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Experimental and Numerical Determination of Casting-Mold Interfacial Heat Transfer Coefficient in the High Pressure Die Casting of A-360 Aluminum Alloy

100%
Koru M., Serçe O.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 1
453-458
EN
Although die casting is a near net shape manufacturing process, it mainly involves a thermal process. Therefore, in order to produce high quality parts, it is important to determine casting-mold interfacial heat transfer coefficient and heat flux. In this paper the effects of different injection parameters (second phase velocity, injection pressure, pouring and die temperature) on heat flux and interfacial heat transfer coefficient were investigated experimentally and numerically. Experiments were performed in cylindrical geometry using a cast aluminum alloy A360 against H13 steel mold. Selected injection parameters were 1.7-2.5 m/s for second phase velocity, 100-200 bar for third phase pressure, 983-1053 K for pouring temperature and 373, 433, 493, 553 K for the die temperature. These parameters were used for both non-vacuum and vacuum conditions in the cavity of the mold. The effects of the application under vacuum conditions were also studied. Temperatures were measured as functions of time, using 18 thermocouples, which were mounted at different depths of casting and mold material. Measured and calculated temperature values are found compatible. Interfacial heat transfer coefficient h and heat flux q depending on the experimentally measured temperature values were calculated with finite difference method using explicit technique in C# programming language. In addition to experiments, Flow-3D software simulations were performed using the same parameters. Interfacial heat transfer coefficient and heat flux results obtained from Flow-3D are also presented in the study. Interfacial heat transfer coefficient has decreased as a result of increasing of temperature of mold and pouring. In addition, interfacial heat transfer coefficient values have increased slightly with the increase of injection speed and pressure. It was observed that the values of interfacial heat transfer coefficient and heat flux have also increased when vacuum was applied inside the cavity of the mold. When all injection parameters are considered, it is seen that the interfacial heat transfer coefficient varies between 92-117 kW/m² K.
2
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Investigation of Relationships between Ultrasonic Pulse Velocity and Thermal Conductivity Coefficient in Foam Concretes

81%
Davraz M., Kilinçarslan Ş., Koru M., Tuzlak F.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 1
469-470
EN
In this study, using type CEM I 42.5 R Portland cement, limestone powder, polypropylene fibers and super plasticizer, additive foam concrete specimens were produced. 28 days compressive strengths, dry densities, ultrasonic pulse velocities and thermal conductivity coefficient of these samples were determined. Analysing test results, it was noticed that there underlies a strong relationship between ultrasonic pulse velocity and thermal conductivity coefficient in the foam concrete. It is possible to estimate thermal conductivity by ultrasonic pulse velocity method, easy and credible method.
3
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Investigation of Properties of Foam Concretes Produced Using Pumice at Different Ratios

81%
Kilinçarslan Ş., Davraz M., Koru M., Ekıztaş F.
Acta Physica Polonica A
|
2017
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vol. 132
|
issue 3
708-709
EN
Foam concrete is a type of light weight concrete having self-compacting properties. It can be obtained by mixing the foam, formed by the foaming agent, with a mixture consisting of cement, water and aggregate. It contains independent closed pores with a volume of 75-80% within its body. In this study, three series of foam concrete were produced using different ratio of pumice. Compressive strength, splitting tensile strength and thermal conductivity of foam concrete samples were determined for each density set. It is found that, pumice ratio has a linear relationships with dry bulk density, compressive strength, tensile strength and thermal conductivity. It can also be concluded that strong relationship exist between higher correlation coefficients and pumice ratio.
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