bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous control of forward and backward locomotion by spinal sensorimotor circuits
Authors: Audet Johannie , Lecomte Charly G. , Harnie Jonathan , Yassine Sirine , Al Arab Rasha , Soucy Félix , Morency Caroline , Mari Stephen , Jéhannin Pierre , Merlet Angèle N. , Frigon Alain
Published: November 2023

Mammals walk in different directions, such as forward and backward. In human infants/adults and decerebrate cats, one leg can walk forward and the other backward simultaneously on a split‐belt treadmill, termed hybrid or bidirectional locomotion. The purpose of the present study was to determine if spinal sensorimotor circuits generate hybrid locomotion and if so, how the limbs remain coordinated. We tested hybrid locomotion in 11 intact cats and in five following complete spinal thoracic transection (spinal cats) at three treadmill speeds with the hindlimbs moving forward, backward or bidirectionally. All intact cats generated hybrid locomotion with the forelimbs on a stationary platform. Four of five spinal cats generated hybrid locomotion, also with the forelimbs on a stationary platform, but required perineal stimulation. During hybrid locomotion, intact and spinal cats positioned their forward and backward moving hindlimbs caudal and rostral to the hip, respectively. The hindlimbs maintained consistent left–right out‐of‐phase alternation in the different stepping directions. Our results suggest that spinal locomotor networks generate hybrid locomotion by following certain rules at phase transitions. We also found that stance duration determined cycle duration in the different locomotor directions/conditions, consistent with a common rhythm‐generating mechanism for different locomotor directions. Our findings provide additional insight on how left–right spinal networks and sensory feedback from the limbs interact to coordinate the hindlimbs and provide stability during locomotion in different directions.

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Key points

Terrestrial mammals can walk forward and backward, which is controlled in part by spinal sensorimotor circuits.

Humans and cats also perform bidirectional or hybrid locomotion on a split‐belt treadmill with one leg going forward and the other going backward.

We show that cats with a spinal transection can perform hybrid locomotion and maintain left–right out‐of‐phase coordination, indicating that spinal sensorimotor circuits can perform simultaneous forward and backward locomotion.

We also show that the regulation of cycle duration and phase duration is conserved across stepping direction, consistent with a common rhythm‐generating mechanism for different stepping directions.

The results help us better understand how spinal networks controlling the left and right legs enable locomotion in different directions.
An Optimal Numerical Strategy for Intake in Crosswind Conditions
Authors: Chennuru Venkata Y. T. , Zhao Fanzhou , Vahdati Mehdi
Published: November 2023

Crosswind can reduce the operability of an aeroengine significantly at static or near static operating conditions. Computational fluid dynamics predictions of the flow at crosswind conditions will play an important part in future designs, however, accurate numerical predictions of the flow within the intake remain challenging even for simulations of cases with intake only. The main objective of this paper is to demonstrate the importance of numerical setup and to determine an optimal computational model for crosswind investigations that can be used by other researchers. By considering the flow to be inherently unsteady, the influence of inlet and exit boundary conditions, and grid sensitivity is studied by using unsteady Reynolds-average Navier–Stokes (URANS) simulations. Numerical predictions of the time-averaged intake pressure recovery (IPR) and the motion of the vortex on the ground are compared against the existing experimental data. The results show that for an intake under crosswind, the ground vortex that forms under the intake and the in-duct separation, when present, exhibit unsteady behavior that become stronger as the crosswind velocity is increased. The steady-state simulation is only representative at lower crosswinds. The intake flow separation and ground vortex predictions are influenced by the inlet boundary layer profiles. Moreover, acoustic reflection was observed at the intake exit boundary which propagates upstream, creating artificial unsteady frequencies in IPR. The reflection is generated from the use of uniform boundary conditions at the intake exit and is not dissipated in the grid due to the long wavelength; this can be mitigated by using a choked nozzle at the intake exit. Acoustic reflection was also observed at the far-field exit boundary. These reflections are caused from interaction of trailing vortex and far-field boundary.
Updating Turbomachinery Aerodynamics Teaching on an Undergraduate Course Using Three-Dimensional Design Tools
Authors: Ingram Grant
Published: November 2023

This paper outlines the update of a turbomachinery course to cover three-dimensional (3D) aerodynamics using a Reynolds-Averaged Navier Stokes solver. Prior to the activities outlined in this paper, the course was taught in a conventional way with a series of lectures and a timed, written, open book examination in a formal exam setting. Students were equipped with a calculator and set of notes including correlations from Howell and Soderberg. The students had around 1 h to answer the turbomachinery question, which was revealed to them only when they opened the paper at the start of the exam. This limited the depth of any aerodynamic problem they could get through and so they were restricted to simple design or analysis exercises. The genesis of the course update was the release in 2017 of “MULTALL OPEN” (Denton, J. D., 2017, “Multall: An Open Source, Computational Fluid Dynamics Based, Turbomachinery Design System,” ASME J. Turbomach., 139(12), p. 121001), a freely available turbomachinery design system, and this was adopted as the course software—although other software choices were considered. Students now produce two turbomachinery designs during the course. These are both based on the J85 turbojet—largely to keep cycle calculations to a minimum but it was also important to ensure that students recognize that they were completing a real engineering task. The first task was a 3D aerodynamic design of multistage turbine, which includes compressible flow, tip clearance, and stacking techniques such as lean or sweep. The second task was a midspan (two-dimensional) compressor design. The exact cycle conditions were varied each year to explore design scenarios such as an increase in firing temperature. Assessment was by means of a short report where the best students report on their design choices, provide critical analysis of the design using appropriate postprocessing techniques, and compare their designs to the state of the art in the wider literature. As well as describing the successes and challenges of the update to 3D design methods the paper provides some guidance for educators thinking about adopting a similar approach.
Experimental Study on Thermal Management of Nano-Enhanced Phase Change Material Integrated Battery Pack
Authors: Vali P. S. N. Masthan , Murali G.
Published: November 2023

In recent years, lithium-ion batteries (LIBs) have gained attention and popularity due to their extended cycle life and high energy density. A hexagon-shaped 18,650 lithium-ion cylindrical cell battery pack was designed, incorporating paraffin wax (PA) as a phase change material (PCM) and nano-enhanced phase change material (Ne-PCM). However, the low thermal conductivity of the PCM causes a significant challenge to the development of electric vehicles (EVs). The highest temperature in the cylindrical cell battery pack is reached in the midregion, leading to an uneven temperature distribution across the cells. To overcome these challenges and achieve efficient battery module performance, phase change with nanomaterials such as graphene platelet nanopowder (GPN), multiwalled carbon nanotubes (MWCNTs), and graphite-synthetic powder (GSP) was placed in the center of four cells. Studies on the battery module were conducted without cooling, with PCM cooling, and with Ne-PCM cooling. The investigation revealed that the battery pack with Ne-PCM performed well, maintaining the temperature below 50 °C at different discharge rates of 1C, 2C, and 3C, and ensuring a uniform temperature variation within the cells. Ne-PCM decreased the temperature differential between the modules at 1C, 2C, and 3C discharge rates by 85.49%, 91.47%, and 84.21%, respectively, compared to PCM.
Uncertainties in In-Structure Response Spectra Due to Uncertainties in Input Motion Amplitude and Phase Spectra
Authors: Nie Jinsuo R. , Xu Jim , Graizer Vladimir , Seber Dogan
Published: November 2023

We concluded in PVP2020-21132 that the four or five time histories in the current practice are not sufficient for estimating stable mean in-structure response spectra (ISRS), therefore a check of their power spectral density functions is necessary. The time histories used in that work were not developed based on typical response spectrum (RS) convergence criteria and did not consider the uncertainties in Fourier amplitude spectra. This paper examines how the uncertainties in both Fourier phase spectra and Fourier amplitude spectra of the input motions resulting from seed time histories and a new RS-matching algorithm affect the uncertainties in ISRS. This study finds that the coefficient of variation in ISRS reached as high as 68%, generally confirming previous results obtained using a different RS-matching algorithm. This level of ISRS variation continues to support our conclusions in PVP2020-21132. Therefore, a check of the power spectral density functions of the multiple input time histories in the current practice is necessary to ensure the estimated mean ISRS would vary on the conservative side, although not as stable as necessarily required for reasonable confidence levels. These results provide the necessary technical bases for consistent technical positions between industry standards and regulatory guide for nuclear power plants.
Experimental Evaluation of Contribution of Content Liquid to Uplift Commencement Condition of Cylindrical Liquid Storage Tanks Subject to Horizontal Base Excitation
Authors: Yoshida Yuichi , Taniguchi Tomoyo
Published: November 2023

This study experimentally investigates contribution of content liquid to the uplift commencement condition of flat-bottom cylindrical shell tanks subjected to the horizontal base excitation. The conventional analytical models assume that the tank bottom plate uplifts when the overturning moment overcomes the resistant moment consisting of dead weight of a side shell (including the fixed roof and the appurtenances). In other words, the conventional uplifting resistance system in tanks does not implicitly expect any contribution of the content liquid to it.

In this study, a tank model made of PVC was set on a shaking table and the required horizontal acceleration to commence uplift of the tank bottom plate was investigated by increasing the amplitude of the horizontal sinusoidal base excitation step by step. In this experiment, several aspect ratios (Liquid depth / Diameter = 0.25, 0.30, 0.35, 0.40) of the content liquid, which were adjusted by changing the liquid depth, were used. Despite aspect ratio of tanks, the observed acceleration required to commence uplift was larger than that estimated from the conventional analytical model. These results imply existence of the content liquid contributing to the uplift commencement condition of the liquid storage tanks and necessity of its quantification.
Literature Review on Testing of Mini-CT Specimen to Characterize the Ductile-to-Brittle Transition Range and the Upper Shelf Regime
Authors: Sánchez Marcos , Cicero Sergio , Arrieta Sergio
Published: November 2023

In recent years there have been significant research efforts toward the miniaturization of specimens when characterizing the fracture toughness of ferritic steels. In particular, the nuclear sector has been especially interested due to the strict structural integrity controls to which the different nuclear components are subjected, with the reactor pressure vessel being one of the most critical. In this sense, the use of the mini-CT specimen (a compact tension 4 mm thick specimen) constitutes a promising alternative that has been widely studied together with the Master Curve approach to characterize steels within the ductile to brittle transition range. Additionally, this type of specimen has also been used to characterize steel operating within the upper shelf regime. Within the transition regime, the majority of the results reveal an excellent correlation between the results obtained using mini-CT specimens and those obtained when using well-known conventional size specimens (e.g., 1T-CT specimens or PCCv specimens), which seems not to be the case when dealing the ductile regime. However, testing such a small geometry brings a series of peculiarities that are necessary to consider. This work intends to briefly gather the knowledge found in the literature and to expose the best practices when testing this type of specimen. The effect of the specimen geometry, the possible use of side grooves, the measurement of the displacement (front face vs load line), or different conditions during testing (e.g., selection of testing temperatures) are analyzed and discussed.
Buckling Strength of the Liners of Type IV Hydrogen Storage Cylinders
Authors: Feng Heyi , Jiang Yongshan , Bo Ke , Deng Guide , Wu Xiaofei , Yang Hao
Published: November 2023

Type IV hydrogen storage cylinders have the advantages of long fatigue life, high hydrogen storage density, and low cost, which makes it a popular research and development topic. Local buckling phenomena of the cylinder liners are observed during rapid depressurization of the type IV hydrogen storage cylinders. The buckling strength of their liners against external pressure was studied by numerical simulation and vacuum test, and the factors that may influence the buckling strength were investigated by numerical simulation. Three sets of liners with 60 L volume capacity were selected, for which the length-to-diameter ratio was around 2.5. An experiment was performed to study the buckling strength of the liner against external pressure. The test result shows that the buckling strength of the liner is about 0.06 MPa. Finite element analysis shows that the liner used in the experiment has a buckling strength around 0.03 MPa. The reason why the difference occurs may be the leakage of the liner induced by poor sealing technique in the experiment. Finite element analysis was used to conduct a parametric study on factors that may affect the buckling strength, which are left-over weld height and thickness-to-diameter ratio. The FEA results show that the buckling strength of the liner is much smaller than 0.1 MPa. The left-over weld height during the fabrication process slightly increases the buckling strength when thickness is greater than 2 mm, while it does not have a significant effect on buckling mode. The buckling strength of the liner increases with an increasing thickness-to-diameter ratio.
Numerical Simulations of the Dynamic Response of Gas Handling Manifolds Mounted on an Impulsively Loaded Confinement Vessel
Authors: Valdiviez Robert , Spernjak Dusan , Scarafiotti Jesse
Published: November 2023

A new vessel system is being developed for performing small-scale shock-physics experiments in a proton beam imaging facility at the Los Alamos National Laboratory (LANL). The Inner Pressure Confinement Vessel (IPCV) is the impulsively loaded vessel that confines the detonation products from the explosively driven experiment and provides access for the proton beam, and other diagnostics, to interrogate the dynamic event. The products of the detonation, that are either in a gaseous state or a solid state, are confined within the IPCV. The gaseous products are to be vented from the IPCV prior to allowing personnel to reenter the experiment area and be in close proximity to the IPCV.

The IPCV is connected to the overall gas handling system, known as the Vessel Gas Handling System (VGHS) via three independent manifold assemblies. Each manifold is operated remotely to allow for the venting of the gaseous products in the IPCV. Each manifold is rigidly connected to the top cover of the IPCV, and each receives significant dynamic loading from the IPCV performing its impulsively loaded confining function.

The basic design requirement for the VGHS manifolds is to meet the requirements of the standard ASME B31.3, Process Piping. ASME B31.3 in turn allows for analyzing unlisted components to the requirements of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, or designated as ASME VIII-2 for the structural response. Each IPCV VGHS manifold assembly is analyzed per ASME VIII-2 for its dynamic loading response because all components are unlisted for this loading regime. This paper reports on the simulation effort performed to predict the structural response of the manifold assemblies to the impulsive loading environment of the IPCV.
Development of Prediction Tool for Flow-Accelerated Corrosion (4) Development and Validation of Prediction Software “FALSET” With Water Single-Phase FAC Data Obtained in Japanese PWR Plants
Authors: Morita Ryo , Uchiyama Yuta , Fujiwara Kazutoshi , Yoneda Kimitoshi
Published: November 2023

Pipe wall thinning is one of the important issues to be managed in the maintenance of power plants. In Japan, as utilities manage wall thinning on the basis of pipe wall thickness measurements, a large number of wall thickness measurements are necessary for each outage in power plants. Therefore, the authors have developed a wall thinning prediction software, “FALSET”, for the improvement of wall thinning management. This report describes details of FALSET, and its validation and modification using Japanese PWR plant data with high-pH operation and all secondary system temperature conditions. The results show that FALSET can evaluate the wall thinning rate that is close to the measured thinning rate of actual Japanese plant, thereby improving the reliability of FALSET.
Study on the Small Leakage Characteristics and Noise Reduction Methods of Liquid Pipelines Based on Internal Acoustic Detection
Authors: Ma YunDong , Dong ShaoHua , Wei Haotian , Qian WeiChao , Zhang Hang , Xu LuShuai
Published: November 2023

Timeously detecting pipeline small leakages caused by corrosion, aging, and crack can critically impact structural safety. However, identifying small leaks is challenging and small leaks can gradually develop into significant leakage problems. Although the negative wave method is currently the most common approach used for pipeline leakage detection, it is limited by the working conditions, length, and diameter of the pipeline and cannot be employed to identify small leaks of less than 1 L per min in pipeline. Therefore, to address this problem, this paper established a technique based on passive acoustic internal detection. This study simulated the variation laws between the leakage rates and sound power levels with different leakage apertures and internal pressures using the Ansys Fluent 19.0 software and performed small leakage detection experiments to verify the feasibility of the finite element simulation method. The findings indicated a positive correlation change in the leakage rates and sound power levels in conjunction with the leakage apertures and internal pressures. Furthermore, a denoising algorithm based on a small leakage of self-encoder was proposed, and a denoising model was introduced for signal. This improved denoising efficiency and reduced the dependence on sample data. The signal-to-noise ratio (SNR) of this algorithm exceeded that of traditional denoising methods, while the root mean square error (RMSE) was lower, verifying its feasibility in denoising. It also provided a research basis for denoising in complex operational environments.
Check Valve Rotor Concept to Form an Imploding Liquid Liner for Magnetized Target Fusion Application
Authors: Dick Jean Sebastien , Bernard Scott , Khalzov Ivan
Published: November 2023

Magnetized Target Fusion (MTF) is an approach to fusion energy generation through the implosion of a liquid metal cavity to compress a deuterium-tritium (D-T) plasma. We propose a method to drive a cavity collapse through direct interaction between the liquid liner with pressurized gas. Our method involves the use of passive check valves to provide a cost-effective and partially reversible process of collapse generation. A subscale cylindrical rotating cavity experiment is designed and constructed to analyze the performance of the concept using pressurized air and a water liner. A high-speed camera and image processing methods are used to identify the trajectory of the free surface of the water liner and identify the impact of rotational speed and gas pressure on the cavity collapse. Experimental data is compared with a simplified dynamic model derived from inviscid Navier-Stokes equations, and two-dimensional axisymmetric computational fluid dynamics (CFD) simulations with the commercial code Ansys Fluent. We see agreement between experiment and both numerical approaches within measurement uncertainty. We discuss how our results will inform the development of larger-scale prototypes.
Vortex Shedding Dynamic in Tandem Circular Cylinders Placed in a Turbulent Crossflow
Authors: Habowski Patrick Batista , Neumeister Roberta Fátima , Möller Sergio Viçosa
Published: November 2023

This article presents an experimental exploration with numerical support of two circular cylinders tandem placed to a turbulent crossflow with L/D ratios of 5, 7.5, 10, and 12.5, where L is the axial distance between the cylinders, and D is the diameter of the cylinder. The force coefficients, flow visualization, and Strouhal numbers were obtained from the numerical simulations. The wake flow velocity and the lateral acceleration of the cylinders were acquired from the experiments. In both studies, a free flow velocity of 10 m/s was imposed, maintaining the Reynolds number in the subcritical flow range, considering the cylinder diameter. Numerical studies employed the gmsh software to generate the mesh and the OpenFOAM software to compute the results. A wind channel with a square cross-section of 1m and two circular slender cylinders were used to obtain the signals of lateral acceleration and wake flow velocity. These signals were post-processed by Matlab software using the wavelet and Fourier analyses. The main conclusions pointed out that the L/D spacing ratio of 5 was the configuration most influenced by the vortex shedding. This was observed in the experimental values of the lateral acceleration and in the numerical results of lift fluctuations. All the proposed L/D spacing ratios presented shear layer reattachment and lateral oscillation caused by the vortex shedding from the upstream cylinder.
Effect of Stress-Strain Curve on Burst Pressure Prediction for Pipelines With and Without Corrosion Defects
Authors: Tao Gang
Published: November 2023

Recent research in remaining burst strength prediction models for corroded pipeline has found that the material strain hardening property (stress-strain curve shape) is crucial for improving the prediction accuracy. The comparison between finite element analysis (FEA) and full-scale burst test results in a recent study also demonstrated strong evidence of the plastic instability failure mechanism for pipe samples with corrosion defects, suggesting that the strain hardening property has a key role in the burst strength of corroded pipes.

In this paper, analytical burst pressure prediction models for pipes with and without corrosion defects are briefly reviewed to illustrate the theoretical basis for including the strain hardening property in the model prediction. A suite of parametric FEA was then conducted on previously tested pipe samples with two different materials to further investigate the effect of the strain hardening property on the burst pressure prediction of corroded pipelines. Based on the test evidence from a recent study, a plastic instability-based failure criterion was proposed for FEA prediction of the burst pressure. The proposed failure criterion was further validated by full-scale burst test results referenced in this study. Based on the FEA burst pressure prediction with the new failure criterion, the effect of the strain hardening property on burst strength of pipe samples with corrosion defects was quantitatively evaluated. Using the parametric FEA results, selected remaining burst strength models were critically examined. The outcome of the model assessment provided a basis for future improvement of these models.
A Novel Strain-Based Fracture Evaluation Method For Long-Distance Pipeline Girth Weld With The Crack Tip Under Large Scale Yield Condition
Authors: Wu Kai , Dong Jie , Guo Guangfei
Published: November 2023

The strain-based failure assessment diagram is an important method to assess the crack defects in the pipeline, especially when the nominal stress of the pipeline exceeds the yield strength of the material. The weld strength matching factor is an important parameter affecting the fracture behavior of the pipeline girth weld, while the traditional strain-based failure assessment diagram method cannot consider the influence of weld strength matching. Given this, a finite element model of the crack driving force for local circumferential cracks on the outer surface of girth welds of pipelines was established by the numerical simulation method. Based on the reference strain calculation method proposed by BS 7910-2019, the effect of crack depth, crack length, weld strength matching factor, and pipe yield strength on the assessment accuracy of SBFAD for pipeline girth weld crack was verified. Based on this, the improved method and calculation model of reference strain is proposed, and the weld strength matching is incorporated into the strain-based failure assessment diagram accurately, which improves the application scope and evaluation accuracy of the BS 7910-2019 evaluation method. The accuracy of the evaluation method is verified by experimental data. The results provide a reference for the engineering critical assessment of pipeline girth welds and also provide technical support for ensuring the intrinsic safety of long-distance steel pipelines.
Safety Assessment of Hydrogen Discharge With Various Types of Vent Exit
Authors: Zhang Chongchong , Feng Heyi , Mu Lijing , Wang Xin , Deng Guide
Published: November 2023

A hydrogen vent is one of the fundamental equipment that ensures safe operation of hydrogen systems. Its venting direction could significantly affect the hydrogen concentration in the surrounding air. As the density of hydrogen is small compared to air, a hydrogen vent is typically installed away from personnel exposure area, which minimizes safety risk during venting process. However, a vent exit with an upward direction has a risk of taking in rainwater. Thus, this article studies the effect of the vent exit directions in hydrogen system from safety perspective; the considered directions are horizontal, vertical downwards, and a miter cut. The analysis was carried out by numerical simulation, in which the effect of discharge speed, wind speed, and nitrogen concentration were considered. The nitrogen concentration was considered because the system may be discharged with nitrogen gas before operation, some left-over nitrogen gas in pipelines may mix with hydrogen at the beginning of system operation. The safety margin in the study was taken as 25% of hydrogen lower explosive limit (LEL), which is 1% volume concentration of hydrogen. The results show that the vertical downwards vent results in the greatest risk distance. In contrast, risk distance is the smallest with horizontal vent. Compared to pure hydrogen discharging, hydrogen-nitrogen mixture gas would increase the risk distance. The distance reaches maximum for horizontal, vertical downwards, and miter cut when the nitrogen concentration is 95%, 75%, and 55%, respectively. The maximum distances are 0.8m, 0.5m, and 0.2m, respectively. It can be observed that the wind speed significantly affects the hydrogen diffusion at the vent exit, in which the increasing amount of vertical downwards vent is greater than horizontal vent at level 1 wind speed (0.3 m/s). The risk distance decreases at level 2 wind speed (1.6 m/s) because the hydrogen concentration is reduced due to diffusion. Among the studied vent exit direction, the horizontal vent has the best overall performance, while vertical downwards vent has the worst overall performance.
Stress Evaluation for Class 2 and 3 Pipes With Reinforcement and Wall-Thinning Using Equivalent Stiffness Concept
Authors: Kim Jae-Yoon , Hwang Jin-Ha , Kim Yun-Jae
Published: November 2023

Due to various reasons, wall-thinning can occur in nuclear piping under the operating environment. When wall-thinning occurs in large-diameter Class 2 and 3 pipes, reinforcement is typically applied before replacement. To check structural integrity of reinforced pipes, stress analysis should be performed, which is not straightforward due to three-dimensional nature of reinforced pipes. Full 3-D FE analysis would not be so useful because calculated stresses would not be compatible to the equations given in ASME BPVC Sec. III NC/ND-3650 for Class 2 and 3 piping system.

In this paper, stress evaluation methods for reinforced wall-thinned pipes are presented using the equivalent straight pipe concept. The equivalent straight pipe is defined as the pipe having the same elastic stiffness as reinforced wall-thinned pipe. Analytical expressions for the stiffness of wall-thinned pipe with reinforcement are given for axial tension and bending moment, using which the dimensions of the equivalent pipe can be obtained. The equations in ASME BPVC Sec. III NC/ND-3650 for Class 2 and 3 piping system are then used using the dimensions of the equivalent pipe. Finally, a method to quantify the stress concentration factor of reinforced wall-thinned pipe for fatigue evaluation is presented using the structural stress method.
Theoretical Analysis of Natural Frequencies and Mode Shapes of Three-Dimensional Piping Systems
Authors: Tamura Shinji
Published: November 2023

The vibration of piping system subjected to earthquake is a severe problem. However, the actual piping system is seems to be too complicated to analyze theoretically. Therefore, the finite element method is used to obtain the natural frequencies and mode shapes. For two-span beam, the theoretical method for the natural frequencies are written in the textbook of the vibrations of continuous systems. In this method, the beam is divided at the intermediate support, and the function for the displacement including unknown coefficients is assigned for each divided beam. The boundary conditions for the divided beams yield the characteristic equation for whole beam. In this paper, same approach is extended for the piping system with the elbows.
Mechanical Behavior of 316L-IN718 Interface Produced by Directed Energy Deposition Investigated Using Miniaturized Specimens
Authors: Rzepa Sylwia , Uhlík Matouš , Melzer Daniel , Koukolíková Martina , Konopík Pavel , Džugan Ján
Published: November 2023

Functionally graded materials (FGMs) are materials distinguished by gradual variation in structure and composition within their volume. Nowadays, the development of FGMs is also accelerated by development and expansion of additive manufacturing (AM) technology, which represents a tool for their relatively easy and precise production. This contribution is focused on the characterization of mechanical performance of SS316L-IN718 interface in terms of local tensile behavior that was investigated using miniaturized tensile test (MTT). The tensile behavior of single material zones (SS316L and IN718) as well as two-material interface zones were examined in parallel and perpendicular orientations with respect to the direction of deposition. The strain maps of MTT specimens were compared and used as a tool for failure process evaluation. Beside the sharp two-material interface observed using scanning electron microscope (SEM), a diffusion zone of certain elements was detected via wavelength-dispersive spectroscopy (WDS) line scan. The specimen orientation at the interface is a decisive factor considering the material failure location. The fractographic analysis of MTT specimen machined in vertical orientation showed that the fracture process was observed preferably in the SS316L zone. The strain within IN718 zone was very limited until the end of the test. Contrary to that, in the case of the specimen oriented horizontally, the failure process was initiated in the zone of IN718, which was characterized by higher strength but the plastic capacity was depleted earlier. The recorded stress level yielded the values above these of vertical specimen (SS316L) but below IN718. This suggests that the stress was carried preferably by the IN718 part of horizontally-oriented specimen.
Assessing Residual Stresses in PE-RT Pipes and Annealing Temperature Sensitivity Analysis
Authors: Biradar Arun , Palacios Moreno Jorge , Mertiny Pierre
Published: November 2023

Pipe made from polyethylene with raised temperature (PERT) service capability offers several advantages in terms of material performance, and has broad application in the industry. However, residual stresses are typically present in PE-RT pipe after fabrication, which may affect pipe strength under service conditions. Research on this phenomenon in PE-RT pipe is limited, and hence, the present study investigated the residual stresses and means for mitigating them through annealing at elevated temperatures. Residual tensile and compressive stresses are formed on the inner and outer portions of extruded pipes, respectively, due to the rapid cooling that is typically applied on the outside of the pipes after the extrusion process. The objective of the present work was to assess experimentally residual stresses in PE-RT pipes. In addition, using the experimental methods, a sensitivity study on the annealing temperature for mitigating residual stresses was performed. The experimental procedures were adopted from the ASTM E1928-13 standard. In compliance with this standard, the PE-RT pipes under investigation can be considered as thin-walled tubes for analysis purposes. Moreover, the creep behavior of plastics was incorporated in the final calculation of residual stress values. Two types of slitting methods were applied to assess the residual stresses: (i) To determine the residual hoop stress, a 45-degree section was cut from ring samples, and then the change in ring diameter was observed; (ii) for the longitudinal residual stress, a tongue-like section was cut lengthwise into pipe samples, and the deformation of these sections was observed. For all cutting purposes, coolant was used to avoid any heating effects. The sample lengths varied from 0.2 to 3.0 times the outer pipe diameter. In this manner, effects of specimen length on the test results were ascertained. Experiments conducted for non-annealed PE-RT pipe, as well as pipe annealed at 90 degree Celsius, revealed substantial residual stresses. Using the developed procedures, the study seeks to identify the annealing temperature that yields the lowest possible residual stresses in the PE-RT pipes. Present work includes a discussion on whether the ratio of ideal annealing temperature to melting point can be extrapolated as a key parameter from PE-RT to other thermoplastic polymer materials.
Using Detection Performance to Assess Outlier Sizing on Truncated Data Sets
Authors: Skow Jason , Krynicki Joseph W.
Published: November 2023

The third edition of the American Petroleum Institute (API) 1163 recommended practice (RP) “In-line Inspection Systems Qualification”, released in September 2021, includes many improvements over previous editions including updates to Section 8 “System Results Validation”, which defines the methodologies to validate ILI run measurement tolerances. The recommended practice describes three levels of validation, with ‘Level 3’ requiring operators estimate ILI tool measurement performance with real-world data measured in validation spools and excavation sites. It is an advancement over Level 2 which is a statistical significance test of validation measurements against a vendor specification. Two examples of Level 3 validations are provided in Appendix C, one describes statistical tolerance intervals, the other describes a hierarchical Bayesian model. This paper uses the second model to estimate measurement performance when a data set is truncated.

In a previous paper, the authors described using the Hausman and Wise algorithm to model sizing performance on truncated data sets. When the data is truncated, this algorithm corrects for the ‘missing’ data, improving the results of a linear regression between inspection measurements and validation measurements. However, the algorithm is a based on several assumptions, which do not hold for some outlier data. When an outlier under-predicts the validated size, the Hausman and Wise correction overcompensates because it assumes that every outlier represents a larger number of missed anomalies of similar size. In this paper, we discuss an improvement to the Hausman and Wise algorithm that incorporates the probability of detection of the measurement tool. The probability of detection informs the truncation algorithm by providing the necessary parameters to determine if outliers are purely sizing errors, or whether they also present a risk that a similar sized anomaly was not detected.

This paper includes examples of real field measurement data where the improved algorithm is compared to the original algorithm. In addition, similarly characterized simulation cases are summarized to show edge cases and limits to the algorithm improvement. Finally, the paper offers further improvements that could be made to the truncation algorithm and comments on a similar application for censored data sets.
EPR Piping Material Study: Effects of Sampling Location and Temperature on Low Cycle Fatigue in Air
Authors: Seppänen Tommi , Alhainen Jouni , Arilahti Esko , Solin Jussi , Vanninen Rami
Published: November 2023

Individual research projects often plan experimental test matrices using a restricted batch of materials to study fatigue phenomena and performance. Often the results of these studies are aggregated into databases of material behavior. However, many important scientific findings can be lost in such databases, where complex experimental results can be condensed to generalized tables containing few details. In some scenarios this aggregation and condensing of results in unable to adequately describe the original research.

Dedicated research in Finland aims to support application of risk-informed inspection and LTO strategies, which benefit from addressing material-specific behavior in fatigue management. Initial experimental in-air fatigue results on stainless steel 12” schedule 140 Z2CND1812 N2 class 1 pipe material, which is representative for the EPR reactor in Olkiluoto, were reported in PVP2022-84007. This paper presents an update on continued experimental progress, focusing on material sampling location effects and influence of test temperature on in-air fatigue behavior.
Probabilistic Assessment Tool for Graphite Component Reliability
Authors: Bass Joseph , Iyengar Raj , Ulmer Christopher
Published: November 2023

Assessment of graphite component reliability is important in providing the technical basis to support the safe operation of advanced non-light water reactors. Computational modeling of aging and degradation in graphite components would enable quantitative assessments of stress generation, failure, and associated uncertainties. A graphite modeling tool has been developed in a finite element framework, MOOSE, which was created at Idaho National Laboratory. This tool was developed for the assessment of graphite components intended for nuclear applications. The tool is capable of computing stresses in graphite which result from mechanical loads as well as temperature and irradiation gradients in graphite components. The effect of irradiation creep is included in the graphite behavior model. The graphite tool is also capable of modeling the effects of oxidation. This includes computing temperature dependent density profiles which can be generated by the reaction between graphite and oxygen. Stresses in the oxidized graphite can be computed using material properties which are implemented as a function of mass loss. The tool has been parameterized for graphite grade IG-110, but other grades of graphite can be assessed by providing the necessary material properties. The tool was also developed to work with the graphite assessments in Subsection HH Subpart A in Section III Division 5 of the ASME BPVC. These assessments use a Weibull-based probabilistic approach to assessing a graphite component. Python codes have been created which implement the full and simplified assessments in the 2021 version of the ASME BPVC and utilize the outputs from the MOOSE-based analysis. Initial verification and validation work using this tool has produced promising results.
Dependence of Clearing Effect on Building Dimensions
Authors: Geng Jihui , Thomas J. Kelly
Published: November 2023

Blast waves exhibit both positive and negative phases. The relative magnitude of these phases is a function of standoff distance from the explosion source to targets of interest. When an incident blast wave reaches a target building, the blast wave reflects off the front wall (i.e., that facing the blast source). Both the positive and negative phases of the blast wave are enhanced by the reflection process. A fully reflected blast wave would be produced if an incident blast wave reflected from an infinitely tall and wide wall in a normal orientation. However, when an incident blast wave reflects off a wall of finite size in a normal orientation, rarefaction waves are created at the wall edges and roof, and these rarefactions sweep down from the roof and inward from sides. These rarefaction waves result in a clearing effect for both the positive and negative phases. Clearing relieves some of the applied blast load on the reflected wall for the positive phase. However, this is not always the case for the negative phase. As shown in PVP2022-84288[1], clearing may either relieve or enhance the applied negative phase blast load, depending on the blast wave profile and the wall dimensions.

This paper extends the referenced prior study by examining negative phase clearing as a function of building dimensions and non-planar blast waves. The negative phase blast load adjustment factor (i.e., the ratio of cleared to fully reflected blast load) distribution on the front wall is determined. The purpose of this study is to generate a database of negative blast load clearing for engineering modeling applications.
Challenges in the Life Management of Steam Methane Reformer (SMR) Components
Authors: Bridges Alex , Gagliano Michael , Siefert John , Dalal Mitul , Penso Jorge
Published: November 2023

Steam methane reforming (SMR) is a process in which methane from natural gas is heated, with steam, usually with a catalyst, to produce a mixture of carbon monoxide and hydrogen used in organic synthesis and as a fuel. The steam-gas mixture enters the reformer from the inlet manifold. The reforming reaction is an endothermic reaction requiring a large amount of heat to be supplied to the system. Because of the high temperature and high heat input required for the reaction, it is carried out in directed fired, catalyst filled tubes keeping the temperature of the mixture > 1,500°F (815°C). At these temperatures, methane (CH4) reacts with steam (H2O) to produce hydrogen (H2) and carbon monoxide (CO). The presence of a catalyst helps this process react more quickly and to retain more hydrogen gas. The hydrogen-carbon monoxide mixture exits the reformer via the outlet manifold. In the energy sector, SMR is the most widely used process for the generation of hydrogen.

This paper focuses on the impact of time-dependent damage (creep) on critical steam methane reformer components such as tubes, pigtails, and outlet headers. Specific challenges linked to material variability, well-pedigreed databases, damage development, and standard or feature testing will be addressed.
Free Drop Impact Data Acquisition Using Digital Image Correlation
Authors: Montgomery Veronica , Martinez Oscar , Nogradi Paul , Lowe Lance , Adeniyi Abiodun
Published: November 2023

Radioactive materials are widespread throughout our everyday activities and are used in many different types of industries. There are about 3 million shipments of radioactive materials that occur each year in the United States. Because radioactive materials are so widespread, safety and security are top priorities for the Package Testing Program (PTP) at Oak Ridge National Laboratory (ORNL), and effective and accurate data collection methods are imperative. The packaging used to carry nuclear materials is subjected to rigorous tests to verify its durability. One such test is the free-drop test. Impact data are often collected through an accelerometer attached to the test unit. Unfortunately, these devices are easily broken in the testing environment and are expensive to procure, install, and post process. Digital image correlation (DIC) using high-speed images offers a non-contact alternative. DIC is an optical method that employs image registration techniques to accurately measure changes in images. To verify the suitability of the cameras and process, a test weight was dropped from various heights, and the impact acceleration was derived using DIC. This paper compares the results with data from the attached accelerometer. A total of nine drop tests were performed with three different image capture rates (frames per second) and from three different package drop heights. An ANSYS LS-Dyna model was also used to determine theoretically predicted deceleration rates for comparison with the DIC and accelerometer data.
Linking Deterministic Leak-Before-Break to Probabilistic Framework Using xLPR
Authors: Uddin M. , Cofie N. , Dedhia D. , Dominguez G. , Harrington C. , Glunt N. , Shim D. J.
Published: November 2023

In this paper, several studies are described to compare the current SRP 3.6.3 deterministic leak-before-break (LBB) approach to a corresponding probabilistic approach using the NRC/EPRI developed Extremely Low Probability of Rupture software tool (xLPR) to establish a correlation between the approaches. These studies involve two generic nozzle/pipe sizes (large and medium diameters) with dissimilar metal (DM) butt welds susceptible to primary water stress corrosion cracking (PWSCC). First, deterministic fracture mechanics (DFM) analyses were performed consistent with the SRP 3.6.3 methodology. Then probabilistic fracture mechanics (PFM) evaluations with xLPR were performed assuming single circumferential through-wall flaws consistent with that used in the deterministic approach to establish a correlation. Furthermore, for simplicity, the evaluations were based on a single weld location rather than on a whole piping system.

On a preliminary basis, this correlation indicates that although the deterministic LBB approach may not meet the required SRP 3.6.3 margins in certain cases, a probabilistic LBB approach using xLPR may be used to show low probability of rupture meeting the proposed probabilistic acceptance criteria. However, there are several limitations in developing the correlation that have been identified and more studies are needed to address those limitations.