bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Depression Under Heat Sources With Cylindrical Contact Thermocouples
Authors: Abbasi Kayvan , Kang Sukhvinder
Published: November 2015

The thermal performance of heat sinks is commonly measured using heat sources with spring loaded thermocouples contained within plastic poppets that press against the heat sink to measure its surface temperature where the heat is applied. However, when the thickness of the heat sink base is small or the effective heat transfer coefficient on the fin side is large, the temperature at the thermocouple contact point is less than the nearby temperature where the heat source contacts the heat sink. This temperature depression under the contact thermocouples has been studied. The heat conduction equation is solved analytically to determine the temperature distribution around the contact thermocouple using a one-dimensional approximation and also a detailed two-dimensional approach. Two dimensionless groups are identified that characterize the detailed two-dimensional solution. The combination of the two dimensionless groups also appears in the one dimensional solution. The temperature distributions are validated using finite difference numerical solutions. It is shown that the one dimensional solution is the limit of the detailed solution when one of the dimensionless groups tends to infinity. A simple equation is provided to estimate the temperature measurement error on the heat sink surface.
Analysis of Interfacial Shear Stress and Risk of Debonding in TSVs
Authors: Udupa Anirudh , Subbarayan Ganesh , Koh Cheng-Kok
Published: November 2015

Through-Silicon Vias are a key enabler of 3D technology and reliability of these structures is a source of concern. TSVs are typically made of copper and therefore have a large CTE mismatch with the surrounding Si. When subjected to a thermal load during BEOL processing, they experience stress and deform. An important reliability concern that the stress poses is the debonding of the TSV-Si interface, and has been observed experimentally. A possible reason for the debonding is the high interfacial shear stress which could potentially be singular. The authors have obtained analytical estimates of the far-field stress and protrusion in a prior work. In this work the stress singularity at the tip of the TSV-Si interface is obtained. The order of the singularity is correlated to the risk of interfacial delamination.
Mechanistic Modeling of the Anisotropic Steady State Creep Response of SnAgCu Single Crystal
Authors: Mukherjee Subhasis , Zhou Bite , Dasgupta Abhijit , Bieler Thomas R.
Published: November 2015

A multiscale modeling framework is proposed in this study to capture the influence of the inherent elastic anisotropy of single crystal Sn and the inherent heterogeneous microstructure of a single crystal SnAgCu (SAC) solder grain on the secondary creep response of the grain. The modeling framework treats the SAC microstructure as having several distinct length scales. The smallest length scale (Tier 0) consists of the Sn BCT lattice. The eutectic Sn-Ag micro-constituent, consisting of nanoscale Ag3Sn IMC particles embedded in the single crystal BCT Sn matrix, is termed Tier 1. The single-crystal SAC microstructure, consisting of Sn dendrites and surrounding eutectic Sn-Ag phase, is termed Tier 2. Dislocation recovery mechanisms, such as Orowan climb and detachment from nanoscale Ag3Sn particles, are found to be the rate controlling mechanisms for creep deformation in the eutectic Sn-Ag phase (Tier 1) of a SAC single crystal. The anisotropic secondary creep rate of eutectic Sn-Ag phase (Tier 1), is then modeled using the above inputs and the saturated dislocation density calculated for dominant glide systems during secondary stage of creep. Saturated dislocation density is estimated as the equilibrium saturation between three competing processes: (1) dislocation generation; (2) dislocation impediment caused by back stress from pinning of dislocations at IMCs; and (3) dislocation recovery due to climb/detachment from IMCs. Secondary creep strain rate of eutectic Sn-Ag phase in three most facile slip systems is calculated and compared against the isotropic prediction. At low stress level secondary steady state creep rate along (110)[001] system is predicted to be ten times the creep rate along (100)[0-11] system. However, at high stress level, secondary steady state creep rate along (110)[001] system is predicted to be ten thousand times the creep rate along (100)[0-11] system. The above predictions are in strong agreement with (1–4) orders of magnitude of anisotropy observed in steady state secondary creep response in SAC305 solder joints tested under identical loading conditions in experiments conducted by several authors. The above model is then combined with Eigen-strain methods and average matrix stress concepts to homogenize the load sharing between the Sn dendrites and the surrounding eutectic Ag-Sn matrix. The resulting steady state creep rates are predicted for a few discrete single crystal SAC305 specimens. Very good agreement is observed between the predicted steady state creep rate and the measured creep rates for two SAC305 single crystal specimens.
Modeling the Reflow Soldering Process in PCB’s
Authors: Costa João , Soares Delfim , Teixeira Senhorinha F. , Cerqueira Fátima , Macedo Francisco , Rodrigues Nelson , Ribas Luis , Teixeira José Carlos
Published: November 2015

In the present work two different types of case studies are modelled, carried out involving the fusing of a material using the CFD (Computational Fluid Dynamics) software Ansys Fluent, using the VOF method (Volume of Fluid) to capture the position of the existing interfaces and the Solidification/melting method which uses an enthalpy-porosity approach to simulate the fusion of the material.

The first case focus itself in the analysis of fusing process and dropping behavior of the melted plate in the presence of a thermal source. The validation is made using a study found in the bibliography and then using water as the melting material given that its behavior is well known. Then tin is used as the melting material followed by the use of SAC 405 as the melting plate. This study compares various materials properties and verifies the influence of some of these particular properties by changing them (surface tension and heat of fusion).

The second case focus on the simulation of a geometry obtained at balance at a constant temperature by the SAC 405 soldering alloy in the presence of a component and the copper substrate on top of a PCB.
Prognostics Health Management Model for LED Package Failure Under Contaminated Environment
Authors: Lall Pradeep , Zhang Hao , Davis Lynn
Published: November 2015

The reliability consideration of LED products includes both luminous flux drop and color shift. Previous research either talks about luminous maintenance or color shift, because luminous flux degradation usually takes very long time to observe. In this paper, the impact of a VOC (volatile organic compound) contaminated luminous flux and color stability are examined. As a result, both luminous degradation and color shift had been recorded in a short time. Test samples are white, phosphor-converted, high-power LED packages. Absolute radiant flux is measured with integrating sphere system to calculate the luminous flux. Luminous flux degradation and color shift distance were plotted versus aging time to show the degradation pattern. A prognostic health management (PHM) method based on the state variables and state estimator have been proposed in this paper. In this PHM framework, unscented kalman filter (UKF) was deployed as the carrier of all states. During the estimation process, third order dynamic transfer function was used to implement the PHM framework. Both of the luminous flux and color shift distance have been used as the state variable with the same PHM framework to exam the robustness of the method. Predicted remaining useful life is calculated at every measurement point to compare with the tested remaining useful life. The result shows that state estimator can be used as the method for the PHM of LED degradation with respect to both luminous flux and color shift distance. The prediction of remaining useful life of LED package, made by the states estimator and data driven approach, falls in the acceptable error-bounds (20%) after a short training of the estimator.
Thermal Behavior of Aluminum Alloy Metal Foam Heat Sinks: A Computational and Experimental Approach
Authors: Al-Athel Khaled S. , Aly Shahzada P. , Arif Abul Fazal M. , Mostaghimi Javad
Published: November 2015

Metal foams are structures of a cellular nature that contain a high percentage of porosity that can be produced in either a closed or open cell forms. The use of metal foams in engineering applications has increased significantly over the last decade due to their enhanced mechanical and thermal properties. An innovative approach for three-dimensional (3D) detailed finite element modeling of open cell metal foam has been taken to capture the versatile nature of metal foams’ geometry and predicting its thermal performance. The interior complex geometry of metal foams has limited studies to create computational model via common approaches. Therefore, not much computational work has been done in open cell metal foam applications. To overcome this difficulty, computed tomography (CT) scan has been used to extract the 3D structure surface model with extreme precision. Computer-Aided Design (CAD) software has been used for “stitching” and “healing” of the CT scan model before importing it to a finite element domain. The 3D computational model is used in a heat sink application and is calibrated against experimental results for the temperature distribution of one case. The validated and calibrated model is then used for simulating different metal foam heat sink cases to assess the thermal and mechanical behavior under different conditions.
Unsteady Heat Flux Measurements in Agitated Channel Flows
Authors: Agrawal Smita , Simon Terrence , North Mark , Cui Tianhong
Published: November 2015

In this experiment, agitation is used in a rectangular channel for convective heat transfer enhancement. The channel under study is representative of a flow channel in an electronics cooling finned heat sink module. It is open at one end and has a translationally oscillating plate within it that agitates the flow. Contrary to the heat sink cooling channel, the test channel has no net through-flow so that agitation, isolated from throughflow effects, is studied. The channel is divided into three regions. The entry region is close to the open end of the channel. This would be near the fin tips in the finned heat exchanger channel. The base region is close to the other end of the channel where the flow makes an abrupt U-bend around the agitator plate. This is near the fin base region of a finned channel of a heat sink heat exchanger. The central region is between the two. Each region has special flow and convective heat transfer features for study. Ensemble-averaged velocities and RMS fluctuations of velocity are measured over the cycle. Measured data lend insight into the mixing phenomena in each region over the oscillation cycle. Unsteady heat flux measurements were made in each region and over the cycle to help in understanding the mechanisms affecting heat transfer. The unsteady heat flux characteristics in the entry and base regions seem to be more influenced by the RMS fluctuations of velocity, indicating that heat transfer in these regions is governed by turbulence generated by agitation. The unsteady heat flux trends in the central region seem to be more influenced by acceleration/deceleration of the flow than by turbulence-like structures.
Effect of Flow Guide Integration on the Thermal Performance of High Performance Liquid Cooled Immersion Server Modules
Authors: Gess Joshua , Dreher Tyler , Bhavnani Sushil , Johnson Wayne
Published: November 2015

Liquid immersion cooling technology, currently in its nascence as a commercially available solution for data center installations, is growing in popularity as the power density of next-gen electronics necessitates a matriculation to thermal management techniques capable of handling incredibly high heat fluxes reliably and efficiently. The use of boiling and single-phase convective solutions using dielectric fluids can result in dramatic reductions in chip temperatures, thus increasing reliability. The latter method is growing in popularity faster than the former but, as both of these approaches gain acceptance, packaging engineers will require insight into how coolant is distributed throughout the enclosure for either solution. More specifically, analytical and experimental techniques will be required to ascertain how thermal performance and system efficiency of more critical elements, such as processor chips, are affected by the auxiliary components, heated or not, that must exist within a computing device. These supplemental components, whether entirely passive or modestly heated, if placed strategically can be integrated in such a way to improve the thermal performance of the system by guiding the coolant through the liquid filled enclosure. To this end, flow guides, which simulate these auxiliary components, have been integrated into a small form factor high performance server module. The relationship between the surface temperature and the power dissipated by the primary heated elements within the device has been explored as well as the pressure drop experienced by the coolant flowing through the enclosure. Power dissipations near 450W have been achieved at a surface temperature of approximately 75°C with the use of flow guides, a near 50W improvement over previous results. Furthermore, this value was attained at a modest pressure drop of 0.71 psi for the dielectric fluid flowing through the cartridge. Slightly over 300W of power dissipation was achieved at an even lower pressure drop of 0.13 psi at a similar operating temperature. Pool boiling results have shown that passive elements can have a significant impact on thermal performance. Reductions of nearly 50W in the maximum power dissipation achieved have been shown when the largest flow guide is integrated. A PIV analytical method is proposed and applied to the current experimental facility to assess the effectiveness of the flow guide design proposed.
LED Chip Deformation Measurement During the Operation Using the X-Ray CT Digital Volume Correlation
Authors: Lall Pradeep , Wei Junchao
Published: November 2015

A high-power LED can generate tremendous heat under the operation, which causes the LED chip undergo large deformation. LED Wire Bonds may undergo deformation because of the mismatch between the LED chip and substrate. Presently, measurements of deformation and strain in operational electronics are limited to measurement on a cut-plane using techniques including digital image correlation and moiré interferometry based techniques. There is need for tools and techniques that can help quantify the in-situ chip deformation and interconnects inside the LED. Digital Volume Correlation (DVC) has been used in conjunction with X-ray Micro-CT for three-dimensional measurement of deformation and strain in LEDs under operational stresses. The Digital Volume Correlation has been used to correlate the undeformed image with deformed images by computing correlation functions throughout each voxel. The deformed images have been generated by CT scanning over the object while the LED is operational. The correlation function computation starts at specific fixed subset window in the reference image, and searches every possible subset window in the deformed image to identify the deformation in the electronic structure. Once the displacement components have been derived, the strain components have been computed by calculating the gradients of the displacement field. In this paper, the full strain field, both in-plane and out-plane strain, will be presented, and the LED chip deformation shape will be analyzed.
Users’ Thermal Response to a Simulated Tablet Computer Surface
Authors: Zhang Han , Hedge Alan , Guo Beiyuan
Published: November 2015

It has been reported that tablet computer surface temperatures can rise from room temperature up to 47°C. Holding a warm or hot computer surface might cause user’s thermal discomfort and possibly skin burns. The use of a tablet often requires holding the device for prolonged time with multiple fingers and palm areas in contact with the tablet lower surface. Previous research has not tested whole finger/palm thermal sensation at a specific surface temperature in a moderate environmental heat range. The current research investigates user’s thermal sensations on the palm and fingers, in response to warm/heat stimuli in a tablet size device with a longer contact duration than used in previous studies, to provide ergonomic design guidelines for electronic device designers and manufacturers. A tablet-size heating surface was developed comprising of nine rectangular aluminum heating pads connected with computer-controlled heaters and thermal sensors. Participants were asked to report their finger/palm thermal sensation and comfort every 45 seconds when they held the prototype for 90 seconds. Results showed a positive linear relationship between surface temperature and user’s thermal sensation and thermal discomfort. Duration of holding the prototype had no significant effect on user’s thermal comfort, but it did significantly affect thermal sensation ratings.
Design of 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 research of the key equipment which is diverless full structure permanent pipeline repair clamp in the technology has just started. The main components which contain the main body, axial seal, circumferential sealing module, the tighten flange, tension slips and sacrificial anode, and the design principles of the diverless full structure permanent pipeline repair clamp are introduced in detail. The processes of repair work used in subsea oil and gas pipeline clamp are elaborated. What it expected is to lay technology foundation for breaking through the blockade of foreign technology, and the development of independent intellectual property rights of diverless full structure permanent pipeline repair clamp.
Hyper Compressor Revamp Procedures to Extend MTBM
Authors: Lankenau Harry , Damberg Stefan , Wagner Bernd
Published: November 2015

The LDPE process involves an extremely high gas pressure in the range of 200 to 300 MPa (2000 to 3000 bar / 29 to 44 kpsi) being provided by so called Hyper compressors. Many of the old machines are still in operation and kept fit for purpose since they still render good service and maintenance costs are well acceptable versus the investment for a new unit. Legacies have been taken over by others if the original OEM does no longer exist.

The Hyper compressor cylinder performance is very much associated with the special arrangement of the frame, and the operation implies a perfect movement of the plungers to reduce radial loads on the packing internals to a minimum. High accuracy alignment procedures are therefore of the essence to obtain the best life of the packings and the driving gear.

Despite their substantial size and mass the manufacturing tolerances, internal gaps and clearances — particularly for the bearings and crosshead guides — are within the 1/100 mm (0.4 mil) range. As practiced for decades for old Hypers the crosshead shoes are still today scraped by hand to make them perfectly fit into their guide.

On the other hand modern laser technique has proven to be the appropriate equipment to ensure the proper quality for the refurbishment of all parts and pieces. The application of such technique — both in the workshop as well as in the field — increases the accuracy of complicated assemblies and also, since laser measurement is quick, reduces down time tremendously.

Last not least carefully followed check list procedures for condition verification provide the best achievable MTBM (Mean Time between Maintenance).

This paper outlines particular focus points of a Hyper to keep it smoothly running for a long time.
Compressor General Arrangement Dynamic Design Guided by Preliminary Cylinder Manifold Forced Response
Authors: Passeri Marco , Bagagli Riccardo , Maggi Carmelo
Published: November 2015

Today market requires machinery with ever larger performance increasing compression system vibrations risks. Knowledge of dampers pulsation-forces phenomena and best practices allows their minimization. Loads acting on foundation are early defined allowing a proper design, while “Cylinder-Gas-loads” depending upon compressor data-sheet cannot be adjusted unless to change requirements. Considering their high amplitudes and frequencies spectrum, some exciting frequencies often coincides with system mechanical natural frequencies.

This involves expensive efforts in preliminary Cylinder Manifold response studies to guide compressor General Arrangement design. Specific software that includes Compressor standard elements selection and that allow building dampers by parametric inputs is cost effective in model creation. Together with the cost benefits it facilitates the designer to simulate multiple configurations rebuilding the model in a short time and exploring several solutions to optimize the system vibration control.

A FEM specialist is not required for the Model build-up, the Software allow automatically applying cylinder gas loads, run analysis and compare results vs allowable ones. In case of allowable limits exceeding or design changes, G&A Designer can easily change input and iterate the loop till satisfactory results are achieved in a timely and quality manner, optimizing dampers and supports.
Development of a Contactless Measurement Method Using an LED-Optical Displacement Sensor for Vibration Stress of Piping Systems
Authors: Maekawa Akira , Tsuji Takashi , Takahashi Tsuneo
Published: November 2015

The present paper proposes an efficient contactless measurement method for vibration stress of piping systems, by which the measurement tasks are performed within an extremely short time and the measured stress can be evaluated immediately after the measurement. The proposed method includes two processes, in which the bending shape of a pipe induced by vibration response is identified by a transmission-type optical displacement sensor and the vibration stress is calculated based on beam theory using the curvature radius estimated by approximating the bending shape. The proposed method uses only one LED-optical sensor to measure the vibration stress though multiple sensors must be used in the previous method developed by the authors. Therefore, the measuring system could be reduced in size and a light-weight and portable measurement instrument was developed. The measurement accuracy and reliability of the new method were verified by the vibration experiment using a mock-up piping system.
Validation of ACE Analytical Criterion for Warm Pre-Stress Evaluation in RPV Integrity Assessment
Authors: Moinereau Dominique , Landron Caroline , Chapuliot Stéphane , Marie Stéphane
Published: November 2015

Numerous experimental and numerical studies have been conducted in France to demonstrate the beneficial effect of warm pre-stress (WPS) on the brittle fracture resistance of reactor pressure vessel (RPV) steels and take into account this effect in French RPV integrity assessment. A large panel of experimental data is available, obtained on small, medium and large scale specimens. These data have been included in a specific EDF WPS experimental database.

An analytical criterion — ACE criterion — is proposed by French organizations (AREVA, CEA and EDF) for analytical evaluation of warm pre-stress effect on the brittle resistance of RPV steels.

After a description of ACE criterion and the EDF WPS database, the validation of the criterion is shown — based on this database — by comparison between experimental results and predictions of the model.
Proposed Changes to the ASME Boiler and Pressure Vessel Code Section III Appendix N for Flow-Induced Vibrations
Authors: Banyay Gregory A. , Meyer Gregory A. , Walker Adam P.
Published: November 2015

This article outlines changes proposed for implementation in the ASME Boiler and Pressure Vessel Code Section III Appendix N pertaining to Flow-Induced Vibrations (FIV). Several portions of Appendix N were originally written multiple decades ago and are not necessarily readily prescriptive for present-day analyses. An ASME Task Group on Flow-Induced Vibrations has been formed to identify areas of improvement to Appendix N so that the Appendix may be more useable in present-day FIV analyses, and a means of establishing consensus for characterization of this complex phenomena. This paper identifies opportunities for improvement to portions of Appendix N pertaining to Turbulence, Acoustic, and associated Structural Dynamic Modeling, and Data Processing.

Specific suggestions are made for the following: Characterization of acoustic damping and acoustic harmonic responses, updated considerations for aeroacoustic phenomena, structural damping quantification of nuclear components, systematic approaches to modeling (random) turbulence-induced vibrations (including RMS-to-Peak ratio), considerations for leakage flow-induced instabilities, and opportunities to employ computational methods are discussed. Opportunities for the applicability of data processing algorithms such as the proper orthogonal decomposition and circumferential wavenumber decomposition are also discussed and an updated methodology for combination of random and deterministic loads for FIV analyses is presented.
The Effects of Thermal Aging on Microstructural and Mechanical Properties of GH3535 Alloy Welded Joint
Authors: Shuangjian Chen , Chaowen Li , Kun Yu , Zhijun Li , Zhou Xintai , Zhong Li
Published: November 2015

Ni-Mo-Cr alloys are the main structure materials for the Thorium molten salt reactor. In order to investigate the properties of welded joints of Ni-Mo-Cr alloy under long-term elevated temperature service, mechanical behavior and microstructure of joints aged at 650°C for 250h, 500h, 1000h, 2000h and 4000h were studied. Optical microscopy and scanning electron microscopy were used to study the effects of aging time on the grain size and carbides. Meanwhile, hardness, strength and fracture morphology of welded joints were also analyzed. In this study, the eutectic was observed in the weld metal and heat affected zone. The grain sizes of base metal of welded joints under different aging time were steady at 100μm approximately. Hardness test of welded joints indicated a slight climbing trend by increasing of aging time. The results of tensile test showed that the performance of welded joints after aging was better than that of as-welded joint and increased by growth of aging time, it was stable for the mechanical properties of aged welded joints in long term aging for up to 4000h as well. Moreover, the fracture morphology and the mechanism were observed by mean of SEM, the main fracture mechanism was ductile fracture for all the joints under different aging time. The second phase precipitations with increasing of aging time were the main contributing factor to enhance of mechanical properties.
Study on a Countermeasure Using Walls Made of Perforated Plate for High Level Sound
Authors: Ishihara Kunihiko , Nakaoka Masanori
Published: November 2015

Vortices occur when gas flow passes through a duct with a tube bank of heat exchangers, such as a gas heater and/or a boiler. Very high level noise called a “self-sustained tone” occurs due to the interference of the vortices and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions are vague. Then, perforated plates are used in both sides of the duct walls to suppress the self-sustained tones. Because we thought that the perforated plate might have acoustic damping and resonance mode of the duct perpendicular direction to the flow may be suppressed by its damping effect, when the self-sustained tone occurred. Some experiments were carried out to examine the suppression effect of the perforated plates installed. As a result, the suppression effect appeared in all cases. The purpose of this study is to clarify the effectiveness of the perforated plates for self-sustained tones.
Phase-Lag-Induced Fluctuating Lift Forces on Two Tandem Bluff Bodies
Authors: Alam Md. Mahbub , Zhe Ma
Published: November 2015

A numerical simulation at a Reynolds number Re = 200 is conducted to find how flow-induced forces on two tandem circular cylinders is connected to the phase lag between vortex sheddings from the cylinders. The spacing ratio L* (= L/D) is varied from 2 to 9, where L is the cylinder center-to-center spacing and D is the cylinder diameter. Here we mainly focus on fluctuating lift coefficient CLf of the upstream cylinder, vortex dynamics in the gap between cylinders, and phase lag ϕ between the vortex sheddings from the two cylinders for L* larger than the critical where the co-shedding flow prevails. ϕ is indeed nonlinear function of L*, Strouhal number (St) and convection velocity of vortices in the gap between the cylinders. We unearth that the upstream cylinder CLf is affected by both L* and ϕ. While the contribution of L* to CLf diminishes rapidly with L*, that of ϕ makes the L*-dependent CLf variation damped-sinusoidal, persisting in the L* range examined. The inphase and antiphase flows respectively correspond to a local maximum and minimum CLf. How CLf is correlated with L* and ϕ can be deduced as,

C L f = A e −α L * + B e −β L * sin ϕ + π 2 + C ,

where A, α, B, β and C are constants. The physics behind the damped-sinusoidal variation in CLf is discussed.
Experimental Investigation of Landing Light Orientation on Landing Gear Noise
Authors: Salt Eric , Arezina Marko , Lepore James , Ziada Samir
Published: November 2015

A simplified model of a landing gear is tested in a wind tunnel to investigate the effect of the landing light orientation on the resulting noise generation. Examination of the near-field pressure fluctuations, combined with phase-locked stereoscopic particle imaging velocimetry (SPIV) of the unsteady wake identified two distinct sources of pressure fluctuations. The higher frequency source has a wide frequency band and is situated in the outer regions of the wake near the lights. However, the lower frequency source is found to be stronger, has a narrower frequency band, and is developed further downstream in the wake, closer to the wake centerline. The lower frequency source is observed to be rather robust as it is hardly affected by the orientation of the landing lights, whereas the higher frequency source becomes weaker as the distance between the lights is reduced. The effect of a splitter plate positioned downstream of the strut is also investigated as a means of disrupting the lower frequency pressure fluctuations. Although the lower frequency source is considerably reduced by the splitter plate, substantial enhancement of the higher frequency source is observed.
EDF/NRC High-Cycle Fatigue Database Proposal
Authors: Métais T. P. , Stevens G. , Blatman G. , Le Roux J. C. , Tregoning R. L.
Published: November 2015

Revised fatigue curves for austenitic stainless steels are currently being considered by several organizations in various countries, including Japan, South Korea, and France. The data available from laboratory tests indicate that the mean air curve considering all available austenitic material fatigue data may be overly conservative compared to a mean curve constructed from only those data representative of a particular type of material. In other words, developing separate fatigue curves for each of the different types of austenitic materials may prove useful in terms of removing excess conservatism in the estimation of fatigue lives.

In practice, the fatigue curves of interest are documented in the various international design codes. For example, in the 2009 Addenda of Section III of the ASME Boiler and Pressure Vessel (BPV) Code [1], a revised design air fatigue curve for austenitic materials was implemented that was based on NRC research models [2]. More recently, in Japan, various industrial groups have joined their efforts to create the Design Fatigue Curve Sub-committee (DCFS) with the objective to reassess the fatigue curves [3]. In France, EDF/AREVA and CEA are developing a new fatigue curve for austenitic stainless steels [4]. More specifically, in 2014, EDF presented a paper on high-cycle fatigue analysis which demonstrated that the factor on the strain amplitude could be reduced from 2 to 1.4 for the RCC-M austenitic stainless steel grades [5].

Recently, discussions between EDF and the U.S. Nuclear Regulatory Commission (NRC) have led both parties to recognize that there is a need to exchange worldwide research data from fatigue testing to promote a common, vetted database available to all researchers. These discussions have led EDF and NRC to pursue a collaborative agreement and associated fatigue data exchange, with the intent to assemble all available fatigue data for austenitic materials into a standardized format. The longer term objective is to perform common analyses on the consolidated set of data.

This paper summarizes the intent and of the preliminary results of this cooperation and also provides insights from both organizations on possible future activities and participation in the global exchange of fatigue research data.
New Classification Assessment Rule for Defects Fitness
Authors: Chen Zhao-he
Published: November 2015

Based upon three typical materials and metrology stipulated in GB/T 19624, a new classification assessment rule for defects which exceed the acceptance criteria in construction code is given, which includes three levels depending upon the information acquired during assessment. Following its implementation into in-service inspection projects, the compliance with normal assessment can be attained without much effort.
Overview of French Proposal of Updated Austenitic SS Fatigue Curves and of a Methodology to Account for EAF
Authors: Métais Thomas , Courtin Stéphan , Genette Pierre , De Baglion Laurent , Gourdin Cédric , Le Roux Jean-Christophe
Published: November 2015

Environmentally Assisted Fatigue is receiving nowadays an increased level of attention not only for new builds but also for the installed bases which are currently having their lives extended to 60 years in various countries. To formally integrate these effects, some international codes have already proposed code cases. More specifically, the ASME code has used the NUREG/CR-6909 [1] as the basis for Code Case N-792 [2] and suggests a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which is to be multiplied by the usual fatigue usage factor.

The various methodologies proposed are not finalized and there is still a significant level of discussion as can be illustrated by the recent update of NUREG/CR-6909 [3]. In this context, EDF, AREVA and the CEA have also submitted two RCC-M Rules in Probatory Phase (RPP) (equivalent to ASME code-cases) to AFCEN to propose respectively an update of the fatigue curve for austenitic stainless steels and a methodology to incorporate EAF in fatigue evaluations.

The approach is globally similar to the one in the ASME code: it consists in an update of the mean air and design fatigue curves as well as the calculation of an environmental penalty factor. Nevertheless, the methodologies differ in their detailed implementation by especially introducing the Fen-integrated which accounts for the environmental effects already covered by the fatigue curves. This paper is the sequel to the proposal already described in [4] [6].
Enhancing Trapezoidal Threads Using a Parametric Numerical Approach
Authors: Galle Timothy , De Waele Wim , De Baets Patrick
Published: November 2015

A parametric program designed for modeling tapered, trapezoidal threaded connections is used in combination with Abaqus to investigate the behavior of couplings subjected to static load combinations containing make-up, axial tension and internal pressure. Three criteria are defined and used to quantify the performance of the connection: load distribution, helical gap size between the threads and the amount of global plasticity. From these parameters, the load distribution provides valuable information about the effectiveness of the load bearing characteristics of the thread and can be used to detect possible overstressing of the connection. The helical gap size is used to estimate its tendency to provide a leak tight thread seal, while the global plasticity reflects the total amount of plastic deformation within the connection. During the investigation, the effects of taper angle, load flank angle, wall thickness, size of threads and initial thread clearance are considered. The presented modeling approach consists of three parts. First, the optimal make-up position for a trapezoidal threaded 4.5 inch TN80 connection is calculated using the plasticity criterion. Next, the results for the three performance parameters as a function of both axial tension and internal pressure are discussed. Finally, after investigating the various isolated effects induced by geometric changes, a newly defined, enhanced threaded geometry is suggested and compared with the standardized API-buttress thread.
Industry’s First NRC Approved Appendix L Flaw Tolerance Evaluation to Manage Fatigue in a Surge Line
Authors: Gilman Timothy D. , Alleshwaram Aparna , Satyan-Sharma Tirumani
Published: November 2015

Appendix L flaw tolerance was incorporated into ASME Section XI as an alternative approach for addressing fatigue and to justify period extended operation (PEO) of nuclear power plants to 60-years or beyond. A flaw tolerance analysis consists of performing a baseline inspection of the component to verify absence of a flaw, and then determining that a postulated flaw, initially sized at the detection threshold of the inspection, will not grow to the critical crack size by the time of the next inspection. For license renewal, the U.S. Nuclear Regulatory Commission (NRC) expects consideration of reactor water environmental effects in the postulated crack growth laws for any Appendix L evaluation. However, these environmental effects for austenitic stainless steel components have not yet been incorporated into the ASME Code. This paper describes the overall techniques that were used to successfully perform a flaw tolerance evaluation for a pressurizer surge line piping system. This was the first flaw tolerance evaluation to have been submitted and approved by the NRC as an acceptable approach for managing environmentally-assisted fatigue in the period of extended operation.
Computational Methods to Support Brittle Fracture Assessment of PSVs Involving Autorefrigeration
Authors: Subramanian Kannan , Penso Jorge , Pordal Harbi
Published: November 2015

Pressure safety relief valve (PSV) operation generally leads to cooling of the valve itself and the piping connected to the PSV. The temperatures may reach values below the minimum design metal temperature (MDMT) of the valve, and therefore the valve needs to be assessed for brittle fracture susceptibility. Simplistic determination of the minimum metal temperature in the valve may disqualify these valves during the brittle fracture assessments (BFA). Replacement may be time consuming and may not be cost effective. In such circumstances, a sophisticated and more representative BFA approach involving the use of computational fluid dynamics (CFD) followed by finite element method (FEM) based stress analysis which may be further followed by fracture mechanics can be adopted based on the concepts defined in ASME/API 579.

The accuracy of the BFA depends on the accuracy of each of the computational method involved in the assessment. Among all the computational methods, CFD poses significant challenge. The low temperature may have been caused due to Joule-Thompson effect or auto-refrigeration. While Joule-Thompson effect can be best captured with easy to implement and robust CFD methods, auto-refrigeration involving adiabatic flashing which causes additional complexity and requires multiple sensitivity studies performed to determine the accuracy of the CFD approach. In this paper, an overview of the computational methods used in the brittle fracture assessment of PSVs is presented. Specific CFD method details are provided for PSV involving the flashing of liquid hydrocarbon to vapor is presented in the form of a case study derived from downstream industry application.
Effect of Cavity Volume on the Flow-Excited Acoustic Resonance of a Shallow Cavity in a Pipe-Line
Authors: Mohamed S. , Ziada S.
Published: November 2015

The effect of cavity volume on the aeroacoustic source generated by fully developed pipe flow through an axisymmetric shallow cavity is investigated experimentally. Nine cavity sizes are studied in three different groups of length, L, to depth, H, ratios (L/H = 1, 2 and 3) with three different cavity volumes for each group of L/H. The Sound Wave Method (SWM) is used to measure the aeroacoustic sources as function of the Strouhal number. This methodology does not require knowledge of the details of the unsteady flow-sound interaction in the cavity region because it considers the cavity as a black box with a dipole sound source or sink. The aeroacoustic source strength and the Strouhal number corresponding to its maximum value are found to increase in a systematic manner as the cavity volume is increased for the same L/H ratio. These results indicate that the aeroacoustic sources of shallow cavities are affected not only by the ratio L/H, but also by the cavity volume.
Low Cycle Fatigue Behavior in Air and in PWR Water of Type 304L and 316L Austenitic Stainless Steels Manufactured by Hot Isostatic Pressing Process
Authors: De Baglion Laurent , Cedat Denis , Ould Pascal , Chitty Walter-John
Published: November 2015

Because “safety” is still the key point in the Nuclear industry, more than in any others, the use of new materials or new manufacturing methods is really challenging. Among many characterizations required for a new steel grade or a new manufacturing process to be accepted and then introduced in a Nuclear design code, the fatigue properties must be determined with great care.

Nowadays, the consideration of the Pressurized Water Reactor (PWR) primary water environment effect on the Low Cycle Fatigue (LCF) behavior of Austenitic Stainless Steels (ASS’s) is an important issue for both Nuclear Power Plants (NPP) lifetime extensions and new builds as described in the NUREG/CR-6909 [1], [2].

This paper aims to present the LCF behaviors in air and in PWR water at 300°C of type 304L and 316L ASS’s manufactured by Powder Metallurgy coupled with Hot Isostatic Pressing process (PM/HIP) and to compare them with those observed on usual ASS nuclear grade products [3]-[6].

As already introduced in our previous paper [7] dedicated only to the PM/HIP 304L steel fatigue behavior, it appears that the microstructures, mechanical properties and LCF behaviors in air and in PWR water of both type 304L and 316L steels manufactured by PM/HIP process are better or at least similar to those observed on wrought ASS’s.
Comparison of the Stress Intensity Factor Influence Coefficients for Axial ID Surface Cracks in Cylinders of RSE-M and API 579-1
Authors: Le Delliou Patrick , Chapuliot Stéphane
Published: November 2015

Analytical evaluation procedures for determining the acceptability of flaw detected during in-service inspection of nuclear power plant components are provided in Appendix 5.4 of the French RSE-M Code. Linear elastic fracture mechanics based evaluation procedures require calculation of the stress intensity factor (SIF). In Appendix 5.4 of the RSE-M Code, influence coefficients needed to compute the SIF are provided for a wide range of surface axial or circumferential flaws in cylinders, the through-wall stress field being represented by a cubic equation. On the other hand, Appendix C of API 579-1 FFS procedure provides also a very complete set of influence coefficients.

The paper presents the comparison of the influence coefficients from both documents, focused on axial ID semi-elliptical surface flaws in cylinders. The cylinder and crack geometries are represented by three ratios: Ri/t, a/t, and a/c, where Ri, t, a, and c are respectively the inner radius, the wall thickness, the crack depth and one-half of the crack length. The solutions for the coefficients G0 and G1 at the deepest point and at the surface point are investigated.

At the deepest point, the agreement between the solutions is good, the relative difference being lower than 2 %, except for the plate (Ri/t = ∞) at a/c = 0.125 and 0.0625 and a/t = 0.8 (around 5 %). At the surface point, the agreement between both solutions is not so good. At this point, the relative differences depend strongly on the a/c ratio, being larger for elongated cracks (with low a/c ratios). However, it must be recalled that the absolute values of the coefficients are low at the surface point for elongated cracks, and that for these cracks the critical point regarding the stress intensity factor is the deepest point.
Analysis of Powder Airborne Release Fractions for Vessel Ruptures
Authors: Laurinat James E. , Hensel Steve J.
Published: November 2015

The Department of Energy handbook for airborne releases from nonreactor nuclear facilities bases its bounding airborne release fraction (ARF) for pressurized powders on tests conducted at Pacific Northwest Laboratory (PNL). An analysis is presented that correlates the ARF from these tests. The amount of powder that becomes airborne is correlated in terms of an adjusted airborne release fraction (AARF) equal to the product of the powder entrainment from the powder bed and the ratio of the total vessel volume to the volume occupied by the powder bed. Powder entrainments and release fractions at low pressures are correlated using a fluidized bed analogy. The analysis shows that the entrainment is enhanced by a sonic shock if the pressure prior to the rupture exceeds approximately 33 psig. A secondary, three-dimensional shock is predicted to occur at an initial pressure of approximately 332 psig. A correlation based on this analysis is used to predict the ARF for ruptures of vessels containing plutonium oxide. It is assumed that the oxide is pressurized by hydrogen that is radiolytically generated from adsorbed moisture.
Simulation of Creep Deformation and Rupture of Notched Bar Specimens of Grade 92 Steel
Authors: Shigeyama Haruhisa , Takahashi Yukio , Parker Jonathan
Published: November 2015

Creep strain equations of Grade 92 steel which is used in boilers and piping systems of ultra-supercritical (USC) thermal power plants were developed based on the results of creep tests on smooth round bar specimens of three kinds of Grade 92 steels. In these equations, primary creep behavior was represented by a power-law and tertiary creep behavior was described by an exponential function. Creep parameters were determined as a function of creep rupture times which were calculated from stress and absolute temperature. Additionally, generalized creep failure criteria considering the multiaxial stress were established on the basis of results of creep tests on circumferentially notched round bar specimens. These creep strain equations and creep failure criteria were incorporated into finite element analysis software. Then, creep failure analyses were carried out and the resulting deformation behavior and rupture times were compared with the experimental results. Creep rupture lives were predicted with a good accuracy, within a factor of two in most cases.