I am excited to announce that our PhD student Eric Bryant has successfully defended his dissertation "Capturing Evolving Size-Dependent Anisotropy from Brittle Fracture to Plasticity for Geological Materials" and will join Los Alamos National Laboratory as postdoc research associate. His primary appointment will be with the fluid dynamics and solid mechanics group of the Theoretical Division (T-3).

During his tenure in the Sun research group, Eric has been awarded the Presidential Fellowship and the Guggenheim Fellowship. His PhD work focuses on modeling the size effect of evolving anisotropy of fracture and plastic deformation. Traditionally, one may introduce scaling law to incorporate how shear and tensile strengths depend on the size of the specimen. In his work, the main focus is also to investigate how does the rotation among the principal directions of the elastic strain, tensorial internal variables and stress tensor evolves across length scales and during the deformation process. He is the authors of 4 journal articles and one manuscript very close to completion. Among them, three of them published in Computer Methods in Applied Mechanics and Engineering, and one in International Journal of Fracture as listed below. 

Congratulations, Eric! 

Published work:

1. A. Qinami, E.C. Bryant, W.C. Sun, M. Kaliske, Circumventing mesh bias via r-and h-adaptive refinement techniques for the variational eigenfracture model, International Journal of Fracture, doi:10.1007/s10704-019-00349-x, ​2019. 
2. E.C. Bryant, W.C. Sun, Mixed-mode phase field fracture for secondary cracks in isotropic and anisotropic brittle rocks with consistent kinematics, Computer Methods in Applied Mechanics and Engineering, doi:10.1016/j.cma.2018.08.008, 2018. [PDF]
3. E.C. Bryant, W.C. Sun, micromorphic-regularized anisotropic Cam-clay-type model for capturing size-dependent anisotropy, Computer Methods in Applied Mechanics and Engineering, doi:10.1016/j.cma.2019.05.003, 2019. 
4. S. Na, E.C. Bryant, W.C. Sun, A configurational force for adaptive re-meshing of gradient-enhanced poromechanics problems with history-dependent variables, Computer Methods in Applied Mechanics and Engineering, doi:10.1016/j.cma.2019.112572, 2019. [PDF]
5. E.C. Bryant, W.C. Sun, ​Phase field modeling of frictional slip with slip weakening/strengthening  under non-isothermal conditions, in preparation. 

Our postdoctoral research scientist Chuanqi Liu has just received an offer from the Institute of Mechanics in the Chinese Academy of Sciences (CAS). He is selected by the 100 talent program (pioneering project) of CAS and is offered the position as an associate professor. During his tenure with us, Chuanqi has been a productive member of our team and has published the following peer-reviewed articles: 

1. C. Liu", W.C. Sun, ILS-MPM: an unbiased implicit level-set-based material point method for frictional particulate contact mechanics of deformable particles, Computer Methods in Applied Mechanics and Engineering, accepted, 2020. [PDF]
2. C. Liu", W.C. Sun, Shift domain material point method for solids in the finite deformation range, special thematic issue for Meshfree and Particle Methods for Modeling Extreme Loadings, Computational Particle Mechanics, doi: 10.1007/s40571-019-00239-y, 2019. [PDF]

Congratulations, Chuanqi! 

It is my great pleasure to announce that my PhD student SeonHong Na has accepted a tenure-track position as assistant professor in the department of civil engineering at McMaster University in Canada. He will officially join McMaster in the spring of 2019. SeonHong joined our research group as PhD student in Fall 2014 after obtained his B.S. (2008) and M.S. (2010) in civil engineering from Seoul National University, Korea. Prior to joining Columbia, he worked as a civil engineer for two years (Kunhwa, Korea) and spent another two years in Coastal Development & Ocean Energy Division in Korea Institute of Ocean Science and Technology (KIOST) as a research scientist. SeonHong's research is currently funded by Army Research Office (frozen soil) and the DOE NEUP (crystalline rock) as well as the Fulbright Fellowship and has just recently graduated in July 2018. He is the 2nd PhD graduated from our group and the 3rd research group members who secured tenure-track position, following Yang Liu (Northeastern) and Jinhyun Choo (University of Hong Kong) since 2014. His published journal articles during the last 3+ years at Columbia are listed below. 

Congratulations again, SeonHong! ​

• S. Na, W.C. Sun, Wave propagation and strain localization in a fully saturated softening porous medium under the non-isothermal conditions, International Journal for Numerical and Analytical Methods in Geomechanics, doi:10.1002/nag.2505, 2016. [PDF][Bibtex]
• K. Wang, W.C. Sun, S. Salager, S. Na, G. Khaddour, Identifying material parameters for a micro-polar plasticity model via X-ray micro-CT images: lessons learned from the curve-fitting exercises, International Journal of Multiscale Computational Engineering, 14(4):389-413,  doi:10.1615/IntJMultCompEng.2016016841, 2016. [PDF][Bibtex]
• S. Na, W.C. Sun, Computational thermo-hydro-mechanics for multiphase freezing and thawing porous media in the finite deformation range, Computer Methods in Applied Mechanics and Engineering, 2017. [DRAFT][Bibtex]​
• S. Na, W.C. Sun, H. Yoon, M. Ingraham, Effects of elastic heterogeneity on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian Tests, Journal of Geophysical Research:Solid Earth, accepted, ​2017.
• S.H. Jang, S. Na, Y-L Park, Magnetically Assisted bilayer composites for soft bending actuators, materials, 10(6), 646, doi:10.3390/ma10060646, 2017. [PDF] (unaffiliated research conducted with the Dr. Sung-Hwan Jang). 
• S. Na, W.C. Sun, Computational thermomechanics of crystalline rock. Part I: a combined multi-phase-field/crystal plasticity approach for single crystal simulations, Computer Methods in Applied Mechanics and Engineering, accepted, 2018.
• S. Na, E.C. Bryant, W.C. Sun, Capturing size effects of anisotropic fluid-infiltrating materials via a higher-order Cam-clay-type model with property-preserving adaptive meshing, in preparation., in preparation. 
• S. Na, W.C. Sun,  phase field modeling of fracture opening, interfacial frictional closure and capillary-driven flow in porous media, in preparation. 

 

It is my great pleasure to announce that our postdoc research scientist, Dr. Jinhyun Choo has accepted a tenure-track position as assistant professor at the University of Hong Kong. Jinhyun joined our research group as a postdoctoral research scientist in Fall 2016 after finishing his PhD under the tutelage of Professor Ronaldo Borja at Stanford University. During his productive tenure at Columbia, we have submitted three journal articles with Jinhyun, of which one is accepted. He is the first author of the other two works on modeling brittle-ductile transition and on chemoporomechanics of brittle porous materials. Prior to Stanford and Columbia, he obtained his B.S. and M.S. degrees from Seoul National University, and worked at an engineering firm and a government funded research institute in Korea. He is the recipient of several prestigious awards including a Fulbright Scholarship and a Charles H. Leavell Fellowship for research on sustainable built environment. For more information, please visit his website: http://jinhyunchoo.com/
 
His work with us are listed below.

• W.C. Sun, Z. Cai, J. Choo, Mixed Arlequin method for multiscale poromechanics problems, International Journal for Numerical Methods in Engineering, ​doi:10.1002/nme.5476, 2017. [PDF]
• J. Choo, W.C. Sun, Coupled phase-field and plasticity modeling of geological materials: From brittle fracture to ductile flow, under review.
• J. Choo, W.C. Sun, ​Cracking and damage from crystallization in pores: Coupled chemo-poro-mechanics and phase-field modeling, under review. ​

Congratulations Jinhyun for this wonderful and well-deserved accomplishment! I am very proud to have the privilege to be your colleague and friend! 

It is my great pleasure to announce that our former PhD student of the research group, Dr. Yang Liu has accepted a tenure-track position as assistant professor of mechanical and Industrial Engineering at Northeastern University. Yang currently works as a postdoctoral scholar at the Institute For Soldier Nanotechnologies of MIT. She is the first PhD graduate of our research group. In 2015, she won the best paper competition among students from more than 100 minisymposia at USNCCM San Diego. She has published the following two journal articles during her tenure in our group.  

• Y. Liu, W.C. Sun, J. Fish, Determining material parameters for critical state plasticity models based on multilevel extended digital database, Journal of Applied Mechanics, 88(1),  doi: 10.1115/1.4031619, 2015. [PDF][Bibtex]
• Y. Liu, W.C. Sun, Z-F. Yuan, J. Fish, A nonlocal multiscale discrete-continuum model for predicting mechanical behavior of granular materials,  International Journal for Numerical Methods in Engineering, doi: 10.1002/nme.5139, 2015. [PDF] [Bibtex]

​Congratulations Yang for this wonderful accomplishment! 

Recently graduated group member Yang Liu (pictured left) will start her Postdoctoral Associate Appointment in the Department of Aeronautics and Astronautics at MIT in November 2015. She will work with Professor Raul Radovitzky on high-performance computing, computational modeling and simulation of material fracturing.
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Yang defended her PhD thesis entitled “Multiscale Modeling of Granular Materials” in August 2015 under the supervision of Professors WaiChing Sun and Jacob Fish in the Department of Civil Engineering and Engineering Mechanics at Columbia University.
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Congratulations Yang!