The main aim of this paper is to investigate bending behavior in sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets with considering the effects of carbon nanotube (CNT) aggregation. The sandwich plates are assumed resting on Winkler-Pasternak elastic foundation and a mesh-free method based on first order shear deformation theory (FSDT) is developed to analyze the deflection of sandwich plates. In the face sheets, volume fraction of CNTs and their clusters are considered to be changed along the thickness. To estimate the material properties of the nanocomposite, Eshelby-Mori-Tanaka approach is applied. In the mesh-free analysis, moving least squares (MLS) shape functions are employed to approximate the displacement field and transformation method is used for imposition of essential boundary conditions. The effects of CNT volume fraction, distribution and degree of aggregation, and also boundary conditions and geometric dimensions are investigated on the bending behavior of the sandwich plates. It is observed that in the same value of cluster volume, FG distribution of clusters leads to less deflection in these structures. تفاصيل المقالة

Various parameters can affect shot peening such as the number of particles and distance between particles and the surface layer. In this computational study, these parameters' effects on the creation of residual stress and mechanical behavior of Ti-6Al-4V alloy were described. For this purpose, Molecular Dynamics (MD) method is applied in two main steps. First, the simulated titanium surface was equilibrated for 1 ns. Next, the shot peening process was done on the equilibrated surface by using the various numbers of particles and distance. MD simulation results indicated, that by increasing the number of particles from 1 to 5, the mechanical behavior of the titanium surface was improved, and residual stress and hardness of the surface increased and reached 452.02 MPa and 494.46 HV in model 1 (Lj potential between particle and titanium surface), respectively. Furthermore, the results indicated that decreasing the distance from 15 Å to 5 Å led to increasing compressive residual stress and hardness of titanium surface mechanical. Numerically, by decreasing the shot peening distance from 15 Å to 5 Å, residual stress and hardness of titanium surface layer increased and reached -419.63 MPa and 510.83 HV in model 1, respectively. تفاصيل المقالة

The use of electro-hydraulic valves, particularly the proportional valve, has been important progress in the development of modern automated manufacturing equipment such as cutting or forming machine tools. Using these valves, electrical control signals can be converted into fluid energy in hydraulic systems. The main purpose of this study was to implement a control system for a 4-3 proportional hydraulic valve to control the position and speed of a double-acting cylinder. In this paper firstly the equipment is introduced and then the results of the implementation of the closed-loop control of this hydraulic valve controlled by PLC have been presented. The purpose of the control system is to equalize the extending and retraction times of the double-acting hydraulic cylinder. The practical results showed the electro-hydraulic system has performed well and the system has achieved the control goal to an acceptable level. In the simulation section, the performance of an open-loop control electro-hydraulic system for tracking a harmonic voltage input signal has been investigated. The electro-hydraulic circuit was designed in such a way that the stroke time of the hydraulic cylinder is independent of the external load. The results showed that applying input harmonic voltage between -10 and 10 volts causes the cylinder rod to move back and forth under external load. تفاصيل المقالة

Thick-walled cylindrical vessels are used widely in petrochemical and power plants. New additive manufacturing technology has made it possible to make FGMs. This research studies the creep analysis in the cylindrical FGM pressure vessel by considering three models and yield criteria. Also, the governing equations were extracted by considering the FGM models, and for determining creep stresses, the partial differential equations, were solved. Norton's equation is used to determine creep strain rates. The advantage of the exponential model is that in the inner radius for all n radial and circumferential creep strains rates have a constant value that is maintained by increasing the internal pressure up to 400 MPa. The graphs are smooth, and their values tend to zero in the outer radius. The changes of creep strain rate in terms of n in different internal pressures for the exponential model in the inner radius of the vessel show that increasing n from -4 to 0, these parameters have a reduction to the form of an exponential function, and the slope of the graph has the highest value at 360 MPa. تفاصيل المقالة

This paper deals with dynamic Stability of single walled carbon nanotube. Strain gradient theory and Euler-Bernouli beam theory are implemented to investigate the dynamic stability of SWCNT embedded in an elastic medium. The equations of motion were derived by Hamilton principle and non-local elasticity approach. The nonlocal parameter accounts for the small-size effects when dealing with nano- size structures such as single-walled carbon nanotubes. Influences of nonlocal effects, modulus parameter of elastic medium and aspect ratio of the SWCNT on the critical buckling loads and instability regions are analyzed. It is found that the difference between instability regions predicted by local and nonlocal beam theories is significant for nanotubes. تفاصيل المقالة

Cold rolling process is a complicated process which can be optimized by changing in variables and settings. This paper presents a set-up optimization system developed to calculate reductions and inter-stand tensions for each stand of a five stand tandem cold mill. The main objective in this optimization is minimization of power consumption. First, by using the analytical method, the equations of roll force and roll torque have been determined. The Genetic algorithm has been used to find out the optimum reduction setting and inter-stand tension which minimized the power consumption in five roll stands. The results have been compared with experimental data. Finally, the influence of effective parameters such as lubricants and strength of plates is studied. The results have been shown a similar pattern in reduction setting. تفاصيل المقالة

The objective of this paper is path planning of a 3 DOF planer robot with hydraulic actuator using genetic algorithm. First the geometric and kinematic parameters of robot were established. The equations of motion are derived by Lagrange method. We proposed the model for proportional valve and hydraulic actuators. Then using the genetic algorithm we minimized the hydraulic energy consumption as a fitness function during the mechanism motion between two specified points. تفاصيل المقالة