Department of Mechanical Engineering

Permanent URI for this community

https://hdl.handle.net/10919/23261

The Virginia Tech Mechanical Engineering Department serves its students, alumni, the Commonwealth of Virginia, and the nation through a variety of academic, research and service activities. Our missions are to: holistically educate our students for professional leadership as creative problem-solvers in a diverse society, conduct advanced research for societal advancement, train graduate students for scholarly inquiry, and engage with alumni, industry, government, and community partners through outreach activities. In order to produce engineers prepared for success across a range of career paths, our academic program integrates training in engineering principles, critical thinking, hands-on projects, open-ended problem solving, and the essential skills of teamwork, communication, and ethics.

Browse

Now showing 1 - 20 of 623

3D printed graphene-based self-powered strain sensors for smart tires in autonomous vehicles
Maurya, Deepam; Khaleghian, Seyedmeysam; Sriramdas, Rammohan; Kumar, Prashant; Kishore, Ravi Anant; Kang, Min-Gyu; Kumar, Vireshwar; Song, Hyun-Cheol; Lee, Seul-Yi; Yan, Yongke; Park, Jung-Min (Jerry); Taheri, Saied; Priya, Shashank (2020-10-26)
The transition of autonomous vehicles into fleets requires an advanced control system design that relies on continuous feedback from the tires. Smart tires enable continuous monitoring of dynamic parameters by combining strain sensing with traditional tire functions. Here, we provide breakthrough in this direction by demonstrating tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis. Ink of graphene based material was designed to directly print strain sensor for measuring tire-road interactions under varying driving speeds, normal load, and tire pressure. A secure wireless data transfer hardware powered by a piezoelectric patch is implemented to demonstrate self-powered sensing and wireless communication capability. Combined, this study significantly advances the design and fabrication of cost-effective smart tires by demonstrating practical self-powered wireless strain sensing capability. Designing efficient sensors for smart tires for autonomous vehicles remains a challenge. Here, the authors present a tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis.
3D printing vending machine
(United States Patent and Trademark Office, 2016-08-16)
A vending machine for creating a three-dimensional object having an enclosure having an exterior and interior. The interior receives and houses at least one three-dimensional printer. An interface for accepting an instruction associated with an object to be printed and transmitting the instruction to the printer. A storage section for storing a printed object that provides access to the printed part but limits or prohibits access to the interior.
Accelerometer Based Method for Tire Load and Slip Angle Estimation
Singh, Kanwar Bharat; Taheri, Saied (MDPI, 2019-04-28)
Tire mounted sensors are emerging as a promising technology, capable of providing information about important tire states. This paper presents a survey of the state-of-the-art in the field of smart tire technology, with a special focus on the different signal processing techniques proposed by researchers to estimate the tire load and slip angle using tire mounted accelerometers. Next, details about the research activities undertaken as part of this study to develop a smart tire are presented. Finally, novel algorithms for estimating the tire load and slip angle are presented. Experimental results demonstrate the effectiveness of the proposed algorithms.
Achieving anti-roll bar effect through air management in commercial vehicle pneumatic suspensions
Chen, Yang; Peterson, Andrew W.; Ahmadian, Mehdi (Taylor & Francis, 2019-12-02)
This paper introduces the concept of managing air in commercial vehicle suspensions for reducing body roll. A conventional pneumatic suspension is re-designed to include higher-flow air hoses and dual levelling valves for improving the dynamic response of the suspension to the body roll, which commonly happens at relatively low frequencies. The improved air management allows air to get from the air tank to the airsprings quicker, and also changes the side-to-side suspension air pressure such that the suspension forces can more readily level the vehicle body, much in the same manner as an anti-roll bar (ARB). The results of a multi-domain simulation study in AMESim and TruckSim indicate that the proposed suspension configuration is capable of providing balanced airflow to the truck’s drive-axle suspensions, resulting in balanced suspension forces in response to single lane change and steady-state cornering steering maneuvers. The simulation results further indicate that a truck equipped with the reconfigured suspension experiences a uniform dynamic load sharing, smoother body motion (less roll angle), and improved handling and stability during steering maneuvers commonly occurring in commercial trucks during their intended use.
Acoustic Effects Accurately Predict an Extreme Case of Biological Morphology
Zhang, Z. W.; Truong, S. N.; Müller, Rolf (American Physical Society, 2009-07-17)
The biosonar system of bats utilizes physical baffle shapes around the sites of ultrasound emission for diffraction-based beam forming. Among these shapes, some extreme cases have evolved that include a long noseleaf protrusion (sella) in a species of horseshoe bat. We have evaluated the acoustic cost function associated with sella length with a computational physics approach and found that the extreme length can be predicted accurately from a fiducial point on this function. This suggests that some extreme cases of biological morphology can be explained from their physical function alone.
An acoustic micro-transmitter enabling tracking of sensitive aquatic species in riverine and estuarine environments
Deng, Zhiqun Daniel; Li, Huidong; Lu, Jun; Xiao, Jie; Myjak, Mitchell J.; Martinez, Jayson J.; Wang, Yuxing; Zhang, Jiguang (2021-05-19)
Conservation of aquatic species requires in-depth understanding of their movement and behavior and their interactions with man-made hydraulic structures. Acoustic telemetry is a primary method to remotely track in 3 dimensions (3D) aquatic animals implanted with transmitters. The transmitter's weight and size are the major limiting factors because the transmitter should not affect the animals' natural behavior. Here, we present an acoustic micro-transmitter that weighs 0.08 g in air, only 1/3 that of existing technologies. The transmitter offers a source level of 148 dB (reference: 1 mu Pa at 1 m) and a service life of 30 days at a 5-s transmission rate. Nearly 100% of tagged fish were detected in field studies, demonstrating the viability of this technology for studying species of early life stages. Information resulting from the use of this technology provides valuable insight for ecological and environmental policy making and resource management worldwide.
Acoustic performance of a stretched membrane and porous blanket combination
Thomas, W. A. Jr.; Hurst, Charles J. (Acoustical Society of America, 1976)
The sound absorption performance of an acoustic absorber consisting of a stretched circular membrane placed a short distance in front of a fiberglass blanket was both measured and predicted. Both theoretical and experimental analyses were restricted to plane acoustic waves. Theoretical predictions indicated that the membrane-blanket combination would have a sound power absorption coefficient nearly equal to the sound power absorption coefficient of the blanket alone if the incident acoustic plane wave drove the membrane at one of its resonance frequencies. Theoretical analysis also predicted that the sound power absorption coefficient would approach zero when the membrane was driven at an antiresonance frequency by the incident acoustic plane wave. Experimental agreement with theoretical predictions was good for several membrane-blanket combinations. The results show that membrane-blanket combinations can be effective acoustic absorbers in frequency ranges which do not include the antiresonance frequencies of the membrane. The equations developed may be used to predict the acoustic performance of any membrane-blanket combination.
Acoustics 1991: Active structural acoustic control
Fuller, Chris R.; Silcox, Richard J. (Acoustical Society of America, 1992-01-01)
In summary, the ASAC technique has demonstrated much potential in aerospace and marine applications. Future work will center on extending these techniques to broadband disturbances, more complex structures and improved modeling. It is known that optimizing transducer positions is as important as increasing the number of control channels. A multidisciplinary approach is required to synthesize a design procedure that integrates the elements of structural acoustics, transducer, and control technology. The pay off will be in significant cost and weight savings, and in performance improvements for other industrial applications.
Acousto-dielectric tweezers enable independent manipulation of multiple particles
Shen, Liang; Tian, Zhenhua; Yang, Kaichun; Rich, Joseph; Zhang, Jinxin; Xia, Jianping; Collyer, Wesley; Lu, Brandon; Hao, Nanjing; Pei, Zhichao; Chen, Chuyi; Huang, Tony Jun (AAAS, 2024-08)
Acoustic tweezers have gained substantial interest in biology, engineering, and materials science for their label-free, precise, contactless, and programmable manipulation of small objects. However, acoustic tweezers cannot independently manipulate multiple microparticles simultaneously. This study introduces acousto-dielectric tweezers capable of independently manipulating multiple microparticles and precise control over intercellular distances and cyclical cell pairing and separation for detailed cell-cell interaction analysis. Our acousto-dielectric tweezers leverage the competition between acoustic radiation forces, generated by standing surface acoustic waves (SAWs), and dielectrophoretic (DEP) forces, induced by gradient electric fields. Modulating these fields allows for the precise positioning of individual microparticles at points where acoustic radiation and DEP forces are in equilibrium. This mechanism enables the simultaneous movement of multiple microparticles along specified paths as well as cyclical cell pairing and separation. We anticipate our acousto-dielectric tweezers to have enormous potential in colloidal assembly, cell-cell interaction studies, disease diagnostics, and tissue engineering.
Actin Filaments Couple the Protrusive Tips to the Nucleus through the I-BAR Domain Protein IRSp53 during the Migration of Cells on 1D Fibers
Mukherjee, Apratim; Ron, Jonathan Emanuel; Hu, Hooi Ting; Nishimura, Tamako; Hanawa-Suetsugu, Kyoko; Behkam, Bahareh; Mimori-Kiyosue, Yuko; Gov, Nir Shachna; Suetsugu, Shiro; Nain, Amrinder Singh (Wiley-VCH, 2023-03)
The cell migration cycle, well-established in 2D, proceeds with forming new protrusive structures at the cell membrane and subsequent redistribution of contractile machinery. Three-dimensional (3D) environments are complex and composed of 1D fibers, and 1D fibers are shown to recapitulate essential features of 3D migration. However, the establishment of protrusive activity at the cell membrane and contractility in 1D fibrous environments remains partially understood. Here the role of membrane curvature regulator IRSp53 is examined as a coupler between actin filaments and plasma membrane during cell migration on single, suspended 1D fibers. IRSp53 depletion reduced cell-length spanning actin stress fibers that originate from the cell periphery, protrusive activity, and contractility, leading to uncoupling of the nucleus from cellular movements. A theoretical model capable of predicting the observed transition of IRSp53-depleted cells from rapid stick-slip migration to smooth and slower migration due to reduced actin polymerization at the cell edges is developed, which is verified by direct measurements of retrograde actin flow using speckle microscopy. Overall, it is found that IRSp53 mediates actin recruitment at the cellular tips leading to the establishment of cell-length spanning fibers, thus demonstrating a unique role of IRSp53 in controlling cell migration in 3D.
Activation of bacterial channel MscL in mechanically stimulated droplet interface bilayers
Najem, Joseph S.; Dunlap, Myles D.; Rowe, Ian D.; Freeman, Eric C.; Grant, John Wallace; Sukharev, Sergei; Leo, Donald J. (Springer Nature, 2015-09-08)
MscL, a stretch-activated channel, saves bacteria experiencing hypo-osmotic shocks from lysis. Its high conductance and controllable activation makes it a strong candidate to serve as a transducer in stimuli-responsive biomolecular materials. Droplet interface bilayers (DIBs), flexible insulating scaffolds for such materials, can be used as a new platform for incorporation and activation of MscL. Here, we report the first reconstitution and activation of the low-threshold V23T mutant of MscL in a DIB as a response to axial compressions of the droplets. Gating occurs near maximum compression of both droplets where tension in the membrane is maximal. The observed 0.1-3 nS conductance levels correspond to the V23T-MscL sub-conductive and fully open states recorded in native bacterial membranes or liposomes. Geometrical analysis of droplets during compression indicates that both contact angle and total area of the water-oil interfaces contribute to the generation of tension in the bilayer. The measured expansion of the interfaces by 2.5% is predicted to generate a 4-6 mN/m tension in the bilayer, just sufficient for gating. This work clarifies the principles of interconversion between bulk and surface forces in the DIB, facilitates the measurements of fundamental membrane properties, and improves our understanding of MscL response to membrane tension.
Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
(United States Patent and Trademark Office, 1996-05-07)
An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz.
Active control of coupled wave propagation in fluid-filled elastic cylindrical shells
Brevart, Bertrand J.; Fuller, Chris R. (Acoustical Society of America, 1993-09-01)
A control approach to reduce the total power propagating along fluid-filled elastic cylinders is analytically investigated. The motion of the cylinder is described by the Kennard shell equations fully coupled to the interior acoustic field. The vibration disturbance source is a pre-determined free propagating wave of either n = 0 or n = 1 circumferential order and the control forces considered are appropriate harmonic line forces radially applied to the structure. The radial displacement of the shell wall at discrete locations downstream of control forces is minimized using feedforward quadratic optimal theory. The difference of total power flow through the system before and after control is then used to evaluate the impact of the fluid on the performance of the control approach. For the breathing circumferential mode (n = 0), owing to the coupling between the two media, the fluid decreases the control performance when the disturbance is a structural-type incident wave. When the disturbance is a fluid-type incident wave, with a pressure near field concentrated at the shell wall, significant reductions of the transmitted power flow can be achieved. For the beam mode (n = 1), even though the control is applied to the structure, the fluid increases the control performances below the first acoustic cut-off frequency and decreases it above this frequency.
Active control of far-field sound radiated by a rectangular panel - a general analysis
Pan, Jie; Snyder, Scott D.; Hansen, Colin H.; Fuller, Chris R. (Acoustical Society of America, 1992-04-01)
In this paper a general analysis is presented for the active control of the far-field harmonic sound radiated by a rectangular panel that is built into an infinite baffle. In this analysis, the panel vibration may be generated by either airborne sound (incident sound field) or by structure borne vibrations. The far-field radiated sound is controlled either by acoustical sources or vibration sources. Minimization of both the local sound pressure and the total power output is considered. Analytical results for the particular case involving minimization of the sound pressure at a single point are compared with experimental data. The physical mechanisms involved for different control sources (vibration or acoustic) are demonstrated analytically. For the case of vibration control sources, the panel modal velocity components are adjusted to produce far-field sound control. This can be done either by decreasing their amplitudes, and/or by changing the temporal phases of the panel modes. However, for acoustic control sources, the far-field sound is minimized by alteration of the radiation impedance seen by the vibrating panel and the control sources.
Active control of noise transmission through rectangular plates using multiple piezoelectric or point force actuators
Wang, Bor-Tsuen; Fuller, Chris R.; Dimitriadis, Emilios K. (Acoustical Society of America, 1991-11-01)
This paper analytically demonstrates the use of multiple piezoelectric actuators bonded to the surface and point force actuators applied directly to a plate to reduce sound transmission through the plate. A harmonic plane wave incident on a simply supported, thin rectangular plate mounted in an infinite baffle was considered as the primary source. Both multiple piezoelectric and point force actuators are separately used as secondary (control) sources to attenuate the sound transmission through the plate. An optimal process was applied to obtain the input voltages of the piezoelectric actuators and the magnitude of the point forces, so that the radiated acoustic power can be minimized. Results show that a reduction of sound transmission through the plate is successfully; achieved, if the proper size, number, and position of the piezoelectric or point force actuators are selected. Additionally, a comparison showed that point force actuators provide more effective control of the sound transmission than piezoelectric actuators; however, piezoelectric patches have more practical implementation than point force shakers, because of their low cost and light weight.
Active control of sound radiation due to subsonic wave scattering from discontinuities on fluid-loaded plates. I: Far-field pressure
Gu, Yi; Fuller, Chris R. (Acoustical Society of America, 1991-10-01)
Active control of sound radiation due to subsonic wave scattering from discontinuities represented by a line constraint or by a uniform reinforcing rib positioned on a fluid-loaded infinite plate is analytically studied. The mathematical models are based on the plate vibration and sound radiation due to a line force or a line moment solved in the spectral k domain. For simplicity, the far-field pressure is estimated by the stationary phase approach. Feed-forward control is achieved by adding secondary line forces applied to the plate near the discontinuity. The amplitudes of control forces are determined by the optimal solution of a cost function that integrates the far-field radiated acoustic intensity in a semicylindrical space around the discontinuity. The results show that for subsonic incident waves, high reduction in radiated pressure due to spectral wave scattering at the discontinuities is possible with two active control forces located near the discontinuity. The amount of sound reduction as well as the residual directivity pattern is shown to depend upon the number and location of the control forces.
Active control of sound radiation from a fluid-loaded rectangular uniform plate
Gu, Yi; Fuller, Chris R. (Acoustical Society of America, 1993-01-01)
Active control of sound radiation from a simply supported rectangular fluid-loaded plate is analytically studied. The plate is assumed to be excited by a point force at subsonic frequencies. The solution to the plate motion is based on the admissible functions for an in vacuo homogeneous plate, which is also the basis for Fourier decomposition of the fluid loading [B. E. Sandman, J. Acoust. Soc. Am. 61, 1502-1510 (1977) ]. Feed-forward control is carried out by using point forces applied to the plate. The amplitudes of the control forces are determined by the optimal solution of a quadratic cost function that integrates the far-field radiated acoustic pressure over a hemisphere in the radiation half-space. The results show that for subsonic disturbances, a high global reduction in radiated pressure is possible. For on-resonant excitations, a reasonable sound reduction can be achieved with up to two properly located active control forces, and for off-resonant excitations, up to four control forces may be necessary. The results thus indicate that the active structural acoustic control approach will provide large attenuations in radiated sound when edge mode coupling induced by heavy fluid loading is present. The number and location of the control forces are determined so as to suppress the efficiently radiating modes. The far-field directivity pattern, the plate velocity autospectrum in the two-dimensional wave number domain, and the near-field pressure distribution are studied.
Active control of sound radiation from a plate using a polyvinylidene fluoride volume displacement sensor
Charette, Francois; Berry, Alain; Guigou, Catherine (Acoustical Society of America, 1998-03-01)
This paper presents a new volume displacement sensor (made of shaped strips of PVDF film) and the experimental implementation of this sensor in an active control system. A design strategy for a PVDF sensor detecting the volume displacement induced by a vibrating 2D structure is presented. It is based on the modal representation of the plate response. It actually consists in designing a PVDF sensor, composed of several shaped PVDF strips bonded to the surface of the structure, in such a way that the output signal of the sensor is directly proportional to the volume displacement. The design methodology is based on the experimental measurements of the plate mode shapes (eigenfunctions) and is valid for any type of boundary conditions. The experimental implementation of such a volumetric sensor in an active control system is then presented. The experimental results obtained validates this new type of volume displacement sensor.
Active control of sound radiation from a simply supported beam: Influence of bending near-field waves
Guigou, Catherine; Fuller, Chris R. (Acoustical Society of America, 1993-05-01)
Active control of sound radiation from a baffled simply supported finite beam is analytically studied. The beam is subjected to a harmonic input force and the resulting acoustic field is minimized by applying a control point force. For a single frequency, the flexural response of the beam subject to the input and control forces is expressed in terms of flexural waves of both propagating and near-field types. The optimal control force complex amplitude is derived by minimizing the acoustic radiated pressure at one point located in the far field. The far-field radiated pressure, the displacement of the vibrating beam, and the one-dimensional wave-number spectrum of the beam velocity are extensively studied. In order to further understand control mechanisms, the radiated pressure due to the flexural propagating wave and the flexural near-field wave, respectively, is investigated at the minimization point before and after the control is involved. The analysis shows that, when the control is applied, the combination of the radiated pressure due to the two different types of waves (as their associated radiation is out-of-phase) at the minimization point causes the large pressure attenuation. These results demonstrate that structural near fields are important in terms of predicting performance in active control of structurally radiated sound.
Active isolation of vibration with adaptive structures
Guigou, Catherine; Fuller, Chris R.; Wagstaff, Peter R. (Acoustical Society of America, 1994-07-01)
The problem of actively isolating the periodic vibrations of a rigid machine mounted on a supporting flexible structure is usually approached by applying the active inputs in parallel or series with the passive inputs. This has a number of disadvantages which are related to the development of a high power, compact yet stiff/active isolation unit. In this experimental work, a new approach in which the receiving structure is considered to have adaptive properties is studied. The aim is to control the transmitted vibrations by distributed arrays of piezoelectric transducers bonded to the receiving structure. The experimental rig consists of a rigid thick plate (the machine) supported at the corners by four elastic springs mounted on a thin clamped-free elastic steel plate (the receiving structure). The thick plate is driven by a harmonic force input. Response in the receiving panel is measured with a scanning laser vibrometer. Active inputs to the receiving structure are induced by three pairs of piezoceramic actuators bonded to the surface and configured to induce bending. The error sensors consist of up to two polyvinylidene fluoride (PVDF) strips attached to the panel surface in various positions. The control approach uses a two channel feedforward adaptive LMS algorithm implemented on a TMS320C25. The results show that the first three modes of the system can be controlled efficiently when driven ''on resonance,'' thus effectively isolating the vibrating structure from the ''machine'' raft input. However, when the system is driven ''off resonance,'' the vibrations of the receiving structure proved more difficult td reduce effectively. The paper presents vibration distribution of the receiving plate with and without control for a number of input frequencies as well as a variety of control transducer configurations.

Browse

Browsing Department of Mechanical Engineering by Title

Results Per Page

Sort Options