bluuebunny/crossref_metadata_2025 huggingface dataset:
A Structural-Acoustic Finite Element Method for Predicting Automobile Vehicle Interior Road Noise
Authors: Sung Shung H. , Nefske Donald J. , Feldmaier Douglas A.
Published: July 2010

A structural-acoustic finite element model of an automotive vehicle is developed and experimentally evaluated for predicting the structural-borne interior noise in the passenger compartment when the vehicle travels over a randomly rough road at a constant speed. The structural-acoustic model couples a structural finite element model of the vehicle with an acoustic finite element model of the passenger compartment. Measured random road profile data provides the prescribed power spectral density excitation applied at the tire-patch contact points to predict the structural-borne interior road noise. Comparisons of the predicted and measured interior noise for laboratory shaker excitation, tire patch excitation, and vehicle travel over a randomly rough road are used to assess the accuracy of the model.
Vibrations of Partially Fluid-Filled Functionally Graded Cylindrical Shells
Authors: Saeidifar Mahdi , Ohadi Abdolreza
Published: July 2010

In this study, the free vibration of partially fluid-filled functionally graded material (FGM) cylindrical shells with arbitrary boundary conditions has been investigated using the Rayleigh-Ritz method. The analysis has been carried out with strain-displacement relations from Love’s thin shell theory and the contained fluid is assumed irrotational, incompressible and inviscid. The Rayleigh-Ritz method is based on the energy parameters, so after determining the kinetic and potential energies of FGM shell filled with fluid, the eigenvalue problem has been obtained. To demonstrate the validity and accuracy of the obtained theoretical results, comparison has been made with the previous published results and also with the finite element results for the empty and partially fluid-filled shells. Finally, the effects of fluid level and power-law exponent on natural frequencies of partially fluid-filled FGM shells have been investigated.
Development and Characterization of Novel Conductive Polypyrrole-Polylactide Open-Porous Composites
Authors: Chan Christine , Zhang Weijia , Naguib Hani E.
Published: July 2010

Novel polypyrrole-polylactide blends were fabricated and characterized using compression molding, salt leaching, and in situ polymerization. Open-porous polylactide samples were fabricated using compression molding and salt leaching techniques with varying salt-to-polymer mass ratios of 3:1, 6:1, and 9:1. The samples then underwent in situ polymerization of pyrrole and iron (III) chloride to obtain a uniform coating of polypyrrole. Characterization of these novel composites comprised of their physical, mechanical, and electrical properties. With increasing salt-to-polymer mass ratio, it was found that the relative density decreased, the open porosity increased while pore size and pore density generally remained independent. The polypyrrole coating did not have a significant effect on the structure of the pore network. Microscopic polypyrrole nodules were observed to be uniformly coated on the surface and sub-surface of the composites. The compressive modulus decreased with increasing salt-to-polymer mass ratios. In addition, the modulus of the coated 3:1 salt-to-polymer mass ratio sample was twice the value obtained for the uncoated sample while the modulus values for the 6:1 and 9:1 samples did not significantly change. The conductivity increased as the salt-to-polymer mass ratio increased. The relationships observed between the structure and resulting properties provided the basis for future development and characterization of these novel porous composites.
Brain Deformation in Linear Head Impact
Authors: Laksari Kaveh , Darvish Kurosh
Published: July 2010

In this study, a 2D model of the head underwent linear impact and the experiments were simulated by finite element models. A cylinder with a diameter of 100mm and height of 20mm was filled with 5% gelatin, which was used as the brain surrogate material. The physical model was mounted onto a High Speed Computer Controlled Impact System to generate inertial loading of approximately 50 G average deceleration. The deformation of the samples was studied through image processing. Finite element (FE) analysis was used to simulate the experiments. The impact tests were modeled with two methods: a Lagrangian formulation with single point integration and an Arbitrary Lagrangian Eulerian (ALE) formulation with single point integration and void using LS-Dyna FE code. In the model with slip contact, the normal and shear strains reached more than 20% in some regions, which confirmed the risk of axonal injury in the linear impacts applied in this study. It was seen that in the Lagrangian models, in order to stabilize the simulation, high bulk moduli needed to be used; however, this resulted in much smaller void generation in the posterior region of the model. It was shown that the void generation reaches the experimental values by introducing 1–2 mm initial gaps between brain and skull. The ALE model was more stable and less sensitive to the bulk modulus, but showed smaller deformations.
A Piezoelectric on Substrate Phononic Band Gap High-Q Micromechanical Resonator
Authors: Mohammadi Saeed , Eftekhar Ali Asghar , Adibi Ali
Published: July 2010

Micromechanically-fabricated phononic crystal (PnC) structures with phononic band gaps (PnBGs) are gaining a growing attention due to their high efficiency in controlling and confining mechanical energy in micro and nano-scale structures. Preliminary PnC devices such as waveguides and resonators based on the complete PnBG of the micro-machined PnC structures have shown a great potential to improve the characteristics of the conventional micro-mechanical (MM) devices [1–5]. Especially high-frequency, high-quality factor (Q) MM resonators are of great interest as they are main building blocks for realizing compact and complex devices such as filters, multiplexers and de-multiplexers for wireless communications and sensing applications. Therefore, development of high-Q, high-frequency PnC-based MM resonators is an important step towards realizing functional PnC-based devices with potentially better performance compared to their conventional counterparts. In this paper, we report, for the first time, a PnC slab piezoelectric-on-substrate MM resonator operating at VHF frequencies which supports high Q modes. The excitation of the resonant modes in these structures is done directly on the resonant structure (in contrast to the resonant tunneling excitation method reported earlier [5]) and therefore, no coupling from outside of the resonant structure is required. In such a structure, enough number of PnC periods can be placed around the resonant region to provide enough isolation from the surroundings; consequently the loss of the mechanical energy will be limited to material and friction losses only. We report a Fabry-Perot-type PnC slab resonator with an electrode and a piezoelectric medium directly fabricated on top of a resonant structure and show that high quality factors can be obtained in such a compact resonator. As a result, a flexural and a longitudinal mode are excited. Q’s of more than 3600 and 10,000 are obtained for the two modes with motional resistances of 1200 Ω and 5000 Ω. Such piezoelectrically excited high-Q resonators operating at such high frequencies evidence the possibility of suppressing support loss (an important source of loss) in MM resonators through the use of the especial structure of a PnC. Such PnC resonators can have a great impact on the current state-of-the-art MM devices used in wireless communication and sensing systems.
Effects of Segregation on the Strain Fields and Electronic Structures of InAs Quantum Dots
Authors: Hong Kuo-Bin , Kuo Mao-Kuen
Published: July 2010

This paper investigates the influence of indium segregation on the strain fields and electronic structures of self-assembled InAs/GaAs quantum dot structures with and without an In0.15Ga0.85As interlayer. We propose a new out-of-plane mismatch strain to interpret an experimental phenomenon. The new mismatch strain simulation successfully analyzes the strain fields and energy levels of InAs quantum dots (QDs). Numerical results reveal that indium segregation would improve the penetration behaviour of the z-axis strain component and the relaxation of the hydrostatic strain. The transition energy of samples A and B without In segregation are 0.991 and 1.028 eV, respectively. The energy difference of two samples agrees well with the previous experimental results. The transition energy of samples A and B may be consistent with presented experiment data at R = 0.84–0.85. In our calculations, indium segregation not only made the transition energy increase significantly as segregation efficiency increased, but also the confinement position of the electron and the heavy-hole shifted toward the top of the QD. Similar phenomena can also be observed for other segregation efficiencies.
Bipartite Graphical Integration of Dielectrophoresis Process Models for Assembly of Carbon Nanotubes
Authors: Shah Meet , Zeid Ibrahim , Kamarthi Sagar
Published: July 2010

Dielectrophoresis is the process where nonuniform electric field causes the translational motion of uncharged, polarized particles. Recently dielectrophoresis has become the most widely used process in the field of nanomanufacturing as the translational motion of a carbon nanotube caused by the dielectrophoresis assembles it in the spacing between the electrodes. This process enables engineers to replace the traditional metal (copper or aluminum) wire with carbon nanotubes (CNTs) in the miniature electronic devices. Various process models have been developed and parametric studies have been carried out to understand the process better and to improve the quality and reliability of assembly of CNTs. We consolidate the scattered knowledge of the dielectrophoresis process and represent the integrated knowledge in the form of a complex network by connecting the process parameters based on the relationships they shares. We find that the bipartite relationships exist between some of the process parameters and we represent them in the form of bipartite graphs. We also represent these graphs as incidence matrices and verify whether each graph fulfills the condition of being bipartite. We apply the shortest path algorithm to find an even length path between the any two process parameters which turns out to be an efficient method to estimate the unknown state variables of the process and to access the real time state of the assembly process quickly and efficiently. One can also use bipartite graph to identify the non-contributing variables and eliminate the over constraint situation by applying Gauss elimination method.
The α-Prototype of an Ultra-Micro-Gas Turbine at the University of Roma 1: Final Assembly and Tests
Authors: Capata Roberto , Sciubba Enrico
Published: July 2010

The paper describes the realization of the α-prototype of a portable power device consisting of an electrical generator with a power output of about 300 W driven by a small gas turbine set. The device is so small that it can be properly defined an ultra micro device, capable of supplying electric power in stand alone conditions and for prolonged periods of time (up to 24 hours continuously). In practice the device can be used as a convenient substitute (or replacement) for all current battery storage systems and is significantly smaller, lighter and most likely more reliable than the few existing internal combustion engines of comparable power output. The particular nomenclature is UMGTG-UDR1 (Ultra-Micro Gas Turbine Generator). The final configuration of the prototype (for which a patent is pending) is described in the paper as well, together with some of the results of the final operational tests.
Analytical Solutions for the Static Instability of Nano-Switches Under the Effect of Casimir Force and Electrostatic Actuation
Authors: Mojahedi Mahdi , Moeenfard Hamid , Ahmadian Mohammad Taghi
Published: July 2010

This paper deals with the problem of static instability of nano switches under the effect of Casimir force and electrostatic actuation. The nonlinear fringing field effect has been accounted for in the model. Using a Galerkin decomposition method and considering only one mode, the nonlinear boundary value problem describing the static behavior of nano-switch, is reduced to a nonlinear boundary value ordinary differential equation which is solved using the homotopy perturbation method (HPM). In order to ensure the precision of the results, the number of included terms in the perturbation expansion has been investigated. Results have been compared with numerical results and also with previously published analytical results. It was observed that HPM modifies the overestimation of N/MEMS instability limits reported in the literature and can be used as an effective and accurate design tool in the analysis of N/MEMS.
Cyclic Energy Loss of Honeycombs Under In-Plane Shear Loading
Authors: Ju Jaehyung , Summers Joshua D. , Ziegert John , Fadel George
Published: July 2010

In an effort to develop an elastomer-like material with low hysteretic energy loss associated with an energy efficient structural design, a cyclic energy loss model of honeycombs is investigated. In-plane viscoelastic constitutive relations of a honeycomb are developed based on honeycomb geometries and a base material’s viscoelastic properties. Using Prony series parameters for the stress-relaxation of a material, a numerical study on hysteretic energy dissipation is conducted for regular and auxetic honeycombs. Finite element (FE) simulation is carried out to validate the numerical study. Preferred cell geometries of honeycombs are also discussed in terms of minimizing the hysteretic energy loss.
Preliminary NVH Characterization of Metal Foam-Polymer Interpenetrating Phase Composites
Authors: Sharma Satish , Rayess Nassif E. , Dukhan Nihad
Published: July 2010

The damping and basic dynamic properties of a novel type of multifunctional hybrid material known as Metal Foam-Polymer Composite are investigated. This material is obtained by injection molding a thermoplastic polymer through an open cell Aluminum Foam, in essence creating two contiguous morphologies; an Aluminum Foam interconnected “skeleton” with the open pores filled with a similarly interconnected polymer substructure. This coexistence of both materials allows each to contribute its salient properties (e.g. the plastics contributing surface toughness and the metal foams contributing thermal stability). Basic damping testing results are presented for various Aluminum Foam porosities and pore sizes as well as for three types of polymers. A basic mathematical model of the damping is also presented. The integrity of the interface between the Aluminum Foam and the Polymer is discussed in terms of its effect on the overall material damping.
Transient Electrophoretic Motion of Charged Particles Through an L-Shaped Microchannel
Authors: Ai Ye , Park Seungkyung , Zhu Junjie , Xuan Xiangchun , Beskok Ali , Joo Sang W. , Qian Shizhi
Published: July 2010

Direct current dielectrophoretic (DC-DEP) effects on the electrophoretic motion of charged polystyrene particles through an L-shaped microchannel were experimentally and numerically studied. In addition to the electrostatic and hydrodynamic forces, particles experience a negative DC-DEP force arising from the interaction between the dielectric particle and the induced spatially non-uniform electric field occurring around the corner of the L-shape microchannel. The latter force causes a cross-stream DEP motion so that the particle trajectory is shifted towards the outer corner of the turn. A two-dimensional (2D) Lagrangian particle tracking model taking into account the induced DC-DEP effect was used to predict the particle trajectory shift through the L-shaped channel, which achieves quantitative agreement with the experimental data.
Pendulum Animal Impact Testing
Authors: Forrest Stephen , Sodusta John Paul , Herbst Brian , Meyer Steven E.
Published: July 2010

When vehicles collide with large animals, such as cattle, moose, elk or horses, the front seat occupants can be seriously or fatally injured; primarily due to roof deformation. In order to protect the front occupants in these accidents, it is necessary to understand the forces and energy involved in the interaction between the animal and the vehicle roof structure. The authors have developed a pendulum test incorporating an animal dummy to generate similar roof deformation to that experienced in real world animal impact accidents. The energy absorbed by the vehicle roof structure in the accident can then be determined by comparing the accident vehicle roof deformation to the pendulum test vehicle roof deformation. Ultimately, alternative roof structural designs are evaluated to demonstrate that a roof can perform well in this type of accident mode and reduce the risk for serious injuries to the occupants.
Asymptotic Expansion Homogenization Method for Carbon Fiber Composite Structures Reinforced With Carbon Nanotubes
Authors: Lagoudas Dimitris C. , Chatzigeorgiou George
Published: July 2010

The carbon nanotubes (CNTs) with their high mechanical, thermal and electrical properties have attracted the attention of the research community. The wide variety of possible applications of composite structures containing single-walled or multi-walled CNTs has grown the need for correct characterization and understanding of the behavior of such composite structures. The identification of effective properties of CNT composites has been studied extensively the last decade by many researchers.
Harvesting Vibration From Rotating Machinery as a Power Source for a Wireless Sensor Node
Authors: Salleh H. , Rashid N. M. , Wahib K. A.
Published: July 2010

The wireless sensor device which uses battery can cause problems when the wireless nodes are large in number and when the nodes are placed in the difficult area to access. Therefore, it is advantageous for the sensor node to be capable of extracting energy from the environment, making it self-powered, self-sustaining and lowering overall cost of the wireless network. Improvement in integrated circuit (IC) technology has made the overall power consumption of circuit very small which leads to a very promising application of the vibration-based energy harvester micro power generator (VEHM). This paper discusses on some practical design considerations in harvesting vibration from rotating machinery to power up a wireless sensor node. It also focuses on the effect of shape of the VEHM on its power output. These parameters are actually important as part of the key design parameters in harvesting the vibration from ambient. The energy harvester is made of piezoelectric bimorph bender materials poling in series to transform ambient vibrations into electrical energy. The power output for the VEHM made of single and multiple array of PZT bimorph bender are investigated and the effect of triangular and the rectangular PZT bimorph bender are compared. Two sets of VEHM device have been tested to work in the range of 50 Hz–110 Hz to power up a wireless sensor node for condition monitoring application. The experimental results are presented and compared to the previous similar work. It is found that the triangular shape bender generates more power compared to rectangular form whether it is single or multiple connected in series. Testing results proved that triangular VEHM of the same volume and fundamental frequency when compared to rectangular VEHM can improve the overall power generated by the generator.
Fatigue Behavior of Magnesium AZ31 in Friction Stir Spot Welds
Authors: Jordon J. B. , Horstemeyer M. F. , Badarinarayan H. , Grantham J.
Published: July 2010

In this study, the fatigue behavior of AZ31 magnesium friction stir spot welded joints is experimentally investigated. The friction stir spot welds employed here are representative of preliminary welds made in developing the joining process for potential use in automobile manufacturing. Load control cyclic tests were conducted on single weld lap-shear coupons and were fatigued until failure to determine stress-life properties. The fractured coupons were examined under optical and scanning electron microscopes with the intent to determine fatigue crack characteristics. Fractography analysis suggests that long crack growth accounts for a majority of the fatigue life. To predict the fatigue life of the lap-joint coupons, a long crack growth modeling approach, based on a kinked crack stress intensity solution, was employed. The fatigue model predictions compared well to the experimental stress-life results.
Application of Elastic Dispersion Relations to Estimate Thermal Properties of Nano-Scale Rods and Tubes of Varying Wall Thickness and Diameter
Authors: Bifano Michael F. , Kaul Pankaj B. , Prakash Vikas , Roy Ajit
Published: July 2010

This paper reports the dependency of specific heat and ballistic thermal conductance on geometry and size in freestanding isotropic non-metallic crystalline nanowires and nanotubes having varying wall thicknesses and outer diameters. The analysis is performed using real dispersion relations found by numerically solving the Pochhammer-Chree frequency equation of a tube. The frequency equation is derived from the 3D cylindrical elastic wave model with stress free boundary conditions on both the inner and outer wall surfaces. Dimensional dependencies are distinctly noticeable and vary with specimen geometry and temperature. Trends in dimensional transition points are seen by varying the ratio of inner to outer nanotube radius (γ) for a 5 nm fixed outer diameter. With increasing γ, heat capacity and ballistic thermal conductance is shown to collapse onto that of a solid nanowire. Additionally, thermal properties of thick-walled nanotubes (γ = 0.5) having diameters of 5 nm, 10 nm, 15 nm, and 20 nm, are also investigated in this study. Increasing the diameter of a nanotube with a fixed γ is shown to have a similar mechanistic effect as fixing the outer diameter and thinning the tube wall.
Radiation Heat Transfer Environment in Fire and Furnace Tests of Radioactive Materials Packages
Authors: Smith Allen C.
Published: July 2010

The Hypothetical Accident Conditions (HAC) sequential tests of radioactive materials (RAM) packages includes a thermal test to confirm the ability of the package to withstand a transportation fire event. The test specified by the regulations (10 CFR 71) consists of a 30 minute, all engulfing, hydrocarbon fuel fire, with an average flame temperature of at least 800°C. The requirements specify an average emissivity for the fire of at least 0.9, which implies an essentially black radiation environment. Alternate tests which provide equivalent total heat input at the 800°C time averaged environmental temperature may also be employed. When alternate tests methods are employed, such as furnace or gaseous fuel fires, the equivalence of the radiation environment may require justification. The effects of furnace and open confinement fire environments are compared with the regulatory fire environment, including the effects of gases resulting from decomposition of package overpack materials. The results indicate that furnace tests can produce the required radiation heat transfer environment, i.e., equivalent to the postulated pool fire. An open enclosure, with transparent (low emissivity) fire does not produce an equivalent radiation environment.
The Spanwise Dependence of Vortex-Shedding From Yawed Circular Cylinders
Authors: Hogan James D. , Hall Joseph W.
Published: July 2010

Simultaneous measurements of the fluctuating wall pressure along the cylinder span were used to examine the spanwise characteristics of the vortex-shedding for yaw angles varying from α = 60° to α = 90°. The Reynolds number based upon the diameter of the cylinder was 56,100. The results indicate that yawing the cylinder to the mean flow direction causes the vortex-shedding in the wake to become more disorderly. This disorder is initiated at the upstream end of the cylinder and results in a rapid decrease in correlation length, from 3.3D for α = 90° to 1.1D for α = 60°. The commonly used independence principle was shown to predict the vortex-shedding frequency reasonably well along the entire cylinder span for α > 70°, but did not work as well for α = 60°.
Influence of Imperfections on the Collapse of Thick Tubes Subjected to External Pressure
Authors: Di Marcello Valentino
Published: July 2010

Cylindrical shells pressurized from outside are required for several engineering applications, and a growing need of tubes with significant thickness has been recently experienced in the oil industry (very deep water pipelines) and in the frame of integrated primary system nuclear reactors (steam generators). Their collapse behaviour has been explored little if at all, both experimentally and numerically, as witnessed by the extremely conservative attitude that codes assume for very thick tubes. A numerical investigation has been performed in this context at the Politecnico di Milano, which was originally intended as a support for requesting a relaxation of ASME regulations. In fact, in 2007 Code Case N-759 [1] was approved, permitting significant thickness saving in the tube design. Nevertheless, the numerical investigation was pursued to assess the influence of different parameters, such as eccentricity, initial stresses and material hardening, on the collapse of tubes with diameter to thickness ratios D/t<20. Results are thought to be useful under at least two respects: first, they provide some understanding on the collapse behaviour in a thickness range so far unexplored; secondly, they give an indication on the assumptions on which computer codes ought to be based when numerical analyses are required.
Azimuthal Behaviour of Self-Excited Diametral Modes of Internal Cavities
Authors: Aly K. , Ziada S.
Published: July 2010

The aerodynamic excitation of ducted cavity diametral modes, which are inherently antisymmetric acoustic modes, by the oscillation of the axisymmetric free shear layer gives rise to complex flow-sound interaction mechanisms, in which the acoustic diametral modes do not possess a preferred azimuthal orientation. The azimuthal behaviour of this self-excitation mechanism is investigated experimentally. The study is performed for axisymmetric shallow cavities in a duct for a range of cavity length to depth ratio of L/d = 1 to 4, and for Mach numbers up to 0.4. Three pressure transducers flush mounted to the cavity floor are used to determine the acoustic mode amplitude and orientation. The excited acoustic modes are classified into spinning, partially spinning and stationary diametral modes. An analytical model based on the superposition of two orthogonal modes with 90° temporal phase shift is developed to reproduce the spinning and the partially spinning diametral modes. The developed model clarifies the observed complex behaviour of the azimuthal modes.
Security in the Transport of Radioactive Materials
Authors: Pope Ronald B. , Rawl Richard R.
Published: July 2010

The United States Department of Energy National Nuclear Security Administration’s (DOE/NNSA) Global Threat Reduction Initiative (GTRI), the International Atomic Energy Agency (IAEA) and active IAEA Donor States are working together to strengthen the security of nuclear and radioactive materials during transport to mitigate the risks of theft, diversion, or sabotage. International activities have included preparing and publishing the new IAEA guidance document Security in the Transport of Radioactive Material while ensuring that security recommendations do not conflict with requirements for safety during transport, and developing and providing training programs to assist other countries in implementing radioactive material transport security programs. This paper provides a brief update on the status of these transportation security efforts.
Presentation of RCC-MR Code 2007 for High Temperature Reactor and ITER Projects: General Overview
Authors: Marie S. , Drubay B. , Berton M. N. , Gelineau O. , Escaravage C. , Bonne D. , Sperandio M.
Published: July 2010

The fourth edition of the RCC-MR code has been issued in French and English versions on October 2007 by AFCEN (Association Franc¸aise pour les re`gles de Conception et de Construction des Mate´riels des Chaudie`res Electro-nucle´aires). It is the result of an important work by Areva NP, EDF and CEA to develop and improve design and construction rules of the previous edition. This paper presents the code evolution from the 2002 edition of the RCC-MR code, such as: - Adaptation of the code to the European standardization, making use of the Harmonized European Standards. - Improvement of the creep-fatigue rules for shells and pipes. - Improvement of the Leak-Before-Break procedure and related defect assessment tools. - Enlargement of the scope of the code to be applicable not only to high temperature structures but also to the ITER vacuum vessel, with in particular the development of the “class 2 box” and a specific appendix dealing with specific fabrication requirements of the ITER vacuum vessel. - Extension of the scope of subsections devoted to bolts. - Development of the chapter on laser welding. - Introduction of requirements in line with the new European Pressure Equipment decree and its French declination to nuclear equipment (ESPN) which is mandatory for a French site construction.
General Rule of Method for Measurement of Thickness and Crack Size by Electric Potential Drop Technique: Outline of the NDIS3426:2008
Authors: Ju Yang , Hamada Seiichi
Published: July 2010

The Japanese Society for Non-Destructive Inspection (JSNDI) published general rule of method for measurement of thickness and crack size by Electric Potential Drop Technique as the Standard of JSNDI (NDIS3426) in January, 2008. NDIS3426 was established based on the researches for many years including the round robin tests conducted as the academic activities in JSNDI, and the previous technical guideline and standard ASTM E-647-05 ANNEX A6 and BS ISO 12108:2002 established for the measurement of fatigue crack growth in specimens. In this paper, the outline and the background of NDIS3426 was described. The electric potential drop technique is one of the promising methods to monitor or measure the thickness and crack size for the practical use in many industries. For the inspection of the surface deep fatigue crack in the steam turbine casing, the advanced crack depth indicator based on the potential drop technique has been applied. For the monitoring the creep damage accumulated in the seam-welded power piping, the commercialized tool based on the pulsed direct current potential drop technique has been used. For the pipe wall thinning measurement in the operating thermal power plant, the pulsed direct current potential drop technique was applied. This paper shows the present condition of the practical use and the future prospect of the potential drop technique.
A New Approach of Reliability Design for Creep Rupture Property
Authors: Zhao Jie , Li Dong-ming , Fang Yuan-yuan , Zhu Shi-jie
Published: July 2010

It has been noted that the use of safety coefficient can deal with uncertainties existed in practical structures, while reliability concept provides more precise results by considering the real distribution of creep rupture property. Generally, creep rupture data of a heat-resistant steel can be compressed into a narrow band by using a temperature-time parametric method such as Larson-Miller or Manson-Haferd method. In order to describe the scattering of the data, the current paper proposes a “Z parameter” method to represent the magnitude of the deviation of the rupture data to master curve. Statistical analysis shows that the scattering of Z parameter for several types of steels is supported by normal distribution. Using this method, it is possible to achieve unified analysis of the creep rupture data in various temperature and stress conditions. Stress-TTP-Reliability curves (σ-TTP-R curves), Stress-Rupture time-Reliability curves (σ-tr-R curves) and Allowable stress-Temperature-Reliability curves ([σ]-T-R curves) are proposed which could embrace reliability concept into creep rupture property design.
Local Stress Variations at Bead Interruptions in Austenitic Multi-Pass Groove Welds
Authors: Gill Christopher M. , Hurrell Paul , Francis John , Turski Mark
Published: July 2010

This paper presents finite element analyses of residual stress in an austenitic multi-pass groove weld. The aim was to establish the effect upon the residual stress of stop-start interruptions during the deposition of weld beads. Comparison of measured residual stress profiles with the residual stress distributions predicted by finite element (FE) modelling aimed to validate the FE method for predicting residual stresses around stop-start features. This paper presents a comparison of measured and modelled residual stress distributions in a series of simple welded 304 stainless steel plates. The plates were machined with a v-groove designed to be filled using eight weld passes. Samples which included interrupted weld beads contained two stop-start features in the fifth pass. In the first feature the welding power was ramped down over 15 seconds; this represented normal welding good practice. The second feature investigated was an abrupt stop, where the welding power was removed instantaneously; this represented an extreme stop. Three welded plates were considered. One contained five weld passes, such that the final pass contained stop-start features and resulted in partially filling the weld groove. Two welds plates each containing eight passes have also been considered; one contained stop-start features in the fifth pass and the other contained no stop-start features. This allowed a comparison of the effect of stop-start features and the effect that subsequent beads have upon any perturbations in the residual stresses produced. Residual stress measurements have been performed using neutron diffraction. 3D weld modelling has been carried out using VFT and the Abaqus finite element package. Results from the welding FE analyses were compared with the neutron diffraction measurements. Good agreement between the modelled and measured residual stresses is achieved in the uninterrupted 8-pass sample and after deposition of the bead containing stop-start features in the 5-pass sample. Following deposition of subseqeunt beads perturbations in the residual stress profile are retained in the neutron diffraction measurements, but all perturbations are removed from the residual stress profiles predicted using both VFT and Sysweld. This work suggests that modelling welding stop-start features is only necessary in the final weld capping passes, if residual stresses over a short length scale are of interest.
Optimisation of Mixed Hardening Material Constitutive Models for Weld Residual Stress Simulation Using the NeT Task Group 1 Single Bead on Plate Benchmark Problem
Authors: Smith Michael C. , Nadri Brahim , Smith Ann C. , Carr David G. , Bendeich Philip J. , Edwards Lyndon E.
Published: July 2010

A single weld bead deposited on a flat plate is a deceptively simple problem that is in practice a challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in an extensive programme of measurement and simulation extending from 2002 to 2008. As a result, the NeT bead on plate forms an ideal benchmark problem for the development of weld residual stress simulation techniques. One of the conclusions of NeT Task Group 1 is that the most accurate predictions of weld residual stresses in austenitic steels are achieved using mixed isotropic-kinematic material constitutive models. However, the use of these models can require both extensive materials data, and compromises in fitting either the monotonic or cyclic responses. This paper reports a detailed matrix of sensitivity studies aimed at optimising the behaviour of mixed hardening models in welding simulation, using the Lemaitre-Chaboche formulation in the ABAQUS finite element code. Predicted stresses and strains in the NeT bead on plate specimen are compared with the extensive database of residual stress measurements. Further studies examine sensitivity to the handling of high temperature inelastic strains, using a novel two-stage annealing functionality implemented within ABAQUS. The results show that, overall, the most accurate predictions are made if the Lemaitre-Chaboche parameters are optimised to fit the monotonic response over the first 2% of plastic strain. However, further improvements in prediction could be achieved if the constitutive model were capable of independently fitting both the monotonic and saturated cyclic response of the material.
Cold Bending of Advanced Ferritic Steels: ASTM Grades T23, T91, T92
Authors: Cipolla Leonardo , Di Gianfrancesco Augusto , Caminada Stefano , Cumino Giuseppe
Published: July 2010

The metallurgical background of advanced ferritic steels must be considered during every stage of fabrication, including during forming operations, such as cold bending, because they can negatively affect the high temperature properties of the material if they are not performed properly. In this work, the results of a broad cold bending program carried out on ASTM Grades T23, T91 and T92 tubes are presented: the microstructure and the mechanical properties at extrados and intrados positions were investigated and compared with properties of unbent materials. Creep properties were assessed by means of specimens directly machined from extrados and intrados of real bends. This paper aims to integrate the International Codes for cold bending with recommendations for proper post bending heat treatments, in order to obtain a final component with the desired microstructure and mechanical properties, including optimum creep resistance.
Time Domain Models for Damping-Controlled Fluidelastic Instability Forces in Tubes With Loose Supports
Authors: Hassan Marwan , Hossen Achraf
Published: July 2010

This paper presents simulations of a loosely supported cantilever tube subjected to turbulence and fluidelastic instability forces. Several time-domain fluid force models simulating the damping controlled fluidelastic instability mechanism in tube arrays have been presented. These models include the negative damping model based on the Connors equation, fluid force coefficient-based models (Chen and Tanaka and Takahara), and two semi-analytical models (Price and Pai¨doussis; and Lever and Weaver). Time domain modelling and implementation challenges for each of these theories were discussed. For each model the flow velocity and the support clearance were varied. Special attention was paid to the tube/support interaction parameters that affect wear, such as impact forces and normal work rate. As the prediction of the linear threshold varies depending on the model utilized, the nonlinear response also differs. The investigated models exhibit similar response characteristics for the lift response. The greatest differences were seen in the prediction of the drag response, impact force level and normal work rate. Simulation results show that the Connors-based model consistently underestimates the response and the tube/support interaction parameters for the loose support case.
Through Wall Repairs Using the GTAW Ambient Temperature Temperbead Process
Authors: Newton Bruce
Published: July 2010

Ambient Temperature Temperbead welding employs the GTAW machine process, and avoids both the elevated temperature preheat and post-soak heating operations associated with conventional temperbead welding. ASME Code Case N-638-4 governs ambient temperature temperbead welding activities. N-638-4 currently limits the depth of an ambient temperature temperbead weld repair to 50% of the base material thickness. This restriction precludes use of the GTAW ambient temperature temperbead process for buttering of through wall repairs and replacements. This paper describes the ongoing ASME activity to revise N-638-4 to permit through-wall temperbead repairs. The methodology, Code text, applicable restrictions, and technical bases for this Code Case revision will be addressed.
The Influence of Geometric and Welding Parameters on Residual Stress in Thin Welded Steel Structures
Authors: Davies C. M. , Be´resˇ M. , Hughes D. , Dye D. , Nikbin K. M.
Published: July 2010

Residual stress distributions have been established on thin (4 mm thick) plates made from a ferritic steel designated grade DH-36, which is relevant to ship construction. The influence of welding speed (thus energy input) and stiffener dimensions on the residual stress distributions have been studied. The residual stresses in the vicinity of the welds have been measured using the neutron diffraction technique. Increasing the weld speed reduces the weld width and subsequently the width of the high tensile strain region in the vicinity of the butt weld. However, within the practicable limits examined, the weld speed has little effect on the overall stress distribution. It has also been found that the stiffener thickness has relatively little influence on the resultant residual stress distribution.
Experimental and Numerical Characterisation of the Cyclic Thermo-Mechanical Behaviour of a High Temperature Forming Tool Alloy
Authors: Deshpande Aditya , Leen Sean B. , Hyde Thomas H.
Published: July 2010

This paper describes high temperature cyclic and creep relaxation testing and modelling of a high nickel-chromium material (XN40F) for application to the life prediction of superplastic forming (SPF) tools. An experimental test programme to characterise the high temperature cyclic elastic-plastic-creep behaviour of the material over a range of temperatures between 20°C and 900°C is described. The objective of the material testing is the development of a high temperature material model for cyclic analyses and life prediction of superplastic forming (SPF) dies for SPF of titanium aerospace components. A two-layer visco-plasticity model which combines both creep and combined isotropic-kinematic plasticity is chosen to represent the material behaviour. The process of material constant identification for this model is presented and the predicted results are compared with the rate-dependent (isothermal) experimental results. The temperature-dependent material model is furthermore applied to simulative thermo-mechanical fatigue (TMF) tests, designed to represent the temperature and stress-strain cycling associated with the most damaging phase of the die cycle. The model is shown to give good correlation with the test data, thus vindicating future application of the material model in thermo-mechanical analyses of SPF dies, for distortion and life prediction.
Evaluation of Stress States of Components Using Ultrasonic and Micro Magnetic Techniques
Authors: Schneider E.
Published: July 2010

The paper describes the measuring and evaluation procedures of both techniques. The state of art is characterized by discussing experimental results of applications on e.g. turbine rotors, gear parts and welded plates and sheets. Comparisons with the results of established techniques show the reliability of the ultrasonic and micromagnetic techniques. The applicability as well as the limitations of the techniques will be commented in detail.
Buckling Characteristics of Floating Roof Pontoons in Aboveground Storage Tanks Subjected to Both Compressive and Bending Load
Authors: Yoshida Shoichi
Published: July 2010

The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Seven single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at a refinery in Tomakomai, Japan. The pontoons of the floating roofs might be buckled due to circumferential bending moment during the sloshing. The content in the tank was spilled on the floating roof from small failures which were caused in the welding joints of pontoon bottom plate by the buckling. Then the floating roof began to lose buoyancy and sank into the content slowly. The authors had reported the buckling strength of the pontoons subjected to circumferential bending load first and that of the pontoons subjected to both circumferential and radial bending load next in the previous papers. This paper presents the buckling strength of the pontoons subjected to both circumferential bending load and circumferential compressive load. The axisymmetric shell finite element method is used in the analysis. Linear elastic bifurcation buckling analysis is carried out and the buckling characteristics of the pontoon both with and without ring stiffeners are investigated.
Mechanical Properties Distribution in Welds and Forging of VVER-1000
Authors: Chernobaeva Anna A. , Shulgan Natalya A. , Shtrombakh Yaroslav I. , Titova Tatyana I. , Nikolaev Yury A. , Blinova Marina G.
Published: July 2010

Study of weld metal and shell metal of VVER-1000 reactor is carried out. Metal of the control welded joint performed to the welds Nos. 3 and 4 and metal of the test ring of supporting shell is used. For each of the analyzed materials the bending tests of Charpy specimens are carried out according to the surveillance specimens testing procedure. Fabrication of specimens and all the tests are performed by TK “OMZ Izhora”, ltd. Leadership of the tests and assessment of brittle-to-ductile transition temperature is performed by RRC “Kurchatov Institute”. It is shown that guaranteed values of brittle-to-ductile transition temperature (TK0) for VVER-1000 pressure vessel materials (0°C for weld and −25°C for base metal [1]) are the conservative estimation of TK values obtained for all groups of the tested specimens. However in some cases such estimation is super conservative. Assessment of distribution of brittle-to-ductile transition temperature (TK) values of the weld in radial direction has shown that TK varies from layer to layer in the range from −55 to −22°C. Variations of TK values are conceivably random and not connected with changes of the chemical composition of metal. It is shown that the situation is possible when brittle-to-ductile transition temperature of “inner grooving” weld metal is higher than that of the “outer grooving” weld metal. This result should be taken into account when planning the surveillance specimens programmes. Metal of “inner grooving” should be included in surveillance specimens. While assessing the TK values distribution in axial direction it has been determined that the maximum brittle-to-ductile transition temperature is specific for the area adjacent to the line of weld-to-base metal alloying. This effect is stably observed already at a distance of 8 mm from the alloying line. Study of distribution of TK values of supporting shell metal has shown that for the analyzed supporting shell the maximum brittle-to-ductile transition temperature value corresponds to the inner side of the shell middle third, the minimum value — to the shell inner surface. On the whole, shell metal is characterized by rather low values of brittle-to-ductile transition temperature.