bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analytical One-Dimensional Penetration Model
Authors: Reichwein Sarah , Jones Stanley E.
Published: July 2009

In an earlier paper, the authors extended the small parameter analysis of the classic Tate Equations presented by Walters, et al and to the modified penetration equations introduced previously by Jones, et al. The purpose of this extension was to provide an explicit solution to a complex system of nonlinear penetration equations in which penetrator mushrooming was considered, as well as erosion. This has a dramatic effect on the prediction of penetration depth for reasonable values of the strength parameters in the problem. The results were very encouraging and led to our increased understanding of the penetration process. In this paper, we further modify the equations for penetration depth by replacing the fundamental kinematical length relation, considered earlier, by one which was introduced by Wilson, et al. This change does not complicate the system because the mushroom strain is constant, but it does produce some significant changes. In this paper, the results of Cinnamon, et al are used to estimate the mushroom strain. However, instead of applying this result directly, we employ an averaging process to accommodate deviations from cylindrical crater geometry. The changes result in improved penetration depth estimates in high speed metal on metal impacts. A large data set is analyzed using the new results. Application to heavy metal impacts against armor targets is considered as an example.
Current Wall Thinning Measured on Piping System of Main or Auxiliary Boiler Plant in Ships
Authors: Shiihara H. , Matsushita H. , Nagayama Y.
Published: July 2009

A disaster happened in a nuclear power plant in Japan in August 2004, which was caused by failure of condensation water pipe in the secondary line. Shipping industries were concerned for possibility of occurrence of such a disaster in ships due to its construction similarity to marine boiler plant in steam, feed water and condensation piping for main or auxiliary boilers. Nippon Kaiji Kyokai has therefore investigated and gathered data of piping lines corrosion in ships collaborated with major Japanese ship owners right after the disaster. The results show that similar corrosion failure as in the nuclear power plant has occurred in shipboard steam/feed water/condensation water pipes for main and auxiliary boiler plants without causing severe consequences. The wall thickness measurements on actual pipe lines of steam, feed water and condensation water at bend parts, at T-junction, behind orifices, behind valves and at diffusers/reducers with a ultrasonic thickness gauge show a very definite evidence of a reduction in wall thickness of carbone steel pipes. It was confirmed that the amount of actual reduction in wall thickness could be well predicted by Kastner Equation [2–3].
Development of Simplified Plastic Collapse Assessment Procedure for Elbow With an External Surface Flaw Simultaneously Subjected to Internal Pressure and External Bending Moment
Authors: Oyamada Kenji , Konosu Shinji
Published: July 2009

A simplified assessment procedure using the p-M (internal pressure ratio and external bending moment ratio) diagram, which can evaluate the plastic collapse load for an elbow with an external surface flaw simultaneously subjected to internal pressure, p, and external bending moment, M, due to earthquake, etc., is derived. The p-M diagram evaluation is an easy way to visualize the status of components with a flaw. For an elbow with an external surface flaw, the already-proposed p-M diagram by one of authors for the cylindrical part of pressure equipment such as vessels, pipes, etc. with a surface flaw can be applied if the parameters proposed in this paper are used. The plastic collapse loads derived from the p-M diagram method are being verified by comparison with existing experimental and FEA results.
The Study on the Impact of FSI on the Fuel Assembly Design Optimization
Authors: Kim Kyu-Tae , Jang Young-Ki , Kim Jae-Ik
Published: July 2009

The fluid-induced fuel rod fretting wear in PWRs mainly proceeds in the grid-to-rod contact areas. This grid-to-rod fretting wear observed in various PWR fuel assembly designs may depend on external and internal vibration sources. The extent of the external vibration may be governed by reactor coolant flow velocity, non-uniform flow profiles caused by the reactor internals, and inter-fuel assembly gaps and fuel assembly-shroud gaps. The extent of the internal vibration may be controlled by spacer grid mixing vane pattern, irradiation-induced spring force relaxation and/or growth rate differences in fuel rod and guide tube. In this study, the internal vibration sources only are focused and its impact on the grid-to-rod fretting wear is evaluated, based on verification test results of a newly developed advanced fuel assembly as well as their operating experiences in various reactor conditions. In addition, key guidelines of fuel assembly design optimization are provided to prevent the grid-to-rod fretting wear-induced failure.
Structural Integrity of Penetration Nozzle of Reactor Pressure Vessel Head of PWR Plant
Authors: Hojo Kiminobu , Ogawa Naoki , Iwamoto Yoichi , Ohoto Kazutoshi , Asada Seiji , Ito Hajime , Hirano Shinro
Published: July 2009

A reactor pressure vessel (RPV) head of PWR has penetration holes for the CRDM nozzles, which are connected with the vessel head by J-shaped welds. It is well-known that there is high residual stress field in vicinity of the J-shaped weld and this has potentiality of PWSCC degradation. For assuring stress integrity of welding part of the penetration nozzle of the RPV, it is necessary to evaluate precise residual stress and stress intensity factor based on the stress field. To calculate stress intensity factor K, the most acceptable procedure is numerical analysis, but the penetration nozzle is very complex structure and such a direct procedure takes a lot of time. This paper describes applicability of simplified K calculation method from handbooks by comparing with K values from finite element analysis, especially mentioning crack modeling. According to the verified K values in this paper, fatigue crack extension analysis and brittle fracture evaluation by operation load were performed for initial crack due to PWSCC and finally structural integrity of the penetration nozzle of RPV head was confirmed.
Application of Master Curve Method to Fracture Toughness Estimation of the Transport and Storage Cask Material
Authors: Hojo Kiminobu , Yoshimoto Kentaro , Yamamoto Ryuichi , Matsuoka Toshihiro , Mayer Uwe
Published: July 2009

The transportation and storage casks have to be designed by considering transport and handling accidents. IAEA safety standard [1] requires drop test using a scale model and demonstration of structural integrity of the cask container vessel from the view point of leakage and instable fracture. For the fracture evaluation, it has to be verified that brittle fracture does not occur at the lowest temperature −40degC. MHI has developed the MSF-57BG cask whose body is made of forged low alloy steel LF3-m. It is well known that low alloy steel has the brittle-to-ductile transition temperature range of fracture toughness and large scatter of toughness value in this region. For the cask’s integrity evaluation, it is needed to obtain the fracture toughness dependent on temperature of this material by considering data scatter. The Master curve procedure [2] was proposed for estimation of fracture toughness of the pressure vessel on the basis of statistical procedure by using relatively small number of specimens. This paper examined the determination method of fracture toughness considering dynamic loading effect and data scatter in the brittle-to-ductile transition temperature by using the Master curve procedure.
Numerical Simulation of Cup-Cone Fracture in a Round Tensile Bar
Authors: Kim Y. , Chao Y. J. , Lam P.-S.
Published: July 2009

Cup and cone fracture for a round tensile bar under tension is analyzed numerically using finite element method. Finite strain analysis with general solid elements is performed to simulate the development of necking, flat cracking at the center of the bar, propagation of the flat crack towards the free surface, and then slant 45° cracking leading to the final separation of the tensile bar. The key fracture stages and parameters in the simulation of this entire process include (a) a fracture criterion for the flat cracking at the center of the bar, (b) flat crack propagation using a constant crack-tip-opening-angle and/or displacement (CTOA/CTOD), (c) a criterion for determining the transition from flat cracking to slant cracking, (d) slant crack propagation using a constant shear CTOA/CTOD. Details of the numerical process are provided.
Stress Analysis and Sealing Performance Evaluation of Pipe Flange Connection at Elevated Temperature
Authors: Takagi Yoshio , Torii Hiroyasu , Sawa Toshiyuki , Kawasaki Naoki
Published: July 2009

Although a lot of pipe flange connections are exposed to elevated temperature during plant operation, a sealing performance of the pipe flange connections at elevated temperature is not well understood because of the experimental difficulty and the analytical problems due to the lack of the materials properties of gaskets at elevated temperature. The authors have been evaluating the sealing performance of the pipe flange connections at elevated temperature with numerical and experimental analysis and showed the strong effect of the material properties of the gaskets, like a thermal expansion coefficient and a stress-strain curve, on the sealing performance. In order to make a further evaluation, the effect of material properties on the sealing performance was analyzed by using FEM. In the FE analysis, the material properties were varied to evaluate the effect of them on the sealing performance. Furthermore, the material properties and the mechanical characteristic of the gasket were evaluated as a function of temperature. The obtained properties were used to reanalyze the sealing performance of the pipe flange connection. As a result, the gasket stress induced by the mismatch of the thermal expansion between the gasket and flange/bolt increased as increasing the temperature in the case that the thermal expansion coefficient of the gasket was larger than that of bolt/flange material and the sealing performance of the pipe flange connection was improved. However, the improvement in the sealing performance at elevated temperature was not expected so much at higher temperature due to the less increment of the thermal expansion and thermal stress of the gasket. This paper discuss about the change in the sealing performance of the pipe flange connection under elevated temperature considering the material properties and mechanical characteristics of the gasket.
Stress Characteristics of Large Diameter Pipe Flange Connection With Non-Asbestos Gasket Under Elevated Temperature
Authors: Sawa Toshiyuki , Kawasaki Naoki , Takagi Yoshio , Torii Hiroyasu
Published: July 2009

Since the flange rotation caused by internal pressure affects the sealing performance of pipe flange connections more by increasing the pipe nominal diameter, it is important to evaluate the sealing performance of larger nominal diameter pipe flange connection. However, most experiments were conducted with small-scale model due to the difficulty of large-scale experiment and numerical analyses containing uncertainties because of the lack of material models of gaskets. In addition, a sealing performance evaluation at high temperature is more difficult due to the thermal effect though the thermal condition is not avoidable in practical use. In this study, the 20” diameter pipe flange connection was used as a large nominal diameter pipe flange connection to analyze the stresses in the connection. In the FE analysis, the experimentally obtained material properties were used and the effect of diameter on the sealing performance was evaluated. The analysis revealed the thermal effect and the effect of flange rotation on the sealing performance. Moreover, the effect of material properties on the contact stress and hub stress of the pipe flange connections was evaluated. The experimentally obtained result was discussed with the FE result in this study.
Natural Flaw Shape Development Due to Stress Corrosion Cracking
Authors: Rudland D. , Shim D.-J. , Csontos A.
Published: July 2009

Typical ASME Section XI subcritical cracking analyses assume an idealized flaw shape driven by stress intensity factors developed for semi-elliptical shaped flaws. Recent advanced finite element analyses (AFEA) conducted by both the US NRC and the nuclear industry for long circumferential indications found in the pressurizer nozzle dissimilar metal welds at the Wolf Creek power plant, suggest that the semi-elliptical flaw assumption may be overly conservative in some cases. The AFEA methodology that was developed allowed the progression of a planar flaw subjected to typical SCC-type growth laws by calculating stress intensity factors at every nodal point along the crack front, and incrementally advancing the crack front in a more natural manner. Typically crack growth analyses increment the semi-elliptical flaw by considering only the stress intensity factor at the deepest and surface locations along the crack front, while keeping the flaw shape semi-elliptical. In this paper, a brief background to the AFEA methodology and the analyses conducted in the Wolf Creek effort will be discussed. In addition, the natural behavior of surface cracks under normal operating conditions (plus welding residual stress) will be investigated and compared to the semi-elliptical assumption. Conclusions on the observation of when semi-elliptical flaw assumptions are appropriate will be made. These observations will add insight into the conservatism of using an idealized flaw shape assumption.
Elimination of Thermoacoustic Furnace Vibration in a Gas-Fired Package Boiler: A Case Study
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: July 2009

Severe furnace vibration developed in a gas-fired package boiler during initial operation. The vibration occurred at higher loads and was characterized by an acoustic standing wave residing inside the furnace in the front-to-rear direction along burner axis. Theoretical predictions indicated that the thermoacoustic behavior of the burner/furnace system operated in an unstable range explaining the underlying cause of the vibration problem. For the elimination of the vibration problem, a two-step solution was utilized: 1. The mode of fuel injection was modified with the aim of disrupting the interface between the hot furnace gases and the cold burner air region in order to minimize the principal thermoacoustic hot-to-cold driving mechanism. This step was successful in mitigating the vibration in a still thermoacoustically unstable system. 2. A full elimination of the vibration was achieved by making the system thermoacoustically stable by modifying the cold air portion of the system. Both, the step 1 solution which suppressed the thermoacoustic excitation source and the step 2 solution of making the system thermoacoustially stable allowed the boiler to operate without vibration at all loads. The paper gives a detailed description of the issues involved.
Displacement Controlled Stress Intensity Factor Solutions for Structural Integrity Assessments of Welding Residual Stress Distributions
Authors: Toft Adam , Beardsmore David , Madew Colin , Teng Huego , Jackson Mark
Published: July 2009

Within the UK nuclear industry the assessment of fracture in pressurised components is often carried out using procedures to calculate the margin of safety between a lower-bound fracture toughness and the crack driving force. Determination of the crack driving force usually requires the calculation of elastic stress intensity factor solutions for primary loads and secondary loads arising from weld residual stresses and/or thermal stresses. Within established UK assessment procedures weight function solutions are available which allow the stress intensity factors to be calculated from the through-wall opening-mode stress distribution in an uncracked component. These weight-function solutions are generally based on models where either no boundary condition is applied, or where one is applied at a distance either side of the crack plane that is very long compared with the crack size and wall thickness. Such solutions do not take into account any reduction in the stress field that might occur as the distance from the crack faces increases. Weld residual stress fields may often be expected to reduce in this manner. A separate, earlier study has shown that the stress intensity factor for a cracked plate loaded in displacement control decreases substantially as the loading plane is moved closer to the crack plane. It would therefore be expected that a similar reduction in stress intensity factor would be obtained for a residual stress analysis when displacement boundary conditions are imposed at a distance relatively close to the crack plane. This paper describes an investigation of the differences, particularly in terms of a reduction in calculated stress intensity factor, which may arise from application of displacement controlled stress intensity factor solutions, as compared with load controlled solutions, when considering weld residual stresses. Consideration is also given as to how new displacement controlled stress intensity factor solutions could be developed by modification of existing load controlled solutions.
The Department of Energy Replacement for the 110-Gallon Specification 6M Shipping Container for Radioactive Contents
Authors: Arbital Jeffrey G. , Mann Paul T.
Published: July 2009

The Department of Energy (DOE) has been shipping university reactor fuels and other fissile materials in the 110-gallon Department of Transportation (DOT) Specification 6M container for over 20 years. The DOT 6M container has been the workhorse for many DOE programs. However, packages designed and used according to the Specification 6M (U. S. Code of Federal Regulations, 49 CFR 178.354; 2003) do not conform to the latest package safety requirements in 10 CFR 71, especially performance under hypothetical accident conditions. For that reason, the 6M specification containers are being terminated by the DOT. Packages designed to the 6M specification will no longer be allowed for in-commerce shipments after October 1, 2008. To meet on-going transportation needs, DOE evaluated several different concepts for replacing the 110-gallon 6M. After this evaluation, DOE selected the Y-12 National Security Complex for the project. The new Y-12 container, designated the ES-4100 shipping container, will have a capacity of four times the current 6M and will be certified by the Nuclear Regulatory Commission (NRC). The ES-4100 project began in September 2006 and prototypes of the new container are now being fabricated. Details on the design features and the upcoming regulatory testing of this new container are discussed in this paper.
Self-Loosening Mechanism of Nuts Due to Impacts
Authors: Shoji Yasumasa , Sawa Toshiyuki
Published: July 2009

As self-loosening of nuts is really a problem for bolted joints in practical use, countermeasures for the loosening is highly required. In this situation non-loosening fasteners are one of the resolutions for any fastened machinery as an essential mechanical element. Self-loosening of threaded bolt/nut systems has been researched in number of works and many of them were based on experiments historically and some were based on the finite element analyses in these years. Authors have reported the static loosening of nut due to the transverse motion of fastened objects in PVP conferences using finite element analyses and showed the loosening mechanism. This paper will show another case based on the dynamic situation namely impacting of the bolt/nut systems as NAS3350/3354 test situation. In this special case, nut loosening was reproduced, too, and it shows that the loosening mechanism is almost the same as the static loosening, although the loading is quite different. Even in impact condition, the analysis showed that the effect of eccentric nut works to prevent self-loosening.
Spectra Thermal Fatigue Tests Under Frequency Controlled Fluid Temperature Variation: Superposed Sinusoidal Temperature Fluctuation Tests
Authors: Kawasaki Nobuchika , Takasho Hideki , Kobayashi Sumio , Hasebe Shinichi , Kasahara Naoto
Published: July 2009

To clarify frequency-dependent attenuation effects of fluid temperature fluctuation on fatigue strength, thermal fatigue strength tests subjected to superposed sinusoidal temperature fluctuations were performed by the SPECTRA test facility. Fluid temperature waves were generated by superposition of sinusoidal waves, where frequencies were 0.05, 0.2, and 0.5Hz. Two types of superposed waves were selected for the tests, dual and triple ones. The dual one was obtained by superposing two sinusoidal waves whose temperature ranges and frequencies are respectively 200 centigrade and 0.05Hz and 60 centigrade and 0.5Hz at the inlet of test piece. The triple one was the superposition of three sinusoidal waves whose temperature ranges and frequencies are respectively, 150 centigrade and 0.2Hz, 75 centigrade and 0.05Hz and 50 centigrade and 0.5Hz at the inlet of test piece. The longest periods were 20 seconds for both types of waves and it is the fundamental cycle for the thermal fatigue tests. For the dual case, 73,810 cycles fatigue test was performed while for the triple one 116,640 cycles were performed. After these fatigue tests, cylindrical test pieces were cut away from the test loop, and cracks were observed on the inner surface of the test pieces. For the dual wave case, crack initiation occurred from 400 to 600mm position from the inlet of test piece. For the triple wave case, crack initiation occurred from 400 to 600mm position from the inlet of test piece. The corresponded fluid temperature range to crack initiation is from 205 to 220 centigrade for the dual one and from 195 to 215 centigrade for the triple one. Fatigue lives at crack initiation positions were evaluated based on the test conditions. Adopting power spectrum density functions and frequency transfer functions, fatigue lives were predicted within a factor 3 as predicted for single sinusoidal temperature waves in the other tests. To confirm advantages of these functions, fatigue life estimations were compared with those obtained without using these functions. Based on the compared results, these functions are necessary to predict accurate fatigue lives.
Evaluation of Strength and Load Capacity of Reamer Bolts by Numerical Analysis
Authors: Fukuoka Toshimichi , Nomura Masataka , Yamashita Masashi
Published: July 2009

A reamer bolt is widely used when clamping a joint subjected to large shear forces. It has been postulated in some conventional joint design procedures that the applied shear force is transmitted only through the normal force exerted on the cylindrical body of reamer bolt. However, it is also supported, to some extent, by the friction force on contact surfaces involved. Accordingly, in order to establish a design procedure that takes account of the joint safety and efficiency, it is primarily important to evaluate the ratios of the shear forces supported by the reamer surface and the friction force. They are quantitatively evaluated by defining shear force transfer ratio (SFTR). It is predicted that SFTR is largely affected by the fit and the surface condition of the interface between reamer bolt and bolt hole. In this study, the amounts of SFTR are evaluated using three-dimensional FEM as contact problems. Numerical results show that SFTR by the friction force is significant, which implies that the conventional design procedure for bolted joints tightened by reamer bolts needs to be revised. The validity of the numerical analysis proposed here is demonstrated by experimentation, in which the bending stresses in reamer bolts under shear loads are measured. It was found that the numerical results favorably agreed with the experimental ones.
A Survey of Fitness-for-Service Trends in Industry
Authors: Holtam C. M. , Baxter D. P. , Ashcroft I. A. , Thomson R. C.
Published: July 2009

In 2002 TWI Ltd carried out a questionnaire-based survey of ‘user experience of plant life management practices’, to gain a better understanding of the reality of plant life management and the needs of plant operators [1]. In 2003 the European Fitness-for-Service Network (FITNET) reported the results of their survey on ‘current application and future requirements for European Fitness-for-Service (FFS) technology’ [2]. In 2006 the management of ageing plant became a regulatory hot topic in the UK with a Health and Safety Executive document on the subject being released [3]. Considering also the recent release of the new API/ASME joint FFS standard [4] TWI Ltd decided 2007 was the ideal time to carry out an updated industry survey, to assess how developments such as these might affect plant life management practices in different industry sectors across the world. The aims of this survey were to gain an insight into current FFS trends across several industry sectors and how these may change in the future. Information was gathered as to how different companies handle their FFS activities, both in terms of the types of flaw they assess and the complexity of the assessments they carry out. The survey also investigated how Safety Regulating Authorities (SRA) view FFS activities and whether or not they accept the results as the basis for plant integrity management decisions. Closely related to this is whether there is a need for better regulation of FFS activities, FFS training or indeed whether FFS qualifications should be introduced. This paper presents the results of the online industry survey and draws pragmatic conclusions that will be of interest to all those involved with FFS activities, from inspectors to researchers and from engineers to insurers.
Effect of Spatial Variation of Poisson’s Ratio on the Elastic Field in Functionally Graded Pipes
Authors: Mohammadi Mohsen , Dryden John R.
Published: July 2009

In this paper an internally pressurized pipe made of a functionally graded material is considered. The axisymmetric elastic plane strain field is calculated. The elastic properties are considered to vary across the radius. Since the primary aim of this contribution is to investigate the effect of the radial dependence of Poisson’s ratio, the stiffness coefficient is taken to be constant. It is observed that the radial distribution of Poisson’s ratio affects the corresponding stress and strain fields and has a significant effect on the hoop stresses at the inner radius of the pipe.
Heat Exchanger Tubular Inspection: A User’s Perspective
Authors: Reynolds John T. , Wang W. David
Published: July 2009

This paper covers most of the common (and some not so common) types of NDE methods for heat exchanger (HX) tubular in-service inspections. In addition to noting some of the various advantages and limitations with these methods, the paper covers heat exchanger tubular inspection planning, data analysis needs, a consequence rating method for scheduling inspection and bundle renewals, tubular cleaning methods and tubular inspection technician qualifications.
Experimental Study on Girth Welds of X80 High Deformability Pipeline
Authors: He Xiaodong , Huo Chunyong , Han Xinli , Zhu Lixia , Zhuang Chuanjing
Published: July 2009

Girth welds of X80 high deformability pipeline were welded by self-shield flux-cored arc weld (FCAW) and manual shield-metal arc weld (SMAW). The FCAW used E9018-G electrode to weld root and under-matched flux-cored wires to fill welding and cap welding. The SMAW also used the same welding consumable to weld root, but the metal of the filler welding and cap welding is overmatched electrodes. The mechanical properties testing and metallography testing of girth welded joints were carried out. It was found that the qualifications of two welding procedures met the requirements of API Std. 1104. The test results of Charpy impact (CVN) and crack-tip opening displacement (CTOD) of welded joints for FCAW were higher than that of welded joints for SMAW. The microstructures of FCAW welds were polygonal ferrite (PF) and pearlite (P). But the microstructures of SMAW welds were polygonal ferrite (PF), intra-granular nucleated acicular ferrite (IAF) and pearlite (P). The microstructures of fusion zones are granular bainitic ferrite (GBF), and that there is no martensite in coarse grain heat affected zone (CGHAZ) and fine grain heat affected zone (FGHAZ). So heat affected zone (HAZ) exhibited excellent fracture toughness.
Numerical Modelling of Cavitation in Polymer-Rubber Blends
Authors: Benseddiq Noureddine , Nai¨t-Abdelaziz Moussa , Belayachi Nai¨ma
Published: July 2009

In the present study we have investigated the mechanical behaviour of multi-phase solid materials by using the micro-macro computational approach. Spherical rubber particles embedded in amorphous glassy polymer matrix are taken into account as the heterogeneous composite system. In order to predict the micromechanical deformation behaviour of the composite, we propose a combination of an appropriate elastic-viscoplastic constitutive equation describing the nonlinear behaviour of the polymeric matrix with a hyperelastic model for the rubbery phase. The dependence of the macroscopic stress-strain behaviour of matrix deformation, on cavitation of rubber particles is discussed. In order to describe the cavitation of the rubber particles, a criterion of void nucleation is implemented in the F. E. code. A comparison of the numerically predicted response with experimental result indicates that the numerical homogenisation analysis gives quite satisfactory prediction results.
Transformation of BS7448-CTOD to ASTM E1290-CTOD
Authors: Kayamori Yoichi , Inoue Takehiro , Tagawa Tetsuya
Published: July 2009

Experimental and analytical investigations into Crack Tip Opening Displacement, CTOD, were conducted to demonstrate the relationship between BS7448-CTOD and ASTM E1290-CTOD. CTOD test results showed that ASTM-CTOD was occasionally much lower than BS-CTOD both in single edge notch bend specimens and in CT specimens for low-strength structural steels, and this tends to be more remarkable in CT specimens. In addition, the analytical results of simplified elastic-plastic facture parameter calculation using the Electric Power Research Institute scheme demonstrated that the ratio of ASTM-CTOD to BS-CTOD was not constant but varied according to CTOD changes. Material factors such as the yield stress, the strain hardening exponent, specimen size and configurations influenced the CTOD ratio, and low strain hardening exponent in the Ramberg-Osgood relation and CT specimen configuration significantly decreased the CTOD ratio. An equation that transforms BS-CTOD into ASTM-CTOD is proposed in this study. This equation gives a good estimate of ASTM-CTOD from BS-CTOD.
Welding Residual Stress Solutions for Dissimilar Metal Surge Line Nozzles Welds
Authors: Rudland D. , Zhang T. , Wilkowski G. , Csontos A.
Published: July 2009

During the last year, defects had been located by ultrasonic testing in three of the pressurizer nozzle dissimilar metal (DM) welds at the Wolf Creek nuclear power plant. Understanding welding residual stress is important in the evaluation of why and how these defects occur, which in turn helps to determine the reliability of nuclear power plants. The analysis procedure in this paper included not only the pass-by-pass welding steps, but also other essential fabrication steps of pressurizer surge nozzles. Detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. Case studies were carried out to investigate the influences to main weld stress fields with different boundary conditions, material strength, weld sequencing, as well as simulation of the remaining piping system stiffness. A direct comparison of these analysis methodologies and results has been made in this paper. Weld residual stress results from nuclear industry (conducted by Dominion Engineering, Inc.) and the US NRC (conducted by Engineering Mechanics Corporation) are also compared.
Measurement of Sustained-Load Cracking Thresholds for Steels in Hydrogen Delivery and Storage
Authors: Nibur K. A. , Somerday B. P. , San Marchi C. , Balch D. K.
Published: July 2009

Threshold stress intensity factors at crack arrest have been measured for three commercial low alloy pressure vessel steels, SA372 grade J, DOT 3AAX and DOT 3T as well as X100 line pipe steel using sustained load testing. Testing conditions were consistent with the recently published Article KD-10 from Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code. Measured threshold values for these steels suggest a higher resistance to hydrogen-assisted fracture than previously expected, however some improvements to the methodology of Article KD-10 may be required to ensure conservative results are measured. Specifically, conservative measurements of threshold stress intensity factor for hydrogen-assisted fracture cannot be determined without crack propagation.
Nickel Alloy Crack Growth Correlations in BWR Environment and Application to Core Support Structure Welds Evaluation
Authors: Pathania Raj , Carter Robert G.
Published: July 2009

An intergranular stress corrosion cracking (IGSCC) growth model for unirradiated nickel-base alloys (Alloys 82, 182 and 600) in boiling water reactor (BWR) environments has been developed by EPRI. This model has been used for assessment of the crack growth rates in BWR nickel base austenitic alloys with particular application to the BWR shroud support structure materials and welds, including attachments to the reactor pressure vessel fabricated from these alloys. However, the crack growth model can be used for other components with like materials in BWR environments provided that specific parameters such as stresses and stress intensity factor (KI) distributions are determined. The methodology involves development of crack growth disposition curves that can account for the variability of important IGSCC parameters to provide a conservative, yet realistic assessment of crack growth rate in BWR environments. An extensive nickel base alloy crack growth rate database was developed from data generated through the peer review process and includes both experimental data points and in-plant crack arrest verification system data. Most of the data in the database have reasonable definition of environmental conditions and other important crack growth parameters thus permitting a more realistic generic crack growth model to be developed. Although most of the data is for Alloy 182, it bounds the crack growth rate of Alloy 82 and Alloy 600. The database was used to derive crack growth disposition curves under normal water chemistry (NWC) and hydrogen water chemistry (HWC) conditions. The disposition curves have two stress intensity regimes; one for KI < 25 ksi√in where the crack growth is KI-dependent and one for KI > 25 ksi√in where the crack growth is KI-independent. The crack growth disposition curves were used together with a crack growth estimation methodology to determine the crack propagation of the BWR shroud support structure welds which are fabricated from Alloy 82/182. The steps involved in the development of the methodology include determination of residual stresses and operating stresses, development of stress intensity factor (KI) solutions for crack propagation in the through-thickness direction and estimation of crack growth rates. This methodology was applied specifically for crack growth in the through-thickness direction. Application of this crack growth model to BWR shroud support structure welds H8 and H9 indicates that there is an adequate time period between inspections before initial cracks of ≤10% through-wall thickness reaches the allowable flaw sizes, particularly for HWC conditions.
Assessment of the Effect of the Notch Radius on Ductile Stable Crack Growth
Authors: Mourad Abdel-Hamid I.
Published: July 2009

Mode I stable crack growth SCG behaviour emanating from notches of different radii was investigated. Fracture tests were carried out on compact tension (CT) specimen of 8 mm thickness. The specimen was fabricated from EN 34NiCrMo6 low alloy steel (akin to AISI 4330/4340) with various notch radii, r, ranging from 0.08 mm to 3.0 mm (0.08, 0.16, 0.25, 0.50, 1.00, 2.00, 3.00 mm). The notch was introduced in the specimen by using the EDM wire-cutting technique. Three different ratios of initial crack length ao to width W were used (namely a0/W = 0.45, 0.50 and 0.55). Experimental results include the load-load line displacement (L-LLD) diagrams and initiation (Pi and PQ) and maximum fracture loads, Pmax. Pi was taken as the linear limit of the P-ΔLL curve while PQ was identified as the point where a line with a slope of 95% of the initial slope of the P-ΔLL curve intersects the P-ΔLL curve. Tests show that despite more than 37 folds increase in notch radius, the average maximum load percentage increase (for the three ao/W ratios) recorded was no more than 21%. The crack initiation and crack front tunnelling, employing the dye penetrant technique, was observed to diminish with r. Minimal extension around Pmax, at the specimen mid thickness was observed, only under magnification of the fracture surface, in a few number of specimens of a0/W = 0.55 and r = 3 mm. The initiation load for specimen of r ≥ 2 can be predicted satisfactorily by the stress concentration approach also the maximum load may be predicted with a degree of conservatism employing the yield limit load PL for sharp notches. In general, the results suggest that the fracture mechanics approach is likely applicable up to r ≤ 2 mm in predicting crack initiation and instability load.
Seismic Performance of Raised Floor System by Shake Table Excitations
Authors: Liao Wen-I , Chai Juin-Fu
Published: July 2009

Seismic performance of nonstructural elements such as the raised floor system has not attracted much attention. However, damage of expensive equipments that stand in the raised floor system of high-tech FAB was often observed during past earthquake in Taiwan area. This will result in huge loss of manufacturing functions and properties for the high-tech industry. There is a need to understand the dynamic characteristics of the raised floor system for future seismic protection. This paper presents the seismic performance of raised floor system by shake table excitations. The tested raised floor system was a pedestal-stringer frame structure, and supporting a simulated equipment. This raised floor system was the typical system that frequently used in Taiwan semi-conductor FAB. The input motions for the shake table tests were the waffle-slab floor acceleration responses of a typical semi-conductor FAB by input simulated ground motions. The simulated ground motions are base on the phase spectrum and the maximum potential earthquake of site located at Taiwan Hsin-Chu Science Park. The dynamic characteristics include the acceleration amplification and dependence of input motions by raised floor system was studied and discussed. This study also employee the finite element package to carry out numerical simulation on seismic responses of raised floor systems and compared with the experimental data, and show that the proposed simulation model was very excellent.
Investigation of Cyclic Creep Behavior and Life Prediction Method of Notch Specimen During High Temperature Fatigue
Authors: Fan Zhichao , Chen Xuedong , Jiang Heng , Dong Jie
Published: July 2009

Cyclic creeps can bring to additional damage, resulting in shorter fatigue lives, so the effects of fatigue damage and cyclic creep damage should be taken into account in the life prediction. In this case, the mean strain rate model based on ductility exhaustion theory can be adopted. An engineering structure inevitably has some stress concentration area. As to this situation, by high temperature low cycle fatigue tests with different notch sizes, cyclic creep behavior is investigated and compared with that of smooth specimens in this paper. The results indicate that, due to existence of notch, the cyclic creep deformation is restricted within a little range around notch and cannot spread widely, so the fatigue strength of notch specimens increases. Based on the ductility dissipation theory and effective stress concept of continuum damage mechanism (CDM), the mean displacement rate at half life is acted as control parameter, and a high temperature multi-axial fatigue life prediction method is proposed in this paper. The prediction results show that all test data are within ±2.0 error factor, which is better than that of axial maximum stress method. This method has simple form and fewer constants, can be used to predict high temperature stress-controlled fatigue life whatever smooth or notch specimens.
Experimental Study of Acoustic and Flow-Induced Vibrations in BWR Main Steam Lines and Steam Dryers
Authors: Takahashi Shiro , Ohtsuka Masaya , Okuyama Keita , Ito Takashi , Yoshikawa Kazuhiro
Published: July 2009

The boiling water reactor (BWR-3) in the Quad Cities (QC) Unit 2 Nuclear Power Plant experienced a significant increase in steam moisture under extended power up-rate (EPU) conditions. Inspection of the stem dryer showed it was likely that BWR steam dryer had been damaged by high cycle fatigue due to acoustic-induced vibration. The cause of the dryer failure was considered as flow-induced acoustic resonance at the stub pipes of safety relief valves (SRVs) in the main steam lines (MSLs). Acoustic resonance was considered to be generated by interaction between the sound field and an unstable shear layer across the closed side branches of the SRV stub pipes. We have started a research program on BWR dryers to develop their loading evaluation methods. Moreover, it has been necessary to evaluate the dryer integrity of BWR-5 plants which are the main type of BWR in Japan. In the present study, we used 1/10-scale BWR tests and analysis to investigate the flow-induced acoustic resonance in SRV stub pipes and propagation of fluctuating pressure from SRVs to the dryer through the MSLs. The test apparatus consisted of a steam dryer, a steam dome and 4 MSLs with 20 SRV stub pipes. Acoustic analysis was also applied to evaluate the propagation of fluctuating pressure from MSLs to the dryer. We demonstrated that acoustic resonance occurred in SRV stub pipes at higher velocity flows than in the normal operation and fluctuating pressure propagated from SRVs to the dryer. The amplitude of the fluctuating pressure due to several stub pipes was much larger than that in one stub pipe because of interaction between them. The fluctuating pressure generated in stub pipes was propagated to the dryer through the MSLs with decreasing amplitude. The amplitude of the fluctuating pressure observed at the top of stub pipes was reduced significantly in the MSLs and maintained fairly well in the steam dome. The flow-induced acoustic resonance did not occur for Strouhal number above 0.6 in the MSLs system of the BWR-5. Results of the tests were compared with those of acoustic analysis. The acoustic analysis could well predict the dryer loading.
Residual Stress Prediction for Non-Axisymmetric Vessel Penetration Welds
Authors: Ogawa Kazuo , Yanagida Nobuyoshi , Saito Koichi
Published: July 2009

Residual stress distribution in an oblique nozzle jointed to a vessel with J-groove welds was analyzed using a three-dimensional finite element method. All welding passes were considered in a 180-degree finite element (FE) model with symmetry. Temperature and stress were modeled for simultaneous bead laying. To determine residual stress distributions at the welds experimentally, a mock-up specimen was manufactured. The analytical results show good agreement with the experimental measurement data, indicating that FE modeling is valid.
Design and Manufacture of Pressure-Bearing Equipment Based on Risk and Life Analysis
Authors: Chen Xuedong , Wang Bing , Ai Zhibin , Yang Tiecheng , Gu Wangping , Cheng Chuanqing
Published: July 2009

Since the turn of the 21st century, the technical means for engineering risk analysis for safety assurance of in-service equipment such as risk-based inspection (RBI), reliability-centered maintenance (RCM) and safety integrity level (SIL) etc. have been extensively applied in Chinese petrochemical enterprises, and good effect has been achieved. However, it is found that most of the causes for accidents or failures are due to unreasonable design and manufacture, or deviation of design and manufacture requirements from the requirements for service environment. The existing design standards and software are short of database support of failure mechanisms and failure modes, etc. in the service process of pressure-bearing equipment without fully taking into account various kinds of risk factors in the dynamic service environment in the full life process of pressure vessels, therefore, it is unable to determine the service life of pressure-bearing equipment in advance. In this paper, by taking the design and manufacture of hydrogenating reactor and large ethylene spherical storage tank as examples, suggestions are made about the risk and life analysis based design and manufacture to be carried out in China for important pressure-bearing equipment, that is, within the design life (intended service life) of pressure-bearing equipment, considerations should be given to various kinds of failure modes possibly arising under the dynamic service conditions in the full-life process and the effect of risks due to damage mechanism on equipment safety and life so as to control and reduce the risk of pressure-bearing equipment in the full-life process at the early stage of design and manufacture through reasonable material selection, improvement of structural design and optimization of manufacture process, etc. and make the equipment serve to the expected design life safely in combination with other process guarantee measures. Finally, the critical technical bottlenecks waiting for solution for the development of risk and life based design and manufacture in China are described in combination with the latest news about the revision of Chinese technical codes and standards.
Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus
Authors: Kataoka Shunji , Sato Takuya
Published: July 2009

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.