7,986 research outputs found
Ultrasonic imaging of textured alumina
Ultrasonic images representing the bulk attenuation and velocity of a set of alumina samples were obtained by a pulse-echo contact scanning technique. The samples were taken from larger bodies that were chemically similar but were processed by extrusion or isostatic processing. The crack growth resistance and fracture toughness of the larger bodies were found to vary with processing method and test orientation. The results presented here demonstrate that differences in texture that contribute to variations in structural performance can be revealed by analytic ultrasonic techniques
New camera tube improves ultrasonic inspection system
Electron multiplier, incorporated into the camera tube of an ultrasonic imaging system, improves resolution, effectively shields low level circuits, and provides a high level signal input to the television camera. It is effective for inspection of metallic materials for bonds, voids, and homogeneity
Advancements and Breakthroughs in Ultrasound Imaging
Ultrasonic imaging is a powerful diagnostic tool available to medical practitioners, engineers and researchers today. Due to the relative safety, and the non-invasive nature, ultrasonic imaging has become one of the most rapidly advancing technologies. These rapid advances are directly related to the parallel advancements in electronics, computing, and transducer technology together with sophisticated signal processing techniques. This book focuses on state of the art developments in ultrasonic imaging applications and underlying technologies presented by leading practitioners and researchers from many parts of the world
A method for delineation of bone surfaces in photoacoustic computed tomography of the finger
Photoacoustic imaging of interphalangeal peripheral joints is of interest in
the context of using the synovial membrane as a surrogate marker of rheumatoid
arthritis. Previous work has shown that ultrasound produced by absorption of
light at the epidermis reflects on the bone surfaces within the finger. When
the reflected signals are backprojected in the region of interest, artifacts
are produced, confounding interpretation of the images. In this work, we
present an approach where the photoacoustic signals known to originate from the
epidermis, are treated as virtual ultrasound transmitters, and a separate
reconstruction is performed as in ultrasound reflection imaging. This allows us
to identify the bone surfaces. Further, the identification of the joint space
is important as this provides a landmark to localize a region-of-interest in
seeking the inflamed synovial membrane. The ability to delineate bone surfaces
allows us not only to identify the artifacts, but also to identify the
interphalangeal joint space without recourse to new US hardware or a new
measurement. We test the approach on phantoms and on a healthy human finger
Ultrasonic Imaging Systems
The use of ultrasonic imaging systems for non-destructive evaluation is increasing, with particular interest being paid to research into real time and quasi-real time imaging systems. Photos are shown which were taken using an electronically scanned and focused real time ultrasonic imaging system. The system can be operated with longitudinal waves, shear waves, Rayleigh waves, and lamb waves in the 1.5 MHz to 3.5 MHz frequency range, and has been successfully used on composite materials (boron fiber epoxy on titanium) and on a number of metals (steel, aluminum, and titanium). This system has been operated in both transmission and reflection modes; examples of each are shown
Local Oscillatory Rheology from Echography
Local Oscillatory Rheology from Echography (LORE) consists in a traditional
rheology experiment synchronized with high-frequency ultrasonic imaging which
gives access to the local material response to oscillatory shear. Besides
classical global rheological quantities, this method provides quantitative
time-resolved information on the local displacement across the entire gap of
the rheometer. From the local displacement response, we compute and decompose
the local strain in its Fourier components and measure the spatially-resolved
viscoelastic moduli. After benchmarking our method on homogeneous Newtonian
fluids and soft solids, we demonstrate that this technique is well suited to
characterize spatially heterogeneous samples, wall slip, and the emergence of
nonlinearity under large amplitude oscillatory stress in soft materials.Comment: 10 pages, 5 figures, submitted to Phys. Rev. Applie
A match coefficient approach for damage imaging in structural components by ultrasonic synthetic aperture focus
Ultrasonic Synthetic Aperture Focus (SAF) techniques are commonly used to image structural defects. In this paper, a variation of SAF based on ideas borrowed from Matched Field Processing (MFP) is evaluated to reduce artifacts and sidelobes of the resulting images. In particular, instead of considering the full RF ultrasonic waveforms for the SAF time backpropagation, only selected features from the waveforms are utilized to form a “data vector” and a “replica” (expected) vector of MFP. These vectors are adaptive for the pair of transmitter-receiver and the focus point. The image is created as a matched filter between these two vectors. Experimental results are shown for an isotropic and homogenous metallic plate with simulated defects, probed by six piezoelectric patches used as receivers or transmitters
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