bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Modelling of Compression Stress Relaxation and Compression Set of Elastomer O-Ring During Aging
Authors: Zaghdoudi Maha , Weber Mike , Kömmling Anja , Jaunich Matthias , Wolff Dietmar 
Published: October 2020

Abstract
Elastomer seals are used in many industrial applications due to their excellent mechanical properties at a wide range of temperatures. Their high versatility and recovery potential under several load conditions make them well suitable for the application in containers designed for transport, storage and/or disposal of radioactive materials. In containers for low and intermediate level radioactive waste, elastomer seals are used as barrier seals, and as auxiliary seals in storage and transportation casks (dual purpose casks) for heat generating radioactive waste, such as spent fuel and high-level waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered and prohibit an unnecessary cask handling. An extensive knowledge of the change of the elastomer’s properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the permanent safe enclosure of the radioactive material is mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have been already made and are still planned to scientifically support this task.
Compression stress relaxation and compression set were identified as key indicators of elastomer long-term performance and quantitatively investigated in comprehensive test programs. Among other representative types of elastomers, specimens made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the most important of their complex mechanical properties.
In the presented study, exemplary results were used to simulate the compression stress relaxation and the compression set of elastomer O-rings during aging. Regarding the influence of temperature, the time-temperature superposition principle is applied in the relaxation analysis of elastomer O-rings. The proposed model is implemented in the commercial finite element software ABAQUS/Standard® [1] with a sequential temperature displacement coupling. Numerical results match the experimental compression stress relaxation measurements well. The prediction of compression set values after long-term aging shows a relatively good agreement with the experimental results. Nevertheless, all input parameters derived from the specimen tests, additional assumptions concerning boundary conditions and modeling strategy are discussed with regard to the identified slight discrepancies.
The possibility to extend the finite element model to represent the O-ring seal’s ability to recover after a (fast) partial release is taken into account.
CNN Based Defect Recognition Model for Phased Array Ultrasonic Testing Images of Electrofusion Joints
Authors: Shi Jianfeng , Tao Yangji , Guo Weican , Zheng Jinyang 
Published: October 2020

Abstract
Phased Array Ultrasonic Testing (PA-UT) has been proved to be the most feasible way to inspect defects in electrofusion (EF) joints of polyethylene (PE) pipes. The recognition of defects in PA-UT results relies on the experience of operators, and results in inconsistent defective detection rate and low recognition speed. In this paper, an automatic defect recognition model for PA-UT inspection images was proposed based on convolutional neural network (CNN), realizing recognition of four typical defects in EF joint, i.e. wire dislocation, holes, lack of fusion and cold welding. The proposed recognition model consisted of anomaly detection model and defect detection model. The anomaly detection model recognized anomalies of PA -UT inspection images. The Defect detection model classified and located the defects of abnormal PA -UT inspection images. The anomaly detection model was assigned with a large anchor scale, to realize fast recognition, so as to meet the requirement of real-time recognition practical inspection. And defect detection model was designed to achieve high accuracy of defects recognition. By optimizing parameters of learning rate and dataset augmentation, the anomaly detection model and the defect detection reached a good combination of robustness and accuracy. Experiments showed that the proposed recognition model can improve the recognition speed and accuracy compared to single defect detection model.
Effect of Piping System Vibration (FIV, AIV, PIV) on Pipe Support Loads
Authors: Appiah Emmanuel , Wiseman Phillip 
Published: October 2020

Abstract
Integrity of a piping system is a prerequisite for personnel safety and operational reliability in industries where pipelines are critical means of transferring products from one process point to the other, such as power plants, refinery plants, and chemical industries. An essential aspect of designing a reliable piping system is to design supports of suitable load carrying capacity. This also depends on accurate determination of expected support loads including loads due to vibration of the system. Piping design codes such as ASME B31.3 and B31.1 provide a general framework but do not address vibration and its impact from a detailed perspective. In many situations, the potential impact of vibration is overlooked during support load determination. In recent piping system construction, the effect of vibration has increased due to increase in fluid flow rates and use of high strength thin wall materials. Common factors that contribute to vibration include: turbulent flow (flow induced vibration, FIV), relief valve operation (acoustic induced vibration, AIV), rotating and reciprocating equipment (pulsation induced vibrations, PIV). The effect of vibration depends on the strength of excitation and the flexibility of the piping system. As vibration of the piping system increases, loads transfer to the pipe supports also increase. Catastrophic failure of a piping system can occur if its natural frequency lock-in with the frequency of the excitation source. For holistic system integrity, the loads induced due to vibrations need to be accounted for in the support design. In this paper, we investigate the contributions of the various vibration loads in a piping system, the effect of neglecting the various vibration loads on the system integrity, and an empirical method to readily determine the vibration loads to reduce cost and time require in support design processes.
A New Research Method for Corrosion Defect in Metal Pipeline by Using Pulsed Eddy Current
Authors: Zhao Fan , Chen Delu , Pu Zhe , Wang Jielu 
Published: October 2020

Abstract
Pulsed eddy current (PEC) is a new technique to distinguish corrosion defeats inside and outside the metal pipeline. In comparison with other eddy current techniques, the PEC technique has the advantage of being simple and high velocity. In this article, a brand-new PEC probe based on differential conductivity is established through the combination of modules like square wave generator, eddy current coil bridge, differential current, voltage sample circuits and so on. The 50% duty cycle square wave is used as the driving signal. To measure differential conductance, a coil bridge configuration with two legs is adopted. One leg is composed of measurement eddy current coil and the in-series resistor, and the other is reference eddy current coil and the in-series resistor. Because the two legs go through defects in pipeline non-synchronously, there is a differential conductance between the two coils. A trans-impedance amplify circuit is used to detect coil eddy current. At the same time, two amplifiers are used to measure the differential voltage between the two coils. A 14 bit ADC is used to sample differential voltage, measurement and reference eddy currents which transferred to differential current by main processor Complex Programmable Logic Device (CPLD). CPLD is used to get differential conductance by differential current divide differential voltage. At last the eddy current signal sampling sequence is developed. A dynamic testing fixture with artificial defects carved on the pipeline is used to validate PEC probe’s accuracy. The differential conductance signals were displayed on the oscilloscope. Results showed that the inside defect had two peaks, positive peak and negative peak, but the outside defect only had one positive peak. We can conclude that the brand-new PEC probe has high accuracy in distinguishing the inside and outside defects.
Inelastic Analysis of Process Vessel Component Under Creep and Primary Load
Authors: Hoang Tran Quan , Truong Daniel , Truong K. T. 
Published: October 2020

Abstract
In vessel component design by analysis, two failure modes are routinely investigated: Protection against plastic collapse and Protection against local failure. In elevated temperature service, creep rupture stress is the basis for elastic numerical analysis for establishing compliance with protection against the first failure mode. When compliance is not met, Elastic Perfectly Plastic (EPP) being a more accurate tool is proposed to verify the design using a factored rupture-based stress as yield (Sy = 1.25S). It seems that related work about adjusted yield stress has not been presented and validations are still needed using ASME VIII-2, part 5 combined load factor. Regarding local failure, an isochronous stress-strain curve has been used to determine the final stage strain for a total time duration, and compare to limits set by ASME III-NH. Code case 861 is also used to evaluate the minimum total inelastic strain and its conservativeness compared to the isochronous stress-strain curve approach.
CFD Analysis of a Piping-Pressure Safety Valve System Working in Gas/Vapor Service
Authors: Song Xue Guan , Zong Chao Yong , Zheng Feng Jie 
Published: October 2020

Abstract
Configuration of piping-pressure safety valve (PPSV) is widely used but may sometimes show instabilities, which should be avoided or reduced. For exploring the cause of these instabilities, Computational Fluid Dynamics (CFD) provides a powerful tool that can be used not only to reproduce the system-level responses, but also to get the details of the local flows. However, the results of CFD simulations are usually sensitive to their model settings, thus, to ensure accuracy, effects of certain critical model settings (such as time-step size and turbulence model) on transient simulations should be determined. In this paper, a 2-D axisymmetric mesh model is developed first, which can be used to predict the dynamic responds of a PPSV system. With this model, three levels of time-steps are tested. The results indicate that the time-step of 1e−5 is a reasonable choice for transient simulations of the PPSV system. After that, a total of four two-equation turbulence models are used for transient simulations. The results indicate that the SST (Shear stress transport) k-omega model produce the closest results to the experiments. After that, the accuracy of the developed CFD model (with 1e−5s time-step and SST k-omega setting) is verified by experimental tests. The results indicate that the developed CFD model can accurately reproduce the dynamic responds of the PPSV system. Outcomes obtained in this paper can not only provide a reference for the transient CFD model development, but also verify the applicability and high accuracy of 2-D axisymmetric CFD models in PPSV dynamics prediction.
Non-Destructive Evaluation of RPV Embrittlement by Means of the Thermoelectric Power Method
Authors: Niffenegger M. , Mora D. F. , Kottmann H. 
Published: October 2020

Abstract
Nondestructive evaluation (NDE) methods are widely used for inspecting safety relevant components in nuclear reactors. Most of these NDE-methods are optimized and applied for the detection of cracks but there is still no reliable NDE method for measuring the embrittlement of RPV steels. However, since the evaluation of RPV embrittlement of so-called Surveillance specimens with the Charpy test is a destructive approach, NDE methods are highly required. Among the investigated technics are acoustic (Ultrasonic scattering), electric (resistivity, thermoelectric) and magnetic (Barkhausen Noise, Non-Linear Harmonics Analysis, Micromagnetic Multiparameter) methods. However, all the methods under investigation suffer from the fact that fracture toughness of steel depends upon several factors, especially on lattice defects such as vacancies, dissolved atoms, dislocation loops, solute clusters, precipitates and dislocations. A major obstacle to the application of NDE methods for the quantification of material embrittlement is that they may be not only sensitive to these defects but also to other factors, such as magnetic, acoustic and electrical properties, as well as to surface quality and ambient temperature, etc.).
In this paper, we present results gained by the optimization and application of the thermoelectric power method (TEPM) at the Paul Scherrer Institut (PSI) in Switzerland. The TEPM uses the change of the Seebeck coefficient (K) as an indicator for the material embrittlement. A clear almost linear correlation between the shift of the Nil-Ductile-Transition-Temperature (NDTT) and the change of the K was found. Beside the TEPM and its optimization with the finite element method, we describe the influencing parameters and the potential of this promising NDE method.
A Unified Constitutive Model With Optimized Parameters for Base and Diffusion Bonded Alloy 800H
Authors: Mahajan Heramb P. , Hassan Tasnim 
Published: October 2020

Abstract
Current ASME Section III, Division 5 code provides elastic, simplified inelastic and inelastic analysis options for designing nuclear power plant components for elevated temperature service. These analyses methods may fail to capture the complex creep-fatigue response and damage accumulation in materials at elevated temperatures. Hence, for analysis and design of the nuclear power plant components at elevated temperature, a full inelastic analysis that can simulate creep-fatigue responses may be needed. Existing ASME code neither provides guidelines for using full inelastic analysis nor recommends the type of constitutive model to be used. Hence, a unified rate-dependent constitutive model incorporating a damage parameter will be developed, and its parameters for base metal will be determined. In addition, a full inelastic analysis methodology using this model to analyze the creep-fatigue performance of components for nuclear power applications will be developed. Base metal 800H (BM800H) data are collected from literature to determine constitutive material model parameters. The parameter determination methodology for a constitutive model is discussed. The optimized parameter set for BM 800H at different temperatures will be presented in the paper. Recommendations are provided on the constitutive model selection and its parameter determination techniques. In the future, this work will be continued for diffusion bonded Alloy 800H (DB800H) material, and obtained parameters will be compared.
Comparative Stress Analyses of Dropped Spent Nuclear Fuel Assembly in a Prototypal Cask
Authors: Kang Sae-Han-Sol , Kim Dong-Hyun , Chang Yoon-Suk , Lee Sang-Hwan 
Published: October 2020

Abstract
While establishment of appropriate policies and securing key technologies on spent nuclear fuels are state-of-the-arts in the world due to saturation of fuel pools and/or temporary facilities, the details of transportation, storage and repository are different depending on the situation in each country. Thereby, accurate integrity assessment of specific transportation casks and contained fuel assemblies as well as their breakdown effects on the public and environment are becoming more important.
The purpose of this study is to carry out parametric stress analyses of spent nuclear fuel assembly in a prototypal dual purpose cask under development. As the representative postulated accident conditions, four scenarios were selected such as vertical, horizontal, corner and oblique drop from 9 m height on the ground. Then, taking into account computational cost, a simple model that considers only the equivalent mass of the fuel assembly was made for preliminary finite element analyses to determine the most dangerous drop condition and critical location. Subsequently, a detailed model that considers the acceleration of fuel assembly was made based on the preliminary analysis results and finite element analyses were carried out to calculate engineering parameters. Resulting membrane and bending stress intensities were compared with allowable design limits, of which findings will be used as technical background for development of transportation cask and management of the spent nuclear fuel integrity.
Assessment of Section III Appendix XIII-3230 Plastic Analysis
Authors: Reinhardt Wolf 
Published: October 2020

Abstract
Plastic analysis according to Section III Appendix XIII-3230 may be used in lieu of satisfying primary stress limits. The associated definition of plastic collapse load is based on limiting the permanent plastic deformation to not exceed the elastic deformation using a method that is also used to determine the collapse load experimentally. The acceptable load is calculated from the collapse load using a reduction factor that depends on the Service Level. Using some simplified application examples, the strengths and weaknesses of the method are discussed relative to the objectives of primary stress limits. Proposals for modifications of the plastic analysis method in the Code are reviewed and assessed. Elements of a proposal for an updated version of Appendix XIII-3230 are discussed, including providing additional guidance for the computational implementation of the method. The representation of the material stress-strain curve is another important aspect that may require additional guidance.
Efficient and Flexible Finite Element Procedure for Free and Forced Vibration Problems of a Plate Coupled With Fluid
Authors: Ji Ming , Inaba Kazuaki 
Published: October 2020

Abstract
Identifying the coupled system natural frequencies and dynamic behavior of systems in the presence of fluid-structure interaction is one of the most important issues in the engineering design of buildings, road vehicles and aircraft. This paper presents an efficient and flexible finite element procedure using fully vectorized codes for the free and forced vibration analysis of a rectangular plate in contact with fluid. The 4-node MITC plate finite element (MITC4) based on the Mindlin plate theory is used to simulate the plate, while the 8-node acoustic pressure element is used to simulate the fluid. The derived system of equations using structural displacements and fluid pressures yields a non-symmetric system of equations. Solving the generalized eigenvalue problem for the non-symmetric system is more computationally intensive compared to solving the generalized eigenvalue problem for symmetric systems. The modal expansion technique is used to reduce the model size. Then the reduced non-symmetric system is symmetrized by right eigenvectors. The Newmark method is used to solve the forced vibration problem of the coupled systems. The effect of the height of the fluid on the natural frequencies is discussed. The natural frequencies and transient responses are in good agreement with those obtained from the commercial finite element software. Moreover, the technique is proved to be effective to solve the coupled system.
Experimental Investigation on the Friction Coefficients for Different Materials, Lubrication Conditions and Coatings in Bolted Joints
Authors: Croccolo Dario , De Agostinis Massimiliano , Fini Stefano , Olmi Giorgio , Robusto Francesco , Paiardini Luca , Gualdi Gabriele 
Published: October 2020

Abstract
The present paper investigates the influence of several design parameters on the frictional response of a bolted joint, involving screws from strength grades 8.8 to 12.9, with black oxidization coating or zinc coatings. The experimentation deals with different underhead and nut materials (cast iron, aluminum), lubrication conditions (dry, lubricated, two different threadlockers: medium and strong), roughness condition in the underhead (cast, machined, painted, underhead washers) and cosidering also the effect of repeated tightenings. The friction coefficients of the actual application, retrieved based on the relevant operating parameters, are needed to support a correct design. The experimentation has been carried out by a purposely developed specimen, consisting of two parts: an instrumented sleeve, with a double array of strain gauges capable of sampling both the axial preload and the underhead torque, and interchangeable underhead washers. The testing apparatus is provided with a device which allows preventing undesired rotation of the washers. The washer material and surface treatment change among the different specimen sets. The tightening torque is applied by means of a 10-120Nm digital torque wrench. The collected data have been processed by the tools of ANoVa. Such tools allowed assessing the significance of each factor, as well as related interactions.
Cross Weld Tensile Testing With Digital Image Correlation to Determine Local Strain Response
Authors: Siefert William , Rule James , Alexandrov Boian , Buehner Mike , Penso Jorge A. 
Published: October 2020

Abstract
Qualification for weld strength is typically accomplished using cross weld tensile testing. This style of testing only gives the global behavior of the welded joint and limited materials properties, such as elongation at failure and tensile strength of the material where final failure occurs. Qualification for welded structures usually requires the weldment fails in the base metal. Final failure in cross weld tensile tests in the base metal does not provide information about the actual weld metal and heat affected zone properties. There may be weaker points in the microstructure that cannot be identified in a global cross weld tensile test due to being constrained by surrounding microstructures. Additionally, the traditional cross weld tensile test does not quantify how strain accumulates and transfers in the microstructure at various loads. Using Digital Image Correlation (DIC) in combination with tensile testing, local strain of the various microstructures present across the weld was obtained for ferritic to austenitic dissimilar metal welds (DMW), as well as for a typical “matching” ferritic steel filler metal weld with a higher tensile strength than the base metal. This test also showed where and how strain accumulated and transferred during tensile loading of various welded microstructures. Local yield stresses of each region were also obtained. Obtaining such local properties provides insight into design and service limits of welded components in service.