VAST Laboratory

Vibrations, Adaptive Structures and Testing Lab

1348712867

Department of Mechanical Engineering
310 Goodwin Hall
635 Prices Fork Road
Blacksburg, VA 24061
540-231-3200

Dr. Pablo Tarazaga

Founder & Director
Welcome and Mission

Welcome the Vibrations, Adaptive Structures and Testing Laboratory, or as we like to call it, the VAST Lab. We are part of the Center for Intelligent Material Systems and Structures (CIMSS), which is comprised of several labs and is housed in the Mechanical Engineering Department of Virginia Tech.

We love what we do and we spend countless hours playing in the lab. Our work in the academic world and applied research favors our knack for exploration. As our name suggests, we specialize in Vibrations, Adaptive Structures and Testing, but we are always open to new things. Vibrations is one of our passions. The dynamic behavior of structures from very large inflatable satellites (Gossamer Structures) to micron size stereocilia, fuels our interest in this field. By Adaptive Structures we mean “structures that have the ability to adapt, evolve or change their properties or behaviour in response to the environment around them” (taken from Adaptive Structures: Engineering Applications ). As part of CIMSS, we work in the field of Smart Materials and leverage this expertise to aid in the development of adaptive structures. Smart Materials (also called Intelligent Materials), are materials that exhibit coupling between two fields. For example, piezoceramics exhibit electro-mechanical coupling and shape memory alloys (SMA) exhibit thermo-mechanical coupling (there are many others). Testing is where we get our hands dirty and truly have fun. Although frustrating at times, (as any experimentalist will tell you), it can be very rewarding as well. We believe that all models need testing and all testing needs models. We usually strive for a 50/50 ratio between theory and experimentation on all projects.

News

Laboratory

As part of the Center for Intelligent Material Systems and Structures, the lab has a wide variety of equipment. Some of this equipment is housed in the VAST lab and some is shared among CIMSS members.

The list of equipment below is not extensive but serves to showcase some of our capabilities.

  • HP 4194-A Impedance/Gain-Phase Analyzer: used to perform a wide variety of impedance and transmission measurements.  This equipment has been used to study and quantify the electromechanical coupling in the actuator and sensor components of smart material systems.  CIMSS also possesses an HP 4192-A impedance analyzer.
  • Zonic WCA Signal Analyzer: especially useful for experimental dynamic and acoustic structural analysis (also have SigLab and several other PC-based analyzers).
  • HP 3314-A Function Generator:  a multi-mode, programmable function generator featuring sine, triangle, and square wave functions from 1 mHz to 20 MHz.
  • Newport vibration isolation table
  • Polytec PI Laser-Doppler Vibrometer and Scanner: allows mapping of modal data on surfaces of large structures.  (e.g., PSV-400 with a 1 MGHz range and close up modules, OFV-500 and PDV-100 portable units)
  • In addition, complete modal testing facilities are available on a variety of platforms such as LMS Scads and Siglab units.
  • Several d-Space controllers and other digital control systems: allows the use of MATLAB to drive experiments for MIMO control.
  • Altitude and Temperature Chamber: Model 36ST Tenneystrat Environmental Test Chamber allowing the testing of structures and control systems in a range of temperatures from -70° C to +177° C and pressures simulating altitudes of up to 100,000 ft.  This system is fully instrumented and is connected to an IEEE bus for running computer-controlled experiments.
  • VXI Dynamic Signal Analyzer for vibration and acoustic signal analysis.
  • A 3′ x 20′ fume hood for materials fabrication (chemical and bio sensors).
  • Zeiss fluorescent microscope and attachments (filter set, cubic filter, and molecular probe)

The lab also has a variety of smart materials, and associated hardware including PZT, PVDF, SMA, etc., dozens of computers for running test equipment, test benches, a micro pump, an actuator fabrication facility, numerous shakers, strain gauges, accelerometers, proximity probes, and access to numerous other facilities on campus.

Ongoing Research and Projects

  • Inducing and controlling traveling waves in solid structures for multiple purposes


    A mechanical wave is generated as a result of an oscillating body interacting with the well-defined medium and it propagates through that medium transferring energy from one location to another. The ability to generate and control the motion of the mechanical waves through the finite medium opens up the opportunities for creating novel actuation mechanisms. The focus of this study is on understanding the traveling wave generation and propagation by establishing the relationships that illustrate the role of structural and electromechanical parameters. A brass beam with free-free boundary conditions was selected to be the medium through which the wave propagation occurs. Two piezoelectric elements were bonded on the opposite ends of the beam and were used to generate the controlled oscillations. Excitation of the piezoelectrics results in coupled system dynamics that can be translated into generation of the waves with desired characteristics. Theoretical analysis based on the distributed parameter model and experiments were conducted to provide the comprehensive understanding of the wave generation and propagation behavior.
    Publications:
    Malladi V.V.N.S., Avirovik D., Priya S., and Pablo A. Tarazaga . 2014 ,Traveling wave phenomenon through piezoelectric actuation of a free-free beam“.  Proceedings of ASME 2014 Conference on Smart Materials, Adaptive structures and Intelligent Systems, New Port, RI.,September 8-10.

  • Developing a new methodology for acoustic field characterization through continuous acoustic scanning (CAS)


    The development of the Continuous Acoustics Scanning (CAS) methodology is studied in order to characterize an acoustic field. Furthermore, the acoustic emissions of a vibrating source is incorporated in order to analyze the relationship between the source characteristics and its acoustic field. Initial findings suggest that the CAS approach may be capable of not only characterizing the acoustic field at a  distance from the source, but also be capable to characterize the velocity profile of the source itself. The CAS approach utilizes the side bands in a fast Fourier Transform (FFT) of the time-based-data collected by a roving microphone. The present work herein, is an extension and in-depth study of the different parameters affecting these side bands.
    Publications:
    Malladi, S., Lefeave, K. L.,Tarazaga, P. A., 2014. “Parametric Study Of A Continuous Scanning Method Used To Characterize An Acoustic Field,” IMAC XXXII, Orlando, FL, February 3-6.
    Garcia, C. E., Malladi, S., Tarazaga, P.A., 2013. “Continuous Scanning for Acoustic Field Characterization,” IMAC XXXI, Orange County, CA, February 11-14.

  • MFC energy harvesting towards a self-powered structural health-monitoring smart tire


    The goal of this research is to build an MFC based energy harvesting system capable of replacing batteries inside a moving tire. Eliminating the need for batteries makes the possibility of in-tire monitoring systems much more attractive as the tire no longer needs to be removed from the rim to replace worn out batteries. This will be carried out with the aid of representative experiments in order to understand the technique’s capabilities and limitations. The project forms part of the NSF I/UCRC Center for Tire Research (CenTiRe).

  • Towards a self-powered structural health-monitoring smart tire


    The work herein, led by Sriram Malladi, will study the feasibility of using impedance-based structural health monitoring (SHM) on a tire specimen. The project will also study the possibility of establishing an energy-harvesting concept capable of powering the SHM device and creating a self sustained system. This will be carried out with the aid of a representative experiment in order to understand the technique’s capabilities and limitations. The project forms part of the NSF I/UCRC Center for Tire Research (CenTiRe).
    Publication: Malladi, S., Albakri, M. and Tarazaga, P., A., 2014, “High voltage impedance based SHM of highly damped systems”, ASME Conference on Smart Materials, Adaptive structures and Intelligent Systems, New Port, RI.,September 8-10

  • Static and operational characterization of tires modal vibration with novel non-contact techniques


    Noise caused by motor vehicles is a big part of the challenging environmental problem noise pollution. 30.3 % of noise caused by grounds vehicles is due to tire noise. Furthermore, drivers and passenger are being affected by interior noise caused due to tires. The vibration and noise from tires do not create a comfort problem only, they also make focusing harder tiring the eyes, creating emotional distress and lethargy increasing the chances of accidents.  Therefore, it is vital to reduce the vibration and noise caused by tires. Tires have a very nonlinear complex structural and dynamical characteristic which make the modeling very difficult. To be able to model a tire accurately, we need more experimental data that covers wider range of conditions. The objective of this research is to extend current testing methodologies to a more comprehensive bandwidth that would allow us to understand the dynamics of a tires in various cases as stationary, rotating, loaded, unloaded, and low and high speed conditions. To conduct the experiments for rotating tires, continuous laser scanning and continuous acoustic scanning are being used to obtain more reliable continuous data.

  • Mimicking of hair cells using smart materials

    Hair cells are the sensory receptors of both the auditory system and the vestibular system.  VAST is mainly interested in their function in the cochlea and how they serve as the transduction mechanism which, in a simplified manner, converts acoustical energy into electrical energy to signal the nervous system. Bryan Joyce heads the effort of trying to leverage our understanding of smart materials and biological hair cells in order develop new and innovative sensors.

    This program holds the possibility to one day change how we treat people with hearing loss. Most of us take hearing for granted but about 10% of the population of the US alone suffers from some kind of issues related to this. We are highly motivated to make a drastically change in this area and we are motivated by results of this sort: link.
    Publications:
    Joyce, B., S. and Tarazaga P., A., 2014. “Mimicking the cochlear amplifier in a cantilever beam using nonlinear velocity feedback control,” Smart Materials and Structures, 23(7), p. 075019. doi:10.1088/0964-1726/23/7/075019
    Joyce, B., S., and Tarazaga, P., A., 2014, “Active Artificial Hair Cells Using Nonlinear Feedback Control”, ASME Conference on Smart Materials, Adaptive structures and Intelligent Systems, New Port, RI.,September 8-10


  • Structural health monitoring of railway joints


    In this project, sponsored by the Railway Technology Laboratory (RTL) an affiliated laboratory of the Association American Railroads (AAR), we will study the feasibility of using impedance-based structural health monitoring on railroad components. Structural health monitoring is an area of great technical and scientific interest. As safety and reliability become a priority, monitoring the health of equipments and structures is becoming a necessity. SHM utilizes several techniques to assess the state of structural health, detect damage, and predict the remaining life of the structure. With SHM, schedule-driven inspections and maintenance can be replaced by condition-based maintenance, thus saving time and reducing the life-cycle cost. Heading this endeavor is Mohammad Albakri who will also take into consideration the environmental aspect of this work and will consider robust alternatives for sensor survivability given the harsh environment of the railway system.
    Publication: Albakri, M., Tarazaga, P., A., 2014. “Impedance-Based Structural Health Monitoring Incorporating Frequency Shifts for Damage Identification,” IMAC XXXII, Orlando, FL, February 3-6.

  • 3D Printed Beam With SMA Based Variation of Boundary Conditions

    The objective of this research is to develop a variable stiffness mechanism to vary the quasi static region for the response of a 3D printed accelerometer.  In the present work, shape memory alloys have been used to vary the boundary conditions of a 3D printed beam so as to shift the first natural frequency. The goal is to develop a 3D printed accelerometer with all the necessary circuitry imbedded into it.  Sriram Malladi (PhD Student) supervises the work of two undergraduates Jeff Pope and Tarek Alkhulaidy. The work is also carried out in collaboration with Dr. Williams who runs the DREAMS Lab at VT.


  • High Precision Thermally Actuated Morphing Structures


    High Precision Thermally Actuated Morphing Structures can drastically reduce required stiffness, manufacturing tolerance limits, and deployment accuracy requirements of current space systems.  This morphing structure of interest is an anisogrid tube that has clockwise and counterclockwise helical members that are individually actuated.  Local and global thermal gradients are applied to the structure to introduce accurate six degrees of freedom control.  To evaluate the concept a thermally morphing hexapod will be developed as a reduced system demonstration.  A model of the Hexapod morphing accuracy has been developed to optimize morphing accuracy and to ensure no workspace vacancies and verify control capability. A test article will be developed to verify the morphing capability and correlate the Hexapod model.  This correlated model will be used to develop and define the system parameters impact on workspace maximization, morphing accuracy, and frequency response of the morphing thermally actuated morphing structure.  This methodology will be applied to more complex structures to evaluate other structural configurations and applications.

  • Use of traveling surface waves to reduce friction drag in turbulent flow

    In most systems, friction drag is an obstacle to be hurdled and is a large source of energy inefficiency in airplanes, ships, pipes, etc. By reducing the amount of friction drag between a fluid and a surface, large energy savings are possible. In the turbulent flow, the region closest to the wall is known as the viscous sublayer and is characterized by flow velocity that is linearly dependent upon the distance from the wall. The value of this velocity gradient determines the shear stress and thus drag experienced by the surface. The average velocity gradient is strongly dependent upon temporally and spatially evolving vortex structures in the near wall region. Thus, the goal of this research is to generate traveling surface waves moving along the wall perpendicular to the flow (spanwise direction) that interfere with the production of vortices and consequently reduce the drag on the surface. These spanwise traveling surface waves are generated by two piezoelectric actuators variable in amplitude, frequency, and wavespeed. With the use of an open-loop wind tunnel, the drag reduction on a surface with traveling waves can be experimentally determined.


  • Boeing Composite Shaft Health Monitoring


    Seismic demonstrator for outreach
    The determination of the dynamic properties of a building is necessary for insuring a safe and robust building design as well as for use in the detection of possible structural damage, which can occur after large loading from seismic events or weather-related loading from wind or snow. Any changes in the dynamic properties of a building can potentially indicate that damage has occurred.  The dynamic properties of a building can be determined by monitoring output from sensors, such as accelerometers, that are mounted on the building. In order to better understand the dynamic response of buildings, structural models are often studied on a small scale, where a “shake table” is used to demonstrate and analyze a building’s dynamic response. The current construction of the new SEB provides a unique opportunity to embed sensors in the building and develop a small-scale seismic response demonstrator to create a “living laboratory,” where students and visitors can learn about the design and dynamic analysis of buildings. The VT undergraduate ME4015/6 senior design project team will be responsible for the development of the shake table demonstrator, which will illustrate the engineering concepts associated with the design and dynamic response of buildings, in support of the SEB living laboratory. Additionally, ME4015/6 team members will support the establishment of a network of sensors throughout the SEB to monitor the building’s real-time dynamic signature in order to integrate the actual building response into their shake table demonstration design. This design project provides a benchmark for the development of several unique educational and research programs.

  • Hollow composite synchronous


    Hollow composite synchronous drive shafts are used in tandem rotorcrafts to transmit torque from the transmission to the rotors . Properly maintained drive shafts are critical in order to guarantee proper performance. As any mechanical system, these drive shafts are subject to numerous failure modes which could lead to catastrophic failure and loss of life. Currently all drive shafts are inspected visually by a trained technician. A visual inspection does not guarantee detection of all failure modes, nor provide the highest levels of reliability. Improved reliability and maintainability of these shafts could be achieved via the use of a structural health monitoring system. Our team has been tasked with identifying possible failure modes, designing and investigating the feasibility of a health monitoring or interrogation system which could be used to identify damage or degradation in the composite shafts, and evaluate the feasibility and effectiveness of the monitoring system with simple experimentation and recommendations for future development.

Laboratory address:

Signature Engineering Building
635 Prices Fork Road
Virginia Tech
Blacksburg VA, 24061

Phone: 540-231-3200

Department of Mechanical Engineering
College of Engineering, Virginia Tech
635 Prices Fork Road, Blacksburg, VA 24061
540-231-6045