BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:Talk given by Prof. Ghatu Subhash DTSTART:20190614T140000 DTEND:20190614T150000 DTSTAMP:20260407T101416Z UID:5ec3ec441bb609630aa94d6b7d635036d51c5dbc04edfd5e3259b301 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Dr. Ghatu Subhash\nThe talk will be given by Prof. Dr. Ghatu Subhash\, Newton C. Ebaugh Professor\, Mechanical and Aerospace Engi neering\, University of Florida\n \nConstitutive Modeling of Strain Rate Sensitive Polymeric Gels and Biological Tissues\n \nAbstract :\nA compreh ensive experimental and analytical modeling effort is carried out to captu re the visco-hyperelastic response of soft materials. The commonly used th ermodynamic dissipation-based models utilize strain energy density and dyn amic viscous dissipation potentials\, and have been studied to describe sh ort-time memory responses of soft materials for over two decades.\nIn this study\, it is demonstrated that the existing forms of viscous dissipation potential in the literature do not capture strain rate dependence of elas tic moduli and Poisson’s ratio\, a phenomenon which has been experimenta lly observed in many soft tissues and polymeric gels. To capture the overa ll response of these materials\, the current work is carried out in two ph ases:\nFirst\, a generalized thermodynamic stability criterion for isotrop ic finite elastic solids is derived using the fundamental balance laws and field equations of continuum mechanics\, which is then used to formulate constitutive inequalities for the polynomial forms of hyperelastic constit utive equations. It is shown that the model constants of a hyperelastic co nstitutive model should fall within a domain called the Region of Stabilit y (ROS) for all three primary deformation modes\, i.e.\, uniaxial compress ion\, uniaxial tension and shear. It is then shown that experimental data from only a particular deformation mode of deformation may not capture the complex behavior of a material under multiaxial state of stress for hyper elastic materials and hence data must be captured from all three deformati on modes to obtain a realistic constitutive behavior.\nSecond\, a novel ge neralized viscous dissipation potential form is proposed\, which not only captures strain rate sensitivity\, but also consists of physically-based m odel parameters that relate to the material’s strain rate sensitivity be havior. The proposed viscous dissipation potential is combined with standa rd polynomial-based hyperelastic strain energy density function to define visco-hyperelastic constitutive equation\, which is then used to model qua si-static to high strain rate response of soft materials such as hydrogel\ , ballistic gelatin\, human patellar tendon\, porcine brain tissue.\nFinal ly\, challenges of conducting simple shear experiments on hyperelatic mate rials are highlighted. The robustness of constitutive model for capturing deformations under complex loads such as wedge-indentation and high veloci ty long-rod impact on a rigid surface are demonstrated.\n \n \nShort res ume \n\nProfessor Subhash obtained his PhD from University of California S an Diego (UCSD) in 1991 and conducted post-doctoral research at California Institute of Technology (Caltech) during 1992-93. He joined Michigan Tech nological University in 1993 and then moved to University of Florida in 20 07.\nHis research expertise is in multiaxial dynamic constitutive behavior of materials\, processing-microstructure-property-performance relationshi ps in advanced structural ceramics\, and experimental solid mechanics. His research efforts have focused on  understanding the deformation mechanis ms in a range of materials including refractory metals\, bearing steels\, bulk metallic glasses\, ultrahard ceramics\, low-density foams\, nuclear c eramics\, brain tissue\, and polymeric gels. In the context of ceramics\, his research is focused on experimental and computational investigations o n pressure-induced amorphization in icosahedral ceramics. In the field of nuclear engineering\, he has developed rapid processing technology to fabr icate nuclear fuel and control rod pellets in few minutes compared to the traditional methods which take several hours. For this effort\, he has rec eived ‘Significant Contribution Award’ from Materials Science and Tech nology Division\, American Nuclear Society (2014). His contributions in ex perimental solid mechanics have been recognized by the 2018 ‘Frocht Awar d’ from Society 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 ultr ahard bearings received ‘Best Paper Award’ in the Journal of Engineeri ng Materials and Technology (2017). \nProf. Subhash is a fellow of the ASM E and SEM. He serves as an Editor-in-Chief of Mechanics of Materials (an i nternational journal) and as an Associate Editor of the Journal of the Ame rican Ceramic Society.  He has received numerous recognitions for excelle nce in teaching\, research and professional service\, including ‘Technol ogy Innovator Award’ from University of Florida (2016) and Teacher/Schol ar of the year (2013)\, ASME Student Section Advisor Award\, Society of Au tomotive Engineers (SAE) Ralph R. Teetor Educational Award\, and American Society for Engineering Education (ASEE) Outstanding New Mechanics Educato r. He has graduated 34 PhD students and co-authored 190 peer reviewed jour nal articles\, 80 conference proceedings\, and 5 patents. He has co-author ed a book on “Mechanics of Materials Laboratory Course” and is finaliz ing another book on “Dynamic Response of Ceramics”. His inventions hav e received international attention from major TV networks (Fox\, CBS and 4 0 other local TV channels)\, radio stations (including NPR) and articles b y Reuters and ASEE Morning Bell. He has also appeared in a PBS documentary in 2017 (Secrets of Spanish Florida) while discussing the impact response of ‘Coquina’\, a material with which the oldest fort in the United St ates\, the ‘Castillo de San Marcos’ was built in St. Augustine\, Flori da.\n  LOCATION:GC A3 30 https://plan.epfl.ch/?room=GCA330 STATUS:CANCELLED END:VEVENT END:VCALENDAR