Sharif Digital Repository

Fatigue life and crack growth retardation due to periodic tensile overload that superposed on constant amplitude cycles has been investigated. The tests were performed using C(T) specimens made of 7075 aluminium. All periodic overload tests were carried out at the same spacing between overloads and the effect of overload ratio on fatigue life has been investigated. Results of experiments revealed that the at low and high overload ratios, crack growth rate is relatively high and there is an optimum OLR that maximize interaction and thus minimize FCGR. Whit OCR-1=50, overload ratio of 1.85 led to maximum interaction and resulted in 219% increase in specimen's life relative to CA loading. Also... 

Diabete is disability in the body to produce insulin or use it. Body insulin hormone needed to convert starch, sugar and other foods to energy and thus the body is functioning properly. Considering this incurable disease and its complications, many doctors and researchers trying to control the disease, reduce complications and to create favorable conditions and appropriate solutions for preventing its expanding and also strengthening patients mentally. Be destroyed in digestive system, insulin can not through tablets or similar cases received. The best way known to enter insulin to the body, is injection. This project is about a device to reduce the level of blood glucose in patients with... 

The goal of using speed humps is to reduce the velocity of cars to allowable value. Reducing the speed more than necessary before arriving at the hump, causes losing kinetic energy whose compensation needs consuming more fuel. In fact, the total fuel consumption of vehicles is noticeable and it expresses the need for allowable speed definition to prevent wasting fuel. In this project, using different methods in engineering design and by defining allowable speed, an intelligent speed hump is designed and selected from different patterns which may remain protuberant or become like the road surface in level. The parts considered for this hump are selected simple to lower the cost of... 

In this research, the effect of variable stiffness and damping, in suspension system, on car performance was studied. The optimization of car performance was obtained by minimization of an objective function including the body acceleration, suspension travel and tire deflection. Firstly, considering the stochastic input for a quarter car model, minimization of the objective function was done by changing the stiffness and damping coefficients in the frequency domain. The Linear Quadratic Regulator (LQR) method was implemented to minimize the objective function. In order to supply the active force obtained by optimization, different semi-active designs, in which stiffness and damping were... 

In recent decades, emission from automobiles is considered one of the main reasons for global warming. One of the ways to decrease the fuel consumption of the vehicle, increase the power train efficiency and vehicle acceleration is to use Continuously Variable Transmission (CVT) and infinitely variable transmission (IVT). Previous inquiries include investigate miscellaneous types of continuously variable transmissions and their efficiency and different ways of combination of CVT and other power trains in order to create an IVT. The aim of this research is to optimize one kind of IVT transmission. At first, different state of combination of IVT portions will be investigated. Then, a model is... 

Pyroshock Test is one of important environment tests in satellite design process.pyroshock or pyrotechnic shock is one of loads that exerted on spacecraft and it's subsystems during launch process. pyroshock can cause failure in some subsystems like sensitive electronic parts, solar cells and so on. For this reason it's necessary to make sure about strength of component under pyroshock which can be done by pyroshock simulator.The purpose of this research is to design a pyroshock simulator that can simulate a pyroshock with given SRS (Shock Response Spectrum) for satellite components.Requirements and constraints for design have been defined such as test item dimensions,weight range and also... 

Pyrotechnic devices are widely used by the aerospace and defense industries and consist of a broad family ofsophisticated devices using self-contained energy sourcessuch as explosives and/or pyrotechnic compositions.Pyrotechnic shock, or pyroshock, is the transient oscillatoryresponse of a structure to loading (high frequency, highmagnitude stress waves) induced by the detonation ofpyrotechnic devices incorporated into or attached to thestructure.Pyroshock Test is one of importantenvironmental tests in satellite design process. Pyroshock is one of loads that exerted on spacecraft and it's subsystems during launch process. Pyroshock can cause failure in some subsystems like sensitive... 

One of the robots that has become more important recently is radio control helicopters. According to the intrinsic unstability of these helicopters and possibility of crash with the surroundings, it is needed to have a device which the helicopter can be fixed to so the ability of motion is reduced and a safer flight is achieved. In the recent applications of these helicopters, the autonomous flight ability of these devices is more noticed; and a lot of controllers are proposed to achieve this goal. It is obvious that these controllers are needed to be tested; and benchmarking a controller in the software simulation environment is not reliable; so a test stand is needed.
In this project a... 

Recently lots of studies have been done on driving cycles and parameters affecting pollutants emission and fuel consumption. Due to changes of driving behavior and traffic situations, it’s necessary to update driving cycle of a city to obtain more accurate simulation and analysis results. In this project, first of all driving cycle of Tehran city is developed using three different methods. These methods include choosing representative microtrips from specified traffic situations, clustering and choosing representative microtrips from all available data. Results show that using clustering method is more accuarate and parameters of the cycle developed using this method is closer to measured... 

Modern science and technology’s desire is increasing for Control Algorithms Testing Instruments which allow testing autonomics due to advancement in robotic science and increased application for autonomics. In this Thesis, a manufactured tester is equipped with sensors to allow data acquisition and Control algorithms tests for RC helicopters, which are a variety of autonomics. For this purpose; a manufactured 3-DOF tester was used and for control application purposes one degree of freedom was added and it was made to 4-DOF. Also, Mechanical defections which cause vibration resonance failing was solved. In the end, a data acquisition system with an appropriate rate for signal gathering and... 

In recent years passenger cars have been known as the main source of air pollution in urban areas. Despite all the research and efforts in minimizing the fuel consumption and emissions of internal combustion engines (ICE), this is merely a temporary solution. The permanent solution to overcome these disavantages is the use of electric vehicles (EV). The main downside of using electric vehicles is their short driving range. Multi-speed transmissions can be adopted to overcome this problem. Continuously variable transmissions (CVT) and infinitely variable transmissions (IVT) have been proven to enhance fuel economy in ICE vehicles and a great deal of research is being conducted to maximize... 

In this research the vibration of rotating and non-rotating shells was investigated. In the non-rotating shells field, the vibration of joined cylindrical shells and joined conical shells that each sections of them has independent material, thickness, length and angle were investigated. By analyzing the free vibration of joined conical shells, we can perform the free vibration analysis on every complex thin-walled geometry.In the rotating shells field, first the governing equations of the rotating conical shells are derived and then, the vibration of rotating cylindrical-conical shells and joined conical shells were investigated. The governing equations of rotating conical shells and... 

Millions of people are exposed to noise every day in their work and life, and their physical and mental health is at risk due to this issue. Hence, the issue of noise and vibration has become an important factor in car quality. One of the sources of noise and vibration in the vehicle is the engine. The engine is the heart of the car and its most important part. Therefore, reducing Engine noise can have a significant effect on the noise emitted by the vehicle. Engine noise can be divided into three categories: 1 - combustion noise 2 - mechanical noise 3 - aerodynamic noise. This project is in line with a project defined between the university and industry aimed at improving all sources of... 

In this research, the mechanical section of a reduced-scale hybrid vehicle simulator was designed and fabricated. In order to scale down the vehicle dynamics, a method based on dimensional analysis was proposed. An internal combustion engine and an electric motor were selected as power sources and then, scaling was performed, according to the specifications of the combustion engine. Afterwards, the power transmission system was designed first in concept and then in more detail. Finally, the design was manufactured and assembled. The study was made in conjunction with another study responsible for the controlling section of the work, conducted by Safabakhsh The sponsor of these two researches... 

The present research aims at designing a hybrid powertrain for the urban utility vehicles whose internal combustion engines consume more fuel due to idling during most of the time of their mission in the cities. This design has considered development of a hybrid powertrain with the least changes in the vehicle together with a simultaneous lower cost. At first some experiments were conducted to examine the feasibility of using the hybrid powertrain for the urban utility vehicles. One of the results of this test was the speed of these vehicles in different times of working and we can achieved a standard drive cycle though separate methods by analyzing this result. The drive cycle is one of the... 

Cylindrical shells play an important role in a wide range of engineering applications such as mechanics, aerospace, marine engineering, and nuclear applications due to their high load-carrying capacity, light structure, and economic advantages. Because these structures are often made of high lengths and thin sheets, they are very prone to vibration, especially under the conditions that they play a role in the rotating state, which can cause failure. For the reasons mentioned, the vibration analysis of rotating cylindrical shells will be essential in engineering designs. In the present study, after introducing general concepts regarding the analysis of structural vibrations, previous research... 

In recent decades, the air pollution issue and fuel resource constraints have compelled researchers to find ways to replace fossil fuels or reduce their consumption. Since the Vehicles are one of the most important sources of pollution and energy consumer, efforts to reduce vehicles fuel consumption can be an effective action to reduce air pollution. A proper powertrain system has an important task to reduce fuel consumption and air pollution.
Uses of continuously variable transmission system (CVT) and infinitely variable transmission (IVT), which makes the internal combustion engine to operate in optimal condition, can help to achieve this goal. In this thesis, the target is find... 

Each year about 23 thousand people will be death in the road accidents in our country. According to the Legal Medicine Organization of Iran, about 24 percent of pedestrian fatalities in road accidents are the result of a collision with a car and because of that studying the different parameters that reduce pedestrian injury became an important issue to study. There are different techniques such as simulating crash tests on cadavers, experiments on pedestrian dummy and numerical simulation. The purpose of this project is simulating the car-pedestrian crash with numerical software called Madymo. Then optimize of the various parameters such as the height of the front bumper height, hood,... 

Reducing noise, vibration and damage to the vehicle's passenger compartment was always a problem that has been investigatedin many researches. Here engine mounts as connecting members between engine and chassis play a big role. Because both of engine and road vibration put on it. Many studies have been done to optimize the engine mounts. As a result, many of hydraulic engine mounts with different variety of system control. But a few researches did about optimization of location and orientation of engine mounts. Therefore this project is to provide a process to optimize the location and orientation of engine mounts. The optimization process is First the dynamic equations of dynamic system are... 

Unmanned Aerial Vehicles have been used for different applications despite their short life. In last recent years, the developements in technology which leads to producing smaller electronical and electromechanical deveices, attract more attention to the researches in these fields. Among these vehicles, unmanned helicopters are more important because of their special abilities and capabilities. However there are some drawbacks which makes using them more difficult.
In this project, the first principle modeling of a RC helicopter has been accomplished and a parametric model including different sections effects has been created. This model has been implemented for a Trex600 CF helicopter....