Several experimental investigations have shown that elastic-plastic deformations are size dependent for sufficiently small scales. This phenomenon can not be predicted by standard continuum based plasticity theories that do not include any material length scales. In the lecture, a range of experimental observations for metallic and polymeric materials will be presented that show evidence of length scale dependencies. Different alternatives for theoretical models that would have the capability to capture these effects will be discussed. In particular, a continuum based strain gradient plasticity theory that has been developed by the author will be discussed. Of special interest is the treatment of boundary and interface conditions. At the micron scale, bounding surfaces such as interfaces or grain boundaries restrict plastic deformation and become increasingly important as the scale is decreased. A connection to dislocation theory is made. The theory is applied to the simulation of biaxial loading of a thin metallic film on an elastic substrate. It is shown that relevant size dependencies at least qualitatively can be captured. A viscoelastic version of the strain gradient theory is as well presented. The theory is applied to the prediction of thermal expansion of a thin polymeric layer on a large elastic substrate. It is shown that experimental observations of decreasing thermal expansion with decreasing layer thickness can be captured.

Academic degrees 1984 Docent, Solid Mechanics, Royal Institute of Technology, Stockholm, Sweden 1982 PhD, Solid Mechanics, Royal Institute of Technology, Stockholm, Sweden 1979 MSc, Engineering Physics, Royal Institute of Technology, Stockholm, Sweden Professional experience 1993- Professor of Material Mechanics, KTH Solid Mechanics, Royal Institute of Technology, Sweden. 1993-05 Head of department, KTH Solid Mechanics, Royal Institute of Technology, Sweden. 2004 Guest Professor, 2 months, Institute of Materials, EPFL, Lausanne, Switzerland 1989-93 Managing Director, Swedish Institute of Composites, Piteå, Sweden 1987-89 Associate professor (universitetslektor), KTH Solid Mechanics, Royal Institute of Technology, Sweden 1987 Guest researcher, 2 months, Brown Boveri Research Centre, Baden, Switzerland 1985-86 Researcher (half time), KTH Solid Mechanics, Royal Institute of Technology, Sweden 1983-86 Consultant, Tre Konsulter AB, Vaxholm, Sweden (1985-86 half time) 1979-83 Research associate, Brown Boveri Research Centre, Baden, Switzerland Appointments as reviewer for international journals and books Acta Mater., AIAA J., Appl. Phys. Letters, Composites Part A, Comp. Sci. Techn., Eng. Fract. Mech., Eur. J. Mech., Fatigue Fract. Eng. Mat. Struct., Int. J. Damage Mech., Int. J. Fatigue., Int. J. Fract., Int. J. Mech. Sci., Int. J. Plasticity., Int. J. Solids Struct., J. Appl. Comp. Mat., J. Appl. Mech., J. Mech. Comp. Mat., J. Mech. Mater. Struct., J. Comp. Mat., J. Mech. Phys. Solids, J. Sound Vibr., J. Thin Solid Films, J. Vibr. Acoust., Modell. Simul. Mater. Sci. Eng., Polymer Eng. Sci., Proc. Roy. Soc. A, John Wiley & Sons (book proposal), Kluwer Academic Publishers (book proposal), Springer-Verlag (book proposal) In addition, Professor Gudmunson has had numerous other appointments and publications, including but not limited to the following: • Member of the Editorial Advisory Board for Journal of Composite Materials, 2000-. • Member of the board for the Biofiber Materials Research Center BiMaC at KTH, 2001-. • Member of evaluation group for research proposals to Swedish Research Council, 2001-02. • Member of the Scientific Council for Natural and Engineering Sciences, the Swedish Research Council, 2004-06. • Member of EUROMECH Solid Mechanics Conference Committee, 2005-10. • Member of the Research and PostGraduate Education Committee within the KTH Faculty Board (Ledamot i Forskarutbildningsutskottet inom Fakultetsnämnden KTH), 2005- • Member of the board, KTH School of Industrial Engineering and Management, 2005- • Member of the board, KTH School of Engineering Sciences, 2005-. • Expert evaluator of proposals to the Danish Technical Research Council, the Norwegian Research Council, the Finish Academy of Science, the Netherlands Organization of Scientific Research, the Royal Swedish Academy of Sciences • P. Fredriksson, P. Gudmundson, "Competition between interface and bulk dominated plastic deformation in strain gradient plasticity". Submitted for international publication, 2006. • P. Fredriksson and P. Gudmundson, "Modelling of the interface between a thin film and a substrate within a strain gradient plasticity framework". Submitted for international publication, 2006. • J. Agde Tjernlund, E.K. Gamstedt, P. Gudmundson, "Length-scale effects on damage development in tensile loading of glass-sphere filled epoxy". To appear in Int. J. Solids Structures, 2006. • L. Olasz and P. Gudmundson, "Viscoelastic model of cross-linked polyethylene including effects of temperature and crystallinity", Mechanics of Time-Dependent Materials, Online issue, 2006. • P. Gudmundson, "Modelling of length scale effects in viscoelastic materials", Eur. J. Mech. A/Solids, 25, 379-388, 2006.