نشریه مهندسی مکانیک ایران
سال بیست و پنجم شماره 4 (پیاپی 73، زمستان 1402)

In this paper, the behavior of composite tubes made of glass fibers under low velocity impact loads due to falling weight in the temperature range of -15  to 100  is investigated. For this purpose, composite tubes with glass fibers and three types of epoxy resins, vinyl ester and polyester are produced and tested in different impact energy levels and temperature conditions. Maximum impact force, impact time and absorbed energy are compared with each other for different situations. The results indicate that the epoxy resin tubes has a better performance in impact energy absorption than the other two types of resin used. As operating temperature increases, load carrying capacity of the tubes decreases, while the duration of impact time and amount of energy absorption increase.

Cavitation is a complex phenomenon in fluid mechanics. The occurrence of this phenomenon depends on the important factors and the different factors. The present study examined the erosion caused by collapse bubbles using the Eulerian - Lagrangian approach in a venturi. Cavitation flow in a venturi can be simulated with ANSYS - FLUENT software and with the development of a numerical code in MATLAB software, Lagrangian bubble behavior is simulated. Using the Keller - Miksis equation to simulate the variation of bubble radius and by considering different forces entering the bubble and using Newton’s second law, the bubble motion equation is extracted. From the Ochiai model to evaluate the compressive strength of bubbles caused by bubble collapse on a venturi can be used and the erosion rate is studied in different conditions. The results show the erosion intensity dependent on the initial radius of bubbles, fluid type and the formation of bubbles in the flow. in this case, by increasing the initial radius of bubbles, we witnessed an increase in wear strength to 100 micron of radius, but when the radius of bubbles exceeds this value, the bubbles will be affected when the radius of bubbles is increased, and the results of the data show that the bubble radius increases in the continuation of the flow path. Although the evidence showed that the number of blows was higher, the power reduction was evident.

In the test of flying object systems, hardware is used in the loop and activation of angular sensors with the help of a three-degree simulator table with a gimbal mechanism. With the development of the use of light and inexpensive sensors, the need to design a simulator table with three degrees of freedom inexpensive and low weight is evident. In this paper, a cheap, at the same time accurate and practical simulation table with Gimbal seeker test capability is designed and optimized. After extracting equations, according to the high uncertainty due to load changes, the design, simulation and optimization of the collection was done by removing and improving the constituent elements, in this way, this tool has the appropriate performance capability in the most optimal and cheapest case. In the present design, the maximum load of the simulator was reduced and instead of using a slip ring, a conventional roller bearing was used to eliminate the noise caused by the slip ring in addition to the lower price. The motors were changed from AC to DC, and the workspace and visibility of gimbal seeker were taken into account during the design. In addition, type of communication was changed to wireless and the method of power supply was changed to the use of batteries. To analyze the stress, deflection and torque of the motors, simulator in Adams software was modeled and the final design was designed and assembled by CATIA software.

In this study, a piezoelectric cantilever beam energy harvester model with two exponential cross-sections in width and thickness, and a tip weight, was proposed for use in a tire pressure monitoring system (TPMS). The governing equations for energy harvesting were derived for the first time for an exponential cross-section beam under rotational tire excitation conditions, based on the Euler-Lagrange method and coupled with electrical relations. There are few studies that consider both the thickness and width of the beam as variables, and no theoretical research has been conducted on this model under rotational excitation of the tire. The results of this study showed that it is possible to harvest energy by using a beam with an exponential cross section in width and thickness that can be designed with less weight and more electrical power. In future research, the derived equations can be used for optimization to increase electrical power and reduce weight to find the optimal values of the model's geometric dimensions.

This paper develops the concept of reducing environmental impact for the reverse osmosis (RO) system to increase the relationship between water, energy and environment in a solar farm. This concept is used in a RO system driven by an organic Rankine cycle (ORC) that generates power based on heat absorption from a solar field. In the power generation section, a new ORC and operating fluid configurations based on energy analysis (1E), exergy (2E), economic (3E) and environmental effects (4E) have been investigated in order to production of  fresh water. The basic parameters in the optimization are: the ORC configuration choice, selecting the working fluid of the organic Rankine cycle and determining the design parameters of a solar parabolic farm. These values have been determined according to the optimization of the system by genetic algorithm (GA) method. The results show that 12% reduction in environmental effects and 7.5% increase in the exergy efficiency are among the three-objective optimization effects.

This paper aims to facilitate the process of drawing geometrical shapes for specific therapeutic exercises that have been developed for disabled children by designing a robust controller for a six-degree-of-freedom (DOF) rehabilitation robot. Primarily, an extensive analysis of the robot kinematics has been conducted in which the first three actuators are actively controlled, and the rest can function passively. Subsequently, and for effective patient-robot interaction, impedance control is utilized. This helps the patients to get a predetermined desired level of assistance from the rehabilitation robot for the intended motions. Simultaneously, the level of assistance will also decrease with the course of recovery of the patient. To assess the performance of the controller, different scenarios have been examined and the results are compared with alternative robotic systems of the literature. By calculating the Root Mean Square Errors (RMSE) of the examinations, it is determined that desired geometrical shapes can be drawn with an accuracy of about one centimeter.