Sharif Digital Repository

In this work, the viscoelastic fluids flow and their short fiber suspensions has been modeled in contraction geometry using conformation models, these models predict behavior of polymeric chains in contraction geometry. Prediction of viscoelastic fluids flow through a contraction is very important, especially in polymer processing where a polymer melt in barrel of an extruder is going to pass through a narrow die. We expect to see an eddy in each corner of barrel. The result has shown that increasing of De number enhances the eddy magnitude; also with making acute angle, we see decreasing of eddy magnitude. Normal stresses and velocity were investigated in contraction and their results had... 

This thesis was conducted both numerically and experimentally. In the experimental investigations aqueous solutions of high molecular weight Carboxymethylcellulose (CMC) was used. The experimental set-up was composed of a glass syringe, and a piston which can easily move through the syringe. Different die with aspect ratio ranging from 5.25 to 28.8 can be attached to the syringe. The syringe then is filled with the CMC solution with different weight fractions. Then using a force exerting on the piston, the solution comes out of the die and exiting velocity was calculated from weight of CMC solution that exit from die in a definite time. High quality photographs were taken from extrudate... 

Taghizadeh Manzari, M. (In this work, a modified Smoothed Particle Hydrodynamics (SPH) method, with a new moving solid boundary treatment approach, is utilized to simulate the particulateflow problems. The renormalized first and second derivative schemes which lead tothe consistency of the method, are also used along with a modification to the continuityequation which prevents the spurious pressure oscillations. The proposed methodis validated by solving benchmark problems of solid body motion in channel flows.There is a good agreement between the obtained results and those reported in theliterature. The convergence of solutions for different domain discretizations is alsoassessed. In order... 

Although many aspects of helical strand have been carried out, there are still some situations which need more studies. Based on previous studies of wire rope the constitutive equations regarding the rope tension and torque to the rope deformations are carried out. In which constitutive constants depend on both the rope material and geometry of the rope. Equations of motion for straghit rope loaded simultaneously in tension and torque are derived, and with using extensional-torsional deformations in both side of the rope, dynamic stiffness matrix is derived. Some experimental results and currently models are compared with my research model numerically. Finally, mechanic response of helically... 

In the present study, the performance of Viscoelastic Dampers in reducing the seismic response of the structures was investigated. For this purpose, first the effect of added damping to the system was studied. Number of 3-D steel structural models, with and without eccentricity which are designed with the 2800 code (first edition) and 519 code provisions that is not satisfied the provisions of the code-2800(third edition) is considered. It is assume that this system is located on a relatively stiff soil (soil type II based on Iranian Seismic Standard Code - 2800), a number of compatible earthquake records also considered to be used in the parametric studies. The results indicate that in... 

Friction composites, as a part of vehicle safety system, should hold some characteristics such as high wear resistance, low weight, durability, low noise, stable friction coefficient, availability and low price. It is very interested to use mixture of rubber and resin in friction materials to reach good properties of both rubber and resin simultaneously. This mixture is especially used in railway’s brake pads. Fibrous reinforcement is another important ingredient in friction composites. Asbestos used to be the most significant fibrous reinforcement due to its appropriate tribological specifications but the recent ban on asbestos by environmental protection agency has forced the friction... 

Viscoelastic(VE) dampers are among the most practical passive control devices that are used to reduce the seismic-induced response of the structures. In this regard, extensive parametric studies have been conducted so far to investigate the performance of these dampers in reducing the seismic response of the structures under various types of ground motions and site soils. In most of these researches, the effect of soil-structure interaction (SSI) is neglected which is acceptable only for the structures located on stiff soils. In present research, the effect of the soil-structure interaction on the performance of VE dampers in reducing the seismic structural response is investigated. Also,...