bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Proximity Rules for Surface Planar Flaws
Authors: Bouydo Afaf , Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio , Mares Vratislav 
Published: November 2019

Abstract
Flaw assessment according to Fitness-For-Service (FFS) codes is usually based on equations describing the impact of a single flaw in piping or pressure vessels components. However, when multiple flaws are detected, combination rules are to be taken into account to evaluate whether these flaws should be combined into a larger flaw or should be evaluated as separate ones. In recent years, numerous works have been done to evaluate the conservatism of the combination rules required by FFS codes and, if needed, establish new characterization rules. These new characterization rules are based on the distance between flaws, their depths, their lengths or a combination of these three parameters in order to reflect the level of interaction between adjacent flaws. A comparison, focusing on multiple surface planar flaws, between ASME B&PV Section XI current combination rules, other Fitness-For-Service codes and other combination rules established by fellow authors is presented in this paper.
Research Plan and Progress to Realize Fracture Control of Nuclear Components
Authors: Kasahara Naoto , Wakai Takashi , Nakamura Izumi , Sato Takuya 
Published: November 2019

Abstract
For safety improvement after Fukushima daiichi nuclear power plant accident, mitigation of accident consequence for Beyond Design Basis Events (BDBE) has become important. Authors propose application of fracture control concept for mitigation of accident consequence of nuclear plants as follows.
In the case of reactor vessels under high temperature and pressure conditions, small cracks from local failure will release internal pressure and can avoid a large scale ductile fracture of general portions.
For piping under excessive earthquake, repeated elastic-plastic deformation and ratchet deformation dissipate vibration energy and reduce input energy from floor. They can prevent collapse of piping systems or break of pipe wall. Strength of pipe supports can be designed lower than pipe itself. Controlling the failure of supports would lead to plastic deformation without the break. The ratio of the frequency of seismic loading to the natural frequency of the piping system would also affect the failure behavior of piping systems.
This paper describes research plan and progress to realize fracture control of nuclear components.
The first step is clarification of actual failure modes and their mechanisms.
Next step is development of relative strength evaluation method among failure modes.
The third step is proposals of failure control methods. One of example is a vessel under high pressure and high temperature loadings. Another example is pipe under excessive earthquake.
CCG of PE100 and Life Prediction of PE Pipe With Axial Semi-Elliptical Crack
Authors: Zhang Lei , Lin Kaiming , Fu Yang , Gao Bingjun 
Published: November 2019

Abstract
High density polyethylene (HDPE) is widely used in city water and gas piping system and even in nuclear engineering for its excellent properties in flexibility, impact resistance, aging and corrosion resistance, reliable connection, long service life. It is generally believed that the typical failure mode of PE pipe under long-term static pressure load is the slow crack growth (SCG) caused by creep crack initiation (CCI) and creep crack growth (CCG), which is a kind of quasi-brittle failure. Scratching often occurs during PE pipe installation due to the drag of pipe without any protection, which would leave axial cracks as the initial defect. This would harm the long term performance of pressurized HDPE pipe. In the present work, the creep crack kinetics was experimentally determined in term of C* integral, and then CCG behavior of PE pipe with axial semi-elliptical crack was discussed. With the help of a CARE electronic universal testing machine and DIC displacement measuring system, creep tests are performed with smooth bar specimen of PE100 pipe parent material. And the stationary creep law parameters were determined. The crack opening displacement (COD) rates were determined by creep cracking test with cracked round bar specimen. With the help of compliance calibration tests, the COD curves were changed into crack propagation curves and the creep crack kinetics was eventually determined in term of C* integral. By assuming an semi-elliptical crack front with nearly the same C* integral, the creep crack propagation was predicted with the determined crack kinetics. And the allowable initial crack size was also determined for the PE pipe discussed. Compared with that determined in terms of SIF, current study yields much margin for the allowable initial crack.
A Study of the Conservatism in ASME BPVC Section VIII Division 2 Opening Design for External Pressure
Authors: Millet Barry , Ebrahimi Kaveh , Lu James , Kirkpatrick Kenneth , Mosher Bryan 
Published: November 2019

Abstract
In the ASME Boiler and Pressure Vessel Code, nozzle reinforcement rules for nozzles attached to shells under external pressure differ from the rules for internal pressure. ASME BPVC Section I, Section VIII Division 1 and Section VIII Division 2 (Pre-2007 Edition) reinforcement rules for external pressure are less stringent than those for internal pressure. The reinforcement rules for external pressure published since the 2007 Edition of ASME BPVC Section VIII Division 2 are more stringent than those for internal pressure. The previous rule only required reinforcement for external pressure to be one-half of the reinforcement required for internal pressure. In the current BPVC Code the required reinforcement is inversely proportional to the allowable compressive stress for the shell under external pressure. Therefore as the allowable drops, the required reinforcement increases. Understandably, the rules for external pressure differ in these two Divisions, but the amount of required reinforcement can be significantly larger.
This paper will examine the possible conservatism in the current Division 2 rules as compared to the other Divisions of the BPVC Code and the EN 13445-3. The paper will review the background of each method and provide finite element analyses of several selected nozzles and geometries.
Ductile Tearing Simulations to Support Design of Large Scale Tests on Ferritic Pipes to Be Performed in the European Project ATLAS+
Authors: Nicak Tomas 
Published: November 2019

Abstract
The safety and reliability of all systems has to be maintained throughout the lifetime of a nuclear power plant (NPP). This requires a systematic ageing management procedure for justifying their safe long term operation. One fundamental part in this process is to demonstrate the integrity of the nuclear power plant components. The European project ATLAS+ aims to develop and validate advanced methods of structural integrity assessment applicable in the ageing and lifetime management of primary and secondary circuit components.
To support development and validation of those methods, a large scale test program was developed with the aim to investigate fracture behavior of relevant piping material at the component level.
Three of planned large scale experiments focus on the fracture behavior of ferritic piping made of material WB 36 (15 NiCuMoNb 5), that is representative of secondary feedwater lines installed in German NPPs.
In order to verify design calculations conducted by means of the classical fracture mechanics approach based on J-Integral [1], detailed local approach analyses are performed for three mock-ups with different initial defects.
The local approach analyses presented in this paper are based on the local micromechanical model proposed by Gurson and further modified by Tvergaard.
Calibration of required material parameters and prediction of the mock-up behavior during the test is discussed.
In order to support constraint investigations stress triaxiality ahead of the crack front during crack propagation in the mock-ups is evaluated and compared to the stress triaxiality in CT20 and SENT specimens. As high stress triaxiality generally limits plastic deformation and increases the crack tip constraint, it is a good parameter to look at if constraint effects are considered.
Critical Crack Sizes of Pressure Vessels Based on Failure Assessment Diagram Under Design Requirements
Authors: Li Yuebing , Jin Weiya , Zhou Mingjue , Gao Zengliang 
Published: November 2019

Abstract
Standards or codes for defects assessment usually accompany their own design standards, such as, ASME BPVC section VIII and API 579-1/ASME FFS-1, GB 150 and GB/T 19624. The development of defects assessment standards should be adapted to the design requirements of pressure vessels. The consistency between fitness-for-service (FFS) procedures and design requirements of pressure vessels is discussed in this work. As a key link between FFS procedures and design standards, the required material fracture toughness not only depends on the methods of FFS procedures such as failure assessment diagram, but also on the design requirements. A procedure based on failure assessment diagram under design requirements is proposed to calculate critical crack sizes. The result can give some meaningful suggestions for the development of standards or codes.
Interface Microstructure and Thermal Expansion Mismatch in Alloy N/316H Bimetallic Plates
Authors: Xiao Jia , Li Zhijun , Jiang Li , Ye Linfeng , Yu Kun , Liang Jianping , Chen Shuangjian , Chen Zezhong 
Published: November 2019

Abstract
Two Alloy N/316H bimetallic plates have been fabricated by explosive welding and rolling technologies respectively. Metallographic observations indicate that the rolled bimetallic plate has a straight bond interface, in which some cavities and precipitates exist. While the explosive welded plate shows a wavy bond interfaces. The interface thermal expansion mismatch between the two alloys were evaluated in the two plates at high temperature. Results show that the thermal expansion coefficient of 316H is larger than that of Alloy N. The thermal expansion coefficient of the substrate plates depends on the thickness ratio between Alloy N and 316H, which reaches the maximum when the ratio is 1:4.
Vibration of a High Energy PWR Piping System due to Vibro-Acoustic Coupling: Evaluation and Mitigation
Authors: Meyer Gregory A. , Meneely Timothy K. , Koether Jeremy R. , Smith Stephen D. , DiBasilio David C. 
Published: November 2019

Abstract
Vortex Shedding at pipe junctions can create pressure pulsations and flow-induced vibrations. The flow through one pipe may result in a shear layer at the junction with a second pipe. Instabilities such as vortex shedding in the shear layer can then excite acoustic modes in the second pipe, especially when the flow in the secondary pipe is stagnant or weak. The effect is the excitation of a pipe organ mode, which under certain conditions, may result in unacceptable noise and/or vibration levels. Within the nuclear industry this phenomenon has been most frequently observed in boiling water reactors (BWRs), resulting in vortex-induced, main steam line associated stand pipe acoustic resonances.
This phenomenon has not been typically observed in pressurized water reactors (PWRs), especially in primary coolant loops due to the lengths of pipe needed to support acoustic resonances in water systems relevant to driving lower order structural piping modes. However, if certain conditions exist, PWRs do contain large sections of piping which can be susceptible to such flow-induced adverse noise and vibration effects. This paper describes the evaluation and mitigation of structural vibrations due to a vortex-induced excitation of an acoustic mode of a large side branch pipe in a high-energy, water-filled, PWR piping system. Specifically, an acoustic resonance was observed and structurally significant resultant vibration levels were measured on a safety related piping system directly connected to a PWR primary reactor coolant system (RCS) between the reactor and a steam generator.
A rapidly employed evaluation program was implemented, which included significant in-situ structural vibration measurements that informed a combination of acoustic, structural, and fluid-domain numerical modeling evaluations. These evaluations were performed in concert to provide both root cause insights and candidate mitigation strategies. Candidate mitigation strategies were then evaluated prior to inplant implementation via further modeling evaluations and a model-scale testing program. This paper describes the primary vibration characteristics of interest of the affected piping system, the data analyses and modeling methods used to successfully identify the vibro-acoustic phenomena, the developed mitigation strategies, and verification of the final mitigation strategy via model-scale with final demonstration occurring in the plant prior to fuel load.
Damage Evaluation of Grade 91 Thick Cylinder Under Variable Thermal Cyclic Loading Using Continuum Damage Coupled Viscoplastic Models
Authors: Islam Nazrul , Hassan Tasnim 
Published: November 2019

Abstract
This study evaluates creep-fatigue damage in the modified Grade 91 thick-cylinder tested by Japan Atomic Energy Agency (JAEA), to understand the failure mechanism of critical components of Fast Reactor nuclear plants. As modified Grade 91 demonstrated creep-fatigue interaction induced failure mechanisms, finite element analysis of high-temperature components will require a unified constitutive model (UCM) that can simulate various creep-fatigue responses with reasonable accuracy. Hence, a UCM coupled with various advanced modeling features including the continuum damage modeling features is investigated to demonstrate their predictability of the fatigue, creep and creep-fatigue responses of the modified Grade 91 steel. The modified UCM is implemented into ABAQUS for analysis of creep deformation in the thick cylinder benchmark problem. Finite element analysis results are presented to demonstrate how the thermal cycling influences the creep-deformation of this high-temperature component. It is also demonstrated how thermal cycling’s influence on fatigue life can be determined based on the damage variable incorporated in the UCM.
A Method for Directly Assessing Elastic Follow Up in 3D Finite Element Calculations
Authors: Messner M. C. , Jetter B. , Sham T.-L. 
Published: November 2019

Abstract
Elastic follow up significantly influences the creep and creep-fatigue life of structural components in elevated temperature service. As such, assessing the amount of follow up a component sees under a given loading history is critical in properly designing a component for high temperature use. Current methods for quantifying elastic follow up based on an elastic follow up factor use simple constitutive models and are available only for simple component geometries. This work describes a method for assessing the follow up factor, as a function of position and time, from a finite element simulation. The method recovers the simple, analytic solutions for simple geometries and material models but can also provide follow up factors for complicated components, loading histories, and material models. We use this new method to assess the range of follow up factors in a variety of prototypical high temperature structural components. This information can be used to improve design methods by better understanding the magnitude of follow up present in typical high temperature components. The method can also be used to support new design methods that require time-dependent point values of the follow up factor across a component.
A Combined Model Approach for Estimating T0
Authors: Erickson Marjorie 
Published: November 2019

Abstract
The current best-estimate model describing the fracture toughness of ferritic steels is the Master Curve methodology standardized in ASTM E1921. Shortly following standardization by ASTM, efforts were undertaken to incorporate this best-estimate model into the framework of the ASME Code to reduce the conservatisms resulting from use of a reference temperature based on the nil-ductility temperature (RTNDT) to index the plane strain fracture initiation toughness (KIc). The reference temperature RTT0, which is based on the ASTM E1921-defined T0 value, was introduced in ASME Code Cases N-629 (replaced by Code Case N-851) and N-631 to replace RTNDT for indexing the ASME KIc curve. Efforts are continuing within the ASME Code to implement direct use of the Master Curve model; using the T0 reference temperature to index an elastic-plastic, KJc fracture toughness curve.
Transitioning to a direct T0-based fracture toughness assessment methodology requires the availability of T0 estimates for all materials to be assessed. The historical Charpy and NDT-based regulatory approach to characterizing toughness for reactor pressure vessel (RPV) steels results in a lack of T0 values for a large population of the US nuclear fleet. The expense of the fracture toughness testing required to estimate a valid T0 value makes it unlikely that T0 will ever be widely available. Since direct implementation of best-estimate, fracture toughness models in codes and regulatory actions requires an estimate of T0 for all materials of interest it is necessary to develop an alternative means of estimating T0.
A project has been undertaken to develop a combined model approach to estimating T0 from data that may include limited elastic-plastic fracture toughness KJc, Charpy, tensile, ductile initiation toughness, arrest toughness, and/or nil-ductility temperature data. Using correlations between these properties and T0 a methodology for combining estimates of T0 from several sources of data was developed. T0 estimates obtained independently from the Master Curve model, the Simple T28J correlation model, and a more complex Charpy correlation model were combined using the Mixture Probability Density Function (PDF) method to provide a single estimate for T0. Using this method, the individual T0 estimates were combined using weighting factors that accounted for sample size and individual model accuracy to optimize the accuracy and precision of the combined T0 estimate. Combining weighted estimates of T0 from several sources of data was found to provide a more refined estimate of T0 than could be obtained from any of the models alone.
Effect of Internal Pressurization on the Creep-Fatigue Performance of Alloy 617 Based on Simplified Model Test Method
Authors: Wang Y. , Jetter B. , Sham T.-L. 
Published: November 2019

Abstract
The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The original SMT concept [1] considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption is critically evaluated on Alloy 617 using internal pressurized cylindrical SMT specimens at 950 °C. The impact of combined internal pressurization and displacement-controlled creep-fatigue loading on the SMT cycle life is demonstrated at different strain ranges. The effect of primary load on the SMT design method is discussed.
Welding Simulation Integrated With Machine Learning to Train a Meta-Model for Fast Exploration of Various Weld Sequence Scenarios
Authors: Asadi Mahyar , Mohseni Mohammad , Tanbakuei Kashani Majid , Fernandez Michael , Smith Mathew 
Published: November 2019

Abstract
Distortion is a common problem in welded structures, and therefore welding standards require a mitigation plan to be in place before welding. When dealing with multiple welds, an optimal intermittent weld sequence can effectively minimize the distortion by counter-balancing the transient distortion during welding. However, the process of finding an effective weld sequence is a challenging task given a large number of possible combinations, i.e. several thousand for a few welds. As an acceptable approach, welding simulation tools allow engineers to optimize a welding sequence without the need for multiple physical samples. Despite efficient simulation tools and powerful supercomputers, yet simulation tools have been limited by CPU time and therefore not mature for practical designs. To this end, we constructed and integrated an inexpensive low-fidelity machine learning (ML) algorithm with the expensive high-fidelity simulation. This ML model was then trained to increase the fidelity by a wisely chosen train set of simulation to construct a meta-model for active exploration of various weld sequence scenarios. As opposed to existing ML algorithms that require an extensive data set to train, our algorithm picks relatively small training set to construct a meta-model. We present an example of our algorithm implemented in a real welded structure project.
Reliability Prediction of 304 Stainless Steel Using Sine-Hyperbolic Creep-Damage Model With Monte Carlo Simulation Method
Authors: Hossain Md Abir , Stewart Calvin Maurice 
Published: November 2019

Abstract
Typically continuum damage mechanics (CDM) based constitutive models are applied deterministically where the uncertainty of experiments is not considered. This is also true for the Sine-hyperbolic (Sinh) CDM-based constitutive model where the model is calibrated to represent 50% reliability of creep data. There is a need to implement Sinh in a more stochastic manner. The objectives of this study is to incorporate the probabilistic feature in the Sinh creep damage model to reliably predict the minimum-creep-strain-rate, creep-rupture and creep deformation. This will be achieved using Monte-Carlo methods. Creep deformation data for 304 Stainless Steel is collected from literature consisting of tests conducted at 300 and 320 MPa at 600°C with five replicates. The replicate tests exhibited substantial scatter in the minimum-creep-strain-rate, stress-rupture, and overall creep deformation. Subsequently, upon calibration using the Sinh model, the material constants among the replicates varied. The trends of uncertainty carried by each material constant are studied. The interdependence of the material constants is evaluated to determine if the uncertainty carried by each material constant can be regressed using a co-dependence function. The Monte Carlo method was applied to determine the extent that the creep deformation curve varies taking into consideration the variability of the material constants. Monte Carlo simulations show that the predicted creep deformation persists within the bounds of the experimental data. A large number of Monte Carlo simulations using the Sinh model enabled the creation of credible reliability bands for the minimum-creep-strain-rate, stress-rupture, and creep deformation of 304 Stainless Steel. In future work, this statistical method will be applied to the variability of service conditions, pre-existing defects, and material constants to quantitatively establish the reliability of the Sinh model in simulating component-level creep deformation to rupture.