مجله مهندسی مکانیک امیرکبیر
سال پنجاه و پنجم شماره 8 (آبان 1402)

The purpose of this research is to design and build a puppet robot with the capability of deep conversational learning with a deep reasoning approach. Due to the mentioned advances in artificial intelligence and deep learning, it is possible to provide conditions where the puppeteer's dependence on the handler is reduced and communicate with the audience intelligently. This robot, by recognizing the Farsi speech of the audience, determines a suitable answer to the question and broadcasts it in Persian language. The importance of this issue is in creating a suitable dialogue mechanism. This mechanism is a deep learning algorithm that by recognizing the question posed by the user, provides a set of possibilities from the categories included in the robot's dataset, and considering the highest probability, the desired category in which the user's question is placed is determined, and among the answers For that category of questions, an answer is chosen randomly. In addition, the puppet robot dialogue mechanism has a few simple conditional sections that can provide appropriate answers to repetitive or obscure questions. In the results of various trainings, by changing the parameters in the deep learning model of this robot with a 64-class dataset, it was found that the use of crowded layers with many neurons works better than a few layers of them,

This paper examines a parallel robot with 5 degrees of freedom with a linear platform. Parallel robots, have a restricted workspace, and singularities make the workspace even more confined. So the behavior of the robot in the working place is examined by focusing on kinematics and dynamics. To do kinematic analysis, the constraint equations are developed using the geometric relations, and the speed and acceleration equations of the robot are derived. The jacobian matrix is then calculated using the screw theory, and the state of the singularities in the workspace is determined based on the jacobian matrix. Considering the singularity and physical and geometric limitations, an algorithm for calculating the workspace is presented. In addition, the kinematic index of dexterity is investigated using the jacobian matrix as a measure of the robot's closeness to the singular configurations. The results of solving kinematic and dynamic problems are validated with the output of the simulation in MATLAB software.

In this research, the optimal parameters have been investigated with the aim of increasing the efficiency and improving the quality of rock cutting using abrasive waterjet (AWJ) through the modeling of high-velocity two-phase flow (water and abrasive). In the current research, the rock cutting process by AWJ has been simulated using the finite element method-smoothed particle hydrodynamics in LS-DYNA software. For this purpose, the effect of parameters of jet velocity, dwell time, changes in volumetric concentration, and changes in diameter of abrasive particles on the cutting depth and cutting volume of Siltstone and Shale rock specimens have been investigated. Numerical modeling results show that with increasing velocity, the amount of rock cutting depth and cutting volume increases. As the dwell time increases, the energy used by the AWJ to cut the rock increases, which will lead to an increase in the depth and volume of the cut. By increasing the volumetric concentration of abrasive particles up to 3%, the depth and volume of the cut increased with a gentle slope, and after that no significant improvement was observed. Also, by increasing the diameter of the abrasive particles up to 1.25 mm for Siltstone and 1 mm for Shale, the depth and volume of the cut increases at first, and after that the depth and volume of the cut remains constant or decreases.

Polymer electrolyte membrane (PEM) fuel cells, as an energy generator, convert the chemical energy of the fuel directly into electrical energy. An important component of polymer fuel cells are bipolar plates, which are responsible for the distribution of fuel and oxidants and facilitate the management of water inside the cell and transmission of electric current. In this study, the fracture method of graphite-based composite bipolar plates of polymer fuel cells under bending loads was investigated experimentally and numerically. Simple and perforated composite bipolar plates were tested and simulated with the approach of determining flexural stability under static load. In numerical analysis, mechanical simulation using finite element method and Abaqus software were used. Then, after making the laboratory samples, the experimental test of three-point bending was performed on them with the aim of validating the simulation results. Finally, results of numerical and experimental analyzes of the flexural behavior of composite bipolar plates were compared with each other. Comparison of the results of numerical and experimental analyzes showed that the results of these two methods had an acceptable agreement with each other. In addition, the presence of a high percentage of graphite as well as high fragility weakens the body and beams of this material increase the specimen of the sample, which occurs only due to the molecular bond of graphite, which causes the graphite to slip.

the one-of-a-kind properties of series 7xxx aluminum alloys such as high strength, relatively low density, good formability, and good resistance to stress corrosion cracking have made this class of materials a good choice for aerospace, automobile, and marine industries. Watertight, low weight, and fast procedure are the reason why welding is used in many industries. The heat that welding produce causes many problems like softening in the heat-affected zone. In this research with the use of a 3-D finite element model, the heat transfer of the Al-7075-T6 is investigated and verified by comparing them with the experimental model and the reduction of hardness in the heat-affected zone of the aluminum was predicted with good precision. In the next step, the softening of HAZ due to welding was measured with microhardness. With the use of the FEM model kinetic of over-aging was measured. The results show hardness of the alloy has two sources i.e. age-hardening and work-hardening. It seems welding eliminates the effects of age-hardening but has no effect on the hardness that comes from work hardening. Also, the decrease in the hardness of the solution-annealed area can be recovered through proper heat treatment. However, it is unrecoverable in the over-aged area.

Soft robots made of hyperelastic materials are widely used in transportation and medicine. Analyzing the behavior of soft actuators is a challenging process due to the nonlinear nature of hyperelastic materials. This article examines the effect of geometrical parameters such as the thickness of the walls, the distance between the chambers, the layers thickness, the side walls thickness, shape of cross section and selecting the material in the construction of the actuator on the bending behavior, the created stresses in the inner walls and the resulting tip force of the actuator to obtain the optimal geometry and the best material with the aim of creating the maximum bending angle and the maximum tip force of the actuator. For accurate modeling the material behavior of soft actuator construction material such as: DS30, TPU, EF30 and RTV2, the predictions of 5 Hyperelastic models Neo-Hookean, Yeoh3 parameters, Ogden1, Ogden2 and Moony-Rivlin are compared with stress-strain curves are obtained from uniaxial tensile test on these materials and the best model is selected to modeling of each material. The results show that, by reducing the thickness of the walls, the distance between the chambers, the thickness of the lower layers and using the square cross section and RTV2, the actuator maximum bending angle is obtained. Also, by increasing the thickness of the walls, the