bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of a Finite Element Toolbox for Studying Flaw Interaction
Authors: Coules Harry E. 
Published: October 2020

Abstract
Structural integrity assessment often requires the interaction of multiple closely-spaced cracks or flaws in a structure to be considered. Although many procedures for structural integrity assessment include rules for determining the significance of flaw interaction, and for re-characterising interacting flaws, these rules can be difficult to validate in a fracture mechanics framework. int_defects is an open-source MATLAB toolbox which uses the Abaqus finite element suite to perform large-scale parametric studies in cracked-body analysis. It is designed to allow developers of assessment codes to check the accuracy of simplified interaction criteria under a wide range of conditions, e.g. for different interacting flaw geometries, material models and loading cases. int_defects can help analysts perform parametric studies to determine linear elastic crack tip stress field parameters, elastic-plastic parameters and plastic limit loads for simple three-dimensional cracked bodies relevant to assessment codes. This article focusses on the validation of int_defects using existing fracture mechanics results.
Through a set of validation examples, int_defects is shown to produce accurate results for a very wide range of cases in both linear and non-linear cracked-body analysis. Nevertheless, it is emphasised that users of this software should be conscious of the inherent limitations of LEFM and EPFM theory when applied to real fracture processes, and effects such as constraint loss should be considered when formulating interaction criteria.
Failure Limit State Investigation of Misaligned Welded Plates by Using a Damage Model-Based Upon Triaxiality and Lode Parameters
Authors: Santos Iago S. , Sarzosa Diego F. B. 
Published: October 2020

Abstract
This paper presents a numerical study using the finite element method to assess the structural integrity of welded plates. Different levels of weld misalignment were introduced on the FEM models to investigate the influence of this welding imperfection parameter on the limit state of the structure. The models were loaded under displacement-controlled condition to introduce traction and torsion loads seeking to understand the effects of combined loads on the strain capacity of the misaligned welded structure. Surface elliptical cracks having different crack-size ratios were modeled to study the crack growth behavior by taking into account the misalignment of the weld and combined loads. The damage model is based on a failure surface and post-initiation behavior to model the ductile crack initiation and propagation steps, respectively. The models provide useful information to track the evolution of damage on the hot spot point of the welded structure. The model used is dependent on stress triaxiality and a Lode-based parameter and the damage level is driven by the plastic strain. The evolution of stress triaxiality and Lode parameter with loading are presented, and the influence of misalignment on them are shown. An exponential softening law was adopted to predict post-initiation failure behavior. The calibration steps of the parameters required for damage model application are shown for a A285 pressure vessel steel. Overall, the numerical models reveal the deleterious effects of weld misalignment and combined torsional and tensile loads on the strain capacity of the weld.
Practical Estimation of Retorque Requirements
Authors: Bausman Anita 
Published: October 2020

Abstract
The initial assembly of a bolted flanged joint (BFJ) commonly includes several ramped torque steps using various bolt torque patterns, final circular pass(es) at 100% of target torque, and then the choice of whether and when to come back and retorque the just-assembled joint. The value of retorquing a newly assembled bolted flanged joint varies significantly by which gasket material and type is used in the joint. The additional maintenance costs of labor, tool rental, scaffolding, crane usage, etc. to perform a retorque on a joint can be significant, but the larger cost is generally the additional process downtime.
Gaskets based on sheet materials are often retorqued. Conventional practice indicates that BFJs with gaskets made from flexible graphite or fiber sheets typically do not benefit from retorques, or at least do not benefit enough to offset the additional costs. Conversely, industry experience with many polytetrafluoroethylene (PTFE) based gaskets indicates these joints benefit significantly from retorquing a BFJ after initial assembly.
This paper explores some practical methods to estimate potential retorque benefit as a function of retained gasket stress without the retorque at temperatures normally “in range” for the gasket material being considered. That is, at temperatures that would not cause thermal damage to the gasket material. For flexible graphite and fiber materials known to experience mechanical property degradation with time and/or temperature (“aging”), a typical 5-year life is used. For PTFE gaskets known to relax primarily with temperature and that do not appreciably age, use of the Hot Blowout Thermal Cycling test (HOBTC) can provide a quick evaluation of gasket stress loss as a function of temperature. Retained gasket stress in both cases can then be used to estimate tightness for the gasket material using the Room Temperature Tightness (ROTT) data. If the joint is still at or above required tightness, then retorquing the joint soon after initial assembly is of little benefit. If the gasket has lost enough stress, then a retorque can bring the gasket stress back into range to provide sufficient tightness. Knowing this, the end user can make better choices for both gasket material selection and assembly procedures in order to reduce overall job costs.
Development and Test of Liquefied Gas Leakage Rate Measurement Device for Limited Aperture Release
Authors: Liu Cenfan , Ji Fang , Duan Linlin , Chen Sheng , Sun Liang 
Published: October 2020

Abstract
The liquefied gas has been widely used in modern chemical, energy and environment protection industries. To support the integrity management and risk assessment of liquefied gas storage tanks, it is necessary to study the leakage process of liquefied gas with limited holes. There are few researches about the liquefied gas leakage rate from the crack. At present, most measurement methods used to measure leakage rate are flow meter or weighing before and after discharge, which are not suitable for liquefied gas discharge. The discharge of liquefied gas can easily form a two-phase flow in the crack and cannot be measured by the flow meter. However, the method of weighing before and after discharge cannot measure the leakage rate in real time. To realize the leakage rate real-time, online measurement, the new liquefied gas leakage rate measurement device was set up in this study. And the detachable crack leakage modules with different diameters were designed and manufactured. Using R134a refrigerant as leakage experiment medium, the relationship between crack morphology, size, pressure and leakage rate of liquefied gas was studied on the liquefied gas leakage measurement device. The new device can be used as an experimental test platform for evaluating the consequences of different liquefied gas discharge accidents or optimizing the leakage flow coefficient of the specific leakage situation, so as to better simulate the liquefied gas discharge accidents.
Improving Flange Designs Based on ASME Section VIII Div. 1, Appendix 2
Authors: Cary Chris W. 
Published: October 2020

Abstract
Although improved methods for flange design have been under development for many years, ASME Boiler and Pressure Vessel Code Section VIII, Division 1 Appendix 2 continues to be the basis for the design of most custom pressure vessel flanges. While the method does a reasonably good job of calculating flange stress and rotation from the design loadings, it does not closely constrain some of the design input variables, such as gasket width and geometry, allowing the designer to produce poorly-performing designs. Also, the gasket loading factors (m & y values) have long been recognized as needing improvement. These weaknesses occasionally result in flanges which are difficult to seal, even with very high assembly bolt stress. In response to these weaknesses in the Appendix 2 method, various attempts to improve the method may be employed, and are sometimes required by end-user specifications. This paper provides an assessment of the effectiveness of various improvement techniques by examining the actual effects on flange designs across a range of diameter and design pressure, and makes recommendations for the use of such techniques. The analysis methods in PCC-1 and WRC Bulletin 538 are used as the basis of the evaluation, with a focus on gasket stress as fundamental to sealing.
Study on the Predictive Evaluation Method for Liquid Surface Shape and Flow Velocity in Nonlinear Sloshing Based on Simplified Equations
Authors: Ikesue Shunichi , Morita Hideyuki , Takata Tomoshige , Madokoro Hideki , Ishii Hidekazu , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko 
Published: October 2020

Abstract
When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the liquid surface inside the tank called sloshing may occur. If large-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the tank. Also, there is a possibility that the internal components in the tank may be damaged due to the fluid force generated by the flow of the sloshing.
In order to evaluate the load acting on the tank roof, it is considered that the liquid surface shape and the liquid surface velocity are required as input parameters. In order to evaluate the load acting on the internal component in the tank, the flow velocity generated by sloshing is required as an input parameter. If the sloshing wave height is small, these values can be calculated based on the linear potential theory. However, when the sloshing wave height increases, the sloshing becomes nonlinear, and the difference between the nonlinear sloshing behavior and the linear sloshing behavior. Therefore, the method of evaluating nonlinear sloshing behavior is necessary to evaluate the design load of tank under the large sloshing wave height condition.
In this paper, new methods of evaluating nonlinear sloshing behavior are proposed for the first-order sloshing mode of a cylindrical tank, which can evaluate the maximum nonlinear sloshing wave height, the nonlinear liquid surface shape, the liquid surface velocity, and the flow velocity. Proposed methods, which consist of simplified equations, are expected to be applied to a new sloshing load evaluation method in primary design.1
High Frequency Fatigue and Using Frequency Domain Techniques
Authors: Francis Benjamin , Mair David 
Published: October 2020

Abstract
In recent years API 579 has provided the analyst with a detailed outline of the Wang-Brown algorithm (WBCC) for the cycle counting. The WBCC algorithm has become the generally accepted core of cycle counting implementations whenever multi-axial non-proportional fatigue stress histories are encountered. However, for vibration based fatigue, in the absence of any time history at all; it is common in industry to assess fatigue using frequency domain techniques. This paper presents special considerations for determination of the spectral stress fatigue in the spirit of API 579.
In the frequency domain the stress cycles are counted a priori as a set of complex vectors. These complex stress vectors may represent the full stress tensor of a reduced set in an appropriate sub-space. The phase relationship between the vectors represents the time delay between the stress components of the stress field. This paper presents some of the actions that are necessary in order to accurately capture the phase relationships.
It is often the case that the physics of the driving loads are either unknown or too complex to practically model. This is the case for complex fluid and particle interactions with vessel shells, piping or other wetted surfaces. This paper presents some tools and techniques that can be applied in order to characterize the loading spectrum in a manner which is specifically designed to capture the important fatigue characteristics.
Any fatigue estimation technique must convert the stress vector set into a singularly dimensioned scalar metric that represents the stress amplitude of a cycle. However, the maximum stress amplitude from the cycle is not immediately accessible from the complex stress vectors. While a number of papers present techniques that are intended to calculate the maximum stress amplitude in the case where the stress metric is the equivalent stress this paper provides a slightly more general relation for the phase of the maximum amplitude.
Finally the analyst must compare their calculated fatigue stress amplitudes to the API 579 fatigue curves. Closed form expressions for mono-linear spectral fatigue have been extensively investigated in the literature but more complex fatigue curves do not have such simple solutions. To this end this paper investigates the smooth bar carbon steel fatigue curves of ASME VIII-2.
ATLAS+ European Project: Prediction of Large Ductile Tearing in Austenitic Piping Using Local Approach
Authors: Blouin Arnaud , Marie Stéphane 
Published: October 2020

Abstract
In the frame of the European ATLAS+ project it was decided to evaluate if a continuum damage model can simulate a four-points bending test on an austenitic pipe (316L type) with an aged welded joint. In this paper, the theoretical background is presented. Then, based on finite elements analyses, the GTN model damage parameters are defined by simulating laboratory tests on Notched Tensile specimens and Compact Tension specimen. Finally, the four points bending test simulation is also presented.
Modified 9Cr Steel: Coke Resistant Tubes/Pipes Developed by Vallourec for Refinery Furnaces
Authors: Pirón Javier , Hamart Olivier 
Published: October 2020

Abstract
A new modified 9 wt% Cr steel has been developed in order to improve the resistance against coke deposition on the internal surface of refinery tube furnaces, in comparison to widely used grades, such as Grade 5 (5 wt% Cr) or Grade 9 (9 wt% Cr). The new grade has an improved composition, based on Cr and Si and further additions of Cu and Ni. This optimal chemical analysis has been specified after extensive laboratory testing on different laboratory and industrial heats. Thermogravimetric analyses have been performed to benchmark various materials (ferritic and austenitic grades) in terms of coking rate. Specimens of these alloys have been exposed to this coking atmosphere in a wide temperature range. The new modified 9Cr steel exhibits an almost 10 times lower coking rates than typical Grade 9 steel. The new 9Cr steel shows allowable stress levels up to 90% higher than Grade 9 at temperatures below 500°C (time independent regime) and up to 7% higher stress levels at temperatures above 500°C (creep regime). The industrial feasibility of production of elbows has been successfully implemented and a welding solution using a commercially available filler material has been established.
Determination of Transition From Thin Shell to Thick Shell Theory for Torispherical Heads With Head Dish Radius to Thickness Ratios Under 20
Authors: Millet Barry , Ebrahimi Kaveh 
Published: October 2020

Abstract
This paper will clarify the point of transition where the behavior of the dish of a torispherical head goes from thin wall theory (collapse failure and membrane) to thick wall (burst failure) as the head dish radius to thickness ratios (L/t) gets smaller. There are several stated ratio limits for this transition. Three separate Welding Research Bulletins WRC 364 New Design Curves for Torispherical Heads[1], WRC 444 Buckling Criteria for Torispherical Heads Under Internal Pressure [3] and, WRC 501 Design of Torispherical and Ellipsoidal Heads Subjected to Internal Pressure[4] each provide a different definition of the transition point, that being 16.67, 15 and 20 respectively. This paper will review the actual test performed for L/t ratios from 20 down to 15 (which is the lowest ratio test run) and provide the results of a numerical desktop study in lieu of actual testing. Linear elastic, elastic perfectly plastic limit load and elastic plastic limit load finite element analysis will be parametrically run across many L/t ratios and the knuckle radius will be varied across the runs. The results will be reviewed to check through wall behavior to find the transition point of thin to thick wall behavior. These will also be compared against the existing ASME BVP Section VIII Division 2 [5] formulas.
Investigation Into Residual Stresses in a Small Bore Pipe Weld With Stacked Stop/Start Locations
Authors: Pellereau Ben , Walter Simon , Pembury Paul 
Published: October 2020

Abstract
Small bore austenitic stainless steel pipework is used in a number of nuclear plant systems. Many of these locations are subjected to large thermal shocks and therefore have high fatigue usage factors. Their justification therefore often includes a fatigue crack growth and fracture assessment, for which a key input is the residual stress associated with the welding process, in UK assessments these are typically taken from the R6 compendium.
A common process used for these welds is manual tungsten inert gas welding, due to access difficulties each pass is usually completed in two halves. The stop-start locations for each weld run are sometimes stacked, especially in horizontal pipe runs where each weld operation starts at the bottom of the pipe and progresses upwards. The stack up of stop-start locations is likely to lead to considerable circumferential variation in weld residual stress, potentially resulting in stresses that locally exceed the R6 profiles.
This paper presents results from a series of FE models for a single small bore pipe weld. The simulated weld is a 3-pass manual TIG weld with an EB insert in a 2 inch (50 mm) nominal diameter pipe. Both 2D and 3D models were run. The results of the modelling are then compared with measurements of weld mock-ups of the same weld (both with and without the stop-start stack-up).
The results show that, local to the assumed stop location the predicted stresses do exceed even the R6 level 1 profile (a membrane stress equal to the 1% proof stress of the material). However, the locally enhanced stresses drop off quickly away from the peak location, so for defects of a size that may be a concern for a defect tolerance assessment, the R6 Level 1 and 2 profiles remains appropriate or bounding.
Application of Artificial Neural Network to Multi-Variables Regression for Estimations of J-Integral for Surface Cracked Pipes
Authors: Jang Youn-Young , Huh Nam-Su , Kim Ik-Joong , Kim Cheol-Man , Kim Young-Pyo 
Published: October 2020

Abstract
Crack assessment for pipe components of a nuclear power plant or oil/gas pipeline is one of the essential procedures to ensure safe operation services. To assess cracked pipes, J-integral has been considered as a theoretically robust and useful elastic-plastic fracture parameter, so that the estimations of J-integral for various pipe geometries, material properties and loading conditions are highly needed. For this reason, many engineering predictive solutions for J-estimations based on finite element (FE) analyses have been developed. Generally, many engineering predictive solutions have been suggested as a tabular-form or closed-form. Among them, the closed-form solution is more preferred than a tabular-form solution for its convenience when many lots of interpolation are required to use it. However, the accuracy of the closed-form solution tends to be significantly reduced as the number of design parameters increases. Moreover, since there is no strict rule to define the form of functions as well, the accuracy of the closed-form solution is inevitably dependent on the rule of thumb. Therefore, it is highly required to suggest a new approach for J-estimation of cracked pipes with various geometries, material properties and loading conditions.
In this paper, we propose an efficient approach based on a machine learning technique to estimate J-integral for surface cracked pipes with various geometric sizes and material properties under axial displacement loading condition. Firstly, parametric FE analysis studies were systematically performed to produce the coefficients representing the engineering J-estimation for the corresponding cracked pipe. Secondly, artificial neural network (ANN) models based on deep multilayer perceptron technique were trained based on FE results. The five input neurons (pipe geometries and material properties) and the two output neurons (the coefficients representing the engineering J-estimation) were considered. Lastly, the accuracy of the trained ANN model was studied by comparing to that of the closed-form solution from multi-variable regressions.
Benchmark Study of CFD-Based Prediction Accuracy of the Models Evaluating Particle and Droplet Induced Erosion for Engineering Applications
Authors: Qian Shaoxiang , Kanamaru Shinichiro 
Published: October 2020

Abstract
The particles (including solid particles and liquid droplets) existing in multi-phase flow in process plants can cause erosion due to flow turbulence, and thus, result in pipe wall thinning. Hence, it is important to evaluate erosion rate for determining design margin and finding counter-measures. Many models have been proposed for predicting particles induced erosion rate, but there is significant disparity in their prediction accuracy. The present study aims to verify prediction accuracy of some major erosion models utilizing the published experimental data, for applications to engineering. CFD benchmark study was conducted for three different piping geometries to investigate prediction accuracy of solid particle induced erosion rates for five major erosion models. CFD results show that the erosion rates predicted by Grant & Tabakoff model are closest to the experimental results with acceptable prediction accuracy for applications to engineering. Also, CFD benchmark study was also performed to verify the prediction accuracy of droplet induced erosion rates for three erosion models, utilizing the published experimental data. CFD results show that the erosion rates predicted by Haugen model for all the water impingement velocities are closest to the experimental results with acceptable prediction accuracy for applications to engineering.
Application of SA-533 Class 2 Vessels in Floating LNG Plants
Authors: Sakata Mikihiro , Sasaki Shunsuke , Mantovani Pietro , Ngomo Valéry 
Published: October 2020

Abstract
ASME SA-533 Class 2 steel provides 30% higher tensile strength and 90% higher yield strength compared to ASME SA-516 Grade 70 steel, which is commonly used for onshore pressure vessels. Owing to the higher allowable stress, the use of the SA-533 Class 2 steel leads to significant reduction of the vessel weight by permitting thinner vessel walls, which in turn, leads to lighter supporting steel structures. This is quite beneficial for offshore applications, since the space and weight capacity are limited on an offshore platform or the structure modules on a ship. Further, when vessels are intended for use in gas processing plants, depending on the process design, not only higher tensile strength but also greater impact toughness at low temperatures [e.g., minus 29°C (minus 20°F) or lower] are required. This consequently imposes special considerations on the vessel fabrication. Especially, careful attention is needed in establishing welding and heat treatment procedures to achieve both properties in the weldment. This paper presents the use of ASME SA-533 Type C Class 2 steel for a pressure vessel intended for use in the gas inlet facility of a floating LNG plant.