JOURNAL OF MECHANICAL ENGINEERING AMIRKABIR (AMIRKABIR)
Year:2023 | Volume:55 | Issue:6|Papers Count:6

To prevent safety issues such as thermal runaway, lithium-ion batteries must be constantly monitored via an appropriate battery management system. Most thermal management methods are based on designing suitable cooling systems. In addition, since the surface temperature is measurable through a sensor, it is considered the main criterion of thermal management. However, in extremely fast charge-discharge operations, the core temperature can be significantly higher than the surface temperature. Thus, the cooling system may not be able to solely maintain the core temperature in the safe range. The objective of this paper is to combine electrical and thermal management and set the core temperature as the main criterion. To achieve that, model predictive control is implemented to control the supplied or drawn current of the battery cell, and the Sigma point Kalman filter is used to estimate the states of the experimentally derived electrothermal model. The simulation and experimental results indicate that incorporating model predictive controller and Kalman filter Estimators can be a novel strategy to simultaneously manage electrical and thermal states in both charge and discharge operations. It is also expected that controlling the electrical and thermal states of battery cells in fast charge-discharge operations may increase the safety and lifetime of the cell.

One of the most important analyses in the design of various structures, especially pressure vessels and their safety is the fracture mechanics. One of the important parameters in fracture mechanics is the study of the stress intensity factor of cracks in the tank wall. In the present study, the behavior of a semi-elliptical crack in a spherical pressure vessel made of functionally graded materials has been studied using Abaqus finite element software. The effects of parameters such as crack geometry, simultaneous internal and external cracks, pressure distribution, thermal load distribution, changes in the properties of the functionally graded material, and support conditions on the value of the stress intensity factor have been investigated. To model and analyze the stress intensity factor in this type of tank, various power, exponential, and linear functions have been used in the form of MATLAB code as well as a subroutine code. Crack geometry is also an important factor that has a significant effect on the stress intensity factor. So with an increase in the a/c value, the stress intensity factor also increases. Also, the examination of the support conditions shows that with the increase in the number of foundations, the stress intensity factor also increases.

Endplates are one of the most important components of polymer electrolyte membrane (PEM) fuel cell that must apply uniform contact pressure distribution on the membrane electrode assembly (MEA). For this reason, these plates must have good bending rigidity. In this research, the bending behavior of composite sandwich plates has been investigated numerically To achieve a composite structure with high bending stiffness for use in the endplates of PEM fuel cells. For this purpose, the bending strength of composite sandwich panels with grid core was evaluated based on the type of material and relevant standards through numerical simulation. Numerical simulation has been performed in Abaqus software using the finite element method. The effect of different angles of fibers in three different geometries of square, triangular, and diamond grid core for C/Sic and E-Glass Epoxy materials on the bending behavior of composite sandwich panels were analyzed. The obtained results indicate the better performance of C/Sic materials in the stress test, as well as the more suitable bending behavior of triangular mesh geometry with fiber angles (0-45-90).

The drill-string experiences strong vibrations due to its length and interactions with the rock at the bit. The Anti Stick-Slip Tool (ASST), located at the end of the drill-string, effectively prevents the stick-slip and torsional vibrations. A new model has been proposed to analyze the tool, overcoming previous limitations. The model represents the system with two degrees of freedom in its non-activated state and three degrees of freedom when activated based on kinematic constraints. Simulations demonstrate the logical behavior of tools under external forces and torques. The model accurately depicts the effect of weight on bit and weight on the hook on the activation of tool. The proposed model enables researchers to study the nonlinear behavior of ASST resulting from switching between equations in specific operational conditions.

The spherical shell is an ideal geometry for use in pressure vessels under uniform external pressure. The collapse pressure of these types of shells is much lower than its theoretical value due to the high sensitivity to imperfections and the yield stress of the material. Since the imperfections depend on the sheet metal forming method, it is necessary to investigate the effect of the fabrication method on the collapse pressure. This article is focused on the experimental and numerical study of the buckling of hemispherical shells made by the spinning forming method. The most important problem of this method is the lack of control over the thickness. In this method, the imperfections are axially symmetrical, which is one of the advantages of this method.  In this article, buckling analysis due to both diameter and thickness variations is done separately and simultaneously. It has been shown that thickness variations in rotational forming should be considered in the analysis of shell collapse. Also, by comparing the numerical and experimental results shown with the help of quadratic volume elements, thickness changes, and boundary conditions can be applied with higher reliability compared to the shell element.

In this research, the microstructure and wear behavior of high-strength AISI 4340 low-alloy steel coated using austenitic stainless steels ER309, ER312, and cobalt base steel stellite 6 were investigated by tungsten-gas arc welding method. Microstructural investigations were carried out by optical microscope and scanning electron microscope equipped with X-ray energy diffraction spectroscopy system(EDS). Hardness measurement was done by the Vickers method with a load of 30kgf on the surfaces and Vickers microhardness in the transverse sections of the welds in zigzag form. Also, To evaluate the wear behavior, the wear test of the pin on the disc was used to identify the wear mechanism. the highest hardness was related to stellite 6 by the amount of 565(HV), the reason for this increase in hardness is the presence of carbide phases M23C6 and M7C3 as well as chromium-tungsten complex carbides among bright cobalt dendrites. The results of the wear test showed that the highest friction coefficient was related to ER309 weld metal has an average value of 0.68 and the lowest friction coefficient is related to stellite 6 weld metal with an average value of 0.53.