JOURNAL OF SOLID AND FLUID MECHANICS
Year:2016 | Volume:5 | Issue:4|Papers Count:7

In most simulations conducted by researchers in the turning process, damping of system is considered from modal analysis. Indeed, in these studies the contact of the tool with the workpiece is not taken into account that can be reduced the accuracy of the simulation. In this paper, the process damping of the turning process is defined by using time series analysis. The recommended method is based on comparison with the correlation dimension of the simulation to experiment of displacement signal in the feed direction. Therefore, the variation of process damping based on variations feed and spindle speed is calculated. The results simulation of displacement of tool in feed direction in MATLAB software against displacement of tool in experiments, indicate significant accuracy of the proposed method in determinig displacement the tool in the turning process. The results of suggested approach can be used for predicting surface roughness of the manufactured workpiece by using turning process.

In this paper, two types of flows are modeled using the Isogeometric Analysis (IA) method. The first problem is to find the velocity distribution of uniform flow in a sloped channel and the second is irrotational flow around circular and rectangular obstacles. The formulation is derived and its differences with the finite element (FE) method are explained. In the IA method, the unknown function of the governing differential equation and the domain boundaries are approximated by NURBS (Non-uniform Rational B-Splines). Due to the ability of NURBS in constructing curves and surfaces with high precision, channels with complicated boundaries can easily be considered. The IA results are compared with the standard finite element and the accuracy is demonstrated by several examples. Furthermore, the effect of some of the IA parameters such as the irregularity of the control point grid, different knot vectors and the number of control points are also discussed.

Collocated Discrete Least Squares (CDLS) meshfree method, is used for the numerical simulation of the Sain-Venant torsion problem and obtaining the shear stresses in the sections with irregular and complex boundaries. In this paper a matrix formulation is applied in discretizing the governing equations, which make the procedure easy to code and efficient in calculation. In the applied method, a limited number of neighbor nodes are considered in the producing radial basis shape functions, which make the matrices sparse and prepare a suitable condition for sparse matrices algebra and applying available subroutine in this case. In order to validate the proposed method in the analyzing stresses due to torsion, firstly an elliptic section is considered, which in this case, there is an analytical solution. In the second problem, a thin walled section is considered and solved by the theory of Saint-Venant in torsion and results are compared with the closed solution obtaining from the theory of the torsion of thin walled sections. In the third problem, torsion in a hollow elliptical section is solved. Finally, the torsion stresses in sections with more complex geometry is considered.

Tunnel fires are responsible for many fatalities in recent decades and this field of study has received an extensive effort by researchers. Removal of the generated plume and high temperature is the great interest of investigators. In the current study, a numerical test has been performed on a rectangular cross section tunnel with a pool fire at the middle part using FDS5.5. Obtained results were compared with previous results. Then vertical distributions of Carbone monoxide and temperature stratification are presented for various heat release rate of fires and various tunnel aspect ratios and inclinations which have been reported in dimensionless form using their maximum value beneath the ceiling. Results indicate that the vertical values of CO decay faster than temperature values. These profile also helps us to find out about thickness of the plume where one can be aware of smaller thickness for higher aspect ratio.

In this study, the effects of temperature, relative humidity and air velocity the effective difussion coefficient on four different sample clay ceramics were investigated. A full factorial design of experiments on four cubic samples was performed. In each trial mass and volume reduction were measured using an electronic balance and a vision system and the resulting data were recorded and the drying curve was plotted. Effective diffusion coefficient of moisture using drying curves were calculated using of newly developed Firefly algorithm in which the error defined as the difference between the analytical values and the experimental values were minimized. Statistical analysis and analysis of variance showed that in calculation of the effective diffusion coefficient; the velocity, the temperature and the humidity are independent of each other. The greatest impact on the effective diffusion coefficient is related to the velocity, followed by temperature and environmental humidity respectively. Finally from the drying parameters the regression of the diffusion cofficient was obtaion.

In this research, the effect of viscosity of fluid on forming of flat head cylindrical cups by using hydrodynamic deep drawing process assisted radial pressure, was studied experimentally and also by finite element analysis. In this paper Firstly, to determine forming parameters such as maximum pressure and applied pressure path, process was carried out by numerical simulation by finite element method. Then by using several types of fluid with different viscosity as pressure carrying medium, several experiments were carried out. For every fluid, thickness distribution in final part and maximum punch force were investigated. By comparison of experimental results with numerical data, it has been found that results from numerical simulation were in good agreement with the experimental results. In addition in this paper it is shown that increasing the fluid viscosity leads to increasing of maximum punch force. In addition increasing fluid viscosity doesn’t have any effect in maximum blank thickening in the cup wall zone. Finally, in this research it is shown that by selecting fluid with appropriate viscosity, final parts with more uniform thickness distribution could be achieved.