bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Evaluation of a Seismic Capability of Actual LNG Tank Under Severe Seismic Excitation
Authors: Tazuke Hideyuki , Yamaguchi Satoru , Akiyama Hiroshi , Sakurai Tomoki , Chiba Toshio
Published: August 2008

The Hyogoken-Nanbu Earthquake in 1995 has recognized us the importance of the resistance capability against earthquakes on the thermal power plant. In this respect, seismic proving tests on the equipment of the thermal power plant have been planned and carried out. Vibration tests and FEM analysis were performed to demonstrate the earthquake resistant property of the tank. FEM analysis was adopted for analyzing lateral slipping and elephant foot bulge (EFB). To verify the validity of the FEM analysis, the results of tests were compared with those of analysis. Using these analysis methods, we estimate the seismic capability of the LNG tank under severe seismic excitation. As the results, we confirmed that lateral slipping and EFB did not occurred at severe seismic excitation.
Analysis of Dynamic Loading of a Simple Structure to a Blast Wave
Authors: Berg Vanessa , Stofleth Jerome H. , Preece Dale S. , Saul Venner
Published: August 2008

An object in the path of a blast wave generated by an explosion will experience a certain level of structural damage. The degree of destruction seen in a structure from a explosive blast wave is effected by three main parameters, (1) the force applied to the structure, (2) how long the force is acting on the structure, and (3) the specific geometric and material properties of the structure, or architectural surety. Structures capable of large lateral loads can be used for defense against explosions (terrorist threats). However, in order to fully predict the architectural surety of a structure, further investigation of the interaction of explosive blast waves with structures is required. The purpose of our analysis is to determine the efficiency of coupling energy from a blast wave to a simple structure. We performed some explosives tests and computer simulations to provide this analysis. In our experiments, the structures consisted of several free hanging steel plates at various distances from an explosion. The blast wave was generated by a sphere of TNT. We used a standard model to calculate the overpressure incident on this plates, we then calculated the shock energy coupled to the plates, we measured the overpressure at points near the plates (for calibration), we measured the effects of the blast wave on the plates (measured their displacement due to the blast), and we performed computer code calculations to predict the effect of the blast wave on the plates. The computational code Autodyn is currently being used at Sandia National Laboratories for various impact and blast loading problems. The code contains several simulation methods, including ALE (Arbitrary Langrangian Eulerian) simulation. Because explosive blast in air involves both expanding gases as well as solid/solid impacts, ALE codes typically provide better predictive capabilities.
Design of Conical Shaped Charges for Prompt Initiation of TNT Chemical Munition Bursters
Authors: Preece Dale S. , Stofleth Jerome H. , Cole David L. , Cooper Paul W.
Published: August 2008

The Explosive Destruction System (EDS) has been designed at Sandia National Laboratories for the disposal of chemical munitions (phosgene, mustard gas, sarin etc.), many dating back to World War I. EDS is a portable system that is trailer mounted and consists of a vessel into which a chemical munition can be loaded and neutralized with linear and conical shaped charges. Gases are contained within the sealed chamber. The linear shaped charges split the munition in two and the conical is aimed at the explosive burster, in each munition, which is detonated by the shaped charge jet. Toxic chemicals remaining in the vessel following detonation are neutralized and disposed of. This paper documents the development of a new conical shaped charge (CSC) needed to reliably detonate explosive bursters in an expanding array of chemical munitions that are beyond what the device was originally designed to neutralize. Design of this new CSC was controlled by the need to deliver energy above the detonation threshold into the explosive after penetrating the outer steel casing, fluid, the burster casing and finally the explosive. Design considerations were driven by jet conditions at the steel/explosive interface inside the burster. Parameters to consider in CSC design include: 1) diameter, 2) liner thickness, 3) liner position in body, 4) explosive weight, and 5) liner shape or interior angle. The effects of these parameters on final CSC performance are examined in detail. CSC’s meeting the design specifications have been manufactured and tested. The performance of these charges is compared with the original design requirements.
Penetration of a Rate Sensitive Geological Target by the Compaction Ring Theory
Authors: Gilmore Martin R. , Jones S. E. , Foster Joseph C.
Published: August 2008

In an earlier paper, the authors presented a theory for the penetration of geologically based semi-infinite targets [5]. This theory was suitable for application to targets in which compaction due to the crushing of voids is the primary deformation mechanism. This phenomenon has been observed in concrete targets with a ring of dense material around the tunnel region, see figure 1 for a cat scan of a concrete target after penetration. This was the motivation for the model development. A number of simplifying assumptions were made in the application of the theory to data from concrete penetration experiments. One of the assumptions was that the target strength was constant, or independent of strain and strain rate. This assumption leads to generally consistent results for the same ogive nose geometry. However, it was noted that there was a discrepancy between the strength predictions when two different ogive nose geometries were used. This paper investigates the discrepancy by assuming that the target material is rate sensitive. The results indicate that the strain rates in the target are indeed affected by the nose geometry. A detailed analysis for a target material with linear rate sensitivity is provided in the paper and the results provide a favorable comparison with available experimental evidence.
Effect of Compressive Stress on Longitudinal Wave Speed in Cementitious Material
Authors: Hughes Mary L. , Ross C. Allen , Ashley Voncile L.
Published: August 2008

The Air Force has been interested for some time in the development of computer codes that accurately predict the penetrator trajectory created when munitions are fired into concrete and geomaterial targets, as well as the resulting depth of penetration. Recent work has focused on experimental research performed to determine quasistatic, dynamic, unconfined and confined material properties for development of an elastic/viscoplastic constitutive equation. This constitutive equation has shown some promise in predicting stress and strains but lacks a consistent damage parameter to predict damage or fractures exhibited by the target material during experimental impact tests. Current damage level predictors that employ a scalar damage parameter are not sufficient to predict the directional damage or fracture that occurs in simple uniaxial compression tests of concrete and geomaterials. Tensorial or directional damage parameters coupled with constitutive relations are necessary for better understanding and accurate prediction of damage exhibited when munitions impact concrete and geomaterials. The primary objective of the study described herein was to identify, quantify and characterize damage parameters associated with certain constitutive responses of cementitious and geologic materials. To that end, longitudinal wave speed and biaxial strain data were collected simultaneously on a series of grout cubes as they were being loaded to failure in uniaxial compression. The results of these tests, and a comparison to existing related data [1, 2] are presented.
Stress Concentration Factors of Cross-Bores in Thick Walled Cylinders and Square Blocks
Authors: Dixon Ricky D. , Peters Daniel T. , Keltjens Jan G. M.
Published: August 2008

The purpose of this paper is to investigate the stress concentration in stress fields around crossbores for closed-end thick-walled square blocks and cylindrical shells using the finite element method. These stress concentration factors are presented and discussed as a function of the ratio of crossbore radius to the cylinder internal radius (HR/Ri = 0.01 to 0.7) for a range of wall ratios (Y = 1.5 to 5). Charts and simple expressions are provided for ease of use.
Development of Materials, Design, Calculation and Testing of High Pressure Equipment, Especially for Low Density Polyethylene Plants
Authors: Schedelmaier Johannes , Po¨lzl Manfred
Published: August 2008

The trend of new projects for polyethylene plants indicates a significant increase of production capacity per year. There is a continuous enlargement of pressurised cross sections in the product line of heat exchanger, reactor and remote controlled valves. Consequently an essentially higher load has to be considered on the installed high pressure equipment. Basic knowledge about process and load conditions including pressure pulsation are the fundamental information provided by the process licensor for product optimisation. The level and amplitude of pulsation have a very significant impact on lifetime of the equipment. Cyclic load conditions and measures for improvement of fatigue strength are indicated on diagrams and described. In order to follow the process licensor and safety requirements detailed investigations on proper material selection and improvement of mechanical properties have been performed. Fatigue analysis and fatigue testing are included in the material evaluation. Modern steel technology like vacuum technology, electroslag remelting, heat treatment of special steels, several further hot and cold forming processes and autofrettage are mandatory to achieve an optimised product with satisfactory lifetime, which also fulfils the safety requirements. References to material characteristics including fatigue testing are available from literature, Universities, research laboratories and manufacturers. Parameters like geometry, surface finishing and autofrettage have also an essential impact on fatigue strength. Further activities including fatigue testing with different parameters and load conditions are needed in the future in order to extend the available information about material characteristics and design criteria for high pressure applications.
High Pressure Safety Relief Valves in Ethylene Service
Authors: Fo¨llmer Bernhard , Schnettler Armin , Cornelissen Philip
Published: August 2008

Research conducted in a high pressure polyethylene plant in Belgium, indicates that certain conventionally designed and scaled-up safety relief valves did not open consistently with ethylene at 300 barg and also at 250 barg. Comparative tests in the high capacity at the High Pressure Laboratory of a German safety relief valve manufacturer showed that the same conventionally designed and scaled-up safety relief valves tested at a set pressure of 250 barg had high lift fluctuations on air but did not open on water. It was also demonstrated that a safety relief valve designed by a German manufacturer, which opened reliably on air and on water at a set pressure of 250 barg also opened reliably on ethylene at a set pressure of 250 barg (i.e. supercritical condition). The comparative tests with ethylene in the polyethylene plant in Belgium showed also that the blow down values on that valve with ethylene are similar to the blow down values with water. Therefore it looks like the flow behavior in the safety relief valve with supercritical ethylene is similar as with a liquid. This plant testing on ethylene at 250 barg indicates that there are advantages to using the German manufacturer’s designed safety relief valves with the certified “one trim design” for liquid and gas.
Crack Initiation Behaviour in Small Root Radius Zr-2.5Nb Pressure Tube Specimens Under Monotonic and Cyclic Loading Conditions at Ambient Temperature
Authors: Ho Edward T. C. , Choubey Rameshwar , Shek Gordon K. , Sagat Stefan , Scarth Douglas A.
Published: August 2008

To evaluate crack initiation from small radius flaws in Zr-2.5 Nb pressure tubes in operating CANDU reactors, a number of crack initiation tests under both monotonic and cyclic loading in notched tension specimens have been carried out at ambient temperature. Test specimens were machined with the tensile axis parallel to the circumferential or transverse direction in both as-fabricated and ex-service pressure tube materials. The test specimens were first pre-conditioned by subjecting them to a notch-tip creep stress relaxation cycle, and a subsequent hydride formation cycle whereby notch-tip hydrides are produced. Some specimens with no notch-tip hydride were also tested. Test specimens were instrumented with acoustic emission (AE) and DC potential drop (PD) monitoring systems for detection of crack initiation and growth. Test results indicated the following trends: (a) the existence of notch-tip hydride lowers the crack initiation stress, with the hydride effect being much stronger under monotonic loading than under cyclic loading; (b) the greater the hydrogen concentration, the lower the notch-tip hydride crack initiation stress under monotonic loading; (c) for a given alternating elastic peak stress, the smaller the root radius the greater the resistance to crack initiation; (d) as expected, the number of cycles to crack initiation is a strong function of the alternating elastic peak stress, for a given specimen geometry. An analysis of the test results and their impact on flaw evaluation methodology for Zr-2.5 Nb pressure tubes is described.
The Development of Structural Integrity Procedures for the Safe Working of Ceramics Industry Ball Mills with Cast Iron Ends
Authors: Howard I. C. , Pugh A. C.
Published: August 2008

A ball mill at a ceramics materials company in North Staffordshire exploded in the spring of 2000. Luckily, nobody was injured as a result. Even so, the damage was so extensive that many in and around the ceramics industry rapidly concluded that the industry must introduce suitable operating practices so that the risk of a similar explosion was made acceptably small. As a result, a group of engineers, industry representatives and safety professionals has developed a set of Structural Integrity procedures for adoption in this industry. These mills and their operation are very different from the structures in those industries that normally draw upon Fracture Mechanics-based Structural Integrity principles. Hence, the development of these SI procedures for the ceramics industry is a good example of how their rapid acceptance could benefit traditional industries. Ceramics materials are ground wet, and so the mill must be sealed when running, to keep the resultant slurry inside. Since grinding produces a large amount of heat, the pressure in the mill rises as the water vapor and air inside attempt to expand. The mill therefore becomes a pressure vessel if it is left running long enough for the internal pressure to reach significant values. There are more than 250 ball mills in the UK industry. At least one half of those in the ceramics industry have cast iron ends, as did the mill that exploded. They are cylindrical, and rotate around a horizontal axis. Their construction typically involves a steel cylindrical wrapper, fastened, in different ways, to the two end plates. The end plates are therefore the critically sensitive components. The paper describes the work to assess the sensitivity of the cast iron end plates to the presence of cracks, and how this can be related to regular operating practice in the industry. The structure of the industry makes it heavily constrained against large capital expenditure, so effective SI procedures must be affordable by each company. The practicality of the procedures depends crucially upon non-critical flaws being observable by eye for a long period of mill running. As a result, the planned SI procedures can be implemented through a programme of education and training of all plant personnel and their supervisors and managers. This is an excellent example of how SI practice depends upon effective working of all relevant staff in an industry.
A Fracture Mechanics Evaluation of Observed Cracking at a BWR-2 Reactor Pressure Vessel Weld
Authors: Mehta Hardayal S. , Horn Ronald M. , Inch George
Published: August 2008

The reactor pressure vessel (RPV) to shroud support weld (termed as H9 weld) of a Boiling Water Reactor-2 (BWR-2) was examined during a refueling outage. The ultrasonic (UT) examination was performed from the upper conical support plate surface for all accessible areas of the H9 weld. A fracture mechanics evaluation was conducted to justify continued operation of the RPV in the presence of cracking detected during this examination. The evaluation considered crack growth during future operation and was based on the procedures outlined in Paragraph IWB-3600 of ASME Section XI. The structural margin at the shroud support structure was based on the limit load approach. Projected crack growth based on 10 years (approximately 80,000 hours) of operation was included in the evaluation. The results showed that the safety factor is 21.74 compared to the minimum required safety factor of 2.77. Assessment of the potential for cracking progressing into the low alloy steel material of the RPV was also conducted. The evaluation showed that crack depth in the reactor wall is predicted to be less than the allowable value even after an operating period in excess of 100,000 hours. This result, in conjunction with the evaluation result for the shroud support structure, provided technical justification for continued operation of the RPV with the observed H9 weld cracks for at least 5 additional operating cycles, equivalent to 10 years operation.
Unresolved Issues With Regard to Creep and Creep Fatigue Life Prediction
Authors: Oh J. , Katsube N. , Brust F. W.
Published: August 2008

This paper studies intergranular creep failure of high temperature service material under a stress-controlled unbalanced cyclic loading condition. The grain boundary rupture process was numerically analyzed using Tvergaard’s axisymetric model. The present numerical model incorporated the experimentally verified Murakami-Ohno cyclic strain hardening creep law and Norton’s creep law. The numerical results show that void growth accelerates under cyclic loading condition. Also, analysis shows that a steady state creep law is not sufficient to analyze damage evolution under cyclic loading conditions.
Assessment of Typical Pipeline Flaws With SINTAP
Authors: Hamann Rainer , Zerbst Uwe
Published: August 2008

The recently developed European flaw assessment procedure SINTAP is applied to a total of 88 full scale pipe tests (burst tests) with through-wall and surface cracks subjected to internal pressure. Based on the experimental results various analysis levels of SINTAP are discussed with respect to their potential for predicting the failure loads and the margins of conservatism. Different shape functions from Newman & Raju, Zahoor and API 579 were used for the assessment.
Development of a Fatigue Design Curve for Austenitic Stainless Steels in LWR Environments: A Review
Authors: Chopra Omesh K.
Published: August 2008

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components and specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain–vs.–life (ε–N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This paper reviews the existing fatigue ε–N data for austenitic stainless steels in LWR coolant environments. The effects of key material, loading, and environmental parameters, such as steel type, strain amplitude, strain rate, temperature, dissolved oxygen level in water, and flow rate, on the fatigue lives of these steels are summarized. Statistical models are presented for estimating the fatigue ε–N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. Data available in the literature have been reviewed to evaluate the conservatism in the existing ASME Code fatigue design curves.
CF/SCC Interaction on Structural Materials for LWR in High Temperature Water
Authors: Katada Yasuyuki , Ohashi Shigeo
Published: August 2008

A test apparatus was developed to study the interaction between corrosion fatigue (CF) and stress corrosion cracking (SCC) in high-temperature water simulated boiling water reactor environment. Tests were conducted using 1/2T-CT samples of both low alloy and sensitized stainless steels under 3 different types of loading at 0.2–8 ppm in dissolved oxygen concentrations at 563 K in water. Type 1 was a normal cyclic loading test of constant amplitude, Type 2 a monotonic constant loading rate test, and Type 3 a combination of Type 1 + Type 2 loading modes. In the low alloy steel, no striking interaction was observed between CF and SCC, whereas in the case of Type 3 loading condition crack growth rates of the sensitized stainless steel were as much as 3 times higher than those for Type 1 + Type 2. The mechanism of the CF and SCC interaction is discussed.
Background to Recent Revision of the Section III Seismic Piping Rules
Authors: Minichiello John , Branch Ernest B. , Adams Timothy M. , Asada Yasuhide , Barnes Richard W.
Published: August 2008

The new rules for seismic piping design in Section III that were developed and included in the requirements in 1994 Addenda of the ASME Boiler and Pressure Vessel Code (B&PV Code) generated considerable discussion within the industry and from the United States Nuclear Regulatory Commission, (USNRC). The USNRC initiated a review of the results of the previous EPRI/NRC experimental program and the Japanese industry started its own experimental program. To accommodate and address developments resulting from these efforts, the ASME, B&PV Code established a Special Working Group (SWG) to continue the review and study of the questions and information generated. This paper reports on the efforts of this SWG which resulted in refinements of the revised rules. These refinements have been accepted for inclusion in Section III of the ASME, B&PV Code.
ASME Code Ductile Failure Criteria for Impulsively Loaded Pressure Vessels
Authors: Nickell Robert E. , Duffey Thomas A. , Rodriguez Edward A.
Published: August 2008

Ductile failure criteria suitable for application to impulsively loaded high pressure vessels that are designed to the rules of the ASME Code Section VIII Division 3 are described and justified. The criteria are based upon prevention of load instability and the associated global failure mechanisms, and on protection against progressive distortion for multiple-use vessels. The criteria are demonstrated by the design and analysis of vessels that contain high explosive charges.
Natural Focusing for the Detection of Defects Beyond Elbows
Authors: Rose Joseph L. , Avioli Michael J. , Mudge Peter J.
Published: August 2008

Long range ultrasonic guided wave inspection is advancing rapidly and is commonplace today. Benefits of using longitudinal or torsional modes are being established in special circumstances of improved sensitivity, resolution, or penetration power. The possibility of inspection under insulation, coatings, or with water filled pipes or around elbows is possible. Detection of defects beyond a pipe elbow is difficult for axisymmetric wave impingement onto the elbow. For non-axisymmetric input to the elbow region, however, via partial loading around the circumference, allows natural focusing to occur because of angular profile variation around the circumference of the pipe. An experiment is reported here to demonstrate this process.
Generalized Differential Quadrature Method for Burgers Equation
Authors: Mesˇtrovic´ Mladen
Published: August 2008

The generalized differential quadrature method as an accurate and efficient numerical method is developed for the Burgers equation. The numerical algorithm for this class of problem is presented. Differential quadrature approximation of needed derivatives is given by a weighted linear sum of the function values at grid points. Recurrence relationship is used for calculation of weighting coefficients. The calculated numerical results are compared with exact solutions to show the quality of the generalized differential quadrature solutions for each example. Numerical examples have shown accuracy of the GDQ method with relatively small computational effort.
Three Turnaround Heat Treating Studies
Authors: Taagepera Jaan , Clift Marty , DeHart D. Mike , Marden Keneth
Published: August 2008

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.
The Use of FEM in the Revamping of Existing Systems
Authors: Porter Michael E. , Martens Dennis H.
Published: August 2008

Often the revamping of existing sulfur recovery systems requires replacing some of the equipment. At the same time, economic considerations can dictate re-using as much of the existing system as is possible and practical. This paper examines the process used to connect a new thermal reactor to an existing waste heat exchanger. Included are some of the design considerations necessary to ensure a safe and reliable final arrangement. The complexity of the configuration — including the stresses developed in the existing equipment and the interconnection — required the use of Finite Element (FE) to assess the final design.
Condensation Water Hammer Calculation as Basis for Better Design
Authors: Schnellhammer Werner , Diesselhorst Tilman
Published: August 2008

Condensation processes can generate relevant loading on piping systems when large bubbles ore separated vapor volumes are collapsing in a pipe. For prediction of such loads condensation effects in piping systems were modelled and integrated in a pressure surge code for branched systems taking into account fluid structure interaction. From these calculations we get realistic results of condensation water hammer in the piping system. The loads are strongly depending on the initial conditions and operating procedures. By carrying out calculations with the different possible operating conditions the results give the basis to decide which load cases are covered by the system design and where countermeasures have to be taken. These measures may consist of changing the modus of system operation or modifying the system design itself. A typical example is given.
Circular Cylinder Exposed to Cross Flow Fluid Forces – Parameters of Influence – Limits of Numerical Models
Authors: Reichel Christoph , Strohmeier Klaus
Published: August 2008

In many technical fields, e.g. heat exchangers, circular cylinders are involved in Fluid Structure Interaction (FSI) problems. Therefore correct frequency and magnitude of fluid forces, respectively Strouhal number, drag and lift coefficient are needed. If fluid forces are evaluated with Computational Fluid Dynamics (CFD), mostly flow around a rigid cylinder is used to verify model and numerical methods. Unfortunately experimental as well as numerical results show great variation, making verification and testing of models difficult. Reynolds number is regarded as main influencing parameter for a rigid cylinder in cross flow. Most of experimental deviations can be related to other parameters, which differ from experiment to experiment. In this paper such parameters are specified and it is shown, that a closer look is needed, if one really wants to verify a model. Besides experimental results, which can be found in literature, some parameters are investigated by numerical simulation. Like experiments CFD (Computational Fluid Dynamics) simulations show a huge bandwidth of results, even when the same turbulence model is used. Flow around cylinders separates over a wide range of Reynolds numbers. It will be demonstrated that, using CFD, large deviations in fluid forces can often be related to miscalculation of the point of separation.
Ultrasonic Evaluation of Ceramics With Micro-Cracks
Authors: Wu Shih-Jeh , Jeng Ching-An , Kuo Chen-Ming
Published: August 2008

Materials used in high-pressure vessels may be subjected to rapid temperature change, which may induce micro-cracks on the surface and into material. The growth of micro-cracks is detrimental to facility life. Chromium carbide (Cr3C2) has been proved to be a potential structural material for toughening alumina in biomedical and industrial applications because of its high Young’s modulus and erosion resistance. On the other hand, TiC/Al2O3 composite has been used as a magnetic head slider due to its good wear resistance and mechanical strength, and potentially could be an excellent lining material. In this study we thermally shocked ceramic material in disc shape to create different degrees of micro-cracking and use ultrasound attenuation technique to evaluate the damage. This includes narrow band tone burst at different frequency. The results showed significant dependence between ultrasonic attenuation and shock temperature. Corresponding SEM pictures show although the size of micro-crack doesn’t change, the depth of the micro-cracks increases. It is demonstrated that ultrasonic attenuation proves to be a reliable tool for evaluating micro-fractures in solids.
The Effect of Pressure Vessel in Explosive Forming
Authors: Iyama Hirofumi , Raghukandan K. , Nagano Shiro , Itoh Shigeru
Published: August 2008

Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the influence of the configuration of the pressure vessel on the deformation of a metal plate, numerical analysis was performed. This paper reports those results.
A Micromechanics Approach to Assess Ductile Crack Initiation in Damaged Pipelines
Authors: Ruggieri Claudio , Santos Fernando F. , Ohata Mitsuru , Toyoda Masao
Published: August 2008

This study explores the capabilities of a computational cell framework into a 3-D setting to model ductile fracture behavior in tensile specimens and damaged pipelines. The cell methodology provides a convenient approach for ductile crack extension suitable for large scale numerical analyses which includes a damage criterion and a microstructural length scale over which damage occurs. Laboratory testing of a high strength structural steel provides the experimental stress-strain data for round bar and circumferentially notched tensile specimens to calibrate the cell model parameters for the material. The present work applies the cell methodology using two damage criterion to describe ductile fracture in tensile specimens: (1) the Gurson-Tvergaard (GT) constitutive model for the softening of material and (2) the stress-modified, critical strain (SMCS) criterion for void coalescence. These damage criteria are then applied to predict ductile cracking for a pipe specimen tested under cycling bend loading. While the methodology still appears to have limited applicability to predict ductile cracking behavior in pipe specimens, the cell model predictions of the ductile response for the tensile specimens show good agreemeent with experimental measurements.
Remote Inspection of a High Level Radioactive Waste Storage Tank for Cracking, Thinning, and Pitting
Authors: Elder J. B. , Wiersma B. J. , Sindelar R. L.
Published: August 2008

Several of the high level radioactive waste storage tanks at the Savannah River Site (SRS) have been in service nearly 50 years. Periodic visual and ultrasonic (UT) nondestructive examinations (NDE) have been performed on the tanks to monitor the effects of service. These inspections revealed that several of the older tanks had suffered cracking as detected by through-wall visual indications. A new UT in-service inspection program has been recently established to provide for detection and characterization of cracking, thinning, or pitting of the sidewalls of the waste tanks. The program specifies examination of regions of the tank that would be most susceptible to corrosion attack, and to characterize the flaws and demonstrate acceptance to protect against potential leakage and instability. This paper summarizes the implementation of the program and inspection results for a tank that has been in service for over 40 years. No indications of reportable wall loss or pitting were detected. All thickness readings were above minimum design thickness. Several small indications of thinning were detected. The crack detection and sizing examinations detected five previously undetected indications, four of which were only partially through wall. The lengths of cracks that were examined are slightly longer than expected, but well below instability lengths.
Heat Transfer Simulation in the Mould With Generalized Curvilinear Formulation
Authors: Eliseu M. L. M. , Monteiro C. , Rouboa A. I.
Published: August 2008

A large number of mould manufactures need to reduce cost production. In fact, the production of a part by foundry techniques is influenced by its complex geometry configuration, which affects the solidification conditions and subsequent cooling. The simulation of heat transfer phenomena between metal and mould helps to reduce or even eliminate the need of corrective alterations of the mould. This approach will help to reduce its cost. The main objective of this paper is to describe the development of a finite volume method in order to simulate the heat transfer phenomena during the phase change process. Because of the mould design complexity, the finite volume is described using the generalized curvilinear formulation.
Verification of a Finite Element Analysis Procedure for Modeling the Nonlinear, Monotonic In-Plane Behavior of 4 Inch, Schedule 10, Stainless Steel, 90° Elbows
Authors: Wilkins James K.
Published: August 2008

A project has been conducted to verify a finite element analysis procedure for studying the nonlinear behavior of 90°, stainless steel, 4 inch schedule 10, butt welding elbows. Two displacement controlled monotonic in-plane tests were conducted, one closing and one opening, and the loads, displacements, and strains at several locations were recorded. Stacked 90° tee rosette gages were used in both tests because of their ability to measure strain over a small area. ANSYS shell element 181 was used in the FEA reconciliations. The FEA models incorporated detailed geometric measurements of the specimens, including the welds, and material stress-strain data obtained from the attached straight piping. Initially, a mesh consisting of sixteen elements arrayed in 8 rings was used to analyze the elbow. The load-displacement correlation was quite good using this mesh, but the strain reconciliation was not. Analysis of the FEA results indicated that the axial and hoop strain gradients across the mid-section of the elbow were very high. In order to generate better strain correlations, the elbow mesh was refined in the mid-section of the elbow to include 48 elements per ring and an additional six rings, effectively increasing the element density by nine times. Using the refined mesh produced much better correlations with the strain data.
PWR Fuel Assembly Modal Testing and Analysis
Authors: Collard Bruno , Pisapia Ste´phane , Bellizzi Sergio , Witters Fre´de´ric
Published: August 2008

Pressurized Water Reactor (PWR) seismic or Lost Of Coolant Accident (LOCA) loads could result in impacts between nuclear fuel assemblies or between fuel assemblies and the core baffles. Forces generated during these shocks are often the basis for the determination of the maximum loads and of the spacer grid and fuel rod design. The knowledge of the fuel assembly kinematics is essential to compute these maximum loads, and this requires experimental tests. Our study aims at characterizing the behavior of a full-scale fuel assembly subjected to various excitations. The effect of the assembly environment (air, still water and water under flow) is studied. The French Nuclear Reactor Directorate experimental facility HERMES T allows hydraulic and mechanical testing of full-scale fuel assemblies. It is designed for flow rate up to 1200 m3/h and temperature up to 170°C. Specific excitation devices allow mechanical tests with amplitudes of motion up to 20 mm. Laser vibrometry, displacement transducers and tracking camera apparatus measure the fuel assembly displacement. To identify this Multi Degree Of Freedom (MDOF) system (assembly or assembly + fluid), two dependent problems have to be addressed: the linear or non-linear model selection, and the estimation of the corresponding parameters. Under different environments and excitation types, it is shown that the mechanical system is strongly non-linear. The damping term, essentially fluid, increases with flow rate and with motion amplitude, while the stiffness decreases with amplitude. The main results, the measuring and identification methods and the extrapolation to the reactor thermohydraulic conditions are presented and discussed.
Vortex-Shedding of a Multi-Hole Orifice Synchronized to an Acoustic Cavity in a PWR Water Piping System
Authors: Moussou P. , Caillaud S. , Villouvier V. , Archer A. , Boyer A. , Rechu B. , Benazet S.
Published: August 2008

Due to a new design, a multi-hole orifice was arranged on the Spent Fuel Pit Cooling system (SFPC) of a French nuclear power plant. Serious pipe vibrations and a high level of noise were generated during the qualification testing. On-site measurements showed that a pure tone appeared at 640 Hz for a precise value of the mean flow. Furthermore, when the multi-hole orifice was replaced by another one with a different set of holes, the pure tone frequency was shifted to 520 Hz. The Strouhal number of the orifice holes is close to unity in the high-vibration regime. Besides, the acoustic boundary conditions appear highly reflecting. A fully-coupled finite element analysis of the piping system shows that several natural modes in the 500–700 Hz range exhibit simultaneously a shell deformation of the orifice, a pattern of plane acoustic waves upstream the orifice and a shell deformation of the piping system. The phenomenon is explained as a lock-in between vortex shedding inside the multi-hole orifice and the acoustic cavity, enhancing shell deformation of the pipe.
A Study on Damage Detection Procedure for Existing Piles
Authors: Sone Akira , Masuda Arata , Koyama Taihei , Washida Kohei , Yamada Makoto , Yamamoto Shizuo
Published: August 2008

In this paper, a non-destructive damage evaluation procedure is presented, which aims at detecting early or fatal cracks in existing piles after severe earthquakes. The bending motion of a target pile excited by an impulsive load, which is induced by hammering at the ground surface nearly, is measured at the top to obtain the dynamic compliance of the pile in one direction. Numerical simulations and experiments show that evaluating the dynamic compliance in every direction can suggest the severity of the cracks as well as their location and orientation.
Seismic Proving Test of Eroded Piping: Status of Eroded Piping Component and System Test
Authors: Namita Y. , Suzuki K. , Abe H. , Ichihashi I. , Shiratori M. , Tai K. , Iwata K. , Nebu A.
Published: August 2008

In FY 2000, a 3-year testing program of eroded piping was initiated with the following objectives: 1) to ascertain the seismic safety margins for eroded piping designed under the current seismic design code, 2) to clarify the elasto-plastic response and ultimate strength of eroded nuclear piping. A series of tests on eroded piping components and eroded piping systems was planned. In this paper, the results of those tests are presented and analyzed, focusing on the influence of the form and the number of thinned-wall portions on the fatigue life of the piping.
Experimental Study of a Multiple Bay Structure Isolated With Hybrid Bearings
Authors: Tsai C. S. , Chen Bo-Jen , Chiang Tsu-Cheng , Lee Guan-Hsing
Published: August 2008

In conventional earthquake resistance design approach (the ductility-design philosophy), the energy dissipation mechanism is based on plastic deformations at scattered locations in the structure. However, this can produce permanent damage to the joints as well as the larger interstory displacements. In recently years, the base isolation technology has been adopted as a feasible and attractive way in improving seismic resistance of structures. It can shift the natural periods of structures away from the rich periods contents of earthquake motions, but also provide considerable supplemental damping to dissipate seismic energy transmitted into structures during earthquakes. In this paper, uniaxial, biaxial, and triaxial shaking table tests are performed to study the seismic behavior of a 0.4-scale three-story isolated steel structure in the National Center for Research on Earthquake Engineering in Taiwan. Experimental results demonstrate that structures with hybrid rubber bearings can actually decrease the seismic responses of the superstructure. It has been proved through the shaking table tests that the rubber bearing is a very promising tool to enhance the seismic resistibility of structures. Moreover, it is illustrated that the proposed analytical model and finite element formulation in this paper can well predict the mechanical behavior of rubber bearings and seismic responses of the base-isolated structures.
A Comprehensive Review of Ultimate and Allowable Stress Design Methodologies for External Load Calculation of Petrochemical Equipment: Eurocode 8 Versus ASME Codes
Authors: Botsis Ch. , Anagnostides G. , Kokavesis N.
Published: August 2008

The purpose of this paper is to provide a review of design methodologies for process equipment under pressure subjected to seismic loads. Such equipment includes spherical and cylindrical tanks, pressure vessels including towers and reactors, and fired heaters. For this equipment, the wall thickness of the pressure retaining space is designed so that the hoop stress is a fraction of the yield stress, Sy, of the material of construction. This fraction of the yield stress is called the allowable stress, Sm, and it is used in the allowable stress design codes such as ASME and API. However the magnitude of the stresses due to external loads is not determined by code rules. The task of calculating the stresses due to external loads is left up to the designer. Furthermore, process equipment is often sufficiently massive so that anchorage is needed to avoid overturning and a potential fire hazard. The anchors or bolts are imbedded in concrete bases, which are designed using strength design codes such as UBC, ASCE or EUROCODES. The level of stress in such structures is allowed to reach the yield stress of the material of construction. The safety factor in structures sized using allowable stress design philosophy is taken in the allowable stress. The safety factor in structures sized using strength design philosophy is realized by using load factors or increased loads. Guidelines are provided to solve the problem of merging the two design philosophies while avoiding the application of safety factors twice in the mechanical design of process equipment subjected to external loads and pressure.
Confirmation of Reduction Effect Due to Tank’s Rocking Behavior and Proposal for a Simplified Evaluation Method of Nonlinear Seismic Response
Authors: Yamaguchi Satoru , Tazuke Hideyuki , Ishida Kazuo
Published: August 2008

Aboveground LNG storage tank consists of inner and outer cylindrical containers. LNG is stored in the inner container made by 9%Ni steel. Anchorages are attached to some tanks in order to prevent bottom plate from excessive uplifting by seismic overturning moment. However tanks without anchorages have some probability that the seismic response factor decreases since the resonance period of tank is lengthened by nonlinear behaviors, for example uplifting of bottom plate (rocking behavior). In this paper, the reduction effect of response factor due to rocking behavior was quantitatively confirmed by 3-dimensional FEM nonlinear analysis and time-history nonlinear analysis that was modeled with single-degree-of-freedom spring-mass system. And a simplified evaluation method that allows easily calculating the reduction effect was proposed. As the result of study, it was proved that this method gave valid and conservative results.
Gas Generation Measurements of Scrap Pu/U Materials Using a Bell Jar
Authors: Hensel Steve J. , Kies Jonathan R. , Hill Rosa D. , Watkins Robert W.
Published: August 2008

A bell jar is used to determine containment vessel pressurization due to gas generation from plutonium/uranium materials. Seventy eight food pack cans containing plutonium and uranium oxide bearing materials have been tested to date. Minimal change in pressure (increase or decrease) occurred in fifty one cases, depressurization occurred in seventeen cases, and pressurization occurred in ten cases. Pressurization is considered linked to the presence of certain impurities such as magnesium oxide.
Anodic Behavior of Alloy 22 in Calcium Chloride and in Calcium Chloride Plus Calcium Nitrate Brines
Authors: Evans Kenneth J. , Day S. Daniel , Ilevbare Gabriel O. , Whalen Michael T. , King Kenneth J. , Hust Gary A. , Wong Lana L. , Estill John C. , Rebak Rau´l B.
Published: August 2008

Alloy 22 (UNS N60622) is a nickel-based alloy, which is extensively used in aggressive industrial applications, especially due to its resistance to localized corrosion and stress corrosion cracking in high chloride environments. The purpose of this work was to characterize the anodic behavior of Alloy 22 in concentrated calcium chloride (CaCl2) brines and to evaluate the inhibitive effect of nitrate, especially to localized corrosion. Standard electrochemical tests such as polarization resistance and cyclic polarization were used. Results show that the corrosion potential of Alloy 22 was approximately −360 mV in the silver-silver chloride (SSC) scale and independent of the tested temperature. Cyclic polarization tests showed that Alloy 22 was mainly susceptible to localized attack in 5 M CaCl2 at 75°C and higher temperatures. The addition of nitrate in a molar ratio of chloride to nitrate equal to 10 increased the onset of localized corrosion to approximately 105°C. The addition of nitrate to the solution also decreased the uniform corrosion rate and the passive current of the alloy.