Phase Fraction Distribution Research Articles

Generation of micrograph-annotation pairs for steel microstructure recognition using the hybrid deep generative model in the case of an extremely small and imbalanced dataset

Insufficient annotated samples coupled with class imbalance problem largely restrict the wide application of deep learning (DL)-based approach in microstructure recognition and quantification. In this work, we present a micrograph augmentation approach using the hybrid deep generative model to generate SEM image-annotation pairs for the establishment of a large-scale and well-balanced augmentation dataset. In this method, a generator is established to produce the desired annotations and then a translator is trained to translate these synthetic annotations into high-quality SEM images. The proposed method is successfully applied to an extremely small and imbalanced additively manufactured (AM) steel dataset containing only one SEM image-annotation pair with a very low martensite/austenite (MA) fraction, to significantly augment the initial dataset and achieve a more balanced distribution of phase fraction. The effectiveness of the present method is well demonstrated by the fact that the extensibility of microstructure recognition model to unseen micrographs is improved through the utilization of synthetic data. Furthermore, the impact of synthetic data proportion on the model's performance and the underlying reasons for synthetic data to improve the extensibility of trained models are also discussed in detail.

Ice slurry pigging technology in drinking water distribution system: From flow mechanisms to pipelines cleaning application

Drinking water distribution systems are prone to (bio)fouling over time, negatively impacting drinking water quality. Ice slurry pigging is a promising technology used to remove solids attached to the inner parts of the pipe walls with ice-water mixture. To understand the ice slurry pigging flow characteristics and optimize its operations, this study presents the development of a Computational Fluid Dynamics model (CFD) combined with the Kinetic Theory of Granular Flow model (KTGF) and a thermal model. Firstly, the model is validated with experimental data from the literature on solid-liquid Two-Phase Flow (TPF), including flow characteristics and thermal effects. Secondly, simulations for a typical ice slurry pigging process show uneven ice phase fraction and shear stress distributions in the main pipe flow and vertical direction. Results indicate that the main limitations of effective pipe cleaning are due to buoyancy and thermal effects. Moreover, ice slurry with 1.0 mm ice particles performs better in providing effective shear stress compared to 0.1 mm, 0.5 mm, and 1.5 mm ice particles. Additionally, the optimal injection ratios of ice slurry with 1.0 mm are determined to be over 0.3 and 0.26 when cleaning pipeline lengths within 500 m and 1000 m, respectively.

Performance prediction of tube-in-shell thermal storage devices with different inner tube positions using the HHO-BP neural network

This paper presents a numerical simulation study and a machine learning based prediction of the melting process in the Tube-in-shell thermal storage device. The two-dimensional Tube-in-shell thermal storage devices models are built to represent the position of the inner tube by two parameters, the eccentricity distance e and the eccentricity angle θ. The melting process of phase change material (PCM) under different conditions is simulated using computational fluid dynamics (CFD) to determine the effects of the inner tube position, inner tube radius and heating temperature on the variation of liquid phase fraction. Then, on this basis, a neural network of HHO-BP is constructed and trained by simulation data to predict the change of liquid phase fraction when the PCM melts under other conditions. The results show that the change of position in the vertical direction of the inner tube has a great influence on the melting. However, the change in the position of the inner tube in the horizontal direction has little effect on the melting rate, and the melting time is almost the same. In addition, the inner tube radius and the heating temperature both contribute significantly to the melting rate. The melting time of the model with an inner tube radius of 20 mm is 51.08 % faster than that of the model with an inner tube radius of 10 mm. The liquid phase fraction distributions of the models with heating temperatures of 60 °C and 70 °C are 0.697 and 0.935 when the melting of the models with heating temperature of 80 °C is completed. The prediction data of the HHO-BP neural network can respond to the simulation results more accurately, and all kinds of evaluation indexes are within the acceptable range. The machine learning model developed in this paper can reduce the simulation computation cost and shorten the optimization design cycle.

Chordal measurement of phase fraction distribution in a static gas-liquid system using collimated gamma-ray densitometer and artificial neural networks

Two-phase flow occurs in various industries, as in the production of oil and gas. A collimated gamma-ray densitometer is applied for the study of a static gas-liquid system that simulates a stratified flow pattern. It stands out for its non-intrusive measurement capacity, its high sensitivity to density variations and its good spatial resolution. Chordal phase fraction distributions are obtained in a tube containing water and air at room conditions, with the water level varied between 25%, 50% and 75%. The results obtained highlight the usefulness of the collimated gamma-ray densitometer to determine phase fraction distributions along the pipe’s cross section. Furthermore, this study suggests the use of an artificial neural network (ANN) model for predicting holdup in pipeline systems using a dataset of 110 experimental data points. The ANN model considers factors such as absorbed intensity, water cut percentage, and dimensionless h/D ratio. The adopted configuration includes the use of the Adam solver, Rectified Linear Unit (ReLU) activation function, a batch size of 3, two hidden layers (60 neurons each), and a learning rate of 0.001. The model achieves good accuracy, with a minimum mean square error (MSE) of 0.3% and a low mean absolute error (MAE) of 0.028.

Residual stresses in linear friction welding of TC17 titanium alloy considering phase fraction

To obtain accurate residual stresses in linear friction welding of TC17 alloy, a numerical relationship between the elastic constants and phase fraction of TC17 alloy was established. The elastic constants with gradient distribution were obtained by combining the phase fraction and introduced into the contour method. The results show that the elastic constants of TC17 alloy are positively correlated with α phase fraction and present a significant gradient distribution in the welding area with a width of about 4 mm. The relative error in calculating the welding residual stresses can be up to 36.06% if the gradient distribution of phase fraction is ignored. The corrected residual stresses in the welding area exhibit a bimodal distribution, with a peak stress of ∼442 MPa located at the edge of the heat-affected zone. The results demonstrate the necessity of considering the phase fraction with gradient distribution.

Understanding the role of tetragonal phase in oxidation behaviour of different zirconium-based alloys in air and water vapour conditions – Phase fraction and stress field distribution

The paper investigates the influence of oxidation atmosphere on the corrosion behaviour after 7, 15, and 24 h of different zirconium-based materials, including pure metal, E110, and Zircaloy-2 alloys. The study utilises scanning electron microscopy to perform cross-sectional characterisation. Raman imaging was employed to determine the content and distribution of the tetragonal phase in the oxide scale depending on oxidation parameters. The obtained results were compared with previous thermogravimetric measurements and correlated with stress distribution calculated based on the shift of the selected tetragonal phase band. Additionally, the study reveals a relaxed tetragonal phase in a bulk monoclinic phase. A thorough analysis of Raman spectra allowed correlating spectral features with tetragonal phase stabilisation mechanisms for the tetragonal phase occurring at the metal/oxide interface and in the bulk monoclinic phase.

Time-of-flight polarization contrast neutron imaging for enhanced characterization of ferritic phase fractions in Fe-Mn-Si shape memory alloys

The determination of the amount and distribution of different phase fractions in additively manufactured shape memory alloys processed with laser powder bed fusion is crucial for understanding the correlation between processing parameters, microstructure, and mechanical properties. Neutron imaging techniques, such as Bragg edge imaging and polarization contrast neutron imaging (PNI), have been introduced to complement and overcome the limitations of traditional characterization methods, which are often destructive and limited to surface analyses and small-sized specimens. Bragg edge imaging can distinguish and quantify crystallographic phase fractions with spatial resolutions of a few tens of micrometers, while PNI is highly sensitive to crystallographic phases and is particularly suited for sub-percent phase fractions and in-situ, time-resolved, and tomographic analyses. In this work, we present a time-of-flight PNI method that enables simultaneous measurements of phase fractions.

Dual-Modal Electrical Imaging of Two-Phase Flow-Experimental Evaluation of the State Estimation Approach.

Accurate measurement of two-phase flow quantities is essential for managing production in many industries. However, the inherent complexity of two-phase flow often makes estimating these quantities difficult, necessitating the development of reliable techniques for quantifying two-phase flow. In this paper, we investigated the feasibility of using state estimation for dynamic image reconstruction in dual-modal tomography of two-phase oil-water flow. We utilized electromagnetic flow tomography (EMFT) to estimate velocity fields and electrical tomography (ET) to determine phase fraction distributions. In state estimation, the contribution of the velocity field to the temporal evolution of the phase fraction distribution was accounted for by approximating the process with a convection-diffusion model. The extended Kalman filter (EKF) and fixed-interval Kalman smoother (FIKS) were used to reconstruct the temporally evolving velocity and phase fraction distributions, which were further used to estimate the volumetric flow rates of the phases. Experimental results on a laboratory setup showed that the FIKS approach outperformed the conventional stationary reconstructions, with the average relative errors of the volumetric flow rates of oil and water being less than 4%. The FIKS approach also provided feasible uncertainty estimates for the velocity, phase fraction, and volumetric flow rate of the phases, enhancing the reliability of the state estimation approach.

Diffuse-Interface Blended Method for Imposing Physical Boundaries in Two-Fluid Flows.

Multiphase flows are commonly found in chemical engineering processes such as distillation columns, bubble columns, fluidized beds and heat exchangers. The physical boundaries of domains in numerical simulations of multiphase flows are generally defined by a conformal unstructured mesh which, depending on the complexity of the physical system, results in time-consuming mesh generation which frequently requires user-intervention. Furthermore, the resulting conformal unstructured mesh could potentially contain a large number of skewed elements, which is undesirable for numerical stability and accuracy. The diffuse-interface approach allows for the use of a simple structured meshes to be used while still capturing the desired physical (e.g., solid-fluid) boundaries. In this work, a novel diffuse-interface method for the imposition of physical boundaries is developed for the incompressible two-fluid multiphase flow model. This model is appropriate for dispersed multiphase flows which are pervasive in chemical engineering processes, in that this flow regime results in high levels of mass and energy transfer between phases. A diffuse interface is used to define the physical boundaries and boundary conditions are imposed by blending the conservation equations from the two-fluid model with that of the nondeformable solid. The results from the diffuse-interface method are compared with results from a conformal unstructured mesh for different interface functions and widths. For small interface widths, the accuracy of the flow profile is unaffected by the choice of interface function and the phase fraction distribution and flow behavior are within 3% compared to those from a conformal mesh. As the interface width increases, the diffuse-interface solution deviates from the conformal mesh solution in both the localized gas fraction and the overall gas hold-up, resulting in a difference up to 30%. In the case of flow past a cylinder, where the solid interacts with the flow, the presence of the diffuse interface extends the thickness of the solid boundary and results in a deviation from the conformal mesh solution as time increases.

Balanced multiphase mixing through a narrow gap

Mixing of a two-phase flow through a gap connecting adjacent channels was investigated for a variety flow rates and two gap heights. The mixing was characterized by the amount of gross liquid and net gas mass transfer from one channel to the other. The liquid mixing through the gap was calculated based on the measured mass flow rates and dye tracer concentrations at the inlet and outlet of each channel. The gas net transfer, phase fraction distributions, bubble size distributions, and gas interface velocity were measured using dual-plane wire mesh conductivity sensors at both inlets and outlets. Additionally, imaging of the fluorescent tracer dye and air bubbles were used together with Spectral Proper Orthogonal Decomposition (SPOD) to further characterize the mixing mechanisms. The water inlet Reynolds number was varied from 4 to 10×104 and the volumetric gas quality from 0 to 0.35 which resulted in gas volume fractions up to 15%. All conditions were in the bubbly flow regime. Air was introduced by a needle array producing nominally monodispersed bubbles at lower gas flow rates with broader bubble size distributions at higher gas flow rates. The Sauter mean diameter varied from 3 to 8 mm, depending on flow rates. For these balanced flows large coherent structures dominated the mixing. However, even mere O(5%) volumetric quality gas injection could significantly suppress the coherent structures reducing mixing by over 50%.

Experimental investigation of the development of surfactant stabilized oil-water pipe flow downstream of a choke valve

In wells and multiphase flowlines the presence of valves, pumps and other complex geometries will considerable contribute to dispersion of the phases. In combination with the droplet stabilizing effect of natural surfactants contained in the crude oil and other production chemicals, this may lead to a considerable development length of the flow. Such effects should be understood and considered by future simulation tools. In the presented work, the described scenario was experimentally tested under controlled conditions. The development of dispersed oil-water flow downstream of a valve was monitored. Surfactant was added to the mineral oil to obtain a suitable droplet stability. The near horizontal test section was 220 m long and had an inner diameter of 109 mm. The vertical phase fraction distributions were measured at six locations along the pipe with traversing gamma densitometers. The test section was further instrumented with nine pressure transducers, four optical sections, and three droplet sampling points to monitor flow development. The flow development showed a characteristic behavior of a rather sudden separation after a certain length with stable dispersed flow conditions. The degree of inlet mixing and thus initial droplet size governed by the pressure drop over the mixing valve was found to be crucial for the development length. Flow rate and initial water fraction were of minor importance. The separation behavior was coalescence controlled as it would be expected for a surfactant stabilized system. Still, even if static separation bench tests resulted in very long separation time scales, the in-flow separation happened much faster. This indicates the importance of dynamic flow conditions and associated effects such as shear and a certain mixing to be preferential for the separation. The measured pressure drop of the dispersed flow was more than 20% higher than separated flow with otherwise the same conditions. As the flow separates, the pressure drop decreases and, as expected, finally approaches the value for separated flow. The work presents a detailed data set as basis for model development.

A process to spatially control the fraction of SS420 and bronze phases in binder jet infiltrated parts

Additive manufacturing (AM) is a useful tool to fabricate components with unique spatial control over material composition, phases, and geometry. However, spatially controlling the material phases in AM metals typically requires changing powder during the printing process or using multiple nozzles, and most methods only offer control in one dimension. This requires a significant printer hardware upgrade. This paper presents a method that exploits the binder jet additive manufacturing process to spatially control the fraction of stainless steel 420 (SS420) and infiltrated bronze. In our method, we modify the CAD file of the binder jet part to include completely enclosed voids within the printed part, which result in enclosed regions of loose steel powder without binder. This process does not induce extra porosity, nor require hardware modifications. Post-sintering, we use optical microscopy to show that zones of enclosed SS420 without binder contain up to a 25 % increase in SS420 phase compared to the zones printed using the conventional method (i.e., with binder). To understand the mechanisms behind the spatial distribution of phase fraction, we employ the method to print parts with higher SS420 concentration channels of different thicknesses in horizontal and vertical directions. Results show that the relative phase fraction of SS420 and bronze depends on channel size, channel orientation, and sintering direction. Further, the SS420 percentage can be uniform or spatially graded inside the channels depending on the sintering direction relative to the printing directions. We hypothesize that the underlying mechanisms of phase fraction variation in this method are powder spreading, packing during the print process as well as the effect of gravity on loose powder during sintering step. To establish a possible application of the method, the spatial variation of Rockwell B hardness was measured in selected samples. The hardness results show that our method obtains spatial variation of mechanical properties, and qualitatively corroborate the phase fraction variation obtained from optical microscopy. Although here we show phase fraction control over two dimensions, the method could be applied to obtain a 3D phase fraction control. The method only requires changes in the CAD model of the printed part, without any hardware or software modifications of the typical binder jet AM process.

Investigation of Gas-Water-Sand Fluid Resistivity Property as Potential Application for Marine Gas Hydrate Production.

The phase fraction measurement of gas-water-sand fluid in downhole is an important premise for safe and stable exploitation of natural gas hydrates, but the existing phase fraction measurement device for oil and natural gas exploitation can’t be directly applied to hydrate exploitation. In this work, the electrical resistivity properties of different gas-water-sand fluid were experimentally investigated using the multiphase flow loop and static solution experiments. The effect of gas phase fraction and gas bubbles distribution, sand fraction and sand particle size on the relative resistivity of the multiphase fluid were systematically studied. The measurement devices and operating parameters were also optimized. A novel combined resistivity method was developed, which demonstrated a good effect for the measurement of phase fractions of gas-water-sand fluid, and will have a good application potential in marine natural gas hydrates exploitation.

Analysis of high strength composite structure developed for low-carbon-low-manganese steel sheet by laser surface treatment

In the present work, a high-strength composite steel structure developed by imparting laser surface hardening treatment on a low-carbon low-Manganese automotive steel sheet has been comprehensively analysed. The layered composite steel structure has been successfully developed by re-engineering the surface of the steel using diode laser hardening treatment up to a depth of 250–300 µm through its thickness. Hardness at the treated surface improved by 150% to that of its base due to formation of a mixture of hard phases constituting martensite and bainite along with retained ferrite. Indeed, coupling EBSD technique with Weibull distribution of various phase fractions determined by image quality helped analyse microstructure effectively. The tensile property of the layered composite steel sheet was found to yield significant improvements in both Yield Strength (YS) (40–44%) and Ultimate Tensile Strength (UTS) (19–21%) due to sandwich effect of composite layer constituting hardened layer and soft base accomplished by a strengthening mechanism associated with rule of mixtures concept. In fact, Young’s modulus of the composite steel sheet, determined from slope of tensile stress–strain diagram was found to be convergent with ultrasonic test result. Additionally, the crystallographic texturing effects of the hardened layer and untreated base measured using standard XRD technique re-confirmed their influence on Young’s Modulus and r-bar values obtained.

Cavitation failure analysis of 90-degree elbow of mixing point in ethylene glycol recovery and concentration system

For the failure case of the 90-degree elbow of mixing point in the ethylene glycol recovery and concentration system of a refining and chemical company in China, the surface morphology of different cavitation degree was observed by scanning electron microscope(SEM). The composition and content of chemical material and working condition was calculated and analyzed by Aspen technical process simulation software to draw the conclusion that the failure form of elbow is cavitation of liquid water. The failure location of elbow was investigated by CFD numerical simulation used the VOF multiphase flow model and Schnerr and Sauer cavitation model. The distribution and variation of gas phase fraction is used to describe the cavitation dynamic development process at different times. The cavitation corrosion angle of elbow in the axial and circumferential direction was determined by the value of phase transformation rate, actual cavitation failure angle in the circumferential direction is basically consistent with that of numerical simulation, which verifies the reliability of the characterization method to a certain extent. The cause of the angle deviation between actual and simulation in the axial direction is explained. This paper can provide some reference for using phase transformation rate to predict cavitation location and characterize cavitation intensity.

Evaluation of hydrogen effect on the fatigue crack growth behavior of medium-Mn steels via in-situ hydrogen plasma charging in an environmental scanning electron microscope

Fatigue crack growth (FCG) tests were conducted on a medium-Mn steel annealed at two intercritical annealing temperatures, resulting in different austenite (γ) to ferrite (α) phase fractions and different γ (meta-)stabilities. Novel in-situ hydrogen plasma charging was combined with in-situ cyclic loading in an environmental scanning electron microscope (ESEM). The in-situ hydrogen plasma charging increased the fatigue crack growth rate (FCGR) by up to two times in comparison with the reference tests in vacuum. Fractographic investigations showed a brittle-like crack growth or boundary cracking manner in the hydrogen environment while a ductile transgranular manner in vacuum. For both materials, the plastic deformation zone showed a reduced size along the hydrogen-influenced fracture path in comparison with that in vacuum. The difference in the hydrogen-assisted FCG of the medium-Mn steel with different microstructures was explained in terms of phase fraction, phase stability, yielding strength and hydrogen distribution. This refined study can help to understand the FCG mechanism without or with hydrogen under in-situ hydrogen charging conditions and can provide some insights from the applications point of view.

Heat transfer from glass melt to cold cap: Computational fluid dynamics study of cavities beneath cold cap

AbstractEfficient glass production depends on the continuous supply of heat from the glass melt to the floating layer of batch, or cold cap. Computational fluid dynamics (CFD) are employed to investigate the formation and behavior of gas cavities that form beneath the batch by gases released from the collapsing primary foam bubbles, ascending secondary bubbles, and in the case of forced bubbling, from the rising bubbling gas. The gas phase fraction, temperature, and velocity distributions below the cold cap are used to calculate local and average heat transfer rates as a function of the bubbling rate. It is shown that the thickness of the cavities is nearly independent of the cold cap shape and the amount of foam evolved during batch conversion. It is ~7 mm and up to ~15 mm for the cases without and with forced bubbling used to promote circulation within the melt, respectively. Using computed velocity and temperature profiles, the melting rate of the simulated high‐level nuclear waste glass batch was estimated to increase with the bubbling rate to the power of ~0.3 to 0.9, depending on the flow pattern. The simulation results are in good agreement with experimental data from laboratory‐ and pilot‐scale melter tests.

Multimodal Two-Phase Flow Measurement Using Dual Plane ECT and GRT

This work assesses the accuracy of two-phase flow measurement, based on cross correlation (XC) and cross-spectrum (CS) velocity computation, using dual plane nonintrusive electrical capacitance tomography (ECT), over a broad spectrum of horizontal flow configurations, combined with fraction distribution measurements from gamma-ray tomography (GRT). The measurement of two-phase flow encompasses the measurement of both the velocity and the phase concentration of the flow components. The accuracy of the flow velocity is still an open discussion and remains a key challenge in the field of multiphase flow measurement. The velocities of the two-phase components vary, both in between them and across the pipe cross section. This study assesses the use of XC techniques as methods for calculating the cross-sectional velocity distribution by deriving the transit time of the fluid flowing through two parallel ECT sensor arrays mounted on the perimeter of a pipe. The spectral distribution of the velocities is assessed for improved accuracy of individual component velocities. A dual-plane ECT is adopted for the velocity measurements and is combined with state-of-the-art density-based cross-sectional phase fraction distribution from a GRT system to measure the volumetric flow rates of the two phases. The results show that the CS method provides enhanced velocity estimation for both flow phases over the conventional XC technique. Further improvement was reported using a simple predictive correction model resulting in flowrate estimation accuracy of ±10%. The method for two-phase flow measurement suggested in this work leverages the accuracy of the tomography systems on accurate fraction measurement and fast data acquisition to lead to potential enhancement in process control by enabling a more accurate prediction of components velocities.

Correlation of microstructure with magnetic properties in Pr0.67Sr0.33MnO3 thin films

Strain can be used to modulate magnetic properties of manganite thin film by affecting not only its crystal structure but also the microstructure, including the cluster size and fraction of ferromagnetic phase. In this work, epitaxial Pr0.67Sr0.33MnO3 thin films deposited on (001)-SrTiO3 single-crystal substrate are studied. The magnetization-temperature curves with zero-field cooling and field cooling show the typical feature of cluster-glass system. With the increase of film thickness, strain relaxation occurs in 80 nm Pr0.67Sr0.33MnO3 film with a wide temperature range of phase transition. By fitting the freezing temperature Tf dependence on magnetic field according to Almeida–Thouless equation, the 80 nm film has a larger local anisotropy and exchange bias compared to that of the 15 nm Pr0.67Sr0.33MnO3 film. Detailed analysis suggests that the strain-induced phase fraction and size distribution of ferromagnetic phase are responsible for the different magnetic properties of Pr0.67Sr0.33MnO3 film with different thickness.

On-route to dryout through sequential interfacial dynamics in annular flow boiling around temperature and heat flux controlled heater rod

A numerical methodology is used to track the interfacial dynamics of the dryout mechanism for flow boiling around the heated cylindrical rod. The mathematical model is based on the Volume of Fluid interface capturing technique for two-phases of fluids. A single set of Navier-Stokes equations with an added source term to take care of vapor mass flux generation due to phase change is utilized. The simulations are carried out for various combinations of flow parameters and heating conditions at a representative higher working pressure of 40 bar, which is usually observed in Boiling Water Reactors (BWR). Various mechanisms of dryout, such as disturbance wave generation, droplet entrainment, deposition, rewetting, nucleation beneath the thin annular film, and its dynamics are illustrated with pictorial representations. The liquid phase fraction distribution across radial and axial planes, wall temperature, and heat transfer coefficient are used to quantify the dryout characteristics.