The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
A. M. Assar - One of the best experts on this subject based on the ideXlab platform.
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Effect of melt superheat and chill material on interfacial heat-transfer coefficient in end-chill Al and Al-Cu alloy Castings
Journal of Materials Science, 1992Co-Authors: M. A. Taha, N. A. El-mahallawy, A. M. Assar, R. M. HammoudaAbstract:Solidification of Metal Castings inside moulds is mainly dependent on the rate of heat removal from the Metal to the mould. During casting solidification, an air gap usually develops at the interface between the solidfying Metal and the surrounding mould or chill. This condition occurs in most casting geometries, except in some cases such as the cast Metal solidifying around a central core. An overall heat-transfer coefficient, which includes all resistances to heat flow from the Metal to its surroundings can be determined. The objective of this work was to determine the overall heat-transfer coefficient, h , using experimental and computersimulation results on commercial purity aluminium and Al-4.5 wt% Cu alloy solidifying in a vertical end-chill apparatus. The cast ingots had a cylindrical shape with 12.5 mm diameter and different lengths of 95 and 230 mm. It solidified at different superheats (ranging from 50–110 °C) against two different chill materials: copper, and dry moulding sand. A computer program solving the heat-conduction equation and taking into consideration the convection in the melt, was used to compute the temperature history at numerous points along the ingot length. Different h values were assumed as a function of time, until agreement between experimental and computed cooling curves was obtained. The variation of h as a function of time, surface temperature, specimen length for each melt superheat and chill material was found. The thickness of the air gap was also evaluated. The results indicate that the variation of heat-transfer coefficient with time followed a pattern of sudden increase for the first few seconds, followed by a steady state, after which h decreased and reached another lower constant value. The h values were also found to decrease rapidly when the liquidus temperature was reached in the melt. For longer specimen and higher melt superheat, the heat-transfer coefficient increased. It was also higher for a copper than for a sand chill.
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Effect of melt superheat on heat transfer coefficient for aluminium solidifying against copper chill
Journal of Materials Science, 1991Co-Authors: N. A. El-mahallawy, A. M. AssarAbstract:Solidification of Metal Castings inside moulds is mainly dependent on the heat flow from the Metal to the mould which is in turn proportional to an overall heat transfer coefficient h which includes all resistances to heat flow such as the presence of an air gap. In the present work the heat transfer coefficient is determined using a directional solidification set-up with end chill for solidifying commercial-purity aluminium with different superheats (40 K and 115 K) against copper chill. A computer program solving the heat conduction and convection in the solidifying Metal is used together with the experimental temperature history in order to determine the heat transfer coefficient at the interface. The variation of h as a function of time, surface temperature and gap temperature for each melt superheat is found. The results indicate that h reaches a maximum value for surface temperature close to the liquidus. The analysis of heat flux from the Metal to the mould indicates that it is mainly by conduction. The air gap size is evaluated with time, surface temperature and with melt superheat. It is found that higher h values and smaller gap sizes are obtained with higher superheats.
Baode Sun - One of the best experts on this subject based on the ideXlab platform.
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Mechanism of Filling and Feeding of Thin-Walled Structures during Gravity Casting
Materials, 2015Co-Authors: Jiao Zhang, Fenggang Bian, Yanling Xue, Fucheng Yin, Yu Xie, Baode SunAbstract:The filling and feeding of thin-walled structures in Metal Castings pose significant difficulties in manufacturing aerospace structural materials. Samples containing 2 mm and 5 mm thin-walled structures were designed to study the kinetics of filling. The microstructural evolution of the solidification of thin-walled structures was studied with synchrotron X-radiation imaging. The formation of dendritic networks and the isotherm profiles of samples of different thickness were examined. The experimental results showed solidification microstructures of 2 mm and 5 mm thin-walled parts containing elongated equiaxed grains and normal equiaxed grains, respectively. The filling and feeding abilities of thin-walled parts were found to depend more on the wall thickness than on the pouring temperature.
N. A. El-mahallawy - One of the best experts on this subject based on the ideXlab platform.
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Effect of melt superheat and chill material on interfacial heat-transfer coefficient in end-chill Al and Al-Cu alloy Castings
Journal of Materials Science, 1992Co-Authors: M. A. Taha, N. A. El-mahallawy, A. M. Assar, R. M. HammoudaAbstract:Solidification of Metal Castings inside moulds is mainly dependent on the rate of heat removal from the Metal to the mould. During casting solidification, an air gap usually develops at the interface between the solidfying Metal and the surrounding mould or chill. This condition occurs in most casting geometries, except in some cases such as the cast Metal solidifying around a central core. An overall heat-transfer coefficient, which includes all resistances to heat flow from the Metal to its surroundings can be determined. The objective of this work was to determine the overall heat-transfer coefficient, h , using experimental and computersimulation results on commercial purity aluminium and Al-4.5 wt% Cu alloy solidifying in a vertical end-chill apparatus. The cast ingots had a cylindrical shape with 12.5 mm diameter and different lengths of 95 and 230 mm. It solidified at different superheats (ranging from 50–110 °C) against two different chill materials: copper, and dry moulding sand. A computer program solving the heat-conduction equation and taking into consideration the convection in the melt, was used to compute the temperature history at numerous points along the ingot length. Different h values were assumed as a function of time, until agreement between experimental and computed cooling curves was obtained. The variation of h as a function of time, surface temperature, specimen length for each melt superheat and chill material was found. The thickness of the air gap was also evaluated. The results indicate that the variation of heat-transfer coefficient with time followed a pattern of sudden increase for the first few seconds, followed by a steady state, after which h decreased and reached another lower constant value. The h values were also found to decrease rapidly when the liquidus temperature was reached in the melt. For longer specimen and higher melt superheat, the heat-transfer coefficient increased. It was also higher for a copper than for a sand chill.
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Effect of melt superheat on heat transfer coefficient for aluminium solidifying against copper chill
Journal of Materials Science, 1991Co-Authors: N. A. El-mahallawy, A. M. AssarAbstract:Solidification of Metal Castings inside moulds is mainly dependent on the heat flow from the Metal to the mould which is in turn proportional to an overall heat transfer coefficient h which includes all resistances to heat flow such as the presence of an air gap. In the present work the heat transfer coefficient is determined using a directional solidification set-up with end chill for solidifying commercial-purity aluminium with different superheats (40 K and 115 K) against copper chill. A computer program solving the heat conduction and convection in the solidifying Metal is used together with the experimental temperature history in order to determine the heat transfer coefficient at the interface. The variation of h as a function of time, surface temperature and gap temperature for each melt superheat is found. The results indicate that h reaches a maximum value for surface temperature close to the liquidus. The analysis of heat flux from the Metal to the mould indicates that it is mainly by conduction. The air gap size is evaluated with time, surface temperature and with melt superheat. It is found that higher h values and smaller gap sizes are obtained with higher superheats.
Guha P. Manogharan - One of the best experts on this subject based on the ideXlab platform.
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Re-Thinking Design Methodology for Castings: 3D Sand-Printing and Topology Optimization
International Journal of Metalcasting, 2019Co-Authors: Jiayi Wang, Santosh Reddy Sama, Guha P. ManogharanAbstract:Additive manufacturing of sand molds and cores for Metal Castings, often called 3D sand-printing (3DSP), is an efficient “freeform” fabrication process that enables rapid production of sand Metal Castings. The ability to create highly complex molds and cores for advanced Metal casting geometries via 3DSP provides unparalleled design freedom, particularly for low-volume production. However, there is a need to thoroughly understand the opportunities and restrictions of 3DSP in a systematic approach similar to well-established design guidelines for traditional sand casting. This study presents a knowledge-based design framework for 3DSP with the goal of developing new part design guidelines under such 3DSP framework. In particular, constrained topology optimization approach for the part redesign is developed for 3DSP. The presented design framework is compared with traditional sand-casting rules and validated through a case study on an existing Metal component. Advantages of the developed 3DSP design framework are illustrated and validated through a case study where a 30% improvement in factor of safety and a 50% reduction in weight of a mechanical part is achieved. Other advantages, such as reduced lead time and production cost, are also observed. This research provides the first known investigation into systematic implementation of simultaneous constraints of 3DSP sand-casting rules mechanical strength through the integration of topology optimization and novel design rules to Castings via 3D-printed molds. 3DSP also eliminates multiple design constraints in conventional mold-making and core-box fabrication. Findings from this study can be applied for a wide range of alloy systems, part geometries and loading conditions for sand Castings in industrial applications.
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Non-conventional mold design for Metal casting using 3D sand-printing
Journal of Manufacturing Processes, 2018Co-Authors: Santosh Reddy Sama, Jiayi Wang, Guha P. ManogharanAbstract:3D Sand-Printing (3DSP) is a relatively new Additive Manufacturing (AM) technology that enables direct digital manufacturing (DDM) of complex sand molds and cores for sand casting applications. Ever-growing interest in this indirect hybrid Metal AM process is attributed to its ability to rapidly produce tooling (i.e., cores and molds) for complex Metal Castings that are otherwise impossible to manufacture using conventional techniques. Knowledge-based design rules for this process is currently very limited and is being progressively realized on an ad-hoc basis to produce economicaly viable low-batch Castings. In this research, non-conventional design rules for gating and feeding (also known as rigging) is developed to improve casting performance (i.e., filling, feeding and solidification). Several case studies are presented to illustrate the improved casting performance by systematically redesigning each element of the rigging system. Computational simulations of the melt flow are developed to evaluate the effectiveness of redesigned rigging system. This research further illustrates the ability of 3DSP to not only impact part performance, i.e., optimized Metal casting designs via 3DSP but also drastically improves the casting performance which could potentially transform the industry of sand casting to produce high quality Castings.
Jiao Zhang - One of the best experts on this subject based on the ideXlab platform.
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Mechanism of Filling and Feeding of Thin-Walled Structures during Gravity Casting
Materials, 2015Co-Authors: Jiao Zhang, Fenggang Bian, Yanling Xue, Fucheng Yin, Yu Xie, Baode SunAbstract:The filling and feeding of thin-walled structures in Metal Castings pose significant difficulties in manufacturing aerospace structural materials. Samples containing 2 mm and 5 mm thin-walled structures were designed to study the kinetics of filling. The microstructural evolution of the solidification of thin-walled structures was studied with synchrotron X-radiation imaging. The formation of dendritic networks and the isotherm profiles of samples of different thickness were examined. The experimental results showed solidification microstructures of 2 mm and 5 mm thin-walled parts containing elongated equiaxed grains and normal equiaxed grains, respectively. The filling and feeding abilities of thin-walled parts were found to depend more on the wall thickness than on the pouring temperature.