University of Thi-Qar Journal for Engineering Sciences

The paper investigate the vibration of the rotating shafts and whirling were theoretically by dealing with only the shaft bending without torsion. It is shown that the shaft whirling result from vibration consider for this particular system will have critical whirling speed which increases as the inertia forces of the rotor. Whirling is associated with fast-rotating shafts. When a shaft rotates it is subjected to radial or centrifugal forces, which cause the shaft to deflect from its rest position.These centrifugal forces are unavoidable, since material inhomogeneities and assembly difficulties ensure that the center of gravity of the shaft or its attached masses cannot coincide with the axis of rotation. The centrifugal forces involved and determined that the only destabilizing or restoring force was that due to the elastic properties or stiffness of the shaft. Hence, to deduce the critical speed caused an infinite deflection of shaft due to whirling. Loading response analysis can simulate the response of the rotor using Ansys program, which can help to identify the main modal frequency. To a rotating shaft, the modal analysis can give a serial of Eigen frequency, but only some of them are just the right modal frequency value we need. The harmonic analysis can extract the eigenvector of the modal analysis result, integrate them together, and show the amplitude frequency response, deformation and stress distribution characteristics of some special place of the rotating shaft

This paper presents an experimental study on the fracture toughness in similar and dissimilar of resistance spot welded dual phase and ferritic stainless steel sheets. The sheet materials were joined by using resistance spot welding as a lap joint. Tensile-shear tests were applied to the welded specimens. The variation of the Nugget diameter according to welding current was investigated. Also, the microhardness distribution was investigated. The results were discussed and plotted as graphs.

This paper focuses on the thermal comfort inside a selected Iraqi ship’s (GOUGE) cabin space whom working in the Umqaser port. Because of limited space and low ceiling height of these cabins, a low mixing ratio between the supplied conditioned air and the indoor air is expected. This lack of homogeneity of the air mixture causes many health problems for the crew and reduces their effectiveness. A computational fluid dynamics (CFD) has been used within the program (ANSYS 15) for the purpose of analysis and solving the equations of mass, momentum and energy and to compare the numerical results obtained from the program with the experimental results for distribution the temperature, velocity and relative humidity of the air conditioned inside Iraqi ship’s cabin, where the results showed good matching.A full scale test cabin has been designing and building as a simulator cabin with the same specifications of the real cabin to validate the measurements which carried out on this test cabin with the experimentaland numerical results on the real cabin. In this study different supply diffusers are tested, such as square and circular ceiling diffusers, side wall register and slot diffuser. It was found that the ceiling square diffuser is the proper diffuser for thecabin. This study focuses on the air changing per hour, also on the air diffusion inside the cabin, taking into consideration the climatic basrah where the temperature and high humidity.

A steady developing fluid flow and heat transfer through a wavy corrugated square cross-sectional passage (V-shaped and trapezoidal) was experimentally studied for a fluid with a Prandlt number of 0.7. In the present study, the experimental investigation on the heat transfer and flow distributions in the channel with various geometry configuration wavy plates under constant heat flux conditions of 600 W/m² and 1100 W/m² is considered.Effects of geometry configuration of wavy plates, wavy plate arrangements, and air flow rates on the temperature and flow developments are considered.Reynolds number is range from (2.19 -3.3) ×103. The results indicated that the enhancement of heat transfer coefficient factors are obtained from the wavy plate structures were essentially independent of the operated heat flux. The enhancement of heat transfer coefficient was ranged between the (1.036 to 1.062) and (1.042 to 1.066) for heat fluxes (600) W/m² and (1100) W/m² respectively for the V-shaped.While the enhancement of heat transfer coefficient for trapezoidal it was ranged between the (1.052 to 1.077) and (1.058 to 1.082) for heat fluxes (600) W/m² and (1100) W/m²,respectively. The corrugated channel pressure drop was higher than the plain smooth surface.The deterioration percentages of pressure drop for the corrugated plate when compared with that of flat plain surface was ranged between (15.4%) and (24.7%) for the V-shaped and (18.2%) and (27.5%) for trapezoidal with heat fluxes of 600 W/m² and 1100 W/m², respectively.

This paper deals with the problem of optimal design of reinforced concrete silos using genetic algorithms and minimizing the maximum objective method. The study provides two types of concrete silos circular and rectangular. Janssen theory method is used to analyze the structure design of silos. The cost function represents the cost of concrete, steel, and form work for the silos. The design variables are taken such as diameter, long wall, short wall, height of cylinder and box for circular & rectangular silo respectively with free board,depth of the hopper, thickness of the wall, dimensions of ring beam, thickness of slab, angles of incline of the hopper and the amounts of reinforcement for silos. The formulation of the problem is according to ACI (313-97) code and is carried out by using a toolbox of MATLAB program. The change of design capacity related to total cost approximately linearly. The effect of the change of the concrete grade, unit price of steel and concrete, and finally the unit cost of form work leads to increasing the total cost, while changing the steel grade leads to decreasing the total cost of both types of silo.

This paper presents experimental study of refrigeration by using a direct contact evaporation process. The process was performed by using a direct contact evaporator, which is a reservoir containing a water column. The water column was cooled by injecting a refrigerant, R12, directly into the water. The refrigerant absorbed the heat required for evaporation from the water, causing the water to cool, or freeze, in proportion to the heat transferred between the two fluids. The experimental results showed that the process resulted in a decrease in water temperature to a lower limit of temperature (12 0C, and may be reach a freezing point in perfect cases). The decrease in water temperature along the evaporator and the performance coefficient of the evaporator are used as criteria to evaluate the refrigeration system. By using the heat balance concept between the heat removed from water and the electrical work COP was 4.86. Also by assuming an isentropic process for the experimental conditions, the theoretical COP was 7.7.

In this paper, the performance of Energy Detection (ED) over K-M shadowed fading channel is investigated using the Moment Generating Function (MGF) of the received Signal-to-Noise Ratio (SNR). The K-M shadowed is a generic composite fading channel of K- M fading and which represents the impact of multipath in line-of sight (LoS) communication scenario and Nakagami - m distribution. The study is then extended to include Maximal Ratio Combining (MRC), Square Law Combining (SLC), and Square Law Selection (SLS) diversity receivers. The simulation and numerical results for the Complementary Receiver Operating Characteristics (CROC) and average Area under the CROC (CAUC) curves are given for different scenarios and compared with some previous works. These results show an improvement in the overall detection capability of ED is noticed when the diversity receptions are employed. In contrast to previous works which are limited by the values of the fading parameters, the proposed approach is not restricted by any condition.

This paper aims to calculate the vertical ionization velocity of maximum peak height of F2 layer of the ionosphere. Also, this paper deals with the effects of the latitudinal, daily and the solar activity variations on Another goal is to construct a simplified correlations for as a function of the latitude and month as a function of monthly mean with the monthly mean sunspot number MMSN shows an abnormal relation, also the hourly variation of obeys the fact that the electron density have the minimum values at sunrise and sunset, and has a maximum value for January month

The reduction in the power consumption is very important especially in areas with high temperatures such as Iraq, where the power consumption by the air conditioner is very high. The conventional split-type air conditioner widely used in small and medium size buildings, e.g. residences, offices, and schools. In this work the evaporative cooling unit is designed at the department of Mechanical Engineering of the College of Engineering University of Basrah.. The evaporative cooling unit is connected in front of the condenser to decrease the inlet temperature of the condenser. In addition, their performances depend on the heat transfer between condenser and the ambient airflow. The reduction in the inlet air temperature to the condenser of the air conditioning that leads to reduce the power consumption and enhancement of the coefficient of performance for the refrigeration cycle. The experimental results show: the average power saving is 23%.

This work aims to study the effect of cutting speed and feed rate on surface roughness and tool temperature by prediction mathematical models from the experimental data using LAB-Fit Data software. The mathematical models have been used to study the behavior of both surface roughness which is considered an indicator of workpiece quality and tool temperature that is related to tool wear and surface roughness. The experiments were conducted on AISI 1045 carbon steel that has wide range of applications by using CNC turning machine under dry cutting condition. The results shows that surface roughness decreases with increasing cutting speed while it increases with increasing feed rate, also it has been noticed that the temperature of cutting tool increases with increasing both cutting speed and feed rate.