bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long-Term Durability of Pitch-Based High Modulus Carbon Fiber Reinforced Plastics
Authors: Kobayashi Satoshi , Osada Toshiko 
Published: October 2020

Abstract
Static tensile and tensile-tensile fatigue were conducted on PITCH-based high modulus carbon fiber reinforced plastics (CFRP). PAN-based intermediate and high modulus CFRP were also tested for comparison.. Unidirectional laminates were prepared with wet panel method. The damage mode for high modulus CFRP was fiber breakage for both static and fatigue loading, whereas splitting was dominant for intermediate modulus CFRP. The slope of the S-N curve was larger for the intermediate modulus CFRP than that for the high modulus CFRP. This is attributed to the lower failure strain of the high modulus carbon fibers. That is, the larger strain on intermediate modulus CFRP at lower stress level comparing with high modulus CFRP caused severer matrix damages during fatigue loading. This results indicated the higher durability of high modulus CFRP. Residual strength measurement were conducted on the un-broken PITCH-based CFRP up to 1,000,000 cycles with acoustic emission measurements. The Kaiser effect was not satisfied for the specimen with lower residual strength at the stress level of the fatigue test. In addition, gradual acoustic emissions with longer duration and rise time were measured before final fracture in the static tests. These results indicated the possibility to detect the microscopic damage monitoring for the CFRP with acoustic emission measurement focusing on the duration of the acoustic wave.
Using Machine Learning Tools for Forecasting Natural Gas Market Demand
Authors: Yang Kai , Hou Lei 
Published: October 2020

Abstract
Providing reliable and accurate forecasts of natural gas consumption can keep supply and demand of natural gas pipelines in balance, which can increase profits and reduce supply risks. In order to accurately predict the short-term load demand of different gas nodes in the natural gas pipeline network, a hybrid optimization strategy of integrated genetic optimization algorithm and support vector machine are proposed. Factors such as holidays, date types and weather were taken into account to build a natural gas daily load prediction model based on GA-SVM was established. A natural gas pipeline network in China includes three gas supply nodes of different user type gas is forecasted, and a variety of error evaluation method, the GA-SVM evaluation index compared with other prediction methods, and through different data set partition is discussed in the periods of peak gas and gas resources in the GA — the applicability of the SVM prediction model, the ends of a natural gas pipeline network in China includes four gas supply nodes of different user type gas is forecasted, and a variety of error evaluation method, the GA-SVM evaluation index compared with other prediction methods, The applicability of the method is also discussed by dividing different data sets. By predicting the gas load forecast of the three nodes, the results show that GA-SVM hybrid prediction model has high prediction accuracy compared with other single models, and the three gas nodes MAPE of GA-SVM is respectively 3.66%, 5.17% and 3.43%. Through further analysis, even with the data samples reduced, the winter gas peak of gas prediction can still maintain good prediction effects. The research shows that the GA-SVM model has high accuracy and strong applicability in predicting gas consumption at different nodes of the natural gas pipeline network. This study can provide a research basis for analysis of gas supply uncertainty and further gas supply reliability evaluation of pipeline network.
Experimental Study on the Effect of Core Support Frame on Seismic Behavior of Fast Reactor Core
Authors: Matsubara Shinichiro , Iwasaki Akihisa , Harada Hidenori , Yamamoto Tomohiko 
Published: October 2020

Abstract
The fast reactor core is composed of hundreds of core elements that self-stand on the lower support plate, and core elements does not have support to constrain vertical displacement in order to avoid effects such as thermal elongation. When an earthquake occurs, the group vibration behavior including the rising of core elements in the vertical direction, the collision with adjacent core elements in the horizontal direction, and the fluid structure interaction is observed. The three dimensional core group vibration analysis code (REVIAN-3D) for evaluating these has been constructed.
In this study, to grasp and estimate the group vibration behavior with and without a core former under the earthquake motion, seismic experiment of hexagonal multi bundle model using core element mock-up was conducted. These test results show that the presence of the core former decrease the horizontal displacements and increases core compaction. And the test results are used for the verification data of the analysis code REVIAN-3D.[1]
Study on Design Approach for Tall Pressure Vessels With Intermediate Support in Consideration of Bottom Structure Flexibility
Authors: Sasaki Shunsuke , Nanjo Takanori , Miyashita Toshikazu , Kataoka Shunji , Uno Yoshiaki 
Published: October 2020

Abstract
The skirt and shell thicknesses of vertical tall pressure vessels are sometimes much increased in FPSO (Floating Production, Storage and Offloading) due to ship motion acceleration. In that case, intermediate support is used as an additional support from steel structure surrounding the vessels. By theoretical calculation, Nanjo et.al. introduced dimensionless parameter N that can represent stiffness of pressure vessel and acceleration load with the assumption of structure drift at intermediate support [1]. The authors proposed N-chart to investigate the necessity and effective elevation of intermediate support by using the parameter N. The flexibility of steel structure on the bottom affects the function of intermediate support (e.g. increasing reaction force at intermediate support, effect on bottom skirt calculation); however, the flexibility is not included in the parameter N. In this paper, an additional factor for the flexibility was studied and introduced by structural analysis. A model with flexibility of structure supporting the bottom skirt was used for the analysis. The variable flexibility of steel structure was applied to the bottom of the model to study the impact of bottom structure flexibility on the pressure vessel design. The analysis result was compared with the bottom fixed model without structure flexibility to study an additional factor. Finally, appropriate design approach for tall pressure vessels with intermediate supports was proposed.
Study on Vibration Mitigation of Connected Cabinets Storing Electronics Subjected to Seismic Input Using Elasto-Plastic Damper
Authors: Shintani Atsuhiko , Yoshida Takuma , Nakagawa Chihiro , Ito Tomohiro 
Published: October 2020

Abstract
This paper deals with the motion of coupled cabinets containing electronics subjected to seismic input. In power plants, chemical plants, etc., several rectangular cabinets containing important electronics are always lined up in the control center. These electronics are necessary for the control of the entire plant; thus, when they are damaged, the entire plant cannot be controlled, and a serious accident may occur. These cabinets are frequently put directly on the floor. Thus, it is perceived that in the worst case, cabinets may turn over by rocking motion during earthquakes and electronics may break. Moreover, even when the cabinets do not overturn, there is a concern about a large acceleration applied to the internal electronics due to the seismic waves. Hence, the need to develop methods that can reduce rocking motion and prevent electronics damage simultaneously.
First, we consider the single cabinet with electronics. The cabinet is modeled as a rotating rigid body around its corner. The internal electronics are modeled as a rigid body moving in the translational direction in the cabinet. This system is referred to as single system. We input a seismic wave to the single system and investigate the rocking angle of the cabinet and the acceleration of the electronics in the cabinet.
Consequently, we consider the adjacent cabinets connected by an elasto-plastic damper containing electronics. The cabinets are modeled as rotating rigid bodies. The internal electronics are modeled as rigid bodies moving in the translational direction in the cabinets. The whole system is known as a connected system. The elasto-plastic damper has bilinear hysteretic characteristics and can absorb the energy of earthquake inputs. We input the same seismic wave to the connected system to obtain the rocking angle of cabinets and the acceleration of electronics in the connected system. In these simulations, it is assumed that cabinets do not collide with each other. Then, we investigate the effect of the parameters of the elasto-plastic damper suppressing the rocking angle of the cabinets and the acceleration of electronics.
Finally, we compare the maximum rocking angle and the maximum acceleration of the single system with that of the connected system and consider an ideal method to reduce the rocking angle and the acceleration simultaneously.
Proposal of Simulation Materials Test Technique and Their Constitutive Equations for Structural Tests and Analyses Simulating Severe Accident Conditions
Authors: Hashidate Ryuta , Kato Shoichi , Onizawa Takashi , Wakai Takashi , Kasahara Naoto 
Published: October 2020

Abstract
Nuclear structure’s integrity must be confirmed under severe accident conditions. However, performing structure tests using actual steels is very difficult and expensive. Therefore, the authors conducted structure tests using the lead alloy to evaluate the structure integrity under severe accident conditions. Because the strength of the lead alloy is considerably less than that of actual steels, structure tests can be conducted under low-pressure, low-temperature conditions. To quantitatively correlate the structural response of the lead alloy to that of actual steels, finite-element analyses (FEAs) must be performed. Because the inelastic constitutive equations, namely, inelastic stress–strain relationship equation, creep rupture equation, and creep strain equation, are required to perform the inelastic FEA, the authors introduced material tests using the lead alloy and, subsequently, proposed the inelastic constitutive equations based on the material test results in a previously conducted PVP conference. However, the proposed inelastic constitutive equations could not successfully express the material characteristic of the lead alloy because of large variations observed in the material tests of the lead alloy. Furthermore, the authors observed that the material characteristic of the lead alloy could be stabilized by aging. In this study, we propose the improved inelastic constitutive equations of the lead alloy on the basis of test results newly obtained from a series of material test performed using aged alloy.
A Method for Measuring Combined Stress of Small Bore Piping Around Weld in Field Using Strain Gauge Holder
Authors: Takahama Tsunemichi 
Published: October 2020

Abstract
This paper proposes using the strain gauge holder which has 12 elements of strain gauge in order to measure the 2 directional bending stresses and the torsional stress synchronously around the weld in small bore piping. The paper also provides the actual measured dynamic stresses around the welds in real fields including combined stress by the strain gauge holder. The measured stresses are shown on a time axis, on a frequency axis, on an X-Y display like Lissajous figure, and on an X-Y-Z 3D display.
It was confirmed that the strain gauge holder was able to be installed within 20 minutes, to be used on 180°C piping, and to be reused in real fields because it was not necessary to adhere the strain gauges on the piping.
The measured strains obtained by using the strain gauge holder can provide useful information of the piping system to decide whether the reinforcements are necessary, to enhance the accuracy of the design and calculation, and to improve the validity of fatigue evaluation.
It is planned in future to develop a methodology of fatigue evaluation based on the measured stresses obtained by using the strain gauge holder.
Fracture Toughness Tests on Western RPV Steels Using Small Scale Specimen Technique
Authors: Obermeier Florian , Altstadt Eberhard , Hein Hieronymus , Das Aniruddh 
Published: October 2020

Abstract
In order to ensure continued safe operation of European nuclear reactors, it is necessary to solve specific issues that arise from irradiation induced reactor pressure vessel (RPV) embrittlement under long term operation. This requires an extension of the RPV surveillance programs to cover longer operation times than originally planned. The limited availability of surveillance materials poses a challenge for the feasibility of such programs. Among others, the use of the small specimen technology is a promising option to overcome the lack of materials. For example, a number of not less than 16 sub-sized 0.16 C(T) specimens (4 mm thickness) can be manufactured from two tested Charpy sized (10 mm × 10 mm × 55 mm) specimens, allowing a reliable determination of the reference temperature T0. Such Charpy sized fracture mechanics specimens are currently widely used in the RPV surveillance programs.
To establish the methodology for fracture mechanics testing of irradiated and unirradiated RPV steels using sub-sized specimens, a joined R&D project was launched partly financed by the German Federal Ministry for Economic Affairs and Energy. Moreover the following points shall be addressed:
• Manufacturing, pre-cracking procedure, measurement of the crack opening displacement and load line displacement under hot cell conditions
• Demonstration of the transferability of fracture mechanics data
The purpose is to demonstrate that the results measured on sub-sized specimens can safely be used in the safety assessment of RPVs. In addition, the results will establish a basis to assess results from international projects regarding sub-sized fracture mechanics specimens.
Assessment of Compact Heat Exchanger Design Following Elastic Perfectly Plastic Methodology
Authors: Shaw Avinash , Mahajan Heramb P. , Hassan Tasnim 
Published: October 2020

Abstract
Compact Heat Exchangers (CHXs) have a large number of miniature channels inside their core, which makes them highly thermal efficient and thus, prime utile for Next Generation Nuclear Plant (NGNP) applications. The fabrication of a CHX involves diffusion, brazed or welded bonding of plates to form CHX block with a channeled core. The elevated temperature and transient conditions of NGNP operation may induce excessive strain and creep-fatigue failure in channel ligaments. The primary objective of this study is to evaluate the design of CHX for application to NGNPs, following the ASME Code Elastic Perfectly Plastic (EPP) Analysis criteria in a draft ASME Code Section III, Division 5 and using the currently available Division 5 Code Cases (N-861 and N-862). As global analysis considering channels in the core is computationally intensive, a new analysis method is evaluated. In this method, the global analysis is performed by representing the channeled core by an elastic orthotropic material core. Subsequently, at the local level, EPP analysis is performed using models that include the channels, with thermal and pressure loading conditions. An ASME Draft Code Case is under development for the construction of CHXs. The analysis results are used to assess proposed stress limits and classification for load controlled stresses. For strain limits, the analysis results are evaluated using Code Cases N-861 and N-862 against the strain limit and creep-fatigue damage using the channel level submodel analysis. The applicability of the new analysis method, and use of the analysis results for evaluation against ASME proposed limits for various regions of the CHX are presented and discussed.
Effect of Material and Lubrication Conditions on the Underhead Frictional Response in High Strength Socket-Head Screws
Authors: Croccolo Dario , De Agostinis Massimiliano , Fini Stefano , Olmi Giorgio , Robusto Francesco , Vincenzi Nicolò 
Published: October 2020

Abstract
The present paper investigates the influence of several design parameters on the frictional response at the underhead in a bolted joint, involving high strength socket-head screws: M8 class 14.9 with black oxidization coating. The experimentation deals with different underhead materials (Steel, Aluminium), lubrication conditions (dry, lubricated) and repeated tightening operations. The awareness of the actual friction coefficients, depending on the current operating parameters, is a useful tool, to support the most proper design of a bolted joint. The experimental campaign has been run by a testing rig for friction coefficient estimation, complying with the recommendations by International Standard ISO 16047 and the automotive Standard VW01131-1 in order to consider the effect of the tightening speed normally adopted in the automotive field. The axial preload generated upon tightening induces a high pressure on the remarkably small underhead surface of the utilized high strength socket-head screws and is therefore likely to affect the tribological response. Consequently, some differences may be expected with respect to the tribological behavior of screws belonging to lower strength grades. This is particularly true, when tightening is done without bearing lubrication, and through several repeated assembly-disassembly operations. The collected data have been processed by the tools of ANOVA and F-Test, in order to assess the significance of each factor, as well as related interactions.
Fracture Mechanics Integrity Assessment of Stud Bolts Subjected to Cathodic Protection
Authors: de Castro Mario A. L. , Alves Fabio , Karpanan Kumarswamy , Venkatesh Anand 
Published: October 2020

Abstract
Exposure of metallic parts to cathodic protection (CP) in sea water leads to production and diffusion of atomic Hydrogen into the metal matrix. Absorption of atomic Hydrogen into the metal could lead to hydrogen embrittlement (HE).
In order to study the influence of stresses related to HE, FEA and Fracture Mechanics (FM) assessments were performed on a stud bolt threaded geometry. Effects of manufacturing tolerances, interface between nut and stud bolt and a defect in the form of a semi-circular crack placed in highest stress location of a thread root were also considered. Investigations of stress profiles when tension or bending are applied in test samples for measurement of HE threshold were also done, aiming at showing gaps on ASTM F1624-12 [1].
Tolerance assessment shows a relative maximum increase of 260% of nominal linearized membrane plus bending (NLMB) stresses regarding the nut runout [2] and for the proprietary nut geometry, such relative increase drops to 126% of NLMB stresses. Highest Hydrogen concentrations could be observed in the neighborhood of the first loaded thread root. FEA of cracked geometry shows that Hydrogen concentration could increase by around 283% around the crack tip, when compared to stud bolt in unloaded condition. Integrity assessment according to API 579-1 [3] or BS 7910 [4] and tests conducted according to ASTM F1624-12 [1] show less conservative results.
Estimation of Bending Stresses in Piping Systems Subjected to Transient Pressure
Authors: Taghva Maral , Damkilde Lars 
Published: October 2020

Abstract
Modifications in aged process plants may subject piping systems to fluid transient scenarios, which are not considered in the primary design calculations. Due to lack of strict requirements in ASME B31.3 the effect of this phenomenon is often excluded from piping structural integrity reassessments.
Therefore, the consequences, such as severe pipe motion or even rupture failure, are discovered after modifications are completed and the system starts to function under new operational conditions. The motivation for this study emanated from several observations in offshore oil and gas piping systems, yet the results could be utilized in structural integrity assessments of any piping system subjected to pressure waves.
This paper describes how to provide an approximate solution to determine maximum bending stresses in piping structures subjected to wave impulse loads without using rigorous approaches to calculate the dynamic response. This paper proposes to consider the effect of load duration in quasi-static analysis to achieve more credible results. The proposed method recommends application of lower dynamic load factors than commonly practiced values advised by design codes, for short duration loads such as shock waves. By presenting a real-life example, the results of improved and commonly practiced quasi-static analysis are compared with the site observations as well as dynamic analysis results. It is illustrated that modified quasi-static solution shows agreement with both dynamic analysis and physical behavior of the system.
The contents of this study are particularly useful in structural strength re-assessments where the practicing engineer is interested in an approximated solution indicating if the design criteria is satisfied.
Application of Low Heat Input Gas Metal Arc Welding for Corrosion Resistant Weld Overlays
Authors: Babyak Timothy , DeCenso Vincent , Alexandrov Boian , Penso Jorge 
Published: October 2020

Abstract
Preventing failure due to corrosion poses a challenge to the oil and gas industry. A cost-effective way to prevent such failures is the application of corrosion-resistant nickel-based weld overlays using arc welding processes. Previous research performed at The Ohio State University indicates low heat input GMAW processes, such as cold metal transfer (CMT), produce weld overlays which corrode up to ten times slower than overlays produced with cold wire GTAW [1, 2], with up to ten times higher deposition rates [3]. However, formation of lack of fusion and lack of penetration defects has been a major concern related to the widespread application of low heat input GMAW processes in the industry. In this study, optimal windows of CMT welding parameters for producing defect-free welds were established using a design of experiment approach. CMT weld overlays were compared with hot wire (HW)-GTAW overlays currently used in industry with respect to bead characteristics, microstructure, and process capability. As compared with the HW-GTAW process, the CMT process produced weld overlays with up to four times lower dilution, seven times smaller interdendritic arm spacing, and four times higher deposition rates. Additionally, average heat affected zone and fusion boundary hardness values in the CMT overlays were below 248 HV0.1 and may not require the post weld heat treatment specified by NACE MR0175.