bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural Network Modeling in Model-Based Control of a Data Center
Authors: Kansara Nachiket , Katti Rohit , Nemati Kourosh , Bowling Alan P. , Sammakia Bahgat
Published: November 2015

This paper presents the development of a neural network model of the server temperature to be used in model-based control of a data center. Data centers provide the optimal environments for operation of servers and storage devices. Conventionally, computational fluid dynamics (CFD) has been used to model the dynamic and complex environment of the data center. However, the drawback of this approach is its computational inefficiency. The effects of changing a single input may take an entire day to compute. Thus the CFD model is not well suited for model-based control. Instead, we propose to use an artificial Neural Network (NN) model which predicts server temperatures in significantly less time. In addition, this NN model has the capability of learning the environment in the data center by adapting its parameters in real time based on sensor data continuously taken from the data center. This work discusses the current development of the neural network, work being done at the University of Texas at Arlington, to include modeling of transient conditions, or time related changes, using data generated in a test bed Data Center at SUNY Binghamton.
Enhancement and Optimization of Planar Impingement Heat Transfer for Thermoelectric Power Generation
Authors: Yazawa Kazuaki , Heister Stephen D. , Fisher Timothy S.
Published: November 2015

We present an analytic model and optimization of impingement heat transfer in fluid-to-fluid heat exchangers with integrating a thermoelectric (TE) generator between the hot and cold fluid flows. In power generation systems, designing for maximum power output generally involves balancing the external thermal resistances while the generator contacts the hot and cold temperature reservoirs. In fluid-to-fluid heat exchangers, fluid temperatures are not constant or uniform. They gradually change along the flow direction. In general, counter-flow heat exchangers outperform parallel flow configurations in maximizing TE power generation using internal fluid flows. We show here the performance of our impingement model compared with a counter-flow configuration as the base line.

To obtain the maximum power output from practical thermoelectric materials (ZT values are 1.2–1.8), the enhancement of liquid-to-wall heat transfer is significant. An array of traditional impinging jet orifices provides a uniformly planar and focused heat transfer process that spatially targets the TE elements. This approach provides more uniform hot and cold side temperatures among the TE elements. We investigate the impact of introducing impingement orifices directly at the locations of the TE elements. The major focus of this work is the trade-off between the advantage of increasing power generation by impingement and the disadvantage of introducing additional pressure drop.

Decreasing the external thermal resistances yields not only a larger maximum power output but also requires thinner TE elements. This enables lower cost per power generation capacity approaching the 0.2–0.3 $/W range as well as a more lightweight design. We report here the associated cost impacts for the impinging jet arrangement.

Design optimization depends on the specific constraints and parameters, such as TE material and substrate thickness, flow design to avoid the stagnation, and required exit temperatures. In some cases, active pumping by an additional actuator can augment the enhancement, while a fraction of generated power is consumed for the actuation. In the paper, we show examples of gas and liquid flow cases.
Art and Science Towards Noiseless Driving of Liquid Metal for Advanced Thermal Management of High Heat Flux Device
Authors: Liu Jing , Deng Zhong-Shan , He Zhi-Zhu
Published: November 2015

The room temperature liquid metal cooling is quickly emerging as a powerful way for the thermal management in many advanced high heat flux devices, spanning from electronics, optoelectronics, battery, to power system etc. Except for its pretty high conductivity that a metal coolant could offer, the unique merit lying behind this new generation cooling strategy is its drivability of the highly conductive coolant through the electromagnetic effect where no moving elements are involved and thus only very few energy consumption is needed. In addition, even waste heat could be strong enough to generate applicable electricity for such flow driving purpose. More directly, the temperature gradient intrinsically generated between the heat source and the sink has also been managed to drive the flow of the coolant and realize an automatic practical enough cooling in some situations. All these practices lead to a totally noiseless pumping of the heat delivery and a compact and reliable cooling modular can thus be possible. Starting from this basic point, we are dedicated here to present an overview on the art and science in developing the technical strategies for a smart driving of the liquid metal cooling of the target devices. Designing philosophy for an innovated thermal management will be discussed. Particularly, electromagnetic pumping, waste thermoelectricity driving, thermosyphon flow effect, etc. will be comparatively evaluated with each of the working performances interpreted. Power consumption rate and efficiency will be quantitatively digested. Typical application examples in the cooling of a series of device areas will be illustrated. Further improvement on the cooling solution along this category will be suggested. Challenging issues in pushing the new technology into large scale utilization will be raised. It is expected that such silent self-driving of the liquid metal coolant will find unique and important values in a wide variety of thermal management areas where reliability, compactness, low noise and energy saving are urgently requested.
High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes
Authors: Houshmand Farzad , Lee Hyoungsoon , Asheghi Mehdi , Goodson Kenneth E.
Published: November 2015

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.
Liquid Flow Analysis in Porous Media for Large Vapor Chamber With Multiple Heat Sources
Authors: Escobar Sergio , Kumari Niru , Shih Rocky , Anthony Sarah , Bash Cullen
Published: November 2015

The increasing addition of hot components on a single module comes with the challenge to cool the module. The cooling challenges are due to the presence of hot spots and the reduce space for attaching heat sinks to each component. The proposed cooling solution for a multi-chip module is a single vapor chamber shared amongst the multiple heat sources. Designing an application-optimized vapor chamber requires detailed understanding of the different processes occurring, including heat transfer by conduction, two-phase heat transfer, and fluid mechanics in porous media. In this work, a relatively large module with many heat sources is considered. We present a case of two 100W heat sources surrounded by eight heat sources of 10W each. We explore different configurations and their capillary limitations for a vapor chamber (110 mm × 110 mm). We present the comparison of numerical results using two point flux approximation method, CFD model, and a simplified model using potential flow theory to represent flow in the porous media. Results are used to analyze the capillarity limitation of the large vapor chamber in delivering liquid flow to heat source locations for steady state.
Survivability of MEMS Accelerometer Under Sequential Thermal and High-G Mechanical Shock Environments
Authors: Lall Pradeep , Abrol Amrit , Simpson Lee , Glover Jessica
Published: November 2015

Reliability data on MEMS accelerometers operating in harsh environments is scarce. Micro-electro-mechanical systems (MEMS) are used in a variety of military and automotive applications for sensing acceleration, translation, rotation, pressure and sound. This research work focuses on dual axis MEMS accelerometer reliability in harsh environments. Structurally an accelerometer behaves like a damped mass on a spring. Commercially there are three types of accelerometers namely piezoelectric, piezoresistive and capacitive depending on the components that go into the fabrication of the MEMS device. Previously, majority of concentration was focused on an effective internal design, performance enhancement of CMOS-MEMS accelerometers and packaging techniques Cheng [2002], Qiao [2009], Lou [2005], and Weigold [2001]. Studies have also been conducted to obtain an enhanced inertial mass SOI MEMS process using a high sensitivity accelerometer Jianbing [2013], Chen [2005]. There have been prior test(s) conducted on MEMS accelerometers, Jiang [2004], Cao [2011], Chun-Sun [2009], Lou [2009], Tanner [2000] and Yang [2010] but the availability of data on reliability degradation of such devices in harsh environments Brown [2003] is almost little to none which thereby generates the importance of this work and also makes way for a whole new path involving the reliability assessment techniques for MEMS devices. Concentration of our work is primarily on the reliability of this accelerometer upon sequential exposure to harsh environment(s) and drop-shock. Reliability of accelerometers in high G environments is unknown. The effects of these pre-conditions along with the drop test condition has been studied and analyzed. In this piece of research work, a test vehicle with a MEMS accelerometer, ADXL278 dual axis capacitive accelerometer, has been tested under high/low temperature exposure followed by subjection to high-g and low-g shock loading environments. The test boards have been subjected to mechanical shocks using the method 2002.5, condition G, under the standard MIL-STD-883H test. The stress environment and the test condition used for this paper are 1500g and 70g respectively where 70g is the full scale range output of ADXL278 in the drop direction with pulse duration set to 0.5millisecond. The deterioration of the accelerometer output has been characterized using the techniques of Mahalanobis distance and Confidence intervals. Scanning Electron Microscopy (SEM) has been used to study the different failure modes inside of the accelerometer, which were potted and polished and later de-capped. Furthermore, the non-destructive evaluations of the MEMS accelerometer have been demonstrated through X-rays and micro-CT scans.
Atomic Layer Deposited TiO2 as Sacrificial Layers and Internal Coatings for Nanoscale Gaps
Authors: Liew Li-Anne , Lin Ching-Yi , Yersak Alexander , Lewis Ryan , Coolidge Collin , Lee Y. C.
Published: November 2015

A key component of the MEMS cryogenic cooling systems we are developing is a MEMS compressor. Its function is to compress the refrigerants used in the cooling cycle. Layers of polyimide are stacked and patterned on a silicon wafer to create micro check-valves and a compression chamber over which a diaphragm is suspended. To achieve the high (4:1) pressure ratio needed for the refrigeration cycle, the polyimide diaphragm needs to be fabricated with minimal dead volume beneath it, hence the need for a sacrificial layer with thickness of 100–300 nm. The topography created by the check-valves and valve-seats makes atomic layer deposition (ALD) ideal due to its conformality. Furthermore, following sacrificial layer release, the inside of the compression chamber will also need to be coated with a hermetic moisture barrier layer to enable the device to operate at 4 atmospheres without leaking. ALD is therefore also ideal for the final internal coating because it does not require line-of-sight. Towards this end, we demonstrate here the concept of using ALD TiO2 as a sacrificial layer to create a 5 mm × 5 mm × 20 m-thick polyimide membrane, suspended by ∼ 100–350 nm above a silicon wafer, followed by a second thinner ALD coating of the interior surfaces bounded by wafer and membrane. The air gap under the membrane, defined by the released sacrificial layer, was measured at about 130–370 nm using two independent methods: reflectometry, and FIB cross sectioning followed by SEM imaging of the air gap’s cross section. The membrane was removed from one chip and the thickness of the internal coating on the underlying silicon was measured with the reflectometer to be about 40 nm. We thus demonstrate the use of ALD TiO2 as both a sacrificial layer for fabricating nanoscale gaps, as well as for coating nanoscale internal cavities and channels.
New Super-Low CTE (0.7 ppm/K) Core Material for Next Generation Thin CSP
Authors: Nakamura Yukio , Oohashi Kenichi , Morita Koji , Nomoto Shuji , Suzuki Takayuki , Takanezawa Shin , Tsuchikawa Shinji , Takekoshi Masaaki
Published: November 2015

The thinner and higher density PKG (package) is being required strongly for the growth of smaller mobile devices. Especially, package on package technology (PoP) has become a mainstream for application processors which are installed in smartphones and tablets.

However, the warpage of thinner PKG often causes a problem at the chip mounting process. The main factor of warpage is the mismatch of CTE (coefficient of thermal expansion) between substrate and chip. Therefore, the lower CTE core materials are needed for the thinner PKG.

Recently, Hitachi Chemical has developed the super-low CTE material, core and prepreg, applying our new resin system and filler treatment technology, and placed it on the market. Furthermore, a super-low CTE material of 0.7 ppm/K is currently under development. The super-low CTE material shows the best warpage performance in our low CTE core material lineups, maintaining its higher Tg, high modulus and low Dk/Df values.
Effects of High Frequency Hydrodynamic Loads on Structural Integrity and Mechanical Operability of Valves
Authors: Isbiliroglu Yigit , Ozgur Cagri , Ulku Evren , Vaidya Nish , Paserba Kristofor
Published: November 2015

In-line valves are qualified for static as well as dynamic loads from seismic and hydrodynamic (HD) events. Seismic loads are generally characterized by frequency content less than about 33 Hz whereas HD loads may exhibit a broad range of frequencies greater than 33 Hz. HD loads may also result in spectral accelerations significantly in excess of those due to the design basis seismic events. Current regulatory guidelines do not specifically address the evaluation of equipment response to high frequency loading. This paper investigates the response of skid and line mounted valves of piping systems under HD loads by using several independent rigorous finite element analysis solutions for various piping system segments. It presents a hybrid approach for the evaluation of the response of valves to HD and seismic loads. The proposed approach significantly reduces the amount of individual analysis and testing needed to qualify the valves. First, valve responses are evaluated on the basis of displacements since HD loads are generally characterized by high frequencies and small durations. Second, the damage potential of the loads on the valve actuators is represented by the energy imparted to the actuator quantified in terms of Arias intensity. The rationale for using the energy content is based on the fact that damage due to dynamic loading is related not only to the amplitude of the acceleration response but also to the duration and the number of cycles over which this acceleration is imposed.
Fatigue Strain–Life Behavior of Austenitic Stainless Steels in Pressurized Water Reactor Environments
Authors: Wilhelm Paul , Steinmann Paul , Rudolph Jürgen
Published: November 2015

A statistical model for austenitic stainless steels for predicting the effect of pressurized water reactor environments on fatigue life for a range of temperatures and strain rates is developed based on analysis of available material data. The compiled fatigue curve data include not only results from America (Keller (1971), Conway (1975), Hale (1977), and Argonne National Laboratory (1999–2005)), but also from Europe (Solin (2006), Le Duff (2008–2010), De Baglion (2011, 2012), Huin (2013) …) and Japan (Kanasaki (1997)). Only fatigue data from polished specimens of wrought material tested under strain control were considered; hollow specimens were not treated herein. The fatigue life correction factor used in this paper was defined as the ratio of life in water at 300 °C (reference conditions) to that in water at service conditions. The model is recommended for predicting fatigue lives that are 103–105 cycles.
Effects of Local Wall Thinning With Crack on Limit Loads for Pipes Subject to Combined Pressure and Bending
Authors: Tao Joy (Xiaoya) , Zhu Lei
Published: November 2015

As power plants age, local thinning often occurs in pipework due to erosion/corrosion or other reasons. Local thinning reduces the strength of a pipe and increases the local stress. When the pipework is subject to cyclic loading, a crack could initiate from corrosion pit or welding defect at the local thinning. It is often required to carry out engineering critical assessment for a crack at the local thinned area to support safety case. Limit load or reference stress solution is needed to carry out flaw acceptance assessment to R6 or BS7910. These components are normally subject to combined internal pressure and global bending. Current practice for assessing these kinds of components is based on the minimum measured thickness or a factored minimum thickness. The former is overly conservative on limit load, leading to early sentencing of a component, whilst the latter is potentially non-conservative depending on the proposed factor, thinning profile and dominant load. For pipe with a crack or local thinning subject to internal pressure and global bending many closed form limit load solutions are available. However, limited information and solutions are available on how to determine the limit load of a cylinder with both crack and local wall thinning under combined pressure and moment loading. In this paper, the limit load solutions for pipe with a crack at the local thinned area are investigated using 3D finite element analysis for a range of pipe geometries with different internal excavations (local wall thinning) and circumferential cracks subject to combined pressure and global bending moment. The study also considers the differences between the global limit load of the thinned section (net-section collapse), the local limit load at the thinned area (local collapse) and the ligament limit load at the crack tip (ligament yield). Comparison is made between the elastic-plastic FE analyses and the handbook solutions.
Numerical Evaluation of Environmentally Assisted Fatigue (EAF) in Consideration of Recent Updates of the Formulas and Hold Time Effects
Authors: Reese Sven H. , Seichter Johannes , Klucke Dietmar , Karabaki H. Ertugrul
Published: November 2015

Environmentally Assisted Fatigue (EAF) has been focus of various research activities and has been addressed in nuclear Codes and Standards like German safety standard KTA 3201.2 [1], 3211.2 [2] or ASME CC N-792 [3] for example.

Based on experimental investigation under laboratory conditions a numerical correction factor Fen was proposed in NUREG CR-6909 [4] in 2007 after precursors in the Japanese JSME code [6]. In 2012 the EPRI Technical Report “Guidelines for Addressing Environmental Effects in Fatigue Usage Calculations” [7] introduced some practical guidelines for the application of the EAF to real plant components based on the set of formulas from 2007. Since this report the set of formulas have been adapted several times (e.g. in ANL-LWRS 47-2011 [8]) while the current revision of NUREG/CR-6909 in 2014 [9] describes the current state of the art.

At E.ON Kernkraft GmbH a goal-oriented and engineering based research program called NuMEA (Numerical Methods to take Environmentally Assisted Fatigue into Account) has been established, focusing on recommendations of the EPRI guideline in the context of application to real plant components and available temperature measurement data.

First main focus of the R&D activity is to calculate the EPRI sample for verifying developed procedures and taking different procedures for determining the sign to be assigned to the relevant stress intensity into account. The documentation of the procedures applied within the EPRI guideline is not comprehensive enough for real-plant evaluation application. Thus, additional definitions and procedures have been developed to ensure practical application of the procedures being developed. Additionally, updated formulas being recently introduced in the context of the NUREG/CR-6909 Rev. 1 [9] have been implemented.

Second topic of the activities is to develop a procedure to take hold-time effects into account numerically based on existing experimental data. Motivated by the fact that the introduction of a potentially beneficial effect of hold times is foreseen in the framework of piping design of the German KTA safety standards, the existing engineering approach (PVP2014-2819 [10]) is appended to fatigue calculation of NPP components.

This paper presents the results and the highlights of the E.ON R&D project NuMEA.
External Pressure Charts for Carbon and Low Alloy Steels in the Creep Range
Authors: Kagita Gurumurthy , Srinivasan Balaji , Banothu Ramu , Achary Gudimella G. S. , Sripada Subramanyam V. R.
Published: November 2015

External pressure charts of ASME Boiler & Pressure Vessel Code do not account for reduction of buckling strength due to creep under long-term loads at elevated temperatures. This restricts the design of ASME boiler and pressure vessel components in the creep range. Although the design factors and equations for creep buckling are available in various other literatures, the external pressure charts in the creep range are not available at present time. External pressure charts are developed for most commonly used elevated temperature materials (Carbon & 1.25Cr-0.5Mo and 2.25Cr-1Mo low alloy steels) in the refinery and petrochemical industry up to a temperature of 550 °C. API 579-1/ASME FFS-1 isochronous stress-strain curves from Omega model, which does not include the effects of plasticity and primary creep, are used. Thus adjustment factors are proposed based on available isochronous stress-strain curves which considers the plasticity and primary creep effects. The developed external pressure chart for 2.25Cr-1Mo steel at 538 °C is validated with ASME B&PV Code Case 2676. The loads and load combinations to be considered in the design and examples illustrating the application of the developed external pressure charts in the creep range are presented.
Effect of Surface Condition on the Fatigue Life of Austenitic Stainless Steels in High Temperature Water Environments
Authors: Platts Norman , Tice David , Stairmand John , Mottershead Kevin , Zhang Wenzhong , Meldrum James , McLennan Alec
Published: November 2015

High temperature water environments typical of LWR operation are known to significantly reduce the fatigue life of Type 300 series austenitic stainless steels in laboratory studies relative to air environments. This environmental impact on fatigue life has led to the issue of US-NRC Regulatory Guide 1.207 and supporting document NUREG/CR-6909 which predicts significant environmental reduction in fatigue life (characterised by an environmental factor Fen) for a range of actual and design basis transients. However, application of this factor to design curves (obtained from laboratory air data by the application of factors for size, surface finish, environment etc) may be unduly conservative. For example there are reasons to expect that a given surface condition will not have the same impact in air compared to water environments.

The aim of the current work was to determine the impact of different surface conditions, typical of operating plant, on the fatigue life in both air and high temperature (300°C) water environments. This work indicates that, in a simulated PWR high temperature water environment, the impact of either a roughly ground/abraded surface finish (simulating flapper wheel dressing) or a simulated surface scratch on fatigue life relative to a polished surface finish is approximately half of the effect observed in ambient temperature air. This suggests that the application of a Fen value calculated in accordance with NUREG/CR-6909 to the design curves may indeed unduly over-estimate the impact of surface finish on fatigue life.
Presentation of the 2015 Revisions to the RCC-M Code
Authors: Malouines Philippe
Published: November 2015

The paper describes the general approach followed by AFCEN, the French Society for Codified Rules for Design, Construction and In-Service Inspection of Nuclear Island Components, from the technical and organizational points of view. The RCC-M code, reissued in 2012 and modified with addenda in 2013 2014, and 2015 is presented. The main new topics of activity of the RCC-M Subcommittee are considered: conformity with regulation(s), use of International Standards, equivalence with other codes and harmonization, and latest publication for the quality management system.

The paper highlights how industrial experience is currently being integrated into the RCC-M code, and how the code is evolving to take into account the enlargement of the AFCEN Membership, new AFCEN organization rules, and the international environment, and best practices. The processes for dealing with requests for modifications and interpretations are described.
ASME Sec VIII Div 3 Fatigue Life Predictions Using Critical Plane Approach
Authors: Karpanan Kumarswamy , Thomas William
Published: November 2015

ASME VIII Div 3 fatigue evaluation is based on the theory that cracks tend to nucleate along the slip lines oriented in the maximum shear stress planes. This code provides methods to calculate the fatigue stresses when the principal stress direction does not change (proportional loading) and axes change (nonproportional loading). When principal stress direction does not change within a fatigue cycle, shear stress amplitude is calculated only on the three maximum shear stress planes. But when the principal stress directions do change within a loading cycle, the plane carrying the maximum shear stress amplitude (also known as critical plane) cannot be easily identified and all planes at a point needs to be searched for the maximum shear stress amplitude.

This paper describes the development of an ANSYS-APDL macro to predict the critical plane at each surface node of an FE model using the FEA stress results. This macro searches through 325 planes (at 10° increments along two angles) at each surface node and for each load step to identify the maximum shear stress and the corresponding normal stress for each surface node. The fatigue life is calculated for each surface node and is plotted as a color contour on the FEA model. This macro can be extended to calculate the fatigue life using other critical plane approaches such as the Findley and Brown-Miller models.
Research of Sealing Property to Subsea Oil and Gas Pipeline Repair Clamp
Authors: Zhao Bingjie , Zhu Hongwu , Zhang Shuli , Zhang Jinya , Tang Deyu
Published: November 2015

The clamp repair technology of subsea oil and gas pipeline has been successfully used in China’s subsea oil and gas pipeline repair projects. However, the key equipment research of flange compression sealing subsea pipeline repair clamp in the technology has just started. The sealing technology is the key technology of subsea oil and gas pipeline repair clamp. The common form of seal in subsea oil and gas pipeline repair clamp is introduced in the paper. The sealing structure of subsea oil and gas pipeline repair clamp is designed and the sealing material is selected for subsea oil and gas pipeline repair clamp. It utilizes the finite element method to calculate sealing property of the rubber sealing which shows the sealing structure can completely meet the sealing request under the pressure of 10 MPa, what can provide a reliable basis for sealing design of subsea oil and gas pipeline repair clamp.
J’s Disability Could Explain all the Test Specimen Size Effects Observed for the Fracture Toughness (Jc) of a Material in the DBTT Region
Authors: Meshii Toshiyuki
Published: November 2015

This paper summarized our recent studies on the test specimen size (TSS) effects on Jc of a material in the ductile-to-brittle transition temperature (DBTT) region. The validity of the deterministic approach to transfer the fracture toughness Jc obtained with different thickness specimens is demonstrated in these works. Based on the detailed finite element analysis results, it was found that the crack-tip stresses were different at the identical J in the test specimen thickness (TST) effect on Jc observed with both the non-proportional and proportional specimens. And adjusting loads to make the stress level equivalent showed increment in J that was equivalent to the Jc difference due to TST effect on Jc. This was similar with the past result obtained for the planar size effect on Jc (the difference in Jc due to the planar specimen configuration including crack length difference for the same specimen type or the specimen type difference). Thus, it was concluded that all of the TSS effects on Jc could be explained as due to J’s disability to characterize the crack-tip stress field accurately, or in a more general explanation, due to the finite size effect. In addition, the (4δt, σ22c) failure criterion (Dodds et al., 1991) was verified to transfer Jcs obtained for different specimen thicknesses and planar configurations. The critical value σ22c varied for only a few percent. The fact that these critical values were always reached at the specimen mid-plane and the fact that cleavage always initiated at the specimen mid-plane supported the validity of the deterministic approach. Because the (4δt, σ22c) failure criterion requires only “single” set of test data for Jc transfer and because σ22c shows only a few percent scatter, it seems to have a possibility to replace what Weibull stress is expected to do.
Study on a New Design Fatigue Evaluation Method
Authors: Asada Seiji , Hirano Takashi , Sera Takehiko
Published: November 2015

In order to develop new design fatigue curves for austenitic stainless steels, carbon steels and low alloy steels and a new design fatigue evaluation method that is rational and has a clear design basis, the Design Fatigue Curve (DFC) subcommittee was established in the Atomic Energy Research Committee in the Japan Welding Engineering Society. Tentative design fatigue curves were developed and studies on the effects of mean stress and design factors are ongoing. Design fatigue curves, including the effects of mean stress and design factors, are needed to establish a new fatigue design evaluation method. This paper describes the study on the new fatigue design evaluation method.
The Effect of Nozzles and Nozzle Loadings on Shell Buckling
Authors: Clarke Edward , Frith Robert
Published: November 2015

This paper investigates the effect of nozzles and nozzle loadings on the overall buckling capacity of a vessel subject to external pressure designed to ASME VIII Div 1.

ASME VIII Div 1 provides a well-established design-by-rule (DBR) approach for vessels subject to external pressure, but this takes no consideration for the presence of openings or nozzles. There are empirical rules regarding nozzle reinforcement for external pressure, but these do not directly consider the buckling capacity of the overall vessel.

This paper therefore assesses the impact of nozzles on the buckling capacity of a cylindrical shell, where the nozzle is reinforced as per code requirements. The effect of reduced reinforcement is also analyzed.

Subsequently the effect of nozzle loads is also assessed. Nozzles are loaded with ‘allowable’ loads, determined using finite element analysis in accordance with industry practice and code principles.

The buckling capacities are assessed using ASME VIII Div 2 Part 5 methods, using a parametric study with over 500 models. Variables considered are vessel diameter, vessel length, nozzle diameter, and both integral and pad-reinforced nozzles are used.
Research on Hold Time Effects in Fatigue of Stainless Steel: Simulation of Normal Operation Between Fatigue Transients
Authors: Solin Jussi , Reese Sven , Karabaki H. Ertugrul , Mayinger Wolfgang
Published: November 2015

In PVP2011-57942 we reported improved endurance in fatigue tests with intermediate annealing to roughly simulate steady state operation between fatigue transients in NPP components. Quantification of this effect is in focus of our continued research on fatigue performance of niobium stabilized stainless steel (1.4550, X6CrNiNb1810mod). Similar effect is expected in nuclear power plants during normal operation — e.g. in a PWR surge line or in pressurizer spray lines.

Holds affect cyclic stress strain response. Stress amplitude, tensile mean stress and apparent elastic modulus are increased immediately after a hold, while decreased by cycles in between. Axial shortening is measured during hot holds at zero stress. This all suggest cyclic accumulation of lattice defects and recovery during holds. Recovery may occur through thermally activated dislocation migration together with diffusion, grouping and annihilation of lattice defects. More than one thermally activated processes control the rates of contraction during hold periods at elevated temperatures. Hold hardening delays crack formation by preventing plastic strain localization, in components also on macroscopic level.

A mechanism informed model is sought for transferring laboratory data to real plant components in terms of improving accuracy of numerical fatigue usage assessment. Anticipated mechanisms behind gradual changes in material responses are discussed in relation to quantitative effects of holds.
Modeling the Creep of Hastelloy X Using the Miller and Walker Unified Viscoplastic Constitutive Models
Authors: Varela J. Luis A. , Stewart Calvin M. , Gordon Ali P.
Published: November 2015

Hastelloy X is widely used in the pressure vessel and piping (PVP) industries, specifically in nuclear and chemical reactors, pipes and valves applications. Hastelloy X is favored for its resistance to extreme environments, although it exhibits a rate-dependent mechanical behavior. Numerous unified viscoplastic models proposed in literature claim to have the ability to describe the inelastic behavior of superalloys subjected to a variety of boundary conditions; typically limited experimental data is used to validate their performance. In this paper, two unified viscoplastic models (Miller and Walker) were experimentally validated for Hastelloy X creep behavior. Both constitutive models are coded into ANSYS Mechanical as user programmable features (UPF). Creep behavior is simulated at a broad range of stress levels. The results are compared to an exhaustive database of experimental data to fully validate the capabilities and performance of these models. Material constants are calculated using the recently developed Material Constant Heuristic Optimizer (MACHO) software. This software uses the simulated annealing algorithm to determine the optimal material constants by using an extensive database of experimental data. A qualitative and quantitative discussion is presented to determine the most suitable model for Hastelloy X PVP components.
Recent Developments in Chinese Glass-Lined Pressure Vessels Codes and Standards
Authors: Qiu Yan-li , Wu Xing-hua , Luo Guo-liang
Published: November 2015

This paper mainly introduced the Chinese codes and standards of glass-lined pressure vessels. The manufacture and major maintenance of pressure vessels shall be subject to supervision and inspection by the authorized inspection institutions in accordance with the safety technical codes. Design, materials, weld, nondestructive testing, glass-lined process, hydrostatic test and leak test were investigated. In addition, test specimens for calculating wall thickness, Welding Procedure Qualification and Glass-lined Procedure Qualification were analyzed. TSG R7004-2013 Regulation on Supervision Inspection for Pressure Vessel specifies Glass-lined Procedure Qualification shall be carried out before glass-lined. Glass-lined procedure qualification is used to control temperature range, heating rate, holding time, and cycle times. The glass-lined process is absolutely critical to the longevity of the glass-lined vessel.
Aerodynamic Flow Separation Control of Bridge Deck Sections Using Plasma Actuators
Authors: Matsuda Kazutoshi , Kato Kusuo
Published: November 2015

In order to suppress wind-induced vibrations of bridge girders, two general methods are applied: aerodynamic and mechanical countermeasures. In this study, a new approach to suppress wind-induced vibrations, “a dielectric barrier discharge (DBD) plasma actuator”, was investigated through wind tunnel experiments to determine its potential as a device for flow control around bridge deck sections. This approach is already in use in other fields, such as in the fluid dynamics flow control for separation control in wing surface flow. In this study, it was found that there is a possibility that DBD plasma actuators could be used in the future as the devices for suppressing wind-induced vibrations of bridge girders.
Stability of Cantilevered Pipes Subjected to Internal Flow and External Annular Axial Flow Simultaneously
Authors: Fujita Katsuhisa , Moriasa Akinori
Published: November 2015

When slender pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In the development of a piping system in the field of ocean mining, and in the field of fluid energy utilization, and so forth, the double walled pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures. In this paper, the pipe structures are assumed to be composed of the cantilevered beam structure which shows the complicated dynamic behavior than the other supported conditions. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence is added to are applied. Changing the flow direction and the fluid velocity of the internal flow and the external flow, and the specifications of modeling, the stability of the double walled pipes is investigated and discussed.
Fitness Analysis of Defects in LPG Storage Tank
Authors: Chen Zhao-he
Published: November 2015

Assessment which includes structure analysis is carried out to evaluate the fitness for service for the defects found during in-service inspection based upon the methodology of Chinese assessment standard, which exceed the acceptance criteria in construction code. In search of potential of tolerance of defect, the limit analysis is also performed. Finally, safety suggestions are provided for the future operation.
Correlation Between Transition Temperature Shifts of Impact Tests Using Standard and Subsize Specimens
Authors: Brumovsky Milan , Kytka Milos
Published: November 2015

Special weld of 15Kh2MFA (Cr-Mo-V) type steel was investigated in several laboratories within the IAEA Coordinated round robin exercise. Specimens were irradiated by several fluences and impact tests of standard Charpy size and 5×5 and 3×4 mm specimens were then tested to determine appropriate transition temperatures and their shifts.

When applied normally used criteria (impact energy, lateral expansion, ductile fracture appearance), shifts in standard specimens and subsize specimens correlate well but not in 1:1 ratio — shifts in subsize specimens were observed to be smaller than in standard ones — the smaller size of specimens, the smaller transition temperature shifts have been obtained.

The paper tries to find appropriate criteria for better correlation between shifts in different sizes of impact specimens that can be supported by proper analysis.
Fluid Compressibility Effects in Steam Hammer Analyses
Authors: Rovagnati Beniamino , Gray John H.
Published: November 2015

In the power industry, steam hammer piping analyses (and fluid transient loads) are often based on incompressible flow principles. Consequently, it is common to use either computer programs based on the Method of Characteristics for incompressible flow or simple hand calculations such as that described by E. C. Goodling (ASME PVP, Vol. 149–157, 1989). Goodling’s paper provides a simplified method to visualize and estimate transient loads resulting from stop valve closure in a main steam system. To account for compressibility effects, the calculated loads are sometimes adjusted by using a correction factor directly applied to the fluid loads with the fluid sound speed assumed constant in time and space. For example, Goodling’s paper suggests that a load increase of 5% may be used. In this paper, a sample steam hammer problem is solved using the Method of Characteristics for compressible flows, where the fluid is assumed to behave as a perfect gas. The effects of steam compressibility are then discussed. Specifically the shortening of the characteristic valve closure pressure wave length, resulting from the increasing magnitude of the sound speed as the pressure wave moves upstream from the closing valve, and resulting higher loads in straight pipe segments shorter than the pressure wave length, are then discussed. It is shown that in these shorter pipe segments fluid transient loads may almost double those calculated using the MOC for incompressible flows or the Goodling methodology (without correction factors) if the distance upstream from the closing valve is of sufficient length.
Overview of NIST Activities on Sub-Size and Miniaturized Charpy Specimens: Correlations With Full-Size Specimens and Verification Specimens for Small-Scale Pendulum Machines
Authors: Lucon Enrico , McCowan Chris N. , Santoyo Raymond L.
Published: November 2015

NIST in Boulder Colorado investigated the correlations between impact test results obtained from standard, full-size Charpy specimens (CVN) and specimens with reduced thickness (sub-size Charpy specimens, SCVN) or reduced or scaled cross-section dimensions (miniaturized Charpy specimens, MCVN). A database of instrumented impact test results was generated from four line pipe steels, two quenched and tempered alloy steels, and an 18 Ni maraging steel. Correlations between specimen types were established and compared with previously published relationships, considering absorbed energy, ductile-to-brittle transition temperature, and upper shelf energy. Acceptable correlations were found for the different parameters, even though the uncertainty of predictions appears exacerbated by the expected significant experimental scatter.

Furthermore, we report on the development of MCVN specimens for the indirect verification of small-scale pendulum machines (with potential energies between 15 J and 50 J), which cannot be verified with full-size verification specimens. Small-scale pendulum machines can now be verified at room temperature with certified reference specimens of KLST type (3 mm × 4 mm × 27 mm), supplied by NIST at three certified absorbed energy levels (low energy, 1.59 J; high-energy, 5.64 J; super-high energy, 10.05 J). These specimens can also be used to verify the performance of instrumented Charpy strikers through certified maximum force values. Certified reference values for both absorbed energy and maximum force were established by means of an interlaboratory comparison (Round-Robin), which involved nine qualified and experienced international laboratories.
Effect of Material Properties of Gasket on the Sealing Performance of Pipe Flange Connections at Elevated Temperature
Authors: Sawa Toshiyuki , Takagi Yoshio , Torii Hiroyasu
Published: November 2015

The sealing performance of the pipe flange connection depends on the compressive gasket stress. Therefore, the unexpected leakage can be avoided by estimating the change in compressive gasket stress during operation. In order to make such estimation, the material properties of the gasket are required as well as those of bolt and flange material. When the pipe flange connection is used under heated condition, the thermal expansion coefficient shows an important role. For example, if the thermal expansion coefficient of gasket is larger than that of pipe flange material, the gasket stress is expected to be increased by increasing the temperature and the sealing performance of pipe flange connection is improved. However, a gasket tends to be softening at high temperature. Beside, the creep phenomenon of gasket induces the decrease of gasket stress. Thus, the behavior of the gasket is complicated and it should be investigated to make a reliable design.

In this paper, the high temperature properties, including thermal expansion and stress relaxation property of spiral wound gasket with expanded graphite are examined by compression tests at elevated temperature. The stress analysis with high temperature material properties obtained from the compression tests also conducted to estimate the sealing performance of pipe flange connection. As a result, the pipe flange connection with spiral wound gasket is expected to keep the superior sealing performance at 300 C for long time.