The Experts below are selected from a list of 2757 Experts worldwide ranked by ideXlab platform
Amauri Garcia - One of the best experts on this subject based on the ideXlab platform.
-
Melt characteristics and solidification growth direction with respect to gravity affecting the interfacial heat transfer coefficient of chill castings
Materials & Design, 2009Co-Authors: Noé Cheung, Ivaldo L. Ferreira, Moisés M. Pariona, José Maria Do Vale Quaresma, Amauri GarciaAbstract:Abstract For purposes of an accurate mathematical modeling, it is essential to establish trustworthy boundary conditions. The heat transfer that occurs at the casting/Mold Interface is one of these important conditions, which is a fundamental task during unsteady solidification in permanent Mold casting processes. This paper presents an overview of the inverse analysis technique (IHCP) applied to the determination of interfacial heat transfer coefficients, h i , for a number of alloy solidification situations. A search algorithm is used to find the transient metal/Mold Interface coefficient during solidification which is reported either as a function of the casting surface temperature or time. Factors affecting h i such as the direction of gravity in relation to the growth Interface, the initial melt temperature profile, the wettability of the liquid layer in contact with the Mold inner surface, were individually analyzed and experimental laws for h i have been established.
-
The variation of the metal/Mold heat transfer coefficient along the cross section of cylindrical shaped castings
Inverse Problems in Science and Engineering, 2006Co-Authors: Eduardo Netto De Souza, Noé Cheung, Carlos Alexandre Dos Santos, Amauri GarciaAbstract:During solidification, the mathematical analysis of heat flow depends on the transient heat transfer coefficient at the metal/Mold Interface. The analysis of heat transfer behavior along a cylindrical section is necessary for a better control of solidification in conventional foundry and continuous casting processes. For this purpose, a water-cooled experimental apparatus was developed, and experiments were carried out with Sn–Pb alloys with different melt superheats. The heat transfer coefficients were determined by a theoretical–experimental fit of thermal profiles (IHCP). The results have shown a variation in heat flow conditions along the metal/Mold Interface provoked by the action of solidification thermal contraction connected with the gravitational effect. In macrostructural terms, this effect was evident with an asymmetric structure due to the variation of metal/Mold thermal contact along the cylinder cross section. Experimental equations correlating heat transfer coefficients as a power function ...
-
Microstructure and solidification thermal parameters in thin strip continuous casting of a stainless steel
Journal of Materials Processing Technology, 2004Co-Authors: José E. Spinelli, Carlos Alexandre Dos Santos, J. P. Tosetti, J. A. Spim, Amauri GarciaAbstract:Abstract The present work focuses on the relationships between solidification thermal parameters and the dendritic microstructure of an AISI 304 stainless steel solidified both in a strip casting pilot equipment (twin-roll) and in a directional solidification simulator. Experimental studies were conducted with a stainless steel strip casting obtained in a twin-roll continuous caster pilot equipment and in samples solidified in a directional solidification simulator with two different melt superheats. In both cases, the surface of the substrates was similar, with mean surface roughness of about 0.3 μm. After solidification, the specimens were cut at different positions from the metal/Mold Interface and etched for metallographic examination. An empirical equation from the literature relating secondary dendrite arm spacing and cooling rates was used to demonstrate the similarity of the cooling efficiency. The results have shown that the simulator can be used in the determination of transient metal/Mold Interface coefficients ( h i ) and in the preprogramming of the strip casting operational conditions as a function of roll materials and surface roughness.
-
The columnar to equiaxed transition during solidification of Sn–Pb alloys
Journal of Alloys and Compounds, 2002Co-Authors: Claudio A. Siqueira, Noé Cheung, Amauri GarciaAbstract:Abstract In the present article, some important trends are shown regarding the influence of solidification thermal parameters on the columnar to equiaxed transition (CET) during the unsteady state solidification of Sn–Pb alloys. A comparison of the results obtained in the present work with results from the literature concerning similar experiments, but undertaken under conditions of lower heat transfer efficiency at the metal–Mold Interface, has shown that a realistic CET criterion should be based on a critical cooling rate at the dendrite tips of about 0.014 K/s, which depends only on the alloy system. The effects of melt superheat, solute concentration and metal–Mold heat transfer coefficient on the CET position are also investigated.
P. Davami - One of the best experts on this subject based on the ideXlab platform.
-
effect of pressure on heat transfer coefficient at the metal Mold Interface of a356 aluminum alloy
International Communications in Heat and Mass Transfer, 2012Co-Authors: Fardi A Ilkhchy, Masoud Jabbari, P. DavamiAbstract:Abstract The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the Interface between A356 aluminum alloy and metallic Mold during the solidification of casting under different pressures were obtained using the inverse heat conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented for correlation between external pressure and heat transfer coefficient. Acceptable agreement with data in literature shows the accuracy of the proposed formula.
-
Modeling of Metal-Mold Interface Resistance in the Al-11.5 wt% Si Alloy Casting Process
Scientia Iranica, 2007Co-Authors: P. DavamiAbstract:In this investigation, a computational model has been developed, including heat transfer and the eects of the resistance of a metal-Mold Interface and pressure, for simulation of the solidication process. Simulation of the Interface resistance is based on the Zero Thickness Element (ZTE), utilizing the Finite Element Method (FEM). Solid boundary conditions, including contact resistances, have been modied by a pressure gradient in each of the ZTE. The pressure gradient has been modeled, based on experimental data. In order to verify the computational results, an Al-11.5 wt% Si alloy was poured into a permanent Mold and the temperature of the Interface was measured by a data acquisition system. Then, the eect of metalo-static pressure on overall heat transfer in the Interface resistance was modeled. Comparison between the experimental and simulation results during the solidication process shows a good consistency, which conrms the accuracy of the model for the eects of Interface resistance on solidication time.
-
modeling of metal Mold Interface resistance in the al 11 5 wt si alloy casting process
Scientia Iranica, 2007Co-Authors: P. DavamiAbstract:In this investigation, a computational model has been developed, including heat transfer and the eects of the resistance of a metal-Mold Interface and pressure, for simulation of the solidication process. Simulation of the Interface resistance is based on the Zero Thickness Element (ZTE), utilizing the Finite Element Method (FEM). Solid boundary conditions, including contact resistances, have been modied by a pressure gradient in each of the ZTE. The pressure gradient has been modeled, based on experimental data. In order to verify the computational results, an Al-11.5 wt% Si alloy was poured into a permanent Mold and the temperature of the Interface was measured by a data acquisition system. Then, the eect of metalo-static pressure on overall heat transfer in the Interface resistance was modeled. Comparison between the experimental and simulation results during the solidication process shows a good consistency, which conrms the accuracy of the model for the eects of Interface resistance on solidication time.
Otavio L Rocha - One of the best experts on this subject based on the ideXlab platform.
-
determination of heat transfer coefficients at metal Mold Interface during horizontal unsteady state directional solidification of sn pb alloys
Materials Chemistry and Physics, 2011Co-Authors: Jose Silva, Ivaldo L. Ferreira, Daniel J Moutinho, Antonio Luciano Seabra Moreira, Otavio L RochaAbstract:Abstract This paper presents a theoretical–experimental study of the metal–Mold heat transfer coefficients during horizontal directional solidification of Sn–Pb hypoeutectic alloys (5 wt%Pb, 15 wt%Pb, 20 wt%Pb and 25 wt%Pb) in presence of thermo-solutal convection. A water-cooled solidification experimental apparatus has been developed, and specimens have been solidified under unsteady state heat flow conditions. Five computer guided thermocouples have been connected with the metal, and the time–temperature data have been recorded automatically. A numerical technique which compares theoretical and experimental thermal profiles is used for investigating the influence of solute content on h i values. This has permitted the evaluation of the variation of metal–Mold heat transfer coefficients along the solidification of Sn–Pb alloys, as well as the analysis of the effects of thermo-solutal convection. The interfacial heat transfer coefficients of alloys studied are represented by equations which show the time dependence during the process. The experimental and calculated values have shown a very good agreement. A comparative analysis between the results of this work and those from the literature proposed to analyze the metal–Mold heat transfer coefficients during upward and downward vertical solidification of Sn–Pb hypoeutectic alloys is conducted.
-
Determination of heat transfer coefficients at metal–Mold Interface during horizontal unsteady-state directional solidification of Sn–Pb alloys
Materials Chemistry and Physics, 2011Co-Authors: Jose Silva, Ivaldo L. Ferreira, Daniel J Moutinho, Antonio Luciano Seabra Moreira, Otavio L RochaAbstract:Abstract This paper presents a theoretical–experimental study of the metal–Mold heat transfer coefficients during horizontal directional solidification of Sn–Pb hypoeutectic alloys (5 wt%Pb, 15 wt%Pb, 20 wt%Pb and 25 wt%Pb) in presence of thermo-solutal convection. A water-cooled solidification experimental apparatus has been developed, and specimens have been solidified under unsteady state heat flow conditions. Five computer guided thermocouples have been connected with the metal, and the time–temperature data have been recorded automatically. A numerical technique which compares theoretical and experimental thermal profiles is used for investigating the influence of solute content on h i values. This has permitted the evaluation of the variation of metal–Mold heat transfer coefficients along the solidification of Sn–Pb alloys, as well as the analysis of the effects of thermo-solutal convection. The interfacial heat transfer coefficients of alloys studied are represented by equations which show the time dependence during the process. The experimental and calculated values have shown a very good agreement. A comparative analysis between the results of this work and those from the literature proposed to analyze the metal–Mold heat transfer coefficients during upward and downward vertical solidification of Sn–Pb hypoeutectic alloys is conducted.
W Zhou - One of the best experts on this subject based on the ideXlab platform.
-
effect of molecular weight and substrate on silicone segregation from uv resin at plasma polymerized Mold Interface
Journal of Polymer Science Part B, 2010Co-Authors: W Zhou, Mary ChanparkAbstract:Pristine-, poly(octafluorotoluene)- (POFT), and polyacetylene (PAc)-coated Si wafers were used as substrates for the study of segregation of silicone diacrylate (SA) from a formulation containing other oligomeric and monomeric acrylates. POFT and PAc were microwave plasma polymerized on the Si wafers. Three SAs with molecular weights ranging from 700 to 6000 Da were synthesized and characterized. Formulations with 2 wt % SA were ultraviolet cured on the silicon wafers. The surface composition of formulation-substrate side of the cured film was analyzed with X-ray photoelectron spectroscopy, and the depth profile was analyzed with time of flight-secondary ion mass spectrometry. The analysis results indicated that SA aggregated on all three types of Si surfaces. However, SA segregation is highest on the low surface energy POFT-coated Si substrate, and low-molecular-weight SA is favorable to the segregation. For high-molecular-weight SA, the different Si substrates do not affect the degree of aggregation at the formulation-substrate Interface. The observed SA aggregation trend can be predicted by the Gibbs-adsorption equation correlated to the resin surface tension and contact angle on substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 442–450, 2010
-
segregation of silicone acrylate from acrylate mixture at resin Mold Interface and its effect on uv embossing
Applied Surface Science, 2006Co-Authors: W Zhou, Mary ChanparkAbstract:When silicone diacrylate was added in small amount (<5 wt.%) to ultraviolet (UV) curable formulations containing other oligomeric diacrylates, there was segregation of the silicone additive at the solid substrate–formulation Interface. The amount was quantified by X-ray photoelectron spectroscopy measurement of the UV cured film surface composition. The effect of silicone diacrylate concentration, resin formulation and substrate polarity on silicone surface excess was systematically studied. Young's–Gibbs adsorption theory was applied to the prediction of the silicone surface excess at the solid substrate Interface for these oligomeric mixtures. Further, we proposed a simplified Young's–Gibbs adsorption theory equation to predict the variation of surface excess from only formulation surface tension and substrate critical surface tension. The selective segregation is beneficial to deMolding in UV embossing since only small amount of release added can result in large decrease of the Mold–resin interfacial energy difference leading to easy deMolding and high replication fidelity.
-
Segregation of silicone acrylate from acrylate mixture at resin–Mold Interface and its effect on UV embossing
Applied Surface Science, 2006Co-Authors: W Zhou, Mary B. Chan-parkAbstract:When silicone diacrylate was added in small amount (
J Sieniawski - One of the best experts on this subject based on the ideXlab platform.
-
investigation of casting ceramic shell Mold Interface thermal resistance during solidification process of nickel based superalloy
Experimental Thermal and Fluid Science, 2017Co-Authors: Dariusz Szeliga, K Kubiak, Waldemar Ziaja, Rafal Cygan, Sz J Suchy, A Burbelko, W J Nowak, J SieniawskiAbstract:Abstract The study of thermal resistance (TR) at the casting-Mold Interface has been performed to describe the solidification process aimed at the improvement of technology and the reduction of defect quantity of investment castings. The analysis of thermal resistance at casting–Mold Interface between the solidifying IN 713C nickel superalloy plate casting and ceramic shell Mold has been presented. The temperature measurements in the plate casting of IN 713C nickel superalloy and the ceramic shell Mold were carried out to determine the casting–Mold Interface heat transfer coefficient (IHTC) with the use of inverse heat conduction method. The calculations were performed using a ProCAST software. It was found that the casting–Mold IHTC (7962 Wm −2 K −1 ) was the highest for the alloy in the liquid state and then it intensively decreased during solidification and cooling followed by its increase close to the end of the solidification process forming another peak on the obtained curve. The formation mechanism of gap between the ceramic Mold and Ni based superalloy casting as well as another peak were proposed taking into account the occurrence of mixed oxide scale at the Interface. On the basis of numerical simulation, it was found that the IHTC had less influence on cooling rate of casting than the thickness, thermal conductivity and emissivity of the Mold for the applied technological parameters of the process.
-
Investigation of casting–ceramic shell Mold Interface thermal resistance during solidification process of nickel based superalloy
Experimental Thermal and Fluid Science, 2017Co-Authors: Dariusz Szeliga, K Kubiak, Waldemar Ziaja, Rafal Cygan, A Burbelko, W J Nowak, J. Sz. Suchy, J SieniawskiAbstract:Abstract The study of thermal resistance (TR) at the casting-Mold Interface has been performed to describe the solidification process aimed at the improvement of technology and the reduction of defect quantity of investment castings. The analysis of thermal resistance at casting–Mold Interface between the solidifying IN 713C nickel superalloy plate casting and ceramic shell Mold has been presented. The temperature measurements in the plate casting of IN 713C nickel superalloy and the ceramic shell Mold were carried out to determine the casting–Mold Interface heat transfer coefficient (IHTC) with the use of inverse heat conduction method. The calculations were performed using a ProCAST software. It was found that the casting–Mold IHTC (7962 Wm −2 K −1 ) was the highest for the alloy in the liquid state and then it intensively decreased during solidification and cooling followed by its increase close to the end of the solidification process forming another peak on the obtained curve. The formation mechanism of gap between the ceramic Mold and Ni based superalloy casting as well as another peak were proposed taking into account the occurrence of mixed oxide scale at the Interface. On the basis of numerical simulation, it was found that the IHTC had less influence on cooling rate of casting than the thickness, thermal conductivity and emissivity of the Mold for the applied technological parameters of the process.