bluuebunny/crossref_metadata_2025 huggingface dataset:
Semi-Infinite Target Penetration by Ogive-Nose Penetrators: ALEGRA/SHISM Code Predictions for Ideal and Non-Ideal Impacts
Authors: Bishop Joseph E. , Voth Thomas E. , Brown Kevin H.
Published: August 2008

The physics of ballistic penetration mechanics is of great interest in penetrator and counter-measure design. The phenomenology associated with these events can be quite complex and a significant number of studies have been conducted ranging from purely experimental to ‘engineering’ models based on empirical and/or analytical descriptions to fully-coupled penetrator/target, thermo-mechanical numerical simulations. Until recently, however, there appears to be a paucity of numerical studies considering ‘non-ideal’ impacts [1]. The goal of this work is to demonstrate the SHISM algorithm implemented in the ALEGRA Multi-Material ALE (Arbitrary Lagrangian Eulerian) code [13]. The SHISM algorithm models the three-dimensional continuum solid mechanics response of the target and penetrator in a fully coupled manner. This capability allows for the study of ‘non-ideal’ impacts (e.g. pitch, yaw and/or obliquity of the target/penetrator pair). In this work predictions using the SHISM algorithm are compared to previously published experimental results for selected ideal and non-ideal impacts of metal penetrator-target pairs. These results show good agreement between predicted and measured maximum depth-of-penetration, DOP, for ogive-nose penetrators with striking velocities in the 0.5 to 1.5 km/s range. Ideal impact simulations demonstrate convergence in predicted DOP for the velocity range considered. A theory is advanced to explain disagreement between predicted and measured DOP at higher striking velocities. This theory postulates uncertainties in angle-of-attack for the observed discrepancies. It is noted that material models and associated parameters used here, were unmodified from those in the literature. Hence, no tuning of models was performed to match experimental data.
Creep Limitation of Bolted Fasteners and Gaskets
Authors: Efremov Anatoly I.
Published: August 2008

Creep of the bolted fasteners and gaskets is one of principal causes of plant leakages that lead to untimely bolt corrosion and failure of bolted flanged connections and other engineering equipment responsible for tight joints between adjacent members of pressure vessels, piping systems, reactors, steam generators, heat exchangers, and the like. Leak-tight flange design based on application of shape memory materials is experimentally studied. The preliminary results accompanied by analytical approach reveal that bolts and gaskets with insertions manufactured from shape memory alloys display significant limitation of operating creep.
Inelastic Analysis of Dissimilar Material Flanges With Metal Ring Gaskets at Elevated Temperature
Authors: Sato Takuya , Kado Kenichiro
Published: August 2008

The dissimilar material flange connections are often adopted to connect the austenite stainless steel pipes to the low alloy steel pressure vessels operated at an elevated temperature. The behavior of this flange connection is very complicated because of the non-uniform temperature distribution and the thermal expansion difference of dissimilar materials. The application of the metal ring gasket makes the behavior more complicated. An elastic plastic finite element analysis is one of the adequate ways to investigate the behavior of the following dissimilar material flanges with the metal ring gasket under the high pressure and elevated temperature operation. (1) Pipe flange: standard configuration, austenite stainless steel, (2) Nozzle flange: forged thick nozzle neck, low alloy steel covered with stainless steel overlay. The material of ring gasket is also an austenite stainless steel. This ring gasket contacts to and slips on the ring groove surfaces of flanges. The axi-symmetric analyses were made considering the sequence of initial bolting, internal pressure and non-uniform temperature distribution. The elastic plastic properties and temperature dependency of the materials were considered. From these analyses, the effects of the non-uniform temperature distribution and the thermal expansion difference of dissimilar material flanges on the contact pressure of the ring gaskets were made clear. The effect of flange size (14”–36”) was also investigated.
Continuum Damage Mechanics From Specimen to Component Level
Authors: Dutta B. K. , Guin S. , Sahu M. K. , Samal M. K.
Published: August 2008

Continuum damage mechanics is applied from specimen to component level to compute fracture behaviour. The computed parameters are load-displacement and J-Δa curves. A parametric study is done to show the effect of variation of f0 and fn on J-R curve. It is suggested to use a variation of q2 parameter near crack tip instead of a constant value in Gurson constitutive model. Such variation helps to obtain Jinitiation as well as complete J-R curve in close agreement with experimental values. The Gurson material parameters obtained from specimen level analyses are then used to analyze reactor grade straight pipe and elbows with circumferential flaws. The close agreement between computed and measured parameters show the importance of continuum damage mechanics in real life applications.
Case Study: Seismic Rehabilitation of a Historical Building Using CUBC 97 Guidelines
Authors: Pong Wenshen , Nazir Mumtaz A. , Bozkurt Murat
Published: August 2008

The proposed research project consists of the seismic rehabilitation of a 1930’s historic building situated in Stockton, California (Seismic Zone 4), using the 1997 Uniform Code for Building Conservation and the Federal Emergency Management Agency FEMA-356 guidelines. The 2-story building was originally built for the Southern Pacific Railroad Company and served as the Stockton Train Depot. The structure consists of un-reinforced brick masonry walls and flexible wood diaphragms. A three-dimension analytical model will be developed and a comparative study will be done for the two approaches. A detailed comparison of the FEMA-356 provisions and the 1997 Uniform Building Code for Conservation (UCBC-97) is performed to establish cost/benefit analyses of the proposed retrofit strategy. A comprehensive comparison of structural capacities of major load-carrying members will also be conducted. Based on the parametric results of this study, a performance-based design scheme will be proposed for retrofitting the existing building to meet the intended seismic performance in the event of major earthquake events.
A Study on Semi-Active Control Using Maxwell-Model Variable Damper
Authors: Sone Akira , Masuda Arata , Iba Daisuke , Ito Kenichiro
Published: August 2008

In recent years, semi-active control has been studied more often in vibration control fields. Semi-active system belongs to a nonlinear system and controller design is not easy. Therefore, the definitive control rule is still not established. This study proposes easy control rule which has only changing the damping coefficient of the seismic isolation system to the maximum and the minimum using the Maxwell-model variable damper and clarifies the influence in numerical analysis which design parameter affect the system further compares the effect with the case of passive system.
Probabilistic Fracture Assessment of Wall Thinning Pipe
Authors: Machida Hideo , Ando Kotoji
Published: August 2008

This paper describes failure probability assessment of thinning pipe of a nuclear-power plant. The rupture of the feed water piping in the turbine building due to wall thinning happened in Kansai Electric Power Company (KEPCO) Mihama nuclear power plant Unit-3 on August 9, 2004. The variation between the prediction and measured wear rate was evaluated using the published data from KEPCO, and the probability density function was created. Using this probability density function, the failure probability of wall thinning pipe was evaluated using Monte Carlo simulation. The parameters of this evaluation are thinning patterns, wear rate, an applied stress and an inspection interval. The requirements to the inspection were clarified from the probability of failure.
Frequency Equations for Vibration Analysis of Fuel Rod
Authors: Kim Hyeong Koo , Kim Jae Ik , Kim Kyu Tae , Kim Moon Saeng
Published: August 2008

In this study, the frequency equations for calculating the natural frequencies of the beams with generally restrained boundary conditions by both translational and rotational springs are derived in matrix form using Fourier sine series. In order to show the validation of the solution, numerical results for two degenerate cases are compared with existing results for natural frequency obtained by the conventional analysis. And as a specific application, the natural frequencies of fuel rod for KSNP (Korean Standard Nuclear Plant) fuel assembly are calculated and compared with the external excitations. As a result, the frequency equation derived by present paper seems to be very useful to evaluate the natural frequencies of the double span beams with various boundary conditions. Especially, when some parametric analyses are needed to modify fuel design, the equation can be applied very easily.
Slip Blinds at Pressures Causing Permanent Deformation
Authors: Taagepera Jaan , Seipp Trevor G.
Published: August 2008

Slip blinds are frequently used for hydrotesting piping. In addition, when maintaining equipment or piping, the equipment or piping must be isolated to assure a safe working environment. Separating flange pairs and inserting a blind flange against the process side prevents hazardous substances from entering the work area. Slip blinds are often used for this type of service. However, slip blinds are generally limited to low pressure service since at excessive pressures the blind will become dished and may leak or become impossible to remove. For this paper, slip blinds of various sizes and thicknesses were hydrostatically tested to determine their deformation as a function of pressure. Nonlinear finite element analysis was used to determine the theoretical deformation of slip blinds. The goal of the testing and FEA was to determine allowable pressures which would limit permanent deformation of the blinds to specified values.
Two-Phase Flow Modeling in a Pipe Related to Flow-Induced Vibration
Authors: Sim W. G. , Mureithi N. W. , Pettigrew M. J.
Published: August 2008

To understand the fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. The distributions of flow parameters across a pipe, such as gas velocity, liquid velocity and void fraction, may be assumed to follow a power law (Cheng 1998, Serizawa et al. 1975). The void fraction profile is, for example, uniform for bubbly flow while it is more or less parabolic for slug flow. In the present work, the average values of momentum flux, slip ratio, etc. are derived by integral analysis, based on approximate power law distributions. A parametric study with various distributions was performed. The existing empirical formulations for average void fraction, proposed by Wallis (1969), Zuber et al. (1967) and Ishii (1970), are considered to obtain the present results. In particular, the unsteady momentum flux for slug flow is approximated.
Effect of Small Variation in the Composition of Plates and Weld Filler Wires on the General Corrosion Rate of Ni-Cr-Mo Alloys
Authors: Fix David V. , Estill John C. , Rebak Rau´l B.
Published: August 2008

The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials within the range of the standards.
Correlation Between Two Types of Surface Stress Mitigation and the Resistance to Corrosion of Alloy 22
Authors: Yilmaz Ahmet , Fix David V. , Estill John C. , Rebak Rau´l B.
Published: August 2008

When metallic plates are welded, residual tensile stresses may develop in the vicinity of the weld seam. Processes such as Low Plasticity Burnishing (LPB) and Laser Shock Peening (LSP) could be applied locally to eliminate the residual stresses produced by welding. In this study, Alloy 22 (N06022) plates were welded and then the above-mentioned surface treatments were applied to eliminate the residual tensile stresses. The aim of the current study was to compare the corrosion behavior of as-welded (ASW) plates with the corrosion behavior of plates with stress mitigated surfaces. Immersion and electrochemical tests were performed. Results show that the corrosion resistance of the mitigated plates was not affected by the surface treatments applied.
Theoretical Underpinning of the Constraint Effect Between Deeply Cracked C(T)- and SEN(B) Specimens
Authors: Ludwig Michael
Published: August 2008

In the standard test method for the determination of the reference temperature T0 in the transition range, ASTM E 1921-03 [1], the remark is given that different specimen types could lead to discrepancies in the calculated T0 values. Especially C(T) and SEN(B) specimens indicate by experimental evidence that a 10 °C to 15 °C difference in T0 has been observed. In the course of the European research project VOCALIST [2] a ferritic RPV steel has been investigated by conducting numerous fracture toughness experiments as well as intensive numerical studies. A local approach model based on the Weibull stress has been developed and calibrated for this material [3]. For the calculation of the constraint effect between SEN(B) and C(T) specimens with a crack to ligament ratio of approx. 0.5 the model has been applied to predict the constraint effects on fracture toughness and the resulting theoretical difference in the reference temperature T0. For this purpose the according specimens have been calculated by several finite element models and a reference solution in the small scale yielding space allowed for the calculation of the “constraint free” reference transition temperature T0. By means of theoretical constraint functions derived from the Weibull stress model, the difference for each specimen compared to the reference solution could be calculated. From the results a theoretical difference of ΔT0 = 10°C between SEN(B) (lower value) and C(T) specimens (higher value) caused by the different crack tip constraint has been obtained. This value confirms the experimental observations.
Wedge-Shaped Shell Structure Impacting a Water Surface
Authors: Constantinescu Adrian , Bertram Volker , Fuiorea Ion , Neme Alain
Published: August 2008

This paper presents a study of fluid structure interaction during the impact of a ship on a water surface. The analysis combines the assumption of small displacements for the ideal fluid and the solid with an asymptotic formulation for accurate pressure evaluation on the wet surface boundary. A fluid-heat analogy is used to obtain the regular displacement, velocity and pressure fields in the fluid domain with ABAQUS/Standard finite element code. PYTHON and FORTRAN languages are also employed to connect fluid and structure data. Two methods are developed. The first method employs a weak fluid-structure coupling. The average discrepancy between our numerical results and experiments was 22% for the peak pressures for conical shell structures. The wet surface velocity was well predicted. The second method (implicit fluid-structure coupling using a convergence criterion) is more accurate. Recent results with an improved, numerical hydrodynamic model based on CFD are also presented.
A Numerical and Experimental Investigation of Wall-Pressure Fluctuations Induced by Sheet Cavitation Instabilities on Lifting Surface
Authors: Astolfi Jacques-Andre´ , Leroux Jean-Baptiste , Coutier-Delgosha Olivier , Deniset Franc¸ois
Published: August 2008

The paper is based on some previous works of the authors aimed to study the phenomenology of cavitation instabilities. In the present work, a particular attention is paid to the analysis of spatio-temporal wall-pressure fluctuations in the context of fluid structure coupling investigations. The work is based on a numerical and experimental study, whose objective was to analyze the wall-pressure fluctuations beneath an unsteady partial cavitating flow developing on an hydrofoil. Experiments were carried in a water tunnel, on a partially cavitating hydrofoil based on extended multi-point wall pressure measurements together with flow visualizations. 2D Navier-Stokes simulations solves the RANS equations combined with a physical model of cavitation The two-phase flow mixture is considered as a homogeneous medium for which the ratio of liquid and vapor is controlled by a barotropic state law. The numerical resolution is based on the SIMPLE algorithm, modified to take into account the high compressibility of the liquid/vapor mixture. The results show that various dynamics are caught by the model in agreement with the experiments. Two main unstable dynamics were observed leading to a strong variation of surface loading. The paper provides quantitative data about the severe unsteady loading that is experienced by the structure, which should very useful in a fully problem of Fluid Structure Interaction. The possibility of a structural response of the foil to the unsteady loading and how it could promote the cavitating flow instability is also discussed.
Experimental and Numerical Analysis of a Coupled Fluid-Structure Subjected to Dynamic Acceleration
Authors: Sigrist Jean-Franc¸ois , Conessa Vincent
Published: August 2008

The present paper deals with a numerical and experimental study carried out on a coupled fluid/structure system subjected to an imposed dynamic acceleration. The coupled system is an clamped/free elastic cylinder surrounded by a heavy, incompressible fluid, contained in a concentric rigid tank, with a fluid free surface. The whole system is subjected to a transverse imposed motion, characterized by a short time duration (∼ 10 ms) and a large acceleration amplitude (∼ 400 m/s2). The principle of the study lies on both an experimental and numerical approach of the problem. This analysis is carried out in order to better understand the dynamic of the coupled system, with industrial application related to the design of embarked naval propulsion nuclear structure. From the numerical point of view, several approaches of the coupled problem are proposed: linear and non linear model are exposed, and various numerical techniques are developed. Strong coupling techniques based on finite element or boundary element are coupled to solve the linear model. Weak coupling techniques are developed to solve the non linear problem. In such technique, the numerical resolution is based on a finite volume method for the fluid problem and finite element method for the structure problem. The fluid and structure problems can be coupled with a staggered explicit or implicit algorithm. From the experimental point of view, a experimental system is designed on a shock table. Structural data (such as displacement, acceleration) are recorded with accelerometers and displacement sensors, fluid data (such as pressure and free surface motion) are recorded with pressure gauge and high-speed numerical camera.
Seismic Analysis of a Nuclear Reactor With Fluid Structure Interaction
Authors: Broc Daniel
Published: August 2008

In the framework of the studies on the seismic behaviour of the PWR reactor cores, models have been built to describe the dynamic behaviour of one fuel assembly, one assembly row or of the whole core. Behaviour models currently restrain the study to the central row of the core. These “One Row Models” (2D vertical models) use beam models for the assemblies and do not consider interactions between the assemblies by the fluid. Recent models consider the whole core (2D horizontal models), with the objective to describe the interactions between the different rows by the fluid. This paper presents a new step to build a complete 3D whole core model, with calculations of vertical fluid flow that can take place in a 2D “one row model”. These vertical flows leads to interactions between the assemblies, even if only one row is considered.
Dynamic Strength Estimates for a High Strength, Experimental Steel
Authors: Torres Karen L. , Clements Hollie A. , Jones Stanley E. , Dilmore Morris , Martin Bradley
Published: August 2008

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the tunnel is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental, high-strength steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain-rate can be assessed through a strain-rate of roughly 105/second. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.
Air Cooling Temperature Analysis of Spent Fuel
Authors: Laursen A. L. , Moody F. J. , Law J. C.
Published: August 2008

Spent nuclear fuel is currently being stored at nuclear reactor sites. The spent fuel removed from the reactor is first placed in a large water pool to remove the initial decay heat. After several years, when the decay heat has dropped below a set level, the fuel is moved into concrete storage casks where natural circulation continues the cooling process. The purpose of this report is to predict, using a simplified analysis, how hot the fuel rods get when cooled by air in the cask. The increase in temperature and the decrease in density cause a chimney effect in the cask. This paper presents an analytical method of obtaining maximum fuel clad temperature in the cask. A non-dimensional model is derived, which is used to calculate the entrance and exit air velocities of the cask. The relationship between these velocities and the temperature used to obtain the maximum fuel clad temperature. A numerical scheme used to predict the maximum temperature is presented here and the results are compared to the analytical model. Both methods yielded corroborating results for fuel placed in the casks after spending similar amounts of time in a spent fuel pool.
Predicting the Brittle-to-Ductile Fracture Initiation Transition Temperature for Surface-Cracked Pipe From Charpy Data
Authors: Wilkowski Gery , Rudland Dave , Wolterman Richard
Published: August 2008

Much work has been done to assess constraint effects on the crack-driving force for specimens and cracks in pipes. The material’s transition temperature where the fracture process changes from ductile tearing to cleavage fracture at crack initiation is affected by the constraint conditions, but is a material property that cannot be determined analytically. This paper presents a methodology to account for constraint effects to predict the lowest temperature for ductile fracture initiation and relates that temperature to Charpy impact data for typical ferritic pipe materials. It involves a series of transition temperature shifts to account for thickness, strain-rate, and constraint to give a master curve of transition temperatures from Charpy data to through-wall-cracked or surface-cracked pipes (with various a/t values) under quasi-static loading. These transition temperature shifts were based on hundreds of pipe tests and thousands of specimen tests over several decades of work by numerous investigators. It is equally applicable to ferritic nuclear pipe for Class 2, 3, or balance of plant piping, or for older linepipe materials. If found to be reasonable, then the procedure could be used in the ASME pipe flaw evaluation procedures as a screening criterion between LEFM and EPFM failure modes.
Asymptotic Crack-Tip Fields in Perfectly Plastic Solids Under Combined In-Plane and Out-of-Plane Shear Loading Conditions
Authors: Pan J.
Published: August 2008

In this paper, governing equations and solutions for asymptotic singular and non-singular crack-tip sectors in perfectly plastic materials are first summarized under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode II/III loading conditions are then investigated. An assembly of crack-tip sectors is adopted with stress discontinuities along the border of the two constant stress sectors. The solutions of the crack-tip fields under pure mode II, mixed mode II/III, and nearly pure mode III loading conditions are presented. The trends of the angular variations of the mixed mode II/III crack-tip stresses agree with those of the available computational analysis and the asymptotic analysis for low strain hardening materials. The pure mode II crack-tip stresses are similar to those of Hutchinson and the nearly pure mode III stresses are similar to those of the pure mode III crack-tip field of Rice.
Steady-State Thermal Simulation of Weld Applied to a Practical Axisymmetric Weldment
Authors: Uchida Ken , Sumiya Rie , Murofushi Tadashi , Jimbo Masakazu
Published: August 2008

Steady-state Eulerian analysis on thermal simulation of welds using moving coordinates is known as a very computationally efficient method. This paper presents a method of Eulerian analysis that uses commercial computational fluid dynamics (CFD) code. In order to show the practical availability of the Eulerian method, the method is applied to an analysis of a circumferential weld of a core shroud in a boiling water reactor (BWR). In this analysis, the double ellipsoidal power density distribution model proposed by Goldak et al. (1984) is applied for the weld heat source, the temperature dependency of thermal properties is considered, and the effect of latent heat is treated by enthalpy method. Comparison of the analyzed temperature histories at several locations on the surface of the weldment to the measured results shows that the numerical results reproduce the measured results well.
Stabilizing and Packaging Pu Materials per 3013 at SRS
Authors: Hensel S. J. , McNew R. T.
Published: August 2008

The Savannah River Site (SRS) began packaging Pu metals into 3013 containers in April, 2003 and oxides in October, 2003. A total of 919 outer 3013 containers were made in the FB-Line at SRS on a very aggressive schedule (average of nearly 42 containers per month). Stabilization and packaging was completed in January, 2005. Experiences, lessons learned, and an overview of packaging activities are presented.
An Attempt to Scale the Vibrations of Water Pipes
Authors: Moussou P.
Published: August 2008

The goal of the paper is to provide an estimation of the vibrations of a water pipe subjected to standard turbulent excitations. Firstly, a simplified expression of the acoustic pressure generated by a standard valve or orifice is proposed. It is based on the hydraulic pressure drop and a Strouhal number. Secondly, a theoretical analysis of Fluid-Structure Interaction yields a screening expression of the structure velocity Power Spectral Density (PSD), as a function of the acoustic pressure source. Field data are used for validation. It is shown that cavitation-induced vibration can be directly identified by plotting the structure velocity PSD in non-dimensional form.
Response of a Dry Storage Spent Fuel Cask to Hypothetical Loading
Authors: Aramayo Gustavo A. , Ammerman Douglas J. , Smith Jeffrey A.
Published: August 2008

This paper addresses the analytical methods used to determine the response of a dry storage spent fuel cask to hypothetical loading. Because of the sensitive nature of the topic under discussion, the response of the cask is described in qualitative terms, and the paper is intentionally vague on the parameters and results. This research was sponsored by the U.S. Nuclear Regulatory Commission (NRC) Spent Fuel Project Office. The work was performed under contract from the Sandia National Laboratory (SNL), Transportation Risk and Packing organization. The analytical effort was performed at the Oak Ridge National Laboratory (ORNL) facilities with loading specified by SNL.
Analysis of a Soft Catch for Conventional Warheads
Authors: Pope Matthew , Martin Bradley , Lambert David , Jones Stanley E. , Muse Jonathan
Published: August 2008

A “soft catch” is a device with which an explosively formed projectile can be decelerated to zero velocity without sustaining significant damage. The recovered projectile provides data, via metallurgical analysis, on the deformation conditions found within the explosively formed projectile. At Eglin AFB, FL, the soft catch consists of a sequence of sections (Figures 1–3), each roughly one meter long, filled with various soft media. Velocity screens are placed at the entrance and exit of each section. This enables investigators to experimentally determine the time at which the projectile passes each station in the catch. Based on these experimental measurements, average velocity estimates for each section of the soft catch can be made. The purpose of this paper is to support the soft catch design process with a one-dimensional analysis. The mathematical modeling is based on observations presented in studies by Allen, Mayfield, and Morrison [1,2]. Their work addresses the penetration of sand, but their modeling is appropriate for materials in the soft catch. The current paper describes application of their model to interpreting three soft catch experiments where Tantalum projectiles with initial velocities of approximately 1400 m/s were successfully recovered.
Gaseous Explosions in Pipes
Authors: Kolbe M. , Baker Q. A.
Published: August 2008

Gaseous explosions occurring in industrial piping and process systems have been recorded and documented since the early days of industrialization. Despite the efforts put forth by the academic and scientific communities in understanding these phenomena, these explosions are still occurring in industry. Often times, operating companies that suffered the explosions were unaware of the possibilities of explosion in their piping systems and as a result, installed control and safety systems were not adequate. The mitigation of gaseous explosions in pipes requires a basic understanding of combustion and detonation theory. These events are not confined to chemical and petroleum refining facilities; potentially, they can occur in any system where a flammable mixture can form in pipes. Gaseous explosions arise from the formation of a fuel and oxidizer mixture. Although many systems are known to carry both a fuel and an inert gas to dilute or suppress combustion, the flammability limits of this mixture are often a point of uncertainty. However, it must be understood that there are several factors that can lead a flammable mixture to a strong deflagration or potentially even a detonation. The following paper will discuss the basics of gaseous pipe explosions by defining the chemical and physical limits of both deflagrations and detonations. Examples of industrial accidents involving unique gaseous pipe explosions are provided in the paper as well as recommendations for prevention and mitigation of gaseous pipe explosions.
Fretting-Wear Damage at Hydraulic Snubber Pins
Authors: Engel Robert
Published: August 2008

During the refueling outage at the Leibstadt Nuclear Power Plant in August 2002 and 2003 some severely worn hydraulic snubber pins were found at a main steam line support inside the turbine building. Possible causes of the failure were considered to be increased loads due to the implementation of a snubber reduction program in the 1996 to 1998 time period, or flow-induced vibration from the extended power uprate implemented in four steps from 1998 to 2002. During the 2003 outage, a vibration measurement program as well as a root cause analysis were started to check the integrity of the whole system and to reduce or eliminate the degradation mechanism. The dynamic measurement data obtained during the 2003 power ascension showed that the vibration acceptance criteria were met. However, the main steam line support with the worn snubber pins experienced a horizontal relative movement between the pins and the clamps. This started at a power level corresponding to an intermediate power uprate step. Four different pragmatic local design solutions were considered to prevent the severe wear.
Study on 3-D Measurement Method in Shake Table Tests Using Image Processing Technique: 3rd Report, Examination of Upgrading for Measurement Accuracy in Actual Fracturing Test
Authors: Fujita Satoshi , Furuya Osamu , Mizuno Hiroki
Published: August 2008

In recent years, the importance of the fracturing test using the full-scale model is recognized in order to upgrade an earthquake resistant design. It is, moreover, important to develop a new measurement method which can measure a complex three-dimensional behaviour in such fracturing test. This study has been doing research and development of three-dimensional measurement method using an image processing technique for a measurement of dynamic displacement in shake table test without any contact. This measurement system is a very convenient system because it can measure the three-dimensional dynamic displacement in the simple experimental condition that the several makers are only attached to the surface of an experimental structure. The system therefore is the most suitable measurement system for an evaluation of complex 3-dimensional behavior of test model. Fundamental hardware and software for the measurement system has been constructed until now. The fundamental dynamic measurement accuracy and effectiveness of the measurement system has been also confirmed from several shake table tests. This paper describes the examination of the upgrading for the measurement accuracy in actual fracturing test. Moreover, the shake table test results using actual wooden house model were also indicated.
Verification Test for Hybrid Seismic Experimental Method Using Nonlinear Finite Element Method
Authors: Dozono Yoshihiro , Fukuyama Mayumi , Horiuchi Toshihiko , Konno Takao , Sakai Michiya , Ohtomo Keizo , Hagiwara Yutaka
Published: August 2008

An improved substructure hybrid seismic experimental method has been developed. This method consists of numerical computations using a general-purpose nonlinear finite element analysis tool and a pseudo-dynamic vibration test. Therefore, it enables seismic testing of large-scale structures that cannot be loaded onto a shaking table. The method also visualizes both data measured by sensors placed on the specimen and the results of the numerical analysis, and it helps us to understand the behavior of an entire structure consisting of a specimen and a numerical model. We performed verification tests for a piping system, in which we used a numerical model including supports, valves, and a branch pipe, and a specimen including two elbows. As results of tests, we conclude that the developed system has enough accuracy to be used as a seismic testing method.
Supplementary Technical Basis for ASME Section XI Code Case N-597
Authors: Scarth Doug
Published: August 2008

Efforts to develop clear and conservative methods to measure and evaluate wall thinning in nuclear piping have been underway since the late 1980’s. The Electric Power Research Institute (EPRI) carried out a successful campaign to address programmatic issues, such as locating and predicting flow-accelerated corrosion (FAC) degradation. This included developing a computer code (CHECWORKS), a users group (CHUG), and a comprehensive program guideline document for the effective prediction, identification and trending of flow-accelerated corrosion degradation. U.S. Nuclear Regulatory Commission (NRC) guidelines are provided in the NRC Inspection Manual Inspection Procedure 49001. At the same time, committees under Section XI of the ASME Boiler and Pressure Vessel Code have addressed evaluation of structural integrity of piping subjected to wall thinning. Code Case N-480 of Section XI provided acceptance criteria that focused on primary piping stresses, with evaluation based on a uniform wall thinning assumption for evaluating the minimum wall thickness of the piping. However, when applying this methodology to low pressure piping systems, Code Case N-480 was very conservative. Code Case N-597 was first published in 1998, and supercedes Code Case N-480. The current version is N-597-2. Code Case N-597-2 provides acceptance criteria and evaluation procedures for piping items, including fittings, subjected to a wall thinning mechanism, such as flow-accelerated corrosion. Code Case N-597-2 is a significant improvement over N-480, containing distinct elements to be satisfied in allowing the licensee to operate with piping degraded by wall thinning. The Code Case considers separately wall thickness requirements and piping stresses, and maintains original design intent margins. The Code Case does not provide requirements for locations of inspection, inspection frequency or method of prediction of rate of wall thinning. As described in the original technical basis document published at the 1999 ASME PVP Conference, the piping stress evaluation follows very closely the Construction Codes for piping. Five conditions related to industry use of Code Case N-597-1 have been published by the NRC in Regulatory Guide 1.147, Revision 13. A number of these issues are related to a need for additional explanation of the technical basis for the Code Case, such as the procedures for evaluation of wall thickness less than the ASME Code Design Pressure-based minimum allowable wall thickness. This presentation addresses these NRC conditions by providing additional description of the technical basis for the Code Case.
A Proven Process for Assessing the Technical Integrity of Aging Pressure Equipment
Authors: Reynolds John , Larsen Greg
Published: August 2008

This paper describes a detailed process for assessing two important aspects of aging pressure equipment infrastructure: 1) First by determining if the pressure equipment management systems (MS) are sufficiently effective to maintain and sustain the integrity and reliability of aging pressure equipment (vessels, tanks, and piping systems), 2) Secondly, by detailed individual equipment reviews (ER) to determine what vessels and piping systems may need recapitalization or major maintenance within the next 5–10 year timeframe. The two focused asset integrity reviews (FAIR®+MS & FAIR®+ER) can be completed in combination or separately in order to identify the strengths and weaknesses of a pressure equipment integrity maintenance program, as well as the actual condition of the highest risk pieces of pressure equipment and piping. The management system review surveys the 101 essential elements of pressure equipment integrity management and results in a benchmarking score for the operating site on the basis of 1000 points of excellence. This score allows the recipient to benchmark their status against many other sites that have already been reviewed and also facilitates the measurement of progress over time when the integrity reviews are repeated. The equipment specific review of individual pieces of equipment allows the recipient to determine how much it is likely to cost to maintain the facility (and to recapitalize, as necessary) in reliable operating order to support the on-going business. Both reviews result in specific recommendations on how the owner-operator can improve the pressure equipment management systems and maintain specific equipment.
Life Prediction of Furnace Heater Tube Using Omega Parameter and Life Fraction Rule
Authors: Han Sang-In , Choi Song-Chun , Kim Ji-Yoon
Published: August 2008

Recently, predicting the remaining life of petrochemical equipment that is used in high temperature and pressure service is an essential element. Specifically, predicting the life of furnace heater tubes used in the range of 850°C to 950°C is an important subject. For economic reasons, it is desirable to replace degraded tubes before tube fails occur. Remaining life assessments are used to help in making tube replacement decisions at proper time. This paper contains Ω parameter and life fraction rule used to life assessment factor to predict remaining furnace tube life, compares the two methods. As the result of assessment, two methods show that the general life of the furnace heater tubes are about 160,000hr and future remaining life is 50,000hr. Based on this result, the heater tubes are enabling to operate until 4years.
Stress Intensity Factors for Under-Clad and Through-Clad Defects in a PWR RPV Submitted to a Pressurised Thermal Shock
Authors: Chapuliot S. , Me´nager Y. , Marie S.
Published: August 2008

CEA has launched important work on the development of a Stress Intensity Factors compendium for cracks in RPV walls taking into account the cladding. The work is performed by a F.E. analysis with a parametric mesh for two types of defects (under-clad defect and through-clad defect) in a wide range of geometrical and material parameters. In addition, an analytical stress solution for PTS on the RPV is proposed to allow a complete analytical estimation of the stress intensity factor KI for the PTS problem. The results are validated by their application on a complex and realistic case study, and the comparison with the complete 3D finite element calculation.
Study of Correlation Between Beam Vibration and Oval Vibration on Cylindrical Water Storage Tank
Authors: Maekawa Akira , Shimizu Yasutaka , Suzuki Michiaki , Fujita Katsuhisa
Published: August 2008

A large cylindrical water storage tank, widely used at power stations and chemical plants, typically has a large radius/wall-thickness ratio. The relatively thin sidewall of such a tank can deform easily during an earthquake due to vibrations of the tank structure. In order to improve the seismic-proof design practices for a water storage tank of flexible structure and to develop a new seismic resistance evaluation method to be adopted in future, it is important to understand the dynamic responses of such a tank to seismic motions including the nonlinearity of responses to large amplitude vibrations. This paper reports on the results of vibration test, in which sinusoidal wave excitations with large amplitude were conduced to the scale model tank of a thin-walled cylindrical water storage tank, and the theoretical analysis of the dynamics of the vibratory behaviors that were observed during the vibration test. First, a frequency sweep test was performed over the range that covered the natural frequency. The response of the test tank as a whole to given vibrations remained almost the same over the excitation frequency range. Frequency analysis of the response of the tank failed to locate any resonance points at or around frequencies that had been determined by the basic vibration characteristic test that we had conducted in advance. Next, a large amplitude excitation tests were carried out, in which the test tank was excited intensively by several tens of sinusoidal waves of a fixed frequency that was in the vicinity of the resonant frequency. The response of the tank as a whole in the form of beam vibrations did not intensify in proportion to the input acceleration; it did not go beyond a certain level. Since both of the tests produced significant oval vibrations on the sidewall of tank, the influence of oval vibrations over beam vibrations was analyzed. The analysis concerning the deflection of the sidewall of tank by the additional appearance of oval vibrations in the presence of beam vibrations revealed that a major decrease in the flexural rigidity reduced the response (beam vibrations) of the whole tank. The phenomenon was modeled using a nonlinear equation of motion, assumed that the rigidity depended on the amplitude of oval vibrations. The analysis using this equation explained the results of the above-mentioned tests very well. Thus, it was demonstrated both empirically and analytically that beam vibrations of a cylindrical water storage tank are reduced by the appearance of oval vibrations that have the effect of lowering the natural frequency.
Progress in TMCP Technology and Expansion of Its Range of Application
Authors: Tanaka Yoichi
Published: August 2008

More than twenty years have passed since the development and commercialization of water-cooling-type TMCP (Thermo-Mechanical Controlled Processing) steel. At present, the technology is used in various areas as a reliable process. Features of TMCP steel are excellent weldability and toughness, which make it extremely useful as a tank material. This paper aims to contribute to the safety and workability improvement in the tank construction field as in other areas by the effective use of TMCP steel. The paper first describes the characteristics of material properties and workability of TMCP steel and the metallurgy to realize these characteristics. It then introduces a several examples of recent development in the application of TMCP technology. The use of TMCP steel realizes better toughness in high-heat-input welding, improved low-temperature toughness and sour gas resistance, in addition to reduced weld pre-heating temperature thanks to its low carbon content. Recently, because of its excellent characteristics, it has become possible to apply TMCP steel to nuclear energy areas, medium- to high-temperature regions, and ultra-high strength types such as 780 MPa and 950 MPa. Examples of the latest commercial application include surface ultra fine grain steel whose excellent brittle crack arrestability is comparable to that of high-Ni steel for cryogenic use, and ultra-thick structural steel plate that allows super-high welding heat input over 100kJ/mm.
Simplified Modeling and Detailed Crack Propagation Analysis for Cracked Pipes
Authors: Iijima Tadashi
Published: August 2008

Two analysis approaches for a cracked pipe subjected to a seismic load were focused on. The first approach is a simplified modeling technique using a nonlinear spring element. A degrading model called a deteriorating distributed element was improved to simulate the asymmetric and degrading behavior of a cracked pipe. The second approach is a detailed crack propagation analysis using the finite element method (FEM). This approach is based on fracture mechanics, and crack growth is determined by using fracture parameters such as the J-integral range obtained from the FEM. Iterative re-meshing of the analysis model using solid elements was conducted to evaluate fatigue crack growth for cyclic loads. These two approaches were applied to a cracked pipe test. In comparing the test results, it was confirmed that the simplified modeling and detailed analysis approaches are applicable to a seismic analysis for a cracked pipe.