bluuebunny/crossref_metadata_2025_split huggingface dataset:
Change of Crack Initiation and Propagation Modes in Hydrogen-Related Failure of a Precipitation-Strengthened Ni-Based Superalloy 718 Under Internal and External Hydrogen Conditions
Authors: Ogawa Yuhei , Takakuwa Osamu , Okazaki Saburo , Matsuoka Saburo , Matsunaga Hisao 
Published: November 2019

Abstract
The influences of internal and external hydrogen on the tensile ductility loss and fracture behaviors of a precipitation-hardened Ni-based superalloy 718 were investigated via slow strain rate tensile (SSRT) testing under hydrogen pre-charged conditions (internal hydrogen) or in gaseous hydrogen environments (external hydrogen) . Severe degradation of tensile ductility was confirmed both in internal and external hydrogen conditions, and the degree of such degradation became more significant with increasing hydrogen content or hydrogen gas pressures. Moreover, the loss of tensile ductility was more pronounced in internal hydrogen conditions than external hydrogen environments. In association with such degradation of macroscopic tensile ductility, hydrogen also altered fracture mode from ductile microvoid coalescence to some brittle appearances. Whereas typical intergranular fracture combined with a decent fraction of quasi-cleavage fracture appeared on the fracture surface formed in external hydrogen environments, several types of unique faceted characteristics were found on the fracture surfaces in internal hydrogen conditions. The detailed observation of the mid-sectioned lateral surfaces of post-mortem samples successfully revealed that the observed distinctions consisted of the fracture along grain boundaries and {111} crystallographic planes including annealing twin boundaries, besides the frequency of the cracking along twin boundaries evidently increased at higher hydrogen concentration. On the basis of the series of experimental results, the initiation and propagation mechanisms of those hydrogen-induced cracks are discussed in terms of hydrogen distribution, intrinsic deformation character of the material itself as well as the alteration of plastic deformation mode caused by dissolved hydrogen.
Analysis of Defect Interaction in Inelastic Materials
Authors: Coules Harry E. , Bezensek Bostjan 
Published: November 2019

Abstract
Procedures for structural integrity assessment such as R6 and BS7910 often need to consider the possibility of closely-spaced structural defects interacting with one another. Typically, this comes in the form of a simplified interaction rule: if a criterion based on the size, shape and separation of the defects is satisfied, then they are judged to interact and cannot be analysed independently. When interaction is judged to occur, the defects may be re-characterised as a larger, enclosing defect. Rules for predicting defect interaction and then specifying the size of the re-characterised defect need to be conservative across a wide range of situations, so they are often informed by studies using parametric finite element analysis and laboratory testing. This article discusses the interaction of defects in inelastic materials, focussing on the determination of limit loads and the elastic-plastic crack driving force for co-planar crack-like defects. New methods for parametric modelling and data analysis are introduced, with examples demonstrating the use of inelastic modelling in formulation of interaction criteria.
Fatigue Benchmark Comparison Effort Between Code_Aster and CNNC/NPIC Software: Part 1
Authors: Xie Hai , Shao Xuejiao , Liu Han 
Published: November 2019

Abstract
Fatigue is identified as a significant degradation mode that affects nuclear power plants world-wide. Several international codes and standards (ASME, RCC-M, JSME, etc...) offer rules to predict its damaging effect on the locations of the various components of an NPP. These rules, which ensure conservatism and safe operation, have grown in complexity over the years because they have integrated R&D results showing aggravating effects that were not included in the original analyses (such as Environmental Assisted Fatigue[1][2]) but also because an economically viable design of components has required optimization and refinement of mechanical assessment methods.
CNNC/NPIC has been following carefully the recent evolutions in the fatigue rules and has today finalized an in-house software enabling the evaluation of fatigue per ASME and RCC-M rules, with integration of environmental effects.
On the other hand, EDF has been developing since 1989 its own in-house FEA code baptizedCode_Aster that is included in the Salome-Meca mechanical package. Salome-Meca is open-access and can be used freely by international users. Within Code_Aster, the fatigue postprocessor offers a span of criteria (Dang Van, Stress Intensity, etc...) to pick and choose from and even offers the possibility to make up owns one fatigue criteria. It also offers the possibility to post-process fatigue according to the RCC-M rules (POST_RCCM operator). It has been recently updated to perform industrial calculations integrating environmental fatigue[2][3].
Both entities have come to agree that validating a fatigue computer code is not an easy task. On the one hand, the full validation using hand calculations would be a highly tedious effort, given the technicality and the multiple choices to make along the various steps of the fatigue analysis. On the other hand, there are no experiments today which enable to directly lead a benchmark calculation to validate fatigue numerical results.
In consequence, an accepted way of validating a code is to perform a benchmark analysis against another industrial fatigue code. CNNC/NPIC and EDF R&D China have therefore launched an effort to benchmark their respective codes, with the final objective of progressing together towards safe structural assessment practical methods for their power plants components.
Study on Incorporation of a New Design Fatigue Curve Into the JSME Environmental Fatigue Evaluation Method
Authors: Asada Seiji , Zhang Shengde , Takanashi Masahiro , Nomura Yuichirou 
Published: November 2019

Abstract
A new fatigue analysis method was developed in the Subcommittee on Design Fatigue Curve in the Atomic Energy Research Committee in the Japan Welding Engineering Society JWES). If the new design fatigue curves are incorporated into the Environmental Fatigue Evaluation Method of the Japan Society of Mechanical Engineers (JSME), the environmental fatigue analysis can be optimized. The Subgroup on Fatigue Evaluation of the Subcommittee on Nuclear Power in the Main Committee on Power Generation Facility Codes in the JSME is reviewing the new design fatigue curves to incorporate into the JSME Environmental Fatigue Evaluation Method. This paper discuss the new design fatigue curves which is under review.
Case Study of Pipe Support and Restraint Stiffness
Authors: Wiseman Phillip , Mayes Alex , Appiah Emmanuel 
Published: November 2019

Abstract
Pipe support and restraint assemblies are an integral part of engineered piping systems for power, petrochemical, refinery, and process industries. Such assemblies are specially designed and analyzed for the purpose of transferring loads from piping to building structure or supplemental steel structure. Thus, a support assembly protects the piping, or any other components, from damage that may result from startup, shutdown, shocks from valve operation, water hammer, steam hammer, wind, seismic, and other catastrophic events such as pipe rupture or explosions. It also restrains against unacceptable movements in the piping system while preserving movement due to thermal growth. The support and restraint stiffness values are utilized based on assumptions and calculations of load versus displacement. A case study of pipe support elements is performed in various static and dynamic load cases to determine the effects of assumptions of utilizing one stiffness value versus multiple stiffness values within an assembly. Additionally, the stiffness for the connected building structure opens more assumptions within industry practice. Multiple industry practices of stiffness values are integrated into this research to compare and contrast the realistic attributes of each.
The Non-Effect of Yield Strength on RTT0 and on the Master Curve
Authors: Kirk Mark , Erickson Marjorie 
Published: November 2019

Abstract
During the August 2018 ASME Committee Week, a Code Change Inquiry was presented to the Working Group on Operating Plant Criteria (WGOPC):
Question 1: Is it the intent of G-2110 to limit RTT0 use to ferritic materials with specified minimum room temperature yield strengths 50 ksi or less?
Question 2: If the reply to Question 1 is “No”, is it the intent of G-2110 that G-2110(b) requirement must be met before RTT0 may be used for ferritic materials above 50 ksi but not exceeding 90 ksi?
During that meeting the WGOPC replied “no” to both questions. This paper provides an evaluation of available fracture toughness data augmented by an understanding of the underlying mechanisms of cleavage fracture to demonstrate the veracity of the WGOPC’s answer with regards to RTT0 and, more generally, with respect to the Master Curve.
Experimental Study of Near-Fault Effect on Sloshing Mode of Storage Liquid in Tanks
Authors: Chai Juin-Fu , Lin Fan-Ru , Hsu Wei-Hung , Chien Tzu-Chieh , Lai Zhi-Yu , Lin Zhen-Yu 
Published: November 2019

Abstract
The long period velocity pulse is recognized as one of the characteristics of near-fault ground motions, and hence the response of vibration modes with lower frequencies will be amplified owing to the resonant effect. In general, the sloshing frequency of storage liquid is low and the period is similar to the pulse period of near-fault ground motions. Compared to the far-field ground motions, the induced sloshing height will be amplified by the near-fault ground motions. Therefore, it is worth paying attention to the resonant effect of near-fault ground motions on the sloshing mode of storage liquid in tanks.
An experiment was implemented to study the resonant response of sloshing mode. The purpose of this experiment is to estimate the slosh height and the associated total volume of water splashing out of the tank under near-fault ground motions, and also to determine the relationship between the resonant response and the input velocity pulse. This paper aims to describe the test plan in detail, and it consists of (1) design of the scaled storage tank and water depth, (2) selection and processing of the input motions including the original near-fault ground motions, extracted velocity pulse or extracted bandpass signals for resonance analysis, and also impulse motion for free vibration, (3) setup of measure instrument, and (4) the experimental procedures as well. Preliminary analysis results are compared with the code-specified values that is determined by the industrial standards and guidelines for general seismic conditions. It is noted that the proposed prediction equation can be applied to the seismic design and evaluation of spent fuel pool in nuclear power plants.
Influence of Vibration Behavior on the Energy Dissipation of the Bolted Joints
Authors: Xu Wenxiang , Cai Ligang , Liu Zhifeng , Cheng Qiang , Li Ying 
Published: November 2019

Abstract
Bolted joints are widely used for the mechanical assembly of engineering structures. It has been widely observed that fasteners turn loose when subjected to dynamic loads in the form of vibration or cyclic loading. Preload relaxation of threaded fasteners is the main factor that influences the joint failure under normal cyclic loading, but it is difficult to monitor the energy dissipation between the interface of the bolted joint. This paper presents an energy dissipation model for the bolted joint based on two-degree-of-freedom vibration differential mathematical model. A non-uniform pressure at the interface is considered and the resulted distinct stick-slip transitions along the contact interface are presented. The parameters of the model is calculated by using the fractal theory and differential operator method. Experiments are conducted to verify the efficiency of the proposed model. The results show that the theoretical mode shapes are in good agreement with the experimental mode shapes. According to the change of cyclic load and vibration frequency, the vibration response and the law of energy dissipation under different factors can be obtained. The results show that the vibration frequency and cyclic load are the main factors affecting the energy dissipation between interfaces. The energy dissipation of the contact surface of the bolted joints account for the main part of the energy dissipation of the bolted structure. As the preload increases, its energy dissipation decrease gradually. The results provide a theoretical basis for reducing micro-slip at the bolted joints interface.
Use of CFD to Improve Control Valve Effectiveness
Authors: Reich Alton 
Published: November 2019

Abstract
Control valves are used to adjust fluid flow rates in an extremely wide variety of applications. This paper discusses a steam flow control valve that is required to operate with a fairly wide range of inlet conditions (steam pressure) and provide effective control over a fairly wide range of steam flow rates. In this particular case a valve design was developed using “classical” methods — a combination of experience and hand calculations. The valve was tested and it did not provide adequate control over the flow for the application. The valve redesign effort used CFD to gain insight into the flow through the valve in order to evaluate control performance before the valve was fabricated and assembled. Several internal geometries were assessed and compared in order to identify two configurations that would meet the flow control requirements. These configurations were fabricated and tested and deemed to be adequate.
Assessment of Leak Before Break of a Newly Developed Type II Pressure Vessel With High-Pressure Hydrogen Gas
Authors: Okano Hiroshi , Nagao Akihide , Matsubara Kazuki , Ishikawa Nobuyuki , Takagi Shusaku , Kitagawa Satoshi , Takano Toshio 
Published: November 2019

Abstract
A Type 2 pressure vessel for hydrogen storage, which is made of a combination of a seamless linepipe steel liner and carbon fiber reinforced plastic (CFRP), was developed for hydrogen refueling stations operated at over 70 MPa hydrogen. This newly developed vessel was designed based on various standards such as ASME Sec. VIII Div. 3. However, a leak before break (LBB) methodology has not yet been established for hydrogen. The current study assessed LBB of the Type 2 vessel by a cyclic pressure test in a hydrogen gas atmosphere. The vessel with an artificial flaw was subjected to a cyclic test at pressures between 35 and 93 MPa hydrogen. Hydrogen gas leaked at 7,973 cycles. Eventually, LBB failure was confirmed. This number of cycles to leak was in good agreement with the simulated number, of 9,082 cycles using the crack growth properties in the presence of hydrogen and stress distribution of the thickness direction of the liner calculated by a finite element method. It is suggested that the fatigue crack growth behavior of the pressure vessel can be accurately estimated by using the fatigue crack growth properties in the presence of hydrogen, which correspond to the crack-tip stress-intensity range of an actual pressure vessel.
Boron Injection Tank Repair at Indian Point Unit 3
Authors: Crane David P. 
Published: November 2019

Abstract
In the Fall of 2018 Westinghouse designed a welded plug to repair a leak around a previously capped nozzle in the Boron Injection Tank at Indian Point Unit 3. The leak was caused by weld cracking around the nozzle. In order to complete the repair, the existing nozzle and weld needed to be removed by boring into the tank so that a custom plug could be installed. Due to site procedures, welding could not be performed inside the tank, so a single weld on the outside of the tank needed to be designed to meet ASME B&PV Code, Section III requirements. In addition, the tank was manufactured from carbon steel with a stainless steel cladding, so future corrosion of the carbon steel needed to be assessed. The leak was an outage related incident, which required the design to be expedited. This paper will discuss the technical challenges in designing the welded plug to meet the site and code requirements.
Experimental Investigation of Fluid-Elastic Vibration of Square Array Tube Bundle in Two Phase Flow
Authors: Kawakami Ryoichi , Azuma Seinosuke , Nariai Toshifumi , Hirota Kazuo , Morita Hideyuki , Kondo Yoshiyuki , Komuro Yoshiteru 
Published: November 2019

Abstract
The in-plane (in-flow) fluid-elastic instability (in-plane FEI) of triangular tube arrays caused tube-to-tube wear indications as observed in the U-bend regions of tube bundles of the San Onofre Unit-3 steam generators[1]. Several researches revealed that the in-plane FEI is likely to occur in a tightly packed triangular tube array under high velocity and low friction conditions, while it is not likely to occur in a square array tube bundle. In order to confirm the potential of steam-wise fluid-elastic instability of square arrays, the critical flow velocity in two-phase flow, (sulfur hexafluoride-ethanol) which simulates steam-water flow, was investigated.
Two types of test rigs were prepared to confirm the effect of the tube diameter and tube pitch ratio on the critical velocity. In both rigs, vibration amplitudes were measured in both in-flow and out-of-flow directions in various flow conditions. In any case, in-flow fluid elastic instability was not detected. Based on the results of the tests, it is concluded that the flow interaction force is small for concern to occur the fluid-elastic instability in the in-flow direction of the square tube bundles of steam generators.
Design of an Intelligent Python Code for Validating Crack Growth Exponent by Monitoring a Crack of Zig-Zag Shape in a Cracked Pipe
Authors: Fong Jeffrey T. , Marcal Pedro V. , Rainsberger Robert , Heckert N. Alan , Filliben James J. 
Published: November 2019

Abstract
When a small crack is detected in a pressure vessel or piping, we can estimate the fatigue life of the vessel or piping by applying the classical law of fracture mechanics for crack growth if we are certain that the crack growth exponent is correct and the crack geometry is a simple plane. Unfortunately, for an ageing vessel or piping, the degradation will, in practice, change not only the crack growth exponent but the crack shape from a simple plane to a zig-zag pattern. To validate the crack growth exponent for an ageing vessel or piping, we present the design of an Intelligent PYTHON (IP) code to convert the information of the growing crack geometry measured by monitoring a small crack that was initially detected and subsequently continuously monitored over a period of time such that the IP-based analysis code will use the realistic zig-zag crack geometry as a series of re-meshed finite-element meshes for finding the correct crack growth exponent. Using a numerical example, we show that such an IP-assisted continuous monitoring program, using PYTHON as the management tool, TRUEGRID as the topological crack meshing tool, and two finite-element analysis codes for verifiable stress analysis, is feasible for predicting more accurately the fatigue life of a cracked vessel or piping because the material model has a field-validated crack growth exponent. Significance and limitations of this IP-assisted approach are discussed.
Simulation of Piping Ratcheting Experiments Using Advanced Plane-Stress Cyclic Elastoplasticity Models
Authors: Chatziioannou Konstantinos , Huang Yuner , Karamanos Spyros A. 
Published: November 2019

Abstract
Industrial steel piping components are often subjected to severe cyclic loading conditions which introduce large inelastic strains and can lead to low-cycle fatigue. Modeling of their structural response requires the simulation of material behavior under strong repeated loading, associated with large strain amplitudes of alternate sign. Accurate numerical predictions of low-cycle fatigue depend strongly on the selection of cyclic-plasticity model in terms of its ability to predict accurately strain at critical location and its accumulation (referred to as “ratcheting”). It also depends on the efficient numerical integration of the material model within a finite element environment.
In the context of von Mises metal plasticity, the implementation of an implicit numerical integration scheme for predicting the cyclic response of piping components is presented herein, suitable for large-scale structural computations. The constitutive model is formulated explicitly for shell-type (plane-stress) components, suitable for efficient analysis of piping components whereas the numerical scheme has been developed in a unified manner, allowing for the consideration of a wide range of hardening rules, which are capable of describing accurately strain ratcheting.
The numerical scheme is implemented in a general-purpose finite element software as a material-user subroutine, with the purpose of analyzing a set of large-scale physical experiments on elbow specimens undergoing constant-amplitude in-plane cyclic bending. The accuracy of three advanced constitutive models in predicting the elbow response, in terms of both global structural response and local strain amplitude/accumulation, is validated by direct comparison of numerical results with experimental data, highlighting some key issues associated with the accurate simulation of multiaxial ratcheting phenomena. The very good comparison between numerical and experimental results, indicates that the present numerical methodology and, in particular, its implementation into a finite element environment, can be used for the reliable prediction of mechanical response of industrial piping elbows, under severe inelastic repeated loading.
Mechanical Behaviors of Reinforced Thermoplastic Pipe Under Combined Load
Authors: Wang Baodong , Zhang Hong , Liu Xiaoben 
Published: November 2019

Abstract
Reinforced thermoplastic pipe (RTP) is used in the oil and gas industry for its good flexibility, corrosion resistance and wear resistance, especially in offshore oil and gas production process. However, they are subject to internal pressure, external pressure and tension loads that are important aspects affecting the integrity and security of the flexible pipe. Their reinforced layers are designed for bearing internal pressure and tension. In this paper, the mechanical behaviors of reinforced thermoplastic pipe with 3 layers, where the reinforced layer is aramid fiber braid layers, is investigated by numerical methods. The internal pressure burst test of reinforced thermoplastic pipes was carried out to determine the burst internal pressure and failure behaviors of RTP. A finite element model that considers the material nonlinearity as well as the friction interactions between layers was created using ABAQUS. The mechanical behavior of reinforced flexible pipe subjected to internal pressure and tension load as well as its failure model was investigated in detail. Effects of the braided angle of aramid fiber braid layers were elucidated. This study can be referenced for the applications of reinforced thermoplastic pipe in marine oil and gas production.