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ultrasonics
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Total 245 records
Effect of Temperature Gradient on Ultrasonic Flowmeters
, M.Sc. Thesis Sharif University of Technology ; Sadrhosseini, H (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor)
Abstract
Ultrasonic flowmeters are one of the common and profitable measurement tools and applied in many industrial fields.Ultrasonic flowmeters work based on transit-time technique. The transit-time utilizes the propagation time of the ultrasonic signal in the fluid. Since ultrasonic signals can also penetrate solid materials, a pair of transducers is installed on the surface of tube. Each transducer works alternatively as both transmitter and receiver of ultrasonic signals.In this study, effect of temperature gradient on flowmeter measurements by applying constant temperature and uniform heat flux on the boundary is investigated numerically for methane gas in laminar flow regime and the results...
Structural Health Monitoring of Oil Pipeline Using Guided Lamb Waves
, M.Sc. Thesis Sharif University of Technology ; Zabihollah, Abolghasem (Supervisor) ; Selk Ghafari, Ali (Supervisor)
Abstract
Pipeline systems are one of the cheapest ways for distribution and transportation of petroleum and natural gas. The testing of pipes used in the petroleum industry is necessary to avoid unplanned process interruptions, environmental pollution and provide good safety. One of the methods which is used for pipeline inspection is the ultrasonic non-destructive testing (NDT) technique. The use of conventional NDT techniques such as ultrasonic thickness gauging is a slow inspection process, which becomes very expensive when full inspection is needed. Ultrasonic guided waves provide an appropriate fast screening technique. These waves stress the whole pipe wall and propagate along the length of the...
Ultrasound Image Reconstruction using Capacitive Micromachined Ultrasonic Transducers
, M.Sc. Thesis Sharif University of Technology ; Vosoughi Vahdat, Bijhan (Supervisor)
Abstract
In this thesis its considered the characterization of an ultrasound wave in a medium with some obstacles. Derivation of speed of molecules and pressure of the wave is carried out in the Cartesian coordinates system. Simulation is carried out to prove the dependency of wave speed to set up parameters such as the target point (x,y,z) at which the speed value is obtained, the location of the obstacles, the amplitude of original wave emitting from the source, and the propagation speed in different layers of the medium. From the numerical results, it is apparent that the amplitude of the speed wave gets degraded as the wave travels through the medium which is a function of reflection and...
Structural Health Monitoring and Damage Detection of Pipelines
, M.Sc. Thesis Sharif University of Technology ; Haj Sadeghi, Khosro (Supervisor)
Abstract
Pipelines are the preferred means for transporting of liquid or gas phase materials. The economy of many countries is extremely dependent upon a large network of pipelines systems to transport and distribute the nation’s energy resources. Damages to the pipe structure may cause leakage and result in economic losses or even loss of life. Developing methods for detecting the anomalies and damages to the structure before they lead to catastrophic events is vital. Multiple pipeline misadventures over the past several years have resulted in hundreds of fatalities and billions of dollars in property damages. These accidents demonstrate that the current monitoring methods are not sufficient...
The Application of Ultrasonic Waves for Determining the Liquid Level in Reactor for Monitoring a Process Reactor
, M.Sc. Thesis Sharif University of Technology ; Hajsadeghi, Khosrow (Supervisor)
Abstract
In this research non-contact ultrasonic based method is used for liquid level measurement in a container. A system has been designed and developed to determine the liquid level and show the results on a personal computer. The system contains three main parts, which are mechanical and electronic parts and the programming. The setup can measure the liquid level with the accuracy of 1cm. An ATMEGA8 microprocessor commands to relays and controls the pumps. The pumps are used to change the height of the liquid in the containers to accurately calibrate the sensor and test its operation. The ultrasonic sensor, which is mounted above the vessel, transfers the data to an ATMEGA64 microprocessor for...
Flow Simulation to Assess Effects of Various Parameters on Performance of a Gas Ultrasonic Flowmeter
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
In this thesis we are going to improve an ultrasonic flowmeter accuracy by considering the influence of different parameters like temperature, pressure, etc. Firstl of all different cases of flow condition in which ultrasonic flowmeter may work are specified, then velocity and temperature profile of pipe flow are determined using Fluent software. In thr next step ultrasonic pulses transmitted are simulated by the use of code written in Matlab to find wave travel time in the flow. Evetually an accurate relation of calibration for flowmeter is determined by the use of travel time and all other flow properties to evaluate the accuracy of flowmeter in diffent cases. Relation extracted can be...
Experimental Analysis of Immiscible Displacements of Heavy Oil in Heterogeneous Porous Media under Ultrasonic Effect
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Siroos (Supervisor) ; Ghazanfari, Mohammad Hossein (Supervisor)
Abstract
In the recent years, there has been an increasing attention toward usage of ultrasonic for enhanced oil recovery practices. But, thorough knowledge of active mechanisms and spreading and characterization of developed fingers during this practice is not available. From the other hand, due to limited amount of light oil fields, more attentions towards recovery from heavy oils is the need of the hour. Documents show that the big issues during the enhanced oil recovery from heavy crudes are high density of reservoir oil as well as poor development of fingers during injection due to high mobility ratios. In this study, results of ultrasound effect on the heavy oil recovery and its effect on the...
Durability Evaluation and Health Monitoring of Microcracked Slag-Based Geopolymer Concrete Due to Step by Step Pressure Loading
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor) ; Toufigh, Vahab (Co-Supervisor)
Abstract
The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder...
Evaluation of Mechanical Properties of Rammed Earth Exposed to High Temperature and Flame with Destructive and Non-Destructive Tests
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
The environmental friendliness and sustainable development of rammed earth structures has attracted the attention of numerous researchers in recent years. Obviously, a better understanding of the structural and mechanical performance of rammed earth is the way to use rammed earth as a sustainable building material. Structural fire safety is one of the primary considerations in the design of structures. Several experiments and investigations had been conducted to investigate the behavior of materials at high temperatures. Base on author knowledge at present, few studies are available on thermomechanical properties of earthen construction materials at temperatures higher than 100°C and even...
Deep learning-based Models for Distributed Damage Detection and Quantification in Concrete Using Sinusoidal Ultrasonic Response Signals
,
M.Sc. Thesis
Sharif University of Technology
;
Toufigh, Vahab
(Supervisor)
Abstract
In this thesis, supervised and unsupervised deep learning-based frameworks were proposed for distributed damage detection and quantification in concrete using sinusoidal ultrasonic response signals. Before the main study on ultrasonic-based concrete damage assessment, a preliminary study was performed on deep learning-based concrete compressive strength prediction. In this study, convolutional neural networks were utilized to predict the compressive strength of concrete through its mix proportions. The Genetic algorithm was employed to find the optimum number of filters in each convolutional layer of the convolutional neural networks. The proposed framework demonstrated high accuracy in...
HPASC – OPCC bi-surface Shear Strength Prediction Model Using Deep Learning
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Selecting a suitable material is crucial for repairing the old concrete structures and joining precast panels of bridges, especially the bond strength between the substrate concrete and the overlay material. In this regard, this research focused on high-performance alkali-activated slag concrete (HPASC) as a new concrete used as an overlay on ordinary Portland cement concrete (OPCC) as a block of old concrete. Approximately four hundred bi-surface shear (BSS) tests were performed to evaluate the interface properties of OPCC and HPASC. HPASC specimens were designed with different NaOH molarity, silica fume (SF) content, steel fiber content, age of repair material, and proportion of grooved...
Ultrasonic Evaluation for the Detection of Contact Defects of the Timer and Fiber-reinforced Polymer (FRP)
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Fiber-reinforced polymer (FRP) composites have been used tremendously to repair and rehabilitate timber structures due to their formability, ease of use, and high specific strength. The quality of the bond between FRP and timber substrate is critical for having complete composite action. In this paper, a comprehensive set of linear and nonlinear ultrasonic methods was performed to investigate the bond between carbon-FRP (CFRP) and timber. For this purpose, one hundred and twenty-six specimens of reinforced timber were prepared. Two techniques were considered to bond CFRP and timber: 1) externally bonded reinforcement (EBR) and 2) externally bonded reinforcement on the groove (EBROG). The...
Damage Detection and Health Monitoring of Geopolymer Concrete Using Ultrasound Waves and Machine Learning
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
The behavior of construction materials at high temperatures has been an important aspect of researches in recent years. The first part of the current research aims to non-destructively monitor the formation and growth of damage at geopolymer concrete (GPC) after being exposed to high temperatures using linear and nonlinear ultrasonic techniques. Ultrasonic waveform and pulse velocity (UPV) tests were conducted on the specimens before and after exposure to the temperatures. Nonlinear wave signals were processed in phase-space domain for qualitative health monitoring of GPC. Furthermore, feature extraction was applied to phase-plane attractors using fractal dimension for quantitative...
Experimental Investigation of the Durability of Rammed Earth Materials in Different Environments
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Rammed earth structures have attracted the attention of engineers and researchers in recent years due to their economic advantages, sustainable development, and environmental sustainability. One of the main concerns for public opinion for acceptance of Rammed Earth as a reliable construction material is their durability. Previous studies have investigated the durability of rammed earth materials by conducting wet and dry cycle test, accelerated erosion test, and rain simulation in the laboratory environment. This research studied the durability of cement stabilized rammed earth (CSRE) for one year under the aggressive environments. Three cement contents were considered for preparing the CSRE...
Effect of Harsh Environments on the Mechanical Properties and Durability of Fly Ash-Based Geopolymer Concretes
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor) ; Toufigh, Vahab (Supervisor)
Abstract
In the present study, the performance of fly ash-based geopolymer concrete blended with cement as an additional calcium source under exposure to marine, acidic and alkaline environments was evaluated. Three mixtures of fly ash-based geopolymer concrete with different cement ratios (0, 10 & 20%) were prepared and immersed in tap water, seawater, sulfuric acid, and sodium hydroxide solutions for up to one year. Change in the appearance, weight, compressive strength, splitting tensile strength, energy absorption and microstructure of the specimens were evaluated at 1, 3, 6, 9 and 12 months of exposure. Ultrasonic pulse velocity test was also used to determine its relationship with the...
Investigating the Behaviour of Some Kind of Fibre-reinforced Concrete
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
While there are many advantages associated with concrete, including high compressive strength, durability and so forth, on the contrary, it has several disadvantages which may make engineers somewhat reluctant to use it. These include low tensile strength, high brittleness, low resistance to impact, large dimensions of structural cross sections, etc. In recent years, there have been many attempts to surmount these disadvantages by various means such as adding pozzolans, using FRPs, fibres, etc. In this project, the effects of using a special type of high strength steel fibre is studied. In order to investigate the effect of this fibre on the compressive behavior of concrete, 30 cylindrical...
Investigating the Tensile Behaviour of a Type of Fibre-Reinforced Concrete
,
M.Sc. Thesis
Sharif University of Technology
;
Khonsari, Vahid
(Supervisor)
Abstract
Low tensile strength and also low strain capacity make plain concrete a ‘brittle’ material. To overcome this shortcoming, the addition of fibre as a reinforcing material has proved to be a reasonable solution. One of the crucial factors in deciding to make this type of concrete is the cost of fibre, which varies depending on its type. In this project a special type of fibre which does not cost a lot and at the same time has a high strength has been used. To investigate the effect of the fibre on the tensile strength of concrete, splitting tensile test (Brazilian test) was adopted. Altogether, 30 standard cylindrical specimens with dimensions of 15 × 30 cm2 were made (3 of each type) which...
The Evaluation of Distributed Damage in Concrete Based on Sinusoidal Modeling of Ultrasonic Response
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Ultrasonic wave attenuation is an effective descriptor of distributed damage in inhomogeneous materials. Methods developed to measure wave attenuation have the potential to provide an in-site evaluation of existing concrete structures insofar as they are accurate and time-efficient. In this study, material classification and distributed damage evaluation were investigated based on the sinusoidal modeling of the response from the through-transmission ultrasonic tests on polymer concrete specimens. The response signal was modeled as single or the sum of damping sinusoids. Due to the inhomogeneous nature of concrete materials, model parameters may vary from one specimen to another. Therefore,...
Experimental Investigation of Fracture Behavior and Mechanical Characteristics of Rammed Earth Materials
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Rammed earth (RE) structures are getting popular due to sustainability, environmental-friendly and economic advantages. Various studies have investigated the mechanical behavior and the energy performance of RE materials. However, little is known about the fracture behavior of RE materials. In this research, the fracture properties of RE materials containing different percentages of various stabilizers were investigated using a modified wedge splitting test. The stabilizers were cement, pozzolan, microsilica, glass-fiber, guar-gum and phase change material. In addition, the effect of stabilizers on the microstructure and the phase composition was inspected using scanning electron microscope...
Development of Dynamic Simple Shear Apparatus for Small Strain Dynamic Tests on Unsaturated Granular Soils by Bender Element and ultrasonic Sensors
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Shear modulus and confined modulus are important parameters for static and dynamic analysis in geotechnical applications. Elastoplastic and nonlinear constitutive models has been formulized by these parameters. Cyclic simple shear apparatus had been developed by mounting bender element and ultrasonic sensor to measure continuous shear wave and pressure wave velocities for determination of G_max and M.For this purpose two new pedestals have been fabricated on which HAE ceramic disc and sensors were mounted. A pressure control panel and a hanging column system have been designed to apply high and low matric suction with high accuracy.At first two small strain tests were conducted for...