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Full-Text Articles in Engineering
Scatterer Size Estimation In Pulse-Echo Ultrasound Using Focused Sources: Calibration Measurements And Phantom Experiments, Timothy A. Bigelow, William D. O'Brien
Scatterer Size Estimation In Pulse-Echo Ultrasound Using Focused Sources: Calibration Measurements And Phantom Experiments, Timothy A. Bigelow, William D. O'Brien
Timothy A. Bigelow
In a companion paper [T. A. Bigelow and W. D. O'Brien Jr., J. Acoust. Soc. Am. 116, 578 (2004)], theory, supported by simulations, showed that accurate scatterer size estimates could be obtained using highly focused sources provided that the derived generalized attenuation-compensation function was used and the velocity potential field near the focus could be approximated as a three-dimensional Gaussian. Herein, the theory is further evaluated via experimental studies. A calibration technique is developed to find the necessary equivalent Gaussian dimensions for a focused source using reflections obtained from a rigid plane scanned through the focus. Then, the theoretical analysis …
Scatterer Size Estimation In Pulse-Echo Ultrasound Using Focused Sources: Theoretical Approximations And Simulation Analysis, Timothy A. Bigelow, William D. O'Brien
Scatterer Size Estimation In Pulse-Echo Ultrasound Using Focused Sources: Theoretical Approximations And Simulation Analysis, Timothy A. Bigelow, William D. O'Brien
Timothy A. Bigelow
The speckle in ultrasound images has long been thought to contain information related to the tissue microstructure. Many different investigators have analyzed the frequency characteristics of the backscattered signals to estimate the scatterer acoustic concentration and size. Previous work has been mostly restricted to unfocused or weakly focused ultrasound sources, thus limiting its implementation with diagnostically relevant fields. Herein, we derive equations capable of estimating the size of a-scatterer for any reasonably focused source provided that the velocity potential field in the focal region can be approximated as a three-dimensional Gaussian beam, scatterers are a sufficient distance from the source, …
New Stereology For The Recovery Of Grain-Boundary Plane Distributions In The Crystal Frame, Brent L. Adams, Ryan J. Larsen
New Stereology For The Recovery Of Grain-Boundary Plane Distributions In The Crystal Frame, Brent L. Adams, Ryan J. Larsen
Faculty Publications
One of the authors (RJL) is grateful to the Office of Naval Research for fellowship support. BLA acknowledges the support of the NSF through the Materials Research Science and Engineering Center, Carnegie Mellon University (Grant No. DMR-0079996). A new experimental method is given for recovering the probability-distribution function Sv(ns/g). The function Sv(na/g) is the grain-boundary area per unit volume as a function of grain-boundary plane orientation (na), given a lattice misorientation (g) between the adjoining grains. The grain-boundary normal (na) is expressed in the crystal frame in which the misorientation g originates. The proposed method recovers the three-dimensional Sv(na/g) function …
Effects Of Friction Stir Processing On The Microstructure And Mechanical Properties Of Fusion Welded 304l Stainless Steel, Colin J. Sterling
Effects Of Friction Stir Processing On The Microstructure And Mechanical Properties Of Fusion Welded 304l Stainless Steel, Colin J. Sterling
Theses and Dissertations
Friction stir processing (FSP) has been utilized to locally process regions of arc weldments in 304L stainless steel to improve the microstructure and mechanical performance. The cast microstructure and coarse delta-ferrite has been replaced with a fine-grained wrought microstructure. Furthermore, twins were introduced throughout the friction stir processed region. Although sub-surface sigma and carbides were introduced during FSP, their presence is not expected to adversely affect the resulting mechanical or corrosion properties of friction stir processed 304L arc welds. The resulting mechanical properties of FS processed weldments were also an improvement over as-welded arc welds. FSP resulted in an increase …
Effects Of Friction Stir Welding On Polymer Microstructure, Seth R. Strand
Effects Of Friction Stir Welding On Polymer Microstructure, Seth R. Strand
Theses and Dissertations
This work establishes the relationships between several key Friction Stir Welding process parameters and the resulting microstructural and flexural properties of the welded joint. A series of four single parameter experiments were run. The parameters investigated were pin diameter, feedrate, shoe temperature, and pressure time. Butt welds were made in 6 mm thick stress-relieved extruded polypropylene sheet. Three-point bend tests were used to determine the ultimate flexural strength and coincident strain. The maximum bend angle before failure was used to label the welds as "good or bad." An optical microscope capable of cross polarization was used to examine and photograph …
Effect Of Microstructure On The Stability Of Retained Austenite In Transformation-Induced-Plasiticity Steels, I B. Timokhina, P D. Hodgson, E V. Pereloma
Effect Of Microstructure On The Stability Of Retained Austenite In Transformation-Induced-Plasiticity Steels, I B. Timokhina, P D. Hodgson, E V. Pereloma
Faculty of Engineering and Information Sciences - Papers: Part A
Two Fe-0.2C-1.55Mn-1.5Si (in wt pct) steels, with and without the addition of 0.039Nb (in wt pct), were studied using laboratory rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the individual behavior of all …
Effect Of Aging And Deformation On The Microstructure And Properties Of Fe-Ni-Ti Maraging Steel, A Shekhter, H I. Aaronson, M K. Miller, S P. Ringer, E V. Pereloma
Effect Of Aging And Deformation On The Microstructure And Properties Of Fe-Ni-Ti Maraging Steel, A Shekhter, H I. Aaronson, M K. Miller, S P. Ringer, E V. Pereloma
Faculty of Engineering and Information Sciences - Papers: Part A
The age-hardening behavior of Fe−25.3Ni−1.7 Ti (wt pct) alloy both in undeformed specimens and in specimens cold deformed by 10 or 20 pct prior to aging was studied. The microstructural changes during aging were observed using transmission electron microscopy (TEM) and atom probe analysis and there were related to the mechanical properties as measured by microhardness and shear punch testing. An excellent combination of hardness, strength, and ductility was achieved after only 5 seconds aging at 550°C. We propose that this rapid strengthening is due to a dislocation friction effect arising from the formation of a fine dispersion of Ni−Ti …
Role Of Cr And P Additions In The Development Of Microstructure And Texture In Annealed Low Carbon Steels, E V. Pereloma, I B. Timokhina, A I. Nosenkov, J J. Jonas
Role Of Cr And P Additions In The Development Of Microstructure And Texture In Annealed Low Carbon Steels, E V. Pereloma, I B. Timokhina, A I. Nosenkov, J J. Jonas
Faculty of Engineering and Information Sciences - Papers: Part A
The recrystallisation behaviour of four warm rolled steels was investigated during annealing. The extra-low carbon (ELC) steel displayed the highest rate of recrystallisation, the steels with additions of chromium and phosphorus (LC(Cr)), (LC(Cr,P)) recrystallised at intermediate rates, while the interstitial-free (IF) steel exhibited the lowest rate. The additions of Cr and Cr/P increased the fraction of g-fibre in the annealing textures compared to that present in the ELC steel; this effect was particularly pronounced up to 50 % recrystallisation. After the completion of recrystallisation, the steel textures were characterized by a dominant g-fibre in the IF steel, while in the …
Microstructure Design Of A Two Phase Composite Using Two-Point Correlation Functions, Brent L. Adams, H. Garmestani, G. Saheli
Microstructure Design Of A Two Phase Composite Using Two-Point Correlation Functions, Brent L. Adams, H. Garmestani, G. Saheli
Faculty Publications
This work has been funded under the AFOSR Grant no. F49620-03-1-0011 and Army Research Lab contract no. DAAD17-02-P-0398 and DAAD 19-01-1-0742. Two-point distribution functions are used here as to introduce "Microstructure Sensitive Design" in two-phase composites. Statistical distribution functions are commonly used for the representation of microstructures and also for homogenization of materials properties. The use of two-point statistics allows the composite designer to include the morphology and distribution in addition to the properties of the individual phases and components. Statistical continuum mechanics is used to make a direct link between the microstructure and properties (elastic and plastic) in terms …
Microstructures By Design: Linear Problems In Elastic-Plastic Design, Brent L. Adams, B. Henrie, M. Lyon
Microstructures By Design: Linear Problems In Elastic-Plastic Design, Brent L. Adams, B. Henrie, M. Lyon
Faculty Publications
Materials microstructure is considered to be a design variable in the methodology called microstructure sensitive design (MSD). Based upon existing homogenization relations, relating the first-order representation of microstructure (the local state distribution function) to elastic and yield properties, the paper describes the construction of properties closures. These establish the theoretically-possible combinations of properties achievable by the set of all possible microstructures, which is called the microstructure hull. Exemplary homogenization relations are shown to be, typically, hypersurfaces (often hyperplanes) in the Fourier space in which the microstructure hull resides. All points lying on (or to one side of) the hypersurface, that …