Center for Computing Research (CCR)

Center for Computing Research

John A. Mitchell

John A. Mitchell
Computational Multiscale
Email: jamitch@sandia.gov
Phone: 505/844-3435
Fax: 505/845-7442

Mailing address:
Sandia National Laboratories
P.O. Box 5800, MS 1322
Albuquerque, NM
87185-1320

Brief Research and Project History

Nonlinear solver algorithms and implementations for solid mechanics
Engineering project management
Technology maturation and assessment
Constitutive model development (particularly Peridynamics)
GPU programming
Inverse problems
Models for grain growth in metals using Kinetic Monte Carlo (KMC)
Data analytics applied to metal material microstructures, insitu pyrometry data
Grain morphology effects on dynamic response of additively manufactured metals

Current Activities

My work is at the confluence of engineering mechanics (especially continuum mechanics), materials and data science, mathematics, algorithms development, and software implementations. I am especially interested in bridging the gap between engineering and applied mathematics, and demonstrating and/or developing novel solutions and implementations for emerging problems.

Microstructure effects on dynamic response of materials
Grain growth modeling of welding and additive manufacturing processes using KMC (see SPPARKS)
Data analytics & machine learning applied to material microstructures
Peridynamics constitutive model development towards multiscale analysis and upscaling
Processing and analysis of measured additive manufacturing pyrometer data

Recent Project Work and Activities (See reports/presentations below)

SPPARKS tutorial
Micromechanics calculations using Eshelby approach
Nonlinear kinematics for dielectrics (especially piezoelectric materials)
Mean curl discretization for 2D nonlinear magnetic diffussion equations
Vectorization of uniform gradient hexahedron for solid mechanics calculations on a GPU
Kinetic Monte Carlo modeling of grain growth associated with weld process for metals

Other Activities and Interests

I'm from Homer Alaska and I like to visit there during the summer for camping/hiking/fishing and visiting with friends. I also like to exercise and at one time was very active in training for triathlons -- now I just try to move a bit every day.

Education/Background

B.S. Ocean Engineering Texas A&M University (1987)
M.S. Engineering Mechanics Virginia Tech (Advisor: J.N. Reddy, Thesis topic: Finite element formulation and implementation for piezoelectricity) (1992)
Ph.D. Mechanical Engineering Texas A&M University (Advisor: J.N. Reddy, Thesis topic: Multilevel/hierarchical preconditioning for p-finite elements) (1997)

Selected Publications & Presentations

2020	Mitchell, John A., Thomas A. Ivanoff, Daryl Dagel, Jonathan D. Madison, "Linking pyrometry to porosity in additively manufactured metals," Journal Article, Additive Manufacturing, Vol. 31, Accepted/Published January 2020.
2019	Mitchell, John A., Thomas Ivanoff, Jonathan D Madison, Daryl Dagel, Bradley Howell Jared, Joshua Robert Koepke, David J. Saiz, "Linking in-situ pyrometry to pores," Presentation, TMS2019: 148th Annual Meeting and Exhibition, San Antonio Tx, March 2019.
2018	Mitchell, John A., "Clustering to upscale microstructural morphologies," Poster, 9th International Conference on Multiscale Materials Modeling, Osaka, Japan, October 2018. Mitchell, John A., "Towards upscaling microstructural effects using data analytics," Presentation, WCCMXIII: World Congress in Computational Mechanics, New York City, July 2018.
2017	Rodgers, Theron, John A. Mitchell, Veena Tikare, "A Monte Carlo model for 3D grain evolution during welding," Journal Article, Modelling and Simulation in Materials Science and Engineering, Vol. 25, No. 6, Accepted/Published September 2017.
2016	Castillo, Andrew R, John A. Mitchell, Stephen D Bond, "Using and Developing Novel Data Analytics for Digitalized Microstructures ," SAND Report, November 2016. Mitchell, John A., "Potts model for grain growth during welding using SPPARKS," Poster, 8th International Conference on Multiscale Materials Modeling, Dijon France, October 2016.
2015	Mitchell, John A, "Ordinary Isotropic Peridynamic Models; Position Aware Viscoelastic(PA'VE)," Presentation, 1st Pan-American Conference on Computational Mechanics, Buenos Aires, April 2015. Mitchell, John A., Stewart A. Silling, David John Littlewood, "A position-aware linear solid constitutive model for peridynamics," Journal Article, Journal of Mechanics of Materials and Structures, Vol. 10, No. 5, pp. 539–557, Accepted/Published November 2015. Mitchell, John A., Veena Tikare, Philippe F Weck, "Towards Using Eshelby Calculations to Enhance Kinetic Model for Zirconium Hydride Precipitation," SAND Report, October 2015.
2014	Mitchell, John A, Stewart Silling, David Littlewood, "Ordinary Isotropic Peridynamic Models: Position Aware Linear Solid (PALS) ," Presentation, 17th US National Congress on Theoretical & Applied Mechanics, June 2014.
2013	Mitchell, John A, Christian R Trott, "Algorithms and Cuda Concepts: Hexahedron for FE Solid Mechanics," Presentation, PGI OpenACC Short Course, October 9-10, 2013, October 2013. Mitchell, John A, Tim J Fuller, "Nonlinear Kinematics for Piezoelectricity in ALEGRA-EMMA," SAND Report, September 2013. Mitchell, John A., "On the ’DSF’ and the ’Dreaded Surface Effect’ ," Presentation, Workshop on Nonlocal Damage and Failure, San Antonio Texas , March 2013.
2012	Mitchell, John A, "Mean Curl Formulation on Quadrilaterals with Application to Implicit Magnetics Diffusion Equations in Alegra 2D," SAND Report, June 2012.
2011	Mitchell, John A, "A Non-local, Ordinary-State-Based Viscoelasticity Model for Peridynamics," SAND Report, October 2011. Mitchell, John A, "A Nonlocal, Ordinary, State-Based Plasticity Model for Peridynamics," SAND Report, May 2011.
2009	Mitchell, John A, Marco Alvares, Michael S Baker, Mathew A Spletzer, Danelle M Tanner, "The Sandia MEMS Passive Shock Sensor: FY09 Maturation Activities Reaching TRL 5+," SAND Report, November 2009.
2008	Mitchell, John A, Michael S Baker, Jill Blecke, Rebecca C Clemens, Doug A Crowson, David S Epp, Jack E Houston, Jeremy A Walraven, Jon W Wittwer, "The Sandia MEMS Passive Shock Sensor: FY07 Maturation Activities," SAND Report, August 2008.
2007	Mitchell, John A, "Measuring the Maturity of a Technology: Guidance on Assigning a TRL," SAND Report, October 2007.
2006	Mitchell, John A, Beatriz R Bailey, "On the Integration of Technology Readiness Levels at Sandia National Laboratories," SAND Report, September 2006.
2005	Mitchell, John A, Jonathan W Wittwer, David S Epp, "On the Modeling, Design and Validation of Two Dimensional Quasi-static Eddy Currents Forces in a Mechanical Oscillator," SAND Report, October 2005.
2003	Mitchell, John A., "A Simple One Step Line Search For Use in Quasi-static Solid Mechanics Contact Calculations," Presentation, 7th US National Congress On Computational Mechanics, July 2003.
2002	Mitchell, John A., Martin W. Heinstein, "Verification Testing of Contact in a Finite Element Code For Quasi-Static Solid Mechanics Equilbrium," Conference Paper, Fifth World Congress on Computational Mechanics, Vienna, Austria, July 2002.
2001	Mitchell, John A, Arne S. Gullerud, William M. Scherzinger, Richard Koteras, Vicki L. Porter, "Adagio: non-linear quasi-static structural response using the SIERRA framework," Conference Paper, First MIT Conference on Computational Fluid and Solid Mechanics, June 12-15, 2001. In proceedings : Computational Fluid and Solid Mechanics, Volume 1, pp 361-364, June 2001.