bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Emission Monitoring During Fatigue Crack Growth in Standard C(T) and Miniature Single Edge Notch Tension Specimens
Authors: Prakash Raghu V. , Mukhopadhyay Chandan K. , Pokharkar Prathmesh , Thomas Manuel
Published: October 2020

The fatigue crack growth rate studies in a structural alloy has been carried out using ASTM E-647 standard compact tension (C(T)) specimens and miniature single edge notch tension specimens (SEN(T)) at two different stress ratios of 0.1 and 0.7. Standard C(T) specimen had a dimension of 63.5 × 61 × 8 mm thickness while the miniature SEN(T) specimen had a size of 20 mm effective length × 10 mm wide and 0.7 mm thickness. A starter notch of 0.5 mm was cut using wire EDM process to initiate fatigue crack growth in miniature SEN(T) specimen. A special fixture was designed for testing the miniature SEN(T) specimen.

During the fatigue crack growth experiments, Acoustic Emission (AE) activity was monitored on-line using AE sensors from Physical Acoustics, Mistras Group, USA. For the experiments on standard C(T) specimens, a standard probe (R15A) of 15 mm diameter was used, while for small size compact tension specimen, a Nano30 AE probe was used. The crack growth was monitored by visual methods as well as by compliance technique. The cumulative counts and absolute energy information obtained during fatigue crack growth testing was used to correlate the crack growth rate with acoustic emission activity. Empirical fit of data was used to obtain cross-correlation between crack growth rate and AE parameters for both the specimen geometries. The study suggested that suitable selection and placement of sensors is essential to obtain good results using AE sensor technique.
Correlation Analysis Between Time-Dependent Creep Crack-Tip Stress and Constraint Effect on Creep Crack Initiation Time
Authors: Lee Seung-Ho , Jung Hyun-Woo , Kim Yun-Jae , Nikbin Kamran , Ainsworth Robert A.
Published: October 2020

In this study, to qualify the constraint effect on creep crack initiation, the correlation analysis between proposed constraint parameter Q’ using time-dependent creep crack-tip stress and creep crack initiation time variable Ai was performed. Ai implies the influence of constraint effect on creep crack initiation. The procedure to calculate the Ai and the Q’-parameter was presented. To evaluate various status of constraint effect, creep crack growth tests for twenty-one compact tension specimens of Type 316H stainless steel at 550°C were investigated. The results of correlation analysis explain the reason for the different initiation time at the same C* level in respect of constraint effect.
Fatigue Life Prediction of Notched Specimen Based on Stress Gradient
Authors: Takanashi Masahiro
Published: October 2020

Many failure accidents have indicated fatigue as the primary cause for the failure of a machine or structure. In general, the origin of failure is a structural discontinuous part such as a welded joint or a notched member that causes stress concentration. While designing such a component, a finite element analysis (FEA) has to be conducted, and the peak stress has to be compared with a design fatigue curve obtained from small-sized specimens to evaluate whether the component satisfies the design life. However, it is known that a fatigue life prediction at a stress concentration part based on a peak stress always provides an excessively conservative estimation. This is due to the stress gradient of the component. This paper discusses the stress-gradient approach to eliminate the conservatism and rationalize a fatigue design. Using literature test data, the relationship between the stress gradient calculated using FEA, and the fatigue strength reduction ratio was determined. Later, a fatigue test was conducted on a notched specimen of low-alloy steel to verify the stress-gradient approach, and the fatigue life of the notched specimen was predicted considering the stress gradient at the notch root. The predicted fatigue life agreed well with the experimental results.
Comparison of Stress Intensity Factor Coefficients for Plates and Cylinders Under Membrane Stress
Authors: Lee Darrell R. , Cipolla Russell C. , Liu Michael C.
Published: October 2020

Until the 2000 Edition of API-579 [1], the geometries (Ri/t, a/ℓ, a/t in cylinders or spheres) for which a complete set of stress intensity factor influence coefficients (Gi) existed was limited. To bridge that gap, many analysts have used the G0 and G1 coefficients for flat plate geometries to represent axial or circumferential flaws in cylinders. Because the cylindrical geometry contains additional stiffness effects due to curvature, it was generally assumed that the plate geometry (Ri/t = ∞) will be bounding and therefore conservative [2].

Since 2007, extensive sets of Gi coefficient have been published for plates, cylinders and spheres based on finite element models. These coefficients for cylinders have been curve fit and are available in Appendix A of the ASME Boiler and Pressure Vessel Code, Section XI [3]. This paper compares the G0 coefficients at the deepest point of semi-elliptical flaws from a plate to those for an OD and ID circumferential flaw in a cylinder to confirm the conservatism of the G0 coefficients from a plate geometry.
Damage to Oil Tanks Caused by Severe Strong Ground Motion due to the 2018 Hokkaido, Japan Iburi-Tobu Earthquake (Mw6.6)
Authors: Hatayama Ken , Nishi Haruki , Hayashi Masahiko , Tokutake Koya
Published: October 2020

Damage and influences to oil tanks caused by severe strong ground motion due to a large earthquake (Mw6.6) that occurred in the district of Iburi-tobu, Hokkaido, Japan on September 6, 2018 are reported in this paper. In the vicinity of the seismic source region, two large-scale crude-oil storage bases are located. The neighboring two bases had in total 86 large oil storage tanks with a capacity of 115,000 m3. The oil storage bases were hit by strong ground motion with peak ground accelerations of 590 to 1,570 cm/s2 and with peak ground velocities of 50 to 80 cm/s. Shell plates of a small bunker A tank with a capacity of 306 m3 suffered diamond buckling and elephant-foot buckling. No large oil storage tanks lost their function of oil storage despite of the severe strong ground motion. However, most of them splashed oil from the gap between the floating roof and the shell plate, and many of them had damage to their pontoons, gauge poles, guide poles, rolling ladders, liquid-level meters, and shoulders of foundation. One of the 115,000-m3-in-capacity tanks was equipped with a displacement gauge system to measure uplift of the bottom of the shell plate from the shoulder of tank foundation. The system recorded a maximum uplift of 4.4 cm. This is the world’s first record of uplift of a large tank caused by a natural earthquake.
Hydrogen Embrittlement Evaluation of Different Heats of AISI 8630 Steel in Subsea Applications
Authors: Li Xiaoji , Thodla Ramgopal , Alves Fabio , Castro Mario , Venkatesh Anand
Published: October 2020

AISI 8630 steel used in subsea applications is subject to hydrogen embrittlement from externally applied cathodic protection. In this work, susceptibility variation on three grades of 8630 steel of different yield strength (YS), 100 ksi, 110 ksi and 120 ksi, were evaluated in terms of fracture toughness. Two different testing methods, slow rising displacement and incremental step loading testing, were used to generate J-R curves and determine the fracture toughness. The tests were performed at 40°F in air and simulated sea water (3.5 wt.% NaCl) with applied CP of −1050 mV SCE.

The normalized fracture toughness values are discussed in this work. In all three grades, regardless of the test methods, the environmental toughness under CP conditions were significantly lower than the in-air values indicating that they are susceptible to hydrogen embrittlement. Effect of YS on the hydrogen embrittlement was also observed. The incremental step loading technique showed that Jth and the J-R curve slope decreased as the YS increases. The rising displacement method also clearly showed the lowest toughness and the flattest J-R curve slope in the highest strength grade (120ksi) despite showing similar performance between the 100ksi and 110ksi grades. The true stress-true strain analysis showed different strain hardening behavior among the three grades that may suggest the strain hardening plays a role in influencing the hydrogen embrittlement behavior among the grades. Overall, slight variation could be observed in the results from the two test methods which, however, did not appear to be biased against each other in determining lower bounds of the results.
Mechanical Properties of Ion-Irradiated Stainless Steel Determined by Nanoindentation Tests and Finite Element Analyses
Authors: Sim Jae Min , Chang Yoon-Suk , Kong Byeong Seo , Jang Changheui
Published: October 2020

While austenitic stainless steels (ASSs) have been widely adopted for reactor vessel internals because of their excellent material properties, diverse ageing-related degradation may occur due to high temperature, corrosive and neutron radiation environments during operation. In particular, since the change of mechanical properties is a major concern in long-term operation but it is difficult to prepare and handle standard specimens influenced by neutrons, most of experimental researches for enhanced understanding of the radiation effects have been focused on high-energetic ion-irradiation and tests of small specimens.

In this study, systematic finite element analyses were carried out to quantify changing mechanical properties based on both virgin and ion-irradiated nanoindentation test data of typical ASS material. First of all, numerical analysis was carried out to obtain unirradiated material constitutive parameters by using trial set along the miniature specimen and comparing test data, and then indentation stress-strain (ISS) curve was derived. Subsequently, ISS was converted into uniaxial stress-strain response taking into account simple correlation. Finally, with regard to the irradiated material, similar analytical procedures were established. 304 SS was irradiated with 2 MeV proton and radioactivity is being measured. Comparison between analysis result and experimental one will be carried out, of which details and key findings will be discussed.
Validation of the Incremental Step Loading Technique Application to Small Punch Tests in Aggressive Environments in X80 Steel
Authors: Arroyo B. , Andrea L. , González P. , Álvarez J. A. , Cicero S. , Fernández A. , Lacalle R.
Published: October 2020

The Small punch test, which consists on punching a small plane specimen up to failure, is a technique to be taken into account for the estimation of mechanical properties when there is shortage of material. In recent works it has been applied to the estimation of mechanical properties steels in aggressive environments.

In aggressive environments, tests under a constant load are usually employed for the threshold stress determination, but this a slow and sometimes inaccurate technique. The standard ASTM F1624 solves these issues; it consists on applying steps of constant loads subsequently increased up to the specimen’s failure. In a previous work, it was indicated how to implement this technique for Small Punch testing of steels in hydrogen embrittlement scenarios, adapting the steps duration. This proposal allows to obtain a threshold load by using at least 3 specimens in a total time of around a week.

In the present work, the incremental step loading technique from ASTM F1624 standard is applied to the Small Punch test in order to estimate tensile threshold stress of a X80 high strength steel in hydrogen embrittlement environments by cathodic polarization in an acid electrolyte. Regular standard tests on cylindrical tensile specimens were carried out following the ASTM F1624 standard, in order to validate the methodology proposed.
Fatigue Life Estimation Using Frequency Domain Technique and Probabilistic Linear Cumulative Damage Model
Authors: Pascualinotto Junior Vagner , Burgos Diego Felipe Sarzosa
Published: October 2020

Engineering critical structures, such as pressure vessels and pipelines, are designed to withstand a variety of in-service loading specific to their intended application. Random vibration excitation is observed in most of the structural component applications in the offshore, aerospace, and nuclear industry. Likewise, fatigue life estimation for such components is fundamental to verify the design robustness assuring structural integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still largely used for damage assessment on fatigue estimations, even though, its limitations are well-known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects, and trans-granular crack propagation are hardly predicted, indicates that a probabilistic characterization of the material behavior is needed. In this work, the methodology was applied to a Titanium alloy structural component. Low alloyed titanium alloys have no tendency to corrosion cracking in high-temperature high-pressure water containing impurities of chloride and oxygen found in a steam generator of nuclear power plants. The inherent uncertainties of the fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL) statistic method. Furthermore, a frequency domain technique is used to determine the response power spectrum density (PSD) function of a structural component subjected to a random vibration profile excitation. The fatigue life of the component is then estimated through a probabilistic linear damage cumulative model.
Numerical Simulation of the Assembly Process of Bolted Flange Joints Used in Rotating Machinery
Authors: Zhu Linbo , Bouzid Abdel-Hakim , Hong Jun , Shi Zhenming
Published: October 2020

Bolted joints are widely used to connect structural components in rotating machinery. However, the initial tightening of the bolts is a delicate operation because it is extremely difficult to achieve the target load and uniformity due to elastic interaction. The scatter in the bolt preload has a major impact on the concentricity and consequently the dynamic behavior of rotating machinery. The risk of failure due to vibration and fatigue under service loading becomes an issue. This paper treats the effect of elastic interaction on the eccentricity during the tightening of bolted joints of rotating machinery using finite element (FE) method. In this regard, a two-component bolted flange joint of a high pressure compressor (HPC) of an aero-engine is investigated. The component surface tolerances measured by Rotary Precision Instruments (RPI) are taken into account in the numerical simulation. A method is proposed to calculate the concentricity of components obtained from the radial runout data based on the Least Square method (LSM). The scatter in bolt preload under different interference fit, surfaces tolerance, initial preload, and tightening sequence are evaluated. Furthermore, the influence of these structures and tightening sequence parameters on the concentricity are investigated. The validity of the finite element analysis is supported by experimental tests conducted on scaled specimens of HPC. This study can provide guidance and enhance the dynamic performance of bolted joints for rotating machinery.
Elastic-Plastic Analogy for Examination of Softening Response for Strip Yield Models
Authors: Metzger Don , Reinhardt Wolf
Published: October 2020

The manner in which the spread of inelastic deformation of a softening cohesive zone affects the load capacity is examined. The analysis makes use of an elastic-plastic analogy to the strip yield model applied to pure bending. The example of pure bending is one case where inelastic deformation contributes to enhancing the load capacity. The analytical solution to the elastic-plastic case is developed for zero hardening (baseline for strip yield case for which analytical solution is known) as well as for a range of linear softening rates. Evaluation of the results shows that the maximu m bending load capacity is always reached before the stress at the surface becomes zero.
Evaluation of High Temperature Material Models for High Temperature Advanced Reactor Component Analysis
Authors: Casagranda A. , Pitts S. A. , Spencer B. W. , Chakraborty A. , Messner M. C. , Capolungo L.
Published: October 2020

The high temperature environments in proposed advanced reactor designs pose unique challenges for the integrity of structural components. Capabilities to model metals in this environment are being developed in Grizzly, a finite element-based structural simulation code developed at Idaho National Laboratory. To represent the constitutive behavior of metals at high temperatures, Grizzly offers two distinctly different approaches.

The first is to use phenomenological engineering models with a unified representation of creep and plasticity. These models are provided through a library developed at Argonne National Laboratory. These models represent the effects of multiple important phenomena on the aspects of the material response important to engineering analysis and are calibrated to engineering-scale material data. The second modeling approach is being developed at Los Alamos National Laboratory and is based on mesoscale models that directly account for the effects of material texture. These models directly represent the underlying physical phenomena that affect the engineering-scale material response. Through the use of data analytics, reduced order models based on the mesoscale models have been developed. These models can be efficiently used in engineering calculations, while faithfully representing the behavior of the high fidelity mesocale models. This paper provides brief summaries of both modeling approaches, and demonstrates their application on a common set of bench-mark problems to assess their applicability to component-level simulations.
Development of “Material Specific” Creep Continuum Damage Mechanics-Based Constitutive Equations
Authors: Vega Ricardo , Cano Jaime A. , Stewart Calvin M.
Published: October 2020

The objective of this study is to introduce a method for creating “material specific” creep continuum damage mechanics-based constitutive models. Herein, material specific is defined as a constitutive model based on the mechanism-informed minimum creep strain rate (MCSR) equations found in deformation mechanism maps and calibrated to available material data. The material specific models are created by finding the best MCSR model for a dataset. Once the best MCSR model is found, the Monkman Grant inverse relationship between the MCSR and rupture time is employed to derive a rupture equation. The equations are substituted into continuum damage mechanics-based creep strain rate and damage evolution equations to furnish predictions of creep deformation and damage. Material specific modeling allows for the derivation of creep constitutive models that can better the material behavior specific to the available data of a material. The material specific framework is also advantageous since it has a systematic framework that moves from finding the best MCSR model, to rupture time, to damage evolution and, creep strain rate. Data for Alloy P91 was evaluated and a material specific constitutive model derived. The material specific model was able to accurately predict the MCSR, creep deformation, damage, and rupture of alloy P91.
Establishing AMR Structural Integrity Codes and Standards for UK GDA (EASICS): Overview of Activities to Provide Guidance for the UK Generic Design Assessment Process for High Temperature Advanced Modular Reactors
Authors: Chevalier Marc , James Peter , Underwood Nicholas
Published: October 2020

The UK government has committed to achieving “net-zero” carbon emissions by 2050. Nuclear power is expected to play an important role in this undertaking. Therefore delivering new safe and cost efficient nuclear technologies is seen as essential by both the UK Government and industry. Included in these new nuclear technology are small modular Generation VI reactors, referred to as Advanced Modular Reactors (AMRs). It has previously been identified that there is currently no clear route to demonstrating the structural integrity of such high temperature reactors to the UK regulator, with known short falls in the available codes and standards.

Therefore EDF, Rolls-Royce and the National Nuclear Laboratory have collaborated to deliver the “Establishing AMR Structural Integrity Codes and Standards for UK GDA” (EASICS) project (part funded by the UK Government). This project looks to provide guidance on how existing design codes (such as RCC-MRx and ASME Section III Division 5) and assessment methodologies (such as R5 and R6) can be used to demonstrate the integrity of design within a UK regulatory framework. In addition, the project looks to make technological advancements in a number of key areas to address some known shortfalls in the available design codes and standards. These include 1) probabilistic design, 2) thin section defect tolerance and 3) creep-fatigue behaviour.

This paper provides a summary of the current findings and an overview of the planned activities regarding Codes and Standards aspects of the project. This includes a review of the challenges within a UK regulatory framework for high temperature plant, key differences between available high temperature design codes and assessment methodologies, operational experience of high temperature nuclear reactors and key shortfalls in the available codes and standards. It will finally provide a description of what the final EASICS guidance document will be expected to contain when delivered in 2021.
Comparison of Evolution Fatigue With Simplified Elastic Plastic Analysis, Plastic Analysis and a Fracture Mechanics Approach
Authors: Cedergren Joakim
Published: October 2020

Fatigue analyzes are performed to ensure that no damage leading to failure will occur in a component.

In ASME III NB-3222.4(e), a method is provided for analyzing a component’s resistance against cyclic loads. In ASME NB-3228.5 or alternatively NB-3653.6 (c) a simplified elastic-plastic method is given to take plasticity into account. According to NB-3228.4 (c), fatigue evaluation is allowed with plastic analysis where the stress amplitude is determined from the numerically maximum principal total strain range.

This report examines the fatigue life, using a continuum mechanics approach, of a pipe penetration that is subjected to a rapid cooling down followed by a slow heating up. Simplified elastic-plastic analysis and plastic analysis are performed. The analysis also takes into account the FEN-factor according to the method given NUREG/CR6909.

The fatigue life is also determined by a fracture mechanics approach using a R6 based fracture assessment and crack growth analysis.

The results show a large difference in fatigue life depending on the method used.

For the plastic analyzes it is of great importance to the result in which direction the evaluation is made. For the present case the maximum principal total strain range is obtained in the radial direction. The stresses in this direction are small. A crack tangentially to this direction lacks physical significance to a pipe geometry and cannot lead to failure. In this case it is recommended that evaluation is made for the strain range in the axial direction for pipe geometries instead of the maximum principal total strain range.
Comparison of Residual Stress Measurements on Single Bead-on-Plate Welds of a Martensitic Steel Using Neutron Diffraction
Authors: Alexandratos Spyridon A. , Wimpory Robert C. , Lee Tung-Lik , Mac Ardghail Padraig , Leen Sean B. , O’Dowd Noel P.
Published: October 2020

During the welding process, a material is subjected to thermal cycles with rapid heating and cooling rates resulting in residual stress in the weld and the base metal. These residual stress may affect the mechanical performance leading to premature failure of components. Therefore, it is critical to have a detailed knowledge of the residual stress distribution in the weld region as well as in the vicinity in order to predict the service life of components. Due to the high neutron penetration power, neutron diffraction is one of the most useful techniques for nondestructive evaluation of residual stress in welded regions within the bulk. In this paper, neutron diffraction was used to investigate the residual stress distribution within three single bead-on-plate welds of P91 martensitic steel. Residual stress measurements were performed at different neutron diffraction instruments and different methodology of stress determination was applied. Measurements were carried out at the diffractometers Engin-X (ISIS Neutron Source, Rutherford Appleton Laboratory), E3 (BER-II, Helmholtz-Zentrum Berlin) and SALSA (Institut Laue-Langevin). The results of the measurements presented here, were used to determine the variability of the three instruments and compare the effect of different welding parameters on residual stress. The residual stress measurements were also compared with the respective results of the Task Group 1 (TG1) of the European Network on Neutron Techniques standardization for structural integrity (NET).
Development of Valve Performance Qualification Methodology and Testing
Authors: Josodipuro Irawan
Published: October 2020

Valves play important roles in piping systems. In the oil and gas industry, for example, they are used to control flow rates in pipes, isolate flow, and provide over pressure protection of equipment. Given the role of valves in process industries, it is important that valve end-users feel confident that the valves they procure meet the design and qualification requirements in the specification. This paper presents a case study where there have been breakdowns in the qualification of valves being offered by valve suppliers to the industry that did not comply with industry standards which can adversely impact plant operations and personnel safety. The loss of valve supplier credibility is a concern that rarely occurs in mature economies but seem to be more prevalent in countries where design and testing standards are either relatively new or non-existent. To address this issue, the author presents a systematic approach that can be used to ensure that valves supplied to end-users in oil and gas industries in emerging countries meet the design requirements and standards they are required to meet. The process used to control the manufacturers begins with a qualification plan which each supplier has to establish for its product line. Following compliance with the qualification plan, a valve type criticality matrix is introduced to the manufacturers that classifies the criticality of each valve in the system and the associated testing program(s) that the manufacturers need to meet. The qualification program is conducted by the national oil and gas company and acknowledged by the country’s regulator. The recently established program has shown some merit and could be applied to all manufacturers in emerging countries to ensure consistency. The details of the qualification program used and how the process is evaluated are covered in the body of the paper together with examples of how the process has worked.
Effect of Friction Coefficients Regarding Bolt Self-Loosening
Authors: Shoji Yasumasa
Published: October 2020

As there have been many researches for bolt self-loosening and a lot of knowledge have been accumulated, the phenomena has been understood more and more clearly. On the other hand, it is quite difficult to achieve both non-self-loosening and easy bolting tasks. In practical situations, easy and stable bolting is more focused and torque control is employed for tension control in the fields. For the stable bolting, friction of the threads is reduced by lubrication. However, the effect of this friction reduction is not yet investigated in the aspect of self-loosening. In this paper, the effect of frictions between male and female threads and between nut and bearing surface is investigated by FEA simulations. This provides information how self-loosening can be controlled. In this paper, the motion of the fastened plate transverse to the bolt axis is considered. This motion is known as the easiest motion to make self-loosening in experience and also as shown so in the author’s previous researches. The friction seems to increase self-loosening and also decrease self-loosening at the same time. It seems that the friction on the bearing surface drives self-loosening and friction on the thread surfaces prevents it. In this paper, both the frictions are examined in the relative manner with the Finite Element Analyses.
Drop Tests Assessment of Internal Shock Absorbers for Packages Loaded With Encapsulations for Damaged Spent Nuclear Fuel
Authors: Müller Lars , Scheidemann R. , Schönfelder T. , Komann S. , Wille F.
Published: October 2020

Damaged spent nuclear fuel (DSNF) can be loaded in German dual-purpose casks (DPC) for transport and interim storage. Encapsulations are needed to guarantee a safe handling and a tight closure, separated from the package enclosure. These encapsulations shall be durable and leak-tight for a long storage period, because they are usually not accessible within periodical inspections of the DPC. Due to the general design of DPCs for standard fuel assemblies, specific requirements have to be considered for the design of encapsulations for DSNF to ensure the loading in existing package designs. Especially the primary lid system of a DPC is designed for maximum loads due to the internal impact of the content during drop test conditions. The main difference of encapsulations for damaged spent nuclear fuel is that they have usually a much higher stiffness than standard fuel assemblies. Therefore the design of an internal shock absorber, e.g. at the head of an encapsulation is required to reduce mechanical loads to the primary lid system during impacts.

BAM as part of the German competent authority system is responsible for the safety assessment of the mechanical and thermal package design, the release of radioactive material and the quality assurance of package manufacturing and operation. Concerning the mechanical design of the encapsulation BAM was involved in the comprehensive assessment procedure during the package design approval process. An internal shock absorber was developed by the package designer with numerical analyses and experimental drop tests. Experimental drop tests are needed to cover limiting parameters regarding, e.g. temperature and wall thickness of the shock absorbing element to enable a detailed specification of the whole load-deformation behavior of the encapsulation shock absorber.

The paper gives an overview of the assessment work by BAM and points out the main findings which are relevant for an acceptable design of internal shock absorbers. The physical drop tests were planned on the basis of pre-investigations of the applicant concerning shape, dimension and material properties. In advance of the final drop tests the possible internal impact behavior had to be analyzed and the setup of the test facility had to be validated. The planning, performance and evaluation of the final drop tests were witnessed and assessed by BAM. In conclusion it could be approved that the German encapsulation system for damaged spent nuclear fuel with shock absorbing components can be handled similar to standard fuel assemblies in existing package designs.
Fatigue Assessment of Dented Pipeline Specimens
Authors: Freire J. L. F. , Paiva V. E. L. , Gonzáles G. L. G. , Vieira R. D. , Diniz J. L. C. , Maneschy J. E. , d’Almeida A. L. F. S.
Published: October 2020

This paper reports results from an investigation program launched with the objective of assessing fatigue lives of actual pipeline specimens with dents. Nine pipeline 3m-length specimens were constructed with low carbon steel pipes API 5L Gr. B. The specimens had 323mm diameter and 6.35mm wall thickness. The specimens were loaded with hydrostatic internal pressure pulsating at a 1Hz rate. Six specimens had 15% deep longitudinal smooth dents (ratio between dent depth and outside specimen diameter) and three specimens had complex longitudinal 6% deep dent shapes. Nominal and hot spot stresses and strains were determined by experimental techniques (Fiber Optic Bragg Strain Gages - FBSG, and Digital Image Correlation - DIC) and by a numerical technique (Finite Elements - FE). The stresses and strain fields determined from nominal loading conditions or from experimental measurements and from the finite element analyses were combined with different fatigue assessment methods. The estimated lives were compared with the actual test results. The fatigue assessment methods encompassed those proposed by the Pipeline Defect Assessment Manual (PDAM) and by the API 579-1/ASME FFS-1 Level 2 methods described in parts 12 (Dents) and 14 (Fatigue). Most of the predicted lives exhibited high level of conservatism. A Level 3 method that employed experimentally and numerically determined hot-spot strains in conjunction with a fatigue strain-life equation proposed by Coffin-Manson predicted fatigue lives very close to the test results.
Challenging the Industry Practices of Temperature Distribution, SIF and its Effects on Piping Design
Authors: Bhende Gaurav , Jagdale Amit , Patel Jitendra
Published: October 2020

The piping, welding and its fittings contributes to around 25–35% of the total material [1] of any process plant. The quantity of the piping and fittings required in critical pipes (lines) is largely influenced by the flexibility requirements to comply with applicable codes. Since the pressure and weight driven stresses are primary in nature and taken care by the thickness & supports respectively. The Secondary stresses are mainly caused due to temperature and determines the route of the pipe. Unfortunately, there is no sufficient awareness amongst the Process engineers, who dictate the temperature, about the effect of temperature (listed in line list) on the plant cost. To make the situation worse, very often the pipe stress engineers follow thumb rules, conservative design basis while applying temperature to pipes without questioning process engineers the basis and without having experimental evidences which in turn ends up adding to the cost, labor and time of the plant. Another factor influencing the ‘flexibility need’ is ‘Stress Intensification Factor’ which, as well, incorrectly multiplied by conservative numbers, especially in case of 45° branch fittings. Even ‘Flange leakage analysis’ needs to be performed to ensure safety of the plant.

This paper challenges the mis-concepts in temperature distribution of a piping system by analyzing a real-life problem. Also, it provides the actual temperature measurements and compares it with theoretical values. At the end it provides a ‘Temperature de-rating factor, @(Taa)’ which can be used to derive actual expected temperature distribution. Further this paper provides a table to get the actual SIF of Tee and Fittings obtained by FEA. At the end it provides comparison between the results obtained by present industry practices against practical analysis and its effect on cost.
Investigation of the relationship between classical and nonclassical ultrasound nonlinearity parameters and microstructural mechanisms in metals
Authors: Levy Katherine Marie Scott , Kim Jin-Yeon , Jacobs Laurence J.
Published: October 2020

This research studies two nonlinear ultrasound techniques: second harmonic generation and nonlinear resonant ultrasound spectroscopy, and the relationship to microstructural mechanisms in metals. The results show that there is a large change in both the classical, β, and nonclassical, α, ultrasound nonlinearity parameters in response to three specific microstructural mechanisms: precipitate growth in and along the grain boundaries, dislocations, and precipitate pinned dislocations. For example, both β and α increase with the growth of the precipitate radii (precipitate-pinned-dislocations). Additionally, both β and α increase when there is a growth of precipitates in and along the grain boundaries. As expected, β and α decrease when there is a removal of dislocations in the material. The relationship between β and α, and the microstructural mechanisms studied provide a quantitative understanding of the relationship between measured nonlinearity parameters and microstructural changes in metals, helping to demonstrate the possibility of using these two independent, but complementary, nonlinear ultrasound procedures to monitor microstructural damage.
Bioinspired wing and tail morphing extends drone flight capabilities
Authors: Ajanic Enrico , Feroskhan Mir , Mintchev Stefano , Noca Flavio , Floreano Dario
Published: October 2020

The combination of bioinspired morphing wing and tail made of artificial feathers improves the flight performance of drones.
Whole-Genome Sequence of Cyanobacterium
Oxynema
sp. AP17, Isolated from an Indian Mangrove Forest
Authors: Basu Shayontani , Maruthanayagam Veerabadhran , Pramanik Arnab , Mukherjee Joydeep
Published: October 2020

Oxynema
sp. AP17 is the second distinct species of the
Oxynema
genus, and it differs from the first (
Oxynema thaianum
) in 16S-23S internal transcribed spacer (ITS) sequence, morphology, and optimal salinity. The genome size is 6.37 Mbp; 4,801 protein-coding genes, 74 tRNAs, and 5 each of the 16S, 23S, and 5S rRNAs constitute the genome.
Draft Genome Sequence of Streptomyces mexicanus Strain Q0842, Isolated from Human Skin
Authors: Boxberger Manon , Ben Khedher Mariem , Levasseur Anthony , La Scola Bernard
Published: October 2020

In 2003,
Streptomyces mexicanus
was reported as a novel xylanolytic bacterial species isolated from soil; a partial genome sequence was determined. In 2019, a strain from the same species was isolated from a hand skin swab sample from a healthy French woman. Genome sequencing revealed an 8,011,832-bp sequence with a GC content of 72.5%.
Functional Characterization of Core Regulatory Genes Involved in Sporulation of the Nematophagous Fungus Purpureocillium lavendulum
Authors: Chen Mi , Yang He-Yu , Cao Yan-Ru , Hui Quan-Quan , Fan Hai-Feng , Zhang Chen-Chen , Han Jing-Jing , Guo Zhi-Yi , Xu Jianping , Zhang Ke-Qin , Liang Lian-Ming
Published: October 2020

Plant-parasitic nematodes cause serious damage to crops throughout the world.
Purpureocillium lavendulum
is a nematophagous fungus which is a natural enemy of nematodes and a potential biocontrol agent against plant-parasitic nematodes. The conidia play an important role during infection of nematodes. In this study, we identified and characterized genes involved in regulating asexual development of
P. lavendulum
. We found that these genes not only regulate conidiation but also influence secondary-metabolite production. This work provides a basis for future studies of fungus-nematode interactions and nematode biocontrol.
Estimating the contribution of tributary sand inputs to controlled flood deposits for sandbar restoration using elemental tracers, Colorado River, Grand Canyon National Park, Arizona
Authors: Chapman Katherine A. , Best Rebecca J. , Smith M. Elliot , Mueller Erich R. , Grams Paul E. , Parnell Roderic A.
Published: October 2020

Completion of Glen Canyon Dam in 1963 resulted in complete elimination of sediment delivery from the upstream Colorado River basin to Grand Canyon and nearly complete control of spring snowmelt floods responsible for creating channel and bar morphology. Management of the river ecosystem in Grand Canyon National Park now relies on dam-release floods to redistribute tributary-derived sediment accumulated on the channel bed to higher-elevation sandbars. Here, we used multivariate mixing analysis of sediment elemental compositions to evaluate the extent to which flood deposits derive from tributary-supplied sand compared to reworked, relict predam sediment. The concentrations of seven major and trace elements (Fe, Ca, K, Ti, Rb, Sr, and Zr) were measured in very fine–, fine-, and medium-grained sand from flood deposits using X-ray fluorescence and interpreted using a Bayesian mixing model to characterize the proportion of sand originating from the Paria River, the only major tributary within the study reach. Flood deposits from the 2013 and 2014 controlled floods contained 69% ± 16% and 84% ± 20% Paria River–derived material, respectively, with substantial variation among sites. Based on a sand mass balance, we calculated that under decreasing storage conditions since 1963, ∼77%–83% of the annual Paria River sand flux needs to be retained within the mass of active sand stored in Marble Canyon each year to reach the observed concentration of Paria River sand at sample locations. This finding suggests that the use of controlled floods may continue to be effective for sandbar maintenance, provided sand inputs from the Paria River do not decline.
Dilemma of crystalloid resuscitation in non-exsanguinating polytrauma: what is too much?
Authors: van Wessem Karlijn , Hietbrink Falco , Leenen Luke
Published: October 2020

Background

Aggressive crystalloid resuscitation increases morbidity and mortality in exsanguinating patients. Polytrauma patients with severe tissue injury and subsequent inflammatory response without major blood loss also need resuscitation. This study investigated crystalloid and blood product resuscitation in non-exsanguinating polytrauma patients and studied possible adverse outcomes.

Methods

A 6.5-year prospective cohort study included consecutive trauma patients admitted to a Level 1 Trauma Center intensive care unit (ICU) who survived 48 hours. Demographics, physiologic and resuscitation parameters in first 24 hours, Denver Multiple Organ Failure scores, adult respiratory distress syndrome (ARDS) data and infectious complications were prospectively collected. Patients were divided in 5 L crystalloid volume subgroups (0–5, 5–10, 10–15 and >15 L) to make clinically relevant comparisons. Data are presented as median (IQR); p value <0.05 was considered significant.

Results

367 patients (70% men) were included with median age of 46 (28–61) years, median Injury Severity Score was 29 (22–35) and 95% sustained blunt injuries. 17% developed multiple organ dysfunction syndrome (MODS), 4% ARDS and 14% died. Increasing injury severity, acidosis and coagulopathy were associated with more crystalloid administration. Increasing crystalloid volumes were associated with more blood products, increased ventilator days, ICU length of stay, hospital length of stay, MODS, infectious complications and mortality rates. Urgent laparotomy was found to be the most important independent predictor for crystalloid resuscitation in multinominal regression analysis. Further, fresh frozen plasma (FFP)<8 hours was less likely to be administered in patients >5 L compared with the group 0–5 L. With increasing crystalloid volume, the adjusted odds of MODS, ARDS and infectious complications increased 3–4-fold, although not statistically significant. Mortality increased 6-fold in patients who received>15 L crystalloids (p=0.03).

Discussion

Polytrauma patients received large amounts of crystalloids with few FFPs <24 hours. In patients with<10 L crystalloids,<24-hour mortality and MODS rates were not influenced by crystalloid resuscitation. Mortality increased 6-fold in patients who received >15 L crystalloids ≤24 hours. Efforts should be made to balance resuscitation with modest crystalloids and sufficient amount of FFPs.

Level of evidence

Level 3.

Study type

Population-based cohort study.
The impact of preconditioning exercise on the vascular response to an oral glucose challenge
Authors: Au Jason S. , Beaudry Kayleigh M. , Pancevski Kristian , Hughson Richard L. , Devries Michaela C.
Published: October 2020

Exercise elicits direct benefits to insulin sensitivity but may also indirectly improve glucose uptake by hemodynamic conditioning of the vasculature. The purpose of this study was to examine the modifying effect of 3 different types of exercise on the vascular response to an oral glucose challenge. Twenty healthy adults (9 women, 11 men; aged 23 ± 3 years) completed a standard oral glucose tolerance test (OGTT) at rest, as well as 1.5 hours after moderate continuous cycling exercise (30 min; 65% peak oxygen consumption), high-intensity interval cycling exercise (10 × 1 min at 90% peak heart rate), and lower-load higher-repetition resistance exercise (25–35 repetitions/set, 3 sets). Brachial and superficial femoral artery blood flow, conductance, and oscillatory shear index were measured throughout the OGTT. Regardless of rested state or exercise preconditioning, the OGTT induced reductions in brachial artery blood flow and conductance (p < 0.001), and transient increases in brachial and superficial femoral artery oscillatory shear index and retrograde blood flow (p < 0.01). Continuous cycling and resistance exercise were followed with a small degree of protection against prolonged periods of oscillatory flow. Our findings imply transient peripheral vasoconstriction and decreased limb blood flow during a standard OGTT, for which prior exercise was unable to prevent in healthy adults.

Novelty: We investigated the impact of continuous, interval, and resistance exercise on the hemodynamic response to an OGTT. Our findings suggest decreased upper-limb blood flow during an OGTT is not prevented by prior exercise in healthy adults.
Finite difference method for solving a physical problem in fluid flow
Authors: Abualnaja Khadijah M.
Published: October 2020

Interaction between nonuniform heat source/sink, magnetic field and thermal radiation with heat flux through the flow of non-Newtonian power-law fluid due to a linearly stretching sheet was studied numerically using an implicit finite difference method (FDM). The heat flux is assumed to depend on both the thermal conductivity and the thermal radiation. Besides, the effects of all governing parameters, such as the magnetic parameter, thermal conductivity parameter, the power-law index parameter, Prandtl number, the space-dependent heat source/sink parameter, the temperature-dependent heat source/sink parameter, and the radiation parameter, on the profiles of velocities and temperature are studied and discussed. In particular, thermal radiation was found to play a key role in the heat transfer characteristics and in the formation of thermal boundary layer. Generally, our numerical results reveal that both the velocity and temperature distributions are marginally influenced by both the magnetic parameter and power-law index. A good agreement is observed between our results via finite difference method and the previously published numerical results for some special case.
A criterion for the existence of nilpotent hall π-subgroups
Authors: Ahanjideh Neda
Published: October 2020

Let [Formula: see text] be a nontrivial normal subgroup of [Formula: see text] and [Formula: see text]. In this paper, we show that if [Formula: see text] and for every [Formula: see text]-element [Formula: see text] with [Formula: see text], [Formula: see text], for some integer [Formula: see text], then [Formula: see text] has nilpotent Hall [Formula: see text]-subgroups. Further, we show that if [Formula: see text], then [Formula: see text] has abelian Hall [Formula: see text]-subgroups.