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Spring 2018 Seminar Series

Schedule

Date Description Location
Thursday, January 25 Departmental Seminar: Safety Overview

Learn the essential safety precautions that must be followed to keep the CEE labs safe.

 

405 John D. Tickle Building
Thursday, January 25 TBA

TBA

109 Estabrook
Thursday, February 1 GEOTECH/STRUCT/MAT/CONSTR Seminar: Matt Trammell, P.E., S.E.

 

Bio

Mr. Trammell founded Trammell Engineering Group, LLC  in 2014. He has over 17 years experience in the structural design of large and small commercial, industrial, retail and institutional buildings across the United States.  He also has extensive experience in the design of steel connections in both low and high seismic regions across the United States.

405 John D. Tickle Building
Thursday, February 15 GEOTECH/STRUCT/MAT/CONST Seminar: Bridging Computational Materials Science and Structural Mechanics: A New Paradigm for Predictive Simulation, Caglar Oskay

Abstract

Over the past couple of decades, tremendous effort has been devoted to the development of multiscale computational modeling and simulation strategies for physics-based prediction of structural response. Among these strategies, concurrent multiscaling holds great potential in effectively bridging the “material” response to that of the “structure”. Yet these approaches are so computationally intensive that they remained within the academic realm, and have yet to make impact on realistic engineering problems.

We propose the Eigendeformation-based Reduced Order Homogenization Method (EHM) for computationally efficient and accurate concurrent multiscale analysis. We build and demonstrate this method to predict the response of structures made of polycrystalline materials, where crystal plasticity finite element (CPFE) simulations are concurrently coupled to a large scale structural analysis. EHM employs the idea of precomputing certain information on the material microstructure such as the influence functions, localization operators and coefficient tensors through RVE scale simulations, prior to the macroscale analysis. The reduced order modeling is achieved by being selective in what “physics” we choose to embed at the fine scales, as well as by developing sparse and scalable computational algorithms that can very efficiently solve the resulting multiscale systems.

We demonstrate the efficiency of the proposed approach in simulating the response of large structural problems (resolving each grain throughout the domain of the structure!) with modest computational resources. We also demonstrate the ability of the reduced order model to accurately capture the local, grain-scale features (grain level stress, strain, dislocation density evolution) and failure initiation mechanisms in the context of a high-performance titanium alloy (Ti-6242S).

Bio

Caglar Oskay is Associate Professor of Civil and Environmental Engineering, and the Mechanical Engineering Departments at Vanderbilt University. He received M.S. in Applied Mathematics, M.S. in Civil Engineering and Ph.D. in Civil Engineering at Rensselaer Polytechnic Institute. His research focuses on nonlinear response of heterogeneous materials and structures using computational modeling and simulation, including characterization of the failure response of systems that involve multiple temporal and spatial scales, and method development for failure analysis of composite systems subjected to impact, blast and other extreme loading and environmental conditions. Prof. Oskay is named Chancellor Faculty Fellow at Vanderbilt University in 2016 and Fellow of the American Society of Mechanical Engineers in 2017. Prof. Oskay also serves as the Associate Editor of the International Journal for Multiscale Computational Engineering.

 

405 John D. Tickle Building
Thursday, March 22 Departmental Seminar: Bonded-Particle Modeling of Fracture and Flow, David Potyondy

Abstract

Discrete-element methods allow one to simulate the movement and mechanical interaction of hundreds of thousands of discrete particles. Bonded-particle models (Potyondy, 2015) represent a solid as a bonded collection of discrete particles, and provide a synthetic material whose
mechanical behavior ranges from that of a solid material (such as rock, concrete or ceramics) when the bonds are intact to that of a granular material when the bonds have all broken. The macroscopic behavior of such models is an emergent property of the system that arises from a small set of microproperties for the particles, bonds and particle-particle interactions. These models support investigation of the relations between microstructure and material properties under both quasi-static and fully dynamic loading, and can be used to simulate any physical process whose physics can be described by the interaction of discrete particles.

After introducing the basic concepts of a bonded-particle model, examples of how such models are being applied to model rock fracture and material flow are presented. The first example models a rock-cut test (at the mm scale), during which a cylindrical cutter is moved across the rock surface while monitoring forces on the cutter and damage in the rock as shown in Fig. 1. The rock is a sandstone, with the particles and bonds representing grains and cement, respectively. The second example models cave mining (at the 10–100 m scale), during which the
undercutting of a rock mass and subsequent draw of the collapsed material fragments the rock mass in an upwardly progressive fashion (Pierce, 2010). The size of rock fragments in the selfpropagating cave decreases as the cave matures, and is attributed to the attrition of fragments in the course of traveling from their origin to the draw point. PFC3D (Particle Flow Code in 3 Dimensions) was used to study both compression- and shearing-induced secondary fragmentation, and the results of these simulations, in combination with in situ data, were used to develop a rapid draw simulator (REBOP, Rapid Emulator Based on PFC) for cave mining to predict material drawdown and ore recovery. The 30-minute talk focuses on the first example.

Bio

Dr. Potyondy has developed and applied both continuum and discontinuum models to represent damage and flow processes on both a macro- and a micro-scale. He has directed development of the PFC codes, has developed the structural-element logic in the FLAC3D code and has developed novel techniques for applying micro-mechanical discontinuum models to fracture-related boundary-value problems, including the prediction of excavation damage produced by stress, temperature and stress corrosion.

405 John D. Tickle Building

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