BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:Constitutive Modeling of Strain Rate Sensitive Polymeric Gels and Biological Tissues DTSTART:20190920T140000 DTEND:20190920T150000 DTSTAMP:20260528T021134Z UID:354d7fdf9be858be58f446e85bdef74c2c2684eefa3f60efb7ad3984 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Ghatu Subhash\, Newton C. Ebaugh Professor\, Mechanica l and Aerospace Engineering\, University of Florida\nAbstract:\nA comprehe nsive experimental and analytical modeling effort is carried out to captur e the visco-hyperelastic response of soft materials. The commonly used the rmodynamic dissipation-based models utilize strain energy density and dyna mic viscous dissipation potentials\, and have been studied to describe sho rt-time memory responses of soft materials for over two decades. In this s tudy\, it is demonstrated that the existing forms of viscous dissipation p otential in the literature do not capture strain rate dependence of elasti c moduli and Poisson’s ratio\, a phenomenon which has been experimentall y observed in many soft tissues and polymeric gels. To capture the overall response of these materials\, the current work is carried out in two phas es: First\, a generalized thermodynamic stability criterion for isotropic finite elastic solids is derived using the fundamental balance laws and fi eld equations of continuum mechanics\, which is then used to formulate con stitutive inequalities for the polynomial forms of hyperelastic constituti ve equations. It is shown that the model constants of a hyperelastic const itutive model should fall within a domain called the Region of Stability ( ROS) for all three primary deformation modes\, i.e.\, uniaxial compression \, uniaxial tension and shear. It is then shown that experimental data fro m only a particular deformation mode of deformation may not capture the co mplex behavior of a material under multiaxial state of stress for hyperela stic materials and hence data must be captured from all three deformation modes to obtain a realistic constitutive behavior. Second\, a novel genera lized viscous dissipation potential form is proposed\, which not only capt ures strain rate sensitivity\, but also consists of physically-based model parameters that relate to the material’s strain rate sensitivity behavi or. The proposed viscous dissipation potential is combined with standard p olynomial-based hyperelastic strain energy density function to define visc o-hyperelastic constitutive equation\, which is then used to model quasi-s tatic to high strain rate response of soft materials such as hydrogel\, ba llistic gelatin\, human patellar tendon\, porcine brain tissue. Finally\, challenges of conducting simple shear experiments on hyperelatic materials are highlighted. The robustness of constitutive model for capturing def ormations under complex loads such as wedge-indentation and high velocity long-rod impact on a rigid surface are demonstrated.\n\nBio:\nProfessor Su bhash obtained his PhD from University of California San Diego (UCSD) in 1991 and conducted post-doctoral research at California Institute of Tech nology (Caltech) during 1992-93. He joined Michigan Technological Universi ty in 1993 and then moved to University of Florida in 2007.\nHis research expertise is in multiaxial dynamic constitutive behavior of materials\, pr ocessing-microstructure-property-performance relationships in advanced str uctural ceramics\, and experimental solid mechanics. His research efforts have focused on  understanding the deformation mechanisms in a range of m aterials including refractory metals\, bearing steels\, bulk metallic glas ses\, ultrahard ceramics\, low-density foams\, nuclear ceramics\, brain ti ssue\, and polymeric gels. In the context of ceramics\, his research is fo cused on experimental and computational investigations on pressure-induced amorphization in icosahedral ceramics. In the field of nuclear engineerin g\, he has developed rapid processing technology to fabricate nuclear fuel and control rod pellets in few minutes compared to the traditional method s which take several hours. For this effort\, he has received ‘Signific ant Contribution Award’ from Materials Science and Technology Division \, American Nuclear Society (2014). His contributions in experimental soli d mechanics have been recognized by the 2018 ‘Frocht Award’ from Soc iety for Experimental Mechanics(SEM).  His current research interests in biomedical engineering include determination of contractile stresses due to cell growth in tissue phantoms and shock-induced cellular degradation in brain tissue.  His work on rolling contact fatigue of ultrahard beari ngs received ‘Best Paper Award’ in the Journal of Engineering Mater ials and Technology (2017).\nProf. Subhash is a fellow of the ASME and SE M. He serves as an Editor-in-Chief of Mechanics of Materials (an interna tional journal) and as an Associate Editor of the Journal of the Americ an Ceramic Society.  He has received numerous recognitions for excellenc e in teaching\, research and professional service\, including ‘Technol ogy Innovator Award’ from University of Florida (2016) and Teacher/S cholar of the year (2013)\, ASME Student Section Advisor Award\, Societ y of Automotive Engineers (SAE) Ralph R. Teetor Educational Award\, and A merican Society for Engineering Education (ASEE) Outstanding New Mechanics Educator. He has graduated 34 PhD students and co-authored 190 peer revi ewed journal articles\, 80 conference proceedings\, and 5 patents. He has co-authored a book on “Mechanics of Materials Laboratory Course” and i s finalizing another book on “Dynamic Response of Ceramics”. His inven tions have received international attention from major TV networks (Fox\, CBS and 40 other local TV channels)\, radio stations (including NPR) and a rticles by Reuters and ASEE Morning Bell. He has also appeared in a PBS do cumentary in 2017 (Secrets of Spanish Florida) while discussing the impact response of ‘Coquina’\, a material with which the oldest fort in the United States\, the ‘Castillo de San Marcos’ was built in St. Augustin e\, Florida.\n\n  LOCATION:GC A3 30 https://plan.epfl.ch/?room==GC%20A3%2030 STATUS:CONFIRMED END:VEVENT END:VCALENDAR