Articles in This Issue
Abstract
The incorporation of thermal energy storage materials (TESMs) into solar energy systems is a factor that boosts the performance of these systems. In this paper, an experimental study was addressed for enhancing the heat pipe’s thermal performance that works with an Evacuated Solar Tube Collector with Heat Pipe (ETCHP) as a solar water heater system. This is done by adding micro-zinc oxide (ZnO-MP) to the paraffin wax integrated as TESM into the evacuated tube (ET) of the system, where the evaporator section of the heat pipe is completely submerged within the micro-enhanced paraffin wax. Three experimental prototype rigs with one evacuated tube were designed, built, and tested to do the investigation. The most important parameters that have been studied in this study are the thermal resistance and the temperature distribution pattern along the heat pipe. The results show a clear indication of the decrease in the thermal resistance of the heat pipe of the proposed system compared to the system in which pure paraffin wax was incorporated. Also, it was noticed that there is a significant improvement in the temperature distribution along the heat pipe due to the improvement in the conductivity of the micro-enhanced wax compared to the pure wax.
Abstract
In this paper, a new model of beam was built to study and simulate the buckling behavior of function graded beam. All equations of motion are derived using the principal of the minimum total potential energy and based on Euler-Bernoulli, first and high order shear deformation Timoshenko beam theory. The Navier solution is used for simply supported beam, and exact formulas found for buckling load. The properties of material of FG beam are assumed to change in thickness direction by using the power law formula. The dimensionless critical buckling load is calculated analytically by the FORTRAN program and numerically by ANSYS software. In the beginning, the analytical and numerical results are validated with results available in previous works and it is also has very good agreement in comparison with and some researchers. In the present study, the lower layer of the graded beam is made up of aluminum metal. As for the properties of the rest of the layers, they are calculated based on the modulus ratios studied. The effect of length to thickness ratio, modulus ratio, and power law index on the dimensionless critical buckling load of function graded beam calculating by FORTRAN and ANSYS programs are discussed. The numerical analysis of function graded beam offers accurate results and very close to the analytical solution using Timoshenko Beam theory.
Abstract
In this research work, the influence of cutting parameters and drill point angle on the temperature distribution in dry drilling of stainless steel AISI 304 was numerically investigated by using FE method based on DEFORM-3D V.11 commercial software. Two cutting tools of 10 mm diameter but different in point angles, one is 110° and the other is 118°. These tools were imported from specific website in a format of STL and inserted in the program during modeling of cutting tools. The material of the cutting tools is selected as high-speed steel. The workpiece model is created as cylindrical shape with 50 mm diameter and 5 mm thickness. The cutting parameters are selected as three cutting speeds (100, 200, and 300) rpm, with three feed rates (0.15, 0.25, and 0.35) mm/rev. The depth of hole is fixed for all simulations (3 mm). The percentage of increase or decrease in the resulted temperature according to the various cutting parameter was also calculated and discussed. The best cutting performance of tools according to the change of point angles was also investigated. The results provided a significant influence of cutting speed and tool point angle on the temperature generated in the machined models and very small influence of feed speed on the workpiece temperature.
Abstract
The hybrid electric vehicle (HEV) is considered an effective technique to reduce fuel consumption and exhaust emissions. The effectiveness of the HEVs in reducing fuel consumption and exhaust emissions is required an accurate division of the total power demand between energy sources. This aim is reached by an accurate design of energy management strategy (EMS) in the HEVs. Dynamic programming is an effective strategy to found the optimal solution for energy management. This technique requires the driving cycle to be known previously, wherefore it's not suitable to implement in real-time. The Equivalent Consumption Minimization Strategy (ECMS) is an effective technique that can be implemented in real-time. This strategy is used to estimate and adapt the equivalent factor (EF) in real-time, which is used to convert the electric energy from the battery to equivalent fuel cost. The value of the (EF) varies with the driving cycle, therefore, the (EF) is suitable for a certain driving cycle and may lead to weak performance to another. This work proposed a technique based on the battery state of charge feedback called adaptive prediction (AP) to estimate and adapt the equivalent factor in real-time. The best-obtained results are ranged between (11.1 to 32.889) % for several different driving cycles.
Abstract
This paper aims to investigate the effect of Ag nanoparticles addition in different percentages (0.12 wt. %, 0.15 wt. %, 0.25 wt. %, 0.35 wt. %) on the microstructure properties of Cu-21%Zn-6%Al shape memory alloy. Optical and SEM were carried out to studied such effects. Two heat treatments were carried out at (825 ℃ and 850 ℃) for 10 min and quenched in ice water. It was observed that both of heat treatment lead to formation M18R martensite with V-shape and needle like, but raising the temperature of heat treatment from 825 ℃ to 850 ℃ lead to a decrease formation α phase, which leads to improving the shape memory properties. Refinement of the grain size resulted as Ag nanoparticles addition increased from 0 to 0.25 wt. %, the grain size decreases from 1551 μm to 212 μm with reduction of 86.32 wt. % at 0.25 wt. % Ag. The microstructure observation indicated that the Ag nanoparticles addition leads to creating a multi-variant oriented martensite microstructure after quenching process in ice water.
Abstract
This numerical study aimed to investigate the torsional behaviour of hollow cross section reinforced concrete members strengthened with steel fibers (end hooked and corrugated), subjected to pure torsion. The numerical results were compared with experimental results and show good agreement. The experimental study was conducted on ten steel fiber reinforced concrete specimens with low longitudinal reinforcement ratio to investigate the torsional behavior under pure torsion. For this analysis, a computer program (ANSYS 18.2) was used. The brick elements 8-nodes (SOLID65) were used to concrete simulation, while the steel bars simulated as axial members (link 180). The steel fibre was represented theoretically by the stress-strain relationship. The theoretical results indicated that the adopted smeared crack model is capable of making relatively acceptable estimations of cracking and ultimate torsional capacity of the members.
Abstract
This research concerns with the fracture behavior of reinforced concrete beams without shear reinforcement numerically. The software ABAQUS is adapted to simulate the crack propagation using the eXtended Finite Element Method (XFEM), taking into account materials nonlinearities using concrete damage plasticity CDP criteria. XFEM is used to solve the discontinuity problems in the simulation. The maximum principal stress failure criterion is selected for damage initiation, and an energy-based damage evolution law based on a model- independent fracture criterion is selected for damage propagation. The traditional nonlinear finite element analysis is used to specify the crack initiation position, which is required to specify the crack location in the analysis of beams using XFEM. Three-dimensional reinforced concrete beam models are investigated subjected to three and four-point loading tests. Simply supported beams under the effect of applied static load are investigated. An elastic perfectly plastic model is used for modeling the longitudinal steel bars. The main variables considered in the study are beam depth and the shear span with beam length. The numerical results are compared with the available experimental results to demonstrate the applicability of the model. The XFEM provides the capability to predict the concrete member fracture behavior.
Abstract
Al-Robat and Al-Jubyla creeks, which composes the study area, are two of the main six creeks branched from Shatt Al- Arab river in Basrah province, south of Iraq. They are used as open drains for discharging untreated sanitary sewage which caused the depletion of their dissolved oxygen and subsequently the deterioration of their water quality. To study the impact of discharging untreated sanitary sewage on study area water quality, measured in terms of dissolved oxygen concentration, it is necessary to determine the values of deoxygenation coefficient ( K 1 ). The aim of this study is to find K 1 values for the study area using laboratory results of BOD time series analyses. For this purpose, water samples were collected from eight locations distributed along the study area. Thomas graphical method was applied to calculate K 1 . The results showed that the K 1 values for Al-Robat and Al-Jubyla creeks ranged from 0.279 to 0.488 day ˗ 1 at 20 °C with ultimate BOD values varied over the range (40.5-258.6) mg/l. These results revealed that the water in Al-Robat and Al-Jubyla creeks has the characteristics of raw sewage.
Abstract
This research is an analytical study for simulation both sediment transport and flow within the Tigris river reach located downstream of the Al-Amarah barrage within the Maysan province. This study adopted a three-dimensional program (SSIIM) which use the Navier-Stokes equations for calculating the flow, and the convection-diffusion equations for calculating the sediment transport by the finite volume method as approximated method. A structured non-orthogonal three-dimensional grid is employed to perform the simulation. The obtained results are subsequently compared to the field measurements. The determination coefficient ( R 2 ) for this comparison is 0.96 for flow velocity distribution and 0.94 for sediment concentration distribution. The results also showed through the simulation of the water flow, the state of the secondary flow and its effect on both the main flow and the erosion of the river bed in the studied cross sections. According to the high convergence of the results of this model with the field measurements, this model is a powerful tool for simulating flow and sediment concentrations in river systems and channels.
Abstract
The finite element method is used to simulate the soil vibration behavior due to the Basrah-Baghdad passenger train and its effect on a targeted building in the Al-Ma'qal quarter, Basrah governorate. Three-dimensional dynamic elastic analyses are performed to calculate the particle velocities for a train speed of 120 km/hr. The effectiveness of screening using active (10 m long) open trench barriers with variable depth (2 m - 5 m) and width (0.4 m - 0.8 m), is being studied. For a given trench width (0.4 m), the results of the parametric study revealed a considerable effect of trench depth where the screening capability near the trench is increased by (10.4 %, 26.1 %, 36.3 %) due to a (50 %, 100 %, 150 %) increase in depth. The results are less sensitive to the variation in trench width. The screening capability of a double open (0.4 m × 10 m × 2 m) trench system was also investigated, where a mitigation improvement of (36.4 %) was achieved. The vibration mitigation using single and double trench systems, filled with (40 %) rubber content mixture, was also analyzed. It is concluded that using the additional passive trench increases the mitigation of the single system by around 19.1 %. An important finding is that the (40 % rubber + 60 % native cohesive soil) mixture proved to be a good filling material, since the infilled-trench systems produced comparable screening ratios to the open systems, where (97.7 %) and (85.4 %) were accomplished for the single and double systems, respectively.