Sharif Digital Repository

This thesis has been done in two parts. In part I,a rupture disc wasdesigned. The rupture disc is an important part of a gas gun and is used as a fast response valve whichburst at a predefined pressure. Afterdesign,it has been used instead of an electric valve to increase the maximum velocity that can be achieved by the gas gun. Toavoid fragmentation and to have a better control on rupture pressure,a groove isusuallygraved on the disc. Cross and circumferential grooves werestudied in this thesis. It was found that in most cases the discs with a cross groovewere not fully opened because they have four independent failure paths and these paths should be opened simultaneously. However, having... 

Since mid-twentieth century the shear lag phenomenon has attracted many scientists’ attention which led to a wide range of researches to be carried out on this topic and the results are considered in the design codes. In tension members in which all parts of the member in the vicinity of the connection are not connected, only some parts of the section contribute to load distribution and non-connected parts do not play any role in load transfer and this leads to non-uniform distribution of stress and stress concentration. This phenomenon is called shear lag which causes reduction of tensile strength of the member. The effect of this phenomenon is introduced as a reduction coefficient... 

The present paper discusses the possibility of adding recycled polymer fibres to high performance concrete (HPC). Fibres used in this study were recovered from discarded car timing belts. To investigate different characteristics of the concrete specimens several destructive and non-destructive tests, such as compressive strength, modulus of rupture, flexural toughness, ultrasonic velocity and electrical resistance tests were carried out. In addition, slump flow tests were conducted on the fresh concrete. Experimental results from the study showed that the use of low percentages (up to 0.5%) of waste fibres improved the modulus of rupture and flexural toughness. Based on ultrasonic and... 

Tortuosity is an abnormality that may occur in some arteries, such as carotid. It can reduce the blood flow to distal organs, and even in severe cases, causes ischemia and stroke. Tortuosity can be congenital or occurs due to hypertension and reduced axial pre-stretch of artery, in which case called buckling. Since atherosclerotic plaques disrupt the normal pattern of blood flow, and thus make the artery more susceptible to buckling, in this study, the effect of atherosclerotic plaques on arterial stability has been investigated using computational simulation of fluid-structure interaction under pulsatile flow and large deformation. Ideal geometry of normal and atherosclerotic carotid artery... 

Liquid ammonia atmospheric tank (20000 ton) attached to Pardis Petrochemical Complex was ruptured on 8th August 2011 due to overpressure blast injury so that ammonia gas was spread throughout the complex. The current study was aimed to evaluate ammonia leakage and emission from the tank. For this purpose, in addition to evaluate ammonia emission into the air, pressure changes were investigated to simulate the rupture. First of all, ammonia tanks and urea stocks were simulated and then considering two aerial classes (D and B), the incident was stimulated. According to this model, up to 1000 m, was contaminated with 1000 ppm of ammonia. Since there was no experimental data for validating the... 

Coronary arteries often experience tortuosity under internal blood pressure and longitude axial twisting. Arterial tortuosity can enhance the stress concentration on the artery walls. Now if the coronary arteries suffer from atherosclerosis (a common disease among adults) the stress concentration on the tortuous artery plaque will be enhanced as well. Increased stress on the plaque may result in plaque rupture and its consequent damages. This study aims to investigate the stress concentration on the plaques and blood flow patterns within the coronary arteries with plaque. Moreover, the plaque growth was predicted taking into account various geometrical parameters including fibrous cap... 

The purpose of the current study is to investigate the base metal capacity of stiffened seated angle connections and to inspect their behaviour. The effect of different parameters on the capacity of connections is examined, considering the damage in the column. This research is important since for welding design, codes require the designer to control the base metal capacity to check the connection capacity, while the method of calculating this capacity is not provided, and this issue is not considered in the design. In this research, ABAQUS finite element software was used to model and analyze the results. A total of 90 stiffened seated angle connections, which were connected to the flange... 

The Ni-base superalloy CM88Y has good hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of gas turbine hot components. In most applications, heat treatment is required in order to achieve the desired mechanical properties and corrosion resistance of the working conditions; often three stages of heat treatment is designed for precipitation hardening nickel-base superalloy. In general, the effective parameters of heat treatment cycles includes temperature, time, heating rate and the cooling rate. In this study, the effect of cooling rate from partial solution temperature (second stage of heat treatment) on the...