- Indian Institute of Science, Mechanical Engineering, Graduate Studentadd
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In this study, identical experiments of bottom-cooled solidification of water-23 wt% KNO3 and water-24 wt% NH4Cl, which exhibit faceted and dendritic microstructures respectively, were performed. The primary objective of this... more
In this study, identical experiments of bottom-cooled solidification of water-23 wt% KNO3 and water-24 wt% NH4Cl, which exhibit faceted and dendritic microstructures respectively, were performed. The primary objective of this investigation is to understand the role of solidification morphology (mushy zone) and the flow characteristics on the temperature of the bulk fluid. The strength of compositional convection was correlated with the help of Rayleigh number in both mushy and bulk-fluid zones and was further used to assess the flow behaviour during faceted and dendritic growths. Based on the liquid temperature profile during faceted growth, three distinct regimes of heat transfer were observed in the liquid, namely - convection-dominated, transition, and conduction-dominated. The experimental findings revealed an anomalous temperature rise of the bulk liquid when the mushy-zone permeability was restricted by the faceted grain morphology. The observed temperature rise was further as...
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The cutting-edge radius of the tool has significant effects on the machining process, as it influences the cutting forces, stresses, and temperature at the tool–chip interface. These parameters ultimately affect the tool life and surface... more
The cutting-edge radius of the tool has significant effects on the machining process, as it influences the cutting forces, stresses, and temperature at the tool–chip interface. These parameters ultimately affect the tool life and surface integrity of the finished workpiece. The presence of cutting-edge radius in the tools protects them from easily chipping off during the cutting process. A finite element based ABAQUS™ model is used to evaluate the effect of cutting-edge radius for 20, 40, and 60 μm on the cutting forces for orthogonal cutting of Ti6Al4V alloy at different cutting parameters. It was observed that the cutting-edge radius influences both the cutting and thrust forces. An increase of 4–8% and 12–14% in the cutting force and thrust force was observed when the cutting-edge radius changes from 20 to 60 μm. The temperature in the tool was increased with increasing cutting-edge radius.
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The prediction of precipitated graphite nodules size and distribution in a large industrial casting is critical to understand the mechanical behavior of cast iron components used in heavy vehicles. An accurate prediction of the graphite... more
The prediction of precipitated graphite nodules size and distribution in a large industrial casting is critical to understand the mechanical behavior of cast iron components used in heavy vehicles. An accurate prediction of the graphite nodules requires a validated and integrated macro-micro modeling framework, which forms the motivation behind the present study. Classical theories in the literature (Lesoult et al. in Acta Mater 46:983–995, 1998) proposed two stages of graphite growth: in (i) liquid stage, after encapsulation by the austenite grain, and in (ii) solid stage, surrounded by only austenite phase. In this work, a new stage of graphite growth was proposed, where a graphite nodule was in direct contact with the liquid metal, existing in the presence of an austenite grain separated from the nodule. The resulting three-stage graphite growth in a microscopic control volume was formulated using a volume-averaged micro-model. This was made to evolve with the help of a macroscop...
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The present work reports real-time observations of the phenomena of partial crystallization of one of the glass-forming materials, namely enstatite (MgSiO3) from its supercooled liquid droplet. Initially, the molten droplet has been held... more
The present work reports real-time observations of the phenomena of partial crystallization of one of the glass-forming materials, namely enstatite (MgSiO3) from its supercooled liquid droplet. Initially, the molten droplet has been held under purely non-contact conditions using the aerodynamic levitation technique. The desired levels of undercooling have been achieved by deliberately making the levitated molten droplet touch a thin molybdenum wire and hence to initiate heterogeneous nucleation from the point of contact. Influence of thermal parameters like undercooling, cooling rates and recalescence on the process of crystallization is investigated. To understand and report the morphological properties and extent of crystallinity, the solidified enstatite samples have been characterized using optical/scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively, which confirmed the formation of partially crystallized enstatite spherules and fully glass spherules. XRD...
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In this study, identical experiments of bottom-cooled solidification fluidic mixtures that exhibit faceted and dendritic microstructures were performed. The strength of compositional convection, created due to the rejection of a lighter... more
In this study, identical experiments of bottom-cooled solidification fluidic mixtures that exhibit faceted and dendritic microstructures were performed. The strength of compositional convection, created due to the rejection of a lighter solute, was correlated with the solidifying microstructure morphology via separate Rayleigh numbers in the mushy and bulk-fluid zones. While the bulk fluid in dendritic solidification experienced a monotonic decrease in the temperature, solidification of the faceted case revealed an unconventional, anomalous temperature rise in the bulk liquid after the formation of a eutectic solid. Based on the bulk-liquid temperatures, three distinct regimes of heat transfer were observed in the liquid, namely, convection-dominated, transition and conduction-dominated. The observations were analysed and verified with the help of different initial compositions and cooling conditions, as well as other mixtures that form faceted morphology upon freezing. The observed...
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A numerical model to study the growth of dendrites in a pure metal solidification process with an imposed rotational flow field is presented. The micro-scale features of the solidification are modeled by the well-known enthalpy technique.... more
A numerical model to study the growth of dendrites in a pure metal solidification process with an imposed rotational flow field is presented. The micro-scale features of the solidification are modeled by the well-known enthalpy technique. The effect of flow changing the position of the dendrite is captured by the Volume of Fluid (VOF) method. An imposed rigid-body rotational flow is found to gradually transform the dendrite into a globular microstructure. A parametric study is carried out for various angular velocities and the time for merger of dendrite arms is compared with the order estimate obtained from scaling.
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Development and proposition of a numerical model to capture the shrinkage induced flow during directional solidification of a pure substance in a bottom cooled cavity are carried out. A novel numerical scheme involving fixed grid-based... more
Development and proposition of a numerical model to capture the shrinkage induced flow during directional solidification of a pure substance in a bottom cooled cavity are carried out. A novel numerical scheme involving fixed grid-based volume fraction updating is proposed to track the solid–liquid interface, considering the inclusion of the shrinkage effect. Directional solidification in bottom cooled orientation is of particular interest since shrinkage and buoyancy effects oppose each other. The results from the proposed numerical model indicated the existence of an unprecedented flow reversal phenomenon during the progression of the solidification process, caused by the opposing nature of shrinkage and buoyancy effects. The flow reversal phenomena predicted by the numerical model are validated by conducting experiments involving directional solidification of coconut oil in a bottom cooled cavity. Qualitative and quantitative measurements of the velocity field and interface growth are obtained using the particle image velocimetry technique and compared with three dimensional numerical results. Once the flow reversal phenomena are established through numerical and experimental evidences, case studies are performed, considering varying material properties, cold boundary temperatures, initial temperatures of the melt, and cavity heights to find the effect of each of these parameters on flow reversal phenomena. The parametric study also allowed us to check the robustness and consistency of the proposed model. The proposed model will serve as an important milestone toward the development of numerical models for capturing macro-scale shrinkage defects and prediction of composition heterogeneity during directional alloy solidification.
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Solidifying ternary systems can exhibit complex natural convection phenomena, particularly due to the presence of two porous zones (cotectic and primary mush), and the rejection of two differently dense solutes. The primary objectives of... more
Solidifying ternary systems can exhibit complex natural convection phenomena, particularly due to the presence of two porous zones (cotectic and primary mush), and the rejection of two differently dense solutes. The primary objectives of this study are to investigate the following: (i) the natural convection patterns in various compositional regimes of a typical ternary system, and (ii) the role of the combined existence of the microstructure (facets and dendrites) in the porous zone on natural convection, with a motivation to enhance the current understanding of the microstructure–convection relationships. A ternary mixture is chosen such that different compositions of the three primary solidifying components lead to the formation of distinct ice, dendritic and faceted solid structures that cover the complete span of microstructure–convection relationships. The observations of flow in different compositional regimes show convection occurring in the form of plumes, random mixing and...
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Direct laser metal deposition (DLMD) is a promising additive manufacturing technique which has a huge potential in remanufacturing and restoration of high-value dies/molds and aerospace components. The residual stresses developed in the... more
Direct laser metal deposition (DLMD) is a promising additive manufacturing technique which has a huge potential in remanufacturing and restoration of high-value dies/molds and aerospace components. The residual stresses developed in the material deposited via DLMD affect the structural integrity of the restored components. The service life of the restored component will be compromised if tensile residual stresses are present in the deposited layer. The residual stresses originate due to differential thermal expansion/contraction and martensitic transformation-driven volumetric dilation and transformation-induced plasticity. The influence of martensitic transformation and processing conditions on the residual stresses of DLMD-processed components needs to be understood and modeled for sustainable repair. Hence, a finite element model has been developed to capture the coupled effect of thermomechanics and martensitic transformation on the evolution of residual stresses in DLMD. In thi...
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In this review, we present an overview of significant developments in the field of in situ and operando (ISO) X-ray imaging of solidification processes. The objective of this review is to emphasize the key challenges in developing and... more
In this review, we present an overview of significant developments in the field of in situ and operando (ISO) X-ray imaging of solidification processes. The objective of this review is to emphasize the key challenges in developing and performing in situ X-ray imaging of solidification processes, as well as to highlight important contributions that have significantly advanced the understanding of various mechanisms pertaining to microstructural evolution, defects, and semi-solid deformation of metallic alloy systems. Likewise, some of the process modifications such as electromagnetic and ultra-sound melt treatments have also been described. Finally, a discussion on the recent breakthroughs in the emerging technology of additive manufacturing, and the challenges thereof, are presented.
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The present work reports the morphological transition during solidification of a non-metallic system. Pure magnesium silicate (Mg2SiO4) is chosen as the model material and the solidification experiments have been conducted under purely... more
The present work reports the morphological transition during solidification of a non-metallic system. Pure magnesium silicate (Mg2SiO4) is chosen as the model material and the solidification experiments have been conducted under purely non-contact conditions using the principles of aerodynamic levitation. The influence of the undercooling and cooling rates on the surface features observed in the solidified samples is investigated. Levitation experiments have been performed for different samples, which are solidified for a range of undercooling levels between 360 to 1100° C. In order to understand and report the morphological transitions, solidified samples have been observed using scanning electron microscopy, which showed the formation of highly branched faceted microstructure for an undercooling regime of 360–800° C, and non-dendritic microstructure for even higher undercooling regime of 800–1100° C. Further experiments performed on this non-metallic system for different cooling r...
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Abstract The premature failure of cutting tools during machining of titanium alloys is primarily attributed to their low thermal conductivity and strain hardening. The coefficient of friction (CoF) at the tool –chip contact depends on the... more
Abstract The premature failure of cutting tools during machining of titanium alloys is primarily attributed to their low thermal conductivity and strain hardening. The coefficient of friction (CoF) at the tool –chip contact depends on the high stress–strain values, interface temperatures, and the velocity of the chip. In this work, a new tribometer is developed to overcome the drawbacks of the existing tribometer and evaluate the adhesive CoF, the heat partition ratio (HPR), and contact pressure. The experiments were conducted on Ti-6Al-4V alloy to estimate the variable CoF and HPR along the rake face. The extent of heat accumulation at the tool–chip interface was quantified using an infrared thermal imaging camera, and the approach successfully mimicked machining conditions, where the tangential force measured up to 900 N and contact pressure was up to 3 GPa. The experiments showed a clear indication of the adhesion of Ti alloy on the tool, strongly suggesting the existence of distinct CoF values for sliding and sticking. The results were further used to develop and validate a finite element model to predict the adhesive CoF, by taking into account the heat partitioning. The results showed considerable dependence of the CoF and HPR on the sliding velocity when implemented in a machining model where 13% maximum error was found in the cutting forces.
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Abstract The quality and integrity of laser direct metal deposition (DMD) processes primarily depend on the substrate dilution and the nature of residual stresses in the deposited layer. An adequate amount of melting of the substrate is... more
Abstract The quality and integrity of laser direct metal deposition (DMD) processes primarily depend on the substrate dilution and the nature of residual stresses in the deposited layer. An adequate amount of melting of the substrate is required to ensure the formation of sound metallurgical bond between the deposited layer and substrate. Insufficient melting and excessive dilution may lead to adverse effects. Furthermore, the dilution also controls the location of the melt front in substrate where maximum tensile residual stresses occur. The presence of tensile residual stresses in the deposited layer may be detrimental to service life, especially, for components repaired using DMD. These challenges can be overcome by predicting and controlling the dilution and the nature of residual stress as a function of process parameters. To model the direct metal deposition process, a 3D coupled metallo-thermomechanical finite element model is employed to predict the temperature and the residual stress due to thermomechanical interactions and metallurgical transformations and the substrate dilution. Non-dimensional process parameters affecting the dilution in laser DMD have been identified using Buckingham-Π theorem. The metallo-thermomechanical model is used to develop empirical relationships via regression to correlate the dimensionless process parameters with the dilution. These correlations are employed in developing the isopleths in the form of process maps, which could predict regions of inadequate fusion and excessive dilution (unduly large substrate melting). It may be noted that the limiting value of dilution corresponds to the condition where the entire deposited layer (cladding) is under compressive residual stresses. Any dilution higher than this will result in excess substrate melting which is undesirable. The limiting values of normalized dilution are estimated to be 1 and ~1.3 corresponding to complete deposit-substrate fusion and presence of entirely compressive residual stress in deposition, respectively. These process maps are designed to provide a theoretical framework for understanding the influence of process parameters and provide informed decisions on the selection of appropriate process parameters for ensuring the quality and integrity of the deposition.
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The alloy casting process is one of the major manufacturing processes to produce near net shape components. The casing process is prone to a wide variety of defects, with hot tear being one of the most detrimental. The two main factors... more
The alloy casting process is one of the major manufacturing processes to produce near net shape components. The casing process is prone to a wide variety of defects, with hot tear being one of the most detrimental. The two main factors generally recognized as the primary cause for formation of hot tears are the mechanical response of the mush (which effects its permeability), and the solidification range (solidification time). The response of the mushy zone under deformation is mainly affected by the solid fraction, strain rate and grain morphology. Even though the science behind the formation of hot tear is understood, there is no general criterion to quantify the hot tear formation under varying casting conditions. The development of ultra-fast X-ray imaging has facilitated the means to quantify the effects of the critical parameters in-situ and develop better correlations for hot tear prediction. The in situ experiments will also provide insights into mush rheology, which has sig...
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Abstract A coupled level-set and immersed-boundary-method (CLSIBM) is proposed for simulation of liquid and gas phase flow during filling of a complex geometry based mold using a modified cut-cell technique. The CLSIBM uses Cartesian... more
Abstract A coupled level-set and immersed-boundary-method (CLSIBM) is proposed for simulation of liquid and gas phase flow during filling of a complex geometry based mold using a modified cut-cell technique. The CLSIBM uses Cartesian computational domain, with two level-set functions: for liquid-metal and gas interface and ϕf,s for liquid-metal/gas and solid (mold box) interface. The cut-cell based immersed boundary method enable us to handle any internal two-phase flow in complex geometry using a Cartesian grid. Numerical results are presented for filling in four different tanks/molds, demonstrating the robustness of the proposed method during mold filling in complex geometry mold box.
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Abstract Laser heating is often used to perform the surface treatment by modifying local microstructural and mechanical properties of components having complex geometries. In this study, the laser surface heat treatment of a rotating... more
Abstract Laser heating is often used to perform the surface treatment by modifying local microstructural and mechanical properties of components having complex geometries. In this study, the laser surface heat treatment of a rotating cylindrical work-piece was investigated using both experimental and numerical modeling approaches, with an aim to correlate and predict the temperature distribution during the process. The depth of the laser affected zone was predicted by solving the transient heat transfer with a moving laser heat source, using finite element analysis. The temperatures derived from the microstructural examination of the experimental specimen were found to closely agree with the predicted results from the numerical simulations. The numerical and experimental results have also led to a new observation, indicating a linear variation of the absorptivity with the laser scan speed. The prediction of the cooling curves from simulation suggested the β → α ʺ phase transformation and the recovery of the β phase, and the existence of new phases were confirmed through electron microscopy. The rapid cooling during the laser surface treatment was found to induce a flake-structure that consisted of both martensite ( α ʺ ) and regained bcc ( β ) phase. A new polynomial input power function has been proposed to achieve uniform distribution of the heat penetration along the cylinder axis, saving about 10% of the material wastage.
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ABSTRACT The main objective of this work is to characterise the frictional phenomena at the tool–chip interface and evaluate the contact pressure in the secondary deformation zone of machining. Due to the tool–chip–workpiece trio contact... more
ABSTRACT The main objective of this work is to characterise the frictional phenomena at the tool–chip interface and evaluate the contact pressure in the secondary deformation zone of machining. Due to the tool–chip–workpiece trio contact complexity in machining, there is a lack of fundamental understanding related to tribological parameters. During cutting, the coefficient of friction (CoF) and contact pressure along the rake face depend upon stresses, interface temperature, the velocity of the chip and tool–chip contact length. Under critical conditions, stresses and temperature are very high at the cutting edge which results in tool wear and sometimes premature failure of the tool. Existing pin-on-disc technique fails to reproduce the extreme contact conditions observed on the rake face while cutting. Accurate predictive models, considering separate sticking and sliding zones for the secondary deformation zone are yet to be developed. A new tribometer was designed to correlate the coefficient of friction and pressure distribution with variable chip velocities. Based on this tribometer design, pin-on-workpiece experiments were performed on Ti-6Al-4V with tungsten carbide spherical pins. It was observed that sliding velocity is one of the most influential parameters affecting the coefficient of friction. However, the variation in pressure distribution along the rake face was observed to be very less.
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Density variations arising from thermal and compositional gradients in multi-component fluids can lead to natural convection flows. The double-diffusive layer is one such flow phenomenon, commonly observed in oceanic and phase change... more
Density variations arising from thermal and compositional gradients in multi-component fluids can lead to natural convection flows. The double-diffusive layer is one such flow phenomenon, commonly observed in oceanic and phase change systems. The solidification of high Prandtl number fluids offers a suitable platform to study multi-diffusive convection owing to continuously evolving temperature and compositional fields. In this work, an experimental investigation was conducted to study the influence of transport phenomena on the double-diffusive layer formation, by performing full-field measurements of concentration and flow velocities during bottom-cooled solidification of a hyper-eutectic aqueous mixture. Using a Mach-Zehnder interferometer, the first-ever real-time, quantitative observations of solutal mixing, plume formation, and the evolution of the double-diffusive layers by forming a stepped compositional distribution have been reported. In addition, the associated flow velocities were measured using the particle image velocimetry technique which clearly characterizes the compositional and thermal natural convection patterns along the vertical and horizontal directions, respectively. The study revealed a life-cycle for the existence of the double-diffusive layers, wherein they undergo onset, development, and disappearance depending on the initial composition, and identified critical Rayleigh numbers for each of these stages. The experimental observations were further supported with analytical scale estimates of the critical length, time, and velocities of the system. The quantitative results elucidate the conditions, including a newly hypothesized threshold composition difference, which led to the formation as well as the disappearance of the layers.Density variations arising from thermal and compositional gradients in multi-component fluids can lead to natural convection flows. The double-diffusive layer is one such flow phenomenon, commonly observed in oceanic and phase change systems. The solidification of high Prandtl number fluids offers a suitable platform to study multi-diffusive convection owing to continuously evolving temperature and compositional fields. In this work, an experimental investigation was conducted to study the influence of transport phenomena on the double-diffusive layer formation, by performing full-field measurements of concentration and flow velocities during bottom-cooled solidification of a hyper-eutectic aqueous mixture. Using a Mach-Zehnder interferometer, the first-ever real-time, quantitative observations of solutal mixing, plume formation, and the evolution of the double-diffusive layers by forming a stepped compositional distribution have been reported. In addition, the associated flow velocities were measured usi...
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In a wide variety of fluidic systems involving thermal and compositional gradients, local density changes lead to the onset of natural convection that influences the process itself, for example, during phase-change phenomena and magmatic... more
In a wide variety of fluidic systems involving thermal and compositional gradients, local density changes lead to the onset of natural convection that influences the process itself, for example, during phase-change phenomena and magmatic flows. Accurate knowledge of the flow characteristics is essential to quantify the impact of the flow of the processes. In this work, the first-ever demonstration of flow reversal during bottom-up solidification of water using full-field thermal and flow measurements and its direct impact on the solidifying interface is presented. Based on prior optical interferometric measurements of full-field temperature distribution in water during solidification, we use the particle image velocimetry technique to quantify and reveal the changing natural convection pattern arising solely due to the density anomaly of water between 0 °C and 4 °C. The independently captured thermal and flow fields show striking similarities and clearly elucidate the plausible mechanism explaining the fo...
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Natural convection during solidification of liquids is known to impact the freezing characteristics and also lead to defect formation. In this study, we report the findings of real-time interferometric observation of bottom-cooled... more
Natural convection during solidification of liquids is known to impact the freezing characteristics and also lead to defect formation. In this study, we report the findings of real-time interferometric observation of bottom-cooled solidification of pure water in a cubical cavity. The results show first quantitative evidence of full-field thermal history during solidification, clearly depicting the anomalous expansion of water below 4 °C. Furthermore, based on the strength of natural convection, characterized by the Rayleigh number, we identify and report four distinct regimes of solidification, namely—conduction dominated, early convection, front instability, and sustained convection. A critical Rayleigh number that initiates instability in the solidifying front has been proposed, which is significantly different from conventional calculations of Rayleigh number relating to the initiation of flow. The study shows full-field quantitative evidence of a well-known phenomenon and provid...
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Abstract Understanding the temperature distribution in drilling tool and workpiece is crucial for enhancing the drill performance and the process efficiency. However, a complete analysis of the same is extremely challenging, particularly... more
Abstract Understanding the temperature distribution in drilling tool and workpiece is crucial for enhancing the drill performance and the process efficiency. However, a complete analysis of the same is extremely challenging, particularly for difficult-to-machine materials such as titanium. The existing analytical and finite element analysis techniques normally assume a sharp drill point, which is not true as the drill may wear during the process. The main objective of the present study is to develop a comprehensive finite element model for evaluating temperature distribution in the process considering a variable heat partition model and ploughing forces, by incorporating a cutting edge radius of the tool. The cutting edge of the drill is divided into a series of independent elementary cutting tools (ECT). The model presented efficiently calculates forces encountered during drilling and then evaluates temperature distribution in the drill by considering the heat partition factors adopted. An experimental procedure is developed to measure the temperature in work piece with the help of an IR camera and observed results are successfully validated. The simulation results obtained are in agreement with the prior studies on tool temperature distribution, and the experimentally measured work piece temperatures.
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Elongated hydrogen porosity appears in aluminum based cast components and can lead to crack initiation. In this study, a comparison between the growth rates of hydrogen bubbles and the solidifying front during the process of engulfment is... more
Elongated hydrogen porosity appears in aluminum based cast components and can lead to crack initiation. In this study, a comparison between the growth rates of hydrogen bubbles and the solidifying front during the process of engulfment is presented. Extending upon a previously developed order estimate for the ratio of growth rates of the two interfaces, it is found that dimensionless grouping leads to two distinct time scales that correspond to solidification and hydrogen diffusion. The analysis proves the hypothesized thought-experiment and explains the mechanism of hydrogen bubble elongation. The scaling prediction is also validated with available experimental studies, and shows that the rate of elongation varies directly with the pore radii and inversely with the cooling rates. (C) 2016 Elsevier Ltd. All rights reserved.
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Abstract Development of more efficient thermal management systems is of prime importance not only in the context of environmental and energy concerns, but also due to ever-increasing demands of computational power. Flow boiling in... more
Abstract Development of more efficient thermal management systems is of prime importance not only in the context of environmental and energy concerns, but also due to ever-increasing demands of computational power. Flow boiling in microchannels holds a lot of promise and is capable of removing high heat fluxes. However, the physics behind the heat transfer and fluid flow during flow boiling at micro scales is not completely understood. Various studies have been performed to classify the flow regimes and identify the dominant mode of heat transfer in two phase flow through microchannels. In the present work, a numerical study is performed to investigate the bubble dynamics in a confined microchannel. A DGLSM (Dual-Grid Level Set Method) based numerical model is used to capture the unsteady bubble interface dynamics. The Navier–Stokes equation is being solved using Finite Volume Method (FVM) based Semi-Explicit Pressure Projection Method. The effect of parameters namely contact angle, surface tension, wall superheat, Reynolds number and system pressure on the bubble dynamics and bubble growth rates is investigated. Three distinct stages of heat transfer corresponding to the rapid reduction, stabilization and enhancement of evaluated Nusselt number are identified from the parametric investigation. The results show that the system pressure plays a vital role in controlling the bubble shape, as compared to remaining parameters.
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ABSTRACT Uniaxial compression and indentation of a semi-solid Al-15wt.%Cu alloy was investigated by high speed synchrotron X-ray microtomography, quantifying the microstructural response of a solidifying alloy to applied strain. Tomograms... more
ABSTRACT Uniaxial compression and indentation of a semi-solid Al-15wt.%Cu alloy was investigated by high speed synchrotron X-ray microtomography, quantifying the microstructural response of a solidifying alloy to applied strain. Tomograms were continuously acquired whilst performing deformation using a precision thermal-mechanical rig on a synchrotron beamline. The results illustrate how defects and shear bands can form in response to different loading conditions. Using digital volume correlation, the global and localised strains were measured, providing quantitative datasets for granular flow models of semi-solid deformation.
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Uniaxial compression and indentation of a semi-solid Al-15wt.%Cu alloy was investigated by high speed synchrotron X-ray microtomography, quantifying the microstructural response of a solidifying alloy to applied strain. Tomograms were... more
Uniaxial compression and indentation of a semi-solid Al-15wt.%Cu alloy was investigated by high speed synchrotron X-ray microtomography, quantifying the microstructural response of a solidifying alloy to applied strain. Tomograms were continuously acquired whilst performing deformation using a precision thermal-mechanical rig on a synchrotron beamline. The results illustrate how defects and shear bands can form in response to different loading conditions. Using digital volume correlation, the global and localised strains were measured, providing quantitative datasets for granular flow models of semi-solid deformation.
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The rheology of semi-solid alloys has been studied by a novel in situ tomographic technique. Via extruding an equiaxed Al–15 wt.%Cu alloy, the inhomogeneous coherent compression of the a-Al grains was quantified, including the... more
The rheology of semi-solid alloys has been studied by a novel in situ tomographic technique. Via extruding an equiaxed Al–15 wt.%Cu alloy, the inhomogeneous coherent compression of the a-Al grains was quantified, including the interdendritic channel closure and formation of a liquid extru- date. This investigation not only provides important insights into the microstructural changes occurring during semi-solid deformation, but also offers a validation benchmark for segregation and rheological models.