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    Assessing Precision of Commercial Ultrasonic Instrument in Detecting Hole and Imperfection in Concrete Bridge Decks

    , M.Sc. Thesis Sharif University of Technology Niki Rashidi, Mohammad Mehdi (Author) ; Joghataie, Abdolreza (Supervisor)
    The conventional methods in concrete are usually divided to destructive and nondestructive tests. Among these, nondestructive tests are more preferable because they don’t damage the structure or at least the damage doesn’t significantly affect its performance. According to precision of estimation of concrete conditions, nondestructive tests have different levels. These tests on concrete bridge decks range from chain drag to more developed test like Ground Penetration Radar in concrete The optimum ease of use, cost and the precision of results of Ultrasonic Pulse Velocity (UPV) test compared with other nondestructive methods have made it a most widely used method. The precision of results of... 

    Experimental Study of Repair to Upgrade Concrete in Concrete Bridge Decks

    , M.Sc. Thesis Sharif University of Technology Mottahed, Jaber (Author) ; Joghatae, Abdolreza (Supervisor)
    This study presents the experimental investigation, the effect of cement based chemical materials (Portland cement as a repair material No1. and 2 other cement base chemical materials) to upgrade the structural behavior of reinforced concrete slabs built with low quality (porous) concrete. The main issues focused in this investigation are: (i) the effect of repair on the flexural behavior of RC slabs in terms of ultimate capacity and ultimate mid-span deflection and ductility of specimens, (ii) the influence of repair materials on failure modes and (iii) evaluating the efficiency of different materials on decreasing the porosity of concrete by ultrasonic test. Because materials used in this... 

    Exprimental Study of Repair of Low Quality and Damaged Concrete in Reinforced Concrete Bridge Columns

    , M.Sc. Thesis Sharif University of Technology Shokri, Mohammad Reza (Author) ; Joghatae, Abdolreza (Supervisor)
    This study presents the experimental investigation, the effect of cement based chemical materials (Portland cement as a repair material No1. and 2 other cement base chemical materials) to upgrade the structural behavior of reinforced concrete slabs built with low quality (porous) concrete. Because materials used in this study are cement base it is expectable to behavior same as base concrete that its result is better compatibility with base structure against external factors. Other advantages of the use of these materials are consideration of economical and construction aspects. A total of four reinforced concrete column (200x200x800 mm) with low quality (porous) concrete have been built,... 

    Investigating the Tensile Behaviour of a Type of Fibre-Reinforced Concrete

    , M.Sc. Thesis Sharif University of Technology Irandoust, Mohammad (Author) ; Khonsari, Vahid (Supervisor)
    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... 

    Investigating the Behaviour of Some Kind of Fibre-reinforced Concrete

    , M.Sc. Thesis Sharif University of Technology Alaei Mahabadi, Alireza (Author) ; Khonsari, Vahid (Supervisor)
    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... 

    Reliability of Ultrasonic Technique Used for Defect Detection of Spot Welded Plates in Automotive Industry

    , M.Sc. Thesis Sharif University of Technology Amiri, Nima (Author) ; Farrahi, Gholamhossien (Supervisor) ; Chizari, Mahmoud (Supervisor) ; kashizadeh, Kazem Reza (Co-Supervisor)
    Resistance Spot Welding (RSW) is one of the common techniques for connecting steel sheets in automotive industries. There are about 3000-5000 RSWs in the automotive chassis and body. Therefore, health and quality of RSW play a critical role in the final product performance. Also, welding process should be performed in a fully controlled program to ensure the durability of the vehicle body. In the automotive industry, there are various non-destructive methods (i.e., Chisel and Ultrasonic tests) and peel test as a destructive test (DT) to control the quality of RSW. Since the DT method is costly (waste of time, manpower, and materials), the main aim of the present research is to evaluate the... 

    X-ray diffraction analysis and williamson-hall method in usdm model for estimating more accurate values of stress-strain of unit cell and super cells (2 × 2 × 2) of hydroxyapatite, confirmed by ultrasonic pulse-echo test

    , Article Materials ; Volume 14, Issue 11 , 2021 ; 19961944 (ISSN) Rabiei, M ; Palevicius, A ; Dashti, A ; Nasiri, S ; Monshi, A ; Doustmohammadi, A ; Vilkauskas, A ; Janusas, G ; Sharif University of Technology
    MDPI AG  2021
    Taking into account X-ray diffraction, one of the well-known methods for calculating the stress-strain of crystals is Williamson-Hall (W–H). The W-H method has three models, namely (1) Uniform deformation model (UDM); (2) Uniform stress deformation model (USDM); and (3) Uniform deformation energy density model (UDEDM). The USDM and UDEDM models are directly related to the modulus of elasticity (E). Young’s modulus is a key parameter in engineering design and materials development. Young’s modulus is considered in USDM and UDEDM models, but in all previous studies, researchers used the average values of Young’s modulus or they calculated Young’s modulus only for a sharp peak of an XRD pattern... 

    Application of ultrasonic models for investigating the properties of the interface between roller compacted concrete (RCC) layers

    , Article NDT and E International ; Volume 124 , 2021 ; 09638695 (ISSN) Ashkar, M ; Toufigh, V ; Ghaemian, M ; Azizmohammadi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    In this paper, a comprehensive set of linear and nonlinear ultrasonic techniques was performed to investigate the properties of the interface between the roller-compacted concrete (RCC) layers. The effect of different time intervals between the pouring of each layer, cement content of concrete and bedding mortar, and various curing periods on RCC specimens were studied in this research. In linear methods, the interlayer led to velocity dispersion and attenuation phenomena except for the inherent inhomogeneity of specimens. The nonlinear parameters showed a general upward at the earlier ages, while the linear methods did not show an apparent regularity. The ultimate strength results were then... 

    Applications of ultrasonic testing and machine learning methods to predict the static & fatigue behavior of spot-welded joints

    , Article Journal of Manufacturing Processes ; Volume 52 , 2020 , Pages 26-34 Amiri, N ; Farrahi, G. H ; Kashyzadeh, K. R ; Chizari, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Ultrasonic Testing (UT) is one of the well-known Non-Destructive Techniques (NDT) of spot-weld inspection in the advanced industries, especially in automotive industry. However, the relationship between the UT results and strength of the spot-welded joints subjected to various loading conditions is unknown. The main purpose of this research is to present an integrated search system as a new approach for assessment of tensile strength and fatigue behavior of the spot-welded joints. To this end, Resistance Spot Weld (RSW) specimens of three-sheets were made of different types of low carbon steel. Afterward, the ultrasonic tests were carried out and the pulse-echo data of each sample were... 

    Damage Detection and Health Monitoring of Geopolymer Concrete Using Ultrasound Waves and Machine Learning

    , M.Sc. Thesis Sharif University of Technology Rahmati, Mohammad (Author) ; Toufigh, Vahab (Supervisor)
    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... 

    Laboratory and in situ investigation of the compressive strength of CFRD concrete

    , Article Construction and Building Materials ; Volume 242 , 2020 Vatani Oskouei, A ; Nazari, R ; Houshmand Khaneghahi, M ; Sharif University of Technology
    Elsevier Ltd  2020
    One of the most essential and costly stages in Concrete Face Rockfill Dams (CFRD) construction is to implement the concrete at the upstream face of the dam without joints. As the face concrete is considered as the most integral part to prevent water penetration in CFRDs, it's quality control is of paramount importance. One of the conventional approaches for quality control of the concrete which is used in CFRD is the compressive strength of laboratory samples. The comparison of laboratory and in situ measurements provides information about the accuracy of the obtained results. This research investigates the correlation of concrete compressive strength determined by using different methods in... 

    Acoustic simulation of ultrasonic testing and neural network used for diameter prediction of three-sheet spot welded joints

    , Article Journal of Manufacturing Processes ; Volume 64 , 2021 , Pages 1507-1516 ; 15266125 (ISSN) Ghafarallahi, E ; Farrahi, G. H ; Amiri, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Ultrasonic Testing (UT) is one of the most common types of nondestructive methods that is being used in various industries, especially in the automotive industry. In this paper, qualitative and quantitative control of resistance spot welds on three-sheet joints was studied. Initially, mathematical model of ultrasonic waves was extracted for triple sheet joints. Then, acoustic simulation of ultrasonic testing on spot welds was performed using Finite Element Method (FEM). Afterwards, A Multilayer Perceptron (MLP) neural network was used to classify spot welds based on their diameter. There was a mean error of 20.9 % between peak amplitudes of numerical and theoretical models which the most... 

    Quality Estimation of Resistance Spot Welding Using Ultrasonic Testing and Artificial Neural Network Approach

    , M.Sc. Thesis Sharif University of Technology Ghafarallahi, Ehsan (Author) ; Farrahi, Gholamhossein (Supervisor)
    One of the most common nondestructive tests is ultrasonic testing which has been paid great attention from specialists of this field. Apart from being economical and efficient, ultrasonic waves are sensitive to small changes in the structure and thus have a high degree of reliability. The most common method of ultrasonic testing is manual single-element A-scan inspection, carried out offline using longitudinal waves with pulse echo technique which is used in this thesis. The purpose of this thesis is to monitor structural health of thin metal joints and estimate quality of resistance spot welds by simulating ultrasonic testing using a finite element software. Initially, acoustic properties... 

    HPASC – OPCC bi-surface Shear Strength Prediction Model Using Deep Learning

    , M.Sc. Thesis Sharif University of Technology Khademi, Pooria (Author) ; Toufigh, Vahab (Supervisor)
    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... 

    Flaw characterization in ultrasonic non-destructive testing method using exponential modeling

    , Article Conference Record - IEEE Instrumentation and Measurement Technology Conference ; 2013 , Pages 1676-1679 ; 10915281 (ISSN) ; 9781467346221 (ISBN) Ravanbod, H ; Karimi, F ; Amindavar, H ; Sharif University of Technology
    Determining the shape, area, volume, and direction of flaws using ultrasonic imaging of metallic pieces, is a method estimating the severity of their defects. Different methods are used to process ultrasound images. Among these methods are spectral analyses, statistical, mathematical and intelligent methods. Within each of these, there are some advantages as well as limitations. Prony algorithm, which has been used as a parametric method for extracting exponential components of a signal, has several applications in signal modeling, system identification and classification. In this paper, after simulating pieces of oil pipeline, digital Wavelet transform has been used to reduce the noise of... 

    Use of polymer fibres recovered from waste car timing belts in high performance concrete

    , Article Construction and Building Materials ; Volume 80 , April , 2015 , Pages 31-37 ; 09500618 (ISSN) Khaloo, A. R ; Esrafili, A ; Kalani, M ; Mobini, M. H ; Sharif University of Technology
    Elsevier Ltd  2015
    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... 

    Influence of different types of nano-SiO2 particles on properties of high-performance concrete

    , Article Construction and Building Materials ; Volume 113 , 2016 , Pages 188-201 ; 09500618 (ISSN) Khaloo, A ; Mobini, M. H ; Hosseini, P ; Sharif University of Technology
    Elsevier Ltd  2016
    The aim of this study was to evaluate the effects of applying low replacement ratios (0.75% and 1.50% of the binder weight) of nano-SiO2 particles with different specific surface areas (200 and 380 m2/g) on the properties of high-performance concrete (HPC). Mechanical (compressive and splitting tensile strengths), electrical resistivity, non-destructive (ultrasonic pulse velocity), and microstructural (mercury intrusion porosimetry, X-ray diffraction, and scanning electron microscopy) tests were conducted to investigate the macroscopic and microscopic effects of nano-SiO2 particles on HPC characteristics. The results indicated that the performance of nano-SiO2 particles significantly... 

    Experimental investigation on effects of hybrid fibers on rheological, mechanical, and durability properties of high-strength SCC

    , Article Construction and Building Materials ; Volume 147 , 2017 , Pages 497-509 ; 09500618 (ISSN) Tabatabaeian, M ; Khaloo, A ; Joshaghani, A ; Hajibandeh, E ; Sharif University of Technology
    The aim of the present study is to investigate the effects of using hybrid fibers on rheological, mechanical and durability properties of the high-strength self-consolidating concrete (SCC). For this purpose, two types of fibers including hooked-end steel fibers and polypropylene fibers were used. In this study, a total of eleven mixtures were used: one as a control mix, one containing 0.5% steel fibers, four containing 0.5% hybrid fibers (steel and polypropylene), one containing 1.0% steel fibers and the four containing 1.0% hybrid fibers (steel and polypropylene). For investigating the rheological properties, slump flow, J-ring and V-funnel tests were performed. Mechanical properties were... 

    Optimizing the mixture design of polymer concrete: An experimental investigation

    , Article Construction and Building Materials ; Volume 167 , 2018 , Pages 185-196 ; 09500618 (ISSN) Jafari, K ; Tabatabaeian, M ; Joshaghani, A ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2018
    Over the last few decades, polymer concrete (PC) has been finding use in quick repairing of concrete structures. However, there have been only few studies on the mechanical behavior of PC. The aim of this study is to evaluate the mechanical behavior of PC using destructive and non-destructive tests (NDT). The mixtures were prepared with three different polymer ratios (10%, 12%, and 14%) and two different coarse aggregate sizes (4.75–9.5 mm and 9.5–19 mm). The samples were subsequently tested under three different temperatures (−15 °C, +25 °C, and +65 °C). The Taguchi method and analysis of variance (ANOVA) were used to optimize PC mixes based on the compressive, splitting-tensile, and... 

    Nitrogen-doped carbon nanotubes for heat transfer applications: Enhancement of conduction and convection properties of water/N-CNT nanofluid

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 138, Issue 1 , 2019 , Pages 69-79 ; 13886150 (ISSN) Bazmi, M ; Askari, S ; Ghasemy, E ; Rashidi, A ; Ettefaghi, E ; Sharif University of Technology
    Springer Netherlands  2019
    In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid...