ME Faculty Candidate Heidi Feigenbaum Research Seminar
- Wednesday, May 15, 2019 from 3:10pm to 4:00pm
- Roberts Hall, Room 209 - view map
Modeling the Macroscale Mechanics of Materials and Structures
Northern Arizona University, Associate Professor Department of Mechanical Engineering
Abstract: In order to fully exploit and optimize materials and structures for engineering design, we must have a good understanding of their mechanics and be able to mathematically model their macroscale behavior. In this seminar, Dr. Heidi Feigenbaum presents an overview of her research modeling the macroscale mechanics of materials/structures. In particular, she discusses her research on three very different materials/phenomenon: magnetic shape memory alloys, the torsional actuation of biomimetic twisted polymers, and metals undergoing plastic deformation.
The relatively large strains and fast response time of magnetic shape memory alloys (MSMAs) make them promising for the development of actuators, sensors, power harvesters, and micro-pumps. In this seminar, Dr. Feigenbaum presents several constitutive models for NiMnGa MSMAs and compares model predictions of the magneto-mechanical response to experimental findings. All of the constitutive models are based on the principles of thermodynamics and ensure that the dissipation is positive during reorientation, but each makes different assumptions in order to isolate a single feature of the model. By isolating each model feature, we are able to conclude where current models fail and which model features are critical to accurately predict experimental observations.
Twisted polymer actuators (TPAs) are thermally driven artificial muscles made by twisting drawn polymer monofilaments, such as fishing line. Because TPAs are light-weight and low-cost, they show much promise for use in advanced prosthesis and robotics. In this seminar, Dr. Feigenbaum develops and experimentally validates a model for the behavior of torsional TPAs under thermal loading. Model predictions show good agreement with the experiments, thereby confirming our theoretical understanding of the actuation process and identifying a theoretical optimal initial twist for maximum free torsion.
Finally, in the portion of this seminar on plastic deformation of metals, Dr. Feigenbaum discusses yield surface shape change and using distorted yield surfaces to predict ratcheting, the accumulation of strain during cyclic plastic loading. Ratcheting is known to reduce the life and lead to unexpected failure of piping components in nuclear power and chemical plants, offshore structures, machinery components, buildings, bridges, and other structures subject to earthquakes, extreme weather, and/or cyclic mechanical and thermal service conditions. Results show that yield surface distortion can improve predictions of multiaxial ratcheting, but current models cannot accurately predict ratcheting under the most complex load scenarios.
Bio: Heidi P. Feigenbaum received a B.S. degree in Civil and Environmental Engineering from Cornell University in 2002 and M.S. and Ph.D. degrees in Civil and Environmental Engineering with emphasis on solid mechanics from the University of California at Davis in 2005 and 2008, respectively. She is currently an Associate Professor in the Department of Mechanical Engineering at Northern Arizona University and the Associate Chair for Graduate Programs. Her Ph.D. dissertation focused on thermodynamic based modeling of directional distortional hardening during plastic deformation of metals. Her current research interests include continuum mechanics, constitutive modeling of materials, adaptive materials and structures, and computational mechanics. She has active research on cyclic plastic deformation in metals, magnetic shape memory alloys, and biomimetic twisted polymer actuators.
- Department of Mechanical & Industrial Engineering