bluuebunny/crossref_metadata_2025 huggingface dataset:
Standardization of CTOD Toughness Correction for Constraint Loss in Steel Components
Authors: Minami Fumiyoshi , Ohata Mitsuru
Published: July 2009

A standardized procedure for correction of CTOD fracture toughness for constraint loss in steel components is presented. The equivalent CTOD ratio β = δ/δWP is developed on the basis of the Weibull stress fracture criterion, where δ and δWP are CTODs of the standard fracture toughness specimen and the wide plate component, respectively, at the same level of the Weibull stress. With the CTOD ratio β, the critical CTOD δWP, cr of the wide plate that is equivalent to δcr at brittle fracture initiation is given as δWP, cr = δcr/β. Nomographs of β are provided as a function of the crack type and size in the component, the yield-to-tensile ratio of the material and the Weibull shape parameter m. The fracture assessment with β is shown within the context of a failure assessment diagram (FAD), which includes the pipeline steel welds with a notch in the weld metal.
The Weibull Stress Model for Predicting Cleavage Fracture in the Ductile-to-Brittle Transition Region
Authors: Gao Xiaosheng , Petti Jason P. , Dodds Robert H.
Published: July 2009

Transgranular cleavage fracture in the ductile-to-brittle transition region of ferritic steels often leads to spectacular and catastrophic failures of engineering structures. Due to the strongly stochastic effects of metallurgical scale inhomogenieties together with the nonlinear mechanical response from plastic deformation, the measured fracture toughness data exhibit a large degree of scatter and a strong dependence on constraint. This has stimulated an increasing amount of research over the past two decades, among which the Weibull stress model originally proposed by the Beremin group has gained much popularity. This model is based on weakest link statistics and provides a framework to quantify the relationship between macro and microscale driving forces for cleavage fracture. It has been successfully applied to predict constraint effects on cleavage fracture and on the scatter of macroscopic fracture toughness values. This paper provides a brief review of the research conducted by the authors in recent years to extend the engineering applicability of the Weibull stress model to predict cleavage fracture in ferritic steels. These recent efforts have introduced a threshold value in the Weibull stress model, introduced more robust calibration methods for determination of model parameters, predicted experimentally observed constraint effects, demonstrated temperature and loading rate effects on the model parameters, and expanded the original Beremin model to include the effects of microcrack nucleation.
Institutional Efficiency of Commonhold Industrial Parks
Authors: Lin Jeng-Wen , Chen Simon Chien-Yuan , Yang Lung-Shih , Lai Mei-Jung
Published: July 2009

The rapidly increased development of gated communities recently attracts many academic interests. This paper is the first research attempt to investigate the application of Homeowners Associations (HOA’s) on industrial land use in comparison to traditional government administration. This comparison, which applies the transaction cost theory and polynomial regression analysis, reveals that HOA’s are superior to conventional government administration in terms of transaction costs and overall efficiency. The results provided through analysis of Taiwan’s commonhold industrial park development of the Nankang Software Park (NKSP) indicate that NKSP’s HOA is institutionally superior to traditional government administration. In addition the results imply that HOA’s are more appropriately applied to industrial rather than residential land use. The whole concept developed here can be applied to the industry of pressure vessels and piping for efficiency promotion.
Influence of Cooling Rate on Predicted Weld Residual Stress Build-Up in a Thick Walled Piping Intersection
Authors: Jiang Wei , Yahiaoui Kadda
Published: July 2009

Welded, thick-walled piping intersections are widely used in many engineering applications including the offshore and nuclear power industries. These components are often fabricated by multipass welding which inevitably introduces undesirable residual stresses. In this contribution, weld-induced residual stresses in a thick-walled piping intersection were predicted using a validated, full three dimensional, sequentially coupled thermo-mechanical finite element simulation. The effect of cooling rate on the final residual stress state, especially at critical areas where the peak residual stresses are located, was then investigated by applying different convective heat transfer coefficients to the exposed piping intersection surfaces. It was found that the magnitudes and overall spatial distributions of residual stresses were very sensitive to cooling rate. Residual stresses on the outer surfaces of the component can be significantly reduced by external cooling. On the other hand, cooling the inner surfaces can dramatically convert residual stresses from tensile to compressive in these regions. The results and modeling technique presented in this contribution show that residual stress profiles in multipass welded complex geometries can be efficiently optimized through convenient cooling rate control.
Hilbert-Huang Transform Based Modal Analysis of Structures
Authors: Lin Jeng-Wen , Chen Hung-Jen , Lin Jeng-Yuan
Published: July 2009

This paper presents a Hilbert-Huang transform based signal reconstruction technique for the modal analysis of structural systems using vibration measurements. The original measured signal is initially undergone a well defined band-pass filter in order to solve the mode confounding problem. After the data preprocessing, each mode of the signal is reconstructed via the proper selection of intrinsic mode functions (IMFs) that are derived from the empirical mode decomposition of the signal’s mode. Through the signal reconstruction mode by mode, the structural parameter such as natural frequency is accurately evaluated, whose accuracy depends on the criterion for selecting the IMFs using the developed component sifting process. Reliable evaluation of systems’ characteristics leads to accurate prediction of systems’ behaviors for structural safety purpose. In this study, data preprocessing is operated to alleviate the problems of mode mixing and noise contaminated signal, as well as to compare with the previous work.
In-Situ Observation of Crack Nucleation in Nuclear Graphite by Digital Image Correlation
Authors: Li Haiyan , Duff Jonathan , Marrow Thomas J.
Published: July 2009

To study the fracture behaviour of nuclear graphite, a full-field digital image correlation technique has been applied to large specimens of isotropic Gilsocarbon graphite. Optical images of the tensile surface in four-point bend tests were recorded throughout the loading history, with a 100 × 100 mm viewing area. Although crack nucleation was not observable in these raw images, the high sensitivity of digital image correlation to the small displacements allows cracks to be detected. Strain maps are derived from the displacements, and surface cracks with lengths from 1 mm can be seen due to the high effective strain that results from crack opening. Post-processing of the strain maps can track the development of every such defect. These unique observations show the distribution of cracks and their sub-critical development and interactions prior to unstable fracture. This information may be used to validate models for the effects of sample size and stress gradient on component fracture strength.
Taylor Cylinder Test Reduction Using a One-Dimensional Theory
Authors: Russo Rachel , Baker Bart , Dutton Nicholas , Torres Karen , Jones Stanley E.
Published: July 2009

A one-dimensional analysis of the Taylor impact test [4] has been used to estimate the quasi-static stress for several different alloys. One criticism of this work was the use of Taylor cylinder test data to estimate the quasi-static true stress/true strain compression diagram. The one-dimensional theory does accommodate this estimate. The purpose of this paper is to demonstrate that this process leads to acceptable results by analyzing a series of high, medium, and low strength materials.
Engineering Relation for Dependence of Threshold Stress Intensity Factor for Delayed Hydride Cracking on Crack Orientation
Authors: Scarth Douglas A. , Shek Gordon K. , Xu Steven X.
Published: July 2009

Delayed Hydride Cracking (DHC) in cold-worked Zr-2.5 Nb pressure tubes is of interest to the CANDU industry in the context of the potential to initiate DHC at an in-service flaw. Examples of in-service flaws are fuel bundle scratches, crevice corrosion marks, fuel bundle bearing pad fretting flaws and debris fretting flaws. To date, experience with fretting flaws has been favourable, and crack growth from an in-service fretting flaw has not been detected. However, postulated DHC growth from these flaws can result in severe restrictions on the allowable number of reactor Heatup/Cooldown cycles prior to re-inspection of the flaw, and it is important to reduce any unnecessary conservatism in the evaluation of DHC from the flaw. One method to reduce conservatism is to take credit for the increase in the isothermal threshold stress intensity factor for DHC initiation at a crack, KIH, as the flaw orientation changes from an axial flaw to a circumferential flaw in the pressure tube. This increase in KIH is due to the texture of the pressure tube material. An engineering relation that provides the value of KIH as a function of the orientation of the flaw relative to the axial direction in the pressure tube has been developed as described in this paper. The engineering relation for KIH has been validated against results from DHC initiation experiments on unirradiated cold-worked Zr-2.5 Nb pressure tube material.
Eulerian Finite Element Formulation for Sloshing Response of Floating Roofs in Aboveground Storage Tanks
Authors: Yoshida Shoichi , Sekine Kazuyoshi , Mitsuta Tsukasa
Published: July 2009

The floating roofs are widely used to prevent evaporation of content in large aboveground oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish in petrochemical and oil refining industries. This paper presents the axisymmetric finite element analysis for the sloshing response of floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof under seismic excitation is taken into consideration in the analysis. It is assumed that the fluid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The theory for the finite element analysis in which the behavior of the fluid is formulated in terms of dynamic pressure as the Eulerian approach is developed. The basic vibration characteristics of the floating roof, such as natural periods and vibration modes, can be obtained from this analysis. These will give engineers important information on the floating roof design.
Brittle Fracture Safety Analysis of German RPVs Based on Advanced Thermal Hydraulic Analysis
Authors: Keim Elisabeth , Hertlein Roland , Ilg Ulf , Ko¨nig Gu¨nter , Schlu¨ter Norbert , Widera Martin
Published: July 2009

During the design stage of the today operating German PWRs, one major design target was to manage the materials ageing behavior of the ferritic reactor pressure vessel (RPV) steel in oder to prevent a brittle fracture of the RPV under all possible loads. Very conservative thermal hydraulic input data were used in this context for the assessment of loss of coolant accidents. Today more realistic thermal hydraulic analyses based on large scale experimental results are available as well as more sophisticated fracture mechanics methods to assess postulated flaws. Using these tools an additional joint analysis of six German PWR RPVs is performed. A fully representative spectrum of all possible large and small break loss of coolant accidents is investigated. Locations of interest are the irradiated RPV core beltline region as well as those regions with negligible irradiation but higher loading, like the RPV MCL nozzles and the flange to cylinder transition area. The thermal hydraulic work comprises global system analyses with subsequent local analysis considering mixing phenomena like plume forming below the injecting nozzles. Dependent on the location of the postulated flaw (core or nozzle region), the postulated leak size is differing. In the core weld region medium leak sizes (100 to 200 cm2) with subsequent injection into the cold leg lead to dominating loading, whereas in the nozzle the small leak sizes (3 to 20 cm2) with injection into the hot leg are more important. This is due to the higher pressure at smaller leak sizes and the larger thermal stresses caused by the high temperature of the nozzle flange and the low temperature of the injected ECCS-water. But independent of the number of transients it turned out that all load paths of the postulated flaws and the investigated leak sizes show a similar behavior. As the result of this additional joint safety analysis of six German PWR RPVs with different injection modes, a brittle fracture of all RPV regions can be excluded with sufficient safety margin.
Technical Specification for Subsea Pipelines Alternative Criteria Based in Fracture Mechanics
Authors: Zumpano Ju´nior Petroˆnio , Donato Guilherme Victor Peixoto , Hippert Ju´nior Eduardo , Kaspary Tiago Bohn
Published: July 2009

Offshore pipeline laying significant high costs are strongly related to the duration of vessel operations. Even though DNV-OS-F-101 requires an Engineering Critical Assessment (ECA) only when expected total longitudinal strain is above 0.4%, contractors usually prefer to launch lines by using alternative defect acceptance criteria for mechanized girth welds based on fracture mechanics approach in order to save time. BS-7910 standard is worldwide acknowledged for fracture and fatigue analysis, but it requires operators to specify additional criteria in the overall ECA methodology for submarine pipelines. In 2006 DNV-RP-F108 was issued establishing new testing methods based in SE (T) and pipe segment specimens as a way of achieving a more realistic estimation of pipeline toughness. Nowadays, a lot of research has been carried out on testing methodology that will likely lead to a SE (T) testing standard. However, many aspects of pipeline launching and operation must be defined for ECA analysis: operators should establish all the cyclic loads to be considered both for installation and operation period assessment; the approach of in-service fatigue may be determinant for the final allowable crack size; sour service conditions may imply that Paris law constants are not valid for in-service VIV and hydrogen charged SE (B) specimens will give fracture toughness results representative of the material in sour conditions. This paper addresses the premises, based in Petrobras previous experience, for establishing a technical specification in order to carry out an ECA with alternative criteria for subsea pipeline or riser girth welds, based in fracture mechanics approach.
Numerical Determination of Sealing Performance of a Rough Contact: Real Versus Synthetic Fractal Surfaces
Authors: Vallet Christophe , Lasseux Didier , Sainsot Philippe , Zahouani Hassan
Published: July 2009

In this work, we adress the issue of sealing performance of metal gaskets using a deterministic approach that allows the analysis of creeping viscous flow and diffusion through a tight contact between rough surfaces taking into account surface deformation. Our analysis is focused on rough surfaces exhibiting fractal properties, and our purpose is to study the validity of the use of synthetic fractal surfaces as a representation of real ones. Two kinds of real surfaces, obtained from two machining processes — lapping and sand-blasting — are considered. After checking the fractal nature of these surfaces, equivalent fractal ones are synthesized. Distributions of contact areas on the one hand, and transport properties K (for viscous flow) and D (for diffusion) on the other, obtained from real and synthetic surfaces are compared for a wide range of tightening. This comparison leads to the conclusion that the fractal representation is adequate to predict mechanical and transport properties of a contact between lapped or sand-blasted surfaces. Finally, using synthetic surfaces, it is shown that sealing performance of a rough contact decreases when the arithmetic roughness Ra and the fractal dimension Df increase.
Impact Testing of Stainless Steel Material at Cold Temperatures
Authors: Morton Dana K. , Blandford Robert K. , Snow Spencer D.
Published: July 2009

Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern are not well documented. However, a previous paper [1] reported on impact testing and analysis results performed at the Idaho National Laboratory using 304/304L and 316/316L stainless steel base material specimens at room and elevated temperatures. The goal of the work presented herein is to add recently completed impact tensile testing results at −20°F conditions for dual-marked 304/304L and 316/316L stainless steel material specimens (hereafter referred to as 304L and 316L, respectively). Recently completed welded material impact testing at −20°F, room, 300°F, and 600°F is also reported. Utilizing a drop-weight impact test machine and 1/4-inch to 1/2-inch thick dog-bone shaped test specimens, the impact tests achieved strain rates in the 4 to 40 per second range, depending upon the material temperature. Elevated true stress-strain curves for these materials reflecting varying strain rates and temperatures are presented herein.
Illustration of the WPS Benefit Through Batman Test Series: Tests on Large Specimens Under WPS Loading Configurations
Authors: Chapuliot S. , Ferry L. , Yuritzinn T. , Moinereau D. , Dahl A. , Gilles P.
Published: July 2009

A study combining modelling and a series of experiments on large specimens submitted to a thermal shock or isothermal cooling has been performed in CEA-Saclay in order to show the WPS benefit on large scale specimen. The test series, named BATMAN, was made on 18MND5 ferritic steel bars, containing a short or large fatigue pre-crack. For the two performed tests (fast thermal shock creating a gradient across the thickness of the bar or for the gradual uniform cooling), the effect of “Warm Pre-Stressing” was confirmed. In both cases, no propagation was observed during the thermal transient. Fracture occurred under low temperature conditions, at the end of the test when the tensile load was increased. The failure loads then recorded were substantially higher than during pre-stressing. To illustrate the benefit of the WPS effect, numerical interpretations were performed using either global approach or local approach criteria. The capability of models to predict the WPS effect was clearly shown.
Radial Expansion of T5-6063 Aluminum Tubes: An Experimental Investigation and Numerical Simulation
Authors: Al-Hajeri A. , Seibi A. C.
Published: July 2009

This paper presents the design of an experimental set-up to mechanically expand T5-6063 aluminum tubes using conical hardened steel mandrels. The effect of the expansion ratio and mandrel angle on the tube wall thickness and drawing force required to expand the tubes as well as failure modes near embedded circular holes are investigated. The experimental study considered four radial expansion ratios of 1.5, 5, 7 and 10% and three mandrel angles of 10, 22.5, and 30 degrees. It was shown experimentally that most of the tubes failed at the 90 degrees position of the hole indicating that the maximum stress concentration takes place at that position as compared to the zero degree location. The experimental study was supplemented by finite element models reflecting the lab tests to determine the drawing force and study the stress concentration around the hole at zero and 90 degrees locations. The finite element analysis took into consideration various parameters such as expansion ratio and mandrel angle. The simulation results, which were calibrated through generated experimental data, confirmed the experimental observations when studying the stress concentration around the hole for various mandrel angles and expansion ratios at 90 degrees angle. The finite element results also showed that the stress concentration is much higher at 90 degrees position where failure occurred in all tested samples as compared to the zero degree angle.
Unique Method for Generating Design Earthquake Time Histories
Authors: Spears R. E.
Published: July 2009

A method has been developed which takes a seed earthquake time history and modifies it to produce given design response spectra. It is a multi-step process with an initial scaling step and then multiple refinement steps. It is unique in the fact that both the acceleration and displacement response spectra are considered when performing the fit (which primarily improves the low frequency acceleration response spectrum accuracy). Additionally, no matrix inversion is needed. The features include encouraging the code acceleration, velocity, and displacement ratios and attempting to fit the pseudo velocity response spectrum. Also, “smoothing” is done to transition the modified time history to the seed time history at its start and end. This is done in the time history regions below a cumulative energy of 5% and above a cumulative energy of 95%. Finally, the modified acceleration, velocity, and displacement time histories are adjusted to start and end with an amplitude of zero (using Fourier transform techniques for integration).
Improvement of CTOD Calculation in Japanese Flaw Assessment Methods of WES2805
Authors: Kayamori Yoichi , Inoue Takehiro , Hiramatsu Hideki , Michiba Koji , Aihara Shuji , Hagihara Yukito
Published: July 2009

The relationship between the average elastic stress concentration factor, Kt and the stress intensity magnification factor, MK, was theoretically indicated, and the applicability of MK to the WES 2805 CTOD design curve was investigated by using the results of finite element analysis for four welded joints. In addition, the average local strain by area around an assumed crack was calculated by the analysis, and the strain was used as the local strain, ε, in the WES 2805 CTOD design curve. It was demonstrated that MK was helpful in calculating accurate Kt, which contributes to a good CTOD estimation using the WES 2805 CTOD design curve. The average local strain also contributes to a good CTOD estimation, especially for a toe crack in the high strain gradient region. These two options, the use of MK and the average local strain, were approved by the Fracture Toughness Study Committee of the Japan Welding Engineering Society, and were adapted for WES 2805 revised in 2007.
Towards a More Comprehensive Environmental Impact Assessment on Post-Earthquake Recovery: Lessons in Taiwan
Authors: Chen Simon Chien-Yuan , Shih Jhih-Chang , Cheng Yi-Chieh
Published: July 2009

The central mountain chain, as the name shows, is located in the central part of Taiwan and divides the island into two parts. This makes transportation between Eastern and Western part of Taiwan become very costly and time-consuming. Taiwanese governments, therefore, build a Central Cross-Island Highway in 1956 to overcome this nature barrier, which enlarges the economic development areas among these mountain areas and hugely changes the local landscape and ecological environment. However, with the major earthquake hit in September 21st, 1999, this mountain highway had been severely damaged. Taiwanese government rebuild soon after the earthquake, however, when the typhoon Mindulle struck Taiwan in 2004 and ruined the highway once again. The re-reconstruction of this highway becomes a high profile social issue debating the value among environmental protection, engineering cost of re-reconstruction, and how to save local people’s life and living. So, this paper try to develop a social and environment impact analytical framework, which uses public choice theory into the framework for enlarging the perspective of impact assessment and increasing policy feasibility.
Evaluation of Damage of Steam Pipeline Steel Using Local Approach to Fracture
Authors: Zrilic Milorad , Rakin Marko , Medjo Bojan , Cvijovic Zorica , Sedmak Aleksandar
Published: July 2009

In the paper, the level of damage of steam pipeline steel after about 100,000 hours at 540°C (1004 °F) under pressure of 42 bars (609 PSI) is analyzed. Material degradation is estimated using a combined experimental and numerical procedure based on micromechanical or local approach to fracture. Detailed analysis is conducted on the samples taken from exploited – used steel and from unused – new steel of the same designation. Damage parameter – void growth ratio – is determined using round notched specimens, (including various notch radii). A comparison of the values for critical void growth ratio, computed for tested steels is made. Based on the values obtained, the possibility of prolongation of the operating life of used steel is discussed.
Application of Aeroelastic Methods in Compressor Cascade Configurations Using Commercial Code Coupling
Authors: Schrape Sven , Nipkau Jens , Ku¨hhorn Arnold , Beirow Bernd
Published: July 2009

This paper presents the results of fluid structure coupled simulations of compressor blade vibrations of two compressor cascade configurations in order to determine aeroelastic parameters such as aerodynamic damping and the corresponding frequency shift. Therefore a partitioned code coupling approach was employed in order to couple the FE-code ABAQUS with the CFD-code FLUENT via MpCCI (Mesh based Code Coupling Interface) developed by Fraunhofer SCAI. The code coupling is used to compute the unsteady, two-dimensional, inviscid and viscid flow around a NACA 3506 airfoil for blade vibrations in a torsional modeshape. This first example is used to validate the results against results from literature. Further on the unsteady, two-dimensional, viscid flow around a research high-pressure compressor airfoil is computed for a bending mode. The results of those computations are implemented into a simplified, structural blisk model approximating the air flow influence by a mechanical model.
The Web-Enabled Materials Database of the European Commission With Its XML Related Data Entry Part and Integrated Analysis Tools to Support GEN IV Nuclear Power Plant Development
Authors: Over Hans-Helmut , Ojala Tauno
Published: July 2009

The development and verification of future GEN IV Reactor Systems is strongly related to materials data and correlated design codes. These systems are high temperature and/or corrosive media exposed. Expensive and extensive materials test programmes have to be launched because materials data which guarantee safe design does not yet exist for the selected materials. The costs of these extensive materials test programmes seem to be too high that they could be invested by one single GIF partner. Therefore a very important issue is data exchange between the partners to save costs and time. Within the web-enabled Mat-DB of JRC Petten an XML (eXtensible Mark-up Language) related data entry part has been installed to ease exchange of experimental materials data. This XML structure will be presented in the following as an initiative to define an internationally agreed, standardised XML schema which can be integrated in the overall MatML schema. Furthermore integrated analysis routines are implemented in the Mat-DB data retrieval part. These tools allow extra- and interpolations to calculate strain limits which are the basis for calculating safety limits against creep failure. Those safety limits are necessary elements for establishing design codes of GEN IV Reactor Systems.
Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE
Authors: Giacomelli Enzo , Schiavone Massimo , Manfrone Fabio , Raggi Andrea
Published: July 2009

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.
Combination Rules for External Volumetric Flaws in a Pressurised Cylinder Subject to External Bending
Authors: Bezensek B. , Duguid L.
Published: July 2009

The pressure-moment (p-M) diagram of Konosu [1, 2] provides an inexpensive method for evaluating fitness for service of internally pressurised cylinders containing volumetric flaws (local thin areas) subject to external bending moment. This work examines the use of the recommended flaw combination rules for volumetric flaws of the ASME Boiler and Pressure vessel code Section XI [3] and Ibaraki fitness-for-service code [4] with the pressure–moment method. Investigation is performed for a thin-wall vessel containing two external volumetric flaws with flaw depths ranging from 25 to 75 percent of the wall thickness under a range of internal pressures. Assessment based on the plastic initiation moments shows that the adjacent flaws are conservatively assessed as single flaws using the above codes’ rules when flaw depths of both flaws do not exceed 60 percent of the wall thickness. This restriction is relaxed to 75 percent of the wall thickness when assessment is performed using the twice elastic slope (TES) collapse moments.
The Ultimate Strength of Cylindrical Liquid Storage Tanks Under Earthquakes: Seismic Capacity Test of Tanks Used in PWR Plants — Part 1, Evaluation Method Verification Test
Authors: Iijima Toru , Suzuki Kenichi , Morita Hideyuki , Murakami Shinsuke , Tai Koichi
Published: July 2009

Since 2002, Japan Nuclear Energy Safety Organization (JNES) has been carrying out seismic capacity tests for several types of equipment which significantly contribute to core damage frequency. The primary purpose of this study is to acquire the seismic capacity data of thin walled cylindrical liquid storage tanks in nuclear power plants and to establish an evaluation procedure of the ultimate strength. As for the refueling water storage tank and the condensate storage tank which are used in PWR plants, elephant-foot bugle (EFB) is the typical buckling behavior of those tanks and the primary failure mode to be focused on. In the study, dynamic buckling tests were performed using scaled models of tanks. The input seismic acceleration was increased until the tanks reached the ultimate state at which internal water leaked from a crack on the sidewall. In addition, static buckling tests were performed in order to compare to the dynamic buckling tests and numerical simulation results. In the dynamic and static buckling tests, EFB occurred and internal water leaked at the EFB cross-section. Incremental deformation growth observed in the static buckling test was simulated by FEM, and analysis results showed a practically sufficient consistency in terms of out-of-plane displacement and local strain.
Reliability Estimation for PVC Pipe Using Probability Theory and Stress Intensity Factor
Authors: Lee O. S. , Kim D. H. , Kim H. M. , Choi H. B.
Published: July 2009

In this paper, the reliability estimation of Polyvinyl chloride (PVC) pipelines is performed by utilizing the probabilistic method, which accounts for the uncertainties in the load and resistance parameters in the limit state function (LSF). The LSF is formulated with the help of fracture control concept including the stress intensity factor (SIF) for the pipeline having crack or crack like defects. The common cracks found at pipeline can be assumed as semi-elliptical shape and the main load is hoop stress due to the internal pressure. The FORM (first order reliability method) and the SORM (second order reliability method) are carried out to estimate the failure probability of pipeline utilizing the SIF for semi-elliptical crack. The reliability is assessed using this failure probability. It is found that the failure probability increases with the operating pressure, and the decrease of the pipeline wall thickness, and the increase of the crack depth, the crack length, the outside diameter of pipeline. The failure probability increases when the initial crack approaches to a semi-circle shape of crack and the failure probability steeply increases at the ratios of larger than 0.5 of a/t and larger than 30 of D/t. Moreover, it is recognized that the effects of the fracture toughness and the pipe wall thickness on the failure probability are the significant one.
Development of a Numerical Optimisation Method for Blowing Glass Parison Shapes
Authors: Groot J. A. W. M. , Giannopapa C. G. , Mattheij R. M. M.
Published: July 2009

Industrial glass blowing is an essential stage of manufacturing glass containers, i.e. bottles or jars. An initial glass preform is brought into a mould and subsequently blown into the mould shape. Over the last few decades, a wide range of numerical models for forward glass blow process simulation have been developed. A considerable challenge is the inverse problem: to determine an optimal preform from the desired container shape. A simulation model for blowing glass containers based on finite element methods has previously been developed [1, 2]. This model uses level set methods to track the glass-air interfaces. The model described in a previous paper of the authors showed how to perform the forward computation of a final bottle from the given initial preform without using optimisation. This paper introduces a method to optimise the shape of the preform combined with the existing simulation model. In particular, the new optimisation method presented aims at minimising the error in the level set representing the glass-air interfaces of the desired container. The number of parameters used for the optimisation is restricted to a number of control points for describing the interfaces of the preform by parametric curves, from which the preform level set function can be reconstructed. Numerical applications used for the preform optimisation method presented are the blowing of an axi-symmetrical ellipsoidal container and an axi-symmetrical jar.
Applications of Multiple Trench Friction Pendulum System to Seismic Mitigation of Structures
Authors: Tsai C. S. , Lin Jeng-Wen , Lin Yung-Chang , Chen Chia-Chi
Published: July 2009

In order to promote seismic resistance capability of structures and simplify the manufacturing processes of an isolator, a new base isolation system called the multiple trench friction pendulum system (MTFPS) is proposed. The investigations for the proposed isolator have been carried out to address its mechanical characteristics and to assess its performance in seismic mitigation through a series of shaking table tests in this study. The MTFPS isolator can provide different natural periods, displacement capacities and damping effects in any two independent directions. The natural period and damping effect for a MTFPS isolator change continually during earthquakes. Results from the shaking table tests on a scaled three-story structure isolated with MTFPS isolators illustrate that the proposed MTFPS isolator can isolate most earthquake induced energy and provide good protection for structures from earthquake damage. In addition, the mathematical formulations for the MTFPS isolator have also been derived to examine its characteristics.
Inelastic Seismic Test of the Small Bore Piping and Support System: Part 2 — Static Failure Test for Piping Support Equipment
Authors: Shirai Eiji , Eto Kazutoshi , Umemoto Akira , Yoshii Toshiaki , Kondo Masami , Shimizu Hiroshi , Tai Koichi
Published: July 2009

In this paper, we focused on small-bore piping with a diameter less than 4 inches including support equipments on base concrete, with the purpose of verifying a sufficient seismic design margin. The support element tests were designed to obtain the relationship between force and displacement at piping, when the seismic force loaded on piping support equipments consisting of a U-bolt, support element, base plate, anchorage on a base concrete by confirming the behavior of the equipments as it reaches its failure. The support element tests are the part of inelastic seismic test program [1, 2] and aimed to obtain the following basic data on small-bore piping support equipments: • Relationship between force and displacement at piping; • Failure capacity of piping equipments; • Ductility ratio of piping equipments. Our results can be separated into 4 categories based on the relationship between piping force and displacement and failure mode. Tested failure capacity was higher than the designed allowable force for all failure by a factor of 1.5 to 23, indicating a margin of failure capacity. Cantilever support type have a low ductility ratio when there is the snap of expansion anchor or U-bolt and a high ductility ratio when there is significant plastic deformation of the support. Like their cantilever type counterparts, frame support type have a low ductility when there is the snap of expansion anchor and a high ductility ratio when there is significant plastic deformation of the support and U-bolt, even with brittle failure.
Full Field Measurement of Plastic Flow Properties in a Multi-Pass Austenitic Stainless Steel Weld Specimen
Authors: Ganguly S. , Turski M. , Fitzpatrick M. E. , Edwards L. , Smith M. C. , Bouchard P. J.
Published: July 2009

Knowledge of constitutive material stress strain properties is important for reliable prediction of weld residual stress fields using analytical stress simulation techniques. The present work investigates the surface stress strain behaviour of a 3-pass groove-welded austenitic stainless steel disc. A relatively novel electronic speckled pattern interferometry (ESPI) technique was employed to monitor the surface deformation pattern across the weld, HAZ and parent metal of the specimens with very high spatial resolution. The deformation data was then analysed to determine the constitutive stress-strain property across the welded specimen. The analyses show very different patterns of proof stress variation across the pass I and pass III weld metal. The accumulated plastic strain in the pass I weld metal resulted in an increase of the 0.2% PS value by 175 MPa.
Code Case Validation of Impulsively Loaded EDS Subscale Vessel
Authors: Yip Mien , Haroldsen Brent , Puskar Joe
Published: July 2009

The Explosive Destruction System (EDS) was developed by Sandia National Laboratories for the US Army Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) to destroy recovered, explosively configured, chemical munitions. PMNSCM currently has five EDS units that have processed over 850 items. The system uses linear and conical shaped charges to open munitions and attack the burster followed by chemical treatment of the agent. The main component of the EDS is a stainless steel, cylindrical vessel, which contains the explosion and the subsequent chemical treatment. Extensive modeling and testing have been, and continue to be used, to design and qualify the vessel for different applications and conditions. This has included explosive overtests using small, geometrically scaled vessels to study overloads, plastic deformation, and failure limits. Recently the ASME Task Group on Impulsively Loaded Vessels has developed a Code Case under Section VIII Division 3 of the ASME Boiler and Pressure Vessel Code for the design of vessel like the EDS. In this article, a representative EDS subscale vessel is investigated against the ASME Design Codes for vessels subjected to impulsive loads. Topics include strain-based plastic collapse, fatigue and fracture analysis, and leak-before-burst. Vessel design validation is based on model results, where the high explosive (HE) pressure histories and subsequent vessel response (strain histories) are modeled using the analysis codes CTH and LS-DYNA, respectively.
Ongoing Work With PVP2007-26387 “Determination and Qualification of Alternative Flange Assembly Procedures” and Resulting Gasket Retorque Dwell Periods Based on Alternative Flange Assembly Procedures
Authors: Frew James E. B. , Waterland Alfred F. , Wyler Chris , Ragsdale Tyler H.
Published: July 2009

As a result of the work from PVP2007-26387, alternative (non-traditional) Flange Assembly Procedures are being adopted for use at one large U.S. chemical producer/shipper. Based on the success of the Alternative Flange Assembly Procedures the Authors decided to further investigate the effects of Alternative Flange Assembly Procedures on Gasket Retorque Dwell Periods, specifically in a General Purpose (GP) Tank Car Hinged/Bolted Manway Connection. This ongoing work can serve as a guide to others in industry as “Best Practices” for selecting and qualifying Gasket Retorque Dwell periods using Alternative Assembly Procedures for their flanged connections for commonly used manway gasket type(s).
Effects of Pipe Dimensions and Outer Surface-Buttering Weld Conditions on Residual Stress Distributions
Authors: Yanagida Nobuyoshi
Published: July 2009

Effects of pipe dimensions and outer surface-buttering weld conditions on residual stress distributions were evaluated using the finite element method. Residual stresses were analyzed for 508–mm-diameter (500A) pipe 38.1 mm thick, 508–mm-diameter (500A) pipe 15.1 mm thick, and 267–mm-diameter (250A) pipe 15.1 mm thick. After the residual stresses at pipe butt joints were analyzed, residual stresses at these joints subjected to the outer surface-buttering welds were analyzed. Residual stresses were determined for various weld widths, thicknesses, and heat inputs. These analyses indicate that tensile axial stress occurred at inner surface of the pipe butt joint and that it decreased with increasing the outer surface buttering-weld width or heat input. They also indicate that compressive hoop stress occurred at inner surface of the joint and that outer surface-buttering weld increased it. The outer surface-buttering weld conditions that generate compressive residual stress at the inner surface of the pipe butt joints were determined.
Study on Stress-Strain Relation for Type 316L Stainless Steel Using Mixed Hardening Law
Authors: Yanagida Nobuyoshi
Published: July 2009

To determine stress-strain diagrams for a pipe butt joint of type 316L stainless steel, stress-strain diagrams for pipe specimens subjected to monotonic uniaxial tensile load were measured. Tensile-test specimens were extracted from the deposited metal area, heat-affected zone, and parent-material area of the pipe butt joint. The specimens of the deposited-metal area and the heat-affected zone were extracted from positions at the pipe inner surface, mid-thickness, and the pipe outer surface. The measurement temperatures were 20, 300, 600, and 800°C. The measured stress-strain diagrams show that measured stress at the same given strain increases from measurement point on the outer surfer of the pipe to that on the inner surface. This stress increase is thought to be related to the number of thermal-load cycles used for the weld. The number of cycles at the pipe inner surface was greater than that at the pipe outer surface. To use the measured stress-strain diagrams in a thermal elasto-plastic analysis of welding residual stress and distortion, the measured diagrams for the deposited-metal-area pipe specimen and the parent-material-area pipe specimen were fitted to calculated diagrams by using an isotropic/kinematic mixed hardening law. Material constants for approximating the stress-strain diagrams for the parent-material specimen and deposited-metal specimen were determined. The calculated stress-strain diagrams derived from the isotropic/kinematic mixed hardening law show good agreement with the measured stress-strain diagrams.
Technical Basis for Alternate Successive Inspection Requirements for Vessels and Piping Welds as Prescribed in Code Cases N-526 and N-735
Authors: Cofie Nathaniel G. , Riccardella Peter C. , Merkle John H. , Do Hien
Published: July 2009

Flaws that are detected during in-service inspections of Class 1 and 2 components (vessels and piping) are first compared to the acceptance standards in ASME Code Section XI, Subsection IWB-3500. When the acceptance standards are met, no further action is required and the component is returned to service. If the acceptance standards are not met, IWB-3600 allows an analytical evaluation to determine the suitability for continued operation. When the provisions of IWB-3600 are used to return a flawed component to service, the Code provides augmented requirements for successive and additional examination of the flawed location. These inspections are believed to be useful for cases where the flaw is service-induced, particularly for surface flaws. However, the usefulness of these augmented examinations for subsurface flaws, which have been clearly shown to be fabrication related, is very questionable. Many of the inspections for these subsurface flaws have not shown any growth and none has resulted in pressure boundary leakage. Section XI currently provides surface proximity rules for discriminating surface from subsurface indications, based on elastic calculations of the stress intensity factor, KI. However, it is believed that these rules may not be sufficiently conservative for granting of an exemption from the requirement for successive examinations, because of the possibility of yielding of the ligament between the flaw and the inside surface. Code Case N-526 provides alternate more conservative proximity criteria for distinguishing subsurface from surface defects in Class 1 and 2 vessels, while Code Case N-735 provides similar criteria for Class 1 and 2 piping welds, in order to eliminate the need for the successive inspection requirements in these components. The technical basis for the criteria in both Code Cases has its foundation on an approach that determines how close a flaw can be to a free surface before the stress in the remaining ligament exceeds the material yield or flow stress, which would potentially put it at risk for rupture of the remaining ligament.