Bio


Prof. Lew's interests lie in the broad area of computational solid mechanics. He is concerned with the fundamental design and mathematical analysis of material models and numerical algorithms.

Currently the group is focused on the design of algorithms to simulate hydraulic fracturing. To this end we work on algorithms for time-integration embedded or immersed boundary methods.

Academic Appointments


Professional Education


  • PhD, Caltech, Mechanical Engineering (2003)

2013-14 Courses


Journal Articles


  • A FAMILY OF DISCONTINUOUS GALERKIN MIXED METHODS FOR NEARLY AND PERFECTLY INCOMPRESSIBLE ELASTICITY ESAIM-MATHEMATICAL MODELLING AND NUMERICAL ANALYSIS-MODELISATION MATHEMATIQUE ET ANALYSE NUMERIQUE Shen, Y., Lew, A. J. 2012; 46 (5): 1003-1028
  • An explicit asynchronous contact algorithm for elastic body-rigid wall interaction INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Ryckman, R. A., Lew, A. J. 2012; 89 (7): 869-896

    View details for DOI 10.1002/nme.3266

    View details for Web of Science ID 000299626600004

  • Adhesive Frictionless Contact Between an Elastic Isotropic Half-Space and a Rigid Axi-Symmetric Punch JOURNAL OF ELASTICITY Kesari, H., Lew, A. J. 2012; 106 (2): 203-224
  • Time integrators based on approximate discontinuous Hamiltonians INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Dharmaraja, S., Kesari, H., Darve, E., Lew, A. J. 2012; 89 (1): 71-104

    View details for DOI 10.1002/nme.3236

    View details for Web of Science ID 000298589300004

  • A family of discontinuous Galerkin methods for nearly and perfectly incompressible elasticity ESAIM: Mathematical Modelling and Numerical Analysis Shen, Y., Lew, A., J. 2012; 46 (5): 1003-1028
  • Effective macroscopic adhesive contact behavior induced by small surface roughness JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS Kesari, H., Lew, A. J. 2011; 59 (12): 2488-2510
  • Parameterization of planar curves immersed in triangulations with application to finite elements INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Rangarajan, R., Lew, A. J. 2011; 88 (6): 556-585

    View details for DOI 10.1002/nme.3189

    View details for Web of Science ID 000296262500003

  • Variational time integrators for finite-dimensional thermo-elasto-dynamics without heat conduction INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Mata, P., Lew, A. J. 2011; 88 (1): 1-30

    View details for DOI 10.1002/nme.3160

    View details for Web of Science ID 000295226200001

  • OPTIMAL CONVERGENCE OF A DISCONTINUOUS-GALERKIN-BASED IMMERSED BOUNDARY METHOD ESAIM-MATHEMATICAL MODELLING AND NUMERICAL ANALYSIS-MODELISATION MATHEMATIQUE ET ANALYSE NUMERIQUE Lew, A. J., Negri, M. 2011; 45 (4): 651-674
  • Assembly of finite element methods on graphics processors INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Cecka, C., Lew, A. J., Darve, E. 2011; 85 (5): 640-669

    View details for DOI 10.1002/nme.2989

    View details for Web of Science ID 000286775000007

  • An optimally convergent discontinuous Galerkin-based extended finite element method for fracture mechanics INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Shen, Y., Lew, A. 2010; 82 (6): 716-755

    View details for DOI 10.1002/nme.2781

    View details for Web of Science ID 000276914300003

  • An adaptive stabilization strategy for enhanced strain methods in non-linear elasticity INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Ten Eyck, A., Lew, A. 2010; 81 (11): 1387-1416

    View details for DOI 10.1002/nme.2734

    View details for Web of Science ID 000274925300002

  • Stability and convergence proofs for a discontinuous-Galerkin-based extended finite element method for fracture mechanics COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Shen, Y., Lew, A. 2010; 199 (37-40): 2360-2382
  • Role of surface roughness in hysteresis during adhesive elastic contact PHILOSOPHICAL MAGAZINE LETTERS Kesari, H., Doll, J. C., Pruitt, B. L., Cai, W., Lew, A. J. 2010; 90 (12): 891-902

    Abstract

    In experiments that involve contact with adhesion between two surfaces, as found in atomic force microscopy or nanoindentation, two distinct contact force (P) vs. indentation-depth (h) curves are often measured depending on whether the indenter moves towards or away from the sample. The origin of this hysteresis is not well understood and is often attributed to moisture, plasticity or viscoelasticity. Here we report experiments that show that hysteresis can exist in the absence of these effects, and that its magnitude depends on surface roughness. We develop a theoretical model in which the hysteresis appears as the result of a series of surface instabilities, in which the contact area grows or recedes by a finite amount. The model can be used to estimate material properties from contact experiments even when the measured P-h curves are not unique.

    View details for DOI 10.1080/09500839.2010.521204

    View details for Web of Science ID 000283319100005

    View details for PubMedID 21152108

  • A discontinuous-Galerkin-based immersed boundary method with non-homogeneous boundary conditions and its application to elasticity COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Rangarajan, R., Lew, A., Buscaglia, G. C. 2009; 198 (17-20): 1513-1534
  • A discontinuous-Galerkin-based immersed boundary method INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Lew, A. J., Buscaglia, G. C. 2008; 76 (4): 427-454

    View details for DOI 10.1002/nme.2312

    View details for Web of Science ID 000260351400001

  • Stability of asynchronous variational integrators JOURNAL OF COMPUTATIONAL PHYSICS Fong, W., Darve, E., Lew, A. 2008; 227 (18): 8367-8394
  • A microstructurally informed model for the mechanical response of three-dimensional actin networks COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING Kwon, R. Y., Lew, A. J., Jacobs, C. R. 2008; 11 (4): 407-418

    Abstract

    We propose a class of microstructurally informed models for the linear elastic mechanical behaviour of cross-linked polymer networks such as the actin cytoskeleton. Salient features of the models include the possibility to represent anisotropic mechanical behaviour resulting from anisotropic filament distributions, and a power law scaling of the mechanical properties with the filament density. Mechanical models within the class are parameterized by seven different constants. We demonstrate a procedure for determining these constants using finite element models of three-dimensional actin networks. Actin filaments and cross-links were modelled as elastic rods, and the networks were constructed at physiological volume fractions and at the scale of an image voxel. We show the performance of the model in estimating the mechanical behaviour of the networks over a wide range of filament densities and degrees of anisotropy.

    View details for DOI 10.1080/10255840801888686

    View details for Web of Science ID 000257669100008

    View details for PubMedID 18568835

  • Adaptive stabilization of discontinuous Galerkin methods for nonlinear elasticity: Motivation, formulation, and numerical examples COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Ten Eyck, A., Celiker, F., Lew, A. 2008; 197 (45-48): 3605-3622
  • Adaptive stabilization of discontinuous Galerkin methods for nonlinear elasticity: Analytical estimates COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Ten Eyck, A., Celiker, F., Lew, A. 2008; 197 (33-40): 2989-3000
  • Parallel asynchronous variational integrators INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Kale, K. G., Lew, A. J. 2007; 70 (3): 291-321

    View details for DOI 10.1002/nme.1880

    View details for Web of Science ID 000245683900002

  • Discontinuous Galerkin methods for non-linear elasticity INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Ten Eyck, A., Lew, A. 2006; 67 (9): 1204-1243

    View details for DOI 10.1002/nme.1667

    View details for Web of Science ID 000239878200002

  • Quantum mechanics based multiscale modeling of stress-induced phase transformations in iron JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS Lew, A., Caspersen, K., Carter, E. A., Ortiz, M. 2006; 54 (6): 1276-1303
  • Effective cohesive behavior of layers of interatomic planes ARCHIVE FOR RATIONAL MECHANICS AND ANALYSIS Braides, A., Lew, A. J., Ortiz, M. 2006; 180 (2): 151-182
  • Importance of shear in the bcc-to-hcp transformation in iron PHYSICAL REVIEW LETTERS Caspersen, K. J., Lew, A., Ortiz, M., Carter, E. A. 2004; 93 (11)

    Abstract

    Iron shows a pressure-induced martensitic phase transformation from the ground state ferromagnetic bcc phase to a nonmagnetic hcp phase at approximately 13 GPa. The exact transformation pressure (TP) and pathway are not known. Here we present a multiscale model containing a quantum-mechanics-based multiwell energy function accounting for the bcc and hcp phases of Fe and a construction of kinematically compatible and equilibrated mixed phases. This model suggests that shear stresses have a significant influence on the bcc<-->hcp transformation. In particular, the presence of modest shear accounts for the scatter in measured TPs. The formation of mixed phases also provides an explanation for the observed hysteresis in TP.

    View details for DOI 10.1103/PhysRevLett.93.115501

    View details for Web of Science ID 000223794400030

    View details for PubMedID 15447350

  • Variational time integrators International Journal for Numerical Methods in Engineering Lew, A., Marsden, J., Ortiz, M., West, M. 2004; 60: 153-212
  • Optimal BV estimates for a discontinuous Galerkin method for linear elasticity Applied Mathematics Research eXpress Lew, A., Neff, P., Sulsky, D., Ortiz, M. 2004; 3
  • Asynchronous variational integrators Archive for Rational Mechanics & Analysis Lew, A., Marsden, J., Ortiz, M., West, M. 2003; 2 (167): 85-146
  • An artificial-viscosity method for the Lagrangian analysis of shocks in solids with strength on unstructured, arbitrary order tetrahedral meshes Journal of Computer-Aided Materials Design Lew, A., Radovitzky, R., Ortiz, M. 2001; 2-3 (8): 213-231

Books and Book Chapters


  • An overview of variational integrators in Finite Element Methods: 1970's and Beyond volume dedicated to T. Hughes in his 60th birthday Lew, A., Marsden, J., E., Ortiz, M., West, M. edited by Franca, L., P., Tezduyar, T., E., Masud, A. CIMNE, Barcelona. 2004: 1

Conference Proceedings


  • Application of assembly of finite element methods on graphics processors for real-time elastodynamics Cecka, C., Lew, A., Darve, E. 2012
  • A discontinuous-Galerkin-based extended finite element method: immersed boundary perspective and optimal convergence Lew, A., Shen, Y. 2011
  • Some new algorithmic ideas for the simulation of ballistic gel penetration Potts, M., A., Lew, A., Ryckman, R., Rangarajan, R. 2010
  • Explicit asynchronous contact algorithm for elastic-rigid body interaction Ryckman, R., A., Lew, A., J. edited by Zavarise, G., Wriggers, P. 2010
  • Towards long-time simulation of soft-tissue simulant penetration Rangarajan, R., Ryckman, R., Lew, A. 2008
  • Parallel Asynchronous Variational Integrators Lew, A. edited by Papadrakakis et al., M. 2007
  • Discontinuous Galerkin methods for nonlinear elasticity Eyck, A., Ten, Lew, A. edited by Mota Soares et al., C., A. 2006
  • Bridging time-scales in solid dynamics: asynchronous variational integrators Lew, A., Ortiz, M. edited by Bathe, K., J. 2003
  • Un programa general de elementos finitos en paralelo Buscaglia, G., Dari, E., Lew, A., Raschi, M. 1999