bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Improved Design of Threaded Closures for Screw Plug (Breech Lock) Heat Exchangers
Authors: Sippy Haresh K. , Chandiramani Dipak K. 
Published: December 2016

Threaded closures for pressure vessels have been in use for decades. Much work has been done to develop convenient, safe and economical threaded closures. Threaded closures are used when there is a need for opening the vessel either for maintenance or as part of its operation.
Heat Exchangers are a typical application where there is a need for opening the vessel and cleaning the tubes at regular intervals to maintain the heat transfer efficiency. These are known as Breech Lock or Screw Plug Exchangers. These are basically U-tube exchangers. The channel side operates at high temperature and pressure and it has a threaded end closure. In some designs, the shell side may also be at high pressure. The tube bundle is removable without having to dismantle the channel or disconnect the nozzles from the pipeline. Thus screw plug exchangers help to reduce fabrication cost and reduce time for in-service maintenance.
The major problem encountered with the use of such end closures are 1) Jamming of the threaded plug, due to deformation of the channel barrel. Thus the opening of the end closure by unscrewing becomes a difficult task. With the increase in operating temperatures and pressures, the problems become more severe, due to which, users are not inclined to use these type of end closures.
A study was undertaken to assess the reasons for bulging of the end of the channel which caused jamming of the screw threads and also for leakage through the gasket.
By shrink fitting a ring over the end of the channel, the deformation was reduced, enabling easy opening of the cover.
2) The leakage through the gasket between the shell and tubesheet, causing the intermixing of shell and tube-side fluids. This on analysing was found that the additional forces were acting on the gasket due to thermal expansion of the internals. This led to changing to a gasket that could withstand the forces and pressure.
Leakage through the gasket was prevented by analysing the additional forces acting on the gasket due to thermal expansion of the internals and changing to a gasket that could withstand the forces and pressure.
Sliding and Rocking Motion Mitigation of a Rigid Body Subjected to Seismic Excitation due to High-Viscous Liquid
Authors: Ito Tomohiro , Sakurai Hideki , Shintani Atsuhiko , Nakagawa Chihiro 
Published: December 2016

After the accident at the Fukushima Daiichi Nuclear Power Plant in Japan, it has steadily become more important to ensure the structural integrity of cask systems containing spent fuels or radioactive debris during seismic events. These cask systems are free-standing cylindrical structures and are believed to show rocking and sliding motions at huge seismic excitations. In the worst case, these cask systems can possibly overturn or collide with each other. Therefore, it is very important to reduce the sliding and rocking motions of the cask system in order to avoid subsequent contamination due to radioactive substances.
To date, the authors have been studying the response behaviors of these motions, and have developed some types of methods that are effective at mitigating sliding or rocking motions, and confirmed the effectiveness of these methods. A system utilizing coaxial circular cylinders and high-viscosity liquid filled into the annular spaces was developed for the suppression of sliding motion. This system was installed at the bottom end of the rigid body. Previous studies show that liquids with high-viscosity provide a very large added damping effect that causes sliding motion to be suppressed significantly. For the suppression of rocking motion, the authors developed a system that utilizes a gyro system, and confirmed it’s effectiveness both analytically and experimentally.
However, the gyro system is slightly complex and requires electric power even during a seismic event. Thus, some passive suppression method is required. On the other hand, the above-mentioned coaxial circular cylindrical system filled with high-viscosity liquid is thought to have a high damping effect on rocking motion, along with suppression of sliding motion.
This study investigated the effect of rocking motion suppression due to the above-mentioned coaxial circular cylindrical system that is utilized for the suppression of sliding motion. First, an analytical model that can account for the coupled rocking and sliding motion was established, and then the rocking behavior of a rigid structure coupled with its sliding motion was studied. Next, shaking table tests were conducted by using a fundamental test model. By comparing the analytically obtained rocking motion with that obtained by the test results, the validity of the analytical model was confirmed. Finally, the analytical model was modified for cask systems equipped with a rocking suppression system, and the rocking motion was analyzed to evaluate its effectiveness.
The proposed rocking suppression system was found to be very effective in suppressing the rocking motion of the rigid body when subjected to base excitations.
Constraint Solutions for Cracked Plates and Cylinders
Authors: Meek Caroline , Gintalas Marius , Sherry Andrew H. , Ainsworth Robert A. 
Published: December 2016

There is little advice in fitness for service procedures for assessing constraint parameters T (elastic) and Q (elastic plastic) for biaxially loaded plates and cylinders.
This paper presents the analytical determination of T stresses for biaxially loaded plates and the determination of Q for plates and cylinders using finite element analyses. It demonstrates the extent to which T can be used to conservatively predict Q and how, near collapse, Q can be estimated from the stress field corresponding to plastic collapse, enabling a significant reduction in computing effort.
The effect of biaxial loading of plates and cylinders on these parameters is discussed as well as the differences found when comparing the values for plates and cylinders.
Development of a New Thermo-Mechanical Environmental Fatigue Testing Facility to Investigate the Impact of Thermal Strain Gradients on Fatigue Initiation
Authors: Platts N. , Brown P. , Gill P. J. , Smith R. D. , Stairmand J. W. 
Published: December 2016

Light water reactor coolant environments are known to significantly reduce the fatigue life of austenitic stainless steels. However, most available data are derived from isothermal testing of membrane loaded tensile specimens, whereas the majority of plant loading transients result from thermal transients and involve significant through-wall strain gradients. This paper describes the development of a high temperature water facility to enable both thin and thick wall hollow fatigue endurance specimens to be subjected to thermal and mechanical loading for a wide range of thermal cycles including rapid shock loading.
Thermal shock loading from 300°C to between 40 and 150°C has been achieved and Finite Element Analysis, FEA, has been used to calculate the thermally induced strain profiles through a 12mm thick-wall specimen. This indicates peak surface thermal strain ranges of up to 0.8% for a transient between 300 and 40°C. Testing is underway to investigate the impact of the strain gradient and thermal waveform on the fatigue life of this specimen where significantly longer lives may be expected compared to membrane loaded specimens.
The ability within the same facility to apply simulated thermal shock profiles to both thick-wall specimens and mechanically loaded thin wall specimens provides a powerful tool to assess the impact of thermal fatigue loading and thermal strain gradients on component life.
Traditional Versus New Technology Boiler Drum Water Level Instruments
Authors: Liu Zhelin , Harris John Michael , Liu Jichuan , Han Dong , Liu Lei 
Published: December 2016

The art and science of boiler drum water level measurement has long been the source of questionable results. A low-tech examination of the boiler drum reveals where the drum level has been controlling — there is a water mark inside the drum. The problem is obvious; the mark in the drum and that in the control system do not agree. The level is off by a wide margin. This paper seeks to explain how poor assumptions are the source of the error. Then two design approaches are considered to eliminate the sources of error. Consider that boiler drum water is not saturated; feedwater entering from the economizer is below saturation. Also consider the constant head chamber. Typically, the reference leg is considered to be at ambient temperature, but it is really a gradient starting at near drum temperature. The effect of these two poor assumptions is a relatively large error such that the true level is different from indicated level.
Once this situation is understood, it is possible to redesign instruments which take the actual situation into account. One such instrument is nearly the same as the original DP-type instrument, but the constant head chamber is located inside the drum. This design change deals with both errors. It eliminates the differences in temperature and density between the constant head leg and the water inside the drum. It also exposes the constant head leg to the exact same temperature as the boiler water, thus eliminating the need for complicated (and incorrect) formulae to compensate for the differences in density. A second design approach is to “steam jacket” an instrument located outside the drum, thus eliminating the differences in temperature and density. This is an appropriate way to deal with the Conductivity Probe and the Boiler Water gauge glass. By steam jacketing these instruments, we can make the water temperature between the indicator and the drum almost the same.
Analysis of Fatigue Crack Growth in Standard Endurance Test Specimens in Support of Total Life Approaches to Fatigue Assessment
Authors: Mann Jonathan , Twite Marius , Burke M. Grace 
Published: December 2016

The ASME Boiler & Pressure Vessel Code Section III method for the evaluation of fatigue in nuclear plant components uses a fatigue design curve derived from the testing of standard cylindrical specimens to describe the fatigue endurance of austenitic stainless steel components. The test results describe the number of cycles to achieve a 25% total load drop within a standard specimen (approximately equal to a 3 mm crack) under membrane loading conditions and the design curve is commonly associated with fatigue initiation. However, for non-standard loading conditions, such as the case of a thermal gradient within a component where a crack may be growing into a decreasing stress field, this description of initiation may be overly conservative.
Alternative approaches, such as the total life approach, may provide better representations of fatigue life in real plant components. By separating out quantifiable portions of long crack growth (Stage II) from the current design curve, alternative definitions of initiation can be derived and subsequently used in conjunction with standard fracture mechanics in order to model fatigue more accurately.
In this paper numerical methods are used to model the fatigue crack growth between starting crack depths of 0.25 mm, and the depth associated with a 25% load drop in a standard cylindrical specimen. The numerical predictions are compared with striation spacings measured at a range of crack depths on the fracture surfaces of austenitic stainless steel specimens tested in both air and water environments, under strain control. A good correlation between numerical predictions and the measured striation spacings was obtained and the results are used to characterise different stages of fatigue cracking.
Based upon the methods developed in this paper, modified fatigue design curves, using alternative definitions of crack initiation, are proposed and their applications in total life approaches to fatigue assessment are discussed, based on a worked example of a thermally fatigued stepped pipe experiment.
Comparison of a One-Dimensional Pursuit Model With Experimental Data for Rarefaction Pressure Wave Catch-Up and Diminishment of a Pressure Shock Within Two-Phase Media
Authors: Pellman Abby M. , Jones Ryan E. , Minichiello John C. 
Published: December 2016

The Waste Treatment Plant (WTP), located at the U.S. Department of Energy’s Hanford Site, will process waste slurries capable of retaining a dispersed non-condensable gas phase while in a quiescent state. Under postulated conditions, a pressure pulse generated from a deflagration or detonation within a flammable gas pocket may be transmitted into piping systems that contain the gas-liquid slurry. It is necessary to understand how a pressure pulse diminishes as it propagates through the system in order to properly quantify the structural loading on the piping and its associated supports. Earlier work presented a set of conservation equations and discussed the dynamics of individual bubble oscillations but still required discretization within a numerical CFD solver (Reference PVP2015-45972). To simplify the computation requirements, a one-dimensional pursuit model that calculated the rarefaction wave catch-up was developed and compared to experimental data.
This paper presents a one-dimensional model that utilizes the difference in speeds of the shock and acoustic rarefaction waves in the two-phase media to model the propagation and diminishment of a traveling pressure shock wave. The rarefaction waves overtake the shock front which is then rapidly diminished and decreases speed accordingly. Results of the pursuit model are compared to experimental data and shown to accurately capture the diminishment behavior and shock propagation.
Fatigue Life Properties and Anomalous Macroscopic Fatigue Fracture Surfaces of Low Carbon Steel JIS-SM490B in High-Pressure Hydrogen Gas Environment
Authors: Ogawa Yuhei , Matsunaga Hisao , Yoshikawa Michio , Yamabe Junichiro , Matsuoka Saburo 
Published: December 2016

Tension-compression fatigue tests using smooth specimens of low carbon steel JIS-SM490B were carried out in air and hydrogen gas environment under the pressure of 0.7 and 115 MPa at room temperature. In 0.7 MPa hydrogen gas, fatigue life curve was nearly equivalent to that in air. On the other hand, in 115 MPa hydrogen gas, fatigue life was significantly degraded in the relatively short fatigue life regime (e.g. Nf < 105). To clarify the effect of hydrogen environment on fracture process, fracture surfaces of these specimens were observed. In general, fatigue fracture process of steels with low or moderate strength is macroscopically divided into 3 stages. In the first stage (stage I), fatigue cracks initiate in some crystalline grains. In the second stage (stage II), the cracks propagate stably on a cycle-by-cycle basis. In the final stage (stage III), a tilted fracture surface, shear-lip, is formed by ductile tearing. In SM490B steel, this general fracture process was confirmed in air and 0.7 MPa hydrogen gas. In contrast, in 115 MPa hydrogen gas, there was no tilted portion in the stage III region, and the fracture surface was totally flat. Observation with scanning electron microscope revealed that dimples were formed by ductile tearing in the tilted fracture region in air and 0.7 MPa hydrogen gas. On the other hand, only a quasi-cleavage fracture surface existed in the final fracture region in 115 MPa hydrogen gas. To understand the cause of this peculiar fracture morphology, we conducted elasto-plastic fracture toughness tests in each environment, and investigated the fracture morphology.
As a result of fracture toughness tests, crack growth rate in air and 0.7 MPa hydrogen gas was approximately equal to each other, and both the fracture surfaces were covered by dimples. This fracture morphology was in accordance with that of stage III morphology in fatigue specimen tested in air and 0.7 MPa hydrogen gas. However, in 115 MPa hydrogen gas, the crack growth was significantly accelerated, and the whole fracture surface was covered by quasi-cleavage.
In this paper, firstly, the similarity of fracture surface between two test methods, i.e. fatigue test and fracture toughness test, is investigated. And then, the formation mechanism of the flat fracture surface is discussed by paying attention to the crack-growth acceleration in high-pressure hydrogen gas.
Residual Stress State of X65 Pipeline Girth Welds Before and After Local and Furnace Post Weld Heat Treatment
Authors: Ren Yao , Paradowska Anna , Wang Bin , Eren Elvin 
Published: December 2016

This research investigated the effects of global (in other words, furnace-based) and local post weld heat treatment (PWHT) on residual stress (RS) relaxation in API 5L X65 pipe girth welds. Two pipe spools were fabricated using identical pipeline production procedures for manufacturing multi-pass narrow gap welds. Non-destructive neutron diffraction strain scanning was carried out on girth welded pipe spools and stress-free comb samples and also thin slices for the determination of lattice spacing. All residual stress measurements were carried out at the KOWARI strain scanning instrument at the Australian Nuclear Science and Technology Organization (ANSTO).
Residual stresses of two pipe spools (in the as-welded condition) were measured through the thickness in the weld material and adjacent parent metal starting from the weld toe. Three line-scans were completed 3mm below outer surface, at mid thickness and 3mm above the inner surface. PWHT was adopted for stress relaxation; one pipe was conventionally heat treated entirely in an enclosed furnace and the other was locally heated by a flexible ceramic heating pad. Residual stresses were measured after PWHT at exactly the same locations as those used for the as-welded condition. Residual stress states of the two pipe spools in as-welded condition and after PWHT were compared and the results were presented in full stress maps. Additionally, through thickness residual stress profiles and the results of one line scan (3mm below outer surface) were compared with the respective residual stress profiles advised in British Standard BS 7910 “Guide to methods for assessing the acceptability of flaws in metallic structures” and the UK nuclear industry’s R6 procedure. The residual stress states of the two pipe spools measured in the as-welded condition were similar. With the given parameters, local PWHT has effectively reduced residual stresses in the pipe spool to such a level that it prompted the thought that local PWHT can be considered a substitute for global PWHT.
Creep Damage Formation and Crack Initiation / Growth Behavior of Notched Specimen for Directionally Solidified Ni-Base Superalloy by Interrupted Observation
Authors: Ozeki Go , Yokobori A. Toshimitsu , Matsuzaki Takashi 
Published: December 2016

Directionally solidified Ni-base superalloy is used for gas turbine blades for high efficiency thermal power plant. Since gas turbine blades are subject to high temperature creep condition due to the high speed rotation of rotor, it is important to evaluate the creep strength. There are many studies using the smooth specimen for directionally solidified Ni-base superalloy. However, these are not so many researches which concern the mechanical behavior of a notched specimen. Therefore, the researches of creep damage formation and the crack growth behavior around a notch tip have not yet been clarified. Recently, electron backscatter diffraction (EBSD) method has been conducted to evaluate the creep damage for Ni-base superalloy. However, most of the studies also use the smooth specimen. When the materials are practically used for the component of structures, creep damage or crack may be originated at the site of stress concentration of equipment such as cooling holes. Therefore, in order to evaluate the creep damage formation and the crack growth behavior, it is important to conduct the research using notched specimens from the view point of application to actual components.
In this study, creep damage formation and crack growth behavior of a notched specimen for directionally solidified Ni-base superalloy CM247LC under high temperature creep condition were investigated by conducting experiment and mechanical analysis. The interrupted observational test of creep crack growth was conducted to investigate the damage formation and the crack growth behavior around notches. In addition, the In-situ observation and the metallographical investigations were conducted for creep damaged specimens using SEM / EBSD analysis. Furthermore, in order to clarify the mechanism of creep damage formation behavior, the designed two-dimensional elastic-plastic creep finite element analysis was conducted for the model with various distributed grains obtained by EBSD analysis. And this analytical results were compared with experimental results.
As a result, the micro creep crack around a notch tip was found to be caused by accumulation of micro damage and voids. In addition, macro cracks were found to initiate just before final unstable fracture.
However, it is necessary to take into account for the variety of mechanical properties of each crystal orientation, the designed two-dimensional elastic-plastic creep finite element analysis was found to well represent the creep damage formation observed in experiments.
Assessment Method to Account for the Rise Time of Complex Waveforms in Stainless Steel Environmental Fatigue Crack Growth Calculations
Authors: Emslie Julian , Gill Chris , Wright Keith 
Published: December 2016

The reference Fatigue Crack Growth (FCG) rate behaviour for austenitic stainless steel in a deaerated Pressurised Water Reactor (PWR) environment is provided in ASME Section XI Code Case N-809. This FCG law is dependent on temperature, R ratio and environment, which is defined through a load rise time parameter. The basis for this law is contained within a large dataset of testing carried out by various industry sources.
Code Case N-809 defines rise time as the time for which the stress is increasing during a stress cycle, based on specimen testing in which sawtooth loading (typically 85% rise/15% fall) was primarily used. However it was found from testing of more complex waveforms carried out by Amec Foster Wheeler, which is reported in a separate paper at this conference, that the FCG rate is not always well characterised by this definition of rise time and was often found to be overly conservative. A number of different waveforms were considered, including simplified two-stage linear waveforms where the loading rate is different in the top and bottom half of the cycle, and those more representative of plant transients.
This paper presents a method to account for the environmental enhancement of complex waveforms with variable loading rate by weighting the loading rate according to its position within the loading cycle. In this way an effective rise time can be obtained for use in Code Case N-809. This method was found to give good agreement with the experimental data generated using complex waveforms.