فهرست مطالب احسان مهرابی گوهری

Double girder cranes are mostlyture or some specific parts of this crane go under Double girder cranes are mostly used for heavy loads. The steel structure or some specific parts of this crane go under extra load during the crane operation. The crane condition depends on many variables that change over time randomly. The current standards of Europe have not solved the effects of the forces on the fatigue damage. In this paper, reasons for the skewing of the crane from the main path, and wear of the wheels and rails of it, and the effect of the lateral and thermal forces on the double girder crane are presented. Experimental measurements and computer simulations are used for the analysis. The existence of symmetry in the crane design and operation period is very important. The carriage location influences the amount of force. The results show that for preventing movement difficulties in the rail and crane, it is recommended to cover the structure with the heat shield and insulation materials, especially those parts in exposure to the hot billet. Creating the expansion gap in rails of the crane needs to be obeyed according to the standards. Also, using the rail guide is very good to reduce the skewing of the crane. Furthermore, heat treatment and hardening of the  used for heavy loads. The steel strucwheels must be completely obeyed.

Tundish, as a continuous metallurgical operator, provides steel for continuous casting molds with optimum flow rates, constant temperatures, uniform chemical compositions and low porosity. Basically, the cleanliness of the molten steel entering the mold is affected by the type of flow pattern and the performance of the tundish in flotation and removal of non-metallic impurities. In this paper, the fluid flow and heat transfer in a tundish in 2 cases, without an obstacle and with an obstacle, turbo-stop, which is installed at its bottom and across the melt input is simulated using the Ansys Fluent at melt heights of 0.5, 0.65, and 0.75 m. Results show that the formation of the secondary circulating flow inside the obstacle is the most important reason for the input melt velocity reduction. Increasing the melt height leads to a more uniform and less turbulent flow. Furthermore, increasing the melt height from 0.5 m to 0.75 m leads to %3 reduction of the average flow velocity. The highest heat transfer loss is from the top surface of the tundish and therefore, the most temperature gradient exists at the top surface of the melt. The flow movement paths from the tundish input show that the melt flow velocity towards the sides of the tundish is increased with the melt height inside it. Furthermore, higher melt height causes the formation of higher stagnant melt volume inside the tundish, which negatively influences the inclusion absorption by the slag.

In this research, by using the combined lattice Boltzmann and smooth profile method, for power law non-Newtonian fluidized bed, the effect of changing the geometric and fluid on the expansion behavior of the bed has been studied. Investigations have been carried out for 7 different geometries and 4 Newtonian and non-Newtonian fluids with a power law index of 0.8 to 1. The results of the bed with Newtonian fluid show more porosity than the bed with non-Newtonian fluid. Also, increasing the index of the power law caused an increase in the porosity of the bed, and the porosity of the non-Newtonian bed decreased with an increase in the density of solid particles and the initial height of the bed. Investigating the porosity ratio in the non-Newtonian bed showed that with the increase in the diameter of the solid particles, this ratio decreases and increases with the increase in the diameter of the fluid bed. In addition, comparing the results of the bed with carboxymethyl cellulose 0.1% solution as fluid showed that the effect of reducing the particle diameter in the bed, to increase the porosity ratio is 2 times more than the effect of increasing the diameter of the bed. Finally, the output of the model showed that the porosity ratio for the bed containing solid particles with different diameters is lower than the bed containing particles with equal diameters.

In the present study, a combined Lattice Boltzmann method-smoothed profile method is used for simulation of a liquid-solid fluidized bed with non-Newtonian Power-law fluids. The geometry is contained circular monodisperse particles in a cylindrical channel. The hydrodynamic model of the flow is based on the Bhatnagar–Gross–Krook Lattice Boltzmann method and the smoothed profile method is adopted to enforce the no-slip boundary condition at the liquid-solid interface. A numerical instance of a fluidized bed involving 416 particles is presented to demonstrate the capability of the combined scheme. The results for both Newtonian and non-Newtonian liquids have compared with the experimental results of other researchers. Porosity and bed height results of Newtonian fluid (water) compared with the Richardson-Zaki equation which was showed good correspondence. Non-Newtonian fluid results compared with the Yu equation for estimating minimum fluidization velocity and the Machač-Ulbrichová equation for porosity and bed height, yet by considering uncertainty in non-Newtonian equations results of comparisons are acceptable.

Nowadays importance of thrusters in movement of space bodies is not obscure. This article is devoted to study and compare two 5 newton lab-scale thrusters Hydrogen peroxide and Nitrous oxide using uncertainty analysis in order to select the more exact and desirable one in case of produced thrust. The data are extracted from experiments tested in aerospace research-center lab. Hydrogen peroxide thruster specifications are 85% of sincerity, 0.15 bar pressure drop in injector, 150 units of catalyst activity, 0.05 bar ambient pressure and 0.01 amount of feed load. On the other hand specifications of Nitrous oxide thruster are 7.36 gr/s mass flow rate, 2.017 mm diameter of throat. Based on calculations, total uncertainty and relative uncertainty for hydrogen peroxide thruster obtained respectively 0.53, 0.73(or14.68%). These amounts for nitrous oxide thruster obtained respectively 0.52, 0.53(or10.27%). Finally the results show that application of nitrous oxide thruster in terms of accuracy, is more desirable and the amount of it’s produced thrust is closer to the amount of five newton desirable thrust.

In this study, the liquid-solid fluidized bed was simulated using a combination of Lattice Boltzmann and smoothed profile method and then by changing the geometrical parameters contains of, particles diameter, width of the bed, initial bed height and the placement of the particles in non-uniform particles bed, their effects on porosity are studied. The hydrodynamic model of the flow is based on the LBM and SPM is adopted to enforce the no-slip boundary condition at the liquid-solid interface. The kinematics and trajectory of the discrete particles are evaluated by Newton's law of motion. Comparison of numerical and empirical results for porosity at different velosities showed acceptable accuracy. Also, Simulations indicate that an increase in width of the bed and particles diameter increased porosity and an increase in initial bed height decreased the porosity of the bed. Finally, the effect of placement of particles in none uniform fluidized bed showed the highest porosity accurse where particles with a small diameter stay on particles with a large diameter, also where the particles are mixed together the lowest porosity was accrued.

Welding laser beams is one of the essential parts of in automobile manufacturing used for joining plates. In this paper, for the first time, simulation of of joining stainless steel to low carbon steel was carried out. For this purpose, at first, thermal analysis was carried out by finite element method and of temperature profile and the dimensions of the melting area was gained as results. This was followed by mechanical analysis. The thermal analysis results were stored in a mechanical element as history to obtain the thermal conditions of the material. As results of this analysis, the strain of elastic and plastic as well as the amount of residual stress The results show that low carbon steel passes through in , because of higher thermal conductivity. Also, low carbon steel saves more residual stress due to higher yield stress. For validation of simulated model, two plates of 304 stainless steel with similar parameters the simulated model by laser welding. Comparing the results obtained from the experimental model with the simulated model shows a very good agreement.

The energy production analysis of a  photovoltaic system depends on the panels tempreture and solar radiation. An endless and free source of solar energy received at the Earth's surface depends on the geographical location, different hours of day and seasons of the year.Hence, its correct evaluation is a strategic factor for the feasibility of a solar system. in this paper, a new method of energy modeling of photovoltaic systems is proposed by using the radiation and temperature data obtained from monitoring of monocrystalline and polycrystalline solar panels installed at the solar site of the Vali-e Asr university of Rafsanjan. The model is derived using data in a period of one year of the solar site by ANN models which is trained and tested by a multi - layer Perceptron neural network. The inputs of the model include the temperature of the panel and the direct solar radiation and Its output is the production power of both monocrystalline and polycrystalline solar panels of this solar site. The results showed that, it is proper to chose The activation function at the hidden layers of logsig, tansig, tansig with the number of [10 10 10] neurons.

One of the major concerns in designing and redesigning the vessel’s propulsion system is adjusting its main components including the engine, gearbox and propeller. Components mismatch leads to overload or overspeed in engine. In this research, a method is presented for selecting a propeller and matching it to a full displacement vessel’s propulsion system, and related calculation for increasing the speed, has been done. The suitable engine and gearbox are selected after the vessel’s power and resistance has been calculated by MAXSURF software for 10 knots. The selected engine has 478 KW power at 2150 RPM and the reduction ratio for gearbox is 3.05. The calculated fixed pitch propeller was from B -Wakening series and had a diameter and pitch of 1.13 meters and 80 cm, respectively. It also had 4 blades and 70% area ratio. The results show that the selected propeller is fully matched with the engine and also the propeller power consumption curve is well suited to the engine’s propeller theoretical power. The value of propeller’s produced thrust is about 45.6 KN at 704 RPM which confirms the situation of having two propellers, 0.2 thrust deduction factor and 73 KN vessel resistance at 10 knots speed. The propeller torque value at final RPM is 6125 N.m which leads to an increment of 4 knots in the vessel’s speed. In this research, the performance of selected propeller in different engine RPMs has been well analyzed.