bluuebunny/crossref_metadata_2025 huggingface dataset:
Limitation of sucrose biosynthesis shapes carbon partitioning during plant cold acclimation
Authors: Kitashova Anastasia , Adler Stephan O. , Richter Andreas S. , Eberlein Svenja , Dziubek Dejan , Klipp Edda , Nägele Thomas
Published: November 2022

Cold acclimation is a multigenic process by which many plant species increase their freezing tolerance. Stabilization of photosynthesis and carbohydrate metabolism plays a crucial role in cold acclimation. To study regulation of primary and secondary metabolism during cold acclimation of Arabidopsis thaliana, metabolic mutants with deficiencies in either starch or flavonoid metabolism were exposed to 4°C. Photosynthesis was determined together with amounts of carbohydrates, anthocyanins, organic acids and enzyme activities of the central carbohydrate metabolism. Starch deficiency was found to significantly delay soluble sugar accumulation during cold acclimation, while starch overaccumulation did not affect accumulation dynamics but resulted in lower total amounts of \sucrose and glucose. Anthocyanin amounts were lowered in both starch deficient and overaccumulating mutants. Vice versa, flavonoid deficiency did not result in a changed starch amount, which suggested a unidirectional signalling link between starch and flavonoid metabolism. Mathematical modelling of carbon metabolism indicated kinetics of sucrose biosynthesis to be limiting for carbon partitioning in leaf tissue during cold exposure. Together with cold‐induced dynamics of citrate, fumarate and malate amounts, this provided evidence for a central role of sucrose phosphate synthase activity in carbon partitioning between biosynthetic and dissimilatory pathways which stabilizes photosynthesis and metabolism at low temperature.
Worsening racial disparity in waitlist mortality for pediatric heart transplant candidates since the 2016 Pediatric Heart Allocation Policy revision
Authors: Wright Lydia K. , Gajarski Robert J. , Phelps Christina , Hoffman Timothy M. , Lytrivi Irene D. , Magnetta Defne A. , Shaw Fawwaz R. , Thompson Consuela , Weisert Molly , Nandi Deipanjan
Published: November 2022

Background

The US Pediatric Heart Allocation Policy (PHAP) was revised in March 2016, with the goal of reducing waitlist mortality. We evaluated the hypothesis that these changes, which increased status exceptions, have worsened racial disparities in waitlist outcomes.

Methods

Children in the Pediatric Heart Transplant Study database listed for first heart transplant from January 2012 – June 2020 were included and stratified by listing before (Era 1) or after (Era 2) the PHAP revision.

Results

A total of 4,089 children were listed during the study period. Compared with white children (n = 2648), non‐white children (n = 1441) were more likely to have an underlying diagnosis of cardiomyopathy in both eras. Waitlist mortality was similar in white and non‐white children in Era 1, but comparatively worse for non‐white children in Era 2. In multivariable analysis controlling for diagnosis, age, and severity markers, non‐white children had a significantly higher waitlist mortality only in Era 2 (Era 1: sHR 1.22 [95%CI 0.90 – 1.66] vs. Era 2: sHR 1.57 [95%CI 1.17 – 2.10]).

Conclusions

Widening racial disparities in waitlist mortality may be an unintended consequence of the 2016 PHAP revision. Additional analyses may inform the degree to which this policy vs. unrelated changes in care differentially contribute to these disparities.
Risk factors for meticillin‐resistantStaphylococcus aureus(MRSA) carriage inMRSA‐exposed household pets
Authors: Cotter Caitlin J. , Ferradas Cusi , Ludwig Shanna , Dalton Kathryn , Larsen Jesper , Laucks Daniel , Iverson Sally Ann , Baron Patrick , Tolomeo Pam C. , Brazil Amy M. , Ferguson Jacqueline M. , Lautenbach Ebbing , Rankin Shelley C. , Morris Daniel O. , Davis Meghan F.
Published: November 2022

Background

Household pets can carry meticillin‐resistantStaphylococcus aureus(MRSA) introduced to the home by their human companions. Specific factors promoting pet carriage of this pathogen have not been fully elucidated.

Objective

This study evaluated MRSA cultured from pets and the home environment in households where a human infected with MRSA had been identified, and aimed to determine potential risk factors for pet MRSA carriage.

Materials and Methods

Humans diagnosed with community‐associated MRSA (CA‐MRSA) skin or soft‐tissue infection (SSTI) in the mid‐Atlantic United States were identified. One hundred forty‐two dogs and cats from 57 affected households were identified of which 134 (94.4%) pets and the household environment were sampled for bacterial culture, PCR confirmation andspa‐typing for MRSA strain determination. Samples were obtained 3 months later from 86 pets.

Results

At baseline, 12 (9.0%) pets carried MRSA. Potential risk factors associated with carriage included pet bed (environmental) MRSA contamination, flea infestation and prior antimicrobial use in the pet. Pets tended to carry human‐adapted MRSA strains andspa‐types of MRSA isolates cultured from pets were concordant with strains cultured from the home environment in seven of eight homes (87.5%) at baseline.

Conclusions and Clinical Relevance

Results may inform risk‐based veterinary clinical recommendations and provide evidence for selective pet testing as a possible alternative to early removal of pets from the homes of humans infected with MRSA. MRSA contamination of the home environment is likely an important risk factor for pet MRSA carriage, and household interventions should be considered to reduce risk of MRSA carriage in exposed pets.
Coke Drum Keyhole Optimization With Alloy Weld Overlay
Authors: Fernando John , Falo Enzo , Kwok Henry , Iverson Millar , Wong Leanne , Yuen Simon , Chan Luke
Published: November 2022

Coke drums are subjected to severe cyclic thermal and structural loading, and have therefore become canonical examples of thermo-mechanical fatigue failure. One of the most common locations of fatigue failure is at the skirt-to-shell attachment weld. To increase the fatigue life of the attachment weld, vertical slots and keyholes are often machined in a circumferential pattern near the top of the skirt to increase local flexibility near the weld. While this methodology provides a cost-effective means to improve the fatigue life of the attachment weld, stress concentrations that form at the keyholes result in crack initiation and propagation. As such, frequent repairs are necessary to prevent crack growth at the keyhole locations. In the present investigation, a new keyhole design consisting of N06625 overlay at the keyhole locations as a means of delaying crack initiation has been studied using FEA simulations. To further optimize the new design, a sensitivity study involving keyholes with and without fillets was also performed to determine the effect of fillet size on fatigue life. The results presented herein indicate that increasing the keyhole fillet radii mitigates the effect of stress concentrations on the corners of the keyholes, which delays crack initiation. Furthermore, it has been demonstrated that adding N06625 overlay at the keyhole protects the base metal from excessive plastic strain. In particular, the proposed design has been shown to improve the fatigue life of the keyhole by at least an order of magnitude when compared to analogous keyhole designs with no overlay, which has the potential to improve the overall cost-effectiveness of keyhole implementation by a significant margin.
Evaluation for Residual Lifetime and Remaining Axial Tension to Loosening Failure on Bolted Joints Used in Long-Life Machine and Plant Equipment
Authors: Hareyama Soichi , Manabe Kenichi , Kobayashi Satoshi
Published: November 2022

The bolted joints used in mechanical structures loosen owing to, for example, a decrease in the initial axial tension (clamping force) and repeated external forces in the direction perpendicular to the axis. A Junker-type loosening test used to evaluate the performance of various types of locking devices in a short period of time has been established. In such a test, it is possible to compare the loosening performance characteristics of various bolted joints and locking devices. However, it has not been possible to absolutely determine the period of time that they can maintain their initial locking performance. This paper presents a method of estimating the absolute locking performance of bolted joints. The absolute evaluation of self-loosening is indispensable for the prediction of the lifetime of locking devices (parts and methods) in actual machines. From the results of our experimental study, we found a strong linear correlation on logarithmic coordinates between the decreases in axial tension (measured/initial axial tension) and the number of operations (or working time or mileage) since the last tightening. The loosening phenomenon of bolted joints can be observed as the tendency of the initial or residual axial tension to decrease. By utilizing the regression formula at logarithmic coordinates, we show an estimation method for residual axial tension to answer various questions such as “How much of the axial tension remains after tens of thousands of hours (operations)?” Therefore, it is possible to determine to what extent can the bolted joints of long-life machines and plant equipment in medium-to-long-term use be considered to loosening failure. Finally, we describe the judgement criterion for loosening. We examine evaluation criteria such as “Is the residual axial tension sufficient for the prevention of loosening failure?” The limit surface pressure is examined as the upper limit axial tension. As the lower limit axial tension, the allowable value of the external transverse force is examined.
New ASME Standard on Plant Systems Design
Authors: Hill Ralph , deLamare Michael , Harper Jared , Shook Jeremy
Published: November 2022

This paper describes the purpose and objectives of the ASME Plant Systems Design Standard (PSD-1) that is currently under development. A general overview of the content of the standard and a more detailed overview of the plant systems design process are provided.

The plant systems design development processes that are the focus of PSD-1 are intended as enhancements to current industry design practices with the objective of reducing design errors or omissions that can increase the cost of design, construction, operation, maintenance, decontamination, decommissioning, and disposal.

PSD-1 integrates a system engineering approach with current industry design processes. Implementing systems engineering processes, methods and tools will provide greater assurance that customer and other stakeholder requirements are addressed at the correct stage of design in an efficient manner. This approach will reduce design errors, avoid re-designs and re-works, and provide a more cost-effective design.
Testing for the Effects of Pressurized Hydrogen on Polymeric Elastomers
Authors: Ellis Jeff , Whitman Jessica , Zoller Laura
Published: November 2022

This work demonstrated an experimental testing process to quantitatively test for the effects of pressurized hydrogen on polymeric materials. It was shown that some o-ring materials are susceptible to deleterious property changes. A high-pressure hydrogen testing system with a window was fabricated and was used to soak elastomeric o-rings in hydrogen at temperatures from 22 to 40°C and 13.8 to 16.5 MPa for up to 96 hours. Next, the o-rings were observed through the window during the depressurization. Finally, the o-rings were characterized before and after hydrogen exposure for hardness, weight, tensile strength, and ultimate elongation. The data showed the following four quantitative trends 1) durometer decreased up to 14%, 2) weight was mostly unchanged, 3) tensile strength decreased up to 35%, 4) ultimate elongation decreased up to 55%.
A Fragment Impact Simulation for a Turbomolecular Vacuum Pump Blade Failure Event
Authors: Valdiviez Robert
Published: November 2022

This simulation effort is of a high-speed fragment impacting a housing wall in order to predict if the housing material and configuration are capable of stopping the fragment. This application involves a turbine style high-vacuum pump, known as a turbomolecular pump, that produces a high-vacuum atmosphere within a given volume that it is connected to. The basic design of the turbomolecular pump has a motor turned rotor with several turbine blades attached to it, and that spins at high rotational speeds, up to 60,000 revolutions per minute. The turbine blades are configured on the rotor to impact and move gas molecules axially through the pump and eventually to an exhaust location. In order to achieve a high pumping speed, the rotor needs to turn at very high rotational speeds. A turbine blade failure, therefore, can throw high-speed fragments against the turbine pump housing, and potentially breach the housing. The safety design objective is to keep all debris captured within the turbine pump housing as the pump rotor spins down from the blade failure event. The dynamic properties of the materials of construction are applied, along with the pertinent initial and boundary conditions to create a simulation model that predicts the results of this high-speed fragment impact case.
An Improved Fixture to Quantify Corrosion in Bolted Flanged Gasketed Joints Subjected to Service Conditions
Authors: Hakimian Soroosh , Hof Lucas A. , Bouzid Hakim A.
Published: November 2022

This study concentrates on the corrosion behavior of bolted flanged gasketed joint systems. A novel fixture is proposed to quantify the corrosion between gaskets and flanges under services conditions. According to the literature, due to the presence of crevices and potential differences between gaskets and flanges, corrosion widely occurs in such joints. Crevice corrosion and galvanic corrosion can create paths to leakage of the pressurized fluid and may cause catastrophic failure. Corrosion in bolted gasketed joints was investigated previously; however, the effects of the operating conditions were not reported. Operating conditions include fluid flow, pressure, pH, conductivity, temperature, and gasket contact pressure. The first step of this research study is to introduce a new experimental setup to examine the corrosion behavior of bolted flanged gasketed joints. The developed setup is a fixture that consists of a pressurized bolted gasketed joint that enables real-time monitoring and recording of the corrosion parameters under the influence of service conditions. In the second step, potentiodynamic polarization test is carried out (according to ASTM G5) to measure the corrosion rate and obtain more details on the corrosion behavior of a pair flange and gasket materials. These tests are conducted using the novel designed setup that reproduce the behavior of industrial bolted flanged gasketed joint systems. It consists of a working electrode (flange material), a reference electrode (Ag/AgCl), and an auxiliary electrode (a stainless-steel rod). Three types of graphite gaskets are considered for electrochemical tests. The 0.6 M NaCl solution is used for the corrosion tests. After each test, the corroded surfaces of the specimens are examined via confocal laser microscopy to visualize the morphology of the damaged zones on the surface and localize corrosion, respectively.
Washers: Are They as Good as We Think?
Authors: Hamilton Scott , Meigs Dan
Published: November 2022

Many bolting professionals in the heavy industrial industry rely on the belief that “Washers play an essential role in generating and sustaining integrity in bolted assemblies.” [1] It is believed that washers improve the reliability of bolted joints by providing a consistent K-Factor by introducing a flat even plane on which the nut can rotate.

During practical training we noticed that using washers resulted in greater difference in bolt load between studs than experienced without washers. That experience led the authors to hypothesize that washers do not improve the accuracy and repeatability of bolted flange joints. This paper reports the findings of a study conducted to test this hypothesis.

The study recorded the variance in measured K-Factor when tightening nuts against various flange surfaces with and without washers and determined that, when properly lubricated, the performance of studs against various flange surfaces did not vary greatly from the performance of studs against washers. Additionally, in some cases washers introduced a source of variance in bolt load.

In addition to their perceived benefit in generating and maintaining tension in the bolted flange joint, washers are understood to provide benefits including preventing damage to the flange surface, preventing galling of the flange surface, and preventing nut embedment. This study focused on the use of washers in generating the expected bolt load and did not assess those additional benefits of washer usage.
Investigation on Mechanical Properties of X80 Pipeline Girth Weld Welded by Semi-Automatic and Automatic Welding
Authors: Ren Wei , Shuai Jian
Published: November 2022

The traditional manual welding in pipeline construction is being gradually replaced by semi-automatic and automatic welding in China. Semi-automatic welding is especially applied to X80 pipeline girth weld welding widely. Compared with semi-automatic welding, automatic welding has features of more efficiency, better quality and higher reliability. As the strength of pipeline steel increasing and the length, diameter as well as wall thickness of pipeline enlarging, automatic welding becomes the main trend at the development of the pipeline welding technology in the foreseeable future. Grasping the mechanical properties of X80 pipeline girth weld is crucial to ensuring the safety of pipeline operation. In order to determine the mechanical properties of X80 pipeline girth weld welded by semi-automatic and automatic welding, the experimental specimens were extracted from X80 pipeline girth weld welded by semi-automatic and automatic welding respectively to carry out the uniaxial tensile tests, fracture toughness tests and Charpy impact tests. In the tensile tests, the ultimate tensile strength of X80 pipeline girth weld welded by automatic welding (GWA) was higher than that of X80 pipeline girth weld welded by semi-automatic welding (GWSA) and the former had smaller dispersions. The fracture toughness tests showed that the fracture toughness of GWA was higher than that of GWSA. The Charpy impact tests results revealed that the impact energy of GWA was higher than that of GWSA. From the overall point of view, the mechanical properties of GWA are better than that of GWSA. The automatic welding technique is recommended for the welding of X80 pipeline, which is vitally important to maintain the structural integrity of X80 pipeline.
Application of Small Punch Testing Methods for Thermal Ageing Assessment at Steam-Generators Materials From Decommissioned V1 NPP to LTO Support on VVER Type Units in Slovakia
Authors: Petzova Jana , Adamech Marek , Slnek David
Published: November 2022

The main degradation mechanism of NPP’s components is radiation damage, but these processes are situated only in the core region of the reactor pressure vessel (RPV). The main mechanical loading of all individual parts of NPP’s primary circuit are the influence of high pressure at elevated temperature till 300°C. These processes lead to the fatigue damage of structural materials, which is characterized as the thermal fatigue or thermal ageing. The decommissioning of two V1 units in Slovakia provides a great opportunity to preserve materials from equipment that was in conditions of real operation for decades (app. 28–29 campaigns). VUJE, in cooperation with other partners, prepared necessary steps to create a material archive and related database including all relevant information from the decommissioned units of WWER-440 reactors. The main goal is to evaluate the real influence of long-term operation (LTO) on the degradation of NPP parts, such as steam-generators (SGs).

The Small Punch Test (SPT) methods are mainly used for evaluation of materials actual state. By the SPT technique it is possible to evaluate the basic tensile properties as the ultimate tensile strength and the yield stress of the tested materials from a very small amount of obtained material. The paper deals with description of special sampling from steam generators of operating units in Slovakia and subsequent testing of samples taken by the SPT method. All these results were compared with reference testing on materials taken from decommissioned V1 NPP.
Creep Life Prediction Using Creep Tests and Omega Method: Practical Application to a 2.25Cr-1Mo Steel
Authors: Planques Pierre , Le Guellaut Anthony , Goti Raphaël , Viguier Bernard
Published: November 2022

In this research, creep tests were carried out on ex-service 2.25Cr-1Mo steel under conditions more severe than those of service. The specimens were tested in a temperature range of 585°C up to 650°C and in a stress range of 65 MPa up to 120 MPa, leading to strain rates values of the order of 10−5 h−1. Conventional creep rupture tests and stepped tests (isothermal and multiple load levels) were conducted. The results of these tests are presented in terms of rupture time and the Omega method parameters Ω, and ε˙0.

The implementation of the Omega method, testing methods and the test conditions are then discussed together with the values of the parameters Ω and ε˙0 obtained. Those values were compared to the corresponding values from API579-1 data base [1] and the adjustment factors ΔcdΩ and ΔsrΩ. Lifetime prediction of the Omega method and the importance to identify the material scatter parameters for a given metallurgical condition are discussed.
An Update of the Assessment Methodology for Civil Ageing Management: Damage Development in Concrete Structures of a Reactor due to Ageing Mechanisms
Authors: Hasa Ledia , de Haan - de Wilde F. H. E.
Published: November 2022

For many nuclear power plants worldwide the operation period will be extended to 60 or 80 years. As the operation period increases, the importance of knowledge of ageing mechanisms increases. In the framework of LTO there is limited knowledge about ageing and structural integrity of concrete structures. Recent developments have shown that ageing of civil structures receive more attention internationally. In order to increase the knowledge in the field of civil structures, this paper focusses on investigation of ageing of civil structures and determining an ageing management strategy. Knowledge of the ageing mechanisms of civil structures and especially concrete, will lead to improvement of ageing management and assessment methods of concrete.

The presented work is part of ongoing research. In the past several steps have been made. Gathering of international information on civil structures ageing issues and management thereof (see PVP2019-93029 [3]), testing of a proposed assessment methodology by application to a nuclear reactor and comparison with another PWR with a steel containment (see PVP2020-21838 [4]) and creating a list of plant specific AMPs dealing with the relevant mechanisms at the various locations in a practical manner (see PVP2021-61499 [5]). The result was a general list with possible relevant locations and what type of measures could be taken. The current steps in the research focus on material behavior of structural concrete and practical assessment in finite element modelling techniques.

In a this step, the concrete material and behavior will be investigated and explained. The characteristic properties of the concrete will be summarized and the degradation mechanisms will be identified. The assessment criteria for concrete finite element modelling are defined.

The overall goal of the project is to obtain more knowledge on ageing management of civil structures and especially concrete. In the current research steps the aim is to create a predictive tool with the FE modelling technique for the damage quantification in concrete due to its ageing mechanism.

The results of this ongoing work are presented in this report. The characteristic properties, degradation mechanisms including modelling options are identified together with an investigation on the assessment criteria for concrete finite element modelling. The behavior of structural concrete will be explained.

The conclusion represents input parameters, modelling options and assessment criteria for finite element modelling of concrete.

In the future steps a practical assessment in finite modelling techniques will be introduced in order to take into consideration the degradation of the concrete. The material properties will be analyzed and adapted in an FE Model.
Development of Probabilistic Analysis Code for Evaluating Seismic Fragility of Aged Pipes With Wall-Thinning
Authors: Yamaguchi Yoshihito , Nishida Akemi , Li Yinsheng
Published: November 2022

The wall-thinning is one of the most important age-related degradation phenomena in nuclear piping, because several accidents of wall-thinned pipe failures have occurred. Furthermore, in recent years, several plants in Japan have experienced severe earthquakes. Therefore, failure probability analysis and fragility evaluation of piping systems, taking both wall-thinning and seismic response stresses into consideration, have become increasingly important in seismic probabilistic risk assessment.

In Japan Atomic Energy Agency, in order to evaluate the failure probability of aged pipes with wall-thinning, a probabilistic analysis code PASCAL-EC (Probabilistic Analysis of Structural Components in Aging LWR – considering Erosion Corrosion) has been developed. In this study, to evaluate the seismic fragility of a wall-thinned pipe, a model of seismic response stress considering the wall-thinning effect, a failure evaluation method for wall-thinned pipes, and functions related to uncertainties treatment have been introduced to PASCAL-EC. In this paper, the improved PASCAL-EC is outlined and preliminary results of the seismic fragility evaluation performed using this code are provided.
A Statistical Study of Mechanical Properties From Mild Steel Welds Deposited via Gas Metal Arc Additive Manufacturing (GMAAM)
Authors: Schaeffer J. Ben , Barnhart Brad , Melfi Teresa
Published: November 2022

Welding has been used for decades to create materials from weld metal that were machined to form components and used as a substitute for long lead-time castings, plate and forgings. Past terms like “shapewelding” or “shape melting” have been replaced with “additive manufacturing” to describe the process, but there is debate whether it should be treated as an additive/subtractive manufacturing process or a welding process followed by machining.

Welding procedure qualifications verify weld metal properties. The properties of qualified welds are quite predictable when the welding parameters (variables) are controlled. The range of variables to be controlled and the allowable limits vary based on the risk tolerance of the application. These variable qualification limits are covered in various welding qualification codes and standards.

In the past, code rules for weld metal buildup were used to qualify additive weld metal, but tighter controls are demanded today. Because of this, ASME Section IX developed and published rules in Code Case 3020 [1] for welding procedure qualifications that are specific to gas metal arc additive manufacturing (GMAAM).

The Code Case 3020 qualification rules require testing weld metal properties at the highest and lowest cooling rates to be used in production. Code Case 3020 rules also require testing the thinnest wall section and a thick section for each of those cooling rates. The rules also require that all of the essential and supplementary essential variables used for weld metal joining and operator qualification in ASME Section IX continue to be followed.

An ASME supported research project was launched to validate these rules. The project included a design of experiments (DOE), created by subject matter experts and vetted by an advisory committee consisting of designers, fabricators, consultants and metallurgists. Approximately two tons of weld metal was deposited using 24 different sets of welding parameter input configurations as set out by the DOE. Over 300 tensile specimens and over 500 Charpy V-notch (CVN) specimens were taken from various orientations and tested to characterize the weld metal properties. The data was analyzed to determine if the variables and interactions provided statistically significant prediction of the weld metal properties. The degree of isotropy and the extent to which manipulated variables predict weld metal properties are key findings. This paper examines those results, and discusses the relationships as they relate to new and existing code rules.
Reliability Improvement Concept on Welded Lip-Seal Heat Exchanger Flange Joints
Authors: Yuen Simon , Fernando John , Penso Jorge , Kwok Henry , Serate Duane
Published: November 2022

Lip-seal flange joints are commonly used in high-pressure heat exchanger design when there exists a significant temperature differential along the circumference of the heat exchanger flanges. This type of joint consists of two metal ring gaskets that are welded together to provide the necessary pressure seal. While conventional metal ring gaskets generally provide sufficient structural reliability, cracks have been reported to develop on the joints unexpectedly. This study investigates several special joint design features that aim to improve the reliability of such joints. Specifically, these features include machined pockets in the flange faces and weld overlay to house/constrain the lip-seal components, a self-alignment lip-seal feature, and tight fabrication tolerances. These improvement features mitigate thermal stresses on the lip-seal joints, thereby increasing the fatigue life of the joints. In addition, the self-alignment feature has the potential to aid in the optimization of field installation procedures. In the current work, the proposed improvement features are assessed using a series of FEA simulations to demonstrate their effectiveness. In particular, stress distributions at critical locations of the joint are compared between the new design and the conventional lip-seal design to quantify the relative improvement of the proposed design changes.
Numerical Study on Buckling Behaviors of Thin-Walled Longitudinal Corrugated Cylindrical Shells Under Axial Compression Loads
Authors: Ma He , Chen Zhiping , Jiao Peng , Lin Xinyi
Published: November 2022

Thin-walled cylindrical shell structures are widely used in various engineering fields due to their highly efficient load carrying capacity. This kind of structures is prone to buckling failure when subjected to axial compression loads. Machining the shell into corrugated shape is an effective method to prevent buckling. Rational design of corrugated shells can improve the load carrying efficiency of shell structures. However, there are few studies focused on the effects of various parameters on the longitudinal corrugated cylindrical shell buckling. In this paper, numerical studies are performed to analyze the factors affecting the buckling behaviors of thin-walled longitudinal corrugated cylindrical shells under axial compression loads. The cross section of the corrugated shell is obtained by superposing the sine curve on the reference circle. The critical buckling load, buckling mode and imperfection sensitivity of the longitudinal corrugated cylindrical shells are examined and compared with ordinary cylindrical shells. The effects of shell dimensions and material yield strength are taken into account. In addition, the influence of cross section shape parameters on the critical buckling load is considered, including the amplitude A and wave number k. Results show that the axial load carrying capacity of longitudinal corrugated cylindrical shells is better than ordinary cylindrical shells, and rational design of cross section shape can enhance the stability of corrugated shells. This work can provide some reference for relevant experimental studies. Furthermore, it can also give some guides for the application of thin-walled longitudinal corrugated cylindrical shells in actual engineering.
Experimental Study on Flow-Induced Vibration Control of Multiple Cylinders in Tandem With Helical Strakes
Authors: Tang Bowen , Fan Xiantao , Tan Wei
Published: November 2022

Flow-induced vibration (FIV) is a significant phenomenon that often occurs in actual situations, such as chemical towers, stacks, risers and offshore structures. Taking effective artificial measurements to control FIV is crucial to achieve the safe and long-period operation of engineering structures. Many researchers have verified that helical strakes can efficiently disturb the Karman vortex streets and suppress the vortex-induced vibration of isolated structures. The effect of helical strakes on controlling the FIV of gathered structures still needs to be investigated due to the complex vortex-structure interactions. A system of multiple cylinders with elastic support is an idealized representative to model the gathered engineering structures, which was used in the present work. The dynamic responses of three tandem cylinders (m*ξ = 0.09) with helical strakes under different spaces were experimentally tested in a wind tunnel. All cylinders were allowed to vibrate in the cross-flow direction. The experimental wind speed range was 0.5∼11 m/s, and the cross-section shapes of the helical strakes were designed to be square, involute and D-shaped. The vibration responses of the cylinders after installing helical strakes were analysed through comparison with those of the plain tandem cylinders. It is concluded that the D-shaped helical strake can decrease the FIV responses of tandem cylinders by 56.8% due to the reduction in the lift coefficients of the cylinders. Furthermore, the optimal parameters of the D-shaped helical strake for the tandem cylinders under different spaces were obtained, which can provide a theoretical basis for the FIV control of gathered engineering structures.
Design of an Intelligent Butt-Fusing Welding Machine for HDPE Pipes
Authors: Wang Zhenchao , Xu Lu , You Qijiang , Peng Yijuan , Zhang Qiuju
Published: November 2022

Reliability of the Butt-Fusing Welding (BFW) joint of High-Density Polyethylene (HDPE) pipes is highly affected by the given parameters of Fusion Procedure Specification (FPS). Due to the operational effect, machine process capability and the impact of environment & climate, the required FPS may not be accurately applied to the joint and may vary largely during the welding process. The methods to assess the mechanical property and life expectation of the welding joint are very complicated. The best performance of welding joint is guaranteed by a capable machine which can execute an approved FPS correctly. The machine innovated and presented here is highly automatic and intelligent. It eliminates operational mistakes and delivers the consistence for joint quality. This machine reacts to the environmental influence, and thus, eliminates or compensates their effect. With the creative calibration system, it can self-detect the faults of those critical parameters. Therefore, welding process reliability is reached. Melted material geometry is used as the criteria to judge the quality of joint, which is a method of non-destructive inspection. In addition, this machine is reliable to be used to assess and define a best FPS to improve joint quality.
Difference of Hydrogen Diffusion Regularity Between Interstice-Doped and Substitution-Doped Formed by Steel Carburizing
Authors: Xing Baihui , Wang Jing , Wei Haotian , Shang Juan , Hua Zhengli , Gu Chaohua , Zheng Jinyang
Published: November 2022

Carburizing treatment can improve the carbon content of the workpiece material, and obtain higher contact fatigue strength, bending fatigue strength, as well as higher surface hardness. After carburizing, the existence of carbon atoms can hinder the adsorption and diffusion of hydrogen, thus reducing the hydrogen embrittlement. First-principles plane wave calculations based on spin-polarized density-functional theory (DFT) and the generalized gradient approximation (GGA) have been used to study the adsorption and permeation of hydrogen on iron in the bulk with carbon interstice solid solution and carbon substitution solid solution. Considering that hydrogen diffusion is faster in martensitic tissue, bcc-Fe structure is selected for the model. The results show that the hydrogen diffusion rate Di in the interstice solid solution is higher than Ds in the substitution solid solution. The formation of substitution solid solution is promoted by more vacancies in the lattice. When the vacancy is occupied by carbon atoms, the hydrogen diffusion rate is reduced. This phenomenon is more obvious for Fe48C16 structure with higher carbon ratio. Besides, charge density diagram and state density analysis are also consistent with this conclusion. Therefore, during carburizing, Increasing the content of carbon and carbon substituted solid solution can reduce the penetration of hydrogen in the material.
Study on Burst Pressure of Type Ⅳ Hydrogen Storage Cylinder Based on Progressive Failure Analysis
Authors: Zhu Ning , Ma Kai , Gu Chaohua , Zhang Ruiming , Hua Zhengli , Wei Liqing
Published: November 2022

Hydrogen has attracted worldwide attention due to its renewable and pollution-free advantages. Hydrogen fuel cell vehicles have become an important direction for the development of the automotive industry. Carbon fiber reinforced composite hydrogen storage cylinder with plastic liner (Type IV hydrogen storage cylinder) is the main research direction of vehicle hydrogen storage because of its lightweight and excellent resistance to fatigue and corrosion. However, its safety still receives much concern. In this paper, the burst pressure prediction model of type IV hydrogen storage cylinder was established by the user subroutine UMAT of finite element calculation software ABAQUS based on the Hashin failure criterion and the damage evolution law of carbon fiber composite. The damage evolution behavior of carbon fiber winding layer of the cylinder in the process of loading was analyzed. In addition, the influence of winding thickness, winding sequence and winding angle on the burst pressure was obtained.
The Mechanical Performance of Additively Manufactured 316L Austenitic Stainless Steel
Authors: Wisbey Andrew , Coon David , Chatterton Mark , Barras Josh , Guo Da , Yan Kun , Callaghan Mark , Mirihanage Wajira
Published: November 2022

Additive manufacturing (AM) offers the potential for significantly reducing the time and cost of new nuclear components. This process may also permit unique design features, for example internal geometries. However, the limitations of the technology need to be better understood to enable implementation and accreditation.

Here a “blown powder” and laser melting process, within a helium shielded environment, was used to fabricate austenitic stainless steel 316L walls of ∼2.4 mm thickness, with the deposition parameters minimizing the surface roughness.

A key aim was to evaluate the effect of the as-deposited surface finish and the bulk material on the tensile and fatigue properties. In addition, the effect of material orientation was also considered to be important.

Microstructural characterization demonstrated the complex nature of the grain morphology arising from the as-manufactured AM process, including elongated grains following the thermal gradients. However, areas of equiaxed grains were also observed at the sample surfaces. Si-Mn-O particles, up to ∼20 μm in diameter, were noted throughout the samples produced. Residual strains have also been measured and correlated with microstructural features.

The tensile performance was generally similar to wrought 316L material but exhibited some anisotropy. The fatigue endurance of as-deposited AM 316L was significantly lower than wrought material. However, surface grinding of the AM 316L was shown to be beneficial. It was noted that in all cases examined, fatigue crack initiation was found to occur at the Si-Mn-O particles, in both surface finishes — clearly a performance limitation.
An Elastic Buckling Pressure Level Comparison for Torispherical Heads - Empirical Equations vs. FEA Results
Authors: Belloni Mark , Shah Pankajkumar K
Published: November 2022

Torispherical heads are known to exhibit buckling due to internal pressure for a variety of vessel configurations. This paper provides an overview of the phenomenon and includes Finite Element Analysis results to confirm the elastic buckling pressure threshold for a set of torispherical head shapes. Internal elastic buckling pressure levels from the ASME Section VIII, Division 2 threshold pressure for buckling and from the FEA results are compared. These results are applicable for the design of the ASME Section III – Class 1 torispherical heads based on Article A-4000 of ASME Section III.

Plots of buckled shapes and corresponding hoop stresses are presented. The vessel geometry diameters studied range from 84 in., to 120 in., to 144 in.. The crown radius to knuckle radius (L/r) ratios included in the study range from 6 to 14. Design pressures used to size the vessel wall range from 100 psi to 1300 psi in non-uniform increments. The data sets generated in the study are discussed. Nonlinear geometric effects are not considered in the buckling pressure level results generation.
Failure Bending Stresses for Small Diameter Thick-Wall Pipes
Authors: Yamaguchi Yoshihito , Hasegawa Kunio , Li Yinsheng , Lacroix Valery
Published: November 2022

Four-point bending tests without internal pressure were performed for Type 304 stainless steel pipes with circumferential flaws at room temperature. The specimens are 1-inch diameter (33.7 mm) Schedule 160 pipes (6.3 mm wall thickness). The flaws were part-through flaws located at the pipe external side. The flaw angles are from 120° to 240°, and the flaw depths are two cases of 50% and 75% of the wall thickness. Plastic collapse stresses obtained from experiments were compared with those calculated using Limit Load Criteria from Appendix C of the American Society of Mechanical Engineers Code Section XI. Limit Load Criteria were developed using flow stress at flawed section of the pipe. The plastic collapse stress test results were larger than those of the calculation results. For flaws with flaw depths less than 50% of the wall thickness, the experimental stresses were significantly large. The Limit Load Criteria given by Section XI provide conservative collapse stresses and could be improved.
Development of the Buckling Evaluation Method for Large Scale Vessel in Fast Reactors by the Testing of Austenitic Stainless Steel Vessel With Severe Initial Imperfection Subjected to Horizontal and Vertical Loading
Authors: Okafuji Takashi , Miura Kazuhiro , Sago Hiromi , Murakami Hisatomo , Ando Masanori , Okajima Satoshi
Published: November 2022

The current buckling design code of Class 1 vessels for fast reactors (FRs) power plant in Japan, “Design and Construction for Nuclear Power Plants, Division 2 Fast Reactors” by the Japan Society of Mechanical Engineers, focuses primarily on plastic buckling of austenitic steel vessel. For next-generation FRs, the higher-yield material, especially ASME Grade 91 steel, plans to be applied to the vessels such as steam generators in addition to austenitic steel. Seismic isolation system is also being devised in the next plant to meet the design seismic load in Japan.

To accommodate these conditions, the standard buckling strength equations were proposed in the previous study, which were modified by considering elasto-plastic buckling of vessel. The modified equations consisted of elasto-plastic axial compression, bending, shear buckling, and their interactions, as well as ASME/BPVC CASE N-284, considering the reduction of buckling strength by cyclic larger vertical load with long-period lower horizontal load under the horizontal seismic isolation plant design. The applicability of the modified buckling equations to high-yield material was confirmed by a series of buckling tests to vessels of Grade 91 steel under cyclic loading considering horizontal seismic isolation, or with the circumferential wrinkle shape corresponding to elephant’s foot buckling (EFB) mode in the previous study.

In this study, the applicability of the proposed modified buckling equations has been confirmed through the test of austenitic steel, which has lower yield stress than Grade 91 steel, with imperfections under the load condition corresponding to seismic isolation design. The experimental result has confirmed the conservativeness of the modified equations under the dominant axial compressive load accompanied with horizontal load, and the austenitic steel vessel which has the circumferential wrinkle shape corresponding to the EFB mode as a significant initial imperfection. The test has also been simulated by elasto-plastic buckling analyses considering stress-strain relationship and imperfections in the test vessels. The result of the test and its analysis have showed the applicability of the modified equations.

Moreover, a series of verification analyses conducted for the modified equations with 3D buckling analysis models under the conditions in FRs power plant. These verification analysis results confirmed the contribution of the factors to the buckling strength such as initial imperfection and material, and showed that the modified equations are applicable to the vessels in FRs power plant.
Study on Fatigue Life of Vehicle Fuel Tank Under Random Vibration Environment
Authors: Tang Yuanzhang , Yang Zhirong , Gao Haibo , Lin Zhiguo , Qin Du
Published: November 2022

The working environment of oil tank is complex and changeable. Aiming at the problem that it is difficult to predict the high cycle fatigue life of a certain vehicle fuel tank, The fatigue life of the tank was studied. Firstly, the natural frequency and modal shape of the structure are obtained by identifying modal parameters of the structure using Eigensystem Realization Algorithm (ERA). Then, the simulation model is established by SolidWorks, and imported into ANSYS for modal analysis. Compared with the bench test, the results show that the errors between dynamic characteristic of modal simulation and modal test are acceptable, which verify the accuracy of simulation model. Finally, the fatigue life of fuel tank is analyzed by frequency domain analysis method in ANSYS nCode DesignLife. The results show that the weak position of the oil tank vibration is always unchanged under multiple power spectral density (PSD) spectrum types, and its life decreases with the increase of PSD amplitude at low frequency. To further verify the accuracy of numerical simulation results, the PSD spectrum corresponding to the shortest life tank will select for random vibration fatigue life experiment in the future.
Failure Estimation Methods for Steam Generator Tubes With Wall-Thinning or Crack
Authors: Yamaguchi Yoshihito , Mano Akihiro , Li Yinsheng
Published: November 2022

The steam generator (SG) tube is one of the important components in pressurized water reactors. Flaws such as wall-thinning or stress corrosion cracking have been reported in SG tubes. The burst pressure where both the internal and external pressures from the primary and secondary coolant systems are considered must be predicted to assess the structural integrity of SG tubes. Burst tests were performed by various organizations. On the basis of the test results, failure estimation methods were proposed. In this study, previous burst test data and existing failure estimation methods for SG tubes with wall-thinning or crack were investigated. As a result, the coefficient of the existing estimation method for SG tube with uniform wall-thinning was updated. In addition, failure estimation methods that are suitable for SG tubes with crack or local wall-thinning were proposed by considering the effects of the flaw shape and size on the burst pressure. The applicability of the failure estimation methods was confirmed by comparing the predicted results with the burst test data in actual SG tubes.