نشریه مهندسی مکانیک و ارتعاشات
سال دوازدهم شماره 4 (پیاپی 45، زمستان 1400)

In this article, the use of Friction Stir Welding (FSW) process to create a proper connection of 7075 aluminum alloy parts and the effect of the number of revolutions of the welding tool on the fatigue life of the weld area have been investigated. After the process, using the optimization parameters, the fatigue life of the base metal and weld metal of the welded samples was obtained. The results show that performing the fusion-friction welding process by changing the number of revolutions of the welding tool on the fatigue life of the T6-7075 aluminum alloy welding zone has increased the fatigue life in the fusion zone, which is caused by the heat produced due to friction and the severe shape change of the material in It is during welding. Also, investigations showed that in the weld metal and its surroundings, a weaker area in terms of fatigue life than the base metal has been formed.

A vast country with a mean solar irradiance of 4.5 kilowatts per square meter, Iran enjoys very high potentials for establishment and utilization of solar systems and, in particular, production of electrical energy from solar power stations. The present study was conducted for Optimal Solar Power Station Site Selection Using the Analytical Hierarchy Process (AHP) in Iran, and the Expert Choice software. AHP is one of the most widespread multi-criteria decision-making tools. The research considered criteria and sub-criteria such as the amount of radiation, number of sunny days, mean temperature, air humidity, precipitation, amount of dust and pollution, and cloudiness factor. For obtaining the optimal location using the AHP method, implemented in Expert Choice, pairwise comparison is made between the sets for weighting after the hierarchical levels, including the goal, criteria, sub-criteria, and alternatives (intended locations), are specified. As the sets are weighted, the compatibility of judgments is analyzed, which must be less than 0.1. The capitals of the provinces of Iran were considered in the research. From among the thirty-one locations in the examined region, the city of Zahedan was selected as the best location for establishment of solar power stations, and the other alternatives were assigned the next priorities given their weights. Moreover, sensitivity analysis was made on the major criteria, and the impact of parameter weight on the alternatives was assessed.

Along with the increasing development of countries, the daily need to transport various goods and equipment and travel in general for many reasons is increasing and for this reason, the number of different types of cars has significantly increased in recent years. In this way, this issue has caused heavy traffic on highways and various roads in big cities. Various actions and approaches, including public transportation, have been taken into consideration to facilitate the traffic. However, in some cases the solution to facilitate traffic jams, especially in big cities, is to build urban tunnels. Therefore, in recent years, urban tunnels have been considered as a solution to facilitate traffic. In this regard, the study of safety in tunnels becomes very important. The aim of this article is to simulate a fire in a short tunnel with natural ventilation to consider the behavior of smoke in different scenarios of natural air flow in the tunnel. The results of CFD simulation showed that limited fire (usual small passenger cars) will not cause problems for people as well as rescue team, especially fire extinguishing.

SVM is one of the popular classification algorithms based on statistics learning, which is presented for two-class problems. In real environments, the problem is usually multi-class. Thus, multi-class separation methods are very important compared to binary classes. In this work, to decrease the complexity of the model and the resulting loss of accuracy, fuzzy game theory is derived, which will be able to map the non-linear to a linear problem. Fuzzy game theory is obtained from the probability of data in each class by using two players (in our problem, each player is equivalent to a class label). Here, the decision matrix is yielded by the fuzzy logic, and then the equations are solved by the linear programming. Obtained results from the computer simulation validate the SVM model by fuzzy game theory.

The purpose of this research is to determine the amount of equipment used in the design of the photovoltaic solar power plant with a capacity of 200 kW. In this research conducted by PVsyst software, 500 w MonoTrina solar panel with 400 pieces, 25kw Growatt MID KTL3-X inverter with 8 pieces, which are arranged in 40 rows and 10 panels in each row. The optimal panel installation angle was 35 Degree °and the optimal azimuth angle was 0 Degree (case study: Qazvin city). According to the considered space and the designs made, including the percentage of permissible losses in cable calculations, the length and cross-sectional area of the DC side cable made of copper and aluminum are 800 meters, 16 and 25 mm square respectively, the length and cross-sectional area . AC side cable made of copper and aluminum is determined to be 100 meters, 16 and 25 mm square, respectively. The amount of total annual production energy of the desired point was determined by considering the losses, which was about 337.1 megawatt hours per year.

Phase change materials are increasingly playing an important role as heat transfer fluids and energy storage sources. This is a new technology in the field of thermal energy storage using phase change materials. In this article, the properties of microcapsules of phase change materials are studied and some widely used materials as core and shell materials were presented. Also, some of the uses of these materials are briefly mentioned. In the following, the method of manufacturing microcapsules based on n-octadecane and silica shell and microcapsule of phase change material with melamine core and formaldehyde shell is discussed.