bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Cyclic J-Integral of a 3D Semi Elliptical Surface Crack
Authors: Beesley Ross , Chen Haofeng , Hughes Martin 
Published: November 2014

This paper investigates an approach for calculating the cyclic J-Integral (ΔJ) through a new industrial application. A previously proposed method is investigated further with the extension of this technique through a new application of a practical 3D notched component containing a semi-elliptical surface crack.
Current methods of calculating the cyclic J-Integral are identified and their limitations discussed. A modified monotonic loading method is adapted to calculate the cyclic J-integral of this 3D Semi Elliptical Surface Crack under cyclic loading conditions. Both the finite element method (FEM) and the Extended Finite Element Method (XFEM) are discussed as possible methods of calculating the cyclic J-Integral in this investigation. Different loading conditions including uni-axial tension and out of plane shear are applied, and the relationships between the applied loads and the cyclic J-integral are established. In addition, the variations of the cyclic J-integral along the crack front are investigated. This allows the critical load that can be applied before crack propagation occurs to be determined as well as the identification of the critical crack direction once propagation does occur.
These calculations display the applicability of the method to practical examples and illustrate an accurate method of estimating the cyclic J-integral.
A Survey Method to Optimize Bolted Flanged Joint Assembly Torques for ASME B16.5 Flanges
Authors: Bausman Anita R. , Waterland A. Fitzgerald (Jerry) 
Published: November 2014

The three critical components within a bolted, flanged connection are the flanges, gasket, and bolts. Until recently, simplified flange assembly target torque values for ASME B16.5 flanges were routinely determined by considering just one or two of these primary components.
One approach considers only the gasket. Gasket-based target torque values are selected to optimize the gasket’s sealing performance by ensuring compression between minimum and maximum seating stress ranges, or based upon achieving specific levels of gasket Tightness (Tp). Another approach, fastener-based torque values, simply targets a specific bolt preload during assembly, typically some percentage of bolt material yield stress. A third approach optimizes gasket seating stress or tightness within the specific preload stress range of particular grades of fasteners. None of these approaches consider the physical limitations and capabilities of the flange itself, which can result in flange damage due to excessive bolt preload or the lost opportunity to gain fatigue resistance and reliability when low fastener preloads are selected [1].
While detailed Finite Element Analysis (FEA) could meet this objective, cost and time constraints limit the number, size, and materials to be considered. The objective of this method to optimize target assembly torques for B16.5 flanges is to identify the likely maximum safe assembly bolt load not exceeding the compression, yield, or tensile limits of any of the three flange components. It is recognized that some localized yielding does occur. Existing industry efforts to study and optimize target torques are surveyed, reviewed, combined, and extrapolated to determine acceptable torque values that conform to selected component limits. The limits are chosen consistent with normal practice in the chemical, process, and power industries.
Crack Initiation and Propagation Under Hydrogen-Enhanced Fatigue of a Cr-Mo Steel for Gaseous Hydrogen Storage
Authors: Briottet Laurent , Escot Marielle , Moro Isabelle , Tamponi Gian Marco , Furtado Jader , Solin Jussi , Bortot Paolo 
Published: November 2014

The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of such vessel used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. Yet, hydrogen can reduce the fatigue life in two ways: by decreasing the crack initiation period and by increasing the fatigue crack growth rate. The European project MATHRYCE aims are to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue.
The study is focused on a low alloy Cr-Mo steel, exhibiting a tempered bainitic and martensitic microstructure, and classically used to store hydrogen gas up to 45 MPa. Due to hydrogen diffusion at room temperature in such steel, tests have to be performed under hydrogen pressure to avoid outgassing.
In the present work, experimental procedures have been developed to study both crack initiation and crack growth. The specimens and tests instrumentation have been specifically designed to quantitatively measure in-situ these two stages under high hydrogen pressure. We developed and tested crack gages located close to a small drilled notch. This notch simulates the presence of steel nonmetallic inclusions and other microstructural features that can affect fatigue crack initiation and propagation. The experimental results addressing the effects of the testing conditions, such as stress ratio, frequency and hydrogen pressure will be compared to the local strain and stress fields obtained by Finite Element Method and correlated to the possible hydrogen enhanced fatigue mechanisms involved.
Extending Replacement Intervals of Elastomeric Components by Evaluating Samples Removed From Service
Authors: Marchesi Jenifer T. , McBrine William J. , Roy Vincent 
Published: November 2014

Elastomers play an essential role in pressure vessels as seals, hoses, gaskets, diaphragms, liners and other critical components [1]. Some polymeric materials used for non-pressure applications such as electric power cable insulation have received much attention with respect to the effects of aging and life management, but many critical elastomeric pressure vessel components such as seals have not. Performance of these seals depends upon the effects of both time- and event-dependent aging. Understanding and addressing aging and degradation are fundamental to effective preventative maintenance and life-cycle management programs.
Proper management of elastomers is necessary for performance requirements and for cost containment. In one of the case studies presented synthetic seals in engines were quite costly to change on the suggested OEM maintenance schedule where replacement intervals were based on assumed operating conditions applicable to other industries. When the actual service for these engines is as emergency diesel generators (EDGs, e.g., in nuclear power plants) the use is primarily in stand-by mode, and the usage is far different than that of the manufacturer’s target application. In this investigation the assessment of pressure seal performance was based on situation-specific operation and environmental parameters. This resulted in much longer replacement intervals. In another case study alternate materials were identified which are expected to improve performance over the original material.
Fluid Damping in an Oscillating Array of Cylinders Submitted to Axial Flow
Authors: Divaret Lise , Depaix Fanny , Moussou Pierre , Cadot Olivier , Doaré Olivier , de Buretel de Chassey Nicolas 
Published: November 2014

Axial flows are known to generate a high level of damping with respect to the lateral oscillations of cylinder arrays. The evaluation of these dissipative forces is crucial for seismic design of fuel assemblies. The present study is focused on the case of an array of 40 cylinders oscillating laterally in an axial flow.
An experiment is performed in a water tunnel with an rectangular array of 8 × 5 cylinders. The cylinder diameters are D = 10mm, and their length to diameter ratio is L/D = 56. The cylinders are equally spaced with a gap of 3 mm. The distance from the array of cylinders to the wall of the water tunnel is equal to 14mm in the lateral direction and 24.5mm in the direction of the oscillations. The axial flow velocity varies between 0.5m/s and 4.5m/s. The array of cylinders is rigidly clamped to a rod connected to a motoreductor system which enforces a sine-like displacement. The oscillation frequency ranges from 3Hz to 7Hz and the amplitude from 5.4mm to 16mm. An impedance head and an optical micrometer are used to measure the lateral force and the displacement.
The added mass and damping coefficients are estimated from the lateral force signal for different axial flow velocities, oscillation amplitudes and frequencies. Results show that the added mass coefficient is almost constant and equal to the potential value proposed by Chen. The damping coefficient depends on only one non dimensional parameter which is the ratio between the oscillation velocity and the axial flow velocity. Two force regimes are also observed: for very low oscillation velocities to axial flow velocity ratios, the damping force is proportional to the oscillation velocity and quadratic otherwise.
The Effects of In-Plane and Out-of-Plane Dimensions of a Curved Wide-Plate on Crack-Tip Constraint for Pipeline Fracture Assessment
Authors: Lee Hwee-Seung , Huh Nam-Su , Kim Ki-Seok 
Published: November 2014

One important element of fracture mechanics assessment in pipelines is how to determine the relevant fracture toughness (J-resistance or CTOD-resistance (crack-tip opening displacement)) for nonlinear fracture mechanics analysis. The general practice using a standard fracture mechanics specimen is known to often provide conservative estimates of toughness due to differences in crack-tip constraints between standard specimens and actual components.
To improve the accuracy of predicting pipeline failure, various non-standard fracture mechanics specimens have been suggested over the past few decades. Among the several non-standard test specimens, a curved wide-plate in tension is often employed to predict fracture behavior of cracked components, for instance, in gas transportation pipelines.
In order to show validity of a curved wide-plate in tension, the fracture toughness values from a full-scale pipeline test have been compared with those from a curved wide-plate in tension, and crack-tip constraints of a curved wide-plate in tension have also been compared with those of actual pipelines or other specimens during last decades. It is well known that a crack-tip constraint of test specimens, including curved wide-plates in tension, depends on many geometric and material parameters, for instance, crack length, thickness and width of specimen and material’s hardening characteristic. Thus, in order to obtain relevant fracture resistance from a curved wide-plate in tension representing accurate crack-tip constraint of pipeline of interest, variations of crack-tip constraints of curved wide-plates in tension according to various in-plane and out-of-plane constraint conditions should systematically be quantified.
In the present study, systematic 3-dimensional finite element analyses attempt to investigate the effect of in-plane and out-of-plane parameters on crack-tip constraints of a curved wide-plate in tension.
RCC-MRx Edition 2012: Bolt Design Rules Criteria
Authors: Borazzo C. , Pétesch C. , Lebarbé T. , Ancelet O. 
Published: November 2014

This paper describes and explains the contents of bolt and bolted connection design rules included in the present 2012 edition of the French RCC-MRx code ([1], applicable to nuclear installation components). The aim of this work is to describe the rules and their technical and historical background, owing to the widespread fields of application in a NPP and to the relative complexity of methods; bolted connections have often a major safety-related role.
The domain of the RCC-MRx covers high temperature sodium reactors, experimental nuclear facilities (Jules Horowitz Reactor, research reactor under construction in France), and fusion reactor components (ITER Vacuum Vessel). The first major application is at present for ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration).
The bolt connection usual domain varies in a wide range, from very complex configurations, like high temperature, pressure retaining under cyclic load, to simpler flanges for low temperature piping.
In order to fulfill such different needs in design, several sets of rules are included at present in RCC-MRx code, issued from the historical development of previous RCC-MR and RCC-MX codes, from which the “RCC-MRx” version is derived.
In the following, the existing four configurations of bolted connections are identified, the respective rules are summarized, and, finally, a short comparison with other nuclear codes and industrial standards is provided. Available rules to-date concern respectively:
1) Preloaded bolts assuring leaktightness (type “B1”)
2) Preloaded bolts not assuring leaktightness (“B2”)
3) Non-preloaded bolts (“B3”)
4) Flange bolts
Application of Advanced Fatigue Damage Parameters in Comparison With Fatigue Analysis Included in Codes and Standards
Authors: Rettenmeier Philipp , Herter Karl-Heinz , Schuler Xaver , Fesich Thomas Markus 
Published: November 2014

Technical components are subjected to cyclic loading conditions that can be arbitrarily complex in the most general case. For analytical fatigue strength verifications in the finite life regime both the uniaxial material characteristics by means of Wöhler curves as well as a representative equivalent fatigue damage parameter (FDP) for multiaxial cyclic loadings have to be determined. For simple loading conditions, the fatigue assessment can be performed using well-known and verified strength hypotheses for quasi-static loading conditions. However, for complex non-proportional cyclic loading conditions with rotating principle stress directions the application of these hypotheses is not sufficiently verified. Hence, advanced stress, strain or energy based strength hypotheses in critical plane formulation are used. These hypotheses require considerable numerical efforts.
The fatigue concept (MPA AIM-Life) enables an assessment of complex fatigue loading conditions with different advanced strength hypotheses. An interface to the finite element code ABAQUS allows the fatigue assessment of complex component geometries. Based on fatigue tests of specimens made from ferritic and austenitic materials under uniaxial and multiaxial loading conditions (tension/torsion) the accuracy of different strength hypotheses is demonstrated. Therefore the fatigue analysis assessment included in codes and standards is compared to different advanced fatigue damage parameters.
Fatigue Crack Propagation Experimental Evaluation and Modeling in an Austenitic Steel Elbow From a LMFBR Primary System Piping
Authors: Garcia-Rodriguez Daniel , Sakakibara Yasuhide 
Published: November 2014

In this work the behavior of high temperature (400C) low-cycle fatigue crack propagation during in-plane bending of an elbow from Monju Liquid Metal Fast Breeder Reactor (LMFBR) is presented in three stages. First, experimental measurements made in a real-size laboratory specimen are presented. This test was carried out under displacement-controlled conditions, with artificial defects introduced in the crown parts, where the maximum stress arises. Second, the experimental setup is simulated making use of Finite Element Analysis (FEA), in order to obtain the actual stress distribution through the loaded elbow. Finally, based on the FEA data, deterministic fatigue crack propagation based on the J-integral criterion is compared with the experimental data.
Overall a good agreement was observed between experimental and analysis results, highlighting our capacity to evaluate such phenomena without necessarily incurring into extensive experimental work. In the future these tools will keep supporting the cost-efficient acceleration and improvement of LMFBR design and inspection criteria.
Damage Analysis and Fatigue Evaluation of an Aluminium Brazed Plate Fin Heat Exchanger
Authors: Hölzl Reinhold , Hecht Thomas , Freko Pascal 
Published: November 2014

During operation of an air separation unit (ASU) a plate fin heat exchanger developed a leak. This apparently simple heat exchanger, exchanging heat between two gaseous streams of air versus nitrogen, was not expected to suffer significant stress levels for producing a damage.
During the analysis of the damage which occurred at the connection welds of three adjacent modules — module construction is widely used in the process industry — an operating situation was discovered leading to high thermal gradients inside the exchanger. It occurred during a stop of the plants nitrogen cycle compressor. The warm flow continued and heated up the exchanger in a very fast way. This led to unacceptably high stresses in the top part of the exchanger. But a more severe situation occurred when the cycle compressor has been restarted. Then cold nitrogen entered the lower end of the exchanger which had been warming up in the meantime.
A finite element analysis based on a modeling technique [4] for brazed plate fin heat exchangers was performed for this dynamic incident showing extreme stress levels at the location of the damage. A fatigue evaluation of the calculated stresses showed that only a few cycles were acceptable for this scenario. As a consequence operational measures have been implemented to protect the exchanger against this severe condition.
Thermal Stress Response to Boundary Oscillation Between Hot and Cold Fluid Temperature
Authors: Soda Kohei , Mizutani Takato , Kasahara Naoto 
Published: November 2014

In nuclear power plants, high cycle thermal fatigue induced by temperature fluctuation of the coolant is one of frequent failure modes. To ensure the safety of nuclear power plant systems, it is important to prevent thermal fatigue failure.
Typical causes of high cycle thermal fatigue are thermal striping at Tee-junction and thermal stratification oscillation. In order to evaluate thermal stress caused by thermal striping, a frequency response function has been developed. This function was derived from a heat transfer and thermal elastic theories, and can adequately evaluate thermal stress induced by temperature gradient into wall-thickness direction.
However, this theoretical method cannot adequately evaluate thermal stress by thermal stratification oscillation, because this phenomenon has the fluid temperature distribution gradient along axial direction.
To investigate the mechanism of thermal stress generated by oscillation of thermal stratification, two types of models were studied. In the first type, fluid temperature oscillates with sinusoidal history at the same location, and in the second one, the boundary layer of hot and cold fluid temperature moves with sinusoidal velocity.
Through clarification of the stress generation mechanism, the frequency response function was improved to evaluate stress by the thermal stratification oscillation. Applicability of this function was verified through agreement with finite element simulations.
Status of the French Methodology Proposal for Environmentally Assisted Fatigue Assessment
Authors: Métais Thomas , Courtin Stéphan , Genette Pierre , De Baglion Laurent , Gourdin Cédric , Le Roux Jean-Christophe 
Published: November 2014

Environmentally Assisted Fatigue is receiving nowadays an increased level of attention for new builds and also for installed bases which are currently having their lives extended to 60 years in various countries. To formally integrate these effects, some international codes have already proposed code cases. More particularly, the ASME code has based itself on the NUREG/CR-6909 [1] to elaborate the Code Case N-792 [2] and suggests a modification of the fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which is to be multiplied by the usual fatigue usage factor.
In France, EDF and AREVA also aim at more explicitly integrating these effects in the RCC-M code. The initiative is technically supported by CEA and bases itself on international methodologies but also on results from French in-house testing campaigns [3] [4]. The approach is globally similar to the one in the ASME code: it will indeed consist in an update of the mean air and design fatigue curves as well as the calculation of an environmental penalty factor. Nevertheless, the methodologies differ in their detailed implementation, as was already hinted in previous papers discussing the French methodology [5] [6]. This paper is the sequel to the proposal already described in [7].
Equi-Biaxial Loading Effect on Austenitic Stainless Steel Fatigue Life
Authors: Bradaï S. , Gourdin C. , Courtin S. , Le Roux J. C. , Gardin C. 
Published: November 2014

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.
In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension.
The aim of this paper is to present the experimental results obtained with a device “FABIME2” developed in the LISN in collaboration with EDF and AREVA. The specimen geometry is optimized by FEM (Cast3M) simulation in order to obtain a stress concentration localized in the central region during the test. This device allows accurate quantification of the effects of both equi-biaxial strain state as well as structure (such as mean stress) on the fatigue life.
Flow-Induced Pulsations in Closed Side Branches With Wet Gas
Authors: Sanna F. , Golliard J. 
Published: November 2014

In a recent paper it has been shown that the presence of liquid has an influence on Flow Induced Pulsations (FIPs) in closed side branches. Even larger effects of liquid in case of whistling in corrugated pipes were reported.
For this experimental study, the “Tandem configuration” with two closed side branches along a main pipe is considered. It is characterized by the distance between the two closed side branches equal to the double of their acoustic length.
The experiments reported in this paper aim at investigating the effect of the mixture water/gas on FIPs measured at the closed end of the two closed side branches. Different water flow rates are injected in the flow to obtain a mass factor rate in the range 0–10−4 m3/s. Furthermore, the relation between the multiphase flow pattern in the main pipe and the trend in the pulsation amplitude and Strouhal number is discussed, by comparison with the test for dry gas. To understand the effect of the type of flow, tests are performed with the injector far from and close to the upstream side branch.
For the far configuration, at both low and high injection rates, pulsations decrease for increasing injection rates. However, in the intermediate region, an increase of pulsations is observed. These different ranges can be attributed to different (multiphase) flow regimes.
Concerning the close configuration, only a decrease of the pulsations is observed over the full range. Furthermore, a decrease of the Strouhal number corresponding to the maximum pulsation level is observed.