Dr. Florin Bobaru, Professor
Mechanical & Materials Engineering
University of Nebraska - Lincoln
W307 Nebraska Hall
Lincoln, Nebraska 68588-0526
office: (402) 472-8348
Our research group is focused on developing computational methods and tools that can provide solutions for very complex and difficult problems for which analytical or experimental methods either do not exist or are too expensive to perform. We apply our computational methods to problems ranging from nano-materials and biological systems, to heat and mass transfer or impact and fragmentation in ceramics. In particular, fields of current focus are: peridynamics for fracture and impact, modeling of nanostructured materials, meshfree methods and their applications to shape and material optimization of solids, granular materials and their interaction with vibrating structures, multidisciplinary optimization, inverse problems, adaptive refinement, and multiscale and multiphysics methods.
Damage and fracture with peridynamics. The peridynamic formulation is a novel reformulation of the classical continuum mechanics theory and has strong ties with molecular dynamics models. Our computational simulations show that Van der Waals forces play a critical role in the deformation and damage behavior of nanofiber networks. Nanofiber networks are a new class of materials with revolutionary properties. With peridynamics it is possible to model trans- and intergranular fracture in polycrystalline ceramics. The method leads to a meshfree implementation able to successfully model complicated fracture and fragmentation patterns at impact, spallation, etc. This research has important applications to modeling of nanostructures materials and multiscale research.
Dynamics of Granular Materials interacting with vibrating plates. Granular materials are one of the most puzzling material systems. Their dynamic behavior is, to a large extent, still unknown. We have developed new computational tools to simulate the dynamic interaction between a layer of granular material and an elastic vibrating plate. These types of computations provide us with an indirect way of inspecting and obtaining material properties for the granular layer, such as cohesion properties. This research has significant applications ranging from mine detection in sands to pharmaceutical industry.
Optimization of material composition. It would be extremely desirable to be able to find the best composition of a multi-component material (such as a composite or a functionally graded material - FGM) for a particular application. Since analytical solutions are not possible in such cases and trial-and-error experimental tests are too expensive and time consuming, we develop computational tools that provide solutions to such complex problems. Our recent results on optimal design of FGMs show that new non-monotonic volume fraction variations are possible when trying to minimize the possibility of failure due to thermal and mechanical stresses.
Optimal shape design. We have developed novel algorithms for computing optimal shape of systems when there are large shape changes between the initial guess and the final optimal design. One such example is that of finding the optimal shape of thermal cooling fins. Simply stated, given an area constraint, temperature and mechanical boundary conditions, ambient temperature and material constants, one has to find the best shape for the cooling fin that maximizes the thermal flux through the base of the fin. Our meshfree approach leads to interesting solutions that mimic naturally occurring systems like the plates on the back of a stegosaurus dinosaur, or the extended surfaces on the inner side of the intestine (intestinal villi). This research has applications to designing systems and structures that perform significantly better while using fewer resources.
Recent PublicationsJournal Publications h-index = 13, i10-index=19, over 550 citations (Google Scholar, August 2013)
1. W. Hu, Y. Wang, J. Yu, C.F. Yen, F. Bobaru, “Impact damage on a thin glass with a thin polycarbonate backing”, International Journal of Impact Engineering, 62: 152- 165 (2013).
2. F. Bobaru, YD. Ha, and W. Hu, “Damage progression from impact in layered glass modeled with peridynamics”, Central European Journal of Engineering, 2(4): 551-561 (2012).
3. F. Bobaru and W. Hu, “The meaning, selection, and use of the Peridynamic horizon and its relation to crack branching in brittle materials” International Journal of Fracture, 176: 215–222 (2012).
4. W. Hu, YD. Ha, F. Bobaru, and S.A. Silling, “The formulation and computation of the nonlocal J-integral in bond-based Peridynamics”, International Journal of Fracture, 176: 195–206 (2012).
5. W. Hu, YD. Ha, and F. Bobaru, “Peridynamic model for dynamic fracture in unidirectional fiber-reinforced composites”, Computer Methods in Applied Mechanics and Engineering, 217–220: 247–261 (2012).
6. F. Bobaru and M. Duangpanya, “A Peridynamic Formulation for Transient Heat Conduction in Bodies with Evolving Discontinuities”, Journal of Computational Physics, 231(7): 2764-2785 (2012).
7. YD. Ha and F. Bobaru, “Characteristics of dynamic brittle fracture captured with peridynamics”, Engineering Fracture Mechanics, 78: 1156–1168 (2011). doi:10.1016/j.engfracmech.2010.11.020.
8. F. Bobaru and YD. Ha, “Adaptive refinement and multiscale modeling in 2D Peridynamics”, International Journal for Multiscale Computational Engineering, 9(6): 635-659 (2011).
9. F. Bobaru, “Peridynamics and Multiscale Modeling” Editorial in Special Issue on “Advances in Peridynamics”, International Journal for Multiscale Computational Engineering, 9(6): vii-ix (2011).
10. W. Hu, YD. Ha, and F. Bobaru. “Modeling Dynamic Fracture and Damage in Fiber-Reinforced Composites with Peridynamics”, International Journal for Multiscale Computational Engineering, 9(6): 707–726 (2011).
11. A.L. Collins, J.W. Addiss, S.M. Walley, K. Promratana, F. Bobaru, W.G. Proud, D.M. Williamson, “The effect of rod nose shape on the internal flow fields during the ballistic penetration of sand”, International Journal of Impact Engineering, 38(12): 951-963 (2011).
12. F. Bobaru and M. Duangpanya, “The peridynamic formulation for transient heat conduction”, International Journal of Heat and Mass Transfer, 53(19-20): 4047-4059 (2010).
13. YD. Ha and F. Bobaru, “Studies of dynamic crack propagation and crack branching with peridynamics", International Journal of Fracture, 162(1-2): 229-244 (2010).
14. K. Rattanadit, F. Bobaru, K. Promratana, J.A. Turner, “Force chains and resonant behavior in bending of a granular layer on an elastic support”, Mechanics of Materials, 41(6): 691-706 (2009).
15. K. Rattanadit, F. Bobaru, K. Promratana, J.A. Turner, “Force chains and resonant behavior in bending of a granular layer on an elastic support”, Mechanics of Materials, 41(6): 691-706 (2009).
16. F. Bobaru, J.S. Chen, J.A. Turner, “Advances in the Dynamics of Granular Materials”, Editorial in Special Issue on Advances in the Dynamics of Granular Materials, Mechanics of Materials, 41(6): 635-636 (2009).
17. F. Bobaru, M. Yang, L.F. Alves, S.A. Silling, E. Askari, and J. Xu, “Convergence, adaptive refinement, and scaling in 1D peridynamics”, International Journal for Numerical Methods in Engineering, 77: 852-877 (2009).
18. P. Qiao, M. Yang, and F. Bobaru, “Impact mechanics and high-energy absorbing materials: review”, /Journal of Aerospace Engineering/ 21(4): 235-248 (2008).
19. F. Bobaru, “Influence of van der Waals forces on increasing the strength and toughness in dynamic fracture of nanofiber networks: a peridynamic approach”, Modelling and Simulation in Materials Science and Engineering 15: 397-417 (2007).
20. F. Bobaru, “Designing optimal volume fractions for functionally graded materials with temperature-dependent material properties”, /Journal of Applied Mechanics/, 74: 861-874 (2007).
21. W. Kang, J.A. Turner, F. Bobaru, L. Yang, and K. Rattanadit, “Granular layers on vibrating plates: Effective bending stiffness and particle-size effects”. Journal of the Acoustical Society of America, 121, 888-896 (2007).
22. F. Bobaru and S. Rachakonda, “E(FG)2: a new fixed-grid shape optimization method based on the element-free Galerkin meshfree analysis”, Structural and Multidisciplinary Optimization 32(3): 215-228(2006).
23. R.K. Lakkaraju, F. Bobaru, and S.L. Rohde, “Optimization of multilayer wear-resistant thin films using finite element analysis on stiff and compliant substrates”, Journal of Vacuum Science and Technology (A) - 24 (1): 146-155 (2006).
24. S.A. Silling and F. Bobaru, “Peridynamic modeling of membranes and fibers”, International Journal of Non-Linear Mechanics, 40(2-3): 395-409 (2005).
25. F. Bobaru and S. Rachakonda, “Optimal shape profiles for cooling fins of high and low conductivity”, International Journal of Heat and Mass Transfer, 47(23): 4953-4966 (2004).
26. F. Bobaru and S. Rachakonda, “Boundary layer in shape optimization of convective fins using a meshfree approach”, International Journal for Numerical Methods in Engineering, 60(7): 1215-1236 (2004).
27. F. Bobaru and Subrata Mukherjee, “Meshless approach to shape optimization of linear thermoelastic solids”, International Journal for Numerical Methods in Engineering, 53(4): 765-796 (2002).
28. F. Bobaru and S. Mukherjee, “Shape Sensitivity Analysis and Shape Optimization in Planar Elasticity Using the Element-Free Galerkin Method”, Computer Methods in Applied Mechanics and Engineering, 190(32-33) 4319-4337 (2001).
29. F. Bobaru, “Prestressed Elastic Solid Containing a Crack, Subjected to Normal or Tangential Loadings”, Revue Roumaine des Science Technique, Serie de Mecanique Applique, 41(5-6): 421-429 (1996).