Resume

• 2013

  Doctor of Philosophy (PhD)

  Adviser - Dr. Laurence J. Jacobs\n\nFocus in the nonlinear propagation of surface (Rayleigh) and bulk waves through structure materials such as aluminum and steel. Rayleigh nonlinear ultrasonic measurements are analyzed and corrected for attenuation

  diffraction

  and source nonlinearity [1]. Absolute measures of material nonlinearity are also obtained with air-coupled transducers in longitudinal waves [2].\n\nRepresentative Publications:\n\n[1] D. Torello

  S. Thiele

  K. H. Matlack

  J.-Y. Kim

  J. Qu

  and L. J. Jacobs. Diffraction

  attenuation

  and source corrections for nonlinear Rayleigh wave ultrasonic measurements. Ultrasonics

  56:417426

  2015.\nhttp://www.sciencedirect.com/science/article/pii/S0041624X14002728\n\n[2] D. Torello

  N. Selby

  J.-Y. Kim

  J. Qu

  and L. J. Jacobs. Determination of absolute material nonlinearity with air-coupled ultrasonic receivers. Ultrasonics

  81:107 – 117

  Mechanical Engineering

  Mechanical Engineering Graduate Association (MEGA)

  Georgia Institute of Technology

• 2009.

  Bachelor of Science (B.S.)

  Undergraduate Research Adviser - Dr. Tony M. Keaveny\nSuperviser - Michael Jekir

  MSME\n\nPrepared and tested rat vertebral specimens to determine efficacy of various treatments on bone biomechanical properties [1].\n\nResulting Publications:\n\n[1] S. K. Easley

  M. G. Jekir

  G. Lu

  D. Torello

  M. Li

  T. M. Keaveny. Lack of effect of ovariectomy and PTH treatment on the biomechanical material properties of bone tissue in rat vertebrae. In: 31st Annual Meeting of the American Society for Bone and Mineral Research

  Denver

  CO

  Mechanical Engineering

  Pi Tau Sigma

  Squelch! Magazine

  IM Soccer

  Orthopaedic Biomechanics Laboratory

  University of California

  Berkeley

• 2009

  Master of Science (M.S.)

  Adviser - Dr. Levent Degertekin\n\nFocus in the fields of Microelectromechanical Systems (MEMS) and Atomic Force Microscopy (AFM). Worked on improvements to high speed AFM imaging via Contact Acoustic Nonlinearities (CAN) to decouple modulated AFM tapping drive signals [1]. Exploited microcantilever and AFM cantilever holder geometry to boost actuation range while maintaining high imaging speeds [2].\n\nResulting Publications:\n[1] Torello

  D.

  and F. Levent Degertekin. \"Actuation of atomic force microscopy microcantilevers using contact acoustic nonlinearities.\" Review of Scientific Instruments 84.11 (2013): 113705.\nhttp://scitation.aip.org/content/aip/journal/rsi/84/11/10.1063/1.4832976\n\n[2] Torun

  H.

  D. Torello

  and F. L. Degertekin. \"Note: Seesaw actuation of atomic force microscope probes for improved imaging bandwidth and displacement range.\" Review of Scientific Instruments 82.8 (2011): 086104. \nhttp://scitation.aip.org/content/aip/journal/rsi/82/8/10.1063/1.3622748

  Mechanical Engineering

  Mechanical Engineering Graduate Association (MEGA) - President and Intramural Sports Coordinator\nAmerican Society of Engineering Education (ASEE) - Treasurer

  Georgia Institute of Technology

• 2007

  UC Berkeley

  Georgia Institute of Technology

  Crane Aerospace & Electronics

  Atlanta

  Georgia

  Academic Professional

  Georgia Institute of Technology

  771 Ferst Drive NW

  Atlanta

  GA 30332

  Full-time lecturing faculty in the George W. Woodruff school of Mechanical Engineering at the Georgia Institute of Technology. Specialization in dynamics of rigid bodies

  dynamics of mechanical systems

  vibrations

  and acoustics.\n\nCurrent courses:\n\nME 2202: Dynamics of Rigid Bodies\nME 3017: System Dynamics\nME 4056: Mechanical Systems Laboratory

  Lecturer

  Georgia Institute of Technology

  Berkeley

  CA

  BS Mechanical Engineering\nProject: Rat Vertebral Specimen Preparation and Testing\nLaboratory: Berkeley Orthopaedic Biomechanics Laboratory\nAdviser: Dr. Tony M. Keaveny\nResponsibilities:\n-Preparation and mechanical testing of human femoral and rat vertebral bone specimens\n-CT scanning of bone specimens\n-fixture design and fabrication for laboratory testing and specimen preparation\n-Data and image processing in MATLAB\n

  Undergraduate Research Assistant

  UC Berkeley

  Atlanta

  GA

  PhD Mechanical Engineering\nProject: Nonlinear Ultrasonic Methods in the Nondestructive Evaluation of Structural Materials\nAdviser: Dr. Laurence J. Jacobs\nResponsibilities:\n-Design and fabrication of scanning and single point measurement setups for generation and capture of Rayleigh surface waves\n-Comparison of contact

  air-coupled

  and laser interferometric measurement systems for measuring Rayleigh wave propagation\n-Exploration of bulk and surface wave mixing phenomena and the relationship\nof generated waves to material nonlinearity\n-Sample preparation in machining and material treatment facilities\n-Matlab/LabView signal processing

  data evaluation

  and automation\n\nMS Mechanical Engineering\nProject: High-Speed Atomic Force Microscopy in Air and Liquid Environments\nAdviser: Dr. F. Levent Degertekin\nResponsibilities:\n-Design of piezoelectric transducers and nonlinear excitation mechanisms\n-Design

  modication

  and fabrication of AFM hardware components\n-Optimization of devices for context specific AFM imaging\n-Finite element analysis of MEMS and macro-scale devices\n-Fabrication of MEMS devices in cleanroom environments\n-Design and implementation of experimental imaging and testing setups\n-GPIB instrumentation

  Matlab/LabView data processing

  Graduate Researcher

  Georgia Institute of Technology

  Burbank

  CA

  Responsibilities:\n-Designed and modeled hydraulic braking system components

  including servo-valves

  fluid pumps

  and brake manifolds in Solidworks\n-Developed packaging for brake systems and contributed to integration into aircraft

  including the Cessna CJ4

  Lockheed C130

  and HondaJet -Checked drawings and models against government and industry specications toensure proper drafting and annotation practices

  Mechanical Engineering Intern

  Crane Aerospace & Electronics

  Atlanta

  GA

  -Designed and modeled power plant components in AutoCAD

  including cooling\nsystems

  ammonia injection grids

  and feedwater heaters\n-Performed site inspections and completed as-built drawings for power plant piping systems\n-Co-chaired committee to facilitate smoother transitions into new work environ-\nments for interns and new hires

  Mechanical Engineering Intern

  Georgia Power Company

  Salem

  OR

  Responsibilities:\n-Designed avionic GPS packaging components for manufacturing using sheet metal

  die casting

  injection molding

  die cutting

  CNC milling

  and rapid prototyping techniques\n-Performed environmental

  mechanical

  and reliability tests on chassis and display components and conducted front end FE and CFD analyses on preliminary and final component designs\n-Researched and wrote white papers on testing procedures and delamination effects relating to display components

  Mechanical Engineer

  Garmin International

  English

  First Place - Student Poster Competition

  First place in student poster competition.\n\nTopic: Measurement and fitting techniques for the assessment of precipitation in alloy steel using nonlinear Rayleigh waves

  PRCI Annual Research Meeting

  First Place - Student Poster Competition

  First place in student poster competition.\n\nTopic: Measurement and fitting techniques for the assessment of material nonlinearity with air-coupled piezoelectric receivers using nonlinear Rayleigh waves.

  QNDE Conference

  First Place - Student Paper Competition

  First Place - Student Paper Competition\nTitle: Characterization of air-coupled ultrasonic receivers for nonlinear Rayleigh wave nondestructive evaluation\nPresented at Fall 2015 ASA Meeting in Jacksonville

  FL

  Nov. 4

  Acoustical Society of America

• Provided professional engineering support and guidance to high school FIRST robotics competition competitors.

  FIRST Robotics Competition

  Salem Oregon

  Simulations

  MEMS

  AFM

  Microsoft Word

  COMSOL

  LaTeX

  Finite Element Analysis

  Microsoft Office

  Mechanical Engineering

  ANSYS

  Rapid Prototyping

  Simulink

  Experimentation

  Thermodynamics

  Labview

  Solidworks

  Manufacturing

  Testing

  Matlab

  PowerPoint

  Diffraction

  attenuation

  and source corrections for nonlinear rayleigh wave ultrasonic measurements

  Jin-Yeon Kim

  Sebastian Thiele

  This research considers the effects of diffraction

  attenuation

  and the nonlinearity of generating sources on measurements of nonlinear ultrasonic Rayleigh wave propagation. A new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects is provided based on analytical models and experimental considerations. A method for extracting the nonlinearity parameter β_11 is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements. Quantitative experiments are conducted to confirm the predictions for the nonlinearity of the piezoelectric source and to demonstrate the effectiveness of the curve-fitting procedure. These experiments are conducted on aluminum 2024 and 7075 specimens and a β_11^7075/β_11^2024 measure of 1.363 agrees well with previous literature and earlier work. The proposed work is also applied to a set of 2205 duplex stainless steel specimens that underwent various degrees of heat-treatment over 24 h

  and the results improve upon conclusions drawn from previous analysis.

  Diffraction

  attenuation

  and source corrections for nonlinear rayleigh wave ultrasonic measurements

  Levent Degertekin

  Mudjat Balantekin

  Review of Scientific Instruments

  We present the proof-of-principle experiments of a high-speed actuation method to be used in tapping-mode atomic force microscopes (AFM). In this method

  we do not employ a piezotube actuator to move the tip or the sample as in conventional AFM systems

  but

  we utilize a Q-controlled eigenmode of a cantilever to perform the fast actuation. We show that the actuation speed can be increased even with a regular cantilever.

  High-speed tapping-mode atomic force microscopy using a Q-controlled regular cantilever acting as the actuator: Proof-of-principle experiments.

  Levent Degertekin

  A new method of actuating atomic force microscopy (AFM) cantilevers is proposed in which a high frequency (>5 MHz) wave modulated by a lower frequency (∼300 kHz) wave passes through a contact acoustic nonlinearity at the contact interface between the actuator and the cantilever chip. The nonlinearity converts the high frequency

  modulated signal to a low frequency drive signal suitable for actuation of tapping-mode AFM probes. The higher harmonic content of this signal is filtered out mechanically by the cantilever transfer function

  providing for clean output. A custom probe holder was designed and constructed using rapid prototyping technologies and off-the-shelf components and was interfaced with an Asylum Research MFP-3D AFM

  which was then used to evaluate the performance characteristics with respect to standard hardware and linear actuation techniques. Using a carrier frequency of 14.19 MHz

  it was observed that the cantilever output was cleaner with this actuation technique and added no significant noise to the system. This setup

  without any optimization

  was determined to have an actuation bandwidth on the order of 10 MHz

  suitable for high speed imaging applications. Using this method

  an image was taken that demonstrates the viability of the technique and is compared favorably to images taken with a standard AFM setup.

  Actuation fo atomic force microscopy microcantilevers using contact acoustic nonlinearities

  Levent Degertekin

  The authors describe a method of actuation for atomic force microscope(AFM) probes to improve imaging speed and displacement range simultaneously. Unlike conventional piezoelectric tube actuation

  the proposed method involves a lever and fulcrum “seesaw” like actuation mechanism that uses a small

  fast piezoelectric transducer. The lever arm of the seesaw mechanism increases the apparent displacement range by an adjustable gain factor

  overcoming the standard tradeoff between imaging speed and displacement range. Experimental characterization of a cantilever holder implementing the method is provided together with comparative line scans obtained with contact mode imaging. An imaging bandwidth of 30 kHz in air with the current setup was demonstrated.

  Note: Seesaw actuation of atomic force microscope probes using contact acoustic nonlinearities

  Jin Yeon Kim

  Jianmin Qu

  Nicholas Selby

  Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample’s absolute acoustic nonlinearity parameter

  β

  making the measurement of β a powerful tool in the NDE toolbox. However

  the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact transducers are sensitive to nonlinear signals

  cheap

  and simple to use

  but they are hindered by the variability of the interfacial contact between transducer and specimen surface. Laser interferometry provides non-contact detection

  but requires carefully prepared specimens or complicated optics to maximize sensitivity to the higher harmonic components of a received waveform. Additionally

  laser interferometry is expensive and relatively difficult to use in the field. Air-coupled piezoelectric transducers offer the strengths of both of these technologies and the weaknesses of neither

  but are notoriously difficult to calibrate for use in nonlinear measurements. This work proposes a hybrid modeling and experimental approach to air-coupled transducer calibration and the use of this calibration in a model-based optimization to determine the absolute β parameter of the material under investigation. This approach is applied to aluminum and fused silica

  which are both well-documented materials and provide a strong reference for comparison of experimental and modeling results.

  Determination of absolute material nonlinearity with air-coupled ultrasonic receivers

  David

  Torello

  Garmin International

  Georgia Power Company