bluuebunny/crossref_metadata_2025_split huggingface dataset:
Location of Initiation Sites in Fracture Toughness Testing Specimens: The Effect of Size and Side Grooves
Authors: Wallin Kim , Yamamoto Masato , Ehrnstén Ulla 
Published: December 2016

Cleavage fracture initiates usually at single locations in front of the fatigue crack in some position along the crack front. If the crack driving force along the crack front is uniform, one should expect the initiation sites to be randomly located along the crack front. Finite element analyses have, however, shown that the crack driving force varies along the crack front. Thus, the location of the cleavage initiation sites should reflect this variation in crack driving force.
Fracture toughness specimens differ both in geometry and size. Also, the specimens may be side grooved or plane sided. All this can be expected to affect the local crack driving force along the crack front. The local crack driving force for cleavage fracture initiation can be divided into two components. The local KJ value describes the local effective stress intensity, whereas Q or Tstress describes the local constraint. To make things even more complicated, the local constraint is also affected by the local effective stress intensity. All of these are also affected by any ductile tearing occurring prior to cleavage initiation.
The testing standards contain specific limitations on specimen sizes and their measuring capacity in order to ensure that the crack driving force in different specimens is sufficiently similar to make the results from different specimen types and sizes comparable.
Classically, the fracture toughness test specimens have been comparatively large. Recently more and more work has been devoted to diminish the size of the specimens, to save material. One very promising specimen type is the miniature C(T) specimen with a 4 mm thickness and total height of 10 mm. Based on a recent international round-robin, the miniature C(T) specimen appears to provide compatible Master Curve T0 values as large specimens, but further validation regarding the similitude of the cleavage initiation is required, since the Master Curve is based on the assumption that specimen size does not affect this similitude.
In this work, the location of cleavage initiation sites along the crack front are examined for different size and type of fracture toughness specimens, focusing on the miniature C(T) specimen. The location distributions are evaluated in terms of load level, specimen type, size and possible side grooving. It is shown that, as long as the standard requirements are fulfilled, the initiation location distributions for the miniature C(T) specimens are similar to larger conventional specimens. Side grooving is shown to have a minor effect on the initiator locations.
The OECD-NEA Programme on Metallic Component Margins Under High Seismic Loads (MECOS)
Authors: Labbé Pierre B. , Reddy G. R. , Mathon Cedric , Moreau François , Karamanos Spyros A. 
Published: December 2016

MECOS is Post-Fukushima OECD/NEA initiative, with the following main objectives:
- To quantify the existing margins in seismic analysis of safety class components and assess the existing design practices within a benchmark activity.
- To make proposals for new design/evaluation criteria of pressurized piping systems, accounting for their actual failure mode under strong input motions.
The first part of MECOS consisted of gathering information on i) current design practices and ii) piping system experimentation carried out around the world that could be suitable for benchmarking. Part 2 is the benchmark itself and Part 3 proposals for new criteria. The purpose of the proposed paper is to present the experimental background and the benchmark exercise.
Fracture Probability Assessment for Embrittled Reactor Pressure Vessels Under Ultimate Response Guideline Operation
Authors: Chou Hsoung-Wei , Huang Chin-Cheng 
Published: December 2016

After the Fukushima nuclear accident occurred in Japan on March 11, 2011, the compound disaster beyond design basis which may severely impact the nuclear safety has been noticed and paid much more attention. In addition to the original emergency operating procedures (EOPs) and severe accident management guidance (SAMG) of nuclear power plant, the licensee in Taiwan developed the ultimate response guideline (URG) when EOPs and SAMG cannot be performed effectively due to loss of power and water supply by the Fukushima-like compound disaster. Once the URG procedures are initiated, the operators will conduct reactor depressurization, low pressure water injection and containment venting to strictly prevent the core damage and the release of radioactive material.
In the paper, the fracture probabilities of boiling water reactor (BWR) pressure vessels with incremental levels of radiation embrittlement under URG operation are evaluated by probabilistic fracture mechanics (PFM) analysis. First, the models of PFM FAVOR code concerning the beltline shell welds of reactor pressure vessels (RPVs) associated with a very conservative flaw distribution are built. Then, the hypothetical transients of URG operation obtained from the thermal hydraulic analyses for Taiwan domestic BWRs are applied as the loading condition. The analysis results demonstrate that performing URG operation will not cause significant fracture probability for RPV, even at an extremely embrittled condition. The URG procedures can ensure the prevention of core damage as well as maintenance of structural integrity of RPV in the situation of long-term loss of electric power when suffering from the Fukushima-like accidents.
Risk Based Inspection Planning for Deteriorating Pressure Vessels
Authors: Haladuick Shane , Dann Markus R. 
Published: December 2016

Pressure vessels are subject to deterioration processes, such as corrosion and fatigue. If left unchecked these deterioration processes can lead to failure; therefore, inspections and repairs are performed to mitigate this risk. Oil and gas facilities often have regular scheduled shutdown periods during which many components, including the pressure vessels, are disassembled, inspected, and repaired or replaced if necessary.
The objective of this paper is to perform a decision analysis to determine the best course of action for an operator to follow after a pressure vessel is inspected during a shutdown period. If the pressure vessel is inspected and an unexpectedly deep corrosion defect is detected an operator has two options: schedule a repair for the next shutdown period, or perform an immediate unscheduled repair. A scheduled repair is the preferred option as it gives the decision maker lead time to accommodate the added labour and budgetary requirements. This preference is accounted for by a higher cost of immediate unscheduled repairs relative to the cost of a scheduled repair at the next shutdown. Depending on the severity of deterioration either option could present the optimal course of action. In this framework the decision that leads to the minimum expected cost is selected. A stochastic gamma process was used to model the future deterioration growth using the historical inspection data, considering the measurement error and uncertain initial wall thickness, to determine the probability of pressure vessel failure. The decision analysis framework can be used to aid decision makers in deciding when a repair or replacement action should be performed. This method can be used in real time decision making to inform the decision maker immediately post inspection. A numerical example of a corroding pressure vessel illustrates the method.
Effective Method of Measuring the Reliability of the Gas Network
Authors: Feng Chen , Changchun Wu 
Published: December 2016

This paper aims at evaluating the gas supply reliability of the gas network, which is meaningful to promote the safe operation of large natural gas transporting system. The solution to solve the problem is put forward by combination of Monte-Carlo method, Random Process Algorithm and hydraulic thermal method.
The reliability of the network depends on the user’s conformance to their requirements and their corresponding degree of gas supply security. Since the matter thing is whether the adequate gas can be sent to the users, the study of gas supply reliability should focus on the common unit states, including the functional state and typical expected failure states. While these familiar states can be obtained by analyzing the historical operating data stored in SCADA system along with the Monte-Carlo simulation, the corresponding failure probability of each state can be achieved. Moreover, the gas flow that expected by the user under various conditions can be performed by the hydraulic and thermal simulation software. Hence, the supply volume of the combined states is defined as the sum of the amount of states to be combined.
This evaluation model can reveal the performance of the gas supply at any time interval and under any degree of gas supply security. Not only can this model develop the classical reliability theory, but also have the benefits for the operation and maintenance of the network.
Evaluation of Design Methodologies for High-Pressure Hazard Barricades
Authors: Kostecki Jodi , Edel Matthew , Bingham Barry 
Published: December 2016

Operation and testing of high-pressure products and equipment are commonly completed in a variety of industrial applications, including oilfield services, industrial gas manufacturing and supply, heat exchangers, refining, chemical, petrochemical, water jetting, and vessel manufacturing, among others. This daily operation has the potential for high consequence (personnel injury, property damage, and business interruption) due to common accidental tool and equipment failures. An increasing number of companies are seeking assistance in providing a testing environment that focuses on improving safety within the industry.
One method for high-pressure hazard mitigation is to use a barricade as a means of protection. This paper investigates a variety of methodologies used for evaluating steel barricades subjected to impact loads from a projectile that produces a flexural response in the plate (rather than penetration). The investigation covers various approaches in hazard (i.e., load) application and structural analysis. The structural models focus on impact loading of steel plates, and the results are directly compared to test results in terms of structural component response.
Application of XFEM to Model Stationary Crack and Crack Propagation for Pressure Containing Subsea Equipment
Authors: Lee Sam (Kwok Lun) , Martin David 
Published: December 2016

The extended finite element method (XFEM) [1, 2] can approximate the discontinuous displacement field near cracks independently of the finite element mesh through the use of interpolation functions, which can describe the displacement field near cracks in the structure. Therefore, XFEM is appearing as an alternative to conventional contour integral method for crack growth analysis. Most benchmarks for XFEM in published literature were mostly for the through-wall crack or loadings were under tension or bending moment. Subsea equipment provided by FMC Technologies is used under the most extreme conditions of pressure and temperature. Due to the fact that most equipment in subsea is pressure containing, assessment of cracks and crack growth under pressure cycles is an essential part of the integrity assessment. The implementation of fracture mechanic based fatigue to analysis can extend equipment life while improving model accuracy.
In this paper, crack growth modelling in a thick wall cylinder was performed by XFEM embedded in Abaqus [3]. The case study of semi-elliptical axial surface crack at internal surface was selected. The fracture and fatigue results based on LCF analysis were compared with contour integral approach and published experimental data [4]. One of the advantages of XFEM is it can easily accommodate changes in the crack propagation direction for mixed mode loading.
A Review of the Shell Buckling and Stiffener Ring Design for Cylindrical Steel Storage Tanks
Authors: Azzuni Eyas , Guzey Sukru 
Published: December 2016

Cylindrical steel storage tanks are shells designed to store different types of products such as liquids or grain. The thickness of the shell is calculated to withstand the circumferential stress resulting from the hydrostatic pressure due to the stored product.
A unique situation when there is no stored product leads to the vulnerability of the shell to buckle when there is wind load due to external pressure.
There are two major types of buckling modes: local and general. The local buckling mode is studied analytically in various studies and is easy to mitigate. The general buckling mode can be more damaging to the tank and more costly to mitigate.
The prevention of general buckling due to wind load pressure is achieved through the addition of stiffener rings. However, the stiffener rings design procedure used by various design standards has little known background. This paper reviews the current design approach’s origin and explains a semi-analytical justification for it. The unfolding of the design expressions can lead to more freedom in design variables selection leading to more economical designs.
RCC-MRx Code: Context, Overview, On-Going Developments
Authors: Pétesch C. , Lebarbé T. , Pascal C. , Blat-Yrieix M. 
Published: December 2016

RCC-MRx Code (ref 1) is the result of the merger of the RCC-MX 2008 developed in the context of the research reactor Jules Horowitz Reactor project, in the RCC-MR 2007 which set up rules applicable to the design of components operating at high temperature and to the Vacuum Vessel of ITER.
This code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires) in 2012, and a new edition was published at the end of 2015.
A significant work has been performed for this edition to improve the code in order to facilitate its use and understandability, and also to have a better fit with the feedbacks of the users.
In parallel, in compliance with the EC’s objectives and its own policy of openness, AFCEN proposes to make its codes evolve, taking into account the needs and expectations of European stakeholders (operators, designers, constructors, suppliers...) through a workshop called CWA phase 2.
This paper gives an overview of the realized work and also will identify the work to be done for an opening of a standard such as RCC-MRx code.
Tests on SENT and CT Specimens to Study Geometry Effects in the Brittle to Ductile Transition
Authors: Le Delliou Patrick , Geniaut Samuel 
Published: December 2016

The accurate prediction of ductile fracture behaviour plays an important role in structural integrity assessments of critical engineering structures under fully plastic regime, including nuclear reactors and piping systems. Many structural steels and aluminium alloys generally exhibit significant increases in fracture toughness, characterized by the J-integral, over the first few mm of stable crack extension (Δa), often accompanied by large increases in background plastic deformation. Conventional testing programs to measure crack growth resistance (J–Δa) curves employ three-point bend, SEN(B), or compact, CT. However, laboratory testing of fracture specimens to measure resistance curves (J–Δa) consistently reveals a marked effect of absolute specimen size, geometry, relative crack size (a/W ratio) and loading mode (tension vs. bending) on R-curves. These effects observed in R-curves have enormous practical implications in defect assessments and repair decisions of in-service structures under low constraint conditions. Structural components falling into this category include pressurized piping systems with surface flaws that form during fabrication or during in-service operation.
A research program was launched by EDF R&D to study geometry effects (e.g. triaxiality effects) in the brittle to ductile transition of carbon-manganese steels using Single-edge notch tension (SENT) specimens, by comparing the results obtained on these specimens with the results obtained on CT specimens.
This paper presents the results of the tests conducted between −40°C and −100°C on a large number of specimens of both types. The toughness values of the SENT specimens appear to be included in the scatter of the CT12.5 ones, so the geometry effect between CT and SENT specimens in the brittle to ductile region is not significant. Moreover, the results of the CT12.5 cut in the L-S direction are not very different of those of the specimens cut in the T-S direction. The Master Curve methodology fits rather well the CT12.5 results, whereas the SENT results are not well covered by this methodology.
The energetic approach called GP has been applied to the analysis of some tests. This approach shows that the geometry effect between both types of specimens is limited, in agreement with the experimental observations.
Fatigue Management During LTO of Nuclear Power Plant Borssele
Authors: Hannink M. H. C. , de Bont C. G. M. , Blom F. J. , Quist P. W. B. , de Jong A. E. , Besuijen W. 
Published: December 2016

Fatigue is an important ageing effect to manage for long term operation (LTO) of nuclear power plants (NPPs). One of the steps in the process of LTO assessment is the revalidation of TLAAs (time limited ageing analyses). The safety margins of NPP Borssele with respect to fatigue were demonstrated by projecting the fatigue analyses to the end of the intended period of LTO. Besides this, it has to be ensured that the analyses remain valid during the entire period of LTO. Periodic verification of the load assumptions that are made in the analyses is therefore an important aspect of adequate fatigue management. In this paper, an integrated fatigue management approach is presented, coupling load monitoring, transient counting and fatigue assessment.
The approach for periodic verification of the load assumptions in the fatigue analyses consists of two parts. First, it is verified whether the occurred numbers of cycles of the different load cases remain smaller than the numbers of cycles assumed in the fatigue analyses. Secondly, it is verified whether the thermal transients defined for the load cases in the fatigue analyses conservatively represent the occurred thermal transients. For the verification, the application LEAF (Load Evaluation Application for Fatigue) was developed. At NPP Borssele, thermal transients occurring during different load cases (e.g. start-up, shutdown, reactor trip) are registered by a temperature monitoring system. The load evaluation application processes the measurement data and verifies the conservatism of the load conditions in the fatigue analysis of the fatigue relevant components in the system. This paper explains the steps that are followed for the load evaluation and gives a demonstration of the results. The presented procedure is an essential part of adequate fatigue management during LTO.
Effect of Carbide Content on Temper Embrittlement of 2.25Cr1Mo Steel
Authors: Wang Yian , Xie Guoshan , Zhang Zheng , Qian Xiaolong , Zhou Yufeng , Li Jing 
Published: December 2016

Temper embrittlement is a common damage mechanism of pressure vessels in the chemical and petrochemical industry serviced in high temperature, which results in the reduction of roughness due to metallurgical change in some low alloy steels. Pressure vessels that are temper embrittled may be susceptible to brittle fracture under certain operating conditions which cause high stress by thermal gradients, e.g., during start-up and shutdown. 2.25Cr1-Mo steel is widely used to make hydrogenation reactor due to its superior combination of high mechanical strength, good weldability, excellent high temperature hydrogen attack (HTHA) and oxidation-resistance. However, 2.25Cr-1Mo steel is particularly susceptible to temper embrittlement.
In this paper, the effect of carbide on temper embrittlement of 2.25Cr-1Mo steel was investigated. Mechanical properties and the ductile-brittle transition temperature (DBTT) of 2.25Cr-1Mo steel were measured by tensile test and impact test. The tests were performed at two positions (base metal and weld metal) and three states (original, step cooling treated and in-service for a hundred thousand hours).
The content and distribution of carbides were analyzed by scanning electron microscope (SEM). The content of Cr and Mo elements in carbide was measured by energy dispersive X-ray analysis (EDS). The results showed that the embrittlement could increase the strength and reduce the plasticity. Higher carbide contents appear to be responsible for the higher DBTT. The in-service 2.25Cr-1Mo steel showed the highest DBTT and carbide content, followed by step cooling treated 2.25Cr-1Mo steel, while the as-received 2.25Cr-1Mo steel has the minimum DBTT and carbide content. At the same time, the Cr and Mo contents in carbide increased with the increasing of DBTT. It is well known that the specimen analyzed by SEM is very small in size, sampling SEM specimen is convenient and nondestructive to pressure vessel. Therefore, the relationship between DBTT and the content of carbide offers a feasible nondestructive method for quantitative measuring the temper embrittlement of 2.25Cr-1Mo steel pressure vessel.
Steel-Concrete Composite Vessel for Stationary High-Pressure Hydrogen Storage
Authors: Wang Yanli , Feng Zhili , Ren Fei , Lim Yong Chae , Chen Jian , Jawad Maan 
Published: December 2016

A novel Steel Concrete Composite Vessel (SCCV) was designed and engineered for stationary high-pressure gaseous hydrogen storage applications. SCCV comprises four major innovations: (1) flexible modular design for storage stations for scalability to meet different storage pressure and capacity needs, flexibility for cost optimization, and system reliability and safety, (2) composite storage vessel design and construction with an inner steel vessel encased in a pre-stressed and reinforced outer concrete shellshell, (3) layered steel vessel wall and vent holes to address the hydrogen embrittlement (HE) problem by design, and (4) integrated sensor system to monitor the structural integrity and operation status of the storage system. Together, these innovations form an integrated approach to make the SCCV cost competitive and inherently safe for stationary high-pressure hydrogen storage services.
A demonstration SCCV has been designed and fabricated to demonstrate its technical feasibility. Capable of storing approximately 89 kg of gaseous hydrogen at 6250 psi (430 bar), the demonstration vessel was designed to include all major features of SCCV design and fabricated with today’s manufacturing technologies and code/standard requirements. Two crucial tests have been performed on this demonstration vessel. A hydro-test was successfully carried out to 8950 psi per ASME VIII-2 requirements. The cyclic hydrogen pressure test between 2000 psi and 6000 psi is currently being performed to validate its use for high-pressure hydrogen storage. Multiple sensors, such as pressure sensors and strain gages, were incorporated in the demonstration SCCV to collect information to validate the design and operation of SCCV. Key design parameters and test data on its performance are summarized in this paper.