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12-Mar-2019

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RESEARCH INTERESTS

  •  Nonlinear Vibration Analysis

  •  Friction Contact Modeling
     Friction Damping, Dry Friction Damper

  •  Vibrations of Gas Turbine Engine Blades / Bladed Disk Systems
     Linear and Nonlinear Forced Response Prediction of Bladed-Disks (Tuned / Mistuned)

  •  Mistuning Identification in Gas Turbine Engines

  •  Automotive Engineering

  •  Gear Dynamics

  •  Vibration Damping, Vibration Isolation

  •  Vibrations of Carbon Nanotubes

  •  Nonlinear Vibrations of Continuous Systems
     Large Scale Vibrations of Beams

  •  Helicopter Blade Vibrations
     Vibration Damping of Helicopter Blades

  •  Dynamic Analysis and Control of Engineering Systems

  •  Analysis of Systems with Fluid-Structure Coupling

  •  Numerical Methods for the Analysis of Nonlinear Systems

 

INTERESTED IN MS or PHD STUDIES?

  • Looking for a graduate student to work on "Modeling Dynamic Cutting Process Micro-Machining" who will be jointly supervised by Dr. Ender Cigeroglu (METU) and Dr. Bekir Bediz (Sabanci Univ.). If you are interested in this joint research, follow the link. (01/03/2019)

  • Joint Research Opportunity between Middle East Technical University and Georgia Institute of Technology. If you are interested in this joint research, follow the link.

  • Looking for a graduate student to work on "Nonlinear Piezoelectric Energy Harvesting" who will be jointly supervised by Dr. Ender Cigeroglu (METU) and Dr. Alper Erturk (Georgia Tech).

  • Looking for Graduate Students (MS or PhD) Who Would Like to Work on Automotive Engineering, Vibrations of Bladed Disks, Gear dynamics, and VIBRATIONS of MICRO & NANO Structures! For Other Research Topics, Please See the Link Given Below.

  • You may e-mail or call me. Follow the Link for Details on Research Topics.

  • Examples of Current MS and PhD Thesis Titles are Listed Below. Note that research subjects are not limited to the ones given below.

  • Broadband Energy Harvesting using Nonlinear Structures

  • Nanoscale Linear and Nonlinear Energy Harvesting

  • Tuned Liquid Column Damper

  • Vibration Isolation of Structures Using Nonlinear Elements

  • Nonlinear Vibrations of CNT based Mass Sensors

  • Nonlinear Vibrations of FGM Micro/Nano Beams/Plates

  •  


    SUMMARY OF RESEARCH ACTIVITIES ON VIBRATIONS OF GAS TURBINE ENGINE BLADES

    The research activities in Vibrations Laboratory are mainly focused on linear and nonlinear vibrations of turbine blades (gas turbine engines and steam turbines). We are interested in developing tools for accurate modeling of friction contact and its effect on blade vibration, identification of mistuning and nonlinear vibrations of tuned and mistuned bladed disk systems.

    One of the major problems in the design of gas turbine engines is the High Cycle Fatigue (HCF) failure of turbine blades due to blade resonance in the operating range. It is reported that HCF failure of engine blades is responsible for more than 50 % of the major engine failures.

    Dry friction dampers are commonly used by engine manufactures in order to decrease vibration levels and increase fatigue lives. There are several types of friction dampers used by the gas turbine engine manufacturers, which can be categorized in the following groups: blade-to-ground dampers, blade-to-blade dampers, shrouds and underplatform dampers.

    Blade-to-ground damper, where damper is in contact with the coverplate or the disk, is stationary with respect to the blade, and energy is dissipated through the friction contact due to the relative motion between the blade and the so-called ground. On the other hand, in blade-to-blade damper, damper is pushed against the adjacent blades and energy is dissipated due to the relative motion between the adjacent blades.

    Shroud dampers can be considered a special type of blade-to-blade dampers which can also increase the overall stiffness of the blades. During engine operation, shrouds come into contact and energy is dissipated due to the relative motion at the contact interface.

    Underplatform dampers can as be considered as a special group of blade-to-blade dampers where the damper is placed under the blade platforms and comes into contact with the blade due to the centrifugal forces. Wedge damper is a commonly used underplatform damper type where the damper has two inclined surfaces in contact with the adjacent blades. It is also referred as cottage-roof damper. Due to centrifugal forces created by the rotation of the engine, the damper contacts with the adjacent blade platforms and energy is dissipated at the two friction surfaces due the relative motion between the blades and the damper. However, due to the nonlinear nature of dry friction, dynamic analysis of the system becomes complicated.

    Some other examples of underplatform friction dampers are cylindrical dampers and cylindrical wedge dampers. In the first one the wedge damper is replaced with a cylindrical damper; whereas, in the later one one side of the wedge damper has a circular form and the other side is an inclined surface. It should be noted that dry friction is a nonlinear phenomenon which complicates the dynamic analysis of the bladed disk system. In order to accurately predict the forced response of turbine blades, accurate modeling of friction contact and dynamics of the bladed disk system with friction dampers are necessary.

    Schematic for Blade-to-Ground (left) and Blade-to-Blade (right) Dampers: In these dampers the normal load is optimized in order to obtain the minimum response. Schematic for Shroud Damper: At each shroud pair, the number of contact areas and the angle of these contact areas (with respect to blades) are optimized in order to obtain maximum friction damping. Schematic for Wedge Damper: Damper weight (normal load) and the angle of the inclined surfaces and platforms are optimized in order to minimize vibratory motion of the blades. Angles at right and left inclined surfaces can be different as well.

    In addition to friction dampers, it is also important to identify mistuning in the bladed disk system. Bladed disk systems are cyclically symmetric structures (composed of cyclic repetition of a sector); however, due to manufacturing tolerances and inhomogeneous material distribution, wear, etc., this cyclic symmetry is lost, which is called as mistuning. Unlike tuned systems, energy localization occurs in mistuned systems that results in increased vibration amplitudes in some of the blades which causes shorter HCF lives. In order to accurately predict, and improve HCF lives of turbine blades, it is necessary to identify mistuning in the manufactured bladed disks.

    The last version of the computer code BDamper (v10) has been developed during my PhD study at the Ohio State University, which is a collection of computer codes developed at CMML for Forced Response Prediction of Bladed Disks. The research activity at OSU was supported by a GUIde Consortium including General Electric, Pratt & Whitney, Mitsubishi, Siemens, Air Force Research Laboratories (AFRL) and funded by AFRL. The developed computer code BDamper v10 (last version) is delivered to these companies and labs which is also purchased by Rolls-Royce later.

    The research activities in Vibrations Laboratory are mainly focused on linear and nonlinear vibrations of turbine blades. We are interested in developing tools for accurate modeling of friction contact and its effect on blade vibration, identification of mistuning and nonlinear vibrations of mistuned bladed disk systems. For this purpose, we conduct research with highly motivated students some of which are sent to Rolls-Royce in UK for 6 months in order to identify and be familiar with current problems of the industry.


     

    RESEARCH PROJECTS

    1. Effect of Double Cardan Shaft on the Vibration of Armed Military Vehicle Suspension, SAYP-FNSS, Principal Investigator, 13/10/2015-13/10/2017.

    2. Türk Traktör, Consultant, 10/01/2015-10/01/2016.

    3. Development of Reduced Order Models for the Dynamics Analysis of Mistuned Blade Disk Systems, DKTM (TAI-TEI), Principal Investigator, 22/12/2014-22/06/2017 (with Prof. Dr. H. Nevzat Özgüven).

    4. Development of a Sensitivity Based Model Updating Software, SAYP-ROKETSAN,  Co-Principal Investigator, 15/12/2014-15/06/2016 (with co-principal investigator Assist. Prof. Dr. Gökhan O. Özgen)

    5. Development of a Methodology to Estimate Torque Loss in bolted Joints, TOFAŞ, Principal Investigator, 10/06/2013-31/12/2014.

    6. Reduction of Dynamic Transmission Error by Profile Modifications in Spur Gears, SAYP-TAI,  Co-Principal Investigator, 15/09/2012-15/09/2016 (with co-principal investigator Prof. Dr. H. Nevzat Özgüven).

    7. Rotor Dynamics and Application of Squeeze Film Damping, TEİ, Consultant, 07/2012-04/2013 (with Prof. Dr. H. Nevzat Özgüven).

    8. Design of an Active Vibration Control System, Researcher, ROKETSAN, 12/2011-05/2012, (with Assist. Prof. Dr. Gökhan O. Özgen ve Assist. Prof. Dr. Yiğit Yazıcıoğlu)

    9. Blade Diagnostics, Consultant, 09/2011-12/2011.

    10. Development and Testing of Passive Vibration Dampers in order to Increase Vehicle Ride Comfort (Araç Sürüş Konforunun Artırılması İçin Pasif Titreşim Sönümleyicilerinin Geliştirilmesi Ve Test Edilmesi), TÜBİTAK 1001, Principal Investigator, 04/2011-10/2013. (with Dr. S. Çağlar Başlamışlı and Asst. Prof. Dr. Gökhan O. Özgen)

    11. Coordinated Guidance of Multiple Unmanned Aerial Vehicles (UAVs) and path Planning (Çoklu İnsansız Hava Aracının (İHA) Koordineli Güdümü ve Yol Planlama), TÜBİTAK 1001, Researcher, 04/2011-04/2014.

    12. Development of Turbotek High Performance Wind Turbine Commercial Product, TURBOTEK, Consultant, 10/2010-05/2012.

    13. Design of a Spacer Damper for Power Transmission Lines, ODAGEM, Consultant (with Asst. Prof. Dr. Gökhan O. Özgen), 04/2010-08/2010.

    14. Design of an Engine Mount, TOFAŞ Türk Otomobil Fabrikası A.Ş., Principal Investigator, 2009-2010.

    15. Development of Friction Models, METU BAP Project, Principal Investigator,  2009-2012.

    16. Kara Hedef Angajmanı için Milimetrik Dalga Radar Teknikleri Geliştirilmesi Projesi – MİLDAR, METEKSAN Defence A.Ş., TÜBİTAK 1007 Project, Researcher (with Asst. Prof. Dr. Gökhan O. Özgen), 2008-2010.

    17. Generator Shaft Critical Speed and Unbalance Vibration Analysis, Diler Elektrik A.Ş., Consultant (with Asst. Prof. Dr. Gökhan O. Özgen), 04/2009-05/2009.

     

    CURRENT RESEARCH GROUP

     

    CURRENT GRADUATE STUDENTS 

    1.  Sinem DEMİRKAYA, TAI, (Ph.D.)

      •  Nonlinear Modeling of Bolted Joints for Satalite Structures, Started in Fall 2009.

    2.  Ali Çağrı BATIHAN, Research Assistant (Ph.D.)

      •  Nonlinear Modeling and Identification of Cracks in Structures, Started in Fall 2011.

    3.  Muhammed Emre BİLEN, TAI (MS, co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •   Coupled Vibrations of Helicopter Baldes and Rotor Hub System, Started in Fall 2013.

    4.  Canan UZ TAİ (PHD)

      •  Nonlinear Vibrations of FGM Microbeams, Started in Spring 2014.

    5.  Özgen IŞIK, FNSS (MS)

      •  Analysis of Vibration of Double Cardan Shaft Suspension System in Armored Vehicles, Started in Fall 2014.

    6.  Sefa KIZILAY, (MS)

      •  On the Solution of Nonlinear Algebraic Equations Resulting in the Periodic Forced Response Estimation of Nonlinear Systems, Started in Fall 2015.

    7.  Gökhan KARAPISTIK, ROKETSAN (MS)

      •  Nonlinear Modeling and Vibrations of Riveted and Bolted Joints, Started in Fall 2015.

    8.  Eren ÖNEY, ASELSAN (MS)

      •  Reduced Order Modeling of Mistuned Bladed Disk Systems, Started in Fall 2015.

    9.  M. Emin DOĞAN, ASELSAN (MS)

      •  Vibration Reduction of Structures by Using Nonlinear Tuned Vibration Absorbers, Started in Fall 2015.

    10.  Behrang Hosseiniaghadam, (Ph.D.)

      •  Identification of Nonlinearities, Started in Fall 2016.

    11.  Doğancan Bahan, ROKETSAN (MS)

      •  Vibrations and Balancing of Nonlinear Rotor Systems, Started in Fall 2016.

    12.  Cem Baykal, Research Assistant (MS, co-supervised with Assoc. Prof. Dr. Yiğit Yazıcıoğlu)

      •  Nonlinear Modeling of Washing Machine Drum, Started in Fall 2016.

    13.  Ranjit Patil, EU Project Research Assistant (Ph.D., co-supervised with Prof. Dr. H. Nevzat Özgüven )

      •  Nonlinear Modeling and Identification of Bolted Joints, Started in Fall 2017.

    14.  Bekir Mert Özceylan, ASELSAN (MS, Supervised with Assoc. Prof. Dr. Alper Ertürk, Gerogia Tech)

      •  Energy Harvesting by Using Nonlinear Metastructures, Started in Fall 2018.

    15.  Caner Türker, ASELSAN (MS, Supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Design and Production of a Vibration Test Apparatus, Started in Fall 2017.

     

    ALUMNI

    1.  Ata DÖNMEZ, ROKETSAN (MS, supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Nonlinear Vibration Isolation of Inertial Measurement Unit, July 2018.

    2.  Birkan ÖNAL, TAİ (MS, Supervised with Assoc. Prof. Dr. Zihni Burçay Sarıbay, TAİ)

      •   Nonlinear Dynamics of A Spiral Bevel Gear Pair, June 2018.

    3.  Veysel Yalın ÖZTÜRK, TAI, (Ph.D., co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •  A Parametric Study on Planetary Gear Dynamics, June 2018.

    4.  Onur SERT, ASELSAN (MS)

      •  Development of a New Adaptive Harmonic Balance Method, February 2018.

    5.  Çağrı TEPE, ASELSAN (MS)

      •  Structural Coupling of Nonlinear Structures, February 2018.

    6.  Şiar Deniz Yavuz, TAI (Ph.D., Supervised with Assoc. Prof. Dr. Zihni Burçay Sarıbay, TAİ)

      •  Nonlinear Dynamic Analysis of A Drivetrain Composed of Cylindrical Gears, Straight And Spiral Bevel Gears, February 2018.

    7.  Doğuş ÜNLÜ, ROKETSAN (MS, supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Finite Element Model Updating Of Aerospace Structures, December 2017.

    8.  Erhan FERHATOĞLU, TAI (MS, co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •  An Adaptive Modal Superposition Method for Dynamic Analysis of Nonlinear Structures, December 2017.

    9.  Cihan YILDIRIM, Research Asistant (MS)

      •  Reduced Order Modeling of Mistuned Bladed Disk Systems by Using Craig–Bampton Method, September 2017.

    10.  Onur ÖZAYDIN, TAI (MS)

      •   Vibration Reduction of Helicopter Tail Shaft by Using Dry Friction Dampers, September 2017.

    11.  Reza AGHAZADEH, THK University (Ph.D., co-supervised with Assoc. Prof. Dr. Serkan D)

      •   New Modeling and Analysis Methods For Micro-plates, August 2017.

    12. Ata ALIPOUR GHASSABI Research Assistant (MS, co-supervised with Prof. Dr. Serkan Dağ)

      •  Free Vibration Analysis of Functionally Graded Rectangular Nano-Plates Considering Spatial Variation of The Nonlocal Parameter, January 2017.

    13.  Yunus Emre ÖZÇELİK, GE (MS, Supervised with Prof. Dr. Mehmet Çalışkan)

      •  Modeling and Experimental Verification of Dynamic Characteristics of The Antenna Structure under Mechanical Shock Using MDOF Models, December 2015

    14.  Tayfun ÇELİK, TÜBİTAK SAGE (MS, Supervised with Assoc. Prof. Dr. Yiğit Yazıcıoğlu)

      •  Dynamic Modeling And Control of Hybrid Fin Actuation System for An Air-to-Air Missile, December 2014.

    15.  Hamed Samandari, Research Assistant (Ph.D.)

      •  Nonlinear Vibrations of Curved Single and Double Walled Carbon Nanotubes, July 2014.

    16.  Ufuk YİĞİT, Research Assistant (MS, supervised with Prof. Dr. Erhan Budak)

      •  Chatter Prevention Using Nonlinear Vibration Absorbers, February 2014.

    17.  Tuğrul KOZAK, TÜBİTAK SAGE (Ph.D., co-supervised with Asst. Prof. Dr. Yiğit Yazıcıoğlu)

      •  Modeling of Aircraft Aeroelastic Effects on External Store Separation, January 2014.

    18.  Canan UZ (MS, co-supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Design of a Test Setup for the Characterization of Vibration Isolators, September 2013.

    19.  Ozan Yavuz BAYTEMİR, METEKSAN (MS, supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  A Detailed Passive Vibration Isolation Analysis and Optimization Study for A 6 DOF Mechanical System, September 2013.

    20.  Reza AGHAZADEH, Research Assistant (MS, co-supervised with Assoc. Prof. Dr. Serkan D)

      •  Static and Free Vibration Analyses of Small-Scale Functionally Graded Beams Possessing a Variable Length Scale Parameter Using Different Beam Theories, September 2013.

    21.  Ozan GERGER, ASELSAN (MS, supervised with Dr. S. Çağlar Başlamışlı, Hacettepe University)

      •  Design, Control and Optimization of Vehicle Suspensions With Inerters, September 2013.

    22.  Anıl KOYUNCU, ASELSAN (MS, co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •  Identification of Nonlinearities in Structural Dynamics by Using Artificial Neural Networks and Optimization, September 2013.

    23.  Burcu ŞAYİN, TAI, (MS)

      •  A New Structural Modification Method for Nonlinear Vibration Analysis of Bladed Disks, February 2013.

    24.  Hasan YILMAZ, ASELSAN, (MS)

      •  Analytical Modeling and Stability Analysis of Spindle-holder-Tool Assembly by Using Spinning and Non-spining Timoshenko Beam Theories, January 2013.

    25.  Hakan ZALOĞLU, ASELSAN, (MS, co-supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Analysis of Recoil Springs Used in Automatic Weapons, January 2013.

    26.  H. Çağlar KARATAŞ, ROKETSAN, (MS, co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •  Possibilistic Interpretation Of Mistuning In Bladed Disks By Fuzzy Algebra, September 2012.

    27.  Zühtü EREN, FNSS, (MS)

      •  Frequency Domain Optimization Of Dry Friction Dampers Used for Earthquake Vibration Damping of Buildings, February 2012.

    28.  Yusuf ELDOĞAN, ASELSAN, (MS)

      •  Vibration Fatigue Analysis of Structures Attached on Air Platforms, February 2012.

    29.  Dilara ÇINAREL, (MS)

      •  Vibration Isolation of Inertia Measurement Unit, January 2012.

    30.  Ahmet OKYAY, (MS, supervised with Inst. Dr. S. Çağlar Başlamışlı)

      •  Sliding Mode Control Algorithm Development for Anti-lock Brake System (ABS), August 2011.

    31.  İsmet BARAN, (MS, co-supervised with Asst. Prof. Dr. Gökhan O. Özgen)

      •  Optimization of Vibration Characteristics of a Radar Antenna Structure, February 2011.

    32.  Caner BORAL, (MS, supervised with Dr. İbrahim Korkmaz)

      •  Design of an Engine Mount with Dry Friction Damping, July 2010.

    33.  Göksu AYDAN, (MS, supervised with Inst. Dr. S. Çağlar Başlamışlı)

      •  Ride Comfort Improvement by Application of Tuned Mass Dampers and Lever Type Vibration Isolators, July 2010.

    34.  Mehmet Ersin YÜMER, (MS, co-supervised with Prof. Dr. H. Nevzat Özgüven)

      •  On the Non-linear Vibration and Mistuning Identification of Bladed Disks, February 2010.

     

    VISITING RESEARCHERS

    1. Behrang. H. Aghdam, (Post-Doctoral Researcher)

      •  Vibration-based crack identification in beams with the use of non-stationary Functional Series Time dependent ARMA model, February 2017 - February 2018.

    2. Behrang. H. Aghdam, (Post-Doctoral Researcher)

      •  Vibration-based Estimation of Tool Wear via Output-only Functional Series TARMA Method, May 2015 - May 2016.

    3. Mohammad Rahmanian, Sharif University of Technology, Iran (Ph.D.)

      •  Nonlinear vibrations of conical shells conveying fluid flows, September 2014 - September 2015.

    4. Behrang. H. Aghdam, K. N. Toosi University of Technology, Iran (Ph.D.)

      •  On‐line Tool Wear Estimation in a Machining Process with the Use of Vibration Signals, January 2014 - April 2015.

     

     

         

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