Author: Orlando E

Mechanical Engineering Lightning Talks

Join us to learn about the exciting research that some of our Faculty and their groups are doing at our Department at our ME Lightning Talks!  Pizza will be provided.  Since space is limited, this event is limited to ME graduate students and faculty, and a limited number of ME undergraduate seniors. If you are an undergraduate senior and would like to attend, please RSVP at https://goo.gl/forms/HypP70ShGSqKTNay2  (spots will be granted in the order that confirmations are received until capacity is filled). You will receive later in the week an email confirming your attendance.

 

Prof. Thanh Nguyen – Novel processing of biodegradable and biocompatible polymers at small scales for medical applications. Biodegradable polymers have a significant impact to medical field. In my talk, I will present researches which aim to further fabricate and process the polymers at small scales, enabling their special functions for use in important medical implant devices. The first part of this talk will be focused on a novel manufacturing technology, which allows to create versatile 3D microstructures of biodegradable polymers for vaccine/drug delivery. The second part of this talk will be emphasized on a new approach, which enables the polymers to be electromechanically-active for use in an implanted biodegradable force-sensor. The presented works, while significantly enhancing functionality and usefulness of the polymers, do not compromise their excellent biodegradability and biocompatibility for medical use.

 

Prof. Georgios Matheou – Numerical model error in simulations of turbulence. Although turbulent flows are prominent and ubiquitous in many applications, their prediction remains challenging. Simulation has the potential to become the primary tool for discovery by utilizing recent advances in computing power. Thus, high fidelity simulations with good characterization of model errors are required. A study of numerical model error in passive scalar mixing is discussed. The range of values of scalar fields in turbulent flows is bounded by their boundary values, for passive scalars, and by a combination of boundary values, reaction rates, phase changes, etc., for active scalars. In practice, this fundamental constraint is often violated with scalars exhibiting unphysical excursions. Analysis of scalar-excursion statistics shows that unphysical scalar excursions in large-eddy simulations result from dispersive errors of the convection-term discretization where the subgrid-scale model provides insufficient dissipation to produce a sufficiently smooth scalar field.

 

Prof. Dianyun Zhang – An Integrated Multi-Scale and Multi-Physics Modeling Tool for Advanced Composite Structures. Fiber-reinforced polymer matrix composites have been increasingly used in aerospace structures owing to the weight and life-cycle cost savings they provide. However, manufacturing these lightweight materials involves curing an epoxy resin under elevated temperatures, which inevitably results in dimensional change and residual stress build-up. To minimize these manufacturing-induced imperfections through an optimal cure cycle, it is critical to develop a physics-based process model underlying the fundamentals of resin curing kinetics and the correlation between the process parameters and the final structural performance. In this talk, an integrated multi-physics and multiscale model will be used to predict the residual stress generation and dimensional change of a composite laminate. Predictions of the warpage of an unsymmetrical panel and the spring-in angle of an L-shaped composite flange will be used to illustrate the advantages of the proposed modeling tool.

Structure Genome: A Revolutionary Multiscale Approach to Bridging Materials Genome and Structural Analysis

Abstract: Materials Genome Initiative (MGI) and Integrated Computational Materials Engineering (ICME) have the potential to accelerate discovery, developing, manufacturing, and deploying of advanced materials. However, it is usually not the material performance, but the structural performance or system performance we are pursuing. To fill the gap between materials genome and structural analysis, the concept of Structure Genome (SG) is proposed. SG is the smallest mathematical building block containing all the constitutive information for a structure. The Mechanics of Structure Genome (MSG) represents a revolutionary approach to multiscale modeling drastically different from the conventional bottom-up multiscale modeling approaches. The principle of minimum information loss (PMIL) is used to avoid a priori assumptions commonly invoked in other approaches. MSG confines all approximations to the constitutive modeling which can construct constitutive models for all types of structures including 3D solids, 2D plates/shells, and 1D beams, directly linking the structural properties with microstructural details. MSG simplifies multiscale constitutive modelling to answer three fundamental questions: 1) what is the original model needed for capturing relevant physics? 2) what is the model wanted for a particular design? 3) what is the SG? MSG allows one to choose the starting scale and ending scale and capture details as needed and affordable without invalid scale separation and assumptions within scales. A companion code called SwiftComp is developed as a general-purpose constitutive modeling software which can be used as a standalone code for virtual testing of structures and materials and as a plugin for conventional finite element software packages such as Abaqus, Ansys, Nastran with efficient high-fidelity composites modeling capabilities. SG concept is applicable to any structures and materials featuring heterogeneity and anisotropy including but not limited to composite materials, 3D printed materials, metamaterials, biomaterials, auxetic materials, smart materials, soft materials, etc.

Biographical Sketch: Dr. Wenbin Yu is a Professor in the School of Aeronautics and Astronautics at Purdue University after serving ten years as a faculty at Utah State University. He received his PhD in Aerospace Engineering from Georgia Tech and MS in Engineering Mechanics from Tsinghua University, China. He serves as Director for the Composites Design and Manufacturing HUB (cdmHUB.org), and Associate Director for the Composites Virtual Factory HUB (cvfHUB.org), and is the CTO for AnalySwift LLC (analyswift.com). His expertise is in micromechanics and structural mechanics with applications to composite/smart materials. He has developed several computer codes used today by thousands of researchers and engineers in government labs, universities, research institutes and companies. He is an ASME Fellow and AIAA Associate Fellow. He served as the chair for ASME Structures and Materials Technical Committee and currently serves as the vice chair for AIAA Materials Technical Committee. He serves on the editorial boards of two international journals.

Prof. Xinyu Zhao Awarded American Chemical Society Grant for Research on Bluff-Body Stabilized Premixed Flame

Dr. Xinyu Zhao has been awarded an American Chemical Society Grant through the Petroleum Research fund for her research entitled “A computational study of the lean blow-off mechanisms for a bluff-body stabilized premixed flame.” The fund supports research directly related to petroleum and fossil fuels at nonprofit institutions around the world.

Computational models capture blowoff at conditions similar to those of experiments.

Increasingly stringent emission requirements have recently generated a great deal of interest in lean and stable combustors, i.e. combustors that manipulate air-fuel ratios to increase fuel efficiency and reduce emissions while maintaining stable combustion. One way to stabilize flames in a combustor is through bluff bodies, but the events that lead to lean blowoff (flame extinction) remain unclear due to a variety of factors that require consideration (e.g. highly-transient turbulent flow fields and finite-rate chemistry).

The three-dimensional structures of the bluff-body stabilized flame.

Professor Zhao’s research aims to further the understanding of this phenomenon by using a large-eddy simulation to model and investigate a bluff-body stabilized lean premixed propane flame undergoing intense turbulence. UConn ME colleagues in Professor Baki Cetegen’s group carry out the experiments using laser diagnostics. The proposed modeling study allows flame characteristics such as turbulent flame speed, flame surface densities, strain rates, and various chemical and flow time scales relevant to blowoff to be studied and compared with real world experiments. Discovering the key time scales that lead to blowoff could yield controlling strategies and operation conditions for bluff-body stabilized flames. 

Recently Professor Zhao also received the Young Investigator (YIP) Award from the Air Force Office of Science and Research. Read more about her research on her website. 

Prof. Zhao Awarded Air Force Young Investigator Program for Work on Turbulent Premixed Flames

The Air Force Office of Scientific Research (AFOSR) Young Investigator Research Program (YIP) has honored Professor Xinyu Zhao as one of just 43 scientists and engineers awarded YIP grants for her research project titled “Pockets in Highly Turbulent Premixed Flames: Physics and Implications on Modeling.” The grant is worth a total of $450,000 over three years and is intended to foster the research of young investigators in science and engineering.

Dr. Zhao’s research aims to understand the underlying physical processes of highly turbulent premixed flames, which impact the efficiency and stability of modern aeronautical engines.

Direct numerical simulations of premixed methane flames.

The investigation targets two specific “pockets”: the fresh-mixture pockets on the product side of the flame (“FiP”) and the product pockets on the fresh mixture side of the flame (“PiF”). The existence of these pockets is a distinctive feature of flames within the broken reaction zones, and is hypothesized to contribute to the deviation of the flame statistics from those within the flamelet regimes.

Mispositioned pockets in highly turbulent flames: red pockets: FiP; blue pockets: PiF.

Aiding the current understanding of combustion in aeronautical engines could have far reaching impacts on a number of fields and industries and would be of great benefit to the Air Force. A better understanding of the factors that affect combustion can eventually allow engineers to improve the efficiency of these engines. You can read more about Professor Zhao’s research on her laboratory’s website

Computational Design Optimization

Abstract: Our ability to manufacture now greatly exceeds our ability to design. Engineers are no longer merely inconvenienced by inefficient trial-and-error design; rather, they are nearly incapacitated by the vast space of possible designs afforded by Advanced Manufacturing (AM) technologies. There are no systematic methods to design systems with such complexity, especially those that exhibit nonlinear, transient, multiscale, and multiphysics phenomena with uncertain behavior.

The opportunity and need to fundamentally transform design is one of the most compelling frontiers of engineering research.  To this end, the Lawrence Livermore National Laboratory’s newly instantiated Center for Design and Optimization is developing algorithms that can optimize immensely complex systems in High Performance Computing (HPC) environments. The complexity comes from two sources, design and physics. Design complexity refers to the intricate shape and material layouts that are made possible by today’s AM technologies; it can take the form of structural composites with intricate morphologies. It also refers to the multifunctional metrics that we optimize, e.g., we maximize electromagnetic response subject to local strength and global mass constraints. And finally, it refers to constraints dictated by the AM processes to ensure manufacturable designs. Physics complexity comes from the mathematical models that are used to predict the performance of our designs. Such models require the solution of partial differential equations that contain complicated nonlinearities, transients, multiple scales, multiple physics, and uncertainties. We iterate through the design space, solving the physics equations using numerical methods. Because our design Degrees-Of-Freedom (DOF) and physics DOF are in excess of 100 million, we must develop efficient, large-scale HPC algorithms. This effort will enable engineers to optimize designs that exhibit unprecedented performance relative to current practice; it is not optional: it is an absolute necessity if we want to drive future innovation.  The work offers immense challenges in engineering, math and HPC.

Biographical Sketch: Daniel A. Tortorelli is the Director for the Center of Design and Optimization at the Lawrence Livermore National Laboratory and the George B. Grim Professor Emeritus at the University of Illinois at Urbana-Champaign (UIUC).  He received his BSME degree from the University of Notre Dame du Lac in 1984 and his MSME and PhD degrees from the UIUC in 1985 and 1988.  His professional career began as senior project engineer for General Motors Advanced Engineering Staff.  In 1990, he embarked on an academic career at UIUC and stayed there until he retired in 2016 to begin his new career at LLNL.

Origami Acoustics and Mechanical Metamaterials: Recent Discoveries with Adaptive Structural and Material Systems for Elastic and Acoustic Wave Propagation Control

Abstract: As form follows function, so shape governs the properties of structural and material systems. Recent studies on adaptive structures have capitalized on these connections to realize unprecedented tunability of system properties and functionality by passive or active transformations of system configuration. This two-part presentation describes integrated theoretical and experimental research efforts that advance these principles to deliver large control over wave propagation properties of adaptive structural and material systems. In the first part, a method is presented that broadly enhances capabilities for acoustic transducer arrays to guide wave energy via harnessing foldable, origami-based tessellations. The foldable arrays enable orders of magnitude change in acoustic energy delivery to points near and far from the surface of the tessellation using shape transformations and without resorting to digital control, and may find future application for instance for medical ultrasound therapy devices transported and deployed in the human body. In the second part of the presentation, strategies to leverage cellular architecture within elastomeric material systems are described that give rise to unusually large elastic wave damping properties. Using this concept, shock energy into the elastomeric metamaterials is found to be dramatically dissipated by tuned pre-compression constraint, and dampened more effectively than the heavier solid elastomer material. This concept is prime for future applications of lightweight personal protective equipment and recoverable shock absorbers. All together, these results encourage ongoing study to probe relations between shape and properties in adaptive structural and material systems to capitalize on potentials for large wave propagation control.

Biographical Sketch: Ryan L. Harne is an Assistant Professor in the Department of Mechanical and Aerospace Engineering at The Ohio State University where he directs the Laboratory of Sound and Vibration Research. Dr. Harne received the Ph.D. degree in Mechanical Engineering at Virginia Tech in 2012. From 2012 to 2015, Dr. Harne was a Research Fellow at the University of Michigan. His research expertise falls in the areas of vibration, acoustics, mechanics, and nonlinear dynamics. The outcomes of his research efforts have included several patents pending, one book, over 40 journal publications, and over 40 conference proceedings, alongside numerous students mentored and guided through their academic programs. Dr. Harne is active in ASME, ASA, and SPIE, where he serves in several elected and appointed roles. Dr. Harne was awarded a 2017 Air Force Research Lab Summer Faculty Fellowship from the Air Force Office of Scientific Research, the 2017 ASME Best Paper Award in Structures and Structural Dynamics, the 2016 Haythornthwaite Young Investigator Award from ASME, and the 2011 ASA Royster Award. He currently serves as an Associate Editor for The Journal of the Acoustical Society of America, Proceedings of Meetings on Acoustics.

Shaping Shells with Swelling

Abstract: Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. In this talk, we aim to describe how the differential swelling of soft materials induces a spontaneous curvature that can dynamically shape materials. The dynamics of fluid movement within elastic networks, and the interplay between swelling and geometry play a crucial role in the morphology of growing tissues, the shrinkage of mud and moss, and the curling of cartilage, leaves, and pine cones. Small volumes of fluid that interact favorably with a material can induce a spontaneous curvature that causes large, dramatic, and geometrically nonlinear deformations and instabilities, yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains still poorly understood. This talk will examine the geometric nonlinearities that occur as slender structures are exposed to a curvature-inducing stimulus – surfaces crease, fibers coalesce and curl apart, plates warp and twist, and shells buckle and snap. I will describe the intricate connection between materials and geometry, and present a straightforward means to permanently morph 2D sheets into 3D shapes. If we can engineer adaptive structures that programmatically morph on command we will enable opportunities for deployable structures, soft robotic arms, mechanical sensors, and rapid-prototyping of 3D elastomers.

Biographical Sketch: Douglas Holmes is an Assistant Professor in the Department of Mechanical Engineering at Boston University.  He received degrees in Chemistry from the University of New Hampshire (B.S. 2004), Polymer Science & Engineering from the University of Massachusetts, Amherst (M.S. 2005, Ph.D. 2009), and was a postdoctoral researcher in Mechanical & Aerospace Engineering at Princeton University. Prior to joining Boston University, he was an Assistant Professor of Engineering Science and Mechanics at Virginia Tech. His group’s research specializes on the mechanics of slender structures, with a focus on understanding and controlling shape change. He received the NSF CAREER Award and the ASEE Ferdinand P. Beer and E. Russell Johnston Jr. Outstanding New Mechanics Educator award.

Prof. David Pierce Wins 3 New Grants

Assistant Professor David Pierce will be deploying his Interdisciplinary Mechanics Laboratory to tackle three projects that just received funding: two from the National Science Foundation (NSF) and one from the U.S. Army Natick Soldier Research Development and Engineering Center (NSRDEC). 

The first NSF-funded project (titled Biomechanical Simulations of Progressing Osteoarthritis to Advance Understanding and Therapies) explores how stress distributions within human cartilage tissue affect the progression of osteoarthritis (OA). As Principle Investigator (PI), Prof. Pierce will collaborate with Co-PI Prof. Cory Neu (CU Boulder). Their team will use mechanical and imaging experiments, simulations of virtual evolving in vivo human cartilage, and longitudinal Magnetic Resonance Images (MRIs) from the NIH-funded Osteoarthritis Initiative (OAI) database to characterize how intra-tissue stress distributions relate to progressing OA.

The second NSF-funded project (titled Understanding the Multiscale Mechanics of Nerve Endings to Address Visceral Pain) investigates the biomechanics of colorectal tissue and the micromechanical environment of the tissue’s sensory nerve endings. As Co-PI, Prof. Pierce will collaborate with the project’s PI, fellow UConn Professor Bin Feng. In colorectal tissue, mechanical stretch (distention) results in visceral pain, the signal for which arises in the peripheral nervous system (PNS). Most drug treatments of visceral pain affect both peripheral and central nervous systems (CNS) and result in adverse side effects on the CNS. Advanced understanding of the biomechanics of visceral nerves could lead to more specific and effective therapeutic targets.

Image courtesy Dr. David Pierce and the Interdisciplinary Mechanics Lab.

Finally, as PI for the NSRDEC-funded project (titled Developing Biofidelic Models as Surrogates for Human Subjects in Protective Clothing and Individual Equipment and Augmentation Testing) Prof. Pierce and his group, in collaboration with NSRDEC, aim to create subject-specific multiscale models of knee joints and cartilage to predict performance of Soldiers carrying various loads. The products of this research will clarify how Soldier-specific loads translate to soft tissues in the joint and how cyclic fatigue under body-borne loads impacts joint health to optimize physical performance and reduce the risk of injury.

For more information about Prof. Pierce’s research, see his Interdisciplinary Mechanics Laboratory website. 

 

The Role of Gas Turbines in Global Energy Conversion

Abstract: It has been remarked that “invention is the mother of necessity” – not the other way around. Technology breakthroughs of themselves, can and do create world markets. In a very short period of history, the gas turbine, youngest of major energy conversion devices, has changed and created global markets in aviation, in marine propulsion and in generation of electric power. In this talk we will discuss how in less than 80 years the gas turbine has come to dominate aircraft propulsion and now, global electrical power generation. In 1939, the first gas turbines had a thermal efficiency of about 18%. Over the years, many thousands of engineers and researchers in academia, government and industry have worked to raise turbine inlet temperatures, increase pressure ratios, enhance combustion, perfect new materials and improve designs, so that modern gas turbines now achieve 40-45% in simple cycle operation. In combined cycle operation, the gas turbine has become the thermal efficiency superstar of the electric power plant world, bringing about combined cycle thermal efficiencies exceeding 60%. Today, gas turbine technology and testing improvements continue apace, and some of these will be discussed. Fuel usage is being drastically reduced in newer land-based gas turbines through the first practical use of recuperators and intercoolers. Small gas turbines are now being used to produce electricity from greenhouse gases at municipal waste water treatment plants. A commercial closed cycle helium gas turbine has been proposed to generate electricity, using a pebble bed modular nuclear reactor as a heat source. The engine in production for the F-135 Joint Strike Fighter is pushing the limits of jet engine technology and will lead to future improvements in gas turbine technology.

Biographical Sketch: Lee Langston received a BSME (1959) from the University of Connecticut, and an MS (1960) and a Ph.D. (1964) from Stanford University. He was with Pratt and Whitney Aircraft as a research engineer working on fuel cells, heat pipes and jet engines from 1964 to 1977. During these years, he also participated in mountain climbing activities in various parts of the world. He joined the mechanical engineering faculty at the University of Connecticut in 1977, rising to the rank of Professor in 1983. At UConn, he has taught graduate and undergraduate courses in heat transfer and fluid mechanics, with research activities involving the measurement, understanding and prediction of secondary flows in gas turbines. He served as Interim Dean of the School of Engineering in 1997-98 and became Professor Emeritus in 2003. He is a Life Fellow of the American Society of Mechanical Engineering Engineers (ASME), has served as Editor, ASME Journal of Engineering for Gas Turbines and Power (2001-2006) and was a member of the Board of Directors of the ASME International Gas Turbine Institute (IGTI). In 2015, he was the recipient of IGTI’s R. Tom Sawyer Award, for outstanding contributions in the field of gas turbines. For the past seventeen years Professor Langston has written a column and a variety of articles on gas turbine technology for IGTI and ASME’s Mechanical Engineering Magazine.