bluuebunny/crossref_metadata_2025 huggingface dataset:
Kendall Analysis of Cannon Pressure Vessels
Authors: Underwood John H.
Published: August 2013

Engineering mechanics analysis of cannon pressure vessels is described with special emphasis on the work of the late US Army Benet Laboratories engineer David P. Kendall. His work encompassed a broad range of design and analysis of high pressure vessels for use as cannons, including analysis of the limiting yield pressure for vessels, the autofrettage process applied to thick vessels, and the fatigue life of autofrettaged cannon vessels. Mr. Kendall’s work has become the standard approach used to analyze the structural integrity of cannon pressure vessels at the US Army Benet Laboratories.

The methods used by Kendall in analysis of pressure vessels were simple and direct. He used classic results from research in engineering mechanics to develop descriptive expressions for limiting pressure, autofrettage residual stresses and fatigue life of cannon pressure vessels. Then he checked the expressions against the results of full-scale cannon pressure vessel tests in the proving grounds and the laboratory. Three types of analysis are described: [i] Yield pressure tests of cannon sections compared with a yield pressure expression, including in the comparison post-test yield strength measurements from appropriate locations of the cannon sections; [ii] Autofrettage hoop residual stress measurements by neutron diffraction in cannon sections compared with expressions, including Bauschinger corrections in the expressions to account for the reduction in compressive yield strength near the bore of an autofrettaged vessel; [iii] Fatigue life tests of cannons following proving ground firing and subsequent laboratory simulated firing compared with Paris-based fatigue life expressions that include post-test metallographic determination of the initial crack size due to firing. Procedures are proposed for Paris life calculations for bore-initiated fatigue affected by crack-face pressure and notch-initiated cracking in which notch tip stresses are significantly above the material yield strength.

The expressions developed by Kendall and compared with full-scale cannon pressure vessel tests provide useful first-order design and safety checks for pressure vessels, to be followed by further engineering analysis and service simulation testing as appropriate for the application. Expressions are summarized that are intended for initial design calculations of yield pressure, autofrettage stresses and fatigue life for pressure vessels. Example calculations with these expressions are described for a hypothetical pressure vessel.
Quantitative Risk Analysis of Hydrogen Events at WTP: Part 1 of 2 — The Operational Frequency Analysis Model
Authors: Lux C. Ray , O’Kula Kevin R. , Wentink Michael G. , Jones Ryan E. , Collin Jean E. , Gross David J.
Published: August 2013

A Quantitative Risk Analysis (QRA) model has been developed to determine the frequency and severity (potential combustion loads) of postulated hydrogen event types in piping systems and proposed as a design-informing tool for the U.S. Department of Energy’s (DOE) Hanford Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford Site near Richland, Washington. Specifically, the QRA provides a systematic, comprehensive methodology for assessing hydrogen events, including deflagrations, detonations, and deflagration-to-detonation transition (DDT) types in piping systems containing legacy nuclear waste streams being processed for vitrification. The events considered include normal operations as well as postulated upset conditions as a result of internal and external accidents. The QRA approach incorporates three sequential phases, including Operational Frequency Analysis (OFA), Gas Pocket Formation (GPF) and Event Progression Logic (EPL) models in the form of an integrated logic framework. The WTP piping design will be evaluated on a specific piping route basis using a probabilistic sampling approach, with the QRA providing the quantitative dynamic loads for evaluation according to the frequency and type of hydrogen event.

The OFA is based on an industry standard fault tree computer model, CAFTA, and analyzes the frequency of combustible gas pocket formation in a piping system from three primary sources: (1) normal operations; (2) piping system-specific upset conditions affecting transfer operations; and (3) plant-wide initiating events such as fire and seismic accidents. A second output from the OFA is duration time for each event, quantifying the length of time that a gas pocket is likely to develop before the initiating event is terminated, with the information provided directly to QRA event tree models for assessing gas pocket growth. A team of safety, operations and engineering, developed the underlying logic of the fault tree model with the overall modeling approach following applicable nuclear/chemical industry guidance and standards for performing QRA applications. Primary inputs to the OFA module are initiating event, equipment reliability, and human/operator error data and their characteristic distributions, and are drawn from Hanford Site safety documentation, government and commercial sector sources, and related nuclear/chemical industry experience. This paper discusses the overall OFA module, its inputs, the outputs to the GPF and EPL modules, the relative importance of different initiating event conditions, key insights obtained to date, upcoming supporting uncertainty/sensitivity analyses, and summarizes technical peer review assessments.
Quantitative Risk Analysis of Hydrogen Events at WTP: Part 2 of 2 — Development of Event Frequency-Severity Model
Authors: Jones Ryan E. , Collin Jean E. , Gross David J. , Wentink Michael G. , O’Kula Kevin
Published: August 2013

In late 2008, a Hydrogen in Piping and Ancillary Vessels (HPAV) Assessment Team was chartered by the U.S. Department of Energy’s (DOE) Office of River Protection (DOE-ORP) to investigate the extent of operational complexity in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) due to conservatisms in hydrogen event analysis methodology and related design constraints. The HPAV Assessment Team recommended that a Quantitative Risk Analysis (QRA) be performed to analyze normal plant operating and upset conditions that can lead to accumulation of hydrogen in piping, and determine the frequency and severity of ensuing postulated hydrogen events such that WTP can make risk-informed decisions regarding hydrogen event mitigation strategies and improve operational flexibility.

The QRA application is based on an in-depth review of hydrogen event-affected systems conducted by an interdisciplinary team of system engineers, process engineers, plant operations modelers, operators, and safety personnel to ensure facility ownership of the overall process. The QRA evaluates hydrogen event-affected systems for both normal system operations and possible upset conditions as a result of internal and external events (including human error). The Operational Frequency Analysis (OFA) and Event Progression Logic (EPL) analysis provide an integrated framework for the analysis of initiating events from which hydrogen accumulation can occur and the quantitative analysis of the physical progression of ensuing hydrogen ignition events. The purpose of this paper is to describe the QRA methodology, models, and testing used to quantify the system demand resulting from postulated hydrogen event types, frequencies, and severities, with emphasis on the latter stages of the QRA, overall execution and application.
Non-Local Damage Model to Predict the Effect of Pre-Strain on Ductile Fracture in Aluminum Alloy 5052
Authors: Alinaghian Yaser , Asadi Mahyar , Weck Arnaud
Published: August 2013

Metallic components may develop plastic deformation before in-service loading (pre-strain) due to manufacturing process and/or unexpected loading. This pre-strain not only affects the yield strength of the material but also influences its fracture properties. The work presented here employed laser drilled model materials to better understand the effect of pre-strain on ductile fracture in aluminum alloy 5052. The micron-size laser drilled holes mimic voids forming during ductile fracture. These laser holes are introduced after the material has been pulled in tension to various amounts of pre-strain. The effect of pre-strain on void growth and linkage leading to fracture is studied. A non-local damage is used in a finite element model to predict linkage between voids. This non-local damage has only two adjustable parameters, namely the local failure strain in uniaxial tension and the characteristic length L which intervenes in the non-local averaging scheme. The precise arrangement of the laser holes can be exactly reproduced in the finite element model which allows the model to be validated with the experimental results.
Numerical Analysis of Hydrofoil Dynamics by Using a Fluid-Structure Interaction Approach
Authors: Rajaomazava Tolotra Emerry , Benaouicha Mustapha , Astolfi Jacques-André
Published: August 2013

In this paper, the flow over pitching and heaving hydrofoil is investigated. The viscous incompressible Navier-Stokes problem in Arbitrary Lagrangian-Eulerian (ALE) formulation is solved using the finite elements code Cast3M. The projection method is used to uncouple the velocity and pressure fields. The implicit Euler scheme is applied for time discretization of fluid equations. The dynamics of the hydrofoil is governed by a non-linear ordinary differential equation. The non-linear coupled problem is solved using the explicit staggered algorithm. The effects of fluid-structure interaction on hydrofoil dynamics and pressure center position are analyzed.
Vibration Characteristics of a Perforated Plate Immersed in Fluid
Authors: Ito Tomohiro , Shintani Atsuhiko , Nakagawa Chihiro
Published: August 2013

Perforated plates are used in many mechanical structures in thermal power plants, nuclear power plants, or chemical plants etc. Cylindrical structures made by the perforated plates are also found in many places. However, vibration characteristics of the structures made by perforated plates are not fully clarified, especially for the structures immersed in liquid. The stiffness of the structures becomes smaller than that of ones made by simple plates with no holes, while the mass of the structures also becomes smaller. According to the balance between the stiffness reduction and mass reduction, natural frequencies will be decided. Moreover, added mass and added damping effects are very large in liquid, and are thought to largely change due to holes.

In this study, as a fundamental step, a perforated plate is treated. The vibration characteristics such as natural frequency and damping ratio are studied for various hole numbers or various opening ratios by both numerical simulations and simple test models. Vibration tests are conducted in liquid as well as in air.
Optimised Modelling of Weld Metal Constitutive Behaviour in the Net TG4 International Weld Simulation and Measurement Benchmark
Authors: Smith Mike C. , Muránsky Ondrej , Austin Colin , Bendeich Philip J. , Edwards Lyndon
Published: August 2013

The NeT TG4 benchmark specimen consists of a three pass type 316L TIG slot weld in a AISI type 316L plate. Phase one of the finite element simulation round robin performed on TG4 by the NeT network made the assumption that the weld metal exhibits the same mechanical behaviour as parent material. A comprehensive series of material characterisation tests on weld metal has now been completed, and these have allowed the derivation of a number of mixed isotropic-kinematic material models specifically for weld metal. The derived models have been used to improve the predicted stresses in the TG4 benchmark specimen. This paper first reviews the weld metal materials testing programme, and then discusses the optimum material hardening model fitting strategy to use for austenitic weld metal. The derived material models are tested by using them to predict residual stresses in the TG4 benchmark, and validating the predictions against the extensive database of measured residual stresses, and distortions.
Failure Analysis of an In-Service Natural Gas Pipeline
Authors: Cao Huai-xiang , Qiu Xing-qi , Yao Xiao-jing , Song Ming-da
Published: August 2013

A natural gas pipeline which had been serviced nearly 10 years burst and led to fire. Analysis on samples taken from the pipeline had been made, the mechanism of crack initiation and propagation was discussed, and the cause of burst and fire of the pipeline was put forward. The analysis results showed that, the pipeline had some grooves along the axial mechanical damages, which caused the stress concentration. Except that, the coating in the mechanical damage area was broken, this caused the failure of cathodic protection (CP). Under the combined action of the stress concentration and the corrosion environment of the soil, localized corrosion in the mechanical damage area was caused, where micro-cracks initiated. Furthermore, in the stage of cracks propagation, the stress corrosion cracking (SCC) occurred due to the corrosion environment of the soil. Finally, with the cracks expanded, connected and grew, the residual wall of the pipe was small, and the accident arose because of insufficient strength.
Power Spectral Density Analysis of Acoustically Induced Vibration in Piping Systems
Authors: Dweib Ahmed H.
Published: August 2013

Acoustically induced vibration near points of large pressure reduction in piping systems can cause fatigue failure of the piping material at points of discontinuity.

Empirical design curves have been used extensively for the assessment of acoustic fatigue risk level in piping systems. Subsequent development in the field resulted in the application of more detailed methods of analysis including, displacement-based and energy-based Finite Element Analysis (FEA) and Statistical Energy Analysis (SEA).

Displacement-based FEA, which provides deterministic approach for the detailed analysis of the vibration response, is suitable for low and intermediate frequency range where the dynamic stresses in the pipe wall can be determined with reasonable certainty.

For large complicated systems and high frequency range, the deterministic FEA becomes impractical due to the large number of mode shapes involved and the sensitivity of the results to small changes in system parameters. In these cases, the results of the FEA can have only a statistical value and SEA methods, which are based on statistical approach in contrast to deterministic approach, become more effective. SEA methods require accurate estimation of energy coupling parameters, on which the validity of the methods is dependent.

In this paper, energy-based FEA is utilized for the evaluation of the system response and the SEA parameters. Power Spectral Density (PSD) analysis is performed for finite element model of a system consisting of pipe and acoustic fluid. The system is subjected to acoustically induced vibration through the input of acoustic energy at the downstream of a pressure-reducing valve. The system response is obtained and the parameters required for SEA, including the coupling power factor, are estimated.
Study on the Stress-Strain Redistribution Caused by Inelastic Deformation in Perforated Plate
Authors: Ikeda Sho , Sato Masakazu , Kasahara Naoto
Published: August 2013

Fast Breeder Reactors and chemical plants that is operated at elevated temperature must be designed considering creep deformation in addition to elastic-plastic deformation. Especially at structural discontinuities, strain concentration induced by stress-strain redistribution reduces creep-fatigue strength. For this reason, a design method is needed for appropriately evaluating inelastic behavior at a structural discontinuity. As one of simplified methods with elastic analysis, a rational method with Stress Redistribution Locus (SRL) has been studied during recent years. Previous studies have shown that SRL does not depend on constitutive equations or on the magnitude of loading. And through the elastic-plastic-creep analysis of a one-dimensional pipe model, it was revealed that there was a relation between stress-strain redistribution and the size of elastic core.

The purpose of this study is to clarify the mechanism of stress-strain redistribution in complex structures like actual components. Multi-dimensional stress-strain distribution and multiaxial stress occur in those structures. For considering those effects, inelastic analyses on perforated plate were performed and the relation between the region of elastic cores and SRL was examined. Then, it was revealed that SRL could be divided into two parts. One half is affected by the region of elastic core and the other half depends on the loading type. Furthermore, this paper proposes the new SRL method based on the mechanism and validates the method.
STYLE: Comparison of Engineering Assessment Methods
Authors: Lauerova Dana , Sharples John
Published: August 2013

The paper presents results of a sub-task of the STYLE project currently running within the 7th Framework EU programme by way of an overview of deterministic engineering assessment methods (EAM) used for evaluation of flawed nuclear plant components, as used in various European countries (Germany, France, UK, Netherlands, Czech Republic, Spain, Finland and Sweden).

Within STYLE, several mock-up experiments are being performed on specimens containing structural features. Structural features being considered include (1) dissimilar metal welds, (2) repair welds, and (3) austenitic cladding on a ferritic pipe. The overview thus focuses on the evaluation of flaws contained within each of these three types of features.

Information on the procedures and codes applied in the various countries are given: KTA standard, ASME Code in Germany; ZG Appendix of RCC-M, A16 Appendix of RCC-MRx, and App. 5.4–5.6 of RSE-M in France; R6 in the UK; BS7910, R6 in the Netherlands; VERLIFE, ASME Code in the Czech Republic; ASME Code in Spain; SSM Handbook, ASME Code in Finland; and SSM Handbook, ASME Code, ProSACC in Sweden.

An overview and brief description of the different methods is included in the paper, highlighting the commonalities and differences among the various approaches.
Design and Development of Pressure Vessel for Improvement of Manufacturing Rice-Powder Efficiency Using Underwater Shock Wave
Authors: Naha Kazuyuki , Shimojima Ken , Miyafuji Yoshitaka , Itoh Shigeru
Published: August 2013

The rice-powder paid to attention in Japan, because the various food made by rice-powder. But, conventional method of manufacturing rice-powder generates heat when crushing of rice. One the other hand, the pressure vessel of oval structure for manufactured rice-powder using underwater shock wave has been developed in Okinawa National College of Technology. The merits of this system manufacture rice-powder without heating.

But, the efficiency of this system is low. Therefore, in this paper, we propose new design of pressure vessel for the highly effective rice-powder manufacturing. To design a new pressure vessel, it is clear that the performance of the oval structure pressure vessel. And, we design and manufacturing new pressure vessel for the highly effective rice-powder manufacturing.
Assessment of J-Integrals for Surface Cracks in a Weld Metal
Authors: Park Young-Chul , Jeong Jae-Uk , Choi Jae-Boong , Chang Yoon-Suk , Kim Sung-Woo , Kim Hong-Pyo
Published: August 2013

Lots of defects due to primary water stress corrosion cracking have been observed at diverse penetration locations of major components in nuclear power plants. To resolve this issue, during the past couple of decades, numerous analytical and experimental researches have been carried out to determine residual stress distributions in dissimilar metal welds that are plausible to crack initiation caused by the primary water stress corrosion. The present research deals with prediction of J-integrals for axial inner surface cracks in a mock-up that is to resemble upper head of reactor pressure vessel with penetrations of control rod driving mechanism. At first, representative residual stress distributions at J-groove welded region of the mock-up were calculated through finite element analyses of un-cracked models according to practical welding procedure. Then, J-integrals were calculated by mapping the residual stress distributions to the cracked models with different shapes. Based on these parametric analyses, effects of varying crack geometries were investigated of which are fully discussed in the manuscript.
Combined Effect of Temper and Hydrogen Embrittlement on Threshold for Hydrogen–Induced Fracture in Cr-Mo Steels
Authors: Shimazu Hidenori , Konosu Shinji , Tanaka Yoichi , Yuga Masao , Yamamoto Hiroshi , Ohtsuka Naotake
Published: August 2013

This paper presents the results of the research activities of the subcommittee on Hydrogen Embrittlement of the Japan Pressure Vessel Research Council (JPVRC). The combined effect of temper embrittlement and hydrogen embrittlement in Cr-Mo steels is discussed. It has been recognized that Cr-Mo steels used widely in the refining and petrochemical industry are quite susceptible to temper embrittlement. Although the synergetic relation between temper embrittlement and hydrogen embrittlement is a matter of major concern, studies regarding this subject are rarely encountered. Task group VIII (TG8) of the JPVRC conducted fracture toughness tests for three kinds of 2.25Cr-1Mo steels and 2.25Cr-1Mo-0.3V steel. These steels were prepared by subjecting them to normalizing, tempering and post-weld heat treatments which simulated actual conditions. Some specimens were embrittled by step cooling (Socal −1 treatment). It was found that the threshold for hydrogen-induced fracture was lowered when the specimen was exposed to pressurized hydrogen gas (15MPa) for 48 hours at 450 °C and there was no marked indication of the synergetic action concerning this embrittlement.
Effects of Simulation Parameters on Residual Stresses of Inconel Alloy 600 in Finite Element Laser Shock Peening Analysis
Authors: Kim Ju Hee , Kim Ji Soo , Kim Yun Jae , Bae Hong Yeol , Kim Joung Soo
Published: August 2013

Laser shock peening (LSP) is an innovative surface treatment technique, which is successfully applied to improve fatigue performance of metallic components. After the treatment, the fatigue strength and fatigue life of a metallic material can be increased remarkably owing to the presence of compressive residual stresses in the material. Recently, the incidences of cracking in Alloy 600 small-caliber penetration nozzles (CRDM (control rod drive mechanism) and BMI (bottom mounted instrument)) have increased significantly. The cracking mechanism has been attributed to primary water stress corrosion cracking (PWSCC) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. For this reason, to mitigating weld residual stress, preventive maintenance of BMI nozzles was considered application of laser shock peening process.

The present study is to predict the residual stresses distribution along the peening surface and the interior of the target (Inconel alloy 600 steel) induced by single and multiple LSP processes using the finite element method. The simulations were accomplished using a commercial finite element package ABAQUS, employing both explicit and implicit methodologies. Effects of parameters related to finite element simulation of laser shock peening process to determine compressive residual stresses of Inconel alloy 600 steel are discussed, in particular parameters associated with the LSP process, such as the maximum pressure, pressure pulse duration, laser spot size and number of shots.

It is found that about 2HEL maximum pressure and a certain range of the pulse duration can produce maximum compressive residual stresses near the surface, and thus proper choices of these parameters are important. But plastically affected depth increase with increasing maximum pressure and pulse duration. For the laser spot size, residual stresses are not affected, provided it is larger than a certain size. Magnitudes of the compressive residual stresses and plastically affected depth are found to increase with increasing number of shots, but the effect is less pronounced for more shots. Thus, the amplitude of the initial tensile residual stresses was remarkably changed by LSP. Additionally, In order to evaluate the influence of initial residual stresses in Inconel alloy 600 steel, the initial condition option was employed in the finite element code.
Experimental Study on Free Standing Rack Loading Full Fuel Assembly
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki
Published: August 2013

The spent fuel storage rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel storage rack must have a high tolerance against large seismic loads. So, the free standing rack is developed in Japan as other countries. The free standing rack structure incorporates the effect of the friction force on the spent fuel pool floor, and the fluid effect.

Under earthquake condition, the free standing rack sliding and rocking motions are induced and the spent fuels rattle in the cells.

In this paper, sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied. To develop an analysis evaluation method for rack motions, we carried out seismic test of a full-scale rack model using a shaking table, and obtained the fundamental data about the free standing rack.
Prediction of Residual Stress Distribution for RPV CRDM Penetration Nozzles
Authors: Bae Hong-Yeol , Kim Yun-Jae , Kim Ju-Hee , Lee Sung-Ho , Lee Kyoungsoo
Published: August 2013

In nuclear power plants, RPV (Reactor Pressure Vessel) upper head CRDM (Control Rod Drive Mechanism) penetration tubes has been fabricated J-groove weld geometry. Recently, the incidences of cracking in Alloy 600 CRDM tubes and their associated welds have increased significantly. The cracking mechanism has been attributed to PWSCC (Pressurized Water Stress Corrosion Cracking) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. Weld induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operating. In this point, we have been conducting detailed welding simulation analyses for Korea Nuclear Reactor Pressure Vessel to predict the magnitude of weld residual stresses in penetration tubes. In the present work, the FE (Finite Element) simulations were conducted to investigate the effects of tube geometry (location and ro/t) and material properties on the residual stresses in the J-groove weld for a different location of CRDM tubes. The variables of tube location included three (center-hole, intermediate and steepest side hill tube) inclination angles (Ψ). And this comparison was performed for different tube geometry (ro/t = 2, 3, 4), different yield strength (σo) of tube. In CRDM tube, when increases in tube inclination angle (Ψ), axial residual stress are gradually increased, but hoop residual stresses are decreased at the nearby weld root. In effect of tube radius and thickness, when the thickness of CRDM tubes increases the residual stresses are gradually decreased at the inner surface of tube. And there is no effect of CRDM tube radius (ro). In effect of plastic properties of Alloy 600 material in CRDM, when yield strength of the tube increases the axial residual stresses decreases but hoop residual stress increases.
Experimental Parameter Study on Free Standing Rack
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki
Published: August 2013

The spent fuel rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a high tolerance against big seismic loads. Sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied [1]. We carried out the seismic test of the free standing rack under some conditions. The distribution of the fuel assembly affects the sliding and rocking motions of the rack, and the outer plate reduces the rack response level by fluid effect. We made sure of them by seismic experiment using a shaking table.

In this paper, sliding and rocking motions of full-scale rack model under some conditions are studied. To develop an analysis evaluation method of the rack sliding and rocking motions, we obtained the fundamental data about the free standing rack by seismic test using a shaking table.
Analysis Study on Free Standing Rack Under the Earthquake Excitation
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki
Published: August 2013

The spent fuel rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a high tolerance against big seismic loads. So, the free standing rack is developed in Japan as other countries. To develop an analysis evaluation method for the free standing rack motions, we carried out seismic experiment of the full-scale free standing rack to obtain the fundamental data about it. The free standing rack motions are sliding and rocking under seismic excitation. To evaluate the sliding and rocking motions of the free standing rack, we reflected test result to analysis method, and developed the dynamic response analysis model.
A Basis for Selecting the Most Appropriate Small Specimen Creep Test Type
Authors: Hyde T. H. , Hyde C. J. , Sun W.
Published: August 2013

Many components in conventional and nuclear power plant, aero-engines, chemical plant etc, operate at temperatures which are high enough for creep to occur. These include plain pipes, pipe bends, branched pipes etc; the manufacture of such components may also require welds to be inserted in them. In most cases, only nominal operating conditions (i.e. pressure, temperatures, system load etc) are known and hence precise life predictions are not possible. Also, the proportion of life consumed will vary from position to position within a component and the plant. Hence, non-destructive techniques are adopted to assist in making decisions on whether to repair, continue operating or scrap certain components. One such approach is to use scoop samples removed from the components to make small creep test specimens, i.e., sub-size uniaxial creep test specimens, impression creep test specimens, small punch creep test specimens and small ring creep test specimens.

Each specimen type has its own unique advantages and disadvantages and it may not be obvious which one is the most appropriate test method to use. This paper gives a brief description of each specimen and associated test type and describes their practical limitations. The suitability of each of the methods for determining “bulk” material properties is described and it is shown that an appropriate test type can be chosen.
R6 V and Proposed Vg Plasticity Correction Terms for Combined Loading Applied to Experiments
Authors: James Peter , Madew Colin
Published: August 2013

Engineering components may contain small crack-like defects that experience combinations of primary and secondary stresses during service. A new formalism of the R6 V factor, Vg, has been introduced over previous years to quantify the influence of plasticity interaction under combined primary and secondary loading based upon such defects within a large range of finite element analyses.

The aim of this paper is provide experimental validation to the Vg approach such that it satisfies validation requirements for potential inclusion to R6. Estimates of failure from implementing Vg, as well as the R6 V approach, to experiments available from literature are presented. These experiments include plate tests subjected to weld residual stresses, cylinders subjected to thermal shock conditions and pre-compressed laboratory specimens. This range of specimens covers those considered in validation of the existing approaches in R6 and some more recent experiments.

When applying the existing R6 V and the Vg plasticity interaction parameters the accuracy of the methods diverges with increasing plasticity; with the Vg approach providing the more accurate result at intermediate and high levels of Lr (i.e. beyond Lr = 0.7). However, since both the existing R6 and the Vg plasticity interaction parameters are conservative the experiments provide useful validation to both methods.
“First Estimate” Plastic Collapse Solutions for Flat and Torispherical Ended Pressure Vessels Subjected to Extensive Corrosion Wall Thinning
Authors: Madew Colin , Wilkes Mark , Charles Richard , Symington Ian
Published: August 2013

Plants in safety-critical industries comprise of a number of different components, including various sizes of pressure vessels, and their integrity is often paramount to the safe running of the plant. In many cases these vessels can contain highly corrosive liquids, which, over time can lead to a degree of thinning in the vessel walls. With corrosion wall-thinning come a number of issues, including a reduced plastic collapse load of the vessel and possible fatigue initiation from corrosion pits. Since failure of these vessels could lead to catastrophic failure and the escape of highly corrosive material, the assessment and maintenance of these vessels is of high importance.

Current Fitness for Service Codes and Standards provide guidance on the assessment of cylinders and pipes with localized wall thinning and general corrosion, with respect to plastic collapse. This guidance, however, is not currently applicable to components with geometric discontinuities (the pressure vessel base-wall junction).

This paper follows a preceding paper presented at the ASME PVP Conference 2010 which derived “First Estimate” plastic collapse solutions for flat-based, corroded, pressure vessels. These solutions have been expanded through further finite element studies to accommodate the estimation of plastic collapse in tori-spherical headed pressure vessels subjected to extensive corrosion wall-thinning. Results from this study are presented in graphical form to enable a quick and efficient first estimate of the effect of wall thinning on the collapse pressure to be attained.
TDFAD Analysis of Creep Crack Initiation in Pre-Strained and As-Received Type 316H Stainless Steel
Authors: Davies C. M. , Dean D. W. , Mehmanparast A.
Published: August 2013

The time dependent failure assessment diagram (TDFAD), an extended form of the low temperature FAD used in the R6 procedure, has been developed to allow creep crack initiation to be predicted using a FAD-based approach. The TDFAD has a number of advantages compared to other methods for predicting creep crack initiation time: detailed calculations of crack tip parameters such as C* are not needed; it is not necessary to establish the fracture regime in advance and the TDFAD can indicate whether initiation occurs under small-scale or widespread creep conditions. The TDFAD approach relies on the availability of appropriate creep toughness, Kcmat, values. In this work, creep toughness data have been derived from experimental creep crack growth (CCG) tests on compact tension fracture mechanics specimens made of Type 316H stainless steel in as-received (AR) material and material that has been pre-compressed (PC) by up to 8% plastic strain. The influence of material pre-conditioning on creep toughness is examined. TDFADs are then constructed for each material condition and creep crack initiation (CCI) time predictions are obtained for the CCG tests performed on the Type 316H steel at 550 °C. The influence of material condition on the predicted CCI mode is examined and discussed.
Hydro-Abrasive Wear Damage at Reactor Recirculation Pump Bearing Journals
Authors: Engel Robert , Fibier André , Heldt Jens , Ronecker Andreas
Published: August 2013

During the refueling and maintenance outage in August 2011 at Leibstadt Nuclear Power Plant in Switzerland, the inspection of the hydrostatic bearings of the two identical recirculation pumps revealed a deep circumferential erosion groove on the inside surface of each of the bearing journals. The bearing journals are made of austenitic stainless steel. The cylindrical journal is welded to the back shroud of the impeller and surrounds the internal stationary heat exchanger of the pump by forming a narrow fluid filled annulus. The location of material removal was the same as in the year 2004 when similar wear damage was fixed by build-up welding.

The plant decided to repair the damage during the subsequent outage in 2012. However, the Swiss Federal Nuclear Safety Inspectorate in return required the plant to identify the precise erosion mechanism, to ensure the structural integrity of the journals by taking into account the rate of material removal from 2004 up to the 2012 outage, and to include provisions for the early detection of a journal failure.

This paper summarizes the previous as well as the latest results of different inspections, investigations, evaluations, and analyses done to meet the requirements of the Swiss regulatory authority. The results show that, from a safety-related and an operational availability perspective, it is acceptable not to repair the damaged bearing journals prior to the 2012 outage.
CFD Analyses of the TN-24P PWR Spent Fuel Storage Cask
Authors: Brewster Robert A. , Baglietto Emilio , Volpenhein Eric , Bajwa Christopher S.
Published: August 2013

Dry storage casks are used to store spent nuclear fuel after removal from the reactor spent fuel pool. Even prior to the Fukushima earthquake of March 2011, dry storage of spent fuel was receiving increased attention as many reactor spent fuel pools near their capacity.

Many different types of cask designs are used, and one representative design is the TN-24P spent fuel cask, a non-ventilated steel cask with a shielded exterior shell and lid. The cask is typically filled with an inert gas such as helium, argon or nitrogen. In this paper, Computational Fluid Dynamics (CFD) calculation results for the thermal performance of the TN-24P cask using the commercial CFD software STAR-CCM+ are presented. Initial calculations employ a common approach of treating the fuel assemblies as conducting porous media with calibrated volume-averaged properties, and comparison to existing measured temperature data shows good agreement.

One of the fuel assemblies is then replaced with a more accurate representation that includes the full geometric detail of the fuel rods, guide tubes, spacer grids and end fittings (flow nozzles), and the results shown are consistent with the initial analysis, but without the need for the assumptions inherent in the porous media approach. This hybrid modeling approach also permits the direct determination of important results, such as the precise location of peak fuel cladding temperatures (PCTs), which is not possible using the more traditional porous media approach.
System for the Automated Mitigation of Hypergolic Propellant Leaks
Authors: Reich Alton
Published: August 2013

Hypergolic liquid rocket propellants consist of fuel and oxidizer liquids stored in separate tanks that ignite when mixed. They are favored for propulsion systems where precise pulsing or throttling is required. High reliability is also insured because the liquid chemicals are stable for long periods of time, and no ignition system is required — the fuel and oxidizer simply need to be brought together. These propellants have relatively high vapor pressures, are toxic, and may be carcinogenic. A pool of the liquid will pose a health, fire, or explosion hazard. Therefore, missiles containing these propellants are stored and shipped in canisters that contain a sensor to detect the leakage of these propellants that will sound an alarm at a set concentration. This paper discusses the development of an automated system that is designed to mitigate a leak of the fuel or oxidizer within the canister in order to render the system safe enough to allow access to the missile. The mitigation system neutralizes the leaked propellant. The design and testing of the system with representative propellants is discussed.
Numerical Analysis of Bolted Trunnion Systems of Packages for Radioactive Materials
Authors: Sterthaus Jens , Ballheimer Viktor , Kuschke Christian , Wille Frank
Published: August 2013

Packages for the transport of radioactive material are generally equipped with particular components for crane operations and supporting the package during transport. As an example of such components the bolted trunnion system of heavy packages are analysed in this paper.

According to the German guideline BAM-GGR 012 created by the BAM Federal Institute for Materials Research and Testing for analysis and assessment of bolted lid and trunnion systems, the finite element (FE) method is to be used preferably in the analysis of such kind of structures to obtain more accurate and detailed information about their stressing. The FE model of a trunnion system should include the trunnion itself, the bolts and an appropriate part of the packaging wall with necessary contact conditions on all interfaces between these components. The use of solid finite elements, which is generally recommended in the BAM-GGR 012 guideline, leads to local stress and strain fields as a result of the calculation. The modelling strategy, e.g. the way of modelling interaction between the components of the trunnion system, has an essential impact on these local values.

The effect of different assumptions in a FE model is demonstrated in this paper using the calculation results for a reference trunnion system. The approaches for preparation and interpretation of results in connection with local or nominal assessment criteria are discussed as well.
Non-Loosening Performance of Plastically Pre-Deformed Nuts Under Cyclic Loads
Authors: Shoji Yasumasa , Kumakura Susumu , Sawa Toshiyuki
Published: August 2013

Self-loosening of bolts and nuts is a significant issue for bolted fasteners. In recent years, this problem has been a hot topic in the field of pressure vessels and piping. Several research papers have been presented from several institutes and the mechanism and phenomena have been almost understood. This paper offers a countermeasure based on the authors’ long time research activity on the non-loosening performance of various types of nuts. Their research has indicated that prescribed plastic deformation of nut heads may prevent or decrease loosening. This phenomenon was reproduced using Finite Element Analysis.
Code Aspects Related to Combination of Stresses due to Hydrogen Detonations: Local Effects
Authors: Minichiello John C. , Ahnert Stephen D. , Ligon Thomas C. , Gross David J.
Published: August 2013

This paper addresses the local effects of hydrogen detonations inside piping. It is the first in a two-part series of papers which assess the effects of detonations in piping systems relative to ASME Code allowables.

The effects of internal detonations in piping systems are typically separated into two regimes: local effects and system effects. Local effects are often simplistically represented as pure hoop stresses resulting from the pressure acting radially on the inside circumference of the pipe. In reality, the interaction of the pipe wall and the propagating detonation wave is relatively complex, resulting in “waves” or “ripples” in the pipe wall. These areas of local, through-wall curvature lead to substantial axial stresses which may even exceed the hoop stresses. Furthermore, in the elastic regime, there is very little damping present in the pipe wall, leading to numerous stress cycles as the local bending waves move axially along the pipe wall.

Fatigue effects of the combined hoop and axial cycling were evaluated using ASME Code Section VIII, Division 2 fatigue evaluation methodology. Analysis of strain gage data from a number of hydrogen detonation experiments in 2-inch and 4-inch Schedule 40 piping showed that the fatigue damage is generally driven by fewer than 10 large-magnitude fatigue cycles, which account for an average of 75% of the total fatigue damage. However, the results also demonstrate that for two detonation events with similar measured peak hoop or axial strain, the number of fatigue allowable events may vary dramatically depending on the shape of the strain response.
Simplified Stress Linearization Method, Maintaining Accuracy
Authors: Strzelczyk Andrzej , Stojakovic Mike
Published: August 2013

ASME PVP Code stress linearization is needed for assessment of primary and primary-plus-secondary stresses. The linearization process is not precisely defined by the Code; as a result, it may be interpreted differently by analysts. The most comprehensive research on stress linearization is documented in the work of Hechmer and Hollinger [1]. Recent non-mandatory recommendations on stress linearization are provided in Annex 5A of Section VIII, Division 2 of ASME PVP Code [2]. In the work of Kalnins [3] some linearization questions are discussed in two examples; the first is a plane-strain problem and the second is an axisymmetric analysis of primary plus secondary stress at a cylindrical-shell/flat-head juncture. Paper [3] concludes that for the second example the linearized stresses produced by Abaqus [5] diverge, therefore they should not be used for stress evaluation for this specific case.

This paper revisits the axisymmetric analysis discussed in [3] and attempts to show that the linearization difficulties can be avoided. The paper explains in details the reason for the divergence; the Abaqus program does not linearize all stress components in axisymmetric elements; two stress components are calculated from assumed formulas and all others are linearized. It is shown that when the axisymmetric structure from [3] is modeled with 3D elements, the linearization results are convergent. Further, it is demonstrated that both axisymmetric and 3D modeling produce the same and correct stress Tresca stress, if the stress is evaluated from all stress components linearized, without any further modification.

The stress evaluation of the axisymmetric model of [3] is the primary-plus-secondary-stresses evaluation for which the limit analysis described in [4] cannot be used. The paper shows how the original primary-plus-secondary-stresses problem can be converted into the equivalent primary-stress problem, that is for a problem for which limit analysis can be used; it is further shown how the limit analysis had been used for verification of the linearization results.
DPIV Around a Flexible Circular Cylinder Undergoing Cross-Flow Forced Oscillations
Authors: Huera-Huarte Francisco J. , Bangash Zafar A.
Published: August 2013

This research is motivated by early experiments [1, 2], in which the main time consistent flow structures in the wake of a flexible oscillating circular cylinder were studied. We have now investigated the wake of a circular cylinder undergoing forced vibrations, by using Planar Digital Particle Image Velocimetry (DPIV) and long exposure photographs for flow visualisation. The focus is given to the node to anti-node transition when the cylinder oscillates in its second structural mode. A flexible cylinder is supported by a structure consisting of a frame that includes a motor that drives a shaft, that actuates a pusher connected to the cylinder at two points, through a crank slider mechanism. We are able to produce forced oscillations of the cylinder, either in its first mode when the pushers are in phase, or in its second mode if the pushers are configured out-of-phase. We have used a high speed camera together with a continuous wave laser, to image seeding particles being illuminated by the laser sheet, at two different heights along the length of the cylinder: the node and the anti-node. We have also produced long exposure images of the particles leading to flow visualisation.