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N. Arab

Abstract

Cast irons are good examples of materials which are more sensitive to chemical composition and production conditions. In this research to improve casting quality, solidification and nucleation process in grey cast iron was investigate. In particular, attempts have been made to rationalize variation in eutectic cells with nucleation sites and eutectic solidification undercooling. Four castings with different diameter and similar chemical composition and pouring temperature and different inoculant percentage was casted. The cooling curve and maximum and minimum undercooling for each castings was measured. Also optical metallography and image analyzer has been used to determine the average eutectic cells diameter, and linear and surface densities, and volume density was calculated. The results of this research show a competitive behavior between nucleation sites and eutectic undercooling. Higher nucleation sites and higher eutectic undercooling cause higher eutectic cell density. But increasing nucleation sites by introducing inoculants to molten metal, is accompanied with reduction in eutectic undercooling. It means that inoculation and undercooling have opposite effect on each other. So, to achieve maximum cell density, it is necessary to create an optimization between these parameters.

Open access

M. Ayaz, N. Banimostafa Arab and D. Mirahmadi Khaki

Abstract

In the present investigation, the effects of processing parameters, such as roughing, finishing and coiling temperatures, on the strain hardening exponent and yield strength of a Nb-microalloyed steel has been studied by Taguchi method. In order to achieve maximum n-value and yield strength, tests were done in a laboratorial pilot considering a L16 orthogonal array of Taguchi method under following condition: roughing temperature of 1000, 1050, 1100, 1150 °C, finishing temperature of 800, 850, 900, 950 °C, coiling temperature of 550, 600, 650, 700 °C. Then, analysis of variance and signal to noise ratios are performed on the measured data. The results indicated that the finishing and coiling temperatures were the major factor affecting the mechanical properties. The confirmation tests at optimal conditions approve the effectiveness of this robust design methodology in investigating the hot rolling process of the microalloyed steels.

Open access

Nageh N. Meleka, Alaa A. Bashandy and Mohamed A. Arab

Abstract

In this research reactive powder concrete (RPC) was prepared using sand from North Sinai. The mechanical properties of locally cast RPC were investigated and evaluated by studying the effects of using different cement and silica fume contents and new steel fibers’ aspect ratios as reinforcement for RPC. Specimens’ preparation, curing regimes and testing procedures to evaluate the compressive strength, the modulus of elasticity, the indirect tensile strength and the flexural strength were discussed. A compressive strength of 154.5MPa, indirect tensile strength of 11.98MPa, modulus of elasticity of 45.1GPa and flexural strength of 30.26MPa have been achieved for reinforced RPC contains 800 kg/m3 cement content and silica fume content 30% of cement weight. The test results showed some improvements by increasing cement and silica fume contentsas well as adding steel fibers on the compressive strength, modulus of elasticity and indirect tensile strength.