bluuebunny/crossref_metadata_2025 huggingface dataset:
Fully Nonlinear Potential/RANSE Simulation of Wave Interaction With Ships and Marine Structures
Authors: Ferrant Pierre , Gentaz Lionel , Alessandrini Bertrand , Luquet Romain , Monroy Charles , Ducrozet Guillaume , Jacquin Erwan , Drouet Aure´lian
Published: July 2009

This paper documents recent advances of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach, a method for simulating fully nonlinear wave-body interactions including viscous effects. The methods efficiently combines a fully nonlinear potential flow description of undisturbed wave systems with a modified set of RANS with free surface equations accounting for the interaction with a ship or marine structure. Arbitrary incident wave systems may be described, including regular, irregular waves, multidirectional waves, focused wave events, etc. The model may be fixed or moving with arbitrary speed and 6 degrees of freedom motion. The extension of the SWENSE method to 6 DOF simulations in irregular waves as well as to manoeuvring simulations in waves are discussed in this paper. Different illlustative simulations are presented and discussed. Results of the present approach compare favorably with available reference results.
On the Research and Development of Floating Offshore Platform
Authors: Ishida Shigesuke , Ohkawa Yutaka , Niwa Toshio , Ohkoshi Shigehiro , Kokubun Kentaroh
Published: July 2009

Japan, a land-resource-poor country, has an Exclusive Economic Zone with the area of the sixth place in the world, 4.47 million km2. In order to utilize the resources in EEZ, the Ministry of Land, Infrastructure, Transport and Tourism started a project of floating offshore platform in 2007 and National Maritime Research Institute is conducting the project. In this paper the outline of the project and some results are mentioned. One of the objectives of this project is to develop key technologies of floating platform necessary for various activities in EEZ. One technology is motion reduction for ensuring the safety and operation in severe seas. Other than hull shape such as semi-submergibles and strong mooring, the effect of fins on reducing not only motion but also drifting at the same time is focused. Another one is deep sea mooring. Composite mooring lines with synthetic fiber, new types of anchors and so on are studied. The third one is maintenance. In order to make the life-time cost minimum, developing a rational maintenance method based on reliability analysis, which should replace the current empirical one, is necessary. This project does not have any specific target platform at the beginning. Therefore, the rough design and evaluation of various types of platforms should be carried out. In order to make it efficiently, the harmonic design program, a software integrating the above-mentioned evaluation tools, ocean database and some other functions is being developed for evaluating the safety, economy and environmental effect of a platform. The other objective of the project is to propose some offshore platforms for promising utilization. For the proposal a database of ocean, including wind, waves, water depth, current and so on, is necessary. In this paper the ocean database is introduced and some utilizations are presented.
Comparison Study of Different Floater Effect on Deepwater SCR
Authors: Dong Yongqiang , Sun Liping
Published: July 2009

With the development of deepwater offshore industries, Steel Catenary Riser (SCR) offers great advantages over other risers and has been widely deployed. SCRs have been installed and in service in offshore oil and gas industries in the Gulf of Mexico, Campos Basin, Brazil and West of Africa since the 1990s. The platforms designed for SCRs range from semi-submersible, Spar, TLP to FPSO. Severe motions of a floating host facility such as a TLP, FPSO or other platform may have implications for the strength and fatigue life of SCR. To better understand the effect of floater motion on deepwater SCR, a comparison study of such effect was conducted. Three typical floaters including semi-submersible, Spar and TLP were selected for comparison purpose. An identical SCR was assumed for all floaters in order to make comparison on the same basis. Study focus was given to the strength and motion fatigue analysis. To illustrate the floater effect on SCR performance, an example was given for an 8.625 inches diameter SCR. Detail finite element analysis were performed by use of ABAQUS. It was found that the floater motion has significant impact on SCR’s both strength and fatigue. Among the selected floaters, it was found that semi-submersible and Spar are much more friendly to SCR, while TLP makes SCR design more challenging. In addition, the effect of different floater concept on SCR global configuration design was also discussed. Meanwhile, the analysis technique was also discussed through this study. It is concluded that focus should be given to SCR motion fatigue and strength for different platforms.
Remote Sensing of Sea Surface Wave by Using CW X-Band Microwave Doppler Radar at Sagami-Bay
Authors: Rheem Chang-Kyu
Published: July 2009

Sea surface waves had been observed remotely by using a continuous wave (CW) X-band microwave Doppler radar at the off Hitatsuka of Sagami-bay in Japan. A new algorithm was applied to retrieve sea surface elevation from radar output Doppler signals. The sea surface waves observed by the microwave Doppler radar had been compared with the waves measured by a supersonic wave height meter. There were good correlations in both the wave height and the wave period between the waves observed by the microwave Doppler radar and that measured by a supersonic wave height meter. The correlation of wave heights was better than that of wave periods. The microwave irradiation width on sea surface does a role of space filter. It seems that the filtering effect is a kind of aliasing, the energy of short wavelength waves moves to low wave number region. The algorithm to retrieve a sea surface elevation is described by the relation of the water surface elevation and the orbital velocity of water particle on water surface that generated by water surface waves. A linear superposition method has been used to retrieve sea surface elevation. No empirical parameters are used in the algorithm, because the water surface elevation can be obtained from the water particle velocity on water surface by using the mathematical relation of the water surface elevation and the orbital motion of water particle. Water particle motion on sea surface is affected by sea surface wind, currents, and sea surface waves. Water particle motion generated by sea surface waves can be separated by the difference of the fluctuation scale of each physical process.
Physical Impact of a Roller Clump on the Seabed
Authors: Ivanovic´ Ana , Zhu Jianfeng , Neilson Richard , O’Neill Finbarr
Published: July 2009

The envionmental impact of towed demersal gears on benthic communities has been of concern for the last couple of decades. Knowledge of the response of benthic habitats to impacts from fishing gears is of great importance to the ecosystem and the long-term management of sustainable fisheries. An on-going EU project, DEGREE (DEvelopment of Fishing Gears with Reduced Effects on the Environment), addresses this concern by focusing on quantifying the environmental and ecological impacts of fishing, developing fishing gears with reduced environmental impact, and assessing the socio-economic consequences of these changes. This paper focuses primarily on the modelling of the interaction between a gear component, the roller clump of a twin trawl, and the seabed in terms of penetration and disturbance of the seabed. A finite element model of this interface has been developed and is able to predict the penetration depth, sediment displacement and the pressure field associated with each gear component. In order to verify these predictions, sea trials have taken place over a range of sediment types at depths accessible to scientific divers using SCUBA diving techniques. This has allowed sampling of the seabed and profiling of the disturbed region for comparison with the model results. Good agreement is found.
WWM Extended to Account for Wave Diffraction on a Current Over a Rapidly Varying Topography
Authors: Hsu Tai-Wen , Liau Jian-Ming , Ou Shan-Hwei , Shin Chih-Yung
Published: July 2009

The WWM (wind wave model) is extended to account for wave refraction-diffraction for wind waves propagating over a rapidly varying seabed in the presence of current. The wave diffraction effect is introduced into the wave action balance equation through the correction of wavenumber and propagation velocities using a diffraction corrected parameter. The approximation is based on the mild-slope equation for wave refraction-diffraction with current effect on a rapidly varying sea bottom. The relative importance of additional terms that influence the corrected diffraction parameter in the presence of currents was first introduced. The comparison of numerical results with other numerical models and experiments show that the validity of the model for describing wave propagating over a rapidly varying bottom with current effect is satisfactory. The implementation of this phase-decoupled refraction-diffraction approximation in WWM shows capability of the present model can be used in most practical engineering situations.
Application of Fluid-Structure Interaction Technique for Underwater Explosion Analysis of a Submarine Liquefied Oxygen Tank Considering Survivability
Authors: Kim Jae-Hyun , Jeon Byung-Young , Jeon Jae-Hwang
Published: July 2009

The design of submarines has continually developed to improve survivability. Explosions may induce local damage as well as global collapse to a submarine structure. Therefore, it is important to realistically estimate the possible damage conditions due to underwater explosions in the design stage. In the present study, the Arbitrary Lagrangian-Eulerian (ALE) technique, a fluid–structure interaction approach is applied to simulate an underwater explosion and investigation of the survival capability of a damaged submarine with clamped liquefied oxygen tank. The Lagrangian-Eulerian coupling algorithm, the equations of state for explosives and seawater, and the simple calculation method for explosive loading were also reviewed. It is shown that underwater explosion analysis using the ALE technique can reasonably evaluate the structural damage caused by explosive load.
Reliability of TLP Tethers Using Evolutionary Strategies
Authors: Barranco Cicilia Federico , Va´zquez Herna´ndez Alberto Omar
Published: July 2009

Tether system is a critical component for the TLPs, since its failure may lead to the collapse of the whole structure involving human lives, economic losses and damages to the environment. Due to this fact, reliability methods have been proposed to design TLP tethers and new codes are being developed to increase their safety level. The objective of this paper is to compare the probability of failure for TLP tethers considering the maximum tension limit state obtained with three methods, which are: a methodology based on Evolutionary Strategies and the Monte Carlo Importance Sampling, the First Order Reliability Method, and the Second Order Reliability Method. Von-Mises failure criterion is used as limit state function for the most loaded tether of a TLP submitted to different sea states. Efficiency of the ES algorithm to find design points and probabilities of failure obtained with the reliability methods are discussed.
Hydrodynamic Analysis of a Horizontal Axis Marine Current Turbine With a Boundary Element Method
Authors: Baltazar J. , Falca˜o de Campos J. A. C.
Published: July 2009

A low order potential based panel code is used to analyse the flow around the blades of a horizontal axis marine current turbine. An empirical vortex model is assumed for the turbine wake which includes the variation of pitch of the helicoidal vortices trailing behind the blades. The analysis is carried out for uniform inflow conditions in steady flow for a turbine with controllable pitch for two different pitch settings in a wide range of tip-speed-ratios. Grid convergence studies carried out to verify the accuracy of predicted pressure distributions and integrated forces show a fast convergence with grid refinement for this geometry. The effect of the helicoidal wake model parameters used in the analysis is found to have a strong influence in the performance curves. The results are compared with experimental data from the literature and with the lifting line theory. A discussion of viscous effects is also provided to help explaining the main discrepancies with the data.
Freak Waves and Giant Breathers
Authors: Zakharov Vladimir E. , Dyachenko Alexander I.
Published: July 2009

It is assumed the solitons could propagate only on the surface of finite depth fluid. We show numerically that the strong localized perturbation of free fluid surface could propagate on the surface of deep fluid also. They are not solitons in a “classical” sense of this term; they are “breathers”. It means that the motion of surface is a periodic function on time in a certain moving framework. This framework moves with the group velocity. Breathers of small steepness (ka < 0.07) are known for years as solitonic solutions of the Nonlinear Schrodinger Equation (NLSE) (Do not confuse with the “breather” solution of the Nonlinear Schrodinger Equation). Our new result is following: The breathers exits without decay up to very high steepness (at least to ka = 0.5). These steep giant breathers can be identified with Freak Waves. The most plausible explanation of the giant breather stability is integrability of the Euler equation describing a potential flow of deep ideal fluid with free surface. So far we don’t have a direct proof of this extremely strong statement, but we have a whole string of indirect evidences of this integrability.
Distribution of Wave Height Maxima in Storm Sea States
Authors: Cherneva Zhivelina , Guedes Soares C. , Petrova Petya
Published: July 2009

The effect of the coefficient of kurtosis as a measure of the nonlinearity of third order on the distribution of the wave height maxima has been investigated. Measurements of the surface elevation during a storm at the North Alwyn platform in the North Sea have been used. The mean number of waves in the series is around 100. The maximum wave statistics have been compared with nonlinear theoretical distributions. It was found that the empirical probability densities of the maximum wave heights describe qualitatively the shift of the distribution mode towards higher values. The tendency for the peak of distribution to diminish with increase of the coefficient of kurtosis up to 0.6 is also clearly seen. However, the empirical peak remains higher than the theoretically predicted one. Exceedance probability of the maximum wave heights was also estimated from the data and was compared with the theory. For the highest coefficients of kurtosis nearly 0.6 the theoretical distribution approximates very well the empirical data. For lower coefficients of kurtosis the theory tends to overestimate the exceedance probability of the maximum wave heights.
A Numerical Simulation of Vortex Induced Vibration on a Elastically Supported Circular Rigid Cylinder at Moderate Reynolds Numbers
Authors: Sigrist Jean-Franc¸ois , Allery Cyrille , Beghein Claudine
Published: July 2009

The present paper is the sequel of a previously published study which is concerned with the numerical simulation of vortex-induced-vibration (VIV) on an elastically supported rigid circular cylinder in a fluid cross-flow (A. Placzek, J.F. Sigrist, A. Hamdouni; Numerical Simulation of Vortex Shedding Past a Circular Cylinder at Low Reynolds Number with Finite Volume Technique. Part I: Forced Oscillations, Part II: Flow Induced Vibrations; Pressure Vessel and Piping, San Antonio, 22–26 July 2007). Such a problem has been thoroughly studied over the past years, both from the experimental and numerical points of view, because of its theoretical and practical interest in the understanding on flow-induced vibration problems. In this context, the present paper aims at exposing a numerical study based on a fully coupled fluid-structure simulation. The numerical technique is based on a finite volume discretisation of the fluid flow equations together with i) a re-meshing algorithm to account for the cylinder motion ii) a projection subroutine to compute the forces induced by the fluid on the cylinder and iii) a coupling procedure to describe the energy exchanges between the fluid flow and solid motion. The study is restricted to moderate Reynolds numbers (Re∼2.000–10.000) and is performed with an industrial CFD code. Numerical results are compared with existing literature on the subject, both in terms of cylinder amplitude motion and fluid vortex shedding modes. Ongoing numerical studies with different numerical techniques, such as ROM (Reduced Order Models)-based methods, will complete the approach and will be published in next PVP conference. These numerical simulations are proposed for code validation purposes prior to industrial applications in tube bundle configuration.
Temperature Prediction in 3013 Containers in K-Area Material Storage (KAMS) Facility Using Regression Methods
Authors: Gupta Narendra K.
Published: July 2009

3013 containers are designed in accordance with the DOE-STD-3013-2004. These containers are qualified to store plutonium (Pu) bearing materials such as PuO2 for 50 years. DOT shipping packages such as the 9975 are used to store the 3013 containers in the K-Area Material Storage (KAMS) facility at Savannah River Site (SRS). DOE-STD-3013-2004 requires that a comprehensive surveillance program be set up to ensure that the 3013 container design parameters are not violated during the long term storage. To ensure structural integrity of the 3013 containers, thermal analyses using finite element models were performed to predict the contents and component temperatures for different but well defined parameters such as storage ambient temperature, PuO2 density, fill heights, weights, and thermal loading. Interpolation is normally used to calculate temperatures if the actual parameter values are different from the analyzed values. A statistical analysis technique using regression methods is proposed to develop simple polynomial relations to predict temperatures for the actual parameter values found in the containers. The analysis shows that regression analysis is a powerful tool to develop simple relations to assess component temperatures.
Remarks to the Upper Shelf Master Curve Concept
Authors: Novak Jiri
Published: July 2009

Recently, several works appeared in which temperature dependence of ductile fracture toughness of ferritic steels on the upper shelf of brittle-ductile transition curve was analyzed and Upper Shelf Master Curve concept was formulated. Generally, fracture toughness at different temperatures characterized by JIc or dJ/da should be proportional to the deformation work of unit volume evaluated from zero to the critical strain for ductile fracture. As in many other cases, critical strain for ductile fracture initiation may be identified with critical strain for initiation of shear bands, calculated for hyperelastic material with the corresponding stress-strain curve. This concept is successful, among others, in determination of the temperature dependence of fracture toughness of ferritic steels on the upper shelf. Two most important physical mechanisms controlling temperature dependence of constitutive behaviour of ferritic steels in the corresponding temperature range, hence the temperature dependence of both deformation work to initiation of ductile fracture and fracture toughness, are friction resistance to dislocation slip (Peierls stress) and dynamic recovery (dislocation annihilation). Predicted Upper Shelf Master Curve shape based on temperature dependence of constitutive parameters of different ferritic steels corresponds well to the published data.
Finite Element Analysis of Sloshing in Axi-Symmetric Vessels
Authors: Papaprokopiou D. , Karamanos S. A.
Published: July 2009

The present paper investigates externally-induced sloshing in axi-symmetric liquid containers, with emphasis on industrial spherical containers, using an efficient numerical formulation, based on modal analysis. Assuming ideal and irrotational flow, small-amplitude free-surface elevation, and considering appropriate trigonometric functions for the sloshing potential, a two-dimensional eigenvalue problem is obtained for zero external excitation, which is solved through a variational (Garlerkin) formulation that uses triangular finite elements. Subsequently, based on an appropriate decomposition of the container-fluid motion, and considering the eigenmodes of the corresponding eigenvalue problem, an efficient methodology is proposed for externally-induced sloshing, through the calculation of the corresponding sloshing (or convective) masses. Numerical results are obtained for sloshing frequencies and masses in spherical vessels and a conical vessel with a semi-vertex angle of 45 degrees. It is shown that, in most of the cases, consideration of only the first sloshing mass is adequate to represent the dynamic behaviour of the liquid container quite accurately and could be used for design purposes. The numerical results are in very good comparison with other analytical or numerical solutions, and available experimental data.
Physical and Numerical Study of the Interaction Between a Fluid and an Oscillating Cylinder
Authors: Duclercq Marion , Broc Daniel
Published: July 2009

This paper deals with a vibratory problem of fluid-structure interaction. It considers the two-dimensional case of a rigid, smooth and circular cylinder undergoing transverse sinusoidal oscillations and immersed in a viscous fluid otherwise at rest. Our work is focused on the in-line force acting on the cylinder in unsteady laminar flow. The aim is to understand the variations of the force with time according to the configuration of the physical system. For that the analysis will also use an energetic approach based on the power balance. The physical system can be characterized by two non-dimensional numbers: the Reynolds number (Re) compares the importance of the fluid viscosity to its inertia, and the Keulegan-Carpenter number (Kc) measures the amplitude of the cylinder displacement compared to its diameter. First the incompressible Navier-Stokes equations are solved numerically by means of a finite elements method. The flow structure is analyzed by determining the evolution with time and throughout the computational domain of flow quantities, such as pressure field, vorticity field or stream lines. We also calculate the values versus time of the different terms occurring in the mean force balance and power balance. We compare these results for several pairs (Kc, Re) of “extreme” values. Thus it appears three characteristic configurations: the inertial Euler case (Kc≪1 and inviscid fluid), the Stokes case (Kc≪1 and Re≫1) and the drag case (Kc≫1). For these three reference configurations the physical mechanisms operating in the system are identified. But in intermediate cases, particularly when Kc>1, every mechanisms interact. Consequently the evolution of the force acting on the cylinder versus time is more complex and its interpretation becomes less straightforward. That is why a quantitative energetic analysis is carried out. We define a measure of the dissipative energy present in the flow. Then we compare the values of that coefficient for different cases throughout the map (Kc, Re).
Continuing Development of a Simplified Method to Account for the Interaction of Primary and Secondary Stresses
Authors: James Peter M. , Hooton Dennis G. , Higham Lorna A. , Madew Colin J. , Sharples John K. , Watson Chris T.
Published: July 2009

The R6 defect assessment procedure, used commonly in the UK nuclear industry to assess the significance of defects in structures, uses the Failure Assessment Diagram to evaluate limiting parameters whilst accounting for the effects of plasticity. The interaction of primary and secondary stress is accounted for within R6 through the use of the ρ, or an equivalent V, term. ‘Look-up’ tables are provided in order to evaluate parameters required to derive the ρ or V terms. In some circumstances, the current methodology has been shown to be excessively conservative and the use of the ‘look-up’ tables is somewhat complex and cumbersome anyway. Previous work has shown that an Alternative Method derived from the Time-Dependent Failure Assessment Diagram approach of the R5 high temperature procedure could potentially be considered. This has since been further modified and termed the Simplified Method. This Simplified Method has the benefit of being less conservative than the current R6 method and of not requiring ρ (or V) factors, and hence not requiring the use of the ‘Look-up’ tables. This paper presents the Simplified Method through comparisons within an extended range of Finite Element Analyses upon both an axial and circumferentially cracked pipe and a centre cracked plate. In addition to the use of the Simplified Method, further work is presented in order to include both out of plane primary and secondary stresses when determining the combined reference stress. A full range of crack opening and out of plane forces, as well as a full range of thermally induced secondary stresses, have been included to provide a broad basis upon which to compare the different methods investigated. Through comparing the full range of cases, some of the assumptions made within the R6 procedure have been reassessed. This has led to an average characteristic length, a¯, being defined to account for differences in loading type and in and out of plane ratios. However, within this paper further positive evidence for the use of the Simplified Method has been demonstrated.
Development of Passive Controlled Structure Assembled With L-Type Diaphragm
Authors: Mikoshiba Tadashi , Minowa Chikahiro , Terai Masakazu , Hiyama Yujiro , Sato Takanori , Chiba Toshio
Published: July 2009

Using the high-strength bolted connection, it is possible to control the quality of the joint and improve the construction of the structure. By setting the energy absorption mechanism on the structure and enhancing the damping effect, it makes it possible to scale back the influence of the earthquake. Based on the statement above, a new type of beam column joint (L-type Diaphragm) was developed and tests and analysis were conducted to validate the performance of this joint and the energy absorption characteristics at the end of the beam were surveyed. The stress transfer mechanism of the joint was investigated in the shaking table test of the actual size frame structure with this joint. As a result, it was found effective and a higher reliability.
Engineering Critical Assessments of Ductile Pipes With Axial Flaws and High Strain Hardening Capacity
Authors: Ruggieri Claudio
Published: July 2009

ECA procedures of crack-like defects based upon the FAD philosophy have undergone extensive developments in the past decade to form the basis for industrial codes and guidelines for structural integrity assessments. However, the application (and validation) of these procedures in defect assessments of structural components made of ductile materials under low constraint conditions remains a potential open issue. A central objective of this work is to assess the capability of the failure assessment diagram methodology to predict the failure pressure of ductile pipes with planar defects having different geometries. Specifically, the present work compares the burst pressure predictions for austenitic steel pipes with axial flaws derived from two widely used FAD procedures:BS7910 and API579. Such an application serves as a prototype for a wide class of integrity assessment problems involving the effects of strain hardening properties and ductility while, at the same time, assessing the robustness of FAD procedures in failure predictions. The direct application of BS7910 procedure indicate rather large margins between the predicted and the actual (measured) failure pressures. In contrast, the API 579 procedure appears to provide better agreement with experimental data. Overall, the results validate the use of FAD-based methodologies for defect assessments of ductile pipes with axial crack-like flaws.
The 2007 Forum on Seismic Design of Piping Systems for the Year 2010
Authors: Slagis Gerry C.
Published: July 2009

A summary of The 2007 Forum on Seismic Design of Piping Systems for the Year 2010 is provided. This forum session was the eleventh in a series that was started in 1992. Previously, the title was Appropriate Criteria and Methods for Seismic Design of Nuclear Piping. In this 2007 forum, the main topics of discussion were: performance-based design, SSE only design, and probabilistic-based design.
J-R Curve Testing of SE(T) Fracture Specimens Using Unloading Compliance and CMOD Data
Authors: Cravero Sebastian , Ruggieri Claudio
Published: July 2009

Laboratory testing of fracture specimens to measure resistance curves (J - Δa) have focused primarily on the unloading compliance method using a single specimen. Current estimation procedures (which form the basis of ASTM E1820 standard) employ load line displacement (LLD) records to measure fracture toughness resistance data incorporating a crack growth correction for J. An alternative method which potentially simplifies the test procedure involves the use of crack mouth opening displacement (CMOD) to determine both crack growth and J. This study provides further developments of the evaluation procedure for J in cracked bodies that experience ductile crack growth based upon the eta-method and CMOD data. The methodology broadens the applicability of current standards adopting the unloading compliance technique in laboratory measurements of fracture toughness resistance data (J resistance curves). The developed J evaluation formulation for growing cracks based on CMOD data provides a viable and yet simpler test technique to measure crack growth resistance data for ductile materials.
The Design of Fabric Expansion Joint Gas Seal Membranes
Authors: Peterson David , Broyles Robert
Published: July 2009

Fabric expansion joints are commonly used in round and rectangular ducting systems for accommodating differential thermal expansion and containing internal pressure. Fabric expansion joints are intended for sustained operation without significant leakage. Failure of fabric expansion joints can lead to plant shutdowns. The outer gas seal membrane is a structural material most commonly made from woven fabric with an elastomeric coating. The fibers in the fabric are comparatively strong and flexible but not chemically resistant. The coating protects the fibers from chemical attack and seals the woven fabric to minimize leakage through the material. The fabric material is typically clamped between metal frames attached to the ducting. The orientation of the fibers with respect to the frames is a critical design factor. Fabric expansion joints are normally designed in accordance with the guidelines of the Fluid Sealing Association Technical Handbook. The handbook gives helpful information but does not provide analytical methods for the mechanical design of gas seal membranes. The intent of this paper is to provide analytical methods for determining the movement capability and pressure capacity of gas seal membranes. Test results and non-linear finite element analysis are used to support the proposed methods.
Rocking and Sliding Motions of a Freely Standing Structure Coupled With Inner Structure
Authors: Furuta Kazuhisa , Ito Tomohiro , Shintani Atsuhiko
Published: July 2009

Many spent fuels coming out of the nuclear power stations are planned to be stored in the special site in Japan until they are reprocessed. In this site, the spent fuels are installed in a cylindrical container called canister. And the canister is installed in an outer cylinder called cask which is a free-standing structure. Therefore, it is very important to reduce the seismic response of the cask during a seismic event. In this study, the sliding and rocking motions of a cask are evaluated analytically. In an analytical model, the cask and the canister are treated as rigid bodies which are connected by a spring, because the cask and canister system is seen as a two-degree-of-freedom coupled system. The equations are derived for the sliding and rocking motions when the floor is subjected to a horizontal excitation. The displacement and the rocking angle of the cask are evaluated by numerical simulations. The effects of the canister vibration on the cask motion are discussed.
Application of the Electrical Potential Drop Technique to the Pipe Wall Thinning Monitoring in Thermal Power Plants
Authors: Yoshino Shin , Hamada Seiichi , Hayakawa Manabu
Published: July 2009

The electrical potential drop technique is one of the promising methods for monitoring the pipe wall thinning. In order to verify this method, preliminary thickness measurements were conducted for uniform and local thinning created on plate specimens. The result showed the electrical potential drop technique had a good performance equal to the ultrasonic testing method. The success in the preliminary tests allowed this technique to be applied to some pipes in thermal power plants in order to monitor the wall thinning and this on-line monitoring has continued for two to three years. It was confirmed that this technique was valid in terms of a long-term durability. Following these results, technical requirements on the potential drop technique were proposed to the JSME (the Japan Society of Mechanical Engineers) Rules on Pipe Wall Thinning Management for Thermal Power Generation Facilities (JSME S TB1-2006) and stipulated in those rules. In this paper, these rules are simply introduced and the on-line monitoring of the pipe wall thinning by means of the electrical potential drop technique is discussed through the results in the plate-specimen-tests and the real-pipe-tests in operating thermal power plants.
Shakedown Bounds of Structures Using Linear and Nonlinear Methods
Authors: Vlaicu Dan
Published: July 2009

For a cyclically loaded structure made of elastic-plastic material it is considered elastic shakedown if plastic straining occurs in the first few cycles and the sequent response is wholly elastic. In this paper the finite element method is used to develop upper and lower bounds limits for the elastic shakedown of structures under periodic loading conditions. Linear methods using elastic compensation approach and the residual stress method derived from Melan’s theorem are used to generate the lower bound limit for the shakedown load while the upper bound is found through a method derived from Koiter’s theorem. Furthermore the results are compared with cycle-by-cycle method based on nonlinear material properties.
Safety Factor of Austenitic Stainless Steel Pressure Vessels With Strain-Strengthening
Authors: Chen Gang , Deng Yang-Chun , Yang Xiao-Feng
Published: July 2009

The yield strength of austenitic stainless steels can be increased significantly through the strain-strengthening process. In this study, we presented the basic principle of strain-strengthening and introduced two strain-strengthening processes of austenitic stainless steels, Avesta process at normal temperature and Ardeform process at cryogenic temperature, in which Avesta process was much easier to operate. The design safety factor of pressure vessels with different levels of strain strengthening by Avesta process was also investigated. It was recommended that the strain during Avesta strain-strengthening process should be limited within 5%.
Thermo-Mechanical Behavior of a Stainless Steel Threaded Fitting With a Pre-Compressed Gasket
Authors: Yang Xianjie , Nassar Sayed A. , Wu Zhijun
Published: July 2009

This paper investigates the clamp load loss in threaded fittings with a collapsible metal gasket for elevated temperature application. Firstly, the joint is tested at room temperature to find the correlation between the joint clamp load, the tightening torque, and the angle of turn. Secondly, a mathematical model for clamp load loss of the bolted joints under temperature cycling is proposed for predicting the clamp load variation. Although the bolt and the joint would normally undergo linear elastic deformation at room temperature, they are more likely to exhibit nonlinear behavior at high temperature due to the reduced material strength. The plastic or creep deformation of the bolt, gasket, and joint would cause permanent clamp load loss that may lead to joint leakage, part separation, or plastic thread deformation that would significantly increase the cost of fitting replacement and/or maintenance. A non-linear finite element model is used with temperature dependent material properties. The FEA model is used to investigate the clamp load loss of the threaded fittings due to plastic and creep behavior. Some measures for enhancing the threaded fitting reliability at elevated temperature are proposed.
A New Tightening Methodology for Gasketed Joints Based on Nonlinear Finite Element Analysis
Authors: Nassar Sayed A. , Wu Zhijun , Yang Xianjie
Published: July 2009

A three dimensional nonlinear finite element model is developed for achieving a uniform clamp load in gasketed bolted joints. The model is used for both multiple and single pass tightening patterns. Geometric nonlinearity of the gasket is taken into account and plastic model parameters are experimentally determined. The effect of the tightening pattern, gasket loading and unloading history, and the preload level is investigated. The validity of the FEA methodology is experimentally verified. This study helps improve the reliability of gasketed bolted joints by minimizing the bolt-to-bolt clamp load variation caused by elastic interaction among the various bolts in the joint during initial joint bolt-up.
Developments in Combined ARCMAC and Strain Mapping Systems for Creep Measurement
Authors: Morris Andy , Maharaj Chris , Palmer Iain , Puri Amit , Dear John
Published: July 2009

The E.ON UK ARCMAC gauge has been developed to provide for point-to-point biaxial creep strain measurements. Research is continuing to provide for strain field mapping about the ARCMAC point-to-point monitoring system. The aim is to have comprehensive monitoring of creep strain in high temperature steam pipes including bends, joints, welds and other pipe structural features. A requirement is that all creep strain measurements made satisfy the standards of the UK National Physical Laboratory that maintain liaison with the standards authorities in other countries. Creep strain and other monitoring equipment for power-station steam pipes need to be rugged and suitable for the many different locations in which they are to be installed. Appropriate equipment is also required for capturing data at different times from the installed gauges. The use of strain mapping is particularly required when monitoring non uniform sections of pipes. Results to be presented will show the current state-of-art measurement techniques now available.
Coupled Thermal-Multiphase Flow Analysis in Quenching Processes for Residual Stress Optimization in Compressor and Turbine Disks
Authors: Springmann Marcel , Ku¨hhorn Arnold
Published: July 2009

The durability of compressor and turbine disks in jet engines is strongly influenced by residual stresses caused by the manufacturing process. The main goal of our work is the simulation and optimization of the heat treatment, to adjust reliably the residual stresses. After forging and drilling the disk blank is heated in a furnace. In the following quenching process the disk is cooled down in an oil bath, whereas plastic deformations occur in the disk. The coupled thermal-flow analysis is accomplished using a commercial CFD code. During the quenching process radiation, boiling and condensation of the oil as well as appropriate heat transfer mechanisms are considered. The heat transfer due to film, transition and nucleate boiling is modeled via user-defined functions. Subsequently, nonlinear residual stress calculations are performed in a commercial FEM program based on the determined temperature field.
A Unified View of Engineering Creep Parameters
Authors: Eno D. R. , Young G. A. , Sham T.-L.
Published: July 2009

Creep data are often analyzed using derived engineering parameters to correlate creep life (either time to rupture, or time to a specified strain) to applied stress and temperature. Commonly used formulations include Larson-Miller, Orr-Sherby-Dorn, Manson-Haferd, and Manson-Succop parameterizations. In this paper, it is shown that these parameterizations are all special cases of a common general framework based on a linear statistical model. Recognition of this fact allows for statistically efficient estimation of material model parameters and quantitative statistical comparisons among the various parameterizations in terms of their ability to fit a material database, including assessment of a stress-temperature interaction in creep behavior. This provides a rational basis for choosing the best parameterization to describe a particular material. Furthermore, using the technique of maximum likelihood estimation to estimate model parameters allows for a statistically proper treatment of runouts in a test database via censored data analysis methods, and for construction of probabilistically interpretable upper and lower bounds on creep rate. Comparisons are made to a generalization of the commonly used Larson-Miller parameterization (namely, the Mendelson-Roberts-Manson parameterization), which is comparable in complexity to the Manson-Haferd parameter, but utilizes a reciprocal temperature dependence. The general framework for analysis of creep data is illustrated with analysis of Alloy 617 and HAYNES® 230® alloy (Alloy 230) test data.
Fluid Transients in a Pipeline With One Open End
Authors: Leishear Robert A.
Published: July 2009

Water hammer during multi-phase flow is rather complex, but in some cases an upper limit to the pressure surge magnitude during water hammer can be estimated. In the case considered here, a two mile long pipeline with a single high point was permitted to partially drain. Due to gravitational effects, air bubbles up through the pipe line to its highest point, but the time required for air to reach the top of the pipe is rather long. Consequently, some transients caused by valve operations are affected by air entrapment and some are not. The intent of this research was to investigate the complex interactions between air, water vapor, and liquid during water hammer in a long pipe with one end of the pipe open to atmospheric conditions. To understand the system dynamics, experimental data was obtained from a long pipeline with an open end and also from a short, transparent tube. Transient calculations were performed for valve closures and pump operations as applicable. The limitations of available calculation techniques were considered in detail.
Physical and Mechanical Aspects of Radiation Embrittlement of RPV Steels
Authors: Margolin B. , Shvetsova V. , Gulenko A. , Nikolaev V. , Lidbury D. , Keim E.
Published: July 2009

A multi-scale approach to brittle fracture of irradiated RPV steels has been developed within the EURATOM FP6 Integrated Project PERFECT, and the EC-sponsored ISTC Project 3072: “Modelling of Brittle and Ductile Fracture and Prediction of Irradiation Damage Effects on Fracture Toughness Properties of Steels for Reactor Pressure Vessels on the Basis of Local Approach”. In the present paper, the physical and mechanical aspects of the irradiation embrittlement phenomenon are analysed on the basis of a multi-scale approach that includes the physical mechanisms of irradiation damage, the physical mechanisms of nucleation and propagation of cleavage microcracks, formulation of a local approach criterion and calculation of fracture toughness. It has become clear from the study performed that irradiation embrittlement is not only due to the hardening of material as traditionally considered. Damage features such as irradiation-induced lattice defects, element precipitation and impurity segregation also affect cleavage microcrack nucleation, although they do not appreciably change the critical stress for microcrack propagation. It is shown that irradiation embrittlement of RPV steels is connected both with the increase of yield stress (mechanical factor) and the decrease of the critical stress for microcrack nucleation (physical factor). This finding allows an interpretation of the experimental observations, showing that for some cases there is no simple one-to-one relationship between the brittle-to-ductile transition temperature shift ΔTtr and the corresponding increase in yield stress ΔσY. For example, this explains why irradiation-induced phosphorus segregation may significantly increase the transition temperature shift ΔTtr but does not result in a significant increase in yield stress. Calculation of the KJC(T) curves has shown that the contributions of mechanical and physical factors in irradiation embrittlement may differ for various steels. So, for low-alloy, low-strength steel the mechanical factor predominates, while for RPV steels both of these factors control irradiation embrittlement. The results obtained have been interpreted with reference to a local cleavage fracture criterion.
Numerical Simulation Analysis on Buckling Load of Large Combined Cylindrical Shells
Authors: Chen Zhiping , Zeng Ming , Yu Chu-Lin , Zhu Jinping
Published: July 2009

To comply with the uniform-strength theory, almost all large tanks are made by welding unequal-thickness cylindrical shell courses together. This structure can be considered as a kind of geometry imperfection of tank walls, which has a great influence on buckling behavior and critical load of tank walls. To obtain the related critical buckling load and to verify the effect regularity on bulking due to hoop stress in various combined unequal-thickness cylindrical shells, the numerical simulation was adopted to analyze the buckling behavior with different loads. The results show that the characteristic factors of unequal-thickness structure can reduce the critical buckling load significantly, such factors as shell layers and the difference in thickness of adjacent shell courses are the most dominant.
A Non-Destructive Testing Method and Analysis for Air Pressure Distribution in the Stacks of Building Drainage Systems
Authors: Cheng Cheng-Li , Liao Wan-Ju , He Kuen-Chi , Yen Chia-Ju
Published: July 2009

A drainage system is one of the most essential facilities in building service engineering. Unfortunately relevant technology used today to analyze it was developed decades ago. This research investigated the case of existing building drainage systems in Taiwan, including our previous studies. The purpose of this paper is the development of a non-destructive testing method of air pressure fluctuation in a stacked building drainage system using field observation and experimental study of stack fluid mechanisms. A portable testing device is developed to execute field testing in existing drainage systems to determine air pressure fluctuation in the stacks of buildings. Meanwhile, the Fourier Transform Process is adopted in this paper to analyze the power spectrum of air pressure fluctuation in a drainage stack and to verify the previous theoretical study. Validation obtained from case-studies can be used to confirm the practicality of this portable and non-destructive testing method. As a result, the proposed testing method can be applied to the diagnosis of existing building drainage systems and improve the design of a drainage system in an existing housing complex.