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Go to Editorial ManagerThe experimental analysis is conducted under the Iraqi climate conditions to investigate the performance enhancement of a solar updraft tower system (SUTS) using the porous copper foam as an absorber plate and conventional absorber plate with absorber inclination angle of 18°. In the present work, a semicircular collector is divided into two identical quarter thermal collectors to become two identical SUTS. One of the quarter circular thermal collectors contains on the metal foam as an absorber plate, while the other quarter collector on the conventional flat copper absorber plate. In this study the air inlet height is changed of (3, 5, and 8) cm. The experimental tests carried out in Baghdad city (latitude 33.3° N). Results showed that the air inlet height variation caused to enhance the solar updraft tower performance. The highest values was recorded when the air inlet height is 3 cm using porous absorber compared to flat absorber plate. Copper material foam as an endothermic surface causes a marked decrease in average surface temperature of the plate. The maximum hourly thermal efficiency of solar collector was increased to about 41.6 % and the maximum enhancement of the power output to about 45.2 % compared with flat absorber plate.
The field of mechanics concerned with studying the propagation of cracks in materials is Fracture Mechanics. Technology systems are meant to withstand the loads to which they are likely to be exposed when in use. Material imperfections arising at the time of production or use of the material are, however, unavoidable and must therefore be taken into account. A stress intensity factor is a fracture parameter that defines the part failure. This paper study’s the effect of cracks on the stresses of rectangular plates having a hole in the center. The plate was subjected to tensile pressure at the top side while maintaining the bottom side fixed. The plate had four cracks distributed around the centered hole at 45o at each side. The effect of the length of the cracks on the resulted stresses and strains was investigated. Also, the effect of the position of the crack on the resulted stresses and strains was studied. Finite element models for the different plate cases were built using ANSYS software. The results showed that increasing the crack length resulted to increase the stresses and strains. The dimension of the plate width, height and thickness were 150 mm, 300 mm and 1 mm respectively, and the crack position was investigated for different crack lengths (5, 10, 15, 20, 25 mm) however the results were not steady as it looks that the crack lengths have changed the stress distribution over the plate.
This paper deals with the elastic stability of a column bolted at its mid-height to a simply supported square plate and subjected to a concentrated load, using energy method. A uniform homogeneous column is assumed to be pinned at both ends. From symmetry considerations, half of the column is modeled by making the plate acting as a torsion spring on the column at its mid-height. The column length and cross-section, plate dimensions and thickness, and the material properties for the column and the plate catch the interest of the author. The problem is solved by using energy method and ultimately, the elastic buckling load is found. The analytical elastic buckling load is compared with a numerical solution obtained from finite element method using SAP2000. The numerical results agree with the analytical solution. The finite element model is refined to catch the actual effect of the bolted plate on the elastic buckling load. It has been found that the elastic buckling load is increased due to the increase in the rotational stiffness provided from the plate.
The present work is a numerical study of thermal performance of modified flat plate solar water collectors. Numerical simulations have been done by solving the governing equations (Continuity, Momentum and Energy) equations in the laminar regime , three dimensions by using the FLUENT software version (14.5). The effect of flow on temperature distribution of flat plate water collectors by inserting (twist strip with twist ratio (3), helical spring surrounding the solid shaft) inside riser pipes is numerically simulated and compared with solar collector without inserting device inside its riser pipes at flow rates of (100)?/h . The numerical simulation results show that the flat plate water, solar collectors with the inserted, twist strip and helical spring that’s surround the solid shaft were higher enhancement of heat transfer than without inserted devices. The useful energy in case of twist strip is (10%) higher than the case of flat plate solar collector without enhancement device. Also, the case of helical spring is increased (6.8 %) than the twist strip, and (16.2%) than collector without enhancement device for the same mass flow rate.
The aim of this study was to support surgeons to decide where to place the screws in order to achieve an optimal fracture healing and to prevent implant failure after a femoral shaft fracture So this paper focus on the analysis of bone-plate construct by using Finite element Analysis (FEA), comminuted femur fractured bone fixed with Dynamic Compression Plate (DCP) 16 holes by 4.5 Cortex screws, to investigate the effects of screws configuration on the mechanical behavior of different seven model as Interfragmentary strain which is the most important factor for femur fracture healing. The results state the relationships between the Von-Mises stress, Total deformation and Interfragmentary strain with respect to the screws configuration. The study shows the regions of maximum stress from stress distribution and also founded that we can decrease the Interfragmentary strain by increasing the number of screws.
The effect of defect on structures and machines has negative consequences on them and it always takes researchers concern and attention in order to find feasible solutions to trace and detect the location of the defect accurately.In this research, the effect of a hole with different diameters on a square composite plate is studied as well as the effects of both the boundary condition and the plate thickness, furthermore, Vibration analysis of composite plate has been studied numerically and experimentally. The Numerical analysis has been carried out by using FEM by building MATLAB program as well as (ANSYS 15). The experimental part of this research is done by using vibration measuring instruments. The rate of error among the experimental tests and the numerical solution is less than 15%. These results have been used an inputs to the Genetic Algorithm model that the defect is located by, with a high percentage of success.
This article is about studying the placing direction effect of a piezoelectric sensor on the shoe insole in the GRF results. Where the sensors used in this research are in two directions, along and perpendicular to the foot midline. In the both cases the sensors were fixed on the shoe insole to sense the foot pressure. For the first set of sensors which are perpendicular to the foot midline the collected data has similar trend to the GRF collected from the force plate, as the small lateral strain in the shoe insole due to the patient weight and GRF is close to the GRF data collected from other measurement system. On the other hand, the collected data from the second set of sensors which are in a longitudinal direction with the foot midline will have different trend and values from the collected data from the force plate or any other GRF measurement system. This different in the results is due to the large longitudinal strain in the shoe insole due to the patient weight which produce dissimilar results from the force plate result data.
The heat exchanger is a device used to transfer heat energy between two fluids, hot and cold. In this work, an output feedback adaptive sliding mode controller is designed to control the temperature of the outlet cold water for plate heat exchanger. The discontinuous gain value of the sliding mode controller is adapted according to a certain adaptation law, where the only information required is the measurement of the outlet cold temperature. A sliding mode differentiator was design to estimate time derivative of outlet hot water temperature. Two constraints which imposed on the volumetric flow rate of the hot water (control input) were considered within the rules of the proposed adaptation law in this work. These are the control input is positive only and has a maximum value. For constructing the sliding variable, the outlet hot water temperature and its time derivative are required. The maximum allowable desired outlet cold water has been estimated as function of heat exchanger parameters and maximum control input. The simulation results demonstrate the performance of the proposed adaptive sliding mode control where the outlet cold water was forced to follow desired temperature equal to . Additionally, the robustness of the proposed controller was tested for the case where the cold inlet temperature is not constant. The results reveal the robustness of the proposed controller.
In this work , experimental investigation has been done for free-convection heat transfer from rectangular fins array on a heated horizontal base plate to surrounding air in the steady-state flow condition with rectangular notch portion effects. Five cases of fins arrays have been employed . One case without notch and other cases with rectangular notches for different percentages of aspect ratio area removal from fin . The horizontal base plate has been heated with various electrical supplied power values. Different number of fins and spacing have been used . The effect of notches from fins on average convection heat transfer coefficient and average Nusselt number at constant aspect ratio of fin height to fin length and varying heat inputs to the heating element have been discussed . The experimental results show that the performance of notched fins array in term of average convection heat transfer coefficient is 28% to 45% higher than unnotched fins array. The present experimental results have been compared with previously works . The results show a good a greement.
Double skin composite (DSC) construction or Steel/concrete/steel sandwich construction (SCSS) is an innovative and relatively new form of composite construction that can be used in submerged tube tunnels, bridges deck, nuclear structures, liquid and gas containment structures, offshore and onshore structures, military shelters, and shear walls in buildings. The system consists of a plain concrete core sandwiched between two steel plates interconnected together by various types of mechanical shear connectors. The DSC construction perceives advantages that the external steel plates act as both formwork and primary reinforcement, and also as impermeable, blast and impact resistant membranes. The major duty of the shear connectors is to withstand longitudinal shear force and beam/slab separation, while in the bi-steel type where shear connectors are friction welded at both their two ends to two parallel steel plates, the longitudinal and transverse shear force, as well as plate buckling are resisted. The present paper highlights the previous prime researches concerning the subjects of SCSS composite construction, specifically on the conducted tests (push-out tests, tensile, direct shear tests, and bending tests) in which the components of partial interaction (uplift and slip forces) are resisted by various types of shear connectors.
Behavior of composite beams with headed stud shear connectors subjected to monotonous and displacement controlled non-reversible repeated loadings has been evaluated through studying influences of the cross-sectional proportioning, the degree of partial interaction, and the level of ductile deformability in the post-yielding stage, in addition to the state of loading (whether monotonous or repeated). Eleven one- third scaled composite beams (with their push-out segments) were manufactured and tested in five pairs (each comprising the two loading cases representing one varying studied parameter) beside the single standard composite beam dedicated to verify accuracy of the test results by comparing them to the prototype ones (three authorized experimental and analytical investigations) where no distinction (other than 7 % difference) between the results of the three authorized refereed investigations (experimental, analytical and Eurocode) and the present one.Regarding the flexural resistance in repeatedly loaded composite beams, it has been found that lowering the neutral axis (by adding bottom steel plate) has significantly increased the beam flexural resistance by an average of 24.7 %. Meanwhile, the intensity of headed studs distribution in stiffened repeatedly loaded composite beams has revealed a vital role in controlling the severity of the post-ultimate flexural weakening, where decreasing number of the headed studs to the half has increased the value of that unfavorite parameter by 160.58%. Furthermore, that specified decrease of headed stud intensity has lowered the advantageous residual cyclic flexural ductility by 19.37 % and 11.48 % without and with stiffening bottom steel plates, respectively. Regarding the effect of the lengthening the headed stud on behaviour of the repeatedly loaded composite beams it has been found that lengthening the medium-length headed studs by 72% has raised the flexural stiffness by 41.1 %, while it has decreased the residual cyclic slippage index by 54.3 %.
The 3-D numerical simulations of the thermal collectors in solar heating systems were conducted to simulate the conventional solar heating system, multipurpose solar water heater (MPSWH), and multipurpose solar air heater (MPSAH). The commercial computational fluid dynamics (CFD), AVL Fire ver. 2009.2 was used to solve and investigate the temperature distributions in the absorber plate and riser tube of both solar water and air heater during summer and winter seasons. The RNG k -turbulence model was employed for this CFD study. The present paper was to provide a good understanding of thermal performance for the solar collector at different operating conditions. The experimental setup and physical data of Venkatesh, R. and Christraj, W. [15] were employed as geometric parameters and initial boundary conditions to model and to validate the predicted numerical values. Comparing to the values of temperatures for the conventional SWH and SAH, the predicted results of the MPSWH and the MPSAH showed a good improvement on the thermal performance. These enhancements on the temperature may have been due to the new design adopted in the multipurpose solar heating systems by using riser tubes and headers to the original design of the thermal systems. Additionally, the thermal performance of solar collectors increases with increasing the mass flow rates and thermal conductivity of absorber plate. For validation aspect, the predicted results of all cases examined showed a good agreement against the measured results in terms of temperature distribution levels and thermal efficiencies.
The mixing technique was applied in this study to enhance the strength performance of the cement. The addition of 3% by weight of hydroxyapatite (HA) nanoparticles were mixed with 97% polymethyl methacrylate (PMMA) acrylic polymer, which has a nano size to serve as the matrix material. The surface roughness and continuous porosity of the bone cement were found to be slightly increased by the incorporation of nanoparticles, which enhanced bone-implant osseointegration and ingrowth. Atomic force microscopy (AFM) analysis revealed that the addition of hydroxyapatite (HAp) nanoparticles resulted in a surface roughness value (Sa) of 16.25 nm, which is similar to that of natural bone. The energy-dispersive X-ray spectroscopy (EDS) mapping results discover precentor material and uniform distribution. The Sample exhibited promising results in the antibacterial test, showing efficacy against bacteria both with and without sterilization, confirming its antibacterial properties. The mechanical tests conducted on the sample, including tensile, compression, bending and Vickers hardness tests, yielded favorable results and indicated that the sample is suitable for its intended application. In the theoretical works the design of the bone, screw, and bone plate was conducted using SolidWorks, followed by an analysis using ANSYS under both axial and bending load conditions. The theoretical analysis revealed that the safety factor was less than 1 when an axial load of 13 N was applied and a bending load of 2 N was applied, indicating that the structure may not be able to withstand these loads safely. Under both ambient and physiologically relevant conditions in the human body, HA and PMMA have demonstrated to be excellent choices for enhancing the clinical performance of bone cement. This, in turn, can lead to increased longevity of implants, decreased patient risk, and lower healthcare costs
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Friction Stir welding (FSW) parameters, which play a vital principle, that impact on the mechanical, microstructural properties of the weldment because of the warmth produced by the contact between the instrument and work-piece, An AA6061-T6 aluminum composite plate with measurements (186*150*4) mm3 welded through various rotational paces 800, 1000, 1200 and 1450 rpm, the created heat measured through thermocouples embedded in study zones of the Weldment, a Finite Element model have been executed by utilizing ANSYS 12.1 bundle charges to ponder the temperature appropriation amid stay stage, the outcomes demonstrates a decent assention between the after effects of exploratory and hypothetical tests. The most extreme temperature measured at this condition was 0.71 from the liquefying temperature of the sample at a maximum rotational speed of (1450) r/min.
The non-woven materials industry is one of the fastest-growing industries in the world with the ability to produce materials in less time, specifications, and better prices. nonwoven materials are defined as a web of guided or random fibers that are bonded by friction, interlacement or adhesion. In this research, the rotary electrospinning system was used and a prototype was made to study the process and the complete visualization in terms of the correlation of the electrostatic forces to the formation of nanofibers by preparing polymeric solutions and exposing them to the electric field between the positive electrode (the serrated cylinder) and the Grounded electrode (plate) and produced high-precision fibers with a diameter (185nm) at 25 kV, whereas the installation of polyvinyl alcohol (PVA) was with different concentrations and the formed fibers possessed an effective surface and deposited on a collector electrode forming nonwoven webs and high productivity is the most important feature of this system compared with the traditional electrospinning system.
In this research the behavior of cylindrical shells under axial load have been studied. The experimental program is included two groups: the first consists of nine cylinders; each has a diameter of 150 mm, while the height varies from 100 to 500 mm and thickness of 1.5 mm, test results show that the optimum height to achieve the maximum strength is 300 mm with L/D equal to 2. The second group consists of two cylinders with diameter of 150 mm and height of 300 and 500 mm strengthened with stiffeners plate welding from inside at four quarters with thickness of 1.5 mm and width 20 mm fabricated from the same metal of the cylinders. After testing these two cylinders were gain an increase in the strength reached to 42% for 300 mm cylinder and 26.4% for 500 mm cylinder. The failure modes for these two groups are: the buckling at bottom like “elephant’s foot” for cylinders height from 100 to 300 mm and “inelastic buckling” for cylinders height from 350 to 500 mm for the first group, and the ” inelastic buckling” for the second group.
The current study presents the plasma cutting process of 2 mm thickness of AISI 1020 carbon steel. The experiment conducted by taking into the account the effect of two process parameters, including cutting current of 15 and 20 A with cutting speed in range of 500 - 4000 mm/min, on the kerf formation, microstructure and microhardness.The results showed that at low cutting current of 15 A the melting occurred at the workpiece surface without cutting action. Increase the current to 20 A led to full penetration of the workpiece material at low and high cutting speed, with kerf width between 1.26 mm and 1.1 mm for cutting speed of 500 mm/ min and 4000 mm/ min, respectively. The plasma arc cutting speed has a high impact on the heat-affected zone HAZ and microstructure development with coarse grains at the HAZ at low cutting speed of 500 mm/min and constant current of 20A, increase the plasma cutting speed led to decreasing the grain size. The microstructure of the HAZ exhibited a presence of perlite and ferrite with some martensite structure. The highest microhardness of the HAZ of 220.8 HV was found in the sample processed at 20 A current and high cutting speed of 4000 mm/ min. However, the minimum microhardness of the HAZ of 156.7 HV was found in the sample processed at 20 A current and low cutting speed of 500 mm/ min.
Magnetic Abrasive Finishing (MAF) process which is a non-traditional polishing technique, is suitable for variety of engineering materials, producing high quality surfaces of parts. An experimental setup study is made to carry out MAF process to improve surface layer quality and hardness of stainless steel grade 321 plate. This study uses two different magnetic pole shapes such as conical magnetic pole without grooves and conical magnetic pole with six grooves. The finally results show that the conical magnetic pole with six grooves can create best surface layer quality and improve hardness in (MAF) process. The process parameters are the applied number of pitches between grooves, finishing time, cutting speed of magnetic pole, voltage, and volume of powder (dose). The magnetic abrasive powder consisted of silicon carbide SiC, particle size 300?m, SiC (65%), it is mixed with the ferromagnetic iron particles (iron powders), particle size 300?m, Fe (35%). Taguchi matrix L18 for five input parameters with mixed level design (2-3) levels was used for designing the experiments and optimal values evaluation for all parameters to improve the hardness. By using MINITAB software data was analyzed, the results indicate that empirical equation (mathematical predicted models) represents the relation of the input parameters with the change in micro Vickers Hardness. The most significant parameters on change in hardness are volume of powder (42.34%) and number of pitches between grooves (25.30%).
The improvement in solar chimneys' thermal performance and thermal behavior that can be achieved by adding metal foam has been tested in computational work. The flow and heat transfer governing equations for solar chimney models were solved using computational fluid dynamics (CFD). It was solved using the control volume numerical method in ANSYS FLUENT 14.5. It is used to construct a finite volume modeling technique for solving the governing equations and the radiation heat transfer equations. With standard flat absorber plates, the results showed that heat transmission was increased by the inclusion of metal foam (10 PPI), leading to an increase in air velocity at the solar chimney of around 13.3%. The highest average air velocity with 10 PPI drops by 54.4% as the height of the absorber plate changes from 5 cm to 25 cm respectively.
The optimal spacing between elliptic tubes cooled by free convection is studied numerically. A row of isothermal elliptic tubes are installed in a fixed volume and the spacing between them is selected according to the constructal theory (Bejan's theory). In this theory the spacing between the tubes is chosen such that the heat transfer density is maximized. A finite volume method is employed to solve the governing equations; SIMPLE algorithm with collocated grid is utilized for coupling between velocity and pressure. The range of Rayleigh number is (103 ? Ra ? 105), the range of the axis ratio of the tubes is (0 ? ? ? 0.5), and the working fluid is air (Pr =0.71). The results show that the optimal spacing decreases as Rayleigh number increases for all axis ratios, and the maximum density of heat transfer increases as the Raleigh number increases for all axis ratios and the highest value occurs at axis ratio (? =0) (flat plate) while the lowest value occurs at (? =0.5) (circular tube). The results also show that the optimal spacing is unchanged with the axis ratio at constant Rayleigh number.