Predicting Damage in Aerospace Structures Due to Adverse Weather Encounters
by İbrahim Güven, Mechanical and Nuclear Engineering, Virginia Commonwealth University
Date: 19.02.2024
Time: 15:30
Location: VYKM1
Abstract:
There is renewed interest in hypersonic flight with applications in defense and civilian aerospace. Nontrivial chances of weather encounters with airborne particles (raindrops, ice particulates, volcanic ash) exist at lower altitudes. Predicting structural damage due to raindrops at hypersonic velocities is an open problem owing to the complex multiphysics involved. This talk will first describe the physics of the high-speed droplet impact and then demonstrate a computational solid mechanics approach, peridynamics, for damage predictions. Droplet-shock layer interactions, coupling with computational fluid dynamics, 2D vs. 3D, and other relevant topics will be discussed.
Short Bio:
Ibrahim Guven is an Associate Professor of Mechanical and Nuclear Engineering at Virginia Commonwealth University (VCU). He was an Assistant Professor of Materials Science and Engineering at The University of Arizona. Ibrahim spent two summers as a Faculty Fellow at the Air Force Research Laboratory. He was a Visiting Professor at the University of Rennes I, France, multiple times. Ibrahim is a recipient of the NASA Group Achievement Award for outstanding work in developing materials for space exploration, which was awarded to participants of the collaborative project he worked on alongside Prof. Wardle, US-COMP Space Technologies Research Institute.
|
CRSS Determination: Combining Analytical Framework and Surrogate Neural Networks |
Human-Machine Interaction with Soft Growing Robots Abstract: |
Material Interfaces Inspired by Catch Bond Adhesins Northwestern University, Department of Mechanical Engineering DATE : November 25, 2022 (Friday) Abstract: Over the last few years, there has been a transition away from traditional engineering materials to new advanced materials that exhibit complex architectures with improved mechanical properties. Most of the inspiration for these new materials comes from nature, where organisms have evolved an immense variety of macro and nanoscale shapes and structures with clever mechanisms. Adhesion proteins are particularly inspiring for novel materials because they exhibit conformational dynamics that enables them to form special non-covalent interactions called ‘catch bonds’ with their ligand, where dissociation lifetime of ligand-protein complexes is enhanced by mechanical force. Intuition suggests that application of a tensile force on a chemical bond should tend to shorten the bond’s lifetime, making it more likely to break, but catch bonds defy this notion. If implemented in material systems, catch bonds are predicted to address trade-offs between strength and reconfiguration, two diametric material properties that are primarily governed by the strength of intermolecular interactions. This work is a multifaceted approach combining molecular simulations and adhesion theory to establish strategies for designing material interfaces that incorporates catch bond features. Based on adhesin properties, we proposed design guidelines for reproducing the catch bond phenomenon in synthetic systems and created mechanical designs that mimicked protein ligand interaction and exhibited catch bond behavior reliably and predictably under thermal excitations. We demonstrate that catch bond functionality can be achieved using simple molecular mechanisms and provides design rules for making catch bond nanoparticles and linkages, which paves the way for engendering emergent force-tunable interfacial kinetics in synthetic materials. Bio: Kerim completed his B.S. in Mechanical Engineering at Bogazici University. After finishing his PhD in Mechanical Engineering at Northwestern University, he continued to work in NU as a Postdoctoral Scholar. His research focuses on applying computational modeling and statistical thermodynamics to design procedures for nanocomposites with adhesin-inspired interfaces. |
Confluence of Electrochemistry and Mechanics: From Engineering the Rechargeable Batteries to Corrosion in Extreme States by Asghar Aryanfar (American University of Beirut, Department of Mechanical Engineering) DATE : October 07, 2022 (Friday) During the recent decades, the portable electronics (cell-phones, laptops, etc.) have entered the daily lifestyle, and require exponentially-increasing versatility and computational power. Hence, they demand portable electricity source necessitating the boost in terms of energy density, safety, efficiency and sustainability. On the other hand, the ever-increasing need for harnessing the green renewable energy as a potential replacement of the pollutant fossil fuels for applications such as electric vehicles, requires their capture and management via stationary smart infrastructures. The electrochemical systems, such as rechargeable batteries are the prominent answer for the in abovementioned applications. Therefore, while the exploitation of new high-energy density materials/composites for high-power applications is unavoidable, herein we delve into the engineering of the advanced electrochemical devices (batteries) and phenomena (corrosion) as well as their coupling with the mechanics at the interfaces, by performing multi-physics modeling and electrochemical experiments as the following:
Bio: Asghar Aryanfar received the B.S. in Civil and Mechanical Engineering (double major, top 2%) from Sharif University of Technology, Tehran, Iran in 2009 and the M.S. and Ph.D. degrees in Mechanical Engineering from California Institute of Technology, in 2010 and 2015, respectively. He is currently Assistant Professor of Mechanical Engineering at American University of Beirut (2019−present). Prior to current position, he was visiting faculty at Caltech (2018 − 2019) as well as lecturer at Faculty of Engineering at Bahçesehir University (2016 − 2019). Before then, he was Postdoctoral Associate at University of California, Los Angeles (UCLA) (2015 − 2016). Aryanfar’s research has been in the application of multi-physics modeling and experimental electrochemistry into engineering of the energy storage and conversion devices, materials and and exploitation of their interfacial phenomena. Particularly, his research on safety of high-energy rechargeable batteries has appeared as the Cover image of the Journal of Chemical Physics and he has been interviewed in CNN for his 1st prize winning invention of novel wastewater treatment system from the Gates Foundation. Current projects are the material/interfacial physics and include analysis and design of state-of-the-art sustainable rechargeable lithium metal batteries and prediction of heterogeneous cracking behavior for electrolytic membranes exposed to extreme temperature/pressure. |
Phononics at the Macroscopic and Microscopic Scales: Recent Advances in Complex Band-Structure Engineering and Atomic-Scale Resonant Thermal Transport |
Quasicrystal-Induced Nucleation Mechanism in Undercooled Liquids by Güven Kurtuldu (Laboratory of Metal Physics and Technology, Department of Materials, ETH Zürich, Switzerland) DATE : July 18, 2019 (Thursday) Abstract: A model alloy Mg69Zn27Yb4 has recently been discovered, which concurrently forms bulk metallic glass (BMG), metastable icosahedral quasicrystals (iQCs), and two crystalline approximant phases from the melt [1]. The following phases were observed (at room temperature) at increasing cooling rate via a recently developed technique, fast differential scanning calorimetry (FDSC): (i) stable Mg and approximant Mg29Zn60Yb11 phase mixture; (ii) metastable Mg and iQC phase mixture; (iii) approximant Mg51Zn20-type metastable particles; and (iv) a glassy phase. Deploying a new experimental strategy, i.e. heating the previously solidified microstructure at ultrafast rates via FDSC, the equilibrium Mg29Zn60Yb11 phase has never been observed to form directly from the melt; instead the metastable iQC phase nucleated first in the liquid and then transformed into a stable approximant phase. Such a transition path (undercooled liquid → metastable QCs → stable equilibrium phase) has also recently been suggested to occur in Al–Zn:Cr [2] and Au–Cu–Ag:Ir [3] alloys. The observations made have significant effects on control over solidification microstructures via grain refinement. The phase transition path minimizes the free energy barrier for nucleation through an intermediate metastable quasicrystal phase due to the low solid–liquid interfacial energy of quasicrystals. The experimental results shed new light on the competition between metastable and stable crystal formation, and glass formation via system frustration associated with the presence of several free energy minima. The rapid heating strategy using FDSC may yield the discovery of hidden transient phases that are key to understanding crystallization pathways in metallic systems, as well as polymers, biological solutions and pharmaceutical substances. [1] Kurtuldu G, Shamlaye K F, Löffler J F. Metastable-quasicrystal-induced nucleation in a bulk glass-forming liquid, PNAS, 115 (24), 6123-6128 (2018). Short Bio: Güven Kurtuldu received his Bachelor of Science degree in 2007 and Master of Science degree in 2009 from the Department of Mechanical Engineering under the guidance of Prof. Sabri Altıntaş working on properties of boron nitride nanotube/epoxy composites at Boğaziçi University. He continued his PhD study in the group of Prof. Michel Rappaz at École Polytechnique Fédérale de Lausanne (EPFL), Switzerland. His thesis focused on effect of minute additions of solute elements on solidification microstructures in metallic alloys. He discovered a nucleation mechanism for which formation of metastable quasicrystals from the liquid is the key to control the as-cast microstructures. He was awarded his PhD degree in 2014. After staying one year as a postdoc in the same group, he joined the group of Prof. Jörg Löffler at ETH Zürich, Switzerland. He is currently working on several projects related to quasicrystal and bulk metallic glass formation, structure of metallic liquids, development of novel experimental strategies via fast calorimetry and microstructure formation in additively manufactured alloys. |
Robust Surfaces for Carbon-Free Energy Conversion |
Tribology of Materials Across Length Scales
|
Rehabilitation in MRI via Pneumatically Driven Systems Magnetic resonance imaging (MRI) has been the flagship scanning technology for brain studies over the last two decades, by virtue of its spatial resolution and ability to monitor human soft tissue. In the recent years, there has been a growing interest in developing MRI-compatible robots to exploit MRI’s capabilities for healthcare applications such as surgical operations and physical rehabilitation. Fluid-driven systems offer the ultimate MRI compliance as such systems can be built with non-ferrous materials; however, they are generally oriented for slow operationswith large time constants. Rehabilitation, on the other hand, requires a relatively larger bandwidth for a stable human-robot interaction. This talk will focus on the recent developments at Georgia Institute of Technology towards the use of pneumatically driven tele-operated systems for stroke rehabilitation in MRI. The challenges in the tele-operation of the pneumatic actuators and novel approaches to mitigate the adverse effects of long transmission in pneumatic drive will be presented. The talk will conclude with a discussion on the potential of pneumatically driven systems in human-machine interaction and the corresponding challenges. Short Bio: Melih Turkseven received his BS degree in Mechanical Engineering from Bogazici University in 2010, and Ph.D. degree in Mechanical Engineering from Georgia Institute of Technology in 2016. As a student member of the Center of Compact and Efficient Fluid Power (CCEFP), he has worked on the design and control of an MRI-compatible rehabilitation robot at the Bio-Robotics and Human Modeling Lab, Atlanta. Currently, he is a postdoctoral research associate at the Center for Modeling, Simulation, and Imaging in Medicine (CemSIM) at Rensselaer Polytechnic Institute. His research interests include human-robot interaction, and dynamic systems and control of compliant systems. |
Advanced Locomotion Control of Exoskeleton Systems: The Role of Active and Passive Compliance The exoskeleton market is exponentially growing as its market size is estimated to surpass 3.4 billion USD by 2024. Likewise, R&D activities for wearable robots and exoskeletons show a significant increase. These systems are increasingly playing an important role in robot-aided walking support, elderly care, and SCI rehabilitation. Since these systems are in physical contact with humans, adjustable physical compliance, transparency and high fidelity control techniques are of importance to shape the next-gen exoskeletons of tomorrow. With this view in mind, the first segment of my talk will succinctly address my earlier research regarding the legged locomotion control of humanoids and quadrupeds. In the second segment of my talk, I will share my hands-on experiences on two different exoskeleton systems: i) TTI-Exo, a whole body exoskeleton built in Toyota Technological Institute, Japan, ii) XoR, the first self-balancing lower limb exoskeleton with adjustable physical compliance and active disturbance rejection capability, built at the Dept. of Brain-Robot Interface, CNS-ATR, Japan. I will emphasize how the prior hands-on experience on legged locomotion enabled me to create exoskeleton systems that have distinguishable characteristics from the others. The third segment of my talk will disclose my vision concerning the next-generation exoskeleton robots and a roadmap to realistically develop such systems. Barkan Ugurlu received his Ph.D. degree in Electrical and Computer Engineering from Yokohama National University, Yokohama, Japan, in March 2010. From May 2010 to March 2013, he was a Post-Doctoral Researcher, at the Istituto Italiano di Tecnologia, Genova, Italy, and Toyota Technological Institute, Nagoya, Japan. Between March 2013 and February 2015, he was a Research Scientist at the Computational Neuroscience Laboratories, Advanced Telecommunications Research Institute International (ATR), Kyoto, Japan. He currently holds an Asst. Prof. position at the Dept. of Mechanical Engineering, Ozyegin University, Istanbul, Turkey. His research interests include active orthoses and exoskeletons, robot-aided rehabilitation, humanoid/quadruped locomotion control, and human-centered manipulation. He is a Marie Skłodowska-Curie Fellow. |
Autonomous Mobile Vehicles and String Stability of Interconnected Vehicles In this introductory part of the presentation, an overview of past research experiences on autonomous mobile vehicle platforms will be presented with some example applications within the field of automotive and robotics. Some design considerations such as sensor and actuator selections besides the different modelling and control approaches for the realizations will be discussed on the following automated vehicle platforms: The ever-increasing demand for mobility in today’s life brings additional burden on the existing ground transportation and logistic infrastructure, for which a feasible solution in the near future lies in more efficient use of currently available means of transportation. For this purpose, development of Cooperative Intelligent Transportation Systems (C-ITS) technologies that contribute to improved traffic flow stability, throughput, and safety is needed. Cooperative Automated Vehicles (CAVs) being one of the promising C-ITS technologies, extends the currently available Advanced Driver Assistance Systems technologies with the addition of information exchange between vehicles through Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) wireless communication.A particularly interesting application is the vehicle platooning concept. The general objective of vehicular platooning is to pack the driving vehicles together as tightly as possible in order to increase traffic throughput while preventing amplification of disturbances throughout the string, the latter of which is known as string instability. This technology relies on longitudinal control known as Cooperative Adaptive Cruise Control (CACC). In the scope of CACC, control over a wireless communication network is the enabling technology that makes this realizable; however, given the fact that multiple nodes (vehicles) share the same medium with a limited bandwidth and capacity, wireless communication introduces network-induced imperfections such as transmission delays and packet losses. The impact of these imperfections on string stability requires a careful analysis and tradeoffs between control performance and network specifications need to be made for achieving desired performance under these network-induced constraints. Therefore, in this study we present the design of a CACC system from a Networked Control System (NCS) perspective and a novel modelling framework is introduced. This modelling framework is extended with analysis tools for string stability in the presence of network effects. These analyses can provide the designer with guidelines for making multidisciplinary design tradeoffs between control and network specifications and support the design of CACC systems that are robust to uncertainties introduced by wireless communication. Moreover, the validity of the presented analysis framework is demonstrated via experimental results performed with CACC-equipped prototype vehicles. Experimental results show that the developed NCS modelling framework captures the dependency of string stability on network-induced effects and confirm the string stable operation conditions obtained by model-based analyses. Sinan Öncü received the B.Sc. degree in electronics and telecommunications engineering and the M.Sc. degree in mechatronics engineering from Istanbul Technical University, Istanbul, Turkey, in 2005 and 2008, respectively, and the Ph.D. degree in mechanical engineering from the Eindhoven University of Technology, Eindhoven, The Netherlands, in 2014. From 2013 to 2016, he was affiliated with the Netherlands Organization for Applied Scientific Research (TNO), The Netherlands, where he worked as a research scientist on the realization of cooperative automated vehicle technologies and their demonstrations with prototype vehicles to governmental institutes, industrial partners, and stakeholders; amongst which are most notably: the first automated driving demo in the Netherlands on public roads in 2013, and The European Truck Platooning Challenge in 2016. Since December 2017, he works as a Senior Software Engineer at Ford Otosan in Istanbul Sancaktepe R&D Center and leads the Horizon2020 project “Optimal fuel consumption with Predictive Power Train Control and calibration for intelligent trucks” (optiTruck). His current research focuses on the development of optimization-based predictive power management control systems for heavy duty trucks. Besides his professional research activities, he is enthusiastic about motorcycles and their dynamics. He combines this interest with travelling, camping, and photography. He enjoys going on long trips with his self-instrumented motorcycle and collects road data for his hobby project on developing an advisory system for safety improvement for motorcyclists. |
Bio-resorbable sensors and MEMS energy harvesters for next-generation transient and self-powered implants Abstract: Implantable medical devices and the concept of integrating sensors/electronics into the human body have been intriguing curiosities especially in medicine for many decades. Recent developments in microfabrication and materials science finally have enabled development of sub-mm-sized implants for monitoring of critical parameters such as blood In the first part of the seminar, a bio-resorbable and battery-free implant for wireless artery pulse monitoring will be presented. Design and fabrication of the proposed implant will be detailed by emphasizing particular diseases and surgical operations that require short-term vascular monitoring. Then, the focus will be on energy harvesting implants Short Bio: Levent Beker received B.Sc. and M.Sc. degrees in Mechanical Engineering and Micro/Nanotechnology from Middle East Technical University in 2010 and 2013, respectively. During his master’s he worked on fully-implantable cochlear implants. Then, he obtained his Ph.D. in Mechanical Engineering from University of California, Berkeley in 2017 where he worked on energy harvesting from cerebrospinal fluid (CSF) flow inside the brain and pressure sensors for harsh environment applications. He is currently a post-doctoral research fellow working with Professor Zhenan Bao in Chemical Engineering at Stanford University. His current research focuses on bio-resorbable wireless implants, flexible/stretchable sensors for electronic-skin applications. He received Postdocs at the Interface award from Stanford University, Howard Hughes Medical Institute (HHMI) International Researcher Fellowship, Best poster award at Berkeley Sensor Actuator Center’s Industry Advisory Board Conference, Outstanding presentation award at Transducers 2013 Barcelona, and Best Thesis award from Middle East Technical University. |
Non-Schmid slip behavior in shape memory alloys |
Rechargeable Next-Generation Magnesium/Oxygen Batteries |
Electrothermal Modeling of AlGaN/GaN Heterostructure Field Effect Transistors |
Harmonic Control Arrays
By Murat Dogruel
13.05.2015, 15:30, Mühendislik Binası VYKM 4
A novel method is presented for systems with periodic references and/or disturbances by employing controllers in an array structure for each dispersed harmonic components. The method is based on automatically and appropriately setting the complex levels of the harmonic components of the control signal. Both computer simulation and real time experimental results are presented to illustrate the usefulness and effectiveness of the proposed method.
Murat Dogruel was born in Istanbul, Turkey in 1967. He received the B.S. degree in Electronics and Communication Engineering from Istanbul Technical University, Turkey, in 1988, and the M.S. and Ph.D. degrees in Electrical Engineering from the Ohio State University, Columbus, in 1992 and 1995. Since 1995, he has been working at the Faculty of Engineering at Marmara University, Istanbul, Turkey, where he is currently a full professor in the Department of Electrical and Electronics Engineering. He served in the military as a faculty member at Turkish Air Force Academy from 1996 to 1997. Then, he was appointed as the chairman of the Department of Electrical and Electronics Engineering at Marmara University. He was a Visiting Associate Professor at University of Miami, Electrical and Computer Engineering Department from 2001 to 2003. He served at the International University of Sarajevo, Bosnia and Herzegovina, as the Dean of Faculty of Engineering and Natural Sciences from 2006 to 2008. He is the Dean of Faculty of Engineering at Marmara University since 2014. His research interests include hybrid state systems, nonlinear control, harmonic control arrays and intelligent systems.
|