bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability Prediction of 304 Stainless Steel Using Sine-Hyperbolic Creep-Damage Model With Monte Carlo Simulation Method
Authors: Hossain Md Abir , Stewart Calvin Maurice
Published: November 2019

Typically continuum damage mechanics (CDM) based constitutive models are applied deterministically where the uncertainty of experiments is not considered. This is also true for the Sine-hyperbolic (Sinh) CDM-based constitutive model where the model is calibrated to represent 50% reliability of creep data. There is a need to implement Sinh in a more stochastic manner. The objectives of this study is to incorporate the probabilistic feature in the Sinh creep damage model to reliably predict the minimum-creep-strain-rate, creep-rupture and creep deformation. This will be achieved using Monte-Carlo methods. Creep deformation data for 304 Stainless Steel is collected from literature consisting of tests conducted at 300 and 320 MPa at 600°C with five replicates. The replicate tests exhibited substantial scatter in the minimum-creep-strain-rate, stress-rupture, and overall creep deformation. Subsequently, upon calibration using the Sinh model, the material constants among the replicates varied. The trends of uncertainty carried by each material constant are studied. The interdependence of the material constants is evaluated to determine if the uncertainty carried by each material constant can be regressed using a co-dependence function. The Monte Carlo method was applied to determine the extent that the creep deformation curve varies taking into consideration the variability of the material constants. Monte Carlo simulations show that the predicted creep deformation persists within the bounds of the experimental data. A large number of Monte Carlo simulations using the Sinh model enabled the creation of credible reliability bands for the minimum-creep-strain-rate, stress-rupture, and creep deformation of 304 Stainless Steel. In future work, this statistical method will be applied to the variability of service conditions, pre-existing defects, and material constants to quantitatively establish the reliability of the Sinh model in simulating component-level creep deformation to rupture.
Predicting Crack Velocity and Fracture Arrest Pressure From Simulations of Dynamic Pipe Rupture
Authors: Williams Bruce W. , Xu Su , Tyson William R.
Published: November 2019

During a gas pipeline rupture event, the crack propagation velocity can exceed 300 m/s and the crack can run for several hundreds of metres before arresting. The current model to predict arrest pressure is the Battelle Two Curve Method (BTCM) using the Charpy V-notch energy to characterize propagation toughness. It has been shown that this model can give non-conservative predictions for high-strength pipe steels. Hence, the Crack Tip Opening Angle (CTOA) has been introduced as a promising parameter to describe crack propagation. The objective of the current work was to study the crack propagation process in pipe by Finite Element Analysis (FEA) techniques to gain a better understanding of crack driving force and factors influencing CTOA. Implicit FEM simulations of dynamic crack propagation in pipes with diameters ranging from 355 mm to 1219 mm with a wall thickness of about 19 mm were performed using material properties representative of either X65 or X80 pipeline steel. The specification of a critical CTOA and the nodal release algorithm in the software WARP3D were employed to propagate the crack up to about two metres in the simulations. For a given critical CTOA, pipe diameter, and pipe thickness a set of simulations was performed where the initial applied gas pressure varied from as low as 4 MPa up to 60 MPa (which corresponds to about 80% of the yield strength of the material). The CTOA values used in the simulations ranged from 5° to 20° and corresponded to CTOA measurements obtained in concurrent work from Drop Weight Tear Tests performed on pipe steels. To accurately predict crack velocity, it was important to apply a flap loading profile near the crack front representative of the gas pressure response during pipe rupture. Comparison of the crack propagation response was carried out between a constant pressure profile just behind the crack front and a pressure profile that varied with circumference a round the pipe. The influence of soil pressure on the flap loading response was also considered in the models. The predicted pressure versus crack velocity profiles and the arrest pressure can then be subsequently used to predict the arrest length for a given CTOA.
Strain Sensing for Compact Heat Exchanger Defect Detection
Authors: Hu Xiaochen , Fan Zhaoyan , Paul Brian
Published: November 2019

The development of Compact Heat Exchangers (CHE) improves heat transfer efficiency with surface-to-volume ratios approaching 2500 m2/m3. In the applications such nuclear plants, CHE need to work for years in a harsh environment of high temperature up to 800 °C and high pressure up to 20 MPa. Any structural failure, i.e. cracks due to material fatigue or residual stress concentration in the CHEs, may result in safety problems and tremendous economy losses. Compared to the conventional heat exchangers, the non-destructive testing for CHE is challenging because the deformation of micrometer sized channels is hard to detect by the conventional means such as strain gauges or ultrasonic sensors. This paper presents a novel approach to detect the presence of cracks using fiber strain sensors embedded in the compact heat exchangers. The fiber sensors are proposed to install the heat exchanger with the microchannel plate stacks in the heat exchanger, measuring the strain distribution in the structure during the operation. Numerical and analytical models of CHE with and without cracks are built to learn crack size influence on strain variation. Sensors’ sensitivity to crack positions was calculated through simulation. A defect retrieval algorithm based on Tikhonov regularization is presented to achieve crack detection according to sensors’ outputs. A sample CHE section with 5x5 channels are simulated to quantitatively test the accuracy and validity of the proposed method.
Brittle Fracture Assessments on Piping Systems: MSOT Curves
Authors: Chakraborty Ishita , Subramanian Kannan , Penso Jorge
Published: November 2019

Brittle fracture assessments (BFAs) of pressure vessels based on API 579-1/ASME FFS-1, Section 3 procedures are frequently easier and more straightforward to implement in comparison to the BFAs on piping systems. Specifically, the development of the MSOT curves. This is due to the complexities involved in the piping systems due to the branch piping interactions, end conditions of piping systems such as nozzle flexibilities at the pressure vessel connections, temperature changes in the length of piping especially when the piping is significantly long as seen in flare header piping systems. MSOT curves that are alternatively used for MAT curves provide a better picture to the plant personnel in understanding the safe operating envelope. Development of MSOT curves is an iterative process and therefore involves significant number of piping stress analyses during their development. In this paper, an approach to develop the MSOT curves is discussed with two case studies that are of relevance to olefin plants.
Screening Technique of Hydrogen Embrittlement Sensitivity in Austenitic Stainless Steels Using In-Situ Small Punch Test Method
Authors: Shin Hyung-Seop , Bae Kyung-Oh , Kim Hyuckmin , Baek Un-Bong , Nahm Seung-Hoon
Published: November 2019

In this study, a simple screening technique using an in-situ small-punch (SP) test and based on the hydrogen embrittlement (HE) sensitivity of austenitic stainless steels was developed for use in hydrogen energy facilities. To investigate the HE behaviors of metallic materials, the in-situ SP tests were carried out under high-pressure hydrogen gas environments. The reductions of thickness at the fractured parts of the specimen were measured. The relative reductions of thickness (RRT) were determined after conducting SP tests in both hydrogen and inert gas environments. Similar to the relative reduction of area (RRA) obtained using the slow strain-rate tensile test, RRT obtained using the in-situ SP test is a quantitative measure of the influence of the HE behaviors. The influence of punch velocity on HE sensitivity was examined. The HE behaviors of austenitic steels were evaluated qualitatively and quantitatively. The high-Mn steels were also evaluated because they are candidates for storage and transportation of hydrogen gas. A screening technique for determining the practical environmental conditions at the point of use could be established by confirming the effectiveness of the influencing factor, RRT, using this in-situ SP test method.
Assessment of Free Standing Body in Dry and Submerged Condition and Under Seismic Loading
Authors: Rovagnati Beniamino , Hoang Phuong H.
Published: November 2019

A free standing, slender body may experience rocking motion followed by overturning when it is subject to strong seismic motions. When the free body is submerged in water, it will also be subject to lateral forces acting along the side of the free body as a result of water sloshing. This highly non-linear situation is of particular interest to engineers in the nuclear industry in need to assess the stability of transfer casks containing spent fuel and submerged in a confined pit or pool. In this work, a three-dimensional finite element dynamic transient model of a free standing cask is developed and analyzed using ANSYS. Both dry and submerged conditions are considered. Cask to floor friction, buoyancy force, and sloshing are accounted for in the assessment. The model is validated against well-accepted contributions on sloshing and rocking provided by G.W. Housner.
Blast Attenuation in Tunnels or Pipes With Turns
Authors: Geng Jihui , Thomas Kelly
Published: November 2019

Shock wave attenuation in a straight tunnel (or pipe) can be evaluated using existing methodologies. Shock attenuation is enhanced when there are right-angle turns along the length of the tunnel over which the shock is transmitted. A repeated set of such turns is generally defined as a blast trap. Little guidance is available in the open literature regarding the blast attenuation enhancement due to a right-angle turn or a blast trap in a tunnel. This paper presents guidance for shock wave attenuation as a function of the number of right-angle turns and blast wave parameters (i.e., peak pressure and duration). Characteristic parameters are utilized in order to define shock wave properties and tunnel dimensions. The shock attenuation due to up to four consecutive right-angle turns is evaluated. The purpose of this work is to provide a database of the shock attenuation within a tunnel due to multiple right-angle turns for use in designing tunnel structural components and evaluating the response of such components to postulated transmitted shock loads.
Production Impact Testing Exemption for Round-Seams (Category B Welds) of Welded Pressure Vessel in ASME-Section-VIII Division-1
Authors: Kilambi Sreelatha
Published: November 2019

In lean manufacturing environments for efficient schedule, most process equipment manufacturers procure shells. When impact-tested shells are required, long-seam (Category-A) weld-procedures differ from round-seam (Category B) weld-procedures, thereby initiating UG-84(i) of ASME Section VIII Division 1. UG-84(i) states that when weld procedures for Category B welds are different, weld production impact test is required.

This paper evaluates possible production impact test exemption for Category B welds based on stress ratio of each category of weld. While long seams require impact testing at lower thickness range, fully radio-graphed round-seams for Curve-D materials may be exempt from production impact testing with weld procedure controls from UCS-67(a)(3) and impact-tested weld metal at desired minimum design metal temperature. Not including temperature shift below impact test temperature due to dynamic impact testing provides added safety and conservatism to UCS66 rules in the code. Change in rules will provide manufacturers significant relief from production impact tests for Category-B welds that are under-stressed with safety factors currently in Figure UCS 66.1.
Nondestructive Evaluation of Metal Strength, Toughness, and Ductility Through Frictional Sliding
Authors: Palkovic Steven , Patel Parth , Safari Soheil , Bellemare Simon C.
Published: November 2019

Traditional assessment of mechanical properties requires the removal of a standardized specimen for destructive laboratory testing. A nondestructive in-situ method is a cost-effective and efficient solution for applications where sample cutouts are not feasible. This work describes developments in contact mechanics that use frictional sliding to evaluate the material strength and toughness of steel pressure vessels and pipelines.

Hardness, Strength, and Ductility (HSD) testing is a portable implementation of frictional sliding that provides a tensile stress-strain curve for assessment of the yield, ultimate tensile strength (UTS), and strain hardening exponent for power-law hardening metals. HSD testing incorporates four styluses of different geometry that generate grooves on the surface of a material as they travel. The measured geometry of these grooves along with the normal reaction forces on the stylus are correlated to representative tensile stress-strain values through finite element analysis (FEA) simulations. These principles have been extended to account for nonlinear strength behavior through the thickness of seam-welded steel pipes by using a combination of the HSD surface measurement, microstructure grain size, and chemistry. Frictional sliding tests are also used to assess material variation across a welded seam to identify different welding processes and the effectiveness of post-weld-heat-treatments (PWHT).

A second implementation of frictional sliding is Nondestructive Toughness Testing (NDTT), which provides an NDE solution for measuring fracture toughness by using a wedge-shaped stylus with an internal stretch passage to generate a Mode I tensile loading condition on the surface of a sample. The test produces a raised fractured surface whose height provides an indication of the materials ability to stretch near a propagating crack and is correlated to the crack-tip-opening-displacement (CTOD) measured from traditional laboratory toughness testing. Experiments on pipeline steel indicate that NDTT can provide an index of fracture toughness to benchmark materials tested under similar conditions. Implementation of these new instruments to gather data for integrity management programs, fitness for service assessments, and quality control of new manufacturing will help to reduce risk and uncertainty in structural applications.
PVB Blast Load Enhancement due to Mach Stem
Authors: Lowry Will , Geng Jihui
Published: November 2019

A pressure vessel burst (PVB) is an explosion scenario commonly encountered at chemical processing and petroleum refining facilities. Existing methodologies are available to predict the blast loads resulting from a spherical or cylindrical PVB source, with the PVB source either at grade or at an elevation. In the case of an elevated PVB source, the resulting blast wave will reflect from the ground at an angle. This ground level reflection will result in the formation of a Mach stem at certain angles between the incident blast wave and ground, with the required angles dependent on the blast wave overpressure. The triple point associated with the Mach stem moves upwards as the Mach stem progresses forwards, which can create a region of high blast pressure. This paper focuses on the investigation of a methodology that can be used to determine the high-pressure region generated by the Mach stem, along with the associated blast pressure, as a function of the PVB source elevation and incident blast pressure.
Master Curve Fracture Toughness Characterization of Eurofer97 Steel Variants Using Miniature Multi-Notch Bend Bar Specimens for Fusion Applications
Authors: Chen Xiang , Sokolov Mikhail A. , Bhattacharya Arunodaya , Clowers Logan N. , Graening Tim , Katoh Yutai , Rieth Michael
Published: November 2019

In this study, we performed fracture toughness testing of ten Eurofer97 steel variants using precracked miniature multi-notch bend bar (M4CVN) specimens based on the Master Curve method in the ASTM E1921 standard. Additional Vickers microhardness and room temperature tensile testing complemented the fracture toughness testing. Compared with standard Eurofer97, the ten variants didn’t show a comprehensive improvement of mechanical properties. The Master Curve method was found to yield a reasonable prediction of fracture toughness results obtained from M4CVN specimens with most valid fracture toughness data within the 2% and 98% tolerance boundaries of the Master Curve. The three-parameter Weibull distribution with Weibull exponent b = 4 also yielded excellent prediction of the relationship between fracture toughness results KJc and the cumulative probability for failure pf for one steel variant.
Numerical Investigations on the Effect of a Cuttings Bed Remover on the Cuttings Carrying Capacity in Horizontal Drilling
Authors: Cao Tong , Yu Kaian , Chen Xuyue , Zhu Hongwu , Luo Yunqing , Zhang Rui
Published: November 2019

With the increasing development of the exploration of unconventional oil-gas resources, people pay more and more attention to horizontal drilling technology. During the process of horizontal drilling, when the deviation angle exceeds the critical value, the falling velocity of the cuttings in annulus will increase with the deviation angle and they are more inclined to slip to the bottom edge. If the drilling parameters are chosen improperly at the same time, the cuttings would be deposited to form a cuttings bed at the bottom edge of the annulus. The high friction and high torque caused by the cuttings bed could greatly reduce the efficiency and the safety of drilling. This paper comes up with a cuttings bed remover with helical grooves to break the cuttings bed and carry cuttings based on the normal drill pipe design, builds 3D models of the cuttings bed removers with different structure parameters to analyze the cuttings carrying capacity with CFD. In addition, an investigation about the effects of the grooves design and drill pipe rotational speed have on the cuttings carrying capacity is accomplished, the grooves design parameters include the number, the length and the helical angle of the groove, and the effects are evaluated by the flow characteristics of fluid field and transportation of cuttings. The remover structure is optimized according to the simulation results, and the good performance of cuttings bed remover is verified by a field test. The whole research about the promotion of cuttings bed remover and its application shall be of great importance to the improvement of horizontal drilling efficiency and safety.
Optimum Design of Composite Pressure Vessel Based on 3-Dimensional Failure Criteria
Authors: Sakai J. , Park Y. H.
Published: November 2019

Anisotropic composite cylinders and pressure vessels have been widely employed in automotive, aerospace, chemical and other engineering areas due to high strength/stiffness-to-weight ratio, exceptional corrosion resistance, and superb thermal performance. Pipes, fuel tanks, chemical containers, rocket motor cases and aircraft and ship elements are a few examples of structural application of fiber reinforced composites (FRCs) for pressure vessels/pipes. Since the performance of composite materials replies on the tensile and compressive strengths of the fiber directions, the optimum design of composite laminates with varying fiber orientations is desired to minimize the damage of the structure. In this study, a complete mathematical 3D elasticity solution was developed, which can accurately compute stresses of a thick multilayered anisotropic fiber reinforced pressure vessel under force and pressure loadings. A rotational variable is introduced in the formalism to treat torsional loading in addition to force and pressure loadings. Then, the three-dimensional Tsai-Wu criterion is used based on the analytical solution to predict the failure. Finally, a global optimization algorithm is used to find the optimum fiber orientation and their best combination through the thickness direction.
Case Study on the Effect of Mean Stress on Ground Storage Vessels for Fuelling
Authors: Peters Daniel T. , Parr Myles , Naugle Matthew
Published: November 2019

The use of high-pressure vessels for the purpose of storing gaseous fuels for land based transportation application is becoming common. Fuels such as natural gas and hydrogen are currently being stored at high pressure for use in fueling stations. This paper will investigate the use of autofrettage in high pressure cylinders and its effects on the life of a vessel used for gas storage. Unlike many high-pressure vessels, the life is controlled by fatigue when cycled between a high pressure near the design pressure and a lower pressure due to the emptying of the content of the vessels.
Uncertainty Quantification and Sensitivity Analysis for Net Section Collapse Criterion of Pipes Under Pressure and Bending
Authors: Garud Y. S. , Stevens Gary L.
Published: November 2019

One of the manifestations of fatigue damage in pressurized components is the development of a crack for which the engineering assessment requires consideration of critical conditions leading to loss of functionality, especially in extreme low probability events under credible accident conditions. This assessment, especially for ductile, tough metals, has been based on the net section collapse (NSC) criterion. The typical inputs used in validating and in applying the criterion have associated uncertainties that can have considerable influence on the resulting or related assessment. The objective of this paper is to provide a formulation for this assessment to enable uncertainty quantification and sensitivity analysis for the NSC validation and application for pipes under pressure and section bending loads. The formulation is developed along the similar approach presented in recent PVP conference papers dealing with the CUF-based fatigue evaluation. The method of analysis is applied to several pipe tests over a wide range of geometries and loadings, and the results are compared with data with the objective of assessing the validity of the NSC criterion. The resulting range of expected uncertainty in the application of the NSC criterion and the ranking of controlling inputs based on the sensitivity analysis are discussed.
Power Piping Grade 91 In-Service Cracks
Authors: Cohn Marvin J. , Paterson Steve R. , Rapkin Keith , Henley Charles , Liebl Erick , Johnson Michael
Published: November 2019

After a power piping system has begun commercial operation, it is recommended that the initial nondestructive examination (NDE) of the welds should be developed and executed to reveal possible fabrication and early service-related material damage. The identified indications and other possible anomalies should be thoroughly documented, evaluated, and dispositioned.

Additional early service-related cracks may initiate and propagate several years after the first examination. This paper considers historical early service-related cracks in weldments of power piping systems operating in the creep regime. Factors that dominate these early service-related cracks are discussed in this paper.

This paper provides a list of more than 20 historical examples of power piping Grade 91 material macrocracks (partial wall or through-wall) that were not present immediately after construction and propagated substantially in service. Five of the examples are discussed in more detail. The study only includes cases where propagating cracks were confirmed. It does not include examples where NDE reportable indications have not propagated in service to large macrocracks. Due to the time-dependent nature of these girth weld cracks, the results of this study may be used to assist in the selection of Grade 91 reexamination locations after the power piping system (e.g., main steam, hot reheat, high pressure, or intermediate pressure) has been several years in service.
Optimizing Analysis Methodology for HPHT Equipment
Authors: Sims J. Robert , Lefkowitz Jay , Dewees Dave , Becht Charles
Published: November 2019

The American Petroleum Institute (API) is continuing to develop technical reports, guidelines and standards for the construction of high-pressure, high-temperature (HPHT) equipment for offshore oil and gas exploration and production. HPHT is considered to be equipment with a pressure rating greater than 103 MPa (15,000 psi) and/or a temperature rating greater than 177°C (350°F). One alternative in the evolving API standards is to use the analysis methodology in ASME Section VIII, Division 3, including fracture mechanics, for determination of the static pressure rating and the design fatigue life. However, detailed requirements for finite element analysis (FEA) parameters such as element type and mesh density are not specified. In addition, specific requirements for fracture mechanics analysis are not provided. This paper explores the effect of variations in those parameters on the calculated static pressure rating and the design fatigue life and gives recommendations for optimizing the parameters of the design itself (e.g. blend radii at transitions) and the analysis considering the required accuracy of the result, analysis time and cost.
Evaluation of Fatigue Crack Growth at Piping of Austenitic Stainless Steel Under Biaxial Stress
Authors: Harada Shogo , Kitada Takanori , Nakamura Takao
Published: November 2019

The fatigue degradation in Nuclear Power Plants (NPPs) is evaluated by a design fatigue curve that is published in ASME code which is based on the results of uniaxial fatigue test data. On the other hand, stress that occurs at actual piping elements, such as elbows, is not uniaxial stress but biaxial stress, with different stress ratios. Stress ratio is defined as the ratio of stress range in one axis to that in the other axis. In this study, a pressurized disc fatigue test machine is developed in order to conduct biaxial fatigue test under different stress ratio more easily and low-cost. A newly designed test specimen is adopted to generate biaxial stress under different stress ratios near the center of the specimen. This test machine can generate a specific biaxial stress with different stress ratios at specimen by adjusting air pressure and shape of the specimen.
Novel Modeling of Mean Stress Effect on the High-Cycle Fatigue Performance of Preloaded Threaded Fasteners
Authors: Nassar Sayed A. , Li Tianwu
Published: November 2019

An experimentally validated model is proposed for the effect of fastener mean stress on its high cycle fatigue (HCF) performance. The model is also used for comparing fatigue performance of ultra-high strength (UHS) fasteners Class 14.8, 15.8 and 16.8 with that of commercially available (CA) Class 10.9 and 12.9 fasteners. Respective mean stress-adjusted S-N curves are constructed using experimental data following applicable ASTM standards. Proposed model results are compared with other existing models that account for the effect of mean stress such as Goodman, Gerber, Morrow, Soderberg, and Elliptic (ASME) models. Detailed discussion of the results, failure mode, and conclusions are provided.
Light Weight Design of Multi-Layered Steel Vessels for High-Pressure Hydrogen Storage
Authors: Ye Sheng , Zheng Jinyang , Yu Ting , Gu Chaohua , Hua Zhengli
Published: November 2019

Large scale storage of hydrogen is one of the key factors in hydrogen energy development. High-pressure hydrogen storage technology is widely used in hydrogen storage. It has advantages of easy operating, quick charge and discharge, simple equipment structure and low cost. The multi-layered steel vessel (MLSV) was developed for stationary hydrogen storage, which was flexible in design, safe in operation and convenient in fabrication. MLSV has been used in several hydrogen refueling stations in China. With the construction of hydrogen refueling stations accelerated, the vessel was required to be larger, lighter and cheaper. First, the basic structure of the MLSV was presented. Second, two light-weight methods were proposed and compared, including reducing the safety factor and increasing the strength of the steel band. Finally, the stress in the cylindrical shell of the MLSV using light-weight design were compared with the previous one. In addition, a MLSV using the light-weight method of reducing safety factor has been designed and fabricated, which can store 211 kg gaseous hydrogen at 50MPa.
Welding Process Development for Spent Nuclear Fuel Canister Repair
Authors: Tang Wei , Chatzidakis Stylianos , Miller Roger , Chen Jian , Kyle Doug , Scaglione John , Schrad Caleb
Published: November 2019

The potential for stress corrosion cracking (SCC) of welded stainless-steel interim storage containers for spent nuclear fuel (SNF) has been identified as a high priority data gap. This paper presents a fusion welding process that was developed for SNF canister repair. Submerged arc welding (SAW) was developed to weld 12.7 mm (0.5 in.) thick 304L stainless steel plates to simulate the initial welds on SNF canisters. The SAW procedure was qualified following ASME Boiler and Pressure Vessel Code requirements. During SAW, the welding temperature was recorded at various locations by using thermocouples. After SAW, weld microstructures were characterized, joint mechanical properties were tested, and the maximum tensile residual stress direction was identified. After SAW procedure qualification, artificial cracks were excavated perpendicular to the maximum tensile residual stress direction in the SAW heat affected zone. Machine cold-wire gas tungsten arc welding (CW-GTAW) was developed and used for repair welding at cracked locations.
Implementation and Validation of a Fully Mechanistic Fatigue Modeling Approach in a High Performance Computing Framework
Authors: Barua Bipul , Mohanty Subhasish , Majumdar Saurindranath , Natesan Krishnamurti
Published: November 2019

Current approaches of fatigue evaluation of nuclear reactor components or other safety critical structural systems use S∼N curve based empirical relations which may have large uncertainty. This uncertainty may be reduced by using a more mechanistic approach. In the proposed mechanistic approach, material models are developed based on the evolution of material behavior under uniaxial fatigue experiments and implement those models into 3D finite element (FE) calculations for fatigue evaluation under multiaxial loading. However, this approach requires simulating structures under thousands of fatigue cycles which necessitates the use of high performance computing (HPC) to determine fatigue life of a large component/system within reasonable time frame. Speeding up the FE simulation of large systems requires the use of a higher number of cores, which is extremely costly, particularly when a commercial FE code is used. Also, commercial software is not necessarily optimized for use in an HPC environment. In this work, an open source parallel computing solver along with a multi-core cluster is used to scale up the number of cores. The HPC-based mechanistic fatigue modeling framework is validated through evaluating fatigue life of a pressurized water reactor surge line pipe under idealistic loading cycles and comparing the simulation results with observations from uniaxial fatigue experiment of 316 stainless steel specimen.
Time-Series Fatigue Damage States Forecasting and Probabilistic Environmental Fatigue Life Prediction Using Markov-Chain-Monte-Carlo Techniques
Authors: Park Jae Phil , Mohanty Subhasish , Bahn Chi Bum
Published: November 2019

In general, probabilistic fatigue life estimation were performed using Weibull analysis and end-of-life fatigue data. This is basically using traditional strain/stress ∼ life (S∼N) data. Although it is always better to estimate the reliability of a component based on probabilistic evaluation of end-of-life data, it may not be always possible to conduct hundreds of costly and time-consuming fatigue experiments for each and every different loading case. The strain/stress ∼ life data are mostly related to push-pull type symmetric (R = −1) loading cases and the traditional Weibull probabilistic model are based on the associated end-of-life data. However, the Weibull approach doesn’t depend on the time evolution of damage but is just based on end-of-life data. It is our assumption that for a given loading and environment, the time-evolution based probabilistic risk assessment (PRA) and reliability model would produce more accurate results compared to a PRA model simply based on the end-of-life data obtained under a different loading conditions. However, the time-evolution based PRA for a particular loading and environment requires hundreds of fatigue tests, which might not always be possible to perform due to the high cost and time requirements. To overcome these issues, we propose the use of Markov-Chain-Monte-Carlo (MCMC) techniques for time series or time-evolution prediction of damage states under a particular loading and environment (e.g. in this case, high-temperature PWR coolant-water condition) condition. Then, the probabilistic fatigue life can be estimated on the basis of the simulated scatter band in damage states for a given failure criteria. In this paper, we discuss the MCMC model based probabilistic damage state estimation and associated probabilistic fatigue life of 316 stainless steel subjected to cyclic loading at 300 °C in-air and PWR-coolant-water conditions.
Multi-Scale Damage Analysis on Fatigue-Creep Process in Industrial Steel Structures
Authors: Guo Huajing , Li Zhaoxia
Published: November 2019

Fatigue-creep damage has been recognized as the elemental cause of failure of industrial steel structures exposed to high temperature. In order to better understand the degradation process, a previously developed multi-scale fatigue-creep damage is applied to evaluate the structural damage due to fatigue and creep process. In the model, the relationship between collective behavior of micro-cracks and fatigue damage variable was established and the nonlinear coupling of fatigue damage and creep damage was taken into consideration. Fatigue-creep damage analysis on a series of existing key connection shafts in industrial steel structures at high temperature are performed under different working condition and their lifetime are predicted based on the numerical calculation on the accumulated fatigue-creep damage up to structural failure. The numerical results indicate that the early stage of degeneration process is dominated by creep damage and the fatigue damage rate increases quickly at the later stage. The fatigue-creep lifetime of industrial steel structures varies significantly with different applied stress level and working temperature.
Fluid-Elastic Coefficients in Single Phase Cross Flow: Dimensional Analysis, Direct and Indirect Experimental Methods
Authors: Lagrange Romain , Piteau Philippe , Delaune Xavier , Antunes Jose
Published: November 2019

The importance of fluid-elastic forces in tube bundle vibrations can hardly be over-emphasized, in view of their damaging potential. In the last decades, advanced models for representing fluid-elastic coupling have therefore been developed by the community of the domain. Those models are nowadays embedded in the methodologies that are used on a regular basis by both steam generators providers and operators, in order to prevent the risk of a tube failure with adequate safety margins. From an R&D point of view however, the need still remains for more advanced models of fluid-elastic coupling, in order to fully decipher the physics underlying the observed phenomena. As a consequence, new experimental flow-coupling coefficients are also required to specifically feed and validate those more sophisticated models. Recent experiments performed at CEA-Saclay suggest that the fluid stiffness and damping coefficients depend on further dimensionless parameters beyond the reduced velocity.

In this work, the problem of data reduction is first revisited, in the light of dimensional analysis. For single-phase flows, it is underlined that the flow-coupling coefficients depend at least on two dimensionless parameters, namely the Reynolds number Re and the Stokes number Sk. Therefore, reducing the experimental data in terms of the compound dimensionless quantity Vr = Re/Sk necessarily leads to impoverish results, hence the data dispersion. In a second step, experimental data are presented using the dimensionless numbers Re and Sk. We report experiments, for a 3 × 5 square tube bundle subjected to water transverse flow. The bundle is rigid, except for the central tube which is mounted on a flexible suspension allowing for translation motions in the lift direction.

The evolutions of the flow-coupling coefficients with the flow velocity are determined using two different experimental procedures: (1) In the direct method, an harmonic motion of increasing frequency is imposed to the tube. (2) In the indirect method, the coefficients are obtained from the modal response of the tube (frequency, damping). The coefficient identification was performed well beyond the system instability boundary, by using active control, allowing an exploration of a significant range of flow velocity.

For a given Sk, the results show that: (a) at low Re, the flow-coupling coefficients are close to zero; (b) at intermediate Re, the flow stabilizes the tube; (c) at high Re, the flow destabilizes the tube, leading to a damping-controlled instability at a critical Re. Reducing the data in terms of Re and Sk clarifies the various experimental “branches”, which are mixed when using Vr. The two identification techniques lead to reasonably compatible fluid-elastic coefficients.
On Design and Analysis of Fastener Locking Tabs in Highly Chaotic Flow of Primary Side of Steam Generator
Authors: Ghafouri-Azar Reza , Stojakovic Mike
Published: November 2019

The primary side of steam generators has a divider plate which separates the heavy water entrance and exit of flow when entering in and out of the U-tubes of tubesheet. The divider plate has a series of plates which are connected by bolting. The bolted connections have positive locking device which prevents the connection from loosening in the highly vibrating turbulent flow conditions. These positive locking devices were failed by breaking into pieces at different occasions and a few cycle of design were completed to address this design failures. In the latest design modification a new design was proposed. The new design was applied to many steam generators. It has proven to be robust with respect to durability, strength and ease of installation. The new design has reduced outage time and activities. It is also reduces radiation exposure while improving conventional safety. The paper describes the design processes and addresses key design and analysis parameters. A Finite Element model was developed to facilitate assessment design calculation. Structural integrity of the newly design part was assessed against ASME Boiler and Pressure Vessel codes. A flow-induced vibration was completed to address fluid-structure interactions.
Susceptibility to Neutron Irradiation Embrittlement of Heat-Affected Zone of Reactor Pressure Vessel Steels
Authors: Takamizawa Hisashi , Katsuyama Jinya , Ha Yoosung , Tobita Tohru , Nishiyama Yutaka , Onizawa Kunio
Published: November 2019

The heat-affected zone (HAZ) of reactor pressure vessel (RPV) steels is known to show large scatter in Charpy impact properties because it has inhomogeneous microstructure due to thermal histories of multi-pass welding for butt-welded joints. The correlation between mechanical properties and microstructure such as grain size, phase-fraction, martensite-austenite constituent, on the characteristics of HAZ of un-irradiated materials was investigated. Neutron irradiation was conducted at Japanese Research Reactor −3 (JRR-3) operated by JAEA. The neutron irradiation susceptibility was evaluated based on post-irradiation examinations consisting of mechanical testing and microstructural analysis. In the experiments, typical RPV steel plate and their weldment were prepared. Simulated HAZ materials that have representative microstructures such as coarse-grain HAZ (CGHAZ) and fine-grain HAZ (FGHAZ) were also prepared based on the thermal histories calculated by finite element analysis. For un-irradiated materials, a part of simulated HAZ materials showed a higher reference temperature of the master curve method than that of the base metal (BM). The irradiation hardening of HAZ was almost the same or lower than that of the BM, and the shift of reference temperature for HAZ materials was comparable with that of BM.
Weld Residual Stress and Fracture Behavior of NASA Layered Pressure Vessels
Authors: Brust F. W. , Dodds R. H. , Hobbs J. , Stoltz B. , Wells D.
Published: November 2019

NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. The number of thinner layers required depends on the thickness required for the complete vessel with most tanks having between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents some initial results which consider weld residual stress and fracture assessment of some layered pressure vessels and is a small part of the much larger fitness for service evaluation of these tanks. This effort considers the effect of weld residual stresses on fracture for an inner layer longitudinal weld. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Finally, cracks are introduced, and service loading applied to determine the effects of WRS on fracture.
The Application of NUPACK to the Design of a Type B Packaging Containment Vessel
Authors: Karius Kathryn , Eberl Kurt R. , McKeel Charles A. , Abramczyk Glenn A.
Published: November 2019

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Section III Division 3 (commonly referred to as NUPACK) was issued in 1997 to address the containments of nuclear transportation packagings. Previously, Section III consisted of only 2 divisions that address the construction of nuclear facility components: Division 1 for metal construction and Division 2 for concrete construction. Type B packagings have historically been designed to Division 1 standards. This paper discusses the application of NUPACK to the design of a Type B packaging containment vessel.
Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack
Authors: Sifford Curtis , Shirani Ali
Published: November 2019

This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.
Numerical and Parameter Uncertainties: Are They Independent?
Authors: Eça Luís , Lopes Rui , Pereira Filipe Soares , Vaz Guilherme
Published: November 2019

In the Validation procedure proposed by the ASME V&V 20 Standard, the quantification of the modeling error of mathematical models solved by Computational Fluid Dynamics (CFD) requires the estimation of the experimental, numerical and parameter uncertainties. In its simplest form, these uncertainties are assumed independent. Parameter uncertainty is typically a consequence of lack of exact values for the boundary conditions and/or fluid properties. Its evaluation is handled by the broad field of uncertainty quantification. However, this evaluation requires simulations that are unavoidably affected by numerical errors. Therefore, it may be questionable if parameter and numerical uncertainties are really independent or, alternatively, how small must be the numerical uncertainty to estimate parameter uncertainties without its influence. In this paper we address the relation between parameter and numerical uncertainties using two test cases: the transition from laminar to turbulent flow on a flat plate at a Reynolds number of 107; the flow around the Eppler 387 airfoil at an angle of attack of 1o and Re = 3 × 105. The mathematical model for the three cases is the Reynolds-Averaged Navier-Stokes equations supplemented by the k–ω SST eddy-viscosity turbulence model and the one-equation γ transition model. Sensitivity coefficients are determined for the selected quantities of interest using the local sensitivity method and finite-differences. These estimates are performed for different levels of grid refinement to check its dependency on the estimated numerical error obtained from power series expansions. Results obtained in this study suggest that the evaluation of the parameter uncertainty only becomes independent of the numerical error when the simulation results are in the asymptotic range.
Bootstrapping and Jackknife Resampling to Improve Sparse-Sample UQ Methods for Tail Probability Estimation
Authors: Jekel Charles F. , Romero Vicente
Published: November 2019

Tolerance Interval Equivalent Normal (TI-EN) and Superdistribution (SD) sparse-sample uncertainty quantification (UQ) methods are used for conservative estimation of small tail probabilities. These methods are used to estimate the probability of a response laying beyond a specified threshold with limited data. The study focused on sparse-sample regimes ranging from N = 2 to 20 samples, because this is reflective of most experimental and some expensive computational situations. A tail probability magnitude of 10−4 was examined on four different distribution shapes, in order to be relevant for quantification of margins and uncertainty (QMU) problems that arise in risk and reliability analyses. In most cases the UQ methods were found to have optimal performance with a small number of samples, beyond which the performance deteriorated as samples were added. Using this observation, a generalized Jackknife resampling technique was developed to average many smaller subsamples. This improved the performance of the SD and TI-EN methods, specifically when a larger than optimal number of samples were available. A Complete Jackknifing technique, which considered all possible sub-sample combinations, was shown to perform better in most cases than an alternative Bootstrap resampling technique.