报告题目：Flexible membrane-based Wave Energy Converters: Time-dependent experimental study and numerical modelling
报告人：Mokarram Hossain 副教授，英国斯旺西大学辛克维奇计算工程中心
Over the past decade, there has been a focus on optimising energy harvesting devices by making use of structural flexibility. Large membranes made of polymeric materials, for instance, can be employed in ocean energy harvesting devices. The transient response of elastomeric polymers is dependent on polymer composition, temperature and the loading history. In particular, hysteresis, dissipation and creep are significant in the choice of material for elastomer membrane wave energy converters. Natural rubber is a good candidate when looking for material for a wave energy harvester since it has an excellent stretchability, is almost resistant to the environment in which the harvester will be used and has good fatigue properties. The mechanical behaviour of the natural rubber used in this work has been deeply characterised: the material resulted to have a very little hysteretical behaviour but also to show a strain-dependency, stress softening, and relaxation at constant stretch. Afterwards, an extended finite strain viscoelastic constitutive model is proposed that is calibrated analytically to the experimental data to identify the relevant material parameters resulting in non-linear viscosity functions in the evolution equations of the constitutive model. The model was able to capture the minimal dissipation behaviour with good degrees of accuracy. Results are shown for a flexible membrane wave energy converter under creep and cyclic loading. A parametric study is made comparing the experimentally characterised polymer with different amounts of viscous dissipation. The response of the wave energy converter shows that even minimal amounts of dissipation manifests itself into changes in the pressure–volume function and reduction in energy capture through hysteresis. The new material model shows, for the first time, that the control of internal pressure in wave energy membranes must take into account transient material effects.
报告人简介：Dr Mokarram Hossain is an Associate Professor at the Zienkiewicz Centre for Computational Engineering (ZCCE) at Swansea University. The ZCCE is considered as the World-leading Centre of Excellence in computational modelling for the last five decades. After completing his Bachelor in Bangladesh University of Engineering and Technology, Dr Hossain obtained Masters in Computational Engineering (2005) from Technical University of Braunschweig, Germany. He obtained a PhD in Mechanical Engineering (2010) from University of Erlangen-Nuremberg, Germany under the supervision of Prof Paul Steinmann. He moved to the UK, at first in Northumbria University as a Lecturer in 2015, then to Swansea University as a Senior Lecturer in 2017.
Dr Hossain’s research interests lie in the wide and interdisciplinary areas of soft polymeric and active multifunctional materials ranging from material synthesis, experimental study to computational modelling. He has been active in the areas of biological tissue modelling and polymeric material characterisations under thermo-electro-magneto-mechanical loads. He has numerous fundamental and cutting-edge contributions in the areas of polymer curing modelling, electro-active, magneto-active polymers, hydrogel experiments and modelling. He has obtained several research grants including from UK Research Council (EPSRC), Royal Society and industries for energy harvesting, soft material characterisations using electro-active/magneto-active polymers. Dr Hossain obtained the best Postdoc Paper Prize from the UK Association for Computational Mechanics (UKACM). He was a Mercator Fellow from Gerrnan Science Foundation (DFG) and ASEM-DUO Fellow from South Korea. Dr Hossain published more than 80 peer reviewed journal papers in many leading journals across disciplines of materials, mechanics and computations He is the Managing Guest Editor of a Special Issue in European Journal of Mechanics-A/Solids.