Albert C. To, Ph.D.

William Kepler Whiteford Professor

Director, ANSYS Additive Manufacturing Research Laboratory

Director, MOST-AM Consortium

Department of Mechanical Engineering & Materials Science, University of Pittsburgh, 508 Benedum Hall, 3700 O’Hara Street, Pittsburgh, PA 15261

Tel: (412) 624-2052 | Email: albertto [at] pitt [dot] edu

 

My primary research interests are in design optimization for additive manufacturing, multiscale methods, and computational mechanics. Currently, my research group is actively working on fast process modeling and topology optimization for metal additive manufacturing.

I joined University of Pittsburgh in 2008 as assistant professor and was promoted to associate professor in 2014 and to full professor in 2019.  I am also directing the ANSYS Additive Manufacturing Research Laboratory at Pitt, which houses several of the most advanced metal 3D printers including the EOS DMLS, Optomec LENS, and ExOne binder jetting.

I did my undergraduate study at UC Berkeley and master's study at MIT. I obtained my Ph.D. from UC Berkeley under the supervision of Shaofan Li and Steve Glaser. I also conducted postdoctoral research with Wing Kam Liu at Northwestern University.

My research has been supported by NASA, DOD, DOE, NSF, America Makes, ANSYS, etc.  I am collaborating with the industry extensively in my computational research for additive manufacturing through the MOST-AM Consortium, which I founded in 2016 and now has 30+ member companies and research labs.

I received the NSF BRIGE award in 2009, the Board of Visitors Faculty Award from my engineering school in 2016, and the Carnegie Science Award in 2018.

 

I am currently looking for Ph.D. student interested in constitutive modeling or topology optimization for additive manufacturing.  Send me a copy of your resume if you are interested.  

NEWS

8/11/2019 - Our research group (I, Wen Dong, Hai Tran, Santanu Paul, and Shawn Hinnebusch) gave presentations at SFF meeting in Austin, TX.

7/28/2019 - Our research group (I, Lin Cheng, Qian Chen, Hao Deng, and Florian Dugast) gave presentations at USNCCM in Austin, TX.

5/1/2019 - The Bi-Annual MOST-AM Consortium meeting was successfully held with 69 attendees.

3/12/2019 - Our research group (I, Hao Deng, and Shawn Hinnebusch) gave presentations at the Topology Optimization Roundtable in Albuquerque, NM.

1/31/2019 - I gave an invited Department seminar on our topology optimization for AM work at Drexel University thru Prof. Ahmad Najafi's invitation.

1/29/2019 - I gave an invited talk on how to reduce residual stress in AM components at the 2019 Air Force Additive Manufacturing Academic Symposium for Additive Manufacturing in Dayton, Ohio.

1/7/2019 - We welcome Dr. Hai Tran and Dr. Florian Dugast to our research group!

12/15/2018 - The Bi-Annual MOST-AM Consortium meeting was held succesfully with 71 attendees from over 25 different organizations.

11/14/2018 - I gave an invited presentation at a NASA workshop on rapid manufacturing in DC.

11/13/2018 - I gave a keynote talk on deformation and failure of AM parts at ASME IMECE in Pittsburgh.

11/6/2018 - I visited Colorado School of Mines and gave a seminar there.  

10/30/2018 - We bid farewell to Dr. Jikai Liu as he joins Shandong university to become a professor there.

10/15/2018 - We welcome Dr. Santanu Paul from IIT Mumbai to our group!

10/12/2018 - I visited UT Arlington and gave a Department seminar there.

8/13/2018 - I gave five presentations at the Solid Freeform Fabrication meeting in Austin, Texas

7/22/2018 - I taught a short course on DfAM and topology optimization at WCCM, and 5 group members also presented their recent work at the conference.  

7/12/2018 - I received a $1M grant from DOE NEUP program to improve AM technology for fabricating complex nuclear components.  [press release]

5/15/2018 - The Bi-Annual MOST-AM Consortium meeting was successfully held with 51 attendees.

3/19/2018 - I received the 2018 Carnegie Science Award in the Advanced Manufacturing and Materials category. [press release]

3/15/2018 - I presented my group's research and toured the AM facilities at NASA JPL.

12/15/2017 - The Bi-Annual MOST-AM Consortium meeting was successfully held with 55 attendees.

12/13/2017 - My senior design team won 1st place among 26 teams in the Department for their design of a de-powdering machine for AM builds.

11/16/2017 - I gave two presentations on grain growth modeling and topology optimization for AM at NASA Langley Center.

11/1/2017 - I served as an AM expert panelist at the DOE - University Turbine Systems Research (UTSR) Workshop.

10/11/2017 - I presented our work on modeling history derivative topology optimization at the Sim-AM conference in Munich, Germany.

8/18/2017 - I presented our work on process-microstructure-property relationship of AM metals at the NSF AM workshop we hosted at Pitt.

8/7/2017 - Our group (Jian Liu, Lin Cheng, Xuan Liang, and Qian Cheng) presented at the SFF meeting in Austin, Texas.

7/19/2017 - Our group (Jikai Liu, Lin Cheng, and I) presented at USNCCM in Montreal, Canada.

5/10/2017 - Lin Cheng won 1st place in student poster session at the RAPID meeting.  Congratulations, Lin!

5/9/2017 - My former PhD student Pu Zhang has accepted an offer to join SUNY-Binghamton as Assistant Professor.  Congratulations, Pu!

5/8/2017 - The MOST-AM Consortium is officially launched!  The kickoff meeting was attended by 25 organizations

12/2/2016 - I received a NASA grant entitled "Prediction of Microstructure Evolution in DMLM Processed Inconel 718 with Part Scale Simulation".

11/30/2015 - I am now on the Editorial Board of the Additive Manufacturing journal.

10/28/2016 - I received the 2016-17 Board of Visitors Faculty Award for the single faculty who have had the most accomplished previous year in the engineering school at Pitt.

10/1/2016 - Dr. Jikai Liu from University of Alberta has joined our group as a postdoc fellow.  Welcome, Jikai!

9/1/2016 - I gave two keynote talks at the International Symposium on Additive Manufacturing Taiwan 2016.

8/15/2016 - I received an NSF award entitled "Novel Computational Approaches to Address Key Design Optimization Issues for Metal Additive Manufacturing" [press release]

8/11/2016 - Oberg Industries signed agreement with Pitt to manage our AM lab [press release].

8/10/2016 - Our group (Lin Cheng, Jian Liu, and I) presented at the Solid Freeform Fabrication Meeting in Austin, Texas.

7/29/2016 - Qingcheng Yang just submitted his Ph.D. dissertation.  Congratulations, Dr. Yang!

7/25/2016 - Lin Cheng's paper on cellular structure optimization has been accepted for publication by Rapid Prototyping Journal.

6/15/2016 - ANSYS Additive Manufacturing Research Laboratory officially opens for business!  ANSYS CEO Jim Cashman, America Makes Director Ed Morris, and many industry leaders join us to celebrate the dedication ceremony [press release].

SOFTWARE

Want to learn topology optimization?  MATLAB codes for the Proportional Topology Optimization (PTO) method solving the minimum compliance and stress constrained problems are available to download for free (www.ptomethod.org).  See also the paper on the method:  E. Biyikli and A. C. To, "Proportional topology optimization:  A new non-sensitivity method for solving stress constrained and minimum compliance problems and its implementation in MATLAB,"PLOS ONE, 10, e0145041, 2015.  [link]

My two former students Emre Biyikli and Qingcheng Yang have been developing the Multiresolution Molecular Mechanics (MMM) method since 2012 and wrote their Ph.D. dissertations about it.  The MMM method is a concurrent coupled atomistic-continuum method similar to the energy-based Quasicontinuum (QC) method.  You can read more about it in the MMM section below.  The C++ source code for implementing the MMM method can be downloaded by following this [link].

Topology Optimization for Residual Stress

The goal of this work is to explore using topology optimization to design support structure to mitigate residual stress induced build failure in laser powder bed fusion. To make topology optimization computationally tractable, the modified inherent strain method proposed by us is employed to perform fast prediction of residual stress in an AM build.  The components with optimized support structures no longer suffer from stress-induced cracking after the designs are realized by AM, which proves the effectiveness of the proposed method.

[1] L. Cheng, X. Liang, J. Bai, Q. Chen, J. Lemon, and A. C. To, “On utilizing topology optimization to design support structure to prevent stress induced build failure in laser powder bed fusion,” Additive Manufacturing, accepted. [link]

[2] L. Cheng and A. C. To, “Part-scale build orientation optimization for minimizing residual stress and support volume for metal additive manufacturing: theory and experimental validation,” Computer-Aided Design, to appear.

Modified Inherent Strain Method for Additive Manufacturing

Residual deformation and stress are one of the most critical issues in metal additive manufacturing (AM) techniques. It is a key challenge to predict the residual deformation in the part-scale by performing detailed process simulation for the entire part, which is prohibitively expensive and hence impractical. In this work, the modified inherent strain theory is proposed to enable efficient yet accurate prediction of residual deformation of AM components. The proposed theory allows for the calculation of inherent strain accurately based on a small-scale process simulation of a small representative volume out of a large component. The extracted mean inherent strain vector will be applied to a part-scale model layer-by-layer in order to simulate accumulation of the residual deformation by static finite element analysis. To verify the accuracy of the proposed method, the residual deformation and stress of different geometries after the AM processing are investigated, and the predicted residual deformation matches well with the experimental results.

[1] X. Liang, L. Cheng, Q. Chen, Q. Yang, and A. C. To, “A modified method for estimating inherent strains from detailed process simulation for fast residual distortion prediction of single-walled structures fabricated by directed energy deposition,” Additive Manufacturing, vol. 23, 471-486, 2018. [link]

[2] Q. Chen, X. Liang, D. Hayduke, J. Liu, L. Cheng, J. Oskin, R. Whitmore, and A. C. To, “An inherent strain based multiscale modeling framework for simulating part-scale residual deformation for direct metal laser sintering,” Additive Manufacturing, to appear.

Variable-density Lattice Optimization for Additive Manufacturing

Cellular structures can be employed effectively in lightweight structural design to overcome some of the manufacturing limitations existing in additive manufacturing (AM). For this purpose, a homogenization-based topology optimization method is proposed to optimize variable-density cellular structures efficiently. First, homogenization is performed to capture the effective mechanical properties of cellular structures through the scaling law as a function of relative density. Second, the scaling law is employed directly in the topology optimization algorithm to compute the optimal density distribution for the part being optimized. Third, a new technique is presented to reconstruct the CAD model of the optimal variable-density cellular structure. The proposed method is validated by comparing the results obtained through homogenized model, full scale simulation, and experimentally testing the optimized parts after being additive manufactured. The test examples demonstrate that the proposed homogenization-based method is efficient, accurate, and is able to produce manufacturable designs.

[1] L. Cheng, P. Zhang, E. Biyikli, J. Bai, J. Robbins, and A. C. To, “Efficient design optimization of variable-density cellular structures for additive manufacturing: Theory and experimental validation,” Rapid Prototyping Journal, 23, 660-677, 2017. [link]

[2] P. Zhang, J. Toman, Y. Yu, E. Biyikli, M. Kirca, M. Chmielus, and A. C. To, “Efficient design-optimization of variable-density hexagonal cellular structure by additive manufacturing: Theory and validation," ASME Journal of Manufacturing Science and Engineering, vol. 137, 021004, 2015.  [link]

Modeling Process-Microstructure-Property Relationship of AM Metals

Advances in additive manufacturing (AM) technology have made it possible to manufacture complex-shaped metal components strong enough for real engineering applications. To date, the process-microstructure-property relationship for AM metals has mostly been investigated experimentally, which is expensive and time-consuming since the parameter space is quite large. The lack of a reliable theoretical model for predicting such relationship makes it difficult to design AM components. The goal of this research is to establish a theoretical model that is capable of predicting the microstructure (texture, grain size, shape and subgrain features length scale) and mechanical properties (strength and anisotropy) of an AM metal based on the input process parameters (beam power, scan speed, preheat, and scanning strategy).

[1] J. Liu and A. C. To, "Quantitative texture prediction of epitaxial columnar grains in additive manufacturing using selective laser melting,” Additive Manufacturing, 16, 58-64, 2017.  [link]

[2]  J. Liu, W. Xiong, A. Behera, S. Thompson, and A. C. To, "Mean-field polycrystal plasticity modeling with grain size and shape effects for laser additive manufactured FCC metals," International Journal of Solids and Structures, 112, 35-42, 2017.  [link]

Mechanics of Bioinspired and Phononic Structures

We believe nature optimizes certain mechanical properties of biological materials by designing microstructure. Recently, we have discovered interesting mechanical behaviors in hierarchical structure found in many biocomposites. For example, hierarchical structure can enhance wave filtering and damping figure of merits significantly.

[1] P. Zhang, M. Heyne, and, A. C. To, “Biomimetic staggered composites with highly enhanced energy dissipation: modeling, 3D printing, and testing” Journal of Mechanics and Physics of Solids, vol. 83, 285-300, 2015 [link]

[2] P. Zhang and A. C. To, "Broadband wave filtering of bioinspired hierarchical phononic crystal," Applied Physics Letters, vol. 102, 121910, 2013. [link]

Journal Publications

Additive Manufacturing Modeling and Simulation | Atomistic/Continuum Theory & Modeling | Finite Elements/Meshfree Methods | Acoustic Emission | Miscellaneous

Mechanics & Physics of Solids: Metamaterials & Phononic Crystals | Nanoporous Metals | Carbon Nanotube Structures | Nanowires | Piezoelectrics 

Additive Manufacturing Modeling and Simulation
  1. J. Liu and A. C. To, “CAD-based topology optimization system with dynamic feature shape and modeling history evolution,” Journal of Mechanical Design, accepted.
  2. H. Deng, L. Cheng, X. Liang, D. Hayduke, and A. C. To, “Topology optimization for energy dissipation design of lattice structures through snap-through behavior,” Computer Methods in Applied Mechanics and Engineering, vol. 358, 112641. [link]
  3. X. Liang, Q. Chen, L. Cheng, D. Hayduke, and A. C. To, “Modified inherent strain method for fast prediction of residual deformation in direct metal laser sintered components,” Computational Mechanics, in press.  [link]
  4. Q. Chen, X. Liang, D. Hayduke, J. Liu, L. Cheng, J. Oskin, R. Whitmore, and A. C. To, “An inherent strain based multiscale modeling framework for simulating part-scale residual deformation for direct metal laser sintering,” Additive Manufacturing, vol. 28, 406-418, 2019. [link]
  5. L. Cheng and A. C. To, “Part-scale build orientation optimization for minimizing residual stress and support volume for metal additive manufacturing: theory and experimental validation,” Computer-Aided Design, vol. 113, 1-23, 2019. [link]
  6. L. Cheng, X. Liang, J. Bai, Q. Chen, J. Lemon, and A. C. To, “On utilizing topology optimization to design support structure to prevent stress induced build failure in laser powder bed fusion,” Additive Manufacturing, vol. 27, 290-304, 2019. [link]
  7. J. Liu, Q. Chen, X. Liang, and A. C. To, “Manufacturing cost constrained topology optimization for additive manufacturing,” Frontiers of Mechanical Engineering, accepted. [invited paper]
  8. D. Hao, L. Cheng, and A. C. To, “Distortion energy-based topology optimization design of hyperelastic materials,” Structural and Multidisciplinary Optimization, in press. [link]
  9. L. Cheng, J. Bai, and A. C. To, “Functionally graded lattice structure topology optimization for the design of additive manufactured components with stress constraints,” Computer Methods in Applied Mechanics and Engineering, vol. 344, 334-359, 2019. [link]
  10. X. Liang, L. Cheng, Q. Chen, Q. Yang, and A. C. To, “A modified method for estimating inherent strains from detailed process simulation for fast residual distortion prediction of single-walled structures fabricated by directed energy deposition,” Additive Manufacturing, vol. 23, 471-486, 2018.
  11. L. Cheng, X. Liang, E. Belski, X. Wang, J. M. Sietins, S. Ludwick, and A. C. To, “Natural frequency optimization of variable-density additive manufactured lattice structure: Theory and experimental validation,” Journal of Manufacturing Science and Engineering. (in press)  [link]
  12. L. Cheng, J. Liu, and A. C. To, “Concurrent lattice infill with feature evolution optimization for additive manufactured heat conduction design,” Structural and Multidisciplinary Optimization, 58, 511-535, 2018.  [link]
  13. J. Liu, A. T. Gaynor, S. Chen, Z. Kang, K. Suresh, A. Takezawa, L. Li, J. Kato, J. Tang, C. C. C. Wang, L. Cheng, X. Liang, and A. C. To, “Current and future trends in topology optimization for additive manufacturing,” Structural and Multidisciplinary Optimization, 57, 2457-2483, 2018.  [link]
  14. M. Lynch, M. Mordasky, L. Cheng, and A. C. To, “Design, testing, and mechanical behavior of additively manufactured casing with optimized lattice structure,” Additive Manufacturing, 22, 462-471, 2018.  [link]
  15. L. Cheng, J. Liu, X. Liang, and A. C. To, “Coupling lattice structure topology optimization with design-dependent feature evolution for additive manufactured heat conduction design,” Computer Methods in Applied Mechanics and Engineering, 332, 408-439, 2018.  [link]
  16. C. Baykasoglu, O. Akyildiz, D. Candemir, Q. Yang, and A. C. To, “Predicting microstructure evolution during directed energy deposition additive manufacturing of Ti-6Al-4V,” Journal of Manufacturing Science and Engineering, 140, 051003, 2018.  [link]
  17. X. Wang, P. Zhang, S. Ludwick, E. Belski, and A. C. To, "Natural frequency optimization of 3D printed variable-density honeycomb structure via a homogenization-based approach," Additive Manufacturing, 20, 189-198, 2018.  [link]
  18. J. Liu, H. Yu, and A. C. To, "Porous structure design through Blinn transformation-based level set method," Structural and Multidisciplinary Optimization, 2018, 57, 849-864, 2018.  [link]
  19. J. Liu, E. Stevens, Q. Yang, M. Chmielus, and A. C. To, “An analytical model of the melt pool and single track in coaxial laser direct metal deposition (LDMD) additive manufacturing,” Journal of Micromechanics and Molecular Physics, 2, 1750013, 2017. [invited paper] [link].
  20. J. Liu and A. C. To, “Arbitrary void feature control in level set topology optimization,” Computer Methods in Applied Mechanics and Engineering, 324, 595-618, 2017.  [link]
  21. J. Liu and A. C. To, “Deposition path planning-assisted structural topology optimization for 3D additive manufacturing subject to self-support constraint,” Computer-Aided Design, 91, 27-45.  [link]
  22. J. Liu and A. C. To, "Quantitative texture prediction of epitaxial columnar grains in additive manufacturing using selective laser melting,” Additive Manufacturing, 16, 58-64, 2017.   [link]
  23. L. Cheng, P. Zhang, E. Biyikli, J. Bai, J. Robbins, and A. C. To, “Efficient design optimization of variable-density cellular structures for additive manufacturing: Theory and experimental validation,” Rapid Prototyping Journal, 23, 660-677, 2017.  [link]
  24. J. Liu, W. Xiong, A. Behera, S. Thompson, and A. C. To, "Mean-field polycrystal plasticity modeling with grain size and shape effects for laser additive manufactured FCC metals," International Journal of Solids and Structures, 112, 35-42, 2017.  [link]
  25. P. Zhang, J. Liu and A. C. To, “Role of anisotropic properties on topology optimization of additive manufactured load bearing structures,” Scripta Materialia, 135, 148-152, 2017.  [link]
  26. J. Liu and A. C. To, "Topology optimization for hybrid additive-subtractive manufacturing," Structural and Multidisciplinary Optimization, 55, 1281-1299, 2017.  [link]
  27. E. L. Stevens, J. Toman, A. C. To, and M. Chmielus, “Variation of hardness, microstructure, and Laves phase distribution in direct laser deposited alloy 718 cuboids,” Journal of Materials and Design, 119, 188-198, 2017.  [link]
  28. Y. Onur Yildiz, H. Zeinalabedini, P. Zhang, M. Kirca, and A. C. To, "Homogenization of additive manufactured polymeric foams with spherical cells," Additive Manufacturing, 12B, 274-281, 2016. [link]
  29. Q. Yang, P. Zhang, L. Cheng, M. Zheng, M. Chyu, and A. C. To, "Finite element modeling and validation of thermomechanical behavior of Ti-6Al-4V in laser metal deposition additive manufacturing,"  Additive Manufacturing, 12B, 169-177, 2016.  [link]
  30. P. Zhang and A. C. To, "Transversely isotropic hyperelastic-viscoplastic model for glassy polymers with application to additve manufactured photopolymers," International Journal of Plasticity, 80, 56-74, 2016.  [link]
  31. P. Zhang and A. C. To, “Point group symmetry and deformation induced symmetry breaking of superlattice materials,” Proceedings A of the Royal Society, 471, 0125, 2015.  [link].
  32. E. Biyikli and A. C. To, "Proportional Topology Optimization: A new non-sensitivity method for solving stress constrained and minimum compliance problems and its implementation in MATLAB,"PLOS ONE, 10, e0145041, 2015.  [link].
  33. P. Zhang, M. Heyne, and, A. C. To, “Biomimetic staggered composites with highly enhanced energy dissipation: modeling, 3D printing, and testing,” Journal of Mechanics and Physics of Solids, 83, 285-300, 2015, 2015.  [link].
  34. P. Zhang, J. Toman, Y. Yu, E. Biyikli, M. Kirca, M. Chmielus, and A. C. To, “Efficient design-optimization of variable-density hexagonal cellular structure by additive manufacturing: Theory and validation," ASME Journal of Manufacturing Science and Engineering, 137, 021004, 2015.  [link]

Atomistic/Continuum Theory & Modeling

  1. Q. Yang and A. C. To, "Multiresolution molecular mechanics: surface effects in nanoscale materials," Journal of Computational Physics, 336, 212-234, 2017.  [link]
  2. E. Biyikli and A. C. To, “Multiresolution molecular mechanics: implementation and efficiency,” Journal of Computational Physics, 328, 27-45, 2017.  [link]
  3. E. Biyikli and A. C. To, “Multiresolution molecular mechanics: adaptive analysis,” Computer Methods in Applied Mechanics and Engineering, 305, 682-702, 2016.  [link]
  4. Q. Yang and A. C. To, "Multiresolution molecular mechanics: a unified and consistent framework for general finite element shape functions," Computer Methods in Applied Mechanics and Engineering, 283, 384-418, 2015. [link]
  5. E. Biyikli, Q. Yang, and A. C. To, “Multiresolution molecular mechanics: dynamics,” Computer Methods in Applied Mechanics and Engineering, 274, 42-55, 2014.  [link]
  6. Y. Fu and A. C. To, “A modification to Hardy’s thermomechanical theory that conserves fundamental properties more accurately: Tensile and shear failures in iron,” Modeling and Simulation in Materials Science and Engineering, 22, 015010, 2014.  [link]
  7. Q. Yang, E. Biyikli, and A. C. To, “Multiresolution molecular mechanics: convergence and error structure analysis,” Computer Methods in Applied Mechanics and Engineering, 269, 20-45, 2014. [link]
  8. Y. Fu and A. C. To, "A modification to Hardy's thermomechanical theory that conserves fundamental properties more accurately," Journal of Applied Physics, 113, 233505, 2013.  [link]
  9. Y. Fu and A. C. To, "On the evaluation of Hardy’s thermomechanical quantities using ensemble and time averaging,” Modeling and Simulation in Materials Science and Engineering, 21, 055015, 2013. [link]
  10. Q. Yang, E. Biyikli, and A. C. To, “Multiresolution molecular mechanics: statics,” Computer Methods in Applied Mechanics and Engineering, 258, 26-38, 2013. [link]
  11. Q. Yang, E. Biyikli, P. Zhang, R. Tian, and A. C. To, “Atom collocation method,” Computer Methods in Applied Mechanics and Engineering, 237-240, 67-77, 2012. [link]
  12. Y. Fu, M. Kirca, and A. C. To, "On determining the thermal state of individual atoms in molecular dynamics simulations of nonequilibrium processes in solids," Chemical Physics Letters, 506, 290-297, 2011. [link]
  13. A. C. To, Y. Fu, W. K. Liu, "Denoising methods for thermomechanical decomposition for quasi-equilibrium molecular dynamics simulations," Computer Methods in Applied Mechanics and Engineering, 200, 1979-1992, 2011. [link]
  14. A. C. To, W. K. Liu, G. B. Olson, T. Belytschko, W. Chen, M. Shephard, Y.-W. Chung, R. Ghanem, P. W. Voorhees, D. N. Seidman, C. Wolverton, J. S. Chen, B. Moran, A. J. Freeman, R. Tian, X. Luo, E. Lautenschlager, D. Challoner, “Materials integrity in microsystems: a framework for a petascale predictive-science based multiscale modeling and simulation system,” Computational Mechanics, 42, 485-510, 2008. [link]
  15. A. C. To, W. K. Liu, and A. Kopacz, "A finite temperature continuum theory based on interatomic potential in crystalline solids," Computational Mechanics, 42, 531-541, 2008.  [link]
  16. S. Li, X. Liu, A. Agrawal, and A. C. To, "Perfectly matched multiscale simulations for discrete lattice systems: Extension to multiple dimensions," Physical Review B, 74, 045418, 2006.  [link]
  17. A. C. To and S. Li, "Perfectly matched multiscale simulations," Physical Review B, 72, 035414, 2005. [link]

Metamaterials & Phononic Crystals

  1. P. Zhang and A. C. To, “Point group symmetry and deformation induced symmetry breaking of superlattice materials,” Proceedings A of the Royal Society, 471, 0125, 2015.  [link].
  2. X. Mu, L. Wang, X. Yang, P. Zhang, A. C. To, and T. Luo, “Ultra-low thermal conductivity in Si/Ge hierarchical superlattice nanowires,” Scientific Reports, 5, 16697, 2015.  [link]
  3. P. Zhang, M. Heyne, and, A. C. To, “Biomimetic staggered composites with highly enhanced energy dissipation: modeling, 3D printing, and testing,” Journal of Mechanics and Physics of Solids, 83, 285-300, 2015, 2015. [link]
  4. P. Zhang and A. C. To, “Highly enhanced damping figure of merit in biomimetic hierarchical staggered composites,” ASME Journal of Applied Mechanics, 81, 051015, 2014. [link]
  5. P. Zhang and A. C. To, "Broadband wave filtering of bioinspired hierarchical phononic crystal,"Applied Physics Letters, 102, 121910, 2013.  [link]
  6. B. J. Lee and A. C. To. “Enhanced absorption in one-dimensional phononic crystals with interfacial acoustic waves,” Applied Physics Letters, 95, 031911, 2009. [link]
  7. S. Gonella, A. C. To, and W. K. Liu, “Interplay between phononic bandgaps and piezoelectric microstructures for energy harvesting,” Journal of Mechanics and Physics of Solids, 57, 621-633, 2009. [link]

Nanoporous Metals

  1. A. Giri, J. Tao, M. Kirca, and A. C. To, “Compressive behavior and deformation mechanism of nanoporous open-cell foam with ultrathin ligaments,” Journal of Micromechanics and Nanomechanics,4, SPECIAL ISSUE: Mechanics of Nanocomposites and Nanostructure, A4013012, 2014.  [link]
  2. A. Giri, J. Tao, M. Kirca, and A. C. To, “Mechanics of nanoporous metals,” in Handbook of Micromechanics and Nanomechanics, edited by S. Li and X. L. Gao (Pan Stanford, Singapore), pp. 827-862, 2013.  [link]
  3. A. C. To, J. Tao, M. Kirca, and L. Schalk, "Ligament and joint sizes govern softening in nanoporous aluminum," Applied Physics Letters, 98, 051903, 2011.  [link]
  4. A. Datta, A. Srirangarajan, U. V. Waghmare, U. Ramamurty, and A. C. To, "Surface effects on stacking fault and twin formation in fcc nanofilms: a first-principles study," Computational Materials Science, 50, 3342-3345. 2011. [link]

Carbon Nanotube Structures

  1. X. Yang, S. Wu, J. Xu, B.-Y. Cao, A. C. To, “Spurious heat conduction behavior of finite-size graphene nanoribbon under extreme uniaxial strain caused by the AIREBO potential, Physica E, 96, 46-53, 2018. [link]
  2. C. Baykasoglu, Z. Ozturk, M. Kirca, A. T. Celebi, A. Mugan, and A. C. To, “Effect of lithium doping on hydrogen storage capacity of heat welded random CNT network structure,” International Journal of Hydrogen Energy, 41, 8246–8255, 2016. [link]
  3. Z. Ozturk, C. Baykasoglu, A. T. Celebi, M. Kirca, A. Mugan, A. C. To, "Hydrogen storage in heat welded random CNT network structures," International Journal of Hydrogen Energy, 40, 403-411, 2015. [link]
  4. X. Yang, Y. Huang, L. Wang, Z. Han, and A. C. To, "Carbon nanotube-fullerene hybrid nanostructures by C60 bombardment: formation and mechanical behavior," Physical Chemistry Chemical Physics, 16, 21615, 2014. [link]
  5. X. Yang, Y. Huang, L. Wang, Z. Han, and A. C. To, "Nanobuds promote heat welding of carbon nanotubes at experimentally-relevant temperatures," RSC Advances, 4, 56313-56317, 2014. [link]
  6. A. T. Celebi, M. Kirca, C. Baykasoglu, A. Mugan, and A. C. To, “Tensile behavior of heat welded CNT network structures,” Computational Materials Science, 88, 14-12, 2014. [link]
  7. X. Yang, D. Chen, Z. Han, and A. C. To, “Effects of welding on thermal conductivity of randomly oriented carbon nanotube networks,” International Journal of Heat and Mass Transfer, 70, 803-810, 2014. [link]
  8. D. Mohammadyani, H. Modarress, A. C. To, A. Amani, ”Interactions of fullerenes (C60) and its hydroxyl derivatives with lipid bilayer: a coarse-grained molecular dynamic simulation,” Brazilian Journal of Physics, 44, 1-7, 2014. [link]
  9. X. Yang, D. Chen, Y. Du, and A. C. To, “Heat conduction in extended X-junctions of single-walled carbon nanotubes,” Journal of Physics and Chemistry of Solids, 2013, 75, 123-129, 2014. [link]
  10. M. Kirca, X. Yang, and A. C. To, “A stochastic algorithm for modeling heat welded random carbon nanotube network,” Computer Methods in Applied Mechanics and Engineering, 259, 1-9, 2013. [link]
  11. X. Yang, F. Qiao, P. Zhang, X. Zhu, D. Chen, and A. C. To, “Coalescence of parallel finite length single-walled carbon nanotubes by heat treatment,” Journal of Physics and Chemistry of Solids, 74, 436-440, 2013. [link]
  12. E. Biyikli, J. Liu, X. Yang, and A. C. To, "A fast method for generating atomistic models of arbitrary-shaped carbon graphitic nanostructures," RSC Advances, 3, 1359-1362, 2013. [link]
  13. X. Yang, Z. Han, Y. Li, D. Chen, P. Zhang, and A. C. To, "Heat welding of non-orthogonal X-junction of single-walled carbon nanotubes," Physica E, 46, 30-32, 2012. [link]
  14. X. Yang, P. Zhang, Z. Han, D. Chen, and A. C. To, “Transformation of non-orthogonal X-junction of single-walled carbon nanotubes into parallel junction by heating,” Chemical Physics Letters, 547, 42-46, 2012. [link]
  15. B. A. Stormer, N. M. Piper, X. Yang, J. Tao, Y. Fu, M. Kirca, and A. C. To, "Mechanical properties of SWNT X-junctions through molecular dynamics simulation," International Journal of Smart and Nano Materials, 3, 33-46, 2012. (invited paper) [link]
  16. N. M. Piper, Y. Fu, J. Tao, X. Yang, and A. C. To, "Vibration promotes heat welding of single-walled carbon nanotubes," Chemical Physics Letters, 502, 231-234, 2011. [link]
  17. A. Datta, M. Kirca, Y. Fu, and A. C. To, "Surface structure and properties of functionalized nanodiamonds: a first-principles study," Nanotechnology, 22, 065706, 2011. link]

Nanowires

  1. X. Yang, A. C. To, and M. Kirca, "Thermal conductivity of periodic array of intermolecular junctions of silicon nanowires," Physica E, 44, 141-145, 2011. [link]
  2. X. Yang, A. C. To, and R. Tian, “Anomalous heat conduction behavior in thin finite-size silicon nanowires,” Nanotechnology, 21, 155704, 2010. [link]
  3. Y. Hu, A. C. To, and M. Yun, “Controlled growth of single metallic and conducting polymer nanowire via gate-assisted electrodeposition,” Nanotechnology, 20, 285605, 2009. [link]

Piezoelectrics

  1. S. Gonella, A. C. To, and W. K. Liu, “Interplay between phononic bandgaps and piezoelectric microstructures for energy harvesting,” Journal of Mechanics and Physics of Solids, 57, 621-633, 2009. [link]
  2. A. C. To, S. Li, and S. D. Glaser, "Propagation of a mode-III interfacial conductive crack along a conductive interface between two piezoelectric materials," Wave Motion, 43, 368–386, 2006. [link]
  3. S. Li, A. C. To, and S. D. Glaser, "On scattering in a piezoelectric medium by a conducting crack,"ASME Journal of Applied Mechanics, 72, 943–954, 2005. [link]
  4. A. C. To, S. Li, and S. D. Glaser, "On scattering in dissimilar piezoelectric materials by an interfacial crack," Quarterly Journal of Mechanics and Applied Mathematics, 58, 309–331, 2005. [link]

Finite Elements/Meshfree Methods

  1. E. Biyikli, J. Liu, X. Yang, and A. C. To, "A fast method for generating atomistic models of arbitrary-shaped carbon graphitic nanostructures," RSC Advances, 3, 1359-1362, 2013. [link]
  2. R. Tian, A. C. To, and W. K. Liu, "Conforming local meshfree method," International Journal for Numerical Methods in Engineering, 86, 335-357, 2011. [link]
  3. X. Yin, W. Chen, A. C. To, C. McVeigh, W. K. Liu, “Statistical volume element method for predicting microstructure constitutive property relations,” Computer Methods in Applied Mechanics and Engineering, 197, 3516-3529, 2008. [link]
  4. Y. Liu, W. K. Liu, T. Belytschko, N. A. Patankar, A. C. To, A. Kopacz, and J.-H. Chung, "Immersed electrokinetic finite element method," International Journal for Numerical Methods in Engineering, 71, 379–405, 2007. [link]

Acoustic Emission

  1. A. C. To, J. R. Moore, and S. D. Glaser, “Wavelet denoising techniques with applications to experimental geophysical data,” Signal Processing, 89, 144-160, 2009. [link]
  2. A. C. To, and S. D. Glaser, "Full waveform inversion of a 3-D source inside an artificial rock," Journal of Sound and Vibration, 285, 835–857, 2005. [link]
  3. J. Ching, A. C. To, and S. D. Glaser, "Microseismic source deconvolution: Bayes vs. Wiener, Fourier vs. wavelets, and linear vs. nonlinear," Journal of Acoustical Society of America, 115, 3048–3058, 2004. [link]

Miscellaneous

  1. S. D. Chambreau, G. L. Vaghjiani, A. C. To, C. Koh, D. Strasser, O. Kostko, and S. R. Leone. “Heats of vaporization of room temperature ionic liquids by tunable vacuum ultraviolet photoionization,” Journal of Physical Chemistry B, 114, 1361-1367, 2010. [link]
  2. A. C. To, H. Ernst, and H. H. Einstein, "Lateral load capacity of drilled shafts in jointed rock," ASCE Journal of Geotechnical and Geoenvironmental Engineering, 129, 711–726, 2003. [link]

Total Number of Journal Publications:  92

Book Chapters

  1. M. Kirca and A. C. To, "Mechanics of CNT network materials,” in Advanced Computational Nanomechanics, edited by N. Silvestre (Wiley, New York), 29-70,2016. [link]
  2. A. Giri, J. Tao, M. Kirca, and A. C. To, “Mechanics of nanoporous metals,” in Handbook of Micromechanics and Nanomechanics, edited by S. Li and X. L. Gao (Pan Stanford, Singapore), 827-862, 2013. [link]
  3. Y. Fu and A. C. To, "Application of many-realization molecular dynamics method to understand the physics of nonequilibrium processes in solids," in Multiscale Simulations and Mechanics of Biological Materials, edited by S. Li and D. Qian, (Wiley, New York), 59-76, 2013. [link]

Ph.D. Dissertations

  1. Lin Cheng, "Functionally Graded Lattice Infill and Cooling Channel Design Optimization for Additive Manufacturing," Ph.D. Dissertation, University of Pittsburgh, 2019. [pdf]
  2. Qingcheng Yang, "Multiresolution molecular mechanics:  Theory and applications," Ph.D. Dissertation, University of Pittsburgh, 2016. [pdf]
  3. Pu Zhang, "Bioinspired hierarchical materials and cellular structures: Design, modeling, and 3D printing," Ph.D. Dissertation, University of Pittsburgh, 2015. [pdf]
  4. Emre Biyikli, "Multiresolution molecular mechanics: Dynamics, adaptivity, and implementation," Ph.D. Dissertation, University of Pittsburgh, 2015. [pdf]
  5. Mesut Kirca, "Mechanics of nanomaterials consisted of random networks," Ph.D. Dissertation, Istanbul Technical University, 2013. [pdf
  6. Yao Fu, "On determining continuum quantities of non-equilibrium processes via molecular dynamics simulations," Ph.D. Dissertation, University of Pittsburgh, 2013. [pdf]

GONE BUT NOT FORGOTTEN

Postdoctoral Fellows

Jikai Liu (2016-2018), now profeessor at Shandong University

Jian Liu (2015-2018), now postdoc fellow at University of Pittsburgh

Xueming Yang (2009-2010), now professor at North China Electric Power University in China

Aditi Datta (2009-2011), now adjunct faculty at Purdue Universtiy Northwest

Ph.D. Students

Qingcheng Yang (Ph.D. 2016), now postdoc fellow in Prof. Samnath Ghosh's group at Johns Hopkinds University 

Pu Zhang (Ph.D. 2015), now assistant professor at SUNY-Binghamton University.

Emre Biyikli (Ph.D. 2015), now senior software engineer at MathWorks.

Mesut Kirca (Ph.D. 2013), now associate professor at Istanbul Technical University in Turkey

Yao Fu (Ph.D. 2013), now assistant professor at University of Cincinnati

 

Visiting Students and Scholars

Akihiro Takezawa (2019-present), associate professor at Hiroshima University in Japan

Cengiz Baykasoglu (2015-2016), now associate professor at Hetit University in Turkey

Lili Wang, (2011-2012), now assistant professor at Shanghai University of Engineering Science

Dariush Mohammadyani, (2011-2012), now postdoc at Johns Hopkins University

M.S. Students

Yiming Ding (M.S. 2017), now an engineer at Groupe PSA 

Jiaxi Bai (M.S. 2016), now software engineer at ANSYS

Yiqi Yu (M.S. 2014), now software engineer at ANSYS

Ashtuosh Giri (M.S. 2012), now PhD student at University of Virginia

 

Our AM lab houses the following AM systems (from left to right):  EOS M290 DMLS, Optomec LENS 450, ExOne M-Flex & X1-Lab, Stratasys Objet260 Connex.