Ongoing research and projects at VAST
In this section of our website, we will discuss some of the ongoing project that we are working on. For collaborative efforts and past projects please visit those sections of our website.
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.
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.
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
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
Use with permission from Widex ©
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
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
Railway insulated joint © 2013 Albakri
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.
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
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.
Aquatic vehicle propulsion by means of travelling waves
The purpose of this project is to couple a solid-state structural propulsion design with a wireless control system to navigate through a liquid medium. This novel approach leverages the structural design capabilities and ties them to performance requirements through solids state manipulation and activation. The solid-state structural propulsion will be generated by traveling waves which will eliminate the need for conventional propulsion methods, such as propellers or jet propulsion. This design also incorporates the steering component with the propulsion as opposed to having separate systems. This will allow the vehicle to be completely scalable which would allow the design to be as small as the customer would like it. The vehicle will excel in withstanding high-pressures and moving through difficult or sensitive environments. The vehicle could also be configured to perform data acquisition, which could be useful for scientific research in areas that would be difficult to access.
Dynamic testing and characterization of Virginia Tech's new Signature Engineering Building (SEB)
Picture by Malladi ©
Instrumentation and dynamic characterization is being implemented on Virginia Tech's Signature Engineering Building (SEB). The projects' aims are twofold. First, we intend to build a research platform or benchmark from which several types of data can be surveyed from the building and feed openly to the community at-large. Second, the project also aims to provide such data for class implementation, giving students real-life data to study. Course examples: digital signal processing (DSP), vibrations, senior labs, mechatronics, etc.
The project requires a great deal of manpower as this is not your conventional lab instrumentation project. Some of our members can be seen on the left with a large group of volunteers. If you are interested in helping and getting some extra experiences under your belt, we are always looking for more volunteers. This project is headed by Joe Hamilton.
Part of this work is in collaboration with Dr. Nima Ameri from the University of Bristol.
The project requires a great deal of manpower as this is not your conventional lab instrumentation project. Some of our members can be seen on the left with a large group of volunteers. If you are interested in helping and getting some extra experiences under your belt, we are always looking for more volunteers. This project is headed by Joe Hamilton.
Part of this work is in collaboration with Dr. Nima Ameri from the University of Bristol.
Non-contact excitation techniques for ultra lightweight systems
Picture by P. Tarazaga ©
Testing of ultra lightweight structures is extremely challenging from various points of view. The use of sensors can easily mass load a structure and greatly affect its dynamic behavior. This hinders the ability to properly study the systems dynamics and can frustrate the validation process between models and experiments. In some cases, the use of non-contact sensors, such as laser vibrometers, can be used to alleviate this problem, although it is not always feasible. In much the same way, the excitation source can deliver many adverse effects. Although techniques such as speaker/acoustic excitation and boundary excitation are sometimes used, they both suffer from delivering a distributed load on the structure. In most cases, this load distribution cannot be characterized and/or is incorrectly assumed as uniform. This also produces considerable errors in the experimental data as it is being processed, which leads to incorrect validation and updating of models. The work here studies the possibility of using a single point "non-contact" excitation by characterizing a pulse of air that is used as the source of excitation. This is implemented experimentally on a 25-micron thick membrane used to simulate inflatable satellite optics.
Model reduction and stability considerations for finite domain time difference (FDTD) acoustic models
Reduced Models © Tarazaga
Finite difference time domain (FDTD) models for predicting acoustic propagation can have an extremely large number of degrees of freedom making it hard to solve and requiring large computational effort. This is due to the small discretization required to accurately approximate the spatial and time domain partial derivatives. This work addresses this problem using Krylov based model reduction techniques by finding a projection such that the reduced system is considerably smaller while maintaining the dominant system dynamics. The system equations are formulated in such a manner that the velocity and pressure can be updated simultaneously, for each iteration, in one matrix. Conventionally the velocity profile is solved at a particular time step first and then used to update the pressure. This two-step process is then avoided and the reduction technique can be applied to one matrix instead of two. The final structure of this updating matrix is not symmetric, thus the Arnoldi method is implemented to obtain the projection.
Currently we are focusing on the stability condition of these reduced systems.
Publication:
Tarazaga, P. A., Johnson, M.E., Inman, D.J., 2008. “Model Reduction of FDTD Acoustic Propagation Models Using Arnoldi” Noise-Con 2008 and SQS, Dearborn, Michigan, July 28-31.
Currently we are focusing on the stability condition of these reduced systems.
Publication:
Tarazaga, P. A., Johnson, M.E., Inman, D.J., 2008. “Model Reduction of FDTD Acoustic Propagation Models Using Arnoldi” Noise-Con 2008 and SQS, Dearborn, Michigan, July 28-31.