bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Toughness Evaluation of Carbon Steels in Piping and Valve for Reactor Primary System
Authors: Uemoto Yoshio , Hirano Akihiko , Hirasawa Daisuke
Published: October 2017

UK very high integrity (VHI) component classification includes design, manufacturing, and inspection requirements that go beyond those established in ASME BPVC Sec. III Subsection NB [1]. One of these requirements is to ensure the component is tolerant of manufacturing defects. This can be demonstrated using a Defect Tolerance Assessment (DTA) based on two parameters fracture mechanics method. The brittle fracture parameter of this assessment requires the analysis of stress occurring in the component against the plane strain fracture toughness, KIC of the material.

This work focuses on the practical determination of KIC for materials chosen for a Boiling Water Reactor (BWR) Main Steam Piping (MSP) and Main Steam Isolation Valve (MSIV), which carbon steel seamless pipe SA-106 Grade C and carbon steel casting SA-216 Grade WCB, are respectively. These materials are usually tested by Charpy impact testing specified in [1], but there are not many studies reporting their KIC, and there is not enough information concerning actual piping and valve materials. Thus the authors implemented fracture toughness testing using J-resistance curve according to ASTM E 1820 [2] for test pipe and test casting block simulating actual MS Piping and MSIV, and evaluated KIC(J) to be used in DTA. KIC(J) is evaluated from elastic-plastic fracture toughness, JIC, gained from the J-resistance curve, and equivalent to KIC [3]. KIC(J) corresponds to KJIc in ASTM E 1820.

There were some cases, however, in which valid JIC values could not obtained, because of the materials high toughness, test specimen size limitations, and uneven final crack sizes. When valid JIC can’t be obtained, retesting or remanufacturing would significantly affect plant construction schedule. Hence, alternative evaluation methods by which JIC can certainly be obtained are desired.

In this study, the authors focused on two types of alternative JIC evaluation methods. The first one is the Stretch Zone Width (SZW) method, in which JIC is calculated from SZW measurements of crack tip plastic blunting on fracture toughness test specimens. The SZW method was well studied in the 1970s, and experimental data showed a clear correlation between JIC values obtained from J-resistance curves and JIC values obtained from SZW measurements [4]. The second method is by correlation of JIC with the energy absorbed during Charpy testing. As represented by Rolf’s study [5], it has been reported that there are correlations between Charpy absorbed energy and KIC for high tensile strength steels. In this study, the validity of the SZW method was first evaluated by comparing its results with JIC obtained from J-resistance curves. Then, the applicability of the JIC values to DTA of actual products was discussed. Finally, by comparing Charpy absorbed energy and KIC(J), the validity and applicability of KIC determination method with Charpy absorbed energy was discussed.
Experimental Investigation on Adhesive Bonded Joints of Carbon Fiber Composite Laminates Containing Disbond Defect
Authors: Qiu Ping , Shi Jianfeng , Zheng Jinyang
Published: October 2017

Adhesive bonding technology is widely used for connecting composite pipes recent years, for the adhesive joints have many advantages such as weight reduction, ease of manufacture, and more importantly, uniform stress distribution and less stress concentration within the joint region. Nevertheless, one of the limitations of adhesive joints is the difficulty in predicting the joint strength due to the presence of defects in the adhesive due to improper curing process. This paper presents an experimental study of single-lap joints with disbond defects at the adherend-adhesive interface. Different sets of adhesively-bonded singlelap joints containing varied disbond conditions were prepared and tested. The joints used carbon fiber reinforced polymer (CFRP) laminates as substrates and epoxy resin as adhesive, with ultrathin aluminum foil (10um) as disbond defects in different sizes and locations. The full deformation fields were measured using the digital image correlation (DIC) method. The samples were subjected to tensile load till failure to determine the bond strength. Before the tensile test, the defective adhesive joints were detected by a phased-array ultrasonic instrument to identify the bond-line quality of joints. The results show that the disbond defects can be detect by ultrasonic phased-array technique, and the detriment of disbond defect to the failure process can be observed and recorded by DIC system. Based on the findings, the failure modes and failure mechanism of bonded CFRP joint were further discussed.
Relative Influence of Offset Spacing and Transition Support Location on Buried Piping Seismic Stresses
Authors: Frazee Glenn R. , Marohl Michael P. H. , Musto Thomas M.
Published: October 2017

The design of buried piping systems requires special considerations. In the evaluation of seismic loads on buried piping, the associated stresses are typically considered to be secondary stresses as the piping is assumed to move with the soil during a seismic event and inertial seismic loads are considered to be negligible. During a seismic event, buried pipes are subject to relative displacement-induced strains, induced primarily by seismic wave passage. Typically, the areas of highest stress are found at offset locations as a result of applied moments (primarily due to axial loads into an elbow or tee) and/or at transition locations near entry into buildings or subgrade vaults as a result of seismic anchor movements and/or differential settlement.

This paper examines the relative influence of the number of diameters of straight piping between offsets and the number of diameters of straight piping in between building/vault entry and the first support on resulting seismic piping loads.
Experiment Verification of Seismic Isolation Device Having Charging Function
Authors: Yamaguchi Takashi , Nakakoji Hayato , Miura Nanako , Sone Akira
Published: October 2017

In late years, many base isolated structures are planned as seismic design, because they suppress vibration response significantly against large earthquake. In addition, to achieve greater safety, semi-active or active vibration control system is installed in the structures as. Semi-active and active vibration control systems are more effective to large earthquake than passive one vibration control system in terms of vibration reduction. However semi-active and active vibration control systems cannot operate as required when external power supply is cut off. To solve the problem of energy consumption, we propose a self-powered active seismic isolation device which achieves active control system using regenerated vibration energy. This device doesn’t require external energy to produce control force.

The purpose of this paper is to propose the seismic isolation device having charging function and verified its performance by experiment. In our previous research[1], we proposed the new model and optimized the control system and passive elements such as spring coefficients and damping coefficients using genetic algorithm. As a result, we proposed the model which is superior to the previous model in terms of vibration reduction and energy regeneration.

In this study, we conducted an experiment and show its results. As a results, we confirmed the vibration reduction and energy regeneration of the seismic isolation device having charging function.
Development of Manufacturing Technologies for the ITER Toroidal Field Coil: Effort for Precise Manufacturing
Authors: Nishijima Yasushi , Hara Daisuke , Kamitani Keisuke , Tsubota Shuho , Toyoda Masahiko , Baba Takashi , Matsumoto Takashi , Kanbayashi Shigeru , Ando Shinji , Matsui Kunihiro , Nakahira Masataka , Koizumi Norikiyo
Published: October 2017

Series production of the toroidal field (TF) coils for the ITER has been launched since Oct. 2013. In advance of manufacturing of the actual products, we have performed the preliminary tests and mock-up tests to clarify and confirm the conditions of the welding and machining processes. The ITER TF coil is a welded-structure to endure strong magnetic forces, and it is a huge component in the ITER machine with dimensions of 16.5m height and 9.0m width and a weight of more than 300 ton per coil. In addition, dimensional requirements to the TF coil are very tight from a view point of stable plasma confinement.

In the following section, features of the ITER TF coil are briefly introduced, and performance tests of manufacturing technologies such as welding processes are described, and typical results are summarized. In order to suppress welding deformation, combination method of Tungsten-inert gas welding (TIG) and beam welding (such as an Electron Beam Welding (EBW) and a Laser Beam Welding (LBW)) has been applied to a thick plate weld. Furthermore, process conditions of the EBW and LBW suitable for the thick plate have been investigated to improve work efficiency.
Seismic Test Result of Motor-Operated Valve Actuators for Nuclear Power Plant
Authors: Kojima Nobuo , Tsutumi Yoshitaka , Yonekura Kazuyoshi , Nishino Koji , Watanabe Yukio , Kumagai Shin , Kamino Hiroyuki
Published: October 2017

Functional requirements of motor-operated valves provided in nuclear power plants during an earthquake have been previously evaluated via seismic tests and so forth; however, since the response acceleration has increased in line with a recent reassessment of standard earthquake ground motions, it is necessary to evaluate functional maintenance with respect to high acceleration. From the viewpoint of equipment fragility in seismic Probability Risk Assessment (PRA) also, it is necessary to determine practical functionality. Here, we used a resonant shaking table (see Ref. [1]) in the Central Research Institute of the Electric Power Industry (CRIEPI), which is capable of seismic tests at acceleration levels that have been unachievable until now, and in seismic tests carried out on motor-operated valve actuators, we obtained results confirming that operability of active components used with an existing design was achieved even at large accelerations exceeding 20×9.8 m/s2,. The results of seismic operability of motor-operated valve actuators will be applied to a fragility analysis of seismic PRA.
An Estimation of the Load Factor and Sealing Performance Evaluation for Bolted Pipe Flange Connections With Gaskets Under Internal Pressure
Authors: Sawa Toshiyuki , Sato Koji
Published: October 2017

In designing bolted pipe flange connections with gaskets, It is necessary to know the actual residual gasket contact stress in the connections under internal pressure. However, the actual reduced gasket stress in the connection has not been sufficiently estimated. In estimating the actual residual contact gasket stress more precisely, it is needed to know the load factor (the ratio of an increment in axial bolt force to the axial force due to the internal pressure per bolt) of the connections with gaskets. The new formula for obtaining the load factor was proposed by one of the authors using the tensile spring constant Ktg and the compressive spring constant Kcg, while the spring constant of bolt-nut system is designated as Kt. In the present paper, for estimating the load factor of the connections with gaskets, the circular plate theory is applied for obtaining the values of Kcg and Ktg and then the load factor is obtained for pipe flanges specified JIS 10K flanges and ASME B 16.5 flanges. The obtained results are in a fairly good agreement with the FEM results. Using the obtained load factor for the connections, a design method is demonstrated taking account of the allowable leak rate. Using the residual contact gasket stress and the fundamental gasket leak rate, an amount of gas leakage is predicted. The predicted amount of gas leakage for 3” and 20” pipe flange connections is fairly coincided with the experimental results and the FEM results. In addition, a design method for determining the bolt preload for a give allowable real rate is demonstrated using the simple method for obtaining the load factor.
Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 2 — Evaluation of Lifetime
Authors: Aida Kiyoshi , Minagawa Keisuke , Tanaka Go , Fujita Satoshi
Published: October 2017

In 2011, Great East Japan Earthquake that is the largest earthquake ever observed occurred. The earthquake had large energy, long duration time and many aftershocks. Huge tsunami caused nuclear accidents. At present, a large number of nuclear power plants in Japan have not been operated yet. Then the base load power in Japan was shifted from nuclear power to coal-fired thermal power. Therefore it is very important to improve aseismic performance of coal-fired thermal power plants.

Boiler structures in coal-fired thermal power plants are generally high-rise structures. In addition its combustion temperature is very high, so boilers are simply suspended from the top of the support structures in order to allow thermal expansion. Therefore boilers easily vibrate. In order to suppress vibration of boilers during earthquakes, stoppers are set between boilers and support structures. The stoppers are made of steel, and dissipate vibration energy by plastic deformation. However aseismic requirements for thermal power plants against large earthquakes having large numbers of repeat counts have been increased.

Then authors have developed a vibration control damper for coal-fired power plants. The damper is set instead of conventional stopper made of steel, and it is able to perform in earthquakes with relatively large numbers of repeat count. Construction of the damper is similar to oil dampers, but inner fluid is viscous fluid.

In this paper, a seismic response analysis using an analysis model of a boiler structure is conducted. The analysis model has plural stoppers or plural dampers. The response analysis result is arranged to investigate lifetime of the stoppers or the dampers. The accumulated plastic displacement of each stopper or damper is used for the evaluation. As a result, it was confirmed that the proposed damper has high durability compared with conventional stopper made of steel.
Numerical Simulation of the Four-Roll Bending Process for 2.25Cr-1Mo-0.25V Thick-Plate at Elevated Temperature
Authors: Wang Yafei , Cheng Guangxu , Zhang Zaoxiao , Li Yun , Zhang Jianxiao
Published: October 2017

In this paper, the four-roll plate bending process of 2.25Cr-1Mo-0.25V steel at elevated temperature is investigated by numerical simulation. This 3-D simulation is finished by using the elastic-plastic dynamic explicit finite element method (FEM) under the ANSYS/LS-DYNA environment. The strain softening behavior of 2.25Cr-1Mo-0.25V steel at elevated temperature is presented and discussed. The stress-strain relationship of the steel plate is modeled using a piecewise linear material model, with the stress-strain curve obtained through tensile tests. The plate bending process with a plate thickness of 150 mm is investigated. The amount and position of maximum plastic deformation are analyzed. The present study provides an important basis for the optimization of bending parameters and further investigation of the effect of high-temperature deformation on the resistance to hydrogen attack of 2.25Cr-1Mo-0.25V steel.
Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 3 — Evaluation of Vibration Control Performance
Authors: Minagawa Keisuke , Aida Kiyoshi , Tanaka Go , Fujita Satoshi
Published: October 2017

After Great East Japan Earthquake in 2011, the base load power in Japan was shifted from nuclear power to coal-fired thermal power. Stable electricity supply is one of important infrastructure, so improvement of seismic reliability of coal-fired thermal power plant and related structures is very important.

Boiler structures in coal-fired thermal power plants are generally high-rise structures, and boilers in the structures are usually hung on the top of the structures in order not to restrict thermal expansion. Therefore boilers easily vibrate by earthquakes. In order to suppress vibration of boilers during earthquakes, stoppers made of steel are installed between boilers and support structures. The stoppers have simple mechanism and dissipate vibration energy by plastic deformation of steel material. However, further improvement of vibration control performance is required from the viewpoint of above-mentioned social requirements and recent large earthquakes such as the Great East Japan Earthquake, the Kumamoto earthquake in 2016 and so on.

This study proposes an application of a damper using viscous fluid to boilers of coal-fired power plants. The damper is set between boilers and support structures. There are many examples of application of the damper using viscous fluid to buildings and civil engineering structures. Therefore the application of the damper to boilers will be effective.

In this paper, a seismic response analysis using an analysis model of a boiler structure is conducted. The analysis model has plural stoppers or plural dampers. The response analysis result is evaluated from the viewpoint of vibration control performance. In other words, story shear force of the support structure is evaluated. In addition various limitations such as the maximum stroke of the dampers are taken into account. As a result, story shear force of the support structure with the proposed damper is smaller than that of the structure with the conventional stopper made of steel, so the proposed damper has high vibration control performance.
Welding Consumables for 2.25Cr-1Mo-V Refining Reactors
Authors: Takauchi Hideaki , Nakanishi Tomoaki , Nako Hidenori
Published: October 2017

Owing to the demands for larger-capacity reactor vessels in petroleum plants and higher temperature processes for the upgrade of heavy oil, enhanced 2.25Cr-1Mo, 2.25Cr-1Mo-V and 3Cr-1Mo-V steels, which suit both high temperatures and pressure operations, have been developed and used for heavy-wall pressure vessels since the 1990s. 2.25Cr-1Mo-V steel, which has very special mechanical properties, resistant to both hydrogen attack and embrittlement under high temperatures and pressure environments in particular, has been used since 2000. The specifications for 2.25Cr-1Mo-V steel pressure vessels, such as ASME Sec. VIII and API RP 934-A, have been established and reviewed to enhance the contents [1–2].

In this report, the transition of materials, the welding techniques for hydrocracking reactors and 2.25Cr-1Mo-V welding materials are introduced. Particularly, for these welding materials, in order to improve the creep rupture and temper embrittlement properties, the effectiveness of precipitates is discussed. It was found that fine carbide (MC) in crystal grains improves creep rupture lifetime and MC at the prior austenite (γ) grain boundaries inhibits temper embrittlement caused by the segregation of impurities.
Reliability Prediction of Long-Distance Transmission Pipelines With a Three-Layer Polyethylene Coating Employing Delay-Time Concepts
Authors: Li Xiufeng , Hu Haijun , Cheng Guangxu , Li Yun , Yin Chengxian
Published: October 2017

Long-distance transmission pipelines with 3PE coating undergo a two-stage failure process, including the damage process of three-layer polyethylene coating and the failure process of metal pipelines. The two stages are random and independent of each other. A reliability model of transmission pipelines under periodic inspection is presented with the assumptions of delay-time concepts. Functions of maximum likelihood estimations and the goodness of model fit are given. The effect of the inspection interval on reliability is investigated. A case study of Xinqin natural gas transmission pipelines is presented. Data of the pitting depth are obtained at 43 excavation locations. Best estimations of distribution parameters are obtained in a genetic algorithm search. Results show that the average time of coating damage is around 1.04 years. The failure probability of a pipe segment after 36 years’ operation is 1.1E−3 if no inspections are carried out. The failure probability is around 5.5 times the failure probability of a pipe segment with a 6-year periodic inspection. The sensitivity of variance of distribution parameters to failure probability is presented.
Stress Intensity Factors of Pipe-In-Pipes With Circumferential Through-Wall Cracks Based on Elastic Finite Element Analyses
Authors: Kim Se-Chang , Choi Jae-Boong , Huh Nam-Su
Published: October 2017

Any defects and cracks in pipe-in-pipes (PIPs) applied to deep-water and harsh environment are potential threats that can cause terrible economic damage or environmental pollution as triggering failures.

In the present study, stress intensity factors (SIFs) of PIPs with circumferential through-wall cracks (TWCs) were investigated via detailed 3-dimensional (3-D) elastic finite element (FE) analyses. In terms of the crack location, the cracks are postulated in the inner pipe which is considered as mainly important part to assess the integrity of PIPs. In the present FE analyses, the effects of cross-sectional shapes of both inner and outer pipes on the SIFs of PIPs were systematically evaluated. As for loading conditions, internal pressure, axial tension and bending moment were considered.

The FE results of the SIFs of PIPs were also compared with the existing solution of single-walled pipes with circumferential TWCs to evaluate the restraint effect by the outer pipe on the SIFs of PIPs, where the dimensions of single-walled pipes are assumed to be identical to those of the inner pipe of PIPs.
Deep-Hole-Drilling of High Pressure Tubes: Process Stability and the Influence of Eccentricity on Autofrettage and Heat Transfer
Authors: Maderbacher Hermann , Pölzl Manfred
Published: October 2017

In this work, the measured values of wall thicknesses over the length and the circumference of nearly 1800 tubes were statistically evaluated and analyzed. With these results, a precise statement about the process reliability can be made. This makes it possible to minimize the costs for high-pressure tubes in such a way that both the demand for raw material and the rejects on manufactured tubes are minimized. In the next step, the influence of eccentricity in a pipe on the desired operating properties was investigated. For this purpose, a sensitivity analysis was performed to quantify the influence on the residual stresses resulting from autofrettage, operating stresses and fatigue endurance over the circumference, as well as the heat conduction between the inner wall and the outer wall of the tube. The results of this sensitivity analysis are finally used to discuss the requirements of manufacturing tolerances of licensors. It was found that there is nearly no influence of eccentricity, in the investigated range, on heat transfer through the tube wall. The influence of eccentricity on autofrettage depth and fatigue behaviour strongly depends on the tube nominal wall thickness.
Repair Welding of Irradiated Reactor Pressure Vessels Steel and Current Direction of Revising JSME Fitness-for-Service Code
Authors: Adachi Hiroyuki , Kimura Ryuji , Kono Yusuke
Published: October 2017

A primary repair option of Light Water Reactors (LWR) components is welding. However, it is known that welding on steels that have been exposed to neutron irradiation [i.e. Reactor Pressure Vessels (RPV) in PWR and Reactor Internals in BWR] can result in Helium Induced Cracking (HeIC). Helium forms from neutron transmutation reactions of Boron (B) and Nickel (Ni) during operation of the plant.

In order to address this issue and establish verified methods for weld repair of irradiated RPV and Reactor Internals materials in Japanese power plants, an investigation denominated WIM (Welding of Irradiated Materials) Project was conducted; the WIM project was carried out between the years of 1997 and 2004 in an analytical conservative manner, correlating the results of weld repaired irradiated materials with the concentration of helium and the heat input used while welding. It was concluded that, under determined conditions, the irradiated materials were able to be successfully welded in accordance with the requirements established in both the JSME and ASME Code Cases. In the light of such discovery, the necessity of establishing and a new code case and revising the standard JSME Rules on Fitness-for-Service concerning the weld repair of irradiated RPV and Reactor Internals steels is currently under investigation.
Fluid Damping in Fuel Assemblies
Authors: Moussou Pierre , Guilloux Adrien , Boccaccio Eric , Ricciardi Guillaume
Published: October 2017

Damping is known to be a major parameter in the seismic design of nuclear facilities. Of special interest is the case of fuel assemblies in PWR plants, which, unlike other components, are submitted to axial flows: it has been known since the late 80s that their frequency response to lateral excitations was largely dependent on the flow velocity, and the issue raised by this observation is to determine a consistent fluid force model which could be used in seismic design.

In the scientific literature, the standard model of fluid forces exerted upon an oscillating slender body was originally derived by Lighthill, and it involves a lift coefficient which, up to a reference frame shift, describes the force generated by a small angle of inclination of the body axis against the flow direction. Recent works by Divaret et al. have provided a value of this lift coefficient equal to 0.11 for a single cylinder, and to 0.18 for a square array of 5 by 8 cylinders, the Reynolds numbers being in the range of 104.

Sticking to the idea that the damping stems from the local angle of inclination of the structure against the flow direction, the present study revisits recent tests performed in the Hermes test rig of CEA Cadarache, where a fuel assembly was submitted to incipient flow velocities varying from 1.5 to 5m.s−1, and to a lateral force exerted upon the middle grid, generating displacements in the ranges of a few mm and of a few Hz. Under the assumption that the fuel assembly behaves in an approximately linear manner and that it undergoes harmonic deformations close to its first natural mode shape, the dissipative fluid force can be expressed by an adequate combination of the hydraulic cylinder force and of the structure displacements. A lift coefficient equal to 0.3–0.4 is obtained with this procedure, which stands for the overall fuel bundle, rods and grids included.
Fracture Behavior of Aged CF8A Austenite Cast Stainless Steel Under Dynamic and Cyclic Loading Conditions
Authors: Kim Jin Weon , Choi Myung Rak , Kim Yun Jae
Published: October 2017

This study conducted J-R fracture toughness tests using aged CF8A cast austenitic stainless steel (CASS) under dynamic and cyclic loading conditions at room temperature (RT) and 316°C and investigated the effect of seismic loading characteristics on the fracture behavior of age-related degraded material. For comparison, J-R fracture tests were also conducted on unaged CF8A CASS. CF8A CASS was made as a static casting, and it was aged thermally at 400°C for 175 days, which is equivalent to thermal aging at the operating temperature of nuclear power plants (NPPs) for 32 effective full power years (EFPYs). Monotonic J-R tests were conducted at both quasi-static and dynamic loading rates, and cyclic J-R tests were conducted at a quasi-static loading rate. The results showed that the fracture resistance of aged CF8A CASS under monotonic load was lower, by ∼35%, than that of unaged CF8A CASS, regardless of test temperatures and loading rates. The dynamic loading effect on fracture behavior was almost negligible for both unaged and aged CF8A CASSs at RT and 316°C. Cyclic loading reduced J-R fracture toughness of unaged CF8A CASS considerably at both test temperatures. Such a cyclic loading effect on fracture behavior was still observed from aged CF8A CASS. Thus, we conclude that the dynamic and cyclic loading effects on fracture behavior of CF8A CASS were not altered by thermal aging at the operating temperature of NPPs for 32 EFPYs.
Stress Linearization Concepts and Restrictions in Elastic Design by Analysis
Authors: Mackenzie Don
Published: October 2017

Stress linearization is widely used in Pressure vessel Design by Analysis based on elastic stress analysis and stress categorization. This paper investigates the structural mechanics basis of stress linearization in the context of limit and shakedown analysis and proposes a new basis for the procedure that relates the stress along a line to the concept of limit load. This removes the need for some conceptual requirements associated with shell analysis from stress linearization, including restriction of SCL location to identified bending planes. It also introduces the concept of selecting stress distributions representative of the limit state to remove the need for some elements of stress categorization in the design procedure.
Combustion Oscillation in Gas Turbine Combustor for Fuel Mixture of Hydrogen and Natural Gas
Authors: Uemichi Akane , Kanetsuki Ippei , Kaneko Shigehiko
Published: October 2017

Hydrogen as one of energy sources is attracting attentions because of CO2 free combustion that can deaccelerate global warming. Recently, hydrogen enriched combustion technology for gas turbine combustors is developing, in which hydrogen is added to natural gas. However, hydrogen-rich combustion has different combustion characteristics from conventional natural gas combustion. In particular, such variety of combustion characteristics may lead to combustion oscillation, which may cause fatigue breaking of structural elements due to resonance with components. Combustion oscillation is mainly induced by thermo-acoustics interaction. Therefore, it is necessary to investigate characteristics of hydrogen-enriched combustion sufficiently. To understand combustion characteristics of enriched hydrogen mixture, combustion experiments were performed for various ratios of hydrogen in the fuel mixture. In this study, a mock-up combustor of a micro gas turbine combustor is used, where a radial swirler is installed to mix fuel and air and stabilize the flame. To grasp the characteristics of combustion oscillation, pressure fluctuation was detected by a pressure sensor installed at the bottom of the combustor. It is found that larger hydrogen ratio in the fuel mixture extends the range of large pressure fluctuation region expressed by the root-mean-square value. Succeedingly, more detail oscillation characteristics were examined by FFT analysis. In the case of natural gas 100%, the oscillation of around 350 Hz was detected. On the other hand, in the case of the hydrogen-contained fuel mixture, two kinds of oscillating frequencies around 200 and 400 Hz were detected. To examine the cause of the difference among these three oscillating frequencies, a simplified stepped tube model with closed- and open-end is considered. For further investigation, acoustic boundary conditions were measured by acoustic impedance method. Moreover, to obtain the representative flame positions and temperature in the combustor, CFD calculations were performed, and the measured acoustic impedance was combined with the CFD results. Then, parametric studies with various thermo-pressure interaction index were performed to obtain the effect of thermo-pressure interaction index on natural frequencies and gains using the Nyquist plot. As a result, it was found that the self-excited oscillation limit is sensitive to the value of thermo-pressure interaction index.
Evaluation of Weld Homogenization Schemes Based on Plastic Loading of Single Edge Notched Tension (SE(T)) Tests
Authors: Naib Sameera , De Waele Wim , Hertelé Stijn
Published: October 2017

Engineering Critical Assessment (ECA) of welds is the process of predicting the structural integrity of a structure in the presence of a weld defect under specified loading conditions. Standardized ECA techniques consider the weld to be equal in properties when compared with base metal or use the concept of ‘strength mismatch’ to distinguish the weld from the base metal. In both cases, the weld region is homogeneous. This is a severe approximation from reality, as welds show complex strength heterogeneity patterns. The authors are concerned with techniques to simplify welds in such way that the structural response of the weld is similar to that of the idealized, homogeneous weld. Two approaches are considered: (a) integrating properties along assumed slip lines originating from the defect tip, and (b) assigning All Weld Metal Tensile Tests (AWMTT) to the entire weld region. A plastic analysis procedure suggested by the ASME BP&V code (‘Twice Elastic Slope method’) is adopted to estimate Plastic Load, whose values are compared for the heterogeneous and equivalent homogeneous welds. Finite Element (FE) simulations were performed for Single Edge notched Tensile (SE(T)) specimens. The results put forward the possibilities of weld homogenization while showing its limitations. This will assist in further improvement of weld ECA.
Sufficiency of Reference Stress Solutions for FFS Evaluation of Crack-Like Flaws
Authors: Oyamada Kenji , Miura Naoki
Published: October 2017

In Japan, a new standard of an assessment procedure for crack-like flaws in pressure equipment at elevated temperature is now under development in the High Pressure Institute of Japan (HPI). In this standard development, it is needed to adopt reference stress solutions for crack-like flaws in pressure equipment being subjected to membrane stress and/or bending stress. Such reference stress solutions have been proposed in various references such as ASME FFS-1/API579-1, BS7910, R5, FBR draft guideline, HPIS Z101-2, etc.

A comparative study of those reference stress solutions was conducted in order to select appropriate one. As a result, reference stress solutions in HPIS Z101-2 were adopted. The sufficiency of adopted reference stress solutions was introduced in this paper.

Also, the reference stress solutions for axially and circumferentially through-wall rectangular flawed cylinders, which were not provided in the HPIS Z101-2 standard but were utilized to derive those solutions adopted in the standard, were introduced in this paper. These solutions should be adopted in a new HPI standard for crack-like flaws in pressure equipment at elevated temperature.
Behavior of Wood Filled Impact Limiters During the IAEA Thermal Test
Authors: Feldkamp Martin , Erenberg Marina , Nehrig Marko , Bletzer Claus , Musolff André , Schönfelder Thorsten , Wille Frank
Published: October 2017

Packages for the transport of radioactive material are often equipped with impact limiters consisting of wood, encapsulated by steel sheets. These impact limiters shall ensure that transport casks meet the IAEA safety requirements. After damage caused by the mechanical tests the package has to withstand a severe fire scenario. It is required that the mechanical tests have to produce maximum damage, taking into account the thermal test. Furthermore, any damage, which would give rise to increased radiation or loss of containment or affect the confinement system after the thermal test, should be considered. Concerning the thermal test, the IAEA safety requirements state that during and following the fire test, the specimen shall not be artificially cooled and any combustion of materials of the package shall be permitted to proceed naturally.

Different works from the French Institute for Radiological Protection and Nuclear Safety (IRSN) and BAM show that additional energy supply from a pre-damaged impact limiter to the cask could occur caused by smoldering of the wood. This effect should be considered within the safety assessment of the package. A heat wave from the fire could overlap with the additional energy from the impact limiter in the sealing system. In 2015 BAM conducted small scale fire tests with wood filled metal drums showing continuing combustion processes during the cooling down phase. As not much is known about smoldering processes in wood filled impact limiters, it is highly complex to define pre-damage of impact limiters, which are conservative, regarding the most damaging energy flow from the impact limiter to the containment system in dependence of time. More research has to be done to develop models to examine the effects of smoldering impact limiters on the containment of packages for the assessment. The process of smoldering is described with regard to the requirements in the thermal safety assessment. Parameters influencing the smoldering process are identified.

BAM operates test facilities to examine the issue of mechanical damage, combustion and heat transfer of packages for transport of radioactive material. A thermal test will take place with a wood filled test specimen with a diameter of about 2.3 meters. The aim is to understand the phenomena of smoldering under the consideration of relevant regulatory boundary conditions.
Nonlinear Buckling Analysis of Cylindrical Shell With Normal Nozzle Subjected to Axial Loads
Authors: Shi Qianyu , Wang Zhijian , Tang Hui
Published: October 2017

Design of Large-scale and light-weight pressure vessels is an inexorable trend of industrial development. These large thin-walled vessels are prone to buckling failure when subjected to compression loads and other destabilizing loads. Thus, buckling analysis is a primary and even the most important part of design for these pressure vessels. Local buckling failure will probably occur when cylindrical shells with nozzle subjected to axial loads. In this paper, a FE model of cylindrical shell with a normal nozzle is established in ANSYS Workbench. The bifurcation buckling analysis is performed by using an elastic-plastic stress analysis with the effect of nonlinear geometry, and a collapse analysis is performed with an initial imperfection. The axial buckling loads are obtained by these two types of method. Some issues about nonlinear buckling analysis are discussed through this study case.
Evaluation of Hydrogen Embrittlement of Cr-Mo Low Alloy Steel by Slow Strain Rate Technique With Cathodically Charged Specimen
Authors: Tsurumi Daichi , Saito Hiroyuki , Tsuji Hirokazu
Published: October 2017

As an alternative method to slow strain rate technique (SSRT) under high-pressure hydrogen gas evaluation, SSRT was performed with a cathodically charged specimen. Cr-Mo low alloy steel with a tensile strength of 1000 MPa grade was selected as a test material. Cathodic charging was performed in 3% NaCl solution and at a current density in the range of 50–600 A/m2. The effect of specimen size on the hydrogen embrittlement properties was evaluated. Relative reduction of area (RRA) values obtained by tests at a cathode current density of 400 A/m2 were equivalent to those performed in hydrogen gas at pressures of 10 to 35 MPa. Fracture surface observations were also performed using scanning electron microscopy (SEM). The quasi-cleavage fracture surface was observed only after rupture of small specimens that were subjected to hydrogen charged tests. It was also necessary for the diameter of the specimen to be small to form the quasi-cleavage fracture surface. The results indicated that to simulate the high-pressure hydrogen gas test, a specimen with a smaller parallel section diameter that is continuously charged until rupture is preferable.
Acoustical Characteristics of Single and Two-Phase Horizontal Pipe Flow Through an Orifice
Authors: Belfroid S. P. C.
Published: October 2017

In this work, the acoustic effects of horizontal air-water flow through an orifice are investigated experimentally. Single phase flow (air) and two-phase flow (air and water) tests are performed for two sets of orifices. One set of straight edged and one set of upstream rounded orifices. For each set, the diameters of the orifices were 2, 5, and 10mm, with a thickness of 5 mm. The two-phase flow is generated by injecting water at a rate of 0 to 40 g/s to air in a pipe with diameter of 25 mm. The air rate is fixed in the range from 5.8 to 14 g/s, where the upstream pressure varies from 1.5 to 4 bar at ambient temperature. Unsteady pressure fluctuations are recorded at two upstream and two downstream position.

The valve noise standard NEN-EN-IEC (60534-8-3, 2011) for dry gas is assessed by means of experimental data in dry conditions at fixed air mass flow rate. Predictions of sound power spectra by means of the standard are found to be more accurate compared to those obtained following Reethof & Ward (1986), also in conditions of a choked orifice.

In case of multiphase flow already at very low liquid fractions of much less than 1%, the standard is no longer valid. The frequency spectrum is no longer determined by the jet noise but starts to be dominated by low frequency general multiphase flow. The Strouhal number based on the jet conditions is an order lower than Sr = 0.2 indicating process variations rather than jet noise. Furthermore, at choking conditions the further expansion which occurs in single phase flow is likely different at multiphase flow. For non-choked flow, the standard can be adapted using multiphase mixture properties. This does lead to a good prediction. However at choked conditions, this method fails.
Exploring M & Y Gasket Factors and Their Degree of Correlation With Proposed PVRC Gasket Factors
Authors: Rice Dale A. , Waterland A. Fitzgerald , Bausman Anita R.
Published: October 2017

The well-known gasket factors, m & y were introduced in 1943 as per ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 for purposes of flange design. The test procedure for determining these factors, ASTM Standard F586, was published in 1979 but then ultimately withdrawn in 1998 with the assumption that these test standards would be replaced by a new test method and with it the generation of improved gasket constants. The original m & y constants had several shortcomings including the fact that many of the listed values assumed asbestos fiber gaskets while new gasket materials such as PTFE (polytetrafluoroethylene) and FG (flexible graphite) were not addressed. Additionally, gasket manufacturers were allowed to publish m and y values for their own specific gasket materials and styles using their own test methods, thus dispensing with industry-wide standardization. ASTM Method F3149-15, “Standard Practice for Determining the Maintenance Factor (m) and Yield Factor (y) Loading Constants Applicable to Gasket Materials and Designs” represents an improvement over F586 but is not linked to standardized tightness levels. The proposed PVRC method with a new set of gasket constants is based on a load versus leakage test standard known as ROTT (Room Temperature Tightness Test). Following the ROTT method, ASTM WK39360, “New Test Method for Leak Rates Versus Y Stresses and M Factors for Gaskets derived from the Room Temperature Test Practice”, is being contemplated. This paper provides a review of the past inconsistencies of m & y values as published as well as an initial assessment of the degree of correlation between m & y values and tightness calculations achieved through the use of a previously documented fugitive emissions calculator for gasket materials which makes use of published ROTT data, and the operating pressure, flange NPS, gasket stress, and other inputs.
Development of Nb-Bearing High Strength Steel Plates for 150,000 M3 Oil Storage Tank
Authors: Gao Zhuzhong , Ding Qingfeng , Yang Hongwei , Li Jingtao , Zhu Genmin , Liu Zhongzhu
Published: October 2017

High strength steel plates for oil storage tanks are usually produced by Quenched and Tempered (Q&T) process which results in high energy cost. On the other hand, large-heat-input welding technologies, such as electro-gas welding, have been widely applied during large oil storage tanks construction. In the present paper, High strength steel plates for 150000 m3 oil storage tanks have been developed by Thermal Mechanical Control Process (TMCP) and Tempered process (TMCP-T). The effects of tempered temperature and Niobium content on mechanical performances of plates are investigated. High strength and high toughness as well as excellent large-heat-input weldability for Nb-bearing steel plates are observed and the reasons are discussed.
Analytical Solutions for Liquid Slugs and Pigs Traveling in Pipelines With Entrapped Gas
Authors: Tijsseling Arris S. , Hou Qingzhi , Bozkuş Zafer
Published: October 2017

Liquid slugs have a relatively low mass and can therefore — when they occupy a full cross-section of a pipeline — be accelerated to very high velocities by means of pressurized gas. When entrapped gas pockets are present, pressures and temperatures may become dangerously high. Simple models and analytical solutions are derived and used to predict transient velocities, pressures and temperatures. The models have a generic character as they also describe the basics of breaking surface waves impacting on a wall, and pigs and bullets propelled by compressed gas.
Load Factors for Concrete Wall Pipe Penetrations With a Wall Mounted Welded Plate
Authors: Costanzo Samuel R. , Mak Chee W. , Hoang Phuong H.
Published: October 2017

The bending moments imposed on welded plate anchors that are part of embedded pipe wall penetrations are often overestimated in the structural evaluations of these penetrations. For this type of restraint, the pipe is embedded in a concrete wall penetration with a welded plate mounted on the surface of the wall. This penetration is typically modeled with a single 6 degree of freedom (DOF) restraint at the plate in the pipe stress analysis. This approach can lead to overestimated loads on the welded plate and the mounting anchor bolts because no credit is taken for reaction on the embedded portion of the pipe. A significant portion of the bending moments from piping on both sides of the penetration is transferred directly to the concrete wall by the normal reaction on a fully grouted pipe, thus reducing loads on the steel plate and the mounting anchored bolts. The objective of this study is to determine load factors for bending moments from both sides of the pipe penetration on the anchored steel plate. A parametric study is performed using ANSYS models of a pipe fully embedded in a concrete wall penetration with a welded plate mounted on one side of the wall by anchor bolts. Various pipe diameters, concrete wall thicknesses and plate thicknesses are considered. For each model, the loading on the plate is compared to the loading applied at the free end of the pipe. Load factors are developed for use in the structural evaluation of the welded plate and the mounting anchor bolts. The maximum compressive bearing pressure at the concrete wall is also calculated for use in the structural evaluation of these types of pipe supports.