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    Defect size estimation in rolling element bearings using vibration time waveform

    , Article Insight: Non-Destructive Testing and Condition Monitoring ; Volume 51, Issue 8 , 2009 , Pages 426-430 ; 13542575 (ISSN) Behzad, M ; Alandi Hallaj, A ; Rohani Bastami, A ; Eftekharnejad, B ; Charnley, B ; Mba, D ; Sharif University of Technology
    2009
    Abstract
    In this paper a new approach to determine the size of defects in rolling element bearings is proposed. This approach is based on the statistical characteristics of the vibration signals generated by rolling element bearings. Although some traditional statistical parameters such as r.m.s. and kurtosis have some diagnostic capabilities, these parameters are not suitable for quantifying the defect size. The proposed new model was validated experimentally for both inner and outer race defects and it is concluded that the newly proposed model can determine the defect length of rolling bearings  

    Simulation and optimization of a semi spherical air bearing

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 7, Issue PARTS A, B, C, D , 2012 , Pages 153-159 ; 9780791845233 (ISBN) Saidimanesh, M ; Shahiri, A ; Nikparto, A ; Sharif University of Technology
    2012
    Abstract
    It is important to test the attitude control systems on satellites before they are launched in space. Traditionally this has been done by dropping the satellite, and firing the thrusters before the satellite makes a soft landing in a net. This method only allows a few seconds of testing and does not lend itself to the measurement of pointing accuracy. A better method is to mount the satellite on a spherical air bearing. In this paper behavior of a semi spherical air bearing is studied and analyzed in various conditions. These bearings are used in different applications such as simulation of approximately frictionless condition which is the satellite's situation in space. In this analysis... 

    Rolling bearing fault detection by short-time statistical features

    , Article Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering ; Volume 226, Issue 3 , 2012 , Pages 229-237 ; 09544089 (ISSN) Behzad, M ; Bastami, A. R ; Mba, D ; Sharif University of Technology
    SAGE  2012
    Abstract
    Rolling element bearing fault diagnosis is a very important part of condition-based maintenance. In this article, a new method for detection of rolling element bearing defects is proposed. The method is based on the concept of the cyclostationarity of the vibration signal to find periodicity in statistical features of the vibration signal. Various statistical features are examined to find the best choice. Several case studies including inner race, outer race, and rolling element defects are investigated in this article. Comparison with the envelope analysis showed that the proposed method benefits from clearer defect frequency identification  

    Experimental investigation on effects of elastomer components on dynamic and mechanical properties in seismic isolator compounds

    , Article Construction and Building Materials ; Volume 135 , 2017 , Pages 267-278 ; 09500618 (ISSN) Abedi Koupai, S ; Bakhshi, A ; Valadoust Tabrizi, V ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    Elastomeric bearings are becoming a preferred device for isolating bridges, buildings, and sensitive equipment structures. The technical specifications used to procure these isolators are considered as important factors for the consumers. Lack of communication between structural engineers and rubber technologists, causes structural engineers have slight understanding of rubber properties. In the present study, a number of compounds were initially designed and manufactured, based on a previously studied and manufactured isolator compound. The outcome of the experiments indicated the physical and mechanical properties. Afterwards, the targeted improvement led to modification of the compounds... 

    Role of collision angle during dissimilar Al/Cu magnetic pulse welding

    , Article Science and Technology of Welding and Joining ; Volume 25, Issue 7 , 2020 , Pages 549-555 Pourabbas, M ; Abdollah Zadeh, A ; Sarvari, M ; Movassagh Alanagh, F ; Pouranvari, M ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    This paper investigates the influence of collision angle on the interface characteristics and mechanical properties of magnetic pulse welded AA4014 tubes/Cu rods. It is shown that the collision angle, which affects the collision velocity, plays a crucial role in controlling the thickness of intermetallic compounds (IMC) layer and defect formation at the weld interface. The creation of a thin and continuous IMC layer at the weld interface is responsible for the higher load-bearing capacity of the sample welded under a collision angle of 4°. The welds made at higher collision angles are featured by a thick IMC layer containing defects such as micro-cracks, pores and cavities, which reduced the... 

    Effect of axial force, unbalance and coupling misalignment on vibration of a rotor gas turbine

    , Article 14th International Congress on Sound and Vibration 2007, ICSV 2007, Cairns, QLD, 9 July 2007 through 12 July 2007 ; Volume 3 , 2007 , Pages 2070-2077 ; 9781627480000 (ISBN) Askarian, A ; Hashemi, S. M. R ; Sharif University of Technology
    2007
    Abstract
    Unbalanced rotors and shaft misalignment are the two main sources of vibration in rotating machinery. These undesired vibrations may destroy critical parts of the machine, such as bearings, gears and couplings. There are lots of investigations about effect of unbalance and coupling misalignment upon the critical speeds and vibration amplitudes in rotary machinery. In this paper, effect of various parameters such as rotational velocity, geometry, variation of temperature and Poisson ratio on the natural frequency of rotating shafts were investigated. The equation of motion was derived from Euler-Bernoulli beam model and strain-stress relations. Results show that the effect of spin softening... 

    Fabrication of a highly ordered hierarchically designed porous nanocomposite via indirect 3D printing: Mechanical properties and in vitro cell responses

    , Article Materials and Design ; Volume 88 , 2015 , Pages 924-931 ; 02641275 (ISSN) Tamjid, E ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Design and development of biodegradable scaffolds with highly uniform and controlled internal structure that stimulate tissue regeneration are the focus of many studies. The aim of this work is to apply a modified three-dimensional (3D) printing process to fabricate polymer-matrix composites with controlled internal architecture. Computationally-designed plaster molds with various pore sizes in the range of 300-800. μm were prepared by employing 3D printing of a water-based binder. The molds were converted to ε-polycaprolactone (PCL) and PCL/bioactive glass (BG) composite scaffolds by solvent casting and freeze drying methods. Optical and electron microscopy studies revealed that the pore... 

    Fabrication of porous NiTi-shape memory alloy objects by partially hydrided titanium powder for biomedical applications

    , Article Materials and Design ; Volume 30, Issue 10 , 2009 , Pages 4483-4487 ; 02641275 (ISSN) Sadrnezhaad, S. K ; Hosseini, S. A ; Sharif University of Technology
    Abstract
    Porous NiTi-shape memory alloy (SMA) is a promising biomaterial with desirable mechanical property and appropriate biocompatibility for human implant manufacturing. In this research, porous NiTi-SMAs have been successfully produced by using thermohydrogen process (THP). This process has capability of production of homogenous structures, appropriate pore-size distributions and short sintering times. The THP-SMA samples produced in this research have a low Young's modulus (19.8 GPa) and a high tensile strength of 255 MPa. These properties are close to those of the natural bone and can meet the mechanical property demands of the hard-tissue implants for heavy load-bearing applications. The... 

    Performance of a novel heat based model for spacecraft attitude estimation

    , Article Aerospace Science and Technology ; Volume 70 , 2017 , Pages 317-327 ; 12709638 (ISSN) Labibian, A ; Alikhani, A ; Pourtakdoust, S. H ; Sharif University of Technology
    Abstract
    This paper presents a novel heat based measurement model for attitude determination (AD) using temperature data via two filtering techniques. Within the space environment, the Sun and Earth are considered as the major sources of external radiation that affect satellite surface temperature. In order to perform the required AD task, the satellite surface temperatures are related to its attitude via a proposed heat model (HM), assuming that the satellite navigational data is available. The proposed HM relates the net heat flux of three satellite orthogonal surfaces to its attitude. Filtering implementation of the proposed HM using the Unscented Kalman Filter (UKF) for AD is the key contribution... 

    Mechanical reinforcement of urinary bladder matrix by electrospun polycaprolactone nanofibers

    , Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3476-3480 ; 10263098 (ISSN) Ghafari, A. M ; Rajabi Zeleti, S ; Naji, M ; Ghanian, M. H ; Baharvand, H ; Sharif University of Technology
    Abstract
    For a successful repair and reconstruction of bladder tissue, fabrication of scaffolds with proper biochemical and biomechanical characteristics is necessary. Decellularized bladder tissue has been proposed in previous studies as a gold standard material for scaffold fabrication. However, weak mechanical properties of such a load-bearing tissue has remained a challenge. Incorporation of both biological and synthetic materials has been known as an effective strategy for improving mechanical and biological properties of the scaffolds. In the present work, a simple process was developed to fabricate hybrid hydrogel scaffolds with a biomimetic architecture from the natural urinary bladder... 

    Prognostics of rolling element bearings with the combination of Paris law and reliability method

    , Article 2017 Prognostics and System Health Management Conference, PHM-Harbin 2017 - Proceedings, 9 July 2017 through 12 July 2017 ; 2017 ; 9781538603703 (ISBN) Behzad, M ; Addin Arghan, H ; Rohani Bastami, A ; Sharif University of Technology
    Abstract
    In this research, a combination of the physical model based on Paris law and probability method is proposed for remaining useful life prediction of rolling element bearings. Level crossing is used as a feature that represents a linear relationship with defect size. Considering this linear relationship and using Paris law, a new model has been developed for bearings that follow degradation pattern with two stages. In this pattern, a bearing starts working in the healthy condition. Then it starts slow degradation stage and finally it goes to fast degradation stage until it reaches to the failure threshold. Considering a normal distribution for transition point from the slow degradation to the... 

    Feature extraction for rolling element bearings prognostics using vibration high-frequency spectrum

    , Article 1st World Congress on Condition Monitoring 2017, WCCM 2017, 13 June 2017 through 16 June 2017 ; 2017 Behzad, M ; Arghand, H. A ; Rohani Bastami, A ; Spectraquest, Inc. (SQi); Swansea Tribology Services Ltd (STS) and Oil Analysis Services Ltd (OSA); UE Systems Inc ; Sharif University of Technology
    British Institute of Non-Destructive Testing  2017
    Abstract
    Remaining useful life prediction of rolling element bearings with offline condition monitoring data is the purpose of this paper. A data driven algorithm based on feedforward neural network is proposed for this aim. Since, usually the number of offline measurements are not much enough, the generalized Weibull failure rated function is used for producing the auxiliary points that are employed for training. Considering the physics of the bearing degradation, level of vibration in the highfrequency bandwidth of the spectrum is used as a feature and its performance in bearing prognostic problem is compared with that of using popular recommended features in the diagnostic standard. Bearing... 

    Explicit finite element modeling of wear within the patellofemoral joint in total knee replacement

    , Article 26th National and 4th International Iranian Conference on Biomedical Engineering, ICBME 2019, 27 November 2019 through 28 November 2019 ; 2019 , Pages 208-212 ; 9781728156637 (ISBN) Bahadoran, M ; Dorri Nokoorani, Y ; Barati, K ; Farahmand, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Total knee replacement (TKR) surgery is one of the most successful and cost-effective procedures for treating knee injuries performed in orthopedics. However, the knee replacement revision surgery will probably be required after some years. Wear at the contact area between femoral metal component and the polyethylene inserts in TKR is recognized as one of the foremost causes of prosthesis failure and necessity of revision surgery. In the present study, focusing on the patellofemoral joint (PFJ), the wear at the contact area between the patellar and femoral components has been simulated employing the explicit finite element modeling. In this regard, common types of patellar component surface... 

    Atomistic insight into the behavior of ions at an oil-bearing hydrated calcite surface: implication to ion-engineered waterflooding

    , Article Energy and Fuels ; Volume 35, Issue 16 , 2021 , Pages 13039-13054 ; 08870624 (ISSN) Badizad, M. H ; Koleini, M. M ; Greenwell, H. C ; Ayatollahi, S ; Ghazanfari, M. H ; Sharif University of Technology
    American Chemical Society  2021
    Abstract
    This research provides an atomistic picture of the role of ions in modulating the microstructural features of an oil-contaminated calcite surface. This is of crucial importance for the rational design of ion-engineered waterflooding, a promising technique for enhancing oil recovery from carbonate reservoirs. Inspired by a conventional lab-scale procedure, an integrated series of molecular dynamics (MD) simulations were carried out to resolve the relative contribution of the major ionic constituent of natural brines (i.e., Na+, Cl-, Mg2+, Ca2+, and SO42-) when soaking an oil-bearing calcite surface in different electrolyte solutions of same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, and... 

    Effect of EPS beads in lightening a typical zeolite and cement-treated sand

    , Article Bulletin of Engineering Geology and the Environment ; Volume 80, Issue 11 , 2021 , Pages 8615-8632 ; 14359529 (ISSN) Khajeh, A ; Ebrahimi, S. A ; MolaAbasi, H ; Jamshidi Chenari, R ; Payan, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    The current study aims to assess the influence of EPS beads inclusion on the strength properties of stabilized poorly-graded sands. Various contents of zeolite and cement as stabilizing agents, with the total amounts of 4, 8, and 12% by dry soil weight, and also 0, 0.25, and 0.5% weight ratios of EPS beads (η) are examined. Zeolite is opted among a variety of pozzolanic materials so as to replace a part of cement (0, 10, 30, 50, 70, and 90%) due to its superior environmentally friendly properties. The stress–strain behavior, unconfined compressive strength (UCS), peak strain energy (Eu), and California bearing capacity (CBR) of the zeolite and cement-treated sand-EPS beads mixtures are... 

    Fabrication of hierarchically porous silk fibroin-bioactive glass composite scaffold via indirect 3D printing: Effect of particle size on physico-mechanical properties and in vitro cellular behavior

    , Article Materials Science and Engineering C ; Volume 103 , 2019 ; 09284931 (ISSN) Razaghzadeh Bidgoli, M ; Alemzadeh, I ; Tamjid, E ; Khafaji, M ; Vossoughi, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In order to regenerate bone defects, bioactive hierarchically scaffolds play a key role due to their multilevel porous structure, high surface area, enhanced nutrient transport and diffusion. In this study, novel hierarchically porous silk fibroin (SF) and silk fibroin-bioactive glass (SF-BG) composite were fabricated with controlled architecture and interconnected structure, by combining indirect three-dimensional (3D) inkjet printing and freeze-drying methods. Further, the effect of 45S5 Bioactive glass particles of different sizes (<100 nm and 6 μm) on mechanical strength and cell behavior was investigated. The results demonstrated that the hierarchical structure in this scaffold was... 

    Thermo-mechanical modeling of high speed spindles

    , Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 282-293 ; 10263098 (ISSN) Zahedi, A ; Movahhedy, M. R ; Sharif University of Technology
    2012
    Abstract
    Prediction of the thermo-mechanical behavior of machine-tool spindles is essential in the reliable operation of high speed machine tools. In particular, the performance of these high speed spindles is dependent on their thermal behavior. The main source of heat generation in the spindle is the friction torque in angular contact ball bearings. This paper presents an effort to develop a comprehensive model of high speed spindles that includes viable models for the mechanical and thermal behavior of its major components, i.e., bearings, shaft and housing. Spindle housing and shaft are treated as six-degree-of-freedom Timoshenko beam elements. Bearings are modeled as two-node elements with five...