bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Stress Development Associated With Hybridization of Monomolecular DNA Film
Authors: Kang Kyungho , Shrotriya Pranav
Published: July 2010

Surface stress changes associated with hybridization of surface immobilized DNA molecules are measured. A novel interferometry technique employing two adjacent micromachined cantilevers a sensing/reference pair is used to measure the surface stress development. Measurement approach relies on coating the sensing cantilever with single stranded DNA (30-mer Adenine (poly A)) and reference cantilever with hybridized DNA. The sensing/reference pair is exposed to varying concentrations of complimentary DNA strand (30-mer Thymine (Poly T)) and differential deflection of sensing cantilever with respect to reference is measured to determine the change in surface stress. Experimental results indicate that surface stress develops only on exposure to complimentary strands (specific binding) and is not affected by exposure to other single stranded DNA (non-specific binding). Varying the poly T concentration from 0.1 to 1.0 μM results in a linear increase of the surface stress changes from 40 to 110 mN/m during DNA hybridization. Surface stress development starts as soon as the complementary poly T is introduced in the fluid cell and reaches a stable value within 15 minutes of injection time.
Application of the Extended Kantorovich Method to the Vibrational Analysis of Electrically Actuated Microplates
Authors: Behzad Mahdi , Moeenfard Hamid , Ahmadian Mohammad Taghi
Published: July 2010

This paper presents an extended Kantorovich approach to investigate the vibrational behavior of electrically actuated rectangular microplates. The model accounts for the electric force of the excitation and for the applied in plane loads. Starting from a one term Galerkin approximation and following the extended Kantorovich procedure, the partial differential equation governing the microplate vibration, is discretized to two ordinary differential equation with constant coefficients. These equations are then solved analytically and iteratively with a rapid convergence procedure for finding microplate natural frequencies and modeshapes. Results in some specific cases are validated against other theoretical results reported in the literature. It is shown that rapid convergence, high precision and independency of initial guess function make the EKM an effective and accurate design tool for design optimization.
Electrical Properties of Nanocomposite Fibers Under Various Loads and Temperatures
Authors: Khan W. , Asmatulu R. , El-Tabey M. M. , Ho J. , Hamdeh H.
Published: July 2010

Multi-wall carbon nanotube (MWCNT) based nanocomposite fibers were fabricated using electrospinning method, and their electrical properties were investigated under various loads and temperatures. MWCNTs were initially dispersed into polyvinylpyrrolidone (PVP) and electrospun at various spinning conditions, including DC voltage, pump speed, concentration and distance. When the mechanical load was applied to a film of PVP nanocomposite fibers, the contact resistance, separation between sites and jumping distance of the charge carriers were gradually reduced, thus likely enhancing the electrical conduction. Additionally, as the temperature increased from 20 to 90 °C, the electrical resistance drastically decreased. These behaviors may be a consequence of conductivity and polarization effects of the nanoscale inclusions in the fibers.
Shock Optimization in a Military Vehicle With Internal Space Frame
Authors: Thota Jagadeep , Trabia Mohamed B. , O’Toole Brendan J.
Published: July 2010

Space frames are usually used to enhance structural strength of the vehicle while reducing its overall mass. These frames are comprised of beams that are joined together. Recently, space frames are being incorporated in military vehicles. Space frames in military vehicles are however subjected to different types of loading than what is encountered in civilian vehicles such as projectile impacts and land mine blasts. Due to the need to replace a damaged section of the space frame quickly, the proposed space frame is composed of hollow square cross-section bars and angle sections that are bolted together. The space frame is enclosed by uniform-thickness armor, except at the turret. The vehicle is subjected to high impact load to simulate a projectile hit. The objective of this work is to minimize shocks at various critical locations of the space frame while maintaining the overall structural integrity of the vehicle. The vehicle model is parameterized to achieve this objective. This problem is solved using the Successive Heuristic Quadratic Approximation (SHQA) technique, which combines successive quadratic approximation with an adaptive random search within varying search space. The entire optimization process is carried out within MATLAB environment.
On the Frequency Domain Analysis of Tire Relaxation Effects on Transient On-Center Vehicle Handling Performance
Authors: Sill Justin , Ayalew Beshah
Published: July 2010

This paper presents an elegant frequency domain approach that can be used to analyze lateral vehicle dynamics for transient understeer and oversteer performance. Commonly used steady-state understeer analysis techniques are not able to expose some effects, such as tire relaxation, in on-center transient maneuvers. The approach presented here addresses such transient issues using a simple two degree of freedom handling model coupled to a model for tire lateral dynamics. In addition to the usual yaw rate and lateral acceleration transfer functions, this paper proposes using an understeer angle transfer function as an easy-to-interpret metric to evaluate transient on-center handling. Using the approach, it is shown that at low vehicle velocities, the inclusion of tire relaxation introduces dramatically different system dynamics by introducing highly undamped poles into the coupled system for both an understeering and an oversteering vehicle.
Nonlinear Elastic Constitutive Relations of Auxetic Honeycombs
Authors: Ju Jaehyung , Summers Joshua D. , Ziegert John , Fadel Georges
Published: July 2010

When designing a flexible structure consisting of cellular materials, it is important to find the maximum effective strain of the cellular material resulting from the deformed cellular geometry and not leading to local cell wall failure. In this paper, a finite in-plane shear deformation of auxtic honeycombs having effective negative Poisson’s ratio is investigated over the base material’s elastic range. An analytical model of the inplane plastic failure of the cell walls is refined with finite element (FE) micromechanical analysis using periodic boundary conditions. A nonlinear constitutive relation of honeycombs is obtained from the FE micromechanics simulation and is used to define the coefficients of a hyperelastic strain energy function. Auxetic honeycombs show high shear flexibility without a severe geometric nonlinearity when compared to their regular counterparts.
Design and Modelling of a MEMS Capacitive Temperature Sensor With Linear Capacitance-Temperature Response
Authors: Shavezipur Mohammad , Wong Chris , Nieva Patricia , Khajepour Amir
Published: July 2010

A capacitive temperature sensor with separate thermal actuation and capacitive readout is introduced. A bi-layer plate with fixed-free boundary condition is used for the thermal actuation to change the gap between two parallel electrodes used for capacitance measurement. Different coefficients of thermal expansion (CTE) of the two layers in actuator cause out-of-plane deformations in the plate when the temperature changes. The proposed design has the capability to control the response of the sensor by increasing its sensitivity in a given temperature range. To obtain the desired characteristic C-T curve, the design utilizes asymmetric geometries. Different design parameters such as the size of the bi-layer plate and the sense electrodes are considered as design variables. ANSYS® FEM simulations are used to extract the C-T responses of different geometries. The results of the FEM simulations show that for a given fabrication process and material properties, the design can be modified to provide the highest sensitivity and linearity in the C-T response for a given temperature range. This temperature sensor can be used for remote and on-chip temperature measurement or temperature compensation.
Cost and Schedule Estimate: Risk Analysis for Transportation Infrastructures
Authors: Cretu Ovidiu S.
Published: July 2010

This paper presents the Risk-Based Estimate Self-Modeling (RBES) which eliminates the need of specialized software by allowing a regular excel user to develop an integrated cost and schedule estimate with limited knowledge of risk analysis. The RBES has the flexibility of entering: • The baseline project cost and schedule along with the different degrees of uncertainty associated with them. • Simple independent risks with their cost and duration components. • Complex risks which are dependent of each other and/or correlated. The RBES integrates project cost and schedule when the project delivery goes as planned with up to 24 risks events. Each risk may have two components (cost, and schedule) and the RBES may compute the effect of risk dependency and risk correlation with respect to project cost and schedule. The outcome of the RBES consists of graphs and tables that present the project cost in current year dollars, and year of expenditure dollars plus the advertisement date, and the end construction date. Additionally, the RBES generates the following summary information: A tornado diagram of the most significant cost and schedule risks, A risk matrix for each of the 24 risks; and a risk map in order to help the management to quickly assess all project risks so that they may initiate the appropriate risk response actions.
Understanding Release Kinetics of Calcium Alginate Microcapsules Using Drop on Demand Inkjet Printing
Authors: Perkins Jessica L. , Desai Salil , Harrison Benjamin , Sankar Jagannathan
Published: July 2010

This paper investigates the use of calcium alginate microcapsules to transport biomaterials for drug delivery. Rhodamine 6G dye was encapsulated in microcapsules for different formulations of the hydrogels using drop-on-demand printing. An experimental design was constructed to compare the effect of different concentrations of calcium chloride (M) and sodium alginate (% w/v) solutions in addition to the microcapsule diameter on the release kinetics profiles of the microcapsules. The results of these findings provide a basis to identify favorable sizes of microcapsules and concentrations of sodium alginate and calcium chloride solutions for controlled release behavior of microcapsules.
Study of Damping Effect of Grass Like Crops
Authors: Doranga Sushil , Zhou Jiang , Yang Yubing
Published: July 2010

The objective of this study was to quantify the dynamic response of the living grass-like crops structure under free and forced vibration. The living grass-like crops may become the key component in a new technology which extract and make use of unwanted energy associated with structural vibration. The proposed procedure is firstly illustrated with a simulated example of the simple pendulum configuration with the tray holding the grass. Output of the vibrating grass is measured through frequency analyzer (FFT Analyzer). The relative decay of the amplitude of vibration is used to measure the damping effect of grass. Secondly, forced vibration effect is studied by designing the slider crank mechanism over a frequency range from 0.7 to 1.7Hz. Resonant effect is studied. The difference in the acceleration, velocity, and displacement between the vibration tray loaded with the crop and the tray without the crop for the same power input will measure the vibration suppression capabilities of grass-like crops. The result of the experiments quantifies this damping effect and extrapolates the data to estimate the effects of a crop-based life support system on a spacecraft.
Research and Application of Virtual Reality and Simulation Techniques Corporately to Tower Crane
Authors: Meng Xian-yi
Published: July 2010

A method using virtual reality and finite element techniques corporately for simulation of tower crane is presented. A training and safety assessment system based on the method is created, which can be used for training operators and assessing the structural safety for a tower crane. The system can help the enterprises using tower crane reduce the training cost and work risk. Virtual reality software Virtools and finite element analysis software ANSYS are corporately used to construct the system.
Comparison of Tooling Materials in Injection Molding of Microscale Features
Authors: Yoon Sung-Hwan , Palanisamy Prabhu , Padmanabha Purushotham , Mead Joey L. , Barry Carol M. F.
Published: July 2010

Although high aspect ratio micro and nanoscale polymer features have been replicated in a range of polymers using injection molding, researchers have also used tooling inserts with a range of sizes, aspect ratios, and tooling materials. In this work, microscale features with molded in polymethylmethacrylates using three types of tooling with similar features. The tooling materials included silicon wafers with an antistiction coating, gold-coated nickel inserts, and a metal-polymer hybrid tooling. Tooling was evaluated based on the ease of melt filling and part ejection; the replication quality as characterized using optical profilometry, confocal microscopy, and scanning electron microscopy; and the damage to the tooling after repeated use. With lower aspect ratio features, the tooling type did not significantly affect replication, but for higher aspect ratio features the hybrid tooling provided far better replication than the silicon tooling. This difference was attributed to retardation of heat transfer in the features of the hybrid tooling. All three tooling materials exhibited polymer-free surfaces after injection molding.
Applications of Abrasive-Waterjets for Machining Fatigue-Critical Aerospace Aluminum Parts
Authors: Liu H.-T. , Hovanski Y. , Dahl M. E. , Zeng J.
Published: July 2010

Current specifications require AWJ-cut aluminum parts for fatigue critical aerospace structures to go through subsequent processing due to concerns of degradation in fatigue performance. The requirement of secondary process for AWJ-machined parts greatly negates the cost effectiveness of waterjet technology. Some cost savings are envisioned if it can be shown that AWJ net cut parts have comparable durability properties as those conventionally machined. To revisit and upgrade the specifications for AWJ machining of aircraft aluminum, “Dog-bone” specimens, with and without secondary processes, were prepared for independent fatigue tests at Boeing and Pacific Northwest National Laboratory (PNNL). Test results show that the fatigue life is proportional to quality levels of machined edges or inversely proportional to the surface roughness Ra. Even at highest quality level, the average fatigue life of AWJ-machined parts is about 30% shorter than those of conventionally machined counterparts. Between two secondary processes, dry-grit blasting with aluminum oxide abrasives until the striation is removed visually yields excellent result. It actually prolongs the fatigue life of parts at least three times higher than that achievable with conventional machining. Dry-grit blasting is relatively simple and inexpensive to administrate and, equally important, alleviates the concerns of garnet embedment.
Reporting on Plant Condition: The Big Picture
Authors: Gryl Quentin D. , Frith Robert H.
Published: July 2010

As industrial plant ages, site management are faced with the decision of whether to replace or refurbish equipment. In many instances the continual exposure to the plant will give maintenance staff and operators an instinctive feel which items of plant are candidates for replacement, refurbishment or overhaul. This “instinct” is not auditable and certainly not in a form presentable to the decision makers. This paper presents a methodology that quantifies the decision on whether to replace or refurbish and in doing so, provides a means for introducing traceability and repeatability into the decision process. In the “KOF” analysis, the acronym for “Keep or Flick”, developed in this paper, four core considerations are treated: the current condition of the plant; the hazard that the equipment presents to the plant and its personnel; the relevancy of the design with respect to current technologies and; the adequacy of the equipment for production and process requirements. Questions targeting each core consideration are weighted by an importance factor to give a quantitative ranking of a piece of equipment. The ranking provides clear appraisal on which equipment are suited for replacement and which are not. Those that fall in between need to be subject to a more rigorous assessment. This paper presents the methodology and reviews the approach as applied to a large segment of aging plant. The outcome was well accepted and has potential to be applied more widely to all varieties of equipment.
DHC Initiation at a Blunt Flaw: The Effect of Flaw Profile
Authors: Smith Edwin
Published: July 2010

Delayed Hydride Cracking (DHC) in Zr-2.5Nb alloy material is of interest to the CANDU (Canada Deuterium Uranium) industry in the context of the potential to initiate DHC at a blunt flaw in a CANDU reactor pressure tube. Modelling and experimental programmes have led to the development of a flaw evaluation procedure that is based on the process-zone methodology, and which has been incorporated into a Canadian Standards Association (CSA) Standard N285.8 for evaluation of fitness-for-service of Zr-2.5Nb pressure tubes. A key feature of the procedure is the importance that has been given to the effect of flaw profile, and in particular the effect of flaw root radius, which implicitly assumes that the flaw root profile is locally parabolic. It is against this background that the paper highlights the characteristics of smooth bottomed flaws that do not have a locally parabolic root profile. Such flaws, even though they are smooth bottomed can have a zero root radius of curvature, according to the accepted mathematical formula for root radius. The paper is a preliminary attempt at discussing the behaviour of non-parabolic root profile flaws, which clearly more closely resemble service flaws than parabolic root profile flaws, in view of their generality. It emphasises the desirability of linking the non-parabolic and parabolic flaw behaviours, so that, when evaluating a flaw found during service, advantage can be taken of the results from the parabolic flaw modelling and experimental programmes.
Taylor Cylinder Testing of High Strength Steels for Hard Target Warhead Applications
Authors: Russo Rachel , Dutton Nicholas , Baker Bart , Torres Karen , Jones Stanley E. , Brewster Richard A.
Published: July 2010

A one-dimensional analysis of the Taylor impact test [4] has been used to estimate the quasi-static stress for several different alloys. One criticism of this work was the use of Taylor cylinder test data to estimate the quasi-static true stress/true strain compression diagram. The one-dimensional theory does accommodate this estimate. The purpose of this paper is to demonstrate that this process leads to acceptable results by analyzing a series of high, medium, and low strength materials.
Understanding and Predicting Weldment Fatigue in Structural Nuclear Supports
Authors: Massingham Matthew , Gibson Robert
Published: July 2010

A critical and detailed review of current knowledge in the field of weldment fatigue has been performed; this review covers the assessment procedures and also the foundations upon which those procedures are based. This review is part of a body of research to support the design of nuclear pressure vessel mounting; the output of which will be a weldment fatigue assessment procedure for application to structural steelwork. The engineering background upon which established codes, such as BS7608, are based will be presented. Historical thinking in this field will be covered, inclusive of the results of recent work. Areas considered during the review include; material properties, post weld treatment, loading regime, variable amplitude loading and assessment procedures. Rolls-Royce is also currently performing testing of samples to tackle issues identified within this review, which will be discussed. Alongside the testing programme, Rolls-Royce is undertaking a numerical assessment of weldment fatigue life prediction tools, both global and local. These tools are being assessed for their consistency, robustness and accuracy. A proportion of the results from this work will also be presented.
Inverse Analysis of Thermal States From Transient Histories With Nonlinear Thermophysical Properties
Authors: Engels D. , Segall A. E. , Drapaca C.
Published: July 2010

When thermal-shock is an issue, the underlying thermal states are often difficult to determine because the boundary conditions must be known. The solution is to use an inverse approach where the boundary conditions are determined from remote data. Unfortunately, the inverse path is inherently ill-posed and therefore sensitive to errors. Moreover, many inverse models are limited to only constant thermophysical properties. Fortunately, generalized solutions based on measured temperature histories can be used to determine the underlying thermal excitation via a least-squares determination of coefficients, even with temperature dependent properties. With this in mind, two situations were studied, namely were the thermal conductivity/diffusivity had either a increasing or decreasing temperature dependence that could be described by a cubic polynomial. In each case, temperatures were determined at a remote location from a finite element simulation with the inverse prediction showing excellent agreement with the prescribed surface temperature. The derived solutions appear to be well suited for many thermal scenarios provided the analysis is restricted to the time interval used to determine the polynomial.
Overview of Vibro-Impact Dynamics of Pipes Conveying Fluids and the Problem of Fluid-Elastic Instability
Authors: Ibrahim Raouf A.
Published: July 2010

This paper presents an overview of vibro-impact dynamics of pipes conveying fluid and the fluid-elastic instability under conditions of turbulence and nonlinearities in nuclear power plants. Different types of modeling, dynamic analysis and stability regimes of pipes conveying fluid restrained by elastic or inelastic barriers are described. The main results reported in the literature will be discussed. The sources of discrepancies in the results will be identified. The main source is primarily the inaccuracy of analytical modeling of the pipe dynamics and impact interaction. The occurrence of flow-induced vibration fretting wear in process equipment such as heat exchangers and steam generators accounts for the majority of failures due to vibration. The fretting wear problem will be first described. This is followed by discussing the computational algorithms used to predict some aspects of vibro-impact dynamics such as the fluid-elastic instability of a tube array by cross flow. Fretting wear prediction requires nonlinear computations of the tube dynamics in which proper modeling of the fluid forcing function plays an important role. Some experimental results pertaining to the vibro-impact motion due to tube-support gaps are discussed with an emphasis on the remote identification of impact forces.
Long Term Behaviour of Stuffing Box Packings Under the Influence of Fluids at High Temperature
Authors: Kockelmann Hans , Bartonicek Jaroslav , Roos Eberhard , Hahn Rolf , Ottens Werner
Published: July 2010

Testing techniques were developed to investigate the long-term behaviour of stuffing box packings under real service conditions. This equipment meets all requirements for the simulation of high temperature applications with gaseous fluids, hot water and steam: • controlled pre-tightening (gland load); • variation of the stiffness of the assembly (e.g. Bellville springs); • determination and monitoring of packing stress - respective gland load; • control of stroke and stem force; • heating-up, pressurization and temperature control; • conditioning of water and steam chemistry. All relevant influencing parameters on the long-term behaviour of varied stuffing box packings based on flexible Graphite, woven PTFE fibres and special packing designs were taken into consideration: • assembly procedure (packing stress); • stroke and number of cycles; • effect of Bellville springs; • medium and temperature. In detail, friction, relaxation and leakage tests were carried out. On the basis of these results an evaluation of the long-term performance of the different packing types based on Graphite and PTFE is possible.
Leakage Detection Problems on Bottom Tubesheets of Vertically Positioned HP Exchangers: An Experience With a Urea Stripper
Authors: Fateh Pervez , Hussain Muhammad , Akhtar Omer
Published: July 2010

The exchanger under consideration is a bimetallic urea stripper, a high pressure heat exchanger used for stripping urea from carbamate solution at urea fertilizer plants. Its typical orientation with respect to ground is vertical, medium pressure steam being used as the shell side fluid. The paper provides an account of problems related to detecting tube leakage(s) at the bottom tube sheet of a urea stripper, primarily because of its positioning and presence of shell side condensate. This caused water to be retained in the tube to tubesheet annular spaces, hence forming a water seal and creating a barrier for the pressurization gas preventing it to pass through the leakage path towards the tube side. In order to save valuable time during a plant shutdown, a new technique of carrying out a helium-ammonia leak test was indigenously developed, tested and applied. However, despite the application of well developed and time-tested techniques of helium and ammonia testing, leakage location could not be ascertained and the tests remained largely inconclusive causing unnecessary delay and anxiety. The only real clue during inspection was a few droplets emerging from one of the tubes and the health of remaining 2387 tubes could not be reliably established. The paper opens with a brief discussion outlining the urea synthesis process along with the technical data specific to the urea stripper under discussion. The focus of the paper, however, remains at sharing with the reader; problems experienced during its leak testing and further recommend possible measures to tackle these problems in order to achieve improved testing effectiveness.
Optimization of Environmental Fatigue Evaluation: Step 2
Authors: Nomura Yuichirou , Tsutsumi Kazuya , Inoue Toshihide , Asada Seiji , Nakamura Takao
Published: July 2010

In order to introduce environmental effects into fatigue evaluation of design and construction codes, the environmental fatigue evaluation method should not only be established, but the conservativeness of the codes, design transient conditions and so on should also be reviewed. The former paper [1] presented in 2007 ASME Pressure Vessels and Piping Conference reviewed and discussed design factors of design fatigue curves, design transient conditions, stress analysis techniques and environmental fatigue evaluation methods. In this paper, rationalization of typical design transient conditions is discussed and design factors of a design fatigue curve for austenitic steels are studied. Rationalized numbers and/or conditions are proposed for the typical design transients that are dominant for fatigue evaluation. A mean fatigue curve of austenitic steels is analyzed by using a statistical method with the latest data. The design factors of the fatigue curve of austenitic steels are investigated for parameters decreasing fatigue life such as size effect, surface finish and data scatter and appropriate design factors are proposed. Future studies are discussed.
Calculating Thermal Gradients in a B31.1 Welding End Transition Joint by Formulae
Authors: Creates David H.
Published: July 2010

Fatigue evaluation in B31.1 is currently done based on Equation 1 & 2 [B31.1-2007] which considers only displacement load ranges. However, fatigue damage, in addition to displacement load ranges, is occurring in B31.1 piping due to pressure cycling and thermal gradients. To exacerbate this, power plant design pressures and temperatures are rising, new materials are being introduced, pipes and attached components are becoming increasingly thick, and owners are requiring power plants to heat-up and cool-down at faster rates. Also, power plant owners are more and more interested in extending the life of power plants beyond their original design life. This paper takes the first step in addressing the pressing need to address this additional fatigue damage by considering thermal gradients. Granted there are several configurations where thermal gradients could be calculated. As the first step, this paper provides formulae to quantify the thermal gradients in the prevalent B31.1 Welding End Transitions Fig. 127.4.2, or Tapered Transition Joints (TTJ) Appendix D [B31.1-2007] which produce bending loads in the pipe around the full circumference and add to the fatigue damage of these welded joints. The disadvantage of this approach is that the conservatisms inherent in the calculations of thermal gradients as per ASME Section III Subsection NB3600-2007 are also inherent in these calculations and may produce unacceptable results when evaluated as per [PVP2009-77148]. If results are unacceptable, it is warning that something else needs to be done. The advantage of this approach is that it eliminates the need for a computer program to quantify these thermal gradients, a computer program that is not normally accessible to the B31.1 designer anyway. Instead, the formulae use data that is available to the B31.1 designer, namely physical geometry, Thermal Conductivity and the Rate of temperature change of the fluid in the pipe. Calculating the magnitude of thermal gradients in a B31.1 TTJ is an essential step in evaluating their fatigue effects for design and in plant life extension considerations (see PVP2009-77148). This will further help to preserve the integrity of the piping pressure boundary and consequently, the safety of personnel in today’s power plants and into the future.
Towards Fast Numerical Studies for Maintenance and Lifecycle Problem Analysis: New Simulation Methods on Example of an Industrial Study Case
Authors: Mikchevitch Alexei , Geniaut Samuel , Nistor Ionel
Published: July 2010

Companies exploiting industrial installations are currently submitted to various constraints in the context of maintenance and lifecycle problem analysis: time and cost of production stops, efficiency of maintenance solutions, production safety criteria, etc. Hence, the reduction of the time of projects may lead to important research perspectives in terms of fast numerical prototyping and solution assessment methods. In this paper, we present a typical industrial problem of fast assessment of mechanical state of a production installation. We focused on the study of a cracked component of a reheater as well as we proposed a new design for this component to improve its mechanical behavior under an exceptional overload. In order to reduce the operational study time, the Extended Finite Element Method (X-FEM) has been used to model non-linear crack phenomenon without any human modification of a complex 3D model on the level of geometric model and mesh. An alternative design of a damageable element has been proposed to avoid all risk of possible cracking. This design task requires a mechanical analysis of locally modified structure under a cyclic loading. We also present a new prototyping method based on direct modification of meshes and allowing reducing the time of numerical study.
A Parametric Study on the Strain Concentration in Field Joint of Concrete Coated Pipelines Using Finite Element Method
Authors: Nourpanah Nikzad , Taheri Farid
Published: July 2010

This paper aims at investigating the strain concentration in the field joints of concrete coated pipelines. A parametric study, using the finite element (FE) method, is conducted to investigate the effect of different geometric and material related parameters on the strain concentration. The selected parameters are believed to be the most influencing ones, and their variations selected as such, so to reflect practical situations. The finite element approach used in this study was discussed and validated by the authors in their earlier work. In this study, twenty three FE models are analyzed and their results are processed and presented in terms of variation of Strain Concentration Factor (SCF) versus the considered parameters, thus enabling us to examine the trend of variation of SCF with respect to each parameter. The observed trends and their underlying mechanics are described. Furthermore, a non-dimensional “geometric parameter” is introduced, which lumps the geometrical parameters investigated into a single parameter, such that it could adequately describe the variations of SCF. It is observed that a threshold exists for this parameter, beyond which the SCF can be deemed constant for design purposes, and below which the SCF would become very sensitive to the geometrical properties.
The Effects of Constraint and Compressive or Tensile Residual Stresses on Brittle Fracture
Authors: Kamel Simon , Wimpory Robert C. , Hofmann Michael
Published: July 2010

Residual stress is a key feature in components containing defects which can affect the crack driving force and alter the crack tip constraint to give a modified fracture toughness. In this paper experimental and numerical investigations are performed on ‘C’ shape fracture mechanics specimens, extracted from a high strength low alloy tubing steel, to examine the effects of constraint and tensile or compressive residual stress on brittle fracture. The residual stress is introduced into the specimens by a tensile or compressive mechanical pre-load to produce, respectively, a compressive or tensile residual stress in the region where the crack is introduced. Neutron diffraction measurements are performed on the pre-loaded specimens prior to introduction of a crack, and compared with predictions of the residual stress from finite-element analysis, using tensile properties derived at room temperature. Fracture toughness tests are carried out on the as-received (non-preloaded) and pre-loaded specimens and the effect of residual stress on crack driving force and constraint is evaluated using the two-parameter J-Q approach.
Packaging and Transportation of Neptunium Oxide
Authors: Watkins Robert W. , Hensel Stephen J. , Jordan Jeffrey M.
Published: July 2010

The Savannah River Site’s HB-Line Facility completed a campaign in which fifty (50) cans of neptunium oxide were produced and shipped to the Idaho National Laboratory in the 9975 shipping container. This shipping campaign involved the addition of neptunium oxide to the 9975 Safety Analysis Report for Packaging (SARP) as a new content and subsequently a Letter of Amendment to the SARP content table. This paper will address the proper steps which should be taken to add a new content table to the SARP. It will also address the importance of product sampling and understanding the material shipping requirements of a SARP.
Optimization of GMAW Welding Parameters in Duplex Stainless Steel Welds Mechanical Properties
Authors: Payares-Asprino Carolina , Steele John P. H.
Published: July 2010

The objective of the current work is to provide sufficient knowledge of the welding industry to allow the optimization of the process so as to achieve best final properties. The welding process is complex with many interacting variables controlling the procedure. In addition, not all of the physics of the process, particularly with regard to the factors which control mechanical properties, are well understood. It is unlikely that a full analytical model can be prepared and physically based numerical techniques will also suffer from a lack of basic understanding. A model for use as an optimization tool will thus have to proceed along different lines. Fortunately, this work has produced a wealth of experimental observations, which can be used for optimization. In this research, several welds were fabricated using Gas Metal Arc Welding process at different welding conditions. The technique of Response Surface Methodology was applied to develop a mathematical model to analyze various effects of GMAW parameters on the and mechanical properties such as yield strength and ultimate tensile strength of Duplex Stainless Steel weldments.
Hydraulic Re-Autofrettage of a Swage Autofrettaged Tube
Authors: Parker Anthony P. , Troiano Edward , Underwood John H.
Published: July 2010

An earlier paper presented a non-linear analysis of hydraulic re-autofrettage following initial hydraulic autofrettage and low temperature heat soak. The benefits from such a sequence derive almost exclusively from the mitigation of Bauschinger effect. As a result yielding during re-autofrettage occurs in the near-bore region. In this paper hydraulic re-autofrettage following initial swage autofrettage and heat soak is analyzed. The benefits in this case derive mainly from the adjustment of stress fields within the wall of the tube, close to the original elastic-plastic interface created during the swage process. Bauschinger effect mitigation is a second order effect. This procedure is the subject of a recently-submitted patent application. The procedure can produce significant improvements in initial re-yield pressure and in safe maximum pressure as defined by additional permanent strain. An increase in fatigue crack growth lifetime is also predicted. At higher re-autofrettage pressures OD residual hoop stresses increase significantly.
Probabilistic Models to Approximate Highly Repetitive Linear and Nonlinear Finite Element Analyses of Nuclear Components
Authors: Vlaicu Dan , Stojakovic Mike
Published: July 2010

In the development and technical support of nuclear plants, Engineers have to deal with highly repetitive finite element analyses that involve modeling of local variations of the initial design, local flaws due to corrosion-erosion effects, material properties degradation, and modifications of the loading conditions. This paper presents the development of generic models that emulate the behavior of a complex finite element model in a simplified form, with the statistical representation based on a sampling of base-model data for a variety of test cases. An improved Latin Hypercube algorithm is employed to generate the sampling points based on the number and the range of the variables that are considered in the design space. Four filling methods of the approximation models are discussed in this study: response surface, nonlinear, neural networks, and piecewise polynomial model. Furthermore, a bootstrapping procedure is employed to improve the confidence intervals of the original coefficients, and the single-factor or double-factor analysis of variance is applied to determine whether a significant influence exists between the investigated factors. Two numerical examples highlight the accuracy and efficiency of the methods. The first example is the linear elastic analysis of a pipe bend under pressure loading. The objective of the probabilistic assessment is to determine the relation between the loading conditions as well as the geometrical aspects of this elbow (pipe wall thickness, outside diameter, elbow radius, and maximum ovality tolerance) and the maximum stress in the elbow. The second example is an axisymmetric nozzle under primary and secondary cycling loads. Variations of the geometrical dimensions, nonlinear material properties, and cycling loading are taken as the input parameters, whereas the response variable is defined in terms of Melan’s theorem translated into the Nonlinear Superposition Method.
Shaking Table Tests With Large Test Specimens of Seismically Isolated FBR Plants: Part 3—Ultimate Behavior of Upper Structure and Rubber Bearings
Authors: Yabana Shuichi , Kanazawa Kenji , Nagata Seiji , Kitamura Seiji , Sano Takeshi
Published: July 2010

This paper describes results of shaking table tests to grasp ultimate behavior of seismic isolation system under extremely strong earthquake motions, including failure of rubber bearings. The results of the shaking table tests are expected to be useful for the design of seismically isolated nuclear facilities, especially fast breeder reactor (FBR) plants. In the test, lead rubber bearings, of which the diameter is 505 mm and about 1/3 scale of a prototype in planning FBR plants, are used; the test specimens are loaded by the largest three-dimensional shaking table in E-defense of National Research Institute for Earth Science and Disaster Prevention (NIED) of Japan. Failure of rubber bearings occurs with amplified tentative design earthquake motions. From the tests, the ultimate responses of the upper structure and rubber bearings are presented. In particular, the change of floor response spectra and restoring force characteristics of rubber bearings according to increase of input motions is discussed. Furthermore, mechanism of the failure of rubber bearings is investigated from the observation of failure surfaces and cut sections, static loading tests, and material tests of rubber bearings. Finally, the function of seismic isolation system after the failure of a part of rubber bearings is confirmed under the tentative design earthquake.
Friction Stir Welding of API Garde 65 Steel Pipes
Authors: Feng Zhili , Steel Russell , Packer Scott , David Stan A.
Published: July 2010

Friction stir welding (FSW), a novel solid-state joining process, was applied to girth weld API 5L Grade 65 steel pipes with an outer diameter of 12.75″ (324 mm) and a wall thickness of 0.25″ (6.35 mm). Fully consolidated single pass butt welds were obtained using a specially designed mechanized portable FSW system suitable for on-site pipe construction welding. The friction stir girth weld shows a slightly overmatched strength and superior impact toughness in comparison with the base metal, a very desirable combination of properties for pipeline weld that can be attributed to the wrought microstructure with refined grains in the stir zone (SZ), the thermal-mechanically affected zone (TMAZ), and the heat-affected zone (HAZ).
Automatic Fatigue Crack Growth
Authors: Mellings S. C. , Baynham J. M. W.
Published: July 2010

One of the critical requirements of fatigue crack growth simulation is calculation of the remaining life of a structure under cyclic loading. This paper presents a method which predicts the remaining fatigue life of a part, and gives information on the eventual mode of failure. The path of a growing crack needs to be understood so that informed assessment can be made of the structural consequences of eventual fast growth, and the likelihood of leakage and determination of leakage rates. For these reasons the use of standard handbook solutions for crack growth is generally not adequate, and it is essential to use the real geometry and loading. The reasons for performing such simulation work include preventive investigations performed at the design stage, forensic investigations performed after failure, and sometimes forensic investigations performed during failure-when the results provide input to the planning of remedial work. This paper focuses on the 3D simulation of cracks growing in metal structures exposed to cyclic loading, and explains the techniques which are used. The loading might arise from transients of pressure or other mechanical forces, or might be caused by thermal-stress variations. The simulation starts from an initial crack which can be of any size and orientation. The relevant geometry of the cracked component is modelled, and the loading is identified using one or more load cases together with a load spectrum which shows how the loading cycles. The effects of the crack are determined by calculating stress intensity factors at all positions along the crack front (it would be called the crack tip if the modelling was performed in 2D). The rate and direction of crack growth at each part of the crack front are calculated using one of the available crack growth laws, together with appropriate material properties. The effects of such growth are accumulated over a number of load cycles, and a new crack shape is determined. The process is repeated as required. The use of multi-axial and mixed mode techniques allows the crack to turn as a result of the applied loading, and the resulting crack path is therefore a consequence of both the detail of the geometry and the loading to which the structure is subjected. Gas or other fluid pressures acting on the crack faces can have significant impact, as can the contact between opposing crack faces when a load case causes part of the crack to close.
Ensuring Integrity of High Energy Piping in the NPP’s of the Czech Republic
Authors: Zdarek Jiri , Dotrel Jan , Jarolimek Vaclav
Published: July 2010

An approach of ensuring the quality of piping of NPP’s on the Czech Republic is described, with focus on high energy piping systems. Basic principles of this approach are described that are aimed to ensure the safety goals while maintaining the effectiveness of NPP operation during its long-term life. This approach ensures defense in depth of the piping. Its application on the high energy piping on +28.8 m level of WWER 1000 type NPP is demonstrated.
Theoretical Representations of a Characteristic Curved Surface for the Life of IN738LC Under High Temperature Creep and Fatigue Interaction Based on Non-Equilibrium Science
Authors: Kobayashi D. , Miyabe M. , Kagiya Y. , Nagumo Y. , Sugiura R. , Matsuzaki T. , Yokobori A. T.
Published: July 2010

The Ni-base supperalloy IN738LC, developed as a gas turbine blade material, is used under the conditions of creep-fatigue multiplication. In this paper, using IN738LC, in situ observational tests under the conditions of creep-fatigue multiplication were conducted and the effects of cycle-dependent and time-dependent mechanisms on the fracture life tf were investigated. Furthermore, on the basis of the concept of non-equilibrium science, the multiple effects of creep and fatigue on the fracture life tf were clarified.
An Analytical Evaluation of the Full Structural Weld Overlay as a Stress Improving Mitigation Strategy to Prevent Primary Water Stress Corrosion Cracking in Pressurized Water Reactor Piping
Authors: Fredette L. F. , Scott Paul M. , Brust F. W. , Csontos A.
Published: July 2010

Full Structural Weld Overlay (FSWOL) has been used successfully to mitigate intergranular stress corrosion cracking in boiling water reactor (BWR) welded stainless steel piping for many years. The FSWOL technique adds structural reinforcement, can add crack resistant material, and can create compressive residual stresses at the inside surface of the welded joint which reduces the possibility of further stress corrosion cracking. Recently, the FSWOL has been applied as a preemptive measure to prevent primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWR) on susceptible welded pipes with dissimilar metal welds common to PWR primary cooling piping. This study uses finite element models to evaluate the likely residual and operating stress profiles remaining after FSWOL for typical dissimilar metal weld configurations, some of which are approved for leak-before-break (LBB) applications in pressurized water reactors. Circumferential cracks were modeled in the dissimilar metal weld area and forced to grow in order to evaluate their crack opening displacements and stress intensity factors vs. depth before and after weld overlay and before and after application of operating pressure and temperature.