bluuebunny/crossref_metadata_2025 huggingface dataset:
Wavelet Analysis of FIV Response for Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side
Authors: Neumeister Roberta Fátima , Petry Adriane Prisco , Möller Sergio Viçosa
Published: November 2019

Flow induced vibration of a single cylinder and two cylinders assembled in the configurations tandem and side-by-side are experimentally investigated in the present study. The rigid cylinder free to vibrate is fixed in two blades, forming two different configurations, to allow transversal and longitudinal vibration, respectively. The mass ratio, m* ranged between 158 and 643 while the damping ratio, ζ, ranged between 0.0006 and 0.005. The pairs of cylinders present a space ratio of 1.26 (P/D and L/D) and one of the cylinders is fixed while the second one is free to vibrate. The aerodynamic channel used in the analysis presents test section with 0.146m height and 0.193m width, the study is executed using accelerometer and hot wire anemometry. The velocity on the test section is varied and generates reduced velocity, Vr = U/fnD, between 4 and 30. The displacement amplitudes, Y/D, are obtained using integration of the acceleration signals, and the root mean square results are adopted. Fourier spectral analysis and continuous wavelets are employed in the analysis of acceleration and velocity signals. The higher amplitudes happen in two distinct reduced velocities and were associated with the vibration modes of the cylinder free to vibrate. In the case with two cylinders side-by-side the amplitude is higher and present small variation on the reduced velocity of occurrence in comparison with single cylinder. For the case with cylinders in tandem the presence of the cylinder in the wake of the cylinder free to vibrate generated amplification of the response in high reduced velocities.
Use of Engineered Materials to Reduce Both Strainer Head Loss and Fiber Bypass for Emergency Core Cooling Systems
Authors: Bilanin Alan J. , Kaufman Andrew E. , Bilanin Warren J.
Published: November 2019

Testing has shown that the use of engineered materials that can be combined with Loss of Cooling Accident generated debris has the ability to reduce debris head loss for boiling water and pressurized water reactors on Emergency Core Cooling System strainers. This engineered material has also been shown to reduce the amount of fiber that penetrates a strainer and continues downstream toward the fuel. Large scale testing is described that demonstrates that engineered materials can reach the strainers and reduce head loss. Small scale testing is described that demonstrates that engineered material can reduce the amount of fiber that can penetrate a strainer.
Adjusted J-R Toughness Curve for Pipes Using J-A2 Crack Constraint of CT Specimens and 3D Crack Meshes
Authors: Thorwald Greg , Bagnoli Ken
Published: November 2019

The objective of this paper is to use two-parameter fracture mechanics to adjust a material J-R resistance curve (i.e. toughness) from the test specimen geometry to the cracked component geometry. As most plant equipment is designed and operated on the “upper shelf”, a ductile tearing analysis may give a more realistic assessment of flaw tolerance. In most cases, tearing curves are derived from specimen geometries that ensure a high degree of constraint, e.g., SENB and CT Therefore, there can be significant benefit in accounting for constraint differences between the specimen geometry and the component geometry.

In one-parameter fracture mechanics a single parameter, K or J-integral, is sufficient to characterize the crack front stresses. When geometry dependent effects are observed, two-parameter fracture mechanics can be used to improve the characterization of the crack front stress, using T-stress, Q, or A2 constraint parameter. The A2 parameter was be used in this study.

The usual J-R power-law equation has two coefficients to curve-fit the material data (ASTM E1820). The adjusted J-R curve coefficients are modified to be a function of the A2 constraint parameter. The measured J-R values and computed A2 constraint values are related by plotting the J-R test data versus the A2 values. The A2 constraint values are computed by comparing the HRR stress solution to the crack front stress results of the test specimen geometry using elastic-plastic FEA. Solving for the two J-R curve coefficients uses J values at two Δa crack extension values from the test data. A closed-form solution for the adjusted J-R coefficients uses the properties of natural logarithms. The solution shows the adjusted J-R exponent coefficient will be a constant value for a particular material and test specimen geometry, which simplifies the application of the adjusted J-R curve.

A different test specimen geometry can be used to validate the adjusted J-R curve. Choosing another test specimen geometry, having a different A2 constraint value, can be used to obtain the adjusted J-R curve and compare it to the measured J-R curves.

The geometry of the component is also expected to have a different A2 constraint compared to the material test specimen. The example examined here is an axial surface flaw in a pipe. The A2 constraint for an axial surface cracked pipe is computed and used to obtain an adjusted J-R curve. The adjusted J-R curve shows an increase in toughness for the pipe as compared to the CT measured value. The adjusted J-R curve can be used to assess flaw stability using the driving force method or a ductile tearing instability analysis.
Towards Understanding Two-Phase Flow Induced Vibration of Piping Structure With a U-Bend
Authors: Bamidele Olufemi E. , Ahmed Wael H. , Hassan Marwan
Published: November 2019

The current work investigates two-phase flow induced vibrations in 90° U-bend. The two-phase induced vibration of the structure was investigated in the vertical, horizontal and axial directions for various flow patterns from bubbly flow to wavy and annular-dispersed flow. The void fractions at various locations along the piping including the fully developed void fraction and the void fraction at the entrance of the U-bend were fully investigated and correlated with the vibration amplitude. The results show that the excitation forces of the two-phase flow in a piping structure are highly dependent on the flow pattern and the flow conditions upstream of the bend. The fully developed void fraction and slip between phases are important in modelling of forces in U-bends and elbows.
Towards a Viable Field Deployable Ultrasonic Technique for Detection of Type IV Creep Damage in CSEF Steels at an Early Stage
Authors: Kumar Harendra , Lambert Jack W. , Nageswaran Channa , Nadendla Hari Babu , Gan Tat-Hean
Published: November 2019

It is now apparent that welds in many of the creep strength enhanced ferritic (CSEF) steel grades are susceptible to Type IV creep damage. Furthermore, due to the complex nature of incubation and growth of localized creep damage in such alloys, state-of-the-practice non-invasive techniques such as hardness, replication and strain measurement alone are insufficient for reliable assessment. Consequently, there is concern in the industry regarding the integrity of existing and proposed installations that utilize CSEF steels such as ASME Grade 91 and Grade 92. To address this concern, in addition to pressing demands for increased efficiency and from environmental regulation, extensive research is underway on various fronts including fracture assessment, online health monitoring and life extension technologies. These rely heavily on the effectiveness of non-destructive testing (NDT) techniques. Therefore, volumetric non-invasive techniques that enable detection and characterization of damage are sought to facilitate effective assessment of welded components operating at high temperature and pressure.

Several NDT methods were reviewed in order to understand the current state-of-the-art in terms of their sensitivity to early stage Type IV damage and their readiness for field implementation. Most of the advanced methods proposed for assessment of creep damage are based on the inversion of certain parameters to correlate to the extent of damage. This limits their selectivity, ability to characterize and determine the severity of localized damage. Using recent developments in electronics and signal processing instrumentation, ultrasonic testing was identified as having the potential to be developed as a reliable approach for detection of Type IV creep damage at an early stage.

This paper presents the outcome of an industry-focused research effort with the goal of developing and validating an ultrasonic technique for reliable detection of Type IV creep damage at an early stage. In this framework, supported by the Core Research Programme at TWI, an ultrasonic technique was developed and tested on a number of creep-exposed specimens. Ultrasonic data was processed and correlated with controlled metallographic investigations to determine the detection, positioning and characterization performance of Type IV creep damage within the heat affected zone of welds.
Investigations of In-Plane Fluidelastic Instability in a Multi-Span U-Bend Test Rig: Tests in Two-Phase Flow
Authors: Feenstra Paul , Sawadogo Teguewinde , Smith Bruce , Janzen Victor , McLellan Anne , Cothron Helen , Kil Sean
Published: November 2019

Tests to study FluidElastic Instability (FEI) in an array of U-bend tubes were recently completed in the Multi-Span U-Bend (MSUB) test rig at Canadian Nuclear Laboratories (CNL). These tests were sponsored by the Electric Power Research Institute (EPRI) and were designed to study In-Plane (IP or streamwise) FEI of steam generator tubes in two-phase cross flow. This instability mechanism was first observed in previous research tests by Atomic Energy of Canada Limited (AECL). Although AECL planned additional research into IP FEI, this mechanism was not thought to be a serious practical concern until it recently caused severe damage to tubes in a new replacement steam-generator. The MSUB tests were conducted both with flows of air and two-phase liquid/vapour Refrigerant 134a. With 22 flexible U-bend tubes supported by a configurable flat-bar arrangement, the tests were focused on the effects of support geometry and tube-to-support interaction. Data was recorded from 33 dynamic signals from accelerometers, displacement probes, force transducers, and void-fraction probes. The paper describes the experimental test setup and reviews some of the initial test results and their implications for steam-generator users and researchers. Tests with two-phase Freon refrigerant (R-134a) are presented here.
Technical Basis for Maximum Allowable Indentation Depths in HDPE Pipes for Proposed ASME Section III Code Case on Alternative Requirements to Appendix XXVI for Inspection and Repair
Authors: Scarth Douglas , Krishnaswamy Prabhat , Rush Phillip , Munson Douglas
Published: November 2019

Mandatory Appendix XXVI of Section III of the ASME B&PV Code contains rules for the construction of Class 3 polyethylene pressure piping systems. The scope is limited to buried portions of Class 3 service water or buried portions of Class 3 cooling water systems, consisting of PE4710 High Density Polyethylene (HDPE) materials. The minimum Pennsylvania Notched Test (PENT) rating for the HDPE material is 2,000 hours. Appendix XXVI contains acceptance standards for the maximum allowable depths of gouges, cuts or other surface conditions that are characterized as indentations. The acceptance standards are considered to be very restrictive, in particular for large diameter HDPE pipes. Less restrictive maximum allowable indentation depths for pipes with a minimum PENT rating of 2,000 hours were developed based on use of results from tests performed on pressurized HDPE pipes containing flaws in the parent material. These maximum allowable indentation depths were implemented into the new Section III Code Case N-891 on alternative requirements to Appendix XXVI for inspection and repair. The technical basis for the maximum allowable indentation depths is described in this paper.
A Flexible Tool for Modeling Thermal Loading in Printed Circuit Heat Exchangers
Authors: Jentz Ian W. , Anderson Mark H.
Published: November 2019

Compact and thermally efficient, Printed Circuit Heat Exchangers (PCHEs) are favored for use in next generation nuclear power plants. Containing thousands of small working fluid channels distributed in a solid 316H or 800H block, PCHEs can handle high pressures and operating temperatures required by generation IV nuclear plants. Advanced nuclear reactors will require the certification of a nuclear service PCHE design by construction codes, such as BPVC Sec-3. Compliance with this standard requires Creep fatigue and ratcheting analyses be performed for expected loading service transients. Realizing this analysis in PCHEs requires a simplified and flexible modeling approach that can be run over dozens of transients for multiple heat exchanger geometries. The Rich Environment Heatex-changer Transient (REHT) model is being developed to provide a full PCHE model needed to properly resolve Sec-3 loading conditions without the complexity inherent in resolving all facets of the PCHE geometry. This work introduces the thermohydraulic model that is the core of the REHT model. An example problem modeling an experimental scaled PCHE is presented. The ability of the REHT model to simulate fluid flow through a directional varying microchannel core of two heat exchanging streams is demonstrated. The REHT model resolves PCHE thermohydraulics using simple model definitions and minimum computational overhead, making it an ideal design tool.
Fitness-for-Service Assessment of Externally Corroded Convection Coil Tube
Authors: van Zyl Gys , Al-Salmi Abdullatif
Published: November 2019

During inspection of a heating coil in the convection section of a steam reformer, significant thickness loss due to external corrosion was discovered in a large number of tubes.

In order to optimize the scope of repairs and ensure further safe operation, a level 3 fitness-for-service and remaining life analysis were performed in accordance with API-579.

This paper will describe the fitness-for-service assessment that was performed, first using an idealized geometry, and thereafter using the actual corroded geometry of a removed tube. The procedure used to estimate the remaining life of the damaged coil will also be presented.
New Model for Ductile Rupture Under Cyclic Loading Conditions
Authors: Remmal Al Mahdi , Marie Stéphane , Leblond Jean-Baptiste
Published: November 2019

Experiments have shown that ductile failure occurs sooner under cyclic loading conditions than under monotone ones. This reduction of ductility probably arises from an effect called “ratcheting of the porosity” that consists of a continued increase of the mean porosity during each cycle with the number of cycles. Improved micromechanical simulations confirmed this interpretation. The same work also contained a proof that Gurson’s classical model for porous ductile materials does not predict any ratcheting of the porosity. In a recent work [6], the authors proposed a Gurson-type “layer model” better fit than Gurson’s original one for the description of the ductile behavior under cyclic loading conditions, using the theory of sequential limit analysis. A very good agreement was obtained between the model predictions and the results of the micromechanical simulations for a rigid-hardenable material. However, the ratcheting of the porosity is a consequence of both hardening and elasticity, and sequential limit analysis is strictly applicable in the absence of elasticity. In this work, we make a proposal to take into account elasticity in the layer model through the definition of a new objective stress rate leading to an accurate expression of the porosity rate accounting for both elasticity and plasticity. This proposal is assessed through comparison of its predictions with the results of some new micromechanical simulations performed for matrices exhibiting both elasticity and all types of hardening: isotropic, kinematic and mixed, to better comply with the hypothesis made to derive the model.
Critical Review of Strain Measures for Characterisation of Fatigue Damage in ASME Section III Fatigue Assessments
Authors: Leary Daniel , Currie Chris , Wright Keith
Published: November 2019

Rules for fatigue evaluation of nuclear pressure vessels and piping components are provided in Subsection NB of Section III of the ASME code. The code prescribed fatigue procedure requires the comparison of an alternating stress amplitude with fatigue allowables (design fatigue curves), usually derived through uniaxial specimen testing. For elastic assessments of multiaxial loading, typical from thermal shocks, a Tresca stress is used to characterise the stress field into a single effective stress measure for comparison with ASME fatigue allowables. For nonlinear elastic-plastic assessments, Appendix XIII-3440(b) of Section III specifies that “the numerically maximum principal total strain range” (interpreted as Maximum Total Principal (MTP) strain range) should be used for comparison with fatigue allowables.

Two alternative methods for the characterisation of multiaxial strain fields are presented in the ASME code. Section VIII Division 2 provides alternative rules for the construction of pressure vessels, with Part 5 specifying the use of a Von Mises based Effective Strain Range (ESR) for elastic-plastic analysis. Section III Division 5 Subsection NBB provides rules for the assessment of components at elevated temperatures, also specifying the use of a Von Mises based Equivalent Total Strain Range (ETSR) measure. The two alternative strain measures are differentiated by their treatment of the elastic strain contribution. In the ESR method an equivalent elastic strain is calculated and summated with the plastic strain component. In the ETSR method the total strain (elastic plus plastic) is used thus evaluating the elastic and plastic contributions simultaneously. More complex critical plane approaches have also been proposed in recent years to better characterise multiaxial loading conditions.

This paper presents a comparison of the various ASME specified strain measures and simplified critical plane approaches for fatigue evaluation of complex multiaxial loading. In support of this comparison, predictions of initiation lives to 0.254 mm defect in the stepped pipe specimen reported in PVP2004-2748 are provided to quantify the additional conservatism contained in elastic-plastic fatigue assessments of nuclear components. Predictions use the methodology presented in the companion paper PVP2019-93847 for the generation of short crack fatigue curves and the associated modification to environmental enhancement factors.

It is concluded that use of the ASME specified strain measures, in conjunction with lower bound stress-strain data, conservatively underestimate the initiation life to a 0.254 mm defect by a factor of four for the example considered. However, use of more complex critical plane strain measures were observed to provide significant improvement in prediction accuracy of elastic-plastic fatigue evaluations.
Reactor Vessel Hazard Assessment Case Study
Authors: Edel Matthew , Van Zyl Gys , Atarji Abdulrahman
Published: November 2019

Operation of a multi-tubular reactor vessel includes some inherent risks and potential hazards. Multi-tubular reactors tend to be large vessels that contain hydrocarbons under pressure. Some potential hazards that may ensue from potential vessel failure include fragments (i.e., debris), blast loads, and heat.

This paper involves the discussion of a case study of a multi-tubular reactor vessel that sustained corrosion cracks on full penetration groove welds near the top and bottom heads. A hazard analysis is conducted that considered various potential scenarios associated with an accidental head failure. The structural response of the vessel is determined using mechanics of materials-based finite element analysis (FEA) models. Blast loads emanating from the vessel as the pressurized water/steam escaped the vessel through a failed opening are estimated. Projectile trajectories for fragments of weldment launched from the failed circumferential weld are also calculated. The results of the models lead to recommended safe standoff distances and potential mitigation options.
Consideration on Fatigue Crack Growth Thresholds Under Negative Stress Ratio
Authors: Hasegawa Kunio , Usami Saburo , Lacroix Valery
Published: November 2019

Fatigue crack growth thresholds ΔKth are provided by several fitness-for-service (FFS) codes. When evaluating cracked components subjected to cyclic loading, maximum stress intensity factor Kmax and/or minimum stress intensity factor Kmin are required. However, the definitions of the thresholds ΔKth under negative stress ratio R are not clearly written, except for BS (British Standards) 7910. In addition, the ΔKth are given by constant values under negative R. Fatigue crack growth rates under negative stress ratio is recommended to use maximum stress intensity factor Kmax by ASTM (American Society of Testing and Materials) E 647, because of the Kmax being close to crack driving force. Therefore, it deems that the ΔKth under negative R seems to be Kmax.

This paper shows that the Kmax converted by the ΔKth are not constant values under negative R based on the survey of experimental data. The Kmax decreases with decreasing the stress ratio R. Therefore, the ΔKth for the FFS codes are less conservative. As experimental data under negative stress ratio R were taken by Kmax – Kmin, the definition of the threshold ΔKth is benefit to use Kmax – Kmin, instead of Kmax.
Low-Cycle Fatigue of Pipe Components: Markl’s Method Revisited
Authors: Pei Xianjun , Dong Pingsha , Song Shaopin
Published: November 2019

In the 1950’s Markl et al. conducted numerous fatigue test of welded piping components that were later used to develop the ASME B31 and other piping design codes. To analyze low cycle fatigue data, Markl proposed an extrapolation method to obtain the pseudo-elastic stress for fatigue data analysis. In this paper, this extrapolation method is revisited to figure out its underlining mechanism, application scope and limitation. Two sets of fatigue data representing 4 point bending and cantilever bending condition are analyzed to support the study. A structural strain method is then proposed as an improvement and generalization of Markl’s approach, which can correlate large amount weldment fatigue data in both low-cycle and high-cycle regime by defining an equivalent structural strain parameter.
Evaluation of the Fatigue Strength of Notched Geometries Using a Microstructural Model and Generative Algorithms
Authors: Balbín Molina J. A. , Larrosa N. O. , Chaves V.
Published: November 2019

In this work, the assessment of a short crack emanating from arbitrarily shaped notches under Mode I loading is done. A parametric algorithmic tool is used to create a wide range of different two dimensional notch shapes for the evaluation of notch fatigue strength by means of the Distributed Dislocation Technique. Comparisons between V-notches, U-notches and semi-elliptical notches establishing similar geometrical parametric relations are shown, so that the simplicity and versatility of the designed tool is demonstrated. This useful properties and advantages make this tool applicable to industrial problems such as the modelling and assessment of the effect of corrosion pits on fatigue strength.
Technical Basis for Master Curve for Fatigue Crack Growth of Ferritic Steels in High-Pressure Gaseous Hydrogen in ASME Section VIII-3 Code
Authors: San Marchi Chris , Ronevich Joseph , Bortot Paolo , Wada Yoru , Felbaum John , Rana Mahendra
Published: November 2019

The design of pressure vessels for high-pressure gaseous hydrogen service per ASME Boiler and Pressure Vessel Code Section VIII Division 3 requires measurement of fatigue crack growth rates in situ in gaseous hydrogen at the design pressure. These measurements are challenging and only a few laboratories in the world are equipped to make these measurements, especially in gaseous hydrogen at pressure in excess of 100 MPa. However, sufficient data is now available to show that common pressure vessel steels (e.g., SA-372 and SA-723) show similar fatigue crack growth rates when the maximum applied stress intensity factor is significantly less than the elastic-plastic fracture toughness. Indeed, the measured rates are sufficiently consistent that a master curve for fatigue crack growth in gaseous hydrogen can be established for steels with tensile strength less than 915 MPa. In this overview, published reports of fatigue crack growth rate data in gaseous hydrogen are reviewed. These data are used to formulate a two-part master curve for fatigue crack growth in high-pressure (106 MPa) gaseous hydrogen, following the classic power-law formulation for fatigue crack growth and a term that accounts for the loading ratio (R). The bounds on applicability of the master curve are discussed, including the relationship between hydrogen-assisted fracture and tensile strength of these steels. These data have been used in developing ASME VIII-3 Code Case 2938. Additionally, a phenomenological term for pressure can be added to the master curve and it is shown that the same master curve formulation captures the behavior of pressure vessel and pipeline steels at significantly lower pressure.
Development of an Apparatus for Chloride Induced Stress Corrosion Cracking Test Using Immersion Method With Constant Displacement Condition
Authors: Jeong Jae-Yoon , Lee Myeong-Woo , Kim Yun-Jae , Sindelar Robert , Duncan Andrew
Published: November 2019

This paper presents a new test method for assessing chloride induced stress corrosion cracking occurred in metal canisters used for storing spent nuclear fuels. The material applied to experiment is austenitic stainless steel, SS304 similarly used on manufacturing canisters and the experiment is carried out with immersing a compact tension specimen to chloride solution made up with artificial sea salt. Constant displacement condition using bolt tightening is applied to the test and a load is measured as a function of time using a load cell. Five specimens are used for the experiment at temperature of 50 °C for several months and stress intensity factor is calculated through the measured relaxed load and crack length on fractured surface of the specimen. Crack growth rate is presented in terms of test periods and consequently this apparatus suggests a method for evaluating structural integrity of chloride stress corrosion cracking.
Inconel X-750 Spacer Fitness-for-Service
Authors: Lau Winnie , Scarth Douglas , Doddihal Preeti
Published: November 2019

The CANDU1 (CANada Deuterium Uranium) reactor core consists of 380–480 horizontal Zr-Nb pressure tubes, which support fuel bundles and provide pressurized heavy water cooling. The pressure tubes are supported by fuel channel annulus spacers, which maintain the gap between the hot pressure tube and colder calandria tube while providing a means of leak detection through the annulus gas system. Research and testing in this area have shown that spacer material degradation in later life operation could impact the ability of the component to meet its design requirements. This paper presents a fitness-for-service strategy that could be utilized in demonstrating continued safe operation of these components. Fitness-for-service is based on analysis of crush tests on ex-service spacers to determine the load carrying capacity projected into the future and endurance tests to determine fatigue life. This paper describes these technical approaches and their application in fitness-for-service evaluation of spacers in CANDU operating plants to satisfy requirements for an annulus spacer surveillance program under Clause 12.5 of the CSA Standard N285.4-14.
Investigation of Relationship Between Microhardness and Charpy Impact Energy for Temper Bead Welding Qualification: Part 1
Authors: Smith Boeing , Ramirez Antonio J. , McCracken Steven L. , Tate Stephen
Published: November 2019

Temper bead (TB) welding is often used as an alternative to post weld heat treatment (PWHT) for repair of pressure vessels and piping in the nuclear power industry. Historically, qualification of TB welding procedures has employed the Charpy V-notch test to ensure acceptable heat-affected-zone (HAZ) impact properties. The 2004 Edition of ASME Section IX provided a new provision in QW-290 that allows temper bead qualification using a peak hardness criterion. The peak hardness provision is appropriate for industries such as oil and gas, where peak allowable hardness is specified to ensure adequate resistance to sulfide stress cracking in sour service environments. However, a peak hardness criterion is not appropriate where impact properties are specified for resistance to brittle fracture during low temperature conditions that can occur during certain postulated accident scenarios at a nuclear power plant.

Work at the Electric Power Research Institute (EPRI) and The Ohio State University (OSU) show that a hardness drop protocol can be used to demonstrate acceptable impact properties in the HAZ of a temper bead weld. This paper presents a quantitative correlation between hardness measurements and HAZ microstructures with presumed optimum impact properties using a hardness drop approach. The overarching goal is to develop a hardness test protocol for temper bead weld procedure qualification for applications where impact properties are specified.
Integrated Smart Seismic Risks Management
Authors: Ciucci Mariano , Marino Alessandra , Paolacci Fabrizio , Bursi Oreste S.
Published: November 2019

Recent events outlined the relevance of the interactions between industrial and natural hazards (NATECH) particularly for that concern seismic risk. EU regulation, namely Directive 2012/18/EU, among its new elements explicitly requires the analysis of NATECH hazards. The development of a risk analysis methodology for major hazard industrial plants allows the individuation of critical elements of the plants with regard to seismic actions. The following implementation of smart technologies (sensors, actuators, innovative systems for seismic protection) to the critical elements allows a relevant reduction of major hazards and related consequences.
Ratcheting due to Thermal Stratification
Authors: Adibi-Asl R. , O’Kane D. , Chen E.
Published: November 2019

Thermal ratcheting is required to be checked by most of the piping design codes, specifically the ASME B&PV Code. For cases where the variation of temperature distribution is not uniform, the existing ratchet check methodology for piping is inadequate and therefore the finite element analysis (FEA) is often used to perform ratchet checks. Thermal stratification, in which cold and hot fluid flows are layered in a relatively steady state condition, is a good example of non-linear/non-uniform temperature distribution across the pipe.

This paper develops straightforward equations to address thermal stratification in piping. Finite element analysis is used to benchmark the results.
A Design Guideline for Random Excitation Forces due to Two-Phase Cross Flow in Tube Bundles
Authors: Taylor Colette E. , Pettigrew Michel J.
Published: November 2019

This paper re-examines the available experimental data to investigate the random excitation forces that affect tube bundles exposed to two-phase cross flow. Much of the experimental data generated over the past four decades has been gathered in an attempt to understand the parametric dependence of the random two-phase forces. The data includes air-water, steam-water and various Freons used in a variety of test sections with either strain gauges to measure the tube amplitude or force tranducers to measure the reaction forces. A review of previous work in this area finds that some authors claim a strong flow regime dependence, while others suggest that this dependence is weak. This work takes a detailed look at this discrepancy and finds that a single design guideline does not adequately bound all flow regimes. As a result, two dimensionless upper bounds are proposed.
Residual Shank Torque of Bolted Joints: A Numerical Investigation
Authors: Fini Stefano , De Agostinis Massimiliano , Croccolo Dario , Olmi Giorgio , Paiardini Luca , Robusto Francesco
Published: November 2019

During operation, the overall stress state of a screw is a function of the direct stress generated by the axial preload, and the external loads, plus the shear stress due to the residual shank torque. All in all, the higher the residual torque, the lower the direct stress the screw can withstand prior to yielding. The residual shank torque stems from the tightening torque, part of which flows through the shank and it is, only partially, released after wrench removal, thanks to springback phenomena involving both the screw and the joined elements. This phenomenon has been tackled in a previous experimental and analytical work by the authors, which investigated the effect of the stiffness and frictional parameters of the joint on the amount of residual shank torque. Such research was based on a sleevelike specimen, and, in fact, the results were strictly applicable to the case of slender cylindrical joint. The present contribution aims at assessing the effect of the same parameters on the residual shank torque, namely: the ratio between the torsional stiffness of the screw and of the plates, the friction coefficients (underhead and thread). Nonetheless, thanks to a novel three-dimensional finite element model, the parameters have been varied in a much wider range, in order to analyze all the likely operating conditions. The model is capable of predicting the residual shank torque for both the cases of slender and thick joint (plate-like joint). The model has been developed in the Ansys R17 software, but the methodology can be extended to other codes with minimal changes.
Verification of Manual Digitization Methods During Experimental Simulation of Knee Motion
Authors: Hargett Zachary , Gutierrez Manuel , Harman Melinda
Published: November 2019

Cadaveric testing is a common approach for verifying mathematical models used in computational modeling work. In the case of a knee joint model for calculating ligament tension during total knee replacement (TKR) motion, model inputs include rigid body motions defined using the Grood-Suntay coordinate system as a spatial linkage between the tibial component orientation relative to the femoral component. Using this approach requires the definition of coordinate systems for each rigid TKR component (i.e. tibial and femoral) based on fiducial points, manual digitization of a point cloud within the experimental setup, and registration of the orientation relative to the relevant bone marker array. The purpose of this study was to compare the variability between two different manual point digitization methods (a hand-held stylus and pivot tool each calibrated in the optical tracking system), using a TKR femoral component in a simulated cadaver limb experimental setup as an example. This was accomplished by verifying the mathematical algorithm used to calculate the coordinate system from the digitized points, quantifying the variability of the manual digitization methods, and discussing how any error could affect the computational model. For the hand-held stylus method, the standard deviation of the origin and, x-, y-, and z-axis calculations were 0.50mm, 1.31 degrees, 0.51 degrees, and 0.62 degrees, respectively. It is important to note that there is an additional error created using the hand-held stylus from required manual digitization of each rigid marker array. This average additional error was 0.54mm for the origin and 1.70, 1.66, and 0.98 degrees for the x-, y-, and z-axes, respectively. For the pivot tool method, the standard deviation was 0.35mm, 0.37 degrees, 1.27 degrees, and 1.24 degrees for the origin, x-, y-, and z-axes, respectively. It is essential to minimize experimental error, as small errors in alignment can substantially alter model outputs. In this study of cadaver simulation of limb motion, the pivot tool is the better option for minimizing error. Careful definition of fiducial points and repeatable manual digitization of the point cloud is critical for meaningful computational models of TKR motion based on cadaver experimental work.
Accuracy of Green's function estimation from correlation of diffuse elastic waves on thin plates
Authors: Chehami Lynda , Moulin Emmanuel , de Rosny Julien , Prada Claire
Published: November 2019

In a reverberant cavity, when a noise field is sufficiently diffuse, the correlation of the signal measured by two sensors provides an estimation of the Green's function (GF) between them. Here, the convergence of this passive estimation in the case of elastic waves on thin plates is studied. A statistical approach is proposed, which relates the similarity between the cross correlation and the GF to the structural properties of the plate and the number of uncorrelated sources. The analysis is sustained by experimental results obtained on an aluminum plate. This study allows us to evaluate the efficiency of passive structural health monitoring of plate-like structures based on noise correlation. Finally, a most interesting finding shows an absolute upper bound of the signal-to-noise ratio for GF quality reconstruction: 4Ns/5, independently of the plate properties.
Insect Hsp90 Chaperone Assists Bacillus thuringiensis Cry Toxicity by Enhancing Protoxin Binding to the Receptor and by Protecting Protoxin from Gut Protease Degradation
Authors: García-Gómez Blanca I. , Cano Sayra N. , Zagal Erika E. , Dantán-Gonzalez Edgar , Bravo Alejandra , Soberón Mario
Published: November 2019

Bacillus thuringiensis
took advantage of important insect cellular proteins, such as chaperones, involved in maintaining protein homeostasis, to enhance its insecticidal activity. This constitutes a positive loop where the concentrations of Hsp90 and Hsp70 in the gut lumen are likely to increase as midgut cells burst due to Cry1A pore formation action. Hsp90 protects Cry1A protoxin from degradation and enhances receptor binding, resulting in increased toxicity. The effect of insect chaperones on Cry toxicity could have important biotechnological applications to enhance the toxicity of Cry proteins to insect pests, especially those that show low susceptibility to these toxins.
Rare case of non-producer variant of plasma cell dyscrasias with circulating plasma cells
Authors: Manthri Sukesh , Zafar Rabia , Cornell Robert Frank , Chakraborty Kanishka
Published: November 2019

Non-producing variant of plasma cell disorders with circulating plasma cells is an aggressive variant of plasma cell dyscrasias with relatively poor outcomes. A 75-year-old man was admitted due to anaemia (90 g/L) and thrombocytopenia (9×109/L). Comprehensive metabolic panel showed creatinine of 1.34 mg/dL, total protein of 6 g/dL, and corrected calcium was normal. Peripheral smear review showed 8% circulating atypical plasmacytoid cells. Bone marrow biopsy (BMB) confirmed plasma cell myeloma involving 90%–95% of bone marrow cellularity. Serum protein electrophoresis showed no monoclonal protein. Due to aggressive biology of non-producer variant and outcomes based on circulating plasma cells, he was started on VD-PACE (bortezomib, dexamethasone, cisplatin, doxorubicin, cyclophosphamide and etoposide) chemotherapy. BMB after cycle 1 chemotherapy showed no morphologic, immunophenotypic, or flow cytometric features of a plasma cell neoplasm. Given excellent treatment response cycle 2 was changed to VRD (bortezomib, lenalidomide and dexamethasone). Following two cycles of VRD, he underwent autologous haematopoietic cell transplantation. Day 80 BMB suggested stringent complete response.
Large volume haemorrhage following transoral robotic surgery (TORS) as a result of fibromuscular dysplasia: first reported case
Authors: Leedman Samuel Robert , Esmaili Aaron , Singh Tejinder , Wee Desmond
Published: November 2019

We present a case of a 61-year-old woman who suffered a haemorrhagic complication of an aneurysmal left lingual artery, secondary to fibromuscular dysplasia, following transoral robotic surgery (TORS). She was admitted through the emergency department 3 days after resection of a central base of tongue tumour. She suffered a massive haemorrhage requiring intensive care admission, blood transfusion, intubation, operative and endovascular intervention. The diagnosis of fibromuscular dysplasia was made at angiography. During attempts to embolise the culprit left lingual artery, the vessel dissected at its origin leading to arrest of bleeding. Repeat angiograms during her admission demonstrated unchanged appearances and ruled out recanalisation of the vessel. She was extubated and remained stable on the ward, discharged home some days later in good health. To our knowledge, this is the first ever reported case of fibromuscular dysplasia affecting the lingual artery leading to aneurysmal dilation and severe haemorrhage following TORS.
Trends in HIV testing in the UK primary care setting: a 15-year retrospective cohort study from 2000 to 2015
Authors: Gompels Mark , Michael Skevi , Davies Charlotte , Jones Tim , Macleod John , May Margaret
Published: November 2019

Objectives

To estimate trends in HIV testing, positivity and prevalence in UK primary care for 2000–2015 as part of a wider investigation into reasons for late diagnosis of HIV.

Design

Retrospective cohort study using the Clinical Practice Research Datalink (CPRD) which is derived from computerised clinical records produced during consultations in primary care.

Setting

404 general practices in England.

Participants

5 979 598 adults aged ≥16 years registered between 2000 and 2015 with 45 093 761 person years of observation.

Outcomes

Annual HIV testing rates, proportion of positive tests and prevalence of HIV-infected people recorded in primary care 2000–2015.

Results

HIV testing in primary care increased from 2000 to 2010, but then declined. Testing was higher in females than in males and in those aged 16–44 years compared with older adults. Rates per 100 000 in women aged 16–44 years were 177 (95% CI 167 to 188); 1309 (95% CI 1282 to 1336); 1789 (95% CI 1757 to 1821) and 839 (95% CI 817 to 862) in 2000, 2005, 2010 and 2015, respectively, and for non-pregnant women: 22.5 (95% CI 19 to 26); 134 (95% CI 125 to 143); 262 (95% CI 250 to 275); 190 (95% CI 179 to 201). For men aged 16–44 years rates were: 26 (95% CI 22 to 29); 107 (95% CI 100 to 115); 196 (95% CI 185 to 206); 137 (95% CI 127 to 146). Over the study period, there were approximately two positive results per 1000 HIV tests. Men were eightfold more likely to test positive than women. The percentage of HIV diagnoses among adults recorded in CPRD may be as low as 55% in London and 67% in the rest of the UK.

Conclusions

HIV testing rates in primary care peaked in 2010 and subsequently declined. Access to testing was higher for women despite the prevalence of HIV being higher in men.

Implications and further research needed

Opportunities remain in primary care for increasing HIV testing to prevent costly late diagnoses and decrease HIV transmission. Interventions to improve targeting of tests and increase adherence to HIV testing guidelines are needed in primary care.
How timely is access to palliative care medicines in the community? A mixed methods study in a UK city
Authors: Miller Elizabeth Jane , Morgan Julie D , Blenkinsopp Alison
Published: November 2019

Objective

To investigate timely access to palliative medicines/drugs (PMs) from community pharmacies to inform palliative care service delivery.

Design

Mixed methods in two sequential phases: (1) prospective audit of prescriptions and concurrent survey of patients/representatives collecting PMs from pharmacy and (2) interviews with community pharmacists (CPs) and other healthcare professionals (HCPs).

Setting

Five community pharmacies in Sheffield, UK and HCPs that deliver palliative care in that community.

Participants

Phase 1: five CPs: two providing access to PMs within a locally commissioned service (LCS) and three not in the LCS; 55 patients/representatives who completed the survey when accessing PMs and phase 2: 16 HCPs, including five phase 1 CPs, were interviewed.

Results

The prescription audit collected information on 75 prescriptions (75 patients) with 271 individual PMs; 55 patients/representatives (73%) completed the survey. Patients/representatives reported 73% of PMs were needed urgently. In 80% of cases, patients/representatives received all PMs on the first pharmacy visit. One in five had to travel to more than one pharmacy to access PMs. The range of PMs stocked by pharmacies was the key facilitating factor. CPs reported practical issues causing difficulty keeping PMs in stock and playing a reactive role with palliative prescriptions. Confidentiality concerns were cited by other HCPs who were reluctant to share key patient information proactively with pharmacy teams. Inadequate information transfer, lack of CP integration into the care of palliative patients and poor HCP knowledge of which pharmacies stock PMs meant patients and their families were not always able to access PMs promptly.

Conclusions

Consistent routine information transfer and integration of pharmacy teams in the care of palliative patients are needed to achieve timely access to PMs. Commissioners of PM access schemes should review and monitor access. HCPs need to be routinely made aware and reminded about the service and its locations.
Protocol for the CREST Choles (Chinese REgistry Study on Treatment of Cholecysto-Choledocholithiasis) study: an ambispective, multicenter, observational, open-cohort study
Authors: Zhu Jie-Gao , Wu Shanshan , Feng Qiushi , Li Fei , Han Wei , Xiu Dianrong , Tan Haidong , Fu Jianzhu , Li Xun , Shang Dong , Liu Houbao , Li Binglu , Yang Li , Kong Yuanyuan , Zhan Siyan , Guo Wei , Zhang Zhong-Tao
Published: November 2019

Introduction

The best approach for choledocholithiasis remains a matter of debate. Choledocholithiasis is usually treated with endoscopic sphincterotomy (EST), laparoscopic common bile duct exploration (LCBDE) or laparoscopic transcystic common bile duct exploration (LTCBDE). Data pertaining to the clinical outcomes of these approaches in the management of patients with cholecysto-choledocholithiasis in China are limited. An analysis of the economic burden associated with these treatments is lacking. The Chinese REgistry Study on the Treatment of Cholecysto-Choledocholithiasis (CREST Choles) was designed to address these issues in a real-world setting.

Methods and analysis

CREST Choles was an ambispective, multicenter, observational, open-cohort study. A total of 2700 patients undergoing one of the three treatments (EST+laparoscopic cholecystectomy (LC), LCBDE+LC and LTCBDE+LC) during the period from 1 January 2013 to 1 December 2018 at participating centres were enrolled in the study. Patients with gallstones and confirmed common bile duct stones were included. Data pertaining to demographics, disease history, procedural details, imaging features and follow-up were collected. Follow-up was conducted at least 6 months after enrolment in the study and annual follow-up will be conducted until December 2020. The primary outcome is the rate of adverse outcomes within 3 years postoperatively. Economic analysis (eg, incremental cost-effectiveness ratio) would be performed to compare expense across treatments.

Ethics and dissemination

Ethical approval was obtained at all participating centres. The registry presented is the first attempt to comprehensively evaluate the cost of treatment for cholecysto-choledocholithiasis in China. Findings are expected to be available in 2020 and will facilitate clinical decision making in such cases.

Trial registration number

NCT02554097.