Archive for November 2008

Friday, November 14, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Dr. Yongmei M. Jin
Department of Aerospace Engineering, Texas A&M University
3141 TAMU College Station, TX 77843-3141

Abstract

This talk will present materials modeling and computer simulation studies ofmicrostructure evolutions in response to external thermal, mechanical andmagnetic stimuli during processing and service in various crystalline solids, with aspecial focus on structural and functional metal alloys. The theoreticalmethodology (phase field model) is based on gradient thermodynamics ofheterogeneous materials, microstructure-dependent free energies ofmicroelasticity and micromagnetism, and semi-phenomenological kinetics ofmicrostructure evolution. Particular examples will be discussed: (1) developmentof compositional and structural domains during decomposition, ordering transition,and martensitic transformation; (2) effects of crystallographic microstructures onmagnetic and mechanical properties in advanced magnetic materials includinghard ferromagnets, magnetostrictive materials, and magnetic shape memoryalloys; and (3) roles of long-range dipole-dipole interactions and evolution kineticpathways in domain microstructure processes and material properties.Connections between mesoscale phase field modeling, atomistic (first principles,molecular dynamics) and continuum (finite element) simulations, thermodynamicand kinetic databases, as well as experiments will also be addressed.

Biography

Dr. Jin received B.E. and M.E. in Mechanical Engineering from University of Science and Technology of China in 1994 and 1997, respectively, and Ph.D. in Materials Science and Engineering from Rutgers University in2003. After two years of postdoctoral research at Rutgers University, she joined the Department of AerospaceEngineering at Texas A&M University in 2005 as an Assistant Professor. Her research interest focuses on materialsmodeling and computer simulation. In particular, she has been working on the development and application ofphase field models to investigate microstructure evolutions in crystalline materials during various physicalprocesses, e.g., martensitic transformation, decomposition, ordering transition, ferromagnetic domain switching,magnetomechanical behaviors, and defect evolutions (dislocations, cracks, voids, and free surfaces) in single- andpoly-crystalline bulk and thin film materials.

Friday, November 7, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Kevin C. Baker, MS
Supervisor, Orthopaedic Research Laboratories
Director, Biomaterials Section
Department of Orthopaedic Research
William Beaumont Hospital
Royal Oak, Michigan

Abstract

Total hip arthroplasty (replacement) is an increasingly common surgical procedure performed toalleviate pain and restore function to joints damaged by trauma, pathology, or congeneitaldeformity.  As the average age of total hip arthroplasty (THA) patients decrease and theaverage human life expectancy increases, the need for longer lasting implants has becomeimperative.  A major factor currently limiting the in vivo term of service of THA systems ismechanical wear between the femoral head (ball) and acetabular liner (socket).  The generationof particulate debris associated with the mechanical wear stimulates a potent immune andinflammatory response, known as wear debris-induced osteolysis.  This biological responseleads to activation of osteoclasts, which resorb the bone around the THA components.Loosening of the THA components due to the resorption of bone alters patient biomechanics,which necessitates a revision surgical procedure.

The prevalence of this problem was lead to a great deal of materials science-based researchinto bearing surfaces to be used in THA systems.  Orthopaedic device manufacturers seek toimprove the current best practice in THA, which is a CoCrMo femoral head articulating with across-linked ultra-high molecular weight polyethylene (UHMWPE) acetabular liner.  Currentdevelopment has involved the use of nanocrystalline ceramic coatings, diamond-like carboncoatings, compliant layer polymer technology and differential hardness bearings.  One area ofresearch within the Department of Orthopaedic Research at Beaumont Hospital is theindependent evaluation of these novel bearing surfaces.  Characterization of the predicted invivo performance of these bearing surfaces is performed from a materials, mechanics andbiologic standpoint.  Test methods, ongoing research, future directions and opportunities forcollaboration will be discussed.