Details

Autor(en) / Beteiligte

• Nicola, L.
• Xiang, Y.
• Vlassak, J.J.
• Van der Giessen, E.
• Needleman, A.

Titel

Plastic deformation of freestanding thin films: Experiments and modeling

Ist Teil von

• Journal of the mechanics and physics of solids, 2006-10, Vol.54 (10), p.2089-2110

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2006

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Experimental measurements and computational results for the evolution of plastic deformation in freestanding thin films are compared. In the experiments, the stress–strain response of two sets of Cu films is determined in the plane-strain bulge test. One set of samples consists of electroplated Cu films, while the other set is sputter-deposited. Unpassivated films, films passivated on one side and films passivated on both sides are considered. The calculations are carried out within a two-dimensional plane strain framework with the dislocations modeled as line singularities in an isotropic elastic solid. The film is modeled by a unit cell consisting of eight grains, each of which has three slip systems. The film is initially free of dislocations which then nucleate from a specified distribution of Frank–Read sources. The grain boundaries and any film-passivation layer interfaces are taken to be impenetrable to dislocations. Both the experiments and the computations show: (i) a flow strength for the passivated films that is greater than for the unpassivated films and (ii) hysteresis and a Bauschinger effect that increases with increasing pre-strain for passivated films, while for unpassivated films hysteresis and a Bauschinger effect are small or absent. Furthermore, the experimental measurements and computational results for the 0.2% offset yield strength stress, and the evolution of hysteresis and of the Bauschinger effect are in good quantitative agreement.