The Experts below are selected from a list of 9387 Experts worldwide ranked by ideXlab platform

Eugene A. Sprague - One of the best experts on this subject based on the ideXlab platform.

  • Human aortic endothelial cell response to 316L stainless steel Material Microstructure
    Journal of Materials Science: Materials in Medicine, 2009
    Co-Authors: Animesh Choubey, Denes Marton, Eugene A. Sprague
    Abstract:

    The role of metal Microstructure (e.g. grain sizes) in modulating cell adherence behavior is not well understood. This study investigates the effect of varying grain sizes of 316L stainless steel (SS) on the attachment and spreading of human aortic endothelial cells (HAECs). Four different grain size samples; from 16 to 66 μm (ASTM 9.0-4.9) were sectioned from sheets. Grain structure was revealed by polishing and etching with glycergia. Contact angle measurement was done to assess the hydrophilicity of the specimens. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the roughness and surface chemistry of the specimens. Cells were seeded on mechanically polished and chemically etched specimens followed by identification of activated focal adhesion sites using fluorescently tagged anti-pFAK (phosphorylated focal adhesion kinase). The 16 μm grain size etched specimens had significantly ( P  

  • Human aortic endothelial cell response to 316L stainless steel Material Microstructure
    Journal of Materials Science: Materials in Medicine, 2009
    Co-Authors: Animesh Choubey, Denes Marton, Eugene A. Sprague
    Abstract:

    The role of metal Microstructure (e.g. grain sizes) in modulating cell adherence behavior is not well understood. This study investigates the effect of varying grain sizes of 316L stainless steel (SS) on the attachment and spreading of human aortic endothelial cells (HAECs). Four different grain size samples; from 16 to 66 μm (ASTM 9.0-4.9) were sectioned from sheets. Grain structure was revealed by polishing and etching with glycergia. Contact angle measurement was done to assess the hydrophilicity of the specimens. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the roughness and surface chemistry of the specimens. Cells were seeded on mechanically polished and chemically etched specimens followed by identification of activated focal adhesion sites using fluorescently tagged anti-pFAK (phosphorylated focal adhesion kinase). The 16 μm grain size etched specimens had significantly (P < 0.01) higher number of cells attached per cm2 than other specimens, which may be attributed to the greater grain boundary area and associated higher surface free energy. This study shows that the underlying Material Microstructure may influence the HAEC behavior and may have important implications in endothelialization.

B A Cheeseman - One of the best experts on this subject based on the ideXlab platform.

  • modeling of aa5083 Material Microstructure evolution during butt friction stir welding
    Journal of Materials Engineering and Performance, 2010
    Co-Authors: Mica Grujicic, H. V. Yalavarthy, Guruprasad Arakere, T He, B A Cheeseman
    Abstract:

    A concise yet a fairly comprehensive overview of the friction stir welding (FSW) process is provided. This is followed by a computational investigation in which FSW behavior of a prototypical solution-strengthened and strain-hardened aluminum alloy, AA5083-H131, is modeled using a fully coupled thermo-mechanical finite-element procedure developed in our prior study. Particular attention is given to proper modeling of the welding work-piece Material behavior during the FSW process. Specifically, competition and interactions between plastic-deformation and dynamic-recrystallization processes are considered to properly account for the Material-Microstructure evolution in the weld nugget zone. The results showed that with proper modeling of the Material behavior under high-temperature/severe-plastic-deformation conditions, significantly improved agreement can be attained between the computed and measured post-FSW residual-stress and Material-strength distribution results.

  • Modeling of AA5083 Material-Microstructure evolution during butt friction-stir welding
    Journal of Materials Engineering and Performance, 2010
    Co-Authors: Mica Grujicic, H. V. Yalavarthy, Guruprasad Arakere, C.-f. Yen, T He, B A Cheeseman
    Abstract:

    A concise yet a fairly comprehensive overview of the friction stir welding (FSW) process is provided. This is followed by a computational investigation in which FSW behavior of a prototypical solution-strengthened and strain-hardened aluminum alloy, AA5083-H131, is modeled using a fully coupled thermo-mechanical finite-element procedure developed in our prior study. Particular attention is given to proper modeling of the welding work-piece Material behavior during the FSW process. Specifically, competition and interac- tions between plastic-deformation and dynamic-recrystallization processes are considered to properly account for the Material-Microstructure evolution in the weld nugget zone. The results showed that with proper modeling of the Material behavior under high-temperature/severe-plastic-deformation conditions, significantly improved agreement can be attained between the computed and measured post-FSW residual- stress and Material-strength distribution results. Keywords

Steve D. Sharples - One of the best experts on this subject based on the ideXlab platform.

  • Spatially resolved acoustic spectroscopy for rapid imaging of Material Microstructure and grain orientation
    Measurement Science and Technology, 2014
    Co-Authors: Richard J Smith, Jethro Coulson, Michael G. Somekh, Matt Clark, Wenqi Li, Steve D. Sharples
    Abstract:

    Measuring the grain structure of aerospace Materials is very important to understand their mechanical properties and in-service performance. Spatially resolved acoustic spectroscopy is an acoustic technique utilizing surface acoustic waves to map the grain structure of a Material. When combined with measurements in multiple acoustic propagation directions, the grain orientation can be obtained by fitting the velocity surface to a model. The new instrument presented here can take thousands of acoustic velocity measurements per second. The spatial and velocity resolution can be adjusted by simple modification to the system; this is discussed in detail by comparison of theoretical expectations with experimental data.

  • Rapid Imaging of Microstructure using Spatially Resolved Acoustic Spectroscopy Aim : to image Material Microstructure
    Symp. on Laser Ultrasonics: Science Technology and Applications, 2008
    Co-Authors: Steve D. Sharples, Matt Clark, Wenqi Li, Michael G. Somekh
    Abstract:

    Microstructure can have profound effects on the bulk mechanical properties of a Material, such as its\nstrength and susceptibility to failure under stress. Several well known methods for imaging Microstructure\nexist, including essentially destructive techniques such as etching and electron back-scattered diffraction,\nand contact techniques such as the scanning acoustic microscope. SRAS – spatially resolved acoustic\nspectroscopy – is a relatively new laser ultrasound technique that uses surface acoustic wave velocity as\nits contrast mechanism. Unlike the techniques above it is non-contact, non-destructive, can be used to\nimage large samples, and provides quantitative velocity information for acoustic waves propagating in\none or more directions. The technique uses the relative efficiency with which waves of either a fixed\nfrequency or k-vector are excited by a grating to obtain the velocity, unlike most laser ultrasound\ntechniques which rely on direct phase or time of flight measurements. This makes SRAS very tolerant to\nacoustic aberrations and poor signal to noise ratios, and hence is a robust technique. Lateral resolutions of\nthe order of 25μm, and velocity resolutions better than 1m/s are illustrated by striking images of\nMicrostructure from industrially relevant Materials.

  • Spatially resolved acoustic spectroscopy for fast noncontact imaging of Material Microstructure.
    Optics Express, 2006
    Co-Authors: Steve D. Sharples, Matthew Clark, Michael G. Somekh
    Abstract:

    We have developed a noncontact and nondestructive technique that uses laser-generated and detected surface acoustic waves to rapidly determine the local acoustic velocity, in order to map the Microstructure of multi-grained Materials. Optical fringes excite surface waves at a fixed frequency, and the generation efficiency is determined by how closely the fringe spacing matches the acoustic wavelength in the excitation region. Images of titanium alloys are presented, acquired using the technique. Methods to improve the current lateral resolution of 0.8mm are discussed, and the ability to measure velocity change to an accuracy of one part in 3300 is experimentally demonstrated.

  • Fast noncontact imaging of Material Microstructure using local surface acoustic wave velocity mapping
    IEEE Ultrasonics Symposium 2005., 2005
    Co-Authors: Steve D. Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    The make-up of the Material Microstructure of multi-grained Materials such as titanium alloys and aluminum is of great interest to many in industries such as aerospace. The ability to map the Material Microstructure - in effect to image the grains - quickly and in a nondestructive manner would be useful from both a process control perspective and in the area of nondestructive evaluation. There are several techniques in the field that are capable of imaging grain structure, including simple etching, orientation imaging microscopy and scanning acoustic microscopy; all have their strengths and weaknesses. We present a new ultrasonic technique that can directly and quantitatively image the local surface acoustic wave (SAW) velocity over the surface of a Material. Material Microstructure can be determined if the phase velocity of the grains varies with grain orientation. The acoustic waves are generated and detected by lasers and as well as being noncontact, the technique is relatively fast, can cope with large samples, and is totally nondestructive. The new technique involves varying the spatial parameters of the excitation pattern in real time to maximize the generation efficiency of the surface acoustic waves at the phase velocity of the Material, in the region of excitation. By repeating this over the sample surface, a surface wave phase velocity map can be produced. As well as describing the velocity mapping technique in detail, several example results of industrially-relevant Materials acquired using our new instrument are presented. The limit to the quantitative lateral resolution of the instrument is discussed, and how this relates to the qualitative lateral resolution. Results indicating the practical limit of the accuracy of velocity measure- ments are also presented. We demonstrate imaging on several samples (40mm 2 )a nd different Materials. This shows that the the instrument can reveal the underlying Microstructure and image areas of anomalous grain structure that may be significant for the performance of the Material. The instrument currently works on smooth samples but can be extended to work on rough surfaces and components with unprepared surfaces and consequently this has high industrial relevance.

  • Dynamic higher-order correction of acoustic aberration due to Material Microstructure
    Applied Physics Letters, 2002
    Co-Authors: Steve D. Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    Material Microstructure, such as grains in metals, can perturb ultrasound as it propagates through—or on the surface of—the Material. This acoustic aberration affects the accuracy and reliability of ultrasound measurements and is a fundamental limit to resolution for many Materials. Using an all-optical approach to generation and detection of surface acoustic waves, we detect the acoustic wave front aberrations, and correct for them by calculating a different generation profile, which is imaged onto the Material using a spatial light modulator.

Michael G. Somekh - One of the best experts on this subject based on the ideXlab platform.

  • Spatially resolved acoustic spectroscopy for rapid imaging of Material Microstructure and grain orientation
    Measurement Science and Technology, 2014
    Co-Authors: Richard J Smith, Jethro Coulson, Michael G. Somekh, Matt Clark, Wenqi Li, Steve D. Sharples
    Abstract:

    Measuring the grain structure of aerospace Materials is very important to understand their mechanical properties and in-service performance. Spatially resolved acoustic spectroscopy is an acoustic technique utilizing surface acoustic waves to map the grain structure of a Material. When combined with measurements in multiple acoustic propagation directions, the grain orientation can be obtained by fitting the velocity surface to a model. The new instrument presented here can take thousands of acoustic velocity measurements per second. The spatial and velocity resolution can be adjusted by simple modification to the system; this is discussed in detail by comparison of theoretical expectations with experimental data.

  • Rapid Imaging of Microstructure using Spatially Resolved Acoustic Spectroscopy Aim : to image Material Microstructure
    Symp. on Laser Ultrasonics: Science Technology and Applications, 2008
    Co-Authors: Steve D. Sharples, Matt Clark, Wenqi Li, Michael G. Somekh
    Abstract:

    Microstructure can have profound effects on the bulk mechanical properties of a Material, such as its\nstrength and susceptibility to failure under stress. Several well known methods for imaging Microstructure\nexist, including essentially destructive techniques such as etching and electron back-scattered diffraction,\nand contact techniques such as the scanning acoustic microscope. SRAS – spatially resolved acoustic\nspectroscopy – is a relatively new laser ultrasound technique that uses surface acoustic wave velocity as\nits contrast mechanism. Unlike the techniques above it is non-contact, non-destructive, can be used to\nimage large samples, and provides quantitative velocity information for acoustic waves propagating in\none or more directions. The technique uses the relative efficiency with which waves of either a fixed\nfrequency or k-vector are excited by a grating to obtain the velocity, unlike most laser ultrasound\ntechniques which rely on direct phase or time of flight measurements. This makes SRAS very tolerant to\nacoustic aberrations and poor signal to noise ratios, and hence is a robust technique. Lateral resolutions of\nthe order of 25μm, and velocity resolutions better than 1m/s are illustrated by striking images of\nMicrostructure from industrially relevant Materials.

  • Spatially resolved acoustic spectroscopy for fast noncontact imaging of Material Microstructure.
    Optics Express, 2006
    Co-Authors: Steve D. Sharples, Matthew Clark, Michael G. Somekh
    Abstract:

    We have developed a noncontact and nondestructive technique that uses laser-generated and detected surface acoustic waves to rapidly determine the local acoustic velocity, in order to map the Microstructure of multi-grained Materials. Optical fringes excite surface waves at a fixed frequency, and the generation efficiency is determined by how closely the fringe spacing matches the acoustic wavelength in the excitation region. Images of titanium alloys are presented, acquired using the technique. Methods to improve the current lateral resolution of 0.8mm are discussed, and the ability to measure velocity change to an accuracy of one part in 3300 is experimentally demonstrated.

  • Fast noncontact imaging of Material Microstructure using local surface acoustic wave velocity mapping
    IEEE Ultrasonics Symposium 2005., 2005
    Co-Authors: Steve D. Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    The make-up of the Material Microstructure of multi-grained Materials such as titanium alloys and aluminum is of great interest to many in industries such as aerospace. The ability to map the Material Microstructure - in effect to image the grains - quickly and in a nondestructive manner would be useful from both a process control perspective and in the area of nondestructive evaluation. There are several techniques in the field that are capable of imaging grain structure, including simple etching, orientation imaging microscopy and scanning acoustic microscopy; all have their strengths and weaknesses. We present a new ultrasonic technique that can directly and quantitatively image the local surface acoustic wave (SAW) velocity over the surface of a Material. Material Microstructure can be determined if the phase velocity of the grains varies with grain orientation. The acoustic waves are generated and detected by lasers and as well as being noncontact, the technique is relatively fast, can cope with large samples, and is totally nondestructive. The new technique involves varying the spatial parameters of the excitation pattern in real time to maximize the generation efficiency of the surface acoustic waves at the phase velocity of the Material, in the region of excitation. By repeating this over the sample surface, a surface wave phase velocity map can be produced. As well as describing the velocity mapping technique in detail, several example results of industrially-relevant Materials acquired using our new instrument are presented. The limit to the quantitative lateral resolution of the instrument is discussed, and how this relates to the qualitative lateral resolution. Results indicating the practical limit of the accuracy of velocity measure- ments are also presented. We demonstrate imaging on several samples (40mm 2 )a nd different Materials. This shows that the the instrument can reveal the underlying Microstructure and image areas of anomalous grain structure that may be significant for the performance of the Material. The instrument currently works on smooth samples but can be extended to work on rough surfaces and components with unprepared surfaces and consequently this has high industrial relevance.

  • Dynamic higher-order correction of acoustic aberration due to Material Microstructure
    Applied Physics Letters, 2002
    Co-Authors: Steve D. Sharples, Matt Clark, Michael G. Somekh
    Abstract:

    Material Microstructure, such as grains in metals, can perturb ultrasound as it propagates through—or on the surface of—the Material. This acoustic aberration affects the accuracy and reliability of ultrasound measurements and is a fundamental limit to resolution for many Materials. Using an all-optical approach to generation and detection of surface acoustic waves, we detect the acoustic wave front aberrations, and correct for them by calculating a different generation profile, which is imaged onto the Material using a spatial light modulator.

Animesh Choubey - One of the best experts on this subject based on the ideXlab platform.

  • Human aortic endothelial cell response to 316L stainless steel Material Microstructure
    Journal of Materials Science: Materials in Medicine, 2009
    Co-Authors: Animesh Choubey, Denes Marton, Eugene A. Sprague
    Abstract:

    The role of metal Microstructure (e.g. grain sizes) in modulating cell adherence behavior is not well understood. This study investigates the effect of varying grain sizes of 316L stainless steel (SS) on the attachment and spreading of human aortic endothelial cells (HAECs). Four different grain size samples; from 16 to 66 μm (ASTM 9.0-4.9) were sectioned from sheets. Grain structure was revealed by polishing and etching with glycergia. Contact angle measurement was done to assess the hydrophilicity of the specimens. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the roughness and surface chemistry of the specimens. Cells were seeded on mechanically polished and chemically etched specimens followed by identification of activated focal adhesion sites using fluorescently tagged anti-pFAK (phosphorylated focal adhesion kinase). The 16 μm grain size etched specimens had significantly ( P  

  • Human aortic endothelial cell response to 316L stainless steel Material Microstructure
    Journal of Materials Science: Materials in Medicine, 2009
    Co-Authors: Animesh Choubey, Denes Marton, Eugene A. Sprague
    Abstract:

    The role of metal Microstructure (e.g. grain sizes) in modulating cell adherence behavior is not well understood. This study investigates the effect of varying grain sizes of 316L stainless steel (SS) on the attachment and spreading of human aortic endothelial cells (HAECs). Four different grain size samples; from 16 to 66 μm (ASTM 9.0-4.9) were sectioned from sheets. Grain structure was revealed by polishing and etching with glycergia. Contact angle measurement was done to assess the hydrophilicity of the specimens. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the roughness and surface chemistry of the specimens. Cells were seeded on mechanically polished and chemically etched specimens followed by identification of activated focal adhesion sites using fluorescently tagged anti-pFAK (phosphorylated focal adhesion kinase). The 16 μm grain size etched specimens had significantly (P < 0.01) higher number of cells attached per cm2 than other specimens, which may be attributed to the greater grain boundary area and associated higher surface free energy. This study shows that the underlying Material Microstructure may influence the HAEC behavior and may have important implications in endothelialization.