Sharif Digital Repository

One of the most practical deformation processes has been used to produce profiles with a diversity of shapes is forward extrusion. Minimizing the extrusion pressure along with reducing the curvature of the final product have always been the main concerns of the researchers in this area. To achieve the former, researchers have designed nonlinear dies and proposed various equations to determine proper die profile. To accomplish the latter, they have used bearing at the exit section of the extrusion die. The primary object of the current study is to design a proper bearing in order to eliminate the curvature of the final product in extrusion process. The effects of both bearing and die profile... 

The goal of this thesis is to devise a guidance law that has the required ability and flexibility to construct a variety of return trajectories for a reentry capsule to the atmosphere. One of the commonly used methods for guiding flying vehicles with a fixed initial position and a fixed target is to load the trajectory data into the vehicle's computer memory. But the devised guidance law in this thesis does not require the trajectory data. Based on the relations governing the Bezier curve, it constructs the desired trajectory online. It also has the ability to provide the desired angle of landing and the desired magnitude of final speed. Further studies indicate that this ability is also... 

In recent years, more attention was devoted to ECAE process than any other Severe Plastic Deformation (SPD) process. Repeatability of the process and high mechanical properties of the exit profile are the reasons of this attention. ECAE process carried out with conventional extrusion process, provides more strain and back pressure. In this thesis an analytical model based on upper Bound analysis and Bezier interpolation functions is presented and the effects of process parameters were studied. According to the presented model, reduction of inner corner angle φ, increases strain, strain rate and press force. Reduction of the outer corner angle ψ, causes the same effect. Moreover, decreasing... 

One of the most common processes in shaping profiles with various cross-sections (with parallel surfaces), is a direct extrusion process. Always in the process, minimize the extrusion pressure and reduce the output profile curvature form of the main goals of researchers. Minimize the extrusion pressure in the mold design using nonlinear, many relationships are presented. Also, to reduce the output profile curvature of the mold, extrusion molding is used mostly at the outlet of the bearing. The purpose of this research is suitable for bearing design eliminates the curvature of the final product is extrusion. In this study interior design templates and profiles bearing acts simultaneously on... 

In this project, in order to model the flat rolling problems, an analytical method based on Bezier functions has been presented. To this goal, using the Bezier functions, the velocity field of the flat rolling has been stablished and the volume constancy condition and velocity boundary conditions have been considered in calculations. Using the achieved velocity field, the strain rate and strain fields has been determined. Then, with derived fields, power, pressure, and force of the deformation in flat-rolled billets from different materials such as copper, aluminium and steel have been calculated. To verify the accuracy of the results, the rolling process has been carried out on the... 

In the present work, the shape and position of internal cooling passages within an axial turbine blade have been optimized to achieve a uniform temperature distribution with the minimum cooling air flow while the maximum temperature is below the allowable value. Four cooling passages are made within the blade. The cross section shape of each passage is parameterized using a new method based on an 8-order Bezier curve. This curve which is represented in terms of Bezier control points has much flexibility and can produce a large variety of shapes. The shape of the blade surface profile remains unchanged during the optimization process. The numerical simulation has been carried out using... 

Bezier curves are among important curves which are broadly used in different fields such as computer graphic, vector graphic and animation. Among softwares in which these curves are used nowadays are: Adobe, Inkscape, GIMP, Adobe Photoshop, and Illustrator. An important concept in drawing the Bezier curves is to plot these curveswith fewer numbers of control points (low degree). Many algorithms have been introduced to reduce the degree of bezier curves. Here we first describe Bezier curves and their properties. Our main concern here is implementation of a new algorithm for multi-degree reduction of Bezier curves which are constrainted. The algorithm has recently been proposed byWozny and...