WEDNESDAY, JUNE 7
Eleni Chatzi, Ph.D.,M.ASCE, Eidgenössische Technische Hochschule (ETH) Zürich(Switzerland)
Title: Nurturing Augmented Twins; From First Principles, to Learning, to Real-time Virtualization
Time: 08:30 – 09:30
Abstract: Modern engineering structures form complex assemblies that operate under highly varying loads and adverse environments. To ensure a resource-efficient and resilient operation of such systems, it is imperative to understand their performance as-is; a task which can be effectuated through Structural Health Monitoring (SHM). SHM comprises a hierarchy across levels of increasing complexity aiming to i) detect, ii) localize and iii) quantify damage, and iv) finally offer a prognosis over the system's residual life. When considering higher levels in this hierarchy, including damage assessment and even performance prognosis, purely datadriven methods are found to be lacking. For higher-level SHM tasks, or for furnishing a digital twin of a monitored structure, it is necessary to integrate the knowledge stemming from physics-based representations, relying on the underlying principles of mechanics/dynamics. This talk discusses implementation of such a hybrid approach to SHM aiming to tackle the aforementioned challenges for robust simulation and monitoring of engineered systems. It offers a view to establishing augmented twin representations, capable of representing the structure as-is, anticipating performance under future stressors, and advising on preventive and remedial actions.
Biographical Sketch: Eleni Chatzi is an Associate Professor and Chair of Structural Mechanics and Monitoring at the Department of Civil, Environmental and Geomatic Engineering of ETH Zurich, Switzerland. Her research interests include the fields of Structural Health Monitoring (SHM) and structural dynamics, nonlinear system identification, and intelligent life-cycle assessment for engineered systems. She has authored more than 300 papers in peer-reviewed journals and conference proceedings, and further serves as an editor for international journals in the domains of Dynamics and SHM. She led the recently completed ERC Starting Grant WINDMIL on the topic of "Smart Monitoring, Inspection and Life-Cycle Assessment of Wind Turbines". Her work in the domain of self-aware infrastructure was recognized with the 2020 Walter L. Huber Research prize, awarded by the American Society of Civil Engineers (ASCE).
Chad M. Landis, Ph.D., University of Texas at Austin
Title: Modeling and Simulation of Shape Memory Alloy Materials and Structures
Time: 13:00 – 14:00
Abstract: In this lecture I will present work with my colleague, Prof. Stelios Kyriakides, and our students on our recent investigations of the physical response of shape memory alloy structures, under a wide range of thermal and mechanical loadings that link careful experiments with detailed numerical simulations. The first part of the talk will focus on the structure of a newly devised constitutive modeling framework describing the thermomechanical response of SMAs. As the ultimate goal of the model is its implementation within finite element calculations of SMA structures, it is a phenomenological model with a small set of internal variables, specifically the transformation strains and the transformation entropy that is directly related to the martensite volume fraction. The construction of the model is based on a usual flow-theory plasticity framework with kinematic hardening. One novelty of the approach is that a single transformation, i.e. yield, surface in effective stress and effective temperature space is introduced, and an associated flow rule then governs the evolution of the transformation strain and entropy. To capture the multitude of SMA behaviors, a transformation potential function is introduced in transformation strain and entropy space for the derivation of the back stresses and back temperatures that define the kinematic hardening behavior. It is this potential function that governs all the important behaviors within the model. The model is capable of capturing the asymmetries in tension versus compression for transformation strain, transformation stress, and in the hardening in tension versus compression with softening allowed in tension along with hardening in compression. The second part of the talk will describe the implementation of the model for the simulation of SMA strips and tubes subjected to a wide range of thermomechanical loadings (tension, compression, bending, iso- and nonisothermal). Meticulously devised experiments were performed that show that these structures exhibit instabilities, e.g. buckling in compression and Lüders-like bands in tension due to softening, that are all reproduced in the simulations. Finally, I will discuss our work on a transformation strain gradient enhancement of the model for incorporating the material length scale associated with the macroscopic interface between austenite and martensite in these structures, and how that length scale can be determined by linking careful experiments to detailed numerical simulations.
Biographical Sketch: Professor Landis has a broad range of interests in the mechanics of materials, including fracture mechanics, plasticity, micromechanics, composites, and finite element methods. He has made contributions to the constitutive modeling and fracture mechanics of ferroelectrics, ferromagnetic materials, and shape memory alloys. He has also made significant contributions to phase-field modeling of fracture where he has applied and extended this approach to dynamic crack propagation, ductile failure, hydraulic fracture, and fatigue crack growth. His work is highly collaborative and he is always looking to cooperate with other researchers both in his own department, nationally, and internationally. Professor Landis serves as an Associate Editor for the International Journal of Solids and Structures, a Regional Editor for the International Journal of Fracture, Associate Editor for the Journal of the American Ceramics Society, and in the past as Associate Editor for the Journal of Applied Mechanics. He also serves on the Editorial Board of Computational Methods in Theoretical and Applied Mechanics. Additionally, he is as a member of the U.S. National Committee for Theoretical and Applied Mechanics, and in the summer of 2022, he served as the co-Chair of the 19th U.S. National Congress on Theoretical and Applied Mechanics.
THURSDAY, JUNE 8
Catherine O’Sullivan, Ph.D., Imperial College London (UK)
Title: Particle Scale Modelling of Clay: Challenges and Opportunities
Time: 08:30 – 09:30
Abstract: Understanding of the mechanical behaviour of granular materials, including sand, has been greatly improved thanks to our ability to use the discrete element method to develop numerical models that explicitly consider the individual particles and their interactions. In many civil engineering projects the more significant geotechnical challenges are posed by clay deposits. In contrast to sand grains, clay particles are platy, the electrostatic forces between them influence their movement, and the interactions are sensitive to the pore water chemistry. This means we cannot directly apply software and algorithms developed for sand to clay; instead the modelling toolkit needs adaptation and extension to enable us to address problems that can have a real impact on civil engineering practice. In other words, the models are, by necessity, significantly more complex. This presentation will lay out the argument in favour of the development of particle-based models of clay. Then, drawing on her own experience, the speaker will lay out the key challenges that must be addressed to develop useful particle-based models of clay. This discussion will encompass the particle interaction models (potential functions) required including their calibration, interparticle friction, system size effects, and the anisotropy of the particle surface charge. The arguments will largely be supported by considering data from recent molecular dynamics simulations of systems of kaolinite particles, however many of the points made are applicable to other mineralogies and other colloidal materials.
Biographical Sketch: Catherine O’Sullivan is a Professor in Particulate Soil Mechanics at Imperial College London. Originally from Ireland, she obtained her PhD from the University of California at Berkeley in 2002. Her research has examined soil behaviour focusing on the particulate scale. Catherine has authored a textbook on the use of discrete element modelling in geomechanics and has authored/co-authored over 100 contributions to international journals. In 2015 she delivered the Géotechnique lecture. Funding for her post-graduate studies and research has been provided by the Fulbright Programme, the O’Reilly Foundation, IRCSET, the EPSRC, the ICE, the Leverhulme Trust and ARUP. Catherine is currently a member of the editorial boards of Soils and Foundations, Computers and Geotechnics, Granular Matter and an Editor of the ASCE Journal of Geotechnical and Geoenvironmental Engineering.
Yuri Bazilevs, Ph.D., A.M.ASCE, Brown University
Title: Recent Advances and Breakthroughs in the Modeling and Simulation of Extreme Events
Time: 13:00 – 14:00
Abstract: In this presentation we’ll first give a broad discussion of computational Fluid—Structure Interaction (FSI), focusing on several classes of problems and the corresponding numerical formulations that deliver efficient, accurate and practical solutions. Next, we’ll discuss a new class of formulations for the immersed coupling of Isogeometric Analysis (IGA) and Meshfree Methods for the simulation of FSI with applications to extreme events. We’ll focus on air- and water-blast FSI applications, and address the computational challenges of immersed FSI methods in the simulation of fracture and fragmentation by developing strongly and weakly volume-coupled FSI formulations and showing these in action. In the present work, we employ Peridynamics as a discretization as a meshfree methods of choice, however, the proposed approach works just as easily with other meshfree methods. We show the mathematical formulations and present several numerical examples in 2D and 3D, and with experimental validation, of inelastic ductile, brittle and quasi-brittle solids under blast loading that clearly demonstrate the power and robustness of the proposed methodologies.
Biographical Sketch: Yuri Bazilevs is the E. Paul Sorensen Professor in the School of Engineering at Brown University, where he was the Lead and Executive Committee representative of the Mechanics of Solids and Structures group. He was previously a Professor and Vice Chair in the Structural Engineering Department at the University of California, San Diego. Yuri’s research interests lie in the broad field of computational science and engineering, with emphasis on the modeling and simulation in solids and structures, fluids, and their coupling in HPC environments. For his research contributions Yuri received many awards and honors, including the 2018 Walter E. Huber Research Prize from the ASCE, the 2020 Gustus L. Larson Award from the ASME, the inaugural 2021 Centennial Mid-Career Award from the Materials Division of the ASME, and the Computational Mechanics Award from the International Association for Computational Mechanics (IACM). He is included in the lists of Highly Cited Researchers, both in the Engineering (2015-2018) and Computer Science (2014-2019) categories. Yuri recently completed his service as the President of the US Association for Computational Mechanics (USACM) and as the Chairman of the Applied Mechanics Division of the ASME. He currently serves on the US National Committee for Theoretical and Applied Mechanics (USNCTAM).
FRIDAY, JUNE 9
Genda Chen, Ph.D., P.E., F.ASCE, Missouri Science & Technology University
Title: Engineering Mechanics Role in Robot-enabled Infrastructure Preservation
Time: 08:30 – 09:30
Abstract: More than 42% of over 617,000 U.S. bridges are 50 years (design life) or older. It is thus imperative to meet more frequent and more rigorous preservation needs to ensure that the aging infrastructure is safe during everyday operations and resilient to catastrophic events. Drones and structural crawlers, or robots in general, are efficient and effective platforms that can be rapidly deployed to support sensor installation, visual inspection, nondestructive evaluation, and preventive maintenance of bridges. This presentation will provide an overview of engineering mechanics problems and solutions to platform dynamics, the probability of deterioration detection, aerial testing and evaluation, and machine learning for data-driven asset management enabled by the INSPIRE University Transportation Center partners. For example, control design equations of structural crawlers and/or drones with robotic arms will be established and solved to support bridge inspection and maintenance tasks. Given k robots, a Np-hard min-max k-Chinese postman problem will be formulated to generate optimal inspection routes using generic algorithms. Aerial impact-echo tests for delamination detection and/or ultrasonic metal thickness measurement will show their superior performance that is comparable to ground-based nondestructive tests. Mathematically rigorous approaches to evaluate the level of deterioration based on the data taken from in-situ sensors will be presented to shed light on the unconservative nature of traditional statistical analysis. Explainable artificial intelligence will engage inspectors at two levels: (1) inspectors-in-the-loop during training and testing of semi-supervised deep learning algorithms and (2) sensitivity analysis to understand the effect of individual key factors to a desirable prediction from neural additive models. This presentation will conclude with a few key challenges and research opportunities in robot-enabled infrastructure preservation.
Biographical Sketch: Dr. Genda Chen is Professor and Abbett Distinguished Chair in Civil Engineering, Director of the Center for Intelligent Infrastructure, and Director of INSPIRE University Transportation Center at Missouri University of Science and Technology. He has authored or co-authored over 400 technical publications and delivered 28 keynote/invited presentations at international conferences. He received the international 2019 Structural Health Monitoring Person of the Year Award and the 1998 National Science Foundation CAREER Award. He is a Fellow of American Society of Civil Engineers and the International Society for Structural Health Monitoring of Intelligent Infrastructure. He serves as Vice President of the U.S. Panel on Structural Control and Monitoring.
Daniel Straub, Ph.D., Technical University of Munich (Germany)
Title: Decision-oriented Sensitivity Analysis with Applications to Engineering Mechanics
Time: 13:00 – 14:00
Abstract: In engineering, models are created and employed to support decision making. Consider a structural engineering model that serves to determine the materials, shapes and dimensions of structural members. Or a fracture mechanics model that is established to assess the safety of a mechanical component against fatigue, to decide if the component can be safely continued in operation. As engineers are aware, such models and their predictions are subject to uncertainty, which must be considered when making decisions based on the model output, e.g., by using safety factors. Sensitivity analysis can be employed to better understand the effect of specific input uncertainties on the model outcome. There exist a myriad of sensitivity measures that can be employed, which can be confusing. Since the engineering model is ultimately used for decision making, what measure could be better suited than one that directly quantifies the effect of the uncertainty on the decision, i.e., a measure of decision sensitivity? Such measures have been around for a while, but have received no attention in the engineering community. They measure the importance of a specific input uncertainty by quantifying how likely this uncertainty causes a change in the decision, and how much can be gained by an improved decision. As I will show in this talk, they are easier to interpret than other sensitivity measures and their computation is not necessarily more demanding than that of other commonly used measures, such as the Sobol’ index. I start out the talk with a brief introduction to sensitivity analysis and its goals. This includes a discussion of uncertainty in engineering models and their treatment in decision support. I then present the decision-theoretic background (which is less complicated than it sounds) and show the derivation of decision sensitivity measures. Since the measures depend on the decision context, I propose a categorization of decisions encountered in engineering mechanics and derive the proper sensitivity measures for these different decision categories. Along the way, the relation to other commonly used sensitivity measures are highlighted – which also helps to better interpret those measures. This is followed by a presentation of different computational strategies to evaluate these sensitivity measures. I show that often the measures can be obtained by a mere postprocessing of results obtained from a standard uncertainty or reliability analysis. Throughout the talk, application examples illustrate the concepts and methods and demonstrate their easy interpretability. The talk ends with a discussion of lessons learnt from real-life applications and remaining challenges.
Biographical Sketch: Daniel Straub is Associate Professor for engineering risk and reliability analysis at Technical University of Munich (TUM). He develops physics-based stochastic models and methods for decision support and safety analysis of engineering systems, with a particular focus on Bayesian techniques and AI methods. Daniel obtained his Dipl.-Ing. degree in civil engineering in 2000 and his PhD in 2004 from ETH Zürich and was a postdoc and adjunct faculty at UC Berkeley before joining TUM in 2009. He is also active as a consultant to the industry on reliability and risk assessments and decision making under uncertainty. His awards include the ETH Silbermedaille, the Early Achievement Research Award of IASSAR and the SAE Ralph H. Isbrandt Automotive Safety Engineering Award.
