bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent Studies Towards Updating the BS7910 Flaw Interaction Rule
Authors: Bezensek Bostjan , Coules Harry E. 
Published: October 2018

Fitness for service assessment procedures rely on flaw interaction rules for assessment of multiple flaws in close proximity. Such rules are aimed at avoiding excessive amplification of the crack driving force that may result in a non-conservative fracture assessment. In BS7910, the 2013 edition [1] introduced a new flaw interaction rule for the co-planar flaws where the proximity of adjacent flaws is judged based on flaw height (i.e. s = 0.5*max(a1,a2) for surface flaws). The rule was introduced for flaws with aspect ratio of a/c < 1 for both flaws, while for other flaw shapes and combinations the earlier rule from the predecessor document PD6493:1993 [2] was retained. This paper summarises the recent work done by the authors and work from literature to examine the applicability of the s = 0.5*max(a1,a2) rule to flaws with aspect ratio a/c ≥ 1 and dissimilar flaw combinations.
It is shown that the current BS7910 rule based on s = 0.5*max(a1,a2) produces a conservative flaw assessment with the use of BS7910 solutions for stress intensity factor and reference stress. An exception are cases of two deep surface flaws where the rule is proposed to change to:
s ≤ max(a1, a2) for two surface flaws with a1/t & a2/t > 0.5
Experimental Study of the Weld Residual Stress in Manually and Mechanically Fabricated Dissimilar Metal Weld
Authors: Duan Xinjian , Glover Andrew , Sun Dongmei , Paddea Sanjooram 
Published: October 2018

The dissimilar metal welds between the Inconel 600 flow element and the SA-106 Grade B carbon pipe with Alloy 82 or Alloy 182 filler material of some CANDU® designs have been identified as being susceptible to Primary Water Stress Corrosion Cracking (PWSCC). Initiation and growth of PWSCC in a Dissimilar Metal Weld (DMW) are driven primarily by Welding Residual Stresses (WRS). The present paper focuses on the experimental study of weld residual stress distribution in manually and mechanically fabricated DMWs with emphasis on the effect of repair.
A series of DMW samples are firstly fabricated in accordance with the original welding procedures for those DMWs in the field, which were fabricated in 1970s and 1980s. Multiple thermocouples were used to record the temperature evolution during the entire welding process. These samples were then examined by ASME qualified personnel in accordance with the requirements for Class 1 weld in Article 9 of Section V of ASME BVPC using Visual Testing (VT) and Radiography Testing (RT). Repair was then performed in some samples, and further NDE examinations were performed. The qualified samples (with and without repair) were finally subject to destructive weld residual stress measurement using contour method.
It is observed that weld repair dramatically changes the distribution of weld residuals tress. The use of a constant through-thickness WRS of 60,000 psi (415 MPa) is justified as the bounding case.
Formulation of Three-Dimensional J-Integral for Finite Strain Elastic-Plastic Fracture Problems Under Any Load Histories (Monotonic and Cyclic Loads)
Authors: Arai Koichiro , Okada Hiroshi , Yusa Yasunori 
Published: October 2018

In this paper, a redefined three-dimensional J-integral for the quadratic tetrahedral element along with some numerical examples are presented. It is known that the J-integral represents the energy release rate and can be computed on an arbitrary path or a domain of integration. This feature is called the “path-independent property”. It requires the assumption of proportional loading in the case of elastic-plastic material. Because of this assumption, when the J-integral is applied to a problem under a non-proportional loading condition, the computed J-integral value depends on the integral path or the integral domain.
To overcome this problem, the authors have proposed a formula to evaluate the energy dissipation inside a finite domain in the vicinity of the crack front, which is an extension of the conventional three-dimensional J-integral. The energy dissipating into a small but finite domain in the vicinity of crack front includes the energy released due to the opening of new crack faces and the deformation energy in the process zone. The numerical evaluation is carried out by the domain integral. In this formula, it is not necessary to evaluate any non-integrable terms at the crack front. Furthermore, the proposed formula has the feature of integral domain independence for any material models without any assumptions in their deformation histories. Therefore, it is possible to evaluate the J-integral for problems with non-proportional loads by using the proposed method.
In this paper, computational method using the quadratic tetrahedral element for the redefined J-integral under non-proportional loading is presented first. Some results of three-dimensional semi-circular surface crack problem are presented as numerical examples.
Negative R Fatigue Crack Growth Rate Testing on Austenitic Stainless Steel in Air and Simulated Primary Water Environments
Authors: Platts Norman , Coult Ben , Zhang Wenzhong , Gill Peter 
Published: October 2018

Light water reactor coolant environments are known to significantly enhance the fatigue crack growth rate of austenitic stainless steels. However, most available data in these high temperature pressurized water environments have been derived using specimens tested at positive load ratios, whilst most plant transients involve significant compressive as well as tensile stresses. The extent to which the compressive loading impacts on the environmental enhancement of fatigue crack growth, and, more importantly, on the processes leading to retardation of those enhanced rates is therefore unclear, potentially leading to excessive conservatism in current assessment methodologies.
A test methodology using corner cracked tensile specimens, and based on finite element analysis of the specimens to generate effective stress intensity factors, Keff, for specimens loaded in fully reverse loading has been previously presented. The current paper further develops this approach, enabling it to be utilized to study a range of positive and negative load ratios from R = −2 to R = 0.5 loading, and provides a greater understanding of the development of stress intensity factor within a loading cycle.
Test data has been generated in both air and high temperature water environments over a range of loading ratios. Comparison of these data to material specific crack growth data from conventional compact tension specimens and environmental crack growth laws (such as Code Case N-809) enables the impact of crack closure on the effective stress intensity factor to be assessed in both air and water environments. The significance of indicated differences in the apparent level of closure between air and water environments is discussed in the light of accepted growth laws and material specific data.
Comparison Between the ASME BPVC Section VIII Division 3 and the Chinese Regulation TSG 21-2016 With Regard to the Design of High Pressure Vessels
Authors: Fuenmayor David , Wink Rolf , Bortz Matthias 
Published: October 2018

There are numerous codes covering the design, manufacturing, inspection, testing, and operation of pressure vessels. These national or international codes aim at providing assurance regarding the safety and quality of pressure vessels.
The development of the Chinese economy has led to a significant increase in the number of installed high-pressure vessels which in turn required a revision of the existing regulations.
The Supervision Regulation on Safety Technology for Stationary Pressure Vessel TSG 21-2016 superseded the existing Super-High Pressure Vessel Safety and Technical Supervision Regulation TSG R0002-2005 in October of 2016.
This new regulation covers, among others, the design, construction, and inspection of pressure vessels with design pressures above 100 MPa. This paper provides a technical comparison between the provisions given in TSG 21-2016 for super-high pressure vessels and the requirements in ASME Boiler and Pressure Vessel Code Section VIII Division 3.
Modelling of Fatigue due to Thermal Mixing by Using a Spectrum Method
Authors: Timperi Antti 
Published: October 2018

Turbulent mixing of cold and hot fluids can lead to high-cycle thermal fatigue in T-junctions, but modelling of the thermal load induced to the structure is challenging. The spectrum method has been recently proposed as an efficient modelling method, which uses a theoretical turbulence spectrum to represent the fluctuating thermal load. In this work, further development and application of the method is presented. Estimation of the frequency of the largest-scale temperature fluctuations is considered in particular, as this is an essential input parameter for the model spectrum.
The method is applied to a T-junction including a mixer pipe and a high temperature difference that induces significant buoyancy effects. The frequency scale of the fluctuations is determined for the flow case based on temperature spectra obtained from a Computational Fluid Dynamics (CFD) simulation. A formula for the frequency scale is proposed, which can be used in approximating the frequency scale for other flow conditions. Fatigue and crack growth analysis of the T-junction wall are carried out by using the spectrum method, and the results are compared with those obtained with sinusoidal and CFD temperature loads. The results indicate improvement in accuracy over the highly simplified sinusoidal method.
Flamanville EPR RPV’s Heads Carbon Segregation: Characterization of the Segregation in the Heads
Authors: Fichot Philippe , Calonne Olivier , Segond Mathieu , Marie Stéphane , Desnoyers Yvon , Hajjaj Mejido , Miller Cecile 
Published: October 2018

To characterize the mechanical properties of the residual carbon segregation of the Flamanville EPR RPV heads, a testing program has been defined by Framatome using three sacrificial representative heads. The first step of this program was a 3D characterization of the carbon content inside each piece.
A specific strategy has been defined using two methods for the carbon measuring:
- In situ measurements using a mobile arc spark spectrometer. This device allows a higher number of non-destructive measurements in a particularly constrained environment and in a short time,
- Conventional spectrometry performed on chips sampled from the pieces. This technique is more accurate but is destructive and more time consuming.
Also, to consolidate the representativeness of the sacrificial vessels heads, the results were analysed using a geostatistical approach. This paper presents how these two techniques have been used to characterize the carbon content in the segregated part of the pieces and the conclusion of the geostatistical analyses.
Stress Intensity Factors for Circular-Arc Cracks in Plates
Authors: Shim D. J. , Tang S. , Kim T. J. , Huh N. S. 
Published: October 2018

Stress intensity factor solutions are readily available for flaws found in pipe to pipe welds or shell to shell welds (i.e., circumferential/axial crack in cylinder). In some situations, flaws can be detected in locations where an appropriate crack model is not readily available. For instance, there are no practical stress intensity factor solutions for circular-arc cracks which can form in circular welds (e.g., nozzle to vessel shell welds and storage cask closure welds).
In this paper, stress intensity factors for circular-arc cracks in finite plates were calculated using finite element analysis. As a first step, stress intensity factors for circular-arc through-wall crack under uniform tension and crack face pressure were calculated. These results were compared with the analytical solutions which showed reasonable agreement. Then, stress intensity factors were calculated for circular-arc semi-elliptical surface cracks under the lateral and crack face pressure loading conditions. Lastly, to investigate the applicability of straight crack solutions for circular-arc cracks, stress intensity factors for circular-arc and straight cracks (both through-wall and surface cracks) were compared.
Experiences in Developing a Practical Algorithm of Identification and Attenuation of Pressure Pulsation and Piping Vibration in Gas Reciprocating Compressor Plants and Other Systems
Authors: Rydlewicz Maciej , Rydlewicz Wojciech 
Published: October 2018

This paper presents results of research on practical engineering solutions to suppress pressure pulsation and mechanical vibrations in piping systems. It concerns both new build and retrofitted plants. Analyses were performed according to ASME B31, EN-13480 and API 618 codes. Solutions were considered for natural gas reciprocating compressor stations (gaseous media) and liquid hydrocarbons plant with various pumps.
Pressure pulsation in a piping system is a source of dynamic forces. Unbalanced pressure layout in the piping system results in the presence of dynamic forces that may excite mechanical vibrations [1,7, 22, 23, 24].
In industrial applications, mechanical vibrations are present mostly in resonant conditions. Since hundreds of eigenvalues can characterise the piping system, it is crucial to identify the key ones, which are likely to be excited to vibrate. Therefore, it is necessary to allow adequate modelling and subsequent analysis of the fluid-structure interaction with available engineering tools.
Limit Strains of X70 Pipes With a Semi-Elliptical Crack Based on Initiation and Ductile Tearing Criteria
Authors: Kang Ju-Yeon , Jang Youn-Young , Huh Nam-Su , Kim Ki-Seok , Cho Woo-Yeon 
Published: October 2018

Crack-tip opening displacement (CTOD) and J-integral have been used for elastic-plastic fracture parameters as a crack driving force (CDF) and crack resistance curve to evaluate tensile strain capacity (TSC) of cracked pipelines based on strain-based design (SBD). The TSC can be determined by using two kinds of failure criteria. One is based on the limit state corresponding to an onset of stable crack growth and the other is tangency approach which determines an onset of unstable crack growth by comparing crack driving force and resistance curve. For this reason, the accurate calculation of crack driving force and crack resistance curve is highly required to determine TSC.
In the present study, the TSCs for X70 pipelines with a circumferential semi-elliptical surface crack were estimated based on both crack initiation and ductile tearing criteria using crack driving force diagram (CDFD) method. The CDF curves of cracked pipelines were calculated through the detailed elastic-plastic finite element (FE) analyses. Crack resistance curves were obtained from experimental data of single edged notch tension (SENT) specimens. Both the CDF and crack resistance curves were represented using CTOD and J-integral, respectively. As for loading conditions, axial strain and internal pressure were considered. The TSCs based on CTOD were compared with those based on J-integral to investigate the effect of choice of the fracture parameters on TSC. From the FE results, the TSCs based on ductile tearing allowed higher TSCs than those based on crack initiation. Although there were some differences between the TSCs using CTOD and J-integral, the effect of choice of fracture parameter on TSC with internal pressure was not significant.
Numerical Investigations on the Interaction of Cracks in Quasi-Laminar Crack Fields
Authors: Swacek Christian , Schuler Xaver , Seidenfuss Michael 
Published: October 2018

Non-destructive testing measurements in the Belgian nuclear power plants Doel 3 and Tihange 2 revealed a high quantity of indications in the upper and lower core shells of the reactor pressure vessels. The most likely explanation is that the indications are hydrogen flakes positioned in segregated zones of the base material of the pressure vessel. These hydrogen flakes have a laminar and quasi-laminar orientation to the pressure retaining surface. Under mechanical loading the crack tips undergo predominantly mixed mode loading conditions, where the induced stress and strain fields of the single crack tips influence each other. Due to these specific loading conditions, the assumptions for classical standardized fracture mechanical methods are not met. Currently, there is no verified concept for the evaluation of such kind of crack fields.
Therefore the mechanical behavior of components with laminar crack fields and the interaction of cracks in such crack fields are investigated in an ongoing research project. Relevant parameters to describe crack fields in terms of crack size, crack location and crack orientation are derived from literature and own nondestructive measurements. Damage mechanical approaches are used in finite element calculations to investigate the interaction of cracks. Advanced damage mechanical models will be used to investigate crack initiation, crack growth and coalescence of cracks in crack fields. According to the results, representative parameters for crack fields will be derived and critical crack formations determined. The results will be evaluated and compared with state of the art approaches and standards.
2018 RCC-MRx Code Edition: Context, Overview, On-Going Developments
Authors: Pétesch Cécile , Lebarbé Thierry , Gelineau Odile , Vallot Damien , Blat-Yrieix Martine 
Published: October 2018

The 2018 edition of the RCC-MRx Code (1) will be issued, by the end of the 2018, in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires). This Code set up rules applicable to research reactor components (coming from the RCC-MX 2008 developed in the context of the Jules Horowitz Reactor project), to reactor components operating at high temperature (coming from the RCC-MR 2007) and to the Vacuum Vessel of ITER (also coming from the RCC-MR 2007).
This edition takes the benefits of an important feedback of the users, such as Jules Horowitz Reactor or ASTRID project, but also from ITER and MYRRHA projects.
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 CEN Workshop 64 phase 2. The end of the workshop, planned for 2018, will allow to integrate recommendations issued from this work in the code.
This paper gives an overview of the performed work and also identifies the work to be done for a development of a standard such as RCC-MRx code.
Analysis of a Weld Overlay to Address Fatigue Cracking in a Stainless Steel Nozzle
Authors: Marlette S. E. , Udyawar A. , Broussard J. 
Published: October 2018

For several decades the nuclear industry has used structural weld overlays (SWOL) to repair and mitigate cracking within pressurized water reactor (PWR) components such as nozzles, pipes and elbows. There are two known primary mechanisms that have led to cracking within PWR components. One source of cracking has been primary water stress corrosion cracking (PWSCC). Numerous SWOL repairs and mitigations were installed in the early 2000s to address PWSCC in components such as pressurizer nozzles. However, nearly all of the likely candidate components for SWOL repairs have now been addressed in the industry. The other cause for cracking has been by fatigue, which usually results from thermal cycling events such as leakage caused by a faulty valve close to the component. The PWR components of most concern for fatigue cracking are mainly stainless steel. Thus, ASME Section XI Code Case N-504-4 would be a likely basis for SWOL repairs of these components, although this Code Case was originally drafted to address stress corrosion cracking (SCC) in boiling water reactors (BWR). N-504-4 includes the requirements for the SWOL design and subsequent analyses to establish the design life for the overlay based on predicted crack growth after the repair.
This paper presents analysis work performed using Code Case N-504-4 to establish the design life of a SWOL repair applied to a boron injection tank (BIT) line nozzle attached to the cold leg of an operating PWR. The overlay was applied to the nozzle to address flaws found within the stainless steel base metal during inservice examination. Analyses were performed to calculate the residual stresses resulting from the original fabrication and the subsequent SWOL repair. In addition, post-SWOL operating stresses were calculated to demonstrate that the overlay does not invalidate the ASME Section III design basis for the nozzle and attached pipe. The operating and residual stresses were also used for input to a fatigue crack growth (FCG) analysis in order to establish the design life of the overlay. Lastly, the weld shrinkage from the application of overlay was evaluated for potential impact on the attached piping, restraints and valves within the BIT line. The combined analyses of the installed SWOL provide a basis for continued operation for the remaining life of the plant.
Influence of Hydrogen on Tensile and Fatigue Life Properties of 304/308 Austenitic Stainless Steel Butt Welded Joints
Authors: Okazaki Saburo , Matsunaga Hisao , Nakamura Masami , Hamada Shigeru , Matsuoka Saburo 
Published: October 2018

To investigate the influence of hydrogen on the tensile and fatigue life properties of welded joints of 304/308 austenitic stainless steels, slow strain rate tensile (SSRT) tests and fatigue life tests were conducted in laboratory air using hydrogen exposed specimens. The specimens were fabricated from welded plates, and to elucidate the role of weld structure on hydrogen-induced degradation, the welded joint was solution-treated. In the SSRT tests of the as-welded (AW) joint, a non-exposed specimen failed at the base metal (BM), whereas a hydrogen-exposed specimen failed near the weld toe. In the case of the solution-treated-welded (STW) joint, the non-exposed specimen failed at the part of solution treated weld metal, whereas an H-exposed specimen failed near the weld toe. As a result, internal hydrogen significantly degraded the elongation of the AW joint.
In the fatigue test, all the specimens failed near the weld toe. Internal hydrogen degraded the fatigue life considerably. However, the pre-charging led to little, if any, reduction in the fatigue limit. Similarly to the AW joint, hydrogen gas exposure notably degraded the fatigue life of the STW joint and led to little reduction in the fatigue limit. To investigate the relationship between the hydrogen-induced degradation and strain-induced martensitic transformation during fatigue testing, the volume fraction of ferrite in the broken specimens was measured by a ferrite scope. The volume fraction of martensitic transformation increased with an increase in the stress amplitude. These experimental results implied that the hydrogen-induced fatigue life degradation in the welded joint was closely related to the martensitic transformation during the fatigue process. The mechanisms of both the degradation in fatigue life and nondegradation in fatigue limit will be discussed further.