Presented By: Aerospace Engineering
AE Dissertation Defense by Sriram Ganesan
Aerospace Engineering Associate Professor Veera Sundararaghavan is the Dissertation Committee Chair
Title: Microstructural Response of Magnesium Alloys: 3D Crystal Plasticity and Experimental Validation
Lightweight materials such as Aluminum are prevalent in aerospace and automotive vehicles, but the use of lighter Magnesium alloys will significantly increase fuel efficiency and cut emissions. In this thesis, a parallel three-dimensional (3D) crystal plasticity finite element open-source code was developed based on the deal.II finite element framework as part of PRISMS-Plasticity. Rate-independent crystal plasticity was implemented by developing a nonlinear algorithm which enables all the slip systems to lie on or inside the yield surface, and a consistent tangent modulus ensures convergence for small loading increments. The code demonstrates parallel performance and scaling on large-scale problems running on hundreds of processors.
Using experimental microstructure images as input, the code has been used to compute, validate and investigate response of crystalline aggregates to mechanical loading; this leads to insights on slip and twin activity. Boundary value problems were set up to compare the displacement and strain fields obtained by Scanning Electron Microscope - surface Digital Image Correlation (DIC) experiments for Magnesium alloy WE-43 T5 and T6 tempers with the crystal plasticity finite element simulations. The results indicate a strong correlation between experiments and crystal plasticity finite element simulations. 3D reconstruction of microstructures is growing to be a major topic of interest in the field of modeling and simulation for comparison with experiments. A generalized inverse Voronoi problem approach is used to construct an approximate Voronoi representation of the surface microstructure by generating a convexified representation of the microstructure. Comparisons are made with surface DIC measurements for random samples of 3D microstructures and they indicate the effect of the underlying microstructure on the surface plastic strain. These developed methods will serve as powerful tools in an Integrated Computational Materials Engineering framework towards accelerating alloy development and in better understanding the mechanical behavior of materials.
Dissertation Committee Names:
Chair: Associate Professor Veera Sundararaghavan
Cognate Member: Professor John Edmond Allison
Members: Associate Professor Samantha Hayes Daly, University of California, Santa Barbara
Professor Krishnakumar R. Garikipati
Professor John A. Shaw
Journal Publications:
1) Ganesan S., Sundararaghavan V., An Atomistically-informed Energy Based Theory of Environmentally Assisted Failure, Corrosion Reviews, 33(6), p. 455-466, 2015.
2) Githens A., Ganesan S., Chen Z., Allison J., Sundararaghavan V., Daly S., “Characterizing microscale deformation mechanisms and macroscopic tensile properties of a high strength magnesium rare-earth alloy: A combined experimental and crystal plasticity approach”, Acta Materialia (submitted)
3) Ganesan S., Rudraraju S., Sundararaghavan V., “ PRISMS-Plasticity – Crystal Plasticity finite element method: Formulation, Numerical Implementation and Examples “, Integrating Materials and Manufacturing Innovation, (Manuscript in preparation)
4) Ganesan S., Githens A., Allison J., Daly S., Sundararaghavan V., “Crystal Plasticity Modeling and correlation of microstructural strain maps and slip activity in Mg alloys: Theory and experimental validation “, International Journal of Plasticity (Manuscript in preparation)
5) Ganesan S., Sundararaghavan V., “Construction of 3D microstructures from surface constrained 2D microstructures using an inverse Voronoi approach “, Acta Materialia (Manuscript in preparation)
Conference Presentations:
1) Ganesan, S., Sundararaghavan, V., “ Crystal Plasticity Modeling and Experimental Validation of Deformation Response in Magnesium Alloy WE-43 “, 4th World Congress on Integrated Computational Materials Engineering (ICME 2017), 21-25 May 2017, Ypsilanti, Michigan, USA
2) Ganesan, S., Sundararaghavan, V., “3-D Crystal Plasticity Finite Element Method: Multiscale Modeling of Deformation Response in Magnesium Alloy WE-43”, WCCM/APCOM 2016: 12th World Congress on Computational Mechanics and 6th Asian Pacific Congress on Computational Mechanics; 24-29 July, 2016, Seoul, South Korea
3) Ganesan, S., Githens, A., Sundararaghavan, V., Allison, J.,” Crystal plasticity modeling and validation of deformation response in Magnesium Alloys”, 15th Pan-American Congress of Applied Mechanics-PACAM XV, 18-21 May, 2015, Champaign, USA
4) Ganesan, S., Sundarararaghavan, V.,“An Atomistically-informed Energy Based Theory Presentations of Environmentally Assisted Failure”, Deformation, Damage, and Fracture of Light Metals and Alloys III, TMS Annual Meeting in San Diego, California, February 16-20, 2014.
Lightweight materials such as Aluminum are prevalent in aerospace and automotive vehicles, but the use of lighter Magnesium alloys will significantly increase fuel efficiency and cut emissions. In this thesis, a parallel three-dimensional (3D) crystal plasticity finite element open-source code was developed based on the deal.II finite element framework as part of PRISMS-Plasticity. Rate-independent crystal plasticity was implemented by developing a nonlinear algorithm which enables all the slip systems to lie on or inside the yield surface, and a consistent tangent modulus ensures convergence for small loading increments. The code demonstrates parallel performance and scaling on large-scale problems running on hundreds of processors.
Using experimental microstructure images as input, the code has been used to compute, validate and investigate response of crystalline aggregates to mechanical loading; this leads to insights on slip and twin activity. Boundary value problems were set up to compare the displacement and strain fields obtained by Scanning Electron Microscope - surface Digital Image Correlation (DIC) experiments for Magnesium alloy WE-43 T5 and T6 tempers with the crystal plasticity finite element simulations. The results indicate a strong correlation between experiments and crystal plasticity finite element simulations. 3D reconstruction of microstructures is growing to be a major topic of interest in the field of modeling and simulation for comparison with experiments. A generalized inverse Voronoi problem approach is used to construct an approximate Voronoi representation of the surface microstructure by generating a convexified representation of the microstructure. Comparisons are made with surface DIC measurements for random samples of 3D microstructures and they indicate the effect of the underlying microstructure on the surface plastic strain. These developed methods will serve as powerful tools in an Integrated Computational Materials Engineering framework towards accelerating alloy development and in better understanding the mechanical behavior of materials.
Dissertation Committee Names:
Chair: Associate Professor Veera Sundararaghavan
Cognate Member: Professor John Edmond Allison
Members: Associate Professor Samantha Hayes Daly, University of California, Santa Barbara
Professor Krishnakumar R. Garikipati
Professor John A. Shaw
Journal Publications:
1) Ganesan S., Sundararaghavan V., An Atomistically-informed Energy Based Theory of Environmentally Assisted Failure, Corrosion Reviews, 33(6), p. 455-466, 2015.
2) Githens A., Ganesan S., Chen Z., Allison J., Sundararaghavan V., Daly S., “Characterizing microscale deformation mechanisms and macroscopic tensile properties of a high strength magnesium rare-earth alloy: A combined experimental and crystal plasticity approach”, Acta Materialia (submitted)
3) Ganesan S., Rudraraju S., Sundararaghavan V., “ PRISMS-Plasticity – Crystal Plasticity finite element method: Formulation, Numerical Implementation and Examples “, Integrating Materials and Manufacturing Innovation, (Manuscript in preparation)
4) Ganesan S., Githens A., Allison J., Daly S., Sundararaghavan V., “Crystal Plasticity Modeling and correlation of microstructural strain maps and slip activity in Mg alloys: Theory and experimental validation “, International Journal of Plasticity (Manuscript in preparation)
5) Ganesan S., Sundararaghavan V., “Construction of 3D microstructures from surface constrained 2D microstructures using an inverse Voronoi approach “, Acta Materialia (Manuscript in preparation)
Conference Presentations:
1) Ganesan, S., Sundararaghavan, V., “ Crystal Plasticity Modeling and Experimental Validation of Deformation Response in Magnesium Alloy WE-43 “, 4th World Congress on Integrated Computational Materials Engineering (ICME 2017), 21-25 May 2017, Ypsilanti, Michigan, USA
2) Ganesan, S., Sundararaghavan, V., “3-D Crystal Plasticity Finite Element Method: Multiscale Modeling of Deformation Response in Magnesium Alloy WE-43”, WCCM/APCOM 2016: 12th World Congress on Computational Mechanics and 6th Asian Pacific Congress on Computational Mechanics; 24-29 July, 2016, Seoul, South Korea
3) Ganesan, S., Githens, A., Sundararaghavan, V., Allison, J.,” Crystal plasticity modeling and validation of deformation response in Magnesium Alloys”, 15th Pan-American Congress of Applied Mechanics-PACAM XV, 18-21 May, 2015, Champaign, USA
4) Ganesan, S., Sundarararaghavan, V.,“An Atomistically-informed Energy Based Theory Presentations of Environmentally Assisted Failure”, Deformation, Damage, and Fracture of Light Metals and Alloys III, TMS Annual Meeting in San Diego, California, February 16-20, 2014.
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