نشریه مکانیک مواد پیشرفته و هوشمند
سال دوم شماره 3 (پیاپی 5، پاییز 1401)

In this paper, the dynamic stability of a thin rectangular plate under the periodic passage of oscillating rigid bodies is studied. Each of the two ends of a rigid body is connected to a wheel through a suspension system. Using the assumed-mode method, the governing equations are derived. The periodic passing of moving objects along a straight path on the surface of the plate results in a dynamic system with periodic coefficients. The Floquet theory is employed as a numerical method to obtained stable and unstable zones of parameters plane. Considering the point moving object model, the effect of moving object modeling on the stability analysis results is also investigated. The results indicate that the stiffness and damping of the suspension system, the mass ratio of the wheels to the whole rigid body, the rigid body’s length and the moving object modeling method are very effective on domains stability and instability of the system. Numerical simulations of the plate middle point verify the accuracy of the obtained results

This article reviews various researches in the field of eco-friendly and cost-effective renewable biosorbents, modification of their surface properties, adsorption operating conditions, adsorption isothermal and maximum adsorption capacity of these adsorbents. Is. Among the renewable biosorbents, green adsorbents can better achieve the goal of the circular economy of the future, where there will be no waste. Among the examined renewable biosorbents, the adsorbents obtained from agricultural wastes are the best adsorbents due to their high adsorption capacity due to the presence of abundant carboxyl and hydroxyl groups on the surface of their pores, easy access, non-toxicity and low price. Modification of biosorbents by using minerals and organic acids leads to an increase in the number of active sites in the adsorbent, which increases their adsorption capacity. Some methods of modifying the properties to increase the absorption capacity of the combination of green adsorbents with other adsorbents, modification with acidic compounds, inoculation of different functional groups on the surface of the adsorbent, and the combination of mineral and metal adsorbents with natural and synthetic polymers have been used in order to increase the adsorption capacity. By chemically modifying green adsorbents and creating cross-links, the properties of these adsorbents and their adsorption capacity and selectivity can be improved. The isothermal model of Langmuir and Freundlich has shown a better agreement with the adsorption equilibrium data in renewable biosorbents. The optimal value of the ratio of adsorbent to pollutant can have the best result in removal.

Deformation of cells and changing in mechanical specifications is one of the most important of cancer as serious illness. In fact, variation of mechanical properties of the cells is one of the important effects of the cancer. Here, the mechanical specifications of normal and cancerous skin cells have been studied. HU02, A-375 and A-431 as the normal and cancerous skin cells respectively have been investigated. The mechanical specifications including elasticity modulus and adhesion have been obtained using nanoindentation using JPK Instruments-Nano Wizard 3 atomic force microscope (AFM). The JPK SPM Data Processing software (v.5.0.96) was used to obtain the mechanical specifications. The results show that cancer can decrease the elasticity modulus of the cells to half in skin and increases the adhesion up to 38 times rather than normal cells. The cancerous cells are more adhesive than normal cells. The height of the cancerous cell is greater than normal cell.

Wire electric discharge machining is one of the newest, most popular and most accurate non-traditional machining processes, which is being studied. The advantages of this process include precision machining of parts with different hardness or complex shapes. Due to the increasing applications of this type of machining and since increasing the cutting speed and reducing the dimensional deviation in this process are very important, the selection of optimal cutting parameters has an important role to achieve high cutting speed and low dimensional deviation. Improper selection of parameters leads to limitations in output parameters and ultimately reduces productivity; Therefore, in this study, using Sobol statistical sensitivity analysis method, which has the advantage of high accuracy over other methods and extracting a small amount of parameter effect, to investigate the effect of various input parameters, including pulse-on time, pulse-off time, servo gap voltage, peak current and wire tension on the two output parameters of cutting speed and dimensional deviation are discussed. The results obtained from the sensitivity analysis of the expression are that the parameters of the pulse off time and pulse on time are the most effective parameters on the cutting speed with 39% and 37%, respectively, and the servo gap voltage parameters and the pulse on time are the most effective parameters on the dimensional deviation with 59% and 31%, respectively.

Buckling analysis of the composite stiffened panel in the aircraft’s wing was performed. The composite panel must meet the requirements of the structure and reduces the weight. For compare the types of stiffeners, the number of skin layers and stiffeners were assumed to be constant at each stage. At first, buckling strength was determined using ABAQUS and it was determined that the Hat-Type stiffner in single state and with the first layup, compared to the T-Type stiffener, 31%, J-Type 35% and The blade-Type, 41% withstand more buckling load. It also withstand higher buckling load for multiple modes and the second type of layup than the T-Type stiffener, 76%, J-Type, 79%, and blade-Type 70%. Next, important parameters such as number, dimensions and different layups on the selected stiffeners were investigated. It was found that the weight of the panel with 2 stiffeners, first layup and cross section 1 is almost equal to the weight of the panel with 3 stiffeners and cross section 3, but the buckling load of the plate with 3 stiffeners is 2.31 and the buckling load of the panel with with 2 stiffeners is 0.89.

The purpose of this research is to design mechanical components for making a brushless direct current motor. One-piece rotor and shaft are used in the design of this engine, and the hollow rotor is intended to access the interior space and reduce weight. Considering the magnetic flux density and taking into account the required strength of the rotor to withstand loads, 52 St steel is used and high strength epoxy pipe glue is used to connect the magnet and the rotor. In order to check the strength of the engine, engine components including power transmission parts and engine installation components were analyzed. The effect of centrifugal force on the normal stress created on the rotor, the effect of the transmission torque from the rotor in creating torsional stress on the shaft, the amount of shear stress at the connection between the magnet parts and the rotor and the amount of stress on the base parts and the required screw force. were analyzed by Nastran software to restrain the force due to the weight of the engine on the engine support bases. According to the stress analysis of the rotor and shaft, by choosing St-52 steel for these parts, a reliability of 2.58 has been obtained. The analysis of the shear stress of the connection between the magnets and the rotor indicates the proper connection of these parts by the glue used in this research with an acceptable reliability of 1.61.

Microstructure control is one of the most challenging issues in forming processes. It affects the quality enhancement of the product directly. The Finite Element Method (FEM) is an appropriate approach in forming analysis which can be applied for predicting microstructure. Many studies have addressed this issue through mathematical and physical models. In addition, several constitutional equations have been developed to model parameters such as grain growth, dislocation density, and recrystallization, etc. In this article, after choosing the appropriate constitutional equations and extracting the required relationships, a subroutine in the Fortran language has been developed. In the next step a rolling process with defined conditions have been analyzed in the finite element software, and the microstructural parameters have been investigated. Then the results were compared with the laboratory data and a remarkable similarity was observed. Finally, the effect of changes in friction, thickness reduction and roller speed have also been investigated.