bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Characteristic of Flow Induced Vibration Caused by Turbulence Relating to Acoustically Induced Vibration
Authors: Nishiguchi Masato , Izuchi Hisao , Minorikawa Gaku 
Published: November 2014

In the flare piping system, it is known that piping vibrations occur caused by Acoustically Induced Vibration (AIV) and Flow Induced Vibration (FIV) corresponding to high flow rate, high pressure drop and relatively thin pipe wall thickness. For FIV, turbulence generated at combining tee with high fluid velocity results in low frequency piping vibration. For AIV, large noise produced through a component with large pressure drop results in high frequency piping vibration. Carucci and Mueller shows the several cases with piping failure due to AIV and most of these cases the piping failure occurred at the combining tee. In these piping failure cases, the velocity at the combining tee would be quite high close or equal to sound speed and this means piping vibrations could occur due to FIV in addition to AIV.
This paper shows the investigation results of FIV at combining tee with 90 degrees using experimental data. The results are compared to the previous study results for 45 degrees combining tee and the difference between 90 and 45 degrees tees are discussed in the view points of pressure fluctuation and piping vibration. This paper also shows that the vibration index proposed by authors is quite effective to evaluate the vibration level caused by FIV for both of 90 and 45 degrees tees. This proposed vibration index is applied to failure and no failure cases presented in Carucci and Mueller paper with some assumptions and it is suggested that the vibration indexes for failure case is relatively higher than those of no failure cases. And this suggests that not only AIV but also FIV could affect the piping failure reported in Carucci and Mueller paper.
Verification Analyses for Newly Developed Automatic 3D Finite Element Crack Propagation System
Authors: Doi Hiroaki , Nakamura Hitoshi , Gu Wenwei , Shim Do-Jun , Wilkowski Gery 
Published: November 2014

In order to calculate the crack propagation in complicated-shaped locations in components such as weld in penetration structures of reactor pressure vessel of nuclear power plants, an automatic 3D finite element crack propagation system (CRACK-FEM) has been developed by the Nuclear Regulation Authority (NRA, Japan). To confirm the accuracy and effectiveness of this analysis system, a verification analysis was performed. The program used for comparison is PipeFracCAE developed by Engineering Mechanics Corporation of Columbus, which has been used for many crack propagation analyses in various applications. In this paper, the axial crack propagation analysis for primary water stress corrosion cracking (PWSCC) in a steam generator inlet nozzle of a pressurized water reactor (PWR) plant is presented. The results demonstrate that the two codes are in good agreement.
The contents of this paper were conducted as a research project of the Japan Nuclear Energy Safety Organization (JNES) when one of the authors (Doi) belongs to JNES. After this project, JNES was abolished and its staff and task were absorbed into NRA on March 1, 2014.
Advances in NDE of DM Welds From RPV ID
Authors: Thigpen B. A. , Glass S. W. 
Published: November 2014

In Pressurized Water Reactors (PWRs), the similar and dissimilar welds joining the reactor pressure vessel (RPV) nozzles to the main coolant piping have normally been volumetrically examined as part of the full 10-year RPV inspection. Generally due to access challenges to the outside diameter (OD) surface, these examinations have been performed from the component inside diameter (ID) surface. In the US and for many plants around the world, these welds fall under the requirements of the ASME B&PV Code Section XI, Appendix VIII performance demonstration as mandated by the applicable safety authority, requiring blind demonstration of detection and sizing accuracy on known defects. Many in-service inspection (ISI) vendors have qualified themselves for ID these examinations under the EPRI Appendix VIII Performance Demonstration (PD) program since it’s initiation in the early 2000s, but examination of the wavy surface DM welds and field welds (closure welds) has been a challenge for virtually all vendors to achieve the target 0.125″ RMS depth sizing error. This has been managed by assuming a larger depth sizing error corresponding to whatever the vendor’s PD assessed error was should an indication be found that required accurate sizing to justify continued plant operation. Moreover, vendors have been reluctant to re-qualify their systems as new tools have immerged due to the high associated cost.
Equipment obsolescence and an interest to apply the latest technology prompted AREVA to undertake a re-qualification for these welds. This has allowed use of more advanced phased array techniques with 3-D wavy surface compensation. In addition, a new nozzle examination tool, NEMO has been developed. Such a tool is particularly suitable for plants where the nozzles must be examined on their 10 year or shorter interval schedule but where the vessel examination can be deferred to 20 years. This paper discusses the detection and sizing advances for these wavy surface DM welds as well as the first deployment of the NEMO tool.
Study of Creep Cavitation in a Stainless Steel Weldment Using Small Angle Neutron Scattering and Scanning Electron Microscopy
Authors: Jazaeri H. , Bouchard P. J. , Hutchings M. T. , Lindner P. 
Published: November 2014

Strain-relief cracking, also referred to as reheat cracking, is a generic creep failure mode that has been observed in many welded stainless steel structures operating at high temperatures in UK nuclear power plant. One of the challenges currently faced by nuclear utility EDF Energy is the need to predict, with high certainty, the life-time of ageing engineering plant operating in the creep regime.
A study of creep cavities near a reheat crack, ∼28 mm long, in an AISI Type 316H austenitic stainless steel header is reported. The cracked component was removed after 65,000 hours operation at a mean temperature of 525°C in a nuclear power plant. Creep cavities in the vicinity of the crack are observed using scanning electron microscopy (SEM) and found to be mainly surrounding inter-granular carbides. Optimized metallographic and image analysis procedures are used to quantify the size and area fraction of creep cavities as a function of distance from the crack along a line normal to the crack face. Small angle neutron scattering (SANS) is used to quantify creep cavitation, averaged over a large gauge volume, ∼20 mm3, at similar positions normal to the crack line. A systematic increase in the true fractional size distribution of cavities is observed approaching the crack. The cavity size distribution peaks between 100–300 nm diameter and this correlates closely with the quantitative metallography results of cavities in this sample. SANS has the advantage of being non-destructive and also the examined volume is several mm3, against an area of hundreds of μm2 in the case of SEM, therefore giving more statistically significant results. However the two techniques are complementary, as the detailed microscopic information from SEM is required to interpret the SANS data.
Further Development of the Nonlocal Damage Model of Rousselier for the Transition Regime of Fracture Toughness and Different Stress States
Authors: Gehrlicher Sarah , Seidenfuss Michael , Schuler Xaver 
Published: November 2014

In nuclear power engineering failure has to be excluded for components with high safety relevance. Currently, safety assessments mainly use fracture mechanics concepts. Especially in the transition region of fracture toughness where limited stable crack extension may appear before cleavage fracture the currently applied methods are limited.
This Paper deals with the development and verification of a closed concept for safety assessment of components over the whole range from the lower shelf to the upper shelf of fracture toughness. The results of classical used local damage mechanics models depend on the element size of the numerical model. This disadvantage can be avoided using an element size depending on microstructure. With high stress gradients and small crack growth rates usually smaller elements are required. This is in conflict with an element size depending on microstructure. By including the damage gradient as an additional degree of freedom in the damage mechanics model the results depend no longer at the element size. In the paper damage mechanics computations with a nonlocal formulation of the Rousselier model are carried out for the evaluation of the upper transition area. For the prediction of fracture toughness from the ductile to brittle transition area the nonlocal Rousselier model is coupled with the Beremin model. Thus ductile crack growth and failure by brittle fracture can be described in parallel. The numerical prediction of the behaviour of fracture toughness specimens (C(T)-specimens and SE(B)-specimens with and without side grooves) and the experimental results are highly concordant. The load displacement behavior of the specimens and the developed crack front from the ductile to brittle transition area can be well calculated with the nonlocal damage model. The instability in relation to temperature calculated with the coupled damage mechanics model predicts the variations of the experimental results very well.
For further application of the nonlocal Rousselier model experiments and numerical calculations of specimens with different stress states and multi-axiality are carried out. Modified fracture toughness specimens like CTS-specimens (compact tension shear specimens) are taken to investigate the applicability of the nonlocal damage model of Rousselier to mixed mode fracture.
Volumetric Examination After PWHT on a Carbon Steel Pressure Vessel
Authors: Becker James W. , Schulte Matthew L. 
Published: November 2014

Carbon steel pressure vessels may require post weld heat treatment (PWHT) for stress relief in accordance with global pressure vessel safety codes. When stress relieved, most of these vessels receive a full volumetric exam, such as radiography or ultrasound. Many supplementary design specifications require the volumetric exam take place after PWHT; however, when a volumetric exam after PWHT is required, vessel fabricators commonly perform an additional examination before PWHT to mitigate the risk of a second PWHT cycle. The increased cost associated with performing two full volumetric exams is passed on to the end-user of the pressure vessel.
This investigation examines the need for a volumetric exam after PWHT on a carbon steel pressure vessel. Following a literature review and after analysis of radiography results from vessel fabricators in the United States, there is little evidence supporting a volumetric examination requirement after PWHT. PWHT does not cause sub-surface flaw development or sub-surface flaw propagation. A surface examination after PWHT is still recommended to confirm flaws have not developed near the surface during PWHT; however, a full volumetric examination on a carbon steel vessel after PWHT may be unnecessary.
Nonlinear Normal Modes and the Dahl Friction Model Parameter Identification
Authors: Hadji Abdallah , Mureithi Njuki 
Published: November 2014

Fretting wear of steam generator tubes due to vibration induced by fluid flow remains a serious problem in the nuclear industry. Azizian and Mureithi [1] have recently developed a hybrid friction model to simulate the friction behavior of tube-support interaction. However, identification of the model parameters remains unresolved.
To identify the parameters of the friction model, the following quantities are required: contact forces (tangential force (friction) and normal force (impact)), the slip velocity and displacement in the contact region. Direct measurement of these quantities by using a steam generator tube interacting with its supports is difficult. To simplify the problem, a beam, clamped at one end and simply supported with consideration of friction effect at the other is used. The beam acts as a mechanical amplifier of the friction effects at the microscopic level. Using this simple setup, the contact forces, the sliding velocity and the displacement can be indirectly obtained from the beam’s vibration response measurements.
A new method based on nonlinear modal analysis was developed to calculate the contact forces. This method is based on the modal superposition principle and Fourier series expansion. The nonlinear normal modes (NNMs) and the generalized coordinates (GCs) have been identified experimentally as functions of the excitation level, the frequency, the preload in the contact area, with and without lubrication.
Three hypotheses and related analyses to identify the NNMs and GCs were tested; the analysis based on the harmonic balance method gives the best results for reconstructing the accelerometer signals with an error less than 2% for all excitation levels compared to more than 2% for other methods.
The successful signal reconstruction makes it possible to accurately identify the parameters of the Dahl friction model. This is also the first step to identify the parameters of the hybrid friction model.
Ultrasonic Sound Field Mapping Through Coarse Grained Cast Austenitic Stainless Steel Components
Authors: Crawford Susan L. , Prowant Matthew S. , Cinson Anthony D. , Larche Michael R. , Diaz Aaron A. , Anderson Michael T. 
Published: November 2014

The Pacific Northwest National Laboratory (PNNL) has been involved with nondestructive examination of coarse-grained cast austenitic stainless steel (CASS) components for over 30 years. More recent work has focused on mapping the ultrasonic sound fields generated by low-frequency phased-array probes that are typically used for the evaluation of CASS materials for flaw detection and characterization. The casting process results in the formation of large-grained material microstructures that are nonhomogeneous and anisotropic. The propagation of ultrasonic energy for examination of these materials results in scattering, partitioning, and redirection of these sound fields. The work reported here provides an assessment of sound field formation in these materials and provides recommendations on ultrasonic inspection parameters for flaw detection in CASS components.
Confirmatory research conducted at PNNL consisted of acquiring sound field data from four CASS components containing columnar, equiaxed, and banded grain structures, and a fine-grained wrought stainless steel specimen used for benchmarking. Phased-array probes with center frequencies of 0.5, 0.8, and 1.0 MHz were used for sound field formation, with a pinducer being raster scanned over the end of the specimen face to capture the sound field energy. Data were collected at multiple refracted and skew angles, and imaging performed for analyses. A 6.4-mm (0.25-in.) thick slice of material was removed from the end of the CASS components and the beam mapping repeated. This slicing and mapping sequence was performed three times to produce multiple beam images through the specimens. Grain sizes were also measured at each mapped specimen face and compared to sound field characteristics. The acquired sound field images were characterized in terms of beam redirection from the theoretical position, beam scatter or coherence, and partitioning. A comparison of the fine-grained beam data to the CASS data is made and conclusions are presented.
Evaluation of Residual Stresses in Small Diameter Stainless Steel Pipe Welds by Two-Dimensional and Three-Dimensional Finite Element Analyses
Authors: Ku Francis H. , Hicks Trevor G. , Mabe William R. , Miller Jason R. 
Published: November 2014

Two-dimensional (2D) and three-dimensional (3D) weld-induced residual stress finite element analyses have been performed for 2-inch Schedule 80 Type-304 stainless steel pipe sections joined by a multi-layer segmented-bead pipe weld. The analyses investigate the similarities and differences between the two modeling approaches in terms of residual stresses and axial shrinkage induced by the pipe weld. The 2D analyses are of axisymmetric behavior and evaluate two different pipe end constraints, namely fixed-fixed and fixed-free, while the 3D analysis approximates the non-axisymmetric segmented welding expected in production, with fixed-free pipe end constraints.
Based on the results presented, the following conclusions can be drawn. The welding temperature contour results between the 2D and 3D analyses are very similar. Only the 3D analysis is capable of simulating the non-axisymmetric behavior of the segmented welding technique. The 2D analyses yield similar hoop residual stresses to the 3D analysis, and closely capture the maximum and minimum ID surface hoop residual stresses from the 3D analysis. The primary difference in ID surface residual stresses between the 2D fixed-fixed and 2D fixed-free constraints cases is the higher tensile axial stresses in the pipe outside of the weld region. The 2D analyses under-predict the maximum axial residual stress compared to the 3D analysis. The 2D ID surface residual stress results tend to bound the averaged 3D results. 2D axisymmetric modeling tends to significantly under-predict weld shrinkage. Axial weld shrinkage from 3D modeling is of the same magnitude as values measured in the laboratory on a prototypic mockup.
Fatigue Behavior of Butt Weld Seams: Experimental Investigation and Numerical Simulation
Authors: Langschwager Kay , Bosch Alexander , Lang Eliane , Rudolph Jürgen , Vormwald Michael , Scholz Alfred , Oechsner Matthias 
Published: November 2014

Austenitic stainless steel of type X6CrNiNb18-10 (1.4550) is a widely used material in piping and components of nuclear power plants. The fatigue behavior of these components is often operationally determined by thermomechanical strains and corresponding stresses. Welded structures lead to complex stresses in the component and potential fatigue lifetime reductions. Various geometrical and microstructural inhomogeneities in welded structures represent the main factors of influence. Nevertheless, clear identification and quantification of various factors of influence are issues still to be resolved.
Within the framework of an ongoing research project, the experimental investigation comprises uniaxial and biaxial fatigue experiments on welded joints which cover temperatures from 25°C to 350°C. Furthermore, a key issue deals with the thermomechanical fatigue behavior of machined and unmachined butt weld seams. A special focus is set on typical low cycle fatigue (LCF) tests in order to explain the behavior of the base material and the weld material to identify the influence of microstructural inhomogeneities. In addition, specimens manufactured directly from the pipe components are tested to examine the influence of the butt weld seam geometry. For a better understanding of the local strain effects, optical strain field measurements (OSFM) are conducted and used to validate numerical simulation. The finite element method (FEM) is utilized to expand the parameter space and identify the main parameters.
Experimental and numerical results show that fatigue failure occurs either in the base metal in the vicinity of the welded zone or in the top layer of the weld, depending on the loading conditions. This knowledge is used to develop an approach to fatigue lifetime estimation.
Limit Plastic Collapse on Remaining Ligament of Flawed Welds for ECA Application
Authors: Carlucci Antonio , Mcirdi Kamel 
Published: November 2014

Engineering Critical Assessments (ECAs) are routinely used to provide defect acceptance criteria for pipelines girth welds. The Failure Assessment Diagram (FAD) concept is the most widely used methodology for elastic-plastic fracture mechanics analysis of structural components and adopted by standards/documents including BS7910 [1], API579-1/ASME FFS-1 [2], R6 [3]. It is defined by two criterion Kr and Lr which describe the interaction between brittle fracture and fully ductile rupture: Kr measures the proximity to brittle fracture whereas Lr reflects the closeness to plastic collapse.
The BS7910 FAD level 2B is the most employed for assessment of flaws under mechanical strain lower than 0.4%, the FAD associated is material-specific and it based on single toughness value obtained from CTOD test, the latter-on gives no information about the tearing initiation.
The objective of this paper is to propose an approach for determination of the critical fracture toughness (associated to zero-tearing: JΔa=0). This approach is based on the comparison between the load-CMOD curve provided from a fracture toughness test to the one obtained by Finite Element Analysis (FEA). The goals is to propose a conservative guidance on how to identify a remote strain level below which it may be considered guaranteed the integrity of the remaining ligament.
Simplified Toughness Resistance Curve
Authors: Carlucci Antonio , Mcirdi Kamel , Auvret Pierre-Louis , Li Jun 
Published: November 2014

This paper presents a method in order to plot a simplified toughness resistance curve (R-Curve) from three single conventional toughness tests.
The simplified toughness resistance curve will be used to carry out a tearing assessment as part of Engineering Criticality Assessment (ECA) (ref. to Level 3B, [2]). This level of assessment takes into account of stable tearing in order to reduce over-conservatism, but it usually requires additional toughness tests to identify the toughness resistance curve. This present method allows to reach this assessment level without impacting the welding procedure qualification (WPQ).
Structural Performance of Steel Pipe Tee-Junctions
Authors: Papatheocharis Theocharis , Diamanti Kalliopi , Varelis George E. , Perdikaris Philip C. , Karamanos Spyros A. 
Published: November 2014

The behavior of steel pipe junctions (Tees) subjected to strong loading in the presence of internal pressure is examined in the present study. The analysis is based on a set of monotonic and cyclic out-of plane bending tests under constant and increasing amplitude displacement-controlled loading schemes leading to low-cycle fatigue failure.
Rigorous finite element models are developed to support the experiments, accounting for detailed dimensional measurements and material testing results obtained prior to testing. A parametric analysis is also conducted focusing on the effect of the geometrical characteristics on the overall junction behavior. The performance of the Tee-junctions with varying geometries under out-of plane bending, in-plane bending and axial loading is also examined numerically accounting for the presence of internal pressure.
Comparison Between ASME Code-Case N-761, NUREG/CR-6909 and Stainless Steel Component Fatigue Test Results
Authors: Harrison H. T. , Gurdal Robert 
Published: November 2014

For Class 1 components, the consideration of the environmental effects on fatigue has been suggested to be evaluated through two different methodologies: either NUREG/CR-6909 from March 2007 or ASME-Code Case N-761 from August 2010. The purpose of this technical paper is to compare these two methods. In addition, the equations from Revision 1 of the NUREG/CR-6909 will be evaluated.
For these comparisons, two stainless steel component fatigue test series with documented results are considered. These two fatigue test series are completely different from each other (applied cyclic displacements vs. insurge/outsurge types of transients). Therefore, they are producing an appropriate foundation for these comparisons.
In general, the severities of the two methods are compared, where the severity is defined as the actual number of cycles from the fatigue tests, including an evaluation of the scatter, divided by the number of design cycles from the two methods. Also, how stable the methods are is being evaluated through the calculation of the coefficient of variation for each method.