generation reactors. The principles are; 1) Design to target reliability, 2) Continuous reliability evaluation from design to fitness-for-service, 3) Update of reliability evaluation based on information obtained during construction and operation. Effectiveness of the methodology is demonstrated using a simple example problem. The problem deals with pipe subjected to internal pressure under conditions which is typical in light water reactors. Following the reliability evaluation of current situation which meets the provisions of design code and fitness-for-serve code published from Japan Society of Mechanical Engineers, the three principles are applied step-by-step and safety factors and reliability indices are newly derived. It is shown that a complete application of the three principles could lead to a set of safety factors that assures consistency in terms of reliability in design and fitness-for-service, and improves allowable stresses as well. Technologies to be developed and issues to be discussed for application of the methodology to more complicated and practical situations are described as well.
Study on High-Temperature Naphthenic Acid Corrosion of Type 304 and Type 316L Stainless Steel and Their Welded Joints
Authors: Fang Zhou , Chen Zhiping , Wang Lei
Published: July 2010

High-temperature naphthenic acid corrosion (HNAC) behaviors of type 304 and type 316L stainless steel have been investigated in the laboratory with the experimental devices, that were designed and built by ourselves and had applied a patent, to evaluate the resistance of the base metal and their welded joints to the HNAC. Corrosion dependencies on the test temperature (ranging 220–320°C), total acid number (TAN) (ranging 1.86–32.0 mg KOH/g) and media physical states (liquid or vapor) were assessed. Specimens after HNAC tests were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy. A database of corrosion rates of type 304 and type 316L steel in high-temperature naphthenic acid solution was established. It was found that the HNAC resistance of both type 304 and type 316L degraded rapidly with increasing temperature and TAN. The tests which were conducted simultaneity in liquid media and gas media revealed that both the type 304 and type 316L stainless steel with weld showed worse HNAC compared to the type 304 and type 316L base metal at all temperatures in liquid media, but the difference between them was not obvious. In gas media, the HNAC rates of the type 304 and type 316L stainless steels with welds were greater than those without welds.
Effect of Frequency and Shape of Thermal Cycling on the Damage of Multi-Material Under Thermo-Elasto-Plastic Behaviour
Authors: Taher Bilal , Abboudi Said , Youness Rafic
Published: July 2010

In this study, we propose a numerical analysis of the thermo-elasto-plastic behavior of a multi-material and its damage under thermal cyclic solicitations. The study is done in two dimensions on a cylindrical multi-material subjected to a periodic heat flux on the internal face and to a convective heat transfer condition on the opposite external face. Lateral faces are supposed to be isolated. The sample is supposed to be fixed in the axial direction and free in the other. The damage model is based on the works of Lemaiˆtre and Chaboche. Numerical results are presented for different shapes of heat flux cycling (triangular, square and sinusoidal excitations, function of time and space) and for a range of periods. We do a comparison of the multi-material damage under these different thermal excitations. The study is concluded by some advice on the use and avoidance of some values of periods, and shapes for the thermal load excitation, in order to obtain the maximum lifetime of the multi-material under thermo-elasto-plastic behavior.
Development and Application of a Streamlined RI-ISI Methodology
Authors: O’Regan Patrick
Published: July 2010

Put abstract text here. Based upon lessons learned from the development of a large number of risk-informed inservice inspection (RI-ISI) applications, EPRI has developed has streamlined process for implementing and maintaining a RI-ISI program. This streamlined RI-ISI process has been codified by ASME in Code Case N-716. While founded on the EPRI RI-ISI methodology contained in EPRI TR-112657, this streamlined approach differs from the traditional RI-ISI approaches in two respects. First, a consequence assessment is not required for every segment. The consequence assessment has been replaced by identifying generic set of high safety significant (HSS) segments coupled with a structured search for plant-specific HSS segments. The second important difference is that partial scope application, which is allowed by previous RI-ISI approaches, is not allowed by this streamlined approach. A distinct advantage of this approach is that this streamlined approach requires fewer resources (i.e. for the initial application as well as maintenance requirements). It also incorporates lessons learned from extension of the EPRI RI-ISI methodologies to other inspection programs (e.g. break exclusion regions, aka HELB areas). The methodology has been approved for use by the USNRC at Grand Gulf (BWR), Cook Nuclear Plant, Units 1 and 2 (West – PWR) and Waterford (CE-PWR). EPRI NDE Center staff are currently supporting the conversion of two previously approved RI-ISI programs to this streamlined approach. The first plant, a Westinghouse NSSS PWR design currently has a program develop using the PWROG RI-ISI methodology on Class 1 piping. The second plant, a General Electric NSSS BWR design currently has a Class 1 and 2 RI-ISI program using the EPRI traditional RI-ISI approach. This paper will present this new methodology and contrast it to other more traditional RI-ISI approaches.
Operational Readiness of the ES-3100 Type B Shipping Container for Fissile Materials
Authors: Arbital Jeffrey G. , Sanders Kenneth E.
Published: July 2010

The U. S. Department of Transportation (DOT) Specification 6M containers had been the workhorse bulk Highly Enriched Uranium (HEU) shipping containers for the U. S. Department of Energy (DOE) and many other shippers for over 20 years. This DOT specification container was terminated for shipment of radioactive material on September 30, 2008. The anticipation of this action prompted DOE to develop and implement the ES-3100 shipping container as a replacement for the 6M. The ES-3100 was first licensed in April 2006. Since then, the license has been revised nine times. The ES-3100 was operationally ready for use at several sites by September 2007, and is now in being used on a regular basis for materials that had been shipped in the DOT 6M. The ES-3100 has also been certified for air transport, in support of foreign research reactor fuel supply and international nonproliferation efforts. This container has a Certificate of Compliance (CoC) from the U. S. Nuclear Regulatory Commission (NRC) and a Competent Authority Certificate from the DOT. The utility of the ES-3100 continues to grow. The ES-3100 CoC allows many forms of fissile material to be shipped, and continues to be amended to authorize additional contents for a variety of shippers. This paper will identify the currently certified contents for the ES-3100 and the planned certificate amendments to expand the content basis, as well as the approach to add new contents to the CoC. The path to becoming a user of the ES-3100 will be outlined. Operational requirements for this container, handling tools and non-standard operating tools needed for the use of this container will be covered. Readiness requirements, maintenance issues, training, and lessons learned will also be discussed. This paper will provide the information necessary for organizations to obtain ES-3100 containers, the special tools, adequate training, and any other information that would be helpful for a site to be able to use this fissile, radioactive material shipping container system.
An Analysis of the Roles of J and Q in the Assessment of Fracture for Quasi-Statically Extending Cracks in Residual Stress Fields
Authors: Beardsmore David W. , Sharples J. K. , Madew C. J. , Jackson M.
Published: July 2010

It is well known that the crack tip stress and strain fields for a crack in an elastic-plastic body depend on the crack tip contour integral J, the Q-stress, and the elastic-plastic properties of the material. This dependence is the fundamental basis of conventional two-parameter J-Q fracture mechanics assessments. It is normally assumed that the crack is created in an unstressed body, or else is inserted concurrently into an existing non-zero stress and strain field such that the crack tip fields build up monotonically and dominate at the crack tip. In such cases, the crack may be regarded as stationary and the J-Q procedure is valid provided that care is taken to calculate J and Q properly when initial stress and/or strains exist. When a crack is introduced progressively and quasi-statically into a component, the location of the crack tip will move along a distinct path. If the component contains residual stress and this is of a significant size along the crack tip path, a re-distribution of the residual stress will occur as the crack tip moves. Specifically, the stress field ahead of the crack tip will unload as the crack tip advances so that non-proportional loading will occur behind the advancing crack tip. In elastic-plastic materials, a wake of plasticity will usually be deposited in the material behind the moving or growing crack tip. Similar effects will also occur when a stationary crack extends due to critical or sub-critical processes. The presence of a plastic wake alters the stress and strain fields at the crack tip so that they do not generally match the fields of a stationary crack. Moreover, J and Q may not describe the stress and strain fields, invalidating the use of the fracture mechanics procedure for such cases. In this paper, a Finite Element analysis of J and Q is carried out for a quasi-statically extending crack inserted in a strip of elastic-plastic material containing an initial residual stress field. Care is taken to model the crack tip conditions appropriately as the crack extends and J is determined using the JEDI post-processing program which can allow for the effects of initial plastic strains and non-proportional loading. An assessment is made of the crack tip field and the likelihood of further extension or fracture is made using local approach models. The analysis considers both cleavage and ductile fracture. The extent of the relationship between J and Q and the crack tip fields is established and the validity of the J-Q procedure to such cases is discussed. The paper considers whether the procedure is conservative when J and Q are determined from an analysis of a stationary crack of the same size inserted into the same initial field.
Flaw Tolerance Evaluation of CASS Piping Materials
Authors: Griesbach Timothy J. , Marthandam Vikram , Qian Haiyang , O’Regan Patrick
Published: July 2010

Prolonged exposure of cast austenitic stainless steels (CASS) to reactor coolant operating temperatures has been shown to lead to some degree of thermal aging embrittlement (reduction in fracture toughness of the material as a function of time). The fracture toughness data for the most severely aged CASS materials were found to be similar to those reported for some austenitic stainless steel weld metal, in particular weld metal from submerged arc welds (SAW). Such similarity offers the possibility for applying periodic inservice inspection flaw acceptance criteria, currently referenced in the ASME Code Section XI, Subsection IWB, for SAW and shielded metal arc weld (SMAW), to CASS component inservice inspection results. This paper presents the data to support both the proposed screening criteria (based on J-R crack growth resistance) for evaluation of the potential significance of the effects of thermal aging embrittlement for Class 1 reactor coolant system and primary pressure boundary CASS components, for those situations where the effects of thermal aging embrittlement are found to be potentially significant. The fitness for continued service is based on the comparison of the limiting fracture toughness data for Type 316 SAW welds and the lower-bound fracture toughness data reported for high-molybdenum, high delta-ferrite, statically and centrifugally-cast CASS materials. These comparisons and the associated flaw acceptance criteria can be used to justify exemptions from current ASME Code Section XI inservice inspection requirements through flaw tolerance evaluation (e.g., see ASME Nuclear Code Case N-481).
Dynamic Analysis of Shipping Cask Subjected to Sequential Bolt Preload and Impact Loads
Authors: Wu Tsu-te
Published: July 2010

This paper presents an improved methodology for evaluating the dynamic responses of shipping casks subjected to the sequential HAC impact loads. The methodology utilizes the import technique of the finite-element mesh and the analytical results form one dynamic analysis using explicit numerical integration scheme into another dynamic analysis also using explicit numerical integration scheme. The new methodology presented herein has several advantages over conventional methods. An example problem is analyzed to illustrate the application of the present methodology in evaluating the structural responses of a shipping cask to the sequential HAC loading.