bluuebunny/crossref_metadata_2025 huggingface dataset:
Scatter in Charpy Data Considered As a Transferrable Parameter
Authors: Mohr William , Birchfield Neal
Published: November 2019

Correlations between Charpy energy transition temperatures and other fracture mechanics parameters have been widely used for many years in steel failure analysis and design. The primary value transferred often has been a transition temperature, such as the 27 J transition temperature. This approach does not consider the scatter in the transition temperature or in the overall Charpy data. This work uses a scatter assessment tool developed by Orynyak et al. and applies it to a wider variety of steels and weldments to see whether it can provide a second parameter to be transferred to fracture assessment. Examples include pipeline steel and structural steel, as well as weldments in both the weld metal and heat-affected zone. While Charpy transition scatter is expected to be high in heat-affected zones, examples can be found in base metals with similarly high scatter.
Experimental Investigation of Absorption and Desorption of Gas in Riser During MPD Well Control
Authors: Kunju Mahendra , Nielsen James L. , Chen Yuanhang , Sun Ting
Published: November 2019

In this experimental work, the absorption and desorption of CO2 (Carbon Dioxide) in oil using a laboratory scale low-pressure experimental apparatus was conducted to study the dissolution behavior of gas in the oil. Estimating the concentration and rate of CO2 transfer from/to a non-aqueous column of static fluid is very important to understand the dissolution of natural gas in an oil-based mud within a well. Studying how natural gas dissolves in an oil-based drilling fluid is of great significance due to risks that a gas kick in an oil-based mud poses to equipment and workers’ health and safety once it is in the riser. By understanding the variables associated with this phenomena, better field practices can be developed and implemented to predict the dynamics of an influx and determine the best course of action when handling the influx.

A laboratory scale experimental apparatus was designed and built to inject CO2 at the bottom of a seven-foot static column of VO. The apparatus has five test chambers that can be closed individually to isolate and measure the concentration of dissolved CO2 in oil in each of the sections. As a part of the experiment, the the backpressure applied to the column of oil was varied to observe how pressure affects the mass transfer due to absorption and desorption within the oil column. The amount of gas injected was 1.0 liter per minute of CO2 with a back pressure of the apparatus ranging from 40 to 80 psi.

The results of this study will influence further experiments and testing using larger scale equipment involving the dissolution of natural gas within various oil-based drilling fluids at higher pressures. This study also allows for the development of an initial time-dependent mass transfer model which will also be used for predicting dissolution dynamics of Methane in diesel for future large-scale testing.
Aerodynamic Analysis of a Wind Turbine With Elevated Inflow Turbulence and Wake Using Harmonic Method
Authors: Win Naung Shine , Rahmati Mohammad , Farokhi Hamed
Published: November 2019

This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.
Numerical Simulation of Damaged Ship’s Motion in Beam Waves
Authors: Wang Qing , Chen Xuanshu , Liu Liwei , Wang Xianzhou , Liu MingJing
Published: November 2019

The dangerous situation caused by the breakage of the ship will pose a serious threat to crew and ship safety. If the ship’s liquid cargo or fuel leaks, it will cause serious damage to the marine environment. If damage occurs accompanied by roll and other motions, it may cause more dangerous consequences. It is an important issue to study the damaged ship in time-domain. In this paper, the motions of the damaged DTMB 5512 in calm water and regular beam waves are studied numerically. The ship motions are analyzed through CFD methods, which are acknowledged as a reliable approach to simulate and analyze these complex physical phenomena. An in-house CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for solving RANS equations coupled with six degrees of freedom (6DOF) solid body motion equations. RANS equations discretized by finite difference method and solved by PISO algorithm. Level set was used for free surface simulation. The dynamic behavior of model was observed in both intact and damaged condition. The heave, roll and pitch amplitudes of the damaged ship were studied in calm water and beam wave of three wavelengths.
Research of Wind Resistance and Flow Field of Container Ship
Authors: Sun Zhiyuan , Li Ping , Sun Hanbing
Published: November 2019

In order to study the super large container ship characteristics of the wind resistance coefficient and the air flow field in the different angle of attack, wind tunnel test based on the 14000 containers ship is carried out on the state of the design draft. The wind resistance coefficient of superstructure is obtained through test. The CFD (Computational Fluid Dynamics) technology is introduced to simulate the wind resistance and yaw moment of the model. The numerical results are basically in agreement with the experimental data. The results indicates that with the increase of the wind direction angle, the longitudinal wind resistance coefficient curve shows a “sine curve” rule and exists opposite resistance extremums, whereas the lateral wind resistance coefficient curve presents a parabolic change rule. Numerical simulation method is proved has high accuracy for wind resistance prediction of container ship. The size of wind load on the ship is related to the form and size of the wake region.
Fatigue Behavior of Large, Rolled-After Heat-Treatment and Hot-Dip Galvanized HT Bolts
Authors: Unglaub Julian , Thiele Klaus
Published: November 2019

As a subproject in the framework of the DFG Research Training Group “Graduiertenkolleg 2075 - Modelling the constitutive evolution of building materials and structures with respect to aging” (GRK 2075), the fatigue behavior of rolled-after heat-treatment and hot-dipped galvanized HT-bolts is examined. Results of fatigue tests of M48x255 10.9 and M36x235 10.9 HT-bolts from different states of manufacturing processes (rolled-after heat-treatment, rolled-after heat-treatment and hot-dip galvanized) will be presented and discussed. If rolled-after heat-treatment HT-bolts are hot-dip galvanized, the fatigue life is significantly reduced. However, it is beyond the fatigue life of rolled-before heat-treatment HT-bolts and hot-dip galvanized HT-bolts.
Sweeplus®: An Integrated Solution to Pipe Vibration Failures
Authors: Liu Yuqing , Diwakar Philip , El Jaouhari Ismat , Lin Dan
Published: November 2019

This paper discusses our efforts to develop a robust branch fitting that can withstand AIV related to higher sound power levels than a standard contour fitting and accommodate FIV related vibration loads, without compromising project cost and schedule. Numerical simulation results and experimental test data are presented to substantiate our claims that a sweeplus® performs much better than any other contoured branch fittings available in the market with respect to any AIV, AR and FIV related risks. The aerodynamically shaped new fitting can withstand higher sound power level (PWL) limits in AIV, has smoother curvature to reduce flow separation, vortex formation and shedding thereby lowering peak stress concentrations and avoiding AR and FIV related risk, has an extended fatigue life, while adhering to ASME B16.9 Code requirements.
Thermal Analysis of the 9975 Package Used for Long Term Nuclear Material Storage
Authors: Tamburello David , Kesterson Matthew , Hensel Steven
Published: November 2019

The 9975 is a double containment shipping package used to transport plutonium bearing materials for the US Department of Energy. The 9975 is also used for long term storage of plutonium bearing materials at the Savannah River Site. The package utilizes a fiberboard overpack to protect against fire and impact events. The 9975 has been shown to maintain containment during a hypothetical facility accident fire even though the facility fire is hotter and longer than the regulatory transportation fire. Fiberboard aging and degradation has been investigated using both laboratory and field surveillance data. This information is used to evaluate an aged 9975 used for nuclear material storage. Variations in fiberboard thermal properties due to aging were shown to have modest effects on the maximum component temperatures, while the package geometry variations due to aging and degradation have a larger effect on the maximum component temperatures. Specifically, the air gap between the upper fiberboard assembly and the drum lid increases during storage due to the deterioration of the lower fiberboard assembly and slumping of the package containment vessel. A limiting air gap distance has been determined via thermal fire analysis, which may be used to estimate a storage life.
A Novel Methodology to Optimize the Tightening Sequence in Bolted Flange Joints
Authors: Zhu Linbo , Bouzid Abdel-Hakim , Hong Jun
Published: November 2019

Bolted flange joints are the most complex structural components of pressure vessels and piping equipment. Their assembly is a delicate task that determines their successful operation during the service life. During bolt tightening, it is very difficult to achieve uniformity of the target bolt preload due to elastic interaction and criss-cross talk. The risk of leakage failure under service loading is consequently increased because of the scatter of the bolt preload.

In previous work, an analytical model based on the theory of circular beams on linear elastic foundation was proposed to predict the bolt tension change due to elastic interaction. Based on this model, this paper presents a novel methodology for the optimization of the tightening sequence. The target preload and the load to be applied to each bolt in each pass can be calculated to achieve uniform final preload and avoid bolt tension reaching yield under a number of specified tightening passes. The validity of the approach is supported by experimental tests conducted on a NPS 4 class 900 welding neck flange joint and by finite element analysis on this bolted joint using the criss-cross tightening and sequential patterns. This study provides guidelines for bolted flange joints assembly and enhances its safety and reliability by minimizing bolt tension scatter due to elastic interaction.
Fatigue Performance of Welded Joints Under Variable Amplitude Loading Spectra
Authors: Liu Xu , Zhang Yan-Hui , Wang Bin
Published: November 2019

Offshore pipelines are generally subjected to variable amplitude (VA) loading in service due to waves or ocean currents. Welded joints often represent the most critical locations for fatigue cracking. Use of the current fatigue design guidance, for example, BS 7608, to assess fatigue performance of the welded joints in such structure may lead to inaccurate estimates depending on the nature of the VA loading spectrum. Further studies on the effect of VA loading spectra on fatigue performance of welded joints are needed. In this research, both uniaxial and 3-point bending fatigue tests were performed on non-load carrying fillet welded plates under VA loading spectra to investigate the effects of mean stress and the type of VA loading spectra. The influence of plate thickness was also investigated. Test results suggest that the spectrum with a high constant maximum tensile stress (cycling-down) could significantly degrade fatigue performance of welded joints, with the damage parameter D only at around 0.5. The severity of this type of loading spectrum depends on the mean stress level and the plate thickness. An analytical model has been developed to predict fatigue crack propagation (FCP) by considering the interaction of stresses in the loading spectrum. The model considers the impact of the mean stress generated by the preceding load on FCP in the subsequent cycles. FCP predicted by the model shows a good agreement with the experimental data.
Determination of Pipeline Yielding Occurred in Hydrostatic Pressure Testing
Authors: Zhu Xian-Kui
Published: November 2019

The pipeline industry has traditionally utilized the “double stroke” concept to define line pipe yielding for limiting plastic deformation of the pipeline during hydrostatic pressure testing. Practice showed that double stroke may define a nominal yield point lying between the elastic limit and the offset yield strength. Recently, a set of field hydrostatic tests were conducted on an X70 pipeline at Enterprise Products, and the test pressure at double stroke was as high as 129% of SMYS, but the von Mises stress was less than the actual yield strength. The entire pipeline was thought in the elastic conditions at double stroke during the hydrostatic testing.

It is well recognized that the classical Tresca and von Mises yield criteria determines a lower and an upper bound of the limit load at yielding, and a newly proposed Zhu-Leis yield criterion determines a medium result of the two classical solutions. Extensive full-scale tests have confirmed that the Zhu-Leis yield solution is the best prediction of experimental data on average. This paper attempts to use the more accurate Zhu-Leis yield criterion to reanalyze the real-world hydrostatic tests of the X70 pipeline to see if pipe yielding occurs and to determine pipe diameter expansion at double stroke during the hydrostatic pressure testing.
Lower Tail Estimation of Fatigue Life
Authors: Harlow D. Gary
Published: November 2019

Uncertainty in the prediction of lower tail fatigue life behavior is a combination of many causes, some of which are aleatoric and some of which are systemic. The error cannot be entirely eliminated or quantified due to microstructural variability, manufacturing processing, approximate scientific modeling, and experimental inconsistencies. The effect of uncertainty is exacerbated for extreme value estimation for fatigue life distributions because by necessity those events are rare. In addition, typically, there is a sparsity of data in the region of smaller stress levels in stress–life testing where the lives are considerably longer, extending to giga cycles for some applications. Furthermore, there is often over an order of magnitude difference in the fatigue lives in that region of the stress–life graph. Consequently, extreme value estimation is problematic using traditional analyses. Thus, uncertainty must be statistically characterized and appropriately managed. The primary purpose of this paper is to propose an empirically based methodology for estimating the lower tail behavior of fatigue life cumulative distribution functions, given the applied stress. The methodology incorporates available fatigue life data using a statistical transformation to estimate lower tail behavior at much smaller probabilities than can be estimated by traditional approaches. To assess the validity of the proposed methodology confidence bounds will be estimated for the stress–life data. The development of the methodology and its subsequent validation will be illustrated using extensive fatigue life data for 2024–T4 aluminum alloy specimens readily available in the open literature.
A Simplified Thermal Load Evaluation Method for Localized Lug Stresses Beyond Sec. III Appendix-Y
Authors: Matsumiya Tsubasa , Garcia-Rodriguez Daniel , Nebu Akira , Takamura Noriyuki
Published: November 2019

In this work an evaluation method for local thermal stresses on class 1 piping due to U-shaped lugs is presented.

First, a three-dimensional finite element analysis (3D-FEA) is used to perform a thermal transient evaluation, obtaining the time-dependent temperature distribution of a realistic range of pipe-lug systems. These results are then used as an input for both a structural 3D-FEA and the corresponding thermal stress term in Non-Mandatory Appendix Y [1]. It was seen that the formula in Appendix-Y cannot account for the thermal stresses obtained through the detailed FEA evaluation.

A parameter study using a simplified two-dimensional (2D) FEA approach, shows that the localized thermal stresses due to lugs are significantly affected by: (1) pipe-to-lug thickness ratio, (2) distance between adjacent lugs, and (3) lug height. A set of correction coefficients depending on these parameters is therefore proposed.

When applying the proposed correction coefficients to the Appendix Y method, adequately conservative (when compared with 3D FEA results) stresses can be obtained. Since these correction coefficients can be obtained from simple geometric considerations, the proposed method successfully accounts for the complex lug-to-lug interaction while retaining the simplicity of the original Appendix Y approach.
Coke Drum Bottom Head Flange Design Optimisation
Authors: Berry Alex , Brown Warren , Seijas Antonio , Cook Sarah
Published: November 2019

Bottom head flange leaks on coke drums are a too common occurrence for coke drum operators. This paper discusses why these complex joints leak, exploring phenomena such as bolt relaxation, flange rotation, bolt hole cracking, plastic deformation of a flange face due to cyclic thermal transients, as well as investigating the effects of gasket stress variation which can lead to gasket movement and distortion during successive drum cycles. The industry trend is to install automatic bottom un-heading devices (BUDs) to facilitate safe, reliable coke removal and to increase production through shortening un-heading operations. A case study is reviewed which shows how a new drum flange, coupled to a BUD, has been optimized using Finite Element Analysis (FEA). The findings show adequate flange thickness and optimized hub dimensions are required to combat plastic deformation of the flange ring and reduce gasket stress variation. Five designs are modelled, varying the flange thickness, outside diameter and hub geometry. Due to the close proximity of a new side nozzle, the full lower section of the drum has been modelled using quarter and half symmetry FEA with applied temperature distributions from each phase of a typical coke drum cycle; heating, coking and quench. This has allowed for nozzle loadings to be evaluated and the location of the flange weld to be optimized to give the greatest fatigue life. An explanation into why periodic re-tightening is required to keep these joints tight is provided along with recommendations on suitable joint assembly techniques using a combination of bolt load verification and alternative bolting patterns from ASME PCC-1.
Experimental Investigation of the Flow-Induced Vibrations of a Rod Cluster Control Assembly Inside Guides With Enlarged Gaps
Authors: Moussou Pierre , Fichet Vincent , Pastur Luc , Duhamel Constance , Tampango Yannick
Published: November 2019

In order to better understand the mechanisms of fretting wear damage of guide cards in some Pressurized Water Reactor (PWR) Nuclear Power Plant (NPP), an experimental investigation is undertaken at the Magaly facility in Le Creusot. The test rig consists of a complete Rod Cluster with eleven Guide Cards, submitted to axial flow inside a water tunnel. In order to mimic the effect of fretting wear, the four lower guide cards have enlarged gaps, so that the Control Rods are free to oscillate. The test rig is operated at ambient temperature and pressure, and Plexiglas walls can be arranged along its upper part, and a series of camera records the vibrations of the control rods above and below the guide cards. The vertical flow velocity is in the range of a few m/s. Beam-like pinned-pinned modes at about 5 Hz are observed, and oscillations of several mm of the central rods are measured, which come along with impacts at the higher flow velocities. A simple non-linear calculation reveals that the main effect of the impacts between Control Rods and Guide Cards is an increase of the natural frequency of the rods by about 10%. Furthermore, as the vibration spectra collapse remarkably well with the flow velocity, the experiments prove that turbulent forcing is responsible for the large oscillations of the control rods, no other mechanism being involved.
A Local Approach to Assess Temperature Effects on Fracture Toughness Incorporating the Measured Distribution of Microcracks
Authors: Ruggieri Claudio , Jivkov Andrey P.
Published: November 2019

This work describes a local approach to cleavage fracture (LAF) incorporating the statistics of microcracks to characterize the cleavage fracture toughness distribution in structural steels. Fracture toughness testing conducted on standard compact tension C(T) specimens for a 22NiMoCr37 pressure vessel steel provides the cleavage fracture resistance data needed to determine the measured toughness distribution. Metallographic examination of etched surfaces for the tested steel also provides the distribution of carbides, which are assumed as the Griffith fracture-initiating particles, dispersed in the material from which the cleavage fracture toughness distribution is predicted. Overall, the analyses conducted in the present work show that LAFs incorporating the statistics of microcracks are a viable engineering procedure to describe the dependence of fracture toughness on temperature in the DBT region for ferritic steels.
Development of a New Austenitic Stainless Steel (Low-C-18Cr-11Ni-3Cu-Mo-Nb-B-N) With High Sensitization Resistance and High Temperature Strength
Authors: Suzuki Yuhei , Aota Shogo , Dan Etsuo , Ueyama Masaki , Osuki Takahiro , Ono Toshihide , Otaki Nao , Okada Hirokazu
Published: November 2019

Austenitic materials with high sensitization resistance and high temperature strength are required for furnace and reaction tower of desulfurizing plants in the petroleum refinery industry. For these requirements, a new steel (LowC-18Cr-11Ni-3Cu-Mo-Nb-B-N) has been developed. The steel shows no intergranular stress corrosion cracking in polythionic acid environment after aging in the temperature range from 565 to 700 °C for up to 10,000 hours. This excellent PTA-SCC resistance is attributed to the prevention of M23C6 carbide precipitation along grain boundary due to extra low carbon content with high ratio of niobium to carbon. The maximum allowable tensile stress of this steel is estimated to be more than 30% higher than that of ASME SA213 Type347H. This excellent strength is based on the precipitation strengthening effect due to fine precipitates of a copper rich phase which are coherent with the austenite matrix in addition to Z-phase (NbCrN). Moreover, boron addition improves creep strength and creep ductility of the steel.

From these results, it is concluded that the newly developed steel is a promising material not only for refinery processes but also for other elevated temperature usages.
Analysis of Detection Quality for Ultrasonic Guided Wave With L(0,2) and T(0,1) in the Pressure Pipe
Authors: Liu Shu-Hong , Ding Ju , Tang Chen-huai , Song Pan , Tang Deng-chao , Zhang Ye , Yang Yu-qing
Published: November 2019

Torsion mode and longitudinal mode are used primarily in ultrasonic guided wave inspection, especially L (0, 2) mode and T (0, 1) mode. There are some differences between them, like excitation method, mode of particle vibration, inspection ability and impact factor. So, it is very important to select the appropriate mode between L (0,2) and T(0,1). In this paper, the detection ability of two guided wave modes are compared and analyzed with regard to four aspects in the pipe: fluid, liquid level, defects, the angle between defect and wave propagation direction. The experimental results show that L (0,2) mode is more suitable for defect detection in pressure pipe than T (0,1) mode, but L (0,2) mode is more sensitive to fluid in a pipe. This paper provides a basis for selecting the mode of guided waves in ultrasonic detection.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.