bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of Fatigue Crack Growth Modeling Solutions Using Measurements Collected on API X65 Piping Specimens
Authors: Loghin Adrian , Harter James
Published: November 2023

Building confidence in different modeling techniques to assess damage tolerance capabilities of components under service conditions relies on a continuous verification and validation effort. The verification benchmarking (usually conducted for mode I stress intensity factors, KI) is accomplished by comparison against analytical or high-resolution numerical solutions while for the validation task, lab-controlled experimental measurements (i.e., crack size vs. cycles) are used as a reference for a complete remaining useful life solution. Different mechanical testing conditions and multiple specimens are often considered to capture experimental variability and provide a large set of measurements that can be used for numerical solution validation and uncertainty quantification.

Four fatigue crack growth experimental measurements [1] were used as a validation reference set for an incremental 3D FE modeling procedure and for a reduced order model-based application. The test procedure consists of a four-point bend 5L X65 pipe specimen subjected to two repeating R-ratio constant amplitude loading blocks to allow formation of beach marks that can be used post-failure to identify crack size and shape during the experiment. The two modeling processes capture all details related to experimental procedure: overall geometry of the specimen, crack location and orientation, two constant amplitude loading blocks: 10000 cycles performed at a stress ratio of R = 0.1 followed by 5000 cycles at R = 0.5. Fatigue crack growth rate data provided by BS 7910 was used to obtain the 3D FEM based explicit crack growth solution as well as the equivalent solution using the reduced-order model. Digitized post-failure beach mark data was used as a reference to validate against the crack fronts generated in the numerical solution for each loading block. Fatigue crack growth rate uncertainty within the bounds provided by BS 7910 is considered in this validation benchmarking.
Variable Inertia Damper Using a Flywheel Filled by MR Fluid: Vibration Tests by Reinforcement Learning
Authors: Matsuoka Taichi , Kubota Shunya
Published: November 2023

The authors have developed a semiactive damper that has a variable inertia mass using a flywheel filled with MR fluid in previous paper. The damper complies with a ball screw mechanism and the flywheel. The magneto-rheological (MR) fluid is filled into the flywheel. Ferrite particles of the MR fluid are clustered at outer edge of the flywheel when magnetic field is applied by 8 electromagnets, a radius of gyration of the flywheel will be changed. So that the damper can have a variable inertia mass effect which has the virtual mass of 50 kg in minimum and 68 kg in maximum. In this paper, to investigate vibration reduction using the variable inertia mass effect, vibration tests of one-degree-of-freedom system with a prototype damper, which is switching the inertia mass effect by reinforcement learning using Deep Deterministic Policy Gradient (DDPG), were conducted by a shaking table. Agents are trained by JMA Kobe and El Centro earthquakes. From the experimental results, peak values of response acceleration and displacement in case with the damper decrease about 1/3 ∼ 1/2 to that in case without the damper. In addition, numerical responses are simulated by using other earthquakes which have not been trained. Finally, vibration reduction was confirmed experimentally and numerically.
A Practical Approach for In-Field Calculation of Autofrettage Pressures for Thick-Walled Cylinders
Authors: Jäger Philippe , Fuenmayor David , Bortz Matthias
Published: November 2023

Autofrettage of pipes or pressure vessels for high pressure applications is a common and well-known procedure to extend the fatigue life by introducing a compressive residual stress at the inner fiber, see, e.g., [1,2].

In general, applying autofrettage to a high-pressure component requires a mechanical calculation, which normally consist of the following three main steps: 1) Calculation of the corresponding pressure based on a desired autofrettage depth, i.e., a restricted portion of the wall thickness 2) Calculation of an upper limit to ensure protection against plastic collapse during the autofrettage process 3). Calculation of an upper limit to prevent reverse yielding upon releasing the autofrettage pressure.

In order to perform that mechanical calculation as efficient as possible, we will present an analytical approach based on dimensionless coefficients that separates geometry and material properties and allows for the determination of the autofrettage pressure as a function of the particular yield strength under consideration.
Statistical Analysis of Waste Tank Pit Depth Measurements for Corrosion Rate Projections
Authors: Harris Stephen , Wiersma Bruce , Elder Jim , Plummer Alan , Waltz Ruel
Published: November 2023

Liquid radioactive waste is stored in large, underground carbon steel tanks at the United States Department of Energy’s Savannah River Site in Aiken, South Carolina. As a component of the site’s Structural Integrity Program, in-service inspection of these tanks is conducted to ensure tank integrity and to verify the effectiveness of waste chemistry requirements for mitigation of corrosion degradation. The inspections are performed using a projection image scanning (P-scan) automated ultrasonic testing device, which is remotely operated on a magnetic wall crawler. The inspections focus on gathering data related to the primary corrosion mechanisms of concern: general corrosion, pitting corrosion, and stress corrosion cracking. The inspections provide a real-time assessment of actual conditions to confirm that the corrosion control program is effectively mitigating corrosion.

A horizontal band of incipient pits was identified on one of these tanks over 25 years ago. As a precaution, the site has monitored this band of pits to determine if they were actively growing (i.e., pit depth increasing). In 2012, the location of nearly 100 of these pits were referenced. In 2022, the inspection plan for this tank required that these same pits be measured. A statistical analysis was performed to determine if a difference between the pit distributions measured in 2012 and 2022 exists. Statistical tolerance limits for pit depth were also calculated assuming the Largest Extreme Value (LEV), negative Weibull and log-Normal probability distributions for comparisons. The analysis confirmed that there was no significant difference between the two distributions and hence pit growth is not occurring. The analysis provided the basis for discontinuing future inspection of the horizontal band on this tank.
Creep Property of Type 316Cb Stainless Steel Heater Tube
Authors: Hau Jorge , Hsieh Bing , Park Neil
Published: November 2023

A metallurgical evaluation was conducted involving a 316Cb tube removed from an atmospheric distillation unit heater, after 18 years of service. Since this steel is not a standard material for heater tubes, the design used creep properties from type 347 stainless steel tube. A tube sample was submitted for remaining life assessment. The material properties reported for type 347H stainless steel were used for this study. The creep tests were conducted following the Omega method, but LMP data were also derived to make an assessment based on this method as well. Applying both methods, the type 316Cb steel appeared creep stronger than 347H steel. The 316Cb steel in this tube sample did not undergo significant microstructure degradation and creep life consumption, thus, estimation indicated ample remaining life for future service. Type 316H steel was not used as reference because the original design used type 347 stainless steel tube properties to determine the required wall thickness.
Considering Gaps Between Tubes and AVBs for U-Shaped Tube Bundle in Steam Generators Using Seismic Linear Analysis Method
Authors: Hirota Kazuo , Monde Masatsugu , Ono Naoki , Nakamori Tomohito , Matsubara Masahito , Mineno Tomonori , Taguchi Koshi
Published: November 2023

Ensuring seismic resistance of the tube bundle of steam generators is very important. In order to predict the vibration behavior of the tube bundle, a linear analysis method was developed by modeling all the components of the tube bundle such as tubes and Anti-Vibration Bars (AVB). First natural frequency and its seismic response calculated using the linear analysis were very consistent with the seismic test results. However, since the calculated tube strain distribution was smaller than the results obtained from the test, we developed a nonlinear analysis model that can take into account gaps between tubes and AVBs. Natural frequencies and seismic response, however, cannot be obtained based on this nonlinear analysis. In seismic response evaluations, since focusing on the first order mode of the tube bundle is important, the strain of the tubes was assessed by simulating the deformation of the first order mode, based on a static analysis that uses horizontal inertial acceleration so that the seismic response can be determined by the linear analysis model.

In this study, an improved linear analysis model was developed in which tubes and AVBs were connected by linear springs only at contact points. A nonlinear analysis model was used to grasp contact points when the tube bundle was deformed due to seismic load. First natural frequency and its stress distribution in the tube array calculated using the improved linear analysis model were very consistent with the test results obtained from U-shaped tube bundles with both triangular and square arrays. Therefore, it has been concluded that the improved linear analysis model can be applied to seismic analysis for both arrays in steam generator.
Modeling of Hardness and Welding Residual Stress in Type 316 Stainless Steel Components for the Assessment of Stress Corrosion Cracking
Authors: Li Suo , Yamaguchi Yoshihito , Katsuyama Jinya , Li Yinsheng , Deng Dean
Published: November 2023

In this work, a framework was proposed on the comprehensive assessment of hardness and welding residual stress in Type 316 austenitic stainless steel welded joints. Firstly, an 8-pass butt-welded joint made of Type 316 stainless steel was fabricated. Finite element analyses of the welded joint were performed to investigate hardness and welding residual stress distributions. The grain growth model was developed for the hardness prediction. The Chaboche combined isotropic-kinematic strain hardening model and time-temperature dependent annealing model were adopted. The relationships between the Vickers hardness and the uniaxial plastic strain as well as grain size were collected from published literatures. The simulation results of the grain size and accumulated equivalent plastic strain were used for the hardness prediction of the welded joint. The predicted hardness was compared with the experimental data of hardness mapping. The distribution of welding residual stress on the outer surface of the welded pipe was measured by using the X-ray diffraction method and strain gauge method, respectively. The predicted welding residual stresses were compared with the measurements. The results obtained showed that the developed numerical approach can predict the hardness and welding residual stress of Type 316 stainless steel welded joints with satisfactory accuracy. The effects of heat input, structural constraint, and repair welding on the hardness and welding residual stress will be investigated as further works.
Understanding Bolt Stress Behavior in Temperature Cycling Environments
Authors: Taylor Robert
Published: November 2023

This study researches and monitors bolt stress readings for different gasket styles in multiple temperature cycling environments and internal pressure settings over a long time period. The testing is performed on ASME B16.5 raised face, weld neck flanges – 4” 300lb with the heat generated through the piping system replicating a more realistic plant/process application. ASTM A193 B7 intelligent bolting is used to monitor the bolt stress throughout testing, this is made possible because of the ceramic dial gauge provided with this style of intelligent bolt. The study shows how the bolt stress values change throughout the set temperature cycling profile, internal pressure present and how the style of gasket can affect the bolt stress at a given point. Several common gasket styles have been tested to provide a better understanding for end users when selecting a gasket type. Relaxation values are also calculated throughout testing to better understand the longevity of the bolted joint connection.

The information generated from this study will provide a better understanding of when a flanged joint may be at risk and the relaxation factor for a given gasket style in service. This can then be implemented into the bolt up procedure and torque value of the flange joint to ensure a leak free start up and long-term service performance.
Temperature Variation in Each Component of the Bolted Flange Joint
Authors: Taylor Robert , Hufnagel Stefan
Published: November 2023

This study researches and monitors the temperature variation in each component of the bolted flange joint, considering the inner pipe temperature, gasket sealing element temperature, and bolt temperature in three positions: top, middle, and bottom.

The study also shows results with different flange / pipe insulation thickness and two types of bolt materials, ASTM A193 B7 and ASTM A320 B8M CL2.

The test unit temperature controller is set at a consistent heat up rate with a maximum temperature setting of 600 Deg F (316 Deg C). Testing starts at ambient temperature, and is then taken up to the maximum set temperature, while each thermocouple is recording the temperature every minute.

Graphical results show the increase and cooldown in temperature of each component and further breaks down the temperature differences between the complete unit, inner pipe versus gasket sealing element, bolt temperature variation — top, middle, and bottom of the bolt length.

Finite Element Method (FEM) will then be performed replicating the test procedure.

Results will aid design and plant engineers to better understand how different types and thicknesses of pipe / flange insulation can affect the temperature variations in certain bolted flange components. Data from the study will also enable design engineers to understand the differences between inner pipe, gasket, and bolt temperatures when calculating stresses and relaxation values in operation.
Thermal Modeling of Hanford Lead Canister’s Heater Bench Tests
Authors: Suffield Sarah R. , Jensen Ben J. , Klymyshyn Nicholas A.
Published: November 2023

A computational fluid dynamics (CFD) model was built to simulate the Hanford Lead Canister (HLC). The HLC is intended to act as a leading indicator of canister degradation as part of the Hanford site’s aging management plan for long term storage of encapsulated cesium and strontium material. It will be deployed with heaters inside to accurately simulate the environmental conditions experienced by units containing radioactive material. The HLC will be placed on a dry storage pad near dry storage systems with encapsulated radioactive material.

A thermal CFD model was developed to verify that the heaters can replicate the decay heat of a canister with nuclear material and to aid in understanding the HLC’s thermal environment, including the local air flow within the canister storage system. In addition to the detailed CFD model, a simple model of the dry storage systems, including the HLC, sitting on the dry storage pad was constructed to understand how wind speed and direction will impact airflow in and around the HLC. The dry storage pad model will explicitly model the external environment and provide boundary conditions to the detailed stand-alone CFD model. Wind flow around the storage modules will cause a pressure distribution along external surfaces and openings, resulting in a pressure difference between the inlets and outlets of the storage module that will impact airflow through the module. The HLC model will need to account for both wind and thermally driven flows in the heated storage module. This study investigates how to account for wind in the stand alone HLC thermal model based on pressure differences at the inlets and outlets for various wind speeds in a larger model that simulates the external environment around the storage module.
Post Weld Heat Treatment and Fracture Toughness Evaluation of Electron Beam Welded SA508 Alloys
Authors: Cooper Adam J. , Wisbey Andrew , Kyffin William , Dutilleul Thomas , Nunn Mike , Punshon Chris , Smith Mike C. , Pickering Ed , Akrivos Vasileios , Carruthers Alex
Published: November 2023

Whilst Electron Beam Welding (EBW) has been in existence for several decades, it typically requires the welded component to be housed within a conventional vacuum chamber in order to minimize diffusion of the electron beam, thus limiting the maximum overall size of the component. Recent advances in EBW by TWI (UK) have led to the development of a local vacuum system, whereby a local vacuum is implemented around only the welded section rather than the whole component, thereby avoiding the component size limitations associated with more conventional systems. A direct comparison between the two EBW systems does not appear to have been published hitherto and thus forms one aspect of the work reported here.

For the EBW low alloy steel SA508 materials employed in this study, the post weld heat treatment (PWHT) regime has also been investigated, since there has been some concern over the appropriateness of employing conventional PWHTs typically used for traditional arc welds. Charpy impact testing was performed to assess the initial toughness of the welds, with the notch located on the weld centre-line, within the HAZ, and within the parent materials. For SA508 Gr.3, Charpy testing suggested that only the full austenitise and temper heat treatment gave weld centre-line properties similar to the parent material. However, for SA508 Gr. 4N, a modified single step PWHT restored a high level of toughness performance to the weld metal, in comparison with the parent.

Finally, fracture toughness testing on the SA508 Gr. 3 and SA508 Gr. 4N materials has been undertaken to determine the upper shelf fracture toughness (J1C) at 250°C, using multi-specimen compact tension (C(T)) test specimens. These data showed that there were little observable differences in the performance of welds produced by either the conventional high vacuum welding system, or the local vacuum system.
Cryogenic Aluminum to Stainless Steel Pipe Transition Joint Qualification
Authors: Ok Ali , Dally John A. , Tentarelli Stephen C.
Published: November 2023

Many cryogenic heat exchanger applications use aluminum pressure vessels that are connected to stainless steel piping typically either by dissimilar metal flange pairs or aluminum to stainless steel transition joints. Transition joints can provide a number of advantages over flanges. Transition joints can save space and weight over flanges, and provide a leak tight connection which can eliminate fugitive emissions. Aluminum to stainless steel transition joints have been built using different technologies, including:

1. Friction welding

2. Explosion welding

3. Nonwelded, diffusion-bonded (heat shrinkage/hot pressing assembly)

This paper focuses on explosion-welded transition joints, although some of the concepts discussed may also apply to other technologies. ASME Pressure Vessel and Piping codes do not provide specific design guidelines or qualification requirements for these joints. ASME Code Case 2493 provides qualification requirements for explosion welding of dissimilar metal plates, but not for the final transition joint design. This paper shall highlight an approach to addressing specific concerns regarding the qualification and production testing of explosion-welded plates and transition joints for cryogenic applications. It shall also cover aspects of the design, qualification, and rating of the cryogenic transition joints made from explosion-welded parent plates.

ASME B31.3 Section 304.7 Pressure Design of Other Components addresses the pressure design of unlisted components in 304.7.2, which provides four acceptable qualification methods. This paper will discuss two of those methods: proof testing and detailed stress analysis, i.e., Finite Element Analysis (FEA). A combination of these two methods can be used to ensure a safe and effective design.
Simplified Method for Adjusting the Shape and Characteristic Strength Parameters of the Weibull Strength Distribution of Graphite Materials
Authors: Saitta Michael , Beirnaert Gwennaël
Published: November 2023

The 2021 version of the ASME Boiler and Pressure Vessel Code Section III, Division 5, Paragraph HHA-3217 utilizes a 3-parameter Weibull distribution to characterize the strength of graphite materials. Subparagraph (g)(2) thereof requires that the designer modify the threshold parameter (S0). However, no guidance is provided to update the other parameters of the Weibull distribution following an update of S0 (i.e., Sc, the characteristic strength parameter, and m, the Weibull modulus or also referred to as the shape parameter). This paper illustrates why failing to update the other parameters results in an unrealistic and overly conservative distribution.

This paper provides a simple method to update the shape and characteristic strength parameters of the Weibull distribution. This method relies on a straightforward, algebraic formulation that is easy to implement and does not require access to the underlying experimental datasets. The performance of the method is evaluated and shown to compare favorably with maximum likelihood estimate (MLE) optimization using both simulated and experimental data. Differences between methods tend to be on the order of a few percent and are negligible for small changes to S0. Moreover, any deviations are further shown to be conservative for the purposes of stress analysis of graphite.
Challenges in KIH Testing Using WOL Samples for Pipeline Applications
Authors: Cravero Sebastian , Cristea Mihaela E. , Deul Marije L. , Walters Carey L. , Valdez Martín E. , Darcis Philippe
Published: November 2023

Gaseous Hydrogen can have detrimental effects on the mechanical performance of carbon steels, and those effects need to be taken into account for the proper design of pipelines for H2 transportation systems. ASTM E1681 is the standard test method used to evaluate fracture toughness in an H2 environment and presents the possibility of testing under constant loading or under constant displacement conditions. Given the comparative simplicity of testing self-loaded specimens in constant displacement, this type of test has become a “standard” for the industry. However, satisfying the different validity checks required by the testing standard presents several challenges that seems to be very difficult to solve. The present paper explores the limits in terms of dimensional requirements and stress intensity factor solutions using finite element simulations and experimental testing.
Sequentially-Coupled Hydrodynamic and Structural Analysis of Radiographic Windows in Blast Confinement Vessels for Proton Radiography of Physics Experiments
Authors: Fister Matthew , Spencer-Coker Christian , Fehlmann Kevin , Spernjak Dusan
Published: November 2023

Characterization of shock-driven materials via radiography is critical to the success of Los Alamos National Laboratory’s (LANL) mission. Radiographic experiments with both hazardous material and high explosives (HE) require a two-part pressure vessel containment system (PVCS) composed of an inner pressure confinement vessel (IPCV) and an outer pressure containment vessel (OPCV). A new PVCS developed for LANL’s Proton Radiography facility (pRad) will enable a suite of experiments with up to 1.06 ounces (30 grams) TNT-equivalent HE. The critical component of the IPCV is the beryllium radiographic window, which must withstand the blast pressures from the HE while minimizing radiographic blur. Because the amount of HE used in the suite of experiments will vary, the IPCV is designed to be modular, such that for each experiment a new radiographic window may be optimized and installed into the IPCV. Each radiographic window design must undergo an HE over-pressure test (OPT) per ASME specifications for impulsively-loaded pressure vessels. To optimize each window’s structural performance and radiographic blur, and to establish confidence that the window will survive the OPT, a sequentially-coupled hydrodynamic and structural analysis workflow has been automated, facilitating design-by-analysis starting at initial concept development and extending through pre-test predictions for qualification tests of a component under extreme environments.
Accuracy of the Time History Analysis of 2DOF Subjected to Base Excitations Based on the Superposition of the Elasto-Plastic Response of Each Mode
Authors: Taniguchi Tomoyo , Ueno Seiya , Shoji Yasumasa , Kimura Yukinobu
Published: November 2023

This paper develops the time history analysis of the elasto-plastic response of the 2DOF, consisting of two masses and springs that exhibit bilinear hysteresis, being subjected to a base excitation, based on superposition of the time history of elasto-plastic response of each mode. The essence of the proposed analysis is that the response of the 2DOF during the yielding of any springs consists of the mode frequencies, shapes and dampings that are readily specified by the eigenvalue problem employing the mass and the secondary stiffness of the spring yielded. First, the equations governing the response of each mode according to the state of spring and all quantities needed for them are described in detail. Next, a displacement time history of each mode is numerically and simultaneously analyzed, because the response of each mode is superposed at every time step to verify the elastic limit or turn-around points of each spring that are only verifiable in the global coordinates system. Once the response exceeds the elastic limit of each spring or the turn-around points, the equations of motion of each mode are switched to those of the next state of spring. Finally, the accuracy of the proposed method is thoroughly discussed. Moreover, the force-displacement diagram of each mode is presented. The applicability of the SRSS method is also examined.
Fracture Load Predictions in 3D Printed Graphene-Reinforced PLA Notched Specimens Using the Average Strain Energy Density Criterion
Authors: Cicero Sergio , Arrieta Sergio
Published: November 2023

This paper applies a methodology in which the Average Strain Energy Density (ASED) criterion is used to estimate fracture loads on 3D printed graphene-reinforced PLA (polylactic acid) SENB (single edge notched bending) specimens containing U-shaped notches. The ASED criterion is based on the quantification of the Strain Energy Density averaged over a control volume specifically defined at the notch tip. The approach is based on the idea that failure takes place when the mean value of the elastic strain energy (W) referred to a specific volume is equal to a critical value (Wc), which may be understood as a material property. The material analyzed in this work was 3D printed with three different raster orientations (0/90, 30/−60 and 45/−45) for which tensile tests on plain specimens and fracture toughness tests on cracked specimens had been previously performed. Then, notched specimens with notch radii of 0.25 mm, 0.5 mm, 1 mm and 2 mm, were conducted to fracture, determining the corresponding experimental fracture loads. Finally, these experimental fracture loads were compared to the fracture load estimations derived from the application of the ASED criterion. The results demonstrate the accuracy of the ASED criterion for estimating fracture loads in this particular 3D printed material.
Proposal for the Design of a Dynamically Loaded Pressure Vessel With the Ratio of the Pulse Period to the Vessel Natural Vibration Period More Than 0.35
Authors: Nourani Mohamadreza , Zimmermann Joerg , Seraj Mohsen , Clayton Alan
Published: November 2023

In ASME BPVC Section VIII Division 3 (2021) [1], impulse loading has been defined as “a loading whose duration is a fraction of the periods of the significant dynamic response modes of the vessel components. For a vessel, this fraction is limited to less than 35% of the fundamental, membrane-stress dominated (breathing) mode”. In this article, designing a pressure vessel for a Fusion Demonstration Plant (FDP) that is exposed to pressure pulses as high as 34.5 MPa at 14.3 msec period is discussed. The vessel and the connected accumulators (gas drivers) to it have a dominant natural frequency of about 102 Hz, related to the breathing mode based on our dynamic analysis was used. The ratio of the pulse period to the natural vibration period of the vessel is 1.457. This is much higher than the 0.35 limit in the code. In this article, the design criteria are detailed, and it is proposed to be added to the ASME BPVC Section VIII Division 3.
A Critical Initial Flaw Size Analysis Approach for Cleavage Fracture in the Circumferential Welds of Layered Pressure Vessels
Authors: Kirby Matthew L. , Riha David S. , Cardinal Joseph W. , Hobbs Joel R. , Stoltz Brian C. , Melia Benjamin D.
Published: November 2023

The National Aeronautics and Space Administration (NASA) operates roughly 300 non-code layered pressure vessels (LPVs) constructed of steels that are at a risk of cleavage fracture during operation. NASA is currently assessing the continued fitness-forservice of these vessels and is employing computational analysis of the critical initial flaw size (CIFS) in key regions in the LPVs, such as the circumferential welds, to guide non-destructive evaluation (NDE) inspections. The NASGRO fatigue crack growth and fracture mechanics software is being used to perform the CIFS analysis. Cleavage fracture toughness varies as a function of crack-front length, but standard procedures for computing the CIFS in NASGRO assume fracture toughness is invariant to crack-front length. Thus, the CIFS analysis procedure in NASGRO was modified to account for a fracture toughness value that is dependent on crack-front length and a varying aspect ratio during the CIFS computations. This paper describes the CIFS analysis approach for cleavage fracture in circumferential welds using NASGRO and provides an example of the analysis for a postulated flaw in the shell-to-shell circumferential weld of a 9-layer exemplar vessel within NASA’s LPV fleet.
Linkage of Fracture Assessment Methodology With Fracture Toughness Testing Procedures
Authors: Cooper Adam J. , James Peter , Sharples John
Published: November 2023

J-Integral, J, is a commonly accepted elastic-plastic fracture mechanics parameter defined as the amount of energy released per unit area of crack surface increase. J can be calculated numerically or measured experimentally using standard test specimen geometries and internationally accepted testing standards. The former is conventionally considered for structural components containing known or postulated defects and the latter for evaluating material fracture toughness. J for the structural component can subsequently be compared with the material fracture toughness J in order to assess structural integrity. R6 is an elastic-plastic fracture mechanics methodology that is inherently based on these two J evaluations. In terms of fracture toughness evaluation, despite J being originally developed to account for crack tip plasticity, it can be challenging to measure valid values of J using conveniently sized fracture toughness test specimens — even as large as B = 25mm Compact Tension (C(T)) — when testing modern, high toughness materials due to the extent of global plasticity generated during loading.

Traditionally, fracture toughness testing procedures like ASTM E1820 have not been “linked” to structural integrity methodologies like R6 other than for the measured fracture toughness values to be “plugged” into the actual evaluations. However, in view of the fracture toughness evaluation challenges referred to above, a study has been undertaken to investigate how the validity limits specified in ASTM E1820 compare with the “plasticity” limit, specified in R6 and defined as Lrmax. The paper shows that C(T) B = 25mm specimens, tested/analysed according to ASTM E1820, produce JIc initiation toughness values residing in the Lrmax domain of the R6 Failure Assessment Diagram (FAD). This is despite the experimental JQ value being successfully qualified as JIc using the validity criteria in ASTM E1820 and J-R curves falling well below Jmax for the selected C(T) B = 25mm specimen size.

This paper highlights the potential challenges associated with measuring valid and meaningful values of fracture toughness (J) for modern high toughness structural steels, without adopting inconveniently large specimen sizes. This further indicates that that there is a potential for reported JIc values to display a specimen size sensitivity due to the anticipated global plasticity experienced during testing.
Comparison of Design Approaches on the Design Lifetime Prediction of Gaseous Hydrogen Storage Tanks
Authors: Fischer Carl , Oesterlin Heiner , Michler Thorsten
Published: November 2023

Stationary tubular hydrogen storage tanks often consist of parallel connected short pipes. The influence of gaseous hydrogen on the lifetime can be assessed following the German AD 2000 code (2021) for pressure vessels. The AD 2000 code proposes a crack initiation criterion based on S-N curves, which should be considered especially for newly designed storage tanks. Due to the special design of the tanks, the lifetime might be also assessed according to the ASME B31.12 (2019), which is a worldwide standard accepted for hydrogen pipelines. This paper presents a comprehensive study of the lifetime assessment of a hydrogen storage tank with the fracture mechanics-based approach of the ASME B31.12, where the influence of different input parameters (e.g. the initial crack depth and aspect ratio, stress intensity factor solution, fatigue crack growth law) are investigated. The results of the two different design philosophies from AD 2000 and the ASME B31.12 codes are compared and differences in the allowable number of loading cycles for the lifetime prediction of hydrogen storage tanks are discussed.
Probabilistic Fracture Mechanics Codes for Piping International Benchmark—Part 2: Probabilistic Comparisons
Authors: Homiack Matthew , Duan Xinjian , Wang Min , Heckmann Klaus
Published: November 2023

This paper is the second in a series of two papers that describe benchmark comparisons of 14 probabilistic fracture mechanics codes. The benchmark problems focus on determining the leak-before-break behavior of a nickel-based alloy weld in a large-bore piping system of a pressurized water reactor. The modeled degradation mechanism is primary water stress corrosion cracking. In Part 1, which is covered in the technical paper PVP2022-84724, the benchmark problem was deterministically analyzed with the probabilistic fracture mechanics codes using their models for crack growth rates, stress-intensity factors, crack-opening displacements, crack transition from inside surface-breaking cracks to through-wall cracks, leak rates, and crack stability. Several output quantities of interest relevant to leak-before-break behavior were compared. In Part 2, the benchmark problem was probabilistically analyzed with the probabilistic fracture mechanics codes by introducing uncertainties in key input parameters, such as the crack growth rate and welding residual stresses. The probabilities of leak and rupture as a function of time were then compared accounting for the effects of leak detection and inservice inspection. Interpretations of the probabilistic comparisons are provided to assess scatter among the probabilistic fracture mechanics code predictions. These interpretations are supported by an enhanced understanding of the different modeling approaches as gleaned from the deterministic benchmark comparisons.
Fluid-Structure Interaction Simulations to Predict Flow-Induced Vibration of Piping Due to CO2 Multiphase Flow
Authors: Pontaza Juan P. , Belfroid Stefan , Bazuin Rens
Published: November 2023

Fluid-structure interaction (FSI) simulations of high-pressure multiphase CO2 flow in 2-inch piping were performed to predict flow-induced piping vibration and stress. Computational fluid dynamics (CFD) was used to predict the unsteady multiphase flow in the piping and the flow-induced forces on the bends. A structural finite element model of the 2-inch piping system was loaded with the CFD-predicted flow-induced loading to predict piping vibration and stress in time domain. A one-way FSI simulation approach was adopted, where the flow interacts with the structure, but it is assumed that the vibration of the structure does not affect the flow field.

The 2-inch piping system is a high-pressure flow loop where piping vibration and stress were measured for a range of CO2 multiphase flow conditions in a test campaign aiming to characterize piping vibration responses with CO2 as the working fluid. The numerically predicted piping vibration and stress are compared against physical measurements collected during the test campaign at locations where accelerometers and strain gauges were installed. The selected flow conditions are for CO2 in gas and liquid phases with operation at a phase transition condition of 55 bara and 18°C. Simulations are performed for three flow conditions with increasing gas rate and fixed liquid rate, resulting in flows with decreasing liquid content by volume: 12.5%, 8.85%, and 6.73%. We find good agreement when comparing the predicted vibration levels against those measured by the accelerometers and find that the predicted stress is conservative relative to the stress measured by the strain gauges. The results validate the FSI predictions and instill confidence in the simulation approach, which is recognized as a powerful tool to predict flow-induced vibration of piping in multiphase systems.
Fire Assessments in Refineries, 20 Years of API 579 Part 11 Use at TotalEnergies
Authors: Le Nevé Charles
Published: November 2023

Fires in refineries and petroleum plants have catastrophic consequences, both in terms of human and material damage. After a fire, it is crucial to assess the extent of the damage to determine the necessary repairs and develop a timeline for restarting operations. The API 579 Part 11 [1] provides a pragmatic and efficient approach for assessing the damage to pressure vessels and piping. TotalEnergies has successfully used this document for more than 20 years. The purpose of this paper is to present the practices for investigating incidents and assessing the associated damage, including its limitations, implementation for different fire types, and necessary organization.

API 579 Part 11 recommends establishing six heat exposure zones. For metallic pressure vessels and piping, only the hot exposure zones (zones 4 to 6) are likely to result in damage, and these zones are the focus of this paper. After heat exposure zones are established, an exhaustive list of affected equipment is necessary to define dedicated inspection plans and associated assessment levels. The results of the inspection plan are then used to determine equipment acceptance, repair requirements, or replacements.
Fluid-Structure Interaction Simulations of a Rod Subjected to a Water Axial Flow in a Nuclear Core Relevant Configuration
Authors: Vivaldi Daniele , Pulicani Roxan
Published: November 2023

Forces exerted by the water coolant flow in nuclear reactor cores result in fuel rod and fuel assembly vibrations. The consistent prediction of such turbulence-induced forces by CFD simulations requires turbulence scale-resolving approaches with highly refined grid sizes. With the goal of assessing the capabilities of CFD simulations to predict fluid-induced vibrations in such configurations, this paper presents fluid-structure coupled simulations of an experimental campaign of a single vertical rod subjected to an axial water flow. The rod is cantilever, the water flow impacts the rod free-end, and then rises upward from the rod free-end towards the clamped end. The flow is confined inside an annular channel. The resulting simplified configuration is relevant for water-cooled reactor cores. The numerical simulations were realized with the CFD code code Saturne, inside which an Euler-Bernoulli finite element beam model was implemented, allowing 2-way coupled calculations. The Arbitrary Lagrangian-Eulerian method was used for taking into account the structure deformation inside the fluid domain. URANS and hybrid URANS/LES simulations were run: as expected, the former was definitely uncapable of predicting the correct rod vibration response, which are largely underestimated; on the other hand, DDES was found to predict vibrations amplitudes of the same order of magnitude as the experimental measurements.
A Continuation of Evaluating the Sealing Performance of Engineering PTFE-Based Gaskets in Fiberglass-Reinforced Plastic Flange
Authors: Berrios Aidan , Rice Tim , Wilson Jeffery
Published: November 2023

Proper gasket selection for fiberglass-reinforced plastic (FRP) flanges is critical to the long-term success of the flanged connection. Typically, the chemical capability and the finical aspects of the gasket material dictate the materials recommended for use in the system. While chemical compatibility is essential and has to be a factor in determining the correct material, the sealing performance of the material should also be heavily considered during this process. However, limited efforts have been allocated to evaluate the sealing performance of the various gasket materials in FRP systems. Historically, full-face elastomer gaskets have been utilized in FRP connections. This is primarily influenced by elastomeric materials’ inherent ability to seal at low gasket stresses and various available elastomeric materials with broad chemical resistance. The low stress to seal materials are a benefit for flange designers; however, elastomeric materials have less than ideal mechanical characteristics in flanged connections, leading to long-term service reliability issues.

The industry has dealt with these issues for decades, and now that engineered PTFE-based products are commercially available, they have started utilizing them with positive results. Based on the testing protocol and research discovered in the PVP paper PVP2022-80474 [1], the authors aim to continue this endeavor by testing additional materials to expand the industry’s knowledge and awareness.

This paper compares the sealing performance of two additional PTFE-based gaskets and two elastomer-based gaskets under these test parameters. This evaluation will provide end-users with a comprehensive method of assessing gasket styles and guiding proper gasket selection for FRP flange services.
PRCI Burst Pressure Model Modernization and Performance
Authors: Lamborn Lyndon , Kwok Ernest , Polasik Steven J. , Hanna Benjamin
Published: November 2023

The Pipeline Research Council International (PRCI) contracted development and deployment of a burst pressure prediction fracture mechanics model in 2001, embodied in the CorLAS™ V2.0 software. Since that time, many North American operators have made this model an integral part of their integrity management processes with excellent track records for both effectiveness and efficiency. Even though the PRCI burst model originally targeted pipe body stress corrosion cracking, operators have found the model performs equally well for discrete crack-like features associated with long seam welds, and highly versatile in estimating burst pressures of irregularly shaped crack-likes reported by both in-line inspection tools and field non-destructive evaluations. The question is: can application of the model evolve to address emerging threats and trends?

As the pipeline industry transitions away from Charpy V-Notch energy as a low fidelity fracture toughness surrogate, Enbridge has repackaged the PRCI burst model to accept K toughness directly, and referred to as KorLAS herein to denote K input built on legacy CorLAS™ equations and empiricism. KorLAS performance over the tested range of flaw dimensions, pipe steel toughness, wall thicknesses, crack morphology, and crack shape are assessed and compared to test and forensic data.

The pipeline industry has emerging technologies which are able to detect, size, and report selective seam weld corrosion (SSWC) features. The predicted burst pressures of SSWC features have historically been difficult to predict. A reasonable and prudent tailored KorLAS input method to assess SSWC fitness for service is presented.

KorLAS performance at lower toughness has been difficult to validate or judge due to the scarcity of available test data. Test data now made available to the public allows tentative envelope expansion down to about the 10th percentile toughness observed in North American vintage line pipe. Although cold welds can be problematic to detect, KorLAS performance in assessment of cold welds is evaluated against available test data.
Development of Prediction Tool for Flow-Accelerated Corrosion: (3) Development and Validation of Prediction Software “FALSET” With Water Single-Phase FAC Data Obtained in Japanese BWR Plants
Authors: Uchiyama Yuta , Morita Ryo , Fujiwara Kazutoshi , Yoneda Kimitoshi
Published: November 2023

The current management of the pipe wall thinning of Japanese nuclear power plants is based on the thinning rate and residual lifetime evaluated using the measured pipe wall thickness. For the improvement of the current management in Japan, we have developed an original prediction software for pipe wall thinning named FALSET. FALSET can predict the maximum thinning rate in each pipe component in one-dimensional pipelines by using our simplified prediction models for the local thinning rate of flow-accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI). In this report, we describe the validation and improvement of FALSET using water single-phase FAC data on feedwater and condensate lines in Japanese boiling water reactors (BWRs) under a neutral pH 7.0 condition with dissolved oxygen. The results show that FALSET has high predictive performance for water single-phase FAC data obtained in Japanese BWR plants.
Seismic Response of Tubes Vibrating Independently in In-Plane Direction for U-Shaped Tube Bundle With Triangular Arrays in Steam Generators
Authors: Monde Masatsugu , Ono Naoki , Nakamori Tomohito , Hirota Kazuo , Matsubara Masahito , Mineno Tomonori , Taguchi Koshi
Published: November 2023

Ensuring a complete integrity of steam generators’ tubes during earthquakes is critical. In order to predict the vibration behavior of tube bundle in in-plane direction, seismic tests for U-shaped tube bundle with square arrays had been carried out. During the tests, vibrations were observed in the tube bundle at the location where the tubes and the AVBs vibrate as a whole structure. Independent vibrations for some tubes were also observed at the location where the tubes slide with the AVBs and impact with the adjacent tubes. As for the seismic design, carrying out an evaluation of the tube stress for independent vibrations was sufficient, because the maximum stress of the tubes was much larger than that of the tube bundle vibration.

Since tube bundles with triangular arrays have different tube pitches, seismic excitation tests were carried out for this study, to grasp the vibration characteristics of the tubes in in-plane direction. Independent vibrations were observed for some tubes during the tests. The effects of the excitation level, the dominant frequency of excitation wave and the bending radius on independent vibration characteristics were investigated. The damping ratio of independent vibrations is mainly caused by friction force at low velocity, and by impact force with adjacent tube at high velocity. Tube stress of the independent vibration was calculated using the minimum damping ratio obtained from the tests. It was concluded that the calculation can conservatively evaluate the stress of tubes vibrating independently by comparing with the test results.