bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the Buckling Evaluation Method for Large Scale Vessel by the Testing of Gr. 91 Vessel Subjected to Horizontal and Cyclic Vertical Loading
Authors: Okafuji Takashi , Miura Kazuhiro , Sago Hiromi , Murakami Hisatomo , Ando Masanori , Miyazaki Masashi 
Published: October 2021

Abstract
The current buckling design standard 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 stainless 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 stainless 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 in Japan were proposed in 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 under the monotonic load to Grade 91 steel vessels with an initial imperfection mode in previous study.
In this study, the applicability of the proposed modified buckling equations was confirmed through a series of buckling tests under cyclic loading considering horizontal seismic isolation, or with the circumferential wrinkle shape corresponding to elephant’s foot buckling (EFB) mode as the conservative initial imperfection shape. These tests were simulated by elasto–plastic buckling analyses considering stress–strain relationship and imperfections in the test vessels with high accuracy, and these test and analysis results showed the applicability of the modified equations.
The effect of initial imperfection shape of large vessels manufactured by multiple plates welding on the buckling load was evaluated via a series of analyses. In these analyses, the superimposition of global imperfection shape due to accumulation of misalignment of plates in the buckling mode imperfection, and the local imperfection and residual stress by welding had minimal effect on the buckling load.
These buckling test and analysis results confirmed the contribution of the factors to the buckling strength such as initial imperfection and loading, and showed that the modified equations are applicable to the vessels in FRs power plant.
Sensitivity Analysis of Tunable Equation of State Material Model In Pulsed Mercury Target Simulation
Authors: Lin Lianshan , Winder Drew 
Published: October 2021

Abstract
A pulsed neutron spallation target is subjected to very short but intense loads from repeated proton pulses. Approximately 60% of the energy from each proton pulse is deposited into the mercury target material and the stainless-steel target structure, leading to a high-pressure region in both the stationary target structure and the flowing mercury. The high-pressure region propagates and leads to fluid-structure interaction. The resultant loading on the target structure containing liquid mercury is difficult to predict, although various simulation approaches and material models for the mercury have been tried. To date, the best match of simulation to experimental data is obtained by using an equation of state (EOS) material model with a specified tensile cutoff pressure, which simulates the cavitation threshold. The inclusion of a threshold to represent cavitation is key to the successful predictions of stress waves triggered by the high-energy pulse striking the mercury and vessel. However, recent measurements of target structure strain show that significant discrepancies remain between the measured and simulated strain values in the EOS mercury model. These differences grow when noncondensable helium gas is intentionally injected into the flowing mercury to reduce the loading on the structure. An EOS-based proportional–integral–derivative (PID) mercury model has been proposed to reduce the gap between the measured and simulated vessel strain responses for targets with gas injection. The conceptual and numerical description and initial investigation of the PID model are presented in previous work. Further studies of this PID model — including the sensitivity of the structure’s strain response to model parameters (the tensile cutoff, PID parameters Kp, Ki, and Kd) — are reported in this article. Results show the strain response is more sensitive to changes in the tensile cutoff value than to changes in the model parameters Kp, Ki, and Kd. These results will aid in future work where the model parameters will be optimized to match simulation data to strain measurements.
Seismic Fragility and Behavior of Spherical Pressure Vessels
Authors: Öztürk Sezer , Akgül Kayahan , Sarı Ali 
Published: October 2021

Abstract
Pressurized tanks are vessels that show high impermeability and strength against large internal pressures. These tanks can be used for liquid or gas storage. The internal pressures of the vessels used in gas storage can be at very high levels. These tanks are used in many different areas in the industry. Therefore, human health and life safety is an important parameter. Thus, the design of the tanks to be produced must be suitable for the purpose, as well as the correct analysis and safe usage conditions. Excessive pressure and the temperature difference can lead to explosions that will cause dangerous and many fatal accidents. As a result, domino effects can occur in industrial facilities. For this reason, the risk analysis and seismic behavior of these vessels should be carefully examined. When the performances of past earthquakes are examined, it has been revealed that especially spherical vessels show seismic fragility. Therefore, evaluating the seismic fragility of these vessels is an important issue in regions with high seismic risk. Fragility curves are important tools to evaluate the vulnerability of structures to earthquakes. Within the scope of this study, fragility curves have been created by considering nonlinear time history analyzes and the limited database analyzed for the damage conditions of spherical pressure vessels in earthquakes that occurred in the past years. The curves obtained were interpreted in relation to the ground motion intensity parameter (PGA). In addition, nonlinear time history analyzes of tank models using the Finite Element Method (FEM) have been performed to evaluate the seismic performance of the vessels. Also, the damage data of horizontal tanks were collected and interpreted.
Strain Based Damage Model Predictions of Ductile Crack Growth in Multiple Fracture Specimen Geometries
Authors: Kalyanam S. , Hill L. T. , Wilkowski G. , Hioe Y. , Brust F. W. 
Published: October 2021

Abstract
Modeling damage and ductile crack growth in metallic materials has been of interest over the last four decades. Damage models of increasing complexity have been employed to characterize and predict the ductile crack growth in materials. A short review of the existing ductile crack growth models has been provided. Recently, a strain-based damage model has been advanced by researchers, which is capable of capturing the stress and strain states for the incipient damage within the material while being able to capture the triaxiality parameter. In this work a strain based ductile fracture damage model has been employed to model specimens with three different crack geometries, namely a single-edge notch tension SEN(T), compact-tension C(T), and outer diameter (OD) axial surface-cracked pipe. The predictions from the ductile crack growth model have been compared to experimental findings of the crack growth (obtained using a d-c Electric Potential measurement technique) and the corresponding load levels and crack opening displacements (CODs). The points of similarity between the experimental measurements and the fracture surface observations of crack growth and the predictions from the finite element modeling (FEM) approach have been discussed. The same X80 material properties and damage model parameters were employed to benchmark the ductile crack growth in two different SEN(T) specimens with differing normalized crack depths (crack/width ratios, a/W), a C(T) specimen (a/W = 0.5), and an OD SC pipe (a/t = 0.6) to shed light on the predictability of the crack initiation event and the subsequent ductile crack growth until failure. The findings provide credence to the applicability of the new approach for piping materials while providing a framework for flaw evaluation methodologies. The investigation also opens the doors for regions where mesh regularization methods and modeling approaches along with mathematical relations can be developed to form a more efficient framework for modeling specimens with diverse constraints efficiently.
Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 11 Optimization of Dampers by Genetic Algorithm
Authors: Minagawa Keisuke , Aida Kiyoshi , Fujita Satoshi 
Published: October 2021

Abstract
In Japan, thermal power generation is one of the important power sources after the Great East Japan Earthquake in 2011. On the other hand, some thermal power plants were damaged by the Great East Japan Earthquake or Hokkaido Eastern Iburi Earthquake in 2018, therefore strengthening of seismic performance of thermal power plants has been required for reliable power supply against large earthquakes that will occur in the future. The authors have proposed an application of visco-elastic dampers to a boiler structure in a coal-fired power plant to improve seismic performance. The application of dampers was effective to reduce the base shear force of a support structure of the boiler, and the dampers had a long lifetime for continuous deformation. In our past papers, the parameters were selected manually. However, to design proper parameters and distribution of the dampers on manual is laborious works with many seismic response analyses. Therefore, the genetic algorithm was introduced to the parameter selection of dampers in this paper. The genetic algorithm is one of the optimization algorithms that was inspired by the evolution process of creatures. The genetic algorithm creates a virtual population having genes in the computer, and only individuals with high fitness remain while repeating generational changes. In this paper, parameters of dampers that can reduce the base shear force were searched by the genetic algorithm. This approach can be applied to vibration controls for other industrial facilities.
Fatigue Life Calculation Method of 4130X High Pressure Hydrogen Storage Cylinder With Initial Crack Defect
Authors: Ge Peng , Chen Zhiping , Liu Mengjie 
Published: October 2021

Abstract
Hydrogen storage cylinders are often used for medium- and short-distance transportation of hydrogen. The presence of hydrogen tends to increase the risk of using the gas cylinders. The alternating stress caused by factors such as hydrogen charging and discharging during the service process of the gas cylinder leads to the expansion of initial cracks inside the cylinder and the final fatigue fracture. At present, the fatigue life calculation of pressure vessels mainly adopts the S-N curve method, however, some steels do not have the S-N curve under the hydrogen environment, it is necessary to use fracture mechanics methods to analyze the fatigue life of gas cylinders in a high-pressure gaseous hydrogen environment. In this work, a method for calculating the fatigue life of fracture mechanics for hydrogen storage cylinders was established according to ASME VIII-3 KD-10. The development of the program was completed by Matlab. An example was given to illustrate the program. Firstly, basic parameters of the material used for the cylinder were obtained. Then, finite element method was used for stress analysis to obtain the fitting curve and the function expression of hoop stress. Finally, fatigue life calculations of high pressure hydrogen storage cylinder were made. The minimum service life of example was predicted to be 40 years. This result is consistent with the good service history of this type of container. This work could contribute to design, safety evaluation of hydrogen storage cylinders.
Design of Piping Systems for Accidental Explosion and Fire Events
Authors: Akinci Necip Onder , Loudoun James , Parvathaneni Krishna , Kim Hyun-Su 
Published: October 2021

Abstract
Piping systems constitute the most critical portion of process plants. Proper blast and fire design of critical piping systems improve safety and resiliency. Design of piping and pipe supports are typically governed by operating and abnormal load conditions depending on the design basis. Well established analysis and design methodologies as per the applicable ASME codes ensure performance of piping systems against load cases such as internal pressure, thermal expansion, self-weight, wind, seismic and vibration. Pipe stress analysis using code based linear elastic analysis methods allow design for these types of conventional load cases in a practical way. However, beyond design basis load cases from hydrocarbon accidents including explosion and fires can pose additional challenges. Limitations of conventional design tools against demands due to extreme events require use of more advanced techniques. This study presents a practical approach for assessment and design of piping systems for hydrocarbon accident events. Performance based failure criteria for piping systems has been shown to reduce the conservatism compared to allowable stress design for extreme events. Examples from major projects and case studies are also presented to demonstrate the technical approach. Consideration of a holistic approach accounting for interaction of piping and its support structure plays a key role in improving the design process.
Numerical Studies on Modal Analysis of Curved Tube and Coil Tube in Coil-Wound Heat Exchanger
Authors: Wang Yue , Ren Peng , Zhu Guorui , Tan Wei 
Published: October 2021

Abstract
Coil-wound heat exchanger, which has a large-scale turbulence in the shell side and a great heat transfer coefficient, has been widely used in chemical industry, such as liquefied natural gas (LNG) and crude pyrolysis of ethylbenzene. To investigate the general vibration characteristics, a complete wound tube can be divided into the curved tube and the coil tube for easy research because of its constraint condition. A finite element analysis is used to obtain the natural frequencies and corresponding mode shapes of the curved tubes and the coil tubes with various parameters. For the curved tube, the deformation of middle position of the tube is larger than that of the clamped ends. The maximum deformation occurs at the transition from the bending tube to the straight tube. With the increase of R1 and the decrease of R2, H1, H and θ, the natural frequencies of curved tube increase which is more likely to avoid the fluid-elastic instability, in which R1 is circumferential radius of the straight part of curved tube, R2 is coil radius, H1 is axial straight tube length, H is axial height of curved tube and θ is deflection angle. And for the coil tube, all the deformation for mode shape occurs in the axial direction, and there is no obvious deformation in the radial direction. With the increase of support number and the decrease of R2, the basic frequency of the coil tube increases. It provides a certain reference for the support layout of coil-wound heat exchanger.
Benchmark Analysis by Beremin Model and GTN Model in CAF Subcommittee
Authors: Hirota Takatoshi , Nagoshi Yasuto , Hojo Kiminobu , Okada Hiroshi , Takahashi Akiyuki , Katsuyama Jinya , Ueda Takashi , Ogawa Takuya , Yashirodai Kenji , Ohata Mitsuru , Minami Fumiyoshi 
Published: October 2021

Abstract
In order to establish a guideline for fracture evaluation without excessive conservatism by considering plastic constraint in the ductile-brittle transition temperature (DBTT) region, the CAF (Constraint-Based Assessment of Fracture in Ductile-Brittle Transition Temperature Region) subcommittee has been launched in 2018 in the Atomic Energy Research Committee of the Japan Welding Engineering Society with a five years’ term. In the committee, fracture tests are conducted using laboratory specimens of C(T), SE(B), and 50mm-thick flat plate with a surface flaw subjected to bending load or tensile load to verify fracture evaluation methods, which strongly depend on numerical simulation. Since simulation results are easily affected by analysis conditions, benchmark analysis is essential for the potential users of the guideline. Therefore, benchmark analyses are executed on brittle and ductile damages by Beremin and Gurson–Tvergaard–Needleman (GTN) models implemented in the FE codes owned by the committee members. The benchmark analyses are carried out in four steps; Step 0 is to confirm the output of finite element (FE) codes in each member with the same input data and the same FE model. Step 1 is to confirm the result of Weibull stress analysis for C(T) specimens tested at −125°C. The Weibull parameter, m, was fixed in this step. At step 2, sensitivity analyses are conducted on Weibull stresses in different conditions. The outputs by the GTN model are also confirmed. At the final step, the fracture simulation will be run for flat plate specimens with less plastic constraint than the standard fracture toughness specimen. As the results of the benchmark analyses up to step 2, a significant difference are not observed in the Weibull stress computed by committee members with the same input data and FE model and it is confirmed that the effects of element type, nonlinear deformation theory employed in FE analysis and convergence procedure for the Weibull parameter m are marginal by the sensitivity analyses. For the calculation of the Weibull parameter m by using the fracture toughness test results and the developed programs by committee members, the converged values of m show good agreement among them. The obtained knowledge by the benchmark analyses is used to establish the guideline for fracture assessment of structural components with different plastic constraints.
Testing a Tunable Diode Laser Absorption Spectroscopy Oxygen Analyzer
Authors: Reich Alton , Shaw James , Bergmans John 
Published: October 2021

Abstract
Chemical processing systems can be controlled using a wide variety of instrumentation. Often pressure and temperature are key parameters that are monitored and controlled, and this instrumentation is extremely mature technology. In some cases, chemical concentrations are a key process parameter that must be monitored and used as an input to the system controller. Chemical concentrations may be monitored indirectly through pH or conductivity. Direct measurements are often made via electrochemical cells, but these tend to have slow response times.
For chemical processes that operate in batch mode, particularly ones that have relatively short cycle times, chemical sensors that have fast response and recovery times are needed, and electrochemical sensors may not be suitable. This paper describes such an application where the chemical concentration of oxygen is an important process and safety parameter. A Tunable Diode Laser Absorption Spectroscopy (TDLAS) oxygen sensor was selected for this application because of the short response and recovery time. When the oxygen sensor was received, it was set up in the laboratory and tested to verify measurement accuracy and data communication with the sensor. During this testing, we discovered that the sensor produced incorrect output over a portion of the system operating pressure range. The root cause of the error was traced to how the firmware (sensor operating software) handled the measured pressure input to produce the oxygen concentration output. The paper discusses the laboratory testing setup, and the testing that was executed. A structured test program was executed that enabled us to understand the nature of the incorrect measurement, and trace the source of the error to the sensor operating software.
Seismic Analysis of VVER-1000 Polar Crane
Authors: Dubyk Yaroslav , Antonchenko Vitalii 
Published: October 2021

Abstract
This article discuss an analytical dynamic model of a polar crane to assess its seismic strength based on artificially generated accelerograms. The polar crane is installed under the dome of the VVER-1000 NPP containment and serves to move various cargoes in the reactor compartment, including nuclear hazardous cargo. The high-rise location of the crane (+ 55m) causes the possibility of significant seismic loads. To build a dynamic model, at the beginning, the stiffness of individual elements was analyzed using numerical and analytical methods. In particular, the stiffnesses of the main beams and the main balancers are analyzed to determine the type of dynamic model required. A feature of the seismic analysis of a polar crane is the nonlinear interaction of its elements, which can lead to the breaking of some connections and the separation of the structure from the supporting elements. The key in the analysis is taking into account the contact nonlinearity of the wheel-rail pair; to model this contact, we used the classical theory of Hertz. The generalized response spectra for the NPP site were used as the load. A method for calculating artificial accelerograms, which are generated for the purposes of dynamic analysis, based on response spectra is used. Also, as a comparison, the results of calculating the seismic strength of the polar crane by the linear response spectrum method are given. As a result of the analysis, weak points in the structure were identified, and the ultimate seismic resistance of the polar crane was determined.
Stress Analysis of Tubes During Die Expansion Process
Authors: Zhao Zijian , Bouzid Abdel-Hakim 
Published: October 2021

Abstract
In practical applications, the stress status of expanded tubes is a critical parameter to control leakage and stress corrosion cracking. Therefore, it is important to study and analyze the stress distribution generated from tube expansion. Unfortunately, there are only a few theoretical approaches available for estimating the stress distribution of formed tubes, especially for cases where the expansion is achieved with spherical and oval dies.
In this study, 3/8 stainless steel and copper tubes were expanded with an oval die in a designed test workbench, and the tangential and longitudinal strains were monitored during the expansion process. A new analytical approach is developed to estimate the stresses and strains in the expanded tube during the expansion process. The different expanded zones are treated using different theories. An axisymmetric finite element model as a numerical approach is used to analyze the stresses based on a multi-linear kinematic hardening behavior to validate the analytical approach.
In addition, the stresses in the expanded tube and the push force of the die are also provided by the analytical, numerical and experimental approaches. Finally, the results from the three approaches are in a relatively good agreement.