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Ductile iron pipes are widely used in modern drinking water and wastewater networks. They often produce by horizontal centrifugal casting process. In this reasearch, the finite element base package ANSYS software has been used for thermal simulation of horizontal centrifugal casting process of ductile iron pipes.The simulation includes obtaining temperature distribution of mold and cast during different temperature cycles. In the simulation, latent heat due to solidification, temperature-dependent thermo-physical properties of material, heat transfer coefficient in metal-mold interface due to mold coating and air gap and thermal boundary conditions proportional to practical conditions, are considered. In this paper, pouring process to get transient thermal distribution in main body of mold and cast are also simulated. The results of the thermal simulation show good agreement with the experimental results conducted in this study and literature. The results can be used as input data for the numerical model to estimate thermal fatigue life of a permanent mold. The results of simulation have shown that, the thermal resistance of the air gap and mold coating has a significant effect on the temperature distribution in the pipe and the mold. Pouring process causes temperature gradients in the axial direction in the mold and the cast.

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In this article, effects of Friction stir welding tool rotational and traverse speeds were studied on the temperature distribution, material flow and formation of defects in the welding zone. Computational fluid dynamics method was used to simulate the process with commercial CFD Fluent 6.4 package. To enhance the accuracy of simulation in this Study, the welding line that is located between two workpieces, defined with pseudo melt behavior around the FSW pin tool. Simulation results showed that with increase of FSW tool rotational speed to linear speed, the material flow in front of tool became more and dimensions of the stir zone will be bigger. The calculation result also shows that the maximum temperature and stir of the material was occurred on the advancing side. The computed results showed that with incompetent heat generation, insufficient material flow caused around the pin and defects formed in weld root. The computed results were in good agreement with the experimental results of other researchers. Based on the welding parameters that used in this simulation, the maximum strain rate is predicted between -4(S-1) to +4(S-1) in the stir zone.

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With the development of micro-mechanical systems, human became interested in concentrating on the small-scale impact on the flow and heat transfer in micro-channels. A micro-channel is required for a gas sensor to guide the gas flow. Reducing the size of channel has lead the scientist to concentrate on micro-sensor. Metal oxide gas micro-sensors are used to detect gases such as O3, SO2, CO2, NO, NH3, CH4 and etc. Metal oxide gas micro-sensors are small in size, low cost in fabrication and consume little power. The purpose of the current study is to numerically investigate the micro-channel wall thickness and diameter on gas inlet temperature under the influence of thermal creeping. The governing nonlinear differential equations, mass, momentum, energy, and species, are coupled and solved by a commercial code. The channel is assumed to be two dimensional. Since the Knudsen number is between 0.01 and 0.1, the slip boundary condition, Maxwell equation, is utilized. The result shows that as wall thickness increases the gas inlet temperature increases and temperature difference between gas inlet and outlet decreases. On the other hand as channel diameter decreases the gas inlet temperature increases.

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Friction stir welding is a solid state process in which no fusion occurring on it. This method of welding is uses for metals that have low weldability or their fusion welds haven’t good quality. The effect of friction stir welding parameters, including rotational speed, linear speed, shoulder diameter and pin diameter on AA5052 to AA6061 dissimilar joints was studied in this paper. These parameters were optimized Using Taguchi method of Design of Experiments. then thermal simulation of process was done with ABAQUS software in which the temperature distribution results were in good agreement with the simulation results. The results of specimens tensile tests were confirmed by metallography and micro-hardness tests result. With increasing the linear speed and reducing the rotational speed, heat input reduced and grain size of all weld areas is decreased. The retreating side of all instances had a smaller grain size than advancing side. This is because of the thermal properties of 6061 alloy (higher conductivity and lower heat capacity), which leads to lower peak temperature and higher thermal diffusivity on that. The optimal parameters including rotational speed of 1400 rpm, linear speed of 80 mm/min, shoulder diameter of 15 mm and a pin diameter of 3.5 mm, was achieved. The maximum tensile strength of 228.3 Mpa achieved in rotation speed of 1400 RPM, linear speed of 80 mm/min, shoulder diameter of 15 mm and pin diameter of 3.5 mm.