Journal of Simulation and Analysis of Novel Technologies in Mechanical Engineering
Volume:8 Issue: 2, 2015

Electrical discharge machining process، is one of the most widely used methods for machining، the electrically conductive parts. In this way the tool is not in contact with the workpiece and the hardness of workpiece does not affect the machining speed. In Electrical Discharge Machining process، selection of the correct machining parameters are effective in final cost and the quality of the products. The special application of this alloy in various industries including tooling industry is attributed to its high hardness and wear resistance. The DIN 1. 2080 steel at low temperature has a high wear resistance. Its hardness depth is high and it is suitable for machining at low temperature. In this paper، the effect of the type and setting parameters and determination of optimal levels in of electrical discharge machining of alloy DIN 1. 2080 using the Taguchi method and optimal determinant is examined The desired setting parameters including gap voltage، current intensity، on time and off time. The material removal rate and surface roughness of produced parts as the output characteristic of the study were investigated. Results showed that the spark current is more effective on the output parameter (more than 65% on material removal rate and more than 48% on a surface roughness)، Other effective parameters are pulse on time، pulse off time and voltage changes، respectively. Higher current and pulse on time values and lower voltage and pulse off time values result in high MRR and low SR.

Nanofluid is made through the nanoscale particles suspended in a fluid base and Nanotechnology is a new attempt in thermal science investigations. As a result of huge investment in developed countries on nanotechnology, research on thermal properties of nano-fluids is of particular interest. Due to the usage of nanotechnology to reduce energy consumptions, in this project CeO2 with EG is used to make the nanofluid.For stabilization of nanofluid ultrasonic wave is used and viscosity is measured by a digital viscometer. In this paper, the effects of temperature and volume fraction on the viscosity of nanofluids are considered.This study indicated that the viscosity decreases in all concentrations when temperature increased. Also it increases when the volume fraction of nanoparticles increases. Results show that viscosity changes related to temperature at higher concentrations are higher. After considering the rheological properties and getting accurate test results, it is possible to obtain a relation to predict the nanofluid viscosity based on the temperature and volume fraction with high accuracy.

Virtual reality (VR) exposure therapy is a common treatment for phobia and the efficacy of this technique has proved. The darkness phobia is one of the most common disorders among the children. This is the first research about the darkness phobia and using VR to treat the patients. The VR system designed in this article is composed from two parts: Mechatronic devices and graphics unit. As a child spends most of his/her time at home, the home environment was simulated in the graphics unit. Also by using the mechatronic devices the head motions of the patients were applied to the graphics unit to close more the VR system to the reality. The treatment was conducted two sessions per week over three months. The results showed that the VR graded exposure therapy was successful for reducing fear of the darkness in children. In addition, the feedbacks of interacting with system from the patients were too satisfactory.

In this study, the effect of small-scale of both nanostructure and nano-fluid flowing through it on the natural frequency and longitudinal wave propagation are investigated. Here, the stationary and axially moving single-walled carbon nanotube conveying fluid are studied. The boundary conditions for the stationary nanotube is considering clamped-clamped and pined-pined and for the axially moving SWCNT is simply supported end where the left-end has been restrained. To apply the nano-scale for fluid the Knudsen number and to apply the structure the nano-rod model and nonlocal theory are utilized. Next, using the approximate Galerkin method the governing equation of motion is discretized and solved. In addition, the ratio of the natural frequency and phase velocity to the wave number and also the influence of velocities of flowing fluid and axially moving structure on the natural frequency would be studied. It can be shown that the natural frequency and wave propagation velocity are depending to the nano-scale of the structure and fluid flowing through it. So that, by increasing the nonlocal parameter, the natural frequency is decreased and by increasing the Knudsen number the system frequency is increased hence, leading to a bigger wave.

In this article, Finite Element Method (FEM) and Eulerian-Lagrangies Algorithm (ELA) formulation were used to numerically simulate the impact of several low-velocity projectiles with water surface. Material models which were used to express behavior of air and water included Null material model. For the projectiles, rigid material model were applied. Results were validated by analyzing the impact of metallic cylinder with a water surface and then the impact of a wedge, sphere and special projectile at low-velocities were simulated. Major outputs were force and pressure applied to the projectile, variations of velocity and acceleration when entering to the water, stress-strain variations and variations of water surface in various steps of the analysis. Results showed that the impact of the structure with fluid can be modeled using finite element model with high accuracy in terms of quality and quantity.Numerical results obtained for cylinder well agrees with the available experimental data. Also the results for other projectiles show a logical trend.

In this paper, the stress concentration around a hole in the single layer composite materials with long fibers is examined. The single layer has an infinite length, limited with and instant thickness and is loaded by a constant tension force p at infinity. The width of the lamina is considered to be finite and bears a hole as a defect. Due to presence of excessive shear stress in the matrix bays bounding the hole, a yielded zone of size is developed around the hole. Shear lag model (SLM) is used to drive the displacement and stress fields. The resulting equations are solved analytically based on boundary conditions and continuity in governing equations. Finally, the stress concentrations around the hole are calculated using a computer code. It is shown that the volume fractions of the fiber and matrix, as well as length of the plastic zone, have considerable effect on the stress concentrations within the lamina. Moreover, the number of broken fibers, the total number of fibers and the hole deformation seem to have considerable effect on hole stress concentrations. It is shown the stress concentration coefficient decreases with the increase of the plastic zone length. Also, the stress concentration factor increases in the elastic case with the increase of the volume fraction but in the plastic case at first it increases and then decreases with the increase of the volumes fraction.