Drugan, Walter J.

continuum mechanics analyses of behavior of modern materials
nonlinear fracture mechanics of ductile materials (single- and poly-crystalline) and interfaces
nonlocal constitutive models of composite materials
dynamic fragmentation
nanoscale fracture
nanoscale shape-memory alloys
discontinuities and shock waves in solids
applied mathematics

Publications

K. Bertoldi, D. Bigoni and W. J. Drugan, "Nacre: An Orthotropic and Bimodular Elastic Material," Composites Science and Technology 68, 1363-1375 (2008).
W. J. Drugan, "Elastic Composite Materials Having a Negative-Stiffness Phase Can Be Stable," Physical Review Letters 98 (5) (2007) [Article 055502].
D. Bigoni and W. J. Drugan, "Analytical Derivation of Cosserat Moduli via Homogenization of Heterogeneous Elastic Materials," Journal of Applied Mechanics 74, 741-753 (2007).
K. Bertoldi, D. Bigoni and W. J. Drugan, "A Discrete-Fibers Model for Bridged Cracks and Reinforced Elliptical Voids," Journal of the Mechanics and Physics of Solids 55, 1016-1035 (2007).
K. Bertoldi, D. Bigoni and W. J. Drugan, "Structural Interfaces in Linear Elasticity. Part I: Nonlocality and Gradient Approximations," Journal of the Mechanics and Physics of Solids 55, 1-34 (2007).
K. Bertoldi, D. Bigoni and W. J. Drugan, "Structural Interfaces in Linear Elasticity. Part II: Effective Properties and Neutrality," Journal of the Mechanics and Physics of Solids 55, 35-63 (2007).
G.A. Shaw, J.S. Trethewey, A.D. Johnson, W.J. Drugan and W.C. Crone, "Thermomechanical High-Density Data Storage in a Metallic Material via the Shape-Memory Effect," Advanced Materials 17, 1123-1127 (2005).
K. Yoshimoto, M. P. Stoykovich, H. B. Cao, J. J. de Pablo, P. F. Nealy and W. J. Drugan, "A Two-Dimensional Model of the Deformation of Photoresist Structures Using Elastoplastic Polymer Properties," Journal of Applied Physics 96, 1857-1865 (2004).
I. Monetto and W. J. Drugan, "A Micromechanics-Based Nonlocal Constitutive Equation for Elastic Composites Containing Randomly-Oriented Spheroidal Heterogeneities," Journal of the Mechanics and Physics of Solids 52, 359-393 (2004).
A. Nakatani, W. J. Drugan, E. Van der Giessen and A. Needleman, "Crack Tip Fields at a Ductile Single Crystal-Rigid Material Interface," International Journal of Fracture 122, 131-159 (2003).
W. J. Drugan, "Two Exact Micromechanics-Based Nonlocal Constitutive Equations for Random Linear Elastic Composite Materials," Journal of the Mechanics and Physics of Solids 51, 1745-1772 (2003).
I. Monetto and W. J. Drugan, "On Micromechanics-Based Nonlocal Modeling of Elastic Matrices Containing Non-Spherical Heterogeneities," in Asymptotics, Singularities and Homogenisation in Problems of Mechanics, Springer (2003).
R. S. Lakes and W. J. Drugan, "Dramatically Stiffer Elastic Composite Materials Due to a Negative Stiffness Phase?," Journal of the Mechanics and Physics of Solids 50, 979-1009 (2002).
W. J. Drugan, "Mechanics-Based Modeling of Dynamic Fragmentation and Comparison with Experiments," Advances in Fracture Research: Proceedings of the 10th International Congress of Fracture, Elsevier Science (2001).
W. C. Crone and W. J. Drugan, "Comparison of Experiment and Theory for Crack Tip Fields in Ductile Single Crystals," Advances in Fracture Research: Proceedings of the 10th International Congress of Fracture, Elsevier Science (2001).
W. J. Drugan, "Asymptotic Solutions for Tensile Crack Tip Fields Without Kink-Type Shear Bands in Elastic-Ideally Plastic Single Crystals," Journal of the Mechanics and Physics of Solids 49, 2155-2176 (2001).
W. J. Drugan, "Dynamic Fragmentation in Brittle Materials: Analytical Mechanics-Based Models," Journal of the Mechanics and Physics of Solids 49, 1181-1208 (2001).
W. J. Drugan, "Elastic-Plastic Crack Growth Along Ductile/Ductile Interfaces," in Multi-Scale Deformation and Fracture in Materials and Structures, The James R. Rice 60th Anniversary Volume, edited by T.-J. Chuang, Kluwer Academic Publishers, 243-274 (2001).
W. J. Drugan, "Micromechanics-Based Variational Estimates for a Higher-Order Nonlocal Constitutive Equation and Optimal Choice of Effective Moduli for Elastic Composites," Journal of the Mechanics and Physics of Solids 48, 1359-1387 (2000).
W. J. Drugan, "Thermodynamic Analysis of Shock Waves in General Media; Applications to Elastic-Plastic Shock Waves and Ductile Crack Growth," in Material Instabilities in Elastic and Plastic Solids, edited by H. Petryk, Springer-Verlag Wein, New York, 53-108 (2000).
W. J. Drugan, "Limitations to Leading-Order Asymptotic Solutions for Elastic-Plastic Crack Growth," Journal of the Mechanics and Physics of Solids 46, 2361-2386 (1998).
W. J. Drugan, "Thermodynamic Equivalence of Steady-State Shocks and Smooth Waves in General Media; Applications to Elastic-Plastic Shocks and Dynamic Fracture," Journal of the Mechanics and Physics of Solids 46, 313-336 (1998).
W. J. Drugan and J. R. Willis, "A Micromechanics-Based Nonlocal Constitutive Equation and Estimates of Representative Volume Element Size for Elastic Composites," Journal of the Mechanics and Physics of Solids 44, 497-524 (1996).
Y. Miao and W. J. Drugan, "Asymptotic Analysis of Growing Crack Stress/Deformation Fields in Porous Ductile Metals and Implications for Stable Crack Growth," International Journal of Fracture 72, 69-96 (1995).
R. M. Brannon, W. J. Drugan and Y. Shen, "Requirements of Thermodynamics in the Analysis of Elastic-Plastic Shock Waves," Journal of the Mechanics and Physics of Solids 43, 973-1001 (1995).

Selected Awards, Honors and Societies

Invited Lecturer, CISM (International Center for Mechanical Sciences), Udine, Italy (1999)
Associate Editor, ASME Journal of Applied Mechanics (1994-2000)
Visiting Fellow, Fitzwilliam College, Cambridge University (1994-1995)
Engineering and Physical Sciences Research Council Senior Visiting Fellow at Cambridge University, Department of Applied Mathematics and Theoretical Physics (1994-1995)
National Science Foundation Presidential Young Investigator Award (1986)
Office of Naval Research Young Investigator Award (1985)

Summary

Our work involves the use of continuum mechanics and applied mathematics to model the mechanical behavior of modern materials, both on the microscale and macroscale.

One area concerns the analysis of stress and deformation fields associated with stationary and growing cracks in ductile materials (both poly- and single-crystalline). We also treat the related problem of interfacial cracking.

Another investigation focuses on the fundamental mechanics modeling of dynamic fragmentation of materials loaded at high rates.

Another topic involves the rigorous micromechanics-based development of macroscopic constitutive equations for composite materials: this permits quantitative assessment of existing ad hoc models, and facilitates development of a macroscopic fracture mechanics framework for composites.

We also analyze whether and under what conditions shock waves can exist during large deformations of many material types; for example, studies have shown that shocks may accompany rapidly growing cracks in ductile single crystals.

New thrusts include the development of analytical models for the fracture mechanics of nanoscale structures, and for the response of nanoscale shape-memory alloys.

Copyright 2008 The Board of Regents of the University of Wisconsin System
Date last modified: 27-Oct-2008
Content by: drugan@engr.wisc.edu
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