bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluid-Structure Interaction Approach for Numerical Investigation of a Flexible Hydrofoil Deformations in Turbulent Fluid Flow
Authors: Benaouicha M. , Guillou S. , Santa Cruz A. , Trigui H. 
Published: October 2018

The study deals with a 3D Fluid-Structure Interaction (FSI) numerical model of a rectangular cantilevered flexible hydrofoil subjected to a turbulent fluid flow regime. The structural response and dynamic deformations are studied by analyzing the oscillations frequencies and amplitudes, under a hydrodynamics loads. The obtained numerical results are confronted with experimental ones, for validation. The numerical model is performed in the same geometric, physical and material conditions as the experimental set-up carried out in a hydrodynamic tunnel.
A polyacetal (POM) flexible hydrofoil NACA0015 with an angle of attack of 8° is considered to be immersed in a fluid flow at a Reynold number of 3 × 105. The structure is initially at rest and then moved by the action of the fluid flow. The numerical model is based on a strong coupling procedure for solving the Fluid-Structure Interaction problem. The Arbitrary Lagrangian-Eulerian (ALE) formulation of the Navier-Stokes equations is used and an anisotropic diffusion equation is solved to compute the fluid mesh velocity and position at each time step. The finite volume method is used for the numerical resolution of the fluid dynamics equations. The structure deformations are described by the linear elasticity equation which is solved by the finite elements method. The Fluid-Structure coupled problem is solved by using the partitioned FSI implicit algorithm.
A good agreement between numerical and experimental results for the hydrodynamics coefficients and hydrofoil deformations, maximum deflection and frequencies is obtained. The added mass and damping are analyzed and then the FSI effect on the dynamic deformations of the structure is highlighted.
RSE-M - ASME XI - API 579: Comparison of Failure Assessment Diagrams (FAD)
Authors: Faidy Claude 
Published: October 2018

After a short review of the 3 Codes in term of flaw evaluation, this paper will consider the Failure Assessment Diagrams (FAD) proposed in each of them.
The cracked components are evaluated by a dedicated diagram for margin evaluation of ductile tearing resistance of the components: the elastic stress intensity factor of the crack normalized by the toughness of the material on one axis and the applied stresses normalized by a Reference Stress in the other axis.
The 2017 Edition of RSE-M Appendix 5.4 and 5.6, the 2017 Edition of ASME XI Appendix H and the 2016 Edition of API 579 Part 9 will be used in this first comparison.
A Compendium of Mechanical Testing of Austenitic Stainless Steels in Hydrogen
Authors: Lam Poh-Sang , Duncan Andrew J. , Morgan Michael J. , Sindelar Robert L. , Adams Thad M. 
Published: October 2018

Archival materials test data on austenitic stainless steels for service in high pressure hydrogen gas has been reviewed. The bulk of the data were from tests conducted prior to 1983 at the Savannah River Laboratory, the predecessor to the Savannah River National Laboratory, for pressures up to 69 MPa (10,000 psi) and at temperatures within the range from 78 to 400 K (−195 to 127 °C). The data showed several prominent effects and correlations with test conditions:
• There was a significant reduction in tensile ductility as measured by reduction of area or by the total elongation with hydrogen. Hydrogen effects were observed when the specimens were tested in the hydrogen environment, or the specimens were precharged in high pressure hydrogen and tested in air or helium.
• There was a significant reduction in fracture toughness with hydrogen (and sometimes in tearing modulus which is proportional to the slope of the crack resistance curve).
• The effects of hydrogen on ductility can be correlated to the nickel content of the iron-chromium-nickel steels. The optimal nickel content to retain the high tensile ductility in these alloys was 10 to at least 20 wt. %.
• The effects of hydrogen can be correlated to the grain size. Large grain sizes exhibited a greater loss of ductility compared to small grain sizes.
The Savannah River Laboratory test data, especially those not readily available in the open literature, along with the sources of the data, are documented in this paper.
Experimental Assessment of the Dynamic Behavior of Polyolefin Thermoplastic Hot Melt Adhesive
Authors: Ciardiello Raffaele , Tridello Andrea , Goglio Luca , Belingardi Giovanni 
Published: October 2018

In the last decades, the use of adhesives has rapidly increased in many industrial fields. Adhesive joints are often preferred to traditional fasteners due to the many advantages that they offer. For instance, adhesive joints show a better stress distribution compared to the traditional fasteners and high mechanical properties under different loading conditions. Furthermore, they are usually preferred for joining components made of different materials.
A wide variety of adhesives is currently available: thermoset adhesives are generally employed for structural joints but recently there has been a significant increment in the use of thermoplastic adhesives, in particular of the hot-melt adhesives (HMAs). HMAs permit to bond a large number of materials, including metal and plastics (e.g., polypropylene, PP), which can be hardly bonded with traditional adhesives. Furthermore, HMAs are characterized by a short open time and, therefore, permit for a quick and easy assembly process since they can be easily spread on the adherend surfaces by means of a hot-melt gun and they offer the opportunity of an ease disassembling process for repair and recycle. For all these reasons, HMAs are employed in many industrial applications and are currently used also for bonding polypropylene and polyolefin piping systems.
In the present paper, the dynamic response of single lap joints (SLJ) obtained by bonding together with a polyolefin HMA two polypropylene substrates was experimentally assessed. Quasi-static tests and dynamic tests were carried out to investigate the strain rate effect: dynamic tests were carried out with a modified instrumented impact pendulum. Relevant changes in the joint performance have been put in evidence. Failure modes were finally analysed and compared. A change in the failure mode is experimentally found: in quasi-static tests SLJ failed due to a cohesive failure of the adhesive, whereas in dynamic tests the SLJ failed due to an interfacial failure, with a low energy absorption.
A Nonlinear Least Squares Logistic Fit Approach to Quantifying Uncertainty in Fatigue Stress-Life Models and an Application to Plain Concrete
Authors: Fong Jeffrey T. , Heckert N. Alan , Filliben James J. , Ziehl Paul H. 
Published: October 2018

A large number of fatigue life models for engineering materials such as concrete and steel are simply a linear or nonlinear relationship between the cyclic stress amplitude, σa, and the log of the number of cycles to failure, Nf. In the linear case, the relationship is a power-law relation between σa and Nf, with two constants determined by a linear least squares fit algorithm. The disadvantage of this simple linear fit of fatigue test data is that it fails to predict the existence of an endurance limit, which is defined as the cyclic stress amplitude at which the number of cycles is infinity. In this paper, we introduce a nonlinear least square fit based on a 4-parameter logistic function, where the curve of the y vs. x plot will have two horizontal asymptotes, namely, y0, at the left infinity, and y1, at the right infinity with y1 < y0 to simulate a fatigue model with a decreasing y for an increasing x. In addition, we need a third parameter, k, to denote the slope of the curve as it traverses from the left horizontal asymptote to the lower right horizontal asymptote, and a fourth parameter, x0, to denote the center of the curve where it crosses a horizontal line half-way between y0 and y1. In this paper, the 4-parameter logistic function is simplified to a 3-parameter function as we apply it to model a fatigue sress-life relationship, because in a stress-log (life) plot, the left upper horizontal asymptote, y0, can be assumed as a constant equal to the static ultimate strength of the material, U0. This simplification reduces the logistic function to the following form:
y = U0 − (U0 − y1) / (1 + exp(−k (x − x0)),
where y = σa, and x = log(Nf). The fit algorithm allows us to quantify the uncertainty of the model and the estimation of an endurance limit, which is the parameter, y1. An application of this nonlinear modeling technique is applied to fatigue data of plain concrete in the literature with excellent results. Significance and limitations of this new fit algorithm to the interpretation of fatigue stress-life data are presented and discussed.
Temporary Acceptance of Leaking Brazed Joints
Authors: O’Sullivan J. E. (Jim) , Hacker Kevin J. 
Published: October 2018

Minor leakage in brazed joints is occasionally detected in nuclear power plant Class 3 piping systems such as emergency service water cooling lines for equipment room and containment area coolers. Detection of such leakage often causes the system to be taken out of service for performance of repair/replacement activities to restore the piping to its original condition. This can lead to plant shutdowns or outage delays which are very costly, and often at increased safety risk, to accomplish the repairs. To avoid such costs and increased risk, a method is needed to establish structural adequacy of leaking brazed joints so that leakage can be controlled and monitored until the next planned opportunity for replacement of the brazed joint.
During industry testing performed in the late 1950s, over 1200 lap joint tensile test specimens were brazed in a round-robin series of tests performed by 10 laboratories. The results of these tests showed that very little overlap is needed in a brazed lap joint to obtain full strength in the joint. In fact, braze metal shear strength exceeded piping collapse strength in all cases when the braze overlap was only 2.3 times the thickness of the members being brazed. Similar testing was performed by the U.S. Navy, and resulted in development of a NAVSEA document that established a conservative percentage of bond required for MIL F-1183 brazed fittings to prevent structural failure of a leaking brazed joint.
This paper discusses an ASME Section XI Code Case that has been developed to incorporate the results of this testing into a methodology for temporary acceptance of leakage of brazed lap joints in copper, copper-nickel, and nickel-copper ASME Code Class 3 nuclear piping systems.
Application of an a priori Jacobian-Based Error Estimation Metric to the Accuracy Assessment of 3D Finite Element Simulations
Authors: Rainsberger Robert B. , Fong Jeffrey T. , Marcal Pedro V. 
Published: October 2018

The determinant of the Jacobian matrix is frequently used in the Finite Element Method as a measure of mesh quality.
A new metric is defined, called the Standard Error, based on the distribution of the determinants of the Jacobian matrices of all elements of a finite element mesh. Where the Jacobian norm can be used to compare the quality of one element to another of the same type, the Standard Error compares the mesh quality of different versions of a finite element model where each version uses a different element type.
To motivate this new Standard Error, we investigate the geometric meaning of the Jacobian norm on 3D Finite Elements. This mesh quality metric is applied to 8, 20, and 27 node hexahedra, 6 and 15 node prisms, 4 and 10 node tetrahedra, 5 and 13 node pyramid, and 3, 4, 6, 8, and 9 node shell elements. The shape functions for these 14 element types, or more precisely their first partial derivatives, are used to construct the Jacobian Matrix. The matrix is normalized to compensate for size. The determinant of the Jacobian is calculated at Gaussian points within each element. Statistics are gathered to form the Standard Error of the mesh.
To illustrate the applicability of this a priori metric, we present two simple example problems having exact answers, and two industry-type problems, a pipe elbow with a crack and a magnetic resonance imaging (MRI) birdcage RF coil resonance, both having no analytical solution.
Significance and limitations of using this a priori metric to assess the accuracy of finite element simulations of different mesh designs are presented and discussed.
Further Validation of the Strain-Life Weighted (SNW) Fen Method for Plant Realistic Strain and Temperature Waveforms
Authors: Currie Chris , Morley Andrew , Leary Daniel , Platts Norman , Twite Marius , Wright Keith 
Published: October 2018

Environmentally assisted fatigue of nuclear plant materials in the Pressurised Water Reactor (PWR) coolant environment is a phenomenon that has been extensively studied over the past 30 years. Methods for accounting for the PWR environment in an ASME Section III fatigue assessment are presented in NUREG/CR-6909. The deleterious effect of environment is described through a Fen factor dependent upon strain rate, temperature and the dissolved oxygen content of the water. The formulae which describe the Fen are based upon correlations observed in test data, predominantly from tests conducted with constant temperature and strain rate (triangular or sawtooth loading). Actual loading histories encountered during service are far more complex, with both strain rate and temperature, and therefore Fen, varying through the cycle. NUREG/CR-6909 Draft Rev 1 recommends the Modified Rate Approach (MRA) to account for this type of loading.
There is a substantial and growing body of data for conditions in which the strain rate and/or temperature change within the load cycle, for which MRA does not generally perform well in describing the deleterious effect of environment in these complex waveform conditions. In particular, MRA does not predict the observed difference in life when the temperature is varied in-phase or out-of-phase within the strain waveform, or when the slow portion of the strain rate is moved from the top to the bottom of the waveform.
An alternative approach called the Strain-Life Weighted (SNW) Fen method was presented in PVP2017-66030 and additional validation testing was proposed.
This paper develops the SNW method further into a general approach for all stainless steels and presents additional new validation data, including a range of isothermal and non-isothermal plant realistic waveforms and a more extensive review of open literature data.
It is concluded that the SNW method offers a significant improvement in fatigue life prediction capability for plant realistic complex waveforms compared to MRA and provides residuals similar to that of standard waveform data. It is thus considered to be suitably validated to propose a code case for use in ASME Section III fatigue assessments.
Thermal Fatigue Evaluation Based on the Methods for Structural Stress Determination According to EN 13445-3 Annex NA: Comparison With Other Codes
Authors: Trieglaff Ralf , Beckert Martin , Rudolph Jürgen , Friers Daniel 
Published: October 2018

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18) of unwelded and welded components. Clause 18 “Detailed Assessment of Fatigue Life” is under principal revision within the framework of the European working group “CEN/TC 54/WG 53 – Design methods” in order to reach a significant increase in user-friendliness and a clear guideline for the application.
This paper is focused on the new recommendations for the thermal fatigue evaluation given in the new informative annex NA “Instructions for structural stress oriented finite element analyses using brick and shell elements”. In this annex NA different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses.
This paper will give a short overview of the proposed approaches of structural stress determination in the new draft annex NA of the revised EN 13445-3 with special recommendations for thermal fatigue evaluation application. This constitutes an extension of the usual and established application of the structural stress approach for welds subjected to mechanical loading conditions. It will present the current state of the approaches based on the results of fatigue analyses according to EN 13445-3 Clause 18 for two different application examples. For validation purposes, these different approaches are compared with the results of Clause 17 of the EN 13445 and other pressure vessel design codes.
The Role of Uncertainty in Machine Learning As an Element of Control for Material Systems and Structures
Authors: Elenchezhian Muthu Ram Prabhu , Raihan Md Rassel , Reifsnider Kenneth 
Published: October 2018

Recurrent neural networks (RNN) have been used to interpret data in situations wherein our knowledge of the active physics is incomplete. The currency of these methods is the data that are generated by a physical system. Unfortunately, if we are uncertain about the physics of the system, we also do not know the level of uncertainty in the data that we use to represent it.
Typically, data provided to an RNN is provided by measurements of system state information, e.g., data that define speed, position, accelerations, configurations of system elements (like the flaps and elevators on an airplane) etc. But recently, data are being collected that indicate the state of the materials themselves that are used to construct the system. Material state may include the defect state of the materials such as the crack density and patterns in composite material in structural elements (obtained from health monitoring data).
In this paper, we address the question of teaching a control system (e.g., for testing equipment, aircraft control systems, health monitoring systems, etc.) to recognize composite material degradation during service and to adjust applied loads and fields as part of a control scheme to avoid failure of the material during service.
Topics will include defining a proper cost function for the above objectives, formulation of a ‘failure hypothesis’ as a regression function, and the quantification of uncertainty when the physics of the situation is not completely defined. Examples of machine learning techniques for a uniaxial fatigue loading of composite coupons with a circular hole are presented. Example models are random forest regression algorithms and artificial neural networks for linear regression.
Fatigue Crack Growth for Ferritic Steel Under Negative Stress Ratio
Authors: Yamaguchi Yoshihito , Hasegawa Kunio , Li Yinsheng 
Published: October 2018

Crack closure during fatigue crack growth is an important phenomenon for predicting fatigue crack growth amount. Many experimental data show that fatigue cracks close at not only negative loads but also positive loads during constant amplitude loading cycles, depending on applied stress levels.
The Appendix A-4300 in the ASME Code Section XI provides two equations of fatigue crack growth rates expressed by stress intensity factor range for ferritic steels under negative stress ratio. The boundary of two fatigue crack growth rates is classified by the magnitude of applied stress intensity factor range with the consideration of crack closure.
The objective of this paper is to investigate the influence of the magnitude of the stress intensity factor range on crack closure. Fatigue tests have been performed on ferritic steel specimens in air environment at room and high temperatures. Crack closures were obtained as a parameter of stress ratio. It was found that crack closure occurs at a smaller applied stress intensity factor range than the definition given by the Appendix A-4300.
Evaluation of Fracture Toughness CTOD Testing and its Standard Test Methods for SENB Specimens
Authors: Zhu Xian-Kui , McGaughy Tom 
Published: October 2018

Crack-tip opening displacement (CTOD) is an important fracture mechanics parameter. Due to different definitions, existing CTOD test methods may determine different CTOD toughness for stationary and growing cracks even for a standard specimen, such as single edge notched bend (SENB) specimen. In the USA, ASTM 1820 uses the J-integral conversion method to determine CTOD, whereas in the UK, BS 7448 adopts the plastic hinge model to determine CTOD. In contrast, ISO 12135 uses the plastic hinge model to determine the initiation CTOD, but the J-conversion method to determine a CTOD-R curve. Thus, those standards may determine different CTOD values for the same material, leading to a long-time dispute. Recently, a double clip gage (DCG) method was used in the oil and gas industry to measure CTOD. As such, there are three typical CTOD test methods: plastic hinge model, J-conversion method, and DCG method.
To better understand those CTOD test methods for SENB specimens, the present paper first gives a brief review of CTOD standard test methods. This includes the CTOD definitions, plastic hinge model, J-conversion method, modified plastic hinge model, and DCG method, BS 7448, ASTM E1820, and ISO 12135. Those CTOD test methods are then evaluated using available test data for various ductile steels in literature. The experimental results of CTOD at fracture initiation and crack tearing are compared, and the differences are discussed.
Pre-Strain Effects on Mixed-Mode Fatigue Crack Propagation Behaviour of the P355NL1 Pressure Vessels Steel
Authors: Ferreira João , A. F. O. Correia José , Lesiuk Grzegorz , Blasón González Sergio , R. Gonzalez Maria Cristina , de Jesus Abílio M. P. , Fernández-Canteli Alfonso 
Published: October 2018

Pressure vessels and piping are commonly subjected to plastic deformation during manufacturing or installation. This pre-deformation history, usually called pre-strain, may have a significant influence on the resistance against fatigue crack growth of the material. Several studies have been performed to investigate the pre-strain effects on the pure mode I fatigue crack propagation, but less on mixed-mode (I+II) fatigue crack propagation conditions.
The present study aims at investigating the effect of tensile plastic pre-strain on fatigue crack growth behavior (da/dN vs. ΔK) of the P355NL1 pressure vessel steel. For that purpose, fatigue crack propagation tests were conducted on specimens with two distinct degrees of pre-strain: 0% and 6%, under mixed mode (I+II) conditions using CTS specimens. Moreover, for comparison purposes, CT specimens were tested under pure mode I conditions for pre-strains of 0% and 3%. Contrary to the majority of previous studies, that applied plastic deformation directly on the machined specimen, in this work the pre-straining operation was carried out prior to the machining of the specimens with the objective to minimize residual stress effects and distortions. Results revealed that, for the P355NL1 steel, the tensile pre-strain increased fatigue crack initiation angle and reduced fatigue crack growth rates in the Paris region for mixed mode conditions. The pre-straining procedure had a clear impact on the Paris law constants, increasing the coefficient and decreasing the exponent. In the low ΔK region, results indicate that pre-strain causes a decrease in ΔKth.