نشریه مهندسی هوانوردی
سال بیست و سوم شماره 1 (بهار و تابستان 1400)

The aim of this study is to provide a model for disaster reduction based on the study of the theoretical principles in the field of air disaster. So, the aim of this study is to provide a model for disaster reduction. The statistical population of this research is the experts of aviation accidents in aviation industry which using purposive non - probability sampling method to determine the sample. this research we have tried to identify the factors affecting flight accidents (human, machine and environment) while familiarity with their performance and detection of hazardous and repetitive defects, identify the defects observed and finally the effect of each of them separately. this paper, first, the history of research has been studied and based on the records of research done to improve the safety of flights using techniques and tools used in this study. Also, data analysis and prediction stages were investigated. Finally, by step - by - step implementation of the steps to capture the results and provide suggestions for improving the safety of helicopters.By comparing and statistical studies, it can be concluded that helicopter accidents share is related to human factor. The technical problems of the helicopter as well as environmental factors can play an important role in aviation accidents. The most important reasons for the occurrence of accidents and injuries related to fatigue are the rotating parts of the helicopter and the most important reasons for disasters in the field of environmental factors are related to adverse weather conditions.

Anthropocentricism in designs and specialties is one of the most significant domains in the industrial sectors all over the world. Some of the main scientific fields in this category are ergonomics, anthropometry, and biomechanics. Despite the history of more than two centuries of the emergence of these sciences in the world and the numerous studies conducted in these fields, no general study has been carried out or recorded until now to apply capacities of these vital sciences to the subject of Iranian aviation. The priority of determining the aircraft and the place of service of the pilots is based only on the scientific Grade Point Average (GPA) and at most the combination of scientific and practical GPA. Thus, in this study, for the first time, an attempt has been made to solve the problem of determining the priority of pilots for a selected aircraft by taking a combination of the aforementioned indicators and anthropometric factors in a real issue while eliminating the mentioned research gap. To achieve this goal, we first try to review the basics and background of research conducted in this area in the world, selected effective indicator, and then by examining the standards associated with the minimum and maximum acceptable status of these indicators have been recognized for a number of selected aircrafts.

Due to the impossibility of performing destructive tests, the need for new and Non-Destructive Tests (NDT) in this area is strongly felt. In the present study, using the non-destructive method of Automated Ball Indentation (ABI) test method, some mechanical properties of 4340 annealed steel and 7075 raw aluminum and prepared from aged aircraft are determined. To perform calculations related to ABI method, the explicit relations routine was coded in FORTRAN and verified. Then samples of uniaxial tensile test of 4340 annealed steel and 7075 raw aluminum and prepared from aged aircraft are prepared and their stress-strain curves are obtained. Also, ABI tests are performed on 4340 annealed steel samples and 7075 raw aluminum and prepared from aged aircraft and the results of the two methods were compared. The comparison of results showed that the calculated error of yield strength and ultimate strength was less than 9 and 14%, respectively. With increasing force, this value in some areas reached less than 0.7%.

In UAV navigation, the simultaneous minimization of distance traveled and the threat of radar detection is two criteria in many military applications. The use of many-objective evolutionary algorithms in problems with conflicting goals can play an effective role in increasing the efficiency of these problems. In this research, the multi-purpose UAV route planning problem is considered and a many-objective optimization algorithm is presented in a multi-purpose UAV route planning problem. The proposed solution method is a reference vector evolutionary algorithm (RVEA). In this research, a platform in the MATLAB software, which is called PlatEMO, has been used. The proposed method is compared and evaluated with other many-objective and multi-objective evolutionary algorithms that have been presented recently and the results are obtained with a volume evaluation criterion that covers all the necessary categories (convergence, diversity, and cardinality). Give, express. The problem has been tested on two groups of optimization problems. Comparing the presented results, it is observed that the reference vector evolutionary algorithm has a better performance than other compared algorithms, and the convergence rate, diversity, and robustness of this algorithm is higher than other compared algorithms.

The use of new materials with suitable mechanical and physical properties in aerial structures can be a good alternative to materials that are commonly used (aluminum alloys, composites, etc). The use of magnesium alloys for various applications and predicting their behavior in simulation software requires complete and accurate identification of the properties and mechanical parameters of the material. One of these identification procedures is digital image correlation method. In this research, the first magnesium plate is prepared in different directions of rolling and then using two-dimensional digital image correlation method, the complete distribution of strain field during uniaxial tensile test in different directions of rolling is extracted and finally strain in three directions of length, width, thickness and anisotropy coefficient in terms of effective strain were calculated. Furthermore, for the first time using the virtual field method, elastic and plastic constants such as modulus of elasticity, Poisson ratio, strength coefficient, strain hardening exponent and yield stress for magnesium sheet in different directions of rolling were calculated.

Micro aerial vehicles are small in size, and with due attention to their small size and low flight speed, they are usually confronted by many problems in terms of aerodynamic forces, and their stall occurs in low angles of attack. In order to increase the maneuverability and improve the performance of fixed-wing Micro Aerial Vehicles (MAV), a passive control method is used as waving the leading edge on their wings which neutralizes the phenomenon of the stall. However, the formation of laminar separation bubbles at pre-stall angles leads to a decrease in the lift coefficient and increase the drag coefficient of the wing. The main goal of this study is to investigate the impact rate of base airfoil geometrical parameters such as thickness, maximum proximity and camber of the airfoil on the aerodynamic performance of the infinite sinusoidal wing’s leading edge at the pre stall. Therefore, numerical simulation of an infinite wing was taken place by finite volume method and using the detached eddy simulation turbulence model. The results demonstrated that increases in thickness and maximum proximity leads to improve micro aerial vehicle aerodynamic performance about 10% and 20% respectively. However, increasing the base airfoil camber had a 4% reverse impact. Also, changes in aerodynamic coefficients show that they have the most sensitivity to maximum proximity.

Path design is one of the open research bottlenecks to develop autonomy in unmanned robots. In urban spaces and closed environments, with increasing the number of obstacles and constraints, the computational complexity required for the completed path planning algorithms increases with order O (n2). The main purpose of this manuscript is to present a path planning algorithm based on the random sampling method for the vertical take-off and landing vehicle (VTLV) and its real-time test in the xPC-Target toolboxes. For this purpose, the rapidly exploring random tree (RRT) algorithm is presented. The proposed algorithm is completely probabilistic and also the non-holonomic constraints of the VTLV are integrated into the vertices of the search tree. In order to validate and evaluate the proposed path planning algorithm before performing risky and costly field tests, the processor-in-the-loop (PIL) test, in MATLAB xPC-Target software environment is considered. In the PIL test, two test scenarios with different complexity have been developed. The results show that the proposed rapidly exploring random tree algorithm is able to plan a primary path for the robot by using its random nature in a rapid manner. Also, due to the involvement of the robot dynamic model in the process of generating random vertices and search tree edges, both types of kinematic and dynamic (kinodynamic) constraints have been considered in the planned path and therefore lead to the design of a practical path with high intercept ability through the robot.

Exposure of the TBCs layers to high temperatures for a long time causes sintering in the ceramic layer, resulting in changes in the porosity. Since the thermal conductivity of air in the porosity of the layers is much lower than the ceramic material in the coating, a decrease or increase in the percentage of porosity will end up with changes in the conductivity of the layer, which subsequently affect the overall efficiency. In this study, a TBC was first applied to the prepared samples from Inconel738 turbine blades. The samples were subjected to an aging process in the furnace for a specified time. The porosity changes in the ceramic layer of the coating during the aging process were investigated using image processing of the SEM images. The porosity of the images obtained from SEM and thermal conductivity in different porosities were determined by OOF2 and ImageJ software, respectively. To validate the numerical results, temperature distribution on the thermal barrier coatings is obtained by the analytical solution of the Fourier equation. According to the analysis performed on the SEM images gathered from the samples during different aging hours, it is observed that by increasing the aging hours during 48 hours, the percentage of porosity of the whole ceramic layer decreased by 8%. According to the results, by decreasing porosity in the ceramic layer, an increase in thermal conductivity has been observed, followed by an increase in the substrate's temperature and a decrease in the overall performance over time.

In this study, the effect of wind speed on the energy and exergy efficiencies of the LS-2 parabolic trough solar collector have been studied. The wind speed on the reflector and receiver has been considered between zero and 27 m/s. Three working fluids of Therminol VP-1, Syltherm 800 and Dowtherm A have been used. The results showed that at the inlet fluid temperature of 650 K and volumetric flow rate of 50 L/min, if the wind speed increases to 27 m/s, the energy efficiency decreases using Therminol VP-1, Syltherm 800 and Dowtherm A are 0.87%, 1.16% and 0.85%, respectively and the exergy efficiency decreases are 0.88%, 1.18% and 0.86%, respectively. Also the results showed that the variations of energy and exergy efficiencies for wind speeds greater than 10 m/s are negligible. The results indicated that although wind speed increase has little effect on the energy and exergy efficiencies of the collector, but the rate of these decreases are comparable with the rate of efficiency increases observed in previous studies using different efficiency enhancement strategies such as turbulators and nanofluids, so wind speed is important. The performance evaluation study revealed that using Therminol VP-1 and Dowtherm A are more suitable than Syltherm 800 to be used as working fluids in parabolic trough solar collectors.

In the present study three composite sandwich structures with grid stiffened core (SSGSC) samples made of different materials and thicknesses are fabricated with hand lay-up method using a silicon rubber mold and epoxy resin. Also, two metallic samples of the same dimensions as the composite ones, including a monolithic and a SSGSC samples made of aluminum are fabricated. In order to study their behavior subjected to the quasi-static transverse loads, the samples undergo three-point bending tests. Results of the practical tests on the composite samples showed that beyond the failure of the face sheets, the grid stiffened core will tolerate load, also there are no delamination between the face sheet layers due to good curing process. The experimental modal testing is achieved on all the samples. The frequency response, mode shape as well as damping coefficients are obtained from each experiment. Finally, numerical modal analysis is done and the results are compared with the experiments.

The purpose of the presented work is to design and analysis flight dynamic of launch abort system of a manned spacecraft in the conceptual stage of development. To this goal, through studying of various conventional configurations and based on the mission considerations, two main variants are selected and several analyses are performed on them for the evaluation of aerodynamic performance in different flow regimes and operational scenarios. Moreover, the effect of exhaust jets of scape tower nozzles on the flow pattern around launch abort system is investigated. The results of simulations indicate that the strut-based low-mounted nozzle configuration has lower drag force in different flight conditions. On the other hand, less interaction between the exhaust jets and spacecraft body is favorably observed for the adaptor-based high-mounted nozzle configuration. The second variant has extra drag due to four projected nozzles that can be handled via redesigning of scape rocket and its nozzles. Accordingly, the final concept of launch abort system of considered manned spacecraft is proposed. Based on the aerodynamic solutions, flight dynamic simulations are carried out for the assessment of designed flight path and the results show that the presented aerodynamic configuration has met the flight path requirements of launch abort mission.

Mixer, a component of turbofan engines is used to mix bypass cold flow with central body hot flow. In this study, the flow passing through the lobed mixer of a high bypass turbofan engine are simulated. First phase of the study was validation of the simulation method. The next phase was assessing the effect of heat transfer and mixing of hot and cold flows in the high bypass turbofan engine mixer. The results show that by raising the mixing length, the admixture of cold and hot flow increases regularly (layered) and the total temperature diminish. Alloy in mixer lobes plays the greatest role in this cooling process. Mixer successfully lowers 800 Kelvin temperature to of 340 Kelvin. The axial velocity of hot flow before entering the lobes is 210 m/s, decrease while passing the mixer lobes, re-boost in a short distance between the nozzle and the central body, eventually decreasing during flow exit. Besides, the transverse velocity generated deep inside the lobes have a substantial role in flow mixing.