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Articles 1 - 30 of 185

Full-Text Articles in Physics

High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian Jan 2019

High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian

Mechanical Engineering Publications

Visual inspections for identifying focusing points in inertial microfluidic flows are prone to misinterpreting stable locations and focusing shifts in the case of non-trivial focusing patterns. We develop and deploy an approach for automating the calculation of focusing patterns for a general channel geometry, and thereby reduce the dependence on empirical/visual procedures to confirm the presence of stable locations. We utilize concepts from interpolation theory (to represent continuous force-fields using discrete points), and stability theory to identify "basins of attraction" and quantitatively identify stable equilibrium points. Our computational experiments reveal that predicting equilibrium points accurately requires upto ×10-20 times ...


Shape-Design For Stabilizing Micro-Particles In Inertial Microfluidic Flows, Aditya Kommajosula, Daniel Stoecklein, Dino Di Carlo, Baskar Ganapathysubramanian Jan 2019

Shape-Design For Stabilizing Micro-Particles In Inertial Microfluidic Flows, Aditya Kommajosula, Daniel Stoecklein, Dino Di Carlo, Baskar Ganapathysubramanian

Mechanical Engineering Publications

Design of microparticles which stabilize at the centerline of a channel flow when part of a dilute suspension is examined numerically for moderate Reynolds numbers (10≤Re≤80). Stability metrics for particles with arbitrary shapes are formulated based on linear-stability theory. Particle shape is parametrized by a compact, Non-Uniform Rational B-Spline (NURBS)-based representation. Shape-design is posed as an optimization problem and solved using adaptive Bayesian optimization. We focus on designing particles for maximal stability at the channel-centerline robust to perturbations. Our results indicate that centerline-focusing particles are families of characteristic "fish"/"bottle"/"dumbbell"-like shapes, exhibiting fore-aft asymmetry. A ...


Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao Dec 2018

Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao

Aerospace Engineering Publications

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from 25-340 K. For ...


Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer Jul 2018

Current Progress And Future Challenges In Rare-Earth-Free Permanent Magnets, Jun Cui, Matthew J. Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer

Ames Laboratory Accepted Manuscripts

Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as ...


Theoretical And Experimental Investigation Of Forward Spatter Of Blood From A Gunshot, P. M. Comiskey, A. L. Yarin, Daniel Attinger Jun 2018

Theoretical And Experimental Investigation Of Forward Spatter Of Blood From A Gunshot, P. M. Comiskey, A. L. Yarin, Daniel Attinger

Mechanical Engineering Publications

A theoretical model predicting forward blood spatter patterns resulting from a round nose bullet gunshot wound is proposed. The chaotic disintegration of a blood layer located ahead and aside of the bullet is considered in the framework of percolation theory. The size distribution of blood drops is determined, which allows for the prediction of a blood spatter cloud being ejected from the rear side of the target where the bullet exits. Then, droplet trajectories are numerically predicted accounting for gravity and air drag, which is affected by the collective aerodynamic interaction of drops through air. The model predicts the number ...


Tip-Enhanced Raman Scattering Of Dna Aptamers For Listeria Monocytogenes, Siyu He, Hongyuan Li, Carmen L. Gomes, Dmitri V. Voronine May 2018

Tip-Enhanced Raman Scattering Of Dna Aptamers For Listeria Monocytogenes, Siyu He, Hongyuan Li, Carmen L. Gomes, Dmitri V. Voronine

Mechanical Engineering Publications

Optical detection and conformational mapping of aptamers are important for improving medical and biosensing technologies and for better understanding of biological processes at the molecular level. The authors investigate the vibrational signals of deoxyribonucleic acid aptamers specific to Listeria monocytogenes immobilized on gold substrates using tip-enhanced Raman scattering (TERS) spectroscopy and nanoscale imaging. The authors compare topographic and nano-optical signals and investigate the fluctuations of the position-dependent TERS spectra. They perform spatial TERS mapping with 3 nm step size and discuss the limitation of the resulting spatial resolution under the ambient conditions. TERS mapping provides information about the chemical composition ...


An Instrument For In Situ Time-Resolved X-Ray Imaging And Diffraction Of Laser Powder Bed Fusion Additive Manufacturing Processes, Nicholas P. Calta, Jenny Wang, Andrew M. Kiss, Aiden A. Martin, Philip J. Depond, Gabriel M. Guss, Vivek Thampy, Anthony Y. Fong, Johanna Nelson Weker, Kevin H. Stone, Christopher J. Tassone, Matthew J. Kramer, Michael F. Toney, Anthony Van Buuren, Manyalibo J. Matthews May 2018

An Instrument For In Situ Time-Resolved X-Ray Imaging And Diffraction Of Laser Powder Bed Fusion Additive Manufacturing Processes, Nicholas P. Calta, Jenny Wang, Andrew M. Kiss, Aiden A. Martin, Philip J. Depond, Gabriel M. Guss, Vivek Thampy, Anthony Y. Fong, Johanna Nelson Weker, Kevin H. Stone, Christopher J. Tassone, Matthew J. Kramer, Michael F. Toney, Anthony Van Buuren, Manyalibo J. Matthews

Ames Laboratory Accepted Manuscripts

In situ X-ray-based measurements of the laser powder bed fusion (LPBF) additive manufacturing process produce unique data for model validation and improved process understanding. Synchrotron X-ray imaging and diffraction provide high resolution, bulk sensitive information with sufficient sampling rates to probe melt pool dynamics as well as phase and microstructure evolution. Here, we describe a laboratory-scale LPBF test bed designed to accommodate diffraction and imaging experiments at a synchrotron X-ray source during LPBF operation. We also present experimental results using Ti-6Al-4V, a widely used aerospace alloy, as a model system. Both imaging and diffraction experiments were carried out at the ...


An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox Feb 2018

An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox

Chemical and Biological Engineering Publications

The extended quadrature method of moments (EQMOM) for the solution of population balance equations (PBE) is implemented in the open-source computational fluid dynamic (CFD) toolbox OpenFOAM as part of the OpenQBMM project. The moment inversion procedure was designed (Nguyen et al., 2016) to maximize the number of conserved moments in the transported moment set. The algorithm is implemented in a general structure to allow the addition of other kernel density functions defined on R+, and arbitrary kernels to describe physical phenomena involved in the evolution of the number density function. The implementation is verified with a set of zero-dimensional cases ...


Multiphysics Analysis Of Electrochemical And Electromagnetic System Addressing Lithium-Ion Battery And Permanent Magnet Motor, Abhishek Sarkar Jan 2018

Multiphysics Analysis Of Electrochemical And Electromagnetic System Addressing Lithium-Ion Battery And Permanent Magnet Motor, Abhishek Sarkar

Graduate Theses and Dissertations

Lithium-ion batteries are the leading energy storage technology in the electronic-driven society. With the need for portable, long-life electronics the demand for lithium batteries has escalated over the decade. Lithium-ion batteries show remarkable electrochemical characteristics, including but not limited to, long cycle-life, high cut-off voltages and high energy-density. However, lithium-ion cells are problematic to design due to their inherent thermal and/or mechanical instability. The objective of the current research framework is to establish the criteria causing thermo-mechanical failure of the battery systems, material properties effecting the performance, and model cycle-life degradation due to electrolyte loss by solid electrolyte interface ...


Interface Energy Transport Of Two-Dimensional (2d) Mos2, Pengyu Yuan Jan 2018

Interface Energy Transport Of Two-Dimensional (2d) Mos2, Pengyu Yuan

Graduate Theses and Dissertations

The bottleneck of most modern technologies and energy solutions has been attributed to the thermal problems at the nanoscale. Especially, the thermal transport across interfaces and in-plane direction can significantly influence the overall performance of 2D nanosystems. So accurate thermal-physical characterization of the 2D materials is very important for both fundamental research and industrial applications.

Focusing on 2D mechanically exfoliated MoS2, at first, we conduct a detailed temperature and laser power dependent micro-Raman spectroscopy study of FL MoS2 (4.2 to 45 nm thick) on c-Si substrate. We measured the interfacial thermal resistance (R) at room temperature decreases with increased ...


Deformation, Lattice Instability, And Metallization During Solid-Solid Structural Transformations Under General Applied Stress Tensor: Example Of Si I -> Si Ii, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson Jan 2018

Deformation, Lattice Instability, And Metallization During Solid-Solid Structural Transformations Under General Applied Stress Tensor: Example Of Si I -> Si Ii, Nikolai A. Zarkevich, Hao Chen, Valery I. Levitas, Duane D. Johnson

Materials Science and Engineering Publications

Density functional theory (DFT) was employed to study the stress-strain behavior, elastic instabilities, and metallization during a solid-solid phase transformation (PT) between semiconducting Si I (cubic A4) and metallic Si II (tetragonal A5 structure) when subjected to a general stress tensor. With normal stresses (σ1, σ2, σ3) acting along ⟨110⟩, ⟨11¯0⟩, and ⟨001⟩, respectively, dictating the simulation cell, we determine combinations of 6 independent stresses that drive a lattice instability for the Si I→Si II PT, and a semiconductor-metal electronic transition. Metallization precedes the structural PT, hence, a stressed Si I can be a metal. Surprisingly, a stress-free ...


Hydrodynamics Of Back Spatter By Blunt Bullet Gunshot With A Link To Bloodstain Pattern Analysis, P. M. Comiskey, A. L. Yarin, Daniel Attinger Jul 2017

Hydrodynamics Of Back Spatter By Blunt Bullet Gunshot With A Link To Bloodstain Pattern Analysis, P. M. Comiskey, A. L. Yarin, Daniel Attinger

Mechanical Engineering Publications

A theoretical model describing the blood spatter pattern resulting from a blunt bullet gunshot is proposed. The predictions are compared to experimental data acquired in the present work. This hydrodynamic problem belongs to the class of the impact hydrodynamics with the pressure impulse generating the blood flow. At the free surface, the latter is directed outwards and accelerated toward the surrounding air. As a result, the Rayleigh-Taylor instability of the flow of blood occurs, which is responsible for the formation of blood drops of different sizes and initial velocities. Thus, the initial diameter, velocity, and acceleration of the atomized blood ...


Hybrid Fs/Ps Coherent Anti-Stokes Raman Scattering For Multiparameter Measurements Of Combustion And Nonequilibrium, Chloe Elizabeth Dedic Jan 2017

Hybrid Fs/Ps Coherent Anti-Stokes Raman Scattering For Multiparameter Measurements Of Combustion And Nonequilibrium, Chloe Elizabeth Dedic

Graduate Theses and Dissertations

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is developed for measuring internal energy distributions, species concentration, and pressure for highly dynamic gas-phase environments. Systems of interest include next-generation combustors, plasma-based manufacturing and plasma-assisted combustion, and high-speed aerodynamic flow. These challenging environments include spatial variations and fast dynamics that require the spatial and temporal resolution offered by hybrid fs/ps CARS.

A novel dual-pump fs/ps CARS approach is developed to simultaneously excite pure-rotational and rovibrational Raman coherences for dynamic thermometry (300--2400 K) and detection of major combustion species. This approach was also used to measure single-shot vibrational ...


Experimental Investigation Of Inclined Cantilever Beams In Vertically Falling Soap Films, Veera Brahmendra Chary Sajjanapu Jan 2017

Experimental Investigation Of Inclined Cantilever Beams In Vertically Falling Soap Films, Veera Brahmendra Chary Sajjanapu

Graduate Theses and Dissertations

Here we investigate the dynamic response of cantilever beam at various angles of attack using theory and experiments. The problem is motivated by separate wind tunnel experiments using energy producing piezoelectric cantilevers. Assuming small vibrational amplitudes, we utilize the Euler-Bernoulli beam theory to test semi-empirical correlations that are compared with measured quantities. To utilize the beam theory, we estimate the aerodynamic loading on the cantilever as the sum of a steady and harmonic component, each proportional to the aerodynamic pressure. Dynamically similar cantilever beams (5000 $<$ Re $<$ 25000) with varying flexural rigidity are studied in a vertically falling soap film experiment to visualize the wake and vortex shedding flow characteristics. High speed video and image analysis were used to estimate quantities such as the average displacement, vibration amplitude and frequency for the cantilevers. From the analysis we find the steady displacement force is linear with respect to the aerodynamic pressure. We define a coefficient which is the ratio of steady displacement force and aerodynamic pressure. We call this steady aerodynamic loading coefficient. We further show that there is a significant effect of inclination on this coefficient. Furthermore, this coefficient was found to be dependent on the flexible nature of the cantilever beam. The wake structure and the vortex shedding are visualized and analyzed for the vortex shedding frequency which is plotted against the frequency of beam vibrations. We also explore the relationship between the Strouhal, Reynolds numbers and angle of attack.


Characterization Of Chlorella Vulgaris And Chlorella Protothecoides Using Multi-Pixel Photon Counters In A 3d Focusing Optofluidic System, Jonathan B. Vander Wiel, Jonathan D. Mikulicz, Michael R. Boysen, Niloofer Hashemi, Patrick Kalgren, Levi M. Nauman, Seth J. Baetzold, Gabrielle G. Powell, Qing He, Nicole Nastaran Hashemi Jan 2017

Characterization Of Chlorella Vulgaris And Chlorella Protothecoides Using Multi-Pixel Photon Counters In A 3d Focusing Optofluidic System, Jonathan B. Vander Wiel, Jonathan D. Mikulicz, Michael R. Boysen, Niloofer Hashemi, Patrick Kalgren, Levi M. Nauman, Seth J. Baetzold, Gabrielle G. Powell, Qing He, Nicole Nastaran Hashemi

Mechanical Engineering Publications

Analysis of microparticle size and fluorescence intensity can be used to classify microparticles. We designed and fabricated an optofluidic system that characterizes microparticles, including fluorescent microparticles and microalgae. A new type of multi-pixel photon counter (MPPC) was employed to miniaturize the device, lower its power consumption, and make it insensitive to magnetic fields. The system uses a 635 nm laser for excitation of the microparticles' fluorescence. The scattered light from the fluorescent microparticles, as well as Chlorella vulgaris and Chlorella protothecoides, were measured. Additionally, we analyzed the width and height of the measured signals generated as a result of microparticles ...


Big Area Additive Manufacturing Of High Performance Bonded Ndfeb Magnets, Li Ling, Angelica Tirado, I. C. Nlebedim, Orlando Rios, Brian Post, Vlastimil Kunc, R. R. Lowden, Edgar Lara-Curzio, Magnet Applications, Inc., Thomas A. Lograsso, M. Parans Paranthaman Oct 2016

Big Area Additive Manufacturing Of High Performance Bonded Ndfeb Magnets, Li Ling, Angelica Tirado, I. C. Nlebedim, Orlando Rios, Brian Post, Vlastimil Kunc, R. R. Lowden, Edgar Lara-Curzio, Magnet Applications, Inc., Thomas A. Lograsso, M. Parans Paranthaman

Ames Laboratory Publications

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties ...


Prediction Of Blood Back Spatter From A Gunshot In Bloodstain Pattern Analysis, P. M. Comiskey, A. L. Yarin, S. Kim, Daniel Attinger Aug 2016

Prediction Of Blood Back Spatter From A Gunshot In Bloodstain Pattern Analysis, P. M. Comiskey, A. L. Yarin, S. Kim, Daniel Attinger

Mechanical Engineering Publications

A theoretical model for predicting and interpreting blood-spatter patterns resulting from a gunshot wound is proposed. The physical process generating a backward spatter of blood is linked to the Rayleigh-Taylor instability of blood accelerated toward the surrounding air, allowing the determination of the initial distribution of drop sizes and velocities. Then the motion of many drops in air is considered with governing equations accounting for gravity and air drag. Based on these equations, a numerical solution is obtained. It predicts the atomization process, the trajectories of the back-spatter drops of blood from the wound to the ground, the impact angle ...


Thermodynamics And Historical Relevance Of A Jetting Thermometer Made Of Chinese Zisha Ceramic, Vincent Lee, Daniel Attinger Jul 2016

Thermodynamics And Historical Relevance Of A Jetting Thermometer Made Of Chinese Zisha Ceramic, Vincent Lee, Daniel Attinger

Mechanical Engineering Publications

Following a recent trend of scientific studies on artwork, we study here the thermodynamics of a thermometer made of zisha ceramic, related to the Chinese tea culture. The thermometer represents a boy who “urinates” shortly after hot water is poured onto his head. Long jetting distance is said to indicate that the water temperature is hot enough to brew tea. Here, a thermodynamic model describes the jetting phenomenon of that pee-pee boy. The study demonstrates how thermal expansion of an interior air pocket causes jetting. A thermodynamic potential is shown to define maximum jetting velocity. Seven optimization criteria to maximize ...


Influence Of Grain Size Distribution On Ultrasonic Scattering, Andrea Arguelles, Joseph A. Turner Jan 2016

Influence Of Grain Size Distribution On Ultrasonic Scattering, Andrea Arguelles, Joseph A. Turner

Review of Progress in Quantitative Nondestructive Evaluation

Elastic wave scattering at grain boundaries in polycrystalline media can be quantified to determine microstructural properties. The amplitude drop observed for coherent wave propagation (attenuation) as well as diffuse-field scattering events (such as the single-scattering response) have been extensively studied. In all cases, the scattering shows a clear dependence on grain size, grain geometric morphology, and material texture (i.e., macroscale anisotropy). Scattering models used to quantify such scattering experiments are often developed under the assumption of a single effective grain diameter implying a very narrow distribution of grain size throughout the sample. However, several microscopy studies suggest that most ...


Novel Methods To Measure Surface Wave Velocity By Using Laser-Generated Tone-Burst Surface Wave, Ju-Ho Lee, Jongbeom Kim, Kyung-Young Jhang Jan 2016

Novel Methods To Measure Surface Wave Velocity By Using Laser-Generated Tone-Burst Surface Wave, Ju-Ho Lee, Jongbeom Kim, Kyung-Young Jhang

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic wave velocity is a characteristic of material, which is considered as a significant factor of nondestructive testing (NDT) techniques. Generally, bulk wave velocity is measured by Time-of-Flight (TOF) of pulse echo from back wall reflection; however, pulse-echo method cannot be applied to surface acoustic wave in a case that an edge does not exist in a close range. Even when we use through-transmission method, it is quite cumbersome to measure the accurate distance between transmitter and receiver; this problem is more critical when using contact angle transducers.

This study proposes two new signal processing methods to measure laser-generated surface ...


Calibration Of Air-Coupled Transducers For Absolute Nonlinear Ultrasonic Measurements, Nicholas Selby, David Torello, Jin-Yeon Kim, Laurence J. Jacobs Jan 2016

Calibration Of Air-Coupled Transducers For Absolute Nonlinear Ultrasonic Measurements, Nicholas Selby, David Torello, Jin-Yeon Kim, Laurence J. Jacobs

Review of Progress in Quantitative Nondestructive Evaluation

We describe a novel calibration technique of air-coupled transducers for nonlinear ultrasonic measurements through homogenous, isotropic media. Our calibration technique combines laser interferometrywith a model-based approach to derive a relationship between received force at the transducer face and the measured output voltage. Conventional nonlinear ultrasonic measurement techniques have relied upon contact receiving transducers that are heavily influenced by contact conditions (e.g. inconsistent coupling) and laser interferometers that are prohibitively expensive and rely on a mirror-finished surface or complicated optics. Air-coupled transducers are significantly less expensive than laser interferometers and are robust relative to surface conditions, but current calibration techniques ...


Thermal Diffusivity Measurements On Certified Standards Using Flash Ir Thermography, Vijay Nalladega, Bryon Knight Jan 2016

Thermal Diffusivity Measurements On Certified Standards Using Flash Ir Thermography, Vijay Nalladega, Bryon Knight

Review of Progress in Quantitative Nondestructive Evaluation

Infrared thermography has been increasingly used as an NDE tool for detection of defects in different types of components. At GE Global Research, the flash IR system is routinely used for inspecting for delaminations, porosity, and coating thickness and integrity. For defects such as delaminations and other larger defects, single-sided imaging, where the heat buildup due to the presence of defects can be visualized is used. However, in some cases, measurement of thermal diffusivity can also be used as an indicator of presence of damage. In this study, we report our findings on the accuracy of the diffusivity measurements using ...


An Annular Array Mpt For Enhanced Generation Of Omnidirectional Sh Waves In A Plate, Chung Il Park, Hong Min Seung, Jun Kyu Lee, Yoon Young Kim Jan 2016

An Annular Array Mpt For Enhanced Generation Of Omnidirectional Sh Waves In A Plate, Chung Il Park, Hong Min Seung, Jun Kyu Lee, Yoon Young Kim

Review of Progress in Quantitative Nondestructive Evaluation

If guided wave transducers are fabricated in an annular array type, the excitation and measurement of target guided wave modes could be considerably enhanced (see, e.g., [1]). Accordingly, various annular array transducers have been developed, including those generating omnidirectional Lamb waves in a plate. Here, we newly consider an annular array type MPT (magnetostrictive patch transducer) to generate enhanced SH (shear-horizontal) waves in a plate. This annular array MPT is based on our earlier development of an omnidirectional SH wave MPT [2]. For wave field analysis by the annular array SH wave MPT, the strain response in a plate ...


Characterization Of An Electrodynamic Flexural Transducer For Air-Coupled Ultrasonics, Tobias J. R. Eriksson, Yichao Fan, Sivaram Nishal Ramadas, Steve Dixon Jan 2016

Characterization Of An Electrodynamic Flexural Transducer For Air-Coupled Ultrasonics, Tobias J. R. Eriksson, Yichao Fan, Sivaram Nishal Ramadas, Steve Dixon

Review of Progress in Quantitative Nondestructive Evaluation

Air-coupled ultrasonics (ACU) has had an increasing importance in non-destructive evaluation (NDE), particularly for inspection of composite materials for example in the aerospace industry [1]. The main problem for ACU is the large impedance mismatch between piezoelectric ceramics and air, and a lack of suitable materials for impedance matching [2]. Many different solutions to this problem have led to a range of transducer technologies and designs, e.g. composite transducers and capacitive micromachined ultrasonic transducers (CMUTs). In previous work by the authors three designs of a novel ACU transducer, combining electromagnetic coupling and flexural mode vibrations, so called electrodynamic flexural ...


Study Of Metal Magnetic Memory (Mmm) Technique Using Permanently Installed Magnetic Sensor Arrays, Zhichao Li, Steve Dixon, Peter B. Nagy, Peter Cawley, Rollo Jarvis Jan 2016

Study Of Metal Magnetic Memory (Mmm) Technique Using Permanently Installed Magnetic Sensor Arrays, Zhichao Li, Steve Dixon, Peter B. Nagy, Peter Cawley, Rollo Jarvis

Review of Progress in Quantitative Nondestructive Evaluation

The Metal magnetic memory (MMM) technique is marketed as a non-destructive testing method to evaluate stress concentration for ferromagnetic materials by measuring variations of the self-magnetic leakage field (SMLF) distribution on the specimen surface. This method has been implemented as a periodic screening inspection tool by several companies, and has been reported to be capable of detecting stress concentration in some instances. However, recent literature has suggested that the performance can be unreliable, with many false-calls; however, the reason for the false calls has not been satisfactorily investigated. In this paper, the normal and tangential components of the stress induced ...


Characterization Of Multi-Layered Impact Damage In Organic Matrix Composites Using Thermography, Travis Whitlow, Satamachary Sathish, Sarah Wallentine Jan 2016

Characterization Of Multi-Layered Impact Damage In Organic Matrix Composites Using Thermography, Travis Whitlow, Satamachary Sathish, Sarah Wallentine

Review of Progress in Quantitative Nondestructive Evaluation

Organic matrix composites (OMCs) are increasingly being integrated into aircraft structures. However, these components are susceptible to impact related delamination, which, on aircrafts, can occur due to a number of reasons during aircraft use and maintenance. Quantifying impact damage is an important aspect for life-management of aircraft and requires in-depth knowledge of the damage zone on a ply-by-ply level. Traditionally, immersion ultrasound has provided relative high resolution images of impact damage. Ultrasonic time-of-flight data can be used to determine the front surface delamination depth and an approximation of the delaminated area. However, such inspections require the material to be immersed ...


A Novel Thermosonic Imaging System For Non-Destructive Testing, Dan Xiang, Micheal Long, Carson Willey Jan 2016

A Novel Thermosonic Imaging System For Non-Destructive Testing, Dan Xiang, Micheal Long, Carson Willey

Review of Progress in Quantitative Nondestructive Evaluation

Thermosonic (Sonic IR) Imaging is a new nondestructive testing (NDT) technique that uses high-frequency sonic excitation together with infrared (IR) detection to image surface and subsurface defects. This Sonic IR imaging technique uses a short (usually fraction of a second) pulse of high frequency (typically 20-40 kHz) sound which is applied at some convenient point on the surface of the object under inspection to produce localized frictional heating at the defect. An IR camera images the heating of the surface resulting from the effects of friction or other irreversible internal surface interactions in the vicinity of defects. These effects result ...


Non-Contact Evaluation Of Residual Stress In Metals With Laser-Generated Surface Acoustic Waves And A Point-Like Fiber-Optic Sagnac Detector, Łukasz Ambrozinski, Ivan Pelivanov, Michael B. Prime, Matthew O’Donnell Jan 2016

Non-Contact Evaluation Of Residual Stress In Metals With Laser-Generated Surface Acoustic Waves And A Point-Like Fiber-Optic Sagnac Detector, Łukasz Ambrozinski, Ivan Pelivanov, Michael B. Prime, Matthew O’Donnell

Review of Progress in Quantitative Nondestructive Evaluation

Stress can remain in a material after the original load is removed. It can be purposely introduced to improve the properties of structural components, but can also be undesired, shortening a component’s lifetime, changing its original geometry or even leading to failure.

There is a large spectrum of problems where residual stress must be evaluated. An acousto-elastic approach is non-destructive and uses stress-dependent alterations in ultrasound (US) speed of bulk or surface modes [1]. However, these alterations are incredibly small (10-3 ÷ 10-5) and, thus, accurate measurement of both the US wave speed and propagation distance is required. Thickness measurement ...


Excitation Duration And Onset Time Effects In Active Thermography, Steven M. Shepard, James R. Lhota Jan 2016

Excitation Duration And Onset Time Effects In Active Thermography, Steven M. Shepard, James R. Lhota

Review of Progress in Quantitative Nondestructive Evaluation

In flash thermography, the surface of a test piece is excited by a pulse of light from a xenon flash lamp that is powered by a capacitor discharge. Typically, the lamps and power supplies are commercial units designed for photography applications. The equipment most often used for thermography has nominal energy output of 4-6 kJ and duration 3-5 msec. However, the actual optical output is more complex, since the energy rating pertains to the electrical discharge of the capacitors, and does not account for efficiency in converting electrical current to light, or resistive losses in the transfer of energy from ...


Study The Nonlinearity In Sonic Ir Imaging Nde, Xiaoyan Han, Qiuye Yu, Omar Obeidat Jan 2016

Study The Nonlinearity In Sonic Ir Imaging Nde, Xiaoyan Han, Qiuye Yu, Omar Obeidat

Review of Progress in Quantitative Nondestructive Evaluation

Sonic IR Imaging combines pulsed ultrasound excitation and infrared imaging to detect defects in materials. The sound pulse causes rubbing due to non-‐unison motion between faces of defects, and infrared sensors image the temperature map over the target to identify defects. It works in various materials, including metal/metal alloy, ceramics, and composite materials. Its biggest advantage is that it's a fast, wide area NDE technique. It takes only a fraction of a second or a few seconds, depending on the thermal properties of the target, for one test over a few square feet. However, due to the ...