Dr. Wenshan Yu Department of Materials Science and Engineering & cascaM, University of North Texas icon

Dr. Wenshan Yu Department of Materials Science and Engineering & cascaM, University of North Texas

Materials Science and Engineering

Seminar Abstracts: Spring 2012


Dr. Wenshan Yu
Department of Materials Science and Engineering & CASCaM, University of North Texas

Friday, January 20th, 2-3pm, Room B155

Interactions between Lattice Dislocation and Σ11 Grain Boundary in Copper

Grain boundaries generally act as barriers for the movement of dislocations, especially for the tilt grain boundary with a larger title angle, which greatly affects the plastic behavior of polycrystalline materials. This talk will focus on the "positive" and "negative" interactions between several specified numbers of piled-up lattice dislocations and symmetrical tilt grain boundaries (STGB) of +Σ11(-3,1,-1) and -Σ11(-1,3,1) in two bi-grain models of copper by using the quasicontinuum method (QCM). The mechanisms of both interactions at representative loading stages will be analyzed in terms of the evolution of grain boundary (GB) configuration and Burgers vector conservation. A unified geometrical criterion is proposed to predict the "hard" and "easy" dislocation transmissions without explicitly distinguishing the "positive" and "negative" dislocation/GB interactions. The pile-up of incoming dislocations (ICDs) has a remarkable influence on both "positive" and "negative" interactions, and can activate dislocation transmissions at smaller external loadings. Critical stress analysis for relatively easier dislocation transmissions in "negative" interactions reveals that they are governed by the ratio of total shear stresses on the incoming and outgoing slip planes, and the ratio of total normal and shear stresses on the outgoing slip plane. Analysis of Burgers vectors of residues produced from dislocation/GB interactions shows that GB impeding dislocation motion is manifested by larger residues values. In addition, the "positive" and "negative" dislocation simultaneously interacting with Σ11 GB will also be introduced.


^ Dr. Alan A. Luo, GM Technical Fellow
General Motors Global Research and Development Center

Friday, January 27th, 1:30-2:30pm, Room B155

Alloy Development and Process Innovation for Lightweight Automotive Applications

Lightweighting is a critical approach to improving the fuel economy of automobiles powered by conventional gasoline internal combustion engines or alternative energy powertrains. Magnesium and aluminum, the lightest structural metals, have emerged as promising automotive materials for replacing cast iron and steels in the automotive industry. This talk presents the latest development of new cast and wrought magnesium alloys using computational thermodynamics and experimental techniques. The work illustrates the role of calculated phase diagrams, solidification paths and phase fractions in predicting and interpreting the final microstructure and properties of several magnesium alloy systems for room and elevated temperature applications. This talk will also summarize some major process innovation in light metals manufacturing for structural applications. Examples are given in the material and process evolution of lightweight powertrain, interior, chassis and body structures. Future trends in mixed material applications and integrated computational materials engineering (ICME) are also discussed.


^ Professor Ramanathan Krishnamurthy
Purdue University

Monday, January 30th, 2-3pm, Room B155

Transport, Microstructure and Mechanics Interplay in Thin Films and Advanced Materials

The interplay between the chemistry, microstructure, mechanics and transport produces rich materials physics, an understanding of which is essential to successfully process and utilize advanced materials. We demonstrate how this interplay contributes to complex materials behavior in three different technologically important examples.

In the first example, we examine oxygen ion transport in yttria stabilized zirconia (YSZ) –based materials using a multi-scale modeling approach that uses density functional theory methods to calculate activation barriers in local cation environments and kinetic Monte Carlo methods to calculate long-time diffusivities. We demonstrate that the local cation environment surrounding an oxygen vacancy and chemistry-dependent correlation effects conspire to produce the complex dependence of oxygen diffusivity on ytrria (and other dopant) concentration that is observed in experiment.

In the second example, we study the development of coating macrostructures (e.g. mud-crack like patterns) due to the sintering of discrete columns of a yttria stabilized zirconia thermal barrier topcoat by incorporating a variational formulation describing geometry changes due to transport mechanisms associated with the sintering of individual column pairs into a discrete dynamics framework that tracks changes in the macroscopic coating structure due to the sintering of a large number of columns. We correlate statistical variables describing the coating structure to processing variables to analyze the impact of topcoat sintering on the thermomechanical failure of thermal barrier coatings in engines.

In the third example, we study morphology evolution during the annealing and growth of thin films using a thermodynamics-based modeling approach that simultaneously includes grain growth, grooving and deposition physics. We demonstrate that the relative values of surface diffusivity and grain boundary mobility play an important role in determining evolving film morphologies, and aggregate features such as the complex time-evolution of film surface roughness. We also show that large deposition fluxes can stymie lateral grain growth resulting in a fine-grained film microstructure.


^ Professor Kenneth M. Liechti
University of Texas, Austin

Friday, February 3rd, 2-3pm, Room B155

Mechanical and Adhesive Behavior of Self-Assembled Monolayers

This seminar will describe the use of an interfacial force microscope (IFM) for conducting low force adhesive contact experiments in displacement control. The experiments are conducted on amine and carboxy-terminated self-assembled monolayers (SAMs) deposited on ultra-smooth Si (111) surfaces. The measured force-displacement response is compared with the results of a hybrid molecular/continuum analysis in which molecular dynamics simulations of the SAMs under simple stress states are used to inform continuum level analyses of the IFM experiments.


^ Professor Antonio F. Avila
School of Aeronautics and Aerospace, Purdue University

Monday, February 6th, 2:30-3:30pm, Room B155

Self-cleaning Fluorescent Multi-functional Composites Membranes

This talk deals with synthesis and characterization of super-hydrophobic composite membranes with fluorescent capabilities. The super-hydrophobic surface is based on micro/nano-fibers of polystyrene doped with fluorescent dyes (CdS or ZnS). The electrospinning technique associated to ultra-sonication for dyes dispersion was employed for super-hydrophobic surface preparation. First, the polystyrene (PS) was dissolved into N,N, dimetylformamide (DMF) and then the fluorescent dyes were dispersed into the PS/DMF solution. The PS/DMF solutions had a weight ratio of 20/80 and 35/65, while the nanoparticles concentrations varied from 0 5 weight percentage. The membranes with 35/65 ratio had an average water contact angle (WCA) of 141o, while the 20/80 membrane had a WCA of 146o. The addition of nanoparticles lead to a WCA of 152o for the 20/80 membrane with 5.0 wt. % CdS, and 163o with 5.0 wt.% ZnS. The fiber morphology was also affected by the fluorescent dyes addition. The fiber roughness increases with the CdS or ZnS addition due to their electrical conductivity properties.


^ Professor Samir Aouadi
Department of Physics, Southern Illinois University

Wednesday, February 8th, 2-3pm, Room B155

Enhanced Functionality through Surface Engineering

Surface modification of solids is a dynamic research field in which innovative techniques are used to exploit novel materials properties. Modification of the surface of a material is performed to enhance specific physical, chemical and/or biological attributes. This presentation provides an overview of state-of-the-art techniques that are currently being employed to engineer surfaces with nanoscale features to enhance specified functionality. Some of the main techniques currently utilized to enhance the functional properties of surfaces include thin film coating deposition, surface texturing, growth of one-dimensional nanostructures, and surface functionalization through chemical or biological manipulation. These techniques will be discussed in detail with an emphasis on the following applications: (1) high temperature tribology for space and aerospace application; (2) determination of the effects of surface topology and peptide functionalization on vascular endothelialization; and, (3) control of local atomic structure and design architecture of one-dimensional nanostructures for use in energy harvesting, photocatalytic activity, and tailored thermal properties of materials.


^ Dr. Stephen R. Niezgoda
Los Alamos National Laboratory

Monday, February 13th, 2-3pm, Room B155

A New Materials Innovation Infrastructure:
Building Materials Knowledge via Characterization, Modeling, and Simulation

The idea that accelerating the pace of discovery and deployment of advanced materials is central to our future economic security and humanities overall well being is the driving force behind the recently announced Materials Genome Initiative for Global Competitiveness. Central to the success of the Materials Genome Initiative is the concept of a Materials Innovation Infrastructure (MII) that links the key computational and experimental areas of materials science with industrial design, testing, development and certification. This seminar will focus largely on what a MII might look like and how current research initiatives in ICME, or Materials by Design, could be integrated into the larger infrastructure. It is envisioned that such an infrastructure will encompass three broad areas: 1) Materials Data Generation, which includes characterization, experiment and simulation. 2) Materials Data Storage, Manipulation and Visualization and 3) Materials Design, Testing and Certification. The seminar will also explore two aspects of the MII where significant short term advancement can be made: The co-design of materials characterization and computational tools that work in conjunction to predict microstructure/local response fields that cannot be measured directly, and 2) the development of a mathematically rigorous multi-scale description of microstructure as a foundation on materials databasing, visualization, and analysis tools can be built. The integration of the new technique of cross-correlation electron backscatter diffraction (sometimes referred to as high-resolution EBSD) with fast Fourier transform micro-mechanical modeling for the in-situ measurement of stress fields in metallic samples, will be used as a case study to motivate the need for characterization/modeling co-design. The second part of the talk will focus on a stochastic description of microstructure and applications to multi-scale modeling, materials uncertainty quantification, quality control/process monitoring and materials data-base applications.


^ Professor Matthias Batzill
Department of Physics, University of South Florida

Wednesday, February 15th, 2-3pm, Room B155

Atomic-scale Control of Surfaces and Interfaces: (i) Titania Surfaces
and (ii) CVD-growth of Graphene

Understanding materials properties and synthesis processes at the ultimate length scale becomes increasingly important in materials design. Here I discuss two very diverse materials systems that illustrate on how UHV surface science methods allow us to gain fundamental insight in surface and interface properties.

In the first part of this talk, I focus on basic surface properties of TiO2. These studies are motivated by strong surface orientation-dependent photocatalytic activity of the same material. I will compare the drastically different majority surfaces of rutile-TiO2 crystals. The gained insight in the electronic and chemical properties is crucial for understanding the photocatalytic activity of this material. While these studies are important for understanding the natural surface properties of materials, for making TiO2 and other materials a better photo catalysts we need to find reliable ways to modify them. Therefore, in ongoing and future work we are introducing surface modifications in TiO2 to enhance their photocatalytic activity beyond the naturally occurring diversity.

In the second part of this talk, we are addressing the CVD growth of graphene on transition metal surfaces, with an emphasis on Ni. Our detailed studies describe the surface phases of carbon on Ni(111) and describe how the existence of a surface carbide phase can affect the formation of graphene. Low energy electron microscopy studies are used to illustrate the kinetics of graphene formation. Defect structures that may form due to interaction of the graphene with the nickel substrate have been characterized by scanning tunneling microscopy and are briefly discussed in this talk. Current and future work is focusing on interfaces of graphene with metals and dielectrics. Recent unpublished work on the characterization of graphene/yttria interfaces will be presented.


^ Dr. Marcus Young
ATI Wah Chang, Albany, Oregon

Friday, February 17th, 2-3pm, Room B155

Shedding Light on Alloys by Synchrotron X-ray Diffraction

Synchrotron X-ray diffraction sources offer the unique ability to directly measure lattice parameters and, therefore, internal elastic strains of all phases within the bulk (rather than near surface) of metal alloys. In this presentation, two different metal alloy systems (ultrahigh-carbon steels and pseudoelastic NiTi shape memory alloys) examined by synchrotron X-ray diffraction will be discussed.

The first of these alloys, ultrahigh-carbon steel (UHCS), can be classified as a metal matrix composite (MMC) consisting of spherical Fe3C particles in a Fe matrix. Metal matrix composites (MMCs) are of technological importance for a variety of applications. One important aspect of MMCs is their unique mechanical behavior, which is controlled by the load transfer occurring between matrix and reinforcement. Load transfer is affected by the mismatch in stiffness between matrix and reinforcement, by plastic deformation of the metallic matrix and by damage of the ceramic reinforcement or its interface with the matrix. In this presentation, the micromechanics of load transfer in this MMC using high-energy synchrotron x-rays in conjunction with in-situ tensile loading to failure will be discussed. Predictions from analytical models (based on rule-of-mixture) and numerical models (based on the finite-element method) will be compared with experimental strain measurements.

The second alloy is a pseudoelastic NiTi shape memory alloy (SMA), which has the unique ability to fully recover from deformation up to ~8 % strain due to a phase transformation from austenite to martensite. Because of their good mechanical and functional properties, NiTi SMAs are currently used in a wide range of medical and technological applications. Here, an ultrafine-grained pseudoelastic NiTi SMA wire examined using synchrotron X-ray diffraction during in-situ uniaxial tensile loading and unloading will be presented. The macroscopic stress-strain curve will be discussed in light of phase volume fractions and lattice strains in various crystallographic directions in the austenitic B2, martensitic R, and martensitic B19’ phases and it will be shown that the phase transformation occurs in a localized manner.


^ Dr. Soumya Nag
University of North Texas

Monday, February 20th, 2-3pm, Room B155

Structure-Property Relationships in Biomaterials for Next Generation Implants

Structural biomaterials like Ti-6Al-4V (Ti64) and Ti-35Nb-7Zr-5Ta (TNZT), used for implant applications, offer an ideal combination of properties such as low elastic moduli, high tensile strength, excellent biocompatibility with no adverse tissue reactions, excellent corrosion resistance in body fluid, high fatigue and wear resistance. Furthermore near-net shape processing technologies, such as the laser engineered with shaping (LENS™) offer a viable processing route for fabrication of functionally-graded implants with site-specific properties. In this study, details of the microstructural evolution, tensile, electrochemical and in-vitro biocompatibility properties of TNZT alloy will be presented. The details of the deformation behavior of beta Ti-Nb based alloys are not well understood. One aspect of interest is the competition between slip dominated versus twin dominated deformation modes in these alloys, strongly influenced by microstructural and thermo-mechanical factors. Finally in order to improve the biocompatibility of implant materials a novel surface modification technique was adopted by laser induced direct melting of Ca-P based hydroxyapatite (Ca10(PO4)6(OH)2) bio-ceramic powder on Ti64 substrate. An in depth analyses of coating-substrate interfacial region was conducted in order to obtain valuable insight towards thermodynamic and kinetic aspects of the interaction.


^ Professor Brandon L. Weeks
Department of Chemical Engineering, Texas Tech University

Wednesday, February 22nd, 2-3pm, Room B155

Applications of Probe Microscopy: High Resolution Lithography, Sensors and Energetic Materials

Scanning probe microscopy continues to evolve at a surprising rate. In this presentation a tour of recent and exciting developments in our group will be presented which will focus on three main areas: Dip-pen nanolithography, micro-cantilever sensors, and nanometer investigations of energetic materials.

Dip-pen nanolithography: This new concept in nanolithography is based upon the transport of a chemically reactive material or "ink" from the tip of a conventional silicon nitride atomic force microscope (AFM) to the surface of interest or "paper." A model will be presented which suggests a water meniscus that forms between the tip and sample acts as a transport medium.

Micro-cantilever sensors: Micro-cantilever sensors are high-sensitivity, point-detection devices that have been applied to quality and process control, diagnostic biosensing for medical analysis, fragrance design ("artificial noses"), and gas analysis. The application of single cantilever sensors to determine quantities below the detection limits of equivalent "classical" methods such as thermal, chemical, stress, mass loading or magnetic signals has been demonstrated. Results will be presented for the selective and specific detection of whole salmonella organisms and their application to explosives for homeland security.

Energetic materials: Understanding the structure and composition of energetic materials at the sub-micron level is imperative for the fundamental studies of hot-spot formation and structural composition of energetic materials. Here we will present data on coarsening of PETN crystals using atomic force microscopy and optical techniques. The ultimate goal it to control the architecture of high explosives on the nanoscale which should yield safer, yet more powerful energetic materials for industrial and defense applications.


^ Dr. Arief S. Budiman
Staff Scientist, Solar PV Energy R&D, SunPower Corporation, San Jose, CA
(Formerly of Center for Integrated Nanotechnologies [CINT], Los Alamos National Laboratory [LANL], Los Alamos, NM; Department of Energy [DOE]'s Energy Frontier Research Center [EFRC]: Center for Materials at Irradiation and Mechanical Extremes [CMIME])
^ Friday, February 24th, 2-3pm, Room B155

Advanced Structural Nanomaterials for Extreme Environments
for Next Generation Energy Technologies

Investigations into the role of mechanics in the advanced structural materials have great importance to the field of materials science, especially in today’s nano-age where nanostructured materials – with microstructural features in the nanometer scale – often exhibit mechanical behaviors that deviate from that of even the micron and larger scales. The creation of such nanoscale materials thus requires a thorough understanding of the mechanical properties at such small length scales. The mechanics in the deformation of such materials at the nanoscale – nanomechanics – depends primarily on the mechanisms of plasticity that are at play in such nanoscale features. The plastic flow response of a material is always controlled by the aggregate behaviors of its individual microstructural crystal defects – vacancies, dislocations, grain boundaries – however in the nanoscale it is often dominated by the characteristic behaviors of a single individual crystal defect. Prediction and eventually control of the plastic flow response of nanomaterials is fundamental to a myriad of technological applications ranging from Micro- and Nano-Electro-Mechanical Systems (M/NEMS) devices, sensors and actuators, to next generation nuclear power reactors, to future energy harvesting systems requiring advanced structural materials that can not only withstand but also maintain their desired properties under extreme environments. Energy supply unquestionably is the major challenge of our times. The prosperity, if not the survival, of our society depends on sustainable energy production. In all its variants, energy production could be vastly improved if materials were able to survive extreme environments of mechanical strain, temperature, corrosion or radiation. Two topics in the current research theme will be highlighted in this seminar. Unique mechanical behaviors of nanoscale Cu/Nb multilayer composite materials were investigated using synchrotron X-ray microdiffraction and it is found that interface-dominated plasticity mechanisms lead to its ability to survive both radiation as well as mechanical extreme environments. In the second topic, indium nanostructures allow us to investigate high temperature plasticity mechanisms at the nanoscales and thus how they might influence the mechanical properties of advanced structural nanomaterials in extreme temperature environments.


^ Dr. Dipankar Ghosh
University of Florida

Monday, February 27th, 2-3pm, Room B155

Structural Response of Advanced Ceramics:
High-Strain Rate Behavior to Electro-Mechanics

Development of advanced materials will continue to propel technological advances for various applications. Whether it is for protection against high velocity impact threats, developing better thermal protection systems in supersonic and re-entry vehicles, or for actuators and sensors, novel synthesis, advanced characterization and intelligent design can revolutionize the properties and performance of materials. Advanced characterization tools help us to probe into the fundamentals of physical response of materials that is critical to understand the structure-property relationships. When structural ceramics are subjected to extreme dynamic (high-strain rate) loading, failure processes evolve at a time scale, which is significantly different than the time scale at which conventional mechanical properties are measured. Thus, conventionally measured mechanical properties do not necessarily capture the correct failure mechanics and not suitable to evaluate the performance. As a result, high-strain rate mechanical experiments are extremely important to extract the properties of armor ceramics. While boron carbide (B4C) is an automatic choice for lightweight ceramic armor systems due to its low density and extremely high hardness, ballistic performance of B4C against high velocity impact has been questionable due to structural change. This presentation will discuss how the localized structural change affects the low- and high-strain rate mechanical properties of B4C ceramics and the role of pressure and strain rate on structural change will be discussed. Another class of structural materials that have received significant attention in recent years is the ultra-high temperature ceramics that are potential to significantly improve the thermal protection systems in aerospace vehicles. However, mechanical characterizations of these materials have been extremely limited. To this end, it will be shown how different inelastic mechanisms evolve in these ceramics under contact load applications. Finally, the presentation will discuss the synthesis and structural-property relationships of electro-active materials for renewable energy applications. In this context, use of time-resolved diffraction techniques to understand the electromechanics of these materials will be addressed.


^ Dr. Sundeep Mukherjee
Yale University

Friday, March 2nd, 2-3pm, Room B155

Multi-Scale Forming of Metallic Glass

The last decade has witnessed the development of a new class of metallic alloys that combine the high strength of structural steels together with the processing ability of plastics. These alloys are referred to as ^ Metallic Glasses and have exceptional stability against crystallization. Metallic glasses have been deemed to revolutionize structural materials due to their unique combination of mechanical properties such as high strength, perfectly elastic behavior, good fatigue resistance, and thermo-plastic processing ability. This processing ability opens new opportunities for simple, scalable, and inexpensive manufacturing of energy storage devices, medical implants, and micro/nano electromechanical systems (MEMS/NEMS).

In this seminar, I will talk about the forming ability of metallic glasses across multiple length-scales. The influence of crystallization behavior, thermodynamics, and kinetics on glass formation will be discussed. Metallic glasses can be cast in fully amorphous, near-net shapes with nano-scale precision. This allowed the fabrication of large surface area structures, ideally suited for catalysis and sensor applications. Recent results on patterning metallic-glass surfaces via novel electrochemical routes will be presented as well.


^ Dr. Sergei A. Shipilov
Metallurgical Consulting Services Ltd., Toronto, Ontario

Friday, March 9th, 11am-12pm, Room B155

Corrosion and Structural Integrity: From Research to Action and Sustainable Solutions

The first part of the paper demonstrates that at present, corrosion and "time-dependent" degradation of materials is at the core of safety and risk analysis in several major industries such as energy generation, transportation (particularly for the aerospace sector where the safe operation of aging aircraft is a major issue for both military and civilian fleets), gas and liquid transmission pipelines, municipal water and wastewater facilities, chemical processing, and refining. Assessing the risk of the failure of corrodible structures presents a unique challenge because the risk increases continually with time, and corrosion processes can shift dramatically from one mode to another with seemingly small changes in environmental or other factors. The concern with human safety extends to public spaces where the reliability of building infrastructure (bridges, overpasses, suspended roofs, etc.) and industrial utilities (nuclear reactors, buried pipelines, etc.) is crucial to saving human lives. When catastrophic failures occur due to corrosion, the consequences can be devastating. Also, corrosion is shown to be a major contributor to environmental pollution, including when it results in the leakage of hazardous materials from pipelines and pressure vessels.

The current practices in "preventing" catastrophic failures in bridges, public infrastructure, aircraft, offshore oil/gas platforms, tankers, pipelines, nuclear facilities, chemical plants, and military facilities is that failures occur first and then the engineering community responds by explaining their observations. In the past, none of the industrial disasters and/or major structural failures that happened were predicted. Some of the failures took many years before they became evident and/or catastrophic . Failures such as corrosion and cracks in the vessel head at the Davis-Besse nuclear reactor in 2002, which almost became the nation’s worst nuclear disaster, and the collapse of the I-35W Bridge in Minneapolis in 2007, which killed 13 people, were preventable and could have been stopped if qualified engineers had been called in.

To ensure that engineering structures and high-risk technologies continue to function throughout their design life, it is important to address corrosion-related problems before they become failures. The determination of long-term performance of materials is crucial for safe and reliable structures, and corrosion science has an essential role to play in this determination. The second part of the paper looks at the role that advanced in corrosion science and engineering can play in preventing such failures, as drawn from the author’s experience in three areas: stress-corrosion cracking, medical implant device corrosion/durability, and corrosion education.

Corrosion almost always involves very complicated situations. Many environmental factors, materials conditions, and design/configuration specifics, can and usually do interact in very complex ways to produce the observed result. In short, they can be very "messy" problems and, if real progress is to be made, the diversity of phenomena which can occur requires a multidisciplinary approach. Despite all of the good intentions and efforts over several decades, real multidisciplinary and interdisciplinary activity is relatively rare on university campuses.

In closing, the paper proposes ways of filling significant gaps in the nation's and researchers' ability to respond to public safety concerns, industrial problems, and the high financial cost of structural failures and environmental contamination due to corrosion, and emphasizes the importance of creating a national knowledge data base that would address a broad spectrum of varied and highly complex challenges in all related areas.


^ Professor Jian Luo
School of Materials Science and Engineering, Clemson University

Friday, April 6th, 2-3pm, Room B155

Interfacial Phase Transitions:
Solving Old Materials Science Problems and Tackling New Energy Challenges

A piece of ice melts at 0°C, but a nanometer-thick surface layer of the ice can melt at tens of degrees below zero. This interfacial phenomenon, known as "premelting," was first recognized by Faraday in 1842. Recent studies of analogous but more complex interfacial phase phenomena shed light on several outstanding scientific problems that have been puzzled the materials science community for 50-100 years, including the origins and atomic-level mechanisms of activated sintering, liquid metal embrittlement, and abnormal grain growth. Furthermore, a potentially transformative concept is to intentionally utilize nanoscale interfacial phases to achieve superior properties that are not attainable by conventional bulk phases. Our recent research projects in this area investigate a variety of advanced materials for energy related applications, including lithium ion battery materials, supported oxide catalysts, liquid metal embrittlement/corrosion systems for applications in nuclear power systems, photocatalysts and photovoltaic materials, and several high-temperature alloys for improving energy efficiency.


^ Professor Tresa M. Pollock
University of California Santa Barbara

Friday, April 20th, 2-3pm, Room B155

A New Tomography Approach for Generation of 3D Datasets for Property Prediction

The development of high fidelity material property models often requires three-dimensional information on the distribution of phases, grains or extrinsic defects.   Concurrently, information on orientation and spatial distribution of elements may also be essential.  Acquisition of this information in appropriate representative volume elements ultimately limits the use of conventional tomography techniques.  The use of femtosecond lasers for rapid layer-by-layer ablation provides new capabilities in terms of the volume of material that can be sampled as well as new opportunities for multimodal analysis.   The characteristics of datasets on Ni-base alloys and steel required for modeling of fatigue and fracture will be discussed.  Femtosecond laser-based datasets will be presented for these materials and the use these datasets to predict properties will be discussed.  Future opportunities for in-situ and ex-situ variants of the FSL technique will be discussed.

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