bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Subsurface Crack Propagation Under Fatigue
Authors: Serizawa Ryosuke , Kikuchi Masanori , Yamada Shinya 
Published: November 2014

There is a proximity rule to calculate residual fatigue life of components in nuclear power plants. It is easy to evaluate soundness of a structure member by using this rule. If a subsurface crack is located near free surface of the structure, this real subsurface crack is transformed to surface crack. The condition to transform subsurface crack to surface crack is defined by relationship between crack size and the distance from crack tip to free surface. However, many organizations proposed proximity rules which differ from each other. It is advisable to verify which rule is preferable in these rules by experiment, but it is difficult to introduce subsurface crack at an optional position. Therefore, numerical simulation is needed for this purpose. Especially, S-version FEM is very useful for as much as model of subsurface crack is independent of global structure, and crack growth is easily simulated.
Both subsurface and transformed surface crack growths are simulated by S-FEM. Subsurface crack grows toward free surface. When subsurface crack tip was touched to free surface, this crack was converted into surface crack by using stress intensity factor calculated at this time. In this way, crack growth behavior from subsurface to surface flaw is represented. By comparing the crack growth rate of surface to subsurface flaw with that of surface flaw transformed by each proximity rule, proximity rules can be verified by numerical simulation.
Authors had proposed the proximity rule at the ASME PVP 2013 conference [1]. However, new rule was proposed by numerical simulation only under cyclic tensile load. In addition, only two proximity rules were studied at the last conference. In this study, the number of proximity rules is increased, and this problem is simulated under other loading condition such as cyclic bending load. New proximity rule gives reasonable and conservative results in numerical simulation.
The Residual Strength of Breathing Air Composite Cylinders Towards the End of Their Service Life: A First Assessment of a Real-Life Sample
Authors: Mair Georg W. , Scherer Florian , Scholz Irene , Schönfelder Thorsten 
Published: November 2014

Emergency response units increasingly use pressure cylinders made from fibre composites for breathing air as elements of personal protective equipment (PPE). Such applications expose the composite cylinders to harsh temperature and handling conditions. At least in Europe, standards have been used for certifying PPE, which are designed and mandatory for the approval of pressure receptacles for the transport of dangerous goods. Therefore, service conditions specific to PPEs are not accounted for in these standards.
In this paper, BAM (Federal Institute for Materials Research and Testing) investigates the residual safety of a composite cylinder design at the end of their designated service life of 15 years. The cylinders (test pressure PH 450 bars; 6.8 Litres) are of one design type with aluminium liner and fully wrapped with carbon fibres, which is commonly considered a “Type III” cylinder. All cylinders were used as PPE by the Berlin fire department and randomly picked in three samples of 25 cylinders each before tested.
At BAM, the cylinder samples underwent hydraulic load cycle tests (LCT), conventional burst tests (BT) and so called slow burst tests (SBT). A concept for quantification of strength degradation already introduced by BAM was applied. This concept is based on a probabilistic assessment of the average strength and scatter of each sample of cylinders. The strength distributions of the used PPE-cylinders is shown and analysed. Some unexpected effects are shown and a refinement of the statistical assessment is introduced.
An Approach for a Statistical Evaluation of Uncertainty in Assessing Fatigue Usage Including Environmental Effects
Authors: Garud Y. S. , Steininger David A. , Wolfe Ken 
Published: November 2014

The assessment for adequacy in managing the effects of fatigue in the ASME Code Class-1 (pressure boundary) components is based on a calculated measure of the projected fatigue damage. This measure is the highest cumulative usage factor (CUF) in a given component under a specified set of cyclic loadings and their expected number of repetitions. The Code-based calculation of CUF and its adjustments for potential environmentally-assisted fatigue (EAF) damage accumulation utilize a multitude of inputs, and conservative assumptions and applied margins. To support the extended service life beyond the original design, or longer life of new designs, changes in inputs and/or conservative assumptions used in these deterministically calculated CUFs are often made to meet a deterministic performance criterion. This makes the impact of uncertainty in the inputs and/or changes in the conservative adjustments difficult to assess.
This paper presents a generic, engineering approach for estimation of the uncertainty distribution of CUF based on the expected statistical characteristics of input variables used in the calculation of EAF-based CUF. The approach does not involve Monte Carlo sampling. The proposed statistical approach analytically combines variances of the inputs leading to an acceptable estimation of the total variance of the CUF. The approach does not require specification of full probability distribution(s) for the input variables, nor is the dependence between variables a critical issue from the analytical point of view. Feasibility and limitations of the approach are discussed in relation to the NB-3200 and NB-3600 procedures of the ASME Code and the current Fen-based augmentation for environmental effects. This approach is further examined in the framework of stress–strength interference methodology to account for the uncertainty in the fatigue performance criterion, that can lead to a rational deterministic safety factor interpretation and its relation to a quantifiable measure of the probability of exceeding the fatigue performance criterion.
A Less-Conservative Approach to Simplified Seismic Analysis for Small Bore Nuclear Piping System
Authors: Lee Joon Ho , Kim In Yeung 
Published: November 2014

Per guidelines for piping system reconciliation such as EPRI NP-6628 (NCIG-14), simplified seismic design methods have been used by nuclear piping designers to deal with small bore piping for many years. These methods are generally based on enveloping the results of rigorous dynamic or conservative static analysis.
Small bore piping is generally more flexible with larger margin in support design comparing to large bore piping. Consequently, Classes 2 & 3 piping less than 2-1/2 inch NPS that is analyzed by a conservative “cookbook method” is excluded from the as-built verification actions in IE Bulletin 79-14. The ASME code’s Subsection NF and B31.1 provide recommended pipe spans by pipe size considering only piping weight; therefore, the seismically qualified piping span must be developed for the peak acceleration of the applicable amplified or floor response spectra.
Simplified seismic analysis method being considered for the Korean nuclear power plants is based on the Load Coefficient Method provided in Appendix N-1225 of ASME Section III. However, since the simplified analysis method involves conservative and enveloping approach in an effort to comply with applicable requirements and results in an excessive number of supports and unrealistically high support loads, the successful implementation largely depends on how the issues related to the excessive conservatism are resolved when determining allowable pipe spans and support design loads of the piping system.
In this paper, simplified engineering equations are presented as a less-conservative approach based on a detailed computer analysis method, which is alternative to the various handbooks and design charts that are based on the conventional hand calculation method.
Investigation on Fatigue Curve Against Cyclic Loads of an Earthquake for Piping Components
Authors: Uesaka Masao , Kojima Nobuyuki , Muroya Itaru , Nomura Hiroshi , Yamazaki Junichi , Otani Akihito 
Published: November 2014

In Japan, seismic assessments considered aging phenomena have been conducted as part of activities for aging measures of nuclear power plants. In the activities, it is found that FAC (Flow Accelerated Corrosion) of piping components made of carbon steel impact on seismic integrity because of decreasing a cross section of piping. Therefore, many destructive tests of piping have been conducted in Japan and the other countries.
At first, factors on which did not focus in the past destructive test have been extracted in this investigation. displacement controlled cyclic tests of piping components which focused on extracted factors have been conducted additionally in order to provide enough test data for past destructive test data of piping components. Moreover, fatigue curve for practical evaluation of piping components made of carbon steel has been settled after obtained test data were put in order including past destructive test data of piping components from a point of fatigue.
Experimental Verification of Finite Element Approach for Designing Robust Bolted Joints Using Titanium and Titanium Alloy Bolts at Elevated Temperature
Authors: Fukuoka Toshimichi , Nomura Masataka , Hirai Takao 
Published: November 2014

When bolted joints are subjected to thermal load, variations of the bolt clamping force are of great concern from the view point of joint safety. It is considered that titanium and titanium alloy bolts have high possibility for clamping machines and structures subjected to thermal load. Its specific characteristic of low thermal expansion expectantly works well to mitigate the reduction of bolt clamping force caused by thermal expansion. Low weight, low Young’s modulus and high resistance to corrosion of titanium and titanium alloy are also highly attractive.
In this paper, the effectiveness of the numerical method proposed in the previous study is validated by experiments using bolted joints composed of titanium bolts and carbon steel plates. Then, thermal and mechanical behaviors of titanium and titanium alloy bolts are analyzed by finite element analysis in order to examine the applicability of those bolts for the joints under elevated temperature. Numerical analyses are executed as in the manner introduced in the previous paper, i.e., by incorporating the thermal contact coefficient into the finite element formulation. Numerical results suggest that titanium and titanium alloy bolts are favorably applied to the joints made of carbon steel whose clamping forces are likely to decrease under elevated temperature.
Leakage Analysis of a High Pressure Flange Connection Under Bending Moments: An Analytic Procedure
Authors: Bortz Matthias , Wink Rolf 
Published: November 2014

High pressure flange connections for LDPE plants are designed using lens ring gaskets and bolted flange connections. The sealing principle is to achieve a high contact pressure between the spherical lens shape and the conical tube end. This contact pressure must exceed the fluid pressure by a safety margin under all operating conditions. Bending moments acting on the flange connection will create an uneven distribution of contact pressure over the lens ring surface.
In this paper a procedure is shown to analyse the influence of the bending moment under consideration of internal pressure on a flange connection using 3-dimensional finite element models. The variations in bolt stress and distribution of contact pressures due to the bending moment are of specific interest. A first approach will be provided to derive some simplified design rules regarding leakage assessment of such flange connections.
Developing an Engineering Based Integrity Management Program for Piping, Pipelines, and Plant Equipment
Authors: Alexander Chris , Bedoya Julian 
Published: November 2014

Establishing integrity for piping and pipelines requires an understanding of the specific threats, their relationship to the overall condition of the system, and the mitigating measures required to assure safe operation. In the past, industry has relied on years of research and experience to develop a set of tools to analyze these threats and apply conservative solutions to ensure integrity and fitness for service. An effective integrity management program as discussed in this paper, known as the Engineering Based Integrity Management Program (EB-IMP), provides operators with a resource for integrating inspection results, analysis, and testing to qualify the components within a pressurized system.
This paper presents a detailed discussion on how experience, advances in analytical techniques, experimental methods, and engineering rigor are combined to develop a tool to characterize and ensure system integrity. Several case studies are included to demonstrate how the EB-IMP method was used to evaluate the integrity of a piping system, as well as rail gondola cars used to transport coal. The intent with the approach presented in this paper is to foster further developments for advanced integrity management efforts.
Study of Acoustic Vibration in Piping Systems by Energy-Based Finite Element Analysis
Authors: Dweib Ahmed H. 
Published: November 2014

Finite Element Analysis (FEA) and Statistical Energy Analysis (SEA) methods have been applied recently to the study of acoustic induced vibration (AIV) in piping systems.
In this paper, the acoustic vibration in the piping systems is studied by performing FEA of a model of the structural pipe with the application of the acoustic excitation as stationary acoustic modes to the structural pipe model. This approach provides an alternative to performing FEA using a combined model for the acoustic fluid and the pipe. The analysis is used for the evaluation of the power flow from the acoustic medium to the pipe. The acoustic part of the system is modeled as a series of acoustic modes that are taken to act on the pipe FEA model. The Coupling Loss Factor (CLF), required for the formulation of the SEA model, is identified and plotted against pipe parameters.
A Strategy for Development of a Mechanistic Understanding of Environmental Fatigue
Authors: Twite Marius 
Published: November 2014

There has been much focus in recent years on development of an empirical understanding of the effects of a range of variables on fatigue performance of nuclear plant materials in relevant operating environments — for example, the influences of surface finish, temperature, and cyclic waveform. To complement these empirical studies, a well-developed mechanistic understanding of Environmental Fatigue initiation behaviour is required to allow extrapolation of results beyond the variable ranges tested and to provide insight into the margins incorporated into fatigue analysis methods, including fatigue design curves.
Mechanistic understanding may be defined as a multi-scale description of physical and chemical effects determining fatigue behaviour through the stages of crack nucleation, small crack (Stage I) growth and the transition to long crack (Stage II) growth.
A review of literature related to mechanistic understanding of Environmental Fatigue initiation in nuclear plant materials in air and PWR primary coolant environments has been carried out. Detailed findings of that review are not presented here; however, high level conclusions are discussed. It was found that very little literature specific to these combinations of material and environment is available, although there exists a substantial body of work related to generic mechanistic understanding of fatigue and environmental effects in metallic materials.
Based on the conclusions of this literature review, a strategy for improvement of mechanistic understanding of Environmental Fatigue initiation has been developed by Rolls-Royce. This strategy is based around three strands of work: metallurgical investigation; numerical modelling; and laboratory testing.
Improvements in mechanistic understanding of Environmental Fatigue initiation offer significant opportunities for collaboration between interested parties. Indeed, attainment of a well-developed mechanistic understanding that may be used, in combination with empirical understanding, to inform advances in fatigue analysis methods is likely to be achievable only through collaborative effort.
Four Points Bending Test on an EPR Type DMW Pipe Containing a Through-Wall Defect: Experimental and Numerical Analysis From Small Specimens Until Pipe Scale
Authors: Bourgeois M. , Chapuliot S. , Marie S. , Ancelet O. , Kayser Y. 
Published: November 2014

Within the framework of European project STYLE [1], a fracture test on a pipe containing a through wall crack in a narrow gap Inconel Dissimilar Metals weld (welds named hereafter DMW) has been performed. The work is focusing on the Inconel - ferritic steel interface which is the weakest area of such welded pipes in front of ductile tearing. The study temperature is 300°C, which covers typical temperatures in components like hot pipes in the primary coolant system of pressurized water reactors.
The four point bending test was carried out by the French Atomic Energy Commission and Alternative Energies (CEA), in order to study the mechanical properties and integrity of component such as the DMW pipes provided and designed by AREVA France. The observations made post-mortem showed a small 2.5 mm ductile tearing at the interface of Inconel and ferritic steel, and after this point, a large crack that has deviated from the interface to propagate in the Inconel and then in the stainless steel.
The DMW Mock-up is presented with previous results concerning the mechanical characterizations of his constitutive materials. The second part of this paper is devoted to the four point bending test at 300°C: procedure, instrumentation and interpretation of large-scale test in terms of initiation and propagation of cracks. A comparison is made with tests performed at a smaller scale on multi-material CT specimens. The third part deals with first numerical analysis of fracture test. The results are interpreted on a small scale using finite element analysis to obtain the parameters of damage models that are needed for global approach. Finally, numerical approaches is presented and applied to simulate the fracture of the large-scale pipe.
The aim of this paper is to propose and discuss the validity of new assessment methods of ductile propagation in a large scale pipe containing a through wall crack in a narrow gap dissimilar metal weld.
An Engineering Procedure for Calculating Cleavage Fracture Toughness From Charpy Specimen Data Using a Mechanistic Approach for Ferritic Steels
Authors: Smith Robin J. , Sherry Andrew H. , Horn Anthony J. , Bannister Adam C. 
Published: November 2014

This research develops an engineering approach which permits the treatment of Charpy specimen absorbed energy data in the lower transition of Charpy specimen fracture behaviour. The procedure has been shown to be applicable to a ferritic steel study material. The calculation method comprises several steps to correct the input Charpy data to the equivalent material fracture toughness of a ferritic steel under consideration. The engineering procedure develops existing methods for constraint and notch correction to data [Sherry et al, EFM 2005] [Horn and Sherry, IJPVP 2012].
Micromechanical modeling of cleavage fracture behaviour has been applied in conjunction with sequential experimental testing. This work addresses the important geometric differences between a single edge notch bend, SEN(B), fracture toughness specimen and the standard Charpy V-notch specimen. The engineering approach is demonstrated using a suitable study ferritic steel material and by undertaking an experimental laboratory testing programme comprising standard fracture toughness specimens and non-standard U-notch and V-notch Charpy sized specimens with a range of notch geometries.
It has been found that constraint and notch assessment methodologies premised upon micro-mechanical modeling of cleavage fracture offer an accurate probabilistic description of fracture behaviour in these specimen geometries. Refinement of a notch angle correction is necessary within the procedure. These findings permit the extension of the approach to develop a material specific guidance to practitioners undertaking structural integrity assessments. The final extension of the research to Charpy impact data requires the measurement of ferritic steel material flow behaviour under dynamic conditions and represents further research.
Research Plan on Failure Modes by Extreme Loadings Under Design Extension Conditions
Authors: Kasahara Naoto , Nakamura Izumi , Machida Hideo , Nakamura Hitoshi 
Published: November 2014

As the important lessons learned from Fukushima-nuclear power plant accident, preparation based on Probabilistic Risk Assessment (PRA) with adequate scenario is strongly recognized as essential countermeasures against severe accidents, which are possible in nuclear plants. IAEA requires design extension conditions (DEC) for considering severe accidents. From a view point of structural design, the strength evaluation approach for DEC is somewhat different from conventional one for design basis accident (DBA). There are additional failure modes by extreme loadings under DEC. Best estimation with possible scenarios is necessary for PRA and planning of accident management (AM).
This paper introduces study plan on failure modes and their mechanisms by extreme loadings under DEC.
First step is the list-up of possible failure modes which should be assumed for extreme loadings such as very high temperature, high pressure and great earthquakes. Next is clarification of failure mechanism and relevant limit strength.
One of examples is the failure modes of structural discontinuities under high pressure such as ductile fracture and local failure. Another example is ones of pipes under severe earthquake such as collapse and low cycle fatigue.
To clarify above questions, such different scale tests were planned and conducted as the fundamental tests with simulated materials, structural element tests and structural tests. Preliminary results of above tests and next plans are explained.
Development of Pressure Vessels Made of 9Cr-1Mo-V Steels for High-Temperature Processes in Refining Industries
Authors: Nakanishi Tomoaki , Ikeuchi Tadashi , Terada Susumu , Yamada Masato , Miyamura Takeo , Nanba Shigenobu , Shinozaki Tomoya , Nakashima Hiroki , Ikeda Tetsunao , Yamashita Ken 
Published: November 2014

Due to the increasing demands for light oil in newly industrializing countries and depletion of conventional oil resources, upgrading of heavy oil and coal-to-liquid processes have been a focus in recent years. The efficiency of these processes depends on temperature and pressure conditions, where a higher temperature, around 500°C, is likely to be used. However, 2¼Cr-1Mo-V steels which have been widely used for heavy-wall pressure vessels for many years cannot be applied to a high temperature process around 500°C since the design temperature of this material is limited to 482°C by ASME Code Section VIII, Division 2 [1].
On the other hand, 9Cr-1Mo-V steels (Grade 91), which has an excellent performance at high temperature in mechanical properties and hydrogen resistance, has been used for tubing and piping materials in power industries and it can be a candidate material for the high temperature processes. However it has not been used for pressure vessels in refining industries.
In order to manufacture heavy-wall pressure vessels using 9Cr-1Mo-V steels, essential techniques including manufacture of large forged shell rings, thick wall welding and overlay welding have been developed.